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Biomedical subjects

R Bandyopadhyay

Publications and source records attributed to R Bandyopadhyay.

At least 19 recordsLinked to original sources
PubMed2001

Short-chain fatty acid derivatives stimulate cell proliferation and induce STAT-5 activation.

Current chemotherapeutic and butyrate therapeutics that induce fetal hemoglobin expression generally also suppress erythropoiesis, limiting the production of cells containing fetal hemoglobin (F cells). Recently, selected short-chain fatty acid derivatives (SCFADs) were identified that induce endogenous gamma-globin expression in K562 cells and human burst-forming units-erythroid and that increase proliferation of human erythroid progenitors and a multilineage interleukin-3-dependent hematopoietic cell line. In this report, gamma-globin inducibility by these SCFADs was further demonstrated in mice transgenic for the locus control region and the entire beta-globin gene locus in a yeast artificial chromosome and in 2 globin promoter-reporter assays. Conditioned media experiments strongly suggest that their proliferative activity is a direct effect of the test compounds. Investigation of potential mechanisms of action of these SCFADs demonstrates that these compounds induce prolonged expression of the growth-promoting genes c-myb and c-myc. Both butyrate and specific growth-stimulatory SCFADs induced prolonged signal transducer and activator of transcription (STAT)-5 phosphorylation and activation, and c-cis expression, persisting for more than 120 minutes, whereas with IL-3 alone phosphorylation disappeared within minutes. In contrast to butyrate treatment, the growth-stimulating SCFADs did not result in bulk histone H4 hyperacetylation or induction of p21(Waf/Cip), which mediates the suppression of cellular growth by butyrate. These findings suggest that the absence of bulk histone hyperacetylation and p21 induction, but prolonged induction of cis, myb, myc, and STAT-5 activation, contribute to the cellular proliferation induced by selected SCFADs.

Animals↗
PubMed2001

A new autotuning algorithm for PID controllers using dead-beat format.

A novel algorithm for PID controllers based on dead-beat control and fuzzy inference mechanism is presented in this paper. The proposition is an extension of the work by the authors where the PI form of the algorithm was presented. The inclusion of the derivative term makes the method suitable for application in all types of processes including the ones having high rate disturbances. The proposed algorithm seems to be a complete and generalized PID autotuner as can be seen by the simulated and experimental results. In all the cases the method shows substantial improvement over the controller tuned with Ziegler Nichol's formula and the PI controller proposed in R. Bandyopadhyay, D. Patranabis, A fuzzy logic based PI autotuner, ISA Transactions 37 (1998) 227-235.

Journal Article↗
PubMed2001

Identification and characterization of satellite III subfamilies to the acrocentric chromosomes.

The centromeres and the short arms of the five pairs of acrocentric chromosomes in humans are composed of tandemly ordered repetitive DNA. Previous studies have suggested that the exchanges between acrocentric chromosomes have resulted in concerted evolution of different DNA sequences in their short arms. The acrocentric chromosomes are clinically relevant since they are involved in Robertsonian translocation formation and non-disjunction resulting in aneuploidy. Here we have identified seven new satellite III repetitive DNA subfamilies, determined their nucleotide sequences and established their chromosomal distributions on the short arms of the acrocentric chromosomes. Knowledge of these related sequences may help to elucidate the molecular basis of Robertsonian translocation formation.

Base Sequence↗
PubMed2001

Satellite III sequences on 14p and their relevance to Robertsonian translocation formation.

Robertsonian translocations (ROBs) are the most common rearrangements in humans, contributing significantly to genetic imbalance, fetal wastage, mental retardation and birth defects. Rob(14q21q) and rob(13q14q), which are formed predominantly during female meiosis, comprise the majority (approximately 85%) of all ROBs. Previous studies have shown that the breakpoints are consistently located within specific regions of the proximal short arms of chromosomes 13, 14, and 21. The high prevalence of these translocations, the consistent breakpoints found, and the fact that roughly 50% of cases occur sporadically suggest that the sequences at or near the breakpoints confer susceptibility to chromosome rearrangement and that the rearrangements occur through a specific mechanism. To investigate this hypothesis, we developed hamster-human somatic cell hybrids derived from de novo rob(14q21q) patients that contained the translocated chromosome segregated from the other acrocentric chromosomes. We determined the physical order of five satellite III subfamilies on 14p, and investigated their involvement in formation of these de novo translocations.

Abnormalities, Multiple↗
PubMed2000

Observation of chaotic dynamics in dilute sheared aqueous solutions of CTAT.

The nonlinear flow behavior of a viscoelastic gel formed due to entangled, cylindrical micelles in aqueous solutions of the surfactant cetyl trimethylammonium tosilate (CTAT) has been studied. On subjecting the system to a step shear rate lying above a certain value, the shear and normal stresses show interesting time dependent behavior. The analysis of the measured time series shows the existence of a finite correlation dimension and a positive Lyapunov exponent, unambiguously implying that the dynamics can be described by that of a dynamical system with a strange attractor whose dimension increases with the increase in shear rate.

Journal Article↗
PubMed2000

Involvement of PL-D in the alternate signal tranduction pathway of macrophages induced by an external stimulus.

The alternate pathway of signal transduction via hydrolysis of phosphatidylcholine, the major cellular phospholipid, has been investigated in murine peritoneal macrophages. A sustained formation of diacylglycerol, is preceded by an enhanced production of phosphatidic acid, when the macrophages were given a stimulus with 12-O-tetradecanoyl phorbol-13-acetate for sixty minutes. Production of choline and choline metabolites are significantly increased too. Propranolol, which inhibits phosphatidate phosphohydrolase, the enzyme responsible for conversion of phosphatidic acid to diacylglycerol, can effectively block the formation of diacylglycerol. Inhibition of protein kinase C either by its inhibitors, staurosporine and H-7 or by depletion, apparently affect the generation of the lipid products. Moreover, based on the results of transphosphatidylation reaction, involvement of a phospholipase D in the phosphatidylcholine-hydrolytic pathway in macrophages is predicted. These observations support the view that probably the phorbol ester acting directly on protein kinase C of the macrophages activate their phosphatidylcholine-specific phospholipase D to allow a steady generation of second messengers, to enable them to participate in the cell signalling process in a more efficient manner than those generated in the phosphoinositide pathway of signal transduction.

Animals↗
PubMed2000

Influence of crystal habit on the surface free energy and interparticulate bonding of L-lysine monohydrochloride dihydrate.

The objective of the present study was to apply a technique to measure the surface energy of crystalline powders without changing the surface properties by compaction, and to relate such measurements to crystal habit and orientation. The surface free energy of uncompacted L-lysine monohydrochloride dihydrate (LH), determined using a modified sessile-drop method, reflected a combined value for the various faces, and was influenced by the relative size of the faces and the orientation of the crystals. The surface free energy values obtained from contact angle measurements were within the possible range calculated from the crystal structure. Discrepancies between the theoretical estimates of interparticulate cohesive strengths and those measured from the tensile strength of powder compacts were used to estimate the flaw sizes (or gaps between the particles) that act as stress concentrators and reduce the tensile strength of the compacts. The flaw sizes indicate packing and compressibility of the various crystal habits. In the absence of compressive load, compacts made out of the equidimensional crystals have the larger flaw sizes (wider cracks or wider gaps between the particles). At higher compaction pressures, the compacts from long rod-shaped crystals have longer crack lengths. The weakness of the compacts made from the long rods at the higher compaction pressures may be because of the longer crack length along the interparticulate boundary, which may result in a higher stress intensity at the crack tip and increased fracture propensity.

Chemistry, Pharmaceutical↗
PubMed1999

Contemporary global movement of emerging plant diseases.

Plant diseases are a significant constraint to agricultural productivity. Exotic plant diseases pose a continued threat to profitable agriculture in the United States. The extent of this threat has increased dramatically in the 1980s and 1990s due to the expansion of international trade in agricultural products and frequent movement of massive volume of people and goods across national boundaries. Introduction of new diseases has not only caused farm losses, but has also diminished export revenue since phytosanitary issues are linked to international commerce. Plant pathogens and their vectors have also moved across national boundaries, sometimes naturally and at other times influenced by the recent changes in trade practices. Sorghum ergot, Karnal bunt of wheat, potato late blight, and citrus tristeza are some of the most recent examples of enhanced importance of diseases due to the introduction of plant pathogens or vectors.

Agriculture↗
PubMed1996

Neither the homeodomain nor the activation domain of Bicoid is specifically required for its down-regulation by the Torso receptor tyrosine kinase cascade.

Bicoid (Bcd) is a maternal morphogen responsible for patterning the head and thorax of the Drosophila embryo. Correct specification of head structure, however, requires the activity of the Torso receptor tyrosine kinase cascade, which also represses expression of Bcd targets at the most anterior tip of the embryo. Here, we investigate the role of both the homeodomain (HD) and the activation domain of Bcd in the anterior repression of its targets. When a Bcd mutant protein whose HD has been replaced by the Gal4 DNA-binding domain is expressed in early embryos, a reporter gene driven by Gal4 DNA-binding sites is first activated in an anterior domain and then repressed from the anterior pole. The down-regulation of Bcd-Gal4 activity requires torso function but does not depend on endogenous bcd activity, indicating that the Bcd protein alone and none of its targets is required to mediate the effect of torso. Functional analysis of a chimeric protein, whose activation domain has been replaced by a generic activation domain, indicates that the activation domain of Bcd is also not specifically required for its down-regulation by Torso. We propose that Torso does not affect the ability of Bcd to bind DNA, but instead directs modification of Bcd or of a potential Bcd co-factor, which renders the Bcd protein unable to activate transcription.

Animals↗
PubMed1995

Camping with a friend. Helping adolescents cope with diabetes.

The Florida Camp for Children and Youth With Diabetes sponsored a weekend in which teenagers with diabetes invited a friend of the same sex without diabetes to participate in a two-day retreat. This program was designed to encourage friends to take an active role in motivating the teen with diabetes to perform his or her diabetes-related tasks in a responsible manner. Forty-six patients ranging in age from 12-17 years brought friends. Those with diabetes participated in rap sessions as well as educational sessions attempting to teach independence in self-care. The friends were taught the basics of diabetes as well as given an opportunity to inject saline and monitor their own blood glucose levels. A choice of activities was interspersed with education.

Adaptation, Psychological↗
PubMed1994

The DNA adenine methyltransferase-encoding gene (dam) of Vibrio cholerae.

The DNA adenine methyltransferase (MTase)-encoding gene (dam) of Vibrio cholerae, an organism belonging to the family Vibrionaceae, has been cloned and the complete nucleotide (nt) sequence determined. V. cholerae dam encodes a 21.5-kDa protein and is directly involved in methyl-directed DNA mismatch repair. It can substitute for the Escherichia coli enzyme and can suppress the phenotypic traits associated with E. coli dam mutants. Overproduction of V. cholerae Dam MTase does not result in hypermutability in either V. cholerae or E. coli cells. Overproduction of V. cholerae Dam in a pUC plasmid, however, fails to suppress the 2-aminopurine (2-AP)-sensitive phenotype of E. coli dam mutants. Homology between the nt and deduced amino acid (aa) sequences of the E. coli and V. cholerae dam genes is only 30-35%.

Amino Acid Sequence↗
PubMed1994

Neoglycosylated liposomes as efficient ligands for the evaluation of specific sugar receptors on macrophages in health and in experimental leishmaniasis.

Receptors interacting with terminal sugars as ligands are involved in the binding of Leishmania donovani promastigotes to the macrophage surface and their subsequent internalization. Mannose and glucose are specifically involved in the binding process. Decreased binding occurs to macrophages already infected with L. donovani either in vivo or in vitro. When mannose- or glucose-bearing liposomes are used as ligands the binding shows similar trends and the percentage inhibition of binding with mannose-bearing liposomes increases when compared to that for the glucose-bearing ones. The decreased binding of the ligand seems to be due to a decrease in the number of receptors after infection. The affinity of the ligands for the binding sites either on the normal macrophages or on the infected macrophages apparently remains the same. The results based on the incorporation of [3H]phenyl alanine and supported by the binding of glycosylated liposomes to both infected and non-infected macrophages suggest that protein synthesis, in general, is suppressed in L. donovani-infected macrophages thus affecting also mannose/glucose receptor protein synthesis, resulting in fewer receptors on the macrophage surface.

Animals↗
PubMed1992

Secondary structure at the beginning of the poly(A) sequence of mouse beta-actin messenger RNA.

A portion of the beta-actin mRNA of mammalian cells is believed to lack a poly(A) tail, because of its failure to bind to oligo(dT)-cellulose. S1 mapping and Northern blot analysis of this mRNA shows it to contain a poly(A) sequence of about 60 nucleotides. Only about 20-40 nucleotides are available for interaction with oligo(dT). The rest is masked, presumably by base-pairing with a poly(U) stretch present in the 3' non-coding region of the mRNA. A similar configuration occurs in the bulk of the actin mRNA, which carries a poly(A) tail with sizes ranging from approximately 60 to 200 nucleotides.

Actins↗
PubMed1990

Fluidity-dependent Mg2(+)-ATPase activity in membranes from Leishmania donovani promastigotes.

The state of the lipid phase of the membrane plays a key role in the exposure of various receptors, antigens and enzymes on the membrane surface. The fluidity of membranes of Leishmania donovani promastigotes was monitored by two independent methods, i.e. influx of sterol from liposomes and removal of phospholipids by treatment with phospholipase C. The altered sterol/phospholipid ratio, in both cases, provided evidence that the activity of the functionally important membrane-bound enzyme Mg2(+)-ATPase is modulated by the state of the lipid phase of the membrane.

Animals↗
PubMed1990

Nuclease activity associated with mammalian mRNA in its native state: possible basis for selectivity in mRNA decay.

Polysome and messenger ribonucleoprotein (mRNP) preparations from various mammalian cells contain tightly bound nuclease activity that causes degradation of the mRNA in the preparations. This activity was found to cosediment with all polysome size classes as well as with free mRNPs and to remain associated with the mRNPs released from polysomes by treatment with EDTA. No association with ribosomal subunits was evident. The rates of mRNA degradation were not affected by serial dilution, an indication that enzyme and substrate are tightly associated. beta-Globin mRNA in purified reticulocyte polysomes was cleaved at AU sequences in the 3'-terminal region. Cleavages at the same sites occurred when deproteinized reticulocyte RNA was incubated with mouse sarcoma 180 (S-180) polysomes. The S-180 preparations caused additional cleavages, primarily at UG sequences. A P40 mRNA in S-180 polysomes was cleaved primarily in the 3' noncoding region, but the cleavages in a P21 mRNA were seen in the 5' noncoding region only. Actin mRNA was cleaved in an internal region, yielding large relatively stable 3'- and 5'-terminal fragments. These data suggest the occurrence of highly specific interactions between one or more mRNA-bound nucleases and individual mRNA species.

Animals↗
PubMed1989

A mutation in the dam gene of Vibrio cholerae: 2-aminopurine sensitivity with intact GATC methylase activity.

Vibrio cholerae mutants sensitive to 2-aminopurine (2AP) but with DNA adenine methylase activity similar to parental cells have been isolated. The mutant strains were sensitive to ultraviolet light (UV), methyl methane sulphonate (MMS) and 9-aminoacridine. The spontaneous mutation frequency of the mutants were not significantly affected. Attempts to isolate dam V. cholerae cells by screening 2AP sensitive cells have not been successful. All the mutant phenotypes could be suppressed by introducing the plasmid pRB103 carrying the dam gene of Escherichia coli into the mutant cells.

2-Aminopurine↗