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Biomedical subjects

S Chakrabarti

Publications and source records attributed to S Chakrabarti.

At least 163 records · Page 9Linked to original sources
PubMed1999

Insulin B-chain reactive CD4+ regulatory T-cells induced by oral insulin treatment protect from type 1 diabetes by blocking the cytokine secretion and pancreatic infiltration of diabetogenic effector T-cells.

The mechanism of protection from type 1 diabetes conferred by regulatory T-cells induced by oral insulin treatment of NOD mice is not well understood. We demonstrate that oral insulin feeding of NOD mice induces the function of insulin B-chain reactive CD4+ regulatory T-cells, which compete with diabetogenic effector T-cells for the recognition of insulin in NOD.Scid recipient mice. These effector T-cells become deprived of interleukin (IL)-2 and interferon (IFN)-gamma and are unable to expand and migrate to the pancreas. Type 1 diabetes-protective splenic regulatory T-cells secrete relatively little transforming growth factor (TGF)-beta1, suggesting that TGF-beta may not contribute to the inactivation of effector T-cells in NOD.Scid recipients. The observed preferential infiltration of insulin-reactive regulatory T-cells rather than effector T-cells in the pancreas results in a nondestructive insulitis that correlates with an increased intrapancreatic expression of macrophage inflammatory protein-1beta. Thus, oral insulin therapy overcomes a deficiency in regulatory T-cells and protects against type 1 diabetes by inducing insulin B-chain reactive regulatory T-cells to block cytokine secretion and migration of diabetogenic effector T-cells to the pancreas. Our data emphasize that continuous oral insulin feeding over a prolonged period is required to prevent type 1 diabetes.

Administration, Oral↗
PubMed1999

Postictal mania following primary generalized seizures.

A 29 year old male with primary generalized seizures for 13 years stopped his anticonvulsants leading to an increase in seizure frequency. Five months later he developed a severe manic episode postictally which responded well to a combination of neuroleptics and anticonvulsants. Postictal psychoses usually follow complex partial seizures. Manic episodes are uncommon. This case had some similarities with other cases of postictal psychoses reported previously. It underlines the need for further investigation of several facets of this complex relationship between mood disorders and epilepsy.

Adult↗
PubMed1999

Evaluation of hematological and hepatorenal functions of methanolic extract of Moringa oleifera Lam. root treated mice.

Methanolic extract of M. oleifera root was found to contain some alkaloids (total alkaloid 0.2%). Effects of multiple weekly (35, 46, 70 mg/kg) and daily therapeutic (3.5, 4.6, 7.0 mg/kg) i.p. doses of the crude extract (CE) on liver and kidney functions and hematological parameters in mice were studied. No alteration in hematological and biochemical parameters at low and moderate dose level of daily and low dose level of weekly treatment of the extract was observed. However, the extract at moderate dose level in weekly treatment changed serum aminotransferase and plasma cholesterol levels significantly. High dose in addition to the above parameters changed total bilirubin, non protein nitrogen, blood urea and plasma protein. High dose of daily treatment and moderate and high dose of weekly treatment of CE increased WBC count and decreased clotting time significantly. The results indicate that the weekly moderate and high dose (> 46 mg/kg body wt.) and daily/therapeutic high dose (7 mg/kg) of CE affects liver and kidney functions and hematological parameters whereas the weekly dose (3.5 mg/kg) and low and moderate daily/therapeutic dose (3.5 and 4.6 mg/kg) did not produce adverse effects on liver and kidney functions.

Animals↗
PubMed1999

The prevalence of antiphospholipid antibodies in cases of recurrent pregnancy loss.

Antiphospholipid antibodies (aPL) are a diverse family of autoantibodies reactive against negatively charged phospholipid-protein complexes. The clinically significant members include lupus anticoagulant (LA), anticardiolipin antibody (aCL) and reaginic antibodies causing biological false positive (BFP) venereal disease laboratory test (VDRL). Although detected in various clinical scenarios, unexplained fetal loss in women of reproductive age group is the commonest association. Fifty pregnant women of first and second trimester with a history of two or more unexplained pregnancy losses were studied for the presence of LA, aCL and reaginic antibodies. Thirty pregnant women of the same trimester without any history of fetal loss were taken as control. LA was detected in nine (18%) cases and aCL in 12 (24%) cases of the study group. The control group was negative for any autoantibody. The prevalence of aPL in the study group found to be statistically significant. Detection of aPL must be considered in women with previous pregnancies complicated by unexplained fetal wastage.

Abortion, Habitual↗
PubMed1999

Psychogenic cough--a case report.

A case study of a 12 year old child evidencing psychogenic cough is presented. The importance of behavioral and family factors in maintaining such cough and an integrated psycho-behavioral approach at management are described. A 1 year follow-up revealed a rapid and complete elimination of psychogenic cough and good adjustment.

Behavior Therapy↗
PubMed1998

C--H...O hydrogen bond involving proline residues in alpha-helices.

Despite proline being assumed to be a helix-breaker, a large number of alpha-helices are found to contain Pro in globular as well as membrane proteins. Proline has no free NH group and therefore cannot form the conventional intra-helical NH.O=C hydrogen bond. An analysis of known protein structures has shown that the Cdelta protons are involved in C--H...O hydrogen bonds, usually two, with the carbonyl groups in the preceding turn of the helix (four and three residues away). These interactions satisfy the hydrogen bond forming potential of the carbonyl groups, which would otherwise, in the case of membrane-bound helices, be unfavorably exposed to hydrophobic surroundings. Depending on the type (based on the location of the carbonyl group, usually three, four or five residues preceding Pro) of C--H...O interactions, the kink in the helix may be of different magnitude. The puckering (UP or DOWN) of the pyrrolidine ring of Pro residues is controlled by the type of the C--H...O bond present, and the form that provides a better hydrogen bond geometry is preferred.

Hydrogen Bonding↗
PubMed1998

Interaction of the antitumor antibiotic chromomycin A3 with glutathione, a sulfhydryl agent, and the effect upon its DNA binding properties.

Chromomycin A3 (CHR), an anticancer antibiotic, blocks macromolecular synthesis via reversible interaction with DNA only in the presence of divalent cations like Mg2+. In the absence of DNA, the antibiotic forms a dimer: Mg2+ complex [(CHR)2Mg2+]. It is the DNA-binding ligand. The antibiotic has potential reactive centers that could interact with GSH, the most abundant non-protein thiol in eukaryotic cells and a putative cofactor involved in the activation of many antibiotics in vivo. To understand the mode of action of CHR in vivo, we studied the interactions of CHR and the (CHR)2Mg2+ complex with GSH and the association of the resultant complexes with DNA by means of absorption, fluorescence, and circular dichroism spectroscopy. The novel finding was that GSH interacts non-covalently with CHR without a chemical modification of the antibiotic. The interaction was reversible in nature. The results are reported in two parts: the interaction of CHR with GSH in the absence and presence of Mg2+, and the effect of this interaction on the DNA-binding properties of the antibiotic. CHR forms a single type of complex with GSH. In contrast, (CHR)2Mg2+ forms two different types of complexes with GSH: a low GSH complex at approximately 12 mM GSH and a high GSH complex at > or = 16 mM GSH. Binding and thermodynamic parameters for the reversible association of the complexes with DNA demonstrated that they bind differently to the same DNA. The thermodynamic parameters indicate that the presence of GSH alters the mode of binding of the (CHR)2Mg2+ complex with DNA. The (CHR)2Mg2+ complex binds to DNA via an entropy-driven process, whereas in the presence of GSH the association is enthalpy-driven. The significance of these results in the understanding of the molecular basis of action of the antibiotic is discussed.

Antibiotics, Antineoplastic↗
PubMed1998

Effect of major histocompatibility complex expression on murine intestinal graft survival.

BACKGROUND: Clinical intestinal transplantation has been plagued by frequent and severe graft rejection. It has been proposed that the major histocompatibility complex (MHC) antigens might play a critical role in this process owing to their extensive expression on enterocytes and mucosa-associated immune cells. METHODS: The present study examined the role of MHC antigens in intestinal graft rejection using MHC class I-deficient and MHC class II-deficient donors. RESULTS: Grafts with normal MHC expression were rejected by 9 days, whereas survival was prolonged to 14 days in the MHC class II-deficient grafts (P=NS) and to 20 days in the MHC I-deficient grafts (P<0.002). In all groups, early rejection was characterized by (1) increased crypt cell apoptosis, as detected by the terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling (TUNEL) technique of in situ labeling; and (2) the increased expression of perforin and a CD8 phenotype in the graft-infiltrating cells. CONCLUSIONS: These data suggest that MHC antigens, CD8-positive T cells, and perforin-expressing cells contribute to intestinal graft rejection. Apoptosis of the progenitor epithelial crypt cells during early intestinal rejection may impair the gut's ability to regenerate and repair mucosal damage.

Animals↗
PubMed1998

Bioaccumulation of manganese and its toxicity in feral pigeons (Columba livia) exposed to manganese oxide dust (Mn3O4).

Manganese tetroxide (Mn3O4) is a product from the combustion of methylcyclopentadienyl manganese tricarbonyl. Exposure to high levels of manganese can lead to serious health effects especially to the central nervous and respiratory systems. Very few studies on the effects of long-term low level exposure to Mn3O4 have been reported. The present study was therefore conducted to examine the bioaccumulation and toxicity of manganese in various organs of feral pigeons (Columba livia) when exposed to low levels of Mn3O4 via inhalation and hence to find any possible relationship between these two parameters. A total of 22 pigeons was exposed to 239 micrograms/m3 of manganese for 7 h/day, 5 days/week for 5, 9, and 13 consecutive weeks. Manganese concentrations in various tissues, e.g., brain (mesencephalon), lung, liver, intestine, pancreas, kidney, muscle, bone, and whole blood, were measured by neutron activation analysis. Various biochemical parameters in blood, e.g., hematocrit, total proteins, glucose, uric acid, alanine aminotransferase, total iron, blood urea nitrogen and triglycerides, were also measured. Manganese concentrations in brain, lung, and bone were significantly higher in Mn3O4-exposed pigeons (0.59, 0.58, and 3.02 micrograms wet tissue, respectively) than in the control group (0.46, 0.19, 1.74 micrograms/g wet tissue, respectively). However, except for total proteins such exposure did not produce any changes in various biochemical parameters which were within the normal values. Thus these results have shown that, despite significant bioaccumulation of manganese in some tissues, no significant toxic effects could be seen.

Administration, Inhalation↗
PubMed1998

Genotypic/phenotypic correlations in genetic hemochromatosis: evolution of diagnostic criteria.

BACKGROUND & AIMS: The identification of a candidate gene for hereditary hemochromatosis in 69%-100% of patients with hemochromatosis has resulted in a diagnostic genotypic test (C282Y). The aim of this study was to reassess the phenotypic diagnostic criteria for hemochromatosis in patients homozygous for the C282Y mutation of the HFE gene. METHODS: Transferrin saturation, ferritin, hepatic iron index, and iron removed by venesection were studied in C282Y++ homozygotes and C282Y-- putative homozygotes. RESULTS: Patients were homozygous for the C282Y mutation in 122 of 128 cases (95%). In C282Y homozygotes, the results were as follows: hepatic iron index, >1.9 in 91.3%; transferrin saturation, >55% in 90%; serum ferritin, >300 microg/L in 96% of men and >200 microg/L in 97% of women; and iron removed, >5 g in 70% of men and 73% of women. There were four homozygotes for C282Y with no biochemical evidence of iron overload. CONCLUSIONS: The sensitivity of the phenotypic tests in decreasing order was as follows: serum ferritin, hepatic iron index, transferrin saturation, and iron removed by venesection. Although the genetic test is useful in the diagnostic algorithm, this study has shown both iron-loaded patients without the mutation and homozygous patients without iron overload.

Adult↗
PubMed1998

Apoptosis in thyroid neoplasms: relationship with p53 and bcl-2 expression.

AIM: Cell gain and loss occurs concurrently in tumours. Apoptosis may play a major role in determining the growth and aggressiveness of the tumours. The aim of this study was to investigate whether apoptosis is related to the degree of differentiation and expression of mutated p53 and bcl-2 in thyroid neoplasms. METHODS AND RESULTS: Fifty-three thyroid tumours of various histological types and 10 multinodular goitres were investigated semiquantitatively for the presence of apoptosis using a DNA end ligase method. Simultaneously, quantitative immunostaining was performed for bcl-2 and p53, two known regulators of apoptosis. No apoptosis was detected in normal thyroid tissues, multinodular goitres and in four follicular adenomas, all of which were positive for bcl-2. On the other hand, two anaplastic and one insular carcinomas showed marked increase in apoptosis along with intense p53 positivity and bcl-2 negativity. The majority of the follicular carcinomas showed results similar to that of follicular adenomas. No apoptosis was detected in 41% of papillary carcinomas, the majority of these being p53 negative and bcl-2 positive. Forty-four per cent of the papillary carcinomas demonstrated low apoptosis rate, with variable bcl-2 positivity and mostly negative for p53. Fifteen per cent of papillary carcinomas showed a high apoptosis rate. They were p53 negative and mostly negative for bcl-2. The differences of staining in various tumours with respect to p53, bcl-2 and apoptosis were statistically significant. Correlation analysis demonstrated a significant relationship between apoptosis and bcl-2 expression in thyroid tumours (P < 0.001), whereas no relationship was seen with p53. CONCLUSION: These data suggest that bcl-2 expression in thyroid neoplasms is related to apoptosis, p53 expression is associated with high grade thyroid tumours, but may not be important in the apoptotic pathways in all thyroid tumours.

Apoptosis↗
PubMed1998

Metallothionein and apoptosis in primary human hepatocellular carcinoma and metastatic adenocarcinoma.

AIMS: Differences in expression of metallothionein (MT) have been reported in various human tumours. MT is mainly expressed in proliferating epithelial tumour cells but in human hepatocellular carcinoma (HCC) there is only a minimal expression of MT. Since MT is a zinc binding protein and certain inducers of MT including zinc play a role in apoptosis, studies were undertaken to compare the expression of MT and the presence of apoptotic cells (APPC) in both primary HCC and metastatic adenocarcinoma. METHODS AND RESULTS: Histological sections of 13 cases of primary HCC and eight cases of metastatic adenocarcinoma were obtained from archival samples. They were stained for MT using a polyclonal antibody which crossreacts readily with human MT and for APPC by the TUNEL technique. Normal human liver had consistent MT staining with no detectable APPC. The primary HCC showed moderate MT staining with a small number of APPC while metastatic adenocarcinoma showed no MT staining with a large number of APPC. CONCLUSIONS: These results suggest a relationship between absence of MT and appearance of APPC in human liver tumours, especially in metastatic adenocarcinomas.

Adenocarcinoma↗
PubMed1998

Distinct differences between morphine- and [D-Ala2,N-MePhe4,Gly-ol5]-enkephalin-mu-opioid receptor complexes demonstrated by cyclic AMP-dependent protein kinase phosphorylation.

The present study demonstrates a conditional, agonist-dependent phosphorylation of the mu-opioid receptor (MOR-1) by cyclic AMP-dependent protein kinase (PKA) in membrane preparations of MOR-1-transfected neuroblastoma Neuro2A cells. Opioid agonist-dependent phosphorylation occurs in a time- and concentration-dependent manner (EC50 approximately 40 nM) and can be abolished by the receptor antagonist naloxone. Stoichiometric analysis indicates incorporation of a maximum of 6 mol of phosphate/mol of receptor in the presence of 1 microM morphine and 6 nM PKA. Although morphine and related alkaloids as well as some peptide agonists (PLO17 and beta-endorphin) stimulated phosphorylation of MOR-1 by PKA, the potent mu-opioid-selective peptide [D-Ala2,N-MePhe4,Gly-ol5]-enkephalin (DAMGO) or other enkephalin analogues such as [D-Ala2]-Met5-enkephalinamide (DALA), [D-Ala2,D-Leu5]-enkephalin (DADLE), and Met5-enkephalin had no effect. The lack of the effect of DAMGO on MOR-1 phosphorylation state was evident also after chronic pretreatment. These results suggest the existence of different agonist-dependent conformations of MOR-1. Furthermore, phosphorylation may be a useful parameter with which to identify different agonist-receptor conformations.

Analgesics, Opioid↗
PubMed1998

Augmented retinal endothelin-1, endothelin-3, endothelinA and endothelinB gene expression in chronic diabetes.

PURPOSE: Endothelins (ETs) belong to a family of vasoactive peptides implicated in several disorders of the microvasculature. In the present study, we investigated ET-1 and ET-3 peptide mRNAs and ETA, ETB receptor mRNAs in the retina of diabetic BB/W rats and age-matched, non-diabetic control animals, following six months of diabetes. METHODS: Total mRNA was extracted from each retina and was subjected to reverse transcriptase polymerase chain reaction for ET-1, ET-3, ETA and ETB. Simultaneously, beta-globin was amplified and used as a housekeeping gene. The products were analyzed on agarose gels and the specificity of the amplification was established by hybridization with amplification-specific biotinylated oligoprobes. For quantification, the products from the linear phase of amplification were subjected to serial dilution slot-blot hybridization and densitometry. RESULTS: ETs and their receptor mRNA expressions were present in the retina. Retinas from the diabetic animals showed significant increases in ET-1, ET-3 ET(A), ET(B) mRNA expressions compared to those from control rats. CONCLUSIONS: These findings indicate that retinal ET-1, ET-3, ET(A) and ET(B) mRNA expression in increased in the chronically diabetic BB/W rat. Augmented gene expression of ETs and their receptors potentially may be of importance in the pathogenesis of retinal microangiopathy in diabetes.

Animals↗
PubMed1998

Fluorescent labelling of abasic sites: a novel methodology to detect closely-spaced damage sites in DNA.

PURPOSE: To test the ability of a new fluorescent reagent to label abasic sites in DNA and to use fluorescent energy transfer as a measure of closely-spaced abasic sites in DNA. MATERIALS AND METHODS: A fluorescein-conjugated hydroxylamine derivative (FARP, 5-(((2-(carbohydrazino)-methyl)thio)acetyl)aminofluorescein, aminooxyacetyl hydrazide) that reacts covalently with open chain aldehydes in DNA has been synthesized. Upon depurination of plasmid DNA and reaction with FARP a stable oxime bond is formed between FARP and the generated open chain aldehydes. RESULTS: By independently quantitating the generated abasic sites, it is shown that most of the generated abasic sites under acidic conditions become fluorescently labelled. The limit of sensitivity with the fluorometer used is approximately 90 femtomole abasic sites, corresponding to 1 abasic site per 17000 base pairs. DNA can be fluorescently labelled over a wide range of FARP:base pair ratios following different extent of depurination, and fluorescent loadings of 1 FARP:20000 base pairs up to 1 FARP:10 base pairs are demonstrated. The heavily labelled samples display significant fluorescence quenching due to the proximity of abasic sites labelled with FARP, that undergo fluorescence energy transfer. Treatment of heavily labelled DNA samples with nuclease P1 results in an increase in fluorescence due to the release of the fluorescent labels in the solution. The relative increase in fluorescence is a quantitative measure of the proximity of labelled abasic sites. Furthermore it is shown that if only 1% of DNA contains abasic sites generated in close proximity (within 10-20 base pairs or less of each other) the resulting quenching is significant enough to detect, even if the rest of the DNA contains isolated abasic sites. CONCLUSIONS: The present approach constitutes a novel fluorescence-based method to detect abasic sites in nucleic acids and demonstrates the feasibility of detecting the presence of closely-spaced damage sites in DNA via fluorescence energy transfer. The technique also comprises a general and convenient method to fluorescently label nucleic acids without introducing strand breaks as a result of the labelling procedure.

Aldehydes↗
PubMed1998

Continuous detection of radiation or metal generated hydroxyl radicals within core chromatin particles.

PURPOSE: The aim of this work was to adapt a recently developed fluorometric method for use in the detection of hydroxyl radical (HO.) generated in the immediate vicinity of chromatin core particles reconstituted from pUC19 plasmid DNA and isolated core histones. MATERIALS AND METHODS: The procedure followed involves labelling nucleosomal histones with SECCA, a non-fluorescent coumarin derivative that generates the fluorescent 7-hydroxy-SECCA after reaction with HO.. Core particles are formed using histones and pUC19 DNA in a salt-dialysis procedure. RESULTS: Electron microscopy and micrococcal nuclease digestion are consistent with successful formation of core particles. No significant differences between core particle formation in the unlabelled and SECCA-labelled samples were detected. Exposure to HO. generated by radiation or copper--ascorbic acid--hydrogen peroxide results in a gradual induction of fluorescence. Studies using dimethyl sulphoxide (DMSO) demonstrate that, unlike HO. produced by radiation, the majority of HO. generated by copper--ascorbic acid--hydrogen peroxide occurs primarily in the immediate vicinity of core particles and DNA and cannot be scavenged. CONCLUSIONS: The present procedure demonstrates the feasibility to quantitate HO. generated by several agents in the immediate vicinity of nucleosomes (chromatin-associated HO.) or associated with specific regions within the genome.

Animals↗