Biomedical subjects
S Basu
Publications and source records attributed to S Basu.
Model-based estimation of population attributable risk under cross-sectional sampling.
The covariate-adjusted population attributable risk (PAR) measures the proportionate reduction in disease prevalence in the target population when the putative risk factor is removed, after adjusting for covariate effects. This paper extends the model-based approach developed for retrospective and cohort studies to the cross-sectional sampling design. An appropriate logit linear model is utilized to estimate the covariate-adjusted attributable risk. The asymptotic variance of this complex ratio estimate is obtained using Taylor series expansions which incorporate the sampling variation of the estimated model parameters and the appropriate estimates of risk factor prevalence. These methods are illustrated with cardiovascular disease risk factor data from the second National Health and Nutrition Examination Survey (NHANES II).
Structure of the O-specific side chain of the Escherichia coli O128 lipopolysaccharide.
The O-specific polysaccharide isolated from Escherichia coli O128 lipopolysaccharide contains D-galactose, L-fucose, and 2-acetamido-2-deoxy-D-galactose in the molar ratios 2:1:2. The primary structure of the O-specific polysaccharide from E. coli was established by compositional analysis, methylation analysis, together with 1H and 13C NMR spectroscopy including two-dimensional shift-correlated and one-dimensional NOE spectroscopy. The polysaccharide moiety was found to consist of a tetrasaccharide backbone containing D-galactose and 2-acetamido-2-deoxy-D-galactose, with L-fucose as a side chain in a branched pentasaccharide repeating unit having the following structure: [formula: see text]
Phosphorylation of Raf by ceramide-activated protein kinase.
The sphingomyelin pathway, initiated by hydrolysis of sphingomyelin to ceramide and stimulation of a Ser/Thr ceramide-activated protein (CAP) kinase, mediates tumour necrosis factor-alpha (TNF-alpha) and interleukin-1 beta action. CAP kinase is membrane-bound and proline-directed, recognizing the minimal substrate motif Thr-Leu-Pro. TNF may use the sphingomyelin pathway to signal Raf1 to activate the MAP kinase cascade. Evidence shows that cytoplasmic Raf1 binds to GTP-ras upon cellular stimulation, is recruited to the plasma membrane, and activated. How membrane-bound Raf1 is activated is uncertain, but regulation of its kinase activity may involve its phosphorylation. Specific Raf kinases, however, have not hitherto been identified. Here we report that CAP kinase phosphorylates Raf1 on Thr 269, increasing its activity towards MEK (MAP kinase or ERK kinase). Moreover, in intact HL-60 cells, CAP kinase complexes with Raf1 and, in response to TNF and ceramide analogues, phosphorylates and activates Raf1, implicating CAP kinase as a link between the TNF receptor and Raf1.
Pressure coefficient of the superconducting transition temperature within the van Hove scenario.
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Role of orthorhombic distortion, second-nearest-neighbor hopping, and Coulomb repulsion on the superconducting transition temperature and isotope-shift exponent.
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Identification of conditions that facilitate the expression of GST fusions as soluble, full-length proteins.
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Comparison of several goodness-of-fit tests for the kappa statistic based on exact power and coverage probability.
We present a general approach based on chi-square goodness-of-fit tests for performing tests of significance about the kappa statistic. We make recommendations for the particular goodness-of-fit test to use under different situations. We also compare the test statistics in terms of the generated confidence intervals about the kappa statistic.
Characterization of regions of herpes simplex virus type 1 glycoprotein E involved in binding the Fc domain of monomeric IgG and in forming a complex with glycoprotein I.
Glycoprotein E (gE) and glycoprotein I (gI) of herpes simplex virus type 1 form a molecular complex that binds the Fc domain of monomeric IgG. Two approaches were used to define regions of gE-1 involved in monomeric IgG binding and complex formation with gI-1. First, we constructed 22 in-frame gE-1 linker-insertion mutants and, in cotransfection experiments with gI-1, assayed each mutant for IgG monomer binding and the ability to complex with gI-1. Nine mutants with insertions between gE-1 amino acids 235 and 380 failed to bind IgG monomers, whereas mutants outside this region retained binding activity. Each mutant reacted with several gE-1 mAbs, was detected at the cell surface, and was fully processed. Only two gE-1 mutants with insertions at residues 235 and 264 lost the ability to co-immunoprecipitate with gI-1, which defines a region of gE-1 that complexes with gI-1. As an additional approach, we assayed 8 gE-1/gD-1 fusion proteins containing large overlapping gE-1 peptides inserted within the ectodomain of gD-1 for binding of IgG monomers and complex formation with gI-1. Three fusion proteins containing gE-1 peptides that overlap at residues 183-402 bound monomeric IgG. This region of gE-1 includes the Fc binding region defined by linker insertion mutagenesis. Five fusion proteins containing gE-1 peptides that overlap at residues 183-288 were co-immunoprecipitated with gI-1, confirming results of gE-1 linker insertion mutagenesis. These studies define two regions on gE-1 involved in Fc binding activity, one that interacts with gI-1, and another that binds IgG.
Purification, properties, and immunological characterization of GalT-3 (UDP-galactose: GM2 ganglioside, beta 1-3 galactosyltransferase) from embryonic chicken brain.
A beta 1-3 galactosyltransferase (GalT-3; UDP-Gal; GM2 beta 1-3 galactosyltransferase) was purified over 5100-fold from 19-day-old embryonic chicken brain homogenate employing detergent solubilization, alpha-lactalbumin Sepharose, Q-Sepharose, UDP-hexanolamine Sepharose, and GalNAc beta 1-4Gal beta-Synsorb column chromatography. The purified enzyme was resolved into two bands on reducing gels with apparent molecular weights of 62 kDa and 65 kDa, respectively. GalT-3 activity was also localized in the same regions by activity gel analysis and sucrose-density gradient centrifugation of a detergent-solubilized extract of 19-day-old embryonic chicken brain. Purified GalT-3 exhibited apparent Kms of 33 microM, and 14.4 mM with respect to the substrates GM2, UDP-galactose, and MnCl2, respectively. Substrate specificity studies with the purified enzyme and a variety of glycosphingolipids, glycoproteins, and synthetic substrates revealed that the enzyme was highly specific only for the glycosphingolipid acceptors, GM2 and GgOse3Cer (asialo-GM2). Ovine-asialo-agalacto submaxillary mucin inhibited the transfer of galactose to GM2 but did not act as an acceptor in the range of concentrations tested. Polyclonal antibodies raised against purified GalT-3 inhibited GalT-3 activity in vitro and Western-immunoblot analysis of purified GalT-3 showed immunopositive bands at 62 and 65 kDa.
Comparative study of biological glues: cryoprecipitate glue, two-component fibrin sealant, and "French" glue.
BACKGROUND: Although biological glues have been used clinically in cardiovascular operations, there are no comprehensive comparative studies to help clinicians select one glue over another. In this study we determined the efficacy in controlling suture line and surface bleeding and the biophysical properties of cryoprecipitate glue, two-component fibrin sealant, and "French" glue containing gelatin-resorcinol-formaldehyde-glutaraldehyde (GRFG). METHODS: Twenty-four dogs underwent a standardized atriotomy and aortotomy; the incisions were closed with interrupted 3-0 polypropylene sutures placed 3 mm apart. All dogs had a 3- by 3-cm area of the anterior wall of the right ventricle abraded until bleeding occurred. The animals were randomly allocated into four groups: in group 1 (n = 6) bleeding from the suture lines and from the epicardium was treated with cryoprecipitate glue; in group 2 (n = 6) bleeding was treated with two-component fibrin sealant; group 3 (n = 6) was treated with GRFG glue; group 4 (n = 6) was the untreated control group. The glues were also evaluated with regard to histomorphology, tensile strength, and virology. RESULTS: The cryoprecipitate glue and the two-component fibrin sealant glue were equally effective in controlling bleeding from the aortic and atrial suture lines. Although the GRFG glue slowed bleeding significantly at both sites compared to baseline, it did not provide total control. The control group required additional sutures to control bleeding. The cryoprecipitate glue and the two-component fibrin sealant provided a satisfactory clot in 3 to 4 seconds on the epicardium, whereas the GRFG glue generated a poor clot. There were minimal adhesions in the subpericardial space in the cryoprecipitate and the two-component fibrin sealant groups, whereas moderate-to-dense adhesions were present in the GRFG glue group at 6 weeks. The two-component fibrin sealant was completely reabsorbed by 10 days, but cryoprecipitate and GRFG glues were still present. On histologic examination, both fibrin glues exhibited minimal tissue reaction; in contrast, extensive fibroblastic proliferation was caused by the GRFG glue. The two-component and GRFG glues had outstanding adhesive property; in contrast, the cryoprecipitate glue did not show any adhesive power. The GRFG glue had a significantly greater tensile strength than the two-component fibrin sealant. Random samples from both cryoprecipitate and the two-component fibrin glue were free of hepatitis and retrovirus. CONCLUSIONS: The GRFG glue should be used as a tissue reinforcer; the two-component fibrin sealer is preferable when hemostatic action must be accompanied with mechanical barrier; and finally, the cryoprecipitate glue can be used when hemostatic action is the only requirement.
Enhanced tumor growth in brain dopamine-depleted mice following 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) treatment.
Brain dopamine influences immune functions and the role of immune functions in tumor growth is well established. Therefore, a study has been carried out to evaluate the correlation, if any, between brain dopamine and tumor growth. MPTP selectively destroys dopaminergic neurons in the brain. In the present study, Ehrlich carcinoma growth was evaluated in MPTP-treated mice. Results showed a correlation between depletion of striatal dopamine and enhanced tumor growth. Since in the present study striatal dopamine depletion in mice was associated with significantly decreased immune responses, the suggested correlation between brain dopamine and tumor growth was possibly mediated by the immune system.
Dobutamine echocardiography and thallium-201 imaging predict functional improvement after revascularisation in severe ischaemic left ventricular dysfunction.
OBJECTIVES: To evaluate the concordance between thallium-201 uptake and echocardiographic wall thickening, which are both indicators of potentially reversible myocardial dysfunction, in patients with chronic ischaemic left ventricular failure and to assess their relative contribution to predicting improvement in regional function after revascularisation in a subgroup. PATIENTS AND METHODS: 45 patients with chronic ischaemic left ventricular dysfunction (mean (SD) ejection fraction 25 (8)%) underwent echocardiography before and after dobutamine infusion (10 micrograms/kg/min). Of these, 22 patients underwent rest echocardiography at a mean (SD) of 9 (1) weeks after revascularisation. 201Tl imaging was performed during dobutamine echocardiography and at rest, 1, and 4 h after treatment with sublingual glyceryl trinitrate on two separate days. Potentially reversible dysfunction was thought to be present when a myocardial segment contained a Tl score of > or = 3 (ascending score 1-4), or showed improved wall thickening of a dysynergic segment during dobutamine stimulation. RESULTS: Of the 201Tl protocols, the redistribution scan 1 h after treatment with glyceryl trinitrate best demonstrated myocardial viability. Concordance between 201Tl and dobutamine induced wall thickening was 82% (kappa = 0.59) for detecting potentially reversible myocardial dysfunction before revascularisation (n = 45). Regional function improved in 18 of 22 patients after revascularisation. There were 168 dysynergic segments before intervention. The sensitivity of echocardiography and 201Tl imaging for detecting "recoverable" or viable segments after revascularisation was 87% and 92% respectively and specificity was 82% and 78% respectively (P = NS). CONCLUSIONS: Dobutamine echocardiography and 201Tl imaging may be used to predict mechanical improvement in dysynergic segments after revascularisation in patients with chronic ischaemic left ventricular dysfunction.
NIDDM is the major cause of diabetic end-stage renal disease. More evidence from a tri-ethnic community.
Diabetes is the single largest cause of end-stage renal disease (ESRD) in adults in the U.S. Insulin-dependent diabetes mellitus (IDDM) has been recognized for some time as an important cause of ESRD, but non-insulin-dependent diabetes mellitus (NIDDM) has been assumed, until recently, to rarely cause ESRD. The objective of this study is to determine the incidence of treatment of diabetic ESRD by diabetic type for three ethnic/racial groups: non-Hispanic whites, African-Americans, and Mexican-Americans. A population-based incidence cohort was assembled from all dialysis centers in Bexar (San Antonio) and Dallas counties in Texas. All patients with diabetic ESRD beginning dialysis between 1 December 1987 (Bexar) or 1 December 1988 (Dallas) and 31 July 1991 were identified. All non-hispanic whites and African-Americans and a 1/2 random sample of Mexican-Americans were approached for enrollment. Individuals were confirmed to have diabetes using the World Health Organization criteria. Diabetes typing was done using a computerized historical algorithm. Age-specific and age-adjusted incidence rates were obtained by diabetic type and ethnic/racial group. NIDDM causes the majority of diabetic ESRD: 59.5% for non-Hispanic whites, 92.8% for Mexican-Americans, and 84.3% for African-Americans. Mexican-Americans and African-Americans, respectively, have 6.1 and 6.5 times higher incidence of treatment for diabetic ESRD than non-Hispanic whites. NIDDM results in more ESRD than does IDDM. Minorities (African-Americans and Mexican-Americans) are at increased risk, and programs aimed at prevention of NIDDM-related ESRD must focus on them.
Genetic marker profile of primitive Kutia Kondh tribal population of Phulbani district (Orissa).
Blood samples from 330 Kutia Kondhs (a primitive tribal population of Orissa) were subjected to a battery of tests for genetic markers to find out the incidence of various blood group polymorphisms (ABO, MN, Duffy, JKa), serum proteins, sickling and G-6-PD deficiency. Predominance of O (39.09%) blood group for ABO, N blood group (53.44) for MN and Fya+b+ (55.72) for Duffy blood group, were observed. High incidence of Hp2-1 (39.33), SS (70.43) and CC (96.65) for haptoglobulin, C3 and transferrin respectively were seen. The overall frequency of sickling was observed to be 16.36 per cent. The sex-wise distribution of G-6-PD was 13.71 per cent for males and 1.84 for females.
Glycosyltransferase activities in human meningiomas. Preliminary results.
The biosynthesis of a given glycosphingolipid is under the control of specific glycosyltransferases, while its catabolism is catalyzed by step-wise action of glycosidases. The net amount of glycolipids apparently result from the difference between these two processes. However, other parameters should be taken into consideration, such as intracellular recycling of catabolic products, membrane insertion, and membrane turnover. In order to establish a possible correlation between ganglioside expression in brain tumor and the activities of the enzymes involved in their metabolism, we analyzed the activities of specific sialyltransferases (SAT-1 and SAT-2), galactosyltransferase (GalT-4), N-acetylgalactosaminyltransferase (GalNAcT-1), and N-acetylglucosaminyltransferase (GlcNAcT-1) in 9 human meningiomas whose ganglioside pattern was characterized either by the predominance ganglioside GM3 (4 out of 9) or ganglioside GD3 (5 out of 9). The results indicated a strong correlation between the GM3/GD3 ratio and SAT-2 activity; to the contrary, SAT-1 activity did not show any correlation if compared with the Lc2/GM3 ratio. In all the samples where GM3 was the main ganglioside, little or no activity of GalNAcT-1 and GlcNAcT-1 was detectable.
Is there a case for haemorheological screening in the haemocompatibility testing of materials?
Bio-interactions between a material and blood govern the compatibility of the material with the human body and, therefore, the single most important requirement for the blood interfacing implants/devices is haemocompatibility. The decisive events which control haemocompatibility occur at the molecular level and affect the various subphases of blood rheology. This effect on the already complex human blood rheology can be used to our advantage in the screening of blood-contacting materials. An attempt has been made in the present work to evaluate the haemocompatibility of materials based on changes in microrheological parameters of human blood. Samples of materials of equal surface area known to be haemocompatible (medical grade silicon, polyvinyl chloride from blood bags) and materials known to be extremely haemo-incompatible (pyrex glass, copper, cotton fabric, all commercial grade) were incubated at 37.4 degrees C in freshly drawn anticoagulated whole human blood, and changes in the haemorheological parameters (whole blood, plasma viscosity, intrinsic viscosity of red cells, platelet aggregation, albumin fibrinogen ratio) have been evaluated. The results of the study show that alterations in the haemorheological parameters are reliable indicators to the compatibility/incompatibility characteristics of well-known substances and that there is a case for haemorheological screening of biomaterials in the overall framework of haemocompatibility tests.