Principles of Toxicology

Question 1

what does TD50 tell you

Answer 1

median toxic dose

Question 2

what values are plotted on a graph to show the relationship between exposure and response

Answer 2

response (% of the population) against log10 dose

Question 3

what does NOAEL stand for

Answer 3

no observed adverse effect level

Question 4

which sort of toxicants do not have a dose below which no adverse respose is evoked

Answer 4

carcinogens and mutagens

Question 5

what shape is the curve of a graph showing a toxicant that demonstrates hormesis

Answer 5

U or J

Question 6

what does a steep slope on the dose/response graph suggest about the toxicant

Answer 6

a small change in exposure ellicits a large change in toxicity ie high affinity toxin

Question 7

what are the 4 aspects of exposure

Answer 7

route, intensity, frequency and duration

Question 8

what is meant by bioavaailability

Answer 8

the extent to which a drug or other substance is taken up by a specific tissue or organ after administration

Question 9

what are the main routes of entry of a toxicant

Answer 9

ingestion and absorption from GI tract, inhalation and absorption from lungs or absorption through skin

Question 10

what is the key property of a toxicant which determines its ability to be absorbed

Answer 10

lipid solubility

Question 11

what are the ways in which toxicants can be removed by the body

Answer 11

excretion in urine, bile or exhaled air
by metabolism
accumulation

Question 12

under what cicumstances does accumulation of a toxicant become threatening

Answer 12

during starvation due to breakdown of fat stores

Question 13

name an example of a toxicant which is not absorbed by diffusion, but instead is transported

Answer 13

paraquat

Question 14

does carbon monoxide bind haemoglobin reversibly or irreversibly

Answer 14

reversibly

Question 15

do organophophate nerve gases bind irreversibly or reversibly to acetylcholinesterase

Answer 15

irreversibly

Question 16

how does binding of a toxicant to a target cause illness generally

Answer 16

it alters target function and cell homeostasis

Question 17

under what circumstances is a toxicant less likely to compromise the fntion of a target cell/tissue/organ

Answer 17

if the target can be rapidly regenerated or is well protected

Question 18

give 2 examples of drugs which elicit hormetic responses

Answer 18

biochanin A and brommodioxyuridine

Question 19

what is the target tissue of paraquat

Answer 19

lung eputhelia

Question 20

where is paraquat and other toxins stored when accumulated

Answer 20

fat tissues

Question 21

give an example of a drug which metabolites are more toxic

Answer 21

paracetamol

Question 22

how does metabolism increase the ability to excrete toxicants

Answer 22

alters lipid solubility

Question 23

what are the 4 circumstances of exposure to toxicants

Answer 23

environment
accidental/intentional
treatment of illness
occupational

Question 24

what are the 4 methods of movement across the epithelia

Answer 24

transcellular (across membrane)
carrier mediated
paracellular (through gaps)
endo/exocytosis

Question 25

name a toxin which crosses the epithelia via carrier mediated method

Answer 25

arsenic

Question 26

how is botox transported across the epithelia

Answer 26

endo/exovytosis

Question 27

how is NOAEL used to calculate the starting dose in clinical trials

Answer 27

NOAEL/100 as 10x more sensitive and 10x slower at removing toxicant than animals

Question 28

what does the threshold of toxicological concern estimate?

Answer 28

quantitatively estimates the size of the population, the intensity, duration and frequency of exposure and the routes of entry

Question 29

what must be carried out if exposure is likely to be higher than TTC

Answer 29

further risk assesment

Question 30

which populations are generally more susceptible to toins

Answer 30

children and elderly

Question 31

which population are more susceptible to toxicity from acetyl due to 90% of them being fast metabolisers

Answer 31

asian

Question 32

when is something deemed to be “safe”

Answer 32

if risks are judged to be acceptable

Question 33

what is REACH

Answer 33

registration, evaluation and authorization of chemicals

Question 34

when was REACH introduced and who by

Answer 34

june 1st 2000

EU

Question 35

what is the purpose of REACH

Answer 35

to improve protection, a more transparent system for risk assessment and control of chemicals

Question 36

does REACH promote non-animal testing

Answer 36

yes