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Biomedical subjects

M Merle

Publications and source records attributed to M Merle.

At least 19 recordsLinked to original sources
PubMed1992

Beta-adrenergic stimulation of C6 glioma cells: effects of cAMP overproduction on cellular metabolites. A multinuclear NMR study.

We used 31P-NMR spectroscopy to investigate the response of living C6 glioma cells to stimulation by a beta-adrenergic agonist, isoproterenol. In the presence of 3-isobutyl-1-methylxanthine, stimulation induced an accumulation of cAMP, making possible the NMR detection of the second messenger in living cells grown on microcarrier beads and perfused in the NMR tube. The cAMP signal rose to a maximum level within 20-25 min of stimulation; thereafter it decreased to the detection threshold within 60 min. At the same time, 40% increases of phosphomonoester and diphosphodiester signals were observed, whereas no significant change in phosphocreatine and nucleotide signals was detected. The kinetics of changes of the cellular content in phosphorylated metabolites were analyzed after recording 31P-NMR spectra of cell perchloric acid extracts as a function of time of stimulation. cAMP accumulation in stimulated cells was evidenced by a near linear increase of its NMR signal as a function of incubation time (from 0 to 60 min). Concomitantly with the production of cAMP, the data showed 30% decreases of phosphocreatine and ATP levels within 60 min of stimulation, and an unexpected redistribution of pyrimidine and purine nucleoside triphosphates. At the same time, levels of phosphomonoesters (phosphorylcholine and phosphorylethanolamine) and phosphodiesters (glycerophosphorylcholine and glycerophosphorylethanolamine) rose (50% increase). 13C-NMR spectra of cell perchloric acid extracts prepared after isoproterenol stimulation of cells incubated in the presence of [1-13C]glucose indicated a higher glucose content in stimulated cells, whereas the resonance of ribose C1 was diminished. Moreover, the resonances of C1 of ethanolamine and choline (and their derivatives) were increased in spectra of stimulated cells, whereas that of C3 of serine was decreased. In addition, the 13C-NMR data indicated that neither the pattern of glutamate carbon enrichment nor the glutamate/glutamine ratio was modified in stimulated cells. On the other hand, the heteronuclear coupling pattern of the lactate (methyl group) resonance in 1H-NMR spectra of cell incubation media indicated that no change occurred in the carbon flux through the pentose-phosphate shunt under stimulation. The results of this multinuclear NMR approach are discussed in terms of metabolic responses of C6 cells to beta-adrenergic stimulation and cAMP overproduction.

Adenosine Triphosphate↗
PubMed1992

Scapho-trapezio-trapezoid arthrodesis in the treatment of Kienböck's disease. A study of 16 cases.

Sixteen scapho-trapezio-trapezoid arthrodeses were performed for Kienböck's disease. In ten cases, a prosthetic replacement of the lunate was inserted at the same time. Clinical results were good with regard to pain and fair with regard to grip strength which was improved by an average of 32%. In contrast, the arc of flexion-extension was 38% less than on the unoperated side. Long-term radiographic assessment showed the efficacy of the procedure in maintaining carpal height. Biomechanical observations and a review of poor results showed the limits of the method and the importance of correct positioning of the scaphoid. We concluded that triscaphe arthrodesis was a useful procedure for the treatment of Kienböck's disease in Decoulx's stage 3.

Adult↗
PubMed1992

The blood supply of digital nerves: a microanatomical study of superficial and deep palmar venous networks.

In this work on vascularization of digital nerves, we have studied the anatomy of the deep network of venae comitantes of digital arteries, and the system of superficial palmar venules. 22 specimens of nerve and artery were dissected as one unit and were infused with Microfil prior to study under the microscope. The deep venous network, a satellite of the digital artery, can be classified into four types. A true network of deep venae comitantes exists in three of these four types, drained by deep veins arising from the transverse anastomotic arches between the palmar digital pedicles. Vascularization of the digital nerve is supplied by numerous anastomotic vessels connecting epineurial vessels, digital artery and the periarterial network (venae comitantes and vasa vasorum). This anatomical configuration lends itself to vascularized nerve grafting; for example, it is possible to use a nerve/artery graft taken as a unit from an amputated finger unsuitable for replantation. Two types of valves in this superficial venous network have been identified and their function is discussed.

Adult↗
PubMed1992

[Lipofibroma of the median nerve. Apropos of a case].

Lipofibroma is a rare, benign nerve tumour corresponding to diffuse fibroadipose infiltration of the nerve, dissociating the fasciculi without invading them. The authors report a case of lipofibroma of the median nerve in a 32 year old man presenting with a soft swelling of the palmar surface of the thumb. Treatment consisted of intraneurodissection of the tumour arising exclusively from the medial collateral nerve of the thumb. With a follow-up of two years, there has been no recurrence of the tumour, but the patient has persistent decreased sensation of the ulnar half of the thumb pulp. The features of the lipofibroma and the therapeutic options are discussed in the light of the data reported in the literature.

Adult↗
PubMed1992

Assessment of the clinical value of urinary trypsin inhibitory activity in elderly people.

To assess the clinical value of urinary trypsin inhibitory activity (UTIA) in elderly people, a prospective study was carried out over 4 months in our internal medicine department. Two hundred and forty-three patients of more than 60 years of age were included. A positive correlation was observed between UTIA and serum creatinine (p < 10(-3)). In the population with serum creatinine of less than 133 mumol/l (200 patients), UTIA was independent of age, sex and serum creatinine. UTIA was compared with seven serum inflammatory proteins titrated on patient admission. The principal interest of UTIA determination appeared in bacterial infections. UTIA was significantly increased in this group (p < 10(-4)). However, a positive correlation was proved only with C-reactive protein (CRP) (p = 9 x 10(-4)). Nevertheless, CRP appeared to be the best marker of bacterial infectious diseases after receiver operating characteristic curves analysis.

Acute-Phase Proteins↗
PubMed1992

Pre-steady state study of beta-adrenergic and purinergic receptor interaction in C6 cell membranes: undelayed balance between positive and negative coupling to adenylyl cyclase.

Interactions between beta-adrenergic and ADP purinergic receptors in C6 glioma cell membrane preparations were investigated under steady state and then pre-steady state conditions of adenylyl cyclase (EC 4.6.1.1) activity, in order to determine how fast the second receptor antagonizes the transduction mechanism of the first. Cell membranes were washed to deplete them as thoroughly as possible of low molecular weight compounds, especially ATP and ADP, and to ensure better control of both substrate and agonist nucleotide concentrations. ATP concentrations were kept constant with the use of an ATP-regenerating system; the C6 cell line exhibited very active ectonucleotidases. The purinergic agonist ADP was replaced by its nonhydrolyzable congener adenosine 5'-O-(2-thio)diphosphate (ADP beta S), which was demonstrated, like ADP, to inhibit isoproterenol-stimulated adenylyl cyclase activity in intact cells (IC50 for ADP, 0.5 +/- 0.1 microM; IC50 for ADP beta S, 25 +/- 2 microM) and in membrane preparations (IC50 for ADP beta S, 79 +/- 20 microM). In the case of membrane preparations, ADP beta S did not compete with ATP, the substrate of the cyclase-catalyzed reaction, and behaved apparently as a non-competitive inhibitor of the enzyme. The pre-steady state kinetics of isoproterenol-stimulated adenylyl cyclase activity measured with a pulsed quenched-flow apparatus have previously been shown to include two steps, the first very rapid (taking place within 1-2 sec) and giving rise to a burst of cAMP synthesis and the second much slower and corresponding to the steady state reaction. ADP beta S inhibited the occurrence of both steps with comparable IC50 values (mean value, 55 +/- 20 microM). In the presence of increasing concentrations of the purinergic receptor agonist, the time constant of the exponential burst reaction was not affected, but its amplitude progressively decreased to zero. These results showed that the extinction of the beta receptor cAMP response by the purinergic ADP receptor occurred within the dead-time of the pulsed quenched-flow apparatus, which was 50 msec. Such a rapid inhibition of cAMP production excluded modulation of isoproterenol-stimulated adenylyl cyclase activity by the ADP receptor by a pathway other than its direct negative coupling to the cyclase via a Gi protein. In this respect, the P2 purinergic ADP receptor of the C6 glioma cell line appears comparable to the P2t receptor of platelets.

Adenosine Diphosphate↗
PubMed1992

[Experimental study of the trophic effects of reinnervation of pedicled muscle flaps].

Any transplanted muscle flap undergoes atrophy to an extent depending mainly on its innervation. Other factors such as the tension at rest and the duration of ischemia play a secondary role. An experimental study was carried out in rats to quantitatively assess the extent of atrophy according to the mode of transplant reinnervation. The gracilis muscle was used as an experimental model of pedicled flap after verifying the axial nature of its vasculature. Results were assessed after three months from a histological point of view and in terms of postoperative weight in four different groups of 13 rats. The first three groups reproduced situation encountered in clinic: intact nerve, sutured nerve, resected nerve. A graft sensory neurotization technique was implemented in the fourth group by diverting a neighboring sensory nerve. The best trophic results were obtained when the motor nerve remained continuous. The sensory neurotization technique did not significantly influence the trophic evolution after three months.

Animals↗
PubMed1992

[Use of intraosseous resorbable implants. Experimental evaluation and clinical applications in hand surgery].

The authors report about their experience with the use of absorbable intramedullary nails. After an experimental phase comprising mechanical tests and animal experiments in rabbits, the first clinical applications were for 24 cases of metacarpophalangeal arthrodesis of the thumb. For this indication, bone stabilization was achieved by associating an absorbable intramedullary nail and a metallic oblique pin. Evaluation in animals included, on one hand, a magnetic resonance imaging study, and on the other hand a histological study after the staggered sacrifice of the animals. This histological study was performed on non-decalcified bones by inclusion in methyl methacrylate resin. The mechanical results confirmed the appropriate resistance of these materials for use in the digital skeleton. The histological assessment showed that absorption begins around the 4th month by progressive fragmentation of the material and lasts over 3 years. The encouraging clinical experience and some obstacles encountered during its implementation hav led to two modifications: on one hand, a larger nail was used, on the other hand an absorbable oblique pin was developed, thus ensuring a fully absorbable osteosynthesis.

Adult↗
PubMed1991

A mammalian tryptophanyl-tRNA synthetase shows little homology to prokaryotic synthetases but near identity with mammalian peptide chain release factor.

Determination of the amino acid sequence of beef pancreas tryptophanyl-tRNA synthetase was undertaken through both cDNA and direct peptide sequencing. A full-length cDNA clone containing a 475 amino acid open reading frame was obtained. The molecular mass of the corresponding peptide chain, 53,728 Da, was in agreement with that of beef tryptophanyl-tRNA synthetase, as determined by physicochemical methods (54 kDa). Expression of this clone in Escherichia coli led to tryptophanyl-tRNA synthetase activity in cell extracts. The open reading frame included two sequences analogous to the consensus sequences, HIGH and KMSKS, found in class I aminoacyl-tRNA synthetases. The homology with prokaryotic and yeast mitochondrial tryptophanyl-tRNA synthetases was low and was limited to the regions of the consensus sequences. However, a 90% homology was observed with the recently described rabbit peptide chain release factor (eRF) [Lee et al. (1990) Proc. Natl. Acad. Sci. 87, 3508-3512]. Such a strong homology may reveal a new group of genes deriving from a common ancestor, the products of which could be involved in tRNA aminoacylation (tryptophanyl-tRNA synthetase) or translation termination (eRF).

Amino Acid Sequence↗
PubMed1991

Phosphorus-31 nuclear magnetic resonance of C6 glioma cells and rat astrocytes. Evidence for a modification of the longitudinal relaxation time of ATP and Pi during glucose starvation.

31P-NMR spectroscopy has been used to study the energy metabolism and the NMR visibility of ATP and intracellular Pi of the C6 glioma cell line and rat astrocyte grown on microcarrier beads with the following results. 1. In vivo NMR spectra of C6 glioma cells and rat astrocytes indicate that these cells were able to maintain their level of ATP resonances during a long anoxic period (more than an hour). Both cell types were sensitive to ischemia which induced a loss of ATP resonances within 40 min. Glucose starvation induced by 40% decrease in ATP resonances correlated to a 50% increase in the intensity of the Pi signal. These changes corresponded to a new steady state which could be reversed by reperfusing the cells with a glucose-containing medium. 2. In contrast to in vivo data, 31P-NMR analyses of perchloric acid extracts of cells incubated in a glucose-free medium showed that their ATP and Pi contents were unchanged during starvation. The changes of NMR visibility of the metabolites in living C6 cells were correlated to modifications of their macroscopic longitudinal relaxation times, evolving from 0.30 +/- 0.08 s and 6.6 +/- 1.5 s in the presence of glucose to 0.68 +/- 0.26 s and 3.2 +/- 0.9 s in the absence of glucose for ATP and Pi, respectively. The changes of the NMR detectability of ATP and Pi indicate that changes in their microenvironment occur during glucose starvation, suggesting the existence of different pools of these metabolites within the cells. 3. Under various experimental conditions, i.e. anoxia, ischemia and glucose starvation, rat astrocytes in primary culture showed a very similar behavior to that of C6 cells, suggesting a similar adaptability to the nature of the energy supply for both the normal and the malignant cell.

Adenosine Triphosphate↗
PubMed1991

Human nerve xenografting in nude mouse: experimental study of graft revascularization.

In the nude mouse, the congenital absence of T lymphocytes makes it possible to implant human nerve grafts without rejection or iatrogenic modifications (by immunosuppression) of human and murine tissues. Medial antebrachial cutaneous nerves were harvested from human cadavers 1-18 hours after death. These nerve grafts were implanted using different techniques in nude mice. All the grafts were macroscopically and microscopically revascularized 3 days after implantation. The modifications in time of this vascularization could be studied with precision through the use of repeated biopsies. The absence of human blood group antigens on the neovessel endothelium suggested a murine origin for angiogenesis. In situ DNA hybridizations with human and mouse DNA confirmed this origin. The topography of the revascularization (maximal in the perineurium and endoneurium) and the almost complete absence of human cells other than Schwann cells in the grafts at the peak of angiogenesis (26 days after grafting) suggested that Schwann cells had a determining role in graft vascularization. The irradiation of the nerve grafts with a dose of 30 grays before implantation did not modify significantly their histologic appearance compared to the control group, whereas an irradiation of 60 grays led to massive lesions. The neurotization of murine axons led to chimerical structures of normal histologic appearance, with vascularization similar to that observed in nonneurotized nerves. Through chimerism (human Schwann cells, murine vessels and axons) this model makes it possible to dissociate the respective role of the host and of the nerve graft in angiogenesis and suggests the existence of growth factors produced by the human Schwann cells.

Adult↗
PubMed1991

Dorsal metacarpal reverse flaps. Anatomical basis and clinical application.

The presence of distal intermetacarpal anastomoses between dorsal and palmar vascular networks makes it possible to raise distally-based cutaneous island flaps oriented along the axis of the dorsal metacarpal arteries. These flaps receive a reverse-flow vascularisation. Distal intermetacarpal anastomoses were found consistently in 35 hands from adult cadavers. The exact location of these anastomoses varied with the course of the dorsal metacarpal artery. Thus, island flaps can be raised consistently from the dorsal aspect of the hand and rotated around a distal intermetacarpal pivot. These flaps are suitable for covering the dorsal aspect of the proximal phalanx and the proximal interphalangeal joint.

Adolescent↗
PubMed1991

Vascularised nerve grafts.

Since Taylor (1976) successfully performed the first vascularised free nerve graft, experimental and clinical data have not provided conclusive support for the superiority of this method of repairing loss of nerve substance. Experimental work yields conflicting results. Histologic results are in favour of vascularised grafts but non-vascularised fascicular grafts placed in a healthy bed recover sufficient neovascularisation within a short period of time (four to six days). In the field of brachial plexus repair, vascularised grafts give consistent results. However, if thrombosis of the anastomoses occurs, the grafts fail completely. In our experience, vascularised nerve grafts used for repairing digital nerves and arteries, have a high rate of thrombosis. There are few potential donor sites. A nerve graft cannot be considered to be physiologically vascularised if it relies only on an artery or on an arterialised vein. Given the present state of immunosuppressant treatments, vascularised allografts are not yet appropriate. Therefore, vascularised nerve grafts have limited applications. In general it is preferable to repair the tissue bed so as to promote revascularisation of conventional nerve grafts.

Adult↗