Biomedical subjects

M Durban

Publications and source records attributed to M Durban.

5 recordsLinked to original sources

PubMed1999

Approximate standard errors in semiparametric models.

We consider semiparametric models with p regressor terms and q smooth terms. We obtain an explicit expression for the estimate of the regression coefficients given by the back-fitting algorithm. The calculation of the standard errors of these estimates based on this expression is a considerable computational exercise. We present an alternative, approximate method of calculation that is less demanding. With smoothing splines, the method is exact, while with loess, it gives good estimates of standard errors. We assess the adequacy of our approximation and of another approximation with the help of two examples.

Agriculture↗

PubMed1998

Chromosome studies in first polar bodies from hamster and human oocytes.

Most studies on preconception diagnosis published so far have used polymerase chain reaction (PCR) analysis to identify single gene defects. Although fluorescent DNA probes have been used to obtain a partial cytogenetic diagnosis of aneuploidies in first polar bodies without defined chromosome structures, the analysis of structural chromosome anomalies in the interphase nucleus is not adequate. We describe a procedure to obtain first polar body chromosome complements from hamster and human oocytes. In 63.6% (105 of 165) of hamster first polar bodies the chromosome complement showed a defined chromosome morphology and in 94.1% (16 of 17) of human oocytes fixed after follicular puncture it was possible to obtain high quality, well spread chromosome complements. First polar body chromosomes are fuzzy and shorter than oocyte chromosomes, but fluorescent in-situ hybridization results obtained in human first polar bodies clearly show that it is possible to detect whole chromosomes, centromeres and unique sequences, including the terminal regions of small chromosomes. This suggests that in fresh oocytes, DNA loss resulting from apoptotic chromosome fragmentation has not yet occurred. Using the procedure described, first polar bodies could be used to analyse the meiotic segregation of maternal structural abnormalities and to detect numerical chromosome anomalies in humans.

Aneuploidy↗

PubMed1992

A mobile crisis program: collaboration between emergency psychiatric services and police.

An emergency psychiatry-mobile crisis program was established in 1987 in Charleston, South Carolina, linking professionals from the mental health center, the university, and the local police department. The program has two goals: to provide emergency psychiatric services to persons in the community and to train psychiatric residents in crisis intervention. Mental health staff act as consultants to the police in some situations, and in others the police provide security. The authors describe the development of the collaboration with police and important features of the program. Three cases illustrate how such collaboration can be of mutual benefit and can save lives.

Adult↗

PubMedDate not supplied

Preimplantation genetic screening and human implantation.

In recent years, preimplantation genetic screening (PGS) has been used and recommended to increase the implantation rate in older women or in couples with previous assisted reproduction (ART) failures, to try to increase pregnancy rates in couples with recurrent abortions, to prevent the transmission of chromosome anomalies to the offspring of carriers of balanced chromosomal rearrangements, or even to try to decrease the incidence of trisomic births in older women. So far, PGS has contributed to increase the implantation rate in older women; however, the rate of clinical pregnancies has not increased, either in older women or in couples with previous ART failures. In couples with recurrent abortions, the pregnancy rate seems to increase, but only when the woman is young (< or =35). In carriers of balanced reorganizations, the prognosis is poor. Attempts to decrease the birth of trisomic children to older women are difficult to evaluate. This absence of relevant results is not related to the technique itself, which is quite safe, but to other still largely unknown factors.

Abortion, Habitual↗

PubMedDate not supplied

PGD in female carriers of balanced Robertsonian and reciprocal translocations by first polar body analysis.

Preimplantation genetic diagnosis (PGD) using the first polar body (1PB) is a modality of PGD that can be used when the woman is the carrier of a genetic disease or of a balanced chromosomal reorganization. PGD using 1PB biopsy in carriers of balanced chromosome reorganizations has not become generalized. Here, we describe our experience based on the analysis of unfertilized or fresh, non-inseminated control oocytes, by fixing separately the 1PB and the corresponding oocyte, and on the study of six clinical cases of PGD using 1PB biopsy (four Robertsonian translocations and two reciprocal translocations). In fresh oocytes, the chromosome morphology of the 1PB was well preserved, and the results were always concordant for each oocyte-1PB pair. This indicates that the 1PB can be reliably used for the diagnosis of chromosome reorganizations. In these studies the technical problems encountered when performing PGD using 1PB biopsies for chromosome studies are also addressed. Three different strategies of 1PB biopsy (laser beam, partial zona dissection and acid Tyrode's) and two different protocols (intracytoplasmic sperm injection before or after 1PB biopsy) and their effect on the percentage of oocytes diagnosed and the fertilization rate, are discussed. In reciprocal translocation cases, published in the literature or studied by us, in which at least nine oocytes had been diagnosed, a correlation has been found between the frequency of nondisjunction observed and the theoretical recombination rate. To date, PGD by 1PB analysis alone or combined with blastomere biopsies in female carriers of chromosomal rearrangements has been used in 18 cases, with a further six cases reported here. A total of 325 cumulus-oocyte complexes have been obtained, of which 294 were biopsied and 224 were diagnosed. A total of 52 embryos was transferred, 19 of which implanted and 17 produced full-term pregnancies.

Adult↗