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Biomedical subjects

M Burnier

Publications and source records attributed to M Burnier.

At least 181 records · Page 10Linked to original sources
PubMed1987

[Renal function after administration of angiotensin-converting enzyme inhibitors].

Angiotensin converting enzyme (ACE) inhibitors are widely used today for the management of hypertension and congestive heart failure. These agents inhibit angiotensin II synthesis. In some particular circumstances they may be responsible for deterioration of renal function, e.g. in hypertensive patients with bilateral renal artery stenosis or with stenosis of the artery supplying a single kidney, or in patients with severe congestive heart failure or marked nephroangiosclerosis. In these patients renal perfusion pressure may become too low to maintain adequate glomerular filtration as there remains no angiotensin II to increase the tone of the efferent arteriole. In high risk patients it is therefore recommended that serum creatinine be checked after initiating therapy with an ACE inhibitor.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1987

Nicotine-induced release of vasopressin in the conscious rat: role of opioid peptides and hemodynamic effects.

Nicotine has been shown to stimulate the release of vasopressin and to cause significant hemodynamic changes. The mechanisms leading to enhanced vasopressin secretion and the vascular consequences of the high plasma vasopressin levels during nicotine infusion have not yet been determined. Therefore, the purposes of the present study were 1) to examine in normal conscious rats the role of opioid peptides in the nicotine-induced increase in plasma vasopressin levels and 2) to assess the role of vasopressin in the hemodynamic effects of nicotine (20 micrograms/min for 15 min) using a specific V1 antagonist of the vascular actions of vasopressin. Plasma vasopressin levels were significantly increased in the nicotine-treated animals (39.5 +/- 10 vs. 3.7 +/- 0.6 pg/ml in the controls, P less than .01). Pretreatment with naloxone, an antagonist of opioids at their receptors, did not reduce the vasopressin levels (47.7 +/- 9 pg/ml). Nicotine also increased mean blood pressure (122.5 +/- 2.5 to 145.2 +/- 3.3 mm Hg, P less than .01) and decreased heart rate (461 +/- 6 to 386 +/- 14.5 beats/min, P less than .05). Administration of the vasopressin V1 antagonist before the nicotine infusion did not affect the systemic hemodynamics or the regional blood flow distribution, as assessed by radiolabeled microspheres. Thus, these results suggest that the nicotine-induced secretion of vasopressin is not mediated by opioid receptors and that the high plasma vasopressin levels do not exert any significant hemodynamic effect on cardiac output or blood flow distribution.

Animals↗
PubMed1986

Renal response to shock.

Renal hypoperfusion such as occurs in shock creates an environment in which cellular injury and organ dysfunction can occur during the episode of shock as well as during reoxygenation and reperfusion. A severe decrement in oxygen delivery compromises energy (adenosine triphosphate) production, leading to various degrees of cell injury ranging from cell swelling to acute cortical necrosis. These different responses of the kidney to shock explain the multiple clinical presentations varying from an isolated loss of concentrating ability to prolonged anuria. Many cellular events contribute to renal cell injury, including cellular ATP depletion, cellular and mitochondrial calcium overload, and activation of phospholipases and oxygen radical formation. Recent clinical and experimental studies suggest that ATP-MgCl2, free radical scavengers, diuretics, vasodilators, and calcium channel blockers appear to be beneficial in preventing acute tubular necrosis after anoxic or severe hypoxic insults. Thus these agents may be helpful in altering the course of acute renal failure in shock patients and may decrease their morbidity and mortality.

Acute Kidney Injury↗
PubMed1986

Idiopathic acute interstitial nephritis and uveitis in the adult. Report of 1 case and review of the literature.

In a 59-year-old female, concurrence of acute interstitial nephritis and uveitis was observed. While the clinical signs resolved after a few weeks, signs of renal tubular dysfunction persisted for 9 months, and creatinine clearance was still impaired (22 ml/min) more than 2 years after beginning of the symptoms. This is the 5th case of idiopathic interstitial nephritis with concomitant uveitis reported in adult patients. In contrast to the benign evolution observed in children, the renal function may remain impaired in adults.

Creatinine↗
PubMed1986

Lithium infusion to study sodium handling in unanesthetized hypertensive rats.

To investigate renal tubular handling of sodium in various types of experimental hypertension, sodium, lithium, and inulin clearances were measured simultaneously in unanesthetized rats. Fractional excretion of lithium was used as an index of proximal sodium reabsorption. Eight groups of animals, all of the Wistar-Kyoto strain, were studied. Three were hypertensive: spontaneously hypertensive rats (SHR), rats with two-kidney, one clip renal hypertension, and uninephrectomized rats with deoxycorticosterone-salt hypertension. The five normotensive control groups included animals given normal, low, or high dietary sodium loads and rats with reduced renal mass. Fractional excretion of lithium was not influenced by moderate changes of glomerular filtration rate, but was sharply enhanced by sodium loading. Increased blood pressure was associated with enhanced urinary sodium excretion in uninephrectomized deoxycorticosterone-salt hypertensive and two-kidney, one clip hypertensive rats, as a result of decreased distal tubular reabsorption ("pressure natriuresis"). In contrast, SHR showed reduced sodium excretion and decreased fractional excretion of lithium, which suggests that increased sodium reabsorption in the proximal tubule may contribute significantly to the maintenance of hypertension.

Animals↗
PubMed1985

Experimental guinea pig ocular infection by Salmonella typhimurium.

The clinical, microbiologic, and cytologic features of the guinea pig model of keratoconjunctivitis with enterobacteria, Salmonella typhimurium were elucidated. Guinea pig eyes were instilled with S. typhimurium and the eyes were studied by biomicroscopy, culture, cytology, pathology, and electron microscopy. All animals developed moderate to severe conjunctivitis that was present in 18% of the animals on day 1. It became more intense, appearing in all of the eyes on day 10 and disappeared before day 30. The cultures for S. typhimurium were almost all positive on days 1 and 2, declined steadily to 10% on day 10, and were negative after that. A coarse, epithelial punctate keratitis was present in more than 90% of the infected eyes at some time during the experiment. The keratitis had a biphasic clinical course. The first peak correlated with the maximum culture results, but during the second peak only 10% of the cultures were positive. Electron microscopy of the cornea showed the S. typhimurium at the epithelial surface within surface epithelial cells during the early phases of infection. The later phase keratitis, with negative culture results, resembles the keratitis of Reiter's syndrome.

Animals↗
PubMed1985

Does renal failure induce a decrease in cyclosporine blood concentrations?

Blood Cys concentrations were monitored twice weekly by RIA in nine patients undergoing renal transplantation. The Cys dose was adapted to obtain blood values between 100-400ng/ml. A negative correlation was found between plasma creatinine and blood Cys, even in those patients in whom the oral dosage was not changed (r = 0.65, n = 23, p less than 0.001). In vitro studies showed no effect of uraemic blood on Cys measurement. It seems probable that uraemia induces changes in distribution volume and/or gastrointestinal absorption of the drug. Careful monitoring of Cys during uraemia is therefore warranted.

Adult↗
PubMed1983

Pressor responses of rats to vasopressin: effect of sodium, angiotensin, and catecholamines.

The pressor response to lysine vasopressin was tested in groups of male Wistar, Brattleboro, Wistar-Kyoto, and spontaneously hypertensive rats. Moreover, the influence of sodium intake, angiotensin II, saralasin, captopril, norepinephrine, and isoproterenol on vasopressin pressor responses was evaluated. The right iliac artery and one or both femoral veins of the animals were catheterized under light ether anesthesia. The experiments were carried out following a 2-h stabilization period with the rats awake and semirestrained. Pressor responsiveness was evaluated acutely on the basis of dose-response curves (0.5-4 mU). In the Wistar rats, angiotensin II (10 and 30 ng/min) and isoproterenol (10 ng/min) markedly decreased the response to vasopressin, whereas variations in sodium intake and blood pressure per se did not seem to exert any influence. Norepinephrine (250 ng/min) slightly enhanced the pressor responsiveness to the smaller doses of lysine-vasopressin. Brattleboro rats with congenital diabetes insipidus were less sensitive to vasopressin than the other animals, and neither angiotensin II nor isoproterenol induced any change. In conclusion, the pressor responsiveness to vasopressin can vary considerably depending on several factors. These must be taken into account when evaluating the possible pressor role of vasopressin in experimental and clinical settings.

Angiotensin II↗
PubMed1983

Plasma vasopressin in rats: effect of sodium, angiotensin, and catecholamines.

A radioimmunoassay was set up to measure plasma arginine vasopressin levels (AVP). Characteristics of the assay include a sensitivity to 0.25 pg, high specificity of the antibody, mean recovery of added unlabeled arginine vasopressin of 80%, and an interassay coefficient of variation of 7.6%. This assay was used to investigate the influence of various factors on plasma vasopressin levels in a total of 121 awake male rats. Blood samples obtained in Wistar rats via an indwelling arterial catheter yielded results similar to those following decapitation, i.e., 1.27 +/- 0.26 vs. 1.68 +/- 0.39 pg/ml. Forty-eight hour dehydration markedly increased plasma AVP to 21.8 +/- 2.39 pg/ml. AVP was less than 0.5 pg/ml in Brattleboro rats. Low and high sodium intake, angiotensin II infusion (10 and 30 ng/min), and converting enzyme inhibition by captopril (100 mg/kg) did not alter plasma AVP. During norepinephrine infusion (250 ng/min) plasma AVP rose to 5.28 +/- 1.29 pg/ml, whereas it tended to fall with isoproterenol infusion (10 ng/min). Plasma AVP was slightly higher in spontaneously hypertensive rats than in Wistar-Kyoto controls.

Angiotensin II↗
PubMed1983

Blood pressure maintenance in awake dehydrated rats: renin, vasopressin, and sympathetic activity.

The role of vasopressin, the renin system, and sympathetic activity in sustaining blood pressure in the dehydrated state was investigated in normotensive nonanesthetized male Wistar rats. After 48-h dehydration, plasma arginine vasopressin was 14.0 +/- 1.7 pg/ml and plasma norepinephrine 0.46 +/- 0.05 ng/ml. In another group of rats in which the angiotensin converting enzyme inhibitor (MK 421, 5 mg po twice daily) was administered throughout the dehydration period, blood pressure was reduced by more than 20% (P less than 0.001), and both plasma arginine vasopressin and norepinephrine were higher at 23.4 +/- 3.9 pg/ml (P less than 0.01) and 0.83 +/- 0.07 ng/ml (P less than 0.01), respectively. Taken together, in rats with or without converting enzyme blockade, there was an inverse correlation between mean blood pressure and plasma arginine vasopressin (r = 0.67, P less than 0.01) as well as plasma norepinephrine (r = 0.82, P less than 0.01) levels. The acute administration of a specific vasopressin pressor inhibitor (dPVDAVP) reduced mean blood pressure in the rats with a blocked renin system by 16.9 mmHg (P less than 0.001). In rats without converting enzyme inhibition, the induced fall was only 6.4 mmHg. These results indicate that following 48-h dehydration the renin angiotensin system interacts with the vasopressin secretory mechanism to sustain blood pressure, with renin playing a predominant role. They further suggest that, following blockade of the renin system, activation of the sympathetic nervous system probably also contributes to blood pressure maintenance.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1981

Three new long-acting converting-enzyme inhibitors: relationship between plasma converting-enzyme activity and response to angiotensin I.

Three new angiotensin converting-enzyme inhibitors were given orally to 20 men in single doses ranging from 1.25 to 40 mg. Two of them induced comparable marked inhibition of both the blood pressure response to exogenous angiotensin I and plasma converting-enzyme activity. Onset of action was relatively slow, but 21 to 24 hr after drug plasma converting-enzyme activity was still clearly reduced. The third was less active. There was a close correlation between blood pressure response on administration of angiotensin I and plasma converting-enzyme activity. There were no adverse effects. These new drugs are interesting because of their long duration of action. The measurement of plasma converting-enzyme activity seems useful for monitoring efficacy of converting-enzyme blockade and compliance to therapy.

Adult↗
PubMed1981

RHC 3659: a new orally active angiotensin converting enzyme inhibitor in normal volunteers.

1 The new converting enzyme inhibitor RHC 3659 was tested in 15 male volunteers. The study consisted of two parts: first, the ability of a single oral dose (5, 10, 20, 40 or 80 mg) to inhibit the pressor response to exogenous angiotensin I was tested with blood pressure and heart rate monitored continuously through an intraarterial catheter. A dose-related shift to the right of the pressor response curve to angiotensin I was observed with a peak occurring within 0.5 to 1 h. The pressor response to angiotensin II was unaffected. 2 In the second part, plasma renin and converting enzyme activity, angiotensin II and aldosterone were measured serially before and up to 8 h after administration of a single oral dose of RHC 3659. As expected. plasma angiotensin II and aldosterone fell within 30 min while plasma renin activity increased. Plasma converting enzyme activity was suppressed at 0.5 h in a dose-related manner with levels still below 30% of control 4 h following 80 mg of the inhibitor. 3 However, in vitro the enzyme-inhibitor complex seemed quited fragile since during storage of the plasma samples at -20 degrees C, converting enzyme activity increased significantly already within days (P less than 0.001, n = 28) and continued to rise for more than 2 months. This fragility may explain the seemingly lower potency of RHC 3659 when compared to captopril. No side effects were observed.

Adult↗
PubMedDate not supplied

A device for subjecting vascular endothelial cells to both fluid shear stress and circumferential cyclic stretch.

The proposal of the role of mechanical forces as a localizing factor of atherosclerosis has led many researchers to investigate their effects on vascular endothelial cells. Most previous efforts have concentrated on either the fluid shear stress, which results from the flow of blood, or the circumferential "hoop" stretch, which results from the expansion of the artery during the cardiac cycle. In fact, arterial endothelial cells are subjected to both fluid shear stress and cyclic hoop stretch in vivo. Therefore, a more complete investigation of mechanical phenomena on endothelial cell behavior should include both kinds of mechanical stimuli. This study was undertaken to design an experimental apparatus that could subject cultured vascular endothelial cells to simultaneous physiologic levels of both shear stress and cyclic hoop stretch. The experimental apparatus consists of four cylindrical elastic tubes so that the following conditions may be studied: (a) static conditions: (b) shear stress only; (c) hoop stretch only; and (d) shear stress and hoop stretch. In order to establish the functional capabilities of the apparatus, bovine pulmonary artery endothelial cells were cultured in the tubes, and their morphology and f-actin structure were observed with confocal microscopy. The cells remained healthy and attached to the walls throughout the 24 hr experiment. Preliminary results indicated that the alignment of endothelial cells subjected to shear stress was significantly enhanced by the addition of hoop strain.

Actins↗
PubMedDate not supplied

Salt- and angiotensin II-dependent variations in amiloride-sensitive rectal potential difference in mice.

1. In the rectum and distal nephron, sodium reabsorption is mediated by the amiloride-sensitive epithelial sodium channel (ENaC). The ENaC-mediated sodium transport is electrogenic and creates an amiloride-sensitive transepithelial potential difference (PD). 2. We have evaluated the salt- and angiotensin (Ang)II-dependent variations in amiloride-sensitive rectal PD in mice and assessed their relationship with renal sodium handling. 3. Rectal PD was measured in vivo in mice maintained on a medium-, low- or high-sodium diet. On a medium-salt diet, the mean (+/- SEM) amiloride-sensitive PD was larger in the afternoon than in the morning (-26.1 +/- 0.9 and -11.2 +/- 0.7 mV, respectively; P = 0.001), indicating a circadian cyclicity. Rectal PD increased on a low-sodium diet and decreased on a high-sodium diet. 4. Amiloride-sensitive rectal PD correlated significantly with the urinary Na+/K+ ratio (P < 0.001) and with sodium reabsorption in the distal nephron as measured by the lithium clearance technique (P < 0.001). 5. In mice treated with an AngII AT1 receptor antagonist, amiloride-sensitive rectal PD was increased in the afternoon compared with controls (-32.8 +/- 2.0 vs -24.4 +/- 0.9, respectively; P < 0.001). 6. At high doses, AngII decreased the amiloride-sensitive rectal PD and this effect was blunted by an AT1 receptor antagonist. 7. These results show the presence of a salt-dependent daily cyclicity of sodium transport in the mouse rectum that follows circadian changes in sodium handling in the distal nephron. Angiotensin II appears to modulate this diurnal pattern of rectal amiloride-sensitive sodium transport.

Angiotensin II↗