摘要:

ObjectiveTo evaluate the relative contribution of sleep and the endogenous circadian rhythmicity in producing the 24-h variations in the plasma renin activity.MethodsTen normal young men were studied, under basal conditions with normal nocturnal sleep from 2300–0700 h and once after a night of total sleep deprivation followed by 8 h daytime sleep from 0700 to 1500 h. Plasma renin activity was measured every 10 min for 24 h and the profiles were analysed using the pulse detection program ULTRA.ResultsDuring the 8 h night-time sleep a significant increase in the mean plasma renin activity levels occurred compared with the subsequent 8-h waking periods. After the shift in the sleep period, a sleep-associated increase was clearly apparent during the daytime hours. The number and the amplitude of the oscillations, linked to the non-rapid eye movement-rapid eye movement sleep cycles, increased during sleep (at whatever time it occurred), and were dependent on the regularity and the length of the sleep cycles. In awake subjects the plasma renin activity generally fluctuated in a more damped and irregular manner, but occasionally the plasma renin activity oscillated at a regular periodicity with two dominant peaks centred around 100 and 50 min.ConclusionThese results demonstrate that the 24-h plasma renin activity variations are not circadian in nature but are related to sleep processes, which create the nycthemeral rhythm by increasing both the frequency and the amplitude of the oscillations.

ISSN:0263-6352    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

ObjectiveTo study exercise blood pressure response in association with exercising muscle maximal vasodilatory capacity in normotensives with a positive and negative family history of hypertension.SubjectsTwenty-eight normotensive healthy subjects were recruited. Of these, two females and 13 males had a positive, and three females and 10 males had a negative, family history of hypertension.MethodsBoth groups of subjects rode a bicycle ergometer while systolic blood pressure, diastolic blood pressure and heart rate were measured at 30%, 60% and peak oxygen uptake rate. The vasodilatory capacity was examined in the lower leg by measuring the minimal vascular resistance during peak reactive hyperemia after 10 min arterial occlusion.ResultsAge, body weight, resting blood pressure, peak oxygen uptake rate and casual lower leg vascular resistance were not significantly different between the two groups of subjects. Significantly higher exercise systolic blood pressure (9%) and diastolic blood pressure (9%) were seen in the subjects with positive family history of hypertension compared with the subjects with negative family history of hypertension. Exercise heart rate was significantly higher in the subjects with negative than in those with positive family history of hypertension. The vascular resistance at peak vasodilation was 22% higher in the subjects with positive than in the subjects with negative family history of hypertension.ConclusionsThis study demonstrates that the dynamic exercise blood pressure is exaggerated and skeletal muscle vasodilatory capacity is limited in normotensives with genetic risk of hypertension. This suggests that the higher pressor response to physical stress that is found in normotensives with a family history of hypertension may be attributed to the resistance vessels in the exercising muscle.

ISSN:0263-6352    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

ObjectiveTo assess the individual and combined effects of exercise and weight loss on the cardiovascular risk factors and cardiac left ventricular structure and function in overweight individuals.MethodsA randomized, parallel-group, crossover study design was adopted. The following treatments were employed: exercise three times a week at 70% maximum work capacity for 30 min; dietary modification to achieve weight loss involving 4200 kJ/day dietary restriction; and a combination of both exercise and dietary modification weight-loss programmes. Each subject was randomly assigned to one group only and was studied after a 12-week treatment and 12-week control period, performed in a random order. Thirty subjects entered the trial, 23 completing both treatment and control phases.ResultsBody weight remained unchanged with exercise alone and fell significantly both with weight loss and with the combination. The corresponding effects on blood pressure were also significant. Exercising groups also showed a significant increase in maximal oxygen consumption and a reduction in heart rate. Serum cholesterol and triglycerides fell significantly only after the combination, whereas high-density lipoprotein-cholesterol increased with exercise, decreased with weight loss and did not change with the combination. Interventricular septum and posterior wall thickness measurements remained unchanged after 12 weeks' treatment in all groups. No significant changes occurred in left ventricular internal diastolic diameter, wall thickness: radius ratio or the heart rate corrected ratio of peak early diastolic filling velocity: peak late diastolic filling velocity. Left ventricular mass and mass indexed to body surface area were not changed in any group.ConclusionsThe results indicate that the effects of exercise and weight reduction on blood pressure are additive, although a positive interaction may exist with respect to lipids. Despite lowering blood pressure, exercise and weight loss had no effect on cardiac left ventricular structure or function in these overweight individuals.

ISSN:0263-6352    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

ObjectiveTo determine whether elevated blood pressure tracks to a greater degree in overweight than in lean children.DesignProspective cohort study.MethodsWe examined 758 adolescents (mean age 1 3.4 years) who participated in a longitudinal study of blood pressure. The degree of tracking was examined by cross-classification of sex-specific tertiles of systolic blood pressure (SBP) and body mass index determined at baseline and 5 years later. Those children that were in the highest fertile of SBP and body mass index were considered to be 'overweight with elevated blood pressure'. Those that were in the highest tertile of SBP but lowest tertile of body mean index were considered to be 'lean with elevated blood pressure'.ResultsOf those boys that were initially classified as lean with elevated blood pressure, 38% remained so classified compared with 54.6% of those that were initially classified as overweight with elevated blood pressure. Among the girls the respective proportions were 48 and 44.2%. The subjects of each sex who were lean with elevated blood pressure were significantly shorter at baseline than their overweight counterparts, and over the follow-up period experienced a greater mean increase in SBP than their overweight peers. This difference was almost totally explained for the boys once the difference in height change was taken into account. For the girls a difference of 5.9 mmHg remained after covariate adjustment for the change in height.ConclusionThese results fail to support the hypothesis that blood pressure tracks differently in obese and in lean adolescents, particularly once differences in sexual maturation are considered.

ISSN:0263-6352    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

ObjectiveTo examine the short-term reproducibility of urinary albumin measurements and the relation of urinary albumin excretion to the clinic and ambulatory blood pressure levels in elderly untreated hypertensive subjects.SettingOutpatient hypertension clinic of a District General Hospital.Main outcome measuresThe within-patient reproducibility of 24-h urinary microalbumin and electrolyte excretion and relation to 24-h and clinic blood pressure levels.PatientsSixty-four untreated elderly hypertensives (mean age 74.7 years, range 64–82) with systolic blood pressure ≥ 160 mmHg or diastolic blood pressure ≥ 95 mmHg, or both, were recruited from general practitioner clinics and current outpatient attenders. The patients had not received antihypertensive treatment for at least 4 weeks.MethodsThe clinic and 24-h non-invasive ambulatory blood pressures were recorded with a simultaneous 24-h urine collection for measurement of the urinary albumin and electrolyte excretion. Thirty-seven subjects performed two consecutive 24-h urine collections for an assessment of the short-term reproducibility of the albumin and electrolyte excretion.ResultsThe coefficient of variation of 24-h urinary albumin excretion was 62%, and for the albumin creatinine ratio 52%, compared with 19% for sodium and 15% for potassium excretion. The urinary albumin excretion correlated with clinic systolic blood pressure (r = 0.33,P=0.01) and with 24-h ambulatory systolic (r = 0.48,P< 0.001) and diastolic (r = 0.32,P= 0.01) blood pressure. The subjects with microalbuminuria (24-h urinary albumin excretion in the range 30–300 mg) had higher clinic and ambulatory blood pressures than those with lower levels of albumin excretion.ConclusionsThe low day-to-day intrasubject reproducibility in the 24-h urinary albumin excretion considerably reduces the potential value of single collections in the assessment of microalbuminuria in elderly hypertensives. The urinary albumin excretion correlates with the clinic and 24-h ambulatory blood pressures in elderly hypertensives.

ISSN:0263-6352    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

ObjectivesTo seek regional differences within the USA in the 'all-cause mortality' of hypertensive men during the 14 years following institution of antihypertensive treatment, and to determine how other pretreatment data can be related to that all-cause mortality.DesignIn the mid-1970s pretreatment clinical data were collected and computerized for 5698 hypertensive veterans. Deaths during the subsequent 14 years were obtained from the Veterans Administration Beneficiary Identification and Record Location System and the National Death Index. Relationships between pretreatment data and death were sought using χ2-and z-tests for bivariate comparisons and logistic regression for multivariate analyses.PatientsHalf of the 5698 previously untreated male hypertensive military veterans were Black. Their mean age was 52.3 years and mean pretreatment blood pressure was 160/104 mmHg. Additional pretreatment data included body mass index, cigarette and alcohol usage, age and self-reported comorbidities. These patients began antihypertensive treatment during 1974–1975 in 28 special Veterans Administration outpatient clinics throughout the USA.ResultsDuring the 14 years after treatment began, 2283 of these patients (40%) died. Those from the southeastern USA, i.e. in the 'Stroke Belt', were 1.32-fold more likely to die than patients living elsewhere. Other pretreatment characteristics positively related to all-cause mortality included age, systolic blood pressure, cigarette and alcohol usage, and self-reported comorbidities. Race was unrelated to mortality.ConclusionAll-cause mortality was increased among hypertensive subjects from the southeastern USA. The reasons for this excess mortality remain unclear. Other pretreatment characteristics were also related to mortality, but race was not.

ISSN:0263-6352    

出版商:OVID    

年代:1994

数据来源: OVID