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Biomedical subjects

K S Bhat

Publications and source records attributed to K S Bhat.

At least 37 records · Page 2Linked to original sources
PubMed1989

Characterization of primary transcripts and identification of transcription initiation sites on the heavy and light strands of mouse mitochondrial DNA.

Total RNA from Ehrlich ascites mitochondria pretreated with RNase-free DNase was capped in vitro with [alpha-32P]GTP and guanylyl transferase. The cappable RNAs representing the primary transcripts show a heterogeneous size distribution with four major species of 46, 63, 94, and 152 nucleotides and four minor species of 19, 24, 104, and 790 nucleotides in size. Hybridization with the D-loop DNA probes shows that the 19-nucleotide-long capped RNA is coded by the H-strand of mitochondrial DNA while the rest are coded by the L-strand. S1 nuclease mapping and primer extension analyses suggest the occurrence of a transcription initiation of H-strand at about 19 nucleotides upstream from the start of the tRNA(Phe) gene. All of the L-strand cappable RNAs have a common 5' end mapping to nucleotide 16,183 +/- 5 of the genome. The 3' ends of four major cappable RNA species line up to the conserved sequence boxes, putative start sites of DH-DNA; and in fact about 2% of these cappable species are found to exist as DNA-linked RNA under steady-state conditions. The 3' end of the 790-nucleotide cappable RNA lies close to the start of the tRNA(Pro) gene, suggesting that it may be the true precursor of L-strand transcript endonucleolytically processed at the 3' end. The level of L-strand-coded cappable RNAs varies markedly under different growth conditions. Treatment with cycloheximide results in a reduction while chloramphenicol caused over 3-fold induction, suggesting that these "primer" RNAs may have an additional regulatory function.

Animals↗
PubMed1985

Expression of the cytochrome b-URF6-URF5 region of the mouse mitochondrial genome.

The nature of RNA coded by the only light-strand (L-strand) open-reading frame unidentified reading frame 6 (URF6) was studied by using a variety of single- and double-strand DNA subclones derived from the 3.6-kilobase (kb) cytochrome b (cyt b)-URF5 coding region of the mouse mitochondrial genome. Northern blot experiments using single-strand-specific M13 clones indicate that both the heavy (H) and L strands of this genomic region are symmetrically transcribed and processed into poly(adenylic acid) [poly(A)] RNAs of comparable size. The 1.2- and 2.4-kb RNAs coded by the H strand, putative mRNAs for cyt b and URF5 reading frames, respectively, are derived from a common precursor of 3.6-kb RNA. The L-strand-coded 1.15-kb RNA, on the other hand, is derived from a short-lived precursor of 3.6-kb RNA by a multiple-step processing involving a 2.4-kb intermediate RNA. The S1 nuclease protection experiments using both the 3'- or 5'-end-labeled DNA probes and also affinity-purified 32P-labeled RNA probes indicate that the 1.15-kb RNA maps between the start of the URF6 reading frame (3' end) and a region 590-600 nucleotides to the 5' end of this reading frame. The 1.15-kb RNA thus contains the entire URF6 coding sequence and an about 590-nucleotide-long 3' untranslated region. The molar abundance of the three mRNAs in the steady-state mitochondrial RNA varies markedly. The 1.15-kb URF6 mRNA is only one-tenth the level of 1.2-kb cyt b mRNA, although it is nearly as abundant as the 2.4-kb URF5 mRNA.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Nature of steady-state and newly synthesized mitochondrial messenger ribonucleic acids in mouse liver and Ehrlich ascites tumor cells.

The steady-state mitochondrial mRNAs in Ehrlich ascites tumor cells and mouse liver were identified by the Northern blot analysis using nick-translated mtDNA and 32P-labeled cDNA probes. The steady-state mRNA species were compared with the poly(A)-containing RNA synthesized in vitro in isolated mitoplasts. The results show that the isolated mitoplast system can efficiently transcribe almost all of the poly(A)-containing RNAs detected in the steady-state RNA population. It is also seen that the mode of transcription and maturation of mitochondrial mRNAs in different mouse tissues are identical. The results of Northern blot analyses suggest that there may be at least two different modes of mRNA maturation depending upon if the reading frames are interrupted by tRNA cistrons or not. mRNAs for reading frames with adjacent tRNA cistrons downstream appear to be processed from very short-lived precursors. In contrast, mRNAs coded by adjacently located reading frames with no interrupting tRNA genes such as URF3 -cyt ox III and URF5 -cyt b are processed from relatively long-lived precursors. The in vitro pulse-labeling studies also show that almost all of the poly(A)-containing mRNAs are transcribed at nearly identical rates, suggesting that the major regulation of mt gene expression may occur at the level of translation or mRNA decay. The present experiments have also identified a 1.85-kb poly(A)-containing RNA as the putative URF5 mRNA.

Animals↗
PubMed1983

Distribution of HMW proteins and crystallins in cataractous lenses from undernourished and well-nourished subjects.

This paper presents results of a comparative study of the HMW proteins and crystallins from 9900 g supernatant fraction of cataractous lens homogenate between undernourished and well-nourished subjects. The proportion of HMW protein from cataractous lenses obtained from undernourished subjects was markedly reduced, the proportion of alpha-crystallin was increased and the proportions of beta- and gamma-crystallins were similar as compared to well-nourished subjects. Values of insoluble/soluble protein ratios were significantly higher in the former group compared to the latter. These results suggest that the process of lens protein insolubilization occurs earlier or faster in undernourished subjects.

Cataract↗
PubMed1982

Changes in lens proteins in undernourished and well-nourished patients with cataract.

1. Patients with cataract were classified into undernourished (twenty-eight subjects) and well-nourished (twenty-seven subjects) groups based on the anthropometric index, weight (kg)/height (m)2. Those with a value for the index of less than 18 were considered as undernourished. 2. Lenses were classified into four groups on the basis of nuclear colour as proposed by Pirie (1968). Lenses of pale uniform colour or yellow colour were included in group 1, those with brownish-yellow nucleus in group 2, those with a yellowish-brown nucleus in group 3 and those with brown nucleus in group 4. 3. Irrespective of group, the wet weight, dry weight, percentage moisture and total protein content of cataractous lenses from undernourished patients were similar, as were the corresponding values for well-nourished patients. On the other hand, the percentage of soluble proteins in lenses tended to decrease with deepening of nuclear colour in both groups of patients. Further, soluble protein concentrations in lenses from undernourished patients were significantly lower as compared to those from well-nourished patients. 4. The results suggest that nutritional factors could influence the composition of cataractous lenses.

Adult↗
PubMed1981

Tissue-irritation potential of dilute formocresol.

Bacteriologic studies indicate that 50 percent formocresol in propylene glycol is an efficient bactericide. The tissue-irritation potential of this concentration was evaluated in rats. Assessment of the subcutaneous connective tissue reactions to 50 percent formocresol, 100 percent formocresol, and normal saline solution (as a control) indicates that formocresol, when diluted with propylene glycol, is significantly less irritating to the subcutaneous connective tissue of rats. The atraumatic implantation technique also seems to influence significantly the intensity of tissue reaction. Dilute formocresol deserves further study to evaluate its use in clinical endodontics.

Animals↗
PubMed1980

Antibacterial properties of dilute formocresol and eugenol and propylene glycol.

Formocresol and eugenol are the two nonspecific intracanal medicaments commonly used in endodontic practice. Both have high tissue irritation potential when used in conventional strength. Propylene glycol is an alcohol that is injectable and itself possesses significant antibacterial action. It is a popular vehicle and hence was used to modify the two drugs. Standard bacteriologic methods were employed to test the antibacterial action of these lower concentrations of the two drugs against four test organisms. The investigations indicate that formocresol at as low as 10 to 20% and eugenol at 75% are bactericidal in action and hence may be useful at these concentrations for clinical use. Evaluation of these lower concentrations is warranted for possible clinical use. Propylene glycol, which possesses antibacterial action and is remarkably innocuous to tissues, appears to be a suitable vehicle for dilution of formocresol and eugenol.

Anti-Infective Agents, Local↗