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Biomedical subjects

S Bhattacharya

Publications and source records attributed to S Bhattacharya.

At least 199 records · Page 11Linked to original sources
PubMed1999

Molecular genetic study of autosomal dominant retinitis pigmentosa in Lithuanian patients.

Lithuanian patients with visual problems were clinically examined for retinitis pigmentosa (RP). A total of 33 unrelated families with autosomal dominant RP (adRP) were identified. Screening for mutations in the rhodopsin (RHO) and peripherin/RDS (RDS) genes was performed using DNA heteroduplex analysis. Direct DNA sequencing in the cases of heteroduplex formation showed the presence of the following mutations and polymorphisms in 14 adRP patients: RHO gene - Lys248Arg (1 case), and Pro347Leu (2 cases); RDS gene - Glu304Gln (12 cases), Lys310Arg (5 cases), and Gly338Asp (12 cases). The presence of these mutations (except Lys248Arg in the RHO gene) was confirmed by relevant restriction enzyme digestion. The frequency of the RDS gene mutations Glu304Gln and Gly338Asp was estimated to be 36.4%, while mutation Lys310Arg was less frequent (15.2%). These 3 RDS gene mutations appear to be polypeptide polymorphisms not related to adRP.

Exons↗
PubMed1999

Inhibitory effect of Trianthema portulacastrum L. diethylnitroso-amine-induced phenobarbital promoted hepatocarcinogenesis.

The chloroform extract (active components from the exotic weed Trianthema portulacastrum L. of Aizoaceae, showed remarkable effect in the reduction of DENA-induced rat hepatocarcinogenesis. Hepatocarcinogenesis was induced in male Sprague-Dawley rats by a single intraperitonial injection of diethylnitrosoamine (DENA) at a dose of 200 mg/kg body weight. Chloroform extract of T. portulacastrum at a dose of 100 mg/kg/body wt. to the basal medium/per animal once daily was administered following DENA injection. Morphometric evaluation revealed that the fraction reduced the incidence, numerical preponderance, multiplicity and size distribution of visible pre-neoplastic nodules. Further focal lesions showed a reduction of altered liver cell foci/cm2 and a reduction of average focal area. A decrease in the percentage of liver parenchyma occupied by foci all seem to suggest the anticarcinogenic potential of Trianthema portulacastrum in DENA-induced rat hepatocarcinogenesis.

Animals↗
PubMed1999

Molecular detection of micrometastases and circulating tumor cells in solid tumors.

The detection of circulating tumor cells and micrometastases may have important prognostic and therapeutic implications. Because their numbers can be very small, these tumor cells are not easily detected using conventional methods. In the last decade, molecular techniques have been widely used for the detection of occult tumor cells. The objective of this report is the application of these molecular tools to solid tumors. A systematic review of all related English-language articles published in the last 32 years was performed. The molecular detection of occult tumor cells can be accomplished by PCR amplification of tumor-specific abnormalities present in the DNA or mRNA of malignant cells. The other main PCR strategy for the detection of CTC and micrometastases involves amplification of tissue-specific mRNA. This latter method was often applied to solid tumors, whereas the former was occasionally used. PCR was shown to be superior to conventional techniques in detecting occult tumor cells, allowing the identification of 1 malignant cell mixed with 1 to 10 million normal cells. In some reports, PCR is shown to be a strong predictor of outcome. The molecular detection of circulating tumor cells and micrometastases in solid tumors can be accomplished using highly sensitive PCR assays. The central question of whether PCR reliably predicts relapse and survival remains unanswered for many types of solid tumor. If PCR-based assays are found to be a reliable tool, they will likely have a major impact on the management of these malignancies.

False Negative Reactions↗
PubMed1999

Association between molecular detection of GAGE and survival in patients with malignant melanoma: a retrospective cohort study.

We used GAGE as a molecular marker to identify melanoma cells with metastatic potential in the peripheral blood and the bone marrow. One hundred thirty-three patients with malignant melanoma (21 clinical stage II, 74 stage III, and 38 stage IV) had a single marrow and/or blood sample drawn immediately prior to surgical resection. Simultaneous bone marrow and blood samples (85 patients), marrow-only samples (35 patients), and blood-only samples (13 patients) were examined for the presence of GAGE expression using reverse transcription-PCR. GAGE expression was associated with adverse overall patient survival, measured from the time of sampling (P = 0.01). When data were stratified for clinical stage, median survival was statistically longer among GAGE-negative patients in the stage III cohort only (P = 0.01). In a multivariate model, only GAGE positivity in blood and/or marrow and clinical stage were significant prognostic variables. It was the detection of GAGE in blood but not marrow that was associated with poor survival. The detection of blood GAGE by reverse transcription-PCR has significant adverse implications for overall survival of patients with malignant melanoma in this cohort, and it warrants further investigation.

Adult↗
PubMed1999

A high incidence of ciprofloxacin resistance in urinary isolates in eastern Nepal.

A study was conducted to examine the incidence of ciprofloxacin resistance in the strains of bacteria isolated from patients with suspected urinary tract infection (UTI) and to analyse the level of resistance. A total of 63 bacterial isolates were grown from quantitative urine culture and were in significant count. Antibiotic susceptibility tests were done by using disc diffusion method of Kirby-Bauer and the level of resistance was analyzed by break point minimum inhibitory concentration (MIC). Majority of bacteria isolated and tested were Gram negative with Escherichia coli as the commonest isolate. Antibiotic susceptibility testing revealed a high prevalence of resistance to nalidixic acid, ampicillin and norfloxacin.

Anti-Infective Agents↗
PubMed1998

Induction of a spectroscopically defined transition by guanidinium hydrochloride on a recombinant calcium binding protein from Entamoeba histolytica.

Sequence analysis and metal ion binding studies reported earlier have established that the calcium binding protein (CaBP) from the parasitic ameboid Entamoeba histolytica protein has four canonical EF hand motifs which bind calcium. Equilibrium denaturation studies on both the apo and the holo forms of this protein indicate the presence of stable transition intermediates at low denaturant concentrations as revealed by the binding of the non-specific hydrophobic dye ANS. Fast reaction kinetics shows that the binding of the Gdn+ ions at or near the Ca2+ sites in the N-terminal domain influences metal ion binding to the sites in the C-terminal domain. Isothermal calorimetric titrations performed using low GdnHCl concentrations reveal the presence of two binding sites of low affinity, both being endothermic in nature. Thus the stabilization of CaBP observed at low GdnHCl concentration represents a native-like intermediate, with the Gdn+ ions mimicking Ca2+ binding at the N-terminal domain of this protein.

Animals↗
PubMed1998

Crystallization and preliminary X-ray studies of a recombinant calcium-binding protein from Entamoeba histolytica.

A calcium-binding protein (CaBP) of Entamoeba histolytica was purified from an E. coli recombinant clone carrying the CaBP gene in a pET-3c expression vector using anion-exchange and size-exclusion chromatography. Examination of the amino-acid sequence of the recombinant protein suggested that it has four independent EF-hand motifs. The protein dissolved in cacodylate buffer was crystallized using the hanging-drop method with 2-methylpentane-2,4-diol (MPD) as the precipitant. X-ray diffraction data have been collected on these crystals using a MAR Research imaging-plate detector system attached to a Rigaku RU200 rotating-anode X-ray generator. The crystals belong to the hexagonal space group P6122 with unit-cell dimensions of a = b = 96.21, c = 65.48 A. Preliminary molecular-replacement computations suggest that the structure of this protein is likely to be similar to that of calmodulin (CAM).

Amino Acid Sequence↗
PubMed1998

Lineage-specific signaling in melanocytes. C-kit stimulation recruits p300/CBP to microphthalmia.

During melanocyte development, the cytokine Steel factor activates its receptor c-Kit, initiating a signal transduction cascade, which is vital for lineage determination via unknown downstream nuclear targets. c-Kit has recently been found to trigger mitogen-activated protein kinase-mediated phosphorylation of Microphthalmia (Mi), a lineage-restricted transcription factor, which, like Steel factor and c-Kit, is essential for melanocyte development. This cascade results in increased Mi-dependent transcriptional reporter activity. Here we examine the mechanism by which Mi is activated by this pathway. Phosphorylation does not significantly alter Mi's nuclear localization, DNA binding, or dimerization. However, the transcriptional coactivator p300/CBP selectively associates with mitogen-activated protein kinase-phosphorylated Mi, even under conditions in which non-MAPK phospho-Mi is more abundant. Moreover, p300/CBP coactivates Mi transcriptional activity in a manner dependent upon this phosphorylation. Mi thus joins CREB as a transcription factor whose signal-responsive phosphorylation regulates coactivator recruitment, in this case modulating lineage development in melanocytes.

Animals↗
PubMed1998

Protective role of Trianthema portulacastrum against diethylnitrosoamine-induced experimental hepatocarcinogenesis.

The chemopreventive efficacy of the Indian medicinal plant Trianthema portulacastrum L. Aizoaceae was tested in a chemical rat hepatocarcinogenesis model in male Sprague-Dawley rats. Hepatocarcinogenesis was induced by the potent carcinogen diethylnitrosoamine (DENA). Treatment of the rats to the basal medium with aqueous, ethanolic and chloroform fractions of the plant extract at a dose of 100 mg/kg body weight once daily reduced the incidence, numerical preponderance, multiplicity and size distribution of visible neoplastic nodules. Morphometric evaluation of focal lesions showed a reduction of altered liver cell foci/cm2 and a reduction of the average focal area. A decrease in the percentage of liver parenchyma occupied by foci seems to suggest the anticarcinogenic potential of the plant extract in DENA-induced hepatocarcinogenesis.

Animals↗
PubMed1998

Evidence of interlipidic ion-pairing in anion-induced DNA release from cationic amphiphile-DNA complexes. Mechanistic implications in transfection.

Complex formation of DNA with a number of cationic amphiphiles has been examined using fluorescence, gel electrophoresis, and chemical nuclease digestion. Here we have addressed the status of both DNA and lipid upon complexation with each other. DNA upon binding with cationic amphiphiles changes its structure in such a way that it loses the ability to intercalate and becomes resistant to nuclease digestion. Fluorescence anisotropy measurements due to 1, 6-diphenylhexatriene (DPH) doped in cationic liposomes demonstrated that upon complexation with DNA, the resulting complexes still retain lamellar organizations with modest enhancement in thermal stabilities. The lipid-DNA complexation is most effective only when the complexation was carried out at or around the phase transition temperatures of the cationic lipid employed in the complexation with DNA. The release of DNA from cationic lipid-DNA complexes could be induced by several anionic additives. Determination of fluorescence anisotropies (due to DPH) as a function of temperature clearly demonstrates that the addition of equivalent amounts of anionic amphiphile into cationic lipid-DNA complexes leads to the ion-pairing of the amphiphiles, the melting profiles of which are virtually the same as those obtained in the absence of DNA. In this process DNA gets released from its complexes with cationic lipids and regains its natural intercalation ability, movement, and staining ability on agarose gel and also the sensitivities toward nuclease digestion. This clearly suggests that combination of ion-pairing and hydrophobic interactions between cationic and anionic amphiphiles is stronger than the electrostatic forces involved in the cationic lipid-DNA complexation. It is further revealed that the DNA release by anions is most efficient from the cationic lipid-DNA complexes at or around the Tm of the cationic lipid used in DNA complexation. This explains why more effective DNA delivery is achieved with cationic lipids that bear unsaturated hydrocarbon chains than with their saturated hydrocarbon counterparts.

Anions↗
PubMed1998

Escherichia coli cytidine deaminase provides a molecular model for ApoB RNA editing and a mechanism for RNA substrate recognition.

ApoB RNA-editing enzyme (APOBEC-1) is a cytidine deaminase. Molecular modeling and mutagenesis show that APOBEC-1 is related in quaternary and tertiary structure to Escherichia coli cytidine deaminase (ECCDA). Both enzymes form a homodimer with composite active sites constructed with contributions from each monomer. Significant gaps are present in the APOBEC-1 sequence, compared to ECCDA. The combined mass of the gaps (10 kDa) matches that for the minimal RNA substrate. Their location in ECCDA suggests how APOBEC-1 can be reshaped to accommodate an RNA substrate. In this model, the asymmetrical binding to one active site of a downstream U (equivalent to the deamination product) helps target the other active site for deamination of the upstream C substrate.

APOBEC-1 Deaminase↗
PubMed1998

The importance of tRNA backbone-mediated interactions with synthetase for aminoacylation.

We have identified six new aminoacylation determinants of Escherichia coli tRNAGln in a genetic and biochemical analysis of suppressor tRNA. The new determinants occupy the interior of the acceptor stem, the inside corner of the L shape, and the anticodon loop of the molecule. They supplement the primary determinants located in the anticodon and acceptor end of tRNAGln described previously. Remarkably, the three-dimensional structure of the complex between tRNAGln and glutaminyl-tRNA synthetase shows that the enzyme interacts with the phosphate-sugar backbone but not the base of every new determinant. Moreover, a small protein motif interacts with five of these determinants, and it binds proximal to the sixth. The motif also interacts with the middle base of the anticodon and with the backbones of six other nucleotides. Our results emphasize that synthetase recognition of tRNA is more elaborate than amino acid side chains of the enzyme interacting with nucleotide bases of the tRNA. Recognition also includes synthetase interaction with tRNA backbone functionalities whose distinctive locations in three-dimensional space are exquisitely determined by the tRNA sequence.

Acylation↗
PubMed1998

Hepatic neoplasms in childhood - a clinicopathologic study.

Primary hepatic tumours are rare in childhood. We observed nine cases between 1976 and 1995, of which eight were hepatoblastomas and one a mesenchymal hamartoma. A male-to-female ratio of 2:1 was noted; 78% of the cases occurred in children below 2 years of age. Five hepatoblastomas were of the pure epithelial type; mesenchymal components encountered in the mixed type were cartilage, bone, and spindle sarcomatous cells.

Child↗
PubMed1998

Mechanisms of signal transduction in the stress response of hepatocytes.

Adaptation of animals to stress is a unique property of life which allows the survival of the species. The stress response of hepatocytes is a very complex phenomenon, sometimes involving a cascade of events. The general stress signals are elucidated by mobilization of carbohydrate stores and akin to the insulin mediators. Oxidative signals are generated by pesticides, heavy metals, drugs, and alcohol which may or may not be under the purview of peroxisomes. Peroxisomal responses are well-defined involving specific receptors, whereas nonperoxisomal responses may be signaled by calcium, the Ah receptor, or built-in antioxidant systems. The intoxication signals are generally thought to be membrane defects induced by xenobiotics which then lead to highly nonspecific responses of hepatocytes. Detoxication signals, on the other hand, are specific responses of hepatocytes triggering de novo syntheses of detoxifier proteins or enzymes. Evidence reveals the existence of two distinct mechanisms of signal transduction in stressed hepatocytes--one involving the peroxisome and the other the plasma membrane.

Acute-Phase Reaction↗
PubMed1998

The ribosomal DNA plasmids of entamoeba.

In most organisms, the nuclear ribosomal RNA (rRNA) genes are highly repetitive and arranged as tandem repeats on one or more chromosomes. In Entamoeba, however, these genes are located almost exclusively on extrachromosomal circular DNA molecules with no clear evidence so far of a chromosomal copy. Such an uncommon location of rRNA genes may be a direct consequence of cellular physiology, as suggested by studies with Saccharomyces cerevisiae mutants in which the rDNA is extrachromosomal. In this review, Sudha Bhattacharya, Indrani Som and Alok Bhattacharya summarize current knowledge on the structural organization and replication of the Entamoeba rDNA plasmids. Other than the rRNAs encoded by these molecules, no protein-coding genes (including ribosomal protein genes) are found on any of them. They are unique among plasmids in that they do not initiate replication from a fixed origin but use multiple sites dispersed throughout the molecule. Further studies should establish the unique biochemical features of Entamoeba that lead to extrachromosomal rDNA.

Journal Article↗
PubMed1998

Admission-discharge policies for hysteroscopic surgery: a randomised comparison of day case with in-patient admission.

OBJECTIVE: To study the effectiveness and acceptability of day case hysteroscopic surgery. DESIGN: Prospective randomised controlled trial. SETTING: Aberdeen Royal Infirmary. SUBJECTS: One hundred and ninety four consecutive women who underwent hysteroscopic endometrial ablation. INTERVENTION: Seventy three women were allocated to day case surgery and 37 to inpatient admission; 84 women though otherwise fit for day case surgery were scheduled for in-patient admission as they lived more than 20 miles away. All women completed a questionnaire 24 h after their operations. Readmission rates were obtained from case notes. Satisfaction rates 12 months after the operation were recorded by means of a follow-up questionnaire. RESULTS: Post-operative pain was absent or slight in 48 (75%) of the women in the day case group 27 (84%) of women in the in-patient group, and 55 (82%) in the non-randomised in-patient group. Post-operative analgesia was necessary in 34 (52%) women in the day case group, 24 (75%) women in the in-patient group and 36 (53%) women in the non-randomised in-patient group. Hospital costs were significantly less in the day case group. Satisfaction with stay 92% in the day case group, and 100% in the other two groups. CONCLUSION: In this setting, day care is a safe acceptable and less expensive alternative to in-patient care for hysteroscopic endometrial ablation.

Adult↗