Toxicology Midterm 2 Flashcards

Question

Describe how metal toxicity can change due to water hardness.

Answer 1

Water hardness changes metal toxicity due to the [] of divalent cations, the higher [] of essential metals in water lowers the bioavailability of metal toxicants because they compete for absorption. -E.g. Ca2+, Mg2+, Cu2+, Cd2+, Zn2+, Co2+

Answer 2

Is the mechanistic approach to determine bioavailability incorporating water chemistry and metal speciation. This model has been developed from the Free-Ion Activity Model (FIAM) & Gill Surface Interaction Model (GSIM) The practical use of this is to understand the competition of free metal ions with other naturally occurring cations for metal binding sites (Ca, Na, Mg)

Answer 3

The reason why free metal ions compete with naturally occurring cations is because of their charges. When we look at Na1+ transporters we notice that the metals that compete are Ag1+ & Cu1+, since the charges are similar they can be up taken by these pathways When we look at Ca2+ transporters we know that the metals that compete are Zn2+, Cd2+, Pb2+, Co2+, Cu2+

Answer 4

Structure-activity relationships (SAR), use molecular qualities of organics to predict activity (e.g. Poly Aromatic Hydrocarbons, they all contain benzene rings) if expressed quantitatively (QSARS- molecular weight, surface area, or charge distribution)

Answer 5

In the environment and food KOW influences the bioavailability of lipophilic contaminants: For very large and hydrophobic compounds the uptake of these compounds are low. PCBs with high KOWs (hydrophobic) adsorb into the soil but are not available for uptake by plants. Many pesticides have low KOWs (hydrophilic) allowing them to be taken up more easily by plants.

Answer 6

Remember ABDE: A. Absorption/Uptake of the toxicant B. Role of Biotransformation D. Is the toxicant Detoxified? E. Is the toxicant Eliminated & how or does it accumulate?

Answer 7

Bioaccumulation is the net accumulation of a contaminant in/on an organism from all environmental sources Sources: Air, Water, Soils/Sediments, Food/Trophic transfer. Bioconcentration is the net accumulation of a contaminant in/on an organism from water (Aquatic Toxicity), and we can use the BCF to determine the fate of this contaminant. When looking at the Accumulation graph understand Accumulation phase, depuration phase, when it's moved into a clean environment, whether it's persistent or leaves the organism (BCF graph is slightly different)

Answer 8

BCF is determined in a steady state (highly monitored conditions), and it tells us the fate of the toxicant in the organism. It is calculated by [] of the toxicant in the tissue (mgKg-1)/ [] of toxicant in water (mgL-1) When looking at the BCF Graphs (Accumulation graph for Bioconcentration) the end point is the will tell you whether or not it has a Low or high BCF

Answer 9

Chemical Properties of the Substance: Lipophilicity Persistence Water Solubility Organism-Specific Factors: Metabolism Life Stage and Size Feeding Habits Sex- female mammals are able to excrete through lactation (milk has very high fat content), males have no mechanism. Environmental Conditions: Temperature pH Water hardness Exposure Pathways: Dietary Intake Direct Uptake from Environment

Answer 10

Some chemicals bioconcentrate due to their high BCF which means that the more lipophilic the contaminant the longer it stays in the body and accumulates.

Answer 11

BCF and lipophilicity can be related: The more lipophilic the contaminant is more it accumulates in the body, it is very persistent but there is a threshold for how much chemical the fat tissue can hold. If its Hydrophilic it's usually easier to excrete. High KOW-> High BCF (e.g., Dioxins and PCBs), there are solubility limits (amount of chemical fat tissue can hold) Low KOW-> Low BCF easier to excrete since hydrophilic or attracted to water (e.g., metals), the only time complications occur is when there are pumps or channels involved

Answer 12

Lipid concentration and composition of the organism, the higher the concentration the more it will accumulate (seals, walruses), the composition of the fat tissue might make it more susceptible to certain chemical. The weight of the organism, it is implied that the more mass an organism has the more it can bioaccumulate/concentrate. Surface ratio is also important smaller species exchange with surrounding aqueous phase faster than larger organisms. The uptake route is also important- An organism can take up a contaminate either from direct exposure from the water or through digestion Metabolic Activity- increased metabolism may result in an increase in excretion of the chemical.

Answer 13

Is the increase of concentration of a chemical as one moves up the food chain (trophic levels). A chemical must bioconcentrate and persist in the body (body burden), when the animal is then consumed by a predator it then builds up in their bodies because they are able to contain high [] of the chemical, the higher the animal is on the trophic level the contaminant will have a higher burden than their prey.

Answer 14

An example is bird eating fish because of the release of DDT in the ocean and the build up of the contaminant from each level of trophic level. DDT effects calcium-dependent ATPase in the shell glands of these birds and their eggs would be extremely brittle and won't survive.

Answer 15

A. Absorption/uptake of a chemical that enters the body D. Distribution of the chemical from the entry site to other sites in the body B. Biotransformation of the chemical from one form to another (metabolites) E. Excretion/elimination of the chemical or metabolite from the body

Answer 16

The speed of transport and path is highly dependent on water solubility, lipophilicity (KOW) and molecular size. The main locations of exposure are gills, lungs, guts, and skin/surface. The 3 routes of uptake are: 1. lipid 2. Aqueous 3. Endocytic

Answer 17

Lipophilic contaminants through the lipid bilayer of the membrane, substances with high lipophilicity can readily diffuse across the lipid bilayer and plasma membrane, passive diffusion is the movement of a chemical down its concentration gradient. Remember diagram

Answer 18

For the aqueous route is via membrane transport proteins (channel/carrier proteins), hydrophilic contaminants transfer into the cell easily through non-specific channels (porins), some are specific like Ca dependent channels and Cd that compete with it. Remember diagram.

Answer 19

Metals that bind to a proteins on the surface of the cell are then engulfed and incorporated into a vesicle which fuses with a lysosome thus releasing the metal into the cell. Remember diagram.

Answer 20

Toxicants travel through the circulatory system by blood lipophilic toxicants bind to the blood cells. Hydrophilic toxicants bind to plasma.

Answer 21

All the blood leaving the gut travels to the liver allowing hepatocytes (power house of xenobiotic metabolism) biotransforms the toxicant for elimination.

Answer 22

Once it is biotransformed toxicant may travel to the liver -> kidney -> adipose tissue -> bones

Answer 23

Biotransformation is a metabolic process where the parent toxicant is transformed into a metabolite to help it be excrete/eliminated by the organism.

Answer 24

The purpose of biotransformation is to convert lipophilic compounds into a more hydrophilic compound so it can be eliminated, the outcomes can differ: the metabolite can become non-toxic or it can be activated and become even more toxic (e.g., parathion converts to paraoxon becoming a very lethal compound)

Answer 25

Since metals can't be destroyed so they are either sequestered (hides the inorganic) or removed from the organism

Answer 26

Microbes transform metals by adding ethyl or methyl groups to deal with the toxic effects of the metals this is called biomethylation. E.g. Sulfur reducing microbes methylate Hg sequestering it created Methyl Mercury

Answer 27

Plant cells can also biomethylate metals to reduce toxicity like As -> monomethylarsonic acid. Higher plant cells sequester or eliminate metals by producing metal-binding proteins called phytochelatins (similar to metallothionein-like protein in vertebrates) The presence of Cd, Cu, Hg, Pb, Zn upregulates gene expression for the genes that code for phytochelatins

Answer 28

Invertebrates may sequester metals and other cations through a process called biomineralization (e.g., an example would be like how insects and molluscans incorporate Pb into their exoskeleton) they either shed their exoskeleton or retain these shells that renders the metal unavailable to have an impact on the organism

Answer 29

Vertebrates sequester metals with the use of proteins called metallothionein's (reduces the availability of metal) Metallothionein's are small sulfur-rich proteins that contain 25-30% of an amino acid called cysteine (contains sulfur), they can bind 6 or 7 metal atoms per molecule. Production of this protein is induced by metals like Cu, Zn. Metallothionein's genes are activated when metals bind to metal-responsive transcription factor 1 (MTF-1) which then bind to metallothionein promoter and induces expression of the metallothionein.

Answer 30

Phase I- Is the first step of biotransformation when an organism wants to deal with an organic toxicant is the enzyme attacks the compound causing oxidation, hydrolysis and reduction reactions. Most phase I enzymes are Cytochrome P450's (CYPs) or a Mixed Function Oxygenases enzymes (MFOs), some times metabolites may become less toxic or more toxic (e.g., epoxide formation) Invertebrates have rudimentary or no CYP enzymes The most potent inducer of CYP is TCDD due to its size and planarity of its ring structure, PAHs/PCBs also induce CYP. Dioxins & PCBs induce CYP1A By isolating microsomes we can find CYP through homogenization. CYP contains a heme group that binds to O2, CO2, CO.

Answer 31

Phase II enzymes conjugate endogenous compounds to make phase I metabolites even more water soluble, once conjugated they could become inactive. Glucuronide -> glucuronyl transferase Glutathione -> glutathione-s-transferase Sulphate -> sulfotransferases Amino acid conjugation It then goes to the kidney for excretion.

Answer 32

Phase I: 1. Oxidation (naphthalene epoxide) 2. Hydrolysis (naphthalene 1,2-diol) Phase II: 3.Conjugation of naphthalene 1,2-diol with glucuronic acid 4. Allows for increased water solubility and subsequent elimination Naphthalene is successfully sequestered without increased toxicity

Answer 33

Phase I: 1. Oxidation (B[a]P-7,8-dihydrodiol-9,10-epoxide) - forms a potent carcinogen Phase II: 2. Conjugated with an amino group (Extremely potent carcinogen) Mutations will occur, some times the body catches it, or mutations are not caught and cause cancer

Answer 34

Major routes of excretion in animals are: Primary sites- Urine, feces, and bile Secondary sites- lungs/gills Other minor sources are breast milk, sweat, saliva, hair, and skin

Answer 35

Plants eliminate toxicants by leaching, evaporation from surfaces, leaf falls

Answer 36

Invertebrates such as arthropods can eliminate metal contamination via exoskeleton moulting (shedding)

Answer 37

An animal cell culture allows us to evaluate cellular toxic effects and molecular changes without using an entire organism and we grow these cells in vitro. We are for mechanisms of cell death and accessing the viability of cells after toxicant exposure. Ross Harrison first developed the cell culture technique, used frog nerve cells grown in lymph clot using the hanging drop method.

Answer 38

1. Sterile environment to manipulate culture (culture hoods) 2. Proper culture environment to support cell growth (Incubator) 3. Nutrient environment to support cell growth (Medium= Antibiotics+ serum) 4. Appropriate physical support (needs attach to surface of viable )

Answer 39

Animal cells are isolated from the tissues using mechanical or enzymatic protocols. 1. Comes the primary culture (derived from initial tissue) 2. Then its placed in a cell line There are 2 types of cell lines: 1. Finite cell line- A cell line that has a limited number of divisions 2. Continuous/immortalized cell line- A cell line that has an indefinite lifespan due to immortal cells.

Answer 40

"Whole organism does not get sick-but only certain cells or group of cells"

Answer 41

Apoptosis: 1. Is a carefully regulated energy-dependent process of cell death 2. It is programmed cell death "cell suicide" 3. DNA is cleaved (180 bp fragments) 4. Blebbing of cell membrane 5. Might be caused by depletion of nutrients Necrosis: 1. Unprogrammed cell death 2. No characteristic changes as seen in apoptosis (DNA cleavage, blebbing) 3. Plasma membrane is disrupted- cellular contents expelled into extracellular environment 4. Caused by sudden severe stress

Answer 42

Cell membrane integrity- Dye exclusion & Retention assays Metabolic activity- MTT & Resazurin assays Lysosomal activity- NR dye assay

Answer 43

The major difference is that a dye exclusion assay stains dead cells blue, where a retention assay uses a dye that penetrates the cell and then becomes fluorescent. Dye Exclusion- Trypan blue is a dye they use to stain dead cells and identify them, trypan blue is is a bulky chemical and viable cells won't allow it enter cell (Measure of dead cells) Retention assay- They add CFDA a non-polar, non-florescent dye to cells that rapidly diffuses into cell and then is converted by non-specific esterase's of living cells to CF a polar fluorescent chemical (Measure of viable cells).

Answer 44

MTT assay measures mitochondrial activity through oxidative metabolism, the dye is reduced by succinate dehydrogenase, yellow dye will turn blue when reduced, sometimes there isn't enough succinate dehydrogenase to get a response from the MTT assay. Resazurin assays- measures both mitochondrial and cellular metabolic activity, through the reduction of resazurin by diaphorase enzyme in cell and mitochondria, will turn purple/pink when reduced.

Answer 45

Neutral Red (NR) is a dye that is used in cell staining determine cell viability, viable and uninjured cells take up NR into the lysosomes, dead cells don't have this ability.

Answer 46

Class A metals (ligands) are associated with targeting molecules such as phospholipids and nucleic acids Class B metal (ligands) are associated with targeting amino acids and proteins Required: Fe, Ca, Zn, Na, K Trace nutrients: Se, Cu, Co, Mg, Mn Non-metabolic: Pb, Cd, Ni, Sn, Hg, Ag

Answer 47

Lead is a ubiquitous toxic metal with multiple routes of exposure: air, water, and food. (ceramic containers with lead glaze, fuel additives, lead-based paints, lead pluming pipes) Inorganic lead is absorbed through the GI tract, skin, and respiratory tract and can be found in blood, liver, kidney and bone tissue with prolonged exposure. Pb targets the hematopoietic system and impacts haeme synthesis, it inhibits the production of ALAD and HS through the mechanism of displacing zinc which is essential to the activity of ALAD. Symptoms include: impacting the development of the nervous system, ataxia, stupor, coma, and convulsions.

Answer 48

Inorganic Hg (Metallic/Inorganic) doesn't bioaccumulate because it is not readily assimilated into the body Organic Hg (MeHg) is readily absorbed by organisms it is highly toxic and bioaccumulates Methyl Hg can easily pass through the blood brain barrier as it forms a complex with cystine in blood plasma becoming structurally similar to methionine and gains passage through methionine carrier proteins- interferes with protein synthesis and neurotransmitter production.

Answer 49

Hg's organic form is where biomagnification occurs with its organic form, both inorganic and organic Hg is primarily excreted via bile (feces) but some reuptake occurs in the gut, most of the body burden is the muscle unlike other POPs who associate it with fatty tissue. Biomagnification occurs through trophic levels and can even reach levels of contamination where they are unsuitable for even occasional consumption

Answer 50

In Japan Chisso Corp dumped larger discharge of Hg waste into Minamata Bay which lead to the consumption of contaminated fish normally found in the diet of the people in the area Poisoned thousands of people they called Minamata disease. Dryden, Ontario- The Dryden chemical company pulp and paper mill generated Hg waste and dumped effluent into English-Wabigoon River, this caused Minamata disease but no official diagnosis was made, health advisory still in effect after 60 years.

Answer 51

Cd has been known to cause acute toxicity in humans symptoms are: nausea, vomiting, abdominal pain (ingested), pulmonary edema (inhalation) Cd chronic toxicity impacts the kidneys In Japan Cd toxicity occurred due to the use of contaminated river water for rice irrigation, Cd replaced Ca in bones and caused severe pain in joints and brittle bones (itah-itah: Japanese for it hurts it hurts) Tobacco plants love to accumulate Cd and this could be a route of exposure for people who smoke, it gets deposited in lung tissue and absorbed into blood circulation

Answer 52

Ammonia expresses itself as a neurological disorder, and it can substitute K at nerve membrane-> compromising nervous system function We can physically see this when the fish have a loss of eq(can't swim), convulsions and death

Answer 53

1. NH3 freely diffuses into the membrane/ NH4+ doesn't 2.If there is a pH change and NH3 becomes ionized NH4+ (similar hydrated radius as K+) the organism will have to expel NH4+ through Na+ active transport and use ATP to do so

Answer 54

pH and temperature influence the toxicity of ammonia, but mostly pH (abiotic modifying factors) When there is a pH shift and it keeps/converts ammonia in its unionized form, as we already know NH3 has an increased bioavailability compared to its ionized form NH4+

Answer 55

The Stockholm Convention is an international agreement to limit the use of persistent and Bioaccumulative chemicals. Annex A: List of chemicals that need to be eliminated Annex B: List of chemicals with restricted use Annex C: Unintentional production

Answer 56

When metabolized PAHs can form reactive metabolites (epoxides) they bind to cellular proteins and DNA- it leads to mutations, developmental malformation and cancer. PAHs may be activated in the liver and undergo AhR-dependant/induction in the lungs they can form DNA adducts, protein adducts or oxidize macromolecules in cells (lead to cancer) E.g. B[a]P transformed in vivo to BP-7,8-epoxide -> further metabolized into BP-7,8dihydrodiol -> then metabolized to BPDE which reacts with DNA - Leads to a mutation on the p35 gene which leads to carcinogenesis linked to human lung cancer

Answer 57

The consumption of bread made from HCB fungicide-treated grain. 3000 people developed porphyria cutanea tarda and mixed porphyria Hypertrichosis, porphyrinuria, and blisters when exposed to the sun. In mammalian studies the oral LD50 are extremely high, chronic exposure can cause hepatomegaly, alopecia, ataxia, and liver/thyroid tumours.

Answer 58

Dioxins induce MFOs, acute toxicity can range. TCDD toxicity is mediated by ArR-signalling They examined the effects of 2,3,7,8-TCDD in fathead minnow, channel catfish, lake herring, medaka, white sucker, northern pike, and zebrafish. They noticed that it caused "blue sac" toxicity in fish larvae (death) We see Cranial edema, jaw and heart malfunctions, Yolk sac edema

Answer 59

It is biologically unavailable but adsorbs through soil/sediment, almost all poisonings are from ingestion (non-volatile & hydrophilic) In aquatic organisms- paraquat is more toxic in soft water and in the early developmental stages of some fauna, such as certain crustacean species and frog tadpoles. In birds- they exhibit excessive drinking, regurgitation, imbalance, muscular incoordination, terminal convulsions In mammals- exhibits time-dependent accumulation in the kidney and lungs. Carrier-mediated transport of paraquat into the cells (it undergoes redox cycling and the production of superoxide) Produces other ROS (mainly H2O2) Phase I- Destructive phase: Alveolar type I & II epithelial cells are destroyed Phase II- Proliferative phase: Extensive fibrosis in the lungs (dyspnea, cyanosis, respiratory failure).

Answer 60

MPTP is a contaminant produced from the synthesis of MPPP. MPTP crosses the blood-brain barrier and gets metabolized by MAOB by the glial cells of the brain and produces MPP+ MPP+ is taken up by dopamine transporters in the brain, it inhibits the electron transport chain resulting in oxidative stress in dopaminergic neurons and 3 days developed symptoms of Parkinson's disease (tremor, hypokinesia, and rigidity)

Answer 61

Effluent is a waste product formed after domestic and industrial processes. Complex effluent is when multiple compounds are added to the mix giving it a complex composition making it hard to treat. (could end up beneficial or detrimental)

Answer 62

Antagonistic- This is when the compounds interfere with one another Additive- Is when the compounds have a combined effect Synergism- This is when the compounds have a greater effect than when acting alone.

Answer 63

BKME is bleached kraft mill effluent is a very complex mix of hundreds of different compounds, and it is important to understand how they all interact with each other and the environment.

Answer 64

3 main toxicants of focus in pulp and paper mills is: Resin acids- E.g., dehydroabietic acid (DHAA) is a class of acids that are the deadliest chemicals in pulp mill effluents to fish (large amounts and persistent in environment) Dioxins & furans- TCDD Chlorinated phenolic compounds: 2,4,5-trichlorophenol

Answer 65

The aryl hydrocarbon receptor (AhR) is activated (binds)when an AhR-inducing agent is present (Dioxin), it will then be allowed into the nucleus with the help of AhR nuclear translocator, they then bind with the dioxin response element and promote the transcription of the CYP1A1 mRNA then carries a code that determine the composition of amino acids that code for the CYP450 enzyme and then the activity can be measured with EROD assay.

Answer 66

Memorize graph