Biomedical subjects

R R Angell

Publications and source records attributed to R R Angell.

23 records · Page 2Linked to original sources

PubMed1983

Chromosome abnormalities in human embryos after in vitro fertilization.

In vitro fertilization and embryo transfer is now an established treatment for certain forms of human infertility. High success rates have been reported following oocyte recovery and fertilization in vitro, the only major remaining difficulty being the high failure rate (80%) of implantation after replacement of the embryo into the mother. One possible reason for this failure of implantation is that some embryos may carry a lethal chromosome abnormality which does not allow development beyond the preimplantation stage. The need for information on the chromosomal status of early embryos fertilized and developed in vitro is recognized but two reported attempts to examine them have met with technical problems. Here we describe a method for examining chromosomes in 8-cell human embryos. Although we have made complete chromosome analyses for only three oocytes, our findings are surprising in that two of the three embryos were chromosomally abnormal. Data on the DNA content of the nuclei in a further eight cases showed that approximately 20% overall may be haploid.

Age Factors↗

PubMed1982

Clinical and cytogenetic aspects of X-chromosome deletions.

Karyotype/phenotype correlations in six non-mosaic patients with dysgenetic ovaries and partial deletions of the X-chromosome (three patients with short arm, and three with long arm deletions) are presented and the pertinent literature is analysed. It would appear that functioning ovarian tissue is present more often in patients with a short arm deletion than in those with a deleted long arm. This may represent a difference in the strength of two sets of controlling factors, but it can also be related to break point position. This in turn may be misinterpreted due to the difficulty in distinguishing between terminal and interstitial deletions in the long arm. Stature may be a heterochromatic effect, but if specific genetic factors influencing stature exist, then they would appear to be situated mostly on the short arm of the X-chromosome, although some 'statural determinants' occur also on the long arm and could be located rather close to the centromere. Deletions of the short arm of the X-chromosome were almost always associated with some features of the Turner phenotype, and could possibly be related to a gene dosage effect.

Adolescent↗

PubMed1978

The origin of human triploids.

A series of 26 triploid foetuses was ascertained in a survey of spontaneous abortuses and the origin of the additional haploid complement determined in 21 of them by the study of foetal and parental heteromorphisms. In 17 the additional haploid set was paternal in origin, in 3 it was maternal in origin and in one the parental origin could not be determined. The best fit for the data using a maximum-likelihood method was that 66.4% of the triploids were the result of dispermy, 23.6% the result of fertilization of a haploid ovum by a diploid sperm formed by failure of the first meiotic division in the male and 10% the result of a diploid egg formed by failure of the first maternal meiotic division. The possible sources of error inherent in the technique are reviewed and our results compared with previously published data.

Chromosomes, Human↗

PubMed1978

Lateral asymmetry in human constitutive heterochromatin: frequency and inheritance.

The relative frequencies and types of lateral asymmetry found in chromosomes 1, 9, 15, 16, and the Y were determined. The pattern of asymmetry is simple in chromosomes 15, 16, and the Y but compound in 1 and possibly also 9. The pattern of compound lateral asymmetry is a stable heteromorphism inherited in a simple Mendelian way and is an efficient morphological discriminator between the members of the no. 1 chromosome pair.

Chromosomes, Human↗

PubMed1975

Lateral asymmetry in human constitutive heterochromatin.

Human lymphocytes were grown for one replication cycle in BrdU, stained with 33258 Hoechst, exposed to UV light and subsequently treated with 2 x SSC and stained with Giemsa. This technique differentially stains the constitutive heterochromatin of chromosomes 1, 9, 15, 16, and the Y. In the heterochromatin of chromosome 9 both sister chromatids stained darkly and symmetrically but in the other four chromosomes the heterochromatin showed lateral asymmetry, one chromatid being darkly stained while its sister chromatid was a pale or paler than the rest of the chromosome. The lateral asymmetry is presumed to reflect an underlying asymmetry in distribution of thymine between the two strands of the DNA duplex in the satellite DNA component of the chromosomes. In some number 1 chromosomes compound lateral asymmetry was seen; darkly staining material was present on both sister chromatids although at any given point lateral asymmetry was maintained so that if one chromatid stained darkly the corresponding point on the sister chromatid was very pale. The pattern of compound lateral asymmetry varied among the number 1 chromosomes studied but was constant for any one homologue from one individual. This technique reveals a previously unsuspected type of polymorphism within the constitutive heterochromatin of man.

Cells, Cultured↗