Abstract # 22:

Scheduled for Thursday, July 31, 2003 01:30 PM-02:30 PM: (Science Theatres 148) Featured Speaker


EARLY PREGNANCY: SUCCESSES AND FAILURES

A. G. Hendrickx
University of California, Davis, Center for Health and the Environment, Davis, CA 95616, USA
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     The first trimester of pregnancy includes critical periods of development that must be successful for delivery of a normal infant. The crucial periods include transportation of the fertilized ovum through the oviduct to the uterus where it implants at one week of gestation. During the second and third weeks, the embryo transforms from a simple cell mass into multiple layers of tissues that differentiate into specialized cells, tissues, and primordial organs. A relatively high level of pregnancy loss occurs during this vulnerable period of pregnancy. In the course of the next five weeks, this simple multi-layered embryo undergoes the process of organogenesis during which all of the major organ systems form. It is during this critical and complex period that developmental abnormalities most often occur since the embryo is unusually susceptible to exogenous agents (drugs/chemicals). For example, thalidomide, a drug marketed for prevention of morning sickness in the early 60's, had highly specific adverse effects on limb development. Following the thalidomide tragedy, the role of the nonhuman primate in the safety assessment of newly developed pharmaceuticals became recognized and additional similarities in humans and Old World monkeys were characterized. Studies involving the developmentally toxic effects of DES (diethylstilbestrol), Accutane (13-cis retinoic acid), and dioxin (TCDD) exemplify the important role played by nonhuman primates in preventing and understanding birth defects.