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Biomedical subjects

S Pathak

Publications and source records attributed to S Pathak.

At least 127 records · Page 7Linked to original sources
PubMed1980

Asynaptic behavior of X and Y chromosomes in the Virginia oppossum and the southern pygmy mouse.

The meiotic behavior of silver-stained X and Y chromosomes of the Virginia opossum, Didelphis virginiana, and the southern pygmy mouse, Baiomys musculus, was studied by light microscopy. While the sex chromosomes of these two species differ in both size and morphology, their meiotic behavior is very similar. In both species a typical sex vesicle is formed during pachytene, but unlike most other mammalian species thus far studied, a synaptonemal complex does not form between the X and Y chromosomes. During pachytene, variable modes of association of the ends of the sex chromosomes (both heterologous and autologous) are sometimes observed. During diplotene, diakinesis, and metaphase I, the X and Y rarely appear to be associated. In some pachytene nuclei of B. musculus, the single axis of the biarmed X chromosome folds back upon itself, and the telomeres form a close association. While synaptic pairing segments of the sex chromosomes of the Virginia opossum may be displaced by telomeric heterochromatin on the X, true pairing regions between the X and Y of the pygmy mouse may be lacking.

Animals↗
PubMed1980

Light microscopic observations on the behavior of silver-stained trivalents in pachytene cells of Sigmodon fulviventer (Rodentia, Muridae) heterozygous for centric fusion.

Silver-stained pachytene cells of male cotton rats, Sigmodon fulviventer, heterozygous for a naturally occurring Robertsonian fusion, were examined by light microscopy. Silver staining clearly revealed synaptonemal complexes of all autosomal bivalents and of the translocation trivalent, as well as X-Y conformations within the sex vesicle. The synaptonemal complex of the trivalent conforms closely in morphology to that observed by electron microscopy in hybrids of other species. In all cases, the proximal telomeric knobs of the two acrocentric elements were paired and projected in the same direction from the metacentric element. The geometry of trivalent pairing in pachytene may predispose to normal disjunction and, therefore, account for the high fertility observed in S. fulviventer heterozygotes.

Animal Population Groups↗
PubMed1979

Induction of prematurely condensed chromosomes from testicular cells of the mouse.

Mitotic CHO cells and mouse testicular cells were fused with polyethylene glycol. Several types of prematurely condensed chromosomes were observed. From chromosome morphology it was possible to determine that most of the PCC represented mouse cells. Labeling of either the CHO cells in vitro or the testicular cells in vivo with 3H-TdR prior to fusion also demonstrated that the PCC were derived from the mouse cells. In some PCC, 20 chromosomes could be counted, the haploid number for mouse. It is assumed that these PCC were induced in mouse spermatid nuclei.

Animals↗
PubMed1979

Observations on the synaptonemal complex in Armenian hamster spermatocytes by light microscopy.

Using the silver staining technique, in somatic and meiotic chromosomes of the Armenian hamster (Cricetulus migratorius), it is possible to stain synaptonemal complexes (SCs) and the nucleolus organizer regions (NORs) in early spermatocytes. There are five pairs of autosomes (Nos. 2, 4, 6, 7, and 8) which have terminally located NORs. Synaptonemal complexes and accessory structures present in the sex chromosomes within the sex vesicle can be easily observed using light microscopy.

Animals↗
PubMed1979

Silver-stained structures in mammalian meiotic prophase.

Silver staining of mammalian spermatocytes revealed, in light microscopy, synaptonemal complex and structures within the sex vesicle. It is feasible to follow the chromosome pairing phenomenon from zygotene to pachytene by examining the behavior of synaptonemal complexes. Nucleolus organizer regions take heavy silver stain in pachytene but are no longer detectable in later stages of meiosis.

Animals↗
PubMed1979

Detection and analysis of a glucose 6-phosphate dehydrogenase phenotype B cell line contamination.

Eight of approximately 100 cell lines derived at the Scott and White Clinic from human solid tumors were found to have the same phenotypes when analyzed for 15 polymorphic enzymes at the Sloan-Kettering Institute for Cancer Research. These data were confirmed at the M. D. Anderson Hospital and Tumor Institute. The similarity was supported by cytogenetic studies at both institutions. The chronology of the establishment of these cell lines and isoenzyme and cytogenetic studies indicated that six of these lines have cross cell contamination. These include SW-527 and SW-613 mammary carcinomas, SW-598 meningioma, SW-608 astrocytoma, SW-732 cervix carcinoma, and SW-733 bladder carcinoma. Our data supported the authenticity of SW-480 and SW-620, which were derived from a colon carcinoma and its metastasis, respectively, from the same patient.

Animals↗
PubMed1979

Sterility in hybrid cattle. I. Distribution of constitutive heterochromatin and nucleolus organizer regions in somatic and meiotic chromosomes.

The distribution of constitutive heterochromatin and nucleolus organizer regions (NOR's) in somatic as well as in meiotic chromosomes of Bos taurus, Bos banteng, Bison bison, and their hybrids are analyzed. C-bands are present in the centromeric regions of every autosome. The X chromosome does not show a distinct C-band in the centromeric region, whereas the Y chromosome contains an appreciable amount of C-band material. In somatic metaphases, NOR's are present on the telomeric ends of five pairs of autosomes. During pachytene, five autosomal bivalents contain NOR's on their terminal ends. Meiotic preparations made from sterile bulls did not contain stages beyond the degenerating pachytene, which are C-banding, more frequently showed clustering of heterochromatin than did the pachytene stage in normal bulls.

Animals↗
PubMed1979

Cytogenetic research techniques in humans and laboratory animals that can be applied most profitably to livestock.

The usefulness of various chromosome banding techniques, i.e., Q, C, G, R, Ag-NOR, and SCE, which are currently in use in many clinical cytogenetics labortories are discussed. Since C-banding revealed the location of constitutive heterochromatin, it must be applied in conjunction with Q, G, or R-banding techniques. For the longitudinal differentiation of mammalian chromosomes one can use either the G-banding or the Q-banding and, if possible, R-banding technique. The results of such studies should not only contribute to our understanding of cytogenetics of domestic animals but also assist breeding programs and improvement of livestock.

Animals↗
PubMed1979

A human breast adenocarcinoma with chromosome and isoenzyme markers similar to those of the HeLa line.

Pleural effusion was obtained from a 51-year-old black woman who had breast adenocarcinoma and had received chemotherapy and radiation therapy after a radical mastectomy. Cytogenetic and isoenzymic analyses of the cells were performed within a few hours of obtaining the sample. Similar analyses were also done with a cell line established from this effusion. The stemline chromosome number was 35, one of the lowest in human neoplasms. In addition to a marker chromosome involving 1q, which is common in human breast tumors, we found several other marker chromosomes whose G-banding patterns were similar to some of the typical HeLa markers. Genetic signature analysis of 15 isoenzyme loci revealed that 13 were identical to those of HeLa. Both HeLa and the cell line described here express glucose-6-phosphate dehydrogenase type a, yet they were derived from heterozygotic individuals (ab). Our data indicate the necessity to extensive cytogenetic and biochemical analysis before conclusions are made that cell lines are actually intercell-line contaminants.

Adenocarcinoma↗
PubMed1978

Responses of mammalian metaphase chromosomes to endonuclease digestion.

Digestion of fixed metaphase chromosomes by endonucleases (micrococcal nuclease and DNase II) under optimal digestion conditions followed by Giemsa staining produces sharp banding patterns identical to G-bands. In 3H-thymidine labeled, synchronized metaphase cells of the chinese hamster (CHO line), the band induction is accompanied by the removal of DNA. The single strand specific nuclease S1 and DNase I do not produce such banding patterns.

Animals↗
PubMed1978

An electron-microscopic study of avirulent and virulent Semliki forest virus in the brains of different ages of mice.

Ultrastructural studies of brains infected with avirulent and virulent strains of Semliki forest virus (SFV) were performed in 2-7, 14, 19, and 21-28 day old mice. Mature virus particles, dense clumps of fine granules, spherules and advanced stages of viral development i.e. cytopathic vacuoles, Type II (CPV II) are seen in the brains at all ages with the virulent strain which is pathogenic to all age group of mice. In the avirulent strain infection which is pathogenic to mice below 15 days old, no mature virus particles or advanced stages of viral development are seen in 19 day old and adult mice in spite of high virus titres. However, dense clumps of fine granules and spherules are seen which seem to have the capacity to develop into lethal highly infectious mature virus when reinoculated into 2-7 day old mice. It is suggested that the dense clumps of fine granules and spherules are very early viral forms, which are seen in all age groups of mice. The cut-off mechanism in pathogenicity of the avirulent strain occurs in mice around 14 days old. Though some mature virus particles and advanced viral developmental stages are seen in these mice they were much less frequent compared to baby mice. Lymphoblastic type cells are numerous in this age group. These cells are seen more frequently in all ages of mice infected with the avirulent strain as compared to the virulent strain. These mononuclear cells can have an immunological role and may play a part in limiting the process of viral maturation and hence preventing death. Polymorphs and macrophages are rare with the avirulent infection but are the predominant infiltrating cells in the virulent strain infections. With the avirulent infections the astrocytes show hypertrophy and intranuclear inclusions are seen in them.

Age Factors↗
PubMed1978

Virus-associated demyelination. A model using avirulent Semliki Forest virus infection of mice.

Lesions produced by the infection of Swiss/A2G mice with a single inoculation of an avirulent strain of Semliki forest virus have been studied by light and electron microscopy. Whilst a mild encephalitis was detected in the great majority of mice infected, focal areas of myelin loss were observed in the cerebellar white matter of only 25% of cases. The incidence of myelin loss in other strains of mice ranged from 21% in BSVS mice to 8% in SJL/J mice. The possible mechanisms involved in the pathogenesis of the myelin loss are discussed.

Animals↗
PubMed1978

Cytogenetic toxicity of gentian violet and crystal violet on mammalian cells in vitro.

The cytogenetic toxicity of gentian violet in Chinese hamster CHO cells in vitro has been studied by analyzing (1) squash preparations from direct fixation for recording mitotic anomalies and (2) air-dried preparations (with colcemid--hypotonic pretreatments) for recording metaphase chromosome aberrations. It was concluded that this compound is a mitotic poison as well as a clastogen in vitro. Its clastogenic property was confirmed in 5 other different mammalian cel types. 10 samples of different gentian violet and crystal violet were surveyed and all were shown to be clastogenic. Unless in vivo studies prove otherwise, gentian violet and crystal violet should be regarded as biohazardous substances.

Animals↗
PubMed1978

Induced Robertsonian fusions and tandem translocations in mammalian cell cultures.

Cultures of a cattle cell line and a Peromyscus eremicus cell line recovering from a pulse-treatment with mitomycin C, actinomycin D, 33258 Hoechst, and nitrosoguanidine exhibited translocations between chromosomes at the centromeric regions (Robertsonian fusions) as well as between centromere and telomere and between telomeres (tandem translocations). The frequency of Robertsonian fusions was found to be dose-dependent and duration-dependent with the mitomycin treatment. Biarmed chromosomes resulting from fusions may be monocentric or dicentric. Analyses of clones isolated from treated cells suggested that fused chromosomes may perpetuate in the cell populations.

Animals↗