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Biomedical subjects

G Kumar

Publications and source records attributed to G Kumar.

At least 91 records · Page 5Linked to original sources
PubMed1993

Hopelessness in adolescent psychiatric inpatients.

To study hopelessness in adolescent inpatients, we administered the Beck Hopelessness Scale to 108 inpatients between 12 and 17 years old who were diagnosed with mixed psychiatric disorders. Moderate to severe pessimism about the future was described by 42.6%. A principal components analysis of the correlations among the scale's 20 items was conducted, and three components reflecting rejection of the possibility of a hopeful future, acceptance of the inevitability of a hopeless future, and resignation to the futility of changing the future were identified. These dimensions were comparable to those previously reported for adults, and the usefulness of the scale for evaluating hopelessness in adolescent inpatients was discussed.

Adolescent↗
PubMed1993

c-MYC mRNA is present in human sperm cells.

Stage-specific expression of proto-oncogenes, including c-myc, has been demonstrated during spermatogenesis in testis. Some of these proto-oncogenes are expressed postmeiotically, especially in the round spermatid stage. Recently, we demonstrated the presence of c-myc protein in mature ejaculated sperm cells with a possible role in sperm cell function. Since the half-life of c-myc protein has been shown to be short, we suspected the presence of c-myc mRNA in human sperm cells. In the present study, the presence of the c-myc mRNA transcript in human sperm cells was investigated by reverse transcriptase-polymerase chain reaction (RT-PCR) analysis and in situ hybridization. Total RNA, 5-10 micrograms, was extracted from 0.2-0.5 ml of pelleted human sperm cells by NP-40 lysis procedure, and was used to construct cDNA with pd(N)6 random primer and Moloney Murine Leukemia Virus (MMLV) reverse transcriptase. The PCR with sperm cDNA and primers #P1 and #P2, both from exon 3, resulted in amplification of the expected 322 bp product. Primers #P3 and #P4, which are located in exon 2 and exon 3, respectively, and are 1.37 kb apart, gave the expected PCR amplified 313 bp product ruling out the possibility of DNA contamination. The presence of c-myc mRNA in human sperm cells was further confirmed by in situ hybridization using a digoxigenin labelled DNA probe, containing exon 2 of the c-myc gene sequence. The c-myc specific DNA probe reacted with the postacrosomal mid-piece and tail regions of both noncapacitated as well as capacitated methanol-fixed sperm cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Base Sequence↗
PubMed1992

Two cat expression vectors for cloning and generation of 3'- and 5'-deletion mutants.

The construction of two versatile cat vectors, pGK0CAT and pGKA10CAT, is reported. These vectors possess multiple cloning sites derived from the Bluescript pKS(+) plasmid that allow the cloning of diverse DNA fragments. From a single cloned insert, i.e., a putative promoter element, one can use the exonuclease III (ExoIII) and S1 or mung-bean nuclease method to generate sequential deletion mutants of the 3' and 5' region. Linker-scanning and internal deletion mutants can thus be created by using appropriate 3'- and 5'-deletion mutants. These plasmids could thus be used for the identification of cis-acting promoter or enhancer elements by either in vivo or in vitro transcriptional analyses. The ability of these vectors to generate deletion mutants from the 3' end make them suitable to identify cis-acting elements in the 5'-noncoding region of the mRNA involved in the translational regulation of protein synthesis. Single-stranded circular mutant plasmids could also be generated from these vectors to study various protein-DNA interactions.

Chloramphenicol O-Acetyltransferase↗
PubMed1992

Incorporation of BrdU in a DNA fragment may affect protein-DNA interactions in a site-dependent manner.

DNA in which BrdU has been randomly incorporated is used to identify specific DNA-binding proteins. We show here that the location of BrdU incorporation in a DNA fragment can significantly affect specific protein-DNA interactions and thereby identification of DNA-binding proteins. We suggest that a radioactive labeled unmodified DNA, rather than BrdU-incorporated DNA, be used for identifying DNA-binding proteins by UV cross-linking.

Base Sequence↗
PubMed1991

A 53 kDa protein binds to the negative regulatory region of JC virus early promoter.

Using gel retardation and photocrosslinking experiments, we have identified proteins of about 53 kDa in size in both rat glioma (C6) and cervical carcinoma (HeLa) cell extracts which bind to the negative regulatory region of JV virus (JCV) early promoter. The glial cell protein binds to its cognate promoter element with lesser affinity when compared to the protein present in HeLa cells. Further, these proteins interacted differentially to an oligonucleotide, containing the neighboring cis-acting domain, which is recognized by nuclear factor 1 (NF1). These findings suggest that the interactions of the 53 kDa HeLa protein may contribute to the negative regulation of JCV early promoter in HeLA cells.

Base Sequence↗
PubMed1991

Presence and role of c-myc proto-oncogene product in mammalian sperm cell function.

The presence and role of c-myc protein was investigated in mature sperm cells of the human, mouse, and rabbit. The monoclonal antibodies against c-myc protein (c-myc) reacted with the acrosomal region of the sperm of these mammalian species in the indirect immunofluorescence technique. The c-myc monoclonal antibody (MCA) recognized c-myc protein of 62 and 64 kDa on Western blots of lithium diiodosalicylate-solubilized sperm preparations of these species. The c-myc MCA showed a dose-dependent inhibition of human sperm penetration of zona-free hamster eggs, inhibition of murine in vitro fertilization, and reduced in vivo fertilization in rabbits. There was no effect of the antibody on percent sperm motility, though the antibody significantly affected various motility characteristics such as mean and maximum amplitude of lateral head displacement and curvilinear velocity involved in hyperactivation phenomenon of human sperm cells. These results suggest that c-myc or c-myc-like protein is present in mature sperm cells and may have a role in sperm cell function especially in capacitation and/or acrosome reaction.

Animals↗
PubMed1989

Gender, differential mortality and development: the experience of Kerala.

This study examines aspects of sex differentials in mortality in India. "The general question of sex bias and excess female mortality is first discussed.... Subsequently the reasons for the regional contrast in sex ratios are explored.... We then focus on the interesting exception to the Indian trend and attempt an explanation for the unusual sexual profile that Kerala displays.... The paper ends...with an attempt to draw some tentative conclusions from the Kerala experience with an eye towards more general issues concerning women and the development process."

Asia↗
PubMed1989

Primary malignant fibrous histiocytoma of the stomach: (a case report).

A case of primary malignant fibrous histiocytoma (MFH) of the stomach is reported. The patient was a 51-year-old man who had a laparotomy for a malignant gastric tumour diagnosed by radiological studies and endoscopic examination. An inoperable gastric malignancy was found at operation. Histopathological studies of tissue biopsied at surgery showed characteristic light microscopic findings and strong positivity for alpha-1-antitrypsin by immunoperoxidase technique indicating the diagnosis of malignant fibrous histiocytoma. The absence of any other soft tissue or retroperitoneal tumour strongly indicated the stomach is the primary site.

Histiocytoma, Benign Fibrous↗
PubMed1989

Transcriptional analysis of minute virus of mice P4 promoter mutants.

A series of 5' deletion, internal deletion, and linker-scanning mutants of the minute virus of mice P4 promoter were constructed and analyzed for transcriptional activity in nuclear extracts of mouse A92L fibroblasts. A GC box and a TATA box essential for in vitro transcription from the P4 promoter were localized between nucleotides 150 and 180 (-55 to -25 relative to the primary RNA start site). Although this region also exhibited homologies to other transcriptional control elements, the simian virus 40 enhancer, and the adenovirus E1A enhancer, only the GC box and TATA box appear functional. These two motifs also play an essential role in vivo, although additional upstream sequences (between -139 and -55) are required for optimal transcription. DNase I footprinting, competitive gel retardation assays, and UV-photocrosslinking were used to identify Sp1-like proteins of 95 and 120 kilodaltons in A92L extracts that interact with the GC box of the minute virus of mice P4 promoter.

Base Sequence↗
PubMed1989

Hemin and cyclic AMP stimulate message-dependent translation in lysates from Friend erythroleukemia cells.

A message-dependent, cell-free translation system was prepared from both uninduced and N,N'-hexamethylene-bis-acetamide-induced Friend erythroleukemia cells following modification of standard protocols. Active extracts were prepared by lysing Friend erythroleukemia cells in hypotonic buffer containing 50 microM hemin and 10 mM cyclic adenosine monophosphate (cAMP), and assaying translation in vitro in the absence of exogenous nucleoside triphosphates. Both hemin and cAMP were required for full activity and appeared to act by prolonging initiation in vitro. Following treatment of cell extracts with micrococcal nuclease, brome mosaic virus, globin, equine herpesvirus type 1, and frog virus 3 mRNA were efficiently translated to yield full-sized products. Using brome mosaic virus as a test message, levels of translation equivalent to 30%-50% of that seen in mock-treated lysates were obtained. These results attest to the translational efficiency of extracts prepared and assayed in the manner described above, and suggest that such extracts may be useful both for routine translational studies, and as a tool to dissect translational changes accompanying erythroid differentiation in vitro.

Acetamides↗
PubMed1988

Minimal change disease as the etiology of the nephrotic syndrome in a patient with angioimmunoblastic lymphadenopathy.

Glomerular lesions have rarely been reported with angioimmunoblastic lymphadenopathy (AILD). A patient with histologically documented AILD developed the nephrotic syndrome. Renal biopsy demonstrated minimal change disease. Both the lymphadenopathy and the nephrotic syndrome spontaneously remitted in this patient. Prior reports of renal disease in AILD and atypical lymphoproliferative disorders are discussed. An association between the minimal change lesions and AILD is suggested.

Humans↗
PubMed1985

Molecular cloning and regulated expression of the human c-myc gene in Escherichia coli and Saccharomyces cerevisiae: comparison of the protein products.

mRNA from human HL-60 cells was used to prepare a cDNA library, from which two full-length clones that encompass the complete c-myc coding region were isolated. One clone, pM1-11, contains all three exons of human c-myc. The second clone, pM4-10, represents a relatively rare transcript that initiated in the first intron and includes the coding exons 2 and 3. The cDNA insert in pM1-11 was used to express the human c-myc protein in both prokaryotic and eukaryotic cells. Insertion of the coding sequences in exons 2 and 3 into the appropriate expression vectors yielded detectable c-myc protein in Escherichia coli lacking the Lon protease and in Saccharomyces cerevisiae upon induction. The protein produced in E. coli has an apparent size of 60 kDa and appears to be unmodified, as it is identical in size to the protein synthesized in an in vitro system. In contrast, yeast cells synthesize two myc proteins, of 60 kDa and 62 kDa. The difference in apparent molecular mass between the two proteins appears to be due, in part, to phosphorylation. Subcellular fractionation of yeast cells showed that the c-myc phosphoprotein is located predominantly in the nuclear fraction.

Base Sequence↗
PubMed1982

The peptidyltransferase center of Escherichia coli ribosomes: binding sites for the cytidine 3'-phosphate residues of the aminoacyl-tRNA 3'-terminus and the interrelationships between the acceptor and donor sites.

The substrate specificity of the acceptor site of peptidyltransferase of Escherichia coli 70 S ribosomes was investigated in Ac-Phe-tRNA . poly(U) . 70 S ribosome (system A) and tRNC-A-Phe . poly(U) . C-A-C-C-A-Phe . 70 S ribosome (system B) systems by using C-C-A-Gly, C-C-A-Phe, C-A-Gly and C-A-Phe as analogs of the 3'-terminus of aminoacyl-tRNA. It was found that an addition of CP residue to C-A-Gly and C-APhe resulted in an increase of the acceptor activity in system A; the increase is more remarkable for C-A-Gly than for C-A-Phe, while the acceptor activities of C-C-A-Gly and C-C-A-Phe are roughly similar. On the other hand, dramatically increased binding affinities of C-C-A-Phe and C-C-A-Gly relative to C-A-Phe and C-A-Gly for the A site of peptidyltransferase were observed in system B using an inhibition assay; C-C-A-Phe binds much more strongly than C-C-A-Gly. The results indicate the important role of the third CP residue and the aminoacyl moiety of the 3'-terminus of aminoacyl-tRNA in the interaction with the acceptor site of peptidyltransferase, as well as the existence of cooperative effects between A and P sites of peptidyltransferase. These effects, depending on an occupancy of P site, may significant the specificity of the peptidyltransferase A site.

Acyltransferases↗
PubMed1979

Active transport of calcium in membrane vesicles from Mycobacterium phlei.

Active transport of calcium ions has been demonstrated in inside-out membrane vesicles from Mycobacterium phlei mediated by respiratory linked substrates as well as by ATP hydrolysis. The uptake of calcium exhibited an apparent Km of 80 microM and V of 16.6 nmol calcium uptake x min-1 x mg protein-1. A fortyfold concentration gradient for calcium ions was calculated for both the ATP-induced and the respiration-induced transport of calcium. Removal of coupling-factor-latent ATPase resulted in the complete loss of ATP-driven Ca2+ transport whereas the respiration-driven uptake was reduced by 40-50%. The uptake of calcium was inhibited by the proton conducting ionophores carbonylcyanide m-chlorophenylhydrazone and Gramicidin-D. The accumulated calcium was freely exchangeable with external calcium and was rapidly released by the addition of inhibitors of energy transduction, proton-translocating uncouplers or the ionophore A23187. The uptake of the weak base, methylamine, upon the oxidation of respiratory-linked substrates or the hydrolysis of ATP showed the generation of a protein gradient (inside acidic) which was partially collapsed on the addition of calcium ions. These results suggest that a Ca2+/H+ antiport mechanism may be responsible for the transport of calcium.

Adenosine Triphosphatases↗