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Biomedical subjects

R N Sharma

Publications and source records attributed to R N Sharma.

At least 73 records · Page 4Linked to original sources
PubMed1979

Multiplicity of induction patterns of rat liver microsomal mono-oxygenases and other polypeptides produced by administration of various xenobiotics.

Induction of hepatic microsomal mono-oxygenase species after administration of various xenobiotics is a well-documented phenomenon. To examine the number and specific species of rat liver microsomal membrane polypeptides involved in such responses, we have used sodium dodecyl sulphate/polyacrylamide-gel electrophoresis to analyse microsomal fractions from animals treated with a number of important xenobiotics. The following are the principal points to have emerged from this study. 1. A minimum of twelve electrophoretically distinct patterns of induction of haemopolypeptides and other polypeptides could be distinguished after administration, either singly or in certain combinations, of phenobarbital, 3-methylcholanthrene, polychlorinated biphenyls, 2-acetylaminofluorene, safrole (or isosafrole), pregnenolone-16 alpha-carbonitrile and ethanol. The patterns consisted of various permutations of the amounts of eight polypeptides of 47000-56000 mol.wt., of which at least three were haemopolypeptides. The possible identities of these polypeptides, which included species of cytochrome P-450, cytochrome P-448 and epoxide hydratase, are discussed. 2. Agents (3-methylcholanthrene, benzo[a]-pyrene, polychlorinated biphenyls, 2,3,7,8-tetrachlorodibenzo-p-dioxin and beta-naphthoflavone) that result in the induction of cytochrome P-448 caused a marked increase in two polypeptides of 54000 and 56000 mol.wt., whereas safrole and isosafrole induced only the former polypeptide. 3. Administration of 2-acetylaminofluorene resulted in the induction of two polypeptides; evidence is presented that suggests that one of these is a species of epoxide hydratase [cf. Levin, Lu, Thomas, Ryan, Kizer & Griffin (1978) Proc. Natl. Acad. Sci. U.S.A. 75, 3240-3243] ANd that the other may be a novel haemopolypeptide. 4. The overall results emphasize the complexity of the responses exhibited by rat liver microsomal fractions to the administration of xenobiotics.

2-Acetylaminofluorene↗
PubMed1979

Suitability of L-[35S]methionine for studying the biosynthesis of the polypeptides of mouse liver endoplasmic reticulum membrane fractions in vivo.

The use of L-[35S]methionine (500-700 Ci/mmol (1 Ci = 37 GBq) for labelling the polypeptides of liver rough (R) and smooth (S)endoplasmic reticulum (ER) membrane fractions in vivo was studied. Adult mice were injected intraperitoneally with 400 muCi of the isotope and killed at various times (2'min to 24 h) thereafter. RER and SER fractions were prepared, stripped of ribosomes, and treated with Triton X-100 to remove intravesicular contents. Sufficient radioactivity was present in individual aliquots (75 microgram protein) of the ER membrane fractions to permit their analysis by fluorography after separation by electrophoresis in polyacrylamide gels containing sodium dodecyl sulphate. By 3 min, although the majority of the labelled components were of intravesicular origin, some 12 membrane polypeptides were labelled in the RER fraction (including one corresponding in migration to cytochrome P-450); some 6 of these latter polypeptides were labelled to a lesser degree in the SER membrane fraction at this time. By 5 min, the patterns of radioactive polypeptides of the RER and SER fractions (including both membrane and intravesicular components) were identical. By 7 min, some 28 labelled membrane polypeptides were detectable in the total microsomal membrane. Analysis of the 24-h samples revealed that all the membrane polypeptides seen by staining with Coomassie blue were visualised by fluorography. Other studies revealed the applicability of the approach used for producing highly labelled cell sap and serum proteins. The overall results demonstrate the suitability of L-[35S]methionine administered in vivo for producing mouse liver ER membrane polypeptides of relatively high radioactivity and are consistent with a rapid conversion of RER to SER by ribosome detachment or membrane flow.

Animals↗
PubMed1979

Normal metyrapone response after 1 month of high-dose methylprednisolone in cancer patients: a phase I study.

A dose of 125 mg of methylprednisolone was given iv each morning for 28 days to six patients with cancer. The posttreatment mean AM/PM serum cortisol (hydrocortisone) level of 19.55/11.27 microgram/dl showed a statistically significant (P less than 0.05) diurnal rhythm and did not differ from the pretreatment level (19.28/11.85 microgram/dl). The response to metyrapone (750 mg orally, every 4 hours X six doses) was assessed in five of the six patients before and after treatment. No abnormally low Compound S (11-deoxycortisol) levels were observed. The mean serum Compound S level (15.30 microgram/dl) achieved after treatment did not differ significantly from the pretreatment mean level (20.24 microgram/dl, P greater than 0.1). No adverse clinical effects were observed during or after this steroid treatment. Since significant hypothalamic-pituitary-adrenal suppression has not been demonstrated, this regimen appears to be safe for use in controlled studies of clinical efficacy.

Adenocarcinoma↗
PubMed1978

Electrophoretic studies on liver endoplasmic reticulum membrane polypeptides and on their phosphorylation in vivo and in vitro.

Sodium dodecyl sulfate-polyacrylamide gel electrophoresis was used to examine the polypeptide patterns of rat liver rough and smooth endoplasmic reticulum (ER) membrane fractions stripped of ribosomes. Approximately 67 polypeptides were resolved from the rough ER membrane fraction. The polypeptide pattern of the smooth ER membrane fraction was similar to that of the rough ER membrane fraction, but exhibited substantially lower amounts of some seven polypeptides. Three of these polypeptides, of apparent molecular weights 63,000, 65,000, and 87,000, were of particular interest, as they could not be ascribed to contamination of stripped rough ER membrane fractions by residual ribosomal polypeptides. Conditions of treatment with low concentrations of trypsin were established that markedly diminished the capacity of the stripped rough ER membrane fraction to bind ribosomes in vitro and that also effected a partial detachment of ribosomes from nonstripped rough ER membranes; the results of electrophoretic analyses of rough ER membrane fractions treated in these manners are described. Comparison of the polypeptide patterns of guinea pig, mouse, and rabbit liver ER membrane fractions with rat liver ER membrane fractions revealed considerable variations in the distribution of the polypeptides of 63,000, 65,000, and 87,000 molecular weight among the ER membrane fractions of these species. The combined results of these studies indicate that the polypeptide of 87,000 molecular weight, although particularly sensitive to attack by trypsin, is not involved in the binding of ribosomes to the rough ER membrane fraction. Studies by others (cf. Kreibich, G., Grebenau, R., Mok, W., Pereyra, B., Rodriguez-Boulan, E., and Sabatini, D. D. (1977) Fed. Proc. 36, 656) have implicated the polypeptides of 63,000 and 65,000 molecular weight in this process. The patterns of phosphorylated polypeptides of rough and smooth ER membrane fractions of rat and mouse liver were also examined, using labeling in vivo with sodium [32p]phosphate or in vitro with [gamma-32P]ATP. Approximately 25 phosphorylated components were resolved by electrophoresis in the ER membrane fractions of both species. Evidence is presented that suggests that the great majority of these components are phosphopolypeptides. Differences were noted in the patterns of phosphorylation produced by in vivo and in vitro labeling; minor differences were also observed between the patterns of phosphorylation of the rough and smooth ER membrane fractions in either situation. The overall results afford an indirect approach toward evaluating the possible involvement of specific rough ER membrane polypeptides in ribosome-binding and reveal that liver ER membranes contain a substantially greater number of phosphorylated polypeptides thatn previously reported.

Animals↗
PubMed1977

Lenticonus in Alport's syndrome. A family study.

A South Indian family with three well documented cases of Alport's syndrome with anterior lenticonus are reported. Clinical features of the syndrome including ocular and laboratory findings have been presented and discussed. Macular pigmentation, 5 cases, subcapsular opacity and nephrotic syndrome, one case each, observed in the present series are of great interest and are quite rare in patients with Alport's syndrome. Critical analysis of the family pedigree revealed autosomal dominance with incomplete penetrance as the possible mode of genetic transmission of the disease.

Adolescent↗
PubMed1976

Lesions of Marek's disease in some modified cutaneous appendages of chicken.

Studies were undertaken to determine the presence of lesions and immuno-fluorescent (IF) antigen of Marek's disease (MD) in the comb, wattles and skin overlaying the shank of MD affected birds. Lesions were more common in the comb than in the wattles and shanks, and were characterized by degeneration of epithelial lining cells and accumulation of lympho-reticular cells around the blood vessels of the dermis. Diffuse infiltration of these cells replacing varialbe areas of dermis were also seen in some cases. Immunofluorescent antigen was mostly confined to epidermal epithelium and was detected in comb from majority of cases, and the frequency of detection of IF antigen was similar to the presence of MD lesions in these tissues. This study indicates that the presence of lesions and viral antigen (If) of MD in these cutaneous appendages might play a significant role in epidemiology and diagnosis of this disease.

Animals↗