ISSN:0263-6352    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

The strong relation between increased left ventricular mass and cardiovascular events makes accurate measurement of left ventricular mass a high priority, especially in patients with hypertension. M-mode echocardiography is used most widely to measure left ventricular mass because of its wide availability, moderate expense, anatomic and prognostic validation and lack of radiation or claustrophobia; however, this technique is expertise-dependent and may give erroneous results in distorted ventricles. Two-dimensional and especially three-dimensional echocardiography increase the precision with which left ventricular mass is measured but they are more time-consuming and difficult to perform on a large scale. Magnetic resonance imaging provides highly accurate left ventricular mass measurements and permits tissue imaging but its use is limited by expensive, fixed facilities and claustrophobia. Cine computed X-ray tomography also measures left ventricular mass accurately and permits perfusion assessment with contrast injection but it involves radiation and the use of fixed facilities of limited availability. Understanding the strengths and limitations of available techniques can facilitate selection of the most appropriate method to measure left ventricular mass in a particular setting.

ISSN:0263-6352    

出版商:OVID    

年代:1997

数据来源: OVID

ISSN:0263-6352    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

Atrial natriuretic peptide (ANP) regulates a variety of physiological parameters, including the blood pressure and intravascular volume, by interacting with its receptors present on the plasma membrane. ANP receptors are of three subtypes: ANP-A, -B and -C receptors. ANP-A and ANP-B receptors are guanylyl cyclase receptors, whereas ANP-C receptors are coupled to adenylyl cyclase inhibition or phospholipase C activation through inhibitory guanine nucleotide-regulating protein. Unlike other G protein-coupled receptors, ANP-C receptors have a single transmembrane domain and a short cytoplasmic domain of 37 amino acids, the cytoplasmic domain has a structural specificity like those of other single-transmembrane-domain receptors and 37 amino-acid cytoplasmic domain peptide is able to exert is inhibitory effect on adenylyl cyclase. The activation of ANP-C receptor by C-ANP4–23(a ring-deleted peptide of ANP) and C-type natriuretic peptide inhibits the mitogen-activated protein kinase activity stimulated by endothelin-3, platelet-derived growth factor and phorbol-12 myristate 13-acetate. C-ANP also inhibits mitogen-induced stimulation of DNA synthesis, indicating that the ANP-C receptor plays a role in cell proliferation through an inhibition of mitogen-activated protein kinase and suggesting that the ANP-C receptor might also be coupled to other signal transduction mechanism(s) or that there might be an interaction of the ANP-C receptor with some other signalling pathways. ANP receptor binding is decreased in most organs in hypertensive subjects and hypertensive animals. This decrease is consistent with there being fewer guanylyl cyclase-coupled receptors in the kidney and vasculature and selective inhibition of the ANP-C receptor in the thymus and spleen. Platelet ANP-C receptors are decreased in number in hypertensive patients and spontaneously hypertensive rats. ANP-A, -B and -C receptors are decreased in number in deoxycorticosterone acetate–salt-treated kidneys and vasculature; however, the responsiveness of adenylyl cyclase to ANP is augmented in the vasculature and heart and is attenuated completely in platelets. These alterations in ANP receptor subtypes may be related to the pathophysiology of hypertension. Several hormones such as angiotensin II, ANP and catecholamines, the levels of which are increased in hypertension, downregulate or upregulate ANP-C receptors and ANP-C receptor-mediated inhibition of adenylyl cyclase. It can be suggested that the antihypertensive action of several types of drugs such as angiotensin converting enzyme inhibitors, angiotensin type 1 receptor antagonists and β2-adrenergic antagonists may partly be attributed to their ability to modulate the expression and function of the ANP-C receptor.

ISSN:0263-6352    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

ObjectiveTo investigate factors affecting the nocturnal decrease in blood pressure.DesignA cross-sectional study of 823 community-based untreated subjects aged > 20 years. Screening and ambulatory blood pressures were measured and the effects of age and the ambulatory blood pressure on the nocturnal decrease were examined.ResultsThe magnitude of the decrease and the percentage decrease in the nocturnal blood pressure increased with increasing daytime ambulatory blood pressure and decreased with increasing night-time ambulatory blood pressure. Although the magnitude of the nocturnal decrease in blood pressure increased with increasing daytime blood pressure, the nocturnal blood pressure levels in hypertensives were still higher than those in normotensive subjects. The magnitude decreased with increasing age for men but not for women, whereas the percentage decrease decreased with increasing age both for men and for women. The SD of the 24 h blood pressure correlated strongly to the magnitude of the nocturnal decrease (systolic blood pressure r = 0.62,P< 0.0001; diastolic blood pressure r = 0.52,P< 0.0001), suggesting that the SD of the 24 h blood pressure is representative of the nocturnal decrease. A minimal nocturnal decrease was observed frequently in elderly normotensive men but infrequently in hypertensive individuals from the general population. A marked nocturnal decrease was observed frequently in hypertensive women aged > 70 years.ConclusionAlthough the magnitude of the nocturnal decrease in blood pressure increased with increasing daytime blood pressure, the nocturnal blood pressure levels increased with increasing daytime ambulatory blood pressure. Therefore, the blood pressure in hypertensive subjects should essentially be lowered throughout the 24 h period. A marked nocturnal decrease in blood pressure in some elderly hypertensive women was observed without treatment. The nocturnal blood pressure levels of such subjects should be considered during treatment.

ISSN:0263-6352    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

ObjectiveTo evaluate the psychophysiological response to mental stress of young healthy salt-sensitive normotensive subjects.MethodsThirty-two healthy volunteers who had previously been phenotyped for salt sensitivity were selected for the study. The 16 salt-sensitive and 16 salt-resistant subjects, who were matched for age, body mass index and family history of hypertension, underwent a mental stress test consisting of an information-processing task performed under time pressure (the Manometer test). During the experimental session the blood pressure, heart rate and pulse-wave velocity were registered continuously. Before and after the mental task subjects were instructed to complete several standardized psychological state and trait questionnaires.ResultsMental stress resulted in a greater rise in blood pressure (P< 0.05) and in pulse-wave velocity (P< 0.01) in salt-sensitive than in salt-resistant individuals. Salt-sensitive subjects also displayed significantly higher levels of anxiety (P< 0.01) and a lower level of control of anger (P< 0.01) than did salt-resistant subjects. Furthermore, the level of irritation of the salt-sensitive subjects was higher both before (P< 0.01) and after (P< 0.05) the stress test.ConclusionsAn increased responsiveness of the blood pressure to mental stress and an increased level of irritation are associated with salt sensitivity in normotensive subjects. These findings are in line with the hypothesis that psychophysiological traits play a role in the development of salt-sensitive hypertension.

ISSN:0263-6352    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

ObjectiveTo examine the relationship between changes in resting and ambulatory blood pressures induced by dietary salt restriction in 90 young normotensive men.MethodsSubjects were given a standardized low-salt diet containing 20 μmol sodium chloride per day for 14 days. To this diet, a daily supplement of 20 tablets of slow sodium (10 μmol NaCl per tablet) or placebo was added in a randomized single-blind cross-over fashion for 7 days. The ambulatory blood pressure was measured on the sixth day and the resting blood pressure was measured on the seventh day of each dietary period.ResultsAlthough salt intake did not affect blood pressure levels in the whole group, the response of the blood pressure was quite variable among individual subjects. Salt-induced changes in resting systolic (r = 0.30,P= 0.006) and mean (r = 0.27,P= 0.014) blood pressures, but not diastolic blood pressure, were correlated positively to changes in daytime ambulatory blood pressure. The changes in resting systolic and mean blood pressures were also correlated significantly to the nocturnal falls in systolic (r = 0.26,P= 0.015) and mean (r = 0.27,P= 0.012) blood pressure levels and heart rate (r = 0.26,P= 0.015) under the high-salt diet. Diet-induced changes in resting mean blood pressure were correlated significantly to the daytime ambulatory blood pressure (r = 0.30,P< 0.005) and the resting heart rate (r = 0.24,P< 0.02) under the high-salt diet.ConclusionSalt-induced changes in resting blood pressure in young normotensive men are correlated positively to changes in ambulatory daytime blood pressure levels as well as to the daytime ambulatory blood pressure and the nocturnal fall in blood pressure under a high-salt diet. These findings suggest that dietary salt-intake restriction can lower both resting and daytime ambulatory blood pressure levels in some normotensive individuals who may be predisposed to the development of hypertension.

ISSN:0263-6352    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

ObjectiveTo evaluate whether a high-salt diet causes retention of Na in Dahl rats.DesignTo compare the whole-body and organ (liver, spleen, kidney, heart, lung, femur, submaxillary gland and muscle) Na contents in Dahl salt-sensitive rats and Dahl salt-resistant rats.MethodsRats aged 6–10 weeks of both strains were fed a normal-salt (0.4% NaCl) or a high-salt (8% NaCl) diet. The whole-body and organs were then ashed and their respective Na contents determined.ResultsSalt-resistant rats fed the normal-salt diet had a higher whole-body Na content than did salt-sensitive rats. The high-salt diet increased the whole-body Na content of salt-sensitive rats significantly, but it did not increase that of salt-resistant rats. The high-salt diet caused a significant increase in the organ weight: body weight ratio for all organs of the salt-sensitive rats, except the submaxillary gland, but had no effect on the ratios for salt-resistant rats, apart from that for the kidney. The kidney, submaxillary gland and muscle Na concentrations were greater in salt-sensitive rats than they were in salt-resistant rats. Nonetheless, regardless of strain, the high-salt diet had no effect on organ and plasma Na concentrations. The high-salt diet increased the organ weights (liver, spleen, kidney, heart and lung) and the organ Na contents per kg body weight significantly for salt-sensitive rats but not for salt-resistant rats.ConclusionsA high-salt diet caused Na retention in salt-sensitive rats only and this was partially due to enlargement of the organs.

ISSN:0263-6352    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

ObjectiveTo determine the changes in serum angiotensin II (Ang II) and endothelin-1 levels induced by vanadium treatment of sugar-fed rats in order to investigate the relationship between changes in blood pressure and Ang II and endothelin-1 levels.MethodsMale spontaneously hypertensive rats (SHR) were fed starch (control), sucrose, and sucrose plus vanadium compounds at various concentrations. The systolic blood pressure of the rats was estimated by tail-cuff plethysmography. Serum Ang II and endothelin-1 levels were measured by radioimmunoassay.ResultsThere were increases in systolic blood pressure (by 8%) and in serum Ang II (by 20%) in sucrose-fed SHR compared with control. In sucrose plus vanadiumfed SHR, the lowering of the systolic blood pressure (by 11–16% of the sucrose-fed value) was accompanied by a significant decrease in Ang II levels (by 25–60% of the sucrose-fed value) and an increase in endothelin-1 level (by 61–76% of the sucrose-fed value).ConclusionThat Ang II levels are elevated in sucrose-induced hypertension and decreased after vanadium therapy suggests that the renin–angiotensin system plays a role in the induction of hypertension in this model. On the other hand, the elevation of endothelin-1 levels associated with a decreased systolic blood pressure might be secondary to vanadium stimulation of endothelial cells. The data suggest that endothelin-1 is not involved in sugar-induced elevations of the blood pressure.

ISSN:0263-6352    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

ObjectiveThe purpose of the present study was to investigate liver microsomal membrane fluidity simultaneously with membrane fatty acid composition and desaturase activities in spontaneously hypertensive rats (SHR).Design and methodsThe membrane fluidity was determined, after electron spin resonance (ESR) measurement, in SHR compared with normotensive Wistar–Kyoto (WKY) rats, by calculating the order parameter S from ESR spectra of 5-nitroxide stearate and 10-nitroxide stearate, used as spin-labelled fatty acids. Desaturase activities were measured by incubating SHR and WKY rat liver microsomes with [14C]-radiolabeled fatty acids as substrates for desaturation reactions. The fatty acid composition of liver microsomal membranes was determined by gas–liquid chromatography.ResultsWhereas no significant difference between S of 5-nitroxide stearate was observed for SHR and WKY rats, S of 10-nitroxide stearate was significantly lower in SHR than it was in WKY rat microsomal membrane, indicating that the core microsomal membrane fluidity was higher in SHR. Significant differences between fatty acid compositions were observed for SHR and WKY rat microsomal membranes. Δ9 and n-6 Δ6 microsomal desaturase activities were significantly lower in SHR.ConclusionThese results suggest that the higher liver core microsomal membrane fluidity observed in SHR might be dependent on the increased proportion of mono-unsaturated fatty acids. Such observed modifications and the alterations in Δ9 and n-6 Δ6 desaturase activities suggest that an impaired polyunsaturated fatty acid biosynthesis is related to changes in microsomal membrane fluidity in hypertension.

ISSN:0263-6352    

出版商:OVID    

年代:1997

数据来源: OVID