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Biomedical subjects

S Chakraborty

Publications and source records attributed to S Chakraborty.

At least 91 records · Page 5Linked to original sources
PubMed1998

Development and evaluation of a multiplex PCR assay for rapid detection of toxigenic Vibrio cholerae O1 and O139.

A multiplex polymerase chain reaction assay was developed for concurrent detection of rfb sequences specific for the O1 and the O139 serogroups of Vibrio cholerae and for ctxA specific sequences. The multiplex PCR assay was found to be highly specific and sensitive and was capable of detecting 65 cfu and 200 cfu per assay of V. cholerae O1 and O139, respectively. Evaluation of the multiplex PCR assay using 121 stool samples from patients admitted to the Infectious Diseases Hospital, Calcutta, showed the assay to be 100% sensitive and 95.2% specific when the culture method was taken as the standard. In addition to the 38 PCR positive stool samples, an additional four samples which were negative by culture method but positive by PCR assay belonged to the O139 serogroup. All the 38 stool samples positive for either O1 or O139 serogroup by PCR assay were also positive for the ctxA amplicon indicating that the O1 and O139 V. cholerae strains have the genetic potential of producing cholera toxin.

Bacterial Proteins↗
PubMed1998

Seasonal prevalence of Anopheles stephensi larvae and existence of two forms of the species in an urban garden in Calcutta City.

A study on the occurrence and seasonal prevalence of Anopheles stephensi (principal vector of malaria in Calcutta) larvae in an urban garden in central Calcutta revealed their presence in collections of fresh and/or rain water in various kinds of temporary and permanent breeding habitats. Breeding sites in shady areas were preferred in comparison to those receiving direct sunlight. The density of An. stephensi larvae was highest in earthen and lowest in wooden pots throughout the study period, as supported by ANOVA and Wilcoxon's signed rank test. During monsoons the larval density was uniformly high in all four, i.e. earthen, stone, cement and wooden kinds of pots. The variation in the density of An. stephensi larvae due to the effect of season and nature of pots was highly significant. Co-existence of An. stephensi larvae with Aedes aegypti, Ae. albopictus and Cx. quinquefasciatus was also observed at times in certain water collections. An. stephensi population in the urban garden in central Calcutta was found to comprise of two forms the type and variety mysorensis.

Animals↗
PubMed1998

Cell apoptosis and proliferation in obstructive uropathy.

Distinct patterns of cell proliferation and apoptosis have been recognized for tubular, interstitial, and glomerular cells in chronic obstructive uropathy (OU). In many experimental models of OU, tubular cell apoptosis develops quickly after ureter ligation, peaks between 7 and 24 days postobtruction (about 30-fold of control), and tapers thereafter. Apoptosis initially involves the dilated collecting ducts, but subsequently spreads to other tubules. Tubular cell apoptosis probably accounts for renal tissue loss in OU because a direct correlation between its degree and the decline in dry kidney weight is well-documented. Pronounced tubular cell proliferation occurs shortly after ureter ligation, peaks at about day 6 (60-fold above control), and quickly subsides to baseline. Because the peak of tubular cell proliferation immediately precedes the onset of tubular cell apoptosis, a pathogenetic link may exist between these two processes. Interstitial cell apoptosis occurs with an increasing frequency throughout the course of OU (up to 35-fold above control). Interstitial cell proliferation appears in a bimodal pattern with the early peak coinciding with that of tubular cell proliferation and consisting mostly of fibroblasts, whereas the later peak consists mostly of inflammatory cells. Glomerular cell apoptosis and proliferation are not different from control, which explains, in part, the structural integrity of the glomeruli throughout the disease course. Although the general pathways of cell apoptosis and proliferation are well known, the molecular control of these processes in OU is poorly understood. In addition, whether apoptosis or proliferation of tubular and interstitial cells is differentially regulated remains to be studied. However, several molecules known to be activated or overexpressed in kidney with OU may modulate cell apoptosis and proliferation. The relevant functions of these molecules include induction of apoptosis (angiotensin II, reactive oxygen species, jun-N-terminal kinase, p53), inhibition of the cell cycle (transforming growth factor-beta, p21), inhibition of apoptosis (clusterin, epidermal growth factor, insulin-like growth factor, bcl-2, osteopontin), or promotion of interstitial fibroblast proliferation (platelet-derived growth factor).

Angiotensin II↗
PubMed1997

Adenoviral delivery of E2F-1 directs cell cycle reentry and p53-independent apoptosis in postmitotic adult myocardium in vivo.

Irreversible exit from the cell cycle precludes the ability of cardiac muscle cells to increase cell number after infarction. Using adenoviral E1A, we previously demonstrated dual pocket protein- and p300-dependent pathways in neonatal rat cardiac myocytes, and have proven that E2F-1, which occupies the Rb pocket, suffices for these actions of E1A. By contrast, the susceptibility of adult ventricular cells to viral delivery of exogenous cell cycle regulators has not been tested, in vitro or in vivo. In cultured adult ventricular myocytes, adenoviral gene transfer of E2F-1 induced expression of proliferating cell nuclear antigen, cyclin-dependent protein kinase 4, cell division cycle 2 kinase, DNA synthesis, and apoptosis. In vivo, adenoviral delivery of E2F-1 by direct injection into myocardium induced DNA synthesis, shown by 5'-bromodeoxyuridine incorporation, and accumulation in G2/M, by image analysis of Feulgen-stained nuclei. In p53(-)/- mice, the prevalence of G1 exit was more than twofold greater; however, E2F-1 evoked apoptosis and rapid mortality comparably in both backgrounds. Thus, the differential effects of E2F-1 on G1 exit in wild-type versus p53-deficient mice illustrate the combinatorial power of viral gene delivery to genetically defined recipients: E2F-1 can override the G1/S checkpoint in postmitotic ventricular myocytes in vitro and in vivo, but leads to apoptosis even in p53(-)/- mice.

Adenoviridae↗
PubMed1997

Prognostic significance of angiogenesis in clinically localized prostate cancer (staining for Factor VIII-related antigen and CD34 Antigen.

Tumour angiogenesis is widely considered to be an important phenomenon in the process of tumour growth and metastasis. We investigated the prognostic significance of the microvascular count (MVC) in prostate cancer of each Gleason grade and compared the results to other established pathologic parameters and progression probability. We also compared the staining of Factor VIII-related antigen (FVIII-RA) with CD34 antigen (CD34 Ag) staining for determination of the MVC. We examined 101 radical prostatectomy specimens from patients who underwent curative therapy for clinically localized adenocarcinoma of the prostate as the first form of therapy. To identify microvessels, immunohistochemical staining of endothelial cells was performed using antibodies to FVIII-RA and CD34 Ag in formalin-fixed, paraffin-embedded tissue. Microvessels were counted in fivex200 fields (0.785 mm(2) on each Gleason grade in the 'hot' areas. We used the highest number of five fields in the worst Gleason grade on each staining for statistical analysis. MVC using FVIII-RA and CD34 Ag staining correlated with pathologic stage, Gleason score and preoperative serum prostate-specific antigen level. In addition, MVC using CD34 Ag staining also correlated with DNA ploidy and total tumour volume. The Gleason score was found to be the best prognostic indicator using Cox proportional hazards regression analysis. In this study, MVC in prostate cancer was predictive of pathologic stage and Gleason grade, but MVC by either FVIII-RA and CD34 Ag staining was not an independent prognostic predictor. The best prognostic indicator in this study was Gleason score.

Journal Article↗
PubMed1996

Human E2F-1 reactivates cell cycle progression in ventricular myocytes and represses cardiac gene transcription.

The "pocket" protein- and p300-binding domains of E1A mediate alternative pathways that, independently, provoke S phase reentry in ventricular muscle cells and repress cardiac-specific transcription. In the present study, we utilized recombinant adenovirus to deliver mammalian E2F-1, whose release from pocket proteins may underlie effects of E1A and mitogenic signaling. Like E1A, E2F-1 proved cytotoxic in the absence of E1B. Used along with E1B to avert apoptosis, E2F-1 inhibited the cardiac and skeletal alpha-actin promoters, serum response factor abundance, and sarcomeric actin biosynthesis, while inducing DNA synthesis and proliferating cell nuclear antigen. Image analysis of Feulgen-stained nuclei corroborated a parallel increase in DNA content, with accumulation in G2/M. Thus, E2F-1 suffices for all observed actions of E1A in cardiac myocytes.

Animals↗
PubMed1996

Dissociation between behavioral and psychophysiological measures of response preparation.

Two measures of response preparation were compared: lateralized readiness potentials (LRPs) and reaction times (RTs) to probe stimuli. Subjects responded with the left and right hands to target S's and T's of one size, withholding responses to nontarget S's and T's of a different size. The size discrimination was more difficult than the S vs. T discrimination, so the name of a nontarget letter was expected to prime the response hand to which it was assigned. This priming had no effect on LRPs but did influence RTs to separate probe stimuli, suggesting that LRPs and probe-RTs are sensitive to different aspects of response preparation.

Adolescent↗
PubMed1996

Effect of DDT on Phlebotomus sandflies in Kala-Azar endemic foci in West Bengal.

Phlebotomous argentipes, the vector of Kala-azar was found susceptible to DDT and found to reappear in the nine months after one time DDT spray at the rate of lg/m2 in three endemic foci of districts North and South 24-Parganas of West Bengal. Ph. papatasi, the other predominant species found resistant to DDT appeared within one month of DDT spray.

Animals↗
PubMed1995

Demonstration that mammalian methionine synthases are predominantly cobalamin-loaded.

Methionine synthase is an important cellular housekeeping enzyme and is dependent on the cofactor cobalamin, a derivative of vitamin B12, for activity. It functions in two major metabolic pathways including the tetrahydrofolate-dependent one-carbon cycle and the salvage pathway for methionine. Its dysfunction has several physiological ramifications and leads to the development of megaloblastic anemia. In addition, it is suspected to be involved in the pathogenesis of neural tube defects. An issue that is central in weighing therapeutic options for methionine synthase-related disorders is the extent to which the enzyme exists as apoenzyme in vivo and, thus, can be potentially responsive to vitamin B12 therapy. despite the importance of this issue, the extent of holo- versus apoenzyme in mammalian tissue is controversial and unresolved. To address this question, we have developed a convenient anaerobic assay that employs titanium citrate to deliver low potential electron equivalents. The reductive activation of this enzyme is essential under in vitro assay conditions. We find that both the human placental and porcine liver methionine synthases exist predominantly in the holoenzyme form (90-100%) in the crude homogenate. In addition, the activity of the pure enzyme measured in the titanium citrate assay is also independent of exogenous cofactor, revealing that the cobalamin is tightly bound to the active site.

5-Methyltetrahydrofolate-Homocysteine S-Methyltran↗
PubMed1995

Old Yellow enzyme: aromatization of cyclic enones and the mechanism of a novel dismutation reaction.

The origin of charge transfer bands that develop on reaction of Old Yellow Enzyme with alpha,beta-unsaturated cyclic ketones such as 3-oxodecalin-4-ene (ODE, numbered according to the convention for steroids), 3-oxodecalin-4-ene-10-carboxaldehyde (ODEC), and 2-cyclohexenone is shown to be due to the aromatization of ODE and ODEC to 3-hydroxy-6,7,8,9-tetrahydronaphthalene (HTN) and of 2-cyclohexenone to phenol. The aromatization of ODEC to HTN is stereospecific and involves the trans dehydrogenation of the 1 beta, 2 alpha hydrogens. The aromatization occurs under aerobic as well as anaerobic conditions. With the exception of ODEC under aerobic conditions, the aromatization of these substrates is accompanied by a dismutation reaction in which the olefinic bond of a second molecule of each substrate is reduced to give the saturated cyclic ketone. Molecular oxygen may serve as the electron acceptor with ODEC and some other substrates under aerobic reaction conditions. The dismutation reaction involves an overall sequence of hydride transfer from one substrate molecule to the beta-carbon of a second substrate molecule along with a solvent proton uptake by the alpha-carbon. 19-Nortestosterone is aromatized to beta-estradiol; however, other 3-oxo-delta 4-steroids such as progesterone, testosterone, and androstene-3,17-dione bind tightly to the enzyme but are not aromatized. The NADPH-dependent reduction of the olefinic bond of alpha,beta-unsaturated carbonyl compounds is limited to aldehydes and ketones. alpha,beta-Unsaturated acids, esters, amides, and nitriles are not reduced. The reduction of the olefinic bond of ODE or cinnamaldehyde by NADPH occurs by an overall sequence of hydride transfer from the reduced pyridine nucleotide to the beta-carbon of the alpha,beta-unsaturated carbonyl compound and a solvent proton uptake by the alpha-carbon. The 4-pro-R hydride of NADPH is transferred in the reduction reaction. Structure-function relationships in the NADPH-dependent reduction of alpha,beta-unsaturated aldehydes or ketones indicate that increasing alkyl substitution at the beta-carbon results in marked decrease in the rate of reduction of the olefinic bond, consistent with a steric hindrance to hydride transfer at the beta-carbon.

Acrolein↗
PubMed1995

A new old yellow enzyme of Saccharomyces cerevisiae.

In 1993, the first gene of Old Yellow Enzyme (OYE) of Saccharomyces cerevisiae was cloned (Stott, K., Saito, K., Thiele, D. J., and Massey, V. (1993) J. Biol. Chem. 268, 6097-6106) and named OYE2 to distinguish it from the first OYE gene cloned from Saccharomyces carlsbergenesis (Saito, K., Thiele, D. J., Davio, M., Lockridge, O., and Massey, V. (1991) J. Biol. Chem. 266, 20720-20724). The analysis of an OYE2 deletion mutant suggested that S. cerevisiae had at least two OYE genes. In the present study, we cloned a new OYE species named OYE3 and analyzed the OYE3 protein expressed in Escherichia coli. OYE3 consists of 400 amino acid residues and its molecular mass calculated by electrospray mass spectrometry is 44,788 daltons, in good agreement with the value of 44,920 daltons predicted from the amino acid sequence derived from the DNA sequence. In the downstream region of the OYE3 gene, the cytochrome oxidase (COX10) gene exists with a 426-base pair intermediate sequence. Some of the physicochemical and kinetic properties of OYE2 and OYE3 have been determined. Although the two enzymes are clearly closely related, they show differences in ligand binding properties and in their catalytic activities with oxygen and cyclohexen-2-one as acceptors.

Amino Acid Sequence↗