Biomedical subjects

Yury Verlinsky

Publications and source records attributed to Yury Verlinsky.

39 records · Page 3Linked to original sources

PubMedDate not supplied

Chromosomal abnormalities in a series of 6,733 human oocytes in preimplantation diagnosis for age-related aneuploidies.

Most chromosomal abnormalities originate from female meiosis and contribute significantly to pregnancy failures, particularly in women of advanced maternal age. A total of 8,382 oocytes were obtained in 1,297 IVF cycles from patients of advanced maternal age (mean 38.5 years). Following a standard IVF protocol, oocytes were tested following removal and fluorescence in-situ hybridization (FISH) analysis of the first (PB1) and second polar bodies (PB2), using probes specific for chromosomes 13, 16, 18, 21 and 22 (Vysis). FISH results were available in 67,33 (80.3%) oocytes tested, 3,509 (52.1%) of which were aneuploid, with the remaining 3,224 (47.9%) normal oocytes available for transfer. In all, 41.7% of oocytes had meiosis I errors, compared to 35.1% with meiosis II errors. Abnormalities in meiosis I were represented by extra chromatids in 15.4%, missing chromatids in 48.1%, missing chromosomes in 5.9%, extra chromosomes in 0.5%, and complex abnormalities in 30.1%. The proportions of abnormal oocytes with missing or extra chromatids in meiosis II were 36.6 and 41.2% respectively, with the remaining oocytes having complex abnormalities, involving missing or extra chromatids of different chromosomes (22.1%) following meiosis II. Overall, 41.8% oocytes had meiosis I, 30.7% meiosis II, and 27.6% both meiotic division errors. A total of 45.1% of the abnormal oocytes had complex errors, involving the same chromosome in both meiotic divisions (21.5%), or different chromosomes (78.5%), of which 74.8% were with abnormalities of two, and 25.2% with abnormalities of three chromosomes studied. Of 3,224 detected aneuploidy-free zygotes, 2,587 were transferred in 1,100 treatment cycles (2.35 embryos per transfer), resulting in 241 (21.9%) clinical pregnancies and 176 healthy children born, suggesting a positive clinical outcome following aneuploidy testing of oocytes in a group of IVF patients of average age 38.5 years.

Adult↗

PubMedDate not supplied

Meiotic and mitotic nondisjunction: lessons from preimplantation genetic diagnosis.

Direct testing of the outcome of the first and second meiotic divisions has become possible with the introduction of preimplantation genetic diagnosis (PGD) for aneuploidies. Testing of oocytes by fluorescent in situ hybridization (FISH) analysis of the first and second polar bodies showed that more than half of oocytes from the IVF patients aged 35 years and older had chromosomal abnormalities, which originated from errors in meiosis I or meiosis II, or both: 41.9% of oocytes were aneuploid after meiosis I and 37.3% aneuploid after meiosis II, with 29.1% of these oocytes having both meiosis I and meiosis II errors. As a result, one third of oocytes detected as normal after meiosis I contained the meiosis II errors, and two thirds of those with meiosis II errors were already abnormal following meiosis I. Although the rates of chromosomal abnormalities deriving from meiosis I and II were comparable, meiosis I errors predominantly resulted in extra chromosome (chromatid) material in oocytes, in contrast to a random distribution of extra and missing chromatids after meiosis II. The majority of meiosis I abnormalities were represented by chromatid errors, which seem to be the major source of chromosomal abnormalities in the resulting embryos. Approximately one third of aneuploid oocytes deriving from sequential errors in the first and second meiotic divisions resulted in a balanced karyotype, representing a possible phenomenon of "aneuploidy rescue" during the second meiotic division. However, the majority of the embryos resulting from such oocytes appeared to be abnormal for the same or different chromosome(s), or were mosaic, suggesting a possible predisposition of the resulting embryos to further mitotic errors. Although the origin of a high frequency of mosaicism at the cleavage stage is not sufficiently understood, the mosaic embryos may originate from the chromosomally abnormal oocytes, as a result of a "trisomy rescue" mechanism during the first mitotic divisions, which renders polar body FISH analysis to have important clinical value for reliable pre-selection of aneuploidy-free embryos for transfer.

Animals↗

PubMedDate not supplied

Fusion as the etiology of chimerism in monochorionic dizygotic twins.

In a dizygotic pregnancy within monochorionic placenta, findings consistent with chimerism were detected. Monochorionicity was confirmed by a combination of ultrasound, histological evaluation and DNA technology. Etiologic hypotheses are offered to explain this rare circumstance.

Amniocentesis↗