Gestation process

The next target is the gestation process itself. As outlined above, a number of alkaloids are mutagenic and lead to malformation of the offspring or directly to the death of the embryo (Table V). The last step would be the premature abortion of the embryo. This dramatic activity has been reported for a number of allelochemicals, such as mono- and sesquiterpenes and alkaloids. Some alkaloids achieve this by the induction of uterine contraction, such as the ergot and lupine alkaloids (312). 

Approximate gestational processes Eye formation Mammalian blastocyst formation Early/mid organogenesis of entire All processes in fish... 

In the view of this and other Shangqing texts, however, the gestation process also accounts for the creation of knots and nodes (jiejie) their function is holding together the five viscera, but eventually they are responsible for one s death ... 

The POMC protein is processed differendy in the anterior lobe than in the intermediate lobe. The intermediate lobe of the pituitary is mdimentary in adult humans, but it is active in human fetuses and in pregnant women during late gestation and is also active in many animal species. Processing of the POMC protein in the peripheral tissues (gut, placenta, male reproductive tract) resem-... 

The process of retinal vascularization is unique. Before the fourth month of gestation, there are no blood vessels in the human retina, the inner layers being nourished by the embryonic system of hyaloid vessels in the vitreous. 

As with the development of other organ systems, the development of the immune system is a highly regulated process. Table 19.1 and Figure 19.1 provide a list of known events or markers that occur during immune system development. In humans, hematopoiesis begins at approximately 3-4 weeks of gestation with the development of blood... 

A similar study examined the role of experience, using the movements of rat fetuses in an externalized uterus in response to intraoral infusion of lemon or mint extracts on day 19 of gestation. Prior experience does indeed affect fetal responses. There is habituation to repeated stimulation, central processing of sensory information, fetal orienting reflexes to novel stimuli, and prenatal states exist that are associated with different response patterns (Smotherman and Robinson, 1988). 

The conduct of clinical research in humans raises numerous legal and ethical issues of significant importance. After a lengthy process of gestation, the European Commission has now officially... 

In mice, exposure to DDT during gestation and in the neonatal stage has also caused developmental neurotoxicity, in the form of behavioral deficits in the learning process, that persisted into adulthood. Human studies have suggested that alterations in functions that are hormonally controlled such as duration of lactation, maintenance of pregnancy, and fertility may occur from DDT exposure. ... 

The information processing capabilities of the brain are enormous. The nervous system starts developing early in gestation and continues to grow and change,... 

This study is performed in two species, a rodent (usually the rat) and a non-rodent (nearly always the rabbit). Pregnant females are fed the treated diet from the day of implantation of the embryo through to the end of gestation (i.e., through the embryonic and fetal periods). The females are euthanized shortly before they would have given birth and the femses are examined to detect any strucmral abnormalities. The dams unfortunately cannot be left to give birth namrally because they tend to eat any malformed pups before they can be examined. The fetuses are sampled and processed for detailed examinations of the soft tissues and the skeleton (see Chapters 16-21). 

Fig. 3. Skeletal and soft tissue anatomical features can be scrutinized and labeled for compilation purposes. (Left) A rat gestational day 21 (GD21) skeletal specimen, 3D volume rendering. (Middle) fsA PO specimen with on-screen thresholding optimized to detail the skeletal features of inferesf. (Right) The same rat PO specimen, processed for soff fissue visualization, with relevant soft tissue features of inferesf highlighted.

Different cell populations die at different times. For example, in rodents, sympathetic neurons are pruned down by mid-gestation, whereas for cranial regions of the neuraxis the phase of cell death extends into the perinatal period. In the mammalian cerebral cortex, it has been estimated that approximately 40% to 50% of neurons die, and this process is completed in rat by the third postnatal week in concomitance to synapto-genesis (Ferrer et ah, 1990 Fig. 1.7). 

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