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Biomedical subjects

S Chatterjee

Publications and source records attributed to S Chatterjee.

At least 235 records · Page 13Linked to original sources
PubMed1995

Effect of inhibitors of poly(ADP-ribose) polymerase on the induction of GRP78 and subsequent development of resistance to etoposide.

We have recently demonstrated that cell lines deficient in poly(ADP-ribose) synthesis due to deficiency in the enzyme poly(ADP-ribose) polymerase (PADPRP) or depletion of its substrate NAD+ overexpress GRP78. Furthermore, this overexpression of GRP78 is associated with the acquisition of resistance to topoisomerase II-directed drugs such as etoposide (VP-16); (S. Chatterjee et al., Cancer Res., 54: 4405-4411, 1994). Thus, our studies suggest that interference with NAD+-PADPRP metabolism could provide an important approach to (a) define pathways of GRP78 induction, (b) study the effect of GRP78 on other cellular processes, (c) elucidate the mechanism of GRP78-dependent resistance to topoisomerase II targeted drugs, and (d) modulate responses to chemotherapy in normal and tumor tissues. However, in the in vivo situation, it is impractical to interfere with NAD+-PADPRP metabolism by mutational inactivation of PADPRP or by depletion of its substrate NAD+. Therefore, we have examined several inhibitors of NAD+-PADPRP metabolism including 3-aminobenzamide, PD128763, and 6-aminonicotinamide for their ability to reproduce the results obtained with cell lines deficient in NAD+-PADPRP metabolism relative to the induction of GRP78 and subsequent development of resistance to VP-16. Our studies show that 6-aminoicotinamide treatment is highly effective in the induction of GRP78 and subsequent development of resistance to VP-16, whereas treatment with 3-aminobenzamide or PD128763 does not induce GRP78 and thus does not result in VP-16 resistance.

6-Aminonicotinamide↗
PubMed1995

Determination of Km and kcat for signal peptidase I using a full length secretory precursor, pro-OmpA-nuclease A.

An effective method for the determination of the activity of signal peptidase I (SPase I) of Escherichia coli is established using the hybrid protein pro-OmpA-nuclease A as substrate. Pro-OmpA-nuclease A, a hybrid secretory precursor was purified to homogeneity under denaturing conditions. When this protein was refolded, it could be quantitatively processed by purified SPase I. The Km of signal peptidase I was 0.0165 mM. The kcat was 8.73 s-1. The Km is 50 to 100 times lower than that obtained with peptide substrates indicating that SPase I has a significantly greater affinity for the protein substrate. The turnover number, kcat, is two to four orders of magnitude greater as well. Thus, the specificity constant, kcat/Km is six orders of magnitude greater with pro-OmpA-nuclease A than with peptide substrates. This is the first determination of kinetics of SPase I with a protein substrate.

Amino Acid Sequence↗
PubMed1995

An improved assay method for the measurement and detection of sphingomyelinase activity.

We have developed an improved assay method to measure sphingomyelinase activity and to detect this enzyme separated on polyacrylamide gels. The assay of sphingomyelinase activity involved immobilizing [N-methyl-14C]sphingomyelin on polyvinyldiflouride (PVDF) membrane, incubation with sphingomyelinase, and the measurement of radioactivity associated with [14C]phosphocholine. The enzyme activity was dependent on the concentration of sphingomyelin, enzyme, pH, and temperature. Thirty minutes of incubation time was optimal for enzyme activity. This enzyme had a bimodal pH optima, in that optimum enzyme activity was measured at pH 5.4 and 7.4. The detection of sphingomyelinase was pursued by separating the enzyme on a polyacrylamide gel and carrying out the enzyme assay by exposure to [14C]sphingomyelin blotted on a PVDF membrane. The enzyme activity on the PVDF membrane was visualized by autoradiography. A white band (depicting hydrolytic removal of [14C]sphingomyelin from PVDF was observed. Our method of detecting sphingomyelinase by immobilizing sphingomyelin on PVDF membrane may serve as a prototype for assaying various other enzymes in which the hydrolytic product is released into the aqueous phase. Moreover, our method for detecting sphingomyelinase on polyacrylamide gels may be helpful in further studies on the molecular biochemistry of this and related phospholipases.

Acrylic Resins↗
PubMed1995

Volume changes of the molten globule transitions of horse heart ferricytochrome c: a thermodynamic cycle.

Volume changes among the unfolded (U), native (N), and molten globule (MG) conformations of horse heart ferricytochrome c have been measured. U to N (pH 2 to pH 7) was determined in the absence of added salt to be -136 +/- 5 mL/mol protein. U to MG (pH 2, no added salt to pH 2, 0.5 M KCl) yielded + 100 +/- 6 mL/mol. MG to N was broken into two steps, N to NClx at pH 7 by addition of buffered KCl to buffered protein lacking added salt (NClx = N interacting with an unknown number, X, of chloride ions), and MG to NClx by jumping MG at pH 2 in 0.5 M KCl to pH7 at the same salt concentration. The delta V of N to NClx was -30.9 +/- 1.4 mL/mol protein, whereas MG to NClx entailed a delta V of -235 +/- 6 mL/mol. Within experimental error, the results add up to zero for a complete thermodynamic cycle. We believe this to be the first volumetric cycle to have been measured for the conformational transitions of a protein. The results are discussed in terms of hydration contributions from deprotonation of the protein, other hydration effects, and the formation and/or enlargement of packing defects in the protein's tertiary structure during the steps of folding.

Animals↗
PubMed1995

A serological survey of influenza a antibody in human and pig sera in Calcutta.

A study was undertaken with a view to assess the distinct pattern of sero-prevalence of influenza A viruses in the city of Calcutta population during the years of 1981-90. Concurrently, based on the fact of increasing pig population, a study was carried out to establish the activity of the human influenza A virus among pigs with a view to the potential threat of emergence of a new strain of influenza A virus that may surface following co-infection with swine and human influenza A viruses. The percentage positivity of the H3N2 antigen was found to be highest (46%), followed by H1N1 (43%), H2N2 (35%) and H0N1 (19%). A similar pattern was noted with pig sera.

Animals↗
PubMed1995

Fine specificity of immune responses to epitopic sequences in synthetic peptides containing B and T epitopes from the conserved Plasmodium falciparum blood-stage antigens.

Immunisation with two chemically synthesised, linear, multiple epitope peptides (MEP) containing B and T cell epitopes from two conserved blood-stage antigens of the human malaria parasite, Plasmodium falciparum, induced high levels of circulating antibodies without the use of a carrier protein. Immunisation of BALB/c mice with MEP constructs (P1 and P2) induced antibodies against the various epitope sequences included in their structures, although the immune response was focused more towards the N terminal and the middle portion of the peptides. In vitro T cell proliferation assays indicated that only one of the two Th epitopes included in P1 and P2 are functional. Both P1 and P2, based on P. falciparum sequences, cross-reacted with sera from P. yoelii-infected mice. Immunisation with P1 in CFA, but not with P2, provided partial protection to BALB/c mice against P. yoelii challenge infection. Peptide P1 was highly immunogenic in alum also, and a somewhat higher level of protection was observed as compared to CFA immunisation. We found that immunisation with P1 induced antibody responses in different strains of mice, although to different extents. These results suggest that linear, multiple epitope peptides may offer attractive alternatives as subunit vaccine candidate molecules, but at the same time highlight the fact that the design principles are far from being clear and have yet to be worked out.

Amino Acid Sequence↗
PubMed1995

The role of arachidonic acid and/or its metabolites in embryo implantation initiated by epidermal growth factor (EGF).

Previous studies have shown that epidermal growth factor (EGF) can replace estrogen for initiating embryo implantation in hypophysectomized rats in which pregnancy was maintained with progesterone, provided that uterine trauma preceded the intravenous dose of the growth factor. The present study has shown that intraperitoneal administration of prostaglandin E2 (PGE2) or histamine dihydrochloride can replace the need for uterine trauma. On the other hand, indomethacin (1 mg subcutaneous), an inhibitor or prostaglandin synthase (PGHS) and phospholipase A2 (PLA2) inhibited the implantation initiated by EGF plus trauma or even EGF plus PGE2, but had no effect upon that initiated by estradiol. A much larger dose of another PGHS inhibitor, ibuprofen, did not inhibit, but appeared to enhance, the effect of EGF plus trauma. The lipoxygenase inhibitor nordihydroguairaretic acid also was ineffective at inhibiting the action of EGF plus trauma. In contrast to the ineffectiveness of these non-steroidal anti-inflammatory agents, the synthetic glucocorticoid dexamethasone inhibited implantation initiated by either EGF or estradiol. These results are consistent with the interpretation that treatment with agents known to inhibit the activity of PLA2, and thus availability of arachidonic acid, are more potent inhibitors of implantation initiated by EGF than those that only inhibit PGHS.

Animals↗
PubMed1995

Glycerol versus radiofrequency rhizotomy--a comparison of their efficacy in the treatment of trigeminal neuralgia.

Ever since the anatomical basis of trigeminal neuralgia has been postulated to be vascular compression, microvascular decompression has been gaining acceptance as the definitive treatment of the condition. However, the majority of patients are over 50 years of age, and posterior fossa procedures carry significant risk in terms of morbidity and mortality. Radiofrequency and glycerol rhizotomy are the two procedures commonly performed in patients considered unsuitable for posterior fossa craniectomy. This study attempts to assess the relative merits and demerits of these two procedures and seeks to establish indications for each. It is felt that glycerol rhizotomy is better as the first line treatment.

Adult↗
PubMed1995

Digalactosylceramide is the receptor for staphylococcal enterotoxin-B in human kidney proximal tubular cells.

We have characterized a glycosphingolipid (GSL) receptor for Staphylococcus enterotoxin-B (SEB) in cultured human kidney proximal tubular (PT) cells. Solid-phase binding of [125I]SEB to the GSL receptor was concentration dependent and was not displaceable by two structurally related toxins, such as staphylococcal enterotoxin-A and toxic shock syndrome toxin-1. Rat kidney cells did not bind [125I]SEB. However, when the rat kidney cells were pre-incubated with digalactosylceramide, there was a concentration-dependent binding of [125I]SEB. Trimethylsilyl derivatization of methyl glycosides, followed by gas-liquid chromatography-mass spectrometry (GC-MS), revealed that galactose was the major sugar component of this putative receptor GSL. The sphingosines present in this GSL were d18:2, d22:2 and d23:0; the fatty acids present were palmitate, oleate and stearate. Permethylation of alditol acetates and GC-MS revealed two predominant sugars, namely 2, 3, 4 and 6 tetramethylgalactital and 2, 3 and 6 trimethylgalactital. The GSL receptor for SEB was sensitive to alpha-galactosidase, and resistant to beta-galactosidase and beta-glucosidase. Taken together, our studies reveal that the tentative structure of the receptor for SEB in human kidney PT cells is CerGal alpha 1-->4Gal. In summary, we have identified a GSL as one of the binding sites of SEB, a food-borne toxin. We believe that our finding may open up rational approaches for the therapy of SEB-induced glycopathology in man.

Animals↗
PubMed1995

A conserved peptide sequence of the Plasmodium falciparum circumsporozoite protein and antipeptide antibodies inhibit Plasmodium berghei sporozoite invasion of Hep-G2 cells and protect immunized mice against P. berghei sporozoite challenge.

Minutes after injection into the circulation, malaria sporozoites enter hepatocytes. The speed and specificity of the invasion process suggest that it is receptor mediated. The region II sequence of Plasmodium falciparum circumsporozoite (CS) protein includes a nonapeptide (WSPCSVTCG) which is highly conserved in all of the CS proteins sequenced to data, including the one from Plasmodium berghei. We have found that two peptides based on the P. falciparum region II sequence, P18 (EWSPCSVTCGNGIQVRIK) and P32 (IEQYLKKIKNS ISTEWSPCSVTCGNGIQVRIK), significantly inhibited P. berghei sporozoite invasion into Hep-G2 cells in vitro. This inhibition was enhanced if either peptide was preincubated with Hep-G2 cells prior to sporozoite invasion. We confirm that region II is a sporozoite ligand for the hepatocyte receptor; moreover, despite the few differences between P. falciparum and P. berghei region II sequences around the nonapeptide sequence (66% homology), the functional characteristics of the motif sequences are not affected. Since the conserved motifs represent a crucial sequence involved in Plasmodium sporozoite invasion of hepatocytes, antibodies to region II should inhibit sporozite invasion into hepatocytes. Indeed, we found that polyclonal antibodies generated to the P. falciparum-based peptide P32 inhibited P. berghei sporozoite invasion of Hep-G2 cells. Furthermore, inbred mice (C57BL/6) immunized with P32 were protected against a lethal challenge of P. berghei sporozoites. Our results suggest that the conserved region II of the CS protein contains crucial B- and T-cell epitopes, that such peptide sequences from the human malaria parasite P. falciparum can be screened in the P. berghei rodent model, and, finally, that region II can be considered useful as one of the components of a malaria vaccine.

Amino Acid Sequence↗
PubMed1995

Effect of protein kinase C inhibitors on the antiviral activity of human alpha interferon in herpes simplex virus-infected human neuroblastoma cells.

Pretreatment of human neuroblastoma cells with an inhibitor of protein kinase C (PKC), staurosporine or H-7, prior to the addition of human alpha interferon (HuIFN-alpha), recombinant HuIFN-alpha, or recombinant HuIFN-beta blocked the inhibitory effect of these IFNs on the release of infectious herpes simplex virus type 1 from treated cells. In addition, staurosporine blocked the inhibitory effect of HuIFNs on the expressions of herpes simplex type 1 glycoproteins B, C, and D in treated neuroblastoma cells. Furthermore, addition of HuIFNs resulted in an increased expression of PKC in treated neuroblastoma cells. These results suggest that inhibitors of PKC block the expression of HuIFN-induced genes in treated human neuroblastoma cells. Thus, the activation of PKC is an important step in the HuIFN-treated cells of neuronal origin.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1995

In vitro folliculogenesis of rat preantral follicles.

The impact of various gonadotropic hormones on the growth and development of secondary follicles from primordial and primary follicles obtained by enzymatic dissociation of the ovaries of immature 14-day-old rats was studied in vitro. The substratum-adherent culture technique developed for studying folliculogenesis in the current study permitted direct visualization of follicular growth on a day to day basis by avoiding the cumbersome process of fixing and sectioning follicles in culture. The cultures were maintained in a serum-free modified McCoy's medium in a humidified atmosphere containing 5% CO2 at 37 C. Daily observation of the culture dishes under the phase contrast microscope revealed that the follicles grew and developed from primordial to primary and secondary follicular stages in the presence of FSH. Large antral follicles were able to secrete estradiol and progesterone into the medium, indicating that the follicles are not merely formed by cellular reorganization, but are physiologically functional competent units. The organized release of the oocyte with accompanying corona radiata was made possible in some secondary follicles with large antral structures by introducing LH into the culture medium. However, introduction of hCG (which has the biological properties of LH) into the cultures on day 1 resulted in follicular degeneration within 3-4 days of culture. Follicular organization was also disrupted when LH was introduced together with FSH into the medium on day 1 of culture. Primordial or primary follicles obtained from the ovaries could survive, but could not transform to secondary follicles in the absence of FSH. The results of our in vitro studies indicate, and therefore are in agreement with earlier in vivo studies, that FSH alone is essential for the progression of folliculogenesis to the preovulatory condition, and that LH is essential for the organized expulsion of the oocyte from a mature follicle. Our technique, described in the current study, for producing physiologically functional secondary follicles in culture not only allows progress in folliculogenesis to be monitored very closely, but also serves as a model for studying the various intrinsic factors that may be involved in the successful development of dominant mature Graafian follicles that can finally ovulate. It also facilitates access to the growing follicle along with its oocyte, which can, therefore, be used as a powerful model to study the effects of various test substances on follicular development.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1995

Physical and motor fitness in twins.

Thirty pairs of monozygotic (MZ) and 20 pairs of dizygotic (DZ) twins, of both sexes, were studied to estimate the role of genetic and environmental factors determining fitness measurements comprising vital capacity (VC), vertical jump, flexibility, agility, and PFI score. Intra-pair variances for VC, vertical jump, and heart rate were significantly smaller (p < 0.05-0.01) in MZ than in DZ twins, where values for flexibility, agility, and PFI were insignificant. Intra-pair correlations for VC, vertical jump, and heart rate were higher (p < 0.01) in MZ than in DZ twins where the opposite was found in the case of flexibility and agility. The correlation value for PFI was higher in both MZ and DZ twins. Following adjustment for physical characteristics including age, weight, and height, none of the results of all the residual fitness measurements were similar to the unadjusted values. Both unadjusted and residual variables with smaller intra-pair variances showed higher heritability estimates. These results suggest that VC, vertical jump, and heart rate are influenced more by genetic factors than environmental factors where the inverse is true of flexibility, agility, and PFI. Thus, the genetic and environmental influence of all the fitness measurements, except VC, more or less depend upon physical characteristics in this study.

Adolescent↗
PubMed1995

Estradiol and chlordecone (Kepone) decrease adenosine 3'5'-cyclic monophosphate concentrations in the ovariectomized immature rat uterus.

Adenosine 3'5'-cyclic monophosphate (cAMP) has been repeatedly shown to mimic some actions of estrogen in the rat uterus. However, the relationship between estrogens and uterine cAMP remains controversial. The effect of chronic exposure (3 days) to a biologically potent, long-acting estrogen, estradiol benzoate (EB), or the xenoestrogen chlordecone (Kepone), which has a long half-life in the circulation, was examined in ovariectomized immature rats. Both compounds, when administered in doses that provided equal increases in uterine weight, produced equivalent decreases in uterine cAMP content. Although the decrease in cAMP was apparent within 48 hr, it was more pronounced at 72 hr. There was no reduction in cAMP produced in response to direct stimulation of uterine adenylyl cyclase by forskolin, indicating that loss of the enzyme was not a factor in the lowering of cAMP content. The pure anti-estrogen ICI-182,780, in a dose-dependent fashion, prevented the action the estradiol benzoate and chlordecone, suggesting that the lowering of cAMP was dependent on an estrogen receptor. The physiological significance of reduced uterine cAMP with chronic estrogen treatment remains to be determined.

Adenylyl Cyclases↗