Dose-response curves and bioassays Flashcards
what is a hazard
a hazard is the intrinsic properties of a toxicant
what is a risk
the probability of an adverse outcome of being exposed to hazardous toxicant
how do governmental regulations manage risk
by banning the toxicant or reducing the probability of an adverse outcome
how are hazards identified
a. epidemiology data
b. in-vitro test
c. structure activity modelling
d. animal bioassays
what does CCAC stand for?
Candian Council on Animal Care
when was the CCAC established
1968
what are the three R’s
replacement, reduction and refinement
considerations for an experimental design
a. test subjects
b. variables (response variable and controlled variable)
c. carriers
d. biological replicates
e. controls
what does acute exposure mean to toxicologists
hours to days
what are parcelsus’ principles
- One should make distinctions between therapeutic and toxic properties of chemicals
*You cant really differentiate these properties unless by dose
*Experimentation is essential in the examination of responses to the chemicals
*One can ascertain the degree of specificity of chemicals and their therapeutic or toxic effects
how can causation be proved
by animal bioassays
what are the goals for toxicity testing
determine the range of doses that have a toxic effect.
identify the nature of responses to a toxicant.
use this data to form risk assessments
in the study to determine the effect of BPA in our brains using the zebra fish larvae, what was used as the positive control
17-B-estradiol because it induces aromatase, an endocrine disrupting compound
what was the response variable in the BPA experiment
aromatase
what was their controlled variable in the BPA experiment?
28 degrees water and 14h light 10h dark cycle
what was their carrier in the BPA experiment?
DMSO
explain what a graded-dose response relationship is
describes how a response to a stimulus changes in magnitude in an organism as the dose of the stimulus increases
a high therapeutic index values suggests what
that the drug is relatively safe
a low therapeutic index value suggests what
that the drug should be rejected
what is the margin of safety
TD1/ED99
What does NOEC mean
No observable effect concentration
what does LOEC mean
Low observable effect concentration
hormesis is not appropriate for what type of toxicant
xenobiotics
hormesis is a dose-response graph for
compounds that are beneficial at low doses but toxic at high doses
non-montomic dose response curves are often observed for
Endocrine disrupting compounds(toxicants that can have high effect at low doses)
often observed with EDC’s at high levels, the receptors
can be deactivated leading to a decrease in response
why do a subchronic test
to determine the maximum tolerable dose
to develop biomarkers of exposure
what is a biomarker
a biochemical response to a toxicant
