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Biomedical subjects

J K Roy

Publications and source records attributed to J K Roy.

11 recordsLinked to original sources
PubMed1995

1(2)gl gene regulates late expression of segment polarity genes in Drosophila.

To analyse the possible roles of Drosophila tumour suppressor genes, 1(2)gl and 1(2)gd, in differentiation programmes of imaginal cells, we investigated their interactions with two segment polarity genes, viz., cubitus interruptus Dominant (ci-D) and engrailed (en), by examining their patterns of expression in tumourous imaginal discs of 1(2)gl4 or 1(2)gd1 homozygous larvae. While the 1(2)gd1 mutation did not have much effect, the areas of expression of ci-D and en in the tumourous discs of 1(2)gl homozygous larvae were significantly increased and the anterior-posterior compartment boundary was no longer identifiable. To examine if the loss of en expression compartment boundary in 1(2)gl tumourous discs was due to overproliferation of the posterior compartment cells or due to a deregulated expression of en in the anterior compartment cells, 1(2)gl4 homozygous cell clones were generated in 1(2)gl4 enlacZ/++ background. A distinct X-gal staining in 1(2)gl homozygous clones in the anterior compartment in wing imaginal discs or in adult wings confirmed deregulated ectopic expression of en in 1(2)gl mutant anterior compartment cells. We suggest that 1(2)gl is involved in regulating post embryonic expression of segment polarity genes.

Animals↗
PubMed1995

The hyperactive X chromosome is not early replicating in mitotically active somatic cells of Drosophila nasuta males.

The temporal order of replication of the X chromosome(s) in mitotically dividing male and female cells in early embryos and in brain ganglia of Drosophila nasuta larvae was examined using [3H]thymidine pulse labelling and autoradiography. Both the X chromosomes in female cells and the single X chromosome in male cells replicated in complete synchrony with the autosome set in the nucleus. Thus, unlike the well-known early completion of replication by the hemizygous X chromosome in polytene nuclei in the salivary glands of male Drosophila larvae, the single X chromosome in mitotically dividing cells does not replicate earlier than the autosomes. We conclude that transcriptional hyperactivity of the single X chromosome required for dosage compensation in somatic cells of male Drosophila is not dependent upon its early replication.

Animals↗
PubMed1979

A study of heterochromatin in Drosophila nasuta by the 5-bromodeoxyuridine-Giemsa staining technique.

Larval brain ganglia of Drosophila nasuta were cultured in vitro in the presence of 5-bromodeoxyuridine for 1 or 5 h at 24 degrees C and the air-dried chromosome preparations stained by the Hoechst 33258-Giemsa technique to reveal bromodeoxyuridine induced sister chromatid differentiation. In 1 h as well as 5 h preparations, 10-15% of well spread metaphase plates show a sister chromatid differentiation in only C-band heterochromatin regions of different chromosomes. We infer that this sister chromatid differentiation in all heterochromatic regions is seen after bromodeoxyuridine incorporation for only one replication cycle and is related to the presence of asymmetric A-T rich satellite sequences in all the C-band regions of D. nasuta karyotype.

Animals↗
PubMedDate not supplied

Factors influencing predation of the waterbugs Sphaerodema annulatum (Fab). and S. rusticum (Fab.) on the disease transmitting snail Lymnaea (Radix) luteola (Lamarck).

Variations in the rate of predation of the waterbugs Sphaerodema annulatum and S. rusticum on the snails Lymnaea (Radix) luteola have been noted in respect to the morphs of the waterbugs, size of the prey individuals, densities of prey and predators, temperature and surface area of the waterbody concerned and the seasons. Consumption rate was highest (7.2 and 2.2 individuals per day per individual of S. annulatum and S. rusticum, respectively) in prereproductive ages of the waterbugs. This was followed by a gradual decline with the increase in age of the predators. The consumption rate was gradually higher with the increase of temperature from 20 degrees C to 35 degrees C. The bugs failed to survive beyond 35 days at 35 degrees C. Though the bugs prey upon the snails of all sizes preference for 6.5 x 4.5 mm to 8 x 5 mm individuals by S. annulatum and for 5 x 3 mm to 6.5 x 4.5 mm individuals by S. rusticum is established. The waterbugs, irrespective of species, consumed the snail individuals belonged to 3 x 2 - 4 x 3 mm size group maximum when supplied separately. The rate of predation gradually declined with the rise of predator's density irrespective of waterbug species. Predation rate increased with increasing prey density. This was level off when the prey snails were 1100 and 700 in number for S. annulatum and S. rusticum respectively. An adult S. annulatum and S. rusticum consumed 5.04, 3.7, 1.43 and 3.36, 2.49, 1.04 snails per day respectively in summer, monsoon and winter.

Age Factors↗
PubMedDate not supplied

Multiple specific chromosomal alterations in a rat ascitic histiocytoma 'AK-5'.

In the rat ascitic histiocytoma, AK-5, chromosome numbers vary between 33 and 41 with a peak at 40 chromosomes. None of the metaphase spreads showed double minute chromosomes. The karyotype of this tumor was characterized by hypodiploid chromosome constitution. Giemsa banding analysis revealed 12 clonal marker chromosomes (M1-M12). Tentative identification of these markers were: M1 = ins(1q); M2 = t(5;?); M3 = t(8;10); M4 = t(8;?); M5 = t(10;X); M6 - t(15;?); M7 = t(5;6); M8 = del(13p); M9-M12 = unidentified. M3 being a large near metacentric chromosome serves as a characteristic marker for this tumor. All marker chromosomes except M2 and M4 were present in single copy per cell. In some metaphases M2 was present in 2 copies while M4 was present in 2 or 3 copies per cell. The total cell cycle duration of AK-5 cells was 15.5 h and the different phases, G1, S, G2 + M were estimated as 1.2, 12.2, and 2 h, respectively.

Aneuploidy↗