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Biomedical subjects

S Guha

Publications and source records attributed to S Guha.

At least 91 records · Page 5Linked to original sources
PubMed1985

Determination of DNA sequences containing methylcytosine in Bacillus subtilis Marburg.

The methylcytosine-containing sequences in the DNA of Bacillus subtilis 168 Marburg (restriction-modification type BsuM) were determined by three different methods: (i) examination of in vivo-methylated DNA by restriction enzyme digestion and, whenever possible, analysis for methylcytosine at the 5' end; (ii) methylation in vitro of unmethylated DNA with B. subtilis DNA methyltransferase and determination of the methylated sites; and (iii) the methylatability of unmethylated DNA by B. subtilis methyltransferase after potential sites have been destroyed by digestion with restriction endonucleases. The results obtained by these methods, taken together, show that methylcytosine was present only within the sequence 5'-TCGA-3'. The presence of methylcytosine at the 5' end of the DNA fragments generated by restriction endonuclease AsuII digestion and the fact that in vivo-methylated DNA could not be digested by the enzyme XhoI showed that the recognition sequences of these two enzymes contained methylcytosine. As these two enzymes recognized a similar sequence containing a 5' pyrimidine (Py) and a 3' purine (Pu), 5'-PyTCGAPu-3', the possibility that methylcytosine is present in the complementary sequences 5'-TTCGAG-3' and 5'-CTCGAA-3' was postulated. This was verified by the methylation in vitro, with B. subtilis enzyme, of a 2.6-kilobase fragment of lambda DNA containing two such sites and devoid of AsuII or XhoI recognition sequences. By analyzing the methylatable sites, it was found that in one of the two PyTCGAPu sequences, cytosine was methylated in vitro in both DNA strands. It is concluded that the sequence 5'-PyTCGAPu-3' is methylated by the DNA methyltransferase (of cytosine) of B. subtilis Marburg.

5-Methylcytosine↗
PubMed1985

A study of the prognostic role of serum fucose and fucosyl transferase in cancer of the uterine cervix.

Serum fucose levels and fucosyl transferase activities have been designated as nonspecific markers of malignancy, and play an important role in the diagnosis of different types of malignancies. In the present study, attempts were made to determine the prognostic significance of these markers in patients with cancer of the uterine cervix after therapy. It was found that both serum fucose and fucosyl transferase, which were elevated in untreated patients declined significantly in patients responsive to therapy at different follow-up intervals, but not in patients unresponsive to therapy.

Adult↗
PubMed1984

Effect of 5-azacytidine on DNA methylation and on the enzymes of de novo pyrimidine biosynthesis in Bacillus subtilis Marburg strain.

In Bacillus subtilis, 5-azacytidine, an analog of cytidine, causes a time- and dose-dependent growth inhibition. Methyl donors are unable to overcome azacytidine-induced inhibition while pyrimidine nucleosides, except orotidine, can revert this inhibition totally. On the other hand, pyrimidine bases, except uracil, are unable to restore growth in azacytidine-treated cells. Uracil, at a high concentration, can revert growth inhibition only inefficiently. However, a considerable relief of growth inhibition by uracil occurs in the presence of a ribose donor. In azacytidine-treated B. subtilis cells methylation of bases in DNA is not affected either quantitatively or qualitatively and DNA methyltransferase activity remains unaltered as compared to the untreated cells, apparently due to the absence of azacytidine incorporation into the DNA. The inability of B. subtilis cytidine kinase to phosphorylate azacytidine is the probable reason for this non-incorporation. Analysis of the enzymes of de novo pyrimidine biosynthesis has shown that orotidine monophosphate pyrophosphorylase is specifically repressed by azacytidine treatment.

Azacitidine↗
PubMed1984

Chemical transformation of Swiss mouse embryo fibroblasts in primary culture.

Trypsinized secondary cultures of various cell systems have been frequently used by different investigators as models to study, in vitro chemical transformation. In the present study, non-trypsinized primary cultures of fibroblasts derived from fetuses of 14 days gestational age have been used to find out the timings of in vitro chemical transformation by 20-methylcholanthrene and has been designated as PMM-14 cells. These PMM-14 cells have been compared with trypsinized cultures of the same cell systems. The criteria for neoplastic transformation considered in the study involved the appearance of morphological changes, indefinite growth in tissue culture, acquisition of tumorigenic potential in vitro as evidenced by in vivo tests and in vivo latency period for palpable tumor formation. The time span of neoplastic transformation of non-trypsinized embryo fibroblasts in culture was remarkably reduced in comparison with trypsinized cultures of same cell systems. Such discrepancy seems to be due to repeated use of trypsin which may replace many of vital cell surface molecules causing a delay in the expression of carcinogen-induced malignancy. Similarly, repeated subculture before transformation may also have a role in the delayed expression of malignancy.

Animals↗
PubMed1984

Circulating immune complexes in sera of patients with oral cancer.

Circulating immune complexes (IC) in the sera of patients with oral cancer have been measured by using polyethylene glycol (PEG) precipitation assay. At least 60% of patients with carcinomatous buccal mucosa were found to have markedly higher amounts of IC. Results have been discussed in view of other types of cancer and the various methods used for the assay of IC.

Adult↗
PubMed1983

Tube leukocyte adherence-inhibition response to related and unrelated tumor antigens in mammary tumor-bearing mice.

Tube leukocyte adherence-inhibition response to syngeneic mammary tumor antigens and alloantigens from Ehrlich ascites carcinoma and fibrosarcoma was studied in spontaneous mammary tumor-bearing C3H/Jax mice. The mice with limited tumor burden responded significantly to the mammary tumor antigen and the Ehrlich ascites carcinoma antigen. The reactivity disappeared with increased tumor load. Oscillatory responses in leukocyte adherence inhibition to the reactive antigens was observed with increasing tumor weight. There was no response to the alloantigen of fibrosarcoma.

Animals↗
PubMed1983

Serum fucosyl transferase activity and serum fucose levels as diagnostic tools in malignancy.

Glycoproteins play a significant role in neoplastic transformations. Both the levels of fucose and the activity of fucosyl transferase, which mediates the assembly of the oligosaccharide moieties of the glycoprotein chains, have been found to be elevated in neoplastic conditions. Since these elevations are common features of a variety of neoplastic cells, these two have been designated as non-specific markers of malignancy. In the present study, the fucose level and fucosyl transferase activity were determined in the sera of cancer patients and an attempt was made to establish a relationship between the two. It was found that both the fucose levels and fucosyl transferase activities showed considerable elevation in the five cancer groups studied, establishing them as useful diagnostic parameters. However, it was also observed that the rate of increased fucosyl transferase activity was not fully reflected in the resulting serum fucose levels in a few cases.

Carcinoma↗
PubMed1977

Specific alteration of the 30S ribosomal subunits of Bacillus subtilis during sporulation.

Active 30S ribosomal subunits were isolated from vegetative and sporulating cells of Bacillus subtilis. Both subunits were able to function in polyuridylic acid of phage phie messenger ribonucleic acid-dependent protein synthesis in vitro. The sporulation 30S subunits were highly active in polyuridylic acid-dependent polyphenylalanine synthesis but showed a reduced activity in the presence of natural messenger ribonucleic acid as compared with their vegetative counter-parts. The reduced activity was independent of the source of 50S particles and initiation factors (vegetative or sporulation). The alteration of the 30S sporulation subunits appears to be related to the sporulation process, since the same subunits isolated from stationary-phase cells of an asporogenic mutant did not show any impairment in protein synthesis in vitro.

Bacillus subtilis↗
PubMed1975

Ribosomal proteins of Bacillus subtilis vegetative and sporulating cells.

The ribosomal subunit proteins(30S and 50 S) from vegetative and sporulating cells of Bacillus subtilis 168M were analyzed by two dimensional acrylamide gel electrophoresis. Twenty two proteins were identified in the 30S subunits and 28 proteins are detectable in the 50S subunits. The number of proteins and their electrophoretic mobility seem to remain unaltered during the sporualtion process. The ribosomal proteins of a thermosensitive sporulation mutant (ts-4), isolated from stationary phase cultures, under permissive (for sporulation) and non-permissive conditions, did not show any qualitative difference in either of the subunits. The 21S precursor particles derived from log phase cell ribosomes show two different proteins, in addition to those present in the 30 S subunit. It is suggested that these two proteins either disappear or are modified during the maturation process.

Bacillus subtilis↗
PubMed1975

Isolation of 30S and 50S active ribosomal subunits of Bacillus subtilis, Marburg strain.

Active 30S and 50S ribosomal subunits were isolated from Bacillus subtilis. These subunits were able to perform not only protein synthesis in the presence of artificial or natural messenger ribonucleic acid but also the specific functions characteristic of each of the subunits. Thus the 30S subunits alone are able to bind formyl-methionyl-transfer ribonucleic acid, and the 50S subunits carry the peptidyl transferase activity.

Bacillus subtilis↗