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B Lévy

Publications and source records attributed to B Lévy.

29 records · Page 2Linked to original sources
PubMed1987

Gene conversion in avian mesotocin and vasotocin genes: a recurrent mechanism linking two neurohypophysial precursor lineages?

Amino acid sequences of the first half of MSEL- and VLDV-neurophysins from goose and chicken have been determined. Identical substitutions in positions 17, 18, 35, 36 and 41 of both neurophysins of a given species when compared with their mammalian counterparts suggest a gene conversion between vasotocin--MSEL-neurophysin and mesotocin--VLDV-neurophysin genes. This event, which has already been observed for three mammalian species, seems recurrent and would link the evolution of the two neurohypophysial hormone precursors.

Amino Acid Sequence↗
PubMed1986

Precursors of mesotocin and vasotocin in birds: identification of VLDV- and MSEL- neurophysins in chicken, goose, and ostrich.

Precursors of neurohypophysial hormones are small proteins processed into nonapeptide hormones and neurophysins during axonal transport to the neurohypophysis. In mammals, oxytocin is associated with VLDV-neurophysin and vasopressin with MSEL-neurophysin. In birds, mesotocin and vasotocin are found instead of mammalian oxytocin and vasopressin. From goose, chicken and ostrich posterior pituitary glands, two types of neurophysins related to mammalian VLDV- and MSEL-neurophysins, respectively, have been identified by their N-terminal sequences. It is assumed that, as in mammals, hormonal peptide and the first 9 residues of the corresponding neurophysin are encoded by a common exon and that mesotocin and vasotocin, evolutionary predecessors of oxytocin and vasopressin, are associated in the precursors with VLDV-neurophysin and MSEL-neurophysin, respectively.

Amino Acid Sequence↗
PubMed1981

["Windkessel" and coronary debit].

The aim of this study was to support the hypothesis that aortic distensibility, resulting in a Windkessel effect of the high pressure compartment, may influence coronary blood flow, principally in the subendocardial layers. A hydraulic model of the arterial circulation including a branch representing the coronary circulation, was constructed. A pump giving pulsed flow with ejection parameters and cycle adjusted so as to produce almost physiological pressure curves, was used. Measurements of "coronary" flow were made with aortic models of the same dimension but of different compliance. The output of the ventricular pump and the hydraulic resistance of the model being constant, considerable variations in coronary flow were observed. With the most rigid aorta (compliance: 0,005 cm3/mm Hg) coronary flow was only 1% of the output of the ventricular pump. With a more distensible aorta (compliance: 0,6 cm3/mm Hg) coronary flow rose to 18% of the pump's output. These results were obtained under conditions very different from those present in vivo: however, they do raise the question of whether an alteration in the mechanical properties of the aorta due to ageing or disease can have an appreciable influence on coronary blood flow.

Aorta↗
PubMed1977

[The heart diet].

Explore the source record for details and available documents.

Coronary Disease↗
PubMed1975

[Interpretation of the limits of survival during circulatory support in the dog].

A total cardiac supplementation through a simple by-pass of the left ventricle was performed on hearts in ventricular fibrillation on 51 dogs not treated with heparin. The right-sided circulation was passive to avoid introducing added disturbing parameters. A bi-valved supple prosthesis was set in motion by a pneumatic pump regulated on the left atrial pressure and the arterial tree proper rate. The 44 cases which survived from 7 to 27 hours were limited by a slow and regular lowering of the blood pressure without notable decrease of the output. This lowered pressure was due to the action of the atrial and pulmonary mechanical receptors responding to a left atrial hypertension, secondary to a mild leak of the inflow valve. The mild haemolysis and the total absence of thrombosis should be related with the rate-regulation of the pump on the arterial tree rate, thus providing a maximal yield.

Animals↗
PubMed1974

[Valvular prosthesis and anticoagulant treatment].

67 patients with prosthetic valvular replacement have been followed up for a period ranging from 6 months to 9 1/2 years; the overall number of valves was: 53 mitral, 24 aortic, 10 tricuspid valves. The average age of our patients was young (23.6 years). Many patients, because of their age or by lack of discipline or because of their social condition, had an inefficient anticoagulant treatment; they were subdivided into three groups. Those who stopped their anticoagulant treatment 6, those treatment was inefficient 25; in these two groups, no thrombo-embolic accident was noted, those whose treatment was efficient with a prothrombin time permanently lower than or equal to 40%: 36. It is in this very series that three cases of thrombosis occurred, two of which were lethal. Thus, although the indication for an anticoagulant treatment in patients with prosthetic valvar replacement remains indisputable, one may wonder, in front of such results, if there are not other factors, besides anticoagulant treatment, that result in thrombo-embolic accidents.

Adolescent↗
PubMedDate not supplied

MR-Guided PTA in experimental bilateral rabbit renal artery stenosis and MR angiography follow-up versus histomorphometry.

PURPOSE: To assess in vivo 1) MR-guided percutaneous transluminal renal angioplasty (PTRA) in experimental bilateral rabbit renal artery stenosis (RAS); 2) postprocedural follow-up by gadolinium-enhanced MR angiography versus histomorphometry. METHODS: Fifteen male NZW rabbits of mean weight 4.0 kg (range 3.5-4.2 kg) underwent bilateral RAS induction by combined overdilation-deendothelialization with a gadolinium-filled balloon, passively MR-guided by the artifact of a 0.014-inch guidewire. After 4 weeks the rabbits were randomized into two groups: group A (n = 8) underwent right-sided PTRA for treatment of RAS, group B (n = 7) underwent left-sided PTRA. After another 4 weeks the rabbits were killed to assess by histomorphometry recurrent stenosis and contralateral induction injury stenosis lesions. Each step was preceded by gadolinium-enhanced three-dimensional MR angiography, and the cortex-to-aorta (C/A) signal intensity ratio was calculated. RESULTS: RAS induction was successful in all cases. Fourteen arteries developed restenosis and 13 only initial stenosis. MR-guided PTRAs were feasible in 22 arteries (73%). For a successful catheterization of the ostium (20 arteries, 66% success rate), 10-25 steps were required. Five to eight steps were required for balloon localization and inflation for each PTRA. The restenosis effect was reflected by a 16% (12%-27%) decrease in C/A values on MR angiograms (p < 0.05). CONCLUSION: MR guidance and MR angiography represent a feasible, less invasive alternative for performing and assessing experimental PTRA in RAS.

Angioplasty, Balloon↗