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Biomedical subjects

A Dasgupta

Publications and source records attributed to A Dasgupta.

At least 163 records · Page 9Linked to original sources
PubMed1995

Clinicopathological study of clinically undiagnosed cases of kala-azar with special reference to grading of parasites.

Clinicopathological study of 34 clinically undiagnosed cases of kala-azar has been undertaken with a view to establish the diagnosis and correlate the quantitative grading of Leishmania donovani in bone marrow/splenic aspirates with clinical features and duration of disease. The ages of the patients were between 5 and 45 years. The duration of illnesses ranged from 2-24 months with 47% having 2 months' duration. Splenomegaly was less than 7 cm in 70.5% cases. Anaemia, leucopenia and mild thrombocytopenia were present in all the cases. Aldehyde test was positive in 47% cases. Bone marrow aspiration revealed the parasites in 82.3% cases. L donovani was also observed in 66.6% cases of splenic aspiration including 6 cases where bone marrow failed to reveal the parasite. Grading of the parasites in bone marrow and splenic aspirates revealed majority of the cases (73.5%) were in 3+ and 4+ grades. No correlation between splenic size and duration of illness or parasite grading was detected. Neither any positive correlation between parasite grading and duration of illness was observed.

Adolescent↗
PubMed1994

Autoantibodies in sclerosing cholangitis against a shared peptide in biliary and colon epithelium.

BACKGROUND/AIMS: A strong association exists between ulcerative colitis and primary sclerosing cholangitis (PSC). Previously, the presence of a unique epitope shared by colon and biliary epithelial cells was shown by using the novel monoclonal antibody (MAb) 7E12H12 developed against a colonic epithelial protein. In the present study, the presence of circulating autoantibody in PSC against this peptide was examined. METHODS: Sera from 16 patients with PSC, 13 with primary biliary cirrhosis, 6 with secondary biliary stricture, and 6 with chronic liver diseases and 10 normal subjects were used. An inhibition immunoperoxidase assay using the 7E12H12 MAb was developed against sections of bile duct and gallbladder. Sera were also examined in an enzyme-linked immunosorbent assay (ELISA) against the gallbladder extract enriched in 7E12H12-reactive protein. RESULTS: About two thirds of the sera from patients with PSC blocked the binding of 7E12H12 MAb on the bile duct and gallbladder, whereas non-PSC sera did not. In the ELISA, 93% of PSC sera had circulating immunoglobulin G antibodies against the enriched gallbladder extract. The reactivity of sera from the PSC group was significantly (P < 0.01 to P < 0.0001) higher than in each of the non-PSC groups. CONCLUSIONS: Sera from patients with PSC contains autoantibodies against a cross-reactive peptide shared by colon and biliary epithelial cells.

Adult↗
PubMed1994

Absorption of therapeutic drugs by barrier gels in serum separator blood collection tubes. Volume- and time-dependent reduction in total and free drug concentrations.

The stability of seven commonly monitored therapeutic drugs in serum was examined following storage in Vacutainer SST and Corvac serum separator blood collection tubes. Significant decreases (ranging from 5.9% to 64.5%) in the measured concentrations of phenytoin, phenobarbital, lidocaine, quinidine, and carbamazepine were observed, as a function of both time and sample volume, when serum was stored in Vacutainer SST serum separator blood collection tubes. In contrast, measured concentrations of theophylline and salicylate did not change under identical specimen storage conditions. No significant changes in the concentrations of phenytoin, phenobarbital, carbamazepine, theophylline, quinidine, and salicylate were observed when serum was stored in Corvac serum separator blood collection tubes. Only serum lidocaine concentrations decreased (ranging from 31.5% to 72.6%, depending on sample volume) after storage in Corvac tubes for 24 hours. The apparent decreases in serum concentrations of therapeutic drugs in both Vacutainer SST and Corvac tubes were most pronounced when small volumes (200-500 microL) of serum remained in contact with the barrier gels for prolonged periods of time (> 2-6 hours). These decreases were due to absorption of drugs by the barrier gels, as demonstrated by the recovery of drugs following chemical extraction of the barrier gels with methanol. For phenytoin and phenobarbital, the reduction in total drug concentrations also resulted in a proportional decrease in free drug concentrations and was dependent on the extent of protein binding by the drug. None of the therapeutic drugs used in this study were adversely affected by prolonged storage in standard red top Vacutainer blood collection tubes without barrier gels. The data suggest that serum separator blood collection tubes should be used with extreme caution for therapeutic drug monitoring, particularly when reduced sample volumes or prolonged specimen storage may be required.

Absorption↗
PubMed1994

A small yeast RNA selectively inhibits internal initiation of translation programmed by poliovirus RNA: specific interaction with cellular proteins that bind to the viral 5'-untranslated region.

We have purified, sequenced, and prepared a synthetic clone of a small (60-nucleotide) RNA molecule from the yeast Saccharomyces cerevisiae that had previously been isolated on the basis of its ability to selectively block the translation of poliovirus mRNA. RNA derived from the clone by transcription with T7 RNA polymerase appears to block translation initiation by internal ribosome entry (cap independent) but does not significantly affect cap-dependent translation. Deletion analysis of the poliovirus 5'-untranslated region (5'-UTR) has shown that yeast inhibitor RNA (I-RNA) requires internal ribosome entry site sequences to inhibit the translation of poliovirus RNA in vitro. Using a bicistronic RNA construct, we show that I-RNA preferentially inhibits translation by internal ribosome entry. Gel retardation and UV cross-linking studies demonstrate that I-RNA specifically binds proteins which interact with RNA secondary structures within the poliovirus 5'-UTR presumably involved in internal initiation. Specifically, purified I-RNA competes with virus RNA structures within the 5'-UTR which bind a cellular protein with an approximate molecular mass of 52 kDa. Finally, when transfected into HeLa cells, I-RNA efficiently inhibits the replication of poliovirus RNA presumably by inhibiting translation of the input virus RNA.

Base Sequence↗
PubMed1994

Expression and subcellular localization of poliovirus VPg-precursor protein 3AB in eukaryotic cells: evidence for glycosylation in vitro.

The poliovirus-encoded, membrane-associated VPg-precursor polypeptide 3AB has been implicated in the initiation of viral RNA synthesis. We have expressed 3AB and 3A polypeptides in eukaryotic cells and examined their localization using indirect immunofluorescence and a direct in vitro membrane-binding assay. Results presented here demonstrate that both 3AB and 3A are capable of localizing in the endoplasmic reticulum and the Golgi apparatus in transfected HeLa cells in the absence of any other poliovirus protein. We have also shown that the carboxy-terminal 18 amino acids of 3A that constitute an amphipathic domain are important in membrane binding of 3A and 3AB. Additionally, we demonstrate that a significant fraction of both 3A and 3AB can be glycosylated in a membrane-dependent fashion during in vitro translation in reticulocyte lysate. We demonstrate that 6-diazo-5-oxo-L-norleucine, an inhibitor of glycoprotein synthesis, significantly inhibits poliovirus RNA synthesis in vivo. The implications of glycosylation of 3AB (and 3A) in viral replication are discussed.

Base Sequence↗
PubMed1994

Circulating immunoglobulin G1 antibody in patients with ulcerative colitis against the colonic epithelial protein detected by a novel monoclonal antibody.

Autoimmunity has been implicated in the pathogenesis of ulcerative colitis (UC). Several studies have shown amplified immunoglobulin G1 (IgG1) antibody response in UC; however the immunoreactive antigen(s) is unknown. To study this antigen(s), mucosal colonic extract was prepared by sonication, ultracentrifugation followed by ion exchange chromatography in fast protein liquid chromatography. The fraction (enriched colonic peptide), that was most reactive to a novel monoclonal antibody, 7E12H12 (IgM isotype), was isolated and used to examine the immunoreactivity against the patients' serum samples. Two hundred and thirteen coded samples from 111 patients with UC (symptomatic and untreated (63), symptomatic and treated (26), remission (22)); 47 with Crohn's disease (CD) (40 were symptomatic and untreated, and 30 had colonic disease); 29 with acute diarrhoea caused by specific pathogen(s); 10 with systemic lupus erythematosus, and 16 normal subjects were examined against the enriched colonic peptide by IgG subtype specific enzyme linked immunosorbent assays (ELISAs). Total IgG antibody reactivity was significantly (p < 0.01) higher only in symptomatic and untreated UC patients compared with each of the non-UC group, but the sensitivity was only 50%. IgG2 and IgG3 reactivities were not different among various groups. The IgG1 antibody reactivity against the enriched colonic peptide, however, differentiated UC patients from CD and each of the other non-UC groups. Seventy nine per cent of the patients with UC, treated or untreated, symptomatic or in remission, had significantly (p < 0.0001) higher IgG1 antibody against the enriched colonic peptide when compared with each of the other non-UC groups. Only 12% of CD serum samples and none of the other control serum samples reacted. Using purified serum IgG1 and 7E12H12-IgM, by 7E12H12 reactive peptide indeed reacts with UC-IgG1 antibody but not with control IgG1.

Adolescent↗
PubMed1994

Fast atom bombardment mass spectrometric determination of the molecular weight range of uremic compounds that displace phenytoin from protein binding: absence of midmolecular uremic toxins.

Uremic compounds are known to displace phenytoin from protein binding, resulting in a higher concentration of the pharmacologically active free fraction of phenytoin. The true chemical identities and molecular weight range of all these compounds are still unknown. We demonstrated that indoxyl sulfate and hippuric acid, which are found at high concentrations in uremic patients, can only partially explain the elevated free phenytoin concentration. Other known uremic compounds, guanidine, methylguanidine, and guanidinosuccinic acid, do not displace phenytoin from the protein-binding sites. Uremic compounds from sera of patients on maintenance hemodialysis were removed using activated charcoal. These compounds were then backextracted from activated charcoal using methanol and analyzed by fast atom bombardment mass spectroscopy. Mass spectra of uremic sera showed no peak over m/z 450, indicating that midmolecular uremic toxins are not involved in displacing phenytoin from protein binding. We also observed additional peaks in the mass spectrum of uremic compounds when compared with the normal serum extract, indicating the presence of several endogenous compounds in uremic sera, as expected.

Drug Interactions↗
PubMed1994

Hepatic histology in chronic liver disease in hepatitis B surface antigen positive cases.

The spectrum of histological changes in needle biopsies of the liver tissue was analysed in 43 patients with chronic liver disease who were positive for hepatitis B surface antigen (HBsAg) in their sera. Majority of the patients were around 40 years and there was a male predominance. According to histopathological pattern, there were 18 (41.8%) cases of chronic active hepatitis, 16 (37.2%) cases of inactive cirrhosis, 3 (6.9%) cases of chronic persistent hepatitis and 2 (4.7%) cases of chronic lobular hepatitis and hepatoma each. Two (4.7%) cases could not be exactly categorised into any particular histological entity. The inflammation, hepatic cell necrosis and fibrosis were more marked in cases of chronic active hepatitis without past history of jaundice. Micronodular cirrhosis was the most common histological pattern in the study. Shikata orcein stain for detection of HBsAg in the hepatocytes was positive in 8 (18.6%) cases only.

Adolescent↗
PubMed1994

Effect of heating sera under conditions necessary for deactivation of human immunodeficiency virus on commonly monitored therapeutic drugs.

Minimizing the risk of infection of laboratory staff from contaminated blood samples is a major safety goal in a clinical laboratory. One dangerous pathogen, the human immunodeficiency virus (HIV) can be deactivated by heating sera at 56 degrees C for 30 min. We studied the effect of such heat treatment on serum concentrations of 11 commonly monitored therapeutic drugs. We used blood specimens collected in serum separator tubes (SSTs), which were routinely submitted for therapeutic drug monitoring in our laboratory for this study. Concentrations of digoxin in sera were measured using a fluorescence polarization immunoassay (FPIA), while concentrations of tobramycin, gentamicin, vancomycin, theophylline, valproic acid, procainamide, N-acetylprocainamide (NAPA), phenytoin, phenobarbital, and carbamazepine were measured by enzyme-multiplied immunoassay technique assays using a Monarch 2000 analyzer. We observed no significant change in the concentration of any drug except phenytoin and carbamazepine following heating at 60 degrees C. The decrease in concentration of phenytoin and carbamazepine after heating was related to absorption of the drug to the gel rather than the instability of the drug under heating conditions. We conclude that blood contaminated with HIV may be deactivated by heating prior to analysis for most of the routinely monitored therapeutic drugs.

Blood Proteins↗
PubMed1994

Microwave-induced rapid preparation of fluoro-derivatives of amphetamine, methamphetamine, and 3,4-methylenedioxymethamphetamine for GC-MS confirmation assays.

We prepared trifluoroacetyl, pentafluoropropyl, and heptafluorobutyl derivatives of amphetamine, methamphetamine, and 3,4-methylenedioxymethamphetamine (MDMA) in 45 s, 1 min, and 6 min, respectively, by using microwave irradiation. Conventional techniques require heating the reaction mixture for 15 min at 40 degrees C for trifluoroacetyl derivatives, 15 min at 75 degrees C for pentafluoropropyl derivatives, and 40 min at 60 degrees C for heptafluorobutyl derivatives. The mass-spectral fragmentation patterns and the gas-chromatographic retention times of the derivatives obtained by both microwave irradiation and conventional heating were similar. Perfluorooctanoyl derivatives of amphetamine can be prepared quantitatively by either heating the reaction mixture for 30 min at 60 degrees C or by 1 min of microwave irradiation. Conversion of methamphetamine and MDMA to the corresponding perfluorooctanoyl derivatives was not quantitative by either technique, although the yield of the derivative in the conventional technique was much higher.

3,4-Methylenedioxyamphetamine↗
PubMed1994

Fine needle aspiration cytology of cervical lymphadenopathy with special reference to tuberculosis.

One hundred eighty cases of cervical lymphadenopathy have been studied by fine needle aspiration cytological examination followed by histopathologic examination of the excised lymph nodes. The diagnostic accuracy was 84.4% for tuberculous lymphadenitis by fine needle aspiration cytological examination. Observation of caseous necrosis (84.2%) and epithelioid cells (73.6%) were the most characteristic diagnostic features in the aspirated smears. Acid-fast bacilli were observed in 45.6% cases. Metastatic carcinoma also yielded a high diagnostic accuracy ie, 89%. Fine needle aspiration cytology has been found to be safe, quick, inexpensive with high diagnostic accuracy in cervical lymphadenopathy.

Adolescent↗
PubMed1994

Reduced in vitro displacement of valproic acid from protein binding by salicylate in uremic sera compared with normal sera. Role of uremic compounds.

Limited studies indicate increased free fraction of valproic acid in uremia. One study also described displacement of valproic acid from protein binding by salicylate in children with epilepsy. The authors studied in vitro interaction of valproic acid and salicylate in uremic sera and compared their results with same interactions in normal sera. As expected, the concentrations of free valproic acid were always significantly higher in uremic sera compared with normal sera. When uremic sera were supplemented with both valproic acid and salicylate, a much lower displacement of valproic acid by salicylate was observed, compared with the effects observed in normal sera. Treatment of uremic sera with charcoal removed those uremic compounds, and the concentration of free valproic acid in charcoal-treated uremic sera were comparable to the concentrations observed in normal sera. When uremic compounds were extracted from charcoal with methanol, lyophilized, and added to normal serum, an increase in free valproic acid concentration in normal serum was observed, indicating that uremic compounds, rather than altering albumin structure, are responsible for elevated free valproic acid concentration in uremia. However, uremic extract failed to produce any further displacement of valproic acid in normal serum in the presence of salicylate. The authors concluded that uremic compounds are responsible for elevated free valproic acid concentrations, but the displacement of valproic acid by salicylate in uremic sera are less remarkable compared with such effect in normal sera.

Charcoal↗
PubMed1993

Differential solubilization of membrane lipids by detergents: coenrichment of the sheep brain serotonin 5-HT1A receptor with phospholipids containing predominantly saturated fatty acids.

Most membrane receptors lose binding activity during purification and we studied the correlation between this event and differential solubilization of membrane lipids by detergents. Both 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate [Chaps; high critical micellar concentration (cmc) approximately 0.5%] and n-dodecyl beta-D-maltoside (DDM; low cmc approximately 0.009%) solubilized the 8-[3H]hydroxy-2-(di-n-propylamino)tetralin ([3H]8-OH-DPAT)-binding serotonin 5-HT1A receptor (5-HT1A-R) optimally at 2% (w/v) detergent concentration despite the widely differing cmc of the two detergents. In contrast, n-octyl-beta-D-glucopyranoside (octyl glucoside; high cmc approximately 0.7%), Thesit (low cmc approximately 0.005%), and Triton X-100 (low cmc approximately 0.013%) solubilized virtually no [3H]8-OH-DPAT-binding activity. The total mass of solubilized lipids was always low at 0.5% detergent concentration and attained a plateau between 1 and 2.5% for all detergents except octyl glucoside. The mass of octyl glucoside-solubilized lipids showed an increasing trend even at 3.0% detergent concentration. The total amount of solubilized lipid is unrelated to the amount of 5-HT1A-R solubilized but the species of lipid is important. Thus Chaps and DDM, with diverse structures and cmc, both preferentially solubilized phospholipids enriched in saturated fatty acids (67 and 72%, respectively). In contrast, octyl glucoside, Triton X-100, and Thesit showed no preference in solubilizing phospholipids. Octyl glucoside, which solubilized significantly higher proportions of saturated fatty-acid-containing phosphatidylethanolamine (slightly higher saturated fatty acids in total phospholipids), also produced more (twofold higher) solubilized 5-HT1A sites than Triton X-100 and Thesit. This suggests an optimum involvement of saturated fatty acid side chains in forming tightly packed vesicles which stabilize the 5-HT1A-R more than the vesicles of higher fluidity formed by phospholipids containing higher proportions of cis-double-bonded unsaturated fatty acids. Indeed, delipidation of the 1.5% Chaps-solubilized receptor preparations by Sephacryl S-200 column chromatography eliminated essentially all [3H]8-OH-DPAT-binding activity. Therefore, for efficient recovery during solubilization and reconstitution of a prototypic heptahelical receptor (5-HT1A), it is essential to stabilize the receptor protein through association with saturated phospholipids.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1993

Autoimmunity to cytoskeletal protein tropomyosin. A clue to the pathogenetic mechanism for ulcerative colitis.

Autoimmunity has been emphasized in the pathogenesis of ulcerative colitis and various anticolon antibodies have been described. Nevertheless, the nature of the autoantigens has been elusive. Using ulcerative colitis colon-eluted IgG antibody, we earlier detected an M(r) 40,000 protein, P40, in colon extract. In our study, we purified P40 from human colon to apparent homogeneity, sequenced two peptides after proteolytic digestion, and demonstrated that the P40 belongs to the tropomyosin family. Furthermore, we demonstrated that blood serum from 95% of patients with ulcerative colitis contains antibodies that are reactive to tropomyosin.

Adolescent↗