ISSN:0263-6352    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

Purpose:The Journal of Hypertension has now produced statistical guidelines for authors. This review highlights some of the important issues in the guidelines.Type I and II errors:The Type I error is essentially the chance of a false positive result and is conventionally set to 5%. Equally important, but sometimes neglected, is the Type II error — the chance of a false negative result.Normality of data:Many statistical tests are only valid if the data are normally distributed. If the data are not normally distributed, non-parametric tests should be used.Multiple comparisons:Type I error rates must be corrected if multiple comparisons are made.Correlation coefficients:In general, regression coefficients are more useful than correlation coefficients. The latter may often be statistically significant but not convey any useful information.Confidence intervals:A confidence interval is a measure of the range which is likely to contain the true value of the parameter of interest; it conveys more information than a P value about the result of a study. Confidence intervals are also very useful for comparing studies.

ISSN:0263-6352    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

Purpose:During the past two decades, molecular biology techniques have had an increasing impact upon hypertension research. This article will thus review the basic methodology in this field.Contents:Protocols are described for the establishment of a genomic library and its use for the cloning of specific genes, as well as methods for the detection and sequencing of DNA. In addition, techniques to detect and quantify specific messenger RNA, such as Northern blotting, ribonuclease protection assay andin situhybridization, and the reporter gene approach for the analysis of regulatory gene sequences, are included. The polymerase chain reaction which, as a newly established technique to detect and amplify DNA, has exerted a strong influence upon all areas of molecular biology is the subject of the concluding paragraph.Conclusions:Molecular biology techniques may be of substantial help in revealing the cause of hypertension and developing tools to prevent and treat this disorder.

ISSN:0263-6352    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

Objective:The aim of this study was to investigate atrial natriuretic peptide (ANP) gene expression in the central nervous system (CNS) during hypertension.Methods:We measured and compared immunoreactive atrial natriuretic peptide (irANP) and ANP messenger RNA (mRNA) in the hypothalamus and brainstem of 17-week-old spontaneously hypertensive rats (SHR) with those of age-matched Wistar-Kyoto (WKY) rats using ribonuclease (RNase) protection assay for ANP mRNA and a specific radioimmunoassay for irANP.Results:RNase protection assay revealed that the concentrations of ANP mRNA in the hypothalamus and brainstem of SHR were higher than those of WKY rats. IrANP concentrations in the hypothalamus and brainstem of SHR were determined by a specific radioimmunoassay and found to be higher than those of WKY rats. Elevated mRNA levels in the hypothalamus and brainstem of SHR indicated that increased level of irANP in the CNS resulted from increased synthesis of ANP.Conclusion:We propose that increased synthesis of brain ANP in SHR may reflect a compensatory mechanism induced by hypertension.

ISSN:0263-6352    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

Objective:To examine the interaction between i.c.v. administration of endothelin and brain natriuretic peptide (BNP) on vasopressin (AVP) secretion in unanesthetized, freely moving rats.Methods:i.c.v. cannulation and femoral artery catheterization were performed 7-8 days and 2 days before the experiment, respectively. Endothelin and BNP were injected into the third ventricle through the guide cannula. One millilitre of blood was collected for AVP measurement 30 min before and 10 min after i.c.v. injection.Results:Central administration of endothelin (20 or 40 pmol/2 (µl) dose-dependently evoked the elevation of plasma AVP levels. Preinjection of BNP (0.2 or 1 nmol/3 µl, i.c.v.) dose-dependently attenuated central endothelin (40 pmol/2 µl)-induced plasma AVP secretion.Conclusions:We have already reported that BNP attenuated central endothelin-induced pressor response and plasma catecholamine secretion. Taken together, the results indicate that BNP attenuated central endothelin-induced pressor response, at least partially, by suppressing sympathetic nervous system activation and plasma AVP secretion.

ISSN:0263-6352    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

Objective:To prove the independence of local tissue renin–angiotensin system (RAS) in brain from classical kidney RAS, we measured local angiotensin levels in bilaterally nephrectomized rats which had been dialyzed with a dialysis technique to greatly prolong survival time.Design:Two groups of animals were used: (1) bilaterally nephrectomized rats with intraperitoneal dialysis, where both kidneys were surgically removed; and (2) controls with intact kidneys and dialysis. By using this protocol, we were able to study plasma and brain angiotensins 5 days after nephrectomy (no longer periods have been attempted).Methods:Plasma sodium, potassium and pH were monitored while rats were dialyzed four times a day. Plasma samples and brain areas were obtained and angiotensin II measured by radioimmunoassay and high-pressure liquid chromatography (HPLC).Results:Plasma angiotensin II was significantly diminished in the nephrectomized rats but was still detectable, the levels being above the minimal detectable value. The identity of angiotensin I and angiotensin II detected by radioimmunoassay was confirmed by HPLC. In the brain, angiotensin II content was significantly increased in all areas studied. The highest increments were in hypothalamus and brain stem.Conclusions:Our results demonstrate that: (1) brain angiotensin II is regulated independently of peripheral angiotensin II; and (2) a reduced plasma angiotensin II persists 5 days after bilateral nephrectomy. We conclude that the angiotensin II in the plasma was derived from non-renal tissue and the results support the conclusion that tissue RAS has paracrine and autocrine functions independent of the endocrine function of circulating plasma angiotensin.

ISSN:0263-6352    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

Objectives:To investigate the renal, haemodynamic and neurohormonal responses to low-dose infusions of atrial natriuretic factor (ANF) in hypertensive humans.Design:Ten patients with mild-to-moderate essential hypertension received incremental infusions of 3 and 6 ng/kg per min ANF or vehicle alone whilst on a constant dietary sodium intake. A 90-min basal clearance period was followed by two 2-h infusion periods, with urine collection in the last 90 min of each period. In each of the three clearance periods, glomerular filtration rate (GFR), renal tubular function, and the activity of the renin–angiotensin and sympathetic nervous systems were determined.Methods:The renal sites of ANF action were established by simultaneous measurements of51Cr-ethylenediaminetetraacetate lithium and sodium clearances. Plasma concentrations of neurohormones were measured by radioimmunoassays.Results:Plasma ANF concentrations increased by 1.6- and 2.5-fold during the lower and higher ANF infusion rates, respectively. Plasma cyclic guanosine monophosphate concentrations increased in parallel. ANF caused no changes in supine systolic and diastolic blood pressure or in heart rate. In contrast, haematocrit values increased progressively across the study. The renal effects of ANF administration were characterized by an unaltered GFR and significant increases in the renal clearances of lithium (a marker of end-proximal fluid delivery) and sodium when compared with vehicle infusions, whereas urine flow did not change. Estimated values of fractional proximal and distal tubular sodium reabsorption decreased significantly. Plasma concentration of active renin decreased during ANF infusions, but no significant changes in plasma levels of renin substrate, angiotensin I, angiotensin II or aldosterone were observed. A subtle activation of the sympathetic nervous system was indicated by a moderate increase in plasma noradrenaline during the ANF infusions.Conclusions:These results indicate that even small increases in plasma ANF, as can be found during physiological conditions, induce natriuresis in patients with essential hypertension by enhancing fluid delivery from the proximal tubules, in addition to impairing distal fractional sodium reabsorption. With minor exceptions, the ANF infusions caused qualitatively and quantitatively similar renal, haemodynamic and endocrine effects in the hypertensive patients as in a previously studied group of normotensive subjects.

ISSN:0263-6352    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

Objective:The existence and localization of reninin situwas examined in human arteries under non-pathological conditions.Design:Biochemical and immunohistochemical procedures were adopted to examine the existence of renin in human gastroepiploic arteries using an antibody raised against human recombinant renin or a specific renin inhibitor.Methods:(1) Renin activity (angiotensin I generating activity sensitive to antihuman recombinant renin antibody or a specific renin inhibitor) in the homogenate of human gastroepiploic arteries with and without endothelium was compared; (2) vascular renin was immunohistochemically stained using a modified avidine–biotin–peroxidase complex method.Results:(1) Renin activity in human gastroepiploic arteries with endothelium was significantly higher than in those without endothelium; (2) immunoreactive staining selectively occurred in the endothelial cells of human gastroepiploic arteries.Conclusions:Renin is present in endothelial cells of human arteries under non-pathological conditions. Endothelial renin may play a role in the control of vascular tone through local production of angiotensin II.

ISSN:0263-6352    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

Objectives:The primary objective of this study was to determine the effect of i.v. angiotensin II infusion on platelet intracellular free calcium concentration in potentially hypertensive primigravid women.Design:Patients at 28-32 weeks gestation were selected on the basis of a diastolic pressure ≤ 80mmHg taken at the antenatal clinic visit.Methods:An angiotensin II infusion test (4-16 ng/kg per min) was performed in 13 women. Platelet intracellular free calcium concentration, platelet angiotensin II binding site density and plasma angiotensin II concentration were measured before and at the end of the infusion. Pregnancy outcome (normotension or hypertension) was recorded.Results:Platelet intracellular free calcium concentration rose in 12 of 13 women during angiotensin II infusion. This rise was not directly correlated with initial or final platelet angiotensin II binding site density, plasma angiotensin II concentration or the evoked change in systolic or diastolic blood pressure. Five women subsequently developed pregnancy-induced hypertension. Although basal platelet intracellular free calcium concentration did not differ between the two groups, platelet intracellular free calcium concentration rose twice as much in response to angiotensin II in the five hypertensive pregnant women. There was a 12-fold increase in platelet angiotensin II binding in the future hypertensives, although basal angiotensin II was the same in the two groups.Conclusion:The enhanced rise in platelet intracellular free calcium concentration in response to angiotensin II administration in women who subsequently became hypertensive, together with their increased angiotensin II binding site density suggest a possible enhanced stimulus–effect coupling. Pregnancy-induced hypertension is a state of marked vasoconstriction, with an enhanced pressor response to angiotensin II. These data supply grounds for a hypothesis concerning the mechanism.

ISSN:0263-6352    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

Objectives:Reduction in plasma volume (Pvol) of women with pregnancy-induced hypertension (PIH; preeclampsia) has both physiological and clinical implications. This study was undertaken to determine the following variables in women with PIH: (1) the incidence of reduced Pvol; (2) the distribution of total extracellular fluid volume (ECFV); (3) the relationship between Pvoland birth weight; and (4) whether any readily available clinical or laboratory parameters predict the presence of reduced Pvol.Setting:Teaching hospital obstetric unit and antenatal clinic.Participants:Forty-nine primigravidae with PIH (28 mild, 21 severe), 54 normotensive primigravidae and 25 non-pregnant controls.Design:Pvolwas measured using Evans Blue dye and ECFV as the mannitol space. These measures were compared amongst groups, and also within groups for those with PIH, according to the severity of their disorder and the presence of proteinuria or oedema. Blood pressure, haematocrit, uric acid and serum albumin were also evaluated as predictive indices of reduced Pvolin women with PIH.Results:Pvol, ECFV and the Pvol: ECFV ratio all increased during normal pregnancy. Pvolin women with PIH was reduced compared with normal pregnancy and correlated significantly with birth weight. Total ECFV was unchanged in women with PIH, but their Pvol: ECFV ratio was significantly reduced compared with normal pregnancy. Although there was a significant correlation between Pvoland haematocrit in women with PIH, haematocrit was a poor predictor for reduced Pvol. Diastolic blood pressure>100 mmHg, persistent proteinuria and severe PIH were the only reliable positive predictors of a reduced Pvol.Conclusions:Pvolis related to birth weight, but is reduced in only approximately half of women with PIH. This reduced Pvolis the result of maldistribution, not loss, of total ECFV, and can be predicted by high diastolic blood pressure, proteinuria or other clinical signs of severity, but not by haematocrit.

ISSN:0263-6352    

出版商:OVID    

年代:1992

数据来源: OVID