Exam 2 Flashcards
What is the difference between venomous and poisonous animals?
Venomous animals = Creatures that produce a poison in highly developed secretory gland which can be delivered during a stinging or biting act.
Poisonous animals = Creatures with tissues (either part or entire tissue) that are toxic. No delivery system, rather those animals are toxic when eaten.
What are the two mechanisms for venomous animals?
Hunting- usually produced by glands associated with the mouth region (in the front)
Defense- usually associated with other parts of the body (hind parts of the body)
What are the different types of biotoxins?
Hemotoxins
Hemolysis, thrombosis, & thrombolysis
Examples include: Crotalid snakes (Pit vipers), Viperid snakes
Neurotoxins
Primarily affect the nervous system of affected animals.
Examples include: Botulism, Black widow spiders, most scorpions, jellyfish, Elapid snakes
Cytotoxins
Toxic at the cellular level (tissue damage), either non-specifically or only in certain cells.
Examples include: Brown recluse spiders, blister beetles
Hymenoptera (bees, hornets and wasps)-
Geographic range and habitat
Widespread
generally greater numbers in mild climates
found in secluded places
nests of mud, papery material or wax
Hymenoptera (bees, hornets and wasps)-
Exposure
Disturbance of nest or swarm
Hymenoptera (bees, hornets and wasps)- Toxin and toxicity
Complex mixture of enzymes and polypeptides
Some common components; some unique to a species:
Bee venom: melittin, apamin (most venomous), phospholipase A, mast cell degranulation peptide, hyaluronidase (spreading factors)
Wasp venom: mastroparan and bradykinin
Depends on the age and species of insect, location of the sting, the amount of venom injected, age and condition of victim
20 stings/kg bw can be lethal
Hymenoptera (bees, hornets and wasps)- diagnosis
Localized pain, heat and swelling
Presence of venom sac and stinger
bees - sting once and has venom sac and stinger in site
Wasps- sting multiple times
Lesions - usually localized and consist of small puncture site, stinger, redness, swelling, heat and eosinophil accumulation. Persist for ~ 24 to 48 hours.
Can be sensitized to stings after initial sting → bigger response in the future
Hymenoptera (bees, hornets and wasps)- treatment
Ice/cold compress- Helps with swelling
Antihistamines- Helps with swelling
Topical corticosteroids
Treat anaphylaxis, shock
Broad spectrum antibiotics- If it gets infected
No specific antidotes (only symptomatic treatment)
Epicauta species- basic information
Nearly 40 species of blister beetle in the U.S.- confirmed toxicosis with relatively few Spp
Toxicosis more common in southern and southeastern U.S.
Found in gardens and crop and hay fields
Manufactured/pelleted feeds- Bugs can travel long distances in feed
Epicauta species- exposure
Poisonous- in live or dead/dried state
Males are more poisonous than females (4x more)
Crimped in hay
Alfalfa hay commonly involved (Medicago sativa)
145 g of dried beetles have been found in a single flake of alfalfa hay!!
Epicauta species- toxin and toxicity
Crystalline cantharidin
Dogs and cats: 1.0 to 1.5 mg/kg
Horses: 0.5 mg/kg
Cantharidin
found in hemolymph and gonads
strongly irritating to mucous membranes
hypocalcemia due to unknown mechanism
GI tract- Anorexia, colic, diarrhea, mucoid to bloody stools
Urinary Tract- Dysuria, hematuria
Respiratory, Cardiac- Tachypnea, tachycardia, slow CRT
Causes cell death and necrosis (die within 48-96 hours)
Used to be used as Spanish Fly”- Blistering agent, diuretic, aphrodisiac
Epicauta species- post mortem
Gross
oral ulceration, vesication, desquamation in GI tract.
hyperemia and hemorrhages in urethra and urinary bladder.
Histologically:
damage (necrosis and ulceration) to the mucosa of the GI tract, epithelium of urinary tract and endothelium of vessels.
Epicauta species- diagnosis
Look carefully for beetles in hay
Analysis for cantharidin in urine, GIT contents, hay, pelleted feeds
Epicauta species- treatment
Treat for shock; correct acidosis, hypocalcemia
AC
50% of affected horses die –prognosis guarded
What are the differences between black widow spiders and brown recluse?
More lethal than brown recluse
BW has more small animal cases than brown recluse
Black widow spider (Lactrodectus mactans)- Exposure
Accidental encounter with nesting area (used to immobilize insects)
Black widow spider (Lactrodectus mactans)- toxin and toxicity
alpha-latrotoxin, a neurotoxin
Ionophore for Ca, Na and K
Increases their permeability and enhances neurotransmitter release
Degeneration of nerve terminals → paralysis
Affects motor and sensory nerve terminals
A single bite may be lethal to a small animal.
Black widow spider (Lactrodectus mactans)- clinical signs
Severe muscle cramps
Anxiety
Painful
Peak of clinical effects 6-12
Black widow spider (Lactrodectus mactans)- diagnosis and treatment
Difficult- observation of bite locus
Pain control
Muscle relaxants
Calcium gluconate
Antivenin (Equine origin, Merck)
Only used if bite but no interaction with tissue (no symptoms)
Used in dogs and cats
Treat shock
recluse spiders (Loxosceles spp.) – geography and basic information
Several species found throughout the U.S.
Brown recluse spider (Loxosceles reclusa)
Females have larger bodies and fangs → only females are able to penetrate skin on mammals
recluse spiders (Loxosceles spp.) – toxin/MOA
Several proteins
Hyaluronidase
Sphingomyelinase
Proteases
hemolysins
Endothelial cell damage
Coagulation
thrombus formation
tissue necrosis
Toxicity- As little as 5 g of toxin causes lesions
recluse spiders (Loxosceles spp.) – diagnosis
lesion consistent with bite
Bulls eye lesion → represents necrosis spreading out
recluse spiders (Loxosceles spp.) – treatment
Wound care- excision of affected area
Antibiotics (open wound)
Dapsone may reduce inflammation
No antivenin- not as poisonous as black widow
What are some Crotalidae (pit vipers)
Rattlesnakes
water moccasins
copperheads
what are some Elapidae
coral snakes
cobras
What are some General characteristics of venomous snakes
Poikilothermic- they are the same temperature as their environment
Carnivorous
Posteriorly curved teeth- teeth / fangs are shed and replaced throughout life
Difficulty seeing stationary objects- generally poor eyesight
Detect movement via ground vibration
What is some information about snake venom?
Venoms are primarily composed of proteins, many with enzymatic activity.- also glycoproteins, lipids and biogenic amines
Proteolytic enzymes catalyze the breakdown of tissue proteins and peptides.
Esterases may mediate bradykinin-releasing and bradykinin-clotting activity.
Thrombin-like enzymes have procoagulant activities.
What are some characteristics of pit vipers?
Deep pit between eye and nostril
Vertically elliptical pupils
Fangs are hollow and retractable, located near the front of the maxilla
Body is narrower than back of the head →“arrow-like” shape
Can be aggressive if disturbed
Most common cause of envenomation in veterinary medicine
What are Rattlesnakes Bite statistics
Relatively common
Dogs most often affected
Bites tend to occur from May to September during late afternoon
Head and front legs are most common sites
often through aggressive or curious behavior
Horses
Bites are most often on the muzzle; lower limbs less so
generally when grazing
Cattle
Bites often to the tongue and muzzle
Cats
More resistant to pit viper venom on mg/kg bw basis
However, lesions often severe due to small size and delay before treatment
Bites often occur on torso
Pit viper toxins and toxicity
Multiple, complex venoms
Collagenase
Hyaluronidase
Phospholipases
Ribonucleases
Polypeptides
Procoagulants and anticoagulants
Toxicity Varies on
species variations
size of snake
location of bite
Amount injected is critical variable
pit viper- clinical signs
Pain
Rapid swelling
Ecchymotic to suffusive hemorrhages in area of bite
Salivation, hypernea, tachycardia, mydriasis
Secondary infections
Some like the Mojave rattle snakes cause neurotoxicity
Bite on face ⇒ difficulty breathing
pit viper- diagnosis
Observation of bite or bite wounds
characterized by two puncture wounds
pit viper- treatment
Emergency!
Small Animal
Shock treatment
Transfusions if severe anemia or hemorrhage
Antibiotics (+/-)
Pain medication
Diphenhydramine
Antivenom: ASAP
Large animals
Establish and maintain airway(tube, tracheostomy)
Anti-inflammatory
Antibiotics (+/-)
Anti-tetanus
Antivenom: risk for serum sickness if equine origin antivenom is given
What are the differences between the two Crotalidae Antivenoms?
CroFab
From sheep
Fab fragments, affinity-purified
4 NA Crotalid species
FDA approval
Anaphylaxis: not reported
Serum sickness: rare
$$$$
Antivenin (Crotalidae) Polyvalent
From horse
IgG, not well purified
2 North & 2 South American snakes
FDA approval
Anaphylaxis: reported
Serum sickness: frequent
$$$$
What is some information about the rattlesnake vaccine?
Sold by Red Rock Biologics in CA
Available only in CA and WA, marketed for dogs and horses
USDA / VS: “conditionally licensed product”
Current approach by the VMTH: Treatment protocol for vaccinated vs. non-vaccinated patient is the same (i.e. antivenom is also given to the vaccinated patient)
Vaccination is not recommended due to lack of good efficacy data, cost, and low incidence rate in area.
What are some facts about elapidae?
Fangs are at anterior end of maxilla and are tubular or deeply grooved and fixed
Coral Snakes- Red into yellow … ⇒ kill a fellow
Two genera in the US:
Micruroides: M. euryxanthus = Arizonan (Sonoran) Coral snake
Micrurus:
M. fulvius fulvius = Eastern Coral snake
M. fulvius tenere = Texas Coral snake
M. fulvius barbouri = South Florida Coral snake
Most members of Elapidae are found in Africa, Asia, and Australia
Round pupils
Small pair of short fixed front fangs
Venom is delivered by chewing
Tend to be non-aggressive, reclusive
Elapidae- exposure
Envenomation relatively uncommon
Coral snakes have small mouths making envenomation difficult
Elapidae- toxin/MOA
Proteins
Curare-like effect
Interferes with Acetylcholine → blocking neuromuscular junction (can’t breath)
paralysis
Local tissue reaction
Phospholipase A
Hemolytic anemia reported in dogs
Elapidae- clinical signs
Limb numbness, weakness, disorientation, paralysis, dyspnea
Parasympathetic signs include salivation, emesis, and diarrhea.
Fang marks are small.
Elapidae- diagnosis and treatment
Dx Difficult
Rx
Antivenin
Respiratory support
Atropine
What is signal transduction? What is the equation for it?
Signal Transduction: A pathway of events by which each component participates in the process of transmitting a hormonal/growth factor signal to the target molecules within the cell.
[L] + [R] ↔ [LR] → [LR] →→→ Response
L- ligand
R- receptor
LR- ligand receptor complex
LR- excitable and leads to a response
alpha= 1 → full response. Fully agonist
Less than one→ less than full response, not as good as an agonist
Affinity = 1/KD
Multiple of these pathways occur simultaneously
Based on the LR equation, what is the implied pharmacological effects?
Pharmacological effects are reversible because the Ligand-receptor complex is reversible.
Pharmacological effects are proportional to the number of receptors occupied.
Pharmacological effects are proportional to the dose of ligand/drug.
Pharmacological effects plateau because they are limited by the total number of receptors.
Types of receptors
Receptors coupled to G-proteins
Receptors tyrosine kinases
Cytosolic and Nuclear Receptors
Ion Channels
Signaling cascade mediators
Ca2+
Ras MAP kinases
Protein Kinase A
Protein Kinase C
How is relative potency seen in graphs?
Relative potency- lower EC50 compared to another drug’s EC50
more left = higher potency
How is relative efficacy seen in graphs?
greater response than another drug
higher curve = higher efficacy
What does drug concentration graph slope mean?
Slope- how receptor is responding to the drug
Hill coefficient- The steepness, Hill coefficient, gives information about the stoichiometry of the drug-receptor interaction (is 1 for 1:1 interaction)
For nH= 1; 20% of effect is obtained at 0.25 x EC50and 80% effect at 4 x EC50
For nH< 1; suggests negative co-cooperativity.
nH> 1; suggests positive co-cooperativity and a 2:1 or higher interaction between receptor and drug → makes concentration-response relationship very steep with large increases in effect at small increases in dose.
How is pharmacodynamics measured?
Graded
Continuous scale (dose ® effect)
Measured in a single biologic unit
Relates dose to intensity of effect
GRADED DOSE-RESPONSE RELATIONSHIP:indicate doses that cause 1/2 maximal response in a given INDIVIDUAL- ED50
Quantal
All-or-none pharmacologic effect
Ex. Cured or not Cured [ex. Parasiticides]
Population studies
Relates dose to frequency of effect
QUANTAL Dose-Response Relationship:indicate doses that cause 1/2 of the POPULATION to respond.– mean or medium ED50
How is quantal pharmacodynamics determined?
General experimental design
Define the population to be tested
Determine the number of individuals to be tested
Determine time (of taking data)
Define endpoint(s) level of pharmacological/toxic response
Randomly assign individuals to dose groups (include placebo)
Results
Score % responding within each dose group
Plot data as frequency distribution, cumulative frequency
Gives rise to how much of population responding, how many hypersensitive, and how many resistant (%)
What arises from a comparison between cumulative and standard deviation plots?
ED50 matches up with the middle of SD plot and halfway for cumulative plot
Higher the ratio → higher TI → safer for population
Higher TI- at higher ED90, lower TD (less overlap between the two)
What is the standard safety margin?
Certain Safety Factor = LD1/ED99
Relates therapeutic effect in all animals in the absence of a risk of producing a hazardous effect. LD is the Lethal Dose of the drug. Certain safety factor is when ED99 must be increased before an LD1is reached.
Standard Safety Margin= (LD1- ED99)/ ED99* 100
The Standard Safety Margin is a percent which ED99 must be increased
Before an LD1is reached.
What is the difference between concentration response and dose response plots?
Concentration Response when talking about in vitro on an isolated receptor- Effective Concentration (EC). Reported as ½ Response; i. e. EC50
Dose Response when talking about in vivo where you use mg/kg body weight- Effective Dose (ED). Reported as ½ Response; i. e. ED50
Terminology used with animal use
what is pharmacodynamics?
A chemical structure contains information which, upon binding biological receptors, can alter their structure and function
What is the difference between agonists and antagonists?
Agonists enhance ongoing function
Antagonist diminish ongoing function
What is an inverse agonist
An inverse agonist is a ligand that binds to the same receptor as the agonist and causes the opposite effect of the agonist ligand.
Requirement: Receptor must have basal activity in the absence of any ligand for an inverse agonist to function.
The efficacy of an inverse agonist is less than 0.
Examples of receptors that bind to inverse agonists are GABAA, melanocortin, mu opioid, histamine and beta adrenergic receptors.
What is the difference between competitive antagonists and noncompetitive antagonists? How about their dose response curve?
comp- Antagonism can be overcome by increasing [agonist] (a property limited by toxicity).
Antagonists added→ right shift in the curve
Schild plot- For competitive antagonists the equilibrium dissociation constant (KB) for the antagonist can be obtained.
When the slope is equal -1 the antagonism is competitive.
pA2is concentration of antagonist, which requires a 2-fold increase in agonist concentration
non- Acts to essentially remove a fraction of the receptors from producing a response to agonist (inhibition not dependent on [agonist]).
Can’t overcome inhibition with increased agonist concentration
Dose response curve
Addition of agonists → efficacy decreases (curve goes lower)
However, EC50 value remains the same because receptors still bind
Q and Qmax is lowered because receptors are not responding to binding
What is drug selectivity?
Drug selectivity- Predictable pharmacological response requires knowledge about relative potency of efficacy at all receptors with which it interacts.
No drug is completely specific in biological action- can be off target effects
Structure-activity relationships reveal receptor subtypes
What is the simple receptor occupancy model?
The magnitude of a specific in vitro response is proportional to the fraction of receptor sites (R) complexed with a reversible ligand (L)
Intrinsic efficacy- Indicate the relation between pharmacologic response and occupancy of receptor sites
What are the alpha intervals for full receptor agonists? What about partial agonists?
full- 1.0> alpha > 0.8
partial- 0.8 > alpha > 0.2
What is clinical potency?
Clinical Potency- Reflects the amount of drug needed to produce a certain level of therapeutic response
Affinity for a drug for its receptor is the principle determinant of clinical potency.
What is intrinsic efficacy?
Reflects the greatest clinical response attainable with a drug at any dose
What are possible dug-drug interaction effects?
Increased effects- additive or synergistic effect
Increased therapeutic effect
Increased toxic or adverse effects
Decreased effect- antagonistic effect
Decreased therapeutic effect
Decreased toxic effect
What is the difference between additive effect and synergistic effect?
Additive effect : Both drugs do not affect the actions of each other, but their actions together equals the sum of the actions of each drug when administered alone.
Synergistic effect: Actions of both drugs administered together promote an exaggerated effect out of proportion compared to the actions of each drug administered alone.
May be called super additive
What is antagonism? What is an example of its mechanism?
Occurs when one drug inhibits the action of another.
AKA sub additive
Pharmacological antagonism: a drug antagonizes the effect of another drug by acting on the same receptor. Two types- competitive and noncompetitive
Ex. Detoxify-reversal therapy- Xylazine and Yohimbine
Xylazine targets the presynaptic alpha2- adrenergic receptor to reduce neural transmission
Yohimbine (competitive antagonist) reverses the effects of xylazine by competing with the alpha2-adrenergic receptor
What measures drug-drug interaction? How is it done?
classical isobologram plot (predicts isoeffect curves when two drugs are together)
Done in vitro
EC50 value is plotted on graph (x and y interval)
In this example, both are 1
Draw line to connect the two
When adding the two drugs together, if it falls
On the line → additive
Below the line → synergistic
Above the line → antagonism
This depends on concentration (proportion of Drug A and B)! If you change the concentration throughout the graph, you will see synergism, antagonism, and additive features all over the graph
What are spare receptors?
How is it graphically represented?
Observation: Only a fraction of the total number of receptors need be occupied to elicit a maximal response in some tissues
Experimental Evidence: Titration of a known noncompetitive antagonist results in an apparent “competitive”shift in the dose-response relationship
Expected:
See overall drop in efficacy, but instead, they got a competitive right shift
As increase non comp antagonists → less receptors available → still enough receptors to reach efficacy → only right shift → but still has less and less receptors to respond → as increased antagonist (don’t have enough receptors for response) → finally have drop in efficacy in response
If EC50 is less than KD → spare receptors
Seen- at 90% pharmacological response, only ~25% of receptors responding
Antagonists → less receptors available → increases EC50 closer to KD
What is therapeutic drug monitoring (TDM)?
A tool for guiding a dosing regimen
Individualize therapeutic regimens for optimal patient benefit
Increasing therapeutic effects and decreasing toxic effects
Assumes a relationship between: Dose, Concentration, and Response
Dose-response relationship (rem. The three assumptions)
What are the indications for TDM?
Animal refractory to medication
Not responsive to medication (seeing if dose in therapeutic range)
Animal showing toxicity
PK differences in individual patients
How drug is eliminated and why you are seeing toxicity
Drug Interactions
Steep dose response curve
Small change in dose leads to massive effect
Drug with a narrow therapeutic range
TDM is not indicated for all drug
What are TDM sample considerations?
Sample Type
Plasma/serum/whole blood- Vast majority of drugs are tested in plasma or serum (either or is dependent on lab and what type of test they have)
Tube type- Glass vs plastic- some drugs bind to glass or plastic→ get artificially low concentrations
Titer top tubes (have silicone plug) → some drugs bind to silicone plug
Detailed History
Any other drugs, when drugs were given, in critical condition?
Assay needs to be rapid (24-48 hours)
Cost
Applicability to patient:
Concentration – effect relationship
Drug needs to have this
Established “therapeutic”range
Qualified individual for interpretation (vet clinical pharmacologist)
TDM- when to collect sample?
Drugs with a long elimination t1/2 relative to dosing interval
Collect at steady state
Steady state = Therapeutic range
Single sample vs. peak (Cmax) and/or trough (Cmin)
Single- make sure if in range
peak - toxicity
Trough- lack of efficacy
Allow time for absorption/distribution (~1-2 hours post admin of EV drug)
How does one get TDM samples for drugs with a short elimination half time relative to dosing interval?
Single sample is often sufficient for monitoring (want to know if within dosing range)
Allow time for absorption/distribution
How does TDM work in association to loading and maintenance doses?
After loading dose- After absorption and distribution to make sure it is at therapeutic level
One t1/2 after maintenance dose starts
Make sure maintenance dose maintains what it achieved by LD
At steady state- Make sure it is maintaining concentration
Elimination half-life calculation:
Peak and trough
What are the steps of TDM in relation to dosing?
Initiate drug dosing schedule
Allow time to reach steady state
Administer another dose
Collect peak sample
Collect trough sample
Assay drug concentrations
Calculate individual PK parameters (half life)
Adjust dosing interval or dose amount
How should TDM be interpreted?
The “therapeutic”range is a population statistic and not a “normal.”
Not based on individual
95% of the population respond somewhere within the range.
What are considerations when adjusting dose regimens?
Drug
Therapeutic index of drug (safety)
Can you give a large amount of drug and pushing interval or would that cause toxicity?
Need to maintain plasma drug concentrations within therapeutic range throughout dosing interval
Would it fall to really small levels before giving next levels?
Some drugs (like the one in lab) protect the drug concentration when it gets low → it is ok when concentrations get low because it is protected
How are adjusted intervals calculated?
proportional method
new interval/old interval = existing conc/desired conc
How are adjusted dose calculated?
proportional method
old dose/existing conc = new dose/desired conc
Important to check peak concentration to see if falls into therapeutic range → not toxic
But therapeutic range is population value → not based on individual, so you should monitor once drug administered
Describe what you can assess with a peak sample and trough sample
peak - assess toxicity
Trough- assess lack of efficacy
Having peak and trough samples allow one to calculate ______
Having both allows to calculate rough estimate of half life
Helpful when drug changes it own half life and metabolism
Define Tolerance
“safe concentration”
Established based on safety to the person consuming the tissue.
Tissue tolerances established in fat, milk, muscle, liver, kidney or skin.
Define Withdrawal Time (WDT)
time required for a drug to be depleted from the animal before the animal’s meat can be marketed for human consumption.
FARAD- provides information to veterinarians about withdrawal times
Esp if used off label
Give examples of factors that affect withdrawal times.
Closely related to elimination half life
Statistical method is used to determine the time it takes for drug residues to deplete below the safe concentration.
Only valid for the specified species, dose, route and frequency of administration.
If used off label → Veterinarians must establish a substantially extended withdrawal period supported by scientific information with ELDU.
Can be affected by physiologic condition (affects elimination half life)
What is neurochemistry?
the study of neurochemicals, including neurotransmitters and other molecules such as psychopharmaceuticals and neuropeptides, that influence the function of neurons. This field within neuroscience examines how neurochemicals influence the operation of neurons, synapses, and neural networks
Endogenous molecules that are imp for determining function of nervous system
What is neuropharmacology?
the study of how drugs affect cellular function in the nervous system, and the neural mechanisms through which they influence behavior. There are four main branches of neuropharmacology: molecular, cellular, systems and behavioral
Drugs specifically that influence neurotransmission
What are some basics about neurotransmission?
Synapse has presynaptic that has chemical signal that triggers post synaptic signal
Pre- electrical
Synapse- chemical
Post- electrical
What are some basics about action potentials?
Electrical signaling (action potential)- dramatic change in membrane potential
At rest- -70 mV
Less positive charge inside compared to outside
Maintained by Na/K pump (can’t cross plasma membrane)
Also ion channels → typically closed at rest
Triggered- depolarization (increased voltage)
Voltage gated Ion channels (Na)- open in response to change to depolarization
Very quickly open Na channels and delays opening of K channels
Na has two pressures to drive it into the cell
Concentration gradient
charge (electrochemical) gradient
Threshold- -55mV→ all or none response
Membrane potential shoots up
repolarization: decrease mV
Set up electrochemical gradient to drive K out
K channels open up → makes cell more negative (Net loss of positive charge)
Overshoot
Why do action potentials travel in only one direction?
Depolarization occurs first from body → positive charges (Na) going in are attracted to the adjacent lateral negative sides → depolarizes neighbor and travels down axon hillock
Why only travel left to right?
Because K channels open and make more negative
Pump
Activation gate opens with depolarization
With delay, activation gate closes and inactivation gate opens → blocks Na flowing through to the left → only travels to the right
What occurs in the chemical synapse?
AP reach axon terminus → cause opening of voltage gated Ca channels → Ca flows inside → activate fusion of synaptic vesicles to presynaptic neuron → synaptic vesicles dumped in synaptic cleft → bind to receptors on postsynaptic side → allows change of ion distribution of neurotransmitter → depolarization on post side
Ca always higher out of cell vs inside
What is the process of chemical transmitters?
Synthesis of neurotransmitter in the presynaptic neuron
Storage of the neurotransmitter and/or its precursor in the presynaptic nerve terminal
Need to be stored or else they will be degraded
Release of neurotransmitter into the synaptic cleft
Binding and recognition of the neurotransmitter by receptors on the target (postsynaptic) cell
Termination of the action of the release neurotransmitter
Always active ⇒ be no signaling
How is neurotransmission terminated?
Binding of it to presynaptic cell receptor
Can decrease how much is being released- autoinhibitory receptors
Decrease synthesis on the presynaptic side
Uptake proteins
On presynaptic side
Recycled for neurotransmission
Taken up into glial cells
All synapse are surrounded by glial cells
Clear them out
Diffuse out of synaptic cleft
Inefficient
Can be metabolized in synaptic cleft
How is neurotransmission physiological response determined?
Neurochemical phenotype of affected cell type(s)
Location of molecular/cellular target(s)
Physiological role of molecular/cellular target(s)
Pharmacokinetics of drug/toxin/toxicant
Where is acetycholine found? What does it do?
A neurotransmitter used by the spinal cord neurons to control muscles, by many neurons in the brain to regulate memory and by peripheral neurons to regulate autonomic function.
In most instances, it is excitatory
Where is dopamine found? What does it do?
The neurotransmitter that produces feelings of pleasure when released by the brain reward system
Dopamine has multiple functions depending on where in the brain it acts
It can be excitatory or inhibitory
Where is GABA (gamma aminobutyric acid) found? What does it do?
The major inhibitory neurotransmitter in the brain
Where is glutamate found? What does it do?
The most common excitatory neurotransmitter in the brain
Where is glycine found? What does it do?
A neurotransmitter used mainly by neurons in the spinal cord
It is probably always acts as an inhibitory neurotransmitter
Where is norepinephrine found? What does it do?
NE acts as a neurotransmitter in the CNS and PNS
In the PNS, it mediates the flight or fight (sympathetic) response
In the brain, it acts as a neurotransmitter regulating normal brain processes
NE is usually excitatory, but is inhibitory in a few brain areas
Where is serotonin found? What does it do?
A neurotransmitter involved in many functions including mood, appetite, and sensory perception
In the spinal cord, serotonin is inhibitory in pain pathways
What is the excitatory-inhibitory balance? What causes shifts in this balance?
Balance of glutamate (excitatory) and GABA (inhibitory)- EI balance
Can change balance by change in excitatory vs inhibitory drive
Glut neurons can inhibit another glut neuron transmission through gaba neuron
Imbalance between Excitatory and Inhibitory Drive (E/I Imbalance) Contributes to Diverse Pathologies
What are some pathologies that can arise from EI balance shift?
Too much inhibition- death
Too much excitatory- seizures and death
A lot of seizure medication → targets this balance (increase GABAergic)
Drugs used to control anxiety target this
Anxiety- too much excitatory drive
Target to decrease excitatory
Critical to peripheral organ function → autonomic function
From hypothalamus, balance of EI
Determines rate of AP firing and strength
Increase in inhibitory- decreased resp output
Increased excitatory - increased resp output
Many organs in periphery are dually innervated
Balance between EI determines what happens in these organs
What is the difference between somatic and autonomic neurotransmission?
Somatic- single circuit
Motor neuron- release acetylcholine → binds to nicotinic acetylcholine receptor → contraction of muscle
Autonomic- two neuron circuit
Preganglionic and postganglionic
Ganglion- collection of neurons
Para- send pre out very far to ganglion
Can be seen in lungs and heart
Post- send out acetylcholine to post and post will release acetylcholine → bind to muscarinic acetylcholine receptor
sympathetic nervous- chain ganglia (lie next to spinal cord) → pre not send out far → acetylcholine to post → post release NE
Pre can also release acetylcholine to nicotinic receptors → EPI released in bloodstream
What is the difference between nicotinic and muscarinic receptors?
Ligand gated ion channels
Mus- activate second messaging signals in cells
What are the targets of autonomic nervous system?
Exocrine glands (sweat, salivary, etc)
Cardiac muscle
β1 receptor stimulation increases heart rate (HR), contractile force, conduction velocity
Muscarinic receptor stimulation decreases HR and contractile force
Smooth muscle
α receptor stimulation causes smooth muscle contraction
β2 receptor stimulation causes smooth muscle relaxation
Muscarinic receptor stimulation causes smooth muscle contraction*
except for blood vessel relaxation, which involves release of nitric oxide from endothelial cells
Describe characteristics of a ruminant
Cloven hooves
No upper incisors
Upper teeth is a dental pad
3 - 4 compartments that make up their digestive system before intestines
Some people consider reticulum as part of other parts
Rumen
Omasum
Abomasum- true acid stomach
Pregastric fermentation
Everything in rumen has first crack at everything eaten before the animal
Ruminate, chew cud
Ruminate comes from when they eat, they stick head in air and “think”
Cattle, sheep, goats, buffalo, deer, antelope, moose, elk, giraffe
What is rumination? Why is it done?
Rumination- brings up food from rumen to chew and then goes back in rumen
Has saliva → neutralize pH, gets wet for microbes to latch onto them
Ruminate 9-10 hrs / day on high forage
5 hrs on finely ground→ No tickle factor- no contractions
Maybe impaired with disease
Ie. vagus nerve damage, displaced abomasum (go to the L or R side, twist)
How does food travel down the digestive system? How does this occur?
Food → reticulum → Esophageal hole → omasum → abomasum → duodenum → out
Pillars are baffles (?) → controls sloshing of fluid, help the fluid stay where it is supposed to be, anchors for smooth muscle (since rumen contracts continuously)
Describe the reticulum. What occurs here? Are there any age associations?
Honeycombed
Stimulation of rumination and eructation (‘Tickle factor’)
Feed “tickles” reticulum → causes it to contract → causes different types of waves of contractions
If fed ground feeds, no tickle factor and not many contractions
Eructation = burping
Fermentation occurs in rumen and need to get rid of gas
If not functioning (no tickle factor), gas is not burped → bloat
Sits near diaphragm
Hardware disease- sharp metal objects (ie wire, screws, nails) → eat them → pierce the reticulum and can go through diaphragm
Reticular groove
Rumen is not functional when born so do not want milk going in there (it will rot → bloat)
Directs milk from esophagus to abomasum
Forms a channel away from the rumen
Fold stimulated by suckling
Occurs only in pre ruminant
Full ruminant at 6 months of age
Describe the rumen. What occurs here?
Runs 2 degrees higher than body temperature (due to fermentation)
39 C
pH just below neutral (6-6.8)
More hay = more alkaline
More grain = more acidic
Saliva production- 100-150 L/d
Plays an important role
Has a lot of buffers and supplies water to rumen
Gas production- 30-50L
Carbon dioxide and methane
Top of rumen has gas → reticulum contracts → gas escapes through esophagus
Todays hay below → big particles of food
Grain and yesterdays hay → microbes and particles of food
Need to be wet for microbes to latch on
No secretions
Liquid supplied by drinking and saliva which contains buffers
Papillae very vascularized for absorption of volatile fatty acids to portal vein
Ruminants also live off of fermentation, in addition to nutrients from food
Contractions move and mix digesta
If rumen acidic, papillae get damaged and decreases ability for absorption of fatty acids
Can cause ulcers and get microbes into portal vein → in liver → necrosis(?)
Movement coordinated by vagus nerve
Blood supply by celiac artery
Describe the Omasum. What occurs here?
round, basketball like compartment
Absorption of H2O, Volatile fatty acids (VFA)
Folds act as filters to trap large particles
Let small particles pass
Filters out by size
Large particles back into rumen for further fermentation
Horses, it is oriented differently → large pieces pass
Muscular action sucks digesta thru retic-omasumal orifice flushes large particles back to rumen
Describe the abomasum. What occurs here?
Acid or ‘true’ stomach pH ~ 2
Covered by mucus to protect from HCL and pepsin
First step of digestion of proteins
What are the different components that make up plants? How does this change while the plant matures?
Plant cell wall = pectin, cellulose, lignin, hemicellulose
Microbes degrade pectin, cellulose, and hemicellulose
Lignin- insoluble glue that holds everything together
Nothing degrades it
More lignin = less digestible, harder to digest
Plant cytoplasm = protein, sugar, starch, lipid
As plant matures, cell wall (lignin) increases, while protein and sugars (18%) decreases
Are ruminant microbes sensitive to any nutrients? How so?
Microbes sensitive to fat, especially non esterified fatty acids (diet must be < 3-5% fat unless it bypasses the rumen)
Double bonds → introduces a kink in it → disrupts membrane → microbes can’t function as it normally would
Triglycerides can also coat the material and prevent microbes from attaching to it
What types of organisms make up the microbial populations in the rumen? What do they do?
Bacteria 60% (5*109 /ml)
very metabolically active
Must attach, ferment locally
Feed must be wet first
Secrete enzymes on surface
Can inhibit fungi - compete for spots on feed, but can be good because increases SA due to breaking down (both can be on there)
Protozoa 30% (5*105 /ml)
but 104-106 larger (half of mass)
Large organisms
maintain stable fermentation
engulf starch
Protect rumen from acidosis
Fungi 10% ( 5*104 /ml)
hard to quantify because they have spores as part of their cycle
Have enzymes that predigest enzymes around them → Easier for bacteria to digest
Have chutes that digest as well → more SA for bacteria to ferment
Long life cycle, attach to feed particles
Increases surface area for microbes
Produce Lactate, Acetate, H+, CO2, formate, ethanol from cellulose and sugars
High fiber diet = more fungi
Diets where fungi is added are available as well
What are the different types of bacteria microbial are in the rumen?
Cellulolytics- break down cellulose → Produces Acetate, H+, ethanol, may require CO2; Must attach to fiber, excrete cellulases
Grows on glucose (cellulose or starch)
Degrades hemicellulose but doesn’t use it
Starch Digestors
Cell bound and extracellular amylase
Can rapidly degrade starch and grow
Generation time = 12 min with unlimited substrate
Don’t depend on Red-Ox (pH) to grow
Can produce a lot of lactic acid
Organic Acid Utilizers
Utilize lactate, formate, citrate, malate, fumarate, succinate, etc.
Reduces CH4 (takes the methane that would go out into environment)
Convert it into things that don’t change rumen pH
Megasphera elsdenii can cause milk fat depression
Don’t want this for dairy cows
Methanogens
Works closely with cellulolytics → produces byproducts for methane
How much hay in diet ⇒ how much methane is produced
strict anaerobe
Converts H2 and CO2 to methane
Use acetate, methanol, methylamines, CO2, H2, formate
Use a protein bound cytochrome as electron carrier
Can produce up to 200L CH4 / day
What are the different types of protozoan microbial are in the rumen? What do they do?
Holotrichs
eat soluble sugars and microbes
cilia all over
Entodinomorphs
engulf starch
prevent acidosis
cilia at end
Not essential:
Produce VFA (volatile fatty acids)
Help with grain diets
Help recycle microbial N when low
Cannibalize other protozoa, and microbes
Tendency to lyse in rumen to feed microbes, not animal
Delays acidosis
What is continuous culture when it comes to microbial populations in the rumen?
Substrate is limiting
How much feed is given determines the rate of culture
Anerobic (no mitochondria)
Must maintain Oxidation / Reduction balance (need free NAD to do glycolysis)
Produce ATP for microbes, leaving acetate and propionate for animal
Aerobic- all ATP for microbes, no acetate or propionate made
Growth rate dependent on feeding rate
Microbe growth rate = rate of microbe passage
Diversity dependent on feed, specialization, volatile fatty acid production
Hay, Fiber Feeds = Acetate
Goes towards fat production
Grains, Concentrates = Propionate
Glucose precursor → supply glucose to the animal
Those are their energy sources
What do rumen microbes need and what do they supply?
Microbes supply: Energy through VFA; Protein by death and passage
Microbes need:
Carbon and nitrogen as substrates (in the form of plants)
pH range 6-6.8
Anerobic environment
How does rumen buffering work?
VFA absorption
Dependent on pH
pH 7 => 4.7 +log Ac- / AcH : 200/1
pH 6 => Ac-/AcH : 20/1
pH 5 => Ac-/AcH : 2/1
Salivation Bicarbonate pKa~6.7
CO2 + H2O = H2CO3 = HCO3- + H+
Salivation keeps pH in 6-6.8 range
Rumination and contractions; Stimulate mixing, eructation, salivation, papillae development (surface area)
More water to ferment and keep pH within range
Water intake- ‘flush’ problem microbes and VFAs to abomasum
Protozoa
Engulf starch- delays acidosis
Target rapidly growing microbes
What is rumen acidosis? How is it caused? What are the two types?
Overgrowth Strep gallolyticus
By having a lot of highly fermentable products (starch)
Low affinity for starch, but if lots, will grow rapidly
At low pH, can only produce Lactic acid
Other ‘good’ microbes can’t grow→ kills the cow
Laminitis weeks or months later
Two types
Overfeeding starch
S gallolyticus overgrowth
Sudden switching between high / low intake
Rumen pH < 5.5 for 4 / 24 hours
VFA builds up in rumen
Chronically low rumen pH = Sub acute ruminal acidosis (SARA)
What are the primary energy sources for ruminants?
Primary energy source are VFA (pro and acetate)
Primary Fuels = acetate, propionate from rumen fermentation
Protein supplied by microbes
Why are cows (ruminants) considered hypoglycemic?
When compared to humans
Glucose is from propionate 70% and amino acids (30%)
Liver needs to convert pro to glucose
If something is wrong with liver, no glucose
All microbes take glucose in rumen
*
They conserve Glucose
Compartmentalization:
Liver is always in gluconeogenesis
Fatty acid synthesis occurs in adipose
In other species, made in the liver
Missing enzymes:
Fatty acid synthesis is from acetate, not glucose
ATP citrate lyase, Malic enzyme are missing from adipose (and liver)
NADPH is from pentose phosphate path and Isocitrate dehydrogenase
In adipose, glucose is used only for NADPH and a-glycerol phosphate (TCA cycle)
*
Lack of glucose = fat mobilization and Ketosis
In starvation, ruminants mobilize adipose
Cows at the beginning of lactation also have negative energy balance because DMI can drop by 30%
Fat ruminants mobilize more fat
But they also have low glucose → ketosis
Liver picks up fatty acids from circulation
Liver enzymes have huge capacity for producing ketones
When starve cow
Microbes die and produce toxins
No more acetate and pro for the cow
Mobilizing fat and ketosis
Compare ruminants vs non ruminants when it comes to continuous vs meal eaters?
Ruminants (foragers) = Eat, then Ruminate
Get the most nutrients from low protein and low glucose food → sit there and they digest a lot
Think of them as continuous eaters (grazers, continuous process in the rumen)
Even though they eat meals
Nonruminants
Predators = Meal eaters, high protein
Switching between glycolysis and gluconeogenesis
Foragers = Continuous eaters
Go for quantity, not quality (low protein, low glucose)
How well do ruminants vs non ruminants digest forage?
Ruminants – Microbes
Nonruminants – cecal fermentation
Doesn’t take advantage of microbial proteins and vitamins
If can’t meet protein requirements, eat their own feces
Ie. pigs, horses
Ruminant vs non ruminant- How well do they handle fat in the diet?
Ruminants - fat primarily from mobilization (VLDL, HDL, etc), therefore limited capacity to metabolize fat and fat interferes with microbial metabolism
Nonruminants - meat, grains have higher fat content, therefore limits are relative to absorption ability
(Bile) and interference with cecal fermentation
What do ruminants (Goats) eat?
Browsers and Grazers:
Grains
Grasses (Legumes)
Vegetation (leaves)
Fruit, Vegetables
Browers- lips are mobile
Ex. giraffe
Very selective about what they eat
Grazers- lips aren’t mobile
Not selective about what they eat
Limitations: Need at least 35 - 50% hay / fiber diet
What do nonruminants (Pigs) eat?
In the wild they are true Omnivores:
Roots
Acorns
Berries
Vegetables
Grains
Grasses (Legumes)
Carcasses (Meat)
Fecal material
Explain how to monitor animal(s) nutrition
= Animal(s) Response
Intake
Production (Milk, Meat, Eggs, Wool)
Body Condition Scoring (BCS)
Excretion (feed) , Fecal sieving
how to modify a ruminant diet in disease
Obesity (fatty liver)
Increase fiber (NDF, ADF)
Starvation (Ketosis)
Increase fiber (microbial health)
Increase starch (reduce ketone formation)
Probiotics? (microbial health)
Disease (off feed)
Increase fiber
What is a monosaccharide? What are some examples?
Monosaccharides – carbohydrates that can not be hydrolyzed into simpler sugars
Hexoses (D-glucose and D-fructose) and pentoses (D-Xylose and L-Arabinose- components of cellulose)
Derivatives of these- glucosamine (glucose with amine attached), sorbitol (glucose w/o alcohol), gluconic acid, glucaric acid, and glucuronic acid (glucose with carboxylic acid attached)
What are linear and branched chains of saccharides? How many monosaccharides do they hold?
Disaccharides (2 monosaccharides)
Oligosaccharides (2-10 monosaccharides)
Polysaccharides (>10 monosaccharides)
What are some disaccharides?
Sucrose (α 1,4 linked glucose and fructose), sweet substance frequently used to increase palatability
sucrose may be used as a humectant to retain moisture in semi-moist foods (give texture)
In diet- sugar and sorbitol helps retain moisture
Lactose (β 1,4 linked galactose and glucose),
digested into monosaccharides by lactase in the brush border of the small intestine
Many adult animals lack sufficient lactase to digest lactose. This is the most common form of carbohydrate intolerance. Signs include diarrhea, bloat, flatulence, stomach cramps, and nausea.
Lactose becomes a fiber, essentially → causes symptoms
Maltose
Safe upper limits for monosaccharides and disaccharides
Cats- lower because they are carnivores so their ability to digest carbs are lower
Cats can’t even taste sucrose due to deletions of receptor that help taste sweet
What are some characteristics of oligosaccharides?
Short changed and soluble → used for probiotics, fermented quickly
What are some characteristics of oligosaccharides? What are some types?
Storage form of carbs
Starch- can be digested by animals (amylases, maltase, isomaltases)
Alpha 1,4 glucose linkages
Fiber- can not be digested by animal enzymes
α 1,4 and α 1,6 glucose linkages)
If digested, depends on microbes
Ie. cellulose- most common fiber component (insoluble fiber)
β 1,4 linked glucose units
Looks like starch, but instead of alpha linkages, it is beta
Stacks up on top of each other → makes it hard to be soluble and hard for microbes to get to it
Dogs and cats can’t digest because there is not enough time, but ruminants do a good job of breaking it down
can be digested by microbial β glucosidases
Hemicellulose (insoluble fiber)
Not similar to cellulose
common cell wall polysaccharide
composed primarily of linked xylose units with side chains of glucuronic acid, glucose, galactose, arabinose, other saccharides in various linkages (grasses)
low solubility and moderate fermentability
Pectins (soluble fiber)
consists primarily of galacturonic acid units with varying proportions of the acid groups present as methyl esters. Other monosaccharides are attached as side chains.
high solubility and fermentability
used commercially for gelling
Gums (soluble fiber)
sticky exudates of plants
diverse monosaccharide subunits
some gums show moderate to high fermentability
Gives structure to diet
Fructans (fructooligosaccharides)
(Fr)n-Gu
Fructose attached to glucose
fructans are found in the roots, stems, leaves and seeds of a variety of plants
cool season grasses (orchard grass, timothy, brome) may have high levels of fructans
Energy reserve for the plant
fructans have been linked with laminitis in horses
Resistant starch
crystallized or physically enclosed starch granules (behaves as a fiber)
Once passed into large intestine, fermented by microbes
Lignin
not a carbohydrate (polymer of phenol derivatives)
closely associated with fiber
Occurs with them
lignin tends to be inversely related to fiber digestibility
Not digested in any animal
Digestibility of Fiber
Insoluble fibers are not well digested by many simple stomached animals
Some fibers, like pectins and gums, show high fermentability in dogs and other simple stomached animals.
Ruminants and monogastric hind gut fermenters can ferment (at least to some extent) hemicellulose, cellulose, pectins, and gums. Lignin is not well fermented by any species.
The volatile fatty acids (acetate, propionate, and butyrate) and lactate are the products of fiber fermentation in the rumen and hind gut.
What are the methods of measuring fiber?
Crude Fiber
measures cellulose and lignin (and some hemicellulose)
Limitations- no soluble fiber measured
Neutral Detergent Fiber (NDF)
measures cellulose, hemicellulose, and lignin (entire plant cell wall)
inversely related to food intake
Give more NDF ⇒ takes longer to ferment
Acid Detergent Fiber (ADF)
measures cellulose and lignin
inversely related to digestibility
Tough part of plant cell wall because hard to ferment
Acid Insoluble Lignin
Lignin- tough and indigestible
Total Dietary Fiber (TDF)
enzymatic method that measures soluble and insoluble fiber
defatted sample incubated with α-amlyase, protease, and amyloglucosidase
To break down starches and protein
sample is treated with ethanol to precipitate fiber and protein
the residue is washed (ethanol and acetone), dried and weighed
duplicated samples are analyzed for protein and ash
TDF = residue (g) – protein (g) – ash (g)
Gives soluble and insoluble fiber
What are some common carbohydrate terms used in feed tables?
Starch – major carbohydrate component in grains
Water Soluble Carbohydrates (WSC) – includes monosaccharides, disaccharides, and fructans
Easily digestible
Ethanol Soluble Carbohydrates (ESC) – primarily monosaccharides and disaccharides
Non Structural Carbohydrates – 100% - (%C. protein - % NDF - % fat - % ash)
Using proximate analysis
Glycemic Index – measure of the increase in blood glucose levels (AUC) caused by a particular feed relative to a reference feed
Greater index ⇒ bigger increase in glucose after meal
Effective NDF (eNDF) – the percentage of NDF effective at stimulating chewing, salivation, rumination and rumen motility
Fiber needs to be large (bigger length) to stimulate rumen
Small fibers do not stimulate rumen
describe basic carbohydrate metabolism
Excess carbohydrate (not used immediately for energy) is stored as glycogen or converted to fatty acids.
Carbohydrates (glucose) are required for energy by the brain and red blood cells.
Carbohydrates (glucose) can be produced (gluconeogenesis) from proteins, glycerol, and propionate.
Are carbohydrates essential?
No standard for min amount of carbohydrate eaten due to how it is metabolized
Herbivores need carbohydrates to maintain proper gastrointestinal function.
Carnivores (and other animals) can synthesize carbohydrates if supplied with excess proteins
Why are starches and fibers included in animal diets?
Increase fecal output or modulate fecal consistency.
Using water soluble or insoluble fibers
Modulate fecal moisture
Treat constipation or diarrhea
Diets for managing diabetes.
Higher amounts of fiber ⇒ Slow transit time of food through the gut.
Slow fat and carbohydrate absorption.
Lower bile acid resorption and reduce blood cholesterol levels.
Fiber binds bile and prevents reabsorption → decreases CHO
improve cardiovascular health
Maintain lower GI tract health.
Increase production of VFAs (acetate, propionate, butyrate)
Change microbial populations
Prevention of colorectal cancer, inflammatory bowel disease, colitis
Decrease energy density/digestibility of the Diet.
Fiber used as bulking agent → dampen hunger but still low calorie
Increase gut fill (short term regulation of appetite)
Energy dilution
Hairball prevention
Bulking agent to help push hair through GI tract
What fibers are used in pet food?
High Fermentability:
Guar Gum, Pectin, Oligosaccharides
Gives structure and gel component
Insoluble in Water and Moderate Fermentability:
Beet Pulp, Oat Fiber, Pea Fiber, Rice Bran, xanthan gum, gum arabic
Gives structure and bulk (push stuff through GI)
Insoluble in Water and Low Fermentability:
Cellulose, Peanut Hulls, Soy Hulls, Sunflower Hulls
Gives bulk and adjust fecal consistency
What are pesticides?
Chemical substances used to prevent, destroy, repel or mitigate any pest
Includes- Insecticides, herbicides, fungicides, rodenticides, molluscicides, bactericides
Where are pesticides used? What are potential consequences of use?
Worldwide estimate (2010): ~1.8 billion people engage in agriculture- most use pesticides to protect the food and commercial products. Major exposure potential.
Exposure via commercial applications (golf courses, residential settings, military bases)
Domestic/home uses for lawn and garden applications and in and around the home.
Unintended environmental exposures due to pesticide residues & pesticide drift, leading to oral, dermal, and pulmonary exposures
Possible bioaccumulation
Where are pesticide incidents reported?
National Pesticide Information Center (NPIC)
Veterinary Pesticide Incident Reporting Portal
CA DPR (CA Department of Pesticide Regulation)
What are pesticide regulations in the US?
Pesticides are more regulated than most industrial chemicals
EPA pesticide regulations protect environmental health mandated by Federal Insecticide Fungicide and Rodenticide Act (FIFRA)
Requires all pesticides sold or distributed in the U.S. (including imported pesticides) to be registered by EPA
Registration is based on evaluation of scientific data and risk/benefit assessment of the product’s use
Label directions control how products are used
Requires brand name, species it is approved for, size of animal (dose), intended use, active ingredients, warnings
EPA can authorize limited use of unregistered pesticides or pesticides registered for other uses to address emergencies
EPA can suspend or cancel a product’s registration
Training is required for workers in pesticide-treated areas and certification and training for applicators of restricted use pesticides
FDA is responsible for enforcing regulations that set the limits of pesticides that are allowed in animal-derived products, and regulates the use of pesticides that act systemically
*All pesticides must be approved and registered by EPA, FDA, or both
Four toxic categories of pesticides
I- high
II-moderate
III- low
IV- low
How do you classify major insecticides based on chemical class?
Botanical insecticides
Synthesized by particular genus or species of plant
Active principle may be localized to specialized tissue of the plant and produced in extremely small quantities
Not toxic to animals
Active principle may have extremely high acute toxicity towards insects, or other pest sp.
Chemically degrade in the environment (safe to the environment)
Historically natural products have provided leads for synthetic organic pesticides
pyrethrum → pyrethroids
Nicotine → neonicotinoids
ryanodine → ryanoids
Botanicals used for home gardening are “generally considered as safe” (NOT ALWAYS TRUE, USE CAUTION!)
How do you classify major insecticides based on mode of action?
Acetylcholine Cholinesterase (AChE) Inhibitors
Voltage-gated sodium channel (VGSC) modifiers (DDT, pyrethrins, pyrethroids)
Nicotinic cholinergic receptor modifiers (nicotine, neonicotinoids)
Gamma amino butyric acid GABA A receptor blockers (chlorinated hydrocarbon, Cyclodiene Insecticides, Polychloroterpenes)
What are Acetylcholine Cholinesterase (AChE) Inhibitors?
Organophosphates and Carbamate Insecticides
monomethyl carbamates
Most widely used in agriculture (worldwide)
Most direct veterinary uses discontinued in USA
Banned from home use in USA and other countries
Acetylcholine Cholinesterase (AChE) Inhibitors- Mechanism
EXAM
AChE →in cleft, allow acetylcholine clearing
Inhibiting → not clearing acetylcholine out of the synaptic cleft
Huge build up of acetylcholine → increased signaling → Stimulation of the sympathetic nervous system may produce sweating, hypertension and tachycardia.
Nicotinic and muscarinic receptors activated
SLUD- Salivation, Lacrimation, Urination, Defecation
DUMBELS- Diarrhea, Urination, Miosis, Bronchospasm, Emesis, Lachrymation, Salivation
Acetylcholine Cholinesterase (AChE) Inhibitors- Toxicity
Both OPs and methylcarbamates have very high acute toxicity w/ OPs having somewhat higher toxicity (in general)
Symptoms usually begin peripherally (eyelid twitch, tingling extremities), rapidly followed by central involvement.
Since OPs and methylcarbamates have the same acute MOA, effects are additive
Certain OPs (mipafox, leptophos) produce a delayed neurotoxicity known as jake-leg paralysis in humans, cattle and chickens.
There is now good evidence that exposure to low levels of OPs over long periods may mediate adverse developmental outcomes that are not mediated by AChE inhibition
morphogenic mechanisms
What is Voltage-gated sodium channel (VGSC) modifiers, DDT (an Organochlorine)
The first major synthetic organic insecticide
Widely used in U.S. from 1942-1973 (600,000,000 lbs/year)
DDT Insecticide (an Organochlorine)The first major synthetic organic insecticide
Currently used in Africa, Malaysia…
Directly applied to animals, including humans
DDT- toxicity
very low mammalian toxicity at insecticidal doses
high doses cause hyperactivity, tremors clonic/tonic convulsions, cardiac or respiratory arrest (Acute oral LD50~115 mg/kg)
extremely effective knockdown toxicity to insects
insect toxicity increases inversely with temperature (negative temperature coefficient)
mechanism very similar to pyrethrins/pyrethroids delays inactivation of axonal Na+channels
DDT- global use risk
Rapidly bioaccumulates, insect resistance leads to higher application rates, metabolized to DDE, DDD
In human and animal foods, environmental exposures
Hormonal effects (endocrine disruption)
egg shell thinning in birds (??)
xenoestrogen-estrogenic effects in mammals (??)
alters thyroid hormones
Breast cancer link (??) Obesogenic (??)
Induces liver enzymes CytP4501A
Voltage-gated sodium channel (VGSC) modifiers-
pyrethrins (Chrysanthemum cinerariafolium) basics
equatorial regions
East African highlands, Asia
achenes 2-5% pyrethrins
Natural Pyrethrins- Mixture of 6 esters comprised of 2 acids & 3 alcohols
Pyrethrin I and Pyrethrin II most common
pyrethrins - toxicity
rapid knockdown of insects
very low acute toxicity to mammal >1000 mg/kg (allergic dermatitis)
rapidly degrades in the environment
insect resistance a big problem
Caution with felines!
Voltage-gated sodium channel (VGSC) modifiers - Pyrethroids basics
Synthetic insecticides
Widely used in domestic applications
Widely used in large scale agriculture (millions of pounds)
Widely used for veterinary applications (topicals, dips, collars)
Rapid knockdown activity
Extra caution for felines due to PK issues
Elimination issue (liver metabolism)
Pyrethroids- toxicity
Generally low mammalian toxicity (rat oral LD50>1000 mg/kg)
Aquatic organism are especially sensitive
Felines may show symptoms after dip (especially with Type II)
Because elimination is not efficient
Dermal and system allergies may be pronounced
Type I- Aggressive behavior, Enhanced startle response, Whole body tremor
Peripheral signs predominate
Type II- Burrowing behavior, Tremors→ convulsions, Choreoathetosis (jerking motions), Profuse salivation
CNS signs predominate
Pyrethroids- Mechanism
Interfere with axonal conductions of neurons
Direct binding to voltage-operated Na+ channels → Delays inactivation of Na+ channels → Prolonged depolarization of axonal membrane → hyperexcitation
Often formulated with piperonyl butoxide (inhibitor of metabolism)
Insect growth inhibitor but also inhibits drug metabolism → increases likelihood of toxic effect
Is there cross resistance when it comes to Voltage-gated sodium channel (VGSC) modifiers?
Cross-Resistance to Pyrethrums & Pyrethroids Due To Extensive Use of DDT Many Years Earlier
DDT and pyrethroids target the same mechanism
Insects mutate resistant sodium ion channels
Nicotinic cholinergic receptor modifiers- nicotine (Nicotiana sp. Endogenous inNorth America/Europe) basics
2-14% nicotine by weight in leaves with organic solvent→ extract with sulfuric acid → ‘Black Leaf 40’ (poison)
Sources- cigarettes, cigar, chewing tobacco, snuff, nicotine gum, nicotine patch, nicotine nasal spray, nicotine inhaler, e cigarettes
apid dermal adsorption
highly toxic to mammals
dermal and oral LD50 ~50 mg/kg
nicotine- Toxicity
Nicotine’s structure mimics acetylcholine at all nAChR (agonist)
Does not bind to muscarinic receptors (All mAChR subtypes are insensitive to nicotine)
Promote neurotransmission
Very rapid progression of symptoms
Activation then desensitization of nAChRs (both PNS & CNS)
Chronic activation → desensitization by internalization
Progression
Stimulation of autonomic ganglia- salivation, nausea, diarrhea, increased respiratory rate, increased heart rate and blood pressure
Depression of autonimic ganglia- decreased respiration, hypotension
CNS involvement- clonic tremors, resp arrest, death
nicotine- Molecular and cellular MOA
nicotine is a selective nAChR agonist
nicotine is much more long-lived than ACh at cholinergic synapses (not metabolized by AChE)
persistent activation of AChRs results in desensitization
Nicotinic cholinergic receptor modifiers - Neonicotinoids basics
Synthetic insecticides
Ie. imidacloprid (advantage and related products)
Kills 98-100% of the fleas on dogs within 12 hours
One treatment prevents further flea infestation for at least four weeks
Kills fleas before they lay eggs
Convenient, easy to apply
Applied as spot-on
Goes into the systemic circulation
Unique mode of action differentiates imidacloprid from organophosphates, pyrethrins, carbamates, insect growth regulators (IGR’s) and insect development inhibitors (IDI’s)
Partial agonist
Imidacloprid is active against adult fleas, flea larvae, eggs
Imidacloprid does not protect against ticks
Resistance is an increasing concern
Imidacloprid is: non-teratogenic, non-hypersensitizing, non-mutagenic, non-allergenic, non-carcinogenic, non-photosensitizing
Safe to use at certain doses, but there are some that are not intended for veterinary use
Imidacloprid insecticide formulations not intended for veterinary use
May be harmful to environment- killing honey bees
Neonicotinoids- advocate for Imidacloprid + Moxidectin
Applied topically formulation controls fleas topically (fleas don’t need to bite- spreads across your dog’s skin and coat)
Prevents deadly heartworm
Protects dog and family against worms
Controls fleas, heartworms, Roundworms, Hookworms
Controls Ear mites and lice
Water resistant
Gamma amino butyric acid GABA A receptor blockers
Gaba- inhibitory (ionotropic GABA receptors) basics
Allows influx of Cl → binding negative charge in the cell → decrease membrane potential
Activation leads to hyperpolarization of mature neurons
Agonist and antagonists can bind
Positive allosteric modulators can also bind to other sites → increase sensitivity to normal ligand → more negative membrane potential
Conduction blockers (pesticide)- prevents Cl from going through pore
Gamma amino butyric acid GABA A receptor blockers- Chlorinated hydrocarbons basics
broad spectrum
insecticidal activity
long persistence in the environment
Due to it being chlorinated
tendency to bio-accumulate along food chains.
Predators have the highest concentration of toxin compared to plants
induce liver enzymes (CyP4501A), increase liver mass
tumor promoters in cell models
enhance risk of cancer
Ie. Lindane
resistant to metabolism and environmental degradation
volatile (> 90% enters atmosphere - ultimately deposited by rain)
Primarily use of exposure is inhalation and skin contact
Spreads easily around the world
Most uses suspende, but some uses remain
Used to treat
Head lice (recently banned in CA)
tree borers
oilseeds (rape, maize) control crop damage by soil dwelling pests
fumigation of grain stores to control weevils
pest control on turf areas; domestic insect control (ants primarily)
Gamma amino butyric acid GABA A receptor blockers- Cyclodiene Insecticides basics
Synthesized after WWII
Stable in soil, don’t break down in UV
Used in control of termites
Gamma amino butyric acid GABA A receptor blockers- Polychloroterpenes basics
Greatest use of a single insecticide
Used on cotton
Gamma amino butyric acid GABA A receptor blockers- toxicity
Acute- all have potent convulsant activity
Why? They inhibit GABA → increased excitatory drive → increase the risk of seizures
Generally safe, but depends on dose (misuse, unexpected exposure)
Nexgard, frontline, dectomax
Frontline banned in france because bees are dying from it
Maintain efficacy→ really smart PK/PD
Insect GABA receptors differ from those expressed in mammals –take advantage of differences to design highly selective (safe) insecticides…
Researchers created insecticides that only work on insects
What is a lipid? Which ones are of nutritional interest?
Lipid- A group of chemicals insoluble in water but soluble in organic solvents (e.g., ether)
Nutritional interest
Fatty acids
Glycerols
Triglycerides (fat)
Phospholipids
Sterols (CHO)
How is lipid nomenclature based on chain length?
volatile fatty acids (C2 – C4)
Products of fermentation
medium chain fatty acids (C6 – C12)
Not as difficult to digest as long chain → go directly to portal vein and it able to be used
long chain fatty acids (C14 – C18)
Produced by terrestrial plants
very long chain fatty acids (C20 and greater)
Made by animals → short chains elongated by animals
What are the terms associated with lipid saturation?
saturated (no double bonds)
monounsaturated (one double bond)
polyunsaturated (two or more double bonds)
What are the terms associated with spatial arrangement around a double bond?
Cis (hydrogen on same side of the double bond)
Trans (hydrogen on the opposite side)
Does not occur naturally in animals, but occurs in microbes
What are conjugated fatty acids? What are they produced by?
conjugated dienes- rather than double bonds separated by a methylene structure
produced by rumen microbes
c9,t11-18:2 and t10,c12-18:2 are the most common (called conjugated linoleic acid)
What are two different types of lipid nomenclature? How do they work?
Chemical Numbers System
example C18:2 ∆9,12
the first number (18) equals the number of carbons
the second number (2) equals the number of double bonds
the numbers after the ∆ are the location of the double bonds counting from the carboxyl end
Enzymes work from that end
Nutrition n (or ω) series
example C18:2 ω6,9
the first number (18) equals the number of carbons
the second number (2) equals the number of double bonds
the numbers after the ω are the location of the double bonds counting from the methyl end
The double bond on the methyl end gives rise to the Omega __ fatty acid name
How are fatty acids synthesized in animals?
Animals can synthesize saturated fatty acids from acetyl-CoA. This fatty acid synthesis requires the enzymes acetyl CoA carboxylase and fatty acid synthase.
Animals can lengthen fatty acids. This involves 2-carbon additions catalyzed by elongase enzymes.
The product of fatty acid synthesis is palmitic acid (C16:0), and this can be elongated to form stearic acid (C18:0).
Animals have desaturase enzymes that can add double bonds. Animals have Δ9, Δ6, Δ5, and Δ4 desaturases. The number after the Δ indicates the location of the double bond counting from the carboxyl end. Animals can not desaturate at distances greater than 9 carbons from the carboxyl end.
Desaturases show the following preference for substrates:
n-3 (omega 3) > n-6 > n-9 > n-7 > n-9 trans
Elongases act on the fatty acids to add 2 carbons to the carboxyl end of the fatty acid.
Not going to see odd length carbon chain
If you do, it might be damaged
What is associated with omega 6 deficiencies?
Trans-epidermal water loss
Drink more but do not urinate more
Omega 6 forms barrier along the skin, when low → it breaks down, hard to keep moisture and water in
Scaly skin
Course, dry hair
Skin lesions
Alopecia
Poor reproductive capacity
Red cell fragility
Increased ratio of n-9 to n-6 fatty acids
Also tries to compensate with omega 9→ hyperproliferation
What is associated with omega 3 deficiencies?
Omega 3 deficiency isn’t something that could be measurable
Visual acuity or brain function
Therefore, recommended estimate amount
What are the different ways to identify/categorize essential fatty acids?
Linoleic Acid (C18:2 n-6)
Base fatty acid
α-Linolenic Acid (C18:3 n-3)
Base omega 3 fatty acids
Required for all animals
Arachidonic Acid (C20:4 n-6)
essential in cats since they have low Δ6 desaturase activity.
n-3 Long Chain Polyunsaturated Fatty Acids (C20:5 n-3 and C22:6 n-3)
may be beneficial for some species, even though it could be made
Required by AAFCO for inclusion in dog and cat diets.
Since a large amount is required for them
What are the functions of essential fatty acids?
Cellular Membranes
Components of phospholipids
Modulate fluidity
Bind to G protein-coupled receptors (n-3)
Precursors of Eicosanoids
Constituents of myelin (neurons), synaptosomal lipids, and the retina (n-3 fatty acids)
Required for reproduction (n-6 fatty acids)
Regulators of gene transcription
Particularly n-3, has impact on inflammation
What are the functions of eicosanoids?
inflammation
Physiologically and pharmacologically active compounds derived from n-3 and n-6 fatty acids. The eicosanoids have a wide range of actions.
The eicosanoids have a short half life and generally act locally as hormones.
The main eicosanoids are the prostaglandins, thromboxanes, and leukotrienes.
The precursors for eicosanoids are n-6 (arachidonic acid) and n-3 (eicosapentaenoic acid) fatty acids.
How does omega 3 and omega 6 competition influence eicosansoid symptoms?
Omega 3 and omega 6 compete with each other for fatty acids
Induces symptoms
*
N-6
Prostaglandins (PGE2)
Fever induction
Increased COX-2 and IL-6
↓ Lipoxygenase, TNF and IL-1
Thromboxanes (TXA2)
Platelet aggregation
Vasoconstriction
Clotting
Leukotrienes (LTB4)
Inflammation induction
Induce Reactive oxygen species
Increased TNF, IL-1, and IL-6
Induce leukocyte chemotaxis
*
**
N-3 - prostaglandins opposite and much more weak
Prostaglandins (PGE3)
Weak inducer of COX-2 & IL-6
↓ TNF-α and IL-1
Thromboxanes (TXA3)
Weak platelet aggregator
Weak vasoconstrictor
Prostacylcin (PGI3)
Vasodilation
Inhibition of platelet aggregation
Leukotrienes (LTB5)
Weak inducer of inflammation
Weak chemotactic agent
**
Why are fats added to diets?
Energy
an energy source in commercial diets (beef tallow, fish oil, animal fat, soybean oil, corn oil, etc.)
weight gain supplements
Carrier of fat soluble
vitamins (A,D,E,&K)
Clinical Reasons
Injury recovery- high fat, increased n-3
Increase energy density of diet
Rebuild tissue and combat inflammation
Increase palatability
Decrease inflammation (n-3 fats)
Digestive disorders - MCT (med chain triglycerides- not as complex digestive process), moderate fat
Increase digestibility (MCT)
Limit fat for improved digestibility
Joint Health - increased n-3
Decrease inflammation (n-3 fats)
Skin Conditions - n-6 and n-3
Insure adequate linoleic acid levels
Decrease inflammation (n-3 fats)
Renal Function - n-3
Decrease glomerular hypertension
Weight Loss - low fat
Decrease energy density
Aging - n-3
Decrease inflammation (n-3 fats)
Palatability
Fat is palatable
Coat Condition
What are fat requirements in the diet?
Dogs- linoleic acid n-6 and n-3
EPA and DHA as well (long chain fatty acid)
Imp function in brain and eye so won’t risk that they can make it easily → just give it to them
Cat- linoleic acid and arachidonic acid (because issue with n-6)
EP and DHA as well
All other animals- linoleic acid n-3 and n-6
What are sources of essential fatty acids?
n-6 fatty acids (linoleic acid)- High in n-6
seeds and cereal grains
safflower, corn, sunflower, canola & soybean oil
n-6 fatty acids (arachidonic acid)
animal fat
Longer so need animal fat source
n-3 fatty acids (α-linolenic acid)- not present in high concentrations in as many products as n-6
green material (leaves)
flaxseed (linseed) oil is best source
soybean and canola oil
corn oil is NOT a good source of n-3
n-3 fatty acids (DHA and EPA)
fish oils
What are some essential nature of metal?
Essential- Regulating functions of proteins by regulating oxidative state
Metals are intrinsic to nature
Toxins because these are naturally occurring
While form (salt vs. organic vs. elemental) or valence of metals can be changed, metals themselves cannot be destroyed
Many metals play essential roles in biologic processes as necessary cofactors for proteins
enzymes (e.g., metalloenzymes)
structural proteins (e.g., zinc finger transcription factors)
transport proteins (e.g., hemoglobin)
At sufficient doses, metals (both essential and non-essential) can be toxic
Essential- can have issues if there is too much or too little
What is on a metal dose response graph?
Classic U shaped → essential dose response curve
Sigmoidal → nonessential dose response curve
On test, seeing this graph → need to fill in the blank which metal belongs to each curve
Need to know examples of essential vs nonessential metals
What are some essential metals? What are some nonessential metals?
essential- Na, Mg, K, Ca, Cr, Mn, Mo, Fe, Co, Cu, Zn, Se
nonessential- the rest (Li, Be, Ag, Hg, Pb, As, …)
What are some environmental sources of metal?
anthropogenic sources (atmospheric), natural sources (volcanoes)
Exposed through environmental source or through diet and feed supplements and medicinal applications
What does metal bioavailability depend on?
Form of metal
inorganic (less bioavailable) vs. organic (more bioavailable)
Organic more because they are not charged → can more easily cross plasma mem
Inorganic- charged → can’t cross plasma mem
Elemental Hg less available (and less toxic) than methyl-Hg
Exception: inorganic As (arsenic) more toxic than organic As
form of salt
Pb acetate (soluble in GI) vs. Pb sulfate (insoluble in GI)
Pb acetate more bioavail
valence state
As+3 is more toxic than As+5
Cr+3 is essential trace element; Cr+6 is toxic
Route of exposure
inhalation vs. oral intake of elemental Hg
Oral- goes through GI and is passed
Inhalation- goes to the brain very quickly
Age of animal
Young animals more susceptible (better bioavail)
WHY? Because younger animals have less developed barriers → more permeable skin and BBB
Diet- very important!
Metal- tissue accumulation
Biologic half-lives vary according to metal as well as organ or tissue
20-30 years for Cd in kidney or Pb in bone
Few hours to few days for As
Metal accumulation is tissue specific
Pb in bone or kidney cortex (Pb-protein complex)
Lead displaces Ca in bone because they have the same valence
Cu in liver (lysosomes)
Some tissues serve as storage sites
Storage sites are not target sites!!!
metal toxicity and MOA
Metals interfere with bioavailability of essential trace elements or function of metalloproteins
ADME of essential mineral nutrients
Through metal metal interactions
Structure/function of metalloproteins
Ex. heme → Pb can displace iron → larger than iron → change shape and function of the heme
Metals promote redox reactions → ↑ ROS → ↑ oxidative damage to critical macromolecules
Metals bind sulfhydryl groups → deplete glutathione → promote oxidative stress
Glutathione- antioxidant
Enzymes in this reaction rely on selenium (essential metal)
Oxidative stress can occur through directly promoting oxidative species or indirectly through this method
How does metal interact with the body?
Metals compete for transport/uptake
Ex. Mo and Cu
Many are similarly charged → need ion channels to cross membrane → compete for ion channels
Metal-metal complexes can sequester metals from site of action
Hg-Se interaction sequesters metals from biological targets (can’t bind to target)
Transport mechanism
Albumin (through blood)
ceruloplasmin (bind Cu in plasma but across mem)
transferrin (iron→ in blood and mem)
divalent metal transporter (DMT) (transmembrane protein that allows divalent metal to cross mem)
Protective mechanism
Metallothioneins (rich in thiols aka SH groups) → can be charged → binds to metals
Homeostatic mechanism that controls conc of metals in the body
Esp nonessential metals
Can cause cell damage by interfering with fxn of proteins that need these metals to function
Ligand binding is the most fundamental chemical process involved in metal toxicity and cellular defense against metals
Metals influence protein function
-Direct
Cofactors of receptor complexes
Cofactors of enzymes
Zinc finger transcription factors
-Indirect
Body levels of metals influence transcription/translation
Iron responsive elements (IRE) - Fe levels in body regulate transcription of protein involved in Fe metabolism
How does acute copper intoxication occur?
Uncommon, occurs due to ingestion or injection of Cu salts (oral dose of 25-50 mg/kg)
Case report in beef calves given supplemental injections of copper (Cu disodium edetate) resulting in acute hepatotoxicity
How does subacute copper intoxication occur?
Can occur in veal calves fed copper-containing hematinics in milk replacers
Case reports in cattle and goats (feed-related)
How does chronic copper toxicosis occur?
Occurs most commonly in sheep (all sheep susceptible – Texel and Suffolk most susceptible) from exposure to excessive dietary Cu (dietary Mo concentration is a critical factor)
Feed supplements, soils and plants with naturally high Cu levels, soils contaminated with poultry or swine manure with high Cu levels
Can occur with normal dietary Cu levels (10-20 ppm) when:
Mo is deficient (< 1 ppm) for several weeks
Optimal Cu:Mo ratio is 6:1
Cu:Mo > 10.1 predisposes to Cu accumulation
Facilitates excretion of Cu as Cu:Mo complex
sulfate is not available
Sulfur is also a factor in facilitating fecal excretion of Cu via bile (as a therapeutic approach, used in ruminants – sulfate converted to sulfide)
Dietary S can influence Cu kinetics as well
Underlying liver disease can predispose to Cu accumulation
What is the MOA of chronic copper storage disease in certain dog breeds?
Inherited as autosomal recessive trait
Bedlington terriers, West Highland terriers, Doberman pinschers, Labrador retrievers
Manifests at 2-6 years of age with no remarkable prior signs
Cu accumulates in hepatocyte lysosomes until storage capacity is exceeded – released causing necrosis and inflammation
What are other species that can get copper toxicity?
Llama
from concentrate feeds
not icteric!
no hemoglobinuria
enlarged liver, hepatic necrosis
want 5 - 10 ppm dietary copper
Goats
need more copper than sheep
Cu toxicity if on long term diet of swine feed, horse feed, or rabbit feed high in Cu
What is the MOA of acute copper toxicity?
Cu salts act as direct tissue irritant to cause coagulative necrosis of GI mucosa
What is the MOA of chronic copper toxicity?
Cu accumulates in hepatocytes
Lysosomal storage (rubeanic acid)
Progressive organelle damage, cellular degeneration or necrosis
Stressful event precipitates sudden release of Cu from liver into blood
Acute hemolytic crisis free Cu forms free radicals (ROS)
What are treatment options for acute copper toxicity?
Therapy is primarily symptomatic and supportive
What are the treatment options of chronic copper toxicosis?
Chelation with D-pencillamine
$$$$$$
IV fluids to flush kidneys, blood transfusions if anemic
Ammonium tetrathiomolybdate
Subcu or IV – aids in rapid Cu binding and excretion
Ammonium molybdate and sodium thiosulfate
PO for 3 weeks
What are some essential information for selenium?
Se is an essential nutrient that has a relatively narrow window between ingested amounts that result in deficiencies and those that cause toxicosis
What are some basic facts about acute selenium intoxication?
Acute intoxication from Se salts (mostly injected)
Resp cyanosis, GI and neurologic symptoms
Garlic odor to breath
What are some basic facts about subacute selenium intoxication?
Subacute intoxication from dietary supplementation (pigs)
Nervous system primarily affected
Focal symmetrical poliomyelolacia- spinal cord
What are some basic facts about chronic selenium intoxication?
Chronic intoxication from ingesting seleniferous plants or dietary supplementation
Primarily affecting dermal system
Infertility as well
Chronic selenosis- abnormal formation in hooves, lameness in the legs
Chronic intoxication of wildlife from food chain contamination
Emaciation
Loss of feathers on head
Loss of claws on feet
Coelomic effusion
Hepatic lesions
Teratogenic and embryotoxic in avian species
abnormal beaks
missing eyes, legs and wings
hydroencephaly or exencephaly
What is the MOA of acute selenium intoxication?
Acute Intoxication: Oxidative damage
Generates ROS (reactive oxygen species)
Binds to sulfhydryl groups to deplete glutathione and other thiol containing antioxidant molecules
What is the MOA of chronic selenium intoxication?
Chronic Intoxication: Replacement of S in amino acids
Affects function of essential proteins
Organic Se incorporated into proteins throughout the body
High affinity for hair, hooves (replaces sulfur)
How is selenium toxicity diagnosed?
History of exposure to Se
Via supplementation, seleniferous plants
Clinical signs
Especially with chronic selenosis
Toxicological testing – Tissue and feed [Se]
Acute toxicosis
Blood, kidney, liver > 2ppm
Chronic toxicosis
Hair and hooves > 5 ppm
What is the treatment for acute selenium toxicosis?
Limited, rarely successful
Supportive treatment to combat gastroenteritis and shock
N-acetylcysteine, a glutathione substitute may be effective
What is the treatment for subacute selenium toxicosis?
Similar to chronic toxicosis
Death may result from complications of paralysis
What is the treatment for chronic selenium toxicosis?
Prevention is best approach
Dietary Cu may help prevent selenosis
Increasing dietary levels of sulfur containing proteins (methionine, cysteine) is beneficial
What are sources and possible exposures to zinc?
Pennies minted after 1982
99.2% Zn, 0.8% Cu
2.44g Zn/penny
Hardware and caging materials
Galvanized metal
Bolts and nuts
Many industrial components
Zn pipes, feeders, waterers for livestock
Medications and dietary supplements
Zinc oxide (rarely causes toxicity)
Desinex, suppositories, calamine lotion
What species is zinc toxicity reported in?
Reported in dogs, ferrets, caged birds, mink, sheep, horses, cattle, ratites
Young dogs
Small dogs- More difficult for small objects to pass pylorus
What are some clinical signs of zinc toxicity?
Dogs and other small animals: GI→ hemolytic anemia
Early: Anorexia and vomiting
Intermediate: lethargy and diarrhea (within several days)
Advanced: moderate anemia, hemoglobinuria and icterus
Cattle
Early: anorexia diarrhea, lethargy
Intermediate: rate of gain milk production
Advanced: Anemia and icterus, PU/PD, paresis, seizures
Foals
Lameness, epiphyseal swelling and stiffness
Birds
General depression, anorexia, weakness and weight loss
PU/PD, dysphagia, diarrhea, crop stasis
What is associated with zinc toxicity pathology?
Regenerative hemolytic anemia
Pancreatic acinar cell necrosis- Relatively unique to Zn intoxication
Renal and hepatic necrosis and fibrosis
What is associated with zinc toxicity MOA?
Not well understood
Competes for absorption with Cu, Fe, Ca
Zn salts have direct corrosive and cytotoxic effects
GI and pancreatic necrosis
Oxidative damage or enzyme inhibition?
Hemolysis
Inhibit collagen metabolism?
Osteochondrosis in horses
How to diagnose zinc toxicity
History of exposure
Clinical signs
especially diagnostic in acute intoxication
Radiology
Presence of radiodense materials in the stomach suggests the possibility of zinc toxicosis in small animals
Toxicologic Testing – Tissue [Zn]
Trace element-free tubes and syringes for blood sampling!
Rubber-free syringes, royal blue plastic cap blood collection tubes
Liver [Cu] often depressed in chronic Zn toxicosis
How is zinc toxicity treated?
Removal of Zn objects
Surgery or endoscopy
Associated with rapid recovery in dogs
GI protectants
Supportive and symptomatic
Bicarbonate for renal support
Transfusion if needed for anemia
Supplement Cu in large animals
Chelation with calcium disodium EDTA
Efficacy not established
What are some basic information about zinc toxicity?
Acute zinc intoxication is most common
Acute onset of gastrointestinal distress along with a hemolytic anemia are common presenting problems
Occasionally subacute to chronic
What is some basic information about lead toxicity?
Lead, no demonstrated biological need
Lead is a global environmental contaminant of significant public health concern
Very low Pb levels toxic to humans
Impaired neurologic development
Subtle cognitive and neurobehavioral deficits
Most species susceptible
In vet med, clinically significant neuro-, hemato- and gastrointestinal toxicity of importance
Pb toxicosis in companion animals should call attention to potential for exposure of children in household
What are some sources of lead?
Long, long list
Most commonly:
Cattle
Old, discarded batteries
Rubbish (putty, old paint tins, oil)
Pets
Lead-based paint, household dust
Solder, foil from bottles, weighted toys, drapery weights
Wildlife
Lead shot, fishing sinkers, mine tailings
What is some information about lead toxicity?
Reported in mammals, birds, reptiles
Dogs, cattle, waterfowl
Cats & sheep intermediate susceptibility
Rare in cats
Associated with paint removal/remodeling
Immature animals more susceptible
GI absorption
Blood-brain-barrier not fully formed
Trace mineral status affects absorption
Greater absorption in mineral deficient animals
Seasonal
Increased incidence in cattle and dogs during spring and early summer
Most cases of Pb poisoning are subacute; ingestion for several days or more may be necessary to reach toxic concentrations; Pb objects persisting in the GI tract provide a continuous source of exposure.
How is lead toxicity associated with ADME?
Absorption in duodenum and respiratory tract is variable
Form of Pb
Pb salts and metallic lead poorly absorbed
Organic forms absorbed more readily
Bioavailability as particle size
Age-dependent
Affected by diet
Acidic diets enhance absorption by promoting dissolution of Pb
Diets deficient in calcium, Zn or protein enhance Pb absorption
Distribution
Transported as lead proteinate on erythrocyte membrane
Crosses the placenta
Deposits briefly in soft tissue (kidney)
Storage site is bone
Excretion
Low blood levels: bile
High blood levels: urine
Pb is excreted in milk
What is associated with lead toxicity MOA?
Toxic effects occur in the nervous system, gastrointestinal tract and hematopoietic systems
Molecular mechanisms of lead toxicosis are not fully known
Binds to –SH groups on proteins
Competes with or replaces Ca and Zn
Nervous System
Capillary damage and neuronal necrosis in the CNS
Demyelination in the PNS
Neuromuscular weakness
Altered neurotransmission
Secondary to interference with Ca signaling
Altered expression of receptors
GI and hematopoietic systems
GI stasis and anorexia
Secondary to neurologic mechanisms(?)
Hematopoietic system
Inhibition of key enzymes in heme synthesis
Inhibition of nucleotidase
Basophilic stippling and erythrocyte fragility
What are some clinical signs of lead toxicity?
Common to most species
Encephalopathy
seizures, tremors, blindness, depression, dementia, ataxia
anorexia and colic
proteinuria
Species-specific clinical signs
How is lead toxicity diagnosed?
Clinical signs
Clinical pathology
Radiology
Tissue [Pb]
Antemortem: whole blood
Must use whole blood for blood Pb levels. Serum won’t work because Pb is bound to RBCs
0.4 ppm generally considered high
Between 0.1 and 0.4 ppm suggest preclinical exposure
Postmortem: kidney and liver
Lead mobilization test using a chelator
What is the clinical pathology associated with lead toxicity?
Hematology
Anemia
Nucleated red blood cells
RBC basophilic stippling
Increased Zn protoporphyrin levels, esp. in dogs
Increased plasma porphyrins with fluorescence under UV characteristic in cattle
Radiology
Pb lines in bones
Histology
Intranuclear inclusion bodies in renal tubular epithelial cells
Neuronal necrosis in cerebral cortex, congestion, edema
What is the treatment for lead toxicity?
Magnesium sulfate, PO
Promotes excretion
Decreases solubility
Seizure control
Removal of Pb material from GI tract
Surgery or endoscopy
Flushing of GI tract
Thiamine appears to promote recovery in cattle
Chelation therapy
Calcium disodium EDTA
Succimer
D-penicillamine
How is general metal toxicity treated?
Treatment
Symptomatic and supportive treatment
Reduction of metal body burdens
Manipulation of dietary levels of competing metals
To decrease body burden of toxic metals
Surgical removal of metal objects
Ingested or embedded in tissue → releases metal over time
Chelation therapy- CaNa2EDTA (injected)
aka calcium disodium versenate or edetate
Do NOT use other salts of EDTA
May chelate Ca and cause hypocalcemia
Use a Ca salt to prevent this
Capable of chelating many metals
When combined with Pb (initially from soft tissues) a stable, soluble compound is formed that is eliminated via the kidneys
Patients should be well hydrated and have an adequate urine flow prior to administration
Prolonged use may damage proximal tubule cells
May initially increase signs of Pb toxicosis
Mobilizing Pb from bone depots, but as more is eliminated, the signs are going to decrease
Chelation- Succimer (Chemet)
Relatively selective, orally active, water soluble chelating agent for the treatment of lead, arsenic and mercury poisoning
Does not have side effects associated with EDTA
Should be used with caution in avian species because one study in cockatiels suggests narrow margin of safety
Does not chelate essential minerals like zinc; not nephrotoxic
NOTE: activated charcoal is NOT effective in treating metal toxicosis
Describe characteristics of adverse drug events
ADE: Any harm that occurs following the use of a drug product.
Can vary from mild to life threatening
Can be expected or unexpected
Includes:
Toxicity
Ineffectiveness
Product defects
human safety associated with handling.
Reasons
Drug-drug interaction
Drug-Herbal (nutrient, etc.) interaction
Disease alters response to drug
Extra-label (off-label) use
Genetic polymorphisms
**Estimates are that only 5-25% of all ADEs reported in vet med
Why it is hard to know how many ADE there are in vet med
Describe types of adverse drug events
Medication Error:
Mistake of someone taking care of the animal- Wrong dose, wrong dose interval, wrong patient
Adverse Drug Reaction (ADR):
Toxicity of medication
Type A (Type I)
Type B (Type II)
What is a Type A ADR?
“Augmented Response”
Dose dependent = Largely predictable
Manifested as:
Exaggerated but expected response
Lack of response
Adverse events unrelated to their pharmacologic effect (cytotoxic adverse reactions)
Therapeutic Drug Monitoring may be helpful
In order to decrease likelihood and severity of ADE
Account for 75-80% of all ADEs.
Organs with the greatest blood flow are most susceptible
Well perfused → more drug goes there
Ie. liver
What is a Type B ADR?
bizarre
“Idiosyncratic”
They just happen
Rare
Account for 6 to 12 % of all ADE’s
But more serious
Not dose dependent in general population
Therapeutic drug monitoring NOT helpful
Since not dose dependent
Usually not related to desired pharmacologic response of drug
May involve hypersensitivity reactions
Not based on population level
Usually requires drug be d/c
Discontinue drug and provide supportive care
Often involves metabolism to a reactive chemical (hapten)
Mechanism is unknown
Oxidative stress → cellular necrosis and apoptosis
Hypersensitivity reactions require previous exposure/treatment (or treatment for an extended period of time
Often involves binding of hapten to epitope
Facilitated by inflammation
What are the primary targets of Type B ADR?
Actively dividing cell (metabolic cells), well perfused, high SA
Liver:
High blood flow
CYP450s
Skin:
Surface area
Antigen presenting cells
CYP450s
Bone Marrow
Circulating Blood Cells
High mass of rapidly dividing cells
Enzymes
Tissues that trap or filter immune complexes (because immune complexes can get stuck there)
Glomerulus
Joints
What transporters are associated with adverse drug reactions?
P-glycoprotein not working
Ie. in collies
ABCG2: blood retina barrier
Keep substances out of the eye
Not as functional in cats as other species
Enrofloxacin (baytril) toxicity in cats
Clinical signs: blindness
MOA: generation of
photoreactive compound (exposed to light → reactive metabolites)
Dysfunctional transporter
More drug getting into eye → exposed to light → metabolites → cats go blind
How do genetic polymorphisms play into adverse drug reactions?
CYP450
Ultra rapid metabolizer → makes more metabolites → can be toxic at high levels
3 copies ⇒ low parent drug levels
Extensive metabolizer- wildtype
2 copies ⇒ normal parent drug levels
intermediate metabolizer
1 copies ⇒ slightly parent high drug levels
Poor metabolizer
0 copies ⇒ high parent drug levels
In dogs, poor metabolizers have Clearance is much lower → higher elimination half life compared to extensive metabolizer
How are drugs FDA approved for human drugs?
Phase I: 5-20 ‘normal’ individuals
Phase II: 10-200 people with disease in question
Phase III: 2,000-5,000 people with disease
Post Market Surveillance: Depends upon potential market; MUST FOLLOW AT LEAST 10,000 PATIENTS TO DETECT 1 IN 3300 PROBLEM WITH 95% CONFIDENCE
Seen more rare events
Seen in individuals with more time on drug compared to pre market
How are drugs FDA approved for animal drugs?
Target animal safety studies: 30-40 animals
Efficacy studies 300-400 animals
Even fewer animals exposed in veterinary drugs
Mostly depends on post market surveillance BUT reporting is not required and, as a result, experts estimate that only a small fraction of ADE’s are reported.
Only drug manufacturer is required to report it
What types of drugs are commonly cited in ADE reports?
NSAIDs –GI ulcers, idiosyncratic reactions
Hormones
CNS agents
Anesthetics
Penicillins – hypersensitivity reactions
Baytril – Blindness in cats
Moxidectin – Overdoses from failure of syringe- locking device
How are risks of ADRs reduced?
Complete history/definitive diagnosis- drug-drug/herbal interactions
Use proper drugs
Use less toxic drugs when possible
Continue to evaluate/monitor patient during therapy
Modify dosing regimens when appropriate
D/C therapy as early as possible
Educate the client as to the side effects or adverse effects
Report ADEs
How to determine whether an ADR has occurred
Temporal relationship-Does it make sense?
Is the event consistent with reported drug side effects?
Are there other possible explanations? Hx
Is there improvement when the drug is discontinued?
What happens if therapy is reinitiated?
What should one do if they suspect an ADR?
Stop use of the drug
Supportive care
Contact manufacturer or FDA-CVM, fill out ADE report
Set aside bottle and any packaging associated with the bottle for potential further testing
What is pharmacovigilance? What is its purpose?
Detection and investigation of the effects of the use of veterinary products, mainly aimed at safety and effectiveness in animals and safety in people exposed to the products.
Purpose is to assess the frequency, similarity and severity of signs so that regulators can assess the possibility of drug association.
Report both when used according to label or when used extra-label.
How are ADRs reported?
Contact Manufacturer or FDA-CVM
Helpful Information:
Physical exam
Medical history
Diagnostic evaluation
Veterinarian’s opinion
Follow up information
Where is ADE information found?
Drug Label/Package Insert
Post approval label changes
Dear Doctor letters on FDA website
ADE summaries webpage
FDA CVM
CVM Updates
Journal Articles
Black box warning ⇒ most important adverse drug effects on label
What are the differences between a pioneer drug, generic drug and a compounded drug
FDA Pioneer (Legend) Drug:
Demonstrated safety/efficacy
Manufacturing under GMP
FDA approved
NADA # tells us that it is an FDA approved drug
Green book- has all FDA approved vet drugs and information
Generic Drug:
Bioequivalent to brand name drug
Manufacturing under GMP
FDA approved
ANDA- generic approved drug
Compounded Drug
Mixtures of approved dosage forms or drugs formulated from bulk chemicals that are not approved by the FDA for use as drugs.
What is the difference between a veterinary medical device and a drug
Medical device- an instrument, apparatus, implement, machine, contrivance, implant, in-vitro reagent, or other similar or related article, including any component, part, or accessory, which is … intended for use in the diagnosis of disease or other conditions, or in the cure, mitigation, treatment, or prevention of disease in man or other animals, or [which is] intended to affect the structure or any function of the body of man or other animal
Ie. needles and syringes
Joint lavage solutions but sometimes advertised as a drug
Approval
FDA does NOT require formal pre-market approval
Manufacturers are not required to list their products with the FDA-CVM.
NO mandatory adverse event reporting requirements.
Responsibility of the manufacturer to assure safety, effectiveness and proper labeling.
Write medical device
What is the Food, Drug, and Cosmetic Act (FD&C)
Established requirement of safety for human medications in 1938
Amended in 1968 to include veterinary medications
Drugs were unsafe unless FDA approved
All ELDU (extra label drug use) became illegal
What is the Animal Medicinal Drug Use Clarification Act (AMDUCA)
Legalized extra-label drug use (ELDU) under specified conditions
Because vets complained that they could do ELDU but it was illegal
Requirements for ELDU:
Permitted only by or under supervision of a veterinarian.
FDA approved animal and human drugs
Valid Veterinary Client Patient Relationship (VCPR)
You examine and diagnose animal and client has agreed to treatment
For therapeutic purposes only (i.e., not for production purposes)
ELDU must not result in violative drug residues in food animals
Food animal and non-food animal algorithms
Legalized compounding (provided starting material is FDA approved) but not from bulk chemicals
In the order from first to last resort, list ways to give a drug to a nonfood animal
Drug used as labeled or identical or human drug
Human or animal drug used extra-Label
Compounding- Cost is NOT a valid reason
In the order from first to last resort, list ways to give a drug to a food animal
Drug used as labeled
Food animal drug used extra-label
Extended withdrawal time
Non-food animal or human drug used extra-label
Compounding
ELDU prohibited for certain medications!
Chloramphenicol
Clenbuterol
Diethylstilbesterol
Dipyrone
Gentian Violet
Nitroimidazoles
Nitrofurans
Phenylbutazone (adult dairy cattle)
Sulfonamides (lactating cows)
Fluoroquinolones
Glycopeptides
What is compounding? What are the regulations?
Drugs are altered in dosage, form and/or flavor to accommodate the needs of a particular patient
Federal Food, Drug and Cosmetic Act
ELDU Regulations
AMDUCA
Relevant state laws
When is compounding appropiate?
Modification of approved drug to sufficiently treat a patient
Flavorings
Different strength
Changing form
Ie. tablet → suspension
Patient or species is sensitive to an ingredient within the formulation
Approved drug not currently commercially available
Cost is not a justification for using a compounded product
What is United States Pharmacopeia (USP)
Standard setting body
Expert committees write standards
Quality, purity of drugs and foods
Non-enforcement
Standards enforced by pharmacy boards
What is approved dosing form of compounded drugs?
Legal under AMDUCA:
Permitted only by or under supervision of a veterinarian.
FDA approved animal and human drugs
Valid Veterinary Client Patient Relationship (VCPR)
For therapeutic purposes only
No animal drug approved for the intended use or not in appropriate formulation/concentration.
Should never compound copies of an FDA approved drug
What is a bulk substance?
a substance used to make a drug that becomes an active ingredient in the finished dosage form of the drug.
Bulk substance is not an FDA approved product
Final product is not the equivalent of an FDA approved product.
***Using an approved finished dosing form for compounding offers a major advantage to bulk substances.
Under GFI #256, how should compounding be done for non food producing animals?
By/under supervision of vet or pharmacist in licensed pharmacy
Should only be done if FDA-approved drugs are not medically appropriate to treat the animal
All substances meet USP standards
Should not be a copy of an approved marketed drug
Office stock should not be compounded from bulk substances except in limited instances
Specific labeling requirements:
“This is a compounded drug. Not an FDA approved drug.”
Report adverse events to FDA
Under GFI #256, how should compounding be done for food producing animals?
Only bulk drug substances identified on the FDA’s List of Bulk Drug Substances for compounding drugs for use in food producing animals.
Copper glycinate is the only bulk compound listed for this use
Includes drugs with sufficient scientific information to establish a WDT.
Under GFI #256, how should compounding be enforced?
Present human or animal health concerns
For Food producing animals
Copies of FDA-approved or indexed products
Distributed as office stock
What are the standards for office use of compounded products?
Office Use- Obtaining a compounded medication not pursuant to a patient-specific prescription to keep on hand for use in future patients
Compounded products are unique medications to address a specific patient’s needs
Not regulated like manufactured products
Sometimes necessary to have on hand to allow therapy to start immediately
Don’t have a lot on hand → like a drug distributor
Can have office stock compounded from FDA approved products on-hand
If compounded from bulk, must be on approved list and only for non-food producing animals.
What is the risk of compounding drugs?
Lacks stability
Stability: “extent to which a dosage form retains, within specified limits and throughout its period of storage and use, the same properties and characteristics that it possessed at the time of its preparation” USP 34/NF 29
Too much Drug/too little drug
Compounding can change how much drug concentration there is
Toxic excipients
Not bioavailable
Failure of Drug Delivery
Reformulation generates a new product
Usually affects absorption
Oral Formulations
Are there FDA approved oral formulations?
Destruction by gastric acid
Extensive first pass effect
Physiochemical properties of the drug
What is the difference between expiration and beyond-use dates
Expiration dates - FDA drugs
Determined based on product-specific studies
Specific formulation
Specific container
Possible conditions
Conventionally
manufactured drug
Product
Beyond-Use Dates- Compounded drugs
Full stability studies generally not performed
Based on data for similar products or USP default dates
Compounded product
Both- Indicates when a drug should no longer be used
Whichever is shorter should be used as reference
