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Biomedical subjects

A Mimran

Publications and source records attributed to A Mimran.

At least 199 records · Page 11Linked to original sources
PubMed1983

Comparative effects of nifedipine and diltiazem on vascular responses to norepinephrine and angiotensin II.

The effects of nifedipine and diltiazem on renal vascular responses to norepinephrine and angiotensin II were investigated in the isolated blood-free perfused rat kidney. The vasoconstrictor response induced by bolus injections of angiotensin II (5 and 10 ng) and norepinephrine (60, 80 and 100 ng) were assessed before and during perfusion of nifedipine (10(-9) mol l-1 to 10(-6) mol l-1) or diltiazem (3 X 10(-7) mol l-1 to 10(-4) mol l-1). At a concentration higher than 10(-9) mol l-1, nifedipine blunted to a similar extent the responses to both angiotensin II and norepinephrine. At concentrations of 3 X 10(-7) mol l-1 and 10(-6) mol l-1, diltiazem inhibited only the response to angiotensin II without affecting the vasoconstrictor effect of norepinephrine. Increase in diltiazem concentration to 10(-5) mol l-1 and 10(-4) mol l-1 was associated with a similar inhibition of the response to angiotensin II and norepinephrine. These results demonstrate that at concentration less than 10(-5) mol l-1, diltiazem acts as a selective antagonist of the effect of angiotensin II whilst no such selectivity of action was observed with all concentrations of nifedipine used in the present studies.

Angiotensin II↗
PubMed1983

The role of the renin-angiotensin system in the hormonal and renal responses to tilt in normal man.

Head-up tilt is associated with rapid increases in total peripheral and renal resistance and falls in the urinary excretion of water and sodium. The influence of the acute oral administration of the converting enzyme inhibitor captopril (50 mg) on the consequences 60 degrees head-up tilt were assessed in 6 normal subjects on unrestricted sodium intake. Captopril did not modify the responses of arterial pressure and heart rate to tilt, although a significant decrease in supine mean arterial pressure was induced by captopril. In addition, the agent blunted by 50-60% all the changes in renal hemodynamics and urinary excretion of water and electrolytes except for that of the fractional excretion of sodium. Urinary kallikrein activity which markedly fell and plasma aldosterone concentration which increased during tilt before captopril were not affected after administration of the drug. These studies indicate that angiotensin might mediate at least in part the renal hemodynamic and functional responses to tilt in normal man and is the primary determinant of the aldosterone stimulating effect of tilt.

Adolescent↗
PubMed1983

Indapamide in hypertension: results of a French multi-centre study in ambulant subjects.

The antihypertensive effect of indapamide (2.5 mg/day) was evaluated in 2184 patients with essential hypertension by 300 French general practitioners over a period of treatment of 3 months. Indapamide produced a significant reduction in blood pressure, the amplitude of which was directly related to pre-treatment blood pressure levels; normalization of blood pressure was achieved in approximately 66% of patients. Addition of a beta-blocker to the treatment regimen on the second month was required in only 10% of patients. No severe side-effect was reported, although a significant reduction in kalaemia was noted in less than 5% of patients.

Aged↗
PubMed1983

Renal aspects of treatment by converting enzyme inhibitors in hypertension.

Converting enzyme inhibitors (CEI) are efficient antihypertensive medications. The acute and chronic effects of captopril (SQ) on renal function and electrolyte balance are analyzed in the present paper. Acute administration of SQ was associated with renal vasodilatation in the patients with essential hypertension (EH) but had no effect in normal subjects with similar renin levels thus suggesting an enhanced renal vascular response to CEI in EH. A variable effect of CEI on renal function was observed in renovascular hypertension; GFR fell when blood pressure decreased by more than 25 mmHg. Three cases of striking recovery of GFR during chronic SQ in young patients with malignant nephrosclerosis maintained on hemodialysis are reported. Such an improvement in GFR never occurred in patients with primary renal disease. When systemic and renal responses to acute isotonic saline loading were assessed, captopril blunted the exaggerated natriuretic response to saline loading observed in EH and unmasked the volume-dependence of arterial pressure. A case of hyperkalemia during treatment with SQ is reported in a patient with bilateral renal artery stenosis who developed moderate renal failure during treatment. This was associated with high plasma aldosterone whilst fractional excretion of K+ was inappropriately low for the level of serum creatinine thus suggesting that tubular unresponsiveness to aldosterone may have developed during SQ.

Acute Disease↗
PubMed1983

[Histologic and ultrastructural forms of benign tumors of the kidney with renin secretion. Functional implications].

Two cases of renal benign renin-secreting tumours (juxta-glomerular cells tumors) have been compared by optical and electron microscopy. The first is the simplest type of tumoral form which can be observed. This contains secretory cells similar to epitheloid cells of normal juxta-glomerular apparatus, which multiply in well developed arteriolar and capillary network. As in afferent arterioles of glomeruli, transformation of parietal smooth cells in secretory cells can be observed. This results in the presence of intermediate cells, containing both contractile filaments and secretory granules. This tumor does not contain nerves. The second tumor has a more complex structure. Beside usual secretory cells, tubular formations and adrenergic amyelinic nerves are observed. Tubes and nerves have been described separated in many juxta glomerular cells tumors but had never been observed in association. Tubules with small lumen are made of highly dystrophic cells. High concentration of "kallikrein" in tumoral tissue, strongly suggests that they proceed from distal tubule. Unmyelinated nerves from varicosities containing densely cored vesicles characteristics of adrenergic nerves, and synaptic terminal endings on secretory cells. The presence of nerve bundles suggest a nervous regulation of tumoral secretions. This hypothesis is confirmed by dynamic explorations of sympathetic system.

Adult↗
PubMed1983

[Pseudohyperkalemia of erythrocyte origin. Passive increase of membrane permeability to potassium].

The pseudo-hyperkalemia is a biochemical abnormality suspected when the blood level of K is increased, contrasting with the absence of usual symptoms of hyperkalemia. The diagnosis is confirmed by the discrepancy between K+ blood levels which are normal if measured immediately after the blood sample is drawn, and increased if the blood sample is incubated at the room temperature. In our case, the pseudo-hyperkalemia is due to the passage of K outside the erythrocytes by an increased passive membrane permeability to K. In vivo, this increased passive outflow of K seems to be compensated by an increased active inflow of K dependent of the sodium pump. Therefore is explained, the absence of true hyperkalemia and clinical symptoms. In vitro, it seems that the sodium pump is no longer able to assure this increased activity. Therefore the abnormality appears as a late increase of kalemia.

Adult↗
PubMed1983

The natriuretic response to acute saline loading in normotensive and hypertensive renal transplant recipients.

The response to acute isotonic saline loading (1800 ml in 3 h) was assessed in 12 normotensive and 11 hypertensive renal transplant recipients. Both groups had similar renal function, daily urinary excretion of sodium and doses of steroids. The natriuretic response to saline was not affected in hypertensive transplants and changes in blood pressure, renin and aldosterone were identical in both groups. Similar correlations between presaline fractional excretion of sodium (FENa+) and the FENa+ obtained during saline were found in normotensive and hypertensive patients. These results demonstrate that recipients of renal transplants who are hypertensive do not show an exaggerated natriuresis in response to saline, thus suggesting that normal kidneys carry their characteristics when transplanted in a new environment. The role of renal denervation remains unclear.

Adult↗
PubMed1982

Evidence for postsynaptic effect of captopril in isolated perfused rabbit kidney.

The influence of captopril (SQ 14225) on the vascular and norepinephrine-releasing responses to nerve stimulation (2, 5 and 10 Hz) was assessed in isolated blood-free perfused rabbit kidney. At a concentration of 0.23 and 0.46 mM in the perfusion medium, captopril markedly attenuated the vasoconstrictor response but did not influence the release of norepinephrine produced by nerve stimulation. These results suggest that captopril may act as an alpha-antagonist at a postjunctional level.

Animals↗
PubMed1982

Scanning electron microscopic study of arterial cushions in rats: a novel application of the corrosion-replication technique.

The morphology and organ distribution of arterial cushions were studied in adult rats (body weight ranging from 200 to 500 gm) by scanning electron microscopic (SEM) observation of corrosion casts. Scanning electron microscopic observations of renal vascular casts were correlated with SEM views of the luminal surfaces of similarly fixed vessels; there was a striking similarity in shape, organ distribution, and dimensions between fixed arterial cushions and indentations at the surfaces of casts. Application of this technique to 11 different organs, some of which had never been studied by SEM before, revealed the occurrence of indentations at branching sites similar to those found in kidneys (and hence they were termed "cushions"). Our findings are in generally good agreement with previous light and transmission electron microscopic studies on rats. Our results support the view that arterial cushions are present throughout the vasculatures of the rat. A quantitative morphologic study of replicated branching sites related to "cushions" showed a great variability of the parent-to-daughter luminal diameter ratio (range 0.87-16.38) and of branching angles. A fruitful application of this technique to other laboratory animals may be anticipated.

Animals↗
PubMed1982

Maintenance of the antihypertensive efficacy of captopril despite consistent reduction in daily dosage.

1 After a period of 7 +/- 1.4 months of good control of hypertension by thrice daily administration of captopril (85 +/- 9 mg three times a day), captopril was given twice daily and the total dose was progressively reduced to sometimes very low levels in 12 patients. Twice daily administration of captopril 85 +/- 9 mg did not modify blood pressure control. 2 During reduction of captopril dosage to a minimum of 36 +/- 4 mg twice a day, the acute effect of the morning dose of captopril (last dose taken at least 12 hours before study) was assessed. Administration of the morning dose induced a decrease in mean arterial pressure from 112 +/- 4 mm Hg (104 +/- 3 mm Hg during administration of 85 +/- 9 mg) three times a day to 106 +/- 4 mm Hg, an increase in plasma renin activity, and a decrease in plasma aldosterone concentration. 3 These acute effects of captopril suggest that blood pressure was well controlled in the presence of a non-blocked circulating angiotensin-converting-enzyme activity, thus raising the possibility of alternate mechanisms by which captopril reduces arterial pressure. 4 The daily dosage of captopril needed to control hypertension may be reassessed after a certain period of good blood pressure control with 50 to 100 mg captopril three times a day.

Adult↗
PubMed1982

The influence of indomethacin and possible role of prostaglandins on calcium renal excretion.

Our aim was to evaluate the possible role of prostaglandins (PG) on renal calcium excretion in humans through the PG inhibitory effects of indomethacin. Renal calcium excretion was evaluated by a technique of impulse analysis which gives a function W(t) specific of the tubular calcium transport. Several parameters were derived from this function: (1) the fractional excretion of filtered calcium as % of total dose (FECa % TD); (2) the peak excretion rate, and (3) the mean transit time (MTT, min). The aforementioned parameters were determined in 7 healthy subjects in basal conditions and again after 10 days of treatment with 100 mg indomethacin daily. FECa was significantly (p less than 0.02) higher with indomethacin (8.18 +/- 0.97) than under basal conditions (5.02 +/- 0.57). The peak excretion rate and MTT remained unchanged after indomethacin. These results indicate that indomethacin increases renal calcium excretion. As indomethacin did not produce any significant change in glomerular filtration rate (125 +/- 7 ml/min before vs. 129 +/- 9 ml/min after) one can assume that PG play a role in tubular calcium reabsorption. However, the mechanism remains to be elucidated: direct action or mediated through the cyclic AMP system.

Adolescent↗
PubMed1982

[Arguments in favor of postsynaptic antagonism by captopril (SQ 14,225) in the perfused kidney].

The potential antagonistic effect of high doses of Captopril on renal vascular response to exogenous administration or nerve stimulated release of norepinephrine (NE) was assessed in isolated blood-free perfused rat and rabbit kidneys respectively. At the doses of 0,09 mM and 0,45 mM in rat kidney, captopril blunted significantly the vasoconstrictor effect of exogenous NE (20, 40 and 100 ng) whilst responses to angiotensin II (2,5 and 10 ng) were slightly reduced at the highest dose and responses to serotonin (20, 40 and 100 mg) remained unaffected by either doses of Captopril. The other effective converting enzyme inhibitor, SQ 20881 had no effect on pressor responses to norepinephrine at similar doses. In preliminary rabbit studies, a likewise blunting of pressor effect of exogenous norepinephrine was obtained at the doses of captopril of 0,23 mM and 0,45 mM. Furthermore, these doses of captopril had no effect on either basal or nerve-stimulated NE release whilst nerve-stimulated vasoconstriction was significantly and reversibly blunted at both doses. These studies suggest a) that the inhibitory effect of Captopril on NE renal vasoconstriction in not primarily dependent on converting enzyme inhibition; b) that the observed alpha-antagonistic activity of high doses of captopril occurs principally at a post-junctional level.

Angiotensin II↗
PubMed1982

[The influence of indomethacin and possible role of prostaglandin on renal calcium excretion (author's transl)].

Our aim was to evaluate the possible role of prostaglandins (PG) on renal calcium excretion in humans through the PG inhibitory effects of indomethacin. Renal calcium excretion was evaluated by a technique of impulse analysis which gives a specific index of tubular calcium transport. Several parameters were derived from this specific transport function W(t): 1) the fractional excretion of filtered calcium as % of total dose (FECa % TD); 2) the peak excretion rate; 3) the mean transit time (MTT, min). The aforementioned parameters were determined in 7 healthy subjects in basal conditions and again after 10 days of treatment with 100 mg indomethacin daily. FECa was significantly (P less than 0.02) higher with indomethacin (8.18 +/- 0.97) than under basal conditions : (5.02 +/- 0.57). The peak excretion rate and MTT remained unchanged after indomethacin. These results indicate that indomethacin increases renal calcium excretion. As indomethacin did not produce any significant change in glomerular filtration rate (125 +/- 7 ml/min before v.s. 129 +/- 9 after) one can assume that PG play a role in tubular calcium reabsorption. However the mechanism remains to be elucidated : direct action of mediated through the cyclic AMP system.

Adolescent↗
PubMed1982

[Reversible acute renal failure and nephrotic syndrome induced by fenoprofene ].

A 71-year old man experienced nephrotic syndrome and acute renal failure 13 months after the introduction of fenoprofen calcium, 900 mg/day, as treatment of right hip osteoarthritis. Clinical course and laboratory data were consistent with toxic nephropathy; kidney biopsy showed tubulo-interstitial nephritis with glomerular minimal change lesion. Renal function returned spontaneously to normal, after withdrawal of the drug. The clinical literature on nephrotic syndrome and reversible acute renal failure associated with non-steroidal anti-inflammatory drugs is reviewed.

Acute Kidney Injury↗