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S Chatterjee

Publications and source records attributed to S Chatterjee.

At least 55 records · Page 3Linked to original sources
PubMed1997

Redox-regulated signaling by lactosylceramide in the proliferation of human aortic smooth muscle cells.

Previously, our laboratory reported that lactosylceramide (LacCer) stimulated human aortic smooth muscle cell proliferation via specific activation of p44 mitogen-activated protein kinase (MAPK) in the p21(ras)/Raf-1/MEK2 pathway and induced expression of the transcription factor c-fos downstream to the p44 MAPK signaling cascade (Bhunia A. K., Han, H., Snowden, A., and Chatterjee S. (1996) J. Biol. Chem. 271, 10660-10666). In the present study, we explored the role of free oxygen radicals in LacCer-mediated induction of cell proliferation. Superoxide levels were measured by the lucigenin chemiluminescence method, MAPK activity was measured by immunocomplex kinase assays, and Western blot analysis and c-fos expression were measured by Northern blot assay. We found that LacCer (10 microM) stimulates endogenous superoxide production (7-fold compared with control) in human aortic smooth muscle cells specifically by activating membrane-associated NADPH oxidase, but not NADH or xanthine oxidase. This process was inhibited by an inhibitor of NADPH oxidase, diphenylene iodonium (DPI), and by antioxidants, N-acetyl-L-cysteine (NAC) or pyrrolidine dithiocarbamate. NAC and DPI both abrogated individual steps in the signaling pathway leading to cell proliferation. For example, the p21(ras).GTP loading, p44 MAPK activity, and induction of transcription factor c-fos all were inhibited by NAC and DPI as well as an antioxidant pyrrolidine dithiocarbamate or reduced glutathione (GSH). In contrast, depletion of GSH by L-buthionine (S, R)-sulfoximine up-regulated the above described signaling cascade. In sum, LacCer, by virtue of activating NADPH oxidase, produces superoxide (a redox stress signaling molecule), which mediates cell proliferation via activation of the kinase cascade. Our findings may explain the potential role of LacCer in the pathogenesis of atherosclerosis involving the proliferation of aortic smooth muscle cells.

Acetylcysteine↗
PubMed1997

Interaction of Gal repressor with inducer and operator: induction of gal transcription from repressor-bound DNA.

Gal repressor inhibits transcription from the gal promoter (P1) when it binds to the cognate operator (O(E)). The repression is relieved by the presence of the inducer D-galactose. Compared with its interaction with free repressor, D-galactose binds to the repressor-operator complex with 10-fold reduced affinity as determined by fluorescence enhancement measurements. Thermodynamic analysis and fluorescence anisotropy showed that the stability of the repressor-operator complex is reduced by only 7-fold by the presence of the inducer in the complex. The formation of the inducer-repressor-operator ternary complex has been confirmed by CD spectral analysis. Fluorescence spectroscopy and energy transfer experiments suggest that individual allosteric effects of the two ligands, inducer and operator, on Gal repressor are responsible for the slightly weakened stability of the ternary complex compared with the stability of the inducer-repressor and repressor-operator complexes. In vitro transcription results demonstrated full derepression of transcription of the P1 promoter under conditions in which the concentrations of the inducer-repressor binary complex are severalfold higher than the dissociation constant of the inducer-repressor-operator ternary complex into inducer-repressor and free DNA. These results strongly suggest that the inducer binding to the repressor-operator complex does not lead to dissociation of the repressor from the operator during transcription induction. Because Gal repressor inhibits transcription by modulating the alpha subunit of the P1-bound RNA polymerase, we conclude that the inducer binding to the operator-bound repressor only allosterically relieves the inhibitory effect of repressor on RNA polymerase without dissociating the repressor from DNA.

Circular Dichroism↗
PubMed1997

A receptor-based immunoassay to detect Staphylococcus enterotoxin B in biological fluids.

A rapid, simple, and inexpensive sandwich enzyme-linked receptor based immunodot assay was developed for the detection of staphylococcal enterotoxin B (SEB) in human fluids by using purified glycosphingolipid digalactosylceramide (diGalCer) receptor for SEB. Three micrograms of diGalCer was immobilized on a polyvinyledene difluoride membrane and the membrane was subsequently incubated with primary and secondary alkaline-phosphatase-labeled antibodies. A positive reaction was discerned as a blue spot. As little as 1 ng/ml of SEB could be detected in the assay. SEB did not bind to structurally related glycosphingolipids, such as glucosylceramide, galactosylceramide, and lactosylceramide in this assay. Of five monoclonal anti-SEB antibodies and commercial anti-SEB antiserum tested, the latter was the most sensitive in our assay. The specificity of SEB assay was assessed by comparison with structurally related toxins, for example, staphylococcal enterotoxin A, and toxic shock syndrome toxin 1 (TSST-1). TSST-1 was not detected in the assay. This was because these toxins were not recognized by the anti-SEB antibody and did not bind to diGalCer. In conclusion, we believe that this assay may be widely applicable because it is highly specific for SEB, it does not require special equipment, and the results can be obtained within few hours with the naked eye. Since the receptor for SEB has a long shelf life, it can be easily stored and used for a long time.

Antibodies↗
PubMed1997

Cisplatin inhibits pinocytosis in Dictyostelium discoideum.

The effects of cis-diamminedichloroplatinum(II) [cisplatin], a potential anticancer drug, were studied on pinocytotic functions in the cellular slime mould Dictyostelium discoideum by administering FITC-dextran as a fluid phase marker. Cisplatin treatment at a concentration of 100 and 200 micrograms/ml for 1 h causes inhibition in pinocytotic uptake in growing Dictyostelium cells in a dose-dependent manner. Cisplatin treatment induced the association of more actin with the cell cortex, thereby presumably restricting the flexibility of the cell membrane and inhibiting the formation of pinosomes. Ultrastructural analysis of cisplatin-treated cells showed a lower number of pinosomes. These results have been discussed in the light of cisplatin's known actions that affect various cellular functions.

Animals↗
PubMed1997

Modification of low density lipoproteins by erythrocytes and hemoglobin under hypoxic conditions.

Oxidation of low density lipoprotein (LDL) has been implicated in atherogenesis. It has also been suggested that modification of LDL in the presence of endothelial and smooth muscle cells is associated with the production of superoxide. Red cells and hemoglobin have been shown to be a source for enhanced superoxide production under hypoxic conditions. We now show that incubation of LDL with both hemoglobin and erythrocytes under hypoxic conditions produces the increased Relative Electrophoretic Mobility (REM) associated with LDL oxidation. With hypoxic hemoglobin, this reaction is over within 10 minutes, appreciably faster than other in vitro methods for LDL oxidation. The increased REM was found to be associated with partial deoxygenation of hemoglobin indicative of appreciable oxygen utilization and a more hypoxic state. At later times, the modified LDL was found to produce enhanced hemoglobin oxidation. The resultant modified LDL was shown to have elevated TBARS indicative of LDL oxidation. In addition, it was found to induce smooth muscle cell proliferation which is one of the biological factors thought to be associated with atherogenesis. The relatively rapid LDL modification detected with hypoxic erythrocytes and hemoglobin suggest that even under in vivo conditions with the antioxidants present in plasma, oxidation may still occur in the circulation with the associated vascular damage occurring as the blood containing elevated levels of oxidized LDL leave the pulmonary circulation.

Animals↗
PubMed1997

Hepatotoxicity of diazepam. Structural and trace metal studies in rat.

Studies of effects of diazepam on liver parenchyma are very scanty. In this study, adult albino rats were treated with diazepam in two different doses (0.25 mg and 0.30 mg/kg body wt) daily for 30 and 60 d. Through light microscopy and electron microscopy, prenecrotic and necrotic changes were noted in the high-dose group. Trace metal analysis indicated that zinc (Zn) was reduced by 30 and 60 day under both the doses, whereas iron (Fe) and copper (Cu) were reduced significantly in these groups only after 60 d of treatment. This reduction in metal contents may have some correlations with necrotic changes in liver parenchyma.

Animals↗
PubMed1997

Impact of carbofuran in the oocyte maturation of catfish, Heteropenustes fossilis (Bloch).

Investigations were undertaken to observe the influence of technical grade carbofuran (CF) on the egg maturational processes of catfish, Heteropneustes fossilis (Bloch). Fish were exposed to sublethal doses (0.5, 1, and 2 mg/L) of CF for 30 days at 25 +/- 1 degrees C. Control fish were maintained in water. The gonado-somatic index (G.S. I. = ovarian weight x 100/body weight) of the fish, treated with 1 or 2 mg/L CF, was decreased significantly compared to that of the controls. The inhibition was almost at the same level in these doses. CF at the dose of 0.5 mg/L was found to be ineffective. From the histomorphological observations of the ovary, it was observed that CF altered both the area and the percentage occurrence of the various types of primary oocytes in the ovary compared to that of the control fish. The stage I primary oocytes were predominantly higher in CF-treated fish than stage II and stage III which was reversed in control animals. The degeneration of follicular walls, connective tissues and vacuolization in the ooplasm of the stage II and III oocytes were observed in CF-treated fish (0.5-2 mg/L). It appears that CF at sublethal concentrations inhibits oocyte maturational processes in catfish.

Animals↗
PubMed1997

Inhibition of nitric oxide facilitates LH release from rat pituitaries.

We examined the effects of nitric oxide (NO) modulators on rat pituitary LH content in vivo and studied their response to LHRH-stimulated LH secretion in vitro in ovariectomized adult female Sprague Dawley rats. Alzet mini pumps (flow rate 10 microl/h) delivering either normal saline (Group I, 1.2 mg nitroglycerin, a donor of NO (Group II) or 50 mg of nitro-L-Arginine methyl ester, a NO synthase (NOS) inhibitor (Group III), were subcutaneously implanted into experimental animals. Following 36 h infusion, pituitaries were removed and either frozen for LH quantitation, or fragmented and challenged in the superfusion system with 10 min pulses of LHRH (1 ng/ml) at 90 min intervals for 10 hours. LH was assayed by radio-immunoassay (RIA) in the homogenates of pituitaries and in aliquots of the superfusate collected every 10 mins. Significantly lower pituitary LH levels were noted in Group III (150.3 +/- 18.6 ng) in comparison to Groups I (215.6 +/- 5.5 ng; p<0.04) or II (221.2 +/- 14.9 ng; p<0.01), suggesting that low levels of NO stimulate LH secretion in vivo. The pituitary LH contents were not significantly different in Groups I and II. In vitro studies reveal that exogenous LHRH stimulated response, measured as average pulse response (90 minute period after LHRH), and total LH released during the 10 hour perfusion, was 290 +/- 23.6 ng and 1646.7 +/- 270.8 ng, respectively, in Group III; 57.9 +/- 3.1, and 344.7 +/- 24.3 ng in Group I, and 105.3 +/- 6.3, and 633.7 +/- 77.1 mg in Group II. Thus, our in vitro studies demonstrate significantly enhanced (p<0.05) LHRH- stimulated LH secretion in Group III in comparison to Groups I and II, while Group II shows higher responsiveness than Group I (p<0.05). The results of the current studies provide evidence that NOS inhibition facilitates pituitary LH secretion. The differential responses to LHRH-stimulated LH secretion in vitro in the 3 groups suggest a possible role of NO in modulating pituitary LHRH receptor concentrations. However, this will have to be tested by further studies.

Animals↗
PubMed1997

Minimally modified low density lipoproteins induce aortic smooth muscle cell proliferation via the activation of mitogen activated protein kinase.

We have investigated the effects of modifying LDL by Cu++ and various hemoglobin preparations on aortic smooth muscle cell proliferation and on the activation of mitogen activated protein kinase. We found that at very low concentrations (10 microg/ml), LDL modified by all of the above agonists markedly stimulated cell proliferation (5-10 fold). This was accompanied by a 2-3 fold stimulation in mitogen activated protein kinase (MAPK) activity. We conclude that modification of LDL under situations that are closer to those found in vivo (i.e. hypoxic conditions), may involve the activation of MAPK as a common biochemical mechanism of action. This in turn, contributes to aortic smooth muscle cell proliferation.

Animals↗
PubMed1997

Oxidized low density lipoproteins stimulate galactosyltransferase activity, ras activation, p44 mitogen activated protein kinase and c-fos expression in aortic smooth muscle cells.

Previously, our laboratory has shown that oxidized low density lipoproteins (Ox-LDL) can exert a concentration-dependent stimulation in the proliferation of aortic smooth muscle cells, "a hallmark in the pathogenesis of atherosclerosis" (Chatterjee, S. (1992) Mol. Cell. Biochem., 111, 143-147). Here we report a novel aspect of Ox-LDL-mediated signal transduction. We demonstrate that in aortic smooth muscle cells, Ox-LDL stimulates the activity of a UDP-galactose:glucosylceramide beta1-->4 galactosyltransferase (GalT-2) and phosphorylation/activation of p44 mitogen-activated protein (MAP) kinase (p44 MAPK). The activity of GalT-2 increased about 2-fold within 2.5-5 min of incubation of cells with Ox-LDL (10 microg/ml). After 5 min of incubation of cells with Ox-LDL, but not LDL, there was a 2-fold increase in the activity of p44 MAPK. Phosphoamino acid analysis employing thin layer chromatography revealed that the tyrosine and threonine moieties of p44 MAPK was phosphorylated by Ox-LDL. D-1-Phenyl-2-decanoylamino-3-morpholino-1-propanol (D-PDMP; a potent inhibitor of GalT-2) impaired the Ox-LDL mediated induction of p44 MAPK activity and the phosphorylation of tyrosine and threonine residues in p44 MAPK. This phenomenon was bypassed by the simultaneous addition of lactosylceramide. The upstream and downstream parameters in MAP kinase signaling pathways were investigated next. We found that Ox-LDL stimulated (9-fold) the loading of GTP on Ras. Interestingly, Ox-LDL specifically induced c-fos mRNA expression (6.5-fold) in these cells, as compared to the control. Thus, one of the biochemical mechanisms in Ox-LDL mediated induction in the proliferation in aortic smooth muscle cells may involve GalT-2 activation, lactosylceramide production, Ras GTP loading, activation of the kinase cascade, and c-fos expression.

Aorta↗
PubMed1997

Catalytic efficiency of signal peptidase I of Escherichia coli is comparable to that of members of the serine protease family.

A method for estimating the activity of bacterial signal peptidase I (SPase I) was used to determine its activation energy (E[act]). Pro-OmpA-nuclease A, a hybrid secretory precursor, was purified to homogeneity under denaturing conditions and used as a substrate. This substrate was used to determine the activity of SPase I at different temperatures. The results show that the conformation of the mature domain of the substrate pro-OmpA-nuclease A has no discernible effect on the activity of SPase I. The activity data at a range of temperatures were then used to determine the activation energy using the Arrhenius equation. We have estimated E(act) to be 10.4 +/- 0.6 kcal/mol. This work indicates that SPase I is as catalytically efficient as the His-Ser-Asp family of proteases.

Bacterial Outer Membrane Proteins↗
PubMed1997

An investigation into the psychobiology of social phobia: personality domains and serotonergic function.

The aim of the present study was to explore a psychobiological perspective in the aetiology of social phobia. The emphasis was on serotonergic function and personality. A total of 20 social phobics according to ICD-10 DCR criteria were assessed with the Schedule for Clinical Assessment in Neuropsychiatry and the International Personality Disorder Examination. They were compared with an age-matched normal population with regard to scores on the Fear of Negative Evaluation Scale, the Social Avoidance and Distress Scale, the Temperament and Character Inventory, and platelet 5HT2 receptor function. Other Axis-I disorders and cluster C personality disorders were frequently encountered. The social phobia group was characterized by high levels of harm avoidance, and low levels of novelty seeking, co-operativeness and self-directedness. Platelet 5HT2 receptor density did not differentiate between the groups, but was associated with severity of social phobia. An integrated psychobiological model is presented.

Adult↗
PubMed1997

Cellular immunotherapy and autologous transplantation for hematologic malignancy.

The success of allogeneic transplantation is in part due to the immunotherapeutic effect mediated by the graft. Autologous transplantation is hampered by the absence of this effect, leading to a higher relapse rate. We have conducted a series of studies designed to augment the immunologic activity of the graft after autologous transplant with a view towards introducing an autologous graft-versus-tumor effect that could decrease the rate of relapse after autologous transplant. These studies have included IL-2 activation of marrow followed by post-transplant infusional IL-2, the development of a novel protocol for the generation of highly efficient cytotoxic effector cells, termed cytokine-induced killer (CIK) cells, with broad and potent antitumor activity. In order to determine the potential for generating peptide-specific cytolytic T cells, studies have been conducted upon transducing antigen-presenting cells (APC) with AAV vector-mediated gene transfer, a vector capable of transducing non-proliferating target cells. Transduction of human monocytes and macrophages resulted in high expression of the transduced gene. This latter study forms the basis for determining whether genetic modification of APC can potentiate specific immune responses to tumor-specific gene products. Taken together, these strategies will hopefully increase the therapeutic efficacy of autologous transplantation.

Animals↗
PubMed1997

Vasectomy-induced superoxide dismutase inactivation in the male reproductive tract of rat: a prerequisite for spermatic granuloma formation.

Post vasectomy spermatic granuloma formation is considered as a favourable development for vasectomized subjects as it maintains physiological hydrostatic pressure within the male reproductive tract. But, the 'state of the art' of the formation of granuloma after vasectomy is not well defined. The present study reveals a link between the postvasectomy free radical status of the male tract and spermatic granuloma formation after vasectomy. A surge in the rate of ascorbyl radical production, directly correlated with oxyradical stress and an abrupt fall in superoxide dismutase activity in the granuloma, indicates 'switching on' of a free radical-dependent machinery for the formation of granuloma after vasectomy.

Animals↗
PubMed1997

The expression cassette determines the functional activity of ribozymes in mammalian cells by controlling their intracellular localization.

In order to better understand the influence of RNA transcript context on RNA localization and catalytic RNA efficacy in vivo, we have constructed and characterized several expression cassettes useful for transcribing short RNAs with well defined 5' and 3' appended flanking sequences. These cassettes contain promoter sequences from the human U1 snRNA, U6 snRNA, or tRNA Meti genes, fused to various processing/stabilizing sequences. The levels of expression and the sub-cellular localization of the resulting RNAs were determined and compared with those obtained from Pol II promoters normally linked to mRNA production, which include a cap and polyadenylation signal. The tRNA, Ul, and U6 transcripts were nuclear in localization and expressed at the highest levels, while the standard Pol II promoted transcripts were cytoplasmic and present at lower levels. The ability of these cassettes to confer ribozyme activity in vivo was tested with two assays. First, an SIV-growth hormone reporter gene was transiently transfected into human embryonic kidney cells expressing an anti-SIV ribozyme. Second, cultured T lymphocytes expressing an anti-HIV ribozyme were challenged with HIV. In both cases, we found that the ribozymes were effective only when expressed as capped, polyadenylated RNAs transcribed from Pol II cassettes that generate a cytoplasmically localized ribozyme that facilitates co-localization with its target. We also show that the inability of the other cassettes to support ribozyme-mediated inhibitory activity against their cytoplasmic target is very likely due to the resulting nuclear localization of these ribozymes. These studies demonstrate that the ribozyme expression cassette determines its intracellular localization and, hence, its corresponding functional activity.

Animals↗
PubMed1997

Longitudinal study of human milk creamatocrit and weight gain in exclusively breastfed infants.

OBJECTIVE: To determine the creamatocrit values of breastmilk at different lactational periods during the first 6 months after delivery and its relation to infant growth. DESIGN: Prospective follow-up study. SETTING: Maternity and well baby clinics of a metropolitan teaching, a rural teaching and a suburban municipal hospital. SUBJECTS: 1322 exclusively breastfed infants and their mothers. There were 160 preterm, 281 term low birth weight (LBW) and 881 term appropriate for date (AFD) babies. METHODS: Creamatocrit of breastmilk and infant's body weight were recorded at 4,8,12,16,20 and 24 weeks after birth. RESULTS: Creamatocrit values of breastmilk in all mothers increased upto 16 post partum weeks and then declined. There were no significant differences in creamatocrit values of breastmilk of mothers of preterm, term LBW and term non-LBW infants. Preterm and term LBW infants showed a catch up in body weight with the term AFD group by 20 weeks post-partum. CONCLUSIONS: The breastmilk creamatocrit progressively rises upto the fourth month of lactation but is not influenced by gestation or intra uterine growth retardation. There is no relationship between breastmilk creamatocrit and infant growth. Exclusive breast feeding adequately supports growth of LBW infants in comparison to their normal peers during the first 6 months of life.

Body Weight↗