Flashcards in 25 - Teratology I Deck (28)
The study of congenital defects
Annual # of birth defects in live births in US
Number of infant deaths, stillbirths, and spontaneous abortions believed to be due to defects in prenatal development.
Percentage of defects due to spontaneous genetic errors
Percentage of defects relatable to the use of certain drugs
Percentage of defects of which the cause remains unknown
How many drugs does the average woman take during her pregnancy?
10 (most without supervision of physician)
How many women are exposed to potential chemical teratogens in their jobs annually in the US?
What % of abnormalities can be detected at birth?
What % of early embryos are estimated to die unrecognized?
What % of recognized pregnancies abort spontaneously?
In some cases a birth defect may be detected but a causal link to a specific agent may not be made, why?
because that defect is only expressed under conditions of a genetic predisposition or of certain physiological or pathological states or environmental stresses
What is a major problem with most human teratological studies?
They are confined to the perinatal period and do not adequately evaluate the maturation process.
If children are monitored for about 5 years after birth the total number of defects discovered...
increases 6 times (and some anomalies such as cardiac defects or behavioural problems may not be detected until even later)
Girls exposed to this do not develop vaginal adenocarcinomas until puberty.
Give an example of a drug that has different teratogenicity in humans vs other species.
Thalidomide - essentially nonteratogenic in rodents but potent teratogen in humans
(Teratogenicity of thalidomide dose 0.5-1 mg/kg in humans = 5 g/kg in rodents)
List 17 proven or suspected human teratogens.
8. Isotretinoin (Accutane)
17. Valproic acid
List 7 teratogenic anticancer drugs
Describe the critical period
The natures and frequencies of birth defects produced by any given teratogen depend on the developmental stage at the time of exposure.
When is a human most sensitive to chemical damage?
As an embryo or fetus
Why is the embryo/fetus so sensitive to chemical damage?
An extremely high rate of cellular proliferation and differentiation over a brief period of time
Give an example of the high rate of cellular proliferation and differentiation in a short amount of time.
the DNA content of a mouse fetus increases 1 million fold in the 1st half of gestation
Describe the developmental process and teratologic consequences for fertilization to blastocyst implantation.
Developmental process - Cellular division
Teratologic consequence - prenatal death
Describe the developmental process and teratologic consequence for embryonic period.
Developmental process - cellular differentiation and organogenesis
Teratologic consequence - major morphologic abnormalities
Describe the developmental process and teratologic consequence for the fetal period.
Developmental process - histologic differentiation and functional development
Teratologic consequence - functional defects and minor morphologic abnormalities
How can cleft palate be induced in mice?
Introduction of teratogens between gestational days 8-13
Describe the 5 steps to the closure of the palate.
1. Initial proliferation of cells
2. Synthesis of intercellular substances
3. Elevation of the two palatal shelves from the vertical to the horizontal position
4. Midline contact and fusion
5. Formation of the bony plate