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Biomedical subjects

A Dasgupta

Publications and source records attributed to A Dasgupta.

At least 181 records · Page 10Linked to original sources
PubMed1993

Identification of the cleavage site and determinants required for poliovirus 3CPro-catalyzed cleavage of human TATA-binding transcription factor TBP.

Host cell RNA polymerase II-mediated transcription is inhibited by poliovirus infection. We have shown previously that the human TATA-binding protein (TBP), a general transcription factor required for transcription of all RNA polymerase II genes, is directly cleaved both in vitro and in vivo by the virus-coded protease 3CPro. 3CPro specifically cleaves glutamine-glycine bonds in the viral polyprotein. Cellular transcription factor TBP contains three glutamine-glycine sites, at amino acids 12, 18, and 108. By using site-directed mutagenesis, we determined that the glutamine-glycine bond at amino acid 18, but not that at amino acid 12 or 108, is cleaved by the viral protease. Both the glutamine and the glycine appear to be important for the cleavage. Further mutations around the glutamine-glycine site at position 18 suggest that determinants other than the glutamine-glycine bond in TBP are also required for 3CPro-induced cleavage. An alanine at position P4 and a proline at position P2, proximal to the scissile glutamine-glycine pair, appear to be important for 3CPro-mediated cleavage of TBP. Our results suggest that the cleavage specificity of 3CPro for a cellular transcription factor is very similar to its mode of cleavage of viral polyproteins.

3C Viral Proteases↗
PubMed1993

Direct cleavage of human TATA-binding protein by poliovirus protease 3C in vivo and in vitro.

Host cell RNA polymerase II (Pol II)-mediated transcription is inhibited by poliovirus infection. This inhibition is correlated to a specific decrease in the activity of a chromatographic fraction which contains the transcription factor TFIID. To investigate the mechanism by which poliovirus infection results in a decrease of TFIID activity, we have analyzed a component of TFIID, the TATA-binding protein (TBP). Using Western immunoblot analysis, we show that TBP is cleaved in poliovirus-infected cells at the same time postinfection as when Pol II transcription is inhibited. Further, we show that one of the cleaved forms of TBP can be reproduced in vitro by incubating TBP with cloned, purified poliovirus encoded protease 3C. Protease 3C is a poliovirus-encoded protease that specifically cleaves glutamine-glycine bonds in the viral polyprotein. The cleavage of TBP by protease 3C occurs directly. Finally, incubation of an uninfected cell-derived TBP-containing fraction (TFIID) with protease 3C results in significant inhibition of Pol II-mediated transcription in vitro. These results demonstrate that a cellular transcription factor can be directly cleaved both in vitro and in vivo by a viral protease and suggest a role of the poliovirus proteinase 3C in host cell Pol II-mediated transcription shutoff.

3C Viral Proteases↗
PubMed1993

Sclerema neonatorum--histopathologic study.

Histopathological study of 10 cases sclerema neonatorum showed subcutaneous fibrosis with lobulation in all the cases. 8 (80 percent) cases showed non-specific chronic inflammation of dermis and thinning of epidermis with atrophy of rete pegs and hypercollgenisation of dermis was evident in 70 percent cases. Fat necrosis with crystallisation of fat content was not a conspicuous feature.

Adipose Tissue↗
PubMed1993

Analytical performance evaluation of EMIT II monoclonal amphetamine/methamphetamine assay: more specificity than EMIT d.a.u. monoclonal amphetamine/methamphetamine assay.

We evaluated a new EMIT II monoclonal amphetamine/methamphetamine assay for screening human urine by comparing it with the EMIT d.a.u. monoclonal amphetamine/methamphetamine assay and a fluorescence polarization assay. The EMIT II assay has a cutoff of 1 mg/L d-methamphetamine. The EMIT II and EMIT d.a.u. assays were run on a BM/Hitachi 704 analyzer; for the fluorescence polarization assay we used a TDx analyzer. All EMIT II positive samples were also analyzed by the fluorescence polarization assay. We used gas chromatography/mass spectrometry (GC/MS) for confirmation of the presence of amphetamine or methamphetamine. Within-run CVs for the Level 1 (1 mg/L) and Level 2 (3 mg/L) calibrators for the EMIT II assay were 0.47% and 0.53%, respectively. Corresponding between-run CVs were 1.48% and 1.60%, respectively. Of the 1007 samples screened for amphetamines, 50 were positive by the EMIT d.a.u. assay; 21 samples (not a subset of the 50 samples) were positive by the EMIT II assay. However, 19 samples that tested positive by EMIT II also tested positive by the EMIT d.a.u. assay. Subsequent testing of the EMIT II positive samples by the fluorescence polarization assay detected in six positive samples. By means of chiral derivatization wer identified two specimens containing primarily l-isomers of amphetamine and methamphetamine. Sympathomimetic amines were identified in several of the samples not containing amphetamine or methamphetamine.

Amphetamine↗
PubMed1993

Malignant lymphoma--a 15-year study report.

Analysis of incidence of different types of malignancies during 15 years showed occurrence of malignant lymphoma in 192 cases (4.1%). There were 82 cases (42.7%) of non-Hodgkin's lymphoma and 110 cases (57.3%) of Hodgkin's disease. Lymphocytic lymphoma, the major type observed among the non-Hodgkin's lymphoma with 58 cases (30.21%), showed a preponderance of well differentiated type (40 cases). Other cases in this group comprised mixed cellularity (2.08%), histiocytic (3.64%) and unclassified one (6.77%). Analysis of the Hodgkin's disease cases showed majority in it belonged to the mixed cellularity type (44.5%) followed by the lymphocytic predominant type (27.3%), lymphocytic depletion type (18.2%) and nodular sclerosing type (10%). The incidence of 14 cases of extranodal lymphomas was 7.3% among the lymphomas with maximum occurrence in the gastrointestinal tract (42.8%).

Adolescent↗
PubMed1992

Enrichment of saturated fatty acid containing phospholipids in sheep brain serotonin receptor preparations: use of microwave irradiation for rapid transesterification of phospholipids.

During enrichment of the 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT)-binding serotonin 5-HT1A receptors from sheep brain gray matter (membrane isolation, detergent solubilization and reconstitution into vesicles) a consistent and striking increase in the composition of saturated fatty acids was observed in phospholipids which were coisolated with the receptors. A rapid procedure has been developed for the methylation of free and phospholipid linked fatty acids which were thus analyzed by gas chromatography-mass spectrometry (GC/MS). Esterification of free fatty acids and transesterification of phospholipid linked fatty acids were achieved with 14% boron trifluoride in methanol (BF3-CH3OH) in 20 s and 50 s, respectively, under low power microwave irradiation (60 W) with a post-reaction cooling of less than 5 min. This is in contrast to the conventional method of heating in a boiling water bath for 10-15 min with BF3-CH3OH which is inevitably preceded by time-consuming and inconvenient clamping of vials and followed by cooling for 10 min before the vials can be safely opened. Analysis of fatty acid profiles in phosphatidylethanolamine (PE) and phosphatidylcholine (PC) from egg yolk, phosphatidylinositol (PI) from bovine liver and phosphatidylserine (PS) from bovine brain by both techniques showed comparable results. During detergent solubilization of sheep brain gray matter, the overall proportion of saturated fatty acids in PE (major lipid), PI, PC (major lipid) and PS increased from 50-60% in sheep brain phospholipids to 70-75% in 1.5% CHAPS solubilized, reconstituted and biologically active serotonin 5-HT1A preparations. In sharp contrast, the proportions of saturated fatty acids in 1.5% Triton X-100 solubilized PE (48.1%) (major lipid), PI (63.6%), PC (60.6%) (major lipid) and PS (62.2%) were not significantly different from those in the original sheep brain membranes. Strikingly, this was coupled with the occurrence of very low levels of 5-HT1A receptor activity in the Triton X-100 solubilized preparations. The abundance of 5-HT1A sites in the enriched vesicles obtained only from the CHAPS-solubilized preparations was further confirmed by specific radiolabeling of a 58-kDa polypeptide by the 5-HT1A specific ligand p-aminophenylethyl-m-trifluoromethylphenylpiparazine (PAPP) which was coupled to a 125I-labeled, photoreactive, heterobifunctional cross-linker, sulfosuccinimidyl-2-(p-azidosalicylamido)ethyl-1,3'-dithiopropiona te (SASD). Thus CHAPS-solubilized 5-HT1A receptor preparations are depleted in the more rigid lipids such as sphingolipids and cholesterol, (Banerjee et al. (1990) Biochim. Biophys. Acta 1044, 305-314), but are enriched in vesicle-stabilizing, phospholipid-linked saturated fatty acids which in turn probably stabilize the heptahelical, membrane bound 5-HT1A receptor.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1992

Evidence for lipase abnormality: high levels of free and triacylglycerol forms of unsaturated fatty acids in neuronal ceroid-lipofuscinosis tissue.

Total lipid obtained from normal and different forms of neuronal ceroid-lipofuscinoses (NCL) tissues was analyzed by high performance thin layer chromatography (HPTLC). We observed a large (greater than 6-fold) increase in a lipid band corresponding to triolein for NCL dog pancreas and spleen and juvenile human NCL brain and infantile NCL spleen. The accumulation was less pronounced for the brain samples but apart from increased dolichol-monophosphate levels, other lipids appeared normal. Normal dog, goat, or human spleen contained virtually no triacylglycerol, and of the pathological controls, beta-mannosidosis goat spleen showed no triacylglycerol band at all. A sample of human spleen from a patient with lymphoma-associated splenomegaly displayed a strong triacylglycerol band, but gas chromatography-mass spectrometry (GC/MS) of the bands showed an equal increase in both saturated and unsaturated fatty acid containing triacylglycerols in the splenomegaly sample, in keeping with the notion of non-specific fat deposition in damaged tissue. In contrast, in all the NCL samples (spleen, pancreas, and brain) a prominent increase in the proportion of unsaturated fatty acids was observed in both free fatty acid and/or triacylglycerol bands following GC/MS. The NCL-English setter dog pancreas showed a major presence of oleic acid (18:1) (twofold increase) as compared to normal, while dog and infantile human NCL spleen samples and juvenile Batten brain (human) displayed a robust increase in linoleic acid (18:2) and sometimes in oleic acid and arachidonic acid (20:4) (for infantile human NCL spleen). For the infantile human NCL spleen sample an increase in linoleic acid in both free fatty acid (3.2-fold) and triacylglycerol (10-fold) was observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

In vitro lipid peroxidation of human serum catalyzed by cupric ion: antioxidant rather than prooxidant role of ascorbate.

The dual role of ascorbate as an antioxidant and a prooxidant has been clearly documented in the literature. Ascorbate acts as an antioxidant by protecting human serum from lipid peroxidation induced by azo dye-generated free radicals. On the other hand, ascorbate is readily oxidized in the presence of transition metal ions, (especially cupric ion) and accelerates lipid peroxidation in tissue homogenates by producing free radicals. Interestingly, we observed an antioxidant rather than an expected prooxidant role of ascorbate when human serum supplemented with 1.2mmol/L ascorbate underwent lipid peroxidations initiated by 2mmol/L copper sulfate. The antioxidant role of ascorbate was confirmed by studying the conventional thiobarbituric acid reactive substances (TBARS) as well as by observing the protective effect of ascorbate on the copper-induced peroxidation of unsaturated and polyunsaturated fatty acids. The antioxidation protection provided by ascorbate was comparable to that of equimolar alpha-tocopherol when incubated for 24h. However, lipid peroxidation products were lower in serum supplemented with alpha-tocopherol after 48h of incubation. This effect may be attributed to the binding of copper by plpha-tocopherol after serum proteins, thus preventing direct interaction between cupric ions and ascorbate. This proposed mechanism is based on the observation that the concentration of ascorbate decreased more slowly in serum than in phosphate buffer at physiological pH. Our results also indicate an outstanding anti-oxidant property of human serum due to the chelation of transition metal ions (even at high concentrations) by various serum proteins.

Antioxidants↗
PubMed1992

Improved lipid profiles in patients undergoing high-flux hemodialysis.

Hyperlipidemia is one of many atherogenic risk factors encountered by patients undergoing chronic hemodialysis (HD). We have studied lipid profiles in these patients and have found less hypertriglyceridemia in those undergoing high-flux HD than those receiving traditional HD. Mean +/- SEM triglyceride level was 1.62 +/- 0.15 mmol/L (143.3 +/- 13.6 mg/dL) in high-flux dialysis patients, 2.39 +/- 0.27 mmol/L (211.6 +/- 24.1 mg/dL) in conventional dialysis patients, and 1.55 +/- 0.13 mmol/L (137.1 +/- 11.5 mg/dL) in normal age- and sex-matched controls. In addition, we found that in patients undergoing high-flux HD, females had higher high-density lipoprotein2 (HDL2) levels (0.62 +/- 0.03 mmol/L [23.8 +/- 1.3 mg/dL]) than males (0.33 +/- 0.04 mmol/L [12.9 +/- 1.7 mg/dL]) (P < 0.01). The mechanism(s) responsible for divergent lipid profiles in subsets of HD patients deserves further investigation. Whether reductions of hypertriglyceridemia and/or increases of HDL2 will diminish the incidence of cardiovascular disease in dialysis patients is unknown.

Adult↗
PubMed1992

Increased free phenytoin concentrations in predialysis serum compared to postdialysis serum in patients with uremia treated with hemodialysis. Role of uremic compounds.

Patients with uremia are reported to have elevated concentrations of free phenytoin as a result of decreases in protein binding. This appears to be related to the presence of uremic compounds. To determine the dialyzability of these compounds, the in vitro protein binding levels of phenytoin in pre- and postdialysis serum (supplemented with phenytoin) of 12 patients with uremia were compared. For these patients, the concentrations of free phenytoin were significantly greater in predialysis serum (lower protein binding) compared to postdialysis serum, although the concentrations of total phenytoin did not vary. Low levels of protein binding of phenytoin in predialysis serum also were observed in two hemodialysis patients receiving phenytoin. Several serum pools, prepared from both normal volunteers and the predialysis sera of uremic patients, were dialyzed (in vitro equilibrium dialysis). Then both undialyzed and dialyzed sera were supplemented with phenytoin and analyzed to determine free and total phenytoin concentrations. The free phenytoin concentrations were increased in equilibrium-dialyzed normal serum pools compared to undialyzed original pools because of decreases in albumin concentrations after equilibrium dialysis. In contrast, free phenytoin concentrations were decreased in the equilibrium-dialyzed uremic serum pools, thereby indicating an attenuation of the albumin dilution effect on free phenytoin concentration, probably by the preexisting uremic compounds. These compounds can be removed completely by treating sera with activated charcoal at pH 3. The results obtained from charcoal treatment experiments, in combination with other results, indicate that these uremic compounds can be removed partially by in vivo hemodialysis and by in vitro equilibrium dialysis.

Adsorption↗
PubMed1992

Yeast cells are incapable of translating RNAs containing the poliovirus 5' untranslated region: evidence for a translational inhibitor.

We have expressed in the yeast Saccharomyces cerevisiae a full-length poliovirus cDNA clone under the control of the GAL10 promoter to better characterize the effect of poliovirus on host cell metabolism. We find that yeast cells are unable to translate poliovirus RNA in vivo and that this inhibition is mediated through the 5' untranslated region of the viral RNA. The in vivo inhibition of translation of poliovirus RNA and P2CAT RNA (which contains the 5' untranslated region fused upstream of the bacterial chloramphenicol transferase gene) can be mimicked in vitro in yeast translation lysates. In fact, a trans-acting inhibitor present in yeast lysates can inhibit translation of either poliovirus or P2CAT RNA in HeLa cell translation lysates. In contrast, when the inhibitor is added to translations programmed with chloramphenicol acetyltransferase RNA, yeast prepro-alpha-factor RNA, or an RNA containing the internal ribosome entry site of encephalomyocarditis virus, no inhibition is seen. The inhibitory activity has been partially purified by DEAE-Sephacel chromatography. The partially purified inhibitor is heat stable, escapes phenol extraction, is resistant to proteinase K and DNase I treatment, and is sensitive to RNase A digestion, suggesting that the inhibitor is an RNA. In an in vitro translation assay, the inhibitory activity can be overcome by increasing the concentration of HeLa cell lysate but not P2CAT RNA, suggesting that the inhibitor interacts (directly or indirectly) with one or more components of the HeLa cell translational machinery rather than with the viral RNA.

Blotting, Northern↗
PubMed1992

Infection of HeLa cells with poliovirus results in modification of a complex that binds to the rRNA promoter.

In HeLa cells, RNA polymerase I (Pol I)-mediated transcription is severely inhibited soon after infection with poliovirus. We have developed a gel retardation assay to analyze DNA-protein complexes formed at the Pol I promoter. We show here that two complexes (A and C) formed by nuclear extracts from uninfected cells disappear after infection of cells with poliovirus. In contrast, a new, rapidly migrating complex (D) is formed in virus-infected cell extract. This change in the mobility of gel-retarded complexes correlates well with the kinetics of inhibition of rRNA transcription in virus-infected cells. Incubation of nuclear extracts from mock-infected cells with bacterially expressed, purified poliovirus protease 3C results in the disappearance of complexes A and C with concomitant generation of complex D. A partially purified transcription factor fraction derived from uninfected cells that contains complex A is able to restore Pol I transcription when added to virus-infected cell extracts, suggesting that this complex plays an important role in Pol I transcription. These results suggest that poliovirus proteinase 3C may have an important role in the shutoff of Pol I transcription in cells infected with poliovirus.

3C Viral Proteases↗
PubMed1992

Mr 40,000 human colonic epithelial protein expression in colonic mucosa and presence of circulating anti-Mr 40,000 antibodies in cotton top tamarins with spontaneous colitis.

Saguinus oedipus, Callithrix jacchus, and Saguinus fuscicollis are three species of New World monkeys which develop a form of colitis that is similar to human ulcerative colitis. Only S oedipus, however, develop colon cancer. We examined intestinal tissues from these animals for the presence of an antigen cross reacting to the Mr 40,000 human colonic epithelial protein that acts as an autoantigen in ulcerative colitis. Using an anti-Mr 40,000 monoclonal antibody (7E12H12, IgM isotype), by an immunoperoxidase assay we showed that all colon specimens from S oedipus reacted with 7E12H12; however, the colonic tissue from C jacchus and S fuscicollis did not. In immunotransblot analysis eluted IgG antibody bound to human ulcerative colitis colon (CCA-IgG) reacted with Mr 40,000 protein(s) present in the extracts of colon from S oedipus animals and humans. Small intestinal tissue reacted neither with 7E12H12 nor with CCA-IgG. In S oedipus, the Mr 40,000 protein was localised exclusively to colonic epithelial cells. Preincubation of seven S oedipus colon specimens with eight of 10 sera from animals with acute or chronic colitis and 0 of four sera from animals without colitis almost completely inhibited the binding of 7E12H12 to the colonic epithelium. Four of these 10 sera inhibited the binding of 7E12H12 to the autologous colon. These results show the presence of circulating autoantibodies in S oedipus with colitis against an epitope(s) on Mr 40,000 protein shared by human and S oedipus colon.

Animals↗
PubMed1992

Increased lipid peroxidation in patients on maintenance hemodialysis.

Lipid peroxidation products, lipid hydroperoxide and malonaldehyde were measured in the serum of patients on maintenance hemodialysis and compared with values obtained from a group of healthy controls. Dialysis patients had significantly elevated levels of lipid peroxidation products (12.9 +/- 1.9 vs. 9.3 +/- 1.3 nmol/ml, mean +/- SD, patients vs. controls, p less than 0.0001). In contrast, the serum transferrin level was significantly lower in the dialysis patients (217 +/- 71 vs. 290 +/- 50 mg/dl, patients vs. controls, p less than 0.0002). Compared to normal controls HDL cholesterol was lower (40 +/- 11 vs. 53 +/- 8, p less than 0.0001) and triglycerides were higher (206 +/- 103 vs. 142 +/- 64, p less than 0.007) in the patient group. The patient group was then divided on the basis of using polysulfone or cupraphane dialyzers. Patients using polysulfone dialyzers had lower levels of 2-thiobarbituric acid-reactive substances (12.3 +/- 0.9 vs. 13.6 +/- 2.1, polysulfone vs. cupraphane, p = 0.05), and higher transferrin concentrations (248 +/- 84 vs. 194 +/- 37, p = 0.03). Thus, in patients on maintenance hemodialysis there was evidence for accelerated lipid peroxidation. This abnormality was more marked in patients using traditional cupraphane dialyzers. The mechanism for this observation remains unclear.

Adult↗
PubMed1992

Differential effects of transition metal ions on in vitro lipid peroxidation of human serum and protein precipitated from serum.

Elevated concentrations of lipid peroxidation products in serum have been documented in some common human diseases. In addition, several reports indicate that peroxidative damage of tissues in laboratory animals are enhanced in acute toxicity from transition metal ions. We studied the effects of four commonly encountered transition metal ions in human acute toxicity: copper, iron, mercury and lead on in vitro lipid peroxidation of human sera. Cupric and ferric ions caused a significant increase in lipid peroxidation products while mercuric and lead ions had no effects. Lipid peroxidation products in sera incubated with 1 mM cupric ion were increased by 210-248% following 24 h of incubation and 340-480% after 48 h of incubation, while the increases were significantly lower in the aliquots of same serum pools supplemented with same molar concentration of ferric ions (110-115% after 24 h and 137-141% following 48 h). On the other hand the effects were reversed when lipoproteins coprecipitated with other serum proteins were incubated with cupric and ferric ions. Under such conditions increases of lipid peroxidation products were significantly higher with ferric ions (240% after 24 h and 600% after 48 h) compared to cupric ions (20% following 24 h and 25% following 48 h). Such differential behavior of cupric and ferric ions in promoting lipid peroxidation can be explained with a different degree of binding of such ions with serum proteins.

Blood Proteins↗