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S Bandyopadhyay

Publications and source records attributed to S Bandyopadhyay.

At least 73 records · Page 4Linked to original sources
PubMed1996

Dimer-dimer interfaces of the lambda-repressor are different in liganded and free states.

Lambda-repressor dimers associate in solution to form tetramers and higher order structures. Dimer-dimer contact is also crucial in cooperative binding to adjacent operators. Fluorescence quenching studies indicate that the tryptophan 230 environment is significantly different in unliganded and adjacent operator-bound tetramers. Acrylodan attached to Cys 235, in a mutant F235C repressor, is also in different environments in the unliganded and adjacent operator bound tetramers. Thermodynamics of protein association, measured by fluorescence anisotropy, indicate that, whereas free repressor dimer association is strongly enthalpy driven, the single-operator (OR1)-bound repressor dimer association is largely entrophy driven with little change in enthalpy. Single-operator-bound dimer association to the corresponding tetramer does not lead to any significant change in tryptophan 230 environment, as was seen in the case of the free repressor. Data are also presented to support the contention that, under the conditions of this study, the free repressor association is predominantly from dimer to tetramer and then to octamer, unlike the dimer to octamer transition observed under a different condition. The results presented here point toward the conclusion that the lambda-repressor dimer-dimer interface is significantly different in the free and operator-bound states and that operator binding plays a crucial role in changing the nature of the dimer-dimer interface.

2-Naphthylamine↗
PubMed1996

Reversal of beta-amyloid-induced retention deficit after exposure to training and state cues.

We explored amnesia induced by posttraining injection of beta-amyloid protein (beta A4) in four experiments. Previous reports showed that beta A4 impaired retention of learning maintained either by food reward or by shock relief. The experiments in this paper attempted to determine (1) if the amnesia is specific to the 1-40 beta A4 amino-acid sequence; and (2) if the amnesia can be attributed to a consolidation process. Subjects were 190 male Sprague-Dawley rats, 3 to 6 months old. Subjects were given five training trials on a left-right discrimination in a Y-maze with a food reward and injected immediately afterward with beta A4(1-40) or vehicle. One week later they were trained to criterion. Experiment 1 used a control group that was injected with the reverse-sequence peptide (40-1). The performance of the beta A4(40-1) group was unimpaired. Experiments 2 and 3 attempted to reverse the amnestic effects of beta A4 using noncontingent presentation of aspects of the training context during the retention interval. Experimental subjects in Experiment 2 were exposed to the Y-maze in the absence of reinforcers, 24, 22, and 2 h before retention testing. In Experiment 3, subjects were given a 1-min exposure to the reinforcers, outside the Y-maze, 24 h before retention testing. Both manipulations reversed beta A4-induced amnesia. In Experiment 4, beta A4-induced impairments were reversed by reinjecting beta A4 immediately before retention testing. Results indicate that beta A4 injected after partial training does not interfere with a consolidation process.

Amnesia↗
PubMed1995

Role of the C-terminal tail region in the self-assembly of lambda-repressor.

Acrylamide quenching of the tryptophan fluorescence of the lambda-repressor at different protein concentrations indicates that one of the three tryptophan residues, W129, W142, and W230, undergoes a change in environment upon self-assembly, from dimer to associated species. Quenching data suggest that this tryptophan residue is inaccessible to low concentrations of acrylamide and is blue-shifted in the associated form. In the dimer, this tryptophan residue is highly accessible to acrylamide and is red-shifted. NBS oxidation, at protein concentrations which favor the associated form, showed that this tryptophan is also significantly protected from NBS oxidation. HPLC peptide mapping of NBS-oxidized lambda-repressor, amino acid analysis, and sequencing indicate that the protected, blue-shifted tryptophan is tryptophan 230. A mutant repressor (F235C) was specifically labeled at Cys 235 with an environment-sensitive probe, acrylodan. The acrylodan fluorescence of the labeled F235C lambda-repressor undergoes a significant blue-shift, accompanied by fluorescence enhancement, upon protein association. Along with other genetic evidence, these results suggest involvement of the C-terminal tail region in the self-assembly of the lambda-repressor.

Acrylamide↗
PubMed1995

An outbreak of viral hepatitis in Jodhpur city of Rajasthan.

An outbreak of Viral hepatitis occurred in Jodhpur city of Rajasthan during April to June, 1994. The attack rate was 3.04 per cent among 0-14 years age group and 5.49% among the age group above 15 years, the overall attack rate being 4.5 per cent. Males were more affected than females. Epidemiological and serological findings suggest that the outbreak was due to enterically transmitted Non A Non B virus. The source of infection was drinking water contaminated with sewage.

Adolescent↗
PubMed1994

Identification of a conserved oxidation-sensitive cysteine residue in the NFI family of DNA-binding proteins.

The nuclear factor I (NFI) family of site-specific DNA-binding proteins plays a role in both transcription and adenovirus DNA replication. The DNA binding domain of NFI family members contains 4 cysteine residues (Cys-2, Cys-3, Cys-4, and Cys-5) that are conserved in all NFI proteins. Mutation of the Cys-2, Cys-4, and Cys-5 residues in the human NFI-C protein to several other amino acids abolished DNA binding, while 8 of 10 mutations of the Cys-3 residue had little or no effect on binding. Wild-type NFI-C was inactivated by N-ethylmaleimide in vitro, while the active Cys-3 mutant proteins were resistant to N-ethylmaleimide. Treatment of wild-type NFI in vitro with the oxidizing agent diamide also inactivated DNA binding, and subsequent reduction with dithiothreitol restored binding activity. The active Cys-3 mutant NFI proteins were resistant to diamide-inactivation, indicating that the Cys-3 residue is required for modulation of DNA-binding by oxidation state. These studies indicate that oxidative-inactivation can play an important role in the modifying NFI-DNA-protein interactions. The presence of this nonessential Cys-3 residue in all known NFI proteins raises the possibility that it may function in a manner similar to redox-sensitive cysteine residues found in other site-specific DNA-binding proteins.

Amino Acid Sequence↗
PubMed1994

Interferon-stimulated response element and NF kappa B sites cooperate to regulate double-stranded RNA-induced transcription of the IP-10 gene.

To understand the mechanisms involved in dsRNA-induced gene expression, we analyzed the poly(I/C)-induced transcription of the IFN-inducible chemokine gene IP-10 using the GRE cell line in which type I IFN genes have been deleted. Accumulation of IP-10 mRNA in GRE cells was more strongly stimulated by treatment with dsRNA than by IFN-alpha or IFN-gamma and was independent of protein synthesis. This same pattern of response was produced when GRE cells were transiently transfected with a plasmid containing 243 bases of sequence from the promoter of the murine IP-10 gene linked to the chloramphenicol acetyltransferase reporter gene. Deletion- and site-specific mutagenesis of the 243 base pair fragment indicated that an ISRE located between residues -204 and -228 was a primary target site for the action of dsRNA on this promoter. This was confirmed by results showing that two copies of this ISRE tandemly arrayed in front of the thymidine kinase promoter were able to mediate reporter gene transcription in dsRNA-stimulated cells. At least one of the two NF kappa B binding sites present in the 243 base pair IP-10 promoter is also necessary for response to dsRNA; mutation of both sites eliminates promoter activity. Thus the ISRE and one NF kappa B site cooperate to produce transcriptional response to dsRNA.

Base Sequence↗
PubMed1994

Synthesis and anthelmintic activity of 3-substituted 5-methylthio-isoxazoles.

Isoxazole derivatives have been shown to possess antiparasitic activity. In the present study, 3-substituted 5-methylthio-isoxazoles were synthesized and tested for anthelmintic activity, along with some other isoxazoles which have been reported but not tested earlier. Nine compounds (2a, 2b, 2e, 2g, 2u, 3a, 3b, 3e and 3f) showed activity against both A. ceylanicum and N. dubius in vitro. Twelve compounds (2a, 2b, 2d, 2e, 2f, 2h, 2l, 2n, 2o, 2u, 3d and 3e) showed activity against N. dubius in vivo, a parasite of veterinary importance.

Ancylostoma↗
PubMed1993

Purification and properties of an Indian major carp (Cirrhinus mrigala, Ham.) pituitary thyrotropin.

Thyroid stimulating hormone (TSH) was isolated and purified from the pituitaries of Indian major carp, Cirrhinus mrigala, with the help of a sensitive in vitro bioassay system, based on incubating isolated thyroid follicles from murrel, Channa gachua. In this assay, addition of test material containing TSH increased thyroxine (T4) release into the medium which was then measured by radioimmunoassay (RIA). TSH activity was eluted as one major peak on Sephadex G-100 gel filtration (peak I), which also contained gonadotropin (GtH) and extraneous proteins as contaminants. GtH was monitored by RIA. Chromatography of peak I of gel filtration on concanavalin A-Sepharose was useful in harvesting glycoprotein hormones; adsorbed (Con A-II) material showed strong TSH activity and low GtH content. To separate TSH from GtH completely, immunoaffinity chromatography was used; more than a 200-fold purification was achieved. Polyacrylamide gel electrophoresis of carp TSH (cTSH) showed a single band, indicating it to be a homogenous protein. The molecular weight (MW) of cTSH was estimated by Sephadex G-100 gel filtration to be 42,000 Da. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of cTSH revealed two dissimilar subunits, alpha and beta, and MW of alpha was 21,000 Da while that of beta was 24,000 Da. When tested in similar doses, cTSH released more T4 from murrel thyroid follicle than bovine TSH (bTSH). cTSH stimulated the T4 release from rat and goat thyroid but its activity was less than that of bTSH. Radiolabeled cTSH (125I-cTSH) bound specifically to a murrel thyroid follicular plasma membrane preparation, and Scatchard analysis showed the Kd to be 0.17 x 10(-10) M and the maximum binding (Bmax) to be 15.2 fmol/mg protein. 125I-cTSH also binds to the goat thyroid plasma membrane preparation with a Kd = 0.23 x 10(-10) M and a Bmax = 9.8 fmol/mg protein. Findings indicate that carp pituitary thyrotropin is approximately similar in size to that of vertebrates, its biological activity is not restricted only to fish but is also observed in rat and goat, and it has a receptor in teleost and goat thyroid.

Animals↗