ISSN:0194-911X    

出版商:OVID    

年代:1990

数据来源: OVID

ISSN:0194-911X    

出版商:OVID    

年代:1990

数据来源: OVID

ISSN:0194-911X    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

The chromogranins/secretogranins are a family of acidic, soluble proteins with widespread neuroendocrine distribution in secretory vesicles. Although the precise function of the chromogranins remains elusive, knowledge of their structure, distribution, and potential intracellular and extracellular roles, especially that of chromogranin A, has greatly expanded during recent years. Chromogranin A is coreleased with catecholamines by exocytosis from vesicles in the adrenal medulla and sympathetic nerve endings. Thus, measurement of its circulating concentration by radioimmunoassay may be a useful probe of exocytotic sympathoadrenal activity in humans, under both physiological and pathological conditions. Here, we explore the storage, structure, and function of chromogranin A, and parameters that influence its circulating levels. We have also measured plasma chromogranin A concentrations in different groups of patients with hypertension, including those with pheochromocytoma.

ISSN:0194-911X    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

To distinguish among genetic, neurohumoral, and hemodynamic explanations for structural and functional differences in the hearts of young spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) control rats, embryonic SHR and WKY rat heart tissue was cultured in the anterior eye chamber of adult SHR and WKY rats. In study 1, atria from E-L2 WKY rat embryos grafted into anterior eye chambers of either SHR or WKY host rats achieved a larger size than did SHR grafts by 8 weeks in oculo (2.98±0.75 and 2.55±0.32 mm2vs. 1.80±0.20 and 2.04±0.44 mm2). Beating rates did not differ between SHR and WKY rat atria implanted into SHR or WKY bost rats. In study 2, ventricles from E-13 embryonic SHR and WKY rat hearts grew to similar size and weight when implanted into SHR or WKY host rats (eg., SHR hearts, 1.81±0J2 vs. 1.74±0–33 mm2; WKY rat hearts, 1.75±0J9 vs. 2J9±0J2 mm1). Ventricle grafts from SHR embryos into SHR host rats beat more rapidly (165±19 beats/min) during weekly measurements than either WKY rat ventricles (92±9 beats/min in SHR hosts and 99±9 beats/min in WKY host rats) or SHR ventricles grafted into WKY host rats (109±7 beats/min,p< 0Ml). In study 3, atria from E-13 SHR and WKY rat embryos were grafted into sympathectomized and intact eye chambers of SHR or WKY host rats. Sympathectomy of the eye chamber compromised growth of grafts into WKY host rats (1.54±0.24 vs. 0.90±0.14 mm2) but not SHR hosts (1.54±0.25 vs. 1.73±0.24 mm2). Grafts into sympathectomized eye chambers of WKY host rats beat more slowly than grafts into eye chambers with sympathetic innervatlon intact (282±14 vs. 202±14 beats/min); sympathectomy did not alter beating rate of grafts in SHR hosts (266±14 vs. 255±18 beats/min). These results suggest that the growth and beating rate of SHR atrial grafts may be less sensitive to sympathetic innervation than WKY rat atrial grafts. In these studies, SHR grafts did not grow larger than WKY heart grafts and did not show an increased intrinsic beating rate, suggesting that the cardiac hypertrophy and increased intrinsic beating rate observed in intact SHR are unlikely to result from direct genetic programming.

ISSN:0194-911X    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

Renal functional reserve, microalbuminuria, and plasma atrial natriuretic factor were measured in 21 offspring (9.5±0.5 years of age, mean±SEM) of hypertensive parents and in eight children (10±0.5 years of age) with no family history of hypertension who were used as a control group. Renal functional reserve was evaluated by measurement of the changes in creatinine clearance after an oral protein load of 45 g/m2. Atrial natriuretic factor levels were determined before and 60 minutes after the protein load, and microalbuminuria in fractional urine before and 120 minutes after the same stimulus as well as in a 24-hour urine collection. All children in the control group significantly increased their creatinine clearance after the protein load (preload, 122±12; 60 minutes, 144±9; 120 minutes, 154±11; 180 minutes, 144±9 ml/min/1.73 m2; all values were significant vs. preload,p< 0.005). In contrast, only 13 of 21 offspring of hypertensive parents increased their creatinine clearance to values within 2 SD of the increase shown by the control group (preload, 144±11; 60 minutes, 153±7; 120 minutes, 202±13 ml/min/1.73 m2;p< 0.001 vs. preload; 180 minutes, 214±19 ml/min/1.73 m2,p< 0.001 vs. preload). The remaining eight offspring of hypertensive parents showed no detectable changes (nonresponders) (preload, 189±18; 60 minutes, 146±11; 120 minutes, 170±14; 180 minutes, 168±13 ml/min/1.73 m2; all values p=NS). No changes in atrial natriuretic factor after the protein load were observed in any group. Offspring of hypertensive parents presented higher microalbuminuria levels in 24-hour urine specimens (3.1 μg/min, tolerance factor [TF]2.2) than controls (2.1 μg/mln, TF 1.5) (p< 0.05). Although microalbuminuria increased significantly after the water load in the control group (p< 0.05) and in the offspring of hypertensive parents (p< 0.01), it returned to baseline at 120 minutes in the former but not in the latter (p< 0.05 vs. baseline). The lack of renal functional reserve in nonresponders was significantly related (<0.05) to the presence of higher levels of microalbuminuria. We conclude that the absence of renal functional reserve and increased microalbuminuria in some normotensive children who are offspring of essential hypertensive parents can indicate that subtle alterations in renal function may precede the onset of clinical hypertension.

ISSN:0194-911X    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

Recombinant human erythropoietin therapy was given to 15 patients undergoing long-term hemodialysis with normal cardiac function. None of the patients had hypertension before the erythropoietin therapy and had received no antihypertensive agents. Before and after the erythropoietin therapy M-mode and pulsed Doppler echocardiographic studies, measurements of plasma volume by radioiodinated human serum albumin, and measurements of atrial natriuretic factor were carried out After 6 weeks of erythropoietin therapy, hematocrit increased from 20.0 to 33.0%. Cardiac output, stroke volume, left ventricular diastolic dimensions, and left ventricular wall stress were all significantly decreased. Total peripheral resistance, interventricular septal thickness, and left ventricular posterior wall thickness were significantly increased. In Doppler echocardiographic studies, the mean velocity of aortic ejection flow and left ventricular acceleration time were decreased. The blood volume derived from plasma volume and hematocrit was not changed, whereas plasma atrial natriuretic factor concentration was significantly decreased. These data suggest that recombinant human erythropoietin administration suppressed the hyperdynamic cardiac state that was required to maintain oxygen delivery to the peripheral tissues in severe uremic anemia.

ISSN:0194-911X    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

To investigate possible alterations in 5-hydroxytryptamine (5HT) kinetics and sensitivity of blood platelets in patients with essential hypertension, 45 essential hypertensive patients and 45 normotensive healthy subjects matched in pairs for age, sex, and smoking status were compared. There were 18 women and 27 men in each group, ranging from 30 to 73 years of age. Results of essential hypertensive patients differed in several ways from those of normotensivesubjects. In essential hypertensive patients, maximal 5HT uptake velocity (Vmax) decreased with increasing blood pressure and age and was reduced the most in older men. Vmaxwas positively related to the EC50of 5HT for inducing a shape change reaction. In essential hypertensive patients, both Vmaxof 5HT uptake and the EC50of 5HT for shape change showed positive correlations with the 5HT content in platelets; the former relation was different between the essential hypertensive and normotensive groups (F= 5.53;p= 0.02). These results indicate reduced uptake of 5HT by blood platelets and suggest enhanced 5HT plasma concentrations in local areas, especially vascular lesions in essential hypertensive patients. Increased periplatelet concentrations of 5HT may lead to preactivatlon of platelets and possibly stimulation of vascular smooth muscle via their 5HT2j-receptors. These changes are likely to be involved in the pathogenesis of increased thromboembolic complications in essential hypertensive patients, particularly in older men.

ISSN:0194-911X    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

The rostral and caudal parts of the ventrolateral medulla play a major role in the control of blood pressure. Both regions contain a high density of receptor binding sites for angiotensin II, and it has been shown previously that microinjection of angiotensin II into the rostral ventrolateral medulla causes a rise in blood pressure. The aims of this study were to determine the cardiovascular effects of microinjection of angiotensin II and its specific antagonist [Sar1Thr8]angiotensin II into the caudal ventrolateral medulla and to characterize the regional vascular effects elicited by both compounds in the rostral ventrolateral medulla. Microinjections of angiotensin II (0.2–20 pmol) into histologically verified sites in the caudal ventrolateral medulla of anesthetized baroreceptor-denervated rabbits produced dose-dependent decreases in blood pressure and renal sympathetic nerve activity, whereas microinjection of [Sar1Thr8]angiotensin II (40 pmol) produced increases in these variables. In the rostral ventrolateral medulla, angiotensin II (0.02–20 pmol) elicited a dose-dependent increase in blood pressure, iliac vascular resistance, and renal sympathetic nerve activity, whereas [Sar1Thr8]angiotensin II (40 pmol) produced decreases in these variables. The effects on heart rate elicited by either compound in the rostral or caudal ventrolateral medulla were small but were in the same direction as the other cardiovascular variables. In contrast, angiotensin II had no detectable effect on sympathoexcitatory neurons within the rostral dorsomedial medulla, a region that lacks angiotensin II receptor binding sites. The results indicate that endogenous angiotensin II acts on specific receptors within the rostral and caudal parts of the ventrolateral medulla and has a tonic excitatory action on sympathoexcitatory and sympathoinhibitory neurons within these respective regions.

ISSN:0194-911X    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

Involvement of the brain renin-angjotensin system in baroreceptor reflex regulation was assessed by recording reflex heart rate and sympathetic nerve responses in normotensive rats that had been infused intracerebroventriculariy with the converting enzyme inhibitor enalapril for 15 days. Reflex bradycardia and sympathetic nerve inhibition during pressor responses to phenylephrine were larger in rats with intracerebroventriculariy infused enalapril than in control rats similarly infused either intracerebroventriculariy with saline or intravenously with enalapril. In contrast, opposite reflex responses to sodium nitroprusside-induced hypotension were mostly unaffected. Because depressor, bradycardic, and sympathoinhlbitory responses to electrical stimulation of the central cut end of the left aortic depressor nerve were also enhanced, intracerebroventriculariy infused enalapril must be affecting the baroreceptor reflex arc centrally. These results are compatible with the interpretation that intracerebroventriculariy infused enalapril enhanced baroreceptor reflex sensitivity by reducing endogenous angiotensin II levels in the brain through converting enzyme inhibition.

ISSN:0194-911X    

出版商:OVID    

年代:1990

数据来源: OVID