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Biomedical subjects

M Merle

Publications and source records attributed to M Merle.

At least 55 records · Page 3Linked to original sources
PubMed1999

The lateral approach to the sciatic nerve at the popliteal fossa: one or two injections?

UNLABELLED: It has not been proven whether one or multiple nerve stimulations and injections provide a higher rate of complete sensory block in both major sciatic nerve sensory distributions below the knee when a popliteal sciatic nerve block is performed using the lateral approach. This prospective, randomized, single-blinded study compared the success rate of the sciatic nerve block using this approach when one or both major components of this nerve (i.e., tibial nerve and common peroneal nerves) are stimulated in 50 patients undergoing foot or ankle surgery. In Group 1 STIM, 24 patients received a single injection of 20 mL of a mixture of 2% lidocaine and 0.5% bupivacaine with 1:200,000 epinephrine after foot inversion had been elicited. In Group 2 STIM (n = 26), 10 mL of the same solution was injected after stimulation of each sciatic nerve component. For patients with complete sensory motor block, there was no difference in onset between groups. However, Group 2 STIM showed a greater success rate compared with the Group 1 STIM (2 STIM: 88% vs 1 STIM :54%; P = 0.007). When two stimulations were used, the onset time of anesthesia in the cutaneous distribution of the common peroneal nerves was shorter than in the tibial nerve (17.5 vs 30 min; P < 0.0001). We conclude that a two-stimulation technique provides a better success rate than a single-injection technique when a popliteal sciatic nerve block is performed using the lateral approach with 20 mL of local anesthetic. IMPLICATIONS: A better success rate is achieved with a double stimulation technique than with a single injection for the sciatic nerve block via the lateral approach at the popliteal fossa when 20 mL of local anesthetics is used.

Adult↗
PubMed1998

Compartmentation of lactate and glucose metabolism in C6 glioma cells. A 13c and 1H NMR study.

13C and 1H NMR spectroscopy was used to investigate the metabolism of L-lactate and D-glucose in C6 glioma cells. The changing of lactate and glucose concentration in the extracellular medium of C6 glioma cells incubated with 5.5 mM glucose and 11 mM lactate indicated a net production of lactate as the consequence of an active aerobic glycolysis. The 13C enrichments of various metabolites were determined after 4-h cell incubation in media containing both substrates, each of them being alternatively labeled in the form of either [3-13C]L-lactate or [1-13C]D-glucose. Using 11 mM [3-13C]L-lactate, the enrichment of glutamate C4, 69%, was found higher than that of alanine C3, 32%, when that of acetyl-CoA C2 was 78%. These results indicated that exogenous lactate was the major substrate for the oxidative metabolism of the cells. Nevertheless, an active glycolysis occurred, leading to a net lactate production. This lactate was, however, metabolically different from the exogenous lactate as both lactate species did not mix into a unique compartment. The results were actually consistent with the concept of the existence of two pools of both lactate and pyruvate, wherein one pool was closely connected with exogenous lactate and was the main fuel for the oxidative metabolism, and the other pool was closely related to aerobic glycolysis.

Aerobiosis↗
PubMed1998

Reconstruction of fingertip amputations by partial composite toe transfer with short vascular pedicle.

Five patients under 15 years-of-age, with a fingertip amputation through the nail plate, were treated with a custom-made partial toe transfer. Two of the patients had had previous attempts at surgical reconstruction using either a local flap or replantation. Delay between initial injury and reconstruction ranged from 2 to 60 days. In all cases the flap was harvested from the second toe. This "custom-made" compound transfer included the exact amount of pulp, nail bed and bone required for reconstruction. All flaps were harvested on a short vascular pedicle, with anastomoses performed at a digital level on the recipient site. Good to excellent cosmetic results were obtained in all cases, with a nearly normal-looking fingertip. Duration of hospital stay ranged from 4 to 7 days. We recommend this technique for treatment of distal amputation close to the proximal nail fold, in young individuals.

Adolescent↗
PubMed1998

Glucose and lactate metabolism in C6 glioma cells: evidence for the preferential utilization of lactate for cell oxidative metabolism.

13C and 1H nuclear magnetic resonance spectroscopy (NMR) was used to investigate the metabolism of L-lactate and D-glucose in C6 glioma cells. The 13C enrichment of cell metabolites was examined after a 4-h incubation in media containing 5.5 mM glucose and 11 mM lactate, each metabolite being alternatively labelled with either [1-13C]D-glucose or [3-13C]L-lactate. The results indicated that exogenous lactate was the major substrate for oxidative metabolism. They were consistent with the concept of the existence of 2 pools of both lactate and pyruvate, of which 1 pool was closely connected with exogenous lactate and oxidative metabolism, and the other pool was closely related to glycolysis and disconnected from oxidative metabolism. The molecular basis of this behaviour could be related to different locations for the lactate dehydrogenase isoenzymes, as suggested by their immunohistochemical labelling.

Animals↗
PubMed1998

Metabolic and cellular characterization of immortalized human microglial cells under heat stress.

Microglia are able to shift from a resting to an activated state during which they acquire functions typical of primitive forms of mononuclear phagocytes, as well as highly differentiated forms of these cell types. Activation of the microglia after a trauma involves functional readjustments including both the resurrection of basic cell functions and the development of functions implicated in cell-cell interactions. Here, the behaviour of the human microglial cell line CHME-5 was observed after hyperthermia. The strong expression of the inducible form of the hsp70 proteins and their nuclear location, like the more nucleolar presence of the hsc70 proteins seemed to confer heat resistance to the cells. Following minor morphological changes, the observation of the cytoskeleton network during stress recovery revealed a differential sensitivity of actin and tubuline to heat shock. The energy metabolism of both the microglial cell line and the monocyte cell line U937 were compared, under basal conditions, using phosphorus-31 NMR, to discern those phosphorylated metabolites which could be specific of either the monocytic or the macrophagic phenotype. A very high content of phosphocreatine was observed in the microglial clone whereas this compound was absent in monocytes. The lower CHME-5 phosphomonoester content as compared to monocytes also suggested that the microglial cell line displayed a more macrophagic metabolic pattern. After heat shock, the CHME-5 phosphorylated compounds showed large, transient, perturbations. Cells recovered their basal metabolic content 24 h after heat stress. This behaviour, in addition to the expression of inducible hsp70 proteins and the cytoskeleton rearrangement, are indicative of the particular adaptation of the microglial cell line to stress situations.

Cell Line, Transformed↗
PubMed1997

Scapholunate dissociation in the skeletally immature carpus.

Scapholunate dissociation is well documented as a condition occurring in adult patients. We report it in a 14-year-old female patient. Persistent wrist pain 9 months after a well healed fracture of the distal radius triggered further investigation. Dynamic clinical and radiological studies demonstrated the instability.

Adolescent↗
PubMed1997

Cold and post-traumatic pain: modeling of the peripheral nerve message.

Hypersensitivity to cold is a relatively frequent sequel of peripheral nerve injuries but its mechanism is not well understood. We suggested that incomplete recovery of diameter of regenerated fibers is one of the factors involved in cold intolerance after nerve damage. Conduction velocity is correlated to fiber diameter, and is slowed down by cold. In normal subjects, cold does not desynchronize the volleys of sensory impulses sufficiently to change the intelligibility of the peripheral 'messages'. Sensory perceptions remain accurate although they acquire a characteristic numbness. On the other hand, post-traumatic reduction in fiber diameters causes a permanent distortion of the messages. We considered that when the distortion is severe, the resulting messages may be perceived by the centers as containing nociceptive components. We further hypothesized that, even in cases of moderate permanent distortion, cold acts by increasing the post-traumatic abnormalities of impulse synchronization. In winter, decompensation is observed when a threshold of desynchronization is reached. We constructed a model of peripheral nerve messages in an attempt to represent and quantitate the desynchronizations produced by cold and crush damage lesions in peripheral nerve messages. A number of parameters concerning fiber anatomy, exposure to cold, and type of nerve damage were taken into consideration. Four elementary types of desynchronization could be recognized by considering the times of arrival of pairs of impulses at the nervous centers. The difference between a normal and a distorted message could be expressed by eight variables. Thus, although our model was quite simple, a large amount of data was obtained and a preliminary statistical study was necessary in order to orient the final analysis. Then, we used factor analysis in an attempt to obtain a satisfactory interpretation of the data. The results indicated that peripheral desynchronization might explain, at least in part, the painful sensations experienced in winter by many patients after peripheral nerve injury.

Analgesics↗
PubMed1997

Chondral lesions of the midcarpal joint.

Wrist arthroscopy performed on 78 patients showed 35 lunates of Type I (44.9%) i.e., having only one facet on their distal (midcarpal) aspect, and 43 lunates of Type II (55.1%), i.e., having two facets on this aspect. Chondral defects and/or arthritic lesions of the ulnar portion of the midcarpal joints were observed in 22.8% of Type I lunates and in 30.2% of Type II lunates. Chondral lesions of the midcarpal joints in Type I lunates were always associated with other ligamentous and/or osteochondral lesions, whereas the same lesions could be found isolated in Type II lunates. The observed association of lesions seemed to point to a trauma as the cause of some chondral lesions. The results of our clinical study were compared with anatomical studies by Viegas, all which showed no hamate pathologic conditions in Type I lunates.

Adult↗
PubMed1997

Functional consequences of isolated nerve stretch: experimental long-term static loading.

The maximum longitudinal tension that can be applied to the stumps of a divided peripheral nerve during surgical repair is not precisely defined. Uncertainty about the threshold of unacceptable nerve tension may be due to the lack of studies on isolated and reproducible stretch, i.e., on quantified elongation without concomitant compression, crush, or transection. The authors devised a simple method for producing isolated, long-term static loading of the nerve in vivo without concomitant compression, crush, or transection. Tension was applied to intact and crushed sciatic nerves in the rat, stretching them by 15 or 30 percent of their initial length, and the corresponding functional consequences were evaluated. Results showed that no measurable functional deficit resulted from stretching a segment of intact nerve to a length 30 percent greater than its initial length. In contrast, a significant delay in functional recovery resulted from stretching a crushed nerve by the same amount. A practical conclusion may be that the site of application of stretch forces during surgical repair, i.e., the location of coapting stitches, could play an important role in clinical practice.

Analysis of Variance↗
PubMed1997

Advances in digital replantation.

Technical advances in revascularization and in skin cover have resulted in increases in the possibilities of digital replantation. In cases of multiple digital lesions and isolated avulsions of the thumb, all attempts to ensure recovery of basic pinch capacity are justified. On the other hand, in cases of proximal amputations with extensive avulsion or crush injury such attempts should be abandoned if results on function are important. Primary and secondary surgery must confront two difficult problems namely, repair of the avulsed flexor tendons and resensibilization. But in the field of replantation one should not be too dogmatic because for cosmetic reasons, some patients may find even a stiff or insensitive finger satisfactory. Distal and very distal replantations yield the best results in all fields. This information should be brought to the attention of all trauma teams that tend to consider such replantations useless. These replantations are both rapid and simple, requiring only mastery of suturing vessels 0.5 mm in diameter. The surgeon responsible for replantation should weigh the indications after assessing the patient's needs and explaining the advantages and drawbacks of this type of surgery and its results on function.

Amputation, Traumatic↗
PubMed1997

Analysis of carbon metabolism in cultured cerebellar and cortical astrocytes.

Carbon metabolism was investigated in cerebellar and cortical astrocytes cultured for 15 or 35 days. The consumption rates of exogenous carbon sources--amino acids and glucose--and the production rates of exported metabolites--citrate, lactate, alanine and glutamine--were determined. The specific 13C-enrichment of lactate and glutamine carbons were determined after cell incubation with [1-13C]glucose. These data were used to evaluate the fluxes through metabolic pathways using a monocompartmental model of the cell metabolism including glycolysis and tricarboxylic acid cycle related pathways. The model concluded to a very large contribution of fatty acids as an endogenous carbon source of acetyl-CoA. As a consequence of the high fatty acid turn-over, there was an important recycling (via pyruvate) of the oxaloacetate molecules generated by citrate lyase activity. This recycling represented in fact the major part of the pyruvate carboxylase activity, which therefore was not directly related to metabolite export. Comparing the data from cerebellar and cortical astrocytes evidenced, on the other hand, some differences in metabolite contents which could be related to different cell maturation stages linked to their different tissular origins.

Animals↗
PubMed1997

[The use of pedicular flap from the squared pronator muscle in the prevention and treatment of neuritis. Report of 8 cases].

The distal third of the forearm is a tendinous area, in which nerves could be irritated by surrounding skin scars or synovitis. In this area, a distally or proximally based pronator quadratus muscle flap could be used to wrap around the median or superficial branch of the radial nerve. Such flaps have been used successfully in eight cases, four cases of chronic neuritis, 2 cases of wrapping a median nerve graft and 2 cases of nerve coverage following trauma. All patients obtained pain relief with no alteration of finger movements.

Adolescent↗
PubMed1996

Mathematical modelling of the citric acid cycle for the analysis of glutamine isotopomers from cerebellar astrocytes incubated with [1(-13)C]glucose.

A mathematical model of the citric acid cycle devoted to the analysis of 13C-NMR data was developed for determining the relative flux of molecules through the anaplerotic versus oxidative pathways and the relative pyruvate carboxylase versus pyruvate dehydrogenase activities. Different variants of the model were considered depending on the reversibility of the conversion of fumarate into malate and oxaloacetate. The model also included the possibility of orientation-conserved transfer of the four-carbon citric acid cycle intermediates, leading to conversion of succinyl-CoA C1 into either malate C1 or C4. It was used to analyse NMR data from glutamine isotopomers produced by cerebellar astrocytes incubated with [1-13C]glucose. Partial cycling (39%) between oxaloacetate and fumarate was evident from the analysis. Application of the model to glutamate isotopomers from granule cells incubated with [1-13C]glucose [Martin, M.. Portais, J.C.. Labouesse. J., Canioni. P, & Merle, M. (1993) Eur. J. Biochem. 217, 617-625] indicated that total cycling of oxaloacetate into fumarate was, in this case, required to get the best fit. The results emphasized some important differences in carbon metabolism between cerebellar astrocytes and granule cells concerning the sources of carbon fuelling the citric acid cycle and the carbon fluxes on different pathways.

Acetates↗
PubMed1996

Glucose and glutamine metabolism in C6 glioma cells studied by carbon 13 NMR.

The question as to whether glutamine and glucose are both required for optimal growth of glioma cells is studied through the role of these substrates on the metabolism of the cells. C6 rat glioma cells grow only very slowly when glutamine is omitted from the culture medium. The rates of glucose consumption and lactate production on confluent cells in glutamine-free medium were 0.88 +/- 0.09 and 1.06 +/- 0.25 mumol/h/mg protein, respectively. In the presence of 4 mM glutamine, glucose utilization increase to 60% leading to a 45% increase of lactate production. We have studied the kinetics of enrichment of intracellular glutamate at C2, C3 and C4 positions on cells incubated with 5 mM 99% enriched [1-(13)C]glucose in the presence or the absence of glutamine in the incubation medium. The specific enrichments at metabolic steady state of all carbon positions were the same under both conditions, but we observed a significantly reduced rate of 13C incorporation in the presence of glutamine, showing an isotopic dilution of tricarboxylic acid cycle intermediates and indicating the use of this amino acid as an anaplerotic substrate. The fact that no dilution occurred at the level of pyruvate suggests strongly the lack of glutaminolysis in these cells. The main conclusion from this work is that glutamine metabolism in C6 cells appears complementary to that of glucose as far as energy production and carbon sources for the growing of the cells are concerned: glutamine is mainly utilized for anaplerosis as carbon donor to replenish the tricarboxylic acid cycle; it is not a substrate for energy metabolism. In contrast, glucose is poorly anaplerotic and is essentially used as energetic fuel by the C6 cells.

Amino Acids↗
PubMed1996

Vascular supply of the palmar subcutaneous tissue of fingers.

The arterial system of the palmar subcutaneous fatty tissue of fingers was studied by injecting a coloured silicone polymer into the vessels of 12 fresh human cadaver hands. Arterial vascularisation of these tissues is ensured by small palmar branches arising from the main digital arteries: there were an average of 7 branches on each side varying between 4 and 12 in the specimens studied. Three anatomical patterns could be distinguished: an I-shaped configuration in 64% of cases, a narrow V-shape in 23%, and a Y-shape in 13%. An accompanying venous network was always present and drained into either the superficial or deep venous network. These anatomical findings confirm the vascular reliability of the homodigital subcutaneous flap described by the authors.

Adipose Tissue↗
PubMed1996

[1-13C]glucose metabolism in brain cells: isotopomer analysis of glutamine from cerebellar astrocytes and glutamate from granule cells.

We analyzed the glutamine isotopomers released into the extracellular medium by cerebellar astrocytes incubated with [1-13C]glucose. We developed a mathematical model of the tricarboxylic acid (TCA) cycle to determine the relative flux of molecules through the anaplerotic versus oxidative pathways and the relative pyruvate carboxylase versus pyruvate dehydrogenase activities. As glutamine C2 and C3 exhibited unequivalent enrichments, we examined the possibility of: (1) both the entry of the label into the TCA cycle from pyruvate and the conversion of the oxaloacetate into citrate before equilibration with fumarate, and (2) the occurrence of an orientation-conserved transfer of the symmetrical 4-carbon intermediates. The best fit required partial cycling between oxaloacetate and fumarate, whereas the occurrence of any orientation-conserved transfer was rejected. On the other hand, the analysis of glutamate isotopomers from perchloric acid extracts of granule cells incubated with [1-13C]glucose indicated that total cycling of oxaloacetate into fumarate occurred in these cells.

Animals↗
PubMed1996

[Reconstruction of amputated thumb: 20 years of development of techniques and indications].

The loss of a thumb is traumatic on the functional, cosmetic and psychological level. If immediate replantation cannot be successfully accomplished, the surgeon must plan to treat the patient within the first days or, at the latest, within the first weeks following the injury. If the patient is left to "mourn" his lost thumb, he will find it difficult to incorporate his new thumb into his body image and this will compromise the results of a late reconstruction. There is a vast range of therapeutic options, even for cases of severe injury. The most classic treatments include lengthening the first metacarpal, osteoplasty, pollicization of long fingers or stump. These techniques were very common up until the late 1970's at which time microsurgical techniques of partial or total toe transfer became popular. For a short time, there was some opposition between proponents of classic techniques and microsurgeons. In fact, there was a role for each method and classic and microsurgical techniques became complementary. Since 1976, we have performed 196 thumb reconstructions in our department; it is interesting to note that classic techniques were used in 14.1% of cases and microsurgical techniques in 85.7% of cases. Very early on, we decided against the use of the big toe because of the resulting plantar sequelae and preferred use of the second toe (50% of cases). Our experience with the reliability of dissection of big toes has led us to prefer partial toe transfer especially the wrap-around technique of Morrison. The failure rate for microsurgical transfer is 3.6%.

Amputation, Traumatic↗