NUSCTX 11 (TOXICOLOGY) MT2 EXAM
QUESTIONS AND ANSWERS
What organic pesticide has been linked as a potential environmental cause of
Parkinson's disease? - Answer-Rotenone which is used for its toxicity to fish
Exocrine - Answer-Juice, often containing enzymes. Transported by ducts and occur
physically near the site of action
Endocrine - Answer-Hormones. Transported in the bloodstream and occur anywhere
in the body with near or distant targets. Hormones are very potent and need to by
narrowly regulated.
Peptide hormones - Answer-Derived from chained amino acids (<=50) and are water
soluble. These include hypothalamic hormones, insulin, glucagon.
Amine hormones - Answer-Derived from modified amino acids (>50), generally water
soluble (except for t3 and t4). These include catecholamines, thyroid hormones.
Steroid hormones - Answer-Derived from cholesterol, lipid soluble. This include sex
hormones, glucocorticoids.
How do water soluble hormones exert their function? - Answer-By interacting with
membrane receptors and triggering secondary messengers and a signalling cascade
How do lipid soluble hormones exert their function? - Answer-By passing through the
cell membrane and into the nucleus to directly affect gene expression.
What is insulin? - Answer-- Peptide hormone produced by pancreatic beta cells
- Secreted when glucose levels are high. Antagonized by glucagon (secreted from
alpha cells) to preserve homo
- Regulates the metabolism of carbohydrate, fat, and protein the absorption
(anabolic)
What is the HPT axis? - Answer-hypothalamus-pituitary-thyroid axis
- Hypothalamus excretes TRH
- TRH triggers the anterior pituitary which excretes TSH
- TSH triggers the thyroid which excretes both T3 and T4, which provide negative
feedback to the anterior pituitary and hypothalamus respectively
What are the means on endocrine disruption and how is it different from toxicants? -
Answer-1) altering hormone levels
2) binding to receptors
3) blocking normal hormone action
4) Altering hormonal responses and many other steps in hormonal action
, These changes are particularly dangerous because endocrine systems are non-
monotonic and so changes can have non-linear responses
What are DDT's endocrine effects? - Answer-DDT is an androgen receptor
antagonist and so exposure causes reproductive abnormalities
What are the concerns with DES? - Answer-DES is a synthetic estrogen with a 3-5x
stronger binding affinity to alpha estrogen receptors than estradiol.
Later found to increase the risk of miscarriage as well as promoting abnormal
proliferation of reproductive duct cells
Additionally, too high levels of estrogen cause excessive fat deposition around hips
and thighs
What are the endocrine concerns of atrazine? - Answer-Atrazine induces aromatase
What are the concerns with PCBs? - Answer-PCBs are concentrated in fat tissues
and so easily accumulate in food chains. PCBs also have estrogenic, anti-
estrogenic, and anti-androgenic effects, as well as thyroid hormonal disruption at
multiple levels.
Additionally, PCBs reduce energy expenditure by inhibiting T3 function
What are the risks of streptozotocin (STZ)? - Answer-Toxic to pancreatic beta cells,
causing an impairment of insulin secretion as STZ is able to enter beta cells through
glucose transporter 2 and cause DNA damage.
What are the differences between the two types of diabetetes? - Answer-Type 1 -
insulin-dependent; auto-immune disorder which causes the destruction of beta cells
Type 2 - insulin-independent; body secretes insulin but it cannot decrease blood
glucose levels
What are the endocrine concerns of BPA? - Answer-BPA has been found to exert
estrogen-like effects and may act as an antagonist for thyroid hormone and
androgen receptors. It can also act as an obesogen by activating PRAPy
How does PRAPy act as an obesogen - Answer-PRAPy is the master transcription
factor of adipocyte differentiation and converts fibroblasts into adipocytes
How does thiazolidinediones (TZDs) act as an obesogen? - Answer-TZDs are class
of synthetic PRAPy ligands that are used as insulin sensitizers for treating
resistance. Prolonged use can cause persistent weight gain as TZDs promote
adipogenesis
How do organotins (like tributyltins) act as an obesogen? - Answer-Organotins are a
class of compounds used as a stabilizer for PVC and as an anti-fungal. Organotins,
however, are potent activators of PRAPy in bone marrow and convert bone
QUESTIONS AND ANSWERS
What organic pesticide has been linked as a potential environmental cause of
Parkinson's disease? - Answer-Rotenone which is used for its toxicity to fish
Exocrine - Answer-Juice, often containing enzymes. Transported by ducts and occur
physically near the site of action
Endocrine - Answer-Hormones. Transported in the bloodstream and occur anywhere
in the body with near or distant targets. Hormones are very potent and need to by
narrowly regulated.
Peptide hormones - Answer-Derived from chained amino acids (<=50) and are water
soluble. These include hypothalamic hormones, insulin, glucagon.
Amine hormones - Answer-Derived from modified amino acids (>50), generally water
soluble (except for t3 and t4). These include catecholamines, thyroid hormones.
Steroid hormones - Answer-Derived from cholesterol, lipid soluble. This include sex
hormones, glucocorticoids.
How do water soluble hormones exert their function? - Answer-By interacting with
membrane receptors and triggering secondary messengers and a signalling cascade
How do lipid soluble hormones exert their function? - Answer-By passing through the
cell membrane and into the nucleus to directly affect gene expression.
What is insulin? - Answer-- Peptide hormone produced by pancreatic beta cells
- Secreted when glucose levels are high. Antagonized by glucagon (secreted from
alpha cells) to preserve homo
- Regulates the metabolism of carbohydrate, fat, and protein the absorption
(anabolic)
What is the HPT axis? - Answer-hypothalamus-pituitary-thyroid axis
- Hypothalamus excretes TRH
- TRH triggers the anterior pituitary which excretes TSH
- TSH triggers the thyroid which excretes both T3 and T4, which provide negative
feedback to the anterior pituitary and hypothalamus respectively
What are the means on endocrine disruption and how is it different from toxicants? -
Answer-1) altering hormone levels
2) binding to receptors
3) blocking normal hormone action
4) Altering hormonal responses and many other steps in hormonal action
, These changes are particularly dangerous because endocrine systems are non-
monotonic and so changes can have non-linear responses
What are DDT's endocrine effects? - Answer-DDT is an androgen receptor
antagonist and so exposure causes reproductive abnormalities
What are the concerns with DES? - Answer-DES is a synthetic estrogen with a 3-5x
stronger binding affinity to alpha estrogen receptors than estradiol.
Later found to increase the risk of miscarriage as well as promoting abnormal
proliferation of reproductive duct cells
Additionally, too high levels of estrogen cause excessive fat deposition around hips
and thighs
What are the endocrine concerns of atrazine? - Answer-Atrazine induces aromatase
What are the concerns with PCBs? - Answer-PCBs are concentrated in fat tissues
and so easily accumulate in food chains. PCBs also have estrogenic, anti-
estrogenic, and anti-androgenic effects, as well as thyroid hormonal disruption at
multiple levels.
Additionally, PCBs reduce energy expenditure by inhibiting T3 function
What are the risks of streptozotocin (STZ)? - Answer-Toxic to pancreatic beta cells,
causing an impairment of insulin secretion as STZ is able to enter beta cells through
glucose transporter 2 and cause DNA damage.
What are the differences between the two types of diabetetes? - Answer-Type 1 -
insulin-dependent; auto-immune disorder which causes the destruction of beta cells
Type 2 - insulin-independent; body secretes insulin but it cannot decrease blood
glucose levels
What are the endocrine concerns of BPA? - Answer-BPA has been found to exert
estrogen-like effects and may act as an antagonist for thyroid hormone and
androgen receptors. It can also act as an obesogen by activating PRAPy
How does PRAPy act as an obesogen - Answer-PRAPy is the master transcription
factor of adipocyte differentiation and converts fibroblasts into adipocytes
How does thiazolidinediones (TZDs) act as an obesogen? - Answer-TZDs are class
of synthetic PRAPy ligands that are used as insulin sensitizers for treating
resistance. Prolonged use can cause persistent weight gain as TZDs promote
adipogenesis
How do organotins (like tributyltins) act as an obesogen? - Answer-Organotins are a
class of compounds used as a stabilizer for PVC and as an anti-fungal. Organotins,
however, are potent activators of PRAPy in bone marrow and convert bone
