Biomedical subjects

M N Nemeh

Publications and source records attributed to M N Nemeh.

4 recordsLinked to original sources

PubMed1990

Basal and stimulated cytosolic platelet calcium in essential hypertension.

It was reported that in essential hypertension, basal platelet free cytosolic (Ca)i measured with the fluorescent dye Quin 2, is elevated, but increases normally after thrombin stimulation. These data, were interpreted to suggest that plasma membrane fluxes are altered but the release of internal Ca2+ stores is intact. Previous studies have shown that Quin 2 inhibits Ca2+ release from internal stores following thrombin (T)-stimulation. Thus, we reassessed resting and T-stimulated platelet (Ca)i using the fluorescent dyes Fura 2 or Quin 2 in 11 subjects, 5 controls and 6 hypertensives. Mean basal (Ca)i with Quin 2 in controls was 138 +/- 15 nM vs 114 +/- 11 nM in hypertensives, (NS). By contrast, in the same platelet preparation (Ca)i with Fura 2 was higher in hypertensives than controls, 217 +/- 27 nM vs 120 +/- 4 nM, P less than .05. Blood pressure was correlated to (Ca)i obtained with Fura 2, R = 0.55. Thrombin 0.5 U/ml added to platelets in Ca-free media caused a multiphasic rise in (Ca)i with Fura 2. Although the absolute rise in (Ca)i in controls (592 +/- 104 nm) vs hypertensives (512 +/- 60 nm) did not differ, the % rise was less in hypertensives. Thus, 1) in the same population a higher resting (Ca)i was detected in platelets from essential hypertensives with Fura 2, but not with Quin 2; and 2) Ca2+ release from internal stores is altered in hypertension. Thus, Fura 2 is superior to Quin 2 in evaluating platelet (Ca)i.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Platelets↗

PubMed1984

Salt depletion inhibits cerebral-induced natriuresis in the dog.

Experiments were carried out in the conscious dog to determine whether renal responses to intracarotid (IC) infusion of hypertonic NaCl are altered in the sodium-depleted state. In the sodium-replete animal, both IC and IV infusion of hypertonic NaCl produced significant increases in sodium excretion and significant decreases in free water clearance. However, both of these renal responses were more rapid in onset with IC infusion. Both IC and IV infusion decreased free water clearance. In the sodium-deplete animal, IC hypertonic NaCl infusion had no effect on sodium excretion but did decrease free water clearance. It is concluded that total body sodium is a determinant of the gain of the cerebral sodium-sensing mechanism and that this mechanism is different from the osmosensitive mechanism.

Animals↗

PubMed1983

Natriuretic activity of human and monkey atria.

Recent evidence indicates that mammalian atria contain a substance that produces a rapid onset natriuresis in anesthetized rats. In the present experiments, small portions of human right atria obtained from patients undergoing coronary bypass surgery, as well as monkey atria and ventricles obtained from the Regional Primate Center, Seattle, were boiled or acid extracted and lyophilized. These materials (30 mg/kg) were dissolved in Ringer's lactate and injected intravenously into anesthetized monkeys to determine their effects on renal function. Their effects were also compared with those of furosemide (0.1 mg/kg) and chlorothiazide (10 mg/kg). Human and monkey atrial extracts produced significant increases in sodium and calcium excretion that were independent of changes in creatinine clearance. Monkey ventricular extract had no consistent renal effects. Furosemide, but not chlorothiazide, mimicked the renal responses to human and monkey atrial extracts in terms of time of onset, duration, and pattern of electrolyte excretion. These data suggest that primate atrial tissue contains a heat- and acid-stable natriuretic factor similar to that first described in the rat, suggesting that mammalian atrial natriuretic factors are cross-reactive among species. In addition, atrial natriuretic factors may have a mechanism of action similar to that of furosemide.

Animals↗

PubMedDate not supplied

Does head-down tilt simulate zero gravity?

Six anesthetized female rhesus monkeys were studied to determine the effect of head-down tilt on renal function. Head-down tilt is believed to simulate zero gravity. Some animals were tilted from 0 degree to -5 degrees or -10 degrees and others from +10 degrees to -10 degrees. None of these maneuvers consistently altered renal function. These results are in accord with those reported in early literature for the human but contrary to more recent reports. The interpretation of the latter are seriously hampered by experimental design. If indeed zero gravity translocates blood to the thorax with a resultant diuresis and natriuresis, head-down tilt is not an appropriate model for weightlessness.

Animals↗