Browsing by Author "T. Sharma"

Now showing 1 - 20 of 78

A comparative study of the chromosomes of birds
(Springer-Verlag, 1969) R. Ray-Chaudhuri; T. Sharma; S.P. Ray-Chaudhuri
Karyotype analysis and morphometric measurement of the chromosomes of eleven species of Indian birds are described. The unequivocal identification of W chromosome in the females of five species of the present investigation further strengthens the generalisation that, at least in Carinatae, the sex chromosome constitutions are of ZZ and ZW types in males and females respectively. - The chromosomes of different species of birds so far worked out in each order have been compared using quantitative methods and tentative conclusions have been drawn regarding chromosomal affinities between species of different taxonomic categories. © 1969 Springer-Verlag.
A Probable Case of True Hermaphrodite With 46,XXq/ XY Mosaicism
(Georg Thieme Verlag, 2024) Shail Khanna; S.N. Maitra; Sushila Khanna; T. Sharma
A married women of 35 years age with primary amenorrhoea and poorly developed secondary sex characters but having a frankly feminine external genitalia was found to be a probable case of true hermaphrodite. There was a normal sized testis with epididymis and vasdeferens within the left swollen labia majora. At the position of the overies two greyish white bodies were present, which looked very much like ovaries, but small in size and inter-connected by a band of fibrous tissue. In buccal as well as vaginal smears a very low percentage of cells had a sex-chromation body. The size of the sex chromation was howeevr, much reduced. The G-band analysis of chromosomes, made from leucocyte cultures, revealed a 46, XXq-|46, XY sex chromosome mosaicism with predominance of 46, XY type of cells. © 2024 Georg Thieme Verlag. All rights reserved.
Asynchronous replication of constitutive heterochromatin on X chromosomes in female Mus dunni - Possible influence of facultative heterochromatin on the adjacent constitutive heterochromatin
(Springer-Verlag, 1982) S. Sen; T. Sharma
Euchromatin DNA of one X chromosome in mammalian females, which becomes facultatively heterochromatinized, is known to replicate asynchronously late in S phase compared to its active homologue. In the females of a pygmy mouse species Mus dunni, which has prominent segment of constitutive heterochromatin as the short arm of its submetacentric X chromosome, we have observed asynchronous replication of c-heterochromatin arm as well, predominant number of cells showing the segment associated with the facultatively heterochromatic X to be terminating later. The preferential later termination of replication of the c-heterochromatic arm on the "lyonized X" appears to be due to the influence of facultative heterochromatin on the adjacent constitutive heterochromatin. © 1982 Springer-Verlag.
Biochemical genetics of Indian pygmy field mice: Superoxide dismutase (Sod-1) as a diagnostic marker in Mus booduga
(Springer New York LLC, 1996) Sunita Singh; T. Sharma
[No abstract available]
Blood lymphocyte culture system: Quantitative analysis of X-ray-induced chromosome aberrations in man, muntjac and cattle
(1983) B.C. Das; T. Sharma
Peripheral blood lymphocytes of 3 mammalian species, man, muntjac and cattle, which have various amounts of DNA and divergent karyotypes, were exposed to 100-400 rad of X-rays, and frequencies of dicentrics and other aberrations were analysed at first post-irradiation metaphases. During experiments, various preparative or physical and biological factors that could influence the yield of chromosome aberrations were taken into account. The frequency of dicentrics scored at first post-irradiation metaphases showed best fit to both linear and quadratic dose-response curves, y = a + bD and y = bD + cD2 with a high correlation coefficient of 0.98 (P < 0.001). The frequency of dicentrics obtained at different post-irradiation fixation times did not show significant variation, indicating a homogeneous sensitivity of peripheral lymphocytes to X-irradiation. BrdU incorporation following X-irradiation showed no increase in the frequency of chromosome aberrations. The frequency of dicentrics in man, muntjac and cattle showed a close correlation with their DNA content, but no meaningful correlation was found between the yield of dicentrics and the chromosome arm number or the nuclear volume. The ratio of dicentric yields, 1.00:0.67:1.04 obtained in man, muntjac and cattle were comparable to the ratio of their DNA contents, 1.00:0.65:1.07. The base-line frequency of SCEs was similar in the 3 species and no significant variation in SCE frequency was noticed even after administration of 400 rad of X-rays. © 1983.
Burrow characteristics of the co-existing sibling species Mus booduga and Mus terricolor and the genetic basis of adaptation to hypoxic/hypercapnic stress
(2009) Sunita Singh; Nge Cheong; Gopeshwar Narayan; T. Sharma
Background. The co-existing, sibling species Mus booduga and Mus terricolor show a difference in site-preference for burrows. The former build them in flat portion of the fields while the latter make burrows in earthen mounds raised for holding water in cultivated fields. In northern India which experiences great variation in climatic condition between summer and winter, M. booduga burrows have an average depth of 41 cm, as against 30 cm in southern India with less climatic fluctuation. M. terricolor burrows are about 20 cm deep everywhere. The three chromosomal species M. terricolor I, II and III have identical burrows, including location of the nest which is situated at the highest position. In contrast, in M. booduga burrows, the nest is at the lowest position. Results. The nest chamber of M. booduga is located at greater depth than the nest chamber of M. terricolor. Also, in the burrows of M. booduga the exchange of air takes place only from one side (top surface) in contrast to the burrows of M. terricolor where air exchange is through three sides. Hence, M. booduga lives in relatively more hypoxic and hypercapnic conditions than M. terricolor. We observed the fixation of alternative alleles in M. booduga and M. terricolor at Superoxide dismutase-1 (Sod-1), Transferrin (Trf) and Hemoglobin beta chain (Hbb) loci. All the three are directly or indirectly dependent on oxygen concentration for function. In addition to these, there are differences in burrow patterns and site-preference for burrows suggesting difference in probable adaptive strategy in these co-existing sibling species. Conclusion. The burrow structure and depth of nest of the chromosomal species M. terricolor I, II and III are same everywhere probably due to the recency of their evolutionary divergence. Moreover, there is lack of competition for the well-adapted 'microhabitats' since they are non-overlapping in distribution. However, the co-existing sibling species M. booduga and M. terricolor exhibit mutual "exclusion" of the 'microhabitats' for burrow construction. Thus, location, structure and depth of the burrows might have been the contributory factors for selection of alternative alleles at three loci Sod-1, Trf and Hbb, which reflect difference in probable adaptive strategy in M. booduga and M. terricolor.
Cell cycle kinetics of PHA-stimulated muntjac lymphocytes in vitro: Part I: BrdU harlequin assay system & demonstration of rapid proliferation of lymphocytes
(1979) M. Jacob; R. Raman; T. Sharma
[No abstract available]
Cell cylce kinetics of pha-stimulated muntjac lymphocytes (in vitro) II. Effect of different concentrations of BrdU on cell-cycle progression
(1980) Mercy Jacob; Rajiva Raman; T. Sharma
[No abstract available]
Characterization of G-banded chromosomes of the indian muntjac and progression of banding patterns through different stages of condensation
(1985) Pramila Sen; T. Sharma
Muntjac prophase and metaphase chromosomes were G-banded following methotrexate-mediated synchronization of peripheral lymphocytes. Bands and subbands were characterized from prophase through metaphase. and the progression of band patterns from late prophase to mid-mctaphase was analyzed. Extended prophase chromosomes exhibited more bands and subbands, a number of which became fused with each other, giving rise to fewer and thicker bands in the condensed metaphase chromosomes. It appeared that the dark bands condensed relatively more than the light bands. Precise delineation of the bands and subbands on extended prophase chromosomes and the usage of a proposed banding pattern nomenclature should aid in better detection and localization of induced chromosomal rearrangements with this extremely useful experimental material. © 1985 S. Karger AG, Basel.
Chromosomal and molecular divergence in the Indian pygmy field mice Mus booduga-terricolor lineage of the subgenus Mus.
(1996) T. Sharma
Mus booduga and Mus terricolor both have 2n = 40. Unlike M. booduga, with all acrocentric chromosomes, M. terricolor invariably has large submetacentric X and acrocentric Y due to an increase of heterochromatin. In contrast to the conservative karyotype of the co-existing sibling species booduga, three chromosome types of terricolor are found in different populations and their divergent karyotypes have autosomal heterochromatin variations established in the homozygous condition. The average genetic distance determined from electrophoretic study of 20 protein loci ranges from lowest (D = 0.106) between chromosome types I & II to highest (D = 0.185) between types II & III. In terricolor, booduga and M. m. tytleri high mean values of variations per locus (range A = 1.604 to 1.928) and heterozygosity per individual per locus (range H = 0.180 to 0.336) have been observed. Sequence divergence of 0.39 to 1.2%, calculated from restriction profiles of mtDNA, shows that the terricolor chromosome types have diverged recently. Hybridizations between type I females and type III males gave a preponderance of males in the F1 with varying degrees of sterility. The 'terricolor complex' is an interesting system for critical probing for the role of heterochromatin in the process of speciation. MtDNA, protein loci and AT-rich musculus-related major and minor satellite DNA data indicate that progenitors of the booduga-terricolor lineage might have evolved simultaneously with the caroli-cookii-cervicolor lineage in the evolution of the subgenus Mus.
Chromosomal damage induced in human lymphocytes by low doses of D-T neutrons
(1986) J. Pohl-Rüling; P. Fischer; D.C. Lloyd; A.A. Edwards; A.T. Natarajan; G. Obe; K.E. Buckton; N.O. Bianchi; P.P.W. van Buul; B.C. Das; F. Daschil; L. Fabry; M. Kučerová; A. Léonard; R.N. Mukherjee; U. Mukherjee; R. Nowotny; P. Palitti; Z. Polívková; T. Sharma; W. Schmidt
Unstable chromosome aberrations induced by in vitro irradiation with zero plus seven low doses of 14.8 MeV D-T neutrons in the range 3.55-244 mGy have been analysed in human peripheral blood lymphocytes. In order to obtain the required large numbers of scored cells for such low doses, fourteen laboratories participated in the experiment. The dose responses for dicentrics, excess acentrics and total aberrations, fitted well to the Y = αD model. The α coefficient of yield for dicentrics, 1.60 ± 0.07 × 10-2 Gy-1, compares well with the values obtained in previous studies with D-T neutrons at somewhat higher doses. Results from a previous collaborative study using 250 kVp X-rays over a comparable dose range indicated the possible existence of a threshold below 50 mGy. In the present study there is no clear evidence for neutrons for such a threshold. However, the data were insufficient to permit the rejection of a possible threshold below ∼ 10 mGy. © 1986.
Chromosome condensation and Hoechst 33258 fluorescence in meiotic chromosomes of the grasshopper Spathosternum prasiniferum (Walker)
(Springer-Verlag, 1979) B.C. Das; Rajiva Raman; T. Sharma
Patterns of Hoechst 33258 fluorescence have been studied in grasshopper chromosomes. At metaphase of mitotic as well as meiotic divisions - when chromosomes were maximally compact - all the chromosomes fluoresced brightly but no differentially fluorescing regions were detected. However, when all the chromosomes, except the X, were highly extended at pachytene and diplotene stages a distinct differential fluorescence was observed: only the centromeres of the autosomal bivalents fluoresced brightly whereas the entire X univalent showed bright fluorescence. Restriction of differentially bright fluorescence to the more condensed regions of chromosomes suggests a modulatory role for chromosome condensation in the production of Hoechst fluorescence. This suggestion was further strengthened by the substantial quenching of fluorescence caused by removal of chromosomal proteins following treatment with H2SO4. Similarly, post-C-band-treatment staining with Hoechst also led to quenching, though now the centromeres of the chromosomes, including the X, retained their differential fluorescence. It is proposed, therefore, that in grasshopper chromosomes, H-fluorescence is modulated by chromosome condensation brought about by differential ratios of DNA/protein at different chromosome regions and at different division stages. © 1979 Springer-Verlag.
Chromosomes and the karyotype of the Pangolin, Manis pentadactyla L. (Pholidota-Mammalia)
(Birkhäuser-Verlag, 1969) S.P. Ray-Chaudhuri; T. Sharma; S. Pathak; L. Singh
[No abstract available]
Chromosomes of Five Species of Indian Vespertilionid Bats
(1969) S. Pathak; T. Sharma
[No abstract available]
Co-cultivation of whole blood from male and female muntjacs and the cell proliferation kinetics in vitro
(1986) B.C. Das; T. Sharma
A mixed blood culture (MBC) of heparinized whole blood from male and female Indian muntjac has been done using the BrdU-Hoechst-sunlight-Giemsa method to study the cell-cycle kinetics in vitro. Blood lymphocytes on both male and female muntjacs show a much shorter cell cycle time, roughly, 10-12 h for the initial but only 8 h for the subsequent cycles. There is a significant difference in the rate of cell proliferation between male and female cells. The male blood cells constitute a majority of the 'slow'-dividing cells which reach a peak at the first cycle of mitosis at 40 h, whereas a similar peak of first cycle mitosis is reached by female cells at 32 h, indicating the occurrence of a high frequency of 'fast' dividing female cells as compared to those of males. This novel sex-based differential cell proliferation kinetics is observed both in mixed and separate cultures. This type of MBC method which is free of interculture variations can be reliably used for comparative studies where two genomes can be distinguished. © 1986.
Constitutive heterochromatin and karyotype variation in Indian pygmy mouse, Mus dunni
(1975) T. Sharma; G.S. Garg
The Indian pygmy mouse, Mus dunni, exhibits great variation in the number of chromosome arms while its diploid number of chromosomes remains constant. The variation seems to be due to addition or deletion of C-band positive constitutive heterochromatin in the short arms of autosomes. © 1975, Cambridge University Press. All rights reserved.
Constitutive heterochromatin variation in two species of rattus with apparently similar karyotypes
(Kluwer Academic Publishers, 1977) T. Sharma; I.K. Gadi
Rattus blanfordi and R. cutchicus medius both have a chromosome complement of 2n=36 and all chromosomes except the submetacentric Y of R. blanfordi are acrocentric. The apparently similar karyotypes of the two species, however, show variations in the nature and quantity of C-band-positive constitutive heterochromatin (C-heterochromatin) as revealed by C- and G-banding and Hoechst 33258 fluorescence. R. blanfordi with large-sized X and Y chromosomes and conspicuously larger centromeric heterochromatin in all the autosomes as compared to that of R. cutchicus medius has much more C-heterochromatin in its genome than the latter. The variation in the quantity of C-heterochromatin has been accomplished without altering the morphology of the acrocentric chromosomes unlike other mammals in which variations have been reported to result generally in the addition or deletion of a totally heterochromatic second arm. © 1977 Dr W. Junk BV Publishers.
Culture media and species-related variations in the requirement of 5-bromodeoxyuridine for differential sister-chromatic staining
(1981) T. Sharma; B.C. Das
Various concentrations of 5-bromodeoxyuridine (BrdU) ranging from 0.01 to 10.0 μg/ml were tried for finding the minimal concentration required for differential staining of sister chromatids in lymphocytes of man, muntjac and cattle grown in three commonly used culture media, namely TC 199, Dulbecco's MEM and Ham's F-10. The lymphocytes grown in TC 199 required the lowest concentration of BrdU whereas it was highest for the lymphocytes grown in F-10. The minimal concentration varied for the 3 species studied, and it was not related to their DNA content. The differing amounts of thymidine and folic acid present in the various culture media seemed to account for the difference in the quantity of BrdU required for eliciting differential staining. Staining may also have depended on the intracellular nucleotide pool and/or on the difference in the substitutable dT sites of the genomes. © 1981.
Cytogenetic relationships in Rattus, Cremnomys, Millardia, Nesokia and Bandicota (Rodentia: Muridae)
(Kluwer Academic Publishers, 1983) I.K. Gadi; T. Sharma
The karyology was studied in different taxa of Rattus, Cremnomys, Millardia, Nesokia and Bandicota. Chromosome banding patterns of 18 taxa belonging to 4 species of the genus Rattus, 2 species of Cremnomys, 1 species each of Millardia and Nesokia and 2 species of Bandicota are presented. Present studies and the karyological information of different taxa available from elsewhere have revealed that the karyotypes of Millardia, Cremnomys, Lenothrix (except L. canus) and Maxomys (M. bartelsii only) are unique and show little resemblance to Rattus, Stenomys, Berylmys and Leopoldamys. G-band comparison has revealed the presence of 4 pairs of similar autosomes in addition to conservation of the G-band pattern of the X chromosome in divergent karyotypes of Rattus rattus, Millardia meltada and Cremnomys cutchieus medius. Chromosome inversions, fusions and variations in constitutive heterochromatin have been identified. The presence of a few similar chromosomes suggests that these taxa have evolved from a common ancestral taxon. The conventional karyotype of Lenothrix canus and the Niviventer group of rats (Marshall, 1977) also reveal a pair of large subtelocentrics and a few pairs of small metacentrics similar to those observed in the subgenera Rattus, Stenomys, Berylmys and Leopoldamys. The autosomal complements of the lesser bandicoot-rats Nesokia indica and Bandicota bengalensis are alike and are related to those of species in the subgenus Rattus through only 2 pericentric inversions. A few pericentric inversions and a deletion may be assumed to compare the karyotype of the great bandicoot-rat B. indica indica with B. bengalensis. The other great bandicoot-rats, B. indica nemorivaga and B. indica savilei, have an additional pair of autosomes and the karyotype of the former subspecies has diversified through a few pericentric inversions also. © 1983 Dr W. Junk Publishers.
Differences in sister-chromatid exchange frequency between homologous chromosomes in Muntiacus muntjak
(1992) A.J. Rachel; T. Sharma; V.V. Menon
The frequency of sister-chromatid exchanges (SCEs) on homologous autosomes was studied in the peripheral blood lymphocytes of the Indian muntjac. The homologous autosomes differed from one another with respect to the SCE frequency on them. © 1992.