toxicology definitions

Question 1

annually in the UK how many people suffer from food bourne illnesses? how many recieve hospital treatment? what is the economic impact?

Answer 1

1 million
20,000
£1.5BN

Question 2

discuss a virus and associated illness that has been on the increase in the UK in the last 6 years

Answer 2

Norovirus

Winter vomitting

Question 3

discuss an illness that in on the decrease in the UK

Answer 3

salmonella

Question 4

what is the difference between a toxin and a toxicant

Answer 4

toxin is a naturally occuring substance which can injure/kill an organism
toxicant is synthetic/manmade substance which can injure an organism

Question 5

define toxic symptom and toxic effect

Answer 5

toxic symptom; the symptoms that occur because of exposure to a toxin
toxic effect; health changes as a result of exposure to a toxin

Question 6

define toxicity

Answer 6

the degree to which a toxin/toxicant is harmful to an organism

Question 7

what is a dose response graph

Answer 7

a graph showing concentration vs effect

Question 8

whats the difference between acute and chronic exposure

Answer 8

acute exposute means short term where as chronic means long term

Question 9

discuss the many oppertunities for food to be contaminated

Answer 9

the crop, the animal, during slaugher, during storage, during processing, during transportation

Question 10

what causes diarrhoea? how many children die annually from it?

Answer 10

contaminated food/water

1.5 million

Question 11

which strategy could eliminate most foodbourne diseases

Answer 11

education on food preparation

Question 12

state the difference between toxicokinetics and toxicodynamics

Answer 12

toxicokinetics; what the body does to a toxin (how its metabolised and excreted and at what time frame)
toxicodynamics; what a toxin does to the body (how it has biological effects and over which time frame)

Question 13

discuss the 4 stages related to toxicokinetics

Answer 13

Absorption
Distribution
Metabolism
Excretion

Question 14

discuss factors effectign how well a toxin is absorbed

Answer 14

is the compound lipid soluble? if so it will be able to cross a plasma membrane
is the compound ionised? if so it will go into solution and therefore will be absorbed

Question 15

discuss 4 factors which effect distribution of a compound

Answer 15

the compounds physical and chemical properties which define how it crosses a membrane

the blood flow to a tissue; does the tissue have a good blood flow, if so the toxin will become distributed here

does the tissue have any transporters on it to allow easy uptake

are there any protective mechanisms in place; the BBB is a system involving tight junctions between cells and lack of transporters so that large molecules and microbes cant enter the brain

Question 16

which compounds tent to stay in systemic circulation rather than being distributed to tissues

Answer 16

those who bind to plasma proteins

Question 17

how are toxins metabolised

Answer 17

usually broken down into water soluble compounds which can be excreted via the urine
Xenobiotic metabolising enzymes

Question 18

discuss the role of xenobiotic metabolising enzymes. state 2 examples

Answer 18

those involved in metbaolism of toxins into water soluble products that can be excreted; 
cytochrome p450 (phase 1 metbaolism) and UDP-glucoronosyltransferase (phase 2 metabolism)

Question 19

how are different toxins eliminated

Answer 19

volatile gasses are exhaled
water soluble compounds are urinated
lipid soluble compounds are altered then urinated
faeces, sweat, hair are other methods

Question 20

discuss advancements in toxicology over timw

Answer 20

• early human ate things and realised they were harmful so didnt eat them again. humans ate things that were harmful and realised that eating other things made the effects less bad (antidotes)
• experimental studies on criminals to look at the effects they had

Question 21

discuss compounds which can potentially be toxic

Answer 21

drugs (legal/illegal)
food additives
industrial chemicals
environmnetal pollutants like smog, pesticides
natural toxins; animals, plants and bacteria

Question 22

which toxin has one of the lowest LC50’s

Answer 22

botulinum; 2x10-8

Question 23

which 4 factors effect toxicity (how harmful the effects of a toxin are)

Answer 23

dose
frequency of exposure/toxin half life
route of exposure
sub population status; sex specific effects due to action on reproductive organs

Question 24

which substance causes damage to testicles

Answer 24

cadmium

Question 25

discuss the different routes of exposure

Answer 25

dermal; thick layer of dead cells which no blood flow. tough keratin.

oral; gut reduces bioavailability of compound; transporters must be used to leave gut. vomiting. stomach acid. proteins bind to toxin

intramuscular; muscle injection; delayed response before the toxin enters systemic circulation

intraperitoneal; injection into a body cavity

inhalation; capillaries mean there is a very short pathway to the systemic circulation pathway

intravenous; 100% of toxins available

Question 26

discuss first pass metabolism

Answer 26

the idea that if you eat a toxin, the liver and the intestines will reduce its concentration before it reaches systemic circulation. enterophytes are cells in the SI which have transporters which move the toxin into the hepatic vein etc.

Question 27

what percentage of toxins does the ingestion route remove

Answer 27

90%

Question 28

discuss toxicology parameters

Answer 28

cmax; max concentration of a toxin (parameter of absorption)
tmax; time at which cmax occurs (absoption parameter)
Bioavailability (F) which percentage of dose enters systemic circulation unchanged
absorption rate constant (Ka)
volume of distribution
clearance (vol/time)
elimination rate constant (Ke)
half life

Question 29

why are the brain and liver more likely to have toxic effects? which structure protects the brain

Answer 29

good blood flow

bbb

Question 30

what is steady state. how many half lives does it take

Answer 30

rate in=rate out

5

Question 31

define toxicogenomics

Answer 31

study of how an individuals genetic effect the toxicity of a compound. differences in expression of toxin metabolising enzymes

Question 32

define hormesis and state examples

Answer 32

low dose of a toxic causes beneficial effects on an organism

cadmium (would normally cuase testicular caancer) in low doses increases expression of prtoeins which protect against testicular cancer

methanol (kills fruit flies) in low doses increases longevity of fruit flies

gamma rays (cause camcer) in low doses decrease risk of cancer.

penicillin (kill bacteria) in low doses increases bacterial growth

Question 33

discuss drug interactions

Answer 33

antagonism
additivea
synergy