The better adaptation of native Tibetans to hypoxia is thought to be partly due to improved umbilical circulation, which results in reduced pre- and postnatal fatalities. We hypothesized that the difference in umbilical circulation between native Tibetans and other high-altitude inhabitants was due to differences in the expression of hypoxia-induced factor (HIF-1) and its target genes vascular endothelial growth factor (VEGF) and inducible nitric oxide synthase (iNOS). We tested this hypothesis by examining the effect of hypoxia on the expression of HIF- 1a, VEGF, and iNOS in cultured umbilical venous endothelial cells (UVECs) from native Tibetans and immigrant Hans. UVECs were collected and cultured under hypoxic (0.5% oxygen) or normoxic conditions for 2, 4, 12 and 24 h. The mRNA levels of HIF-1a, VEGF, endothelialnitricoxidesynthase(eNOS)andiNOSandtheproteinlevelofHIF-1aweredeterminedwithRT-PCRandWesternblotanalyses, respectively. In both immigrant Han and Tibetans, HIF-1a mRNA was constitutively expressed under normoxic condition, and remained constant after hypoxic exposure. In contrast, HIF-1a protein was undetectable under normoxic condition, but underwent dynamic changes in response to hypoxia. It was induced at 4 h, peaked at 12 h, and remained elevated at 24 h. Concurrent with the induction of HIF-1a protein, the mRNA levels of VEGF and iNOS were also up-regulated whereas that of eNOS was down-regulated. The lack of a hypoxia-related difference in the expression of HIF-1a and its target genes suggests that HIF-1a does not play a critical role in high altitude adaptation. Alternative mechanisms may be responsible for the better adaptation of native Tibetans. D 2005 Elsevier Inc. All rights reserved.

The purpose of the study was to investigate the effects of agmatine, an endogenous clonidine-displacing substance (CDS), on systemic hemodynamics in the anesthetized rat. Bolus intravenous (i.v.) injections of agmatine decreased systemic arterial pressure (SAP) and systemic vascular resistance in a dose-dependent manner. The development of acute tachyphylaxis to the systemic vasodepressor response to agmatine did not induce cross-tachyphylaxis to the systemic vasodepressor responses to bradykinin, isoproterenol and nitroglycerin. The present data demonstrate agmatine, as a CDS and agonist for imidazoline (I) receptors, possesses marked systemic vasodilator activity in the rat. The present data suggest that activation of I receptors may represent a novel mechanism of vasodilation in vivo.

ABSTRACT-The importance of gastrointestinal injury in endotoxin-induced shock and multiple organ failureis of great interest. In this paper we describe a method to assess the degree of intravascular congestion and bleeding into the wall of the intestine by determining the hemoglobin content of the tissue. After validating this method, we used it to study the mechanism of jejunal injury induced by intravenous injection of Escherichia coli lipopolysaccharide (LPS, 50 mg/kg bw), the role of nitric oxide release in maintaining the integrity of endothelial cells, and the participation of H202 production in the LPS-induced intestinal damage in rats. Our results show that afterthe administration of LPS at the dose of 50 mg/kg intravenously, the hemoglobin content of the jejunum (17.8 mg/100 mg tissue) increased 7.7-fold over that of control animals (2.3 mg/100 mg), reflecting a serious degree of congestion, bleeding, and damage in the gastrointestinal tract. Administration of nitro-L-arginine methyl ester (L-NAME) not only enhanced this injury, but also markedly decreased the dose of LPS necessary to induce intestinal damage. Infusion of L-arginine (300 mg/kg bolus plus infusion 600 mg/kg'h intravenously) protected the intestine against LPS or LPS plus L-NAME. Inhibition of basal nitric oxide release by L-NAME produced significant changes in cardiovascular variables, but failed to induce a significant bleeding damage. However, when inhibition of NO release was combined with enhanced H202 production by a small dose of LPS, a serious bleeding damage was observed. This was accompanied by a marked decrease in mesenteric blood flow and cardiac output. High dose of LPS induced the above effects, and thus could be responsible for the bleeding damage, while low dose of LPS that fails to inhibit nitric oxide, did not induce any intestinal bleeding. It seems that inhibition of NO release and stimulation of H202 production are both involved in the LPS-induced bleeding damage.

目的 研究制定适合我军高原部队使用的评价高原习服的国家军用标准和方法。方法 遵照国家军用标准制定规范,系统回顾总结多年来的研究成果,广泛征求高原医学有关专家的意见,针对部队的实际情况,本着科学、简便、易行的原则,制定出本标准。结果 将高原习服分为初步习服、基本习服和完全习服,其判断指标和依据为习服时间、基础生理指标（呼吸次数、血压、脉率、红细胞计数、血红蛋白）和体能评价指标（VO2max和1000m跑成绩） 。结论 制定了对我军高原部队有实际指导意义的评价高原习服的标准和方法,并讨论了影响高原习服的因素及意义。