Development of the epicardium is critical to proper heart formation. It provides all of the precursor cells that form the coronary system and supplies signals that stimulate cardiac myocyte proliferation. The epicardium forms from mesothelial cells associated with the septum transversum and is referred to as the proepicardium (PE). Two different methods by which these PE cells colonize the developing heart have been described. In avians, PE cells form a bridge to the heart over which PE cells migrate onto the heart. In fish and mammals, PE cells form vesicles of cells that detach from the mesothelium, float through the pericardial cavity, and attach to the heart. A previous study of rat PE development investigated this process at the histological level. Protein markers have been developed since this study. Thus, we investigated this important developmental process coupled with these new markers using other visualization techniques such as scanning electron microscopy (SEM) and confocal microscopy. Finally, a novel, three-dimensional (3-D) culture system was used to confirm the identity of the PE cells. In this study, we found convincing evidence that the rat PE cells directly attach to the heart in a manner similar to that observed in avians.

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Uncertainty exerts powerful influences on life history decisions. This has been demonstrated in experiments on nonhumans and in mathematical models. Studies of human populations are suggestive of the effects of uncertainty, but they rely on measures of environmental stress. In this paper, we derive a new measure of uncertainty, upsilon (υ), for use in non-experimental studies. We estimate its association with reproductive behaviors in a longitudinal panel sample of adolescents in the United States. Results show upsilon's internal structure is consistent with theoretical models of uncertainty. Its associations with reproductive outcomes are also consistent with theoretical predictions. Upsilon seems to have its largest effect on the timing of fertility-increasing the odds of early fertility by a factor of 7, net of the effects of control variables. We discuss our findings for the association between υ and the timing of reproductive effort as well as our future research on υ.

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During the past four decades, numerous reviews have been published on biological responses to stressful social environments. Reviews targeted for audiences in the social sciences emphasized biological outcomes while skipping over explanations of biological mechanisms. This chapter focuses on the details of the hormonal processes that “report” the state of the environment to the nervous system and regulate cognitive and motor responses to stressful social stimuli. Steroid hormones receive most attention. The chapter concludes with an outline of a sociological model of social action based on current knowledge of hormone actions. It shares some of the basic ideas of previous models such as affect control theory. However, the model proposes a broader role of stress hormones in human social behavior.