ISSN:0194-911X    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

The in vitro uptake of3H-NE by storage vesicles from the hypothalamus of age-matched spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats has been studied using a new reliable procedure for the isolation of biochemically active storage vesicles. In each of 13 paired studies, done in triplicate, storage vesicles of SHR took up more3H-NE than those of WKY. (The mean difference was 37% more uptake by SHR.) Electron-microscopic examination of normotensive sam-ples showed a concentration of intact synaptic vesicles; whereas SHR subfractions were composed of fragmented membranes that resembled swollen, distorted vesicles. These findings in the brain tissues of SHR parallel our previous results found in SHR peripheral tissues. Taken together, we interpret the results to indicate that the membranes of synaptic vesicles of SHR are altered structurally and biochemically.

ISSN:0194-911X    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

We conducted morphometric studies on the afferent arteriole of spontaneous hyperten-sive rats (SHR) and Wistar-Kyoto (WKY) rats to gain a better understanding of its changes with the development of hypertension. Differences may be related to the SHRs' increased renal vascular resistance. Methacrylate vascular casts were made of the renal vasculature after perfusion fixation with glutaraldehyde. These vascular casts were then examined and measurements made with the scanning electron microscope. Results from this examination of the scanning electron microscope demonstrated a smaller afferent arteriolar diameter in the SHR, compared to the WKY, for both the inner and outer cortical glomeruli. This difference was seen in the 6-week-old SHR, prior to a statistically different blood pressure from the WKY controls, as well as in the 12-week-old hyperten-sive SHR. However, this afferent diameter difference between rat strains was more pronounced in rats at 12 weeks of age. The tapering of the afferent arteriole (difference between proximal and distal afferent diameters) was greater in the 12-week-old SHR than in the age-matched WKY or 6-week-old SHR. We conclude that the smaller caliber afferent arterioles of the SHR may predispose and play a role in the pathogenesis of the subsequent hypertension. The increased afferent arteriolar tapering seen in the hypertensive SHR relates to the already present increased blood pressure. Wall thickness/radius ratios are not different between rat strains (SHR and WKY) at either 6 or 12 weeks of age. These results suggest increased vascular constriction or hypoplastic vessels as the cause of the smaller caliber vessels in the SHR rather than increased wall thickness.

ISSN:0194-911X    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

Microchemical techniques were employed to measure the DNA, contractile protein, and connective tissue protein composition of 150 μg samples of mesenteric and cerebral resistance arteries taken from 25-week-old spontaneously hypertensive (SHR) and control Wistar-Kyoto (WKY) rats. The active and passive mechanical properties of intact resistance arteries also were determined. The DNA content of branches of the posterior cerebral and mesenteric arteries (170 μm I.D.) were elevated by nearly 30% in the SHR compared to the WKY. The amounts of act in and myosin when normalized to DNA content were unchanged in SHR mesenteric arteries compared to control, where-as these amounts were decreased by 25% and 49%, respectively, in the SHR cerebral arteries vs control. The functional implications of these contractile protein measurements agreed with determi-nations of active smooth muscle cell stress-generating capabilities, which were found unchanged in the mesenteric arteries and depressed in the SHR cerebral arteries. Neither the absolute amounts and concentrations (relative to tissue mass) of elastin in mesenteric and cerebral arteries, nor the absolute amounts and concentrations of collagen in the mesenteric artery, were changed in the SHR. However, cerebral artery total collagen was elevated by 31% in the SHR, with no change in collagen concentra-tion between the two strains. Under conditions where the smooth muscle cells were fully relaxed, the internal radii of SHR brain and SHR mesenteric arteries were smaller at all pressures with respect to the WKY. However, only the SHR cerebral arteries were actually less distensible than controls. Thus, it is apparent that hypertension-associated changes in the chemical and mechanical properties of the resistance artery wall vary considerably depending upon which vascular bed is examined. The meas-urements made in this study suggest that these changes are more pronounced in brain arteries. This finding could be of significance regarding the autoregulatory capability of, and blood pressure distribution within, brain vessels of hypertensive animals.

ISSN:0194-911X    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

In anesthetized dogs with the left cardiac sympathetic nerves and both vagal nerves intact, angiotensin II (All) induced a substantial, dose-dependent increase in arterial blood pressure and small increments in cardiac cycle length and ventricular contractile force. In dogs in which the cardiac sympathetic and vagal nerves had been interrupted, All produced similar increases in blood pressure and larger increases in contractile force, but it decreased the cardiac cycle length. In both groups of dogs, All augmented substantially the positive inotropic responses to sympathetic nerve stimulation, but it enhanced the positive chronotropic responses only slightly. However, AH did not appreciably prolong the cardiac responses to sympathetic nerve stimulation, nor did it alter signifi-cantly the cardiac responses to norepinephrine infusions. Hence, at the dosage levels used, All probably did not inhibit the neuronal uptake of norepinephrine appreciably nor did it enhance the responsiveness of the cardiac effector sites to norepinephrine. Therefore, the potentiation of the cardiac responses to sympathetic nerve stimulation by All in these experiments was probably achieved principally by facilitating norepinephrine release from the adrenergic nerve terminals in the heart.

ISSN:0194-911X    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

Daily subcutaneous injections of lente insulin reduced the hypertension and bradycar-dia which developed consistently in streptozotocin diabetic rats. Insulin-treated rats also became less hyperglycemic, drank less water, and gained weight faster than untreated diabetic controls. Behavior-al and tachy card lac effects elicited by electrical stimulation of the ventromedial hypothalamus while the rats were awake were similar, but attendant pressor responses were larger in those that had been treated with insulin. Under subsequent urethane anesthesia, pressor and sympathetic responses to hypothalamic stimulation, as well as pressor responses to tyramine and vasopressin, were augmented in insulin-treated rats. A generalized increase in cardiovascular reactivity caused by insulin seemed unlikely since pressor responses to norepinephrine were unaltered. Enhanced hypothalamic respon-siveness was considered due to improvement of diabetic encephalopathy rather than to direct CNS stimulation by insulin because the injected insulin had mostly dissipated by the time pressor responses were recorded. By showing that insulin treatment produced changes opposite to those occurring during induction of diabetes our results suggest that insulin can alleviate cardiovascular and hypotha-lamic dysfunction in streptozotocin-induced diabetes.

ISSN:0194-911X    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

The onset of essential hypertension early in life is indicated by the high tracking of blood pressure during adolescence; intervention in adults with mild hypertension has been found successful. How, then, can high blood pressure levels in children be modified to prevent early hypertensive cardiovascular disease in adulthood? In an entire biracial town (population 9000) we surveyed 1604 (89%) of all children aged 8–18 years for blood pressure and reexamined those in the upper decile of mean blood pressure (for each race, sex, and height) on three additional occasions. On each examina-tion nine blood pressures were taken by trained observers. All children consistently in the top decile were randomly allocated into either a treatment (n = 50) or comparison (n = 50) group. These two groups and an additional midrange blood pressure comparison group (n = 50) were followed regular-ly using school facilities including community and school programs. Treatment consisted of 1) dietary guidance; 2) modifications of school lunches and snacks with healthy substitutes; 3) parental involve-ment; 4) a low dose diuretic and β-antagonist given by usual standards. All study groups were monitored for blood pressure in a blind manner. In 6 months of observation, blood pressure in the treatment group remained 5 and 3 mm Hg (systolic and diastolic) less than controls (p< 0.001 andp< 0.01). An orchestrated community-wide attack on early-stage hypertension is feasible and seems to offer exciting potential for prevention of early hypertensive disease.

ISSN:0194-911X    

出版商:OVID    

年代:1983

数据来源: OVID

ISSN:0194-911X    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

Early differences in hemodynamic variables and vasoactive substances between prog-eny of hypertensive and normotensive parents were sought in normotensive children aged 10–17 years. Forty-two black and 34 white children of hypertensive parents (cases) and an age-balanced group of 20 black and 45 white children of normotensive parents (controls) underwent exercise stress testing. Blood pressure, heart rate, urinary electrolytes, kallikrein, and prostaglandin E-like materi-al, plasma renin activity, and norepinephrine were measured before, during, and after exercise. Analyses compared the findings of four subject groups: black cases with black controls, white cases with white controls, black cases with white cases, black controls with white controls. Based on a family history of hypertension, significant familial differences were found: Black cases “were larger” (p= 0.003) when compared to black control subjects and had higher resting systolic, dlastolic, and maximum exercise diastolic blood pressures, and higher postexercise plasma renin activity (p= 0.04); white cases also were larger (p= 0.004) in comparison with white controls and had higher postexercise heart rates, higher preexercise urinary prostaglandin E-like material, and lower plasma norepineph-rine after exercise (p< 0.05). Significant racial differences were noted in heart rate, blood pressure, urinary electrolytes, and other biochemical substances. Among the cases, black/white comparisons showed that blacks had lower postexercise heart rates, and higher resting and maximum exercise systolic and diastolic blood pressures (p< 0.04 for these comparisons). Additionally, blacks had higher preexercise urinary sodium excretion, lower preexercise urinary potassium excretion (p< 0.003), and lower plasma renin activity before and after exercise (p< 0.003). Finally, urinary kallikrein excretion before and after exercise was lower in blacks (p< 0.03). While blood pressures were similar among the black and the white controls, comparisons revealed that the blacks had higher preexercise sodium and potassium excretion (p< 0.005), lower plasma renin activity at all levels of activity, and lower plasma norepinephrine 10 minutes after exercise (p< 0.05). Thus, significant intraracial and interracial differences in physiological and biochemical variables, thought to be related to the development of hypertensive diseases, have been detected in normotensive children categorized according to a family history of hypertension. With use of these variables, the black case children can be separated from the other three groups and may have increased risk for the develop-ment of adult onset hypertension.

ISSN:0194-911X    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

Children with elevated systolic blood pressure have a wide range of cardiac output. To better understand the mechanisms regulating resting and exercise blood pressure, we investigated the cardiovascular responses to both dynamic and isometric exercise in 264 children who were selected from the low, middle, and upper quintile of the distribution of blood pressure of an entire school population. We sought to identify patterns of response to exercise that correlated with both resting cardiac output and resting blood pressure. During isometric exercise, systolic pressure adjusted for age and body size increased in all groups. The low group's mean pressure remained significantly lower than the high group's pressure throughout the entire exercise period. Body size adjusted group systolic and diastolic blood pressure level differences exist during dynamic exercise. The product of the systolic blood pressure times the heart rate, in the high blood pressure group, was significantly higher throughout dynamic exercise than in the other two groups. Elevated resting resistance is correlated with elevated resistance during isometric exercise and elevated diastolic blood pressure during dynamic exercise. Cardiac index had a significant negative correlation to age (r= −0.58) at all levels of blood pressure. This observation, in children, lends some support to the concept of the evolution from a hyperkinetic circulation in early childhood to a circulation with lower cardiac output and more elevated systemic vascular resistance at an older age.

ISSN:0194-911X    

出版商:OVID    

年代:1983

数据来源: OVID