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This article reviews data that have accumulated since the early 1970s on the role of the dorsomedial hypothalamic nucleus (DMN) in neuroendocrine and autonomic homeostasis. Both the ventromedial hypothalamic nucleus (VMN) and the lateral hypothalamic area (LHA) project to the DMN, which in turn projects to the paraventricular nucleus of the hypothalamus (PVN), thus placing the DMN at an important nodal point of neuroendocrine/autonomic circuitries. The DMN is composed of cells and fibers containing neuropeptide Y (NPY), and the nutritional status (starvation-refeeding) is reflected in NPY levels of both VMN and DMN in Sprague-Dawley, Zucker (fa/fa), and corpulent rats (cp/cp JCR:LA). The DMN is involved in the final common pathway of corticotrophin-releasing hormone (CRH) secretion by the PVN, sympathetic nervous system outflow to the adrenal gland, and brown adipose tissue (BAT) thermogenesis. The DMN is also part of a "fear circuitry" regulating cardiovascular responses to stress such as myocardial blood flow and the tachycardia associated with the defense reaction. This appears to be mediated by a gamma amino butyric acid (GABA) mechanism. Although exhibiting reduced ponderal and linear growth and hypophagia and hypodipsia, the rat with DMN lesions (DMNL rat) has normal body composition, anabolic hormone levels, and intermediary metabolism, and it responds normally to numerous endocrine, nutritional, intra- and extracellular thirst and body weight-regulatory challenges. The DMNL rat shows normal efficiency of food utilization, but shows an attenuated response to the feeding-stimulatory effect of insulin. The only other lesion-induced abnormalities are hyperprolactinemia and a disrupted circadian corticosterone rhythm. The hyperprolactinemia in DMNL rats appears to be related to an attenuation of dopamine (DA). Rats with DMNL are capable of mating and can bear offspring, but there is a dramatic effect on litter size and other litter parameters that only improves when one parent is a DMNL rat. Antiaging effects produced by DMNL are evident in the prevention of age-associated microalbuminuria and kidney lesions, as well as, in prevention of the age-related decline in circulating insulin-like growth factor I (IGF-I). Recent evidence suggests that DMN, together with the VMN and the arcuate nucleus (ARC) of the hypothalamus, may be part of the circuitry that is responsive to the feedback signal from adipose tissue by the hormone leptin. The above findings and others suggest that the DMN plays a diverse role in physiological regulatory processes. 相似文献
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Human aldehyde dehydrogenase isozymes were inactivated by N-tosyl-L-phenylalanine chloromethyl ketone (TPCK), an inhibitor of chymotrypsin. The inactivation was a first-order process that followed saturation kinetics. NAD and chloral when used together protected against inactivation. In steady-state kinetics, TPCK produced only slope effects versus varied NAD, both slope and intercept effects versus varied glycolaldehyde were produced, indicating that TPCK reacted with the same enzyme form with which NAD reacted. Ki values from steady-state kinetics and saturation kinetics were comparable. Use of [3H]-labeled TPCK showed that inactivation was associated with the incorporation of two molecules of TPCK per molecule of enzyme. The label incorporation occurred into a single tryptic peptide and also into a single chymotryptic peptide of the E1 isozyme. Purification of labeled peptides, followed by sequencing, demonstrated that E398 of aldehyde dehydrogenase was labeled. Reaction of a haloketone, TPCK, with a carboxyl group of E398 indicates that E398 occurs as a "naked anion" within the molecule. This paper constitutes identification of the second (after E268) "naked anion" at the active site of aldehyde dehydrogenase. 相似文献