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Biomedical subjects

M Singh

Publications and source records attributed to M Singh.

At least 19 recordsLinked to original sources
PubMed1992

The Mycobacterium tuberculosis 38-kDa antigen: overproduction in Escherichia coli, purification and characterization.

The 38-kDa protein (Ag38) of the Gram+ bacterium, Mycobacterium tuberculosis H37Rv, is an immunodominant antigen of potential utility for diagnosis and vaccine development. Assessment of this potential requires large amounts of the purified protein that would be difficult, if not impossible, to obtain from M. tuberculosis itself. The gene coding for Ag38 had been previously cloned and in the present study was expressed as an unfused protein in Escherichia coli under the control of strong transcriptional (bacteriophage lambda pLpR) and translational (atpE) signals. Fermentation of the recombinant E. coli K-12 strain CAG629[pMS9-2], which is deficient in Lon protease and the heat-shock response, produced recombinant Ag38 (reAg38) at high levels (about 10% of total cellular protein). The reAg38, which accumulated as inclusion bodies, was completely solubilized in 6 M guanidine.HCl, refolded and purified to apparent homogeneity. The product showed the expected amino acid composition and M(r), and had similar reactivities as the native protein with three different mAb. Polyclonal antibodies raised against reAg38 reacted strongly with the native antigen in enzyme-linked immunosorbent assay. These results demonstrate that reAg38, which cannot be distinguished antigenically from the native protein of M. tuberculosis, can be prepared in quantity from E. coli.

Amino Acid Sequence↗
PubMed1992

Decrease of myocardial infarct size with desferrioxamine: possible role of oxygen free radicals in its ameliorative effect.

The ability of an iron chelator, desferrioxamine, to inhibit the infarct size in in vivo rat heart was assessed. Anaesthetised rats were subjected to coronary artery ligation (CAL) for 72 hr and infarct size was measured macroscopically using TTC staining. Systolic blood pressure and ECG were monitored. Desferrioxamine (10 mg/kg and 20 mg/kg i.v.) administered half an hour after CAL markedly reduced the infarct size. However, drug treatment did not alter the systolic blood pressure of animals. In addition, desferrioxamine in vitro and in vivo demonstrated an inhibition of rat PMN-evoked and luminol-enhanced chemiluminescence. The capacity of desferrioxamine to impair the generation or to scavenge directly oxygen free radicals may be responsible for its beneficial effect on myocardial infarct size in rats.

Animals↗
PubMed1992

Differential effects of polyamine homologues on the prevention of DL-alpha-difluoromethylornithine-mediated inhibition of malignant cell growth and normal immune response.

Natural polyamines (putrescine, spermidine, and spermine) are ubiquitous cellular cations that play an important role in cell proliferation and differentiation. Ornithine decarboxylase is the first and a rate-limiting enzyme in the biosynthesis of polyamines. Polyamine depletion using DL-alpha-difluoromethylornithine (DFMO), an inhibitor of ornithine decarboxylase, has been shown to suppress cell growth in a variety of settings, including those of tumor and lymphocyte proliferation. The objective of the present investigation was to examine the inhibitory effects of DFMO on a variety of murine in vitro immune responses, including lymphocyte proliferation in response to T-cell mitogen (concanavalin A), B-cell mitogen (lipopolysaccharide), and alloantigen as well as cytotoxicity. DFMO-mediated inhibition of cell proliferation in these cases correlated with depletion of intracellular polyamines. The inhibitory effects of DFMO were reversed by polyamine repletion with putrescine. Putrescine also reversed the growth-inhibitory effects of DFMO on 4 tumor cell lines that we tested: 28-13-3S, YAC-1, P-815, and K562. However, putrescine homologues exhibited a differential effect in preventing DFMO-mediated inhibition of cell growth in normal lymphocytes and cancer cell lines. Only putrescine homologues containing a shorter methylene chain were effective in preventing the growth-inhibitory action of DFMO on normal immune response. In contrast, only the longer chain homologue 1,5-diaminopentane overcame the effect of DFMO on tumor cell growth. These findings suggest that supplementation with selected polyamine homologues may sustain normal immune response in DFMO-treated individuals while effectively suppressing malignant cell growth. The potential clinical relevance of these observations is discussed.

Animals↗
PubMed1992

Clustering Potyviridae species on the basis of four major traits.

Cluster analysis was used to examine taxonomic relationships among 31 potyviruses, using four categorical variables; genome segmentation, vector, inclusion bodies produced and host range. Analysis showed that regardless of weight given to genome segmentation, the fungus-transmitted viruses clustered in one group and the rest of the viruses in another at 60% level of similarity. It has been concluded that the creation of one family to include both the bymoviruses and potyviruses seems to be a reasonable compromise at the present time.

Animals↗
PubMed1992

Pathogenicity of Sporotrichum pruninosum and Cladosporium oxysporum, isolated from the bronchial secretions of a patient, for laboratory mice.

In this study we have demonstrated the occurrence of Sporotrichum pruinosum and Cladosporium oxysporum in the bronchial secretions of a patient with a presumptive diagnosis of tuberculosis. This observation coupled with the ability of both fungi to cause infection and elicit tissue responses in experimentally infected mice supported a probable etiologic relationship with the patient which could not be confirmed in the absence of histologic evidence. In vitro some antimycotics were tested against S. pruinosum and C. oxysporum by the agar dilution method. Oxiconazole with a minimum inhibitory concentration of 0.1 micrograms/ml-1 after 72 h and amorolfine at a concentration of 0.001 micrograms/ml-1 after 72 h were the most active ones against S. pruinosum and C. oxysporum respectively. It is suggested that the isolation of S. pruinosum and C. oxysporum from patients with bronchopulmonary disorders should be viewed with caution. Clinical and laboratory evaluation of such patients should be done critically before arriving at a firm diagnosis.

Animals↗
PubMed1992

Postural behaviour of intraocular pressure following trabeculoplasty.

Postural behaviour of intraocular pressure (IOP) was studied in 29 glaucomatous eyes before and after argon laser trabeculoplasty (ALT) and compared with that of 60 normal eyes. Although argon laser trabeculoplasty was successful in lowering the IOP below 21 mm Hg, it produced little effect on the postural behaviour of the IOP. No significant change was observed in the amplitude of postural rise of IOP in ALT treated eyes.

Adult↗
PubMed1992

A survey of Blastocystis in reptiles.

A total of 28 species of reptiles were investigated for Blastocystis using light microscopy and in vitro culture in biphasic egg slant medium. Blastocystis species were detected in 8 (28.6%) of these 28 species in 3 tortoises (Geochelone elephantopus, G. elegans and G. carbonaria), 3 snakes (Boiga dendrophilla, Python reticulatus and Elaphe radiata), 1 crocodile (Crocodylus porosus) and 1 iguana lizard (Cyclura cornuta). The reptilian Blastocystis appeared to be morphologically similar to B. hominis.

Alligators and Crocodiles↗
PubMed1992

Branching process with emigration--a genetic model.

Solution of a genetic improvement problem under the model of assortative mating is proposed. This has been achieved through the technique applied to a branching process incorporating a generation-dependent emigration component. The model explains a population subject to culling against genes governing undesirable characters and this work has been tried for a diploid population with two alleles at a single locus, which may be extended to the multilocus case.

Animals↗
PubMed1992

Attenuation of murine acute lethal graft-versus-host disease by the administration of DL-alpha-difluoromethylornithine.

Intravenous injection of 5 x 10(7) C57BL/6 (B6) lymphocytes into adult (C57BL/6 x DBA/2)F1 recipient mice results in acute lethal graft-versus-host (ALGVH) disease. This disorder is characterized by anemia, a diminished number of splenocytes, impaired cytotoxicity (CTX) against third party alloantigen, and impaired natural killer cell (NK) activity. Parental anti-F1 CTX is critical to the induction of ALGVH disease, and CTX in general has been reported to be dependent upon the presence of the low molecular weight polyamines essential for cell growth and differentiation. We now report that DL-alpha-difluoromethylornithine, a specific inhibitor of polyamine biosynthesis, attenuates the clinical expression of disease in mice undergoing ALGVH disease.

Anemia↗
PubMed1992

Active immunization of baboons (Papio anubis) with the bovine LH receptor.

Four baboons (Papio anubis) were actively immunized with bovine LH receptor for periods of 6-22 months. Serum antibody levels were measured by an enzyme immunoabsorbant assay (ELISA). Antibodies against the receptor were detected 2 weeks after the first injection. Antisera caused an inhibition in the binding of human chorionic gonadotropin (hCG) to its receptor as well as inhibited the production of hCG induced testosterone by rat Leydig cells in culture. Serum estradiol and progesterone levels were determined by radioimmunoassay (RIA). Progesterone levels were suppressed during the post immunization period. Two baboons experienced periods of anovulation. Serum estradiol levels were cyclic and appeared elevated. Baboons were mated with males of proven fertility; none of the immunized females conceived over eight cycles of observation. Fertility parameters returned to normal, when antibodies against LH-receptor were undetectable in the serum.

Animals↗
PubMed1992

Hypoplastic right ventricle with mild pulmonary stenosis in an adult.

A rare cyanotic heart disease surviving to adulthood with minimal symptoms is presented. The final diagnosis was hypoplastic right ventricle with mild pulmonary stenosis, where the latter was not responsible for the right-to-left shunting across a large atrial septal defect. The differences from cases reported in the literature are highlighted.

Adult↗
PubMed1992

Discordance between abdominal and atrial arrangement in a case of complex congenital heart disease.

The report describes a rare case of a complex congenital heart disease wherein the splenic status and the relationship of the suprarenal abdominal great vessels strongly suggested right isomerism, but atrial morphology demonstrated usual atrial arrangement. It emphasises the increasing recognition that the arrangement of the abdominal organs need not accurately reflect atrial arrangement.

Abnormalities, Multiple↗
PubMed1992

Inpatient treatment of persistent somatization.

Patients with disabling, persistent somatization pose significant challenges in clinical management. This study describes 92 patients treated on an inpatient psychosomatic medicine unit for persistent somatization. The most important factor in defining clinically significant subgroups of these patients was mood. Compared with depressed somatizing patients, nondepressed somatizing patients had chronic illnesses of early onset, had symptoms that were not correlated with current life stressors, and were generally unresponsive to treatment. There were few clinical predictors of treatment outcome apart from the duration of symptoms, the presence of mood disturbance, and a history of stable interpersonal relationships.

Adolescent↗
PubMed1992

Changes in age at marriage of women in rural north India.

There has been a dramatic increase in age at marriage for women in a rural area of north India. Age at marriage rose from under 12 years before 1930 to about 19 years in 1988, mainly as a result of socioeconomic development and advances in education of women.

Adolescent↗
PubMed1992

A monoclonal-based IgM capture ELISA for detection of antibodies to 22 and 41 kDa membrane antigens of Toxoplasma gondii.

A murine monoclonal antibody which reacts to 22 and 41 kDa Toxoplasma gondii surface antigens was employed in an IgM capture enzyme-linked immunosorbent assay (ELISA). A total of 125 patients' sera were tested in the monoclonal-based assay. When compared with a commercial ELISA test (Abbott Toxo-M EIA) which uses polyclonal anti-T. gondii antibodies, good correlation (Pearsons coefficient r = 0.91) was observed. The specificity of the assay was studied by testing a panel of control sera obtained from healthy individuals and blood transfusion donors; all sera gave negative results. Serum samples positive for T. gondii antibodies were treated with 2-mercaptoethanol (2-ME) to demonstrate the specificity of the test for IgM antibodies. Reactivity of these sera was lost after the treatment. The test is not subject to interference by rheumatoid factor as sera positive for rheumatoid factor were negative in the assay. Reproducibility was good with the coefficients of variation for within-day tests below 10% and not exceeding 18% for day-to-day tests. The monoclonal-based assay is simple to perform and appears to be a viable test for diagnosis of T. gondii infection.

Animals↗
PubMed1992

Effect of carcinogen dose and age at administration on induction of mammary carcinogenesis by 1-methyl-1-nitrosourea.

The objective of the work reported in this paper was to determine if the tumorigenic response to 1-methyl-1-nitrosourea (MNU) in the mammary gland varied with age of administration and was dose dependent when the carcinogen was injected prior to 50 days of age. Using a recently developed method for mammary tumor induction, MNU was injected i.p. at doses ranging from 25 to 75 mg/kg at 35 days of age or 50 mg/kg at 28, 35 or 42 days of age. Treatment with MNU resulted in induction of both benign and malignant mammary tumors. The incidence of mammary gland adenocarcinomas was 100% at and above the 50 mg/kg dose of MNU, irrespective of the age at which carcinogen was administered. The number of cancers increased in proportion to carcinogen dose, whereas cancer latency decreased as the MNU dose increased. In rats injected with 50 mg MNU/kg body weight at 28, 35 or 42 days of age, differences among groups in cancer incidence, number or latency were not statistically significant. Metastases of mammary neoplasms to lung, liver and spleen were observed in rats injected with MNU at 35 or 42 days of age. These data indicate (i) the dose responsiveness of MNU-induced mammary carcinogenesis in rats initiated prior to 50 days of age; (ii) the lack of effect of age at initiation if prior to 50 days on final tumor outcome; and (iii) that the age at which MNU is injected may affect the metastatic potential of the mammary carcinomas that are induced.

Adenocarcinoma↗