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Biomedical subjects

S E Bloom

Publications and source records attributed to S E Bloom.

At least 73 records · Page 4Linked to original sources
PubMed1976

Human nucleolus organizers: the satellites or the stalks?

A silver-staining technique specific for demonstrating nucleolus organizer regions (NOR) showed that the achromatic stalks of the 10 acrocentric autosomes of the human complement represent the NORs. Some variability in number of stained stalks is observed from cell-to-cell and from individual-to-individual. The silver-stained masses may extend beyond the stalks and cover the satellites, especially in chromosomes with short stalks or minute satellites.

Cell Nucleolus↗
PubMed1975

Visualization of nucleolar organizer regions im mammalian chromosomes using silver staining.

A simple ammoniacal silver staining procedure, designated Ag-AS, differentially stains the chromosomal locations of ribosomal DNA in certain mammalian species. This was critically demonstrated by Ag-AS staining of the nucleolus organizer regions in karyotypes of the same species and cell lines used for locating the ribosomal cistrons by DNA/RNA in situ hybridization. With Ag-AS, silver stained NORs (Ag-NORs) are visualized as black spherical bodies on yellow-brown chromosome arms. Ag-NORs were visualized throughout mitosis at the secondary constrictions in the rat kangaroo, Seba's fruit bat, Indian muntjac, and Rhesus monkey. The Chinese hamster and cattle have telomeric Ag-NORs, the mouse subcentromeric Ag-NORs, and the field vole Ag-NORs as minute short arms or choromosomal satellites. Ag-NORs occur at both secondary constrictions and at telomeres in the cotton rat. Variability in Ag-NOR pattern included differences in the number of Ag-NORs per cell within a cell population, size of Ag-NORs among chromosomes of a complement, and presence of Ag-NOR on particular chromosomes in two cell lines of the Chinese hamster. The available cytochemical data suggest that the Ag-AS reaction stains chromosomal proteins at the NOR rather than the rDNA itself.

Animals↗
PubMed1975

Differential fluorescence of sister chromatids in chicken embryos exposed to 5-bromodeoxyuridine.

Differential fluorescence of sister chromatids (SCD) and sister chromatid exchanges (SCE) were visualized in chromosomes obtained directly from growing chicken embryos. SCD was obtained by exposing 3-day embryos to BrdU (12.5-50 mug) in ovo for 26 hours and staining air dried chromosome preparations with 33258 Hoechst. Bright, stable fluorescence and continued SCD were achieved if slides were mounted in McIlvaine's pH 4.4 buffer. Embryo growth, mitotic activity and gross chromosome morphology were not adversely altered by the BrdU treatments. The SCE rate was estimated to be 0.07 SCEs per macrochromosome and 0.75 SCEs per metaphase for two cell cycles.

Animals↗
PubMed1975

Umbra limi: a model for the study of chromosome aberrations in fishes.

Due to the lack of information available on the effect of various clastogenic agents on the chromosomes of fishes, an in vivo cytogenetics model system was developed. The central mudminnow, Umbra limi, was chosen fro this study because of its ideal karyotype consisting of 22 large meta- and submetacentric chromosomes. Various organs of the fish were investigated to determine their suitability for chromosome preparations. The tissues of the intestines, stomach, kidneys, and gills were found to be the most suitable for clastogenic studies. Phase contrast observations were made on the chromosomes of control mudminnows and mudminnows exposed to 325 R of X-radiation. The control rate of spontaneous chromosome aberrations was found to be low (about 0.03%). In contrast, fish exposed to 325 R of X-rays had aberrations in approximately 30% of the metaphases per fish examined. An apparent increase in clumping and a decrease in the mitotic index were also noted. It was concluded that the chromosomes of Umbra limi displayed typical responses to low level radiation exposure and that this fish would be an ideal cytogenetics model for this study of induced chromosome aberrations in fishes.

Animals↗
PubMed1970

Trisomy-3,4 and triploidy (3A-ZZZW) in chick embryos: autosomal and sex chromosomal nondisjunction in meiosis.

The first known cases of trisomy-3, trisomy-4, and triploidy (3A-ZZZW) in chickens are reported. The trisomic embryos were near death at 4 days of incubation; the triploid embryo appeared normal and probably could have developed further. Although the triploid (3A-ZZZW) was found after sampling more than 2000 embryos, the trisomic-3 and trisomic-4 embryos were discovered in the first sampling of a line of chickens selected for low egg production. These studies suggest that the sex chromosomes (Z and W), as well as the autosomes, can undergo nondisjunction in meiosis of chickens.

Animals↗
PubMed1966

Triploid-diploid mosaic chicken embryo.

Cytological analysis of an underdeveloped chicken embryo at 6 days of incubation revealed a triploid-diploid mosaic condition. Of the 30 metaphases observed, 19 were triploid and 11 diploid. The triploid cells were 3A-ZZZ and diploid cells 2A-ZZ, as determined for the six largest pairs of chromnosomes.

Animals↗
PubMedDate not supplied

The effects of MHC chromosome dosage on bursal B-cell subpopulations in embryonic and neonatal chickens.

The effect of MHC dosage on the population structure of developing bursal lymphocytes was studied in the Trisomic strain of chickens. These chickens contain either 2 (disomic), 3 (trisomic), or 4 (tetrasomic) copies of the MHC-encoding chromosome. To assess the developmental profile of bursal cell populations, bursal cells were characterized in the older embryo (18 days of incubation) and at two neonatal ages (1 day and 1 week post hatch) by a number of cellular parameters. Both transient and persistent alterations in cellular composition were revealed in the bursal subpopulations of trisomics and tetrasomics (aneuploids). Aneuploid bursal cells showed increased cell surface expression of MHC class II Ia antigen, at each age, compared to normal disomic cells. Aneuploid cell populations showed an increased incidence of small cells, at each age, a decreased incidence of Ia+ and IgM+ cells during late embryogenesis, and an increased incidence of IgG+ cells in the late embryo and 1-day-old chick. Significantly fewer proliferating cells were observed in the aneuploids, as compared to disomics, in the late embryo and 1-week-old chick. Three subpopulations were observed to be persistently altered in the MHC-aneuploids: an increased pool of Ia , small, IgM+ cells; a decreased pool of Ia+, large, IgM+ cells; and a decreased pool of Ia+, large, IgM- cells. Thus, increasing MHC-chromosome dosage is accompanied by specific alterations in B-cell differentiation. The elevated surface Ia antigen expression found on developing aneuploid B cells may play a role in these alterations.

Aneuploidy↗