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Biomedical subjects

B Lefevre

Publications and source records attributed to B Lefevre.

16 recordsLinked to original sources
PubMed2006

Multiparameter assessment of mouse oogenesis during follicular growth in vitro.

Comparison of oocyte development within the follicle in vitro and in vivo has a major impact on research into ovarian physiology and clinical practice. Despite major differences in ovarian physiology between rodents and humans, mice provide a useful model for studies of the endocrine and paracrine mechanisms controlling follicular development. In this study, early preantral follicles were isolated from 12-day-old mice and cultured individually in microdrops under oil during 6, 9 or 12 days. Taking into account previous observations, several oocyte criteria (diameter, chromatin configuration, transcriptional activity, intracytoplasmic calcium signalling and ability to undergo meiosis) were assessed to check that the development pattern of oocytes during follicle growth in vitro was similar to that already observed for oocytes developing in vivo, and that they reached the fertilizable oocyte stage. Results indicate that, during the 12-day-culture period, the oocytes grew until 74.3 +/- 4.2 microm, they became transcriptionally quiescent with a surrounded nucleolus (SN) chromatin organization, 50% of them exhibited regular calcium signals and 73.4% of them resumed meiosis. These data demonstrate that the protocol used generates oocytes with characteristics similar to oocytes allowed to mature fully in vivo and that it could be useful to set up the experimental culture of human ovarian follicles.

Animals↗
PubMed2004

Intrusion and extrusion of water in hydrophobic mesopores.

We present experimental and theoretical results on intrusion-extrusion cycles of water in hydrophobic mesoporous materials, characterized by independent cylindrical pores. The intrusion, which takes place above the bulk saturation pressure, can be well described using a macroscopic capillary model. Once the material is saturated with water, extrusion takes place upon reduction of the externally applied pressure. Our results for the extrusion pressure can only be understood by assuming that the limiting extrusion mechanism is the nucleation of a vapor bubble inside the pores. A comparison of calculated and experimental nucleation pressures shows that a proper inclusion of line tension effects is necessary to account for the observed values of nucleation barriers. Negative line tensions of order 10(-11) J m(-1) are found for our system, in reasonable agreement with other experimental estimates of this quantity.

Journal Article↗
PubMed2004

[Pindborg tumor: a poorly differentiated form without calcification].

BACKGROUND: Pindborg tumor is a rare benign epithelial calcified odontogenic tumor. Radiological diagnosis is generally suspected because of the presence of calcifications. CASE REPORT: A 61-year-old man presented a polymorphous Pindborg tumor of the anterior maxillary. The diagnosis was hindered due to the nonspecific radiographic image and the lack of calcification. Pathology provided the positive diagnosis of poorly-differentiated young odontogenic epithelial tumor. DISCUSSION: Pindborg tumor is a rare lesions usually found in the posterior mandibular bone. Calcification is a characteristic feature. There are two historical forms, a squamous form with very favorable outcome and a clear-cell form with less favorable prognosis.

Diagnosis, Differential↗
PubMed2001

Accumulation of the proteolytic marker peptide ubiquitin in the trophoblast of mammalian blastocysts.

Ubiquitination is a universal protein degradation pathway in which the molecules of 8.5-kDa proteolytic peptide ubiquitin are covalently attached to the epsilon-amino group of the substrate's lysine residues. Little is known about the importance of this highly conserved mechanism for protein recycling in mammalian gametogenesis and fertilization. The data obtained by the students and faculty of the international training course Window to the Zygote 2000 demonstrate the accumulation of ubiquitin-cross-reactive structures in the trophoblast, but not in the inner cell mass of the expanding bovine and mouse blastocysts. This observation suggests that a major burst of ubiquitin-dependent proteolysis occurs in the trophoblast of mammalian peri-implantation embryos. This event may be important for the success of blastocyst hatching, differentiation of embryonic stem cells into soma and germ line, and/or implantation in both naturally conceived and reconstructed mammalian embryos.

Animals↗
PubMed1997

Effect of laser irradiation on latency of herpes simplex virus in a mouse model.

Low power Laser irradiation is used in medical practice for different indications. Several firms which commercialise Laser claim that Laser irradiation may be beneficial towards Herpes virus pathogenicity. We observe that, in the ear experimental model of HSV latency [3], repeated exposure to infrared Laser radiation of cervical ganglia following HSV inoculation appears to specifically hinder the establishment of virus latency in mouse.

Animals↗
PubMed1993

Effects of gonadotrophin-releasing hormone agonists (GnRHa) on follicle and oocyte quality.

This review summarizes the main clinical and research studies on direct and indirect effects of gonadotrophin-releasing hormone agonists (GnRHa) on follicles and oocytes in animals and humans. There is evidence for extra-pituitary actions of GnRHa, especially on follicle growth, follicular steroidogenesis, and oocyte meiotic maturation. Different effects have been reported from using various GnRHa molecules. However, a direct effect of GnRHa on oocyte quality in gonadotrophin stimulated cycles has not yet been demonstrated. Observed high pregnancy rates per ovarian puncture in in-vitro fertilization cycles using GnRHa, at least in long protocols, might result from higher numbers of oocytes recovered following administration of large doses of gonadotrophins, despite the fact that these oocytes may have a lower ability to fertilize and grow. Although there are obvious clinical advantages of using GnRHa for ovarian stimulation, more studies are needed to clarify the effects of these treatments at ovarian and uterine levels.

Animals↗
PubMed1984

Time relationships between basal body temperature and ovulation or plasma progestins.

The basal body temperature (BBT) curve and the estimated time of ovulation, defined by the onset of gonadotropin preovulatory discharge, were analyzed in 38 spontaneous cycles. The BBT nadir was usually located at the beginning of the luteinizing hormone surge, and the first high point was 8 hours after ovulation, which was itself usually at the time when the temperature passed 37 degrees C. This temperature rise was related to the increases in plasma progesterone and 17-hydroxyprogesterone with 24 to 36 hours' delay. The BBT was found to be an unreliable technique for precise ovulation timing but would be of use if the clinical precision required for the diagnosis of ovulation were less.

17-alpha-Hydroxyprogesterone↗
PubMed1981

Inhibin-like activity and steroid content in human follicular fluid during the periovulatory period.

Inhibin-like activity as well as estradiol-17 beta and progesterone content were assayed in human follicular fluid obtained at different stages of the periovulatory period. Between the start of the midcycle estrogen surge in plasma and the subsequent gonadotrophin peak, follicular fluid was found to contain similar levels of estradiol-17 beta and progesterone (8.2 pmol/microliter) and to induce a marked (44%) inhibition of gonadotrophin-releasing hormone-stimulated release of FSH. The midcycle gonadotrophin peak was characterized by a drop in estradiol-17 beta levels and a tripling in progesterone levels, whereas inhibin-like activity fell to almost half the previous value.

Adult↗