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Biomedical subjects

J N Trochu

Publications and source records attributed to J N Trochu.

31 records · Page 2Linked to original sources
PubMed2000

Role of endothelium-derived nitric oxide in the regulation of cardiac oxygen metabolism: implications in health and disease.

Endothelium-derived NO is considered to be primarily an important determinant of vascular tone and platelet activity; however, the modulation of myocardial metabolism by NO may be one of its most important roles. This modulation may be critical for the regulation of tissue metabolism. Several physiological processes act in concert to make endothelial NO synthase-derived NO potentially important in the regulation of mitochondrial respiration in cardiac tissue, including (1) the nature of the capillary network in the myocardium, (2) the diffusion distance for NO, (3) the low toxicity of NO at physiological (nanomolar) concentrations, (4) the fact that low PO(2) in tissue facilitates the action of NO on cytochrome oxidase, and (5) the formation of oxygen free radicals. A decrease in NO production is involved in the pathophysiological modifications that occur in heart failure and diabetes, disease states associated with altered cardiac metabolism that contributes to the evolution of the disease process. In contrast, several drugs (eg, angiotensin-converting enzyme inhibitors, amlodipine, and statins) can restore or maintain endogenous production of NO by endothelial cells, and this mechanism may explain part of their therapeutic efficiency. Thus, the purpose of this review is to critically evaluate the role of NO in the control of mitochondrial respiration, with special emphasis on its effect on cardiac metabolism.

Diabetes Mellitus↗
PubMed2000

Clinical characteristics of a familial inherited myxomatous valvular dystrophy mapped to Xq28.

OBJECTIVES: The purpose of this study was to describe the phenotypic characteristics of an inherited myxomatous valvular dystrophy mapped to Xq28. BACKGROUND: Myxomatous valve dystrophies are a frequent cause of valvular diseases, the most common being idiopathic mitral valve prolapse. They form a group of heterogeneous diseases difficult to subclassify. The first mapping of the gene for a myxoid valvular dystrophy to Xq28 allowed investigation of the phenotype of affected members in a large family and characterization of the disease. METHODS: Among the 318 members in the pedigree, 89 agreed to participate in this study. Phenotypic characteristics were investigated using clinical examination, transthoracic echocardiography and biological analysis (F.VIII activity). Genetic status was based on haplotype analysis. RESULTS: Among 46 males, 9 were hemizygous to the mutant allele and had an obvious mitral and/or aortic myxomatous valve defect, and 4 had undergone valvular surgery. All had typical mitral valve prolapse associated in six cases with moderate to severe aortic regurgitation. The valve defect cosegregated with mild hemophilia A (F.VIII activity = 0.32 +/- 0.05). The 37 remaining males had normal valves and normal F.VIII activity. Heterozygous women were identified on the basis of their haplotypes. Among the 17 women heterozygous to the mutant allele, moderate mitral regurgitation was present in 8, associated with mild mitral valve prolapse in 1 and aortic regurgitation in 3, whereas 2 women had isolated mild aortic regurgitant murmur. In heterozygotes, the penetrance value was 0.60 but increased with age. CONCLUSION: X-linked myxomatous valvular disease is characterized by mitral valve dystrophy frequently associated with degeneration of the aortic valves affecting males and, to a lower severity, females. The first localization of a gene for myxomatous valvular diseases is the first step for the subclassification of these diseases.

Adolescent↗
PubMed2000

[Late cerebrovascular complications of cardiac transplantation].

The occurrence of stroke after the post-operative period of cardiac transplantation is a rare event, and the role of the cardiac transplant in these patients, who often have various vascular risk factors, is unclear. We reviewed the clinical records of 303 consecutive patients with orthotopic cardiac transplantation performed from March 1985 to December 1996 and selected those who developed a stroke over the first 2 months postoperatively, in order to evaluate the frequency and the mechanisms of late cerebrovascular complications. Four patients had presented cerebral infarct and two intracranial hemorrhage. The overall risk of late cerebrovascular complications was 2.6p.100 at 5 years. Ischemic stroke was related to cardiac embolus in one patient, lacunar infarction in another, and was of undetermined etiology in two cases. In addition to vascular risk factors prior to transplantation and the development of intracardiac thrombus, immunosuppressive therapy, the surgical procedure and cardiac rejection may play a role in the occurrence of stroke in such patients.

Aged↗
PubMed1999

Beta 3-adrenoceptor stimulation induces vasorelaxation mediated essentially by endothelium-derived nitric oxide in rat thoracic aorta.

1. The relaxant effects of isoprenaline may result from activation of another beta-adrenoceptor subtype in addition to beta1 and beta2. This study evaluated the role of a third beta-adrenoceptor subtype, beta3, in beta-adrenoceptor-induced relaxation of rat thoracic aorta by isoprenaline. 2. Isoprenaline produced a concentration-dependent relaxation of phenylephrine pre-contracted rings of the thoracic aorta (pD2=7.46+/-0.15; Emax=85.9+/-3.4%), which was partially attenuated by endothelium removal (Emax=66.5+/-6.3%) and administration of the nitric oxide (NO) synthase inhibitor, L-NG-monomethyl arginine (L-NMMA) (Emax=61.3+/-7.9%). 3. In the presence of nadolol, a beta1- and beta2-adrenoceptor antagonist, isoprenaline-induced relaxation persisted (Emax=55.6+/-5.3%), but occurred at higher concentrations (pD2=6.71+/-0.10) than in the absence of nadolol and lasted longer. 4. Similar relaxant effects were obtained with two beta3-adrenoceptor agonists: SR 58611 (a preferential beta3-adrenoceptor agonist), and CGP 12177 (a partial beta3-adrenoceptor with beta1- and beta2-adrenoceptor antagonistic properties). SR 58611 caused concentration-dependent relaxation (pD2=5.24+/-0.07; Emax=59.5+/-3.7%), which was not modified by pre-treatment with nadolol but antagonized by SR 59230A, a beta3-adrenoceptor antagonist. The relaxation induced by SR 58611 was associated with a 1.7 fold increase in tissue cyclic GMP content. 5 Both relaxation and the cyclic GMP increase induced by SR 58611 were greatly reduced by endothelium removal and in the presence of L-NMMA. 6 We conclude that in the rat thoracic aorta, beta3-adrenoceptors are mainly located on endothelial cells, and act in conjuction with beta1- and beta2-adrenoceptors to mediate relaxation through activation of an NO synthase pathway and subsequent increase in cyclic GMP levels.

Adrenergic beta-Agonists↗
PubMed1999

Interspecies differences in the cardiac negative inotropic effects of beta(3)-adrenoceptor agonists.

The aim of the present study was to compare the effects of three preferential (BRL 37344, SR 58611, CL 316 243) and a partial (CGP 12177) beta-adrenoceptor (beta(3)-AR) agonists on the contractility of ventricular strips sampled from various mammalian species including humans. In the human heart, all beta(3)-AR agonists tested decreased contractility by 40 to 60% below control with an order of potency: BRL 37344 > CL 316 243 = SR 58611 >> CGP 12177. In the dog, the negative inotropic effects produced by beta(3)-AR stimulation were less pronounced than in humans, approximately 30% below control. The order of potency of beta(3)-AR agonists was CGP 12177 > BRL 37344 = SR 58611 >> CL 316 243; i.e., very different from that observed in humans. In rat, only BRL 37344 was efficient to decrease contractility. In guinea pig, only CL 316 243 significantly reduced peak tension. In both species, the reduction in peak tension did not exceed 20 to 30%. Finally, in the ferret, none of the agonists tested induced a negative inotropic effect. In dog, the negative inotropic effects of CGP 12177 were not modified by nadolol, but were abolished by bupranolol, a beta(1-3)-AR. beta(3)-AR transcripts were detected in the dog but not in the rat ventricle by using a reverse transcription-polymerase chain reaction assay. We conclude that cardiac negative inotropic effects related to beta(3)-AR agonist stimulation vary markedly depending on the species. A comparable interspecies variation previously has been reported concerning the lipolytic effects of beta(3)-AR agonist stimulation. Our study demonstrates that the pharmacological profile of a beta(3)-AR agonist on the human myocardium cannot be extrapolated from usual animal models.

Adrenergic beta-Agonists↗
PubMed1998

The negative inotropic effect of beta3-adrenoceptor stimulation is mediated by activation of a nitric oxide synthase pathway in human ventricle.

Beta1- and beta2-adrenoceptors in heart muscle cells mediate the catecholamine-induced increase in the force and frequency of cardiac contraction. Recently, in addition, we demonstrated the functional expression of beta3-adrenoceptors in the human heart. Their stimulation, in marked contrast with that of beta1- and beta2-adrenoceptors, induces a decrease in contractility through presently unknown mechanisms. In the present study, we examined the role of a nitric oxide (NO) synthase pathway in mediating the beta3-adrenoceptor effect on the contractility of human endomyocardial biopsies. The negative inotropic effects of a beta3-adrenoceptor agonist, BRL 37344, and also of norepinephrine in the presence of alpha- and beta1-2-blockade were inhibited both by a nonspecific blocker of NO, methylene blue, and two NO synthase (NOS) inhibitors, L-N-monomethyl-arginine and L-nitroarginine-methyl ester. The effect of the NOS inhibitors was reversed by an excess of L-arginine, the natural substrate of NOS, but not by D-arginine. Moreover, the effects of the beta3-adrenoceptor agonist on contractility were associated with parallel increases in the production of NO and intracellular cGMP, which were also inhibited by NOS inhibitors. Immunohistochemical staining of human ventricular biopsies showed the expression of the endothelial constitutive (eNOS), but not the inducible (iNOS) isoform of NOS in both ventricular myocytes and endothelial cells. These results demonstrate that beta3-adrenoceptor stimulation decreases cardiac contractility through activation of an NOS pathway. Changes in the expression of this pathway may alter the balance between positive and negative inotropic effects of catecholamines on the heart potentially leading to myocardial dysfunction.

Adrenergic beta-Agonists↗
PubMed1998

Mapping of X-linked myxomatous valvular dystrophy to chromosome Xq28.

Myxoid heart disease is frequently encountered in the general population. It corresponds to an etiologically heterogeneous group of diseases, idiopathic mitral valve prolapse (IMVP) being the most common form. A rarely observed form of myxoid heart disease, X-linked myxomatous valvular dystrophy (XMVD), is inherited in an X-linked fashion and is characterized by multivalvular myxomatous degeneration; however, the histopathological features of the mitral valve do not differ significantly from the severe form of IMVP. In this article, we describe the genetic analysis of a large family in which XMVD is associated with a mild hemophilia A. The coagulation factor VIII gene position in Xq28 provided a starting point for the genetic study, which was conducted by use of polymorphic markers. Two-point linkage analysis confirmed this localization, and a maximum LOD score of 6.57 was found at straight theta=0 for two polymorphic microsatellite markers, INT-3 and DXS1008, the first one being intronic to the factor VIII gene. Haplotype analysis of this chromosomal region allowed the definition of an 8-cM minimal interval containing the gene for XMVD, between DXS8011 and Xqter.

Chromosome Mapping↗
PubMed1996

[Recent advances in cardiac pacing].

Over recent years, the increasing complexity of pacemakers has discouraged many cardiologists who considered that their role in the surveillance of patients with pacemakers had become minimal. Fortunately, times have changed, as this sophistication, which has how reached maturity, simplifies the cardiologist's task and should renew this interest in pacemaking. For example, improvement of electronic circuits now allows simpler pacing modes (e.g. single electrode VDD mode) and the development of automation of the main pacing parameters: automatic adjustment of the discharge current, the A-V period, protection algorithms against tachycardia due to electronic re-entry and atrial arrhythmias, automatic mode switching. Finally, the incorporation of large capacity memory functions allows the apparatus to act like an implantable "mini Holter" monitor.

Arrhythmias, Cardiac↗
PubMed1996

[What are the indications for ambulatory mechanical hart-assist devices for the left ventricle?].

Ambulatory mechanical left ventricular assistance has become a reality but clinical experience of long-term tolerance is limited for setting up a randomised trial comparing this technique with cardiac transplantation. On the other hand, it is justified in proposing this long-term circulatory assistance to a subgroup of patients on the waiting list for transplantation but who have little chance of being transplanted before irreversible multivisceral failure sets in. Some specific contraindications to left ventricular mechanical assistance should be respected. After implantation of a portable system, the possibility of being reinscribed on the waiting list for cardiac transplantation should be envisaged if the patient so wishes.

Adult↗
PubMed1993

[Detection of residual myocardial ischemia by Thallium-201 myocardial scintigraphy after myocardial infarction. Apropos of 53 patients treated with thrombolytic agents during the acute phase and with coronary transluminal angioplasty].

The prognosis of silent ischemia after myocardial infarction is similar to that of post-infarction angina. In order to detect this condition two stress myocardial scintigraphies were performed: three weeks after hospital admission for myocardial infarction treated by thrombolytic therapy without any complications or recurrence of chest pain; one month later, after percutaneous transluminal coronary angioplasty on the infarct-related artery in 24 patients or after medical therapy alone when this procedure was not possible (29 patients). Silent ischemia, initially present in two thirds of patients, was less frequently observed in the patients undergoing angioplasty (p < 0.05). In the remaining one third of patients with no silent ischemia, myocardial scintigraphy was unchanged at the follow-up procedure whether or not angioplasty had been performed. These results show that silent ischemia is commonly observed during stress myocardial scintigraphy after acute myocardial infarction treated by thrombolysis, but that this condition can be significantly reduced by coronary angioplasty. When no silent ischemia is observed, coronary angiography and angioplasty do not seem to be indicated.

Adult↗
PubMed1992

Soluble interleukin 2 receptor (Tac chain) is not a reliable marker in kidney transplant recipient monitoring.

T lymphocyte expansion is triggered through interaction of interleukin 2 (IL-2) with its high-affinity receptor (IL-2R). This molecule is a heterodimer comprising an antigen-inducible component, the Tac chain (P55). Activation of T lymphocytes also generates a soluble form of this P55 called S-IL-2R. S-IL-2R is elevated in many T-cell-related pathologies (leukemia, autoimmunity, etc.). In graft recipients, rejection is a result of T-cell activation by graft antigens and therefore might induce a release of S-IL-2R in the circulation; this parameter is now said to be a good indicator of rejection. We have performed a study in renal graft recipients in order to assess the usefulness of circulating S-IL-2R particularly to discriminate the origin of renal failure in cases of rejection or of cyclosporin-A (CsA)-induced nephrotoxicity. We demonstrated that there are no differences between isolated values in the clinical groups at the time of diagnosis. Variations in S-IL-2R are increased compared to steady-state periods during rejection and cytomegalovirus infections, although not in CsA toxicity episodes. However, at the individual level there are too many false-positive and false-negative results, making this parameter no more meaningful than serum creatinine levels alone or even in association (as tested in logistic discriminant analysis). In addition, it seems that the variations in S-IL-2R are partly related to renal function itself, as suggested by the correlation between S-IL-2R levels and serum creatinine levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Biomarkers↗
PubMed1991

Assessment of coronary artery disease by thallium scan in type-1 diabetic uremic patients awaiting combined pancreas and renal transplantation.

Twenty-five type-1 diabetic uremic patients (14 men, 11 women, mean age forty +/- eleven years, range, nineteen to sixty) were prospectively analyzed for coronary artery disease (CAD) by thallium scan (TLS) before synchronus pancreas and kidney transplantation. Duration of diabetes ranged from ten to thirty-two years (mean twenty-two +/- five). Fifteen patients (60%) were in dialysis from two to sixty months (mean twenty +/- eighteen). Advanced diabetic degenerative complications were present in all patients. Twenty exercise and five pharmacologic thallium scans were performed. Forty-four percent of patients (6 men, 5 women, mean age forty-two +/- eleven years, range, twenty-six to sixty) had a positive (reversible or permanent defects) TLS. In 2/11 cases, severe CAD required further cardiac investigations for therapeutic management decision. A statistical correlation with resting ECG nonspecific ST-segment and T-wave abnormalities was observed (p less than 0.05) despite the absence of angor in 8 of the 11 patients. On the contrary, no statistical correlations were found regarding high blood pressure, smoking, hypercholesterolemia, duration of diabetes, and duration of dialysis. In this particular diabetic population (young age, male/female ratio = 1.2) with high incidence of silent ischemia, resting ECG repolarization abnormalities, though predictive, were not specific or prognostic of CAD severity; in these cases, exercise and pharmacologic TLS, a noninvasive and sensitive cardiovascular test, may be of great interest in diagnosis of CAD, allowing adequate cardiac management before, during, and after pancreas transplantation.

Adult↗