Search PubMed⌕ Search

Biomedical subjects

S K Ghosh

Publications and source records attributed to S K Ghosh.

At least 37 records · Page 2Linked to original sources
PubMed2001

Adsorption of Lennard-Jones fluid mixture in a planar slit: a perturbative density functional approach.

A simple perturbative density functional approach is employed to investigate the adsorption behavior of a model Lennard-Jones fluid confined in a slitlike pore. Adsorption of one-component fluid as well as two-component fluid mixtures in varying pore sizes has been investigated. The results on the density profiles and the excess adsorption obtained from this theory are found to be in overall good agreement with the available computer simulation results. The results are also compared with the same from some recent weighted density based calculations.

Journal Article↗
PubMed2001

Dynamical fluctuation of the mesoscopic structure in ternary C12E5-water-n-octane amphiphilic system.

Dynamical fluctuations of the bicontinuous microemulsion and lamellar structures in ternary C12E5-water-n-octane amphiphilic system are studied by means of neutron spin echo (NSE) spectrometry. The decay rates of the time correlation of the concentration were analyzed in terms of three theories: (1) A. G. Zilman and R. Granek, Phys. Rev. Lett. 77, 4788 (1996), (2) M. Nonomura and T. Ohta, J. Chem. Phys. 110, 7516 (1999), and (3) R. Granek and M. E. Cates, Phys. Rev. A 46, 3319 (1992), in the first of which a Langevin equation for membrane plaquettes and in the latter two of which time-dependent Ginzburg-Landau equations for the order parameters are considered. The result shows that the intermediate correlation functions I(q,t) for the ranges of 0<t<15 ns and 0<q<0.2 A (-1) are well fitted to a stretched exponential function in time, I(q,t)=exp[-(Gammat)(2/3)], for the bicontinuous microemulsion and the lamellar phases of the same systems with the relaxation rate Gamma increasing as q(3) in agreement with theory (1) from which the bending modulus of the membrane kappa was estimated. For more restricted ranges of 0<t<5 ns and 0.05<q<0.15 A (-1) the NSE result can be expressed by an exponential function in time in agreement with theory (2) determined exclusively by hydrodynamic interactions and for extended range of 0<t<10 ns and 0.03<q<0.15 A (-1) by a nonexponential function in agreement with theory (3), from both of which the effective viscosities eta(0) and eta(eff) of the system were estimated. The effective viscosity from the nonexponential eta(eff) is five times greater than that from the simple exponential eta(0) that is almost the same as the literature value. The implication of this result is discussed in terms of the effective viscosity eta(eff) that takes into account the renormalization of the bending modulus of the membrane.

Journal Article↗
PubMed2001

A stable single-chain variable fragment expressing transfectoma demonstrates induction of idiotype-specific cytotoxic T-cells during early growth stages of a murine B-lymphoma.

The idiotypic determinants associated with the variable regions of antibody molecules are known to function as tumor-associated antigens (TAAs). However, there is no clear-cut evidence documenting their efficacy in inducing TAA-specific cytotoxic T-lymphocytes (CTLs). In most previous studies, idiopeptides were implicated in elicitation of TAA-specific CD4+ T-cells. Using a murine B-cell lymphoma, 2C3, we earlier demonstrated induction of splenic CD4+ and CD8+ T-lymphocytes directed to idiotypic Ig of the tumor. In the present study, we provide more direct evidence of the existence of Id-specific CTLs in the spleens of 2C3 bearing BALB/c mice using an scFv-transfectoma, P815A4, as a target. While both P815A4 and 2C3 cells were equally susceptible to cytolysis by the effector cells, lysis was evident only during early tumor progression. Moribund animals at the late stage of tumor growth failed to demonstrate any significant cytotoxic immune response against either tumor. Antibodies to MHC class I alleles Kd, Dd, Ld, beta2m and CD8 molecules all inhibited cytotoxicity. The CTL population from early tumor-bearers recognized 2C3 tumor in the context of all major H-2d alleles; however, in case of P815A4 cells, it was restricted to Kd and Dd alleles only. Based on these antibody inhibition studies, it appears that the idiopeptides generated in both tumors are in some way different, yet they were recognized equally by CTLs not only from the tumor-bearers but also by CTLs from 2C3-hyperimmune mice. It appears that scFv-containing transfectomas expressing antibody variable region epitopes would be useful for both elucidating CTL-defined idiopeptides and monitoring TAA-specific CTL response in tumor-bearing animals.

Alleles↗
PubMed2001

The IML3/MCM19 gene of Saccharomyces cerevisiae is required for a kinetochore-related process during chromosome segregation.

The mcm19 mutation in budding yeast affects minichromosome maintenance. In this work we have shown that this mutation leads to defects in the segregation of minichromosomes and chromosomes. The mutant cells show defective kinetochore function as judged by three criteria-- relaxation of the transcriptional block normally associated with a CEN box, stable maintenance of a dicentric plasmid in mutant cells, and mild sensitivity to the antimicrotubule drug benomyl. The MCM19 gene has been cloned and found to be the same as IML3, which codes for the ORF YBR107C. Deletion of the gene was not lethal, nor did it confer any growth defects on the mutant cells. However, the mcm19 null mutation conferred growth defects in the presence of a mutation in the TUB1 gene coding for alpha-tubulin. Two-hybrid experiments showed an interaction between Im13p/Mcm19p and the kinetochore protein Ch14, indicating that the Im13/Mcm19 protein has a role in kinetochore function.

Benomyl↗
PubMed2001

Asymptomatic HIV patient with cardiomyopathy and nephropathy: case report and literature review.

We report a previously asymptomatic HIV patient with high CD4 lymphocyte count and low HIV1 viral load who developed cardiac and renal disease. Management with ACE inhibitor, diuretics and triple antiretroviral combination therapy yielded a rapid clinical response. An understanding of the spectrum of renal and cardiac derangements is essential for clinicians in managing patients with HIV disease.

AIDS-Associated Nephropathy↗
PubMed2001

Effects of T-lymphocyte-dependent and -independent immunity on cholinergic enzyme activity in mouse lacrimal gland.

The nature of the immune response following ocular immunization with a protein and a polysaccharide and the effects such immunization have on the activities of cholinergic enzymes in the lacrimal glands of BALB/c mice were examined. Lacrimal glands are highly innervated by sympathetic and parasympathetic nerve fibres and are involved in mucosal immunity and therefore are excellent sites to study neuro-immune interactions. In this report, a T-lymphocyte-dependent protein antigen, keyhole limpet haemocyanin (KLH) and a T-lymphocyte-independent polysaccharide antigen, dextran (DEX) were administered topically to the eyes or intraperitoneally injected. Both routes of immunization produced a strong serum antibody response when KLH was the antigen. DEX, however, evoked a serum antibody response only after intraperitoneal administration. Eosin-haematoxylin staining indicated no histological abnormality or inflammatory changes in any immunized lacrimal glands, but immuno-staining revealed that only in the KLH-treated tissues were IgG-producing plasma cells discernible. Furthermore, KLH-specific antibody was also detectable using an immuno-blot assay in lacrimal glands. Polymerase chain reaction analysis with cytokine-specific primers revealed induction of interleukin-4 (lL-4) in KLH-treated lacrimal glands, but not in DEX or unimmunized tissues. Thus, the nature of the antigen seems important in the induction of the immune response in lacrimal glands. To delineate the effects that immunogenic differences might have on the activities of the cholinergic enzymes, choline acetyl-transferase (ChAT) and acetylcholinesterase (AChE) were assayed using radiolabelled substrates and measuring labelled products. Both ChAT and AChE activities were influenced following KLH immunization, while DEX had only transient effects on ChAT. This is possibly due to the fact that KLH, a protein antigen, is the effective inducer of the specific immune response in the lacrimal gland, while DEX is not. Experimental Physiology (2001) 86.2, 169-176.

Acetylcholinesterase↗
PubMed2001

Anti-lymphoma immunity: relative efficacy of peptide and recombinant DNA vaccine.

The efficacy of vaccines consisting of (1) Ig idiopeptides of a murine B-lymphoblastoma, 2C3, and (2) a corresponding scFV-expressing DNA construct was determined on the basis of their ability to induce anti-tumor immune response and protection against tumor growth. Peptide-KLH complexes and a plasmid expressing single-chain variable fragment (scFv) corresponding to 2C3 Ig VH and VL chains were used separately as vaccines. Immunized BALB/c mice were bled and then challenged with live 2C3 tumor. Survival of various challenged groups was also determined. The results indicate that CDR3-H (VH3) peptides, and the plasmid DNA when given with GM-CSF, only moderately retarded tumor growth, whereas killed 2C3 tumor vaccine induced lasting protection, as shown earlier. Both peptides and scFv-plasmid induced circulating anti-Id antibodies, but no specific cytotoxic T-cell (CTL) activity was detected. However, in spite of their inability to induce CTL activity, both idiopeptides and the scFv-expressing plasmid DNA displayed epitopes recognized by an Id-specific long-term splenic CTL line (A102) obtained from mice vaccinated with killed 2C3 tumor.

Animals↗
PubMed2001

Epidemic of Vibrio cholerae serogroup O139 in Berhampur, Orissa.

During the months of May-June 2000, 194 patients with watery diarrhoea were admitted to the Infectious Diseases Ward of the M.K.C.G. Medical College, Berhampur. Ninety four rectal swabs were collected and processed according to the standard procedures. Vibrio cholerae strains were isolated from 20 samples. Of these 20 isolates, two were found to be V. cholerae O1 EITor Ogawa strain and 18 were confirmed to be V. cholerae serotype O139. All V. cholerae O139 isolates were of a single phage type (phage type 1) and the two O1 strains were of phage type 3 and phage type 27 respectively. All 20 V. cholerae isolates were positive for CAMP test, and showed uniform resistance to furazolidone and sensitivity to co-trimoxazole, amoxycillin, norfloxacin, tetracycline and gentamycin. V. cholerae O139 serotype has not been reported earlier in south Orissa. This is probably the first report of its isolation from this area.

Cholera↗
PubMed2000

IL-12 gene-deficient C57BL/6 mice are susceptible to Leishmania donovani but have diminished hepatic immunopathology.

To determine the in vivo role of IL-12 in the development of protective immunity in visceral leishmaniasis caused by Leishmania donovani, we examined the course of L. donovani infection in IL-12-deficient C57BL/6 (IL-12-/-) mice. IL-12-/- mice displayed significantly higher parasite burdens in their livers and spleens than wild-type C57BL/6 mice throughout the course of infection. Despite high parasite burdens, the onset of hepatosplenomegaly was significantly delayed in L. donovani-infected IL-12-/-. Moreover, livers and spleens from IL-12-/- mice displayed significantly less inflammation and poorly formed granulomatous lesions than those from IL-12+/+ mice throughout the course of infection. Antigen-stimulated splenocytes from IL-12-/- mice produced significantly less IFN-gamma but more IL-4 than IL-12+/+ mice. These findings indicate that although endogenous IL-12 is critical for the development of protective immunity to L. donovani, it is also responsible for inducing the significant immunopathology associated with visceral leishmaniasis.

Animals↗
PubMed2000

Green tea polyphenols induce apoptosis in vitro in peripheral blood T lymphocytes of adult T-cell leukemia patients.

Green tea polyphenols (TEA) are known to exhibit antioxidative activity as well as tumor-suppressing activity. In order to examine the tumor-suppressing activity of TEA against adult T-cell leukemia (ATL), we cultivated peripheral blood T lymphocytes of ATL patients (ATL PBLs), an HTLV-I-infected T-cell line (KODV) and healthy controls (normal PBLs) for 3 days in the presence of TEA and its main constituent, epigallocatechin-3-gallate (EGCg), to measure cell proliferation and apoptosis, and to quantitate mRNAs of HTLV-I pX and beta-actin genes of the cultured cells. Growth of ATL PBLs was significantly inhibited by 9-27 microg/ml of TEA and EGCg, in contrast to minimal growth inhibition of T cells of normal PBLs. Inhibition of KODV was intermediate between ATL PBLs and normal PBLs. The ATL PBLs and KODV treated with 27 microg/ml of either TEA or EGCg induced apoptotic DNA fragmentation, producing terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL)-positive cells, while the normal PBLs treated with the same concentration of TEA or EGCg produced a negligibly small number of TUNEL-positive cells, in which apoptotic DNA fragmentation was not detectable. Expression of HTLV-I pX mRNA was suppressed more than 90% in ATL PBLs by treatment with 3-27 microg/ml of either TEA or EGCg, while expression of beta-actin mRNA was much less suppressed by treatment with the same concentration of TEA or EGCg. These results indicate that TEA and EGCg inhibit growth of ATL PBLs, as well as HTLV-I-infected T-cells, by suppressing HTLV-I pX gene expression and inducing apoptotic cell death.

Adult↗
PubMed2000

The most abundant glycoprotein of amebic cyst walls (Jacob) is a lectin with five Cys-rich, chitin-binding domains.

The infectious stage of amebae is the chitin-walled cyst, which is resistant to stomach acids. In this study an extraordinarily abundant, encystation-specific glycoprotein (Jacob) was identified on two-dimensional protein gels of cyst walls purified from Entamoeba invadens. Jacob, which was acidic and had an apparent molecular mass of approximately 100 kDa, contained sugars that bound to concanavalin A and ricin. The jacob gene encoded a 45-kDa protein with a ladder-like series of five Cys-rich domains. These Cys-rich domains were reminiscent of but not homologous to the Cys-rich chitin-binding domains of insect chitinases and peritrophic matrix proteins that surround the food bolus in the insect gut. Jacob bound purified chitin and chitin remaining in sodium dodecyl sulfate-treated cyst walls. Conversely, the E. histolytica plasma membrane Gal/GalNAc lectin bound sugars of intact cyst walls and purified Jacob. In the presence of galactose, E. invadens formed wall-less cysts, which were quadranucleate and contained Jacob and chitinase (another encystation-specific protein) in secretory vesicles. A galactose lectin was found to be present on the surface of wall-less cysts, which phagocytosed bacteria and mucin-coated beads. These results suggest that the E. invadens cyst wall forms when the plasma membrane galactose lectin binds sugars on Jacob, which in turn binds chitin via its five chitin-binding domains.

Amino Acid Sequence↗
PubMed2000

Template/primer requirements and single nucleotide incorporation by hepatitis C virus nonstructural protein 5B polymerase.

Nonstructural protein 5B (NS5B) of hepatitis C virus (HCV) possesses an RNA-dependent RNA polymerase activity responsible for viral genome RNA replication. Despite several reports on the characterization of this essential viral enzyme, little is known about the reaction pathway of NS5B-catalyzed nucleotide incorporation due to the lack of a kinetic system offering efficient assembly of a catalytically competent polymerase/template/primer/nucleotide quaternary complex. In this report, specific template/primer requirements for efficient RNA synthesis by HCV NS5B were investigated. For intramolecular copy-back RNA synthesis, NS5B utilizes templates with an unstable stem-loop at the 3' terminus which exists as a single-stranded molecule in solution. A template with a stable tetraloop at the 3' terminus failed to support RNA synthesis by HCV NS5B. Based on these observations, a number of single-stranded RNA templates were synthesized and tested along with short RNA primers ranging from two to five nucleotides. It was found that HCV NS5B utilized di- or trinucleotides efficiently to initiate RNA replication. Furthermore, the polymerase, template, and primer assembled initiation-competent complexes at the 3' terminus of the template RNA where the template and primer base paired within the active site cavity of the polymerase. The minimum length of the template is five nucleotides, consistent with a structural model of the NS5B/RNA complex in which a pentanucleotide single-stranded RNA template occupies a groove located along the fingers subdomain of the polymerase. This observation suggests that the initial docking of RNA on NS5B polymerase requires a single-stranded RNA molecule. A unique beta-hairpin loop in the thumb subdomain may play an important role in properly positioning the single-stranded template for initiation of RNA synthesis. Identification of the template/primer requirements will facilitate the mechanistic characterization of HCV NS5B and its inhibitors.

Genome, Viral↗
PubMed2000

Long terminal repeat regions from exogenous but not endogenous feline leukemia viruses transactivate cellular gene expression.

We have previously reported that the long terminal repeat (LTR) region of feline leukemia viruses (FeLVs) can enhance expression of certain cellular genes such as the collagenase IV gene and MCP-1 in trans (S. K. Ghosh and D. V. Faller, J. Virol. 73:4931-4940, 1999). Genomic DNA of all healthy feline species also contains LTR-like sequences that are related to exogenous FeLV LTRs. In this study, we evaluated the cellular gene transactivational potential of these endogenous FeLV LTR sequences. Unlike their exogenous FeLV counterparts, neither nearly full-length endogenous FeLV molecular clones (CFE-6 and CFE-16) nor their isolated LTRs were able to activate collagenase IV gene or MCP-1 expression in transient transfection assays. We had also demonstrated previously that production of an RNA transcript from exogenous FeLV LTRs correlates with their transactivational activity. In the present study, we demonstrate that the endogenous FeLV LTRs do not generate LTR-specific RNA transcripts in the feline embryo fibroblast cell line AH927. Furthermore, infection of AH927 cells by an exogenous FeLV subgroup A virus did not induce production of such LTR-specific transcripts from the endogenous proviral genomes, although the LTR-specific transcripts from the exogenous virus were readily detected. Finally, LTR-specific transcripts were not generated in BALB/3T3 cells transiently transfected with isolated CFE-6 LTR, in contrast to transfections with LTRs from exogenous viruses. Our data thus suggest that the inability of endogenous FeLV LTRs in gene transactivation is not due to cell line specificity or presence of any upstream inhibitory cis-acting element. Endogenous, nonleukemogenic FeLV LTRs, therefore, do not transactivate cellular gene expression, and this property appears to be specific to exogenous, leukemogenic FeLVs.

3T3 Cells↗
PubMed1999

Poliovirus RNA-dependent RNA polymerase (3D(pol)). Divalent cation modulation of primer, template, and nucleotide selection.

We have analyzed the divalent cation specificity of poliovirus RNA-dependent RNA polymerase, 3D(pol). The following preference was observed: Mn(2+) > Co(2+) > Ni(2+) > Fe(2+) > Mg(2+) > Ca(2+) > Cu(2+), and Zn(2+) was incapable of supporting 3D(pol)-catalyzed nucleotide incorporation. In the presence of Mn(2+), 3D(pol) activity was increased by greater than 10-fold relative to that in the presence of Mg(2+). Steady-state kinetic analysis revealed that the increased activity observed in the presence of Mn(2+) was due, primarily, to a reduction in the K(M) value for 3D(pol) binding to primer/template, without any significant effect on the K(M) value for nucleotide. The ability of 3D(pol) to catalyze RNA synthesis de novo was also stimulated approximately 10-fold by using Mn(2+), and the enzyme was now capable of also utilizing a DNA template for primer-independent RNA synthesis. Interestingly, the use of Mn(2+) as divalent cation permitted 3D(pol) activity to be monitored by following extension of 5'-(32)P-end-labeled, heteropolymeric RNA primer/templates. The kinetics of primer extension were biphasic because of the enzyme binding to primer/template in both possible orientations. When bound in the incorrect orientation, 3D(pol) was capable of efficient addition of nucleotides to the blunt-ended duplex; this activity was also apparent in the presence of Mg(2+). In the presence of Mn(2+), 3D(pol) efficiently utilized dNTPs, ddNTPs, and incorrect NTPs. On average, three incorrect nucleotides could be incorporated by 3D(pol). The ability of 3D(pol) to incorporate the correct dNTP, but not the correct ddNTP, was also observed in the presence of Mg(2+). Taken together, these results provide the first glimpse into the nucleotide specificity and fidelity of the poliovirus polymerase and suggest novel alternatives for the design of primer/templates to study the mechanism of 3D(pol)-catalyzed nucleotide incorporation.

Catalysis↗
PubMed1999

STAT-4 mediated IL-12 signaling pathway is critical for the development of protective immunity in cutaneous leishmaniasis.

Recent studies have demonstrated that two IL-12 signaling pathways, a STAT 4 - dependent and STAT4 - independent, are involved in the development of a Th1-like response. To determine their roles in the development of protective immunity against Leishmania major, we monitored progression of cutaneous Leishmania major infection in STAT4-deficient mice (STAT4-/-) compared to similarly infected wild-type (STAT4+/+) mice. Although the onset of lesion growth was delayed in STAT4-/- mice during the early phase of infection, these mice eventually developed large, non-healing lesions, whereas STAT4+/+ mice resolved their lesions. As infection progressed, both STAT4+/+ and STAT4-/- mice infected with L. major displayed similar titers of Leishmania-specific IgG1 and IgE but later produced lower IgG2a. On days 20 and 40 post-infection, Leishmania antigen-stimulated lymphnode cells from STAT4-/- mice produced significantly lower amounts of IFN-gamma than those from STAT4+/+ mice as measured by enzyme-linked immunosorbent assay. There was no significant difference, however, in IL-4 and IL-12 production between the two groups. These results indicate that STAT4-mediated IL-12 signaling is critical for the development of protective Th1 response following L. major infection in genetically resistant mice. Additionally, they demonstrate that, although genetically resistant mice lacking STAT4 signaling pathway develop large, non-healing lesions, they do not default towards a Th2-like response.

Animals↗