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Biomedical subjects

S Chaudhuri

Publications and source records attributed to S Chaudhuri.

At least 19 recordsLinked to original sources
PubMed2002

Genomic diversity of group A rotavirus strains infecting humans in eastern India.

Between 1998 and 2000, a total of 266 samples were found positive for group A rotaviruses by RNA electrophoresis. Samples were collected from patients admitted to two leading hospitals in Calcutta. Serotyping could be done only with 22% of the positive samples, leaving 78% untypeable. The G (VP7 genotypes) and P (VP4 genotypes) types were determined for 159 samples by reverse transcription and multiplex PCR. The predominant genotype was G1P[8] (20%), followed by G2P[4] (15%) and G4P[8] (6%). A number of uncommon genotypes, G1P[4] (4%), G2P[8] (2.5%), G2P[6] (0.6%), G4P[4] (2.5%), and G4P[6] (1.25%), were also detected during this study period. Twenty two percent of specimens showed mixed infections, 38 (24%) of the total samples remained untypeable for either VP7 or VP4, while only 4 (2.5%) of the samples were untypeable for both genes. Eleven specimens collected from Manipur were also genotyped and revealed a very high degree of genomic reassortment.

Child, Preschool↗
PubMed2001

Facilitation of functional compartmentalization of bone marrow cells in leukemic mice by biological response modifiers: an immunotherapeutic approach.

Biological Response Modifiers (BRMs) including interleukin-2 (IL-2), interferon-gamma (IFN-gamma) and sheep erythrocytes (SRBC) protected N,N'-ethylnitrosourea (ENU) induced leukaemic mice. Two cell types from the bone marrow were isolated in density specific gradient representing two distinct compartments, the low density cells being more CD34 positive than the high density group. Investigations with the functional efficacy of such compartments revealed significant improvement of cytotoxic efficacy and phagocytic burst at the high density compartment (HDC) level. The high density compartment was found to be more responsive towards the BRMs compared to the cells of the low density compartment (LDC). It was suggested that use of BRMs in vivo can stimulate a potent functional progenitor compartmentalization in normal as well as leukaemic mice. These observations are expected to help a logistic approach towards combined BRM therapy at the clinical level.

Animals↗
PubMed2001

Deconfinement and the Hagedorn transition in string theory.

We introduce a new definition of the thermal partition function in string theory. With this new definition, the thermal partition functions of all of the string theories obey thermal duality relations with self-dual Hagedorn temperature beta(2)(H) = 4pi(2)alpha('). A beta-->beta(2)(H)/beta transformation maps the type I theory into a new string theory (type I) with thermal D p-branes, spatial hypersurfaces supporting a p-dimensional finite temperature non-Abelian Higgs-gauge theory for p< or =9. We demonstrate a continuous phase transition in the behavior of the static heavy quark-antiquark potential for small separations r(2)(*)<<alpha(') transitioning through a precise inverse power law at a critical temperature T(D) = T(H)r(*)/(2alpha('))(1/2)pi.

Journal Article↗
PubMed2001

Randomized controlled trial of intrasphincteric botulinum toxin A injection versus balloon dilatation in treatment of achalasia cardia.

As the few randomized controlled trials available in the literature comparing botulinum toxin (BT) injection with established endoscopic treatment of achalasia cardia, i.e. pneumatic dilatation, showed conflicting results, we conducted a prospective randomized trial. Seventeen consecutive patients with achalasia cardia diagnosed during a period between December 1997 and February 2000 were randomized into two treatment groups [pneumatic dilatation by Rigiflex dilator (n=10), BT injection by sclerotherapy needle into four quadrants of lower esophageal sphincter (LES) (n=7) 80 units in five cases, 60 units in two cases] after dysphagia grading, endoscopy, barium esophagogram, and manometry, all of which were repeated 1 week after treatment. Patients were followed up clinically for 35.2+/-14 weeks. Chi-squares, Wilcoxon rank-sum test, Kaplan-Meier method and log-rank tests were used for statistical analysis. After 1 week, 6/7 (86%) BT-treated vs. 8/10 (80%) dilatation-treated patients improved (P=NS). There was no difference in LES pressure and maximum esophageal diameter in the barium esophagogram in the two groups before therapy. Both therapies resulted in significant reduction in LES pressure. The cumulative dysphagia-free state using the Kaplan-Meier method decreased progressively in BT-treated compared with dilatation-treated patients (P=0.027). Two patients with tortuous megaesophagus, one of whom had failed dilatation complicated by perforation previously, improved after BT. One other patient in whom pneumatic dilatation had previously failed improved in a similar manner. BT is as good as pneumatic dilatation in achieving an initial improvement in dysphagia of achalasia cardia. It is also effective in patients with tortuous megaesophagus and previous failed pneumatic dilatation. However, dysphagia often recurs during 1-year follow up.

Adult↗
PubMed2001

Association of ARF and Rabs with complement receptor type-1 storage vesicles in human neutrophils.

During neutrophil activation, the properties of the cell are rapidly altered by increases in the surface expression of functionally important receptors and adherence molecules. At the same time, endocytic and phagocytic activities increase. These alterations require precise regulation of membrane and protein movement, which is achieved, at least in part, by bidirectional movement of small transport vesicles. GTP-binding proteins, including Rabs and ADP-ribosylation factors (ARFs), play critical roles in regulating vesicle trafficking in other types of cells. The ability to immunoisolate the "secretory" vesicle subpopulation in which complement receptor type 1 (CR1) is stored allowed us to determine which types of low-molecular-weight GTP-binding proteins interact with these vesicles and under what conditions. CR1-containing vesicles from resting human neutrophils constitutively copurify with Rabs 3a, 4, and 5a, and reversibly bind an ARF, likely ARF1. ARF binding is dependent on free Mg(2+) and is enhanced by GTPgammaS. Mg(2+) at 0.4 microM is necessary for half-maximal binding of ARFs to CR1 storage vesicles. Artificial phospholipid vesicles and primary and secondary granules from human neutrophils do not bind ARFs themselves and do not compete for recruitment of ARFs to CR1 vesicles, suggesting that specific membrane environments and/or proteins on these vesicles stabilize the ARF-GTP-Mg(2+) complex. Free Ca(2+) at 300 nM does not inhibit ARF binding to CR1 storage vesicles, but 10 mM Ca(2+) does reduce such binding. These findings suggest that ARF-GTP specifically and reversibly interacts with CR1 storage vesicles in human polymorphonuclear leukocytes and may play a role in regulating their transport.

ADP-Ribosylation Factor 1↗
PubMed2000

Genetic susceptibility to breast cancer: HLA DQB*03032 and HLA DRB1*11 may represent protective alleles.

Tumors are believed to emerge only when immune surveillance fails. We wished to ascertain whether the failure to inherit putative protective alleles of HLA class II genes is linked to the development of breast cancer. We molecularly typed HLA DPB1, DQB1, DRB1, and DRB3 alleles in 176 Caucasian women diagnosed with early-onset breast cancer and in 215 ethnically matched controls. HLA DQB*03032 was identified in 7% of controls but in no patients with early-onset breast cancer (P = 0.0001). HLA DRB1*11 alleles were also significantly overrepresented (P < 0.0001) in controls (16. 3%) as compared with patients with early-onset breast cancer (3.5%). HLA DQB*03032 and HLA DRB1*11 alleles may have a protective role in human breast cancer.

Adult↗
PubMed2000

Accelerated proteasomal degradation of membrane Ig heavy chains.

Membrane IgG H chains turn over considerably more rapidly than secretory Ig H chains in the 18-81 A2 pre-B cell line. This rapid degradation occurs in proteasomes. N-Glycosylated membrane Ig H chains accumulate in the endoplasmic reticulum in the presence of proteasomal inhibitors, suggesting that retrotranslocation and proteasomal degradation of membrane Ig H chains may be closely coupled processes. Accelerated proteasomal degradation of membrane Ig H chains was also observed in transfected nonlymphoid cells. At steady state, the membrane form of the H chain associates more readily with Bip and calnexin than its secretory counterpart. The preferential recognition of membrane, as opposed to secretory, Ig H chains by some endoplasmic reticulum chaperones, may provide an explanation for the accelerated proteasomal degradation of the former.

Amino Acid Sequence↗
PubMed2000

Inhibition and stimulation of growth of Entamoeba histolytica in culture: association with PKC activity and protein phosphorylation.

We studied the role of protein kinase C (PKC) and protein threonine phosphorylation in the inhibition and stimulation of growth of the protozoan parasite Entamoeba histolytica. PKC was activated after serum deprivation in E. histolytica and during this period proteins became threonine phosphorylated. Conversely, on serum stimulation of serum-deprived cells, PKC activation was rapidly reversed and the threonine phosphorylation of proteins quickly declined. Growth of E. histolytica was not affected by either PKC inhibitors H-7 and GF109203X or by down-regulation of PKC by Phorbol 12-Myristate 13-Acetate (PMA). Interestingly, very low doses of PMA which caused activation of PKC and were unable to down-regulate PKC after 48 h of culture, negatively influenced the growth of E. histolytica. Serine/threonine phosphatase inhibitors Okadaic acid and Calyculin A drastically inhibited growth of E. histolytica. In conclusion, the growth of E. histolytica is not adversely affected by PKC down-regulation. On the contrary, growth inhibition of E. histolytica is associated with activation of Ca(2+), Diacylglycerol (DAG)-dependent PKC, and threo nine phosphorylation of proteins.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed2000

The effect of shoe lifts on static and dynamic postural control in individuals with hemiparesis.

OBJECTIVE: To determine the effect of lifts to the shoe of the nonaffected leg on weight symmetry and dynamic posturography in individuals with hemiparesis. DESIGN: Quantitative posturography was performed to determine subjects' response to sudden perturbations. Subjects received graded forward and backward perturbations while standing on a movable force platform. Compelled shift of the body weight was induced with sized lifts to the shoe of the nonaffected leg. Balance responses were analyzed in terms of latency and strength of neuromuscular response. Symmetry scores were used to characterize the symmetry of stance. SETTING: Free-standing acute inpatient rehabilitation hospital. PARTICIPANTS: Ten individuals with hemiparesis as a result of unilateral stroke. MAIN OUTCOME MEASURES: Weight symmetry scores, latencies of each leg's active response to the support surface translations, and response strength scores of each leg to the platform translations. RESULTS: When no lift was used, weight symmetry was characterized by underloading of the affected limb, as well as by longer onset latencies for the affected limb compared with the stronger one (158.5 +/- 3.9 vs 151.1 +/- 3.5 ms; p < .01 for large backward translations; 165.7 +/- 7.2 vs 158.0 +/- 5.1 ms; p < .01 for large forward translations). Response strength of the nonparetic limb was 2 times greater than the response strength of the weaker extremity (p < .05). Compelled weight shift induced by lifts applied to the shoe of the nonparetic limb promoted improved weight symmetry, shortened latencies, and increased magnitudes of the response strength. CONCLUSION: Lifts applied to the shoe of the stronger limb induced a body weight shift toward the paretic limb and resulted in improved symmetry of stance and postural control of individuals with hemiparesis. We suggest that compelled weight distribution induced by lifts to the shoe of the stronger limb could help treat ambulatory individuals with asymmetric stance and hemiparesis caused by unilateral stroke.

Adult↗
PubMed2000

13,13a-Dihydro-13-methoxy-9-methyl-1-benzopyrano[4,3-i]dinaphtho[2, 1-c;1',2'-f]-2,8-dioxabicyclo[3.3.1]nonane.

The crystal structure of the title compound, C(32)H(24)O(4), contains three fused dihydropyran rings (A, B and C); ring A is fused with a benzene ring while the other two rings, B and C, are fused with naphthalene rings. Ring A adopts a half-chair conformation with an equatorial methoxy group, whereas ring B assumes a distorted half-chair conformation, the A/B ring junction being trans. Ring C adopts a distorted half-boat conformation and is nearly orthogonal to ring B. Ring C is inclined to the best plane of ring A at an angle of 112.1 (1) degrees.

Crystallography, X-Ray↗
PubMed2000

Quantitative analysis of error bounds in the recovery of depth from defocused images.

Depth from defocus involves estimating the relative blur between a pair of defocused images of a scene captured with different lens settings. When a priori information about the scene is available, it is possible to estimate the depth even from a single image. However, experimental studies indicate that the depth estimate improves with multiple observations. We provide a mathematical underpinning to this evidence by deriving and comparing the theoretical bounds for the error in the estimate of blur corresponding to the case of a single image and for a pair of defocused images. A new theorem is proposed that proves that the Cramér-Rao bound on the variance of the error in the estimate of blur decreases with an increase in the number of observations. The difference in the bounds turns out to be a function of the relative blurring between the observations. Hence one can indeed get better estimates of depth from multiple defocused images compared with those using only a single image, provided that these images are differently blurred. Results on synthetic as well as real data are given to further validate the claim.

Journal Article↗
PubMed2000

Micropropagation of sweet orange, Citrus sinensis Osbeck. for the development of nucellar seedlings.

Protocol for micropropagation of elite plants of sweet orange (Citrus sinensis) through nucellar embryo culture has been standardized. Three to four nucellar embryos and a zygotic embryo could be excised from a single mature seed and successfully generated as healthy plants in basal MS medium. MS medium supplemented with NAA (1 mg/L) or 2, 4.D (1 mg/L) promoted callus development in both nucellar and zygotic embryos. GA3 (1 mg/L) enriched medium induced plantlets initiation but their growth was very poor. No significant differences were observed between initial growth patterns of nucellar and zygotic seedlings developing from the same ovule. Five to six shoots were obtained from collar region of both category of embryos in MS medium supplemented with BAP (1 mg/L) within 60 days of inoculation. The number of plantlets were almost doubled after their transfer in the same medium and culture for another 30 days. Higher doses of BAP resulted in initiation of callus directly from the embryos. The regenerated shoots (2-3 cm) could be rooted in MS medium supplemented with either only NAA (0.75 mg/L) or NAA (0.50 mg/L) and IBA (2.0 mg/L). A number of plantlets could be obtained from a nucellar embryo grown shoot within a limited time period.

Botany↗
PubMed1999

Growth stimulation by serum in Entamoeba histolytica is associated with protein tyrosine dephosphorylation.

Very little protein tyrosine phosphorylation was observed in growing (exponential-phase) Entamoeba histolytica cells by immunoblotting and quantitative immunofluorescence. After 1 h of serum deprivation, two proteins (42 and 38 kDa in SDS-PAGE) were tyrosine phosphorylated and two more proteins (96 and 63 kDa) also showed tyrosine phosphorylation when examined after 4 h of serum deprivation. Intense enhancements of anti-phosphotyrosine immunofluorescence levels were observed during this period of serum withdrawal. Membrane-associated tyrosine kinase activity reached a peak (3.5-fold increase) 1 h after serum deprivation and decreased thereafter reaching a basal level by 2 h of serum deprivation. Interestingly, tyrosine kinase activities remained unaffected by serum stimulation (2-60 min) of serum-deprived cells. Also, during this period of serum stimulation tyrosine phosphorylated proteins of serum-deprived cells were dephosphorylated. Tyrosine phosphatase activities were suppressed during serum deprivation and on serum addition to serum-deprived cells tyrosine phosphatase activities increased significantly. Our data attest that protein tyrosine phosphorylation was associated with growth inhibition of E. histolytica and serum stimulation of E. histolytica produced tyrosine phosphatase activation and protein tyrosine dephosphorylation.

Animals↗
PubMed1999

Membrane anchoring of calnexin facilitates its interaction with its targets.

Calnexin, a chaperone that resides in the endoplasmic reticulum, participates in the quality control function of this compartment. Many glycoproteins in the process of folding associate transiently with this chaperone via interactions involving the recognition of their mono-glucosylated glycans. Some misfolded proteins which are retained in the endoplasmic reticulum exhibit prolonged association with calnexin. We have examined whether the transmembrane and cytoplasmic domains of calnexin influence the association of this chaperone with its targets. Interactions of wild type and truncated calnexin with a glycoprotein that is retained in the endoplasmic reticulum (the lymphocyte tyrosine kinase, Ltk), with membrane IgM heavy chains, and with the MHC class I heavy chain protein were investigated. A soluble calnexin molecule lacking the transmembrane domain and cytoplasmic tail does not associate with any of these proteins. When a heterologous transmembrane domain is fused to the lumenal portion of calnexin, this membrane-bound protein can bind Ltk, IgM heavy chains, and MHC class I heavy chain proteins. These results suggest that calnexin must be membrane-anchored in order to recognize its substrates.

Animals↗
PubMed1999

Autophosphorylation-dependent activation of a calcium-dependent protein kinase from groundnut

Ca2+-dependent protein kinases (CDPKs) containing a calmodulin-like domain integrated in their primary sequence are present primarily in plants. A member of this family was characterized from the groundnut (Arachis hypogea) plant and called GnCDPK (M. DasGupta [1994] Plant Physiol 104: 961-969). GnCDPK specifically uses the myosin light chain synthetic peptide (MLCpep), which is the phosphate-accepting domain of smooth muscle myosin light chains (KKRPQRATSNVFS), as an exogenous substrate under in vitro experimental conditions. In this report we show that GnCDPK undergoes intramolecular autophosphorylation. This self-phosphorylation occurs in threonine residues in a Ca2+-dependent (K0.5 = 0.5 &mgr;M) and calmodulin-independent manner. The kinase activity toward MLCpep and its sensitivity to Ca2+ were unaffected by prior autophosphorylation when measured under saturating ATP concentrations. The role of autophosphorylation in the exogenous substrate MLCpep phosphorylation reaction was reinvestigated at low ATP concentrations. A pronounced lag time of 1 to 2 min, followed by a linear increase of activity for 7.5 min, was seen in the initial rate of MLCpep phosphorylation under such suboptimal conditions. Prior autophosphorylation completely abolished this lag phase, and a sharp rise of exogenous substrate phosphorylation was seen from the 1st min. Our results suggest that autophosphorylation is a prerequisite for the activation of GnCDPK.

Journal Article↗
PubMed1998

Why relapse occurs in PB leprosy patients after adequate MDT despite they are Mitsuda reactive: lessons form Convit's experiment on bacteria-clearing capacity of lepromin-induced granuloma.

It is amazing how after years of scientific research and therapeutic progress many simple and basic questions about protective immunity against Mycobacterium leprae remain unanswered. Although the World Health Organization (WHO) has recommended short-term multidrug therapy (WHO/MDT) for the treatment of paucibacillary (PB) leprosy patients, from time to time several workers from different parts of the globe have reported inadequate clinical responses in a few tuberculoid and indeterminate leprosy patients following adequate WHO/MDT despite the fact that they are Mitsuda responsive. A few borderline tuberculoid patients harbor acid-fast bacilli (AFB) in their nerves for many years even though they become clinically inactive following MDT, a fact which has been ignored by many leprosy field workers. Keeping these patients in mind, we have attempted to investigate the cause of the persistence of AFB in PB cases and have looked into the question of why Mitsuda positivity in tuberculoid and indeterminate leprosy patients, as well as in healthy contacts, is not invariably a guarantee for protectivity against the leprosy bacilli. We have: a) analyzed the histological features of lepromin-induced granulomas, b) studied the bacteria-clearing capacity of the macrophages within such granulomas, and c) studied the in vitro leukocyte migration inhibition factor released by the blood leukocytes of these subjects when M. leprae sonicates have been used as an elicitor. The results of these three tests in the three groups of subjects have been compared and led us to conclude that the bacteria-clearing capacity of the macrophages within lepromin-induced granuloma (positive CCB test) may be taken as an indicator of the capability of elimination of leprosy bacilli and protective immunity against the disease. This important macrophage function is not invariably present in all tuberculoid and indeterminate leprosy patients or in all contacts even though they are Mitsuda responsive and are able to show a positive leukocyte migration inhibition (LMI) test. It is likely but not certain that this deficit of the macrophage is genetically predetermined and persists after completion of short-term WHO/MDT. Thus, after discontinuation of treatment slow-growing, persisting M. leprae multiply within macrophages leading to relapse.

Adolescent↗