CB41: Teratogenesis Flashcards
Define teratogenesis.
The process leading to developmental abnormalities and their causes.
Define teratology.
The study of developmental abnormalities and their causes.
Define teratogen.
A substance, agent or process that induces the formation of developmental abnormalities in a foetus.
What is the teratogen that prevents morning sickness in pregnant women?
Thalidomide
Which potent teratogen is an abti-coagulant causing nasal hypoplasia and when is it most potent?
Warfarin, it’s most potent in the first trimester.
Name general teratogens.
Ionising radiation, chemicals (heavy metals, alcohol, DDT, lead, dioxin), placental failure/malfunction, extreme temperatures, metabolic & dietary imbalances, bacterial/viral/protozoan infections, thalidomide, warfarin.
Which teratogens specifically cause DNA or chromosomal abnormalities?
Ionising radiation, chemicals that combine with DNA (anti-cancer drugs & carcinogens), chemicals that interfere with DNA synthesis (folic acid antagonists) & chemicals that interfere with cell division (benzimidazoles).
What affects the frequency of congenital malformations?
The species, the breed, geographical location and more.
What is the frequency of congenital malformations in liveborn animals of different species?
Infrequent in cats
3-4% in horses, sheep and cattle
6% in dogs and pigs
State Wilson’s 6 principles of teratology.
1) Susceptibility of the conceptus depends on its genotype and its interaction with environmental factors.
2) Access of a teratogen to the conceptus depends on its physical & chemical nature.
3) Susceptibility varies with the age at which the conceptus is exposed.
4) Timing, size & duration of exposure to teratogen all influence its effects.
5) Teratogens act in specific ways to cause abnormalities.
6) The main manifestations of teratogenicity are death, malformation, growth retardation & functional deficits.
Which teratogens have more access to the conceptus?
Small, non-polar molecules.
When is the conceptus most susceptible to teratogens?
During early organogenesis
Why is the conceptus less susceptible to teratogens during histogenesis?
Because the body planes are stable and fixed.
What is simple causation in teratogenesis?
1 teratogen has 1 effect
What is alternative causation in teratogenesis?
When many teratogens have the same effect.
What is partial causation in teratogenesis?
When the teratogen along with something else has an effect, but the teratogen alone does not have an effect.
What is indirect causation in teratogenesis?
When the teratogen activates another teratogen, which activates another teratogen, which activates another teratogen which has an effect.
If the embryo is infected with Bovine Viral Diarrhoea during the first 30 days, what are the effects?
Embryo death
If the embryo is infected with Bovine Viral Diarrhoea between 30-90 days, what are the effects?
Abortion
Mummification
CNS abnormalities
Eye abnormalities
Cerebellar hypoplasia
Alopecia
Microphthalmia
Retinal dysplasia
If the embryo is infected with Bovine Viral Diarrhoea before 120 days, what are the effects?
Permanent infection (immunotolerance)
If the embryo is infected with Bovine Viral Diarrhoea after 120 days, what are the effects?
Signs of disease can be absent as foetus is immunocompetent.
What is veratrum californicum teratogenic to?
Sheep, cattle & goat.
What is the teratogen in veratrum californicum?
Steroidal alkaloid cyclopamine
What are the effects if veratrum californicum is fed to dams before 14 days of gestation?
Head deformities such as cyclopia
