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Biomedical subjects

A Mimran

Publications and source records attributed to A Mimran.

At least 55 records · Page 3Linked to original sources
PubMed1998

Contrasting renal effects of chronic administrations of enalapril and losartan on one-kidney, one clip hypertensive rats.

OBJECTIVE: To compare the effects of chronic administrations of the angiotensin II antagonist losartan and of the angiotensin I converting enzyme inhibitor enalapril on renal function in sodium-depleted rats with one-kidney, one clip hypertension, and to examine the contribution of endogenous kinins to the effect of enalapril. METHODS: We administered enalapril and losartan (10 and 30 mg/kg per day, respectively) for 6 days to hypertensive rats that had been subjected to dietary sodium-intake restriction for 6 days prior to treatment and continued to be subjected to this restriction during treatment. In an additional group, administration of enalapril was combined with infusion of the bradykinin B2-receptor antagonist Hoe 140 (300 microg/kg per day subcutaneously via an osmotic pump). Renal function of anesthetized rats was assessed by using a clearance technique. RESULTS: Despite there being similar falls in arterial pressure, glomerular filtration rate (867 +/- 40 microl/min per g kidney weight in untreated rats) was decreased to a larger extent in enalapril-treated than it was in losartan-treated rats (284 +/- 29 versus 438 +/- 36 microl/min per g kidney weight, P < 0.01). Although infusion of Hoe 140 had no influence on the effect of enalapril on arterial pressure, the level of glomerular filtration achieved in rats of this group (545 +/- 55 microl/min per g kidney weight) was similar to that found in losartan-treated rats. No effect of either treatment on renal plasma flow was detected; as a consequence, the excessive decrease in filtration fraction observed for rats in the enalapril-treated group was corrected by concomitant administration of Hoe 140. Interestingly, administration of enalapril resulted in a greater loss of sodium than did administration of losartan (723 +/- 147 versus 308 +/- 57 micromol during 6 days), and this effect was abolished by infusion of Hoe 140 (353 +/- 42 micromol during 6 days). CONCLUSION: Administration of enalapril to sodium-depleted rats with one-kidney, one clip hypertension reduces their glomerular filtration rate to a greater extent than does administration of losartan despite these agents having similar effects on systemic blood pressure. Combined administration of enalapril and Hoe 140 has a less marked effect on glomerular filtration rate than does that of enalapril alone. This suggests that kinins play a role in the regulation of efferent arteriolar tone in this rat model.

Angiotensin II↗
PubMed1998

Renal endothelial function in humans.

Animal experiments have shown extensively that the endothelial generation of nitric oxide participates in the regulation of renal haemodynamics and function, probably as a factor modulating the effects of endogenous vasoconstrictors. Although the endothelial function of the systemic vasculature is assessed through the vasodilatory effect of acetylcholine, only L-arginine infusion is available for studies of the influence of nitric oxide on the renal circulation in humans. In addition to peripheral vessels, L-arginine is a potent renal vasodilator, having no effect on the glomerular filtration rate; and the renal relaxation induced by L-arginine is markedly blunted in patients with essential hypertension. A few studies showing the renal vasoconstrictor effect of an inhibitor of nitric oxide synthesis have been reported.

Albuminuria↗
PubMed1998

Multicellular stalk-like structures in Saccharomyces cerevisiae.

Stalk formation is a novel pattern of multicellular organization. Yeast cells which survive UV irradiation form colonies that grow vertically to form very long (0.5 to 3.0 cm) and thin (0.5 to 4 mm in diameter) multicellular structures. We describe the conditions required to obtain these stalk-like structures reproducibly in large numbers. Yeast mutants, mutated for control of cell polarity, developmental processes, UV response, and signal transduction cascades were tested and found capable of forming stalk-like structures. We suggest a model that explains the mechanism of stalk formation by mechanical environmental forces. We show that other microorganisms (Candida albicans, Schizosaccharomyces pombe, and Escherichia coli) also form stalks, suggesting that the ability to produce stalks may be a general property of microorganisms. Diploid yeast stalks sporulate at an elevated frequency, raising the possibility that the physiological role of stalks might be disseminating spores.

Candida albicans↗
PubMed1998

A comparison of the effects of mibefradil and atenolol on regression of left ventricular hypertrophy in hypertensive patients.

OBJECTIVE: This study was designed to compare the effect of mibefradil, a selective T-type calcium channel antagonist, with the beta-blocker atenolol on regression of left ventricular (LV) hypertrophy in hypertensive patients. METHODS: In this multicenter, double-blind, active-controlled, randomized, parallel-group comparison, 66 patients with mild-to-moderate hypertension (sitting diastolic blood pressure, SDBP, 95-114 mm Hg) and LV mass index > 102 g/m2 for males and > 88 g/m2 for females were randomized to an initial treatment with 50 mg of either mibefradil or atenolol for 4 weeks. Doses were increased to 100 mg/day if blood pressure was not normalized to < or = 90 mm Hg, and, if needed, 25 mg of hydrochlorothiazide was added. Treatment continued for a total of 24 weeks. LV hypertrophy was assessed by echocardiography, and trough SDBP and adverse events were recorded. RESULTS: Treatment with mibefradil or atenolol resulted in decreases from baseline in LV mass index of 11.1% (p < 0.001) and 9.1% (p < 0.001), respectively. The treatment difference (mibefradil vs. atenolol) was not statistically significant. Reductions in SDBP with mibefradil and atenolol were 14.3 and 10.7 mm Hg, respectively, again not statistically significant. Both drugs were well tolerated; however, overall there were more potentially drug-related adverse events reported with atenolol (48.5%) than with mibefradil (24.2%). CONCLUSIONS: The reductions in LV hypertrophy and blood pressure achieved with mibefradil were larger but statistically equivalent to those with atenolol, but a lower overall incidence of treatment-related adverse events was seen in the mibefradil-treated patients.

Adrenergic beta-Antagonists↗
PubMed1998

Prevention of the cardiovascular and renal effects of angiotensin II by endothelin blockade.

Angiotensin II (Ang II) stimulates the release and gene expression of endothelin-1 in isolated vascular smooth muscle cells. In 47 Sprague-Dawley rats, we assessed the influence of concomitant treatment by the mixed ET(A)/ET(B) endothelin receptor antagonist bosentan (30 mg/kg per day, gavage) on the effect of a 10-day infusion of Ang II (200 ng/kg per minute, SC, osmotic pump) on arterial pressure, renal hemodynamics (microsphere method), albuminuria, cardiac weight, and carotid structure. Ang II increased systolic arterial pressure (SAP) by 49+/-7 mm Hg. Although bosentan alone did not affect SAP, the development of Ang II-induced hypertension was entirely prevented by the endothelin antagonist. In addition, the reduction in renal blood flow induced by Ang II (4.9+/-0.3 versus 7.4+/-0.2 mL x min-1 x g-1 in control rats) was prevented by concomitant administration of bosentan (8.8+/-0.8 mL x min-1 x g-1). The marked increase in albuminuria observed in rats infused with Ang II (2524+/-961 versus 91+/-6 microg/24 h in control rats) was prevented by bosentan. Similarly, bosentan abolished the increase in heart weight index (from 2.96+/-0.03 to 3.41+/-0.08 mg/g body weight) and carotid media thickness (from 73+/-14 to 108+/-6 microm) induced by Ang II infusion. Of interest, the dipsogenic action of Ang II was not influenced by bosentan. In conclusion, endogenous endothelin contributes to the cardiovascular and renal effects of Ang II.

Angiotensin II↗
PubMed1998

[Effect of chronic bradykinin infusion on angiotensin II hypertension in rats].

In previous studies, we demonstrated that in ANG II-treated rats, prevention of cardiac hypertrophy (CH) by enalapril was blunted by bradykinin (BK) blockade by Hoe140. The putative role of BK was assessed by chronic exogenous BK infusion and in 46 male Sprague-Dawley rats infused with ANG II. ANG II (200 ng/kg/min) alone and associated with BK at low (BKlow, 15 ng/kg/day), mid (BKmid, 100 ng/kg/day) and high doses (BKhigh, 100 ng/kg/min) were delivered by Alzet osmotic pumps for 10 days and compared to control animals (Veh). Values of systolic arterial pressure (SAP, mmHg) in conscious rats and heart weight (HW, mg/g bw) at the end of the study are reported below. Results were submitted to ANOVA and are expressed as mean +/- SEM.

Angiotensin II↗
PubMed1998

[Renal alterations in L-NAME hypertension: influence of losartan and bosentan].

The influence of losartan and the endothelin A and B receptor antagonist, bosentan was assessed on the alterations in renal hemodynamic and function as well as urinary albumin excretion (taken as an index of renal lesions) associated with L-NAME hypertension. L-NAME was given for 4 weeks (20 mg/100 mL in the drinking (fluid) followed by a 2-week period of concomitant treatment with L-NAME and losartan or bosentan (30 and 30 mg/kg, gavage). A group of rats received L-NAME without additional treatment and a group of rats were not given L-NAME and served as normotensive controls. Systolic arterial pressure (SAP) was measured before L-NAME, and before and every 5 days of losartan or bosentan treatment period. Urinary excretion of albumin (UAlb) was determined before and at the end of treatment period. Under anesthesia, glomerular filtration rate (GFR) and renal plasma flow (RPF) were estimated by the clearance method and the filtration fraction was calculated [FF = 100* (GFR/RPF)].

Albuminuria↗
PubMed1997

Influence of dopamine receptor and adrenoceptor blockade on the hemoconcentrating and hypotensive actions of atrial natriuretic peptide.

Atrial natriuretic peptide (ANP) lowers mean arterial pressure (MAP) and increases hematocrit through reduction in plasma volume caused by a transcapillary shift of plasma fluid and protein toward the interstitium. We examined the consequences of blockade of the dopaminergic and adrenergic systems on the hypotensive and hemoconcentrating responses to ANP. Changes in MAP, hematocrit, and plasma protein concentration (PPC) were measured in anesthetized acutely binephrectomized rats, during infusion of ANP alone (1 microgram.kg-1.min-1 for 45 min) or in the presence of haloperidol (20 micrograms.kg-1.min-1), phentolamine (15 micrograms.kg-1.min-1), or propranolol (10 micrograms.kg-1.min-1). Infusion of ANP reduced MAP by 8.6 +/- 1.3% and increased hematocrit by 9.0 +/- 0.6% (both p < 0.005 vs. vehicle). PPC increased (4.4 +/- 0.6%; p < 0.005 vs. vehicle) significantly less than hematocrit, indicating extravasation of proteins. The ANP-evoked reduction in MAP was not affected in haloperidol- or phentolamine-treated rats (-8.8 +/- 2.3 and -10.5 +/- 2.4%, respectively; both p < 0.005 vs. vehicle) but was abolished in propranolol-treated rats (+3.2 +/- 1.3%; p = ns vs. vehicle). The ANP-induced increase in hematocrit was slightly attenuated in haloperidol-, phentolamine-, and propranolol-treated rats (7.5 +/- 0.7, 7.3 +/- 0.8, and 6.0 +/- 1%, respectively). In addition, the coefficient of reflection, an index of the permeability to proteins, was higher in these three groups (0.41 +/- 0.06, 0.49 +/- 0.08, and 0.57 +/- 0.14, respectively) than in control rats infused with ANP (0.27 +/- 0.03), indicating an attenuation of the ANP-induced extravasation of proteins. Thus, in binephrectomized rats, the hypotensive activity of ANP requires a beta-adrenergic component, whereas its hemoconcentrating action is, at least in part, dependent upon dopaminergic and adrenergic activation.

Adrenergic Antagonists↗
PubMed1997

[Determinants of the left ventricular mass in obese patients. Influence of lean body mass].

Systolic blood pressure and body mass index (BMI) are the main determinants of the left ventricular mass (LVM). The mechanism of this cardiac hypertrophy in the obese individual is multifactorial and involves hemodynamic as well as metabolic factors. The association of LVM with the morphologic features of the individual are well known. The aim of this study was to assess the influence of the morphologic and metabolic features of obese women on LVM. 2D echocardiography evaluation of LVM was done in 24 normotensive, normoglycemic obese women (BMI [27.5-52.2 Kg/m2). Lean and fat body mass were determined by bio-impedancemetry, insulin sensitivity (Si) by the minimal model (Bergman), and basal metabolism by using indirect calorimetry. There was a positive correlation between LVM and BMI (r = 0.61; p = 0.001), waist to hip ratio (r = 0.45; p = 0.03), basal metabolism (r = 0.61, p = 0.001), lean (r = 0.74, p = 0.0002) and fat (r = 0.49; p = 0.01) body mass. Fasting glycemia was positively correlated with LVM (r = 0.62; p = 0.001), but not Si. LVM was also positively correlated to the triglyceride level. No relations were found with systolic or diastolic blood pressure. Multivariate regression analysis was performed to determine the relative contribution of lean body mass (the morphologic variable with the best association to LVM in univariate analysis), blood glucose, waist to hip ratio, age and triglycerides. The multiple r for the model was 0.87 (p < 0.001). Lean body mass and blood glucose were found to be the only significant and independent predictors of LVM (p = 0.001 and p = 0.03 respectively). We conclude that: 1) lean body mass is an important determinant of LVM in obese normotensive individuals. Hence, in obese women, correcting LVM for lean body mass might be more accurate than correcting it for body surface area or height. 2) There is no relationship between LVM and insulin sensitivity. The link between blood glucose and LVM needs to be studied further.

Adult↗
PubMed1997

[Bosentan attenuates the hypertensive effect of angiotensin II in rats].

The influence of nonspecific blockade of endothelin receptors by bosentan (30 mg/kg per day, gavage) was assessed on hypertension induced by infusion of angiotensin II (AngII 200 ng/kg/min sc for 10 days) in rats. Tail-cuff pressure was measured before and every second day of AngII-infusion period. At the end of experiments, mean arterial pressure (MAP, mmHg), cardiac output (CO ml/min/kg body weight) and renal blood flow (RBF ml/min/g kidney weight) were determined (microspheres technique) in conscious rats, and total peripheral and renal vascular resistances were calculated (TPR = MAP/CO and RVR = MAP/RBF). [table: see text] Tail-cuff pressure increased from 126 +/- 4 to 164 +/- 8 mmHg in rats infused with AngII alone whereas it did not change (basal: 132 +/- 3 and final: 135 +/- 3 mmHg: p = NS) when bosentan was coadministered with AngII. At the end of study in conscious rats, the AngII-induced rise in MAP was accompanied by a reduction in CO and RBF and a marked increased in TPR and RVR. In AngII-perfused rats, CO, RBF, TPR and RVR were restored by bosentan to values observed in untreated rats. These results indicate that blockade of endothelin A and B receptors by bosentan prevents the development of AngII-induced hypertension through attenuation of the effect of AngII on vascular tone and suggest that endothelin is an important mediator of the vasoconstrictor action of angiotensin II in rats.

Angiotensin II↗
PubMed1996

Antihypertensive therapy and renal function.

Although renal abnormalities may be present in patients with untreated, newly diagnosed essential hypertension, predictors of the development of progressive renal failure are of great concern. In addition, unanswered questions are the final arterial pressure achieved during treatment as well as the ideal renal- and cardiovascular-protective drug therapy. Most antihypertensive agents given for periods of several months in monotherapy have no consistent effect on renal function and hemodynamics. However, they may differ with regard to their influence on other factors considered to be markers of significant impact of hypertension on the kidney, such as albuminuria. Studies of very long-term therapy on the evolution of renal function and using reliable indicators of the variation of glomerular filtration rate are needed.

Adrenergic alpha-Antagonists↗
PubMed1996

Chronic kinin blockade and effect of ramipril in renal adaptation to sodium restriction.

The contribution of endogenous kinins to impairment in renal adaptation to a 6-day period of dietary sodium withdrawal associated with treatment with ramipril (5 mg/kg per day) and losartan (30 mg/kg per day) was evaluated by use of concomitant chronic administration of the bradykinin B2-receptor antagonist Hoe 140 (150 or 300 micrograms/kg per day via subcutaneous osmotic pump). A similar level of higher cumulative sodium excretion was observed in ramipril- and losartan-treated rats compared with untreated animals, and the effect of ramipril was not affected by Hoe 140. Similarly, the fall in arterial pressure and the renal vasodilatation associated with ramipril and losartan were not modified by Hoe 140. Glomerular filtration rate (785 +/- 73 microL/min per g KW in untreated sodium-depleted rats) decreased to a larger extent in ramipril-treated rats compared with losartan-treated rats (371 +/- 78 and 550 +/- 55 microL/min per g KW, respectively). Hoe 140 markedly prevented the alteration in glomerular filtration rate associated with ramipril, thus resulting in a final glomerular filtration rate (543 +/- 41 microL/min per g KW) similar to that observed with losartan. These findings demonstrate that despite a lack of influence on arterial pressure and sodium balance, accumulation of kinins markedly contributes to deterioration of the glomerular filtration rate induced by ramipril in sodium-depleted rats.

Adaptation, Physiological↗
PubMed1996

Preglomerular sudanophilia in L-NAME hypertensive rats: involvement of endothelin.

To characterize alterations of renal vessels occurring during systemic hypertension elicited in rats by 5, 10, and 25 days of treatment by the nitric oxide synthase inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME)(20 mg/kg daily), preglomerular vasculatures, consisting of arcuate arteries and their branches, interlobular arteries, and afferent arterioles, were isolated by HCl maceration. Blockade of nitric oxide synthase significantly increased tail-cuff systolic blood pressure by 21 +/- 2% and 42 +/- 3% after 5 and 25 days, respectively. Medias of hypertensive arcuate arterial branches and interlobular arteries but not of afferent arterioles had focal deposits of Sudan black-positive lipid droplets. At 25 days, vessel wall thickness increased by 72 +/- 6% along the sudanophilic areas. Immunostaining of sudanophilic lesions with a panel of antibodies unveiled medial cell proliferation, macrophage invasion, immunoreactive vascular cell adhesion molecule-1, and low-density lipoprotein. The frequency of sudanophilic lesions increased with time to affect 26 +/- 2% and 36 +/- 3% of arcuate arterial branches and interlobular arteries, respectively, at 25 days. Hypertensive L-NAME-treated rats developed glomerular injury probed by albuminuria and glomerular immunostaining for alpha-smooth muscle actin. Administration of the nonselective endothelin antagonist bosentan (30 mg/kg daily) blunted the development of sudanophilic lesions during L-NAME treatment without affecting arterial hypertension or degree of glomerular injury. Therefore, L-NAME hypertension leads to rapid development of focal, inflammatory, proliferative, and sudanophilic lesions along preglomerular vessels, suggesting atherosclerosis-like processes. Furthermore, endothelin is a likely mediator in the development of these lesions.

Animals↗
PubMed1996

[Endothelial dysfunction and cardiac performance in untreated hypertension].

Similar to endothelial modulation of vascular tone, nitric oxide (NO) released from the coronary and endocardial endothelium may modulated LV performance with an improvement of LV diastolic distensibility. The aim of the present study was to assess a potential relationship between endothelial function and LV performance in essential hypertension. Thirty-nine normotensive subjects (NT) and 46 never treated hypertensive patients (HT) were grouped according to the renal vasodilatatory response to infusion of L-arginine (30 g within 60 min). HT patients responders to L-arginine (n = 19) were defined by an increased > or = 5% of renal plasma flow (RPF) estimated by the clearance of I-Hippuran. LV mass index and afterload-corrected fractional shortening were determined by echocardiography. Mitral peak early (E) and late (A) diastolic flow velocity were assessed by Doppler. Results of ANOVA were (means +/- SD): [table: see text] In HT patients E/A was positively correlated with %RPF (r = 0.27; p < 0.01) and negatively correlated with age (r = -0.52 p < 0.01) and systolic BP (r = -0.36 p < 0.01). In multiple regression analysis the relation between E/A and %RPF was dependent of age. This results confirm that aging and hypertension are the main determinants of the alteration of LV diastolic function. The link between these factors may be the endothelium which abnormal regulatory function secondary to aging and HT may be associated to an impairment of NO dependent LV relaxation.

Adult↗
PubMed1996

Microalbuminuria in essential hypertension.

The prevalence of microalbuminuria in patients with essential hypertension ranges between 10 and 25%. The level of albuminuria is highly correlated with arterial pressure and more closely ambulatory arterial pressure. The interaction between albuminuria and arterial pressure is clearly enhanced by overweight and smoking. The renal mechanisms of microalbuminuria are not well elucidated; an increase in filtration fraction suggestive of intraglomerular hypertension was observed in patients with hyperfiltration. The significance of micro-albuminuria as a marker of cardiovascular risk or hypertensive renal disease needs to be confirmed through long-term follow-up studies. Antihypertensive treatment has variable influence on albuminuria; angiotensin-converting enzyme inhibitors, in contrast to other agents, tend to partially correct this abnormality.

Albuminuria↗