Biologic Markers in Reproductive Toxicology (1989) / Chapter Skim
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17. Introduction
17. Introduction
Pages 205-210
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From page 205... ...
Interpretation of markers often is plagued by the absence of critical assays or by inappropriate application of or failure to apply available diagnostic methods. For example, amniocentesis and chorionic villus biopsy have not been used to document potential adverse effects of xenobiotic exposure.
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From page 206... ...
Trophoblast cells in each mammalian species differentiate according to a species-specific series of morphologic and functional changes before interacting with the maternal vasculature and establishing a definitive placenta. During the course of these changes, the embryo initiates rapid cell division, growth, and differentiation that culminates in gastrulation.
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From page 207... ...
EMBRYONIC/FETAL CHANGES In utero development is a time-sensitive process during which all mechanisms of possible interactions between and among cells leading to cellular proliferation or degradation result in modified structural and functional changes. Individual processes indicate not only cellular sensitivity but critical windows of development in which specific agents may induce damage, for example: · Thalidomide appears to produce its major effects on development in humanslimb abnormalities-when exposure occurs between 25-40 days of development.
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From page 208... ...
These interactions between normal physiology and drug therapy demonstrate how xenobiotics can alter fetal and maternal function without compromising fetal survival. The fetal adrenal gland also produces large amounts of cortisol, which is important in the maturation of the lung, pancreas, and other organs and which initiates hormonal events in extraembryonic tissues (including a decrease in progesterone and increases in estrogen production and prostaglandin synthesis)
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From page 209... ...
For instance, hCG is luteotropic; it stimulates increased progesterone production by the corpus luteum cells. hCG also increases placental conversion of precursors to pregnenolone and progesterone and demonstrates thyroid - s ti mutating - ho rmone-like activities.
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