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Biomedical subjects

S K Ghosh

Publications and source records attributed to S K Ghosh.

At least 109 records · Page 6Linked to original sources
PubMed1993

Immunoregulation by processed immunoglobulin on B-cells.

According to Jerne's network hypothesis, the unique amino acid sequences of Ig variable regions, that is, the idiotypic determinants can function in immunoregulatory mechanisms and cellular interactions. Indeed, Id-specific T-cells (mostly CD4+) have since been described, but the nature of Id-positive Ig on B-cells involved in recruiting T-cells is unclear. Studies from our ongoing investigation presented here clearly show that Id can evoke both CD4+ and CD8+ T cells, and exist not only as the integral components of a bona fide antigen-binding receptor Ig but also as distinct molecular entities in processed forms on the cell surface of B-lymphocytes. Using a B-cell hybridoma, 2C3, that expresses anti-hapten (phthalate) antibody receptors on the cell surface, we induced both Id-specific CD4+ and CD8+ T effector cells. The CD4+ T cells were suppressive and mediated generation of Id-loss 2C3 variants, whereas CD8+ T cells were highly cytotoxic and selectively eliminated 2C3 cells both in vitro and in vivo. These effector cells could be induced by cell membrane-associated Ig but not by its soluble form, secreted by 2C3 cells. Antibodies to MHC class I but not class II molecules were inhibitory to this induction. Furthermore, brefeldin A (BFA), an inhibitor of MHC class I mediated processing, blocked induction of CTL but had no effect on the expression of membrane Ig. Moreover, chloroquine, an inhibitor of class II-mediated processing, had no effect. A few reports have recently appeared indicating that an exogenous Ig can be processed by B-cells in the context of MHC class II proteins.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Effect of theophylline on binding of delta-9-tetrahydrocannabinol with mammalian neuronal and non-neuronal membranes.

Delta-9-tetrahydrocannabinol (THC) (1.6 x 10(-6)-13.33 x 10(-6) M) binds to neuronal and non-neuronal subcellular membranes in a biphasic manner. Its binding to neuronal membranes occur in the following order synaptosome > myelin > brain microsome and brain mitochondria. Unlike brain membranes binding of delta-9-THC is greater with liver microsome than liver mitochondria. Irrespective of membranes theophylline (Th) (11.0 x 10(-6) and 550.0 x 10(-6) M) increases the binding of delta-9-THC by exposure of more number of delta-9-THC binding sites on the subcellular membranes without affecting its binding affinity. Failure of Th (11.0 x 10(-6)-550.0 x 10(-6) M) to increase the binding of delta-9-THC (1.6 x 10(-6)-13.33 x 10(-6) M) in solubilized membranes suggests the involvement of membrane lipid in the Th-induced enhancement of delta-9-THC binding.

Animals↗
PubMed1993

Delta-9-tetrahydrocannabinol and theophylline: in vitro interaction with bovine serum albumin.

Delta-9-tetrahydrocannabinol (delta-9-THC) (1.6 x 10(-6) M-13.33 x 10(-6) M) and theophylline (11.0 x 10(-6) M-550.0 x 10(-6) M) both bind to bovine serum albumin (BSA) and the binding is linear with respect to concentration. Further, it is observed that delta-9-THC both at low (1.6 x 10(-6) M and 6.4 x 10(-6) M) and high (13.33 x 10(-6) M) concentrations inhibits the binding of theophylline to BSA; whereas theophylline (11.0 x 10(-6) M-550.0 x 10(-6) M) promotes the binding of delta-9-THC to BSA. Kinetic analysis (using Scatchard plots) shows that delta-9-THC (1.6-13.33 x 10(-6) M) reduces the high affinity binding constant (K1) and the number of low affinity binding sites (n2) of theophylline to BSA; while its low affinity binding constant (K2) increased without affecting the number of high affinity binding sites (n1) under identical conditions. Further, it is observed that at lower concentrations (1.6-6.4 x 10(-6) M) delta-9-THC exerts greater effect on the binding parameters of theophylline-BSA interactions as compared to the effect observed with its high concentration (13.33 x 10(-6) M). Theophylline (11.0-550.0 x 10(-6) M). on the other hand, increases the affinity of the binding of delta-9-THC to BSA without changing the number of its binding sites. These suggest that (a) delta-9-THC and theophylline bind at different sites of BSA molecules and (b) the two drugs interfere with each other in their individual binding with the molecular orientation of the BSA molecule.

Animals↗
PubMed1992

Effect of delta-9-tetrahydrocannabinol and theophylline on hepatic microsomal drug metabolizing enzymes.

Theophylline (Th) under in vitro conditions stimulated the activities of rat liver microsomal aniline hydroxylase, N-demethylase and O-demethylase, while delta-9-tetrahydrocannabinol (delta-9-THC) inhibited the activities of these hepatic microsomal drug metabolizing enzymes under similar conditions. delta-9-THC-induced inhibition of hepatic microsomal drug metabolizing enzymes was significantly reduced in the presence of Th. Analysis of Lineweaver-Burk plots showed that Th-induced stimulation of hepatic microsomal drug metabolizing enzymes occurs due to an increase in substrate affinity (1/Km) and of Vmax. delta-9-THC-induced inhibition of N-demethylase and O-demethylase is probably due to competition of the drug with the substrates for a common intermediate in the microsomal electron transport chain. Non-competitive and mixed-type inhibition caused by delta-9-THC on aniline hydroxylation appears to be associated with a non-specific action of delta-9-THC. Blocking of delta-9-THC-induced inhibition or reduction of Th-induced stimulation of hepatic drug metabolizing enzymes with Th or delta-9-THC was due to an increase or decrease in either Vmax, substrate affinity (1/Km) or both with respect to the corresponding Km and Vmax observed with delta-9-THC or Th alone.

Aniline Hydroxylase↗
PubMed1992

Induction of syngeneic cytotoxic T lymphocytes against a B cell tumor. II. Characterization of anti-idiotypic CTL lines and clones.

In an earlier communication we showed that idiotypic immunoglobulin (Id+ Ig) of a B cell hybrid, 2C3, can induce cytotoxic T lymphocytes (CTL) in the spleens of mice that are hyperimmunized with the irradiated tumor cells. To understand the extent of heterogeneity in the splenic CTL population, stable anti-idiotypic CTL lines and clones were established from 2C3-primed splenocytes. One representative CTL line A102 which exhibited the phenotype of CD3+, CD4-, and CD8+, has been maintained in long-term culture for more than 18 months. Cytotoxic specificity of A102 was determined by cold target inhibition assay using a panel of syngeneic and allogeneic B cell tumors. The CTL line A102 was highly cytotoxic to 2C3, only weakly to other syngeneic tumors, but not at all to allogeneic B cell tumor CH12. Furthermore, CTL-mediated cytolysis was significantly abrogated by blocking 2C3 cells with anti-idiotypic monoclonal and polyclonal antibodies. These results clearly show that 2C3 Id represents the immunodominant epitope(s) recognized by the CTL line A102. To isolate a highly Id-specific effector population, A102 was repeatedly subcloned by limiting dilution. One such clone 102.F5 exhibited considerable specificity toward Id+ 2C3 while another clone 102.E10 showed no such specificity in a competitive cytotoxicity assay. This was further confirmed by the inhibition studies with anti-Id mAb. Thus, hyperimmunization with irradiated 2C3 cells evokes a spectrum of anti-2C3 cytotoxic effector cells, of which a major population is reactive to the idiotypic determinants associated with 2C3 Ig.

Animals↗
PubMed1992

Induction of syngeneic cytotoxic T lymphocytes against a B cell tumor. III. MHC class I-restricted CTL recognizes the processed form(s) of idiotype.

The purpose of this work was to determine the molecular nature of the idiotypic Ig of a B cell tumor, 2C3, involved in the induction of anti-idiotypic cytotoxic T-lymphocytes (CTL). We previously reported that hyperimmunization of mice with irradiated 2C3 cells provides effective tumor protection by inducing MHC class I-restricted CTL. Due to the enormous heterogeneity of the splenic CTL further study could not be undertaken on the idiotype (Id)-CTL interaction. Subsequently an anti-idiotypic CTL line, A102, and a highly Id-specific CTL clone, 102.F5, have been developed. In the present investigation we report that the processed forms of idiotypic determinants are responsible for induction and activation of these specific effector CTL. Inhibition studies using anti-TcR and anti-MHC class I mAbs showed that the TcR-CD3 complex of the anti-idiotypic CTL recognized 2C3 Id in the context of MHC class I antigens. The cytotoxicity of these CTL could not be inhibited with affinity-purified 2C3 Ig used as such or after pulsing with splenic antigen-presenting cells (APC). Furthermore, using brefeldin A (BFA) and chloroquine (CLQ), which are specific inhibitors of cytosolic and endosomal antigen processing pathways, respectively, it has also been observed that exposure of 2C3 to BFA but not CLQ prevents its cytolysis by both anti-idiotypic CTL line and clone. These results clearly indicate that endogenously produced idiotypic determinants of 2C3 Ig are processed in pre-Golgi vesicle, possibly in the ER, along with MHC class I antigens and then are transported to the membrane. Treatment of 2C3 with BFA, however, did not exert any effect on the expression of membrane-associated Ig of 2C3 cells. Therefore, it is the processed form rather than the bona fide receptor Ig on the cell surface that is recognized by the Id-specific CTL.

Animals↗
PubMed1992

Induction of syngeneic cytotoxic T lymphocytes against a B cell tumor. I. Role of idiotypic immunoglobulin.

In previous studies we showed that idiotypic determinants of a B cell hybrid, 2C3, was involved in the generation of idiotype (Id)-specific noncytolytic CD4+ effector T cells that suppressed the Ig expression of wild type 2C3 tumor. In the present investigation we report that Id+ Ig associated with 2C3 was also capable of eliciting syngeneic cytotoxic T lymphocytes (CTL) when mice were hyperimmunized with irradiated 2C3 cells. These effector cells were predominantly Thy 1.2+, CD8+, and CD4- and highly cytotoxic to 2C3 as shown by in vitro and in vivo assays. The unique idiotypic determinants (private Id) of 2C3 Ig was important in the induction of CTL since these effector cells were generated in mice only after immunization with Id+ 2C3 cells. In contrast, immunization of mice with 6B2, an Ig-loss variant of 2C3, and 1BF7, an unrelated syngeneic B cell hybrid which expresses Ig of the same isotype as that of 2C3 but of different Id, failed to elicit any cytotoxic response. Furthermore, incorporation of anti-idiotypic monoclonal and polyclonal antibodies into culture medium abrogated the activation of CTL during in vitro stimulation of the primed splenocytes. Induction of CTL was also inhibited by anti-MHC class I and anti-CD3 monoclonal antibodies, indicating that CD3-TcR complex of the effector T cells were involved in the recognition of Id+ Ig in the context of MHC class I antigens. These results, together with our previous observation, suggest that the anti-2C3 immune response is mediated by two kinds of effector cells, namely, CD4+ noncytolytic and CD8+ cytotoxic T cells. Moreover, the unique private Id associated with 2C3 plays a pivotal role in the induction of both of these effector cells.

Animals↗
PubMed1992

Promotion of murine B cell differentiation by 2-mercaptoethanol in contrast to glutathione.

The role of thiol compounds in B cell proliferation and differentiation was investigated with a stable, homogeneous population of an antigen-specific plasmablastoma, 2C3. This cell line expresses both membrane and secreted forms of immunoglobulin and is arrested at an intermediate stage of B cell development. Attempts to induce its differentiation into plasma cells using antigen, anti-idiotypic antibodies, or mitogens were unsuccessful. However, cultivation of 2C3 in the presence of 2-mercaptoethanol (5 x 10(-5) M) changed its doubling time from 19.8 to 34.9 h. There was also a significant rise in intracellular glutathione and in immunoglobulin production, but little change in non-Ig protein secretion. In contrast, exposure of 2C3 to exogenous glutathione (5 x 10(-3) M) reduced the doubling time to 11.0 h, with marked increases in proliferation. Moreover, there was no significant rise in either intracellular glutathione or immunoglobulin secretion. Distinct morphological differences were also apparent at the ultrastructural level. Thus, there is a dichotomy in the action of the two thiols. Although the effects of 2-mercaptoethanol could not be reversed, the two thiols together abrogated each other's effects, implying that their actions may be mediated through a common regulatory pathway.

Animals↗
PubMed1992

Sensitivity status of Plasmodium falciparum to chloroquine, amodiaquine, quinine, mefloquine and sulfadoxine/pyrimethamine in a tribal population of District Sundargarh, Orissa.

In a malaria-endemic area of Orissa, wherein chloroquine has been in use for over thirty years, 58.3% (14/24) P. falciparum cases did not respond to single dose chloroquine (10 mg base/kg) in in-vivo test. With standard dose (25 mg base/kg) 31.2% cases (10/32) showed resistance, i.e. at RI (15.6%), RII (9.4%) and RIII (6.2%) levels. Standard dose was superior in response to the single dose therapy [p < 0.05; chi 2 (df 1) = 4.11]. Out of eight isolates tested in vitro, two showed resistance to chloroquine, five to sulfadoxine/pyrimethamine (SP) but all were sensitive to amodiaquine, quinine and mefloquine. Whereas the standard dose of chloroquine would be a better option in general, in resistant cases, SP, quinine and mefloquine offer an alternative drug choice. The implications of drug resistance in a malaria-control programme and the need to revise drug policy in India are discussed.

Amodiaquine↗
PubMed1992

Studies on human lenses: II. Distribution and solubility of fluorescent pigments in cataractous and non-cataractous lenses of Indian origin.

Fluorometric studies of cataractous and non-cataractous human lenses were carried out to study the emission characteristics and the distribution and solubility of lenticular pigments. Most of the detected fluorophores were well distributed over the cortical and nuclear portion of the lens. The decrease in solubility of proteins with aging and cataract formation is concomitant with increasing photolysis of tryptophan. However, this is likely a phenomenon independent of the photochemical transformations of the lens proteins. The number of emitting species in the diseased lenses are higher than in the normal mature lenses. A species emitting around 375 or 388 nm is of particular interest (lambda cx 330 nm) in that the emission characteristics of this fluorophore resemble kynurenic acid which has a high photosensitizing efficiency. The concentration of fluorescent pigments in the lenses of Indian origin is significantly high. The intense pigmentation could be attributed largely to the formation of photoproducts in the absence of normal endogenous antioxidant accumulation that is dependent on nutrition standard. If, indeed, any of these fluorescent pigments, because of their photosensitizing ability, are responsible for lenticular opacity, it is not the abundance of sunlight alone but also malnutrition that could account for the high incidence of cataract in India.

Adult↗
PubMed1991

Cloning, sequencing, and expression of two murine 2'-5'-oligoadenylate synthetases. Structure-function relationships.

2'-5'-oligoadenylate synthetases constitute a multimember family of interferon-inducible enzymes which need double-stranded RNA as an obligatory cofactor. We have isolated cDNA clones for two new murine synthetases. These two clones, 9-2 and 3-9, encoded proteins of 414 and 363 amino acid residues, respectively, out of which the amino terminal 346 residues were almost identical. They were also very similar to the corresponding regions of human synthetases E16 and E18. On the other hand, the carboxyl-terminal 68 residues of clone 9-2 had no homology with the carboxyl-terminal residues of E18. These murine clones had only 67% amino acid identity with the previously isolated murine synthetase clone L3. 9-2 and 3-9 proteins were expressed efficiently by in vitro transcription and translation of cDNA clones containing the synthetase coding regions preceded by the 5'-untranslated region of the vesicular stomatitis virus NS gene. These in vitro synthetized proteins bound to double-stranded RNA and catalyzed the synthesis of 2'-5' oligoadenylates. A nested set of deletion mutants of the 9-2 clone was produced by restriction digestion and polymerase chain reaction. Functional testing of the corresponding truncated proteins revealed that a region between amino acid residues 104 and 158 was necessary for binding to double-stranded RNA and a region between residues 320 and 344 was necessary for enzyme activity. Moreover substitution of the lysine residue at position 333 by arginine did not affect the enzyme activity.

2',5'-Oligoadenylate Synthetase↗
PubMed1991

Enzymic methylation of myelin basic protein in myelin.

Myelin fractions with different degrees of compaction were isolated from bovine brain, and post-translational methylation of membrane-associated proteins was studied. When the purified myelin-basic-protein-specific protein methylase I and S-adenosyl-L-[methyl-14C]methionine were added exogenously, the most compact myelin fraction exhibited higher methyl-accepting activity than the less compact dense fractions. The methylated protein was identified as myelin basic protein (18.4 kDa) exclusively among the several myelin proteins from all membrane fractions, by SDS/PAGE/radioautography of methyl-14C-labelled membrane proteins. The methyl-14C-labelled amino acid residue in the basic protein was identified by h.p.l.c. as NG-methylarginine, indicating the high degree of specificity for the arginine residue as well as the myelin basic protein in the intact myelin membranes. The possibility of a charge alteration of myelin basic protein resulting from its arginine methylation was investigated by using the purified component 1 of myelin basic protein. The methylated component was shown to be less cationic than the unmethylated component by Bio-Rex 70 cation-exchange chromatography, since the former preceded the latter. However, in the presence of the denaturant (guanidinium chloride), the two species were co-eluted, indicating that the charge difference between methylated and unmethylated myelin basic protein can only be shown under the renatured condition.

Amino Acids↗
PubMed1991

Malignant and nonmalignant T cell lines from human T cell lymphotropic virus type I-negative patients with Sézary syndrome.

The establishment of an in vitro model for cutaneous T cell lymphomas and Sézary syndrome has been difficult since T cells from individuals with these diseases do not proliferate in response to T cell mitogens. We found that conditioned media, collected from mitogen-activated PBMC from Sézary patients, contain an IL-2 receptor inducing factor. Despite their ostensible proliferative disorder, using a combination Sézary cell-conditioned media and rIL-2, we established IL-2 responsive, human T cell lymphotropic virus type I negative T cell lines from 23 patients, nine of which contain cells with the structural and/or genetic characteristics of neoplastic Sézary T cells.

Cell Division↗
PubMed1991

Purification and properties of the low-molecular-weight alpha-crystallin from normal goat lens: comparison with bovine lens.

Low-molecular-weight alpha-crystallin (alpha L-crystallin) isolated from decapsulated lens of goat (Capra hiscus) has been purified to an apparently homogeneous population. Goat alpha L-crystallin closely resembles its bovine counterpart in size, shape, exposition of sulfhydryl groups, subunit composition and the nature of its UV-absorption profile. Like bovine alpha L-crystallin, dissociated subunits of goat alpha L-crystallin assemble upon reassociation into a particle of almost half the size of the native one. However, subunits of goat alpha L-crystallin are found to contain more aromatic amino acid residues than those of bovine subunits leading to a higher value of extinction coefficient (E1cm1%) at 280 nm for the goat protein.

Amino Acids↗
PubMed1991

Effect of cetirizine on histamine- and leukotriene D4-induced bronchoconstriction in patients with atopic asthma.

Cetirizine, a derivative of hydroxyzine, is a new compound with potent antihistaminic property without antiserotonin and anticholinergic activities. The effect of both a single dose (15 mg) and 7 days of treatment (15 mg twice daily) with cetirizine, a potent H1 antagonist on bronchoconstriction induced by histamine and leukotriene D4 (LTD4) has been examined in 10 patients with mild atopic asthma in a placebo-controlled, double-blind, crossover study. Cetirizine, after a single dose and 7 days of treatment with placebo, the geometric mean values of the provocative concentration of histamine causing a 20% fall in FEV1 (millimolars) were 1.60 (95% confidence interval, 0.82 to 3.11) and 1.67 (0.77 to 3.65), compared with 118.07 (77.22 to 180.54) (p less than 0.0001) and 53.16 (20.50 to 137.84) after cetirizine administration (p less than 0.0002). The mean inhibition after a single dose was twofold higher than after 1 week of treatment (p less than 0.05). After a single dose and 7 days of treatment with placebo, the geometric mean values of the provocative concentration of LTD4 causing a 20% fall in FEV1 (micromolars) were 2.26 (1.74 to 2.94) and 2.37 (1.77 to 3.17), compared with 3.90 (2.60 to 5.86) (p less than 0.05) and 3.21 (2.28 to 4.52) after cetirizine administration. This result suggests that cetirizine is a potent H1 antagonist in the human airways. Diminished activity after 1 week of treatment suggests subsensitivity of H1 receptors developing in human airways. The small protective effect after a single dose against LTD4-induced bronchoconstriction indicates a nonspecific rather than a specific receptor antagonism.

Adult↗