摘要:

BackgroundA major source of error in the longitudinal assessment of the intima–media thickness (IMT) is the difficulty in retrieving the same echographic view of the vessel.ObjectiveTo present a method for increasing the reproducibility of IMT measurements by ultrasound in large arteries.MethodThe Fourier descriptor is a well-known means of describing an object's shape. By means of the discrete Fourier transform (DFT), the shape was represented in a frequency domain; the computational advantages of the DFT then permitted a measure of unlikeness between different shapes (the ‘distance’ measure; DM) to be defined and used as a criterion for reproducing the contour. When the sonographer compared successive images of a complex vascular segment, like the carotid bifurcation, the identity of the echographic cut was deduced from the identity of the vessel's contour. The best match of the baseline image was the view that minimized the contour DM.ResultsPreliminary studies in the carotid artery bifurcations of eight subjects showed that the DM responds to systematic variations in the ultrasound interrogation angle and reveals minimal changes in transducer position. Duplicate scans of 12 subjects were performed by three sonographers with different strategies for acquisition of the same images: a low DM was associated with a low difference in pairs of IMT measurements. Data were classified into two groups (normal or borderline vessels with a pooled mean IMT of 0.62 mm and overtly thickened segments with a pooled mean IMT of 1.31 mm). When minimization of the DM was the criterion for the acquisition of replicate scans, the mean absolute difference of paired data for the mean IMT of the distal common carotid artery was 0.03 ± 0.02 mm for the first group and 0.06 ± 0.03 mm for the second group. This is a significant reduction in comparison with non-quantitative alternative criteria for image reproduction. For the maximum IMT of the same segments the mean absolute differences were 0.07 ± 0.03 and 0.13 ± 0.06 mm in the first and second groups, respectively.ConclusionThis method can be applied to the serial assessment of single atherosclerotic segments. The computational time is negligible. By reducing the scatter in sequential IMT data, longitudinal investigations (e.g. of the results of antihypertensive therapy) with shorter durations and smaller sample groups may be rendered feasible.

ISSN:0263-6352    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

ObjectiveTo examine the relationship between hyperinsulinemia and clusters of cardiovascular risk factors in middle-aged hypertensive patients.DesignA population-based study.SettingPieksämäki District Health Center, and the Community Health Center of the city of Tampere, in central Finland.SubjectsHypertensive men and women aged 36, 41, 46, and 51 years (n = 161) in the town of Pieksämäki, and a normotensive control population of 177 subjects aged 40 and 45 years in the city of Tampere.Main outcome measuresClusters of obesity (body mass index > 30.0 kg/m2), abdominal adiposity (waist: hip ratio > 1.00 for men and > 0.88 for women), hypertriglyceridemia (> 1.70 mmol/l), a low level of high-density lipoprotein cholesterol (< 1.0 mmol/l in men and < 1.20 mmol/l in women) and abnormal glucose metabolism (impaired glucose tolerance or noninsulin-dependent diabetes as defined by World Health Organization criteria) according to statistical quartiles of the fasting plasma insulin concentration.ResultsAmong the hypertensives, there was a 2.0- to 3.6-fold higher risk of having a clustering of the insulin-resistance associated cardiovascular risk factors compared with that of the normotensives. Among the hypertensive subjects in the highest quartile of fasting plasma insulin there was a six- to 12-fold increase in risk associated with having two or more insulin resistance associated cardiovascular risk factors compared with the subjects in the lowest quartile. There was a positive correlation between a high number of ascertained risk factors and high levels of fasting plasma insulin.ConclusionIn clinical practice, knowledge of the close relationship between risk-factor cluster status and fasting plasma insulin levels offers a tool to evaluate the occurrence of hyperinsulinemia in middle-aged hypertensive men and women.

ISSN:0263-6352    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

BackgroundResults from previous studies suggested that a blunted response of renal plasma flow (RPF) to angiotensin II infusion during a high-sodium diet (a phenotype associated with nonmodulation) is an intermediate phenotype for essential hypertension.ObjectiveTo determine whether RPF traits used to investigate nonmodulation have the characteristics of intermediate traits when examined in a population-based sample of adults aged 20–49.9 years.Design and methodsWe examined the frequency distribution of baseline RPF and of its response to All infusion using maximum-likelihood commingling analysis in order to investigate the null hypothesis that the distributions of these traits are unimodal. We also examined the null hypothesis that there is no association between these candidate intermediate traits and the parental history of essential hypertension.ResultsThere was some evidence for the commingling of multiple distributions underlying these traits both for women and for men but the commingled distributions overlapped substantially and the inferences about the commingling of distributions were sensitive to the method of RPF measurement, exclusion of outliers, and the method of adjustment for concomitants. There was no statistically significant association between any of the RPF traits and a parental history of essential hypertension.ConclusionsThere is not sufficiently strong evidence to advocate the use of this set of intermediate traits to identify high-risk individuals or to relate genetic variation to the variation in risk of essential hypertension within this age range in the population at large.

ISSN:0263-6352    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

ObjectiveTo assess whether interindividual variation in renal plasma flow or in its response to angiotensin II infusion is associated with interindividual differences in blood pressure in a population-based sample of 287 non-Hispanic whites (143 women and 144 men), aged 20–49.9 years.MethodsAfter seven days of eating a high-sodium diet (260 mmol/day), the renal plasma flow was determined by measuring the clearance ofp-aminohippurate before and after infusion of 3 ng/kg per min angiotensin II. Multiple linear regression methods were used to assess whether measures of the renal plasma flow and of its response to angiotensin II infusion were predictive of systolic or diastolic blood pressures measured prior to administration of the high-sodium diet, on day 6 of the high-sodium diet, or during the renal clearance procedure on day 7 prior to angiotensin II infusion.ResultsThere was some evidence that measures of the renal plasma flow and of its response to angiotensin II infusion during the high-sodium diet were statistically significant predictors of measures of blood pressure in women; there was less evidence for this for blood pressures in men. Interindividual variation in measures of the renal plasma flow and of its response to angiotensin II infusion explained less than 10% of the interindividual variation in any measure of the blood pressure in both sexes.ConclusionThese results suggest that interindividual variation in renal plasma flow and in its response to angiotensin II infusion during a high-sodium diet will be of limited utility in elucidating the basis for interindividual differences in blood pressure.

ISSN:0263-6352    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

ObjectiveTo examine whether the angiotensinogen M235T and angiotensin converting enzyme insertion/deletion (I/D) variants are related to the severity of hypertension in patients with established essential hypertension.DesignA cross-sectional study.SettingThe hypertension clinic of the Benjamin Franklin University Hospital, Free University of Berlin.ParticipantsThree hundred and forty-three consecutive Caucasian patients who presented with treated or untreated (n = 115) hypertension were enrolled into the study. Twenty-two patients were excluded from analysis because they had secondary hypertension.Main outcome measuresAngiotensinogen M235T and angiotensin-converting enzyme I/D genotypes, 24 h ambulatory blood pressure values, the number of antihypertensive medications administered and left ventricular dimensions assessed by two-dimensional echocardiography.ResultsNeither the angiotensinogen nor the angiotensin converting enzyme genotype was related significantly to the average ambulatory blood pressure and left ventricular dimensions in hypertensives. Furthermore, neither the number of antihypertensive medications administered to treated patients nor blood pressure levels in untreated patients (n = 115) differed significantly between the genotypic groups.ConclusionsThese results do not support the hypothesis that the studied molecular variants of the renin–angiotensin system may represent clinically useful markers of the severity of hypertension in Caucasians with established essential hypertension.

ISSN:0263-6352    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

ObjectiveTo elucidate the different effects of sodium intake on renin messenger RNA (mRNA) in the hypothalamus and the kidney and to investigate the role of hypothalamic renin in sodium-induced hypertension.Design and methodsWe investigated the expression of the renin gene in the hypothalamus and the kidney of rats with altered sodium intake and those administered either deoxycorticosterone acetate (DOCA) or sodium. Diets containing a high (8% NaCl), normal (2% NaCl), or low (0.2% NaCl) amount of sodium were administered to 12-week-old male Wistar rats for 10 days or 8 weeks before the rats were killed. Male Wistar rats administered either DOCA or 1% NaCl were killed 2 weeks (during the prehypertensive stage) or 6 weeks (during the hypertensive stage) after the start of treatment. The hypothalamus and kidneys were excised for extraction of total RNA. Competitive polymerase chain reaction of renin mRNA and deletion-mutated renin RNA was performed, and the renin mRNA concentration was calculated.ResultsA high sodium intake for 10 days increased the renin mRNA in the hypothalamus; the hypothalamic renin mRNA had not been suppressed after 8 weeks of a high sodium intake despite the lowering in renal renin mRNA. Renin mRNA levels in the hypothalamus were not suppressed either in the prehypertensive or in the hypertensive stage in rats treated with DOCA or sodium, or both, although the renal renin mRNA was reduced in rats administered DOCA or sodium, or both, compared with that in sham-treated control rats, during both stages.ConclusionsThe expression of the renin gene is regulated differently in the rat hypothalamus from that in the kidney. The constant expression of the renin gene in the hypothalamus during a chronic high sodium load might be related at least in part to the mechanism of the activated brain renin–angiotensin system in sodium-induced hypertension.

ISSN:0263-6352    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

ObjectiveThere is evidence that kinins contribute to some of the renal, cardiovascular, and endocrine effects of the diuretic furosemide. The aim of the present study was to investigate the role of kinins in the regulation of renin secretion, blood pressure, and heart rate under resting conditions and after administration of furosemide.MethodsThe effects of icatibant, a potent, specific, and long-lasting bradykinin B2receptor antagonist, on resting renin secretion, blood pressure, and heart rate, and on the responses of these variables to administration of furosemide, were investigated in conscious, chronically prepared rabbits.ResultsInjection of icatibant in doses of 0.1 and 1.0 mg/kg blocked the hypotensive response to intravenous injections of bradykinin completely. The lower dose of icatibant decreased plasma renin activity in some animals, but did not alter their blood pressure or heart rate. The higher dose suppressed resting plasma renin activity from 10.2 ± 2.2 to 5.6 ± 1.4 ng/ml/2 h (P< 0.01), without changing the blood pressure or heart rate. Injection of furosemide (2 mg/kg) caused a sustained increase in plasma renin activity from 6.7 ± 1.6 to 15.9 ± 3.3 ng/ml/2 h (P< 0.01), a transient increase in mean arterial pressure from 72 ± 3 to 78 ± 3 mmHg (P< 0.05), and a sustained increase in heart rate from 228 ± 8 to 253 ± 6 bpm (P< 0.01). Neither dose of icatibant altered the cardiovascular and renin responses to furosemide.ConclusionsThese results provide evidence that bradykinin B2receptors participate in the regulation of resting renin secretion, but not in the renin secretory or heart rate responses to furosemide.

ISSN:0263-6352    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

ObjectiveTo investigate the vasoactive properties of large (aorta) and small (mesenteric) arteriesin vitroafter chronic losartan treatment of normotensive rats, hence providing information on the role played by angiotensin II in vascular tone.MethodsWistar rats were treated with 10 mg/kg per day losartan for 3 weeks. Ring segments of thoracic aorta and mesenteric resistance arteries (200 μm diameter) were mounted in myographs and wall force measured isometrically.ResultsThe mean carotid blood pressure was reduced significantly after chronic losartan treatment (108 ± 3 mmHg, n = 17 versus 116 ± 2 mmHg, n = 16 in control rats,P< 0.05). In the mesenteric resistance artery the contractile response to 125 mmol/l K+, phenylephrine and angiotensin II was not affected significantly by losartan treatment. A subcontractile concentration of angiotensin II (0.1 nmol/l) induced a significant potentiation of the response to 0.03–100 μmol/l phenylephrine (450 ± 180 to 150 ± 20% of the previous response to phenylephrine in control rats). This potentiation was attenuated significantly in the losartan group (240 ± 80 to 100 ± 15% of the previous response,P< 0.01 versus control rats). In the aorta, the response to 125 mmol/l K+was not affected by chronic losartan treatment. The concentration required for the half-maximal effect for phenylephrine was increased significantly in the losartan group (0.51 ± 0.11 μmol/l versus 0.17 ± 0.03 μmol/l in controls rats; no change in maximum response) and the maximum response to angiotensin II was reduced significanatly (0.7 ± 0.08 mN/mg tissue versus 1.9 ± 0.2 mN/mg tissue in control rats; the concentration for the half-maximal effect was not affected). Potentiation of phenylephrine-induced tone by 0.1 nmol/l angiotensin II (273 ± 55 to 122 ± 12% of the previous response in control rats) was attenuated significantly by losartan treatment (91 ± 46 to 95 ± 23% of the previous response,P< 0.01 versus control)ConclusionsChronic administration of losartan could act on resistance arteries in normotensive rats by blocking the potentiation by angiotensin II of the agonist-induced tone.

ISSN:0263-6352    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

ObjectiveTo evaluate the effect of different 4-week doses of deoxycorticosterone acetate (DOCA), together with 0.9% sodium chloride in the drinking water (DOCA-salt) on the blood pressure and on the accumulation of low-density lipoprotein (LDL) and fibrinogen in artery walls and other tissues in conscious, unrestrained, normotensive Wistar–Kyoto rats.MethodsThe accumulation of LDL labelled with125I via the adduct tyramine cellobiose ([125I]-TC-LDL) and of fibrinogen similarly labelled with131I ([131I]-TC-fibrinogen) was compared in aortic walls, heart, liver, kidney, lung, skeletal muscle, and adrenal gland tissues during the final 24 h of a 4-week administration of DOCA–salt, with vehicle–salt and saline as controls.ResultsIn control and vehicle rats the blood pressure did not change significantly during the last 5 days of treatment. Administration of DOCA–salt produced a dose-dependent increase in blood pressure during the same period. DOCA–salt administration increased LDL accumulation in the aorta and the heart and decreased LDL accumulation in the adrenal gland compared with those in rats of the control and vehicle groups. DOCA–salt administration did not affect fibrinogen accumulation significantly.ConclusionDOCA–salt treatment produces an increase in arterial blood pressure accompanied by an increase in LDL accumulation by the aortic wall and heart and a decrease in LDL accumulation by the adrenal gland. These observations raise the possibility that one mechanism by which hypertension affects atherosclerosis is through increased LDL accumulation in arterial walls.

ISSN:0263-6352    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

BackgroundHypertension and coronary heart disease are programmed by maternal undernutritionin utero. The feeding of low-protein diets to rats during their pregnancy results in higher blood pressure in the offspring from the age of weaning.ObjectiveTo determine whether a low-protein diet increases foetal exposure to glucocorticoids of maternal origin, resulting in altered hypothalamic–pituitary–adrenal axis function and hypertension.DesignRats were fed an 18% casein diet (control) or a 9% casein diet (low protein) during pregnancy. Low-protein-fed dams were injected with metyrapone to inhibit corticosterone synthesis or with metyrapone plus a replacement dose of corticosterone. The offspring of these pregnancies had their blood pressure determined when they were aged 7 weeks.MethodsThe systolic blood pressure was determined using an indirect tail-cuff method. Glucocorticoid action in the hypothalamus was measured using glycerol-3 phosphate dehydrogenase as a reference enzyme.ResultsBlood pressures of rats exposed to maternal low-protein dietsin uterowere elevated significantly relative to those of control rats. The animals that had been exposed to a maternal low-protein diet also exhibited increased glycerol-3 phosphate dehydrogenase (GPDH) activity in the hypothalamus, whereas their pyruvate kinase activity was not changed. The offspring of rats injected with metyrapone did not have raised blood pressure or GPDH activities. Replacement of corticosterone during pregnancy had no effect upon the blood pressures and GPDH activities of male offspring, but it reversed the effects of metyrapone in female offspring.ConclusionsExposure to a maternal low-protein dietin uteroprogrammes hypertension in the rat. The data are consistent with the hypothesis that corticosteroids of maternal origin play a role in this programming effect.

ISSN:0263-6352    

出版商:OVID    

年代:1997

数据来源: OVID