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S Ray

Publications and source records attributed to S Ray.

At least 217 records · Page 12Linked to original sources
PubMed1994

Characterization of DNA polymerase-alpha/primase complex from developing embryonic chicken brains.

DNA polymerase-alpha and primase activities present in a complex, have been isolated, partially purified, and characterized from embryonic chicken brain. DNA polymerase-alpha activity, characterized by its sensitivity to N-ethyl-maleimide, high sedimentation coefficient (11.3 S), and acidic isoelectric point (5-5.5) was found in all embryonic ages. Primase activity, the enzyme responsible for the initiation of DNA synthesis, co-sedimented with DNA polymerase-alpha activity on a continuous glycerol velocity gradient. A complex containing both DNA polymerase-alpha and primase activities was isolated by DE-23 cellulose column chromatography of cell-free extracts of different embryonic ages of chicken brain. In addition to the primase complexed with DNA polymerase-alpha, a free primase activity was isolated by DE-23 cellulose column chromatography of an ammonium sulfate (0-45%; w/v) precipitated fraction of embryonic chicken brain cell-free extract. DNA polymerase-alpha activity from developing chicken brains in the embryonic stage was purified by immuno-affinity column chromatography. Of all the single-stranded DNA templates tested, primase activity was found to be maximally active with poly dC. Primase activity was not inhibited by a high concentration of alpha-amanitin. The results obtained may provide insight into further understanding of regulation of chromosomal DNA replication in developing tissues.

Animals↗
PubMed1993

Inhibition of glycolysis and mitochondrial respiration of Ehrlich ascites carcinoma cells by methylglyoxal.

The effect of methylglyoxal (MG) on the aerobic glycolysis of Ehrlich ascites carcinoma (EAC) cells has been tested. Methylglyoxal inhibited glucose utilization and glucose 6-phosphate (G6P) and L-lactate formation in whole EAC cells. Methylglyoxal strongly inactivated glyceraldehyde 3-phosphate dehydrogenase (GA3PD) of the malignant cells, whereas MG has little inactivating effect on this enzyme from several normal sources. Methylglyoxal also inactivated only the particulate hexominase of the EAC cells, but this inactivation was less pronounced than the effect on GA3PD. Methylglyoxal has little inactivating effect on glucose 6-phosphate dehydrogenase (G6PD), and no effect on L-lactate dehydrogenase (LDH) of the malignant cells. Glucose-dependent L-lactic acid formation of EAC-cell-free homogenate was strongly inhibited by MG, but when GA3PD of normal cells was added to this homogenate, significant lactate formation was observed even in the presence of MG. Methylglyoxal also inhibited the respiration of EAC-cell mitochondria. Respiration of mitochondria isolated from liver and kidney of normal mice, however, remained unaffected. As a consequence of the inhibition of glycolysis and mitochondrial respiration, the ATP level of the EAC cells was drastically reduced. Studies reported herein strongly suggest that the tumoricidal effect of MG is mediated at least in part through the inhibition of mitochondrial respiration and inactivation of GA3PD, and this enzyme may play an important role in the high glycolytic capacity of the malignant cells.

Adenosine Triphosphate↗
PubMed1993

Recoverin's role: conclusion withdrawn.

In the chart accompanying Christopher Anderson's News & Comment article "Clinton asks for a greener DOE" (9 Apr., p. 153), the budget figures for Basic Energy Science were incorrect. The correct figures are $861 million for the 1993 appropriation and $802 million for the 1994 request.

Animals↗
PubMed1993

Purification, characterisation, and carbohydrate specificity of the lectin of Ficus cunia.

A lectin, isolated from the seeds of Ficus cunia and purified by affinity chromatography on fetuin-Sepharose, was homogeneous in PAGE, GPC, HPLC, and immunodiffusion, and had mol wt of 3200-3500. In SDS-PAGE and HPLC in the absence and presence of 2-mercaptoethanol, the lectin gave a single band or peak corresponding to M(r) 3300-3500, thus indicating it to be a monomer. The lectin agglutinated human erythrocytes regardless of blood group, bound to Ehrlich ascites cells and to human rat spermatozoa, and was thermally stable; its activity was enhanced by Ca2+. The lectin is a metalloprotein that was inactivated by dialysis with EDTA followed by acetic acid, but reactivated by the addition of Ca2+. The lectin contained 2.0% of carbohydrates, large proportions of acidic amino acids, but little methionine. In hapten-inhibition assays, chitin oligosaccharides [(1-->4)-linked beta-GlcNAc] and N-acetyl-lactosamine were inhibitors of which N,N',N",N"'-tetra-acetylchitotetraose was the most potent. Among the macromolecules tested that contain either multiple N-acetyl-lactosamine and/or (1-->4)/(1-->6)-linked beta-GlcNAc, asialofetuin glycopeptide was the most potent inhibitor. Thus, an N-acetyl group and substitution at C-1 of D-GlcN are necessary for binding.

Animals↗
PubMed1993

Purification and characterization of a yeast DNA polymerase alpha complex with associated primase, 5'-->3' exonuclease, and DNA-dependent ATPase activities.

We have purified a multimeric form of yeast DNA polymerase alpha with DNA polymerase, primase, 5'-->3' exonuclease, and single-stranded (ss) DNA-dependent ATPase activities to near-homogeneity. The molecular mass of complex was 650 kDa with subunits ranging in sizes from 30 to 180 kDa. The alpha-subunit of the complex could be detected by DNA polymerase alpha antibody. No cross-reactivity of polypeptides within the complex was observed with antibodies directed against polymerase delta or epsilon. The multimeric polymerase alpha could be selectively inhibited by p-n-butylphenyl-dGTP (I50 of approximately 0.2 microM), p-n-butylanilino-dATP (I50 of 1.3 microM), and aphidicolin (I50 of 2.5 micrograms/mL). The complex synthesized RNA primers on various ssDNA templates and rapidly elongated these primers into nascent DNA fragments in the presence of required deoxynucleotides. It has a strong 5'-->3' exonuclease activity. In addition, the complex hydrolyzed both ATP and dATP in a ssDNA-dependent manner. Thus, the multiprotein complex of DNA polymerase alpha had multiple activities (primase, polymerase, and ATPase) which could act concertedly to synthesize primers and elongate the primers to nascent DNA fragments in the lagging strand of the fork.

Adenosine Triphosphatases↗
PubMed1993

Synthesis of novel 6-aza-B- and 11-aza-C-homoestranes as antifertility agents.

Reaction of 3,9 alpha, 17 beta-trihydroxyestra-1,3,5(10)-trien-11-one 17-acetate 3-methyl ether (3) with N3H-BF3 etherate leads mainly to lactam (4) along with the N-azido compound (5) as a minor product. Under similar conditions, 3,17 beta-dihydroxyestra-1,3,5(10)-trien-6-one 17-acetate 3-methyl ether gives lactam (12) and the tetrazole derivative (9). Similar reaction of the diacetate (8) gives only the tetrazole derivative (11). Compounds 4, 6, and 10 prevent implantation in rats at 5-, 10-, and 5-mg/kg doses, respectively. Compounds 4, 6, 9, and 10 show significant estrogenic activity at the respective contraceptive doses.

Animals↗
PubMed1993

The effect of diffusion on two predators exploiting a resource.

This paper deals with the stabilizing effect of diffusion on a system of a living resource supporting two noncompeting predators. It is shown that while the three species mathematical model without diffusion is unstable, the model with diffusion is asymptotically stable provided the diffusion coefficient of the resource exceeds a certain threshold value.

Animals↗
PubMed1993

Kinesin follows the microtubule's protofilament axis.

We tested the hypothesis that kinesin moves parallel to the microtubule's protofilament axis. We polymerized microtubules with protofilaments that ran either parallel to the microtubule's long axis or that ran along shallow helical paths around the cylindrical surface of the microtubule. When gliding across a kinesin-coated surface, the former microtubules did not rotate. The latter microtubules, those with supertwisted protofilaments, did rotate; the pitch and handedness of the rotation accorded with the supertwist measured by electron cryo-microscopy. The results show that kinesin follows a path parallel to the protofilaments with high fidelity. This implies that the distance between consecutive kinesin-binding sites along the microtubule must be an integral multiple of 4.1 nm, the tubulin monomer spacing along the protofilament, or a multiple of 8.2 nm, the dimer spacing.

Adenosine Triphosphate↗
PubMed1993

Transthoracic and transoesophageal echocardiography in the diagnosis and management of a biatrial myxoma.

A 40-year-old female presented with a year's history of atrial fibrillation. Transthoracic echocardiography identified the presence of a biatrial mass and transoesophageal echocardiography delineated its extent. At surgery, a huge myxoma originating from the fossa ovalis and straddling the inter-atrial septum was removed and the atrial septum repaired. This report highlights the role of transthoracic and transoesophageal echocardiography in the diagnosis and management of this extremely rare cardiac tumour.

Adult↗
PubMed1993

Pharmacokinetics of 18F-labeled fluconazole in healthy human subjects by positron emission tomography.

The distribution of fluconazole in tissue of human volunteers was determined by positron emission tomographic scanning over a 2-h period following the infusion of a tracer dose of 18F-fluconazole (5 to 7 mCi) plus 400 mg of unlabeled drug (the standard daily dose of fluconazole). Previous studies have validated this approach for animals. From serial positron emission tomographic imaging and blood sampling, pharmacokinetics of fluconazole in tissue were determined. There was significant distribution of the radiolabeled drug in all organs studied, with nearly constant levels achieved by 1 h. Plateau concentrations of fluconazole in key organs (micrograms per gram) included the following: whole brain, 4.92 +/- 0.17; heart, 6.98 +/- 0.20; lung, 7.81 +/- 0.46; liver, 12.94 +/- 0.24; spleen, 22.96 +/- 2.5; kidney, 11.23 +/- 0.61; prostate, 8.24 +/- 0.58; and blood, 3.76 +/- 0.30. Since levels of fluconazole of > 6 micrograms/g are needed to treat infection with most strains of Candida and levels of > 10 micrograms/g are needed for Cryptococcus neoformans, Coccidioides immitis, and Histoplasma capsulatum, the following predictions can be made. The current standard dose of 400 mg/day should be more than adequate in the treatment of urinary tract and hepatosplenic candidiasis but problematic in the treatment of candidal osteomyelitis, even with the higher levels that develop after multiple doses. Similarly, higher doses should be considered, particularly in immunocompromised patients, with infection with C. neoformans, H. capsulatum, and C. immitis that involves the central nervous and musculoskeletal systems.

Adult↗
PubMed1993

cdc2 phosphorylation of threonine 124 activates the origin-unwinding functions of simian virus 40 T antigen.

Phosphorylation of simian virus 40 (SV40) T antigen on threonine 124 activates viral DNA replication in vivo and in vitro. We have manipulated the modification of T-antigen residue 124 both genetically and biochemically and have investigated individual replication functions of T antigen under conditions suitable for in vitro DNA replication. We find that the hexamer assembly, helicase, DNA polymerase alpha-binding, and transcriptional-autoregulation functions are independent of phosphorylation of threonine 124. In contrast, neither T antigen with an alanine mutation of threonine 124 made in human cells nor unphosphorylated T antigen made in Escherichia coli binds the SV40 replication origin as stably as phosphorylated wild-type T antigen does. Furthermore, modification of threonine 124 is essential for complete unwinding of the SV40 replication origin. We conclude that phosphorylation of threonine 124 enhances specific interactions of T antigen with SV40 origin DNA. Our findings do not exclude the possibility that phosphorylation of threonine 124 may affect additional undefined steps in DNA replication. We also show that DNase footprinting and KMnO4 modification assays are not as stringent as immunoprecipitation and origin-dependent strand displacement assays for detecting defects in the origin-binding and -unwinding functions of T antigen. Differences in the assays may explain discrepancies in previous reports on the role of T-antigen phosphorylation in DNA binding.

Amino Acid Sequence↗
PubMed1993

Evaluation of enzyme-linked immunosorbent assay in the diagnosis of kala-azar in Malda district (West Bengal).

An immunological test based on indirect (plate) ELISA has been successfully standardized and modified using promastigote soluble antigen. The test carried out on 813 subjects from a kala-azar endemic area (including parasitologically confirmed patients, subjects presenting with clinical symptoms of visceral leishmaniasis and endemic controls) and a non-endemic area (with diseases other than kala-azar and apparently normal subjects) was found to detect, specifically, antileishmanial antibodies. The plate ELISA has been simplified to a more sensitive dot-ELISA where the results are read within 2-3 h. The antigen requirement is 250 ng per test. No cross-reactivity with sera from patients of malaria, tuberculosis, leprosy, amoebiasis and filariasis was observed. The follow up monitoring of antibodies in successfully treated kala-azar patients showed a decline of antibodies. A drop of blood taken on filter paper is sufficient to conduct the test. Dot ELISA therefore is a simple, inexpensive and stable test in serodiagnosis of visceral leishmaniasis.

Animals↗
PubMed1993

Psychosocial correlates of AIDS-risk drug use and sexual behaviors.

Theoretical and empirical research suggests psychosocial functioning is important in drug abuse intervention strategies, especially those focusing on efforts to change AIDS risk behaviors. Self-esteem, depression, anxiety, proneness to risk taking, decision-making confidence, self-assessment of drug use problems, and desire for help with drug problems, along with personal background and health history indicators, were assessed for 194 injection drug users in an AIDS prevention outreach program in New Orleans. Composite index scores for needle risk behaviors were associated with low self-esteem and low decision-making confidence as well as with higher scores on depression, anxiety, drug use problems, and desire for help. However, these psychosocial measures were not significantly related to the composite index for sex risks. Health history measures, represented by previous exposures to hepatitis and sexually transmitted diseases, were significantly related to both needle and sex risk indices. Implications for AIDS intervention efforts are discussed.

Acquired Immunodeficiency Syndrome↗
PubMed1992

Cloning, expression, and crystallization of recoverin, a calcium sensor in vision.

Recoverin, a recently discovered 23-kDa calcium-binding protein, activates retinal rod guanylate cyclase when the calcium level is lowered in the submicromolar range. We report here the cloning and sequencing of a cDNA for recoverin from a bovine retinal expression library. The recoverin coding sequence was inserted into a pET-11a expression vector under control of the T7 phage promoter. A second expression system, in which the coding sequence was placed under control of the lambda phage PR promoter, gave 10-fold higher yields (10 mg of purified recoverin per liter of Escherichia coli culture). The finding that retinal recoverin is myristoylated at its amino terminus led us to coexpress the recombinant protein and N-myristoyltransferase (EC 2.3.1.97). Myristoylated recombinant recoverin formed in this way in E. coli is like retinal recoverin in exhibiting a large calcium-induced shift in its tryptophan fluorescence emission spectrum. The availability of abundant protein enabled us to crystallize unmyristoylated recombinant recoverin and initiate x-ray studies. The space group of tetragonal crystals obtained from 75% saturation ammonium sulfate is I4 with unit cell dimensions a = 85.1 A and c = 59.8 A. These crystals of the calcium-bound form of the protein diffracted to a resolution of 2.2 A. The expression systems described here open the door to high-resolution x-ray crystallographic and nuclear magnetic resonance studies of this new member of the EF-hand superfamily and to the elucidation of its precise mode of action as a calcium switch.

Amino Acid Sequence↗