PubMed Health⌕ Search

Biomedical subjects

B Chevalier

Publications and source records attributed to B Chevalier.

At least 73 records · Page 4Linked to original sources
PubMed1995

Trandolapril decreases prevalence of ventricular ectopic activity in middle-aged SHR.

BACKGROUND: Although severe arrhythmias are still a major problem in patients with left ventricular hypertrophy (LVH), the relationship between ventricular remodeling and its regression or prevention, and the prevalence of ventricular premature beats (VPB) or more sustained arrhythmias are still poorly explored in hypertensive heart disease. METHODS AND RESULTS: Holter monitoring was used to quantify supraventricular premature beats and VPB and heart rate (HR) in middle-aged spontaneously hypertensive rats (SHR) and Wistar rats treated for 3 months with trandolapril (ACE inhibitor, 0.3 mg/kg per day). Hypertrophy and fibrosis were morphometrically determined. Statistical analysis was performed with the use of simple regression and multivariate data analysis (cluster and correspondence analysis). SHR have higher cardiac mass and fibrosis, more VPB, and a decreased HR. Cluster analysis demonstrated that trandolapril was only effective in SHR. Trandolapril significantly reduced cardiac hypertrophy, fibrosis, and VPB incidence and increased the HR. Simple regression analysis showed that VPB incidence correlated to both hypertrophy and fibrosis. Correspondence analysis evidenced a strong correlation between hypertrophy, fibrosis, and VPB, but only for severe hypertrophy, and the correlation disappeared for moderate hypertrophy. CONCLUSIONS: After trandolapril treatment, the regression of VPB incidence not only is linked to hypertrophy and fibrosis, but additional causal factors also are involved including the myocardial phenotype and new calcium metabolism. Our model of Holter monitoring in conscious middle-aged SHR and multivariate data analysis might be useful in correlating myocardial structural modifications and ectopic activity.

Aging↗
PubMed1995

[Extraction of intravascular foreign bodies].

OBJECTIVE: Loss or displacement of foreign material within the cardiovascular system is not an uncommon event. Foreign bodies include fragments of diagnosis equipment, ruptured catheters or malpositioned or displaced intravascular prostheses. The incidence has increased with the development of endovascular catheterism and raises the problem of extraction. METHODS: We report our experience with percutaneous extraction of intravascular foreign bodies. RESULTS: There were 56 cases. Percutaneous extraction was successful in 53. In 11 cases, the procedure was carried out during a catheterism procedure and in the others the initial event had occurred earlier. The delay to extraction varied from a few hours to several years. CONCLUSION: Percutaneous extraction of intravascular foreign bodies should be attempted before surgical removal, an often difficult high-risk procedure. The literature does not provide data on the frequency of intravascular foreign bodies.

Adolescent↗
PubMed1995

[Bactericidal activity of 6 antibiotics and 3 combinations against 6 strains of Salmonella isolated from blood].

The bactericidal activity of 6 antibiotics and 3 combinations was evaluated against 6 Salmonella strains isolated from blood: 3 sensitive to all antibiotics tested (1 Salmonella Typhi, 1 Salmonella Paratyphi A et 1 Salmonella Enteritidis) and 3 harbouring a TEM penicillinase (1 Salmonella Typhi, 1 Salmonella Virchow et 1 Salmonella Typhimurium). MICs of 6 antibiotics, ceftriaxone, cefotaxime, cefoperazone, ciprofloxacin, amikacin and chloramphenicol were determined by microdilution method in Mueller Hinton broth. The bactericidal activity of these antibiotics and 3 combinations (ciprocloxacin + ceftriaxone, ciprofloxacin + amikacin and ceftriaxone + amikacin) was determined by the killing curve method with 10(6) cfu/ml inocula and 4 x MIC for antibiotics concentrations. Chloramphenicol, only tested on typho-paratyphi strains, had only a bacteriostatic effect at 24 hours. Amikacin and ciprofloxacin had a faster and better bactericidal activity than cephalosporins. Combinations were either additive or synergistic. Those including amikacin had the best results, but any can be proposed for initial treatment of severe Salmonella infections in immunosuppressed patients.

Amikacin↗
PubMed1995

[Comparative activity of azithromycin against 100 strains of Neisseria gonorrhoeae].

Azithromycin is a new semisynthetic, acid stable C15 macrolid. In our study, we compared in vitro activity of azithromycin with 6 other antibiotics usually recommended for treatment of N. gonorrhoeae infections: erythromycin, ampicillin, amoxicillin, ceftriaxone, spectinomycin, ciprofloxacin. 100 strains have been selected: 95 clinical strains with different resistance patterns: 60 susceptible to beta-lactams, 25 PPNG, 10 chromosomal decreased susceptibility to beta-lactams. Among these strains, 13 had a decreased susceptibility to erythromycin (MIC: 2 and 4 mg/l) and 5 WHO reference strains: A: spectinomycin resistance, B: wild phenotype, C: chromosomal decreased susceptibility to penicillin and tetracycline, D: chromosomal resistance to penicillin and erythromycin+chromosomal decreased susceptibility to chloramphenicol, E: beta-lactamase producing strain (PPNG) and decreased susceptibility to tetracycline. MICs have been determined by GC agar dilution method. Azithromycin is more active than erythromycin on all N. gonorrhoeae patterns with a two log 10 difference for MIC50 and MIC90 (p < 0.0001). Because of pharmacokinetic properties and activity against Chlamydia trachomatis and urogenital mycoplasms often associated with N. gonorrhoeae, azithromycin is a good alternative for the treatment of genital infections.

Anti-Bacterial Agents↗
PubMed1994

Molecular basis of regression of cardiac hypertrophy.

Cardiac hypertrophy due to a chronic mechanical overload puts into play a biologic cascade, including a trigger (the mechanical stretch), a transmitter (very likely to be the phosphoinositol pathway), and the final target (which is the DNA). The permanent changes in genetic expression resulting from the activation of this cascade allows the heart to produce normal active tension at a lower cost in terms of energy expenditure. The process is reversible, providing the treatment reduces the real load on the heart--i.e., not only the peripheral resistances but also the aortic impedance--during a period of time that has to be several times the half-life of cardiac proteins, and also that the treatment has an effect on the detrimental consequences of cardiac hypertrophy, namely, the systolic and diastolic dysfunction and the incidence of arrhythmias. In this report semisenescent spontaneously hypertensive rats were treated for 3 months with the converting enzyme inhibitor trandolapril. The treatment had a rather modest effect on blood pressure but resulted in a pronounced reduction in cardiac hypertrophy and in cardiac fibrosis, an improved coronary reserve, and attenuated both the effects of anoxia on the left ventricular diastolic compliance and the incidence of ventricular arrhythmias.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1994

"Pseudo-narrowing" during right coronary angioplasty: how to diagnose correctly without withdrawing the guidewire.

The straightening of a sinuous proximal segment of a coronary artery using the stiffness of the guidewire has recently been recognized as likely to cause false coronary lesions. The accurate diagnosis between a true dissection and a pseudo-lesion is usually only done once all intra-coronary material has been removed into the guiding catheter. Such a manoeuvre may prove dangerous in case of dissection. We propose to demonstrate that it is possible to diagnose this phenomenon while leaving the guidewire within the coronary artery, and withdrawing it progressively until its floppy segment rests equally on either side of the suspect lesion.

Angioplasty, Balloon, Coronary↗
PubMed1994

Should we avoid ostial implantations of Wiktor stents?

Complications arising during stent implantations in coronary arteries have been reduced by technological progress and the accumulated experience of interventional cardiologists. Retrospective and prospective randomized studies with several types of stents are currently available and show improved short and mid-term results. Wiktor stent provides increased flexibility for ease of implantation particularly in curved lesions. However, the flexibility of the Wiktor stent is also associated with low resistance in the longitudinal axis. We report four cases (in 4 out of 6 ostial lesions treated and 4 out of 43 Wiktor stents implanted during a 9-month period) in which stents have become unraveled during procedures on ostial lesions (2 saphenous venous grafts and 2 native coronary arteries). Death occurred in one case and one patient was treated by emergency coronary bypass surgery. In three cases the distal extremity of the guiding catheter stretched the stent meshes during the final control angiograms, and in one case the stent was stretched during withdrawal of the deflated balloon into the guiding catheter. We believe that it is preferable to avoid using this stent in ostial lesions.

Angioplasty, Balloon, Coronary↗
PubMed1994

Corticosterone-induced insulin resistance is not associated with alterations of insulin receptor number and kinase activity in chicken kidney.

Chicken renal insulin receptors have been recently characterized; their number and kinase activities vary in response to altered nutritional status. In the present study, the effect of chronic corticosterone treatment was examined in 5-week-old chickens. The development of an insulin resistance following corticosterone was suggested after 1 and 2 weeks of treatment by a significant increases in plasma insulin levels (1.63 +/- 0.13 vs 0.56 +/- 0.14 ng insulin/ml in controls) and in renal cytosolic phosphoenolpyruvate carboxykinase activity (17.2 +/- 0.8 vs 13.7 +/- 0.7 nm/mn/mg tissue in controls). No significant changes were present at the level of insulin receptor number and kinase activity. Therefore, in kidney and, as previously observed, in muscles, corticosterone can induce insulin resistance at postreceptor steps in the cascade of events leading to insulin action.

Animals↗
PubMed1994

Is the senescent heart overloaded and already failing?

Heart failure mainly occurs during the last decades of life, and it is important to know if the senescent heart is not an already failing heart. During aging, both contraction and relaxation of papillary muscle are impaired. Such an impairment is compensated in vivo and the cardiac output remains normal. In spite of a loss in myocytes, the heart weight/body weight ratio is unchanged, but the myocytes are bigger. Arrhythmias are permanent and are accompanied by a loss of the normal heart rate variability. Changes in specific mRNAs include: a shift in myosin heavy chain (MHC) isogene expression leading to an increased beta MHC content; decreased densities of Ca2+ ATPase of the sarcoplasmic reticulum, beta 1-adrenergic receptor, and muscarinic receptors; and attenuation of the Na+/Ca2+ exchange activity. Most of these changes, but not all, resemble those observed during cardiac overload and are accompanied by an increased duration of both the action potential and the intracellular calcium transient. However, the senescent heart is still able to further modify its phenotype in response to mechanical overload. The senescent heart is a diseased heart, and the origin of the "disease" is multifactorial and includes the general process of senescence, hormonal changes, and the myocardial consequences of senescence of the vessels.

Aging↗
PubMed1994

Phenotypic determinants of heart rate variability in cardiac hypertrophy and failure.

Reduced heart rate variability (HRV) has a strong predictive value in terms of sudden death, as compared to other prognostic criteria, but it has never been previously studied in experimental models of cardiac hypertrophy and failure. However, it has been quantified in rats using Holter monitoring and the peak and trough method of analysis. In normal rats, as in humans, short and long oscillations, sensitive, respectively, to atropine and propranolol were detected. Both correlate with heart rate. Cardiothyrotoxicosis was characterized by tachycardia and, independently, by a pronounced alteration in long oscillations. HRV was normal in compensatory cardiac hypertrophy due to aortic stenosis, but in this model the normal correlation existing between HRV and heart rate had disappeared. It is suggested that the main determinants of the above modifications of HRV are the changes in the new myocardial phenotype observed in terms of beta-adrenoceptor and muscarinic densities.

Animals↗
PubMed1994

Paclitaxel (Taxol) and docetaxel (Taxotere): not simply two of a kind.

Paclitaxel and docetaxel are the two presently clinically available representatives of the new class of taxane drugs. They share major parts of their structures and mechanisms of action, but differ in several other aspects. For instance, there is a difference in their tubulin polymer generation, and docetaxel appears twice as active in depolymerization inhibition. In vitro docetaxel also tends to be more potent in different cell lines and investigational models. While in vitro and in vivo studies suggest that prolonged exposure to paclitaxel is better than a brief exposure, no such tendency is seen for docetaxel, indicating it to be a schedule-independent drug. Clinical studies have not confirmed an advantage for prolonged exposure to paclitaxel; but do show differences in the toxicity profiles of the two drugs. These topics will be addressed in detail.

Animals↗
PubMed1994

Regression of left ventricular hypertrophy by converting enzyme inhibition in 12-15-month-old spontaneously hypertensive rats: effects on coronary resistance and ventricular compliance in normoxia and anoxia.

The effects of trandolapril, a converting enzyme inhibitor (CEI), on left ventricular (LV) diastolic stiffness and coronary vascular resistance (CVR), were studied with an isolated heart preparation in 15-month-old spontaneously hypertensive rats (SHR). The hypertensive animals were treated for 3 months with trandolapril (0.3 mg/kg/day) (SHRT), and compared with untreated age-matched Wistar-Kyoto rats (WKY) and SHR. Trandolapril treatment resulted in 15% diminution in blood pressure (BP). In contrast, it completely normalized left ventricular (LV) weight. Untreated SHR, as compared with WKY, had a dilated LV and increased diastolic tissue stiffness. Trandolapril had no effect on either chamber or tissue stiffness. Five-minute anoxia resulted in the same dramatic increase in chamber stiffness in every experimental group. During anoxia, as during normoxia, tissue stiffness was still greater in SHR than in WKY. A major effect of CEI was to normalize the tissue stiffness of SHR under anoxia. Coronary vascular resistance (CVR) was increased in SHR as compared with WKY. Trandolapril improves CVR and significantly shifts the coronary pressure flow curve to the dilatory side. Both collagen concentration (approximately 2 mg/g) and the content in slow V3 myosin isoform, used as biologic markers of cardiac senescence, were the same in the three experimental groups, but higher than in young hearts. Trandolapril had no effect on these parameters. In semisenescent SHR, despite having rather slight effect on arterial pressure, trandolapril completely normalized LV weight. In addition, collagen content and its physiologic counterpart, tissue stiffness, were unaffected by 3-month treatment with trandolapril. Nevertheless, the anoxia-induced increase in LV tissue stiffness was improved by trandolapril in parallel with reduction in LV hypertrophy (LVH).

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1994

Heart rate variability in two models of cardiac hypertrophy in rats in relation to the new molecular phenotype.

The analysis of heart rate variability (HRV) provides information on neural control of the heart. We investigated HRV in normal rats and in models of experimental cardiac hypertrophy using the Holter monitoring and peak/trough method. In normal rats, two heart rate oscillations with different wavelengths, high frequency (HF) and low frequency (LF) oscillations, were detected. The HF oscillations were insensitive to propranolol and suppressed by atropine. The LF oscillations were sensitive to both antagonists. Thyrotoxicosis resulted in cardiac hypertrophy (+20%) and tachycardia. The HF oscillations were unchanged, whereas LF oscillations were hampered at low heart rate in this group. Aortic stenosis resulted in cardiac hypertrophy (+53%), but heart rate oscillations were unchanged. The (number x amplitude) product for both types of oscillations correlated with heart rate in controls but not in the thyrotoxicosis or aortic stenosis models. Alterations of HRV in cardiac hypertrophy occur in rats as in humans. They may reflect the changes in the molecular components of the adrenergic/muscarinic system, which defines the new myocardial phenotype.

Analysis of Variance↗
PubMed1994

Activation of angiotensinogen and angiotensin-converting enzyme gene expression in the left ventricle of senescent rats.

BACKGROUND: During senescence, the plasma angiotensin II concentration is decreased, but the regulation of intracardiac angiotensin II synthesis has never been investigated. The purpose of this work was to determine the cardiac content of both angiotensinogen (ANG) and angiotensin-converting enzyme (ACE) mRNAs in 24-month-old Wistar rats. METHODS AND RESULTS: Total cardiac RNAs and known amounts of ANG and ACE mRNA transcripts, used as standards, were hybridized on slot blots with specific cDNA probes. The quantities of ANG and ACE mRNA were evaluated from the regression lines obtained with fragments of ANG and ACE mRNA in vitro transcripts. With aging, while the overall plasma renin-angiotensin system (RAS) activity decreased, in the left ventricle (LV) the amounts of ANG and ACE mRNAs were increased by fivefold (P < .01) and 2.5-fold (P < .01), respectively, compared with young adult controls. By contrast, in the right ventricle (RV) the same mRNA levels remained unchanged. In parallel, we also found an enhanced expression of the atrial natriuretic factor (ANF) in the LV but not in the RV. CONCLUSIONS: During senescence, the depressed circulating RAS activity is in contrast to the increase of both ANG and ACE mRNA levels in the LV. Such an upregulation in both gene activities is more likely to be related to the age-associated changes in arterial compliance rather than to hormonal changes, since (1) this regulation is found only in the LV and (2) the same pattern of regulation is also observed for the ANF mRNA level.

Aging↗
PubMed1994

Preferential binding of insulin-like growth factors to a binding protein rather than to receptors on chicken hepatoma cell (LMH) membranes.

[125I]IGF-I binding to chicken hepatoma cell (LMH) membranes was displaced by unlabelled IGF-I or IGF-II, but not by insulin. Cross-linking revealed specific binding sites of 128 and 28-31 kDa, which following solubilization could be separated by wheat germ agglutinin (WGA) chromatography. [125I]IGF-I binding to the WGA eluate (128 kDa) could be displaced by insulin although with a 30-fold lower potency than IGF-I. Binding to the WGA flow-through (28-31 kDa) was not inhibited by insulin. This suggested that IGF binding to LMH was due mainly to membrane bound IGFBP rather than to type 1 IGF receptors. A reverse proportion was observed in normal chicken liver. A predominant 28 kDa IGFBP was synthesized and secreted by LMH cells, together with an unusual 60 kDa IGF binding entity which only bound [125I]IGF-II (with weak affinity). This process was not affected by the presence or absence of glucose, dexamethasone, glucagon, insulin or IGF-I.

Animals↗
PubMed1993

Regulation of amino acid transport and protein metabolism in myotubes derived from chicken muscle satellite cells by insulin-like growth factor-I.

The effects of insulin and insulin-like growth factor-I (IGF-I) on amino acid transport and protein metabolism were compared in myotubes derived from chicken breast muscle satellite cells. Protein synthesis was assessed by continuous labelling with [3H]-tyrosine. Protein degradation was estimated by the release of trichloroacetic acid (TCA) soluble radioactivity by cells which had been previously labelled with [3H]-tyrosine for 3 days. Amino acid transport was measured in myotubes incubated in Dulbecco's modified Eagle's medium (DMEM) 0.5% bovine serum albumin (BSA) with or without insulin or IGF-I. Subsequent [3H]-aminoisobutyric acid (AIB) uptake was then measured in amino acid-free medium. IGF-I was more efficient than insulin at equimolar concentration (3.2 nmol/l) in stimulating protein synthesis (127 and 113% of basal, respectively) and inhibiting protein degradation (32% and 13% inhibition of protein degradation following 4 h incubation). Half maximal effective concentrations for stimulation of AIB uptake were 0.27 +/- 0.03 nmol/l and 34.8 +/- 3.1 nmol/l for IGF-I and insulin respectively, with maximal stimulation of about 340% of basal. Cycloheximide (3.6 mumol/l) diminished IGF-I-stimulated AIB uptake by 55%. Chicken growth hormone had no effect on basal AIB uptake in these cells and neither glucagon nor dexamethasone had an effect on basal or IGF-I-stimulated AIB uptake. This study demonstrates an anabolic effect for IGF-I in myotubes derived from primary chicken satellite cells which is mediated by the type I IGF receptor, since the cation-independent mannose 6-phosphate receptor does not bind IGF-II in chicken cells.

Amino Acids↗
PubMed1993

Corticosterone effect on insulin receptor number and kinase activity in chicken muscle and liver.

The effects of chronic corticosterone treatment (6 mg/kg/day) on insulin sensitivity and on liver and muscle insulin receptors were examined in 5-week-old chickens. The hypoglycemic effect of exogenous insulin was completely abolished within 2 weeks of treatment, suggesting a corticosterone-induced insulin resistance. Hepatic insulin receptor numbers were slightly reduced (P < 0.001) after 2 weeks of treatment. After 1 or 2 weeks, corticosterone treatment significantly reduced liver insulin receptor kinase activity toward the artificial substrate poly(Glu4,Tyr1). Muscle insulin receptor kinase activity was also significantly decreased after 1 week of treatment but this effect was accounted for by a decrease in basal activity. Therefore the corticosterone-induced insulin resistance is accounted for, at least in part, by altered hepatic receptor numbers and kinase activity. The impairment of muscle development involves postreceptor defects.

Adipose Tissue↗