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G Foucault

Publications and source records attributed to G Foucault.

At least 19 recordsLinked to original sources
PubMed1999

Role of the C-terminal extremities of the smooth muscle myosin heavy chains: implication for assembly properties.

The two light meromyosin isoforms from rabbit smooth muscle were prepared as recombinant proteins in Escherichia coli. These species which differed only by their C-terminal extremity showed the same circular dichroism spectra and endotherms in measurements of differential scanning calorimetry. Their solubility properties were different at pH 7.0 in the absence of monovalent salts. Their paracrystals formed at low pH differed by their aspect and number. These data suggest a role for the C-terminal extremity of myosin heavy chains in the assembly of myosin molecules in filaments and consequently in the contractility of smooth muscles.

Animals↗
PubMed1999

Presence of enolase in the M-band of skeletal muscle and possible indirect interaction with the cytosolic muscle isoform of creatine kinase.

Glycerol-skinned skeletal muscle fibres retain the defined sarcomeric structure of the myofibrils. We show here that a small fraction of two enzymes important for energy metabolism, the cytosolic muscle isoform of creatine kinase (EC 2.7.3.2), MM-creatine kinase (MM-CK), and enolase (EC 4.2.1.11), remains bound to skinned fibres. CK is slowly exchangeable, whereas enolase is firmly bound. Two-dimensional gel electrophoresis followed by Western blot analyses demonstrates that both alpha (ubiquitous) and beta (muscle-specific) subunits of enolase are present in these preparations. Enolase and CK were co-localized at the M-band of the sarcomeres, as observed by indirect immunofluorescence and confocal microscopy. Cross-linking experiments were performed on skinned fibres with three bifunctional succinimidyl esters of different lengths and yielded a protein complex of 150 kDa that reacted with antibodies directed against either M-CK or beta-enolase. The cross-linking efficiency was greatest for the longest reagent and zero for the shortest one. The length of the cross-linker giving a covalent complex between the two enzymes does not support the notion of a direct interaction between M-CK and enolase. This is the first demonstration of the presence of an enzyme of energy metabolism other than CK at the M-band of myofibres.

Animals↗
PubMed1997

Mobility of creatine phosphokinase and beta-enolase in cultured muscle cells.

The diffusion of beta-enolase and creatine phosphokinase in muscle cells has been studied by modulated fringe pattern photobleaching. Beta-enolase is mobile in the sarcoplasm. At 20 degrees C, the diffusion coefficient is 13.5 +/- 2.5 microm2 s(-1) in the cytosol and 56 microm2 s(-1) in aqueous media. As in the case of dextrans of the same hydrodynamic radius, its mobility is hindered by both the crowding of the fluid phase of the cytoplasm and the screening effect due to myofilaments. A fraction of creatine phosphokinase is mobile in the sarcoplasm. Its diffusion coefficient in the cytosol, 4.5 +/- 1 microm2 s(-1), is lower than that of the dextran of equivalent size. The other fraction (20 to 50%) is very slightly mobile, with an apparent diffusion coefficient varying from 0.0035 to 0.043 microm2 s(-1). This low mobility might be attributed to exchange between free and bound creatine phosphokinase. The bound fraction of the endogenous enzyme was localized by immunocytofluorescence on the cultured muscle cells. Our results favor a localization of bound cytosolic creatine phosphokinase on the M-line and a diffuse distribution in all myotubes.

Animals↗
PubMed1996

Diffusion of fluorescently labeled macromolecules in cultured muscle cells.

Myotubes were obtained from culture of satellite cells. They had a sarcomeric organization similar to that of muscle. The diffusion in the direction perpendicular to the fibers of microinjected fluorescein isothiocyanate-dextrans of molecular weight ranging from 9500 to 150,000 was examined by modulated fringe pattern photobleaching. On the time scale of the observation, 10-30 S, all of the dextrans were completely mobile in the cytoplasm. The diffusion coefficients were compared to the values obtained in water. The ratio D(cytoplasm)/D(w) decreased with the hydrodynamic radius R(h) of the macromolecules. The mobility of inert molecules in muscle cells is hindered by both the crowding of the fluid phase of the cytoplasm and the screening effect due to myofilaments: D(cytoplasm)/D(w) = (D/D(w)) protein crowding x (D/D(w))(filament screening). The equation (D/D(w))filament screening = exp(-K(L)RCh) was used for the contribution of the filaments to the restriction of diffusion. A free protein concentration of 135 mg/ml, a solvent viscosity of cytoplasm near that of bulk water, and a calculated K(L) of 0.066 nm(-1), which takes into account the sarcomeric organization of filaments, accurately represent our data.

Animals↗
PubMed1988

Isolation of a 50 kDa polypeptide from the detergent-resistant unfertilized sea urchin egg cytomatrix and evidence for its change in organization during mitosis.

In this report, we describe the isolation of a 50 kDa polypeptide from the detergent-resistant cytomatrix of unfertilized sea urchin egg. This polypeptide shares with the intermediate filaments the property of insolubility in high ionic strength buffer solution. However, it does not cross-react with anti-vimentin and anti-cytokeratin antibodies. Studies performed by indirect immunofluorescence microscopy with an immunospecific serum raised against this polypeptide show that during the first cell cycle the polypeptide exhibits similar configuration changes as those described for tubulin. Using immunocytochemical light and electron microscopy, we present evidence indicating that this 50 kDa polypeptide is a constituent of the isolated mitotic apparatus; it is mainly located on patches of microfibrillar material found close to the microtubules. The 50 kDa polypeptide is not extracted from taxol-assembled microtubules by the 0.6 M NaCl treatment. However, the difference in solubility between this protein and the previously studied microtubule-associated proteins does not preclude the possibility of the 50 kDa polypeptide on being a "microtubule-associated protein". The possible significance of this novel cytoskeletal component is discussed.

Animals↗
PubMed1987

Cytoskeleton of the unfertilized sea urchin egg.

Unfertilized Paracentrotus lividus egg cytoskeleton is prepared by mild, nonionic detergent extraction at 4 degrees C in buffer systems containing either 2-methyl-2,4-pentanediol (hexylene glycol) or glycerol. These extractions allow the isolation of cytomatrices that maintain the egg form and are 70-80 micron in diameter. DNase inhibition assays show that actin is in polymerized form in these cytomatrices. Ultrastructural observations reveal that the cytoskeletons are made up essentially of 2 categories of filaments, 7-8-nm and 2-4-nm in diameter, respectively. After heavy meromyosin labelling, short, radiating actin filaments are seen in the cortical region, while longer actin filaments are found in the internal region of these cytomatrices. The 2-4-nm filaments of still unknown biochemical nature are organized in a meshwork. In contrast to results found with fertilized eggs, bundles of actin filaments and microtubules are absent; 8-13-nm filaments are not detected.

Actins↗
PubMed1986

DNA synthesis and microtubule assembly-related events in fertilized Paracentrotus lividus eggs: reversible inhibition by 10 mM procaine.

This report describes the effects of 10 mM procaine on microtubule assembly and on DNA synthesis, as followed by [3H]colchicine binding assays and [3H]thymidine incorporation respectively, in fertilized Paracentrotus lividus eggs. In the absence of microtubule assembly inhibitors, about 25% of the total egg tubulin is submitted to two cycles of polymerization prior to the first cell division, this polymerization process precedes DNA synthesis. If the zygotes are treated with 10 mM procaine in the course of the cell cycle, tubulin polymerization is inhibited or microtubules are disassembled. DNA synthesis is inhibited when procaine treatment is performed 10 min, before the initiation of the S-period. However, when the drug is applied in the course of this synthetic period, the process is normally accomplished, but the next S-period becomes inhibited. Moreover, procaine treatment increases the cytoplasmic pH of the fertilized eggs by about 0.6 to 0.8 pH units. This pH increase precedes microtubule disassembly and inhibition of DNA synthesis. Washing out the drug induces a decrease of the intracellular pH which returns to about the same value as that of the fertilized egg controls. This pH change is then followed by the reinitiation of microtubule assembly, DNA synthesis and cell division. Our results show that the inhibition of both tubulin polymerization and DNA synthesis in fertilized eggs treated with 10 mM procaine, appears to be related to the drug-induced increase in cytoplasmic pH.

Animals↗
PubMed1985

Dual effect of procaine in sea urchin eggs. Inducer and inhibitor of microtubule assembly.

An increase in the amount of cytoplasmic filamentous structures (cytoplasmic matrix and aster) which were recovered after hexylene glycol/Triton X-100 treatment of sea urchin eggs (Paracentrotus lividus) activated by 0.2-2.5 mM procaine was observed. At higher activator concentrations, an opposite effect was observed and formation of these cytoplasmic structures was inhibited in the presence of 10 mM procaine. This inhibitory effect was reversed by diluting the drug in the incubation medium. DNase I inhibition assays on egg homogenates which were performed at different time points of the activation process, show that the same amount of actin was induced to polymerize in eggs activated either by 2.5 or 10 mM procaine. However, colchicine-binding assays on the 100 000 g particulate fractions of these homogenates show that in eggs activated by 10 mM procaine, in contrast to those activated by 2.5 mM, tubulin polymerization was inhibited and microtubules were disassembled. These results show that the dual effect of procaine in the organization of the egg cytoskeleton appears to be related to its effect on the state of tubulin.

Animals↗
PubMed1985

[The external fronto-ethmoidal approach].

A lateral fronto-ethmoidal approach simultaneously exposing the frontal sinus and the nasal fossae appears to be a necessity for the surgical treatment of fronto-ethmoidal pathology. It is possible to fashion an osteo-plastic flap in the fronto-naso-maxillary region. The technique of the approach is described. The operation leaves no ocular functional sequelae and the scar is minimal. Twenty one operations by fronto-nasal flap approach are described, 10 for benign tumours of the fronto-ethmoidal system and 11 with the aim of re-aerating the frontal sinus for cases of complicated or iatrogenic serious sinusitis. The results are studied. The indications of the fronto-nasal flap are described: In tumour pathology, this technique must be used for osteomas and mucoceles of the fronto-ethmoidal system as soon as the ethmoidal component reaches or goes beyond the middle ethmoid. If the fronto-ethmoidal lesion only involves the anterior ethmoid, it is then accessible via simple frontal flap. Inverted papillomas which require wide exposure should also be treated via this approach. In infectious pathology, the fronto-nasal flap offers the possibility, after eradication of fronto-ethmoidal lesions and calibration of the naso-frontal canal, of re-aeration of the frontal sinus which seems preferable to its exclusion. The possibility of re-aeration of the frontal sinus by an osteo-plastic procedure is progress in comparison with lost bone craniotomy procedures.

Craniotomy↗
PubMed1984

[Study of a lysis medium stabilizing microfilaments and microtubules in vitro and in vivo].

Determination of experimental conditions which allow the evaluation of the variations in the ratio of non polymerized and polymerized forms of actin and tubulin during the reorganization of the cytoskeletal cell system is of most valuable importance. In order to prepare cell homogenates which would reflect the in vivo situation, we tested in vitro a lysis medium which stabilized both microfilaments and microtubules, which were determined by DNase inhibition assays and colchicine binding assays respectively. This lysis medium containing 10 mM potassium phosphate, 1mM magnesium chloride, 5 mM EGTA, 1 M hexylene glycol, 1% Triton X-100, pH 6.4, used at 4 degrees C a) diffused rapidly into the cells; b) did not denature actin and tubulin; c) did not displace the equilibrium between non polymerized and polymerized forms of actin and tubulin, allowing biochemical assays on cell homogenates; d) blocked the evolution of the cytoskeletal system and permitted structural studies; e) and allowed the decoration of microfilaments by heavy meromyosin.

Actins↗
PubMed1983

Tubulin dynamics during the cytoplasmic cohesiveness cycle in artificially activated sea urchin eggs.

Sedimentation studies and [3H]colchicine-binding assays have demonstrated a relationship between the cytoplasmic cohesiveness cycles and the changes in tubulin organization in Paracentrotus lividus eggs activated by 2.5 mM procaine. The same amount of tubulin (20-25% of the total egg tubulin) is involved in these cyclic process and appears to undergo polymerization and depolymerization cycles. Electron microscopy studies reveal that the microtubules formed during these cytoplasmic cohesiveness cycles are under a particulate form which is sedimentable at low speed. Activation experiments carried out in the presence of cytochalasin B (CB) show that the increase in the cytoplasmic cohesiveness is highly reduced while tubulin polymerization and depolymerization cycles and pronuclear centration are not affected. Although tubulin or actin polymerization can be independently triggered in procaine-activated eggs, the increase in cytoplasmic cohesiveness requires the polymerization of both proteins. However, the cytoplasmic cohesiveness cycles appear to be regulated by tubulin polymerization and depolymerization cycles.

Actins↗
PubMed1982

[Comparative study on the chemical modification of sulfhydryl groups of glyceraldehyde-3-phosphate dehydrogenases from yeast and rabbit muscle. The relationship between structure and chemical reactivity].

Chemical modification of cystein 149 residues from yeast apo-glyceraldehyde-3-phosphate dehydrogenase either by iodoacetamidonaphtol or N-(4-dimethylamino-3,5-dinitrophenyl) maleimide results in the disappearance of free sulfhydryl groups according to "full sites reactivity", whereas loss of the dehydrogenase activity occurs following "half of the sites reactivity". Chemical modification of the same cystein residues of the rabbit muscle apoenzyme by N-(4-dimethylamino-3,5-dinitrophenyl) maleimid shows that both loss of activity and disappearance of the sulphydryl groups may be described as "full sites reactivity" phenomena. After chemical modification by iodoacetamidonaphtol both processes follow "half of the sites reactivity".

Animals↗
PubMed1981

Structure and reactivity relationship in glyceraldehyde-3-phosphate dehydrogenase. Dinitrophenylation of cysteine residues of yeast and rabbit muscle enzymes.

Dinitrophenylation of rabbit muscle and yeast glyceraldehyde-3-phosphate dehydrogenases modifies only SH groups. The rabbit muscle apoenzyme loses 75% of its original activity upon dinitrophenylation of two SH groups per tetramer whereas the yeast apoenzyme is totally inactivated under the same conditions. Dinitrophenylation of the active-site cysteine-149 of rabbit muscle and yeast holoenzymes results in an loss of activity corresponding to a 'half-of-the-sites' and a 'full-sites' reactivity, respectively. Determination of the sulphydryl content of the modified enzymes shows an unmasking of the cysteine residues of the dinitrophenylated rabbit muscle apoenzyme which is not observed for the yeast protein. However, conformational changes are revealed for both dinitrophenylated apoenzymes by differential absorption spectroscopy or by limited proteolysis. Sulphydryl group unmasking is not observed after modification of the cysteine residues of the rabbit muscle holoenzyme but it does occur when dinitrophenylation is performed in the presence of two moles NAD+/mole rabbit muscle enzyme. Although the apoenzyme is sensitive to an induced conformational change, our results favour symmetrical structures for both yeast apo and holo enzymes. The bis-dinitrophenylated rabbit muscle apoenzyme presents all the characteristics of an asymmetrical structure; however, it is not possible to deduce whether this symmetry is due to the chemical modification or whether it preexists in the native apoenzyme. The results of the dinitrophenylation of the rabbit holoenzyme, however, indicate that this enzyme possesses an asymmetrical structure.

Animals↗