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C Astier

Publications and source records attributed to C Astier.

At least 37 records · Page 2Linked to original sources
PubMed1997

Fish muscle cytoskeleton integrity is not dependent on intact thin filaments.

Striated muscle cytoskeleton was studied by ultrastructure and electrophoresis. Treatment of sea bass white muscle myofibrils and glycerinated fibres with calpain caused disruption of costameres, intermediate filaments, and Z-line, without altering sarcomeres. V8 protease also caused loss of costameres and Z-line, and disrupted sarcomeres without affecting the intermediate filaments. Recombinant lipase caused loss of Z-lines and also sarcolemma detachment, without changing sarcomeres or intermediate filaments. DNase-1 removed thin filaments and partially removed Z-lines while leaving intact the sarcolemma attachments and intermediate filaments. Calpain, V8 protease, lipase and DNase-1 treatments induced extensive loss of alpha-actinin from the Z-line, which could be related to titin cleavage (calpain, V8), phosphoinositide hydrolysis (lipase), and actin depolymerisation (DNase-1). These results show that the cytoskeletal components are independent of intact thin filaments.

Actinin↗
PubMed1997

Production and epitopic characterization of monoclonal antibodies against bovine beta-lactoglobulin.

Sixty-nine murine monoclonal antibodies were produced against the bovine beta-lactoglobulin (beta-LG) variant B. Thirty-eight specificity groups of monoclonal antibodies were defined according to the reactivity in indirect or capture ELISA with bovine beta-LG B, for bovine beta-LG B coated at pH ranging from 2.3 to 9.4, and for beta-LG with naturally occurring residue substitutions such as bovine beta-LG variant A and ovine, caprine, porcine, and equine beta-LG. Ten monoclonal antibodies appeared to be monospecific for bovine beta-LG, 58 monoclonal antibodies recognized only ruminants beta-LG, and 1 recognized all species. The specificity of the monoclonal antibodies was also studied with sequenced tryptic peptides of beta-LG variant B. Critical residues involved in the epitopes of nine classes of monoclonal antibodies were characterized. Moreover, 5 monoclonal antibodies were able to discriminate between a fresh solution of beta-LG and a solution that had been stored for > or = 2 d at 4 degrees C, and 3 monoclonal antibodies distinguished bovine beta-LG that has been purified by gel filtration from that purified by salt fractionation. This array of monoclonal antibodies could be efficient probes for characterizing conformational structures involved in biological properties of beta-LG (e.g., interaction with ligands and hypersensitivity reactions) and for studying conformational changes occurring upon physical treatments such as heat denaturation.

Amino Acid Sequence↗
PubMed1996

Development of gene transfer methods for Rubrivivax gelatinosus S1: construction, characterization and complementation of a puf operon deletion strain.

Gene transfer systems were developed in Rubrivivax (Rx.) gelatinosus S1. First, a system for conjugative transfer of mobilizable plasmids from Escherichia coli to Rx. gelatinosus S1 was established. Secondly, optimal conditions for the transformation of Rx. gelatinosus S1 by electroporation were determined. A delta puf strain was constructed. Complementation with the puf operon from a wild-type strain cloned in a replicative plasmid restored photosynthetic growth. Two insertion strains were also selected. All the strains constructed were green, due to a change in carotenoid content. Characterization of these strains provides genetic evidence for a "superoperon" organization in this bacterium.

Bacterial Proteins↗
PubMed1996

Functional alterations in sarcoplasmic reticulum membranes of magnesium-deficient rat skeletal muscle as consequences of free radical-mediated process.

Free radical-induced physiopathologies are generally thought to be mediated by membrane injuries. Using a pro-oxidant model induced by dietary magnesium deficiency, we have recently shown that skeletal muscle lesions occurred with a rise in the calcium level and enhanced free radical production. In this study, we investigated the physicochemical and biochemical properties of sarcoplasmic reticulum membranes isolated from hind limb muscles of weanling male rats pair fed magnesium-deficient or control diets for 12 d. The calcium-induced calcium efflux from preloaded vesicles was increased in membranes isolated from Mg-deficient rat muscle. In agreement with this latter observation, we demonstrated increased ryanodine binding affinity of the calcium channel. The Ca2(+)-ATPase activity of the pump was shown to be reduced. The viscosity state of the membranes, assessed by 1,6-diphenyl-1,3,5-hexatriene fluorescence anisotropy, was significantly increased in Mg-deficient membranes. Moreover, these membranes demonstrated an increased content of protein carbonyls as compared with controls. These functional as well as structural changes are closed to those described in sarcoplasmic reticulum membranes oxidatively modified in vitro. Together, these data fitted well with the concept that free radical-induced membrane damages resulting in calcium overload may be at the origin of skeletal muscle lesion during Mg-deficiency.

Animals↗
PubMed1995

A new mutation in the pufL gene responsible for the terbutryn resistance phenotype in Rubrivivax gelatinosus.

Rubrivivax gelatinosus is a facultative phototrophic non-sulfur bacterium belonging to the beta subclass of the purple bacteria. A terbutryn-resistant mutant of R. gelatinosus has been isolated and characterized. Increased resistance levels to terbutryn (300-fold), atrazine (6-fold) and o-phenanthroline (3-fold) were observed for the mutant compared with wild type. Sequence analysis of the mutant revealed a new mutation in the pufL gene coding for the L subunit of the reaction centre (RC) at codon 192 leading to an amino-acid substitution from Gly in the wild type to Asp in the mutant. This substitution is located in the D helix of the L subunit, suggesting an interaction between terbutryn and this part of the polypeptide in the RC of R. gelatinosus. This is the first report of a mutation leading to herbicide resistance and affecting the D helix in purple bacteria. Furthermore R. gelatinosus wild type is highly sensitive to o-phenanthroline compared with other purple bacteria (Rhodobacter capsulatus and Rhodobacter sphaeroides). Sequence comparison of the L subunit from six purple bacteria in which o-phenanthroline sensitivity was measured suggests that SerL226 might be responsible for this phenotype.

Amino Acid Sequence↗
PubMed1995

Isolation and properties of white skeletal muscle alpha-actinin from sea-trout (Salmo trutta) and bass (Dicentrarchus labrax).

Fish alpha-actinin purified from sea-trout and bass white muscle by means of two different extraction procedures was used to investigate the eventual presence of different muscle isoforms in Z-disks. These fish alpha-actinins have the same apparent molecular weight (100 kDa) and the same isoelectric point (pI = 5.6), and also have a total antigenic identity towards anti-bass and anti-chicken alpha-actinin antibodies, suggesting a single molecular species. The role of fish alpha-actinin as an anchorage site for thin actin filaments and elastic titin filaments in Z-bands was studied. Despite conservation of the actin-binding site, fish alpha-actinin has a better actin-binding ability (kD = 0.3 microM) than chicken smooth muscle alpha-actinin (kD = 1.6 microM). Several other structural and functional characteristics of fish alpha-actinin were also studied: conservation of sequence and domain structure, the role of divalent ions (Ca2+, Mg2+) and the dielectric constant of the medium in alpha-actinin-actin interaction. Although the reason for fish white muscle alpha-actinin's close affinity to actin was not clearly established, our results suggested that the physicochemical environment of the Z-filaments in Z-disks might be crucial.

Actinin↗
PubMed1995

Dietary magnesium deficiency in rats enhances free radical production in skeletal muscle.

Recent studies suggest that free radicals may be involved in tissue injuries induced by magnesium deficiency. The aim of the present study was to assess the effect of magnesium deficiency on free radical production of skeletal muscle tissue. Male Wistar rats were pair-fed from weaning for 12 d either control or Mg-deficient diets containing 960 or 40 mg magnesium/kg diet, respectively. In the Mg-deficient rats, hypomagnesemia was accompanied by significantly lower magnesium and greater calcium concentrations in skeletal muscle tissue. Electron microscopy of skeletal muscle tissue revealed ultrastructural changes, including swelling mitochondria and disorganization of the sarcoplasmic reticulum network. Using the spin-trapping technique, we showed that significantly more hydroxyl radicals were generated in muscle homogenates of Mg-deficient rats. Moreover, the amount of spin trap adducts was increased in the presence of exogenous iron in both groups. In agreement with these observations, a greater concentration of thiobarbituric acid-reactive substances and a lower concentration of thiol groups were found in skeletal muscle of the Mg-deficient group compared with controls. These results strongly support the hypothesis that free radical-mediated injury could contribute to skeletal muscle lesions resulting from magnesium deficiency.

Animals↗
PubMed1995

Magnesium deficiency in rats induces a rise in plasma nitric oxide.

Magnesium deficiency in rats leads to an oxidative stress involving an increased production of radical oxygen species. The present study was designed to examine the effect of experimental magnesium deficiency on plasma nitric oxide (NO) level and nitric oxide synthases (NOS) activities in rats. The data show that the concentration of NO is markedly increased in plasma of magnesium-deficient rats. This rise in plasma NO results from activation of inducible nitric oxide synthase (iNOS) rather than of the constitutive form (cNOS) of the enzyme. These data are in agreement with previous observations indicating that inflammation occurs during magnesium-deficiency and provide an additional cause of oxidative lesions through formation of peroxynitrite from nitric oxide and superoxide anion.

Animals↗
PubMed1993

Effects of different enzymic treatments on the release of titin fragments from rabbit skeletal myofibrils. Purification of an 800 kDa titin polypeptide.

In myofibrils, titin (also called connectin) molecules span from Z line to M line and constitute a third filament system containing an elastic domain in the I band. This giant protein is particularly sensitive to proteolysis in situ. Treatment of rabbit skeletal myofibrils with exogenous proteinases induces a release of titin fragments, which are detected in the soluble myofibrillar fraction. The cleavage of titin occurs at specific points localized at the proximity of Z line and could lead to a concomitant release of alpha-actinin.

Animals↗
PubMed1993

Functional analysis of the two homologous psbA gene copies in Synechocystis PCC 6714 and PCC 6803.

The cyanobacteria Synechocystis 6803 and 6714 contain three genes (psbA) coding for the D1 protein. This protein is an essential subunit of photosystem II (PSII) and is the target for herbicides. We have used herbicide-resistant mutants to study the role of the two homologous copies of the psbA genes in both strains (the third copy is not expressed). Several herbicide resistance mutations map within the psbAI gene in Synechocystis 6714 (G. Ajlani et al., Plant Mol. Biol. 13 (1989): 469-479). We have looked for mutations in copy II. Results show that in Synechocystis 6714, only psbAI contains herbicide resistance mutations. Relative expression of psbAI and psbAII has been measured by analysing the proportions of resistant and sensitive D1 in the thylakoid membranes of the mutants. In normal growth conditions, 95% resistant D1 and 5% sensitive D1 were found. In high light conditions, expression of psbAII was enhanced, producing 15% sensitive D1. This enhancement is specifically due to high light and not to the decrease of D1 concentration caused by photoinhibition. Copy I of Synechocystis 6714 corresponds to copy 2 of Synechocystis 6803 since it was always psbA2 which was recombined in Synechocystis 6803 transformants. PSII of the transformant strains was found to be 95% resistant to herbicides as in resistant mutants of Synechocystis 6714.

Amino Acid Sequence↗
PubMed1991

Induction, regulation and messenger half-life of cytochromes P450 IA1, IA2 and IIIA6 in primary cultures of rabbit hepatocytes. CYP 1A1, 1A2 and 3A6 chromosome location in the rabbit and evidence that post-transcriptional control of gene IA2 does not involve mRNA stabilization.

A study on the regulation and induction of expression of cytochromes P450-IA1, IA2 and IIIA6 genes has been undertaken using primary cultures of adult rabbit hepatocytes grown in a serum-free chemically and hormonally defined medium. In 72-h-old cultures, 50 microM beta-naphthoflavone induced both IA1 and IA2 mRNA, the maximal level being reached after 4 h and 12 h, respectively. This was shown to result from an increase in the rate of transcription of gene IA1. In contrast, gene IA2 was constitutively transcribed in untreated cells, but mRNA only accumulated in the presence of beta-naphthoflavone which, however, did not affect the rate of transcription. Actinomycin D fully blocked induction of both IA1 and IA2 mRNA in response to their inducer. In untreated cells the presence of cycloheximide allowed a 'constitutive' expression of gene IA1, while in beta-naphthoflavone-treated cells, it produced a super-induction of IA1 but no modification of IA2 gene expression. Rifampicin (50 microM) strongly increased the IA1 mRNA level and rate of transcription only in cycloheximide-treated cells. Rifampicin and dexamethasone, two prototypical inducers of P450-IIIAs, induced both large and small IIIA6 mRNAs in a time-dependent fashion, the maximum level being reached after 24 h. This was related to a large increase in the rate of transcription of the gene. Cycloheximide significantly decreased the accumulation of both IIIA6 mRNAs in response to rifampicin, while actinomycin D fully blocked induction. The half-lives of IA1, IA2 and IIIA6 mRNAs were determined by two different methods, namely actinomycin D and [3H]uridine-chase experiments. In untreated cells, the half-lives for IA1, IA2 and IIIA6 mRNAs were 14 h, 16 h and 19 h, respectively when determined by the uridine chase and 18 h, 25 h and 22 h when determined by the actinomycin-D chase. These values were not modified significantly in cells treated with beta-naphthoflavone or rifampicin, indicating that neither of these inducers affected the stability of IA1 and IA2 or IIIA6 messages, respectively.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1991

Sarcomeric disorganization in post-mortem fish muscles.

1. The post-mortem evolution of protein pattern in fish striated muscle was followed by SDS-PAGE, after different conditions of storage time and temperature. 2. Sarcoplasmic and sarcomeric fractions were analyzed respectively by low and high ionic strength extractions of fish muscle samples. 3. No evident modification of electrophoretic patterns was observed during the pre-rigor mortis period. 4. The high mol. wt proteins titin and nebulin were highly sensitive to proteolysis during the rigor mortis period. 5. Myosin extraction was predominantly influenced by the storage temperature. The myosin content of the extracts decreased during the rigor mortis period at storage temperatures greater than 8 degrees C. 6. alpha-Actinin was very resistant to proteolysis, but could be released from Z-disc structure during post-mortem aging.

Actinin↗
PubMed1990

Differential sensitivity of bicarbonate-reversible formate effects on herbicide-resistant mutants of Synechocystis 6714.

Herbicide-resistant mutants of the cyanobacterium Synechocystis 6714, that are altered in specific amino acids in their D-1 protein, shows differential sensitivity to formate treatment. Measurements on oxygen yield in a sequence of flashes, chlorophyll (Chl) a fluorescence transients and Chl a fluorescence yield decay after a flash reveal that the resistance of cells to formate treatment is in the following (highest to lowest) order: [double mutant] A251V/F211S (Az V) greater than [single mutant] F211S (Az I) congruent to wild type greater than [single mutant] S264A (DCMU II-A). Significance of these results in terms of overlapping between the herbicide and bicarbonate binding niches on the D-1 protein is discussed.

Bicarbonates↗
PubMed1990

Towards the understanding of the function of Rb sphaeroides Y wild type reaction center: gene cloning, protein and detergent structures in the three-dimensional crystals.

We report various experiments aimed at the resolution of the 3-dimensional structure of the photosynthetic reaction center from wild type Y Rhodobacter sphaeroides. The genes encoding the L and M polypeptides have been cloned and sequenced. They bear 2 mutations each when compared to those already sequenced in another Rb sphaeroides strain (2.4.1). In the L gene, these codon changes are silent. In the M gene, one is silent and the other one leads to a Leu-Met substitution at position 140. At the present stage of the refinement of the X-ray data (0.3 nm resolution) the structure of the Y reaction center is shown to be highly similar to that of the Rhodopseudomonas viridis reaction center. The binding of spheroidene on the M side of the Y reaction center is shown to be determined by hydrophobic interactions with neighboring amino acids and by steric factors. Preliminary results concerning the localization of the detergent (beta-octylglucoside) in the unit cell are presented. This method combines low angle neutron scattering at different contrasts in H2O/D2O with X-ray crystallographic data.

Carotenoids↗
PubMed1990

A new ioxynil-resistant mutant in Synechocystis PCC 6714: hypothesis on the interaction of ioxynil with the D 1 protein.

A new Synechocystis 6714 mutant, IoxIIA, resistant to the phenol-type herbicide ioxynil was isolated and characterized. The mutation found in the psbA gene (encoding the D 1 photosystem II protein) is at the same codon 266 as for the first ioxynil-resistant mutant IoxIA previously selected [G. Ajlani, I. Meyer, C. Vernotte, and C. Astier, FEBS Lett. 246, 207-210 (1989)]. In IoxIIA, the change of Asn 266 to Asp gives a 3 x resistance, whereas in IoxIA, the change of the same amino acid to Thr gives a 10 x resistance. The effect of these different amino acid substitutions on the ioxynil resistance phenotype has allowed us to construct molecular models and calculate the hydrogen-bonding energies between the hydroxyl group of ioxynil and the respective amino acids at position 266.

Amino Acid Sequence↗
PubMed1989

Mutation in phenol-type herbicide resistance maps within the psbA gene in Synechocystis 6714.

A Synechocytis 6714 mutant resistant to the phenol-type herbicide ioxynil was isolated and characterized. Sensitivity to DCMU and atrazine was tf measured in whole cells and isolated thylakoids. The mutant presents the same sensitivity to atrazine as the wild type and a slightly increased sensitivity to DCMU. A point mutation has been found at codon 266 in the psbAI coding locus (AAC to ACC) resulting in an amino acid change from asparagine to threonine in the D1 protein.

Amino Acid Sequence↗
PubMed1989

Molecular analysis of psbA mutations responsible for various herbicide resistance phenotypes in Synechocystis 6714.

Mutations conferring herbicide resistance in 3 mutant strains of the cyanobacterium Synechocystis 6714 have been characterized by gene cloning and sequencing. The mutants display very different phenotypes: DCMU-IIA is DCMU-resistant and atrazine-resistant, DCMU-IIB is DCMU-resistant and atrazine-sensitive, and Az-V is DCMU-sensitive, atrazine-resistant and presents particular photoinhibition properties. These mutants were originally obtained either by one-step selection (DCMU-IIA) or by two-step selection (DCMU-IIB and Az-V). psbA copies carrying herbicide resistance have been identified by transformation experiments as psb AI in all cases. Sequences of the psb AI copy of each mutant have been compared to the wild-type sequence. In the single mutant DCMU-IIA, a point mutation at codon 264 (Ser----Ala) results in resistance to both DCMU and atrazine. In the double mutants DCMU-IIB and Az-V, two point mutations were found. DCMU-IIB was derived from DCMU-IIA and had acquired a second mutation at codon 255 (Phe----Leu) resulting in a slight increase in DCMU resistance and complete abolition of atrazine resistance. Az-V contains two changes at codons 211 (Phe----Ser) and 251 (Ala----Val) resulting in high atrazine resistance but only slight DCMU resistance.

Amino Acid Sequence↗