Biomedical subjects

R Banerjee

Publications and source records attributed to R Banerjee.

At least 109 records · Page 6Linked to original sources

PubMed1999

Postulated effects on water structure of some salts and protein denaturants as inferred from measurements of viscosity B coefficients: example of HbS polymerization.

Viscosity measurements have been performed on aqueous solutions of some solutes commonly used in biochemical practice, with a view to determine the B coefficients and their temperature dependence. The temperature dependence measured for some anions leads to a ranking of the latter in an order similar to that reported earlier from entropy data for their postulated efficiency in disrupting "water structure". The well known dependence of denaturing power of guanidinium salts on the anions is shown to be related to the temperature dependence of B coefficients. Urea and formamide do not appear from this criterion to be significantly "structure-breaking"; alkyl-substituted derivatives of urea and formamide, on the other hand, possess significant "structure-forming" properties. The results are of interest in relation to the known effects of salts and other solutes on the stability of protein structures in respect of denaturation, subunit dissociation or self assembly. A typical application is illustrated by studying the effect of two anions, namely nitrate and sulphate, on the polymerization of sickle cell hemoglobin (HbS). Nitrate, which is believed to disrupt water structure, acts as an inhibitor of HbS polymerization which, on the contrary, is favoured by sulphate, a postulated structure- former.

Biopolymers↗

PubMed1999

Isolation of verotoxin producing Escherichia coli from diarrhoeal and urinary tract infection patients.

Fourty nine Escherichia coli strains, isolated from diarrhoeal and urinary tract infection (UTI) patients, attending Bareilly district hospital, Uttar Pradesh during October to December, 1998 were screened for verotoxin (VT) production by Vero cell assay. Five strains produced characteristic cytopathic effect on Vero cell line, of which 4 were from diarrhoeal and one was from UTI-patient. The level of VT-production varied widely. Antibiotic sensitivity tests revealed that the VT-producing E. coli (VTEC) were mostly sensitive to kanamycin, norfloxacin and nalidixic acid but resistant to ampicillin and tetracycline.

Bacterial Toxins↗

PubMed1998

Purification of soluble cytochrome b5 as a component of the reductive activation of porcine methionine synthase.

In mammals, methionine synthase plays a central role in the detoxification of the rogue metabolite homocysteine. It catalyzes a transmethylation reaction in which a methyl group is transferred from methyltetrahydrofolate to homocysteine to generate tetrahydrofolate and methionine. The vitamin B12 cofactor cobalamin plays a direct role in this reaction by alternately accepting and donating the methyl group that is in transit from one substrate (methyltetrahydrofolate) to another (homocysteine). The reactivity of the cofactor intermediate cob(I)alamin renders the enzyme susceptible to oxidative damage. The oxidized enzyme may be returned to the catalytic turnover cycle via a reductive methylation reaction that requires S-adenosylmethionine as a methyl group donor, and a source of electrons. In this study, we have characterized an NADPH-dependent pathway for the reductive activation of porcine methionine synthase. Two proteins are required for the transfer of electrons from NADPH, one of which is microsomal and the other cytoplasmic. The cytoplasmic protein has been purified to homogeneity and is soluble cytochrome b5. It supports methionine synthase activity in the presence of NADPH and the microsomal component in a saturable manner. In addition, purified microsomal cytochrome P450 reductase and soluble cytochrome b5 reconstitute the activity of the porcine methionine synthase. Identification of soluble cytochrome b5 as a member of the reductive activation system for methionine synthase describes a function for this protein in non-erythrocyte cells. In erythrocytes, soluble cytochrome b5 functions in methemoglobin reduction. In addition, it identifies an additional locus in which genetic polymorphisms may play a role in the etiology of hyperhomocysteinemia, which is correlated with cardiovascular diseases.

5-Methyltetrahydrofolate-Homocysteine S-Methyltran↗

PubMed1998

Evidence for heme-mediated redox regulation of human cystathionine beta-synthase activity.

Human cystathionine beta-synthase catalyzes the first step in the catabolic removal of the toxic metabolite, homocysteine. It is unique in being dependent on both pyridoxal phosphate (PLP) and heme for activity. The reaction involves condensation of serine and homocysteine to give cystathionine. Although the role of PLP can be rationalized in analogy with other PLP-dependent enzymes that catalyze beta-replacement reactions, the role of the heme is unknown. In this study, we have purified and characterized the recombinant human enzyme and have examined the effect of heme oxidation state on enzyme activity. We find that under reducing conditions, generated by addition of titanium citrate, the enzyme exhibits a 1.7-fold lower activity than under oxidizing conditions. Reoxidation of the ferrous enzyme with ferricyanide results in alleviation of inhibition. This redox-linked change in enzyme activity correlates with changes in heme oxidation state monitored by UV-visible spectroscopy. Dithiothreitol, which does not reduce the enzyme-bound heme, does not perturb enzyme activity. These studies provide the first evidence for redox-linked regulation of cystathionine beta-synthase which is heme-dependent.

Cystathionine beta-Synthase↗

PubMed1998

Interfacial indazolization: novel chemical evidence for remarkably high exo-surface pH of cationic liposomes used in gene transfection.

Cationic liposomes are used as the carriers of polyanionic genes for combating against hereditary diseases in gene therapy. Studies directed to careful biophysical characterizations of the cationic liposomes commonly used in gene delivery have just begun. Herein, we report on a novel liposomal exo-surface bound indazolization reaction of an amphiphilic arenediazonium salt as evidence for the existence of remarkably alkaline exo-surface of cationic liposomes commonly used in gene transfection. Our results demonstrate that formation of 5-hexadecyl-7-methylindazole in thermal indazolization of 2,6-dimethyl-4-hexadecylbenzenediazonium tetrafluoroborate bound to liposome surface is a strong indication for the existence of significantly high exo-surface pH for cationic liposomes commonly used in gene delivery. The present method can be used in determining the relative exo-surface basicities of various cationic liposomes used in gene transfection and subsequently to find any possible correlation between the transfection efficiencies of these liposomes and their exo-surface basicities.

Azo Compounds↗

PubMed1998

Disruption of a regulatory system involving cobalamin distribution and function in a methionine-dependent human glioma cell line.

Cobalamin metabolism and function were investigated at the levels from transcobalamin II (TCII) receptor to the cobalamin-dependent enzymes, methionine synthase and methylmalonyl-CoA mutase, in a methionine-dependent (P60) and a methionine-independent (P60H) glioma cell line. Using P60H as reference, the P60 cells cultured in a methionine medium had slightly lower TCII receptor activity and normal total cobalamin content, a moderately reduced microsomal and mitochondrial cobalamin(III) reductase activity but only trace amounts of the methylcobalamin and adenosylcobalamin cofactors. When transferred to a homocysteine medium without methionine, P60H cells showed a slightly enhanced TCII receptor activity, but the other cobalamin-related functions were essentially unchanged. In contrast, the methionine-dependent P60 cells responded to homocysteine medium with a nearly 6-fold enhancement of TCII receptor expression and a doubling of both the hydroxycobalamin content and the microsomal reductase activity. The mitochondrial reductase and the cobalamin-related processes further down the pathway did not change markedly. In both cell lines, TCII receptor activity was further increased when growth in homocysteine medium was combined with N2O exposure. These data suggest that low methionine and/or high homocysteine exert a positive feedback control on TCII receptor activity. The concurrent increase in hydroxycobalamin content and in microsomal reductase activity are either subjected to similar regulation or secondary to increased cobalamin transport. This regulatory network is most prominent in the methionine-dependent P60 cells harboring a disruption of the network in the proximity of cobalamin(III) reductase.

5-Methyltetrahydrofolate-Homocysteine S-Methyltran↗

PubMed1998

Identification and characterization of an unusual double serine/threonine protein phosphatase 2C in the malaria parasite Plasmodium falciparum.

We have cloned a gene from Plasmodium falciparum with homology to the Mg2+-dependent serine/threonine protein phosphatase 2C (PP2C) family. The predicted coding region is 920 amino acids long, twice the size of other members of this family. We show that this protein can be divided into two halves (Pf2C-1 and Pf2C-2), each a complete phosphatase unit with homology to other phosphatases of this class. To study the function of this PP2C, we have tested the ability of different constructs to complement conditional null mutants of yeast. Our results show that expression of the full-length protein, the first half alone, the second half alone, or a hybrid with the N terminus of the first half and the C terminus of the second half was able to complement the heat shock response defect of a Schizosaccharomyces pombe strain with a PP2C (PTC1) deletion. Recombinant P. falciparum PP2C expressed in Escherichia coli was active in dephosphorylating 32P-labeled casein in an Mg2+- or Mn2+-dependent reaction. Each half alone was also active in recombinant form. Using the two-hybrid system, we have shown that the two halves can interact. Gel filtration assay of P. falciparum protein extracts suggests that full-length PfPP2C is a dimer, and phosphatase activity competition experiments indicate that dimerization of PfPP2C is required for its optimal activity. This unusual phosphatase molecule appears to be composed of four catalytic units on two polypeptide chains.

Amino Acid Sequence↗

PubMed1998

Mephentermine hemisulfate monohydrate: an adrenergic agent.

The title molecule, a hydrated hemisulfate salt of ethyl(2-methyl-1-phenyl-2-propyl)ammonium, C11H18N+.0.5SO4(2-).H2O, consists of a phenethylamine skeleton in which the N atom is protonated. There are two molecules in the asymmetric unit, with the S atom of the SO4(2-) ion lying on a pseudo-twofold axis. The ethylamine side chain is in an extended conformation in both the symmetry-independent molecules. The distance of the N atom from the centre of the benzene ring is 5.1 A for molecule 1 and 5.3 A for molecule 2. The packing is stabilized by N-H...O and O-H...O hydrogen bonds.

Adrenergic Agents↗

PubMed1998

Coagulopathy secondary to vitamin K deficiency in hyperemesis gravidarum.

BACKGROUND: Hyperemesis gravidarum is a condition of pregnancy characterized by excessive nausea and vomiting, which can be associated with malnutrition. Vitamin K deficiency is a known complication of malnutrition as well as a known cause of coagulopathy. To date, there is no reported case in the literature of vitamin K deficiency in hyperemesis gravidarum. CASE: A woman at 15 weeks' gestation presented with hyperemesis gravidarum complicated by an episode of severe epistaxis. Investigation revealed coagulopathy secondary to vitamin K deficiency. The coagulopathy resolved after vitamin K replacement, with complete correction of all clotting factors. CONCLUSION: Vitamin K deficiency and coagulopathy should be considered in women with hyperemesis gravidarum who present with a bleeding diathesis. Prophylactic vitamin K replacement should be considered in cases in which hyperemesis is severe and protracted.

Adult↗

PubMed1998

Amino-terminal region of poliovirus 2C protein is sufficient for membrane binding.

The poliovirus-encoded, membrane associated polypeptide 2C is required for viral replication. We have previously established that, while the 2C protein lacks a defined membrane binding domain, the N-terminal region containing a putative amphipathic helix plays an important role in membrane binding both in vivo and in vitro. In order to determine whether the N-terminal region is sufficient for membrane binding, we have made fusion constructs between this region of 2C (amino acids 1-72 and 1-88) and a soluble protein, chloramphenicol acetyltransferase (CAT). The ability of CAT and the fusion polypeptides to bind to membranes was examined by in vitro translation in the presence of microsomal membrane. While CAT was found in the soluble fraction, both 2C/CAT fusion constructs (1-72/CAT and 1-88/CAT) were membrane associated, suggesting that the N-terminal region of 2C was sufficient to impart membrane binding. To confirm these results in vivo, CAT, 1-72/CAT, and 1-88/CAT were expressed in HeLa cells and their localization was examined using indirect immunofluorescence. Results presented here demonstrate that, while CAT is expressed throughout the cell, 1-72/CAT and 1-88/CAT constructs are capable of localizing to the endoplasmic reticulum (ER) area in transfected cells in the absence of other poliovirus proteins. These results suggest that the first 72 amino acids of 2C contain a membrane binding domain that is capable of targeting soluble proteins to the ER region of the cell.

Binding Sites↗

PubMed1998

Reproductive disorders associated with pelvic pain.

Pelvic pain is common in adolescents and can result from a number of physiological and pathological etiologies, both gynecologic and nongynecologic in origin. The evaluation, diagnosis, and management of these conditions involve both medical and surgical approaches. In this review, the authors present a comprehensive approach to the care of adolescents with pelvic pain associated with dysmenorrhea, endometriosis, and obstruction of the genital tract.

Adolescent↗

PubMed1998

Renal transplantation in a patient with methylmalonic acidaemia.

Renal insufficiency is frequently reported in mutase-deficient methylmalonic acidaemia. We present a case report of a patient with mut- methylmalonic acidaemia who developed chronic tubulointerstitial nephropathy during adolescence. At 24 years of age, she developed end-stage renal failure and underwent renal transplantation. Both plasma and urine methylmalonic acid levels decreased significantly with improved renal function following transplantation. Complications included cyclosporin toxicity and development of diabetes. Renal, metabolic, and clinical status remained improved at 3 years after the kidney transplant.

Adult↗

PubMed1998

Children's understanding of extended identity.

As adults, we appreciate that judgments of us may reflect our associations with other people. This article examines the development of "extended identity" (G.R. Semin & K. Papadopoulou, 1989) in children between 5 and 11 years. In Experiment 1, children were presented with hypothetical scenarios in which they imagined a close associate had committed a rule violation in a highly public context. Only the older children judged that they would be evaluated negatively through their association with the wrongdoer and that they themselves would feel embarrassment. Given the late appearance of extended identity, Experiment 2 addressed contexts in which the child was responsible for a younger child, so that accountability for the other was explicitly demanded. In such contexts, an appreciation of extended identity appeared earlier than it did in Experiment 1, in which no responsibility for the other was involved.

Child↗

PubMed1998

Studies of the interaction between Rad52 protein and the yeast single-stranded DNA binding protein RPA.

The RFA1 gene encodes the large subunit of the yeast trimeric single-stranded DNA binding protein replication protein A (RPA), which is known to play a critical role in DNA replication. A Saccharomyces cerevisiae strain carrying the rfa1-44 allele displays a number of impaired recombination and repair phenotypes, all of which are suppressible by overexpression of RAD52. We demonstrate that a rad52 mutation is epistatic to the rfa1-44 mutation, placing RFA1 and RAD52 in the same genetic pathway. Furthermore, two-hybrid analysis indicates the existence of interactions between Rad52 and all three subunits of RPA. The nature of this Rad52-RPA interaction was further explored by using two different mutant alleles of rad52. Both mutations lie in the amino terminus of Rad52, a region previously defined as being responsible for its DNA binding ability (U. H. Mortenson, C. Beudixen, I. Sunjeuaric, and R. Rothstein, Proc. Natl. Acad. Sci. USA 93:10729-10734, 1996). The yeast two-hybrid system was used to monitor the protein-protein interactions of the mutant Rad52 proteins. Both of the mutant proteins are capable of self-interaction but are unable to interact with Rad51. The mutant proteins also lack the ability to interact with the large subunit of RPA, Rfa1. Interestingly, they retain their ability to interact with the medium-sized subunit, Rfa2. Given the location of the mutations in the DNA binding domain of Rad52, a model incorporating the role of DNA in the protein-protein interactions involved in the repair of DNA double-strand breaks is presented.

Alleles↗

PubMed1998

Hemorheological parameters for biocompatibility evaluation.

Biomaterials have been extensively used for various clinical applications. Since blood is very sensitive to the presence of any foreign substances, testing for hemocompatibility is a major part of biocompatibility evaluation. At present, blood viscosity parameters are being used as screening tests for biomaterial compatibility. Successful use of these parameters will help eliminate many incompatible materials from being subjected to extensive testing. In this study, we evaluated the blood viscosity parameters (n = 10)--whole blood viscosity, plasma viscosity, red cell rigidity, hematocrit, and biochemical parameters (total proteins and albumin). A significant increase in hemorheological parameters after incubation with material was found to be an indicator of incompatibility.

Adult↗

PubMed1998

Hemorheological changes in blood transfusion-treated beta thalassemia major patients.

Beta thalassemia major is an inherited impairment of haemoglobin structure, in which there is partial or complete failure to synthesize a specific type of globin chain. The study was undertaken to assess the hemorheological changes in beta thalassemic major patients. We studied hemorheological parameters in thalassemic patients (n = 37) immediately after blood transfusion. The parameters studied were whole blood viscosity (WBV), plasma viscosity (PV), red cell rigidity (RCR) and hematocrit (Hct). Blood samples from age-and sex-matched normal controls were also analysed for comparison. Statistical analysis was done using Student's t-test and p values were recorded. The results showed a significant decrease in level of WBV and Hct in patients when compared to normal controls. However, the red cell rigidity was higher when compared to normal controls. Increase in RCR should show an increase in WBV. But in our study cases there was a significant decrease in WBV which was probably due to the significant decrease in level of hematocrit.

Blood Transfusion↗

PubMed1998

Hemorheological changes in nephrotic syndrome.

Hemorheological parameters of childhood nephrotic syndrome cases, in relapse and remission (n = 60 in each group), were studied and their results were compared with those of an equal number of age and sex matched normal children free from any renal disease. During relapse, it was noticed that the viscosity parameters, viz. plasma viscosity, red cell rigidity and whole blood viscosity, were deranged when compared to the values obtained in the remission period. These observations were statistically analyzed using t-test with the level of significance p = 0.05. It was also noted that serum/plasma biochemistry played an important role with regards to the fluidity of blood. During relapse period, fibrinogen level was significantly high, which persisted at a high level even during remission when compared to normal controls. The high cholesterol and triglyceride levels during relapse were responsible for a high plasma viscosity, increased red cell rigidity and thereby contributed directly to a marked increase in whole blood viscosity. Total protein and albumin levels were significantly decreased during relapse when compared to remission period. Hence, hemorheological parameters can be used for early detection of cases prone to relapse and could be of prognostic significance.

Blood Viscosity↗

PubMed1998

The diagnostic relevance of red cell rigidity.

Red cell rigidity is an important hemorheological parameter determining the passage of erythrocyte through narrow capillaries and the reduction of blood viscosity under high shear rates. The changes in red cell rigidity in various diseases of altered blood flow - hypertension (HT), diabetes mellitus (DM), myocardial infarction (MI) and cerebrovascular accidents (CVA), using equal sample sizes of 25 each, have been analysed in this paper. One of the essential elements of red cell rigidity is the structural and functional properties of erythrocyte membrane which, in turn, is determined by the membrane biochemistry. Since cholesterol-rich erythrocytes have increased rigidity, the serum cholesterol and triglycerides levels have been monitored in order to detect the extent to which they affect red cell rigidity. No significant change in red cell rigidity have been found in CVA. RBC rigidity is found to be significantly increased in the other diseases. Significant increase in triglyceride levels have been found in all the diseases studied. Cholesterol levels were significantly increased in all diseases except CVA. Hence, increased cholesterol levels have been found to consistently cause a simultaneous increase in RBC rigidity. Triglycerides levels, on the other hand, have not shown a consistent change with changes in RBC rigidity, but have been shown to be a more sensitive marker for early detection of diseased status.

Blood Viscosity↗