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B Guérin

Publications and source records attributed to B Guérin.

At least 73 records · Page 4Linked to original sources
PubMed1993

[Value of adding antibiotics to frozen bovine semen: the example of mycoplasmas and campylobacters].

Two studies have been conducted to control opportunistic pathogen bacteria in frozen bovine semen. The first one was reported by Shin et al. (1988) and was based on (a) an experimental in vitro contamination of raw bull semen with various types of bacteria, (b) adding several antibiotics, alone or in combination with different concentrations. The second experiment, performed in our laboratory, was designed to compare from 240 split ejaculates the effect of adding concentrated solutions of antibiotics to the raw semen vs control (ie addition of antibiotics in the extender). The combination of gentamicin (500 micrograms/ml)-tylosin (100 micrograms/ml)-linco-spectin (300/600 micrograms/ml) was found to be the most effective on the strains of bacteria tested. The addition of a concentrated solution of antibiotics to the raw semen was not found here to be of any advantage on the numbers of CFU. Furthermore, such a protocol contributed to significantly decrease the percentage of motile spermatozoa. In conclusion, opportunistic pathogens such as those here studied may be kept under control with the appropriate antibiotics and with no deleterious effect on semen parameters provided that they are added at the adequate concentrations in the diluents used for semen cryopreservation.

Animals↗
PubMed1992

In vitro evaluation of acaricidal and fungicidal activity of the house dust mite acaricide, Allerbiocid.

The acaricidal and fungicidal activities of a new acaricide Allerbiocid, formulated for the control of house dust mites, were investigated. The components of the Allerbiocid formula are: 3% benzyl benzoate (acaricidal and fungicidal), 1% tannic acid (protein denaturant) and 0.5% Tween (surface active agent) in 70% isopropyl alcohol (antiseptic). At application rates of both 150 and 250 ml/m2, the acaricidal activity appeared to work by both ingestion and contact and remained active upon contact with mites for up to 10 weeks. When Sabouraud agar was treated with Allerbiocid at a concentration of 5 ml/20 ml medium, the preparation was also found to have fungicidal and fungistatic activities on various species of fungi commonly found in house dust. Allerbiocid contains tannic acid which is a protein denaturant. Levels of Der p I in dust were found to be reduced by over 90% after treatment with Allerbiocid. The importance of denaturation of mite faecal allergens and allergens associated with dead fungal spores is discussed.

1-Propanol↗
PubMed1991

Differential sensitivity of the cellular compartments of Saccharomyces cerevisiae to protonophoric uncoupler under fermentative and respiratory energy supply.

The effect of a protonophoric uncoupler (CCCP) on the different cellular compartments was investigated in yeast grown aerobically on lactate. These cells were incubated in a resting cell medium under three conditions; in aerobiosis with lactate or glucose or in anaerobiosis with glucose as energetic substrate. For each condition, in vivo 31P NMR was used to measure pH gradients across vacuolar and plasma membrane and phosphorylated compound levels. Respiratory rate (aerobic conditions) and TPP+ uptake were measured independently. Concerning the polyphosphate metabolism, spontaneous NMR-detected polyphosphate breakdown occurred, in anaerobiosis and in the absence of CCCP. In contrast, in aerobiosis, polyphosphate hydrolysis was induced by addition of either CCCP or a vacuolar membrane ATPase-specific inhibitor, bafilomycin A1. Moreover, polyphosphates were totally absent in a null vacuolar ATPase activity mutant. The vacuolar polyphosphate content depended on two factors: vacuolar pH value, strictly linked to the vacuolar H(+)-ATPase activity, and inorganic phosphate concentration. CCCP was more efficient in dissipating the proton electrochemical gradient across vacuolar and mitochondrial membranes than across the plasma membrane. This discrepancy can be essentially explained by a difference of stimulability of each proton pump involved. As long as the energetic state (measured by NDP + NTP content) remains high, the plasma membrane proton ATPase is able to compensate the proton leak. Moreover, this ATPase contributes only partially to the generation of delta pH. The maintenance of the delta pH across the plasma membrane, that of the energetic state, and the cellular TPP+ uptake depend on the nature of the ATP-producing process.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphatases↗
PubMed1991

Respiration in non-phosphorylating yeast mitochondria. Roles of non-ohmic proton conductance and intrinsic uncoupling.

Respiratory rate, protonmotive force and charge/O ratio were measured under two different kinds of steady state in non-phosphorylating yeast mitochondria: (i) when the electron flux was modulated by a variable limitation in electron supply or (ii) when oxygen consumption was decreased by respiratory chain inhibitor titration. We showed that the relationships between either delta p or charge/O ratio and respiratory rate are different under the two kinds of steady state, indicating different degrees of intrinsic uncoupling in respiratory chain. Moreover, we observed a non-ohmic dependence between H(+)-conductance and delta p. We concluded that the high rate of static-head respiration in yeast mitochondria was determined both by the non-ohmic proton conductance of the inner membrane and the saturation of the redox proton pump slipping.

Electric Conductivity↗
PubMed1991

Isolation and complete amino acid sequence of the mitochondrial ATP synthase epsilon-subunit of the yeast Saccharomyces cerevisiae.

All five subunits of yeast mitochondrial F1-ATPase have been isolated by reverse-phase high performance liquid chromatography. This procedure allows micro-preparative purification of all the subunits with 60% recoveries. The complete amino acid sequence of the epsilon-subunit has been established. This has been achieved by the sequence analysis of subnanomole amounts of the intact molecule and that of peptides derived by enzymatic digestion with endoproteinase Arg-C and by chemical cleavage with hydroxylamine. Yeast ATP synthase epsilon-subunit is composed of 61 residues with a calculated molecular mass of 6612 Da. This polypeptide is rather basic since it contains 7 basic residues and 3 acidic residues. This study shows a slight similarity with the bovine epsilon-subunit ATP synthase since there are 16 identical residues.

Amino Acid Sequence↗
PubMed1991

Characterization of an Agrobacterium tumefaciens lectin.

An Agrobacterium tumefaciens suspension induces a strong agglutination of aldehyde-fixed pig erythrocytes at pH 5.0. The agglutination is inhibited by some polysaccharides, such as fucoidin, and also when the pH is raised to 7.0. Lectins (sugar-binding proteins) associated with the bacterial cell wall of A. tumefaciens strain 84.5 were directly evidenced by spectrofluorimetry using fluoresceinylated neoglycoproteins. The specific binding of the fluorescein-labelled neoglycoprotein bearing alpha-L-fucoside residues was also optimal at pH 5.0. A lectin was purified by affinity chromatography on agarose substituted with alpha-L-fucopyranoside. Furthermore, the haemagglutination activity of this lectin was inhibited by polysaccharides isolated from poplar leaves.

Agrobacterium tumefaciens↗
PubMed1990

Mitochondrial phosphate transport. N-ethylmaleimide insensitivity correlates with absence of beef heart-like Cys42 from the Saccharomyces cerevisiae phosphate transport protein.

The mitochondrial phosphate transport protein (PTP) has been purified in a reconstitutively active form from Saccharomyces cerevisiae and Candida parapsilosis. ADP/ATP carriers that copurify have been identified. The PTP from S. cerevisiae migrates as a single band (35 kDa) in sodium dodecyl sulfate gels with the same mobility as the N-ethylmaleimide-alkylated beef heart PTP. It does not cross-react with anti-sera against beef heart PTP. The CNBr peptide maps of the yeast and beef proteins are very different. The rate of unidirectional phosphate uptake into reconstituted proteoliposomes is stimulated about 2.5-fold to a Vmax of 170 mumol of phosphate min-1 (mg PTP)-1 (22 degrees C) by increasing the pHi of the proteoliposomes from 6.8 (same as pHe) to 8.0. The Km for Pi of this reconstituted activity is 2.2 mM. The transport is sensitive to mersalyl (50% inhibition at 60 microM) and insensitive to N-ethylmaleimide. We have purified peptides matching the highly conserved motif Pro-X-(Asp/glu)-X-X-(Lys/Arg)-X-(Arg/lys) (X is an unspecified amino acid) of the triplicate gene structure sequence of the beef heart PTP. The N-ethylmaleimide-reactive Cys42 of the beef heart protein, located between the two basic amino acids of this motif (Lys41-Cys42-Arg43), is replaced with a Thr in the yeast protein. This substitution most likely is responsible for the lack of N-ethylmaleimide sensitivity of the yeast protein and mersalyl thus reacts with another cysteine to inhibit the transport. Finally it is concluded that Cys42 has no essential role in the catalysis of inorganic phosphate transport by the mitochondrial phosphate transport protein.

Amino Acid Sequence↗
PubMed1990

Flux-dependent increase in the stoichiometry of charge translocation by mitochondrial ATPase/ATP synthase induced by almitrine.

After studying the effects of almitrine, a new kind of ATPase/ATP synthase inhibitor, on two kinds of isolated mammalian mitochondrion, we have observed that: (1) Almitrine inhibits oligomycin-sensitive ATPase; it decreases the ATP/O value of oxidative phosphorylations without any change in the magnitude of delta mu H+. (2) Almitrine increases the mechanistic H+/ATP stoichiometry of ATPase as shown by measuring either (i) the extent of potassium acetate and of potassium phosphate accumulation sustained by ATP utilisation, or (ii) the electrical charge/ATP (K+/ATP) ratio at steady-state of ATPase activity. (3) Rat liver mitochondria are at least 10-times more sensitive to almitrine than beef heart mitochondria. (4) The change in H+/ATP stoichiometry induced by almitrine depends on the magnitude of the flux through ATPase. The inhibitory effect of almitrine on ATPase/ATP synthase complex, as a consequence of such an H+/ATP stoichiometry change, is discussed.

Acetates↗
PubMed1990

Isolation and genetic study of triethyltin-resistant mutants of Saccharomyces cerevisiae.

Three mutants of Saccharomyces cerevisiae resistant to triethyltin (an inhibitor of mitochondrial ATPase) on non-fermentative media, and non-resistant to this drug on fermentative media, were isolated and named TTR1, TTR2 and TTR3. Apart from triethyltin resistance, these mutants show the following common characteristics: (1) Increased intracellular cytochrome c concentration. (2) Increased respiration rate. (3) Decreased growth yield. (4) Increased growth sensitivity to several drugs inhibiting oxidative phosphorylation: namely, CCCP (permeabilizing inner mitochondrial membrane to protons), valinomycin (permeabilizing inner mitochondrial membrane to potassium) and oligomycin (inhibitor of mitochondrial ATPase). (5) Increased sensitivity to carbon source starvation. For each mutant, these characteristics appeared to be due to a single pleiotropic nuclear mutation. Mutation TTR1 causes additional phenotypic characteristics which do not appear in mutants TTR2 and TTR3: (1) Pinkish coloration of colonies which is more pronounced after a long growth period. (2) Inability of the cells to store glycogen. (3) Growth defect of the cells on a galactose-containing medium. (4) Inability of a diploid homozygote mutant strain to sporulate. All these phenotypic characteristics have already been described in yeast mutants deregulated in cAMP-dependent protein phosphorylation. Crossing of a strain bearing the TTR1 mutation with a strain mutated in the adenylate cyclase structural gene suggested that the TTR1 phenotype is due to a modification in regulation of cAPK by cAMP, making cell multiplication possible without intracellular cAMP.

Alleles↗
PubMed1990

Mitochondrial modifications in a single nuclear mutant of Saccharomyces cerevisiae affected in cAMP-dependent protein phosphorylation.

This paper reports studies of bioenergetic modifications in a TTR1 single-nuclear mutant, isolated as resistant to triethyltin, an inhibitor of mitochondrial ATPase, and effective in cAMP-dependent protein phosphorylation. This mutant appears to have lost the wild-type cell ability to respond to a decrease of oxygen concentration in the growth medium by a decrease of cytochrome concentration in the cell. ATP synthesis rate in mutant cells in both the prestationary and stationary phase of growth appeared increased in comparison to wild-type cells, as too was respiration rate. A comparative study of mitochondria extracted from wild-type and from TTR1 mutant cells showed an increase in respiration rate, an increase in ATP synthesis rate, and an increase in TPP+ uptake in mutant mitochondria. The specific ATPase activity, as well as its sensitivity to TET, appears to be similar for mitochondria extracted from both strains. It was proposed that the modification of mitochondrial biogenesis in the TTR1 mutant may be due to a response of the cell to an increase in ATP hydrolysis caused by the mutation. It is also possible that the modification in cAMP-dependent protein kinase regulation which appeared to occur in this mutant affects protein(s) involved in mitochondrial biogenesis.

Adenosine Triphosphatases↗
PubMed1989

Almitrine, a new kind of energy-transduction inhibitor acting on mitochondrial ATP synthase.

At low concentrations, almitrine inhibits yeast cell multiplication by acting on oxidative metabolism. Studies on isolated mitochondria display the following features: (i) almitrine inhibits ATPase activity and decreases ATP/O ratio during oxidative phosphorylation; (ii) no direct effect on respiration can be evidenced; (iii) ATP/O value decreases without any change in the magnitude of delta p; (iv) the higher the ATP synthesis and respiratory fluxes, the larger is the decrease in ATP/O ratio induced by almitrine. These results indicate that almitrine does not act as a classical protonophoric uncoupler nor as previously studied non protonophoric uncouplers (e.g., general anesthetics). Our data show a direct inhibitory effect of almitrine on ATPase-ATP synthase complex. But, in contrast to the classical inhibitors of this complex, almitrine decreases the ATP/O ratio in a flux-dependent manner. Thus, almitrine could induce either an intrinsic uncoupling of H+/-ATPase (i.e., slip in this proton pump) or a change in the mechanistic H+/ATP stoichiometry at the ATPase level.

Adenosine Triphosphate↗
PubMed1988

ATP4, the structural gene for yeast F0F1 ATPase subunit 4.

A plasmid containing the gene coding for the Saccharomyces cerevisiae F0F1 ATPase subunit 4 was isolated from a yeast genomic DNA library using the oligonucleotide probe procedure. The gene and the surrounding regions were cloned into M13 tg 130 and M13 tg 131 phage vectors. A 732-base-pair open reading frame encoding a 244-amino-acid polypeptide is described. The nucleotide sequence predicts that subunit 4 is probably derived from a precursor protein with a hydrophilic and basic 35-amino-acid leader sequence. Mature subunit 4 contains 209 amino acid residues and the predicted molecular mass is 23250 Da. This subunit presents amphiphilic behaviour with two distinct domains. A high alpha-helix content of 77% was predicted from the sequence. Subunit 4 shows homology with the b subunit of Escherichia coli ATP synthase.

Amino Acid Sequence↗
PubMed1988

Specific immunotherapy with a standardized Dermatophagoides pteronyssinus extract. II. Prediction of efficacy of immunotherapy.

House dust mites of the species Dermatophagoides pteronyssinus (Dpt) represent one of the major allergens inducing asthma. However, a strict allergy to Dpt is not always observed in Dpt-allergic patients, since nonallergic and other allergic triggering factors often coexist. It was suggested that specific immunotherapy with house dust-mite extracts is more effective in children than in adults. A controlled study was undertaken in 215 Dpt-allergic patients with asthma ranging in age from 3 to 72 years (mean +/- SD, 28.2 +/- 10.9 years) to investigate parameters that might predict the efficacy of specific immunotherapy before it is started; 171 patients received a rush immunotherapy protocol with a standardized Dpt extract and, subsequently, maintenance injections with 3000 BU of this extract, and 44 patients served as a control group. Before immunotherapy, all patients had a complete evaluation of the severity of asthma by symptom-medication scores and a pulmonary function test, as well as a study of other triggering factors by checking on seasonal and perennial allergens, sinusitis, and other possible causes, such as aspirin intolerance; 196 patients were investigated between 9 and 12 months after the onset of the survey by means of pulmonary function tests and symptom-medication scores. Medications were adapted according to peak flow rates. It was observed that patients with chronic sinusitis, and/or aspirin intolerance, and/or other perennial allergies did not benefit from specific immunotherapy; therefore, the treatment of a major etiologic factor did not demonstrate improvement in the patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1987

[Skin tests and chymopapain-specific immunoglobulins E after chemonucleolysis].

Skin tests (prick tests) with chymopapain were performed on 3 groups of patients: 75 patients awaiting chemonucleolysis with chymopapain (group I), 42 of these 75 patients 2-3 weeks after chemonucleolysis (group II), and 60 atopic patients suffering from asthma and/or rhinitis with positive skin tests to at least one of the airborne allergens (group III). A positive skin test was found in one patient of group I (1.33%), one patient of group III (1.7%) and 11 patients of group II (26.2%). Thus, sensitization to chymopapain is not more frequent among atopic patients, and chemonucleolysis has a highly significant (P less than 0.001) sensitizing effect. Chymopapain-specific IgE's were found in one out of 75 patients (1.33%) before, and in 14 out of 45 patients (31%) after chemonucleolysis; the difference was significant (P less than 0.001). Concordance between skin tests and specific IgE's reached the 74% level. Our results are consistent with those of the literature. They show that prick tests with a 10 mg/ml solution of chymopapain constitute, for the time being, a simple, reliable and cheap method for detecting subjects at risk.

Adult↗
PubMed1987

Subunit 4 of ATP synthase (F0F1) from yeast mitochondria. Purification, amino-acid composition and partial N-terminal sequence.

One subunit of the membrane portion of yeast ATP synthase was purified. Structural data are reported. This subunit (subunit 4) is the fourth polypeptide of the complex when classifying subunits in order of decreasing molecular mass. Its apparent relative molecular mass is about 25,000. The polypeptide was extracted from the complex with a mixture of chloroform/methanol (1/1) and 0.5 M pyridinium acetate pH 6.0. Purification was performed with a combination of gel permeation chromatography on Sephadex G-75 and high-performance gel permeation chromatography with aqueous solvents containing 5% sodium dodecyl sulfate. The amino acid composition is reported here. The following sequence of the NH2-terminal ten residues was determined: Met-Ser-Ser-Thr-Pro-Glu-Lys-Gln-Thr-Asp.

Adenosine Triphosphatases↗