The sympathetic nervous system, leptin, and renin-angiotensin system (RAS) have been implicated in obesity-associated hypertension. There is increasing evidence for the presence of both leptin and angiotensin II receptors in several key brain cardiovascular and metabolic control regions. We tested the hypothesis that the brain RAS plays a facilitatory role in the sympathetic nerve responses to leptin. In rats, intracerebroventricular (ICV) administration of losartan (5 μg) selectively inhibited increases in renal and brown adipose tissue (BAT) sympathetic nerve activity (SNA) produced by leptin (10 μg ICV) but did not reduce the SNA responses to corticotrophin-releasing factor (CRF) or the melanocortin receptor agonist MTII. In mice with deletion of angiotensin II type-1a receptors (AT(1a)R(-/-)), increases in renal and BAT SNA induced by leptin (2 μg ICV) were impaired whereas SNA responses to MTII were preserved. Decreases in food intake and body weight with ICV leptin did not differ in AT(1a)R(-/-) vs. AT(1a)R(+/+) mice. ICV leptin in rats increased AT(1a)R and angiotensin-converting enzyme (ACE) mRNA in the subfornical organ and AT(1a)R mRNA in the arcuate nucleus, suggesting leptin-induced upregulation of the brain RAS in specific brain regions. To evaluate the role of de novo production of brain angiotensin II in SNA responses to leptin, we treated rats with captopril (12.5 μg ICV). Captopril attenuated leptin effects on renal and BAT SNA. In conclusion, these studies provide evidence that the brain RAS selectively facilitates renal and BAT sympathetic nerve responses to leptin while sparing effects on food intake.

These findings implicate mucoinflammatory processes in the CF lung as pathogenic in the absence of clinically apparent bacterial and fungal infections.

We examined the effects of ischemia with and without reperfusion on endothelium-dependent and -independent vascular relaxation in both conduit and resistance coronary arteries. Studies were performed on dogs under control conditions (n = 13) or after 1 hour of circumflex coronary artery occlusion with (n = 10) or without (n=8) 1 ischemia followed by reperfusion, and VanBenthuysen et a13 subsequently extended these observations in a similar model by demonstrating blunted endotheliumdependent relaxation to acetylcholine. The effect of ischemia and reperfusion on the coronary microcirculation has been less well defined. Mehta et a14 reported impaired coronary flow reserve to acetylcholine and bradykinin after ischemia and reperfusion. Evaluation of the microcirculation in vivo is complicated by myocardial compressive forces, autoregulation, and metabolic influences.5 In addition, effects of ischemia on myocardial perfusion in vivo may at least in part be due to vascular occlusion secondary to white cell adhesion and platelet aggregation. 4'6-8 Thus, the direct effect of ischemia with or without reperfusion on coronary microvessels is unclear and to date has not been evaluated by an in vitro method. Because microvessels play a central role in regulation of myocardial perfusion, their function after ischemia

Background-Rapid intra-arrest induction of hypothermia using total liquid ventilation (TLV) with cold perfluorocarbons improves resuscitation outcome from ventricular fibrillation (VF). Cold saline intravenous infusion during cardiopulmonary resuscitation (CPR) is a simpler method of inducing hypothermia. We compared these 2 methods of rapid hypothermia induction for cardiac resuscitation.

Background-Induced external hypothermia during ventricular fibrillation (VF) improves resuscitation outcomes. Our objectives were twofold (1) to determine if very rapid hypothermia could be achieved by intrapulmonary administration of cold perfluorocarbons, thereby using the lungs as a vehicle for targeted cardiopulmonary hypothermia, and (2) to determine if this improved resuscitation success.

SMGs and basal SC compartments are depleted in large and/or small airways of lung allografts, and basal SC proliferative capacity declines with progression of disease and phenotypic changes. Global airway SC depletion may be a mechanism for pulmonary allograft failure.

These studies were performed to test the hypothesis that left ventricular hypertrophy arising as a complication of chronic hypertension is associated with impaired coronary autoregulation. Twelve

Previous in vivo studies have shown that vasopressin, which releases the endothelium-derived relaxing factor and constricts coronary smooth muscle, produces augmented constriction of coronary microvessels perfused by mature collaterals. We hypothesized that chronic perfusion through collaterals produces endothelial dysfunction in the recipient vasculature. Mature collaterals were stimulated in mongrel dogs by the ameroid constrictor technique. After 3-6 months, rings of conduit vessels (obtuse marginals) were studied in organ chambers, and coronary microvessels (100-220 ,um) were studied in a pressurized, no-flow state with a microvessel imaging apparatus. Eleven dogs were used as controls. Large vessels were preconstricted with prostaglandin F2. to 30-70% of the maximum potassium chloride tension, and microvessels were preconstricted to 20-60% of the baseline diameter with the thromboxane mimetic U46619. Relaxations to the receptor-mediated agents acetylcholine and ADP were markedly impaired in collateral-dependent coronary microvessels, whereas relaxations to nitroglycerin were enhanced compared with microvessels from control dogs. Relaxation to the calcium ionophore A23187, which releases the endothelium-derived relaxing factor through nonreceptor-mediated mechanisms, were similar in control and ameroid microvessels. Constriction to vasopressin was augmented in collateral-dependent microvessels compared with controls. Responses to all agonists were similar between control and collateral-dependent large vascular rings. In conclusion, chronic perfusion through collateral vessels selectively impairs receptor-mediated endothelium-dependent relaxations and augments constriction to vasopressin in the coronary microcirculation. These findings may have important implications regarding neurohumoral regulation of perfusion to collateral-dependent myocardium. (Circulation 1990;81:1938-1947 A fter occlusion of a major coronary artery, the only blood flow to the ischemic myocardium arrives via coronary collaterals.