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G Lefebvre

Publications and source records attributed to G Lefebvre.

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

Multiple bacteriocin production by Leuconostoc mesenteroides TA33a and other Leuconostoc/Weissella strains.

Leuconostoc (Lc.) mesenteroides TA33a produced three bacteriocins with different inhibitory activity spectra. Bacteriocins were purified by adsorption/desorption from producer cells and reverse phase high-performance liquid chromatography. Leucocin C-TA33a, a novel bacteriocin with a predicted molecular mass of 4598 Da, inhibited Listeria and other lactic acid bacteria (LAB). Leucocin B-TA33a has a predicted molecular mass of 3466 Da, with activity against Leuconostoc/Weissella (W.) strains, and appears similar to mesenterocin 52B and dextranicin 24, while leucocin A-TA33a, which also inhibited Listeria and other LAB strains, is identical to leucocin A-UAL 187. A survey of other known bacteriocin-producing Leuconostoc/Weissella strains for the presence of the three different bacteriocins revealed that production of leucocin A-, B- and C-type bacteriocins was widespread. Lc. carnosum LA54a, W. paramesenteroides LA7a, and Lc. gelidum UAL 187-22 produced all three bacteriocins, whereas W. paramesenteroides OX and Lc. carnosum TA11a produced only leucocin A- and B-type bacteriocins.

Bacteria↗
PubMed1997

Psychological reactions after multifetal pregnancy reduction: a 2-year follow-up study.

This study had two objectives. Firstly we assessed the effects of multifetal pregnancy reduction on the mothers' emotional well-being and the relationship with the children during the 2 years following intervention. Secondly at 2 years we compared mothers who had a reduction with mothers who had not and had delivered triplets. The comparisons focused on the mothers' health and their relationship with the children. Women having had a reduction in two hospitals in Paris, between May 1992 and June 1993, were contacted just after intervention for a prospective study. In all, 18 women were included. At 1 and 2 years, 10 women participated. At 2 years, 10 additional women were included. The answers of these 20 mothers were compared to those of 11 consecutive mothers of 2 year old triplets, assessed by the same psychologist in a previous prospective study. Semi-structured interviews were conducted at home. The mothers' social characteristics, their parity, the children's condition at birth and 4 months were very similar between the reduction and triplet groups. One year after birth one-third of the women in the reduction group reported persistent depressive symptoms related to the reduction, mainly sadness and guilt. The others made medical and rational comments expressing no emotion. At 2 years all but two women seemed to have overcome the emotional pain associated with the reduction. The comparison with mothers of triplets indicated that the mothers' anxiety and depression, and difficult relationship with the children were less acute in the reduction group. These results presented some limitations, since a high number of women who miscarried or refused to participate in the follow-up were not assessed at 1 and 2 years. However, a majority of women who participated in the study 2 years after intervention seemed able to accept a multifetal pregnancy reduction to achieve parental goals.

Adult↗
PubMed1997

Effects of Low Dissolved-Oxygen Concentrations on Poly-(3-Hydroxybutyrate-co-3-Hydroxyvalerate) Production by Alcaligenes eutrophus.

The bacterial copolyester poly-(3-hydroxybutyrate-co-3-hydroxyvalerate) was produced with Alcaligenes eutrophus DSM 545 from glucose and sodium propionate in a fed-batch fermentation with both nitrogen limitation and low dissolved-oxygen concentrations. When the dissolved-oxygen content was kept between 1 and 4% of air saturation during the polymer accumulation phase, the yield of 3-hydroxybutyrate (3HB) monomer from glucose was not affected, but the propionate-to-3-hydroxyvalerate (3HV) monomer yield was two to three times (0.48 to 0.73 mol of 3HV mol of propionate consumed(sup-1)) that observed in a control experiment (0.25 mol mol(sup-1)), where the accumulation-phase dissolved-oxygen concentration was 50 to 70% of air saturation. The overall polymer productivity of the fermentation was somewhat decreased by low dissolved-oxygen contents, owing to a slower 3HB production rate. The effect of a low dissolved-oxygen concentration is probably attributable to a reduction of the oxygen-requiring decarbonylation of propionyl-coenzyme A (CoA) to acetyl-CoA.

Journal Article↗
PubMed1996

Regulation of spiramycin synthesis in Streptomyces ambofaciens: effects of glucose and inorganic phosphate.

The production of the 16-membered macrolide antibiotic, spiramycin, in Streptomyces ambofaciens is inhibited by glucose, 2-deoxyglucose and inorganic phosphate. The role of intracellular ATP content and phosphorylated metabolites as common regulating signals of both glucose and phosphate inhibitory effects is discussed. Two enzymatic targets of the effect of phosphate on spiramycin biosynthesis were studied. Valine dehydrogenase, the first enzyme of valine catabolism (supplier of aglycone spiramycin precursors), and alkaline phosphatase, which cleaves phosphorylated intermediates, were repressed in the presence of excess phosphate.

Adenosine Triphosphate↗
PubMed1996

Purification and N-terminal amino acid sequence of dextranicin 24, a bacteriocin of Leuconostoc sp.

Leuconostoc mesenteroides subsp. dextranicum strain J24 synthesized a bacteriocin named Dextranicin 24 (Dex-24), which inhibited only other Leuconostoc sp. strains. It was purified by a two-step procedure from the fraction of the bacteriocin bound to the producer cells at the end of the growth: desorption form the cells at acidic pH, followed by reserve phase HPLC. The N-terminal sequence of Dex-24 was the following: NH2(-) K G V L G W L S M A S S A L T G P Q Q . . .

Amino Acid Sequence↗
PubMed1996

HP17, a new pigment-like antibiotic produced by a new strain of Spirillospora.

Spirillospora strain 719 produces several antibiotics. On solid and liquid media, a deep red pigments is formed and diffuses throughout the culture. It was extracted with methanol from the mycelium cake and from the fermentation broth after precipitation at pH 2 and purified using TLC and HPLC. Its u.v. absorption spectrum and its physicochemical characteristics place this antibiotic in the 3.3.2.2.8 of the Berdy et al. classification. In most respects, it resembles proteinaceous pigment from Spirillospora 1655 and 1309-b that was studied and named spirillomycin. However, HP17 differs from spirillomycin principally in molecular weight and chemical nature.

Actinomycetales↗
PubMed1996

Leuconostoc mesenteroides subsp. mesenteroides FR52 synthesizes two distinct bacteriocins.

Mesenterocin 52, a bacteriocin produced by Leuconostoc mesenteroides subsp. mesenteroides FR52, was purified from producing cells by the adsorption-desorption method, combined with reverse-phase high-performance liquid chromatography. The elution profile revealed the presence of two inhibitory peaks of activity, each displaying different inhibitory spectra. Mesenterocin 52A possessed a broad inhibitory spectrum, including anti-Listeria activity, while Mesenterocin 52B was only active against Leuconostoc spp. The amino acid sequence and M(r) of Mesenterocin 52A appeared identical to the previously described Mesentericin Y105. In contrast, Mesenterocin 52B possessed a M(r) of 3446 Da, corresponding to 32 amino acids and a sequence that shared no homology with known bacteriocins: NH2-KGVLGWLSMASSALTGPQQPNSPWLAKIKNHK.

Amino Acid Sequence↗
PubMed1995

Glycerol effect on spiramycin production and valine catabolism in Streptomyces ambofaciens.

Spiramycin production by Streptomyces ambofaciens in a chemically defined medium, with valine as nitrogen source, was controlled by the nature and the concentration of the carbon source. The production of this antibiotic was better in dextrins than in glycerol-containing medium. The negative effect of glycerol could be attributed in part to an excess of energy and a high specific growth rate. The intracellular ATP content, at the start of spiramycin production, was twofold higher in glycerol than in dextrin-containing medium. Increasing the initial concentrations of glycerol led to an increase in the specific growth rate and a drop in spiramycin production. Comparison between glycerol and a protein synthesis inhibitor effects and the use of resting cell systems (RCS) proved that glycerol exerted both inhibitory and repressive actions on spiramycin production independently from the growth. At the enzymatic level, glycerol interfered with valine catabolism by repressing partially valine dehydrogenase (VDH) and alpha-ketoisovalerate dehydrogenase (KIVDH), generator of spiramycin aglycone precursors.

Amino Acid Oxidoreductases↗
PubMed1995

Activity of plantaricin SA6, a bacteriocin produced by Lactobacillus plantarum SA6 isolated from fermented sausage.

Plantaricin SA6, a bacteriocin produced by Lactobacillus plantarum SA6, exhibited an inhibitory action against several mesophilic lactobacilli. It was stable at 90-100 degrees C at pH 2-4 and it remained stable in the presence of several organic solvents, urea or beta-mercaptoethanol. Plantaricin SA6 bound specifically to the cell surface of only plantaricin SA6-sensitive bacteria. The putative receptors are not destroyed by different hydrolytic enzymes added to the phosphate buffer. Plantaricin SA6 acted as a bactericidal agent lysing sensitive strains, that became more permeable to ortho-nitro-phenol-beta-galactoside and lost their intracellular K+ ions and u.v.-absorbing materials. Both the adsorption and lethal action of plantaricin SA6 were maximal between pH 4 and 7, but the range of temperature tested (5-37 degrees C) had no effect. Ions (of several salts such as MgCl2) inhibited the binding of plantaricin SA6 and protected cells against bacteriocin action.

Animals↗
PubMed1995

Regulation of valine catabolism by ammonium in Streptomyces ambofaciens, producer of spiramycin.

In Streptomyces ambofaciens, valine favored spiramycin biosynthesis by supplying aglycone precursors. The kinetics of valine consumption and isobutyrate production showed that isobutyrate accumulated in the cell during the growth phase, was excreted in the stationary phase, and then was reassimilated during spiramycin production. When valine was in excess, its deamination led to high ammonium excretion and to a significant drop in spiramycin production. We demonstrated that ammonium ions were the cause of the negative effect. Addition of a chelator agent, Ca3(PO4)2, improved spiramycin production by sixfold. In contrast, addition of ammonium, between 0 and 48 h, severely reduced spiramycin production. The negative effect of ammonium was reversed by addition of a catabolic intermediate of valine, isobutyrate. In addition to stimulating the specific growth rate, ammonium ions slowed down valine catabolism: the specific valine uptake rate, excretion, and reassimilation of isobutyrate were lowered by the pulse of ammonium. Our study showed that in addition to valine dehydrogenase, which provided the nitrogen necessary to the cell, ammonium ions repressed ketoisovalerate dehydrogenase, which introduced valine as carbon, energy, and aglycone precursor sources. However, valine dehydrogenase and ketoisovalerate dehydrogenase did not constitute the principal enzymatic targets of the negative effect of ammonium in spiramycin production.

2-Oxoisovalerate Dehydrogenase (Acylating)↗
PubMed1995

[Psychological effects of embryonal reduction. From the decision making to 4 months after delivery].

The psychological effect of reducing the number of embryons was studied prospectively in two Paris hospitals. All women who had multifetal pregnancy reduction (n = 18) were contacted for interviews just after the operation, during pregnancy, and four months after delivery. The decision to reduce the number of embryons was painful and led to a guilty feeling. After operation, nearly one-half of the women suffered psychologically. To justify their decision, and contain their emotions, the women spoke of the problems related to having triplets and, most importantly, the medical arguements explained by the physician. Medical counselling is thus essential to help this couples at the time of the operation. The pregnancy period is almost always a period of calm for these women. Nevertheless, four months after delivery, 5 women expressed a psychological malaise related to the reduction, and 2 women refused to continue the study because they did not want to revive their suffering. This study shows that psychological problems are of major importance after multifetal pregnancy reduction and can occur several months after delivery. These negative conclusions should however be examined in light of the consequences if reduction had not been performed.

Adult↗
PubMed1995

AH17, a new non-polyenic antifungal antibiotic produced by a strain of Spirillospora.

An antibiotic (AH17) was produced by Spirillospora strain 719. This substance was obtained only from the broth filtrate after precipitation with acetic acid followed by extraction with n-butanol. Its purification was carried out by thin layer chromatography on silica gel followed by HPLC procedures. It showed activity against Gram-positive and Gram-negative bacteria and fungi. The spectroscopic and chemical properties were examined and indicated that AH17 was a quinone. It seems that this is a new antibiotic from Spirillospora.

Actinomycetales↗
PubMed1995

[Human papilloma virus infection and renal transplantation. Two personally observed cases and a review of the literature].

Two cases of recurrent genital infection due to human papilloma virus (HPV) infection with preneoplasic lesions were observed in kidney transplant recipients. The neoplasic component appears to be very frequent in this immunosuppressed population with a risk estimated at 7%. According to the different authors in the literature [correction of litterature], genital lesions due to HPV, with or without dysplasia are found in 15 to 30% of the transplant population. The factors of risk are not different from the general population and are a function of sexual activity. The clinical expression of the lesions, their clinical course and recurrence are probably related to the immunosuppressor treatment. All such patients should be carefully screened to allow prevention and treatment, which, as seen in these cases, may be insufficient to irradicate the lesions. New therapeutic approaches should be studied in this group of patients at risk.

Female↗
PubMed1994

Effect of the bacteriocin carnocin CP5 and of the producing strain Carnobacterium piscicola CP5 on the viability of Listeria monocytogenes ATCC 15313 in salt solution, broth and skimmed milk, at various incubation temperatures.

Carnobacterium piscicola CP5, isolated from French mould-ripened soft-cheese, produced a bacteriocin named carnocin CP5 in a wide range of incubation temperatures, from 4 degrees C to 30 degrees C. The ability of a crude bacteriocin, of a partially-purified form, and of the producer strain to inhibit growth of Listeria monocytogenes ATCC 15313 was examined in salt solution, broth and skimmed milk between 4 degrees C and 30 degrees C. When carnocin CP5 was added to a L. monocytogenes ATCC 15313 culture, an adsorption on cells and a bactericidal effect with a cell lysis occurred. At 30 degrees C, with carnocin CP5 or with C. piscicola CP5, a transitory bactericidal effect was observed. Subsequent experiments at 4 degrees C, 7 degrees C or 15 degrees C, showed a more prolonged bactericidal effect. Thus at 7 degrees C, partially-purified carnocin CP5 reduced an initial population level of L. monocytogenes of 10(3) cfu/ml to non-detectable level within 7 days. However, in some cases, with extended incubation, the carnocin CP5 effect was no longer visible, the L. monocytogenes population grew again. This phenomenon was probably due to the presence of a sub-population of bacteriocin-resistant variants.

Animals↗
PubMed1994

How many embryos should be transferred in in vitro fertilization? A prospective randomized study.

OBJECTIVE: To maintain the rate of pregnancy, while suppressing high rank multiple pregnancies by limiting the number of fresh embryos transferred after IVF, in a population selected for potential success. DESIGN: A prospective, randomized study. SETTING: Département de Gynécologie Obstétrique, Centre Hospitalo Universitaire, Paris VI, France. PATIENTS: There were two groups of 28 couples. Women were < or = 35 years of age, with > or = 70% cleavage rate and at least four morphologically regular embryos. INTERVENTION: On the day of ET, either four fresh embryos were transferred (group 1) or two fresh embryos were transferred and two were frozen for later transfer (group 2). MAIN OUTCOME: Pregnancy rate and multiple pregnancy. RESULTS: The pregnancy rate was the same in the two groups with one-third of the high rank pregnancies in group 1 and no pregnancies in group 2. CONCLUSION: Only two fresh embryos need to be transferred in this selected population.

Adult↗
PubMed1994

HM17, a new polyene antifungal antibiotic produced by a new strain of Spirillospora.

An antifungal antibiotic (HM17) was obtained from a new isolate classified to the genus Spirillospora on the basis of its chemical and morphological properties. On solid media this antibiotic strongly inhibited the growth of strains of Fusarium oxysporum formae speciales albedinis, Botrytis cinerea, Gaeumaniomyces graminis and several other fungi known to be plant and human pathogens. Antifungal activity in culture collection strains of Spirillospora has not so far been reported. The u.v. absorption spectrum and physico-chemical characteristics place HM17 in the methylpentaene sub-group of polyene macrolides. HM17 is different from other known methylpentaenes. This is the first report of polyene production by a Spirillospora.

Actinomycetales↗