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Biomedical subjects

N Stern

Publications and source records attributed to N Stern.

At least 145 records · Page 8Linked to original sources
PubMed1983

Dopaminergic modulation of meal-stimulated and circadian secretion of pancreatic polypeptide in man.

This study investigated dopaminergic control of human pancreatic polypeptide (hPP) secretion in normal male volunteers. Dopamine infusion blunted the hPP response to a protein-rich meal. Dopamine antagonism with metoclopramide resulted in a hPP response at 5 min and a peak elevation of hPP 10 min after drug administration. Bromocriptine (2.5 mg, three times daily for 5 days) suppressed meal-induced secretory responses of hPP. Although bromocriptine did not alter the basic circadian pattern of hPP secretion, it did slightly increase nocturnal levels of this hormone. These results suggest that dopaminergic mechanisms exert a tonic inhibitory effect on hPP secretion in normal subjects.

Adult↗
PubMed1983

Plasma corticosteroids in hyperreninemic hypoaldosteronism: evidence for diffuse impairment of the zona glomerulosa.

A subgroup of critically ill patients with selective hypoaldosteronism despite hyperreninemia has recently been defined. The mechanism underlying the subnormal response of aldosterone secretion is poorly understood. As cortisol secretion remains intact and the condition usually follows hypotensive episodes, ischemic or functional impairment restricted to the adrenal glomerulosa may be involved. To evaluate the possibility that a specific biosynthetic pathway deficiency exists in hyperreninemic hypoaldosteronism (HH), basal and ACTH-stimulated levels of aldosterone and its immediate precursors 18-hydroxycorticosterone (18-OHB) and corticosterone (B) were determined in eight HH patients, six critically ill subjects with normal aldosterone responsiveness, and nine healthy subjects. Baseline aldosterone (8.2 +/- 3.2 vs. 44.7 +/- 23.6 ng/dl) and 18-OHB (44.7 +/- 13.6 vs. 547.6 +/- 300.4 ng/dl) were lower in HH patients than in Intensive Care Unit controls (both P less than 0.01) despite similarly increased renin concentration and activity. ACTH-stimulated aldosterone and 18-OHB were significantly lower in HH patients, although the percent increase was similar to Intensive Care Unit controls. Plasma B was also lower in HH patients, though not significantly. After ACTH, B was markedly lower than both ICU controls (1764 +/- 576 vs. 6299 +/- 1266 ng/dl, P less than 0.01) and healthy controls (3261 +/- 248 ng/dl, P less than 0.01). All groups had appropriate cortisol responses demonstrating normal zona fasciculata function. Since 18-OHB arises predominantly from the zona glomerulosa, whereas B also derives in part from the zona fasciculata, the data suggest generalized impairment of the adrenal zona glomerulosa probably affecting both early and late pathway corticosteroid biosynthesis.

18-Hydroxycorticosterone↗
PubMed1983

Reduced sodium-potassium dependent ATPase and its possible role in the development of hypertension in spontaneously hypertensive rats.

Ouabain-sensitive Na+-K+-ATPase activity in red cell membranes, kidney cortical tissue, myocardium and adrenal glomerulosa tissue was examined in SHR and WKY rats at 6, 9, and 12 weeks of age. Red cell membrane enzyme activity was decreased (p less than 0.001) at 9 and 12 weeks of age in SHR. This activity was negatively correlated (r = -0.69, p less than .005) with blood pressure at 9 and 12 weeks. Kidney cortical enzyme activity was also decreased (p less than 0.001) in the SHR at 9 and 12 weeks of age. This decreased kidney enzyme activity was also inversely related to 9 and 12 week blood pressures (r = -0.71, p less than 0.001), urinary Na excretion (r = -0.62, p less than .005), and urinary Ca and K excretion. Myocardial enzyme activity was not decreased until 12 weeks in the SHR, and adrenal glomerulosa activity was not different in the SHR and WKY at any of the three ages that this enzyme was measured. Of the tissues examined decreased Na+-K+-ATPase activity in the erythrocyte membrane and in kidney cortical tissue appears to coincide best with the development of hypertension in the SHR. This study lends further support to the concept that alterations in membrane cation transport may be an important factor in the development of high blood pressure in SHR.

Adrenal Glands↗
PubMed1983

Use of oral converting enzyme inhibitor, captopril for lateralizing renal venous renin activity.

Captopril was administered prior to renal vein renin sampling in an attempt to select patients amenable to surgical treatment for renin dependent hypertension. Renal venous blood for plasma renin activity was taken only after captopril stimulation. Sampling from the antecubital vein before and after this provocation showed a marked rise in renin, thereby confirming the efficacy of the test. Elimination of the initial selective renal vein sampling shortens the catheterization period without affecting the accuracy and dependability of the procedure.

Blood Pressure↗
PubMed1983

Corticosteroid modulation of the renin system and blood pressure in the spontaneously hypertensive rat.

This study examines the role of gluco- and mineralcorticoids in the regulation of the renin-angiotensin system and blood pressure in the spontaneously hypertensive rat (SHR). Effects of adrenalectomy and selective treatment with either aldosterone (30 micrograms/kg/day) or dexamethasone (60 micrograms/kg/day) on plasma renin substrate, active renin (PRA), total renin and blood pressure were studied in 10 week old SHR and control WKY rats. Systolic blood pressure was moderately lower in adrenalectomized rats (129 +/- 2 mm Hg vs 137 +/- 4 mm Hg in control WKY and 145 +/- 4 mm Hg vs 160 +/- 3 mm Hg in control SHR) but could be restored to the control range by aldosterone. Dexamethasone repletion induced substantial increments of systolic blood pressure to comparable levels in both species (202 +/- 8 mm Hg in WKY and 192 +/- 6 mm Hg in SHR). Renin substrate was markedly lower in adrenalectomized, saline repleted rats. This could be reversed by dexamethasone in both species and by aldosterone in WKY rats only. Both PRA and total renin were higher (p less than 0.01) in the adrenalectomized, saline repleted state. This increase was not observed in aldosterone repleted rats. However, dexamethasone inhibited the adrenalectomy associated increase of PRA and total renin in SHR but not in WKY rats. Differences in blood pressure between SHR and WKY persist even in adrenalectomized state despite comparable stimulation of the renin system. Conversely, while blood pressure of both species responds similarly to selective corticosteroids therapy, the response of the renin-angiotensin system in SHR and WKY rats is distinct. Therefore factors other than the adrenal gland and the renin system must be involved in the determination of the high blood pressure in SHR.

Adrenal Cortex Hormones↗
PubMed1983

Prolactin secretion in essential hypertension.

This study was designed to evaluate prolactin (PRL) secretion in patients with essential hypertension. PRL secretory pattern was assessed by hourly blood sampling between 2200 and 0800 hours. Additional samples were collected at 0810 and 1000 hours (10 and 120 minutes after assumption of upright posture), as well as at 1200, 1400, and 1800 hours under normal simulated activities. No difference could be detected between the two study groups at any of the sampling times, and the number of secretory episodes were similar. Basal plasma renin activity levels were inversely related to simultaneous PRL levels in the hypertensive patients (r= -0.60, p less than 0.05). In the normal subjects mean overnight PRL levels were inversely related (r= -0.78, p less than 0.05) to the overnight urinary Na/K excretion. There was no PRL response to posture in either group. Hypertensive patients had a greater early response to the dopamine antagonist, metoclopramide than did normal subjects. Our data do not support the previously introduced concept of enhanced PRL responses to normal physiologic stimuli in essential hypertensives. However, it appears that dopaminergic control of PRL secretion may be altered in this disease state.

Adult↗
PubMed1982

Evidence for dopaminergic modulation of pancreatic polypeptide secretion in man.

This study examines the role of dopaminergic mechanisms in the regulation of human pancreatic polypeptide (hPP) secretion in 11 normal male volunteers. Administration of domperidone (20 mg iv), an extracerebral inhibitor of dopamine receptors, resulted in a hPP rise (p less than 0.05) within 10 min and a peak response (p less than 0.01) at 15 min after drug administration. Administration of the dopaminergic agonist, bromocriptine, 2.5 mg tid for 4 days eliminated hPP responses to isometric handgrip exercise in these 11 volunteers. These results suggest that dopaminergic mechanisms may exert a tonic inhibitory effect on hPP secretion in normal subjects.

Adult↗
PubMed1982

The treatment of hypertension by labetalol--a new alpha- and beta-adrenoreceptor blocking agent.

A new alpha- and beta-blocking agent, labetalol, was used to treat 50 hypertensive patients, 34 of them with refractory hypertension. A significant reduction in hypertension was achieved with relatively few adverse reactions. The combination of alpha and beta blockers in labetalol with their mutually opposing characteristics offers an interesting and promising approach to the control of hypertension.

Adolescent↗
PubMed1982

Role of the sympathetic nervous system in blood pressure maintenance in obesity.

A group of 10 borderline hypertensive obese subjects had higher (P less than 0.05) supine plasma norepinephrine (NE), epinephrine, and PRA levels as well as greater (P less than 0.05) NE responses to upright posture and isometric handgrip exercise than 12 nonobese controls. Plasma NE as well as mean arterial pressure (MAP) responses to posture and handgrip in the obese patients demonstrated a significant decrement at week 2 after the onset of a low calorie diet. Decrements in plasma NE and MAP responses to posture were correlated (r = 0.61; P less than 0.05) throughout an 8-week period of weight loss in these borderline hypertensive obese subjects. In 15 normotensive obese subjects as well as in the 10 borderline hypertensive obese subjects, weight reduction associated with a very low calorie intake was accompanied by a reduction in supine plasma NE, epinephrine, and MAP 2 weeks after the onset of dieting. PRA decreased after 8 weeks of dieting in both obese groups, and these PRA decrements were correlated with reductions in MAP and decrements in plasma NE. We conclude that enhanced sympathetic activity may play a role in the maintenance of elevated blood pressure in obese individuals. Decreases in PRA and blood pressure associated with weight loss in both normotensive and hypertensive obese individuals occurs, in part, secondary to reductions in plasma NE levels.

Adult↗
PubMed1982

Dopaminergic control of 18-hydroxycorticosterone responses to posture, isometric exercise, and diuretic administration in normal man.

This study investigates dopaminergic mechanisms involved in the control of corticosteroid secretion in man. The responses of plasma 18-hydroxycorticosterone (18-OHB) and aldosterone levels to upright posture and isometric handgrip exercise and furosemide administration as well as PRA and catecholamine responses to posture and exercise were evaluated in six normal subjects with and without bromocriptine (BEC) treatment. To evaluate the role of PRL suppression by BEC in affecting corticosteroid responses, we evaluated the effect of BEC on plasma 18-OHB and aldosterone responses to 20 mg furosemide in two subjects with autoimmune hypoprolactinemia. BEC (2.5 mg, three times a day for 4 days) markedly suppressed basal levels of 18-OHB, but not aldosterone, in the six normal subjects as well as the two subjects with autoimmune hypoprolactinemia. BEC also suppressed the 18-OHB and aldosterone responses to upright posture, isometric exercise, and furosemide administration without altering electrolytes, PRA, or plasma cortisol levels. Additionally, BEC suppressed basal levels of PRL, norepinephrine, and epinephrine as well as norepinephrine and blood pressure responses to upright posture and isometric exercise in the normal subjects. These results offer additional evidence that dopaminergic mechanisms modulate the secretion of 18-OHB and aldosterone, perhaps indirectly via inhibitory effects of dopaminergic pathways on catecholamine secretion.

18-Hydroxycorticosterone↗
PubMed1982

Influence of sodium homeostasis and circadian rhythm on dopaminergic modulation of 18-hydroxycorticosterone secretion in man.

This study examines the effects of sodium homeostasis and circadian rhythm on plasma 18-hydroxycorticosterone (18-OHB) responses to the dopamine antagonist metoclopramide in seven normal individuals. Responses to metoclopramide were evaluated after receiving a 10-meq sodium diet, a 100-meq sodium diet, and a 200-meq sodium diet for 5 days. On all three occasions the subjects had reached sodium equilibrium states, as determined by urinary sodium measurements, at the time that they received metoclopramide. Percentage incremental 18-OHB responses to metoclopramide were greater (P less than 0.01) in the subjects after 5 days on a 200-meq sodium intake than after 5 days on a 10-meq sodium intake. The percentage increases in plasma 18-OHB after a 200-meq sodium intake were slightly greater (P less than 0.05) than increases after a 100-meq sodium intake. Plasma 18-OHB levels demonstrated a circadian rhythm, with plasma levels reaching their zenith during the later part of sleep and shortly after awakening and reaching their nadir between 2000 and 2400 h. Although basal levels of 18-OHB at 2200 h (15.5 +/- 1.6 ng/dl) were considerably lower (P less than 0.01) than basal levels of 18-OHB at 0800 h, the 18-OHB responses to metoclopramide were similar at 0800 and 2200 h. Administration of the dopamine agonist bromocriptine (2.5 mg three times a day for 4 days) suppressed (P less than 0.01) mean 24-h plasma 18-OHB levels from 21.9 +/- 2.0 to 14.8 +/- 1.4 ng/dl. However, bromocriptine did not alter the circadian rhythm of 18-OHB secretion. These data suggest that increased sodium intake leads to greater tonic dopaminergic inhibition of 18-OHB secretion. Although dopaminergic mechanisms modulate 18-OHB secretion, they do not govern the circadian rhythm of this corticosteroid.

18-Hydroxycorticosterone↗
PubMed1982

Captopril, an orally active angiotensin I converting enzyme inhibitor in the treatment of renovascular and essential hypertension.

The hypotensive response to captopril is described for 12 hypertensive patients, 7 of whom had renovascular hypertension. The drug was effective in lowering blood pressure. The few reversible adverse reactions that occurred included loss of the sense of taste in one patient and rash and fever in another. Three patients with renal failure showed deterioration of renal function during treatment, suggesting the advisability of treating such cases with lower dosages.

Adult↗
PubMed1981

Chronic lymphatic leukemia terminating in acute myeloid leukemia: review of the literature.

A case of acute myeloid leukemia supervening upon a long-standing stable chronic lymphatic leukemia (CLL) diagnosed ten years earlier, is described. Thirty-three cases of acute leukemia terminating CLL were reported. All but three were treated prior to the emergence of the acute leukemia. The question of whether acute leukemia and other malignancies are more frequent in CLL is still controversial. The literature is reviewed.

Aged↗