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Query: UMLS:C0020538 (hypertension)
 170,190 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Three different pressure groups of rats, stroke-prone spontaneously hypertensive rats (SHRSP, 200-270 mmHg), stroke-resistant SHR (SHRSR, 160-240 mmHg), and Wistar rats (WR, 120-160 mmHg) were used to investigate the effect of prior existing hypertension on the severity of brain damage induced by ischemia. The cerebral ischemia was induced by bilateral common carotid artery ligation (BLCL) and the survival rate, cerebral blood flow, cerebral energy metabolites (ATP, lactate c-AMP) and water content were measured. Colloidal carbon perfusion was also performed. Sixteen-week-old male rats were used. The survival rate was observed until 24 hours after BLCL. Cerebral blood flow was measured in parietal cortex by hydrogen clearance method. ATP was measured by luciferin-luciferase method, and lactate by enzymatic method using LDH. c-AMP was measured by radioimmunoassay. Brain water content was measured by freeze-dry method. These measurements were done for animals surviving 6 hours of BLCL. Colloidal carbon perfusion was done according to Ames' Method. The survival rate was lower in the hypertension group. The survival of SHRSP and SHRSR were 20% compared to 71% in WR after 24 hours of BLCL. The cerebral circulation of SHRSP fell abruptly and was near to zero after one hour of BLCL. In SHRSR this fall of cerebral blood flow was prominent in the rats of higher blood pressure. On the other hand there was no apparent fall of cerebral blood flow in WR after BLCL. The cerebral energy metabolites. ATP and c-AMP showed the lowest level in SHRSP which had the negative correlation to blood pressure.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[Experimental cerebral ischemia after bilateral common carotid artery ligation in SHRSP, SHRSR and Wistar rats: correlation between blood pressure and degree of ischemia]. 609 92

The effects of topical application of agents which produce oxygen radicals on cerebral arterioles were studied in anesthetized cats. Xanthine oxidase plus xanthine, which produced superoxide anion radical, hydrogen peroxide, and hydrogen peroxide plus ferrous sulfate, which produced the free hydroxyl radical, induced sustained dilation, reduced responsiveness to the vasoconstrictor effect of hypocapnia, and destructive lesions of the endothelium and of the vascular smooth muscle. Similar effects were produced by arachidonate, 15-HPETE, and PGG2. The effect of arachidonate was inhibited by mannitol, a free hydroxyl radical scavenger, the effect of PGG2 was inhibited by SOD, the effect of 15-HPETE was inhibited by either catalase or SOD. These results suggest that these cerebral vascular abnormalities were produced by a single destructive free radical, probably the hydroxyl free radical, generated via interaction of superoxide and hydrogen peroxide. Cerebral vascular abnormalities similar to those produced by oxygen radicals were also seen after experimental concussive brain injury or after acute hypertension. After brain injury, activation of phospholipase C and increased brain prostaglandin concentration were demonstrated. The vascular effects of brain injury and acute hypertension were inhibited by free radical scavengers. The results suggest that, in these conditions, vascular damage is induced by oxygen radicals generated from arachidonate in association with increased prostaglandin synthesis.
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PMID:Oxygen radicals and vascular damage. 640 99

In order to determine the relative roles of O2 tension and content, CO2 tension, hydrogen ion concentration, arterial blood pressure, and cardiac output in the regulation of fetal cerebral blood flow (CBF), we used radioactively labeled microspheres to measure flow to 20 major brain regions in 24 chronically catheterized fetal lambs. We continually monitored fetal heart rate and blood pressure, and periodically measured arterial PO2, PCO2, pH, and hematocrit. In addition to CBF measurements during control periods, we measured CBF during: 1) hypoxia (O2 content less than 6 ml X dl-1; O2 tension less than 15 torr) induced by having the ewe breathe a gas mixture with low O2 concentration, 2) hypercapnia (PCO2 greater than 50 torr) induced by increasing the maternal inspired CO2, 3) acidosis and alkalosis (7.60 greater than pH greater than 6.60) induced by infusing lactic acid or bicarbonate into the fetus, and 4) hypotension (blood pressure less than 35 mm Hg) and hypertension (blood pressure greater than 55 mm Hg) induced by rapidly phlebotomizing or transfusing the fetus. We used multiple regression analysis and analysis of covariance to examine the dependence of total cerebral blood flow on arterial O2 tension and content, CO2 tension, pH, blood pressure, and cardiac output.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Regional cerebral blood flow: studies in the fetal lamb during hypoxia, hypercapnia, acidosis, and hypotension. 644 Nov 42

Several previous studies have demonstrated an increased prevalence of gout in New Zealand Maoris. The aetiology of the hyperuricaemia and its effect on morbidity, apart from gout, are unknown. A survey of 115 Maori men of working age revealed a history of gout in 10 (8%) and asymptomatic hyperuricaemia in 26 (23%). The relationship of hyperuricaemia with obesity was confirmed. Alcohol did not make an obvious contribution to the prevalence of hyperuricaemia. Hypertension was more common and creatinine clearance lower amongst those with gout, but not significantly so. The frequency of hypertension and mean creatinine clearance were similar to that seen in asymptomatic hyperuricaemia and normouricaemia. Urate clearance was lower in the gouty and hyperuricaemic subjects. The normouricaemic Maoris had a reduced fractional urate clearance compared with normal men elsewhere. They also excreted a relatively small proportion of hydrogen as ammonium. Both these features are characteristic of gout, and suggest that the Maoris' susceptibility to hyperuricaemia has a renal mechanism. Obesity is common amongst the Maoris and accentuates their natural tendency to hyperuricaemia.
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PMID:Hyperuricaemia, gout and kidney function in New Zealand Maori men. 648 33

Sinocarotid baroreceptor control of renocortical and medullary blood flow was examined by hydrogen washout technique in unconscious rabbits. Direction and size of the local renal blood flow depend on the interaction of extravenal nerval influence, the actual blood pressure and the renal autoregulation. The data reveal an important neuroreflectory control of the renal blood flow. The renomedullary flow is not totally determined by the degree of systemic arterial blood pressure. Renal factors thus appear to participate very early and continuously in primary neurogenic forms of arterial hypertension.
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PMID:[The effect of sinocarotid circulatory reflexes on the microcirculation of the kidney]. 653 59

The authors performed a controlled study of induced hypertension therapy for treatment of experimental stroke in unanesthetized monkeys. Ten control and 10 treated animals were subjected to a 4-hour occlusion of the middle cerebral artery (MCA) by an implanted tourniquet. Neurological status and local cerebral blood flow (CBF) were monitored serially. Local CBF was determined by hydrogen clearance in and around the elevated 20% to 40% by intravenous infusion of phenylephrine hydrochloride. Neuropathological evaluation was performed after about 2 weeks. A 4-hour occlusion of the MCA in control animals caused moderate stable neurological deficits, moderate stable decreases in local CBF, and medium-sized infarcts. With induced hypertension, five of 10 treated animals showed neurological improvement, and eight exhibited increased CBF in the ischemic zone. Average infarct size tended to be smaller in the treated group, although the difference did not reach statistical significance. Hemorrhagic infarcts were not observed. In four animals, phenylephrine caused cardiac dysrhythmias and hypotension which were reversed by appropriate measures. In this unanesthetized primate model of moderate experimental stroke, induced hypertension had beneficial effects on neurological status, local CBF, and infarct size without causing hemorrhagic infarction. Induced hypertension may be beneficial for some clinical cases of focal cerebral ischemia.
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PMID:Beneficial effects of induced hypertension on experimental stroke in awake monkeys. 668 9

An experimental study in 12 anesthesized rabbits has demonstrated, by means of the hydrogen clearance test, that carotid sinus baroreceptors participate in the control of both the cortical (CF) and the medullary (MF) renal flow. The direction and magnitude of CF and MF changes in case of sinocarotid reflexes are determined by the relationships between extrarenal nervous effects, systemic blood pressure (BP) and self-regulative response of the cortex and the medulla. Arterial hypotension during depressor sinocarotid reflexes is accompanied by decreased CF and MF, while blood pressure stabilization increases CF and MF in these conditions. Arterial hypertension associated with pressor sinocarotid reflexes is accompanied by decreased CF, whereas MF changes may take different directions depending on the severity of hypertension. In a denervated kidney, sinocarotid reflexes cause CF and MF changes of the same direction as changes in BP, which are, however, less pronounced due to self-regulative intrarenal mechanisms being switched on. Simultaneous denervation of the kidney and BP stabilization can prevent completely CF and MF changes associated with sinocarotid reflexes.
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PMID:[Cortical and medullary circulation of the kidneys in pressor and depressor sinocarotid reflexes]. 674 85

Bilateral carotid artery ligation was made in 14 SHR while rCBF was serially measured with hydrogen clearance. Blood pressure was controlled with an intra-arterial catheter connected to a reservoir. There was no significant correlation between blood pressure and rCBF prior to the carotid occlusion, but afterwards there was a progressively increasingly negative correlation between mean arterial blood pressure and rCBF with time. These observations indicate that the severity of ischemia is greater in the presence of hypertension if the hypertension is present prior to the onset of ischemia and the blood pressure maintained constant thereafter.
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PMID:Amelioration of cerebral ischemia by prior treatment of hypertension. 677 97

Low dose gamma-butyrolactone (GBL) therapy alters the natural history of experimental forebrain ischemia in the awake rat. After 30 minutes of four-vessel ischemia, repeated hydrogen cerebral blood flow determinations in awake rats over 72 hours revealed that low dose GBL therapy prevented the development of regional cerebral hyperemia and later the prolonged cerebral hypoperfusion that was experienced by the nontreated controls. Moreover, the low dose GBL-treated group had significantly less neuronal tissue loss than that in comparable brain regions of the nontreated controls. Before the stroke studies, GBL dose-response experiments performed on normal rats indicated that high dose GBL therapy produced seizures, systemic hypertension, metabolic acidosis, hyperthermia, and death.
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PMID:Effect of low dose gamma-butyrolactone therapy on forebrain neuronal ischemia in the unrestrained, awake rat. 685 68

A rare syndrome has been described in which mineralocorticoid-resistant hyperkalemia of renal origin occurs in the absence of glomerular insufficiency and renal sodium wasting and in which hyperchloremic acidosis, hypertension, and hyporeninemia coexist. The primary abnormality has been postulated to be a defect of the potassium secretory mechanism of the distal nephron. The present studies were carried out to investigate the mechanism of impaired renal potassium secretion in a patient with this syndrome. When dietary intake of sodium chloride was normal, renal clearance of potassium was subnormal (CK/GFR = 3.6 +/- 0.2%; normal subjects, 9.0 +/- 0.9%, N = 4) despite high normal or supernormal levels of plasma and urinary aldosterone. The fractional clearance of potassium remained subnormal (CK/GFR = 5.1 +/- 0.2%) during superimposed chronic administration of superphysiologic doses of mineralocorticoid hormone. Little increase in renal potassium clearance occurred when the delivery of sodium to distal nephron segments was increased further by the i.v. infusion of sodium chloride, despite experimentally sustained hypermineralocorticoidism. But potassium clearance increased greatly when delivery of sodium to the distal nephron was increased by infusion of nonchloride anions: sulfate (sodium sulfate infusion, low sodium chloride diet; CK/GFR = 63.7 +/- 0.4%) or bicarbonate (sodium bicarbonate plus acetazolamide infusion; CK/GFR = 81.7 +/- 1.7%). These findings indicate that mineralocorticoid-resistant renal hyperkalemia in this patient cannot be attributed to the absence of a renal potassium secretory capability or to diminished delivery of sodium to distal nephron segments; instead it may be dependent on chloride delivery to the distal nephron. We suggest that the primary abnormality in this syndrome increases the reabsorptive avidity of the distal nephron for chloride, which (1) limits the sodium and mineralocorticoid-dependent voltage driving force for potassium and hydrogen ion secretion, resulting in hyperkalemia and acidosis and (2) augments distal sodium chloride reabsorption resulting in hyperchloremia, volume expansion, hyporeninemia, and hypertension.
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PMID:Mineralocorticoid-resistant renal hyperkalemia without salt wasting (type II pseudohypoaldosteronism): role of increased renal chloride reabsorption. 702 72


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