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Biomedical subjects

G Bertin

Publications and source records attributed to G Bertin.

34 records · Page 2Linked to original sources
PubMed1995

Effects of live Saccharomyces cerevisiae cells on zoospore germination, growth, and cellulolytic activity of the rumen anaerobic fungus, Neocallimastix frontalis MCH3.

The effects of a live yeast strain of Saccharomyces cerevisiae have been investigated on zoospore germination, metabolism, and cellulolytic activity of the anaerobic rumen fungus Neocallimastix frontalis MCH3. The addition of yeast cells to a vitamin-deficient medium stimulated the germination of fungal zoospores, increased cellulose degradation and hydrogen, formate, lactate, and acetate production. Responses depended on the concentration of yeast cells added and on their viability. Yeast supplementation provided vitamins such as thiamine, which is essential for fungal growth and activity. These results demonstrate that yeasts could enhance plant cell wall colonization by N. frontalis. With certain diets, yeasts could therefore be a good tool to optimize the microbial degradation of lignocellulosic materials, but more research is needed to understand their mechanisms of action, so that they can be used with maximum efficiency as feed supplements.

Animals↗
PubMed1995

In vitro H2 utilization by a ruminal acetogenic bacterium cultivated alone or in association with an archaea methanogen is stimulated by a probiotic strain of Saccharomyces cerevisiae.

The effects of a live strain of Saccharomyces cerevisiae on hydrogen utilization and acetate and methane production by two hydrogenotrophic ruminal microorganisms, an acetogenic bacterial strain and an archaea methanogen, were investigated. The addition of yeast cells enhanced by more than fivefold the hydrogenotrophic metabolism of the acetogenic strain and its acetate production. In the absence of yeasts, and in a coculture of the acetogen and the methanogen, hydrogen was principally used for methane synthesis, but the presence of live yeast cells stimulated the utilization of hydrogen by the acetogenic strain and enhanced acetogenesis.

Acetates↗
PubMed1992

Usefulness of partial dissection of the zona pellucida in a human in-vitro fertilization programme.

The influence of partial zona dissection (PZD) on the fertilization rate was studied in 34 couples with a history of fertilization failure and/or severe sperm deficiency. Overall, PZD improved the rate of monospermic fertilization compared to controls (41/254 versus 6/111: P less than 0.001) and fertilization was achieved in 50% of cases. However, the results differed according to the seminal characteristics. In 10 couples with at least two in-vitro fertilization (IVF) trials entailing total fertilization failure and with semen defined as normal, PZD did not significantly improve the monospermic fertilization rate (6/44 in the PZD group versus 2/39 among controls). A benefit related to PZD was evident in 33 attempts with severe sperm deficiency. In this group, only four of 72 unmanipulated control oocytes were fertilized but the monospermic fertilization rate was 14.6% for PZD oocytes. The rates of polyspermy were 40% and 14.6% in the groups with normal and abnormal semen parameters respectively. Of 33 trials with defective spermatozoa, 20 reached the stage of embryo transfer and three pregnancies were obtained, of which one aborted at 9 weeks.

Female↗
PubMed1982

On the dynamical basis of the classification of normal galaxies.

Some realistic galaxy models have been found to support discrete unstable spiral modes. Here, through the study of the relevant physical mechanisms and an extensive numerical investigation of the properties of the dominant modes in a wide class of galactic equilibria, we show how spiral structures are excited with different morphological features, depending on the properties of the equilibrium model. We identify the basic dynamical parameters and mechanisms and compare the resulting morphology of spiral modes with the actual classification of galaxies. The present study suggests a dynamical basis for the transition among various types and subclasses of normal and barred spiral galaxies.

Journal Article↗
PubMed1977

Discrete spiral modes in disk galaxies: Some numerical examples based on density wave theory.

Discrete growing spiral modes are calculated, on the basis of principles of stellar dynamics, according to the recently developed asymptotic theory of density waves for spiral structure in galaxies. From the growth rates obtained, it appears likely that several spiral modes coexist in a given disk galaxy. General properties of these modes are described for two galaxy models, and some of their important observational implications are discussed.

Journal Article↗
PubMedDate not supplied

Fate of Levucell SC I-1077 yeast additive during digestive transit in lambs.

The fate of a live yeast strain, which was used as a feed additive for ruminants (Levucell SC I-1077), was studied during digestive transit in two gnotoxenic lambs reared in a sterile isolator. The number of live yeast cells were counted in the rumen and in faeces after a single administration or a daily feeding of 100 mg of Levucell SC. If the supplement was not renewed, the live yeast cells persisted in the rumen for approximately 30 h at a level close to the initial value. They were then gradually cleared. They began to be excreted with the faeces approximately 8 h after their consumption and were no longer detected after 102 h. Yeast additives did not colonize the rumen. As 17 to 34% of yeast cells remained alive during their transit through the digestive tract, their effect might extend beyond the rumen the post-ruminal compartments.

Animals↗
PubMedDate not supplied

The effect of Saccharomyces cerevisiae and Aspergillus oryzae on the digestion of the cell wall fraction of a mixed diet in defaunated and refaunated sheep rumen.

The objective of this study was to determine the effect of two probiotics, Saccharomyces cerevisiae (SC) and Aspergillus oryzae (AO), without their culture medium, on the digestion of plant cell wall components in sheep that had been successively defaunated and refaunated. Six sheep fitted with large rumen cannulae were used to study 1) defaunated sheep with no probiotic, 2) defaunated sheep with SC or AO, 3) refaunated sheep with no probiotic, 4) refaunated sheep with SC or AO. The apparent digestibility of the plant cell walls was not altered (P > 0.05) by the probiotics in defaunated sheep but was increased (P < 0.05) with SC (+16%) in refaunated sheep. Simultaneously, SC stimulated the growth of the protozoal population in the rumen. As noted in most previous experiments, the positive effect of the presence of protozoa on plant cell wall digestion (P < 0.001) was confirmed here. The effect (P > 0.05) of SC or AO on in situ ADF digestion was either not significant or negative in defaunated rumens, whereas it became positive in refaunated rumen after a residence time of 12 h. The improvement of in situ ADF digestion due to the presence of protozoa was significant (P < 0.05 for NDF; P < 0.001 for ADF). However, we could not determine whether this was a direct effect of protozoa or an indirect effect operating via bacteria. The limits of the nylon bag technique for evaluating the microbial activity are discussed in relation to the ability of protozoa to enter and grow in the bags, and the pH regulation inside the bags. The pH values below 5.5 noted inside the bags can significantly alter the bacterial and protozoal populations and limit the validity of the technique. SC increased (P < 0.05) the specific activity of CMCase and xylanase of the solid-adherent bacteria (SAB) isolated from the rumen digesta of refaunated sheep. Stimulation of both the bacterial activity and protozoa numbers could explain the positive effect of SC on cell wall digestion in the rumen since the modelling of marker excretion in faeces showed that the ruminal mean retention time of hay measured from the model of Danhoa et al. was not modified (P > 0.05) by either refaunation or the presence of probiotics. AO increased (P < 0.05) the total retention time of the solid particles in the whole digestive tract and increased the ruminal liquid volume in the refaunated animals but it had no effect on the protozoa population or on the polysaccharidase activity of the SAB, which could explain the absence of effect of AO on the total digestibility of plant cell walls. Both probiotics decreased the liquid turnover in defaunated rumens (P < 0.05) but neither had any effect (P > 0.05) on this parameter after refaunation. The improvement of plant cell wall degradation in the whole digestive tract is probably due to a stimulation of digestion at the rumen level as indicated by the higher activity of the SAB in rumen digesta and the growth of protozoa.

Animal Feed↗
PubMedDate not supplied

Enumeration of probiotic bacilli spores in animal feed: interlaboratory study.

Fourteen out of 17 laboratories completed an interlaboratory study comparing 2 pretreatment protocols of feed samples containing authorized probiotic bacilli spores. Both methods used tryptone soy agar for enumeration. Pretreatment A involved preparation of a suspension of the feed sample in 50% ethanol. For pretreatment B, the sample was suspended in peptone salt solution and heated at 80 degrees C for 10 min. Each laboratory analyzed 12 samples (6 per pretreatment), which represented duplicates of a high (10(9) colony-forming units [CFU]/g) and low (10(5) CFU/g) level of bacilli spores or a blank that contained vegetative probiotic bacteria only. For pretreatment A, the repeatability relative standard deviation (RSD(r)) was 2.9% for the low level and 2.5% for the high. The reproducibility relative standard deviation (RSDR) values were 7.8 and 5.9%, respectively. Pretreatment B revealed RSD(r) values of 1.1 and 1.0%, and RSDR values of 5.8 and 3.4%, respectively. The heat treatment (pretreatment B) of feed samples had better precision data, resulted in higher viable bacilli counts, and was more effective in deactivating vegetative background flora. It is therefore recommended for adoption for official control purposes and for CEN and ISO standards.

Animal Feed↗
PubMedDate not supplied

Techniques of sperm selection, improvement and separation in an in vitro fertilization program.

The Authors present a review of the various techniques used for improving the fertility potential of sperm within the context of an in vitro fertilization (IVF) program. After a brief description of the mechanisms leading to normal in vivo fertilization, they discuss the different methods of selecting and improving sperm for IVF. They conclude that centrifugation on discontinuous Percoll gradients would seem to be the most efficient separation method from all points of view, while the addition of pharmacological agents to improve sperm quality and motility lead to extremely unsatisfactory results.

Cell Separation↗
PubMedDate not supplied

Within-subject variations of sperm parameters and their importance in an in vitro fertilization program.

Spermiograms of 150 males were assessed, in view of studying them before an in vitro fertilization attempt. Within subject variations were determined with regard to sperm count and spermatozoal motility pattern. Ultimately these results were compared to the seminological parameters studied at the time of the in vitro-fertilization attempt. Overall results showed a clear drop in semen parameters at the time of egg retrieval. This drop was more marked when semen parameters were amongst the higher values at the start.

Humans↗
PubMedDate not supplied

Assisted fertilization with epididymal spermatozoa.

In vitro fertilization is used for several years as a technique for resolving infertility problems due to moderate or severe oligospermia. More recently, techniques of micro-insemination of oocytes have also become available for cases of extremely severe oligospermia which cannot be resolved by classical I.V.F. Nevertheless, although these particular techniques have already led to results which have gone far beyond initial hopes, they are not able to resolve all cases of male sterility. There are indeed many situations of excretory azoospermia associated with normal spermatogenesis; the spermatozoa remain trapped in a more or less extensive part of the epididymis because its passage is blocked, either because of post-infectious sclerosis, or of agenesis of a variably extensive area of the Wolffian duct. Post-inflammatory occlusions can be treated by micro-surgery, whereas in cases of agenesis, attempts to collect spermatozoa by means of an artificial spermatocele have led to far too many failures, and this technique has now been abandoned, in spite of some successful pregnancies. The extraordinary development of in vitro fertilization techniques has led to the logical idea that it might be possible to collect epididymal spermatozoa for oocyte fertilization.

Epididymis↗