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Biomedical subjects

L Joshi

Publications and source records attributed to L Joshi.

At least 19 recordsLinked to original sources
PubMed1995

Cloning of a cuticle-degrading protease from the entomopathogenic fungus, Beauveria bassiana.

A Beauveria bassiana extracellular subtilisin-like serine endoprotease is a potential virulence factor by virtue of its activity against insect cuticles. A cDNA clone of the protease was isolated from mycelia of B. bassiana grown on cuticle/chitin cultures. The amino acid sequence of this gene was compared to that of Metarhizium anisopliae Pr1, the only pathogenicity determinant so far described from an entomopathogenic fungus, and proteinase K, isolated from Tritirachium album, a saprophytic fungus. The cDNA sequence revealed that B. bassiana Pr1 is synthesized as a large precursor (M(r) 37,460) containing a signal peptide, a propeptide and the mature protein predicted to have an M(r) of 26,832.

Amino Acid Sequence↗
PubMed1995

Recombinant thyrotropin containing a beta-subunit chimera with the human chorionic gonadotropin-beta carboxy-terminus is biologically active, with a prolonged plasma half-life: role of carbohydrate in bioactivity and metabolic clearance.

Recombinant TSH is now successfully being used in clinical studies of thyroid cancer. Because of its therapeutic potential, we have constructed a longer acting analog of TSH by fusing the carboxy-terminal extension peptide (CTEP) of hCG beta onto TSH beta. When coexpressed either with alpha-subunit complementary DNA or alpha minigene in African green monkey (COS-7) and human embryonic kidney (293) cells, the chimera was fully bioactive in vitro and exhibited enhanced in vivo potency associated with a prolonged plasma half-life. The addition of 25 amino acids with 4 O-linked oligosaccharide chains did not affect the assembly and secretion of chimeric TSH. Wild-type (WT) and chimeric TSH secreted by COS-7 and 293 cells displayed wide differences in their plasma half-lives, presumably due to the presence of terminal sialic acid and SO4 on their oligosaccharide chains, respectively. Chimeric and WT TSH secreted by both cell lines demonstrated similar bioactivity in cAMP production, with some differences in [3H]thymidine incorporation. Chimeric TSH appears to be more effective in COS-7 cells than in 293 cells, as judged by growth assay. COS-7-produced chimeric TSH showed the maximum increase in half-life, indicating the importance of sialic acid in prolonging half-life and in vivo potency. Sulfation of both subunits, predominantly beta and to a lesser extent alpha, appears to be responsible at least in part for the increased metabolic clearance of WT and chimeric TSH secreted by 293 cells. Apart from its therapeutic potential, chimeric TSH produced in various cell lines can be used as a tool to delineate the roles of sulfate and sialic acid in the in vivo clearance and, thereby, the in vivo bioactivity.

Animals↗
PubMed1991

Analysis of organotin uptake in Escherichia coli K-12.

The effect of tributyltin chloride (TBT) was potentiated by the presence of Tris ions in the growth medium compared with phosphate ions. The growth of Escherichia coli in the presence of Tris ions was inhibited completely at a concentration of 25 microM TBT whereas 79% growth was recorded in the presence of phosphate ions. Tris ions caused more protein to be released into the medium than phosphate ions. However, apart from protein release the rate of organotin uptake was less in Tris than in phosphate ions. Phosphate ions may play a positive role in the active accumulation of organotin into E. coli cells by providing cellular energy.

Bacterial Proteins↗
PubMed1991

Studies on the lactose character in Salmonella S:41:z10.

A number of plasmids carrying the Lac+ character have been reported. Lac+ character of salmonella S:41:z10:- studied for transfer of Lac+ character to standard Escherichia coli K12 Lac-F- Nalr and Escherichia coli K12 F- Lac- Rifr, failed to transfer in in vitro experiments. Similarly, identification and characterisation of plasmid DNA by agarose gel electrophoresis technique did not show specific plasmid DNA as compared to standard molecular weight plasmids. Plasmid DNA appeared to have been embedded with chromosomal DNA molecule.

Animals↗
PubMed1989

Interaction of EDTA with tributyltin induced cellular toxicity.

Tributyltin inhibited the growth of cells in concentration dependent manner. The inhibitory effect of tributyltin on E. coli was enhanced in the presence of metal ion chelator, EDTA. This was due to EDTA induced increase of permeability of bacterial cell envelope to tributyltin. In case of EDTA treated cells the rate of uptake of tributyltin was more pronounced as compared to control.

Drug Interactions↗
PubMed1980

Demonstration of luteinizing hormone/human chorionic gonadotrophin receptor-binding inhibitor in aqueous extracts of frozen human corpus luteum.

Aqueous extracts of frozen human corpora lutea were tested for the presence of an inhibitor of luteinizing hormone-receptor site binding (LHRBI) and for the subsequent effect on the stimulatory response of luteinizing hormone (LH) on progesterone synthesis by sheep ovarian cells. In the presence of human corpus luteum extract of normal menstrual cycle (30,000-g supernatant), the binding of 125I human chorionic gonadotrophin (hCG) to granulosa and luteal cells of sheep ovaries was markedly reduced, but the ability of rat testicular LH receptors to bind labelled hCG was less affected. However, extracts of corpora lutea of the first trimester of pregnancy appeared to be less inhibitory on the binding of LH/hCG to ovarian cells and had no effect on the binding of rat testicular cells compared to those of normal menstrual cycle. Addition of both extracts separately inhibited the LH-stimulated in vitro progesterone synthesis by granulosa cell cultures and by incubated sheep corpus luteum slices. These findings provide evidence for the presence of LHRBI in human corpus luteum.

Animals↗
PubMed1977

Effect of contraceptive steroids on human lactation.

Biochemical studies to detect changes occurring in the composition of mother's milk from the initiation of proper lactation to weaning were done in a group of 36 postpartum women, volunteers who were either using the conventional contraceptives or taking a low-dose combination pill, a low-dose progestational compound, or a 3 or 6 monthly injection as a mode of contraception. Apart from a significant increase in the protein content of milk and a slight increase in the quantity, the 3 monthly injection group behaved exactly like the control. On the other hand, the 6 monthly injection group showed a significant increase in quantity but with a significant decrease in protein, fats, and calcium. The low-dosage progestogens group showed a significant decrease in the quantity of fats and the calcium content of milk, but, surprisingly, the addition of 10 micrograms of estrogens to the low-dosage progestogen indicated a pattern almost similar to the control.

Contraceptive Agents, Female↗
PubMed1974

Conjoined twins.

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Abortion, Spontaneous↗