8a Flashcards
What are sublethal effects
includes responses to doses or concentrations below those resulting in somatic death
What do you look for when measuring sublethal effects
- Usually looking for an adverse effect
- may look at traits such as growth, reproduction, behavior, development ect.
True or false: the term sublethal effects is used somewhat ambiguously in ecotoxicology
True
True or False: toxin levels that have sublethal effects in the lab will not result in organism’s death in nature
false, they could result in death
What is ecological mortality
described as the reduction of organism fitness in the ecosystem that results in death due to a toxin exposure
Can sterility be considered ecological death
YEs
How can an organism minimize sublethal effects
by avoidance of contaminated areas by animals that are mobile
What are cellular stress responses?
- heat shock
- SOS response
What is the initial stage of selyean stress
fight or flight response
What is selyean stress
a specific set of physiological responses which make up the body’s attempt to reestablish or maintain homeostasis, when under the influence of a stressor
Are reactions that are specific to a given insult included in selyean stress
No, Ex: Metallothionein production in response to metal exposure is not an example of selyean stress
What is selyean stress a part of
General adaptation syndrome (GAS
What is GAS
General adaptation syndrome
What is a fight or flight response
- Sort term response
- HEart rate, blood pressure increases
- Release of adrenaline, reduced blood supply to digestive system, increased blood supply to skeletal muscle
What is an adaptation reaction
- Longer term response to persistent stressor
- Enhanced tissue level response
a. Example: enlarged adrenal glands
b. May also see shrinkage of thymus, lymph nodes, spleen
c. Appearance of gastric ulcers
What is the exhaustion phase
- Long term exposure may result in the stressor exceeding the individual’s ability to maintain homeostasis
a. May eventually lead to death
What is one issue of using growth effects as sublethal effects
One issue is that it does not usually show underlying cause for the growth effects
a. Example: fish growth decreases under acidic conditions
What are some causes of growth effects
i. Lack of food
ii. Dealing with stress therefore less energy can be put into growth
iii. Osmotic regulation problems
iv. Excretion of dissolved metals
v. Interference with growth hormones
vi. Respiration problems due to increased mucus in the gills
vii. Difficulty feeding
viii. Tissue damage (acid burns)
Can growth responses be very complex?
YEs, example: toxin exposure resulting in higher growth rate but decreased longevity
-example: later compensatory growth may mask toxin effects
Can low toxin concentrations actually increase growth compared to a control
Yes,
- Nonspecific response
- Called hormesis
- May result from overcompensation to low levels of stressors
- In some cases can result from the toxin acting as a nutrient at low concentrations.
Example: copper in the copepod data.
What are teratogens
Agents capable of causing damage to the fetus or embryo during development
Name some common teratogens
- Hg
- Thalidomide
- Radiation
True or false: some contaminants slow growth but do not produce physical abnormality
-True,
Do teratogens have a definite threshold dose
yes
do all teratogens roduce characteristic defects
no, some are relatively nonspecific
Are some teratogens only problematic at specific times in development
yes
What is Karnofsky’s Law
any agent will be teratogenic if present at concentrations, or intensities that produce cell toxicity.
What are some biochemical effects that can lead to teratogenic effects
- disrupt mitosis-> abnorm cell interaction
- Interfere with RNA->ab cell migration
- protein sythesis -> abnorm growth
- metabolic disruptions -> excessive cell death
- nutritional deficits -> inadequate cell death
What does the focus of teratogens tend to be on
affect the female and the egg
EX: exposure across placenta
EX: exposures prior to fertilization (contaminants in yolk ect.)
True or false: New evidence suggests that exposure of men and sperm may also result in disease or birth defects
true,
What is behavioral teratology
Exposure to teratogens may also result in behavioral changes in individuals that appear to be morphologically normal.
What type of assay is commonly used to asses teratogenic effects
Fetax assay
How do you preform a Fatax assay
- combine eggs and sperm
- exposure fertilized eggs to various concentrations of contaminants for 96h
- score number of deat eggs and number of living embryos with development abnormalities
What are the benefits and downsides of a Fatax assay
- Easy to obtain large amounts of eggs and sperm
- Procedure is well established
- large comparison database available
- problem: not native to North america or europe
How to you calculate values in a fatax assay
- calculate LC50 bases on eggs and EC50 (TC50) for embryos
- calculate teratogenic index (TI=LC50/EC50
- higher values indicate greater hazard
- some authors believe the hazard is minimal if TI<1.5
What has the fatax assay been proposed to be used for
a screening test for hazard identification to reduce to a minimum the number of mammal used in testing
How many embryos per dose level does a fatax assay usually have
40 to 50 (with 80 to 100 for the concurrent control group)
-This test is also typically done with and without metabolic activation of the toxin
When is a fatax screening test used
- in early stages of product development to guide choices which will result in the least developmental toxicity
- To compare toxicity of new compounds which are only slight alterations of the parent compared
- as a screen for compounds not typically tested for development
What is developmental stability
ability of an organism to develop a consistent phenotype within a given environment
What can developmental stability an indicator for
contamination
-correlated with “fitness” if an organism doesnt achieve a consistent phenotype, then they are less able to survive or reproduce as successfully
What is fluctuating asymmetry
deviations from bilateral symmetry (think of the crab with one huge claw and one little claw)
True or false: Need to know about biological asymmetries that are “normal” for the species in question to avoid unwarranted conclusions.
True
What is one of the most useful yard sticks when measuring sublethal effects
reproduction
What are some indicators you could use as a physiology effect of sublethal effect
- Impaired feeding,
- respiration,
- movement, or social interactions may be caused by toxins interfering with sensory or motor neuron function
What are some physiological effects you might measure in animals
- Speed/stamina
- Ion regulation
- respiration rate
- Osmoregulation
- excretion
- food conversion efficiency
- disease resistance
What are some physiological effects you might measure in plants
- water status
- N and C fixation
- stomatal function
- chlorophyll content
- root growth
- photosynthesis
- Respiration
What is the metabolic scope
differences betwen o2 use under high and low activity levels (crab lab)
What is the O:N ratio
compare o2 consumption vs. N excretion (used to measure relative use of CHO and lipid vs. amino acids for energy
What is scope of growth
A measure of the energy available for growth and reproduction
how do you estimate the scope of growth if you consider that animals and plants have finite amounts of energy
P=A-R-U
P=Growth
A=Energy from food
R=energy used for respiration
U=energy used for excretion
What is the adenylate energy charge
Shows the balance of energy transfer between catabolic and anabolic processes
AEC= ((ATP+0.5ADP)/(ATP+ADP+AMP))
Why has AEC been shown to drop for crayfish exposed to Cd
Cells are less able to build new macromolecules as they have less energy available to do so
Where is behavioral toxicology usually measured?
in a lab setting
Where does bias come from in behavioral toxicology
in scoring (subjectivity)
What are some of the problems with behavioral toxicology
extrapolation from lab to ecosystem
When is behavioral toxicology the most powerful
if combined with other sublethal effect data
What does NOEC stand for
No effect concentration: a. Highest test concentration with results which are not significantly different from the control
What does LOEC stand for
lowest observed effective concentration
-Lowest test concentration which shows results significantly different from control
What does MATC stand for
maximum acceptable toxicant concentration
-A concentration between LOEC and NOEC presumed safe as no observable effect is seen
What does a safe concentration mean?
the maximum amount of toxin in water that still allows normal propagation of fish and other aquatic life
What are some problems with NOEC and LOEC
Highly dependent on experimental design
- High error values or low levels of significance for testing will increase NOEC, LOEC values.
- MATC cannot be generalized beyond that expt.
- Statistical significance does not guarantee biological relevance
