Developmental effects pattern

Figure 7 shows the effect of ectopic administration of T3 to the developing zebrafish embryo. At nontoxic concentration (50 nM), only a moderate fraction (less than 5%) of the zebrafish transcriptome shows significant changes. Ossification, visual processes, and the hematopoietic system were the physiological processes most affected by the treatment, in a pattern consistent with an advancement of the development in these particular functions (Fig. 7b). Genes involved in these three processes are known targets for TDCs during metamorphosis in amphibians, teleost fishes, and lampreys [54—60], and constitute molecular counterparts of different endpoints used to test for TDC in amphibians [56, 58]. Therefore, they are excellent candidates for markers of thyroid disruptors in zebrafish at early developmental stages. Chapter 14 provides a more in-deep description of the developmental effects of thyroid disruption in zebrafish embryos.

Team members provided and coordinated referrals to a variety of community agencies, and supported caretakers in learning about normal infant development, sleep-wake patterns, and feeding schedules and appropriate foods. Caretakers were also helped to understand the infants developmental strengths, what would effectively soothe him/her, and what play activities were appropriate at certain ages. 

Posttraumatic stress disorder (PTSD) refers to a pattern of anxiety, distress, and avoidance following an event experienced as threatening and/or intensely distressing. This disorder has been reported to have behavioral (Zaidi and Foy, 1994) and neurobiological effects into adulthood (Charney and Bremner, 1999). Much of the developmental research on the condition derives from retrospective studies of adults. The many possible biases inherent in such research preclude the generation of firm conclusions on the developmental course of the condition. An important process in the study of PTSD will be to identify the developmental path of the disorder in the context of the prevalence of anxiety disorders in childhood (Costellot et ah, 1996 Pynoos et ah, 1999). 

Minor changes in the stereochemistry and substitution pattern of the steran skeleton result in vastly different yet specific physiological and pharmacological effects, which in turn influence developmental, metabolic, and behavioral phenomena. The organic chemistry and biochemistry of steroids is the subject of many excellent books and an enormous amount of research and patent literature. This chapter compares and contrasts the structure and mode of action of various steroids, their role in regulating hormonal secretion, and the timing of this regulatory action. 

Influence of developmental regulatory genes on one another. An arrow with a plus sign at the arrowhead indicates a positive effect on expression, whereas a minus sign at the arrowhead indicates a negative effect on expression. The gap genes are essential for the establishment of the hairy and runt banded patterns, but the precise way in which they do this is unclear. 

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