Search PubMed⌕ Search

Biomedical subjects

S Basu

Publications and source records attributed to S Basu.

At least 163 records · Page 9Linked to original sources
PubMed1998

Interresidue quiet NOEs for DNA structural studies.

The potential utility of long-range NOEs in DNA has not been exploited since the observed signals have contributions both from the direct magnetization route and from multiple diffusion pathways. The Quiet NOE approach can be used to select for the direct magnetization transfer pathway by suppressing spin diffusion. A single-band Quiet NOE, which allows detection of the direct NOEs between protons in a selected chemical shift window, has been demonstrated on two duplex DNAs, and the NOEs observed can contain important structural information.

Crystallography↗
PubMed1998

Independent prognostic value of the extent and severity of systolic wall thickening abnormality at infarct site after thrombolytic therapy.

BACKGROUND: The prognostic value of systolic wall thickening abnormality after acute myocardial infarction in the thrombolytic era is not clearly known. METHODS AND RESULTS: Accordingly, 119 consecutive patients with acute myocardial infarction who underwent thrombolysis were investigated with exercise electrocardiography and rest echocardiography at predischarge evaluation and were followed up for cardiac events. During a mean follow-up period of 19 months, 43 patients had cardiac events. Multivariate analysis with clinical, exercise electrocardiographic, and rest echocardiographic parameters showed that the independent predictors of cardiac events were systolic wall thickening score at the site of infarct (p = 0.02), end-systolic volume (p = 0.03), and exercise time (p = 0.02). The only independent predictor for both recurrent ischemic (death, unstable angina, and reinfarction) and nonischemic events (congestive heart failure and ventricular tachycardia) was systolic wall thickening score at the site of infarct (p = 0.02 and p = 0.007, respectively). CONCLUSIONS: Systolic wall thickening abnormality at rest is an important independent predictor of cardiac events in patients who have undergone thrombolysis after acute myocardial infarction.

Echocardiography↗
PubMed1998

Radioimmunoassay of 8-iso-prostaglandin F2alpha: an index for oxidative injury via free radical catalysed lipid peroxidation.

8-iso-prostaglandin F2alpha (8-iso-PGF2alpha), a major F2-isoprostane, is biosynthesized in vivo through nonenzymatic free radical-catalysed peroxidation of arachidonic acid. The levels of F2-isoprostanes both free in the circulation and esterified to the tissue phospholipids increase intensely in animal models of oxidant injury. This study presents the development and validation of a radioimmunoassay of 8-iso-PGF2alpha for the measurement of this substance in the body fluids. Furthermore, its application in normal human volunteers, a pharmacokinetic study performed in rabbits with 8-iso-PGF2alpha, and hepatic lipid peroxidation in rats is reported. An antibody was raised in rabbits by immunization with 8-iso-PGF2alpha coupled to BSA at the carboxylic acid by 1,1'-Carbonyldiimmidazole method. The cross-reactivity of the antibody with 8-iso-15-keto-13,14-dihydro-PGF2alpha, 8-iso-PGF2beta, PGF2alpha, 15-keto-PGF2alpha, 15-keto-13,14-dihydro-PGF2alpha,TXB2, 11beta-PGF2alpha, 9beta-PGF2alpha and 8-iso-PGF3alpha was 1.7, 9.8, 1.1, 0.01, 0.01, 0.1, 0.03, 1.8 and 0.6%, respectively. The intraassay precision was 14.5% (CV) at the level of 64 pg/0.1 ml and 12.2% with 512 pg/0.1 ml in the human plasma. Similarly, intra-assay accuracy was 95.6% and 101% for the low and the high standard, respectively. The detection limit was about 23 pmol/l. The appearance and disappearance of 8-iso-PGF2alpha in the blood and urine following intravenous administration of 8-iso-PGF2alpha in the rabbit was rapid. Free 8-iso-PGF2alpha levels in plasma and urine from normal human volunteers are evaluated and found to correlate with the obtained values by gas chromatography-mass spectrometry methods from other studies. The levels of free 8-iso-PGF2alpha in the plasma and urine increased 7- and 102-fold, respectively, after CCl4 administration to rats. Thus, this 8-iso PGF2alpha radioimmunoassay method is relevant to apply in the oxidative injury studies as an index of in vivo lipid peroxidation through free radical catalysis mechanism.

Animals↗
PubMed1998

A high linoleic acid diet increases oxidative stress in vivo and affects nitric oxide metabolism in humans.

Evidence from in vitro studies shows that increased intake of polyunsaturated fatty acids leads to increased oxidative stress, which may be associated with endothelial damage. We measured the urinary levels of 8-iso-PGF2alpha and nitric oxide metabolites as well as plasma sICAM-1 levels from healthy subjects after strictly controlled diets rich in either linoleic acid (LA, C18:2 n-6) or oleic acid (OA, C18:1 n-9). Thirty-eight volunteers (20 women and 18 men, mean age 27 years) consumed a baseline diet rich in saturated fatty acids (SFA) for 4 weeks and were then switched to either a high LA diet (11.5 en%) or a high OA diet (18.0 en%) also for 4 weeks. During the LA and OA diets, nearly all food was provided for the whole day. A control group of 13 subjects consumed their habitual diet throughout the study. Urinary excretion of 8-iso-PGF2alpha was significantly increased after the LA diet (170 vs 241 ng/mmol creatinine, P=0.04), whereas the urinary concentration of nitric oxide metabolites decreased (4.2 vs 2.6 mg/mmol creatinine, P=0.03). No significant changes were seen in the OA group. Significant differences between the LA and control group were found for both 8-oxo-PGF2alpha (P=0.03) and NO (P=0.02), whereas the OA and LA groups did not differ with respect to any parameter. Also plasma sICAM-1 remained unchanged in both groups throughout the study. In conclusion, the high-LA diet increased oxidative stress and affected endothelial function in a way which may in the long-term predispose to endothelial dysfunction.

Adult↗
PubMed1998

Radioimmunoassay of 15-keto-13,14-dihydro-prostaglandin F2alpha: an index for inflammation via cyclooxygenase catalysed lipid peroxidation.

The metabolism of PGF2alpha in human and other species results initially in the formation of 15-keto-dihydro-PGF2alpha and later to several beta-oxidized metabolites, which are species-specific. Since the discovery of cyclooxygenase-2 (COX-2), the importance of measuring various arachidonic acid metabolites during inflammatory conditions is on focus. This study presents the development and validation of a new radioimmunoassay of 15-keto-dihydro-PGF2alpha as an index of lipid peroxidation via cyclooxygenase (COX-1 and COX-2) pathway. Furthermore, its application in endotoxin-induced acute inflammation in pigs is presented. An antibody was raised in rabbits by immunization with 15-keto-dihydro-PGF2alpha coupled to BSA at the carboxylic acid by 1,1'-carbonyldiimidazole method. The cross-reactivity of the antibody with PGF2alpha, 15-keto-PGF2alpha, PGE2, 15-keto-13,14-dihydro-PGE2, 8-iso-15-keto-13,14-dihydro-PGF2alpha, 11beta-PGF2alpha, 9beta-PGF2alpha, TXB2 and 8-iso-PGF3alpha was 0.02, 0.43, < 0.001, 0.5, 1.7, < 0.001, < 0.001, < 0.001, 0.01%, respectively. The intra-assay precision was 12.2% (CV) at the level of 64 pg/0.1 ml and 14.0% with 512 pg/0.1 ml in the human plasma. Similarly, intra-assay accuracy was 108.6% and 103.3% for the low and the high standards, respectively. The detection limit was about 45 pmol/L. 15-keto-dihydro-PGF2alpha levels in plasma from normal human volunteers were evaluated and found to correlate with the obtained values by GC-MS methods from other studies. The levels of 15-keto-dihydro-PGF2alpha in the plasma increased several-fold after endotoxin infusion (10 microg/kg/h over 6 h) to the pigs. Thus, this 1 5-keto-dihydro-PGF2alpha radioimmunoassay method is relevant to apply in inflammatory injury, and other physiological and pathophysiological studies, as an index of in vivo enzymatic lipid peroxidation.

Animals↗
PubMed1998

Visible radiation effects on flavocytochrome b2 in dilute aqueous solution: a steady-state and laser flash photolysis study.

Irradiation of flavocytochrome b2 by visible radiation at 450 nm in dilute aqueous solution is found to have a devastating effect not only on its activity but also on the important flavin mononucleotide (FMN) constituents. The active site and the substrate binding site are also found to be largely modified on exposure to visible radiation. This has a telling effect on the constituent aromatic amino acids, tryptophan and tyrosine, and therefore justifies the role of FMN as a very potent photosensitizer. Partial unfolding of the irradiated enzyme molecule is also observed. Damage is much greater in deaerated conditions, which indicates that molecular oxygen plays a protecting role in this particular system. The inactivation is mediated through rapid electron transfer from tryptophan and tyrosine to excited flavin, forming flavin semiquinone and tryptophanyl and tyrosinyl radicals, which in turn cause permanent damage at the molecular level.

Absorption↗
PubMed1998

A specific monovalent metal ion integral to the AA platform of the RNA tetraloop receptor.

Metal ions are essential for the folding and activity of large catalytic RNAs. While divalent metal ions have been directly implicated in RNA tertiary structure formation, the role of monovalent ions has been largely unexplored. Here we report the first specific monovalent metal ion binding site within a catalytic RNA. As seen crystallographically, a potassium ion is coordinated immediately below AA platforms of the Tetrahymena ribozyme P4-P6 domain, including that within the tetraloop receptor. Interference and kinetic experiments demonstrate that potassium ion binding within the tetraloop receptor stabilizes the folding of the P4-P6 domain and enhances the activity of the Azoarcus group I intron. Since a monovalent ion binding site is integral to the tetraloop receptor, a tertiary structural motif that occurs frequently in RNA, monovalent metal ions are likely to participate in the folding and activity of a wide diversity of RNAs.

Adenine↗
PubMed1998

Transient brain injury from penetration of a halo pin.

This case report describes a patient who had a halo device for traction applied to obtain correction of scoliotic deformity between a two-stage operative procedure. The patient developed a neurological deficit suggestive of brain injury following retorquing of a halo pin. This was confirmed by an MRI scan of the brain. The patient made a full recovery of the neurological deficit following replacement of the pin.

Bone Nails↗
PubMed1998

Contact depigmentation caused by an azo dye in alta.

Alta, a scarlet-red solution used by some Indian women as a cosmetic to colour their feet, was found to be associated with depigmentation at the site of application. Chromatographic and spectroscopic analysis of 3 brands of alta confirmed the presence of 2 dyes: Crocein Scarlet MOO (CSM) (brilliant crocein) and rhodamine B (tetraethyl rhodamine). Patch testing produced depigmentation at the site of application of alta, CSM and para-phenylenediamine (PPD). Although PPD has been reported to produce leukoderma, azo dyes have not previously been reported as depigmenting agents.

Coloring Agents↗
PubMed1998

Antibody feedback and somatic mutation in B cells: regulation of mutation by immune complexes with IgG antibody.

In response to an appropriate antigenic stimulus, and with help from T lymphocytes, naive B cells differentiate into plasmacytes which produce the primary (germline-encoded) IgM and IgG antibody with low affinity for the antigen. The isotype switch from IgM to IgG coincides with the burst of germinal center reaction and the onset of somatic hypermutation. Here we propose that formation of immune complexes between the residual antigen and the primary IgG antibody, which activate complement and localize specifically in the network of follicular dendritic cells, provides an important signal for triggering the mutation mechanism in germinal center B cells. This hypothesis has been supported by studies on immunogenicity of immune complexes in vivo. The experiments have included an immunization with pre-formed antigen/IgG antibody complex and/or an administration of IgG antibody shortly after the antigen injection. Either of these strategies, which are known to augment the germinal center formation, resulted in earlier onset of somatic mutation and increased mutation frequency in VDJ rearrangements in antigen-reactive B cells, provided that help from T cells was also present. It is presumed that the antigen/antibody/complement complex is able to deliver this important signal by cross-linking of antigen receptor with the CD21/CD19/CD81 molecules on B cells. As a corollary, the signaling by immune complexes may lower the threshold of cell activation determined by receptor affinity for antigen and stimulate diverse V-gene repertoire of B-cell clones in germinal centers.

Animals↗
PubMed1998

Antibacterial activity of the antiinflammatory agent diclofenac sodium.

Antimicrobial property of ten antiinflammatory drugs was tested with eleven sensitive bacteria belonging to both Gram positive and Gram negative types. Since most of the bacteria were moderate to highly sensitive to diclofenac (Dc), this compound was tested in vitro against 397 bacteria, most of which were inhibited by Dc at 50-100 micrograms/ml level. When tested in vivo, Dc at 1.5 and 3.0 micrograms/g body weight of a Swiss strain of white mice, could significantly protect the animals challenged with 50 MLD of Salmonella typhimurium NCTC 74. According to chi 2 test the in vivo data were highly significant (P < 0.001).

Animals↗
PubMed1998

Projection of HIV infection in Calcutta.

Starting with the base year of 1991, the HIV infection projection for 1992-99 for the total, as well as various high-risk sub-populations of Calcutta, the first of its kind is provided. These projections are based on statistical methodology developed in this paper. Our methodology for spread of HIV infection takes into account various social interactions and practices and also uses available data. Rates of these interactions and practices and estimates of demographic parameters used in making projections were obtained primarily from surveys and census data. Since one of these estimated rates, that of HIV transmission rate through heterosexual encounters between an infected and an uninfected had a large range, we have provided two sets of projections based on the largest of these rates (worst-case scenario) and another that is consistent with the available data. The total projection of the number of HIV infected cases in Calcutta for 1999 is between 49,000 and 1,26,000. Separate projections are also provided for high-risk sub-groups. Among these, the sex workers expectedly will continue to manifest the highest numbers of newly infected cases. The temporal rate of increase in prevalence is projected to be alarmingly higher in the general population than even among sex workers, although the actual prevalence will continue to be the lowest in the general population compared to all other sub-groups of the population.

Female↗
PubMed1998

The pharmacokinetics of a new antiglaucoma drug, latanoprost, in the rabbit.

Latanoprost (13,14-dihydro-17-phenyl-18,19,20-trinor-prostaglandin F2alpha-1-isopropyl ester) is a unique prostaglandin analogue developed for the treatment of glaucoma. To investigate the pharmacokinetics, tritium-labeled latanoprost was administered topically on the eyes of rabbits and intravenously. About 7.7% of the applied dose was found in the cornea at 15 min after the drug administration. The following Cmax and elimination half-life (interval 1-6 hr) values of the total radioactivity in the eye tissues were found: aqueous humor, 0.09 ng eq/ml and 3.0 hr; anterior sclera, 1.49 ng eq/mg and 1.8 hr; cornea, 1.59 ng eq/mg and 1.8 hr; ciliary body, 0.39 ng eq/mg and 2.8 hr; conjunctiva, 1.41 ng eq/mg and 1.4 hr; and iris, 0.39 ng eq/mg and 2.1 hr. Latanoprost was rapidly hydrolyzed, and most of the radioactivity found in the aqueous humor, anterior eye tissues, and plasma corresponded to the pharmacologically active acid of latanoprost. The initial plasma elimination half-life of the acid of latanoprost was 9.2 +/- 3.2 min after iv and 2.3 +/- 1.9 min after topical administration on the eyes. The plasma clearance of the acid of latanoprost was 1.8 +/- 0.3 liters/hr.kg, and the volume of distribution was 0.4 +/- 0.1 liter/kg after iv administration. Based on the retention times on HPLC and GC-MS, the main metabolite in urine and feces was identified as the 1,2,3,4-tetranor metabolite of acid of latanoprost. This acid existed in equilibration with the corresponding delta-lactone. The AUC of radioactivity in the eye tissues was approximately 1000 times higher than in plasma AUC. The recovery of radioactivity was complete.

Absorption↗
PubMed1998

Hydrophobic nature of mammalian ceramide glycanases: purified from rabbit and rat mammary tissues.

The ceramide glycanase (CGase) activities, which cleave the intact oligosaccharide chain and the ceramide moiety of a glycosphingolipid, have been characterized from two mammalian sources. The enzymatic activities are almost comparable in rabbit and rat mammary tissues. The majority of the activities has been concentrated in the soluble fraction which could be partially purified using hydrophobic columns. The rabbit mammary ceramide glycanase activity has been purified up to 1438-fold using ion exchange and hydrophobic columns in tandem. The purified protein exhibited a molecular mass of 54 kDa which could be immunostained on the Western blot with clam anti-CGase polyclonal antibody. In addition, a 98 kDa protein also exhibited positive immunostain in a successive purified fraction with that antibody and is under investigation. The requirement for the optimal enzymatic activities are similar for both rabbit and rat CGase activities. The CGase activity requires the presence of detergent for optimal activity but is not dependent on the presence of any divalent cations. However, Hg2+, Zn2+, and Cu2+ are inhibitory to the enzymatic activities. It has been observed that rat as well as rabbit CGases are inhibited by both D- and L-PDMP (1-phenyl-2-decanoylamino-3-morpholino-1-propanol.HCl) and its higher analogue PPMP (1-phenyl-2-palmitoylamino-3-morpholino-1-propanol.HCl). Alkyl amines containing C12 and higher chains are also found to inhibit both rat and rabbit CGase activities. Substantial levels of CGase activities have also been observed in various human tumor cells as well as in developing avian brains. These observations are significant in view of the recent findings that ceramide, which is one of the enzymatic reaction products of CGase activity, is mediating different cellular events like signal transduction and apoptosis. The role of this enzyme in development, metastasis and cellular regulation are anticipated.

Animals↗
PubMed1998

Purification and characterization of avian glycolipid: beta-galactosyltransferases (GalT-4 and GalT-3): cloning and expression of truncated betaGalT-4.

Acidic glycolipid of ganglio-(containing sialic acid) and sialyl-lactofucosyl-type, SA-Lex (containing sialic acid and fucose) are developmentally regulated and appear to be ubiquitous on neuronal and cancer cell surfaces of animals. Two glycolipid: beta-galactosyltransferases, GalT-3 and GalT-4, were characterized in embryonic chicken brain (ECB). Based on substrate competition experiments, these two activities were believed to be due to expression of two gene products. A cDNA fragments (about 600 bp) encoding the catalytic domain of the GalT-4 (UDP-Gal:LcOse3Cer beta1,4galactosyltransferase) from ECB and human Colo-204 were isolated. These cDNAs were expressed as a soluble glutathione-S-transferase fusion protein (48 kDa) in Escherichia coli. Interactions between GlcNAc-, UDP-hexanolamine-, and alpha-lactalbumin were studied with the purified fusion protein (recombinant and truncated). Functionally it was similar to that of native GalT-4 purified (40000-fold) from 11-day-old ECB. GalT-3 (UDP-Gal:GM2beta1,3galactosyltransferase) was purified from 19-day-old ECB, and a polyclonal antibody was produced against the peptide backbone for immunoscreening of a lambdaZAP ECB cDNA expression library. Each of the GalT-3 peptides (62 and 65 kDa was analyzed by protein fingerprinting analysis indicating a similar peptide mapping pattern.

Animals↗
PubMed1997

Superiority of nitrate-enhanced 201Tl over conventional redistribution 201Tl imaging for prognostic evaluation after myocardial infarction and thrombolysis.

BACKGROUND: 201Tl imaging has been widely used for postinfarction risk stratification. However, thrombolytic therapy and aspirin have significantly changed outcome, and there are few nuclear imaging studies that assess prognosis in such patients. Furthermore, newer techniques of 201Tl imaging, such as reinjection and nitrate-enhanced rest 201Tl imaging, have been shown to improve the detection of viable but jeopardized myocardium. METHODS AND RESULTS: We studied 100 consecutive patients, who remained event free 6 weeks after myocardial infarction and thrombolysis. Patients underwent conventional exercise and 4-hour redistribution imaging, followed on a separate day by nitrate-enhanced rest 201Tl study. Planar images were reported semiquantitatively by two experienced observers blinded to clinical data. Redistribution and rest injection images were classified as demonstrating reversible ischemia if they showed improvement in uptake by at least two grades in at least two segments in comparison with the initial exercise scintigram. Patients were followed up for 8 to 32 months (mean, 21 months); during this period, 37 patients had first cardiac events. Reversible ischemia was present in 29 patients on redistribution, of whom 14 (48%) had events; of 71 without reversible defects, 23 (32%) had events (hazard ratio, 1.5; 95% CI, 0.8 to 3.0; P=NS). Nitrate-enhanced rest 201Tl imaging detected reversible defects in 68 patients, of whom 33 (49%) had events, whereas of 32 without reversible defects, only 4 (13%) had subsequent cardiac events (hazard ratio, 8.1; 95% CI, 2.7 to 23.8; P<.001). CONCLUSIONS: Thus, after myocardial infarction and thrombolysis, even "stable" patients have a high (68%) incidence of viable but jeopardized myocardium, causing a high event rate. Those identified to be at high risk by perfusion imaging may benefit from early intervention.

Adult↗
PubMed1997

Heat shock protein-peptide complexes, reconstituted in vitro, elicit peptide-specific cytotoxic T lymphocyte response and tumor immunity.

Heat shock protein (HSP) preparations derived from cancer cells and virus-infected cells have been shown previously to elicit cancer-specific or virus-specific immunity. The immunogenicity of HSP preparations has been attributed to peptides associated with the HSPs. The studies reported here demonstrate that immunogenic HSP-peptide complexes can also be reconstituted in vitro. The studies show that (a) complexes of hsp70 or gp96 HSP molecules with a variety of synthetic peptides can be generated in vitro; (b) the binding of HSPs with peptides is specific in that a number of other proteins tested do not bind synthetic peptides under the conditions in which gp96 molecules do; (c) HSP-peptide complexes reconstituted in vitro are immunologically active, as tested by their ability to elicit antitumor immunity and specific CD8+ cytolytic T lymphocyte response; and (d) synthetic peptides reconstituted in vitro with gp96 are capable of being taken up and re-presented by macrophage in the same manner as gp96- peptides complexes generated in vivo. These observations demonstrate that HSPs are CD8+ T cell response-eliciting adjuvants.

Adjuvants, Immunologic↗