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Biomedical subjects

S Chakrabarti

Publications and source records attributed to S Chakrabarti.

At least 19 recordsLinked to original sources
PubMed2007

Clinical significance of the RT-PCR positive sentinel node in melanoma.

BACKGROUND: The clinical relevance of RT-PCR positivity for melanoma markers in the sentinel node remains controversial. Our purpose was to determine whether patients with a histologically negative but RT-PCR positive node were at an increased risk for recurrence than their RT-PCR negative counterparts. METHODS: Thirty-nine adult patients underwent sentinel node biopsies for melanoma between 1998 and 2000. Each sentinel node was bivalved. Half was serially sectioned and examined by routine hematoxylin and eosin (H&E) and immunohistochemistry (IHC; S100, HMB-45, melanA, and tyrosinase). The other half was analyzed by a nested RT-PCR assay for tyrosinase. RESULTS: Patients were followed for recurrence with a mean follow-up of 71.1 months. The odds ratio of recurrence for RT-PCR positive versus RT-PCR negative patients was 1.39 (0.34, 5.62; p = 0.73). Within the histology negative subgroups, the risk of recurrence in the RT-PCR positive group (26.7%) was not significantly different from the risk of recurrence in the RT-PCR negative group (22.2%) (p = 0.33 chi-squared). RT-PCR of the sentinel node was not a predictor for recurrence on multivariate analysis (p = 0.65). CONCLUSION: Sentinel node RT-PCR positivity did not risk stratify histologically negative melanoma patients beyond routine pathologic examination in this series.

Adult↗
PubMed2006

Direct limits on the oscillation frequency.

We report results of a study of the B(s)(0) oscillation frequency using a large sample of B(s)(0) semileptonic decays corresponding to approximately 1 fb(-1) of integrated luminosity collected by the D0 experiment at the Fermilab Tevatron Collider in 2002-2006. The amplitude method gives a lower limit on the B(s)(0) oscillation frequency at 14.8 ps(-1) at the 95% C.L. At delta m(s) = 19 ps(-1), the amplitude deviates from the hypothesis A= 0(1) by 2.5 (1.6) standard deviations, corresponding to a two-sided C.L. of 1% (10%). A likelihood scan over the oscillation frequency, delta m(s), gives a most probable value of 19 ps(-1) and a range of 17 < delta m(s) < 21 ps(-1)at the 90% C.L., assuming Gaussian uncertainties. This is the first direct two-sided bound measured by a single experiment. If delta m(s) lies above 22 ps(-1), then the probability that it would produce a likelihood minimum similar to the one observed in the interval 16-22 ps(-1) is (5.0 +/- 0.3)%.

Journal Article↗
PubMed2006

Cascade PSI-BLAST web server: a remote homology search tool for relating protein domains.

Owing to high evolutionary divergence, it is not always possible to identify distantly related protein domains by sequence search techniques. Intermediate sequences possess sequence features of more than one protein and facilitate detection of remotely related proteins. We have demonstrated recently the employment of Cascade PSI-BLAST where we perform PSI-BLAST for many 'generations', initiating searches from new homologues as well. Such a rigorous propagation through generations of PSI-BLAST employs effectively the role of intermediates in detecting distant similarities between proteins. This approach has been tested on a large number of folds and its performance in detecting superfamily level relationships is approximately 35% better than simple PSI-BLAST searches. We present a web server for this search method that permits users to perform Cascade PSI-BLAST searches against the Pfam, SCOP and SwissProt databases. The URL for this server is http://crick.mbu.iisc.ernet.in/~CASCADE/CascadeBlast.html.

Internet↗
PubMed2006

The effect of aspirin and warfarin therapy in trabeculectomy.

AIM: The management of patients on antiplatelet and anticoagulation therapy (APACT) in glaucoma surgery currently has no specific recommendations. We aimed to establish the risk of haemorrhagic complications and surgical outcome in patients on APACT in glaucoma surgery. METHODS: We retrospectively examined 367 consecutive trabeculectomies performed between 1994 and 1998. Preoperatively 60 (16.4%) patients were on APACT (55 on aspirin and five on warfarin). The incidence of hyphaema and haemorrhagic complications between patients with and without APACT was documented. Surgical success was defined in two categories as an intraocular pressure (IOP) <21 mmHg and an IOP <16 mmHg 2 years following trabeculectomy with and without antiglaucoma medication. RESULTS: None of the patients on aspirin suffered significant intra or postoperative haemorrhage. Aspirin was associated with a significantly higher risk of hyphaema (P=0.0015) but this was not found to significantly affect IOP control at 2 years. Patients on warfarin suffered haemorrhagic complications and trabeculectomy failure. CONCLUSIONS: Aspirin appears to be safe to continue with during trabeculectomy. Patients on aspirin have an increased risk of hyphaema following trabeculectomy. This however does not appear to affect surgical outcome. Warfarinised patients are at risk of serious bleeding complications. They require careful monitoring pre- and postoperatively and are at risk of trabeculectomy failure.

Adolescent↗
PubMed2006

Electrically injected quantum-dot photonic crystal microcavity light sources.

The design, fabrication, and characterization of an electrically injected quantum-dot photonic crystal microcavity light source are described. The optical gain in the GaAs/AlGaAs-based device is provided by self-organized InGaAs quantum dots with ground-state room-temperature emission at 1.1 microm. The carriers are injected directly into the photonic crystal microcavity, which contains approximately 50 dots, avoiding surface state recombination in the photonic crystal pattern. The spectral characteristics of a single-defect photonic crystal microcavity show a single 2 nm broad microcavity resonance. The output power is of the order of a few tens of nanowatts.

Journal Article↗
PubMed2006

Search for the Higgs boson in H --> WW(*) decays in pp collisions at square root of 1.96 TeV.

We present a search for the standard model Higgs boson in H --> WW(*) decays with e+e-, e+/-mu-/+, and mu+mu- final states in pp collisions at a center-of-mass energy of square root of s = 1.96 TeV. The data, collected from April 2002 to June 2004 with the D0 detector, correspond to an integrated luminosity of 300-325 pb(-1), depending on the final state. The number of events observed is consistent with the expectation from backgrounds. Limits from the combination of all three channels on the Higgs boson production cross section times branching ratio sigma x BR(H --> WW(*) are presented.

Journal Article↗
PubMed2006

A pilot study of nonmyeloablative allogeneic hematopoietic stem cell transplant for advanced systemic mastocytosis.

Systemic mastocytosis (SM) is a disease characterized by tissue infiltration of neoplastic mast cells originating from hematopoietic stem cells. Patients with advanced SM have a poor prognosis, and there is no mast cell ablative therapy available for most patients who carry an activating point mutation in the c-kit gene. We report results of a prospective study evaluating the safety, engraftment, and possibility of inducing a graft-versus-mast cell (GvMC) effect after allogeneic nonmyeloablative hematopoietic cell transplantation (HCT) from an HLA-identical sibling. Three patients with advanced SM were transplanted. All achieved complete donor T cell chimerism followed by clinical evidence for GvMC effect. However, all patients experienced disease progression with the longest response duration of 39 months. The GvMC effect can be observed after nonmyeloablative HCT with limited efficacy. Effective cytoreductive therapy prior to HCT may be required for long-term disease control and cure.

Adult↗
PubMed2006

Frequency of major affective disorders in first-degree relatives of patients with type 2 diabetes mellitus.

BACKGROUND & OBJECTIVES: A genetic link between diabetes and depression has been proposed, but hardly explored. Data on family studies exploring relation between depression and diabetes are scanty. This study attempted to assess the prevalence of major affective disorders in first-degree relatives of patients with type 2 diabetes mellitus (T 2 DM). METHODS: Fifty probands with T 2 DM, in whom other psychiatric disorders had been excluded, were chosen. Morbid risks and prevalence figures for depression and mania were estimated in 481 first-degree relatives of these 50 probands using the family interview for genetic studies. RESULTS: Of the 481 first-degree relatives of probands, only six had affective disorders. The morbid risk for depression in first-degree relatives was 2.99 and 3.87 per cent, assuming age of risk at 15-60 and 15-50 yr respectively, while the morbid risk for mania was 0.59 and 0.77 per cent in these age groups. INTERPRETATION & CONCLUSION: The morbid risks/prevalence rates among first-degree relatives of probands with T2 DM were not higher than those of the general population rates derived from earlier Indian and western studies. This study did not demonstrate a family aggregation of affective disorders in patients with T 2 DM. Increased prevalence of affective disorders in diabetes could be due to non-genetic factors.

Adult↗
PubMed2005

Measurement of semileptonic branching fractions of B mesons to narrow D** states.

Using the data accumulated in 2002-2004 with the D0 detector in proton-antiproton collisions at the Fermilab Tevatron collider with a center-of-mass energy of 1.96 TeV, the branching fractions of the decays B --> D0(1)(2420)mu+ vmuX and B --> D2(*0)(2460)mu+ vmuX and their ratio have been measured: B(b --> B) x B(B --> D0(1)mu+ vmuX) x B(D0(*0) --> D*- pi+) = [0.087 +/- 0.007(stat) +/- 0.014(syst)]%; B(b --> B) x B(B --> D2(*0) mu+ vmuX) x B(D2(*0) --> D*- pi+) = [0.035 +/- 0.007(stat) +/- 0.008(syst)]% and [B(B --> D2(*0)mu+ vmuX) x B(D2(*0) --> D*- pi+)]/[B(B --> D0(1)mu+ vmuX) x B(D0(1) --> D*- pi+)] = 0.39 +/- 0.09(stat) +/- 0.12 (syst), where the charge conjugated states are always implied.

Journal Article↗
PubMed2005

Measurement of the lifetime difference in the B0(s) system.

We present a study of the decay B0(s) --> J/psiphi. We obtain the CP-odd fraction in the final state at time zero, Rperpendicular = 0.16 +/- 0.10(stat) +/- 0.02 (syst), the average lifetime of the (B0(s), B0(s)) system, tau(B0(s)) = 1.39(+0.13)(-0.16)(stat)(+0.01)(-0.02)(syst) ps, and the relative width difference between the heavy and light mass eigenstates, DeltaGamma/Gamma tripple bond (GammaL - GammaH)/Gamma = 0.24(+0.28)(-0.38)(stat)(+0.03)(-0.04)(syst). With the additional constraint from the world average of the lifetime measurements using semileptonic decays, we find tau(B0(s)) = 1.39 +/- 0.06 ps and DeltaGamma/Gamma = 0.25(+0.14)(-0.15). For the ratio of the B0(s) and B0 lifetimes we obtain tau(B0(s))/tau(B0) = 0.91 +/- 0.09(stat) +/- 0.003(syst).

Journal Article↗
PubMed2005

A comparison between long-term survivors of Hodgkin's disease and their siblings on fatigue level and factors predicting for increased fatigue.

PURPOSE: To compare the level of fatigue in survivors of Hodgkin's disease and their siblings, and to explore factors associated with increased fatigue. METHODS: Survivors of Hodgkin's disease 5 years or more from diagnosis and their siblings completed a questionnaire study. Fatigue level was measured using the Functional Assessment of Chronic Illness Therapy-Fatigue (FACIT-F) instrument, with lower scores reflecting increased fatigue. Multiple regression models were used to identify factors associated with fatigue level in the two populations. RESULTS: Five hundred and eleven survivors (median age 44 years; range 16-82) and 224 siblings (median age 44 years; range 16-79) returned the completed questionnaire. The response rates were 61% and 58%, respectively. Compared with siblings, survivors were significantly more likely to report the presence of cardiac disease (26% versus 16%; P = 0.001) and hypothyroidism (65% versus 3%; P <0.001), and had a significantly lower mean FACIT-F score (40.7 and 42.2; P = 0.05). On multivariable analysis, factors significantly associated with increased fatigue in survivors were reports of cardiac disease (P <0.001), psychiatric condition (P <0.001), history of tobacco use (P = 0.004) and low exercise frequency (P = 0.03). For siblings, the only independent factor associated with increased fatigue was low exercise frequency (P = 0.03). CONCLUSIONS: Survivors of Hodgkin's disease were more fatigued than their siblings. The difference was modest but statistically significant. The significant association between fatigue and cardiac disease suggests the importance of screening for underlying cardiac dysfunction in survivors with symptoms of fatigue. The association between fatigue and smoking history may be due to exacerbation of late medical complications of Hodgkin's disease by tobacco use.

Adolescent↗
PubMed2005

Search for large extra spatial dimensions in dimuon production with the d0 detector.

We present the results of a search for the effects of large extra spatial dimensions in pp collisions at sqrt[s] = 1.96 TeV in events containing a pair of energetic muons. The data correspond to 246 pb(-1) of integrated luminosity collected by the D0 experiment at the Fermilab Tevatron Collider. Good agreement with the expected background was found, yielding no evidence for large extra dimensions. We set 95% C.L. lower limits on the fundamental Planck scale between 0.85 and 1.27 TeV within several formalisms. These are the most stringent limits achieved in the dimuon channel to date.

Journal Article↗
PubMed2005

Search for supersymmetry via associated production of charginos and neutralinos in final states with three leptons.

A search for associated production of charginos and neutralinos is performed using data recorded with the D0 detector at a pp center-of-mass energy of 1.96 TeV at the Fermilab Tevatron Collider. This analysis considers final states with missing transverse energy and three charged leptons, of which at least two are electrons or muons. No evidence for supersymmetry is found in a data set corresponding to an integrated luminosity of 320 pb-1. Limits on the product of the production cross section and leptonic branching fraction are set. For the minimal supergravity model, a chargino lower mass limit of 117 GeV at the 95% C.L. is derived in regions of parameter space with enhanced leptonic branching fractions.

Journal Article↗
PubMed2005

Search for neutral supersymmetric Higgs Bosons in multijet events at sqrt[s]=1.96 TeV.

We have performed a search for neutral Higgs bosons produced in association with bottom quarks in pp collisions, using 260 pb-1 of data collected with the D0 detector in Run II of the Fermilab Tevatron Collider. The cross sections for these processes are enhanced in many extensions of the standard model (SM), such as in its minimal supersymmetric extension at large tanbeta. The results of our analysis agree with expectations from the SM, and we use our measurements to set upper limits on the production of neutral Higgs bosons in the mass range of 90 to 150 GeV.

Journal Article↗
PubMed2005

Ion detection with photonic crystal microcavities.

We have experimentally demonstrated a cation and anion sensor by using short linear photonic crystal microcavities with an embedded quantum dot active region. The photonic crystal microcavity covered with an ion-selective polymer forms a submicrometer optical detection system sensitive to small changes of perchlorate anion (ClO4(-)) and calcium cation (Ca2+) concentrations.

Journal Article↗
PubMed2005

Glucose-induced Akt1 activation mediates fibronectin synthesis in endothelial cells.

AIMS/HYPOTHESIS: Increased expression and decreased degradation of extracellular matrix (ECM) proteins are key features of chronic diabetic complications. Fibronectin, a predominant ECM protein, has been shown to be overexpressed in all target organs of diabetic complications and in endothelial cells cultured in high levels of glucose. The present study was designed to elucidate the role of protein kinase B (Akt/PKB) in glucose-induced fibronectin mRNA expression and protein production in vascular endothelial cells. METHODS: Human umbilical vein endothelial cells were cultured in the presence of high glucose to study Akt/PKB activation. The upstream and downstream mediators in the Akt/PKB pathway were also investigated using dominant negative transfections and specific inhibitors of signalling pathways. Cells were subjected to real time RT-PCR, western blotting, and confocal microscopy to assess Akt1/PKBalpha activation and fibronectin mRNA expression and protein production. To detect transcription factor activation, electrophoretic mobility shift assay was carried out. RESULTS: Our data demonstrate that fibronectin mRNA expression and protein production that are induced by high glucose are mediated via activation of Akt/PKB, which is modulated by mitogen-activated protein kinase, phosphatidylinositol 3-kinase, and protein kinase C. Glucose-induced fibronectin mRNA expression and protein production are also mediated by Akt1/PKBalpha-dependent activation of the transcription factors nuclear factor-kappaB and activating protein-1. CONCLUSIONS/INTERPRETATION: Our study provides insight into the mechanical basis of glucose-induced increases in fibronectin mRNA expression and protein production. High levels of glucose may increase fibronectin mRNA expression and protein production by activating Akt/PKB.

Cell Survival↗