Federation proceedings
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The respiratory control system is influenced by classical neurotransmitters and by neuromodulators. The neuromodulators are neuroactive substances that can be secreted at a distance from their receptors and must diffuse to their site of action. ⋯ The assignment of a natural role for a neuromodulator in respiratory control is strengthened by evidence from a variety of experimental approaches, including localization of receptor sites in respiratory-related areas and evidence for natural binding of neuromodulators to these receptors, neurophysiological and respiratory responses to the neuromodulators and their antagonists, and, finally, modulation of specific respiratory responses by neuromodulator antagonists to document the role of the endogenous modulator in eliciting the original response. Neuromodulators that are considered seriously as natural participants in respiratory control include dopamine in peripheral chemoreception and adenosine, endorphins (including enkephalins), serotonin, and substance P in central respiratory regulation.
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Local mechanisms within the intestine allow it to control its own blood flow independently of nervous or humoral influences. The evidence favoring the metabolic theory of local control is discussed within the framework of a two-component model in which a metabolic feedback signal from parenchymal cells maintains tissue oxygenation by two means: 1) by acting on arterioles to determine blood flow and capillary PO2 and 2) by opening or closing precapillary sphincters to regulate O2 extraction through changes in capillary surface area and diffusion distance. This purely metabolic model correctly predicts the observed responses of both resistance vessels and exchange vessels in most of the phenomena indicative of local control: functional hyperemia, reactive hyperemia, hypoxic vasodilation, pressure-flow autoregulation, and the enhanced pressure-flow autoregulation produced by lowering the prevailing O2 availability-to-demand ratio. The possibilities are discussed that interstitial hypoxia or adenosine might be the feedback signal in the metabolic regulation of intestinal blood flow.
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Federation proceedings · Jun 1981
Neural effects on cerebral vessels: alteration of pressure-flow relationship.
Cerebral vessels are well innervated by adrenergic and cholinergic fibers. Effects of sympathetic stimulation on cerebral blood flow (CBF) are controversial, but we have concluded that, during normotension and hypotension, sympathetic nerves have little effect on CBF. During acute hypertension, however, sympathetic nerves may have important effects of CBF. ⋯ Disruption of the blood-brain barrier, which occurs during severe hypertension, also is minimized by sympathetic stimulation. Thus, the concept has emerged that, in contrast to minimal effects of sympathetic nerves under most conditions, sympathetic stimulation may have important protective effects during hypertension. The role of cholinergic nerves in regulation of CBF has not yet been clarified.
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National Nutrition Surveillance includes nutritional assessment surveys to ascertain the extent of malnutrition in populations, to identify possible causes, to establish baseline data for monitoring nutrition, and to select mechanisms for nutrition surveillance (in a restricted sense). An example of the results from a recent nutritional assessment survey in the United States is the negative association of obesity with energy intake, exercise and socioeconomic status, which has implications for public nutritional policy. Nutritional monitoring measures changes in population nutrition over time. ⋯ This research indicates that malnutrition involves more than under-nutrition, and greater emphasis should be given in National Nutrition Surveillance to this wider context of malnutrition. These results will in turn help set priorities for basic and applied research in nutrition. It is important that the research community participate in the review presently under way of the role of the National Center for Health Statistics in National Nutrition Surveillance.