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Biomedical subjects

S Ganguly

Publications and source records attributed to S Ganguly.

At least 91 records · Page 5Linked to original sources
PubMed1990

Detection of preferential NRAS mutations in human male germ cell tumors by the polymerase chain reaction.

We have studied 31 male germ cell tumors (GCTs) for probable mutations in codons 12, 13, and 61 of HRAS, KRAS, and NRAS oncogenes using the polymerase chain reaction. Twenty of the thirty-one tumors exhibited NRAS gene mutations, 14 in codon 61, and six in codon 12, whereas no mutations were detected in HRAS and KRAS genes. The NRAS mutations were equally prevalent in seminomatous and nonseminomatous GCTs. Thus 13 of 22 seminomas, six of seven embryonal carcinomas, and one of two mixed tumors exhibited mutations. Two non-seminomatous tumors (an embryonal carcinoma and a yolk sac/teratoma) had mutations in both codons 12 and 61. The high frequency of NRAS mutations observed in the present study suggests that NRAS gene products may play an important role in growth regulatory functions of premalignant and malignant germ cells.

DNA Mutational Analysis↗
PubMed1990

Clinical aspects of centipede bite in the Andamans.

Clinical aspects of centipede bite as seen in the Andamans are reported. Centipede bite produces excruciating local pain and burning. Local bleeding is common but transient. Occasionally local infection or necrosis develops. Constitutional upset occurs in a small minority. Centipede bites are never fatal and pain-relief is the cornerstone of treatment.

Adolescent↗
PubMed1989

Multiple enhancer-like sequences in the HLA-B7 gene.

Enhancer-like sequences have previously been identified in the promoter region of the mouse major histocompatibility complex (MHC) class I genes. We have screened for such sequences in and around a human MHC class I gene, HLA-B7. Various restriction fragments of the B7 gene were assayed for their ability to enhance transcription of a bacterial chloramphenicol acetyltransferase gene from a simian virus 40 promoter in transiently transfected mouse LTA cells. Our results demonstrate that enhancer activity is located in introns 3 and 5 as well as 5' to the transcription initiation site. RNase protection experiments corroborate the results. Preliminary experiments indicate that B7 enhancers are active in various cell types. The role of these enhancers in B7 gene expression is not known at present. We speculate that the position of the enhancer elements may be related to the occurrence of Hpa II tiny fragment islands.

Animals↗
PubMed1989

Construction, stable transformation, and function of an amber suppressor tRNA gene in Drosophila melanogaster.

Drosophila melanogaster strains with a stably incorporated amber suppressor tRNA gene have been generated. A tRNATyr gene was site specifically mutated to produce an anticodon sequence that recognizes the amber codon and then introduced into Drosophila by using P-element-mediated transformation. Transformants from four integration events were recovered. Two integrations resulted in both male and female sterility, whereas the other two resulted in male sterility but female fertility. Strains derived from the two female-fertile integration events were shown to have a low level of amber-suppressing activity by their ability to suppress an amber mutation in a chloramphenicol acetyltransferase gene.

Animals↗
PubMed1988

Differential synthesis of beta-major and beta-minor globin proteins in murine erythroleukemia cells is regulated at the transcriptional level.

We compared the transcription and translation of globin genes in three mouse erythroleukemia cell lines under different conditions in which there is differential expression of beta-major (beta ma) and beta-minor (beta mi). Transcription was measured by pulse labeling of whole cell RNA with [3H]uridine, and translation by labeling whole cell protein synthesis with [3H]leucine. Induction with dimethyl sulfoxide led to increased transcription of alpha, beta ma, and beta mi genes, and the proportion of beta mi RNA synthesized was similar to the proportion of beta mi globin protein produced, whether the cells produced 30-40% beta mi (lines 745 and 9M) or greater than 80% beta mi (clone 25-66). Induction with hemin did not lead to increased globin gene transcription in any line, although globin protein synthesis did increase. Thus, the mechanism of beta globin chain induction depends on the inducing agent, and not on the cell line or the type of beta globin gene product. The relative proportion of beta mi and beta ma globin chain proteins reflects the relative transcription of the two beta genes, whether or not transcription increased following induction.

Animals↗
PubMed1988

Tissue-specific and cell surface expression of human major histocompatibility complex class I heavy (HLA-B7) and light (beta 2-microglobulin) chain genes in transgenic mice.

We introduced the human genes HLA-B7 and B2M encoding the heavy (HLA-B7) and light [beta 2-microglobulin (beta 2m)] chains of a human major histocompatibility complex class I antigen into separate lines of transgenic mice. The tissue-specific pattern of HLA-B7 RNA expression was similar to that of endogenous class I H-2 genes, although the HLA-B7 gene was about 10-fold underexpressed in liver. Identical patterns of RNA expression were detected whether the HLA-B7 gene contained 12 or 0.66 kilobase(s) (kb) of 5' flanking sequence. The level of expression was copy number dependent and as efficient as that of H-2 genes; gamma interferon enhanced HLA-B7 RNA expression in parallel to that of H-2. In addition to the mechanism(s) responsible for gamma interferon-enhanced expression, there must be at least one other tissue-specific mechanism controlling the constitutive levels of class I RNA. Tissue-specific human beta 2m RNA expression was similar to that of mouse beta 2m, including high-level expression in liver. Cell surface HLA-B7 increased 10- to 17-fold on T cells and on a subset of thymocytes from HLA-B7/B2M doubly transgenic mice compared to HLA-B7 singly transgenic mice. The pattern of expression of HLA-B7 on thymocytes resembled that of H-2K as opposed to H-2D. These results confirm that coexpression of both human chains is required for efficient surface expression and that HLA-B7 may share a regulatory mechanism with H-2K, which distinguishes it from H-2D.

Animals↗
PubMed1988

Saccharomyces cerevisiae SUP53 tRNA gene transcripts are processed by mammalian cell extracts in vitro but are not processed in vivo.

We describe the results of our studies of expression of a Saccharomyces cerevisiae amber suppressor tRNA(Leu) gene (SUP53) in mammalian cells in vivo and in cell extracts in vitro. Parallel studies were carried out with the wild-type (Su-) tRNA(Leu) gene. Extracts from HeLa or CV1 cells transcribed both tRNA(Leu) genes. The transcripts were processed correctly at the 5' and 3' ends and accurately spliced to produce mature tRNA(Leu). Surprisingly, when the same tRNA(Leu) genes were introduced into CV1 cells, only pre-tRNAs(Leu) were produced. The pre-tRNAs(Leu) made in vivo were of the same size and contained the 5'-leader and 3'-trailer sequences as did pre-tRNAs(Leu) made in vitro. Furthermore, the pre-tRNAs(Leu) made in vivo were processed to mature tRNA(Leu) when incubated with HeLa cell extracts. A tRNA(Leu) gene from which the intervening sequence had been removed yielded RNAs that also were not processed at either their 5' or 3' termini. Thus, processing of pre-tRNA(Leu) in CV1 cells is blocked at the level of 5'- and 3'-end maturation. One possible explanation of the discrepancy in the results obtained in vivo and in vitro is that tRNA biosynthesis in mammalian cells involves transport of pre-tRNA from the site of its synthesis to a site or sites where processing takes place, and perhaps the yeast pre-tRNAs(Leu) synthesized in CV1 cells are not transported to the appropriate site.

Animals↗
PubMed1988

Description of a human placental anti-insulin receptor polyclonal antibody that activates insulin binding to the receptor in vitro.

A polyclonal anti-human placental insulin receptor antibody has been developed, and its interaction with the receptor has been studied in vitro. This antibody enhances insulin binding to the receptor, both in the immunoprecipitate and also in in vitro binding assay. In the Scatchard analysis of the insulin-receptor interaction, in the presence of the antiserum, a marked increase in Bmax is observed, while Kd remains more or less unaffected. This antibody recognizes insulin receptor from all tissues of old world monkey but does not recognize new world monkey, rat or mouse receptor. Insulin receptor binds to this antibody very strongly on a immunoaffinity column and cannot be eluted by gentle means, but it retains insulin stimulated tyrosine kinase activity while immobilized to immunoaffinity column. This antibody also activates insulin receptor mediated histone phosphorylation in vitro. It has been proposed that this antireceptor antibody modulates receptor function by causing conformational perturbation in vitro.

Animals↗
PubMed1987

Iodination-induced alterations in biochemical properties of human placental insulin receptor.

Insulin receptors from human placenta have been labeled by using an oxidative iodination procedure (iodogen-mediated or chloramine-T-mediated), Bolton-Hunter reagent or [3H]acetic anhydride. The oxidative iodination procedure reduces the affinity for 131I-insulin and the receptor protein becomes fragmented into smaller pieces with an s20,w value of 5-6. However, treatment with Bolton-Hunter reagent or [3H]acetic anhydride does not alter the Kd of 131I-insulin binding and the s20,w value remains unchanged with respect to the native receptor. It is proposed that for labeling multisubunit sulfhydryl-linked protein drastic oxidative iodination procedures should be avoided.

Acetic Anhydrides↗
PubMed1987

Transfection of normal human and Chinese hamster DNA corrects diepoxybutane-induced chromosomal hypersensitivity of Fanconi anemia fibroblasts.

Cultured cells from individuals affected with Fanconi anemia (FA) exhibit spontaneous chromosome breakage and hypersensitivity to the cell killing and clastogenic effects of the difunctional alkylating agent diepoxybutane (DEB). We report here the correction of both of these DEB-hypersensitivity phenotypes of FA cells achieved by cotransfection of normal placental or Chinese hamster lung cell DNA and the plasmid pSV2-neo-SVgpt. Transfectants were selected for clonogenic survival after treatment with DEB at a dose of 5 micrograms/ml. At this dose of DEB, the clonogenicity of normal fibroblasts was reduced to 50% and that of FA fibroblasts was reduced to zero. DEB-resistant (DEBr) colonies selected in this system exhibited a normal response to DEB-induced chromosome breakage and resistance to repeated DEB treatment. The neo and gpt sequences were detected by Southern blot analysis of DNA from one of four DEBr colonies independently derived from transfection of human DNA and one of three DEBr colonies independently derived from transfection of Chinese hamster DNA. In addition, Alu-equivalent hamster sequences were detected in three of seven additional independently derived colonies from transfection of Chinese hamster DNA. The DEBr phenotype of these colonies was stably maintained over several subcultures. Our results demonstrate that DNA sequences that complement the two hallmark cellular phenotypes (cellular and chromosomal hypersensitivity to alkylating agents) of FA are present in human as well as Chinese hamster DNA. The cloning of these genes using transfection strategies can be expected to enable molecular characterization of FA.

Anemia, Aplastic↗