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Biomedical subjects

M Plachot

Publications and source records attributed to M Plachot.

At least 19 recordsLinked to original sources
PubMed2001

Chromosomal abnormalities in oocytes.

Since the beginning of in vitro fertilization (IVF), basic research has provided insight in the field of human reproduction, especially in genetics. Indeed, the contribution of chromosomal abnormalities to oocyte disorders and impaired embryonic development is now well known. Of oocytes that fail to fertilize after in vitro insemination, 26.5% have been found to be abnormal, with 13.3% showing hypohaploidy, 8.1% hyperhaploidy, 1.6% structural abnormalities and 3.5% diploidy. The total incidence of abnormalities seems to be correlated with the fertility status of the woman. It is higher in oocytes from women with tubal or unexplained infertility than in those from women whose husband's infertility is the sole cause of infertility in the couple. Although few oocytes recovered during natural cycles have been studied, gonadotropins, which are widely used to stimulate follicle growth and ovulation, do not increase the risk of abnormalities. The effect of maternal age on fetal aneuploidy, well documented at birth, has not been unambiguously shown to result from an increase in the frequency of aneuploid oocytes. Intra- and extra-follicular influences (perifollicular microvasculature, oxygenation, and the presence of residues from cigarette smoke) may disturb maturation, leading to immaturity and aneuploidy. Thus, oocyte meiosis is very sensitive to endogenous and exogenous factors that could result in oocytes with chromosomal abnormalities and therefore, abnormal zygotes.

Chromosome Aberrations↗
PubMed2000

ESHRE guidelines for good practice in IVF laboratories. Committee of the Special Interest Group on Embryology of the European Society of Human Reproduction and Embryology.

Education has always been a priority for the European Society of Human Reproduction and Embryology (ESHRE). Many efforts have been dedicated to promoting knowledge of techniques, procedures and strategies in order to ensure use of the highest quality practices in reproductive medicine. The need to develop a set of guidelines was a logical consequence that found its first expression in 1990, when Focus on Reproduction (vol. 1, pp. 10-38) published the first guidelines which were distributed among the membership. Five years later a new, more complete edition with several novel techniques and developments appeared in Human Reproduction (vol. 10, pp. 1246-1271). Both have proved to be invaluable references. Five more years have now passed. The necessity to produce current guidelines for good IVF laboratory practice has provided the strongest motivation. This originated from the increasing awareness that embryologists have a duty to prevent unintentional incidents that might result from poor practice in the laboratory. Therefore, the Embryology Special Interest Group (SIG) undertook to draw up guidelines aimed at giving support and guidance to the laboratory staff. All the aspects required to provide a safe working system were taken into consideration by members of the SIG and their effort produced this document. We hope that it will assist staff in achieving the best clinical outcome for their patients.

Cryopreservation↗
PubMed2000

Fertilization.

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Fertilization↗
PubMed2000

The blastocyst.

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Blastocyst↗
PubMed2000

Blastocyst stage transfer: the real benefits compared with early embryo transfer.

With the development of commercially available sequential media it is now possible to grow human embryos to the blastocyst stage without feeder cells. The transfer of blastocysts offers several advantages, the most important being synchronization of the embryos with the uterine endometrium and selection of the best quality embryos with a high implantation potential. This study was conducted to compare the efficiency of day 2 and day 5 transfer in a prospective randomized trial involving patients for whom embryo selection was possible (i.e. those with more than three embryos on day 2 following insemination). We obtained equivalent clinical pregnancy rates per cycle for day 2 (41.7%) and day 5 (38.8%) transfer, but fewer embryos were transferred on day 5 (2.24 versus 3.03). The implantation rates were 18.9% on day 2 and 24.1% on day 5. Selected patients with a good response to gonadotrophins (at least eight good quality metaphase II oocytes) may therefore benefit from blastocyst transfer by a reduction in the multiple pregnancy rate, provided no more than two (or even one) blastocyst is transferred.

Adult↗
PubMed1999

[In vitro maturation of human oocytes].

Maturation of human oocytes has 3 aspects: nuclear maturation leading to the extrusion of the 1st polar body, membranar maturation essential for the fixation of spermatozoa to the zona pellucida and penetration into the oocyte and cytoplasmic maturation which allows protein synthesis required for normal fertilisation and embryo development. In vitro maturation (IVM) of human oocytes may be appropriate in 5 different situations: for PCOs patients (natural cycle), in normoovulatory patients (natural cycles), for oocytes not exposed to hCG (stimulated cycle), for immature oocytes recovered in the course of an ICSI protocol (stimulated cycle) and after freezing-thawing of immature oocytes. Data from the literature show that in vitro maturation of human oocytes together with ICSI can lead to normal fertilisation, embryo development, pregnancies and the delivery of healthy children. However, the overall efficiency is still very low, indicating that embryo viability is compromised. The incidence of chromosome abnormalities in mature oocytes obtained after IVM is similar to that of oocytes recovered after in vivo maturation and therefore does not seem to be the reason of the failures. Conversely, protein synthesis abnormalities and abnormal calcium signalling might explain the poor viability of the embryos. The key factor seems to be cytoplasmic maturation not yet fully understood in the human.

Female↗
PubMed1999

[Intra-uterine insemination].

Artificial insemination has been proposed for a number of years in the treatment of unexplained or male factors related to infertility with very low results. In recent years, the association of intra-uterine insemination with gonadotropin ovulation induction has demonstrated its effectiveness and it is now the first treatment to propose in these cases before in vitro fertilization.

Female↗
PubMed1998

Chromosome methylation patterns during mammalian preimplantation development.

DNA methylation patterns were evaluated during preimplantation mouse development by analyzing the binding of monoclonal antibody to 5-methylcytosine (5-MeC) on metaphase chromosomes. Specific chromosome patterns were observed in each cell stage. A banding pattern predominated in chromosomes at the one-cell stage. Banding was replaced at the two-cell stage by an asymmetrical labeling of the sister chromatids. Then, the proportion of asymmetrical chromosomes decreased by one-half at each cell division until the blastocyst stage, and chromosomes became progressively symmetrical and weakly labeled. Our results indicate that chromosome demethylation is associated with each DNA replication and suggest that a passive mechanism predominates during early development.

5-Methylcytosine↗
PubMed1998

Cryopreservation in human assisted reproduction is now routine for embryos but remains a research procedure for oocytes.

Human embryo cryopreservation represents an indispensable extension of in-vitro fertilization (IVF) programmes as long as they are based upon the recovery of a large number of oocytes. The most widely used procedures include the cryopreservation of human zygotes or embryos in early cleavage, using 1,2-propanediol and sucrose as cryoprotectants. Our results over a 10 year period (1986-1995) on 5032 thawed cycles involving 14 222 stored embryos make it possible to appraise the results and the contribution of embryo freezing to assisted reproduction. Embryos survived the freeze-thaw process in 73% of cases leading to 4590 transfers of 2.2 embryos (91% of thawed cycles). The clinical pregnancy rate per transfer was 16%, the live birth rate 12%, and the rate of babies born alive per transferred embryo was 6%. Embryo freezing monitored 10 years later produced an average of 8% of additional births. By then, 86% of stored embryos had been thawed for transfer to patients. Destruction or donation were required for only 8% of all frozen embryos and there was no news from the parental couple in relation to almost 6% of embryos. The fate of the vast majority of embryos was decided during the first 5 years of storage. Blastocyst cryopreservation is making new strides, thanks to co-culture systems and embryo selection. Micromanipulation procedures seem to have little impact on the outcome of embryo freezing. Human oocyte freezing is again clinically applied. Indeed, much of the concern about injuries to the oocyte structures through the freeze-thaw process do not seem to be justified, and the problems with frozen-thawed oocyte fertilization has been overcome using intracytoplasmic sperm injection (ICSI). As long as oocyte in-vitro maturation is not well controlled, better results will probably be obtained with mature oocyte cryopreservation. Emerging methods include the freezing of immature oocytes, follicles and ovarian tissue.

Cryopreservation↗
PubMed1998

Incidence of sex chromosome abnormalities in spermatozoa from patients entering an IVF or ICSI protocol.

OBJECTIVE: The objective of this study was the determination of sex chromosome aneuploidy frequency in spermatozoa from patients included in an in vitro fertilization (IVF) or intra cytoplasmic sperm injection (ICSI) protocol. METHODS: Spermatozoa from nineteen patients, including patients with normal seminal parameters according to World Health Organization (WHO) criteria and patients exhibiting abnormal seminal parameters, were analyzed by dual color fluorescence in situ hybridization (FISH) for aneuploidies of the X and Y chromosomes. Our technique, using only probes for sex chromosomes and not for autosomes, does not discriminate between hyperhaploid and diploid sperm nuclei. The results were analyzed in two different ways: in relation to the semen status, denoted normal or abnormal and with regard to the ability of the sperm to fertilize oocytes when IVF or ICSI was performed. RESULTS: Abnormal semen showed a significant increase in the overall rate of sperm nuclei with XY, XX and YY sex chromosome complements, 1.59% compared to normal semen, 0.78% (p<0.02). Semen shown to be able to fertilize oocytes only by ICSI showed a higher incidence of XY-bearing spermatozoa, 1.26%, compared to semen able to fertilize oocytes by conventional IVF, 0.37% (p<0.001). The incidence of XX-or YY-bearing sperm nuclei was also significantly elevated in the ICSI group (0.25% XX, 0.50% YY) (p<0.02) as compared to the IVF group (0.06% XX, 0.16% YY). CONCLUSIONS: We concluded that infertile men requiring ICSI treatment showed a higher incidence of sex chromosome aneuploidy, due to meiosis I and II nondisjunction, in their spermatozoa as compared to men requiring IVF for reasons of predominantly female infertility.

Aneuploidy↗
PubMed1997

Influence of co-culture with established human endometrial epithelial and stromal cell lines on sperm movement characteristics.

The effects of co-culture of human spermatozoa with human immortalized endometrial cells - epithelial or stromal - on sperm movement characteristics, including hyperactivation, were studied using computer-assisted sperm analysis (CASA). Epithelial and stromal cell types could be separated following 8-10 days of culture of endometrial cells originating from human biopsies. Both cell types were immortalized by the SV 40 large T antigen. Co-incubation of sperm with epithelial and stromal monolayers enhanced the rate of hyperactivation: 24.9% (P <0.05) and 17.8% (P = 0.05) versus 9.5% as control, respectively, whereas the majority of motility parameters remained unchanged. Conditioned media had no effect upon sperm parameters, including hyperactivation. Co-incubation with either monolayer was able to maintain sperm motility over a longer period than incubation in control medium alone. In four patients whose spermatozoa did not exhibit hyperactivation, co-incubation with epithelial cells, but not conditioned medium, allowed normal rates of hyperactivation (range: 6.9-15.6%).

Antigens, Polyomavirus Transforming↗