Effects that begin at low levels of organization cascade up organization levels, give example
biochemical –> subcellular –> cellular –> tissue –> organ –> individual –> population –> community –>ecosystem –> landscape –> biosphere
Why the interest in biomarkers and biochemical mechanisms (4)
- understanding biochemical mechanisms may allow prediction of a new compound’s actions based on currently understood mechanisms
- may allow effects of mixtures to be separated
- may provide basis for understanding cellular or tissue effects
- may provide an early warning system for exposure
True or false - Indicator organism is the same as a sentinel species
TRUE
define a biomarker
a biochemical, physiological, morphological or histological quality used to imply exposure to, or effect of a toxicant
What are biomarkers used for
- used to indicate enough exposure for a sufficient time to generate a response
- usually detectable before higher level damage is measurable
- useful for monitoring cleanup
What is an issue that can arise with biomarkers
showing how biomarkers are ecologically relevant can be an issue
list some useful criteria for biomarkers
- measurable before higher level damage
- measurement should be rapid, inexpensive & easy
- should accommodate QA/QC measures
- should be specific for a toxin or family of toxins
- should be applicable to many sentinel species
- established relationship between biomarker changes & decreased individual fitness
- biological system should be well understood
- biomarkers can include elements of many different responses to toxic substances
define a Sentinel species
Feral, caged or endemic species used in measuring & indicating contamination levels
- look for biomarkers in sentinel species
- can also be called indicator species
True or false - Can detoxification reactions & their products act as biomarkers of exposure to toxins ?
TRUE
Describe phase 1 reactions as biomarkers
depends on cytochrome P450 monooxygenase proteins
- known as a set of isoenzymes
- may have slightly different specificities but same basic reaction
define an Isoenzyme
different forms of the same enzyme coded by different genes
What is the general reaction of a phase 1 reaction as biomarkers ?
& what does it do ?
RH + NaDPH + O2 + H+ –> ROH + NADP+ + H2O
- usually increases solubility of xenobiotics
- may result in increased toxic activity rather than deactivation
- catalyzes hydroxylation reactions
- catalyzes epoxidation, dealkylation, oxidative deamination, oxidation, desulfurations, oxidative & reductive dehalogenation
How may inductions of these phase 1 proteins as biomarker be studied ?
using DNA, mRNA or protein methods
Name a way to detect proteins and list its steps
antibody assays such as ELISA
- Homogenize tissue sample
- Apply to ELISA plate
- Detect with monoclonal antibody vs. marker protein
- Detect 1~ antibody with 2~ antibody linked to a fluorescent marker or enzyme
- Read fluorescence or colour change vs. standard curve
Name another way to detect proteins and list its steps
Detection of mRNA or DNA with specific DNA probes
- Bind mRNA or DNA to nitrocellulose membrane
- label probe with fluorescent or radioactive nucleotides
- Mix probe with membrane
- detect specific binding
What are 3 ways of quantifying the P450 activity by testing for activity of specific enzymes from this group.
- AHH assay - benzo[a]
