Teratology I Flashcards
4 Causes of teratology?
- Genetic
- Nutritional
- Infectious
- Toxins
Definition of teratogen
Increases the occurence of structural or functional abnormalities in the offspring after administration to:
Either parent before conception
Female during pregnancy
Directly to the developing fetus
What does susceptibility vary with?
Developmental stage at time of exposure
What occurs if exposure occurs durring predifferentiation (1-32 cells)
Interferes with implantation
Typically ends in death
What occurs if exposure occurs during early differentiation (gastrulation, patterning, morphogenesis)
Impacts on structural development
Greatest impacts of teratogens
What occurs if exposure occurs during Advanced organogenesis?
Major structural abnormalities
Difference between exposure at early differentitation and advance organogenesis?
Early differentiation - can have complete absence of organ
Advanced organogenesis - At least portion of organ present
What is Aneuploidy?
Abnormal number of chromosomes
What is polyploidy?
More than two paired (homologous) sets of chromosomes
What is most common result of chromosome abnormalities?
Most are aborted
Affect of gametogenesis arrests in females
Longer they are arrested the greater the chance of abnormalities
What is the most common chromosomal abnormality in the horse?
XO, only a single sex chromosome is present
What is dysgenesis?
Abnormal-growth
What are chimeras?
Sharing of genetic material because of vascular anastomoses in twins of opposite sex
What are freemartins in cows/
Male sex hormones of male twin influence female twin, male can be affected too
What is intersex
External characteristics of both male and female, cant tell difference whether male or female
What are the most common reasons for abnormal chromosome structure?
Radiation
Chemicals
Two possible abnormal chromosome structures
- Chromosome breakage or deletions
- Translocations, inversion and centric fusion
Abnormality caused by assisted reproductive technologies?
Large offspring syndrome in cattle and sheep
What is hydroallantois
One of the membranes of placenta has a lot of H2O
What is the gene in sheep which causes for large offspring syndrome
Insulin growth factor 2 (IGF2)
WHat is the importance of placenta differences?
Different types of drugs which cant cross placenta in one species may cross in another
What is the importance of SER?
Any chemical/drug/toxin that requires metabolic activation to act as teratogen requires presence of SER
What does effect of toxicity depend upon?
Route or site of exposure
Amount or dose
Duration
Frequency or rate of exposure
Individuals genetic resistance, developmental stage, health status and age
Forms of absorbtion?
Oral
Mucous membranes
Skin
IV/IM
Why are teratogens not specific, and what does this result in?
Teratogens are usually not specific because of common pathways
Therefore can see different manifestations with same teratogen
What are 5 common pathways
Cell division
Mitochondria
Cell migration
Blood vessel
Limb development
9 Teratogen Mechanisms
Precursors, lack of
Mutation
Altered DNA
Reduced Energy Source
Enzyme inhibition
Mitotic Interference
Osmolar Imbalances
Chromosomal Abnormalities
Altered Membranes
What is syndactyly
Failure of cell death between digits
Fusion of digits
6 causes of abnormal embryogenesis
Mechanical Disruption
Cell Death
Failure of Cell interaction
Altered Differentiation Schedules
Impaired Morphogenetic movement
Reduced Biosynthesis
4 types of mechanical disruption
Hematoma
Tumor
Xrays
Edema
What does ectopic ureters mean
Ureters dont end up where they should, not connecting to bladder
Two examples of Impaired morphogenic movement
Ectopic ureters
Arthogryposis
Two ways that arthogryposis occurs
Extrinsic
- Crowding
- decreased amniotic fluid
Intrinsic
- Neurological
- Connective tissue abnormalities
3 characterizations of Arthogryposis
Joint Contracture - Joint is smaller
Muscle weakness
Fibrosis
