Biomedical subjects

M Bras

Publications and source records attributed to M Bras.

23 records · Page 2Linked to original sources

PubMed1991

The effects of endotoxins on gametes and preimplantation embryos cultured in vitro.

Culture media used for human in-vitro fertilization (IVF) can be contaminated with bacterial endotoxins. All five tested types of commercially available albumin, sometimes used as a protein supplement to IVF media, were shown to contain endotoxins in varying concentrations. Endotoxins are suspected to cause embryo fragmentation and low pregnancy rates in human IVF. However, human sperm viability and the IVF of mouse oocytes and subsequent culture of the zygotes were shown to be unaffected by relatively high endotoxin concentrations. Therefore these techniques cannot be used as quality control assays to detect endotoxins in the IVF culture media.

Animals↗

PubMed1991

Evaluation of human sperm morphology using strict criteria after Diff-Quik staining: correlation of morphology with fertilization in vitro.

New, very strict criteria were used after Diff-Quik staining for evaluating sperm morphology. The results of morphology scoring were correlated with the fertilization rate in vitro. Semen samples from 64 men participating in an in-vitro fertilization programme were used for this study. All men had to have a sperm concentration of greater than or equal to 20 million/ml and a progressive motility of greater than 30%. The morphology evaluation using strict criteria was performed on the same aliquot of semen as that used for in-vitro insemination. If strict criteria showed that normal morphology was less than or equal to 4%, the fertilization rate per oocyte was 23%. If normal morphology was greater than or equal to 11%, 77% fertilization occurred. For proportions of normal morphology between 4 and 11%, the fertilization rate per oocyte was 59% (P less than 0.000001). Among all these morphology groups, classical semen parameters, such as the mean volume, the mean concentration and the mean motility, did not differ significantly, except for the morphology evaluation using WHO criteria. The correlation with fertilization was better for morphology evaluation using strict criteria than for WHO. In conclusion, the method of evaluating sperm morphology based on very strict criteria allows a more accurate prediction of the chance of fertilization in vitro. Further studies should be done to establish the most appropriate cut-off points for severely impaired, intermediate and high fertilization rates.

Azure Stains↗

PubMed1991

Immaturity and aneuploidy in human oocytes after different stimulation protocols.

OBJECTIVE: To study immaturity and aneuploidy in human oocytes after two different stimulation protocols. DESIGN: Retrospective. SETTING: Outpatient IVF clinic/laboratory. PATIENTS: One hundred forty-three patients of whom 65 were stimulated with clomiphene citrate (CC)/human menopausal gonadotropin (hMG) and 78 were stimulated with gonadotropin-releasing hormone agonist (GnRH-a)/hMG. Only patients with at least one oocyte unfertilized were included in this study. RESULTS: Stimulation with GnRH-a/hMG, as compared with CC/hMG stimulation, resulted in larger numbers of oocytes (P less than 0.00001), a higher fertilization rate (P less than 0.02), and oocyte retrieval at a later average cycle day (P less than 0.000005). Cytogenetic findings of immaturity were observed in 33.9% of unfertilized oocytes after CC/hMG stimulation, compared with only 17.8% after GnRH-a/hMG stimulation (P less than 0.0005). Aneuploidy findings were the same for both groups. CONCLUSION: In GnRH-a/hMG stimulation, oocytes approach the normal day of ovulation more closely. This may allow for better oocyte maturation and higher fertilization and pregnancy rates.

Aneuploidy↗

PubMed1990

Human in vitro fertilization using spermatozoa capacitated in hyperosmotic media.

In two separate prospective randomized series of 38 and 16 attempts of human in vitro fertilization (IVF), respectively, the fertilizing abilities of human spermatozoa capacitated in hyperosmotic media and in normosmotic medium were compared. Oocytes from each IVF attempt were divided into two equal groups and inseminated with spermatozoa incubated for 2 h in medium with an osmolality of 285 mosm/kg or in hyperosmotic medium of 315 (first experiment) or 345 mosm/kg (second experiment). The fertilizing capacity of the spermatozoa was not affected by incubation in medium of 315 mosm/kg as compared to spermatozoa incubated in medium of 285 mosm/kg. However, the fertilizing capacity of the spermatozoa incubated in medium of 345 mosm/kg was significantly reduced. The present study indicates that there is no advantage in the use of hyperosmotic media of 315 or 345 mosm/kg for capacitation of spermatozoa in human IVF.

Culture Media↗

PubMed1989

Cytogenetic analysis of in vitro fertilization (IVF) failures.

Cytogenetic studies were carried out on 150 oocytes obtained in a human in vitro fertilization (IVF) program. Although all cells lacked signs of fertilization at light microscopy, 46 (30.7%) appeared to show cytological evidence of fertilization. At least one-third of these cells (with development arrested before first cleavage) had chromosomal aberrations. An aneuploidy rate of 35% was found in unfertilized oocytes. The results of this study explain some of the fertilization failures and of the failures of postfertilization development.

Aneuploidy↗