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Toxicology > Dose Responses > Flashcards

Dose Responses Flashcards

1
Q

Hazard

A

intrinsic toxic properties of a toxicant mixture

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2
Q

Risk

A

Probability of an adverse outcome based on the exposure and potency of the hazardous toxicants

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3
Q

risk assessment

A

characterization of the probability of potentially adverse health effects from human exposures to hazardous agents

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4
Q

risk management

A

process by which policy actions are chosen to control hazards

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5
Q

epidemiology

A

studies the patterns, causes, and effects of health and disease conditions in defined populations

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6
Q

epidemiology data

A

correlative

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7
Q

correlation

A
  • whether two variables are changing together

- correlation does not indicate causation

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8
Q

bioassays

A
  • prove causation
  • quantitative estimation of the intensity or concentration of a biologically active chemical
  • measured via some biological response under standardized conditions
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9
Q

goals of toxicity testing

A
  • determine the range of doses over which the toxic responses are produced
  • identify the nature of the responses to a toxicant
  • extrapolate these results for risk assessment analyses for human exposure
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10
Q

uses of bioassays in environment toxicology

A
  • determine of the most sensitive species or life stage in an assemblage of organisms
  • compare effects of different pollutants on a single organism
  • compare effects of other environmental factors acting with the pollutant that modify its effects
  • determine the maximum level of a pollutant that may occur in the environment without causing biological change
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11
Q

dose-response

A

-quantify the relationships between the exposure concentration and a defined endpoint

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12
Q

endpoints

A

whatever we are most interested in measuring

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13
Q

dose-response relationships

A
  • standardize the doses to body weight
  • duration and frequency important
  • often the endpoint is mortality
  • compare relative toxicity of toxicants
  • ranked into toxicity classes
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14
Q

acute exposure

A

hours to days

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15
Q

chronic exposure

A

months to years

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16
Q

lethal concentration

A

how long an individual was exposed to a toxicant to reach the endpoint

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17
Q

lethal dose

A

taken orally

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18
Q

graded dose response

A
  • use a continuous variable and occur in a single individual

- characterized by a dose-related increase in the severity of the response

19
Q

quantal dose response

A
  • occur in a population

- individual is classified as a “responder” or “non-responder”

20
Q

route of exposure

A
  • change dose-response curves
  • injection, inhalation, ingestion, dermal
  • speed of the response is related to how quickly a toxicant enters the bloodstream
21
Q

linear relationships

A
  • y-axis converted to “probits”
  • Normal equivalent deviation
  • 5=50% of the population
22
Q

effective dose (ED50)

A

where the drug is doing what we want it to do in 50% of the population

23
Q

toxic dose (TD50)

A

where bad things start happening in 50% of the population

24
Q

lethal dose (LD50)

A

lethal in 50% of the population

25
Q

therapeutic index (TI)

A
  • ratio of TD50 and ED50
  • high values drug is relatively safe
  • low values rejection of the drug from further clinical testing
26
Q

potency

A

the amount required to produce an effect of given intensity

27
Q

efficacy

A

refers to the maximum response achievable

28
Q

No observable effect concentration (NOEC)

A

highest concentration with no mortality

29
Q

Lowest observable effect concentration (LOEC)

A

point of first effect or mortality

30
Q

vehicle or carrier

A
  • distribute the contaminant to the animals

- contaminants are usually hydrophobic

31
Q

u-shaped curves

A

essential nutrients can have adverse effects at low and high doses

32
Q

hormesis

A

compounds that are beneficial/stimulatory at low doses but toxic at high doses

33
Q

nonmonotonic dose-response curves

A
  • toxicants have effects at low levels
  • low levels they interact with a hormonal receptor
  • high levels receptor can burn out, response decreases
34
Q

sub-lethal responses

A

toxic events occur before the animals die

35
Q

subchronic bioassay

A
  • high dose that causes toxicity but not more than 10% fatalities
  • an intermediate dose
  • low dose that should cause no toxic effects
  • exposure for longer periods of time
36
Q

why do a sub chronic test

A
  • information on all types of sub chronic toxicity that might occur
  • establish dose regimens for chronic studies
  • provide data which will allow an estimate to be made of the MTD (maximum tolerable dose), no significant impairment of growth
  • biomarkers of exposure
37
Q

observed during the study

A
  • altered growth rate

- behavioural changes

38
Q

after the exposure period see what deviates from normal

A
  • mass
  • blood chemistry
  • biochemical
  • cell membrane permeability
  • enzyme activity
  • organ and tissue damage
39
Q

Biomarker

A

a cellular or biochemical response to a toxicant that is measurable in a biological system or sample

40
Q

biomarkers include

A
  • enzyme activity
  • changes in cellular receptor amount and activity
  • changes in hormone levels
  • increased/decreased expression of genes that respond to toxicants
  • changes in the histology of cells to detect cellular damage
41
Q

carcinogens

A
  • classified based upon what is known from humans and animals
  • experiments are expensive
42
Q

reasons for low testing of chemicals

A
  • not required
  • lack of funds
  • expensive
  • difficult to test interactions
43
Q

test results and who does them

A
  • considered innocent until proven guilty
  • government does not test
  • industry conducts tests and gives the results to the government

Toxicology (14 decks)

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