ISSN:0263-6352    

出版商:OVID    

年代:1992

数据来源: OVID

ISSN:0263-6352    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

Objective:To compare three different software versions [read-only memory (ROM) versions 1.22, 1.24 and 1.28] of the SpaceLabs model 90202 ambulatory blood pressure monitorDesign:Simultaneous measurements in a two-arm crossover design.Methods:Ten measurements each in 14 normotensive persons were performed to compare each pair of monitors. The results were corrected according to the deviation from a mercury column. The systolic (SBP), diastolic (DBP) and mean arterial blood pressure (MAP) was noted and the factor K = (MAP — DBP)/(SBP — DBP) was calculatedResults:The K factor in the two older ROM versions was close to 0.25, with no statistically significant difference. In contrast the K factor was higher in the most recent ROM version than in one of the previous versions. This could be explained by a 5.4mmHg increase in MAP found by the new version. A significant difference in blood pressure was observed even between two monitors with the same ROM version.Conclusion:Unnotified changes in the software version in the SpaceLabs 90202 monitor operating by an oscillometric technique seriously affect the reliability of MAP measurements. Whenever possible in clinical trials the same monitor should be used for the same patient on each occasion. The industry should inform clinicians of the consequences of updating apparently identical monitors

ISSN:0263-6352    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

Objective:To test the hypothesis that enhanced expression of the vasopressin gene accompanies- the development of deoxycorticosterone acetate (DOCA)—salt hypertension in the rat and to compare the response with those observed during chronic hypernatremiaMethods:Transcript levels were determined by measurement of vasopressin messenger RNA (mRNA) in the supraoptic nucleus and paraventricular nucleus by in situ hybridization, autoradiography and image analysis. Plasma, urinary and pituitary vasopressin were determined by radioimmunoassayDesign:High-resolution localization and measurement of specific mRNA in the supraoptic and paraventricular nuclei before and during development of DOCA—salt hypertension were compared with corresponding results in both age-matched controls and normal rats that drank hypertonic salineResults:Vasopressin mRNA levels were increased in the paraventricular nucleus during the established and chronic stages of DOCA—salt hypertension, but were unchanged in the supraoptic nucleus. Urinary excretion of vasopressin was increased in the prehypertensive, established and chronic phases of DOCA—salt hypertension, whereas plasma vasopressin levels were increased only in the chronic phase. Pituitary vasopressin levels were unchanged. In comparative studies, vasopressin mRNA levels in both the supraoptic and paraventricular nuclei and plasma vasopressin were significantly increased in normal rats drinking 2% salineConclusion:Whereas hypernatremic rats showed markedly elevated vasopressin transcripts in the supraoptic and paraventricular nuclei, DOCA—salt hypertension is associated with increased vasopressin mRNA in the paraventricular but not the supraoptic nucleus. The response in the paraventricular nucleus may explain part of the increased peripheral vasopressin levels and suggests that this nucleus makes a critical contribution to the pathogenesis of DOCA—salt hypertension

ISSN:0263-6352    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

Objective: Our previous electrochemical studies in the normotensive Wistar—Kyoto (WKY) rat showed a positive correlation between the hypotensive effect of low doses of clonidine (2-1up,g/kg intravenously) and inhibition of the activity of catecholaminergic neurons within the brainstem, and that this action was mediated by imidazoline-preferring receptors. In the present study the possibility of a relationship between the centrally mediated hypotensive effect of clonidine and the metabolic activity of catecholaminergic neurons of the ventrolateral and dorsomedial medulla oblongata was investigated in pentobarbital-anaesthetized spontaneously hypertensive rats (SHR). Design and methods: Neuronal metabolic activity was monitored by in vivo electrochemistry in the nucleus reticularis lateralis region of the ventrolateral medulla and in the nucleus tractus solitarii region of the dorsomedial medulla oblongata. Results: Hypotensive doses of intravenously administered clonidine dO^g/kg) failed to inhibit the neuronal metabolic activity of the nucleus reticularis lateralis region; fivefold higher doses were required to inhibit these neurons. The low dose of clonidine (10 (J.g/kg) decreased the metabolic activity of the nucleus tractus solitarii region. Nevertheless, this effect did not appear to be correlated with a reduction in blood pressure and it was not attenuated by a prior central injection of idazoxan (5 nmol/kg intracisternally), which almost completely prevented the hypotensive and the neuronal inhibitory effects of clonidine in the nucleus reticularis lateralis region of the normotensive rat. Conclusion: Both the site and the mechanism of the central hypotensive action of clonidine in the SHR appear to be different from those in normotensive control WKY rats.

ISSN:0263-6352    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

Aim:To compare the effects of dietary salt on sodium-calcium exchange and the ATP-driven calcium pump in arterial smooth muscle between Dahl salt-sensitive (DS) and salt-resistant (DR) ratsMethods:Aortic rings freshly excised from 16 DS rats and 16 DR rats on a low- (0.3% or high- (8% ) NaCI diet for 4 weeks were superfused with physiological saline and isometric tension was measured. In the presence of 10(imol/l phentolamine, 10(imol/l verapamil and 5 mmol/l caffeine, relaxation of a Iow-Na + contraction was promoted by external calcium removalResults:On the high-salt diet, the rate of relaxation at 1.2 mmol/l extracellular sodium (calcium extrusion by calcium ATPase) was significantly lower in aortic rings from DS rats than from DR rats. The increase in the rates of relaxation from 1.2 mmol/l to normal (139.2 mmol/l) extracellular sodium (calcium extrusion by sodium-calcium exchange) was significantly greater with the high-salt diet than with the low-salt diet in rings from DR rats, but it was not different between the high- and low-salt diets in DS rats. The rate of increase in tonic tension by reducing extracellular Na+ from normal to 1.2 mmol/l in the presence of verapamil, caffeine and phentolamine (calcium entry by sodium—calcium exchange) was significantly lower in rings from DS rats than in those from DR rats on the high-salt dietConclusions:These observations suggest that the effects of dietary salt on the sodium—calcium exchange system in arterial smooth muscle differ between DS and DR rats and that calcium extrusion by the calcium pump is decreased in DS rats compared with DR rats. The lack of an increase in sodium—calcium exchange in salt-fed DS rats might lead to an elevation in cellular calcium and contribute to the mechanism of hypertension

ISSN:0263-6352    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

Objective:To investigate the role of the renal medulla in early hypertension in spontaneously hypertensive rats (SHR), and to explore whether the attenuated increase of pressure induced by enalapril treatment is affected by chemical medullectomyDesign:Forty-four male SHR were studied from 5 to 18 weeks of age: 22 remained intact; 22 were medullectomized at 5.5 weeks of age with 2-bromoethylamine hydrobromide; 11 of each of these two groups were treated with enalapril from 6 to 12 weeks of age. Blood pressure, heart rate and body weight were recorded intermittently, and at 18 weeks renal function was also analysedResults:The results indicate a protective effect of the renal medulla against severe pressure rises in SHR, although even when enalapril also lowered blood pressure in medullectomized SHR, persistent improvements of glomerular filtration rate and renal flow conductance occurred only in intact SHR. Furthermore, after enalapril treatment ended blood pressure rose to higher levels in medullectomized SHR, despite greater sodium—water lossesConclusion:The renal medulla seems to exert a protective role both during and after enalapril treatment.

ISSN:0263-6352    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

Aim:To localize and measure angiotensin converting enzyme (ACE) in different vascular beds of genetically hypertensive ratsMethods:Quantitative autoradiography using the angiotensin converting enzyme (E.C. 3.4.15.1) inhibitor [125I]351AResults:[125I]351A binding was significantly increased in the ascending aorta (both adventitia and intima), descending (abdominal) aorta, carotid artery and coronary arteries of adult, 12-week-old spontaneously hypertensive rats (SHR) compared with Wistar—Kyoto (WKY) rats. Increased [125I]351A binding was also present in the descending aorta of 1-week-old SHR compared with age-matched WKY rats, and both groups of young rats had much higher binding than adult rats. No difference in [125I]351A binding was found in the caudal (tail) artery of adult SHR compared with WKY rats. In both the atria and the ventricles of adult SHR, [125I]351A binding was very significantly reduced.Conclusions:Our results indicate that higher ACE concentrations occur in some arteries of genetically hypertensive rats, and support the hypothesis that local arterial concentrations of ACE affect the development and maintenance of genetic hypertension

ISSN:0263-6352    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

Objective:AATo study the inotropic response to β-adrenoceptor stimulation in isolated hypertrophied hearts from hypertensive ratsDesign and methods:Cardiac hypertrophy was induced in Wistar rats by stenosing the abdominal aorta. Functional responses to isoprenaline, dobutamine, terbutaline and salbutamol were measured in paced (5 Hz), aortically stenosed hearts (18—20 and 32—34 weeks of age) and compared with those of sham–operated spontaneously hypertensive (SHR) and Wistar—Kyoto (WKY) ratsResults:Following aortic stenosis, which was accompanied by less hypertension than that sustained by SHR, the Wistar rat hearts showed more pronounced cardiac hypertrophy. An initially equal inotropic response to the p-adrenoceptor agonists (18—20 weeks) was reduced to 45% at 32—34 weeks in SHR but not in WKY rat hearts. The response to P-adrenoceptor stimulation in the hypertrophied Wistar rat hearts was reduced at 18—20 weeks to 30% and at 32—34 weeks to 10% of controls, respectively. The response by all hypertrophied hearts to forskolin and N,2'-0-dibutyryladenosine 3': 5' monophosphate was also diminishedConclusions:The impaired contractile response to β-adrenoceptor agonism is more clearly related to cardiac hypertrophy than to hypertension.

ISSN:0263-6352    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

Objectives:To determine the effects of different dihydropyridine calcium antagonists on cardiovascular mass and function in normotensive Wistar—Kyoto (WKY) rats and spontaneously hypertensive rats (SHR)Methods:The rats were treated daily for 3 weeks with nitrendipine (20 mg/kg), nifedipine (30 mg/kg), nisoldipine (6 mg/kg) or their vehicles. At the conclusion of that period left ventricular pumping ability and aortic distensibilty were determined, and the aortic, cardiac and left and right ventricular massesResults:Each drug reduced arterial pressure in both rat strains; each decreased left ventricular mass in SHR but not in WKY rats. All three agents increased right ventricular mass in WKY rats; only nisoldipine did so in SHR. Each compound improved left ventricular pumping ability in WKY rats, maintaining function even when pressure was abruptly increased to preteatment levels. In contrast, although all three calcium antagonists improved cardiac performance in SHR at the pharmacologically reduced pressures, pumping ability was not maintained when pressure was increased to pretreatment levels in nisoldipine-treated SHR. All three agents improved aortic distensibility in both strains, but only in SHR was reduced aortic mass demonstratedConclusions:These data not only continue to demonstrate a functional/structural dissociation associated with antihypertensive therapy, but also suggest subtle functional and structural effects that differ even within the same class of calcium antagonists.

ISSN:0263-6352    

出版商:OVID    

年代:1992

数据来源: OVID