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Biomedical subjects

S Chatterjee

Publications and source records attributed to S Chatterjee.

At least 109 records · Page 6Linked to original sources
PubMed1999

Targeting of the mammalian nucleoporin p62 to the nuclear envelope in the yeast Saccharomyces cerevisiae and HeLa cells.

We have analyzed the sorting of the mammalian nucleoporin p62 in human culture cells and in the yeast Saccharomyces cerevisiae. To this end, gene fusions were generated that carry Aequorea victoria green fluorescence protein and defined portions of p62. Upon transient gene expression fluorescent fusion proteins were localized in HeLa cells. Likewise, fusion proteins were studied in S. cerevisiae using wild-type as well as mutant cells that cluster nuclear pore complexes. Our results demonstrate that evolutionarily distant organisms, such as humans and yeasts, recognize the same sequence elements of p62 for sorting to the nuclear envelope. Specifically, the entire sequence of p62 or its complete C-terminal domain targeted fusion proteins to the nuclear membranes. In contrast, truncations of the C-terminal domain or the N-terminal segment of p62 failed to associate with the nuclear envelope in either organism. In HeLa cells overexpression of several p62-containing fusion proteins resulted in nuclear fragmentation. The C-terminal domain of p62 caused this effect, and amino acid residues 477 to 525 were sufficient to induce aberrant nuclei. Thus, overexpression of 49 amino acid residues located at the C-terminal tail of p62 interferes with the nuclear integrity in human culture cells.

Blotting, Western↗
PubMed1999

Bronchodilatory and anti-allergic effect of PulmoFlex--a proprietary herbal formulation.

PulmoFlex, a poly-herbal anti-asthmatic formulation has been reported to possess antihistaminic, mast cell stabilizing, anti-anaphylactic and antiallergic properties in experimental animals and clinical trials. The present study was undertaken to determine the effect of PulmoFlex on isolated perfused rat lung. The lung tissues were perfused at a pressure of 50 mmHg using oxygenated Krebs solution at 37 degrees C. PulmoFlex (1 & 2 mg/ml) increased the pulmonary perfusion flow indicating its bronchodilatory action. PulmoFlex (500 mcg) significantly prevented histamine (50 mcg), acetylcholine (50 mcg) and C-48/80 (10 mcg), induced bronchoconstriction indicating its antihistaminic, anticholinergic and mast cell stabilizing actions on pulmonary vascular beds and bronchioles, respectively. Lung tissue of sensitized (BSA) rats treated with PulmoFlex (20 mg/kg x 10 days) showed better perfusion following Ex vivo antigenic challenge as compared to untreated rats. This indicates the possibility of suppression of IgE mediated immune reaction by PulmoFlex. Thus, the present findings, suggest that PulmoFlex acts as an antiasthmatic by its bronchodilatory, membrane stabilizing, antihistaminic, anticholinergic and immunomodulatory (reaginic antibody mediated) effects.

Animals↗
PubMed1999

Electrophysiological evidence of cortical fusion in children with early-onset esotropia.

PURPOSE: To investigate sensory fusion responses in infants and children with early-onset esotropia to gain insights into the sequence of events that leads to strabismus. METHODS: Sensory fusion was tested by measuring visual evoked potential (VEP) responses to dynamic random dot correlograms (DRDCs) in a group of children (n = 23) with early-onset esotropia. Thirteen children were tested before surgical alignment, and 13 children were tested after surgical alignment (three children were tested before and after surgery). If the angle of strabismus was larger than 5 prism diopters, it was corrected with Fresnel prisms (Fresnel Prism and Lens, Scottsdale, AZ). RESULTS: Five (38%) of the 13 children who were tested before surgery showed detectable VEP responses to correlogram stimuli compared with 11 (85%) of the 13 children who were tested after surgical alignment. There were no significant statistical differences between VEP responses to DRDCs from the postsurgery group and VEP responses from an age-matched control group with normal binocular vision. CONCLUSIONS: The presence of cortical sensory fusion in children with early-onset esotropia suggests that a congenital defect of sensory fusion cannot be the root cause of esotropia in most children. The data suggest that sensory fusion, when measured by VEP responses to DRDCs, is more robust than stereopsis to abnormal binocular experience and support the notion that pathways processing correlated/anticorrelated stimuli may not completely overlap with pathways processing disparity information.

Child↗
PubMed1998

Lactosylceramide mediates tumor necrosis factor-alpha-induced intercellular adhesion molecule-1 (ICAM-1) expression and the adhesion of neutrophil in human umbilical vein endothelial cells.

The endothelial expression of adhesion molecules by proinflammatory cytokines such as tumor necrosis factor-alpha (TNF-alpha) has been suggested to contribute to the initiation of atherosclerotic plaque formation. Since lactosylceramide (LacCer) accumulates in large quantities in human atherosclerotic plaque, we have explored its role in TNF-alpha-induced expression of intercellular adhesion molecule-1 (ICAM-1) in human umbilical vein endothelial cells and their consequent adhesion to polymorphonuclear leukocytes (PMNs). We found that TNF-alpha increased LacCer synthesis by way of stimulating the activity of UDP-galactose:glucosylceramide beta(1-->4)-galactosyltransferase in a time-dependent fashion. The TNF-alpha-induced expression of ICAM-1 was abrogated by D-1-phenyl-2-decanoylamino-3-morpholino-1-propanol (D-PDMP), an inhibitor of UDP-galactose:glucosylceramide beta(1-->4)-galactosyltransferase. However, the addition of LacCer reversed the D-PDMP effect on TNF-alpha-induced ICAM-1 expression in human umbilical vein endothelial cells. Northern hybridization analysis of mRNA levels and enzyme-linked immunosorbent assays revealed that LacCer (5 microM) specifically stimulated ICAM-1 at both the transcriptional and translational levels. This was accompanied by the adhesion of PMNs, which was visualized by confocal microscopy. Further studies revealed that LacCer stimulated the endogenous generation of superoxide radicals (O-2) about 5-fold compared with the control by specifically activating plasma membrane-associated NADPH-dependent oxidase. This phenomenon was blocked by the antioxidant N-acetyl-L-cysteine, pyrrolidine dithiocarbamate, and the NADPH oxidase inhibitor, diphenylene iodonium. Overexpression of endogeneous CuZn-superoxide dismutase via an adenoviral vector carrying cDNA for CuZn-superoxide dismutase, also inhibited LacCer-induced ICAM-1 expression in endothelial cells. In sum, our findings suggest that LacCer may play the role of a lipid second messenger in TNF-alpha-induced pathogenesis by activating an oxidant-sensitive transcriptional pathway that leads to the adhesion of PMNs to endothelial cells.

Antigens, CD↗
PubMed1998

Purification of a multipotent antideath activity from bovine liver and its identification as arginase: nitric oxide-independent inhibition of neuronal apoptosis.

Catalase is an antioxidant enzyme that has been shown to inhibit apoptotic or necrotic neuronal death induced by hydrogen peroxide. We report the purification of a contaminating antiapoptotic activity from a commercial bovine liver catalase preparation by following its ability to inhibit apoptosis when applied extracellularly in multiple death paradigms. The antiapoptotic activity was identified by protein microsequencing as arginase, a urea cycle and nitric oxide synthase-regulating enzyme, and confirmed by demonstrating the presence of antiapoptotic activity in a >97% pure preparation of recombinant arginase. The pluripotency of recombinant arginase was demonstrated by its ability to inhibit apoptosis in multiple paradigms including rat cortical neurons induced to die by glutathione depletion and oxidative stress, by 100 nM staurosporine treatment, or by Sindbis virus infection. The protective effects of arginase in these apoptotic paradigms, in contrast to previous studies on excitotoxic neuronal necrosis, are independent of nitric oxide synthase inhibition. Rather, arginase-induced depletion of arginine leads to inhibition of protein synthesis, resulting in cell survival. Because inhibitors of nitric oxide synthesis and of protein synthesis have been shown to decrease necrotic and apoptotic death, respectively, in animal models of stroke and spinal cord injury, arginine-depleting enzymes, capable of simultaneously inhibiting protein synthesis and nitric oxide generation, may be propitious therapeutic agents for acute neurological diseases. Furthermore, our results suggest caution in attributing the cytoprotective effects of some catalase preparations to catalase.

Amino Acid Sequence↗
PubMed1998

137Cesium-induced chromosome aberrations analyzed by fluorescence in situ hybridization: eight years follow up of the Goiânia radiation accident victims.

The radiation accident in focus here occurred in a section of Goiânia (Brazil) where more than a hundred individuals were contaminated with 137Cesium on September 1987. In order to estimate the absorbed radiation doses, initial frequencies of dicentrics and rings were determined in 129 victims [A.T. Ramalho, PhD Thesis, Subsidios a tecnica de dosimetria citogenetica gerados a partir da analise de resultados obtidos com o acidente radiologico de Goiânia, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil, 1992]. We have followed some of these victims cytogenetically over the years seeking for parameters that could be used as basis for retrospective radiation dosimetry. Our data on translocation frequencies obtained by fluorescence in situ hybridization (FISH) could be directly compared to the baseline frequencies of dicentrics available for those same victims. Our results provided valuable information on how precise these estimates are. The frequencies of translocations observed years after the radiation exposure were two to three times lower than the initial dicentrics frequencies, the differences being larger at higher doses (>1 Gy). The accuracy of such dose estimates might be increased by scoring sufficient amount of cells. However, factors such as the persistence of translocation carrying lymphocytes, translocation levels not proportional to chromosome size, and inter-individual variation reduce the precision of these estimates.

Brazil↗
PubMed1998

Sphingomyelinase activity in human platelets.

The sphingolipid metabolites, ceramide, sphingosine, and sphingosine-1-phosphate, may be involved in several signalling pathways and may regulate cell functions such as cell growth, secretion, differentiation, and apoptosis. During activation of human platelets by thrombin, sphingosine-1-phosphate is released from platelets and can potentiate their aggregation. Thrombin also causes an increase in platelet sphingosine levels. Since these molecules can be derived from sphingomyelin, we have determined whether platelets possess sphingomyelinase and whether this enzyme is regulated during platelet function. Using radioactive sphingomyelin as substrate, we assayed sphingomyelinase activity over the range of pH 4 to 10 and observed optimal activity at pH 5.0-5.5. Little activity was found at neutral or alkaline pH, and the presence of Mg++, Ca++, Zn++, or EDTA in the reaction mixture had little effect on the pH profile. Activation of platelets by thrombin or ADP had no effect on sphingomyelinase activity, but thrombin caused secretion of the acid-sphingomyelinase activity into the media. Thus, human platelets contain an acid-sphingomyelinase which is secreted during thrombin-induced platelet activation.

Acid-Base Equilibrium↗
PubMed1998

Lactosylceramide stimulates human neutrophils to upregulate Mac-1, adhere to endothelium, and generate reactive oxygen metabolites in vitro.

Glycosphingolipids (GSLs) and their metabolites play important roles in a variety of biological processes. We have previously reported that lactosylceramide (LacCer), a ubiquitous GSL, stimulates NADPH oxidase-dependent superoxide generation by aortic smooth muscle cells and their consequent proliferation. We postulated that LacCer may upregulate adhesion molecules on human polymorphonuclear leukocytes (hPMNs), perhaps also via NADPH oxidase-dependent reactive oxygen metabolite (ROM) generation. Incubation of hPMNs with LacCer upregulated CD11b/CD18 (Mac-1) and CD11c/CD18, as determined by fluorescence-automated cell sorting. LacCer also stimulated these hPMNs to generate superoxide via NADPH oxidase, as determined by lucigenin-enhanced chemiluminescence. However, the upregulation of Mac-1 by LacCer did not itself appear to be mediated by ROMs, since neither an antioxidant nor an NADPH oxidase inhibitor substantially inhibited the Mac-1 upregulation. However, this Mac-1 upregulation was significantly inhibited by two disparate phospholipase A2 (PLA2) inhibitors. Moreover, LacCer induced arachidonic acid metabolism, which was inhibited by the PLA2 inhibitors, but not by an NADPH oxidase inhibitor. To evaluate the effect of LacCer on hPMN adhesion to endothelium, hPMNs stimulated with LacCer were allowed to adhere to unstimulated human endothelial cell monolayers. LacCer stimulated hPMN adhesion to endothelial cells, which was blocked by anti-CD18 and by the PLA2 inhibitors. We conclude that LacCer stimulates both Mac-1 upregulation and superoxide generation in hPMNs but that ROMs are not the upstream signal for Mac-1 upregulation. This mechanism may well be relevant to acute endothelial injury in inflammation and other pathological conditions.

Antigens, CD↗
PubMed1998

Tumor necrosis factor-alpha stimulates the maturation of sterol regulatory element binding protein-1 in human hepatocytes through the action of neutral sphingomyelinase.

The mechanism by which genes involved in cholesterol biosynthesis and import are preferentially up-regulated in response to sterol depletion was elucidated with the cloning of sterol regulatory element binding protein-1 (SREBP-1). SREBP-1 is a transcription factor whose entry into the nucleus is gated by sterol-regulated proteolysis. We have investigated the role of tumor necrosis factor-alpha (TNF-alpha) as a mediator of SREBP-1 maturation in human hepatocytes. TNF-alpha is capable of inducing SREBP-1 maturation in a time- and dose-dependent manner that is consistent with the kinetics of TNF-alpha-mediated activation of neutral sphingomyelinase (N-SMase). Antibodies to N-SMase inhibit TNF-alpha-induced SREBP-1 maturation suggesting that N-SMase is a necessary component of this signal transduction pathway. Ceramide, a product of sphingomyelin hydrolysis, is also capable of inducing SREBP-1 maturation. The mature form of SREBP-1 generated by TNF-alpha, sphingomyelinase or ceramide treatment translocates to the nucleus and binds the sterol regulatory element. This promotes transcription of the gene upstream of the sterol regulatory element. A unique finding of our studies is that ceramide stimulated SREBP-1 maturation even in the presence of cholesterol and 25-hydroxycholesterol both of which are known suppressors of SREBP-1 maturation. Our findings indicate that ceramide-mediated maturation of SREBP-1 maturation is a novel sterol-independent mechanism by which cholesterol homeostasis may be regulated.

Antibodies↗
PubMed1998

Comparison of antiviral compounds against human herpesvirus 6 and 7.

Four classes of antiviral compounds were evaluated for inhibitory activity against two variants of human herpesvirus 6 (HHV-6A and -6B) and human herpesvirus 7 (HHV-7). These included: (1) a pyrophosphate analog, phosphonoformic acid (PFA); (2) beta-guanine analogs, 9-(2-hydroxyethoxymethyl)guanine (acyclovir or ACV), 9-[(1,3-dihydroxy-2-propoxy)methyl]guanine (ganciclovir or GCV) and 9-(4-hydroxy-3-hydroxy-3-hydroxymethylbutylyl)guanine (penciclovir or PCV); (3) acyclic nucleoside phosphonates, (S)-1-[(3-hydroxy-2-phosphonylmethoxy)propyl]cytosine [cidofovir or (S)-HPMPC] and its cyclic derivative (S)-cyclic-HPMPC (cHPMPC), 9-[[2-hydroxy-1-phosphonomethoxy)ethoxy]methyl]guanine (HPMEMG) and 9-[(2-phosphonylmethoxy)ethyl]-2,6-diaminopurine (PMEDAP), and the seven other related compounds; and (4) a series of benzimidazole ribonucleosides, including 2-bromo-5,6-dichloro-1-(beta-D-ribofuranosyl)benzimidazole (BDCRB). End-point inhibitory concentration (EPC) and 50% effective inhibitory concentration (EC50) values were determined by a dot-blot antigen detection method in cord blood mononuclear cells infected with HHV-6A, HHV-6B or HHV-7 at a multiplicity of infection of 0.004 CCID50/cell. (S)-HPMPC and cHPMPC had an EC50 value of approximately 0.3 microg/ml for HHV-6A, 1.2 microg/ml for HHV-6B and 3.0 microg/ml for HHV-7. These compounds were the most active of those tested against each virus. The EC50 value of GCV for HHV-6A was 0.65 microg/ml, 1.33 microg/ml for HHV-6B, and >7 microg/ml for HHV-7. The EC50 values of ACV and PCV were approximately 6-8 microg/ml for HHV-6A, 16-24 microg/ml for HHV-6B and 121-128 microg/ml for HHV-7. These drugs were the least active. The sensitivity of HHV-7 to the guanine analogs was different from HHV-6, suggesting a difference in selectivity of specific viral enzymes.

Antiviral Agents↗
PubMed1998

Exploration of the importance of the P2-P3-NHCO-moiety in a potent di- or tripeptide inhibitor of calpain I: insights into the development of nonpeptidic inhibitors of calpain I.

Calpain I, an intracellular cysteine protease, has been implicated in the neurodegeneration following an episode of cerebral ischemia. In this paper, we report on a series of peptidomimetic ketomethylene and carbamethylene inhibitors of recombinant human calpain I (rh calpain I). Our study reveals that the -NHCO-moiety (possible hydrogen-bonding site) at the P2-P3 region of a potent tripeptide or a dipeptide inhibitor of calpain I is not a strict requirement for enzyme recognition. Compounds 7d ((R)-2-isobutyl-4-oxo-4-(9-xanthenyl)butanoic acid ((S)-1-formyl-3-methyl)butyl amide), 31 ((R)-2-isobutyl-4-(2-sulfonylnaphthyl)butyric acid ((S)1-formyl-3-methyl)butyl amide) and 34 ((R)-2-isobutyl-4-(2-sulfoxylnaphthyl)butyric acid ((S)-1-formyl-3-methyl)butyl amide) which exhibited good activity in the enzyme assay, also inhibited calpain I in a human cell line.

Calpain↗
PubMed1998

Aerobiologic and immunochemical studies on Borassus flabellifer pollen: evidence for a 90-kD allergen.

BACKGROUND: The pollen grains of Arecaceae have been proved to be a very common aeroallergen in India. Except for the pollen grains of Cocos nucifera, detailed information about the allergenicity of other dominant Indian palm pollen is not available. OBJECTIVES: To explore the aerobiologic and allergenic significance of the pollen of palmyra palm (Borassus flabellifer Linn.), one of the important and common palm trees in India, with a view to isolate and purify its major allergenic components. METHODS: The aerobiologic survey was performed continuously using Burkard volumetric and Rotorod samplers from July, 1994 to June, 1996 in a northern suburb of greater Calcutta. The allergenic potential of the pollen extract and different fractions were studied by skin prick tests (SPT). ELISA and ELISA inhibition experiments were performed with individual and pooled patient sera to detect the specific IgE level. By 2-step ammonium sulphate fractionation and gel filtration study, the allergic fraction Fr.IIA1 was isolated. Its molecular weight was determined by SDS-PAGE and homogeneity was confirmed by rocket and crossed immunoelectrophoresis using rabbit antisera. RESULTS: Pollen grains of B. flabellifer were found to be present in air from February to May and June contributing more than 7% of the total airborne pollen load of the study area. The pollen elicited maximum concentration at 19 to 20 hours in the evening and at a height of 4 m from ground level. Skin prick testing of 455 respiratory allergic patients with whole pollen extract exhibited 31.64% positive response. After 2-step ammonium sulphate fraction and gel filtration, a fraction (Fr.IIA1) having remarkable allergenicity was isolated. In native and SDS-PAGE, it was found as a single protein component of 90 kD and as homogeneous in RIE and CIE. The soluble protein-carbohydrate analysis indicated the probability of the component to be a glycoprotein. CONCLUSION: The aerobiologic, clinical, and immunochemical, studies demonstrated that the pollen of B. flabellifer is a dominant aeroallergen to cause respiratory trouble in the area where these trees grow. The isolated 90-kD component is one of the major allergens present in the pollen extract.

Adult↗
PubMed1998

Blocked hepatic-stage parasites and decreased susceptibility to Plasmodium berghei infections in BALB/c mice.

The BALB/c strain of mice is comparatively more resistant to sporozoite infections of Plasmodium berghei than the C57BL6 strain. Infection with live sporozoites results in the formation of small hepatic forms in the BALB/c liver that persist for as long as 6 days. Upon infection with small numbers of sporozoites, some of the parasites are destroyed in the liver whereas the rest persist as blocked forms. When larger numbers of sporozoites are injected the same process occurs but, in addition, a fraction of the liver-stage parasites complete full development and give rise to blood forms. Although blocked liver forms persist until day 6 post-infection they actually develop to only 24 h of maturity. The nature of these persistent forms is similar to those obtained from irradiated sporozoite immunization. There is a stronger cell proliferation to liver-stage antigens by spleen lymphocytes of irradiated sporozoite-immunized BALB/c mice in comparison to that of immunized C57BL6 mice suggesting that a stronger priming to liver-stage antigens, probably due to the presence of blocked hepatic forms in the liver for a longer period of time (as compared to C57BL6), occurs in the BALB/c mice. This could be a reason for the long-lasting protective memory observed in BALB/c mice.

Animals↗
PubMed1998

Immunohistochemical localization of constitutive and inducible cyclo-oxygenases in rat uterus during the oestrous cycle and pregnancy.

The uterus is a rich source of eicosanoids synthesized from arachidonic acid metabolism through the cyclo-oxygenase pathway. Two isoforms of cyclo-oxygenase, constitutive (COX-I) and inducible (COX-II) enzyme, have been reported. In the present study, we have immunohistochemically mapped the distribution of both COX-I and COX-II during various physiological states of the rat uterus. Uterine tissue was collected from female rats (a) during different stages of the oestrous cycle, (b) on days 1, 4, 8 and 18 of gestation, (c) after spontaneous delivery and (d) post partum, and fixed in Bouin's fixative. After paraffin wax embedding, 5-microm-thick sections were immunohistochemically stained by the ABC technique. Observation of the stained sections under the light microscope revealed that, in non-pregnant rat uterus, both COX-I and COX-II were abundantly expressed in the endometrium, with minimal staining observed in the myometrium. Staining was more prominent in epithelial cells than in stromal cells. The intensity of staining in epithelial cells was highest at pro-oestrus and oestrus and lowest at dioestrus. In pregnant rats, although the expression of both COX-I and COX-II was localized primarily to the endometrium with very little staining in the myometrium on day 1 of gestation, both of these enzymes were also apparent in myometrial cells by day 4 of gestation. The staining intensity of endometrial and myometrial cells increased further with the progression of gestation, being maximal at the time of spontaneous delivery. During the post-partum period, however, the staining intensity for both of the enzymes in endometrium and myometrium was decreased. Thus, our studies show that the expression of cyclo-oxygenases in various uterine cells vary with the oestrous cycle and with pregnancy. Furthermore, prominent increases in the expression of cyclo-oxygenases in the myometrium during pregnancy and parturition imply that the cyclo-oxygenase system in the myometrium may play a major role in modulating uterine contractility during pregnancy and labour.

Animals↗