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Biomedical subjects

R P Sinha

Publications and source records attributed to R P Sinha.

At least 19 recordsLinked to original sources
PubMed1995

Disintegration of phycobilisomes in a rice field cyanobacterium Nostoc sp. following UV irradiation.

The effects of ultraviolet-B (UV-B, 280-315 nm) irradiation on survival, growth and phycobilisome assembly have been studied in the N2-fixing cyanobacterium Nostoc sp. Survival and growth were virtually arrested after 120 min of UV irradiation. The phycobiliprotein fractions showed a decrease in absorption and fluorescence as well as a shift towards shorter wavelengths indicating the impairment of energy transfer from phycobiliproteins to the photosynthetic reaction centers. This was further supported by SDS-PAGE analysis of the fractions which revealed a loss in high molecular mass rod-core and core-membrane linker polypeptides. Also the low molecular mass phycobilin (alpha beta) monomers decreased, showing that the supra-molecular organization of the phycobilisomes disintegrated during UV irradiation.

Bacterial Proteins↗
PubMed1994

Effect of combination therapy in Mycobacterium paratuberculosis infected rabbits.

Rabbits, infected with M paratuberculosis of caprine origin, were treated with streptomycin sulphate and rifampicin in combination with levamisole hydrochloride for a period of 2 months. Marked clinical response including significant rise in total serum protein, albumin and globulin were recorded in treated groups. Highly significant higher leucocyte migration inhibition indicating enhanced CMI reaction, occurred in rabbits treated for 4 weeks. Complete elimination of M. paratuberculosis from faeces, intestines and mesenteric lymph nodes was observed. They were also absent from spleen, kidneys, lungs and liver of rabbits treated with rifampicin and levamisole, whereas were present in lungs of the rabbits administered with streptomycin and levamisole. Absence of characteristic lesions of paratuberculosis and evidence of regenerative reaction were observed in visceral organs of rabbits treated with rifampicin and levamisole. Effectiveness of rifampicin is attributed to its effect on lymphocyte, the primary cell involved in cell mediated immunity. Rifampicin-levamisole combination appeared superior to streptomycin-levamisole in eliminating the infection of M. paratuberculosis from infected rabbits. Approximate cost of treatment was calculated to be Rs 8.50 per kg body weight. Cattle, sheep and goats, if treated in early stage of infection may recover from paratuberculosis.

Animals↗
PubMed1991

Stability of plasmids in lactococci during extended incubation in growth media.

The stability of plasmids in Lactococcus lactis ssp. lactis strains C2 and ML3, and L. lactis ssp. cremoris strains ML1 and SC607, was investigated by extended incubation of bacterial cells in low nutrient media under acidic conditions. Strains were grown overnight (16-18 h) in skim milk and unbuffered medium (M17-) at 32 degrees C and subsequently held at that temperature for extended periods (greater than or equal to 96 h). Lac- variants were obtained from each strain in milk and (M17-) broth. The plasmid profiles of Lac- variants when compared with their parental Lac+ strains showed loss of one or more plasmid bands. None of the Lac- mutants showed loss of smaller plasmids (less than 5 MDa) indicating that smaller plasmids in lactococci are more stable under these conditions than larger plasmids (greater than 10 MDa). Concomitant loss of the Lac+ phenotype and plasmids by the method used in the present investigation may have application for isolating mutants devoid of one or more plasmids.

Electrophoresis, Agar Gel↗
PubMed1989

A new simple method of curing plasmids in lactic streptococci (Streptococcus cremoris; Streptococcus lactis, plasmids).

A simple method for curing plasmid DNA from lactic streptococci is described. When strains of lactic streptococci are grown overnight at 32 degrees C in an unbuffered medium (M17-) and held at the same temperature for an extended period (96 h), the acid environment induces loss of plasmid DNA of different sizes. If the process of growth in M17- broth followed by extended incubation at 32 degrees C is repeated, most of the plasmids are lost, as revealed by gel electrophoretic profiles of DNA. The method is simple and efficient in curing plasmids of lactic streptococci without use of any mutagenic chemical.

Culture Media↗
PubMed1986

Toxicity of organic acids for repair-deficient strains of Escherichia coli.

The wild-type strain and four DNA repair-deficient strains (uvrA6, uvrB5, recA56, and polA1) of Escherichia coli K-12 were treated with acetic acid, lactic acid, and p-aminobenzoic acid at pH 3.5 during their stationary phase of growth. All three acids were highly toxic to the polymerase-deficient strain. The greater sensitivity of the strain carrying the polA1 gene than its isogenic pol+ derivatives suggested that damage caused by acidity requires polA+ gene products for repair.

4-Aminobenzoic Acid↗
PubMed1986

Development of high-level streptomycin resistance affected by a plasmid in lactic streptococci.

Some lactose-negative (Lac-) mutants of Streptococcus lactis C2 and ML3 exhibited development of very high level streptomycin resistance after incubation with subinhibitory concentrations of the drug for 18 to 22 h. These drug-resistant mutants showed no loss of resistance even after 6 months of subculturing in broth without any drug. The parental Lac+ strains did not show mutation to high-level streptomycin resistance. The Lac+ characteristic of the parental strain was conjugally transferred to Lac- derivatives of C2 and ML3, showing the ability to mutate to high-level resistance. When transconjugants were analyzed for this characteristic, they showed both mutable and nonmutable Lac+ types. The results suggested that genetic information for mutation to high-level streptomycin resistance in lactic streptococci resides on the chromosome, and its expression is affected by a plasmid. The plasmid profiles of strains C2, ML3, C2 Lac-, ML3 Lac-, and two kinds of transconjugants confirmed the presence of a plasmid of approximately 5.5 megadaltons in strains showing no mutation to high-level streptomycin resistance, while strains missing such a plasmid exhibited high-level streptomycin resistance after incubation with subinhibitory concentrations of the drug.

Drug Resistance, Microbial↗
PubMed1977

Acriflavine-resistant mutant of Streptococcus cremoris.

Selection for resistance to acriflavine in Streptococcus cremoris resulted in cross-resistance to the drugs neomycin, streptomycin, ethidium bromide, mitomycin C, and proflavine. Furthermore, the mutants showed resistance to lytic bacteriophages to which the parental strain was sensitive, and, unlike the parent, the mutants grew well at higher temperatures (40 degrees C). Revertants selected independently either for temperature sensitivity or for acriflavine sensitivity lost resistance to all the drugs and dyes but retained the bacteriophage resistance phenotype. The acriflavine-resistant mutation resulted in an increase in resistance by the bacterial cells to sodium dodecyl sulfate, a potent solvent of lipopolysaccharide and lipoprotein. It is suggested that the acriflavine resistance mutation determines the synthesis of a membrane substance resistant to higher temperatures.

Acridines↗