4.6 Toxic Plants Flashcards
why are plants toxic (3)
1) protect against herbivory
2) reduce palatability
3) toxic effects -> revenge!
compounds derived from what plant are used to treat heart disease
foxglove: cardenolides (digoxin, digitoxin)
compounds derived from what plant are used to treat transmissible venereal tumors (TVT)
Madagascar or rosy periwinkle: vinca alkaloids (vincristine, vinblastine)
the yew plant is unique in that some components are helpful in treating neoplasia whereas other components produce a toxic effect similar to a heart attack
what components of the plant are beneficial?
what components are toxic?
beneficial (antineoplastic): fruit
toxic: wood, bark, leaves, seeds
both yew and periwinkle are antineoplastic, how are they different
periwinkle: destabilizes microtubules (prevents assembly)
yew: stabilizes microtubules (prevents disassembly)
sudden death occurs in plants containing (3)
1) cyanogenic glycosides
2) toxic alkaloids
3) nitrates
what are some sources of cyanogenic glycosides (4)
- sorghum
- flax
- sudan grass
- leaves of wild cherries (chokecherry, pincherry, blackcherry, service berry)
what are two examples of cyanogenic glycosides
prunasin, amygdalin
MOA of cyanogenic glycosides
cyanide poisoning: binds to cytochrome C oxidase and inhibits the electron transport chain -> decreased ATP production -> cell death
signs of cyanogenic glycoside poisnoning
distress, weakness, labored breathing, collapse, convulsions, acute death
how can we diagnose cyanogenic glycoside poisoning
cherry red venous blood, plant material in GI
why does cyanogenic glycoside poisoning cause the venous blood to be cherry red
it blocks the electron transport chain -> oxygen is not consumed -> oxygen accumulates in blood
cassava is an example of a plant that contains what type of cyanogenic glycoside
linamarin
how do we treat cyanogenic glycoside poisoning
administer sodium nitrite -> forms met-Hb -> binds HCN -> removes HCN from cytochrome C oxidase -> forms cyanmethemoglobin
what are 3 plants that produce toxic alkaloids
water hemlock (poison parsnip), monkshood, larkspur
what is one of the most toxic native plants in north america
water hemlock (poison parsnip)
what toxin does water hemlock produce
cicutoxin (a neurotoxic alkaloid)
what are 4 types of cardiotoxins
1) taxine alkaloids
2) cardiac glycosides
3) grayanotoxins
4) persin
what is an example of a plant that contains taxine alkaloids
Japanese yew
MOA of taxine alkaloids
depress cardiac conduction by inhibiting Na and Ca channels
signs of taxine alkaloid ingestion
trembling, dyspnea, bradycardia, diarrhea, cardiac failure, sudden death
what toxin do cardiac glycosides produce
cardenolides
what is the MOA of cardiac glycosides (cardenolides)
inhibit membrane Na/K pumps -> increased intracellular Ca -> myocardial contraction
also interferes with cardiac conduction
plants can be toxic to the digestive system and cause what 3 signs
excessive salivation (trauma and irritation), vomiting (lactones), diarrhea (lectins, glycoalkaloids)
what is an example of a plant that causes oral irritation (excessive salivation) -> give some specific examples of this family
dieffenbachia (pothos, dumbcane, arrowhead vine)
how does dieffenbachia cause oral irritation and excessive salivation
formation of calcium oxalate crystals
what is an example of a plant that causes digestive signs via diarrhea by producing lectins -> what are its toxins
castor bean (ricin, ricinin)
how do lectins (ex. castor bean) cause diarrhea (MOA)
ricin and ricinin (the toxins produced by castor beans) inhibit ribosomal protein synthesis
what are signs of castor bean (lectins - ricin and ricinin) poisnoning
hypovolemic shock, abdominal pain, hemorrhagic diarrhea
what are examples of plants that cause primary photosensitization through contact?
poison ivy, giant hogweed
what are examples of plants that cause primary photosensitization through ingestion
St. Johns Wort, buckwheat
secondary photosensitization of plants that cause direct irritation impacts function of what organ
liver
what lesions does St. John’s wort create
erythema -> ulcers of lightly pigmented areas
what are examples of plant compounds that impact the liver (4)
1) pyrrolizidine alkaloids (ragwort)
2) unknown hepatotoxins (alsike clover)
3) microcystins (blue green algae/cyanobacteria)
4) amatoxins (mushrooms)
what is the toxin produced by ragwort and what species are susceptible
pyrrolizidine alkaloids; cows and horses
what part of ragwort contains pyrrolizidine alkaloids
above ground parts
what are the MAIN clinical signs produced by ragwort in the following cases:
- acute
- chronic
acute: tachycardia, death
chronic: photosensitization -> hepatic injury
what are the 4 characteristic lesions in the liver of a cow or horse that ingested ragwort
1) chronic liver disease
2) bile duct proliferation
3) portal fibrosis
4) megalocytosis
give an example of a plant that does the following:
1) myelosuppression
2) hemolysis
3) clotting abnormalities
1) bracken fern
2) red maple
3) moldy sweet clover
what parts of bracken fern are toxic? is the plant palatable? how does it become injested?
all parts; not palatable; ends up in hay during harvesting
what is the main sign of bracken fern toxicosis in horses and in cows and what is the main toxin/reason
horses: bracken staggers (incoordination) - thiaminase (causes thiamine or vitamin B1 deficiency)
cows: hematuria - ptaquiloside
what are the signs of bracken fern toxicosis in horses
weight loss, depression, weakness, incoordination, wide stance, twitching, arrhythmias, recumbency, convulsions, death
what are the signs of bracken fern toxicosis in cows
hematuria, anemia, leukopenia, thrombocytopenia, fever, anorexia, hemorrhage, melena
what lesions does bracken fern cause in horses (2)
epicardial and pericardial hemorrhage
what lesions does bracken fern cause in cows
hemorrhage, aplastic BM, abomasal ulcers, papillomas, carcinomas, hemangiomas, hyperplasia, inflammation, bladder lesions
the toxin produced by red maple is _________ and its metabolite is _________
gallic acid; pyrogallol
what species are susceptible to red maple toxicosis
horses
what are signs of red maple toxicosis
cyanosis, icterus, depression, anemia, hemoglobinuria
what does red maple cause (MOA)
hemolysis
what lesions are produced by red maple
acute hemolytic anemia, methemoglobinuria, Heinz body formation, icterus, periacinar hepatic necrosis, hemoglobinuric nephrosis
what are 5 examples of plants containing neurotoxins
1) locoweed
2) crown vetch
3) white snakeroot
4) yellow star thistle
5) russian knapweed
what is the neurotoxin produced by russian knapweed called and what species does it impact
repin; horses
what are signs of russian knapweed toxication
constant chewing, hypertonicity of facial muscles, paralysis of lips and tongue, hyperemia, depression
MOA of repin from russian knapweed
glutathione depletion -> increased ROS -> oxidative damage -> neuron necrosis
inhibits dopamine release -> Parkinson’s like signs
what areas of the brain are most susceptible to repin and what is the consequence
areas of dopamine metabolism -> inhibition of dopamine release -> Parkinson’s like signs
what specific areas of the brain are affected by repin (russian knapweed)
substantia nigra, globus pallidus (bilaterally affected)
what are two examples of nephrotoxins and a plant that contains them
1) oxalates (red-root pigweed, rhubarb)
2) tannins (oak)
T/F the toxin of lily is unknown
T
what species are susceptible to lily neprhotoxicosis
cats
what are signs of lily toxicosis
depression, vomiting, renal failure
what does lily do to the kidneys
tubular necrosis
what are examples of plants that affect the musculoskeletal system in the following ways:
1) calcinosis (vitamin D analogues)
2) cardiac mm degeneration
3) laminitis
4) selenosis
1) calcinosis: day blooming jessamine
2) cardiac mm degeneration: cottonseed
3) laminitis: black walnut
4) selenosis: milk vetch
what are examples of teratogenic plants (impact reproduction) (4)
1) false hellebore
2) milk vetches
3) locoweeds
4) lupines
what species are susceptible to false hellbore
sheep only
what signs does false hellebore cause in the mother sheep
salivation with frothing, irregular gait, coma, convulsions, fast and irregular heartbeat, short and shallow breathing, vomiting
what does false hellebore do to the fetus at the following stages:
Day 14 gestation:
Day 28-31 gestation:
Day 14: cyclopia, anopthalmia, cleft palate, shortened maxilla
Day 28-31: arthrogryposis, shortened long bones
