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Biomedical subjects

M S Patil

Publications and source records attributed to M S Patil.

11 recordsLinked to original sources
PubMed1991

DNA synthesis in nuclei and nuclear matrices of regenerating rat liver: effect of whole-body gamma irradiation.

Partial hepatectomy (PH) of rats (Wistar strain) resulted in acceleration of DNA synthesis in liver which reached a maximum at 36 h after PH. Whole-body radiation exposure (10 Gy) of the rats at 12 h after PH completely arrested this stimulation in DNA synthesis. The elevation of DNA synthetic rate in response to PH and complete obliteration of this stimulation by whole-body radiation exposure were found to be the reflection of levels of DNA polymerase-alpha in nuclei and nuclear matrices isolated from the rat livers. Studies based on assays of DNA polymerase in nuclei and nuclear matrices, with and without exogenous DNA template (activated calf thymus DNA), revealed that whole-body irradiation blocked induction of DNA polymerase-alpha and, in turn, assembling of DNA polymerizing apparatus. Irradiation of nuclei (suspended in buffer) in vitro at doses as high as 500 Gy did not have any inhibitory effect on DNA polymerase-alpha activity.

Animals↗
PubMed1990

Terminal deoxynucleotidyltransferase containing megadalton complex from young rat thymus nuclei: identification and characterization.

Nuclear matrix prepared from 2-3 week old rat thymuses contains tightly bound TdT activity which has been quantitatively solubilized with nonionic detergent and sonication. TdT is contained in a discrete complex with a sedimentation value of 23 S. The complex is retained on an anti-TdT antibody column and contains DNA ligase and 3'-5' exonuclease activities as well as DNA and several other proteins but is devoid of replicative DNA polymerases. Such a type of multienzyme complex is absent from the nuclear extracts of thymus prepared from older rats and also from liver and spleen extracts of young and old rats.

Animals↗
PubMed1989

A sensitive assay for Staphylococcus aureus nucleases.

A sensitive assay for staphylococcal nuclease involving incubation of the enzyme sample with heat-denatured [3H]thymidine labelled DNA from E. coli, precipitation with trichloroacetic acid and measurement of the radioactivity of acid-soluble nucleotides released has been developed. The assay is sensitive enough to be used for comparing the levels of nucleases elaborated by different strains of S. aureus as well as for determining the extent of contamination of S. aureus in food and water samples even at levels at which the conventional spectrophotometric and toluidine blue-DNA methods are totally inadequate.

Deoxyribonucleases↗
PubMed1985

Radiation-induced thymine base damage and its excision repair in active and inactive chromatin of HeLa cells.

The extent of production and excision repair of 5,6-dihydroxydihydrothymine type base (t') damage was determined in transcriptionally active and inactive chromatin of HeLa cells after exposure to 6.8 MeV electrons. It was observed that not only the yield but also rate of repair of t' products was greater in the active chromatin compared to the inactive chromatin of HeLa cells. The results strongly indicate that the conformation of chromatin is an important factor in determining the sensitivity to radiation damage and accessibility to enzymes required for repair of such damage.

Chromatin↗
PubMed1978

Syntheses of DNA and chromosomal proteins in the rat thymus following whole-body X-irradiation.

Syntheses of chromosomal proteins was studied in relation to DNA syntheses in the rat thymus following whole-body X-irradiation (600 rad). There was a considerable depression of the syntheses of DNA and histones during the first 4--48 hours after irradiation. The syntheses of histones H3 and H4 plus H2A were affected to a much greater degree than those of histones H1 and H2B, suggesting a tight coupling between the syntheses of DNA and histones H3 and H4 plus H2A. A part of the lysine-rich histones H1 and H2B, however, seems to be synthesized, even in the absence of DNA synthesis. Biosynthesis of non-histone proteins was also depressed in the thymus after irradiation. The degree of inhibition, however, was very low, except for the syntheses of a few non-histone protein components which were depressed to a considerable extent. This implies that the synthesis of the majority of non-histone proteins is independent of DNA synthesis.

Animals↗
PubMed1975

Effect of whole-body irradiation on transcription in the rat thymus.

Studies were carried out to elucidate the mechanism underlying the impairment in RNA synthesis in the rat thymus after whole-body exposure to X-rays (1000 rad). The ability of thymus nuclei to catalyse RNA polymerization in vitro was adversely affected in irradiated rats. Further experiments showed that whole-body irradiation caused a considerable decrease in both the activity of RNA polymerase and the template efficiency of chromatin but not in that of DNA isolated from chromatin. These radiation-induced changes in transcription seem to arise partly from the direct effect of radiation on the thymus itself and partly from the abscopal mechanism(s).

Animals↗
PubMedDate not supplied

Nuclear matrix bound terminal deoxynucleotidyl transferase in rat thymus nuclei. I. A possible site for TdT mediated function.

Approximately 80% of the terminal deoxynucleotidyl transferase (TdT) in thymus glands from 3-4 week old rats was found to be localized in the nucleus and the remaining 20% in the cytosol. Following endogenous nuclease digestion of the thymus nuclei, 70-85% of the nuclear TdT could be removed by low salt and high salt extractions, whereas 15-30% of the enzyme remained tightly bound to the residual nuclear matrix. Low salt and high salt extracts of the nuclei contained a mixture of 58, 56, 45 and 44 kDa species of TdT whereas only 58 kDa species of the enzyme was found to be associated with the matrix. In addition to TdT, 20-25% of the nuclear DNA polymerase alpha was also tightly bound to the isolated nuclear matrix. These observations lead us to propose that besides being the site of DNA replication via-matrix bound replicational complexes [Van der Velden H.M.W. & Wanka F., Molecular Biology Reports 12 (1987): 69], nuclear matrix may also be the site of TdT mediated function and that matrix bound TdT and free TdT could be the functional and nonfunctional forms of the enzyme, respectively, in the thymus gland.

Affinity Labels↗
PubMedDate not supplied

Nuclear matrix bound terminal deoxynucleotidyl transferase in rat thymus nuclei. II. Effect of ATP on free and matrix bound TdT.

Endogenous nuclease digestion of thymus nuclei from 3-4 week old rats followed by a step wise extraction with low salt, 0.5 M salt and 1 M salt removed approximately 70-85% of total nuclear terminal deoxynucleotidyl transferase (TdT) whereas approximately 15-30% of the enzyme remained tightly bound to the residual nuclear matrix. The cytoplasmic TdT as well as the bulk of nuclear TdT extracted in low salt and 0.5 M salt was found to be strongly inhibited at low concentration of ATP whereas matrix bound TdT and a significant portion of the enzyme in 1 M salt extract was completely insensitive to this nucleotide. The ATP resistant enzyme in the 1 M salt extract was unstable and slowly converted to ATP sensitive form upon prolonged preincubation on ice whereas under similar conditions it remained unaffected in the matrix bound form. These observations lead us to suggest that ATP resistant matrix bound TdT being capable of discriminating unnatural rNTPs against the natural dNTP substrates, may be the functionally organized form of the enzyme and that free TdT having lost the capability to distinguish between dNTP and rNTP may be the nonfunctional form of the enzyme in the thymus gland.

Adenosine Triphosphate↗