ISSN:0263-6352    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

ObjectiveTo assess the strength of evidence for an inverse relationship between blood pressure and birth weight.DesignA systematic review of the published literature.SettingPublished studies describing the relationship between blood pressure and birth weight since 1956.SubjectsMore than 66 000 subjects aged 0–71 years.ResultsThirty-four studies described the relationship of blood pressure with birth weight. The majority of the studies of children and adults showed that blood pressure fell with increasing birth weight. Studies of adolescents were inconsistent. In neonates there was a positive relationship between blood pressure and birth weight. The pattern with age was supported by the limited number of studies with repeated measures and was dependent neither on the method of analysis nor on work from a single academic group or country.ConclusionsBlood pressure is inversely related to birth weight in children and in adults. The positive results in neonates and the inconsistency in adolescence may be related to the unusual growth dynamics during these phases of growth. Further studies should concentrate on the mechanisms which underlie the relationship.

ISSN:0263-6352    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

ObjectivesTo investigate the associations of the orthostatic blood pressure changes in older patients with isolated systolic hypertension.MethodsA total of 2716 patients, 917 men and 1799 women, aged ≥60 years, were examined at three separate outpatient visits whilst receiving placebo during the single-blind run-in phase of the Syst-Eur trial. The orthostatic blood pressure changes were calculated by subtracting the average of two blood pressure readings with the patient in the supine position from the mean of two readings obtained after the patient had stood for 2 min. An orthostatic blood pressure drop by at least 20mmHg systolic or 10mmHg diastolic was considered exaggerated.ResultsFor the three run-in visits combined, the supine blood pressure was 175 ± 13 mmHg systolic and 86 ± 6 mmHg diastolic (means ± SD). With the patients standing the systolic blood pressure was 5 ± 12 mmHg lower, whereas the diastolic blood pressure was 2 ± 7 mmHg higher. An exaggerated fall in systolic blood pressure was observed on at least 1 visit in 21.0% of the patients and on all three visits in 2.5%. The corresponding values for diastolic blood pressure were 9.7 and 0.4%. The orthostatic fall in systolic blood pressure increased with previous antihypertensive treatment, age and smoking, but decreased with a higher sitting pulse rate and usual alcohol consumption versus none. The rise in diastolic blood pressure upon standing was higher in women than in men, was curvilinearly associated with age and increased with the sitting diastolic blood pressure. By multiple logistic regression analysis, the odds of having a persistent or occasional exaggerated orthostatic fall in systolic blood pressure were 22% higher in women than in men. The odds increased with previous antihypertensive treatment (by 42%), age (by 1.4%/year), electrocardiographic left ventricular mass (by 15%/mV) and sitting systolic blood pressure (by 0.9%/mmHg), but decreased with sitting pulse rate (by 1.9%/beat per min). An exaggerated orthostatic fall in diastolic blood pressure was 30% more likely in men; the likelihood increased with age (by 6.4%/year) and decreased with sitting diastolic blood pressure (by 6.6%/ mmHg).ConclusionAn exaggerated orthostatic blood pressure fall in older patients with isolated systolic hypertension is associated mainly with gender, age and blood pressure level. Previous antihypertensive treatment, a lower pulse rate and a lower electrocardiographic left ventricular mass were also associated with an exaggerated orthostatic fall in systolic blood pressure.

ISSN:0263-6352    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

ObjectiveTo examine Dickinson's hypothesis in mild essential hypertension, in which neurogenic mechanisms are believed to be particularly relevant, by combining measures of cerebral oxygen consumption with the concurrent assessment of sympathetic nervous activity.Design and methodsTwenty-five untreated essential hypertensive subjects and 28 healthy age-matched volunteers underwent direct blood sampling using percutaneously inserted catheters advanced into the internal jugular vein, with cerebral blood flow scans to differentiate between cortical and subcortical venous drainage of the brain. Veno-arterial blood gas measurements and internal jugular vein blood flows were used to calculate cerebral respiratory quotients and cerebral oxygen utilization. The total body rate of noradrenaline spillover into plasma was measured to assess relationships between cerebral oxidative metabolism and sympathetic nervous activity.ResultsCompared with controls, the hypertensive subjects exhibited reductions in internal jugular vein blood flow (482 ± 29 versus 410 ± 15 ml/min), cerebral oxygen consumption (27 ± 2 versus 23 ± 1 ml/min) and cerebral oxygen supply (93 ± 6 versus 78 ± 3 ml/min). The cerebral respiratory quotients were identical (1.00 ± 0.04 in normotensives and 0.98 ± 0.03 in hypertensives). Technetium blood flow scans revealed that the reductions in internal jugular blood flow and cerebral oxygen consumption in the hypertensive patients were confined to cortical brain regions. Cortical blood flow was quantitatively linked to the matching respiratory quotient and oxygen consumption, neither of which bore any relation to the level of sympathetic nervous activity. The spillover of noradrenaline into the plasma for the body as a whole did not differ between the two groups.ConclusionsIn accord with Dickinson's hypothesis, we have established a reduction in internal jugular vein blood flow and cerebral oxygen utilization in hypertension. These reductions were confined to cortical brain regions. However, cerebral respiratory quotients in our hypertensive study group were no different from those in our controls, suggesting that glucose remained as the major cerebral metabolic substrate in hypertension. We were not able to establish a link between cerebral metabolism and blood pressure or sympathetic nervous activity in mildly hypertensive patients.

ISSN:0263-6352    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

ObjectivesTo investigate the influence of angiotensin II (All) receptors in isolated hepatic nuclei on other genes regulated by All and to determine whether the function of these intracellular receptors is influenced by alterations in the endocrine renin system.MethodsNuclei were isolated from hepatic tissue of normal and bilaterally nephrectomized or adrenalectomized Wistar rats. Following nuclear run-off, in the presence of varying All concentrations, specific messenger RNAs (mRNA) were determined by slot blot hybridization. Tissue levels of renin system components were measured by radioimmunoassay and nuclear receptors characterized by displacement of radiolabeled All with specific All receptor antagonists.ResultsAll binding in the presence of DUP 753 and PD 123177 confirmed that nuclear All receptors can be classified as AT1receptors and that as much as 10% of the specific binding is attributable to nuclear chromatin. All stimulated not only the production of mRNA for renin system components such as renin and angiotensinogen, but also that of mRNA for growth-related factors such as platelet-derived growth factor and the oncogene c-myc.Maximal stimulation occurred at 10−9mol/l All; higher concentrations reduced this response. After stimulation or suppression of the plasma renin system by adrenalectomy or bilateral nephrectomy, nuclei isolated from rat hepatic tissue contained elevated endogenous levels of growth-related and renin system mRNA including AT1and AT2All receptors. However, despite the level of receptor mRNA having been elevated, the total All receptor density of isolated nuclei decreased. In addition, after both maneuvers, isolated nuclei were refractory to All-induced gene transcription.ConclusionThe existence of mechanisms producing intracellular All and regulating its level, which in turn exert local regulatory responses via nuclear All receptors, lends significance to the presence of a functional intracrine renin system that could act in concert with or independently of the endocrine renin system.

ISSN:0263-6352    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

ObjectiveTo examine whether Na+-Li+countertransport (SLC) activity is linked to erythrocyte membrane lipid content.DesignAn observational case-control study. The maximal efflux rate of SLC, plasma cholesterol, triglycerides, phospholipids, low- and high-density lipoprotein cholesterol levels and the erythrocyte membrane cholesterol, phospholipids and fatty acids contents were determined both in fasting normolipaemic normotensive subjects and in hypertensive patients.MethodsThe Li+-stimulated Na+efflux was measured in Li+-preloaded erythrocytes. Membrane cholesterol and phospholipids levels were determined by the latroscan technique. Membrane fatty acids were identificated by gas chromatography. Several derived indices were also obtained.ResultsErythrocyte membranes of hypertensive patients showed an increase in cholesterol:phospholipid ratio and a decrease in the total amount of polyunsaturated fatty acids, mainly at the expense of arachidonic acid and docosatetraenoic acid. SLC activity was higher in hypertensive patients and correlated positively with the plasma triglycerides level and negatively with the ratio of C20:4 to C20:3.ConclusionOur data from untreated normolipaemic hypertensive patients show that a higher SLC activity was accompained by parameters that indicate a lower membrane fluidity.

ISSN:0263-6352    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

ObjectiveTo determine the quantitative roles played by the different vasoconstrictor systems in the acute pressor response in conscious rats before and after inhibition of nitric oxide synthase with Nw-nitro-L-arginine methyl ester (L-NAME).MethodsIn conscious male Sprague-Dawley rats, previously instrumented with aortic and venous catheters, the contributions of the different systems were assessed by maximal cumulative pharmacological blockade of α1-adrenoceptors (1 mg/kg prazosin intraperitoneally), AT1receptors (30 mg/kg losartan intraperitoneally) and V1/V2receptors (10 mg/kg [(β-mercapto-β,β-cyclopenta-methyl-enepropionyl1, O-Et-Tyr2-Val4-Arg8]-vasopressin per min intravenously). In addition, the contribution of endothelin-1-induced vasoconstriction in response to 100 mg/kg L-NAME intraperitoneally to the hypertension was assessed by administering 5–100 mg/kg ETA/ETBreceptor antagonist PD145 065 intravenously under three different conditions: as the last step of a series of antagonists in the cumulative pharmacological blockade after having induced the L-NAME pressor response; alone before L-NAME treatment; and alone after the full development of the L-NAME pressor response. A separate group of rats was treated acutely with 30 mg/kg losartan intraperitoneally or pretreated for 3 days with 30 mg/kg angiotensin I converting enzyme inhibitor enalapril via drinking water alone or in combination with 1 % salt was used to assess the role of the renin-angiotensin system in the L-NAME-induced hypertension.ResultsShort-term administration of the combined ETA/ETBreceptor antagonist PD 145 065 did not change the arterial pressure under control conditions. Inhibition of the reninangiotensin system, α1-adrenoceptors or vasopressin receptors alone or in combination did not alter the magnitude of the L-NAME pressor response. In contrast, our results show that both treatments before and during acute nitric oxide synthase blockade hypertension using the ETA/ETBreceptor antagonist PD 145 065 abolished almost completely (approximately 85%) the pressor response.ConclusionsThese studies indicate that the predominant mechanism of hypertension, at least in the acute phase, after acute nitric oxide synthase blockade with L-NAME is associated with a marked increase in ETA/ETBreceptor activation rather than with increases in α1, AT1and V1/V2receptor activation. It remains to be determined whether endothelin participates also in the chronic phase of nitric oxide-deficient hypertension.

ISSN:0263-6352    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

ObjectiveTo investigate the effects of vasopressin and endothelin-1 on the intracellular free calcium concentration ([Ca2+]i) and on contractile responses in endothelium-denuded resistance vessels of prehypertensive (5-week-old) and adult hypertensive (17-week-old) spontaneously hypertensive rats (SHR) and age-matched Wistar-Kyoto (WKY) rats.MethodsSegments (2 mm long) of third-order branches of small mesenteric arteries were mounted in a perfusion myograph and maintained at 60mmHg pressure. Endothelium was removed by intraluminal passage of air. The vessel [Ca2+]iwas measured by fura-2 fluorescence and contraction was determined using a video imaging system to record lumen diameter.ResultsLumen diameter was significantly smaller in 5-and 17-week-old SHR than it was in age-matched WKY rats (5 week-old SHR versus WKY rats: 178 ± 4.0 versus 195 ± 4.3 μm; 17-week-old SHR versus WKY rats: 168 ± 7.0 versus 230 ± 3.1 μm). The basal [Ca2+]iwas significantly higher in 5− and 17-week-old SHR than it was in age-matched WKY rats. Infusions of vasopressin and endothelin-1 increased [Ca2+]iand contractile responses in a dose-dependent manner in all groups. The vasopressin-induced change in [Ca2+]iwas significantly greater in 5− and 17-week-old SHR than in age-matched controls. The sensitivity of [Ca2+]ito vasopressin was increased in adult SHR compared with WKY rats (pD29.0 ± 0.1 in SHR, 8.2 ± 0.3 in WKY rats). Vasopressin-stimulated contractile responses were increased in adult SHR. The endothelin-1-induced change in [Ca2+]idid not differ between WKY rats and SHR. The contractility of vessels in response to endothelin-1 infusion was similar in age-matched groups.ConclusionsEndothelin-1-induced changes in [Ca2+]iand contractile responses in small arteries are similar in age-matched WKY rats and SHR, whereas responses to vasopressin are significantly enhanced in SHR compared with WKY rats. Thus [Ca2+]jsignalling for vasopressin is more active than is that for endothelin-1. Vasopressin but not endothelin-1 might play a role in the development of hypertension in SHR.

ISSN:0263-6352    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

ObjectiveTo investigate the elastic characteristics of the wall of isolated subcutaneous resistance arteries from patients with essential hypertension, the response of the vessels to endothelium-dependent and -independent vasodilators and the dependence on calcium.MethodsSubcutaneous resistance arteries were isolated from 16 patients with never-treated essential hypertension and from 16 normotensive controls matched for age and sex. The vessels were mounted in a myograph for isometric force development. The passive elastic characteristics were determined and then the response to acetylcholine, nitroprusside, felodipine, caffeine and calcium (in the presence of noradrenaline and prazosin or yohimbine) were determined.ResultsYoung's elastic modulus as a function of wall stress was similar in the two groups of vessels. The relaxation of vessels from hypertensive and normotensive in response to acetylcholine, nitroprusside and felodipine was also similar. However, the response to caffeine was increased in vessels from the hypertensive patients, although the relationship between the dependence on the effect of calcium on the behaviour of arteries from hypertensives and controls was similar in the presence of prazosin and yohimbine.ConclusionsThe altered morphology of subcutaneous resistance arteries from hypertensives is not caused by a change in the elastic characteristics of the wall material. The data support our previous observation of abnormal calcium handling in vessels from hypertensives, although they do not support the hypothesis that a generalized abnormality in endothelium-dependent or endothelium-in-dependent relaxation is of importance in essential hypertension.

ISSN:0263-6352    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

ObjectiveTo assess the response of internal mammary artery (IMA) flow of hypertensive hearts to nitroprusside infusion.MethodsFifteen patients were studied with a high-frequency duplex Doppler probe from the supraclavicolar approach. All the patients had undergone coronary artery bypass surgery with an IMA graft into the left anterior descending artery. The investigated patients were normotensives (controls, n = 5) and hypertensive with a normal (group 1, n = 5) or a hypertrophic (group 2, n = 5) left ventricle. Values of the left ventricular mass index were 102 ± 11 g/m2in controls, 115 ± 18 g/m2in group 1 and 153 ± 8 g/m2in group 2. The IMA flow volume was studied at baseline and continuously during nitroprusside infusion. The arterial blood pressure was measured each minute by a cuff sphygmomanometer. In each patient we considered the peak flow volume (percentage increment from baseline) and the flow volume at the end point (the lowest tolerated diastolic blood pressure).ResultsNitroprusside infusion induced a comparable flow-volume increment in controls (38 ± 27%) and in group 1 (24 ± 11%). Conversely, the flow-volume increment was trivial in group 2 (6 ± 6%). At the end point, the flow volume was similar to the baseline value in controls (with diastolic blood pressure 67 ± 9 mmHg) and in group 1 (diastolic blood pressure 61 ± 4 mmHg), whereas the flow volume declined significantly from baseline (by 23%) in group 2 at a perfusion pressure of 79 ± 9 mmHg.ConclusionHypertensive patients with a normal left ventricular mass exhibit a coronary flow behaviour similar to that of normotensives in response to a nitroprusside infusion. Conversely, hypertrophic hypertensives show a blunted nitroprusside-induced coronary vasodilator response and are much more vulnerable to coronary flow reductions in the face of hypotension. This dynamic assessment of flow patterns can be obtained non-invasively by duplex Doppler monitoring of IMA graft flow.

ISSN:0263-6352    

出版商:OVID    

年代:1996

数据来源: OVID