摘要:

Sympathetic factors play a central role not only in cardiovascular homeostatic control but also in the pathogenesis and/or in the progression of several cardiovascular diseases, such as essential hypertension, myocardial infarction, cardiac arrhythmias and congestive heart failure. This explains why assessment of adrenergic neural function in humans has been, and certainly still remains, one of the major fields in cardiovascular research.The present paper will review in detail the haemodynamic, pharmacological, biochemical, neurophysiological, neurochemical and neural imaging techniques by which sympathetic activity is assessed in humans, highlighting the main advantages and limitations of each of them. Although plasma noradrenaline measurement represents a useful guide to assess sympathetic neural function, direct recording of sympathetic nerve traffic via microneurography and noradrenaline radiotracer methods have in recent years largely supplanted the plasma noradrenaline approach. This is because they allow (1) discrimination between the central or peripheral nature of increased plasma noradrenaline levels, and (2) precise estimation of the behaviour of regional sympathetic neural function both under physiological and pathological conditions. In contrast, the approach based on spectral analysis of heart rate and blood pressure signals has been shown to have important limitations which prevent the method from faithfully reflecting sympathetic cardiovascular drive. Neural imaging techniques, which require expensive technical support, allow direct visualization of sympathetic enervation of human organs, thus providing information on the ‘in vivo’ metabolism of noradrenaline in different cardiovascular districts.Although technical improvements have allowed a more precise assessment of human adrenergic function, no technique so far available can be viewed as a ‘gold standard’ with which the others might be compared. Limitations and disadvantages of the various techniques may be reduced if these methods are seen as being complementary and employed in combination, allowing more reliable information to be achieved on the sympathetic abnormalities characterizing cardiovascular diseases, and thus hopefully providing a stronger rationale for newer therapeutic approaches involving pharmacological modification of the sympathetic nervous system and adrenoreceptors.

ISSN:0263-6352    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

While the recent evolution of guidelines for arterial hypertension also includes the need to evaluate coexistent cardiovascular risk factors and target organ damage in the base work-up for arterial hypertension, it does not include echocardiography systematically, because there is no evidence that information on LV geometry and function can modify management strategy in every circumstance, and there is concern about the technical variability of repeated echocardiographic examinations in the individual patient. The present issue of the Journal publishes a paper showing that adherence to the 1993 World Health Organization – International Society of Hypertension recommendations leaves untreated a proportion of patients with ‘mild hypertension’ who instead would have been treated if decision was also based on echocardiographic information on LV geometry. These findings challenge the most recent positions of national Societies, reserving the indication for echocardiography to patients with high risk (the vast majority). The present study appears indeed to reinforce the notion that echocardiographic examination might be very important in patients in whom, based on guidelines adherence, no pharmacological treatment would be required, whereas, based on the present evidence, echocardiographic information might be less important and perhaps superfluous for decision making in patients assigned to a high risk score, for whom aggressive treatment has been already scheduled.

ISSN:0263-6352    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

BackgroundRegular exercise has been associated in prospective studies with reduced incidence of cardiovascular disease (CVD) and death.ObjectiveTo assess in a cohort study whether there is a similar protective effect of regular exercise among hypertensive individuals.DesignPopulation-based prospective cohort study. Spare time physical activity was assessed by structured interview.SettingMalmö, Sweden.ParticipantsHealthy men (n= 642) born in 1914. A baseline examination took place in 1969–1970.Main outcome measuresAll-cause and cardiovascular mortality rates during 25 years of follow-up in relation to blood pressure and other risk factors for atherosclerosis.ResultsOne-hundred (16%) men reported vigorous spare time physical activity. In this group, 31 had hypertension (blood pressure ≥ 160/95 mmHg or treatment for hypertension), 47 were smokers and 39 had hyperlipidaemia. Among the 173 men with hypertension, vigorous physical activity was associated with markedly reduced rates of all-cause (17.3 versus 40.0 deaths per 1000 person-years) and cardiovascular mortality (6.3 versus 21.0 deaths per 1000 person-years). The risk reductions associated with exercise remained statistically significant after adjustment for smoking, systolic blood pressure and antihypertensive therapy. The relative risk was 0.43 (confidence interval 0.22–0.82) for total mortality and 0.33 (confidence interval 0.11–0.94) for CVD mortality.ConclusionPeople who regularly perform physical activity constitute a heterogeneous group with regard to their exposure to known cardiovascular risk factors. Our results support the view that regular physical activity is associated with a reduced incidence of cardiovascular disease and death and suggest that this protective effect may be enhanced among hypertensive individuals.

ISSN:0263-6352    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

ObjectiveCoronary heart disease (CHD) risk factors have been consistently related to an increase in carotid intima–media thickness (IMT) in selected populations. However, few studies were population-based and furthermore little attention has been given to the influence of CHD risk factors on IMT in low-risk populations for CHD.DesignWe examined the association between carotid IMT and CHD risk factors in a large (n= 1013) and representative sample of middle-aged men and women in one of the European populations with the lowest CHD risk.MethodsHigh-resolution B-mode ultrasonography of the common carotid arteries was performed.ResultsAge, smoking (not significant in women), body mass index, waist to hip ratio, systolic (SBP) and diastolic blood pressure, alcohol consumption, total and low-density lipoprotein cholesterol, triglycerides, glycaemia, fibrinogen (not significant in women), haematocrit (not significant in men) and insulin (not significant in women) were positively and significantly associated with mean IMT. High-density lipoprotein (HDL) cholesterol (not significant in women) was negatively and significantly associated with mean IMT. In a subsample of 355 men, IMT was not associated with angiotensin I-converting enzyme gene polymorphism. Multivariate analyses showed, in men, independent associations between mean IMT (0.61 ± 0.11 mm) and age, pack-years, SBP, HDL cholesterol, alcohol and the interaction between age and alcohol. In women, only age and SBP were independently associated with mean IMT (0.58 ± 0.09 mm).ConclusionsWe found thinner IMT than those found in high-risk populations, suggesting that an increased IMT might reflect local atherosclerosis. Protective factors such as HDL cholesterol or regular and moderate alcohol consumption are probably important determinants of the early stages of atherosclerosis in these low-risk populations.

ISSN:0263-6352    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

ObjectiveTo determine the relationships between lifestyle and cardiovascular risk factors among the Brazilian Amondava, one of the world's most isolated populations.DesignCross-sectional, population-based study. Four ageand sex-matched samples from Brazil Africa, Italy and Poland, representing different levels of modernization, were compared. Body weight, height, blood pressure, serum cholesterol and glycaemia were measured, and a standard questionnaire administered. Data concerning dietary habits and physical activity were collected. A personal socio-economic score was calculated, on the basis of type of economy, level of formal education, type of occupation, type of habitat, availability of piped water and electricity, main source of income, housing conditions, availability of radio, television or personal computer, knowledge of a second language, and organized health facilities.SettingPrimary epidemiological screening, at an institution.ResultsAmong the Amondava blood pressure was always < 140/90 mmHg, it did not increase with age and was not correlated with any other variable; 46.6% of subjects had systolic blood pressure < 100 mmHg. Blood pressure among the Amondava (109.6 ± 11.1/69.5 ± 6.4 mmHg) was on average lower (P< 0.0001) than in all other samples. Among the Amondava, the concentration of total cholesterol was always < 200 mg/dl, i.e. similar to that of Africans whose diet included large amounts of vegetable foodstuffs; 90% had glycaemia (< 80 mg/dl), and their mean value was the lowest (55.1 ± 14.9 mg/dl) of all the groups.ConclusionsIn addition to a possible genetic predisposition not analysed in this study, a traditional lifestyle (no contact with civilization, diet based on complex carbohydrates and vegetables, high energy expenditure) may protect against the development of hypertension, hypercholesterolaemia, and diabetes.

ISSN:0263-6352    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

BackgroundAccumulating evidence has supported the pathophysiological role of angiotensinogen in essential hypertension. However, some studies of molecular genetics have implicated that there may be an ethnic variation concerning the disease susceptibility of theAGTgene.Objectives and methodsTo evaluate the importance of this candidate gene for hypertension, we undertook an extensive association study in the Japanese. This case–control study was conducted in a total of 1232 individuals consecutively enrolled in a single institution, divided into two subgroups: one subgroup comprised 254 hypertensive and 224 normotensive subjects and the other comprised 463 hypertensive and 291 normotensive subjects. A meta-analysis was subsequently performed on six Japanese studies including the present study.ResultsNo significant association was observed between a molecular variant ofAGT, Thr235, and hypertension status in our case–control study. Moreover, this finding was extendible to anotherAGTpolymorphism, G-6A, one of the potential functional polymorphisms in the promoter region, because these two polymorphisms proved to be in complete linkage disequilibrium in the studied population. The meta-analysis revealed that the pooled estimate of the odds ratio across the studies was 1.22 (95% CI 1.05–1.42), and that there was significant evidence against homogeneity of the odds ratios among the studies included (χ2= 19.8, df = 5,P= 0.0014). In particular, a large range of variation (60–83%) was found for the allele frequency of Thr235 among control subjects of the six Japanese case-control studies.ConclusionsAlthough the meta-analysis appears in favour of association between theAGTvariant and essential hypertension in the Japanese, there is considerable heterogeneity among the studies and the evidence is also rather borderline. Further comprehensive approaches are needed to resolve this debatable issue.

ISSN:0263-6352    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

ObjectiveTo investigate the hypothesis that preeclampsia is associated with a common insertion–deletion polymorphism in the angiotensin-converting enzyme gene.DesignSeventy-two women with pre-eclampsia and 83 normotensive pregnant women participated in the study. Pre-eclampsia was defined as a blood pressure exceeding 140/90 mmHg in a previously normotensive woman, associated with proteinuria in excess of 300 mg/l in a 24 h collection. Samples for fetal genotyping were available from 66 pregnancies complicated by pre-eclampsia and 79 normotensive pregnancies.MethodsMaternal and fetal samples were genotyped at the insertion–deletion (I–D) polymorphism in intron 16 of the angiotensin-converting enzyme gene by the polymerase chain reaction followed by agarose electrophoresis.ResultsNeither the I–D genotype distributions nor the allele frequencies differed significantly between preeclamptic and normotensive pregnancies in maternal or fetal samples (χ2< 0.3, not significant). The odds ratio for pre-eclampsia in women with the DD genotype, compared with the ID and II genotype, was 1.09 (95% confidence interval 0.55–2.16). The odds ratio associated with the DD genotype in the fetus was 1.14 (0.56–2.32).ConclusionThis study has found no evidence that the insertion–deletion polymorphism in the angiotensinconverting enzyme gene is associated with pre-eclampsia.

ISSN:0263-6352    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

ObjectiveTo investigate the effects of chronic treatment with simvastatin (SV) on endothelium-dependent relaxation and ouabain-induced contractions in aortic rings from spontaneously hypertensive rats (SHR), comparing with normotensive Wistar–Kyoto rats (WKY).MethodsAfter a 12-week period of administration of 1 or 2 mg/kg SV to SHR and WKY, systolic blood pressure (SBP) and vascular reactivity in endothelium-intact aortic rings were assessed.ResultsRelaxation in response to acetylcholine (ACh) in WKY remained unaltered, but in SHR treated with 1 mg/kg SV, enhanced ACh-induced relaxation (P< 0.05 versus untreated SHR) reached values observed in untreated WKY. The 2 mg/kg treatment also improved ACh relaxation (P< 0.01 andP< 0.05 versus untreated SHR and WKY respectively). Inhibiting cyclo-oxygenase (COX) with indomethacin (INDO) improved ACh relaxation in SHR (P< 0.05) but not in WKY, independent of treatment with SV. Inhibition of nitric oxide synthase (NOS) withNG-nitro-L-arginine (L-NOARG) abolished ACh relaxations in all cases (P< 0.001). The result was unaltered when combining INDO plus L-NOARG. SV treatment also decreased ouabain-induced contractions in endotheliumintact aortic rings from SHR, diminishing the percentage effect of contraction from 64.56 ± 2.95 (untreated SHR) to 26.98 ± 7.06 and 38.10 ± 8.21 (1 and 2 mg/kg treated SHR respectively). Response to ouabain in WKY was not significantly affected by SV treatment.ConclusionsChronic treatment of SHR with SV improves endothelium-dependent ACh relaxation of the aortic rings, probably by an NO-involving mechanism more than by inhibiting contractile COX-derived factors. An improvement in endothelial modulation of ouabain-induced contractions was also observed after treatment with SV in SHR, which might be due to an inhibition of a calcium–sodium exchanger.

ISSN:0263-6352    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

ObjectiveThe present study aimed to determine whether there were alterations in intestinal calcium homeostasis in the spontaneously hypertensive rats (SHR) and to identify at which interface of the intestinal epithelial cell (brush border or basolateral) this occurs.DesignControversy exists as to whether intestinal calcium transport is altered in association with hypertension. Studies using perfused duodenal segments of the SHR have shed little light on the problem; other studies have only measured calcium transport in brush border membrane vesicles. This study allows specific focus on calcium transport mechanisms at both the brush border and basolateral membrane using simultaneously prepared membrane vesicles.MethodsCalcium transport was studied by measuring radiolabelled calcium (45Ca) uptake in isolated brush border and basolateral membrane vesicles, prepared from the small intestines of SHR and Wistar–Kyoto (WKY) rats. Calcium uptake was measured when vesicles were incubated in solutions containing different concentrations of ATP and calcium. Orientation and membrane marker assays were used to confirm the phenotypes of the two membrane vesicle preparations.ResultsATP-dependent calcium efflux was only observed in the basolateral membrane, which contains the Ca2+-ATPase pump. SHR brush border membrane vesicles displayed no significant increase in calcium incorporation, whereas WKY brush border vesicles showed a 500% increase in uptake (ANOVA,P< 0.05,n= 7).ConclusionsThis study indicates that deficiencies exist in SHR intestinal calcium transport at the brush border membrane of intestinal epithelial cells. While further studies are required to ascertain the exact mechanisms involved, postulated deficiencies in the actions of calcium regulating hormones at this membrane suggest the need for concurrent intake of a calcitrophic agent to assist calcium uptake at the brush border membrane.

ISSN:0263-6352    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

ObjectiveTo determine the relationships between blood pressure, membrane microviscosity, plasma lipids and cytosolic pH in Dahl rats susceptible or resistant to salt hypertension.Design and methodsBlood pressure, plasma triglycerides and total cholesterol, platelet cytosolic pH (pHi) and the microviscosity of both outer membrane leaflet (TMA-DPH fluorescence anisotropy) and membrane lipid core (DPH fluorescence anisotropy) were studied in platelets and erythrocyte ghosts of Dahl salt-sensitive (SS/Jr) and salt-resistant (SR/Jr) rats fed either a low-salt diet (0.3% NaCl) until the age of 9, 15 or 24 weeks or a high-salt diet (4% NaCl) for 5 or 10 weeks after weaning.ResultsAt low salt intake, DPH but not TMA-DPH anisotropy increased with age in platelets of SS/Jr rats. Chronic high salt intake was accompanied by an increase of DPH anisotropy in platelets but not in erythrocyte ghosts of SS/Jr rats. Platelet DPH anisotropy correlated positively with blood pressure of salt-loaded SS/Jr rats. Chronic high salt intake also reduced pHi in platelets, the regulation of which seemed to be related to the changes in TMA-DPH anisotropy. This especially concerns the thrombin-induced pHirise which was inversely related to basal pHi, plasma lipids and TMA-DPH anisotropy. Altered membrane lipid composition might be the underlying mechanism because both membrane microviscosity and platelet pHi regulation were reported to correlate significantly with plasma triglycerides and/or cholesterol.ConclusionsPlatelets of salt hypertensive Dahl rats are characterized by an increased microviscosity of membrane lipid core which correlated positively with blood pressure. The major influence of plasma triglycerides on DPH anisotropy should be taken into consideration when investigating the links between membrane microviscosity and blood pressure. On the other hand, the changes in microviscosity of the outer membrane leaflet might be involved in pHiregulation (probably through control of the Na+/H+exchanger).

ISSN:0263-6352    

出版商:OVID    

年代:1999

数据来源: OVID