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Biomedical subjects

S Biswas

Publications and source records attributed to S Biswas.

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

Crystallization and preliminary X-ray analysis of ervatamin B and C, two thiol proteases from Ervatamia coronaria.

Two highly stable cysteine proteases, ervatamin B (ERV-B) and ervatamin C (ERV-C), purified from the latex of the medicinal plant E. coronaria have been crystallized at room temperature. Crystals of ERV-B and ERV-C diffract to 2.5 and 2.6 A, respectively. The space group is P212121 for the crystals of both proteases with unit-cell parameters a = 47.5, b = 58.8 and c = 68.8 A, and a = 43.8, b = 82.6 and c = 133.1 A, respectively. A self-rotation function for ERV-C indicates a twofold non-crystallographic symmetry relating the two molecules in the asymmetric unit.

Crystallization↗
PubMed1999

Potentiation of immune response against the RESA peptides of Plasmodium falciparum by incorporating a universal T-cell epitope (CS.T3) and an immunomodulator (polytuftsin), and delivery through liposomes.

Synthetic peptides representing repeat sequences of ring-infected erythrocyte surface antigen (RESA) of Plasmodium falciparum have shown poor immunogenicity and protection. In this study, the RESA peptides [(EENVEHDA)2 and (DDEHVEEPTVA)2] were chemically linked to a universal T-cell determinant, CS.T3, derived from the CS protein of P. falciparum. Polytuftsin (TKPR)40, a polymer of naturally occurring immunomodulator "tuftsin," was physically mixed with these conjugates. These preparations in alum and liposomes were immunized in four inbred strains of mice with different genetic backgrounds to study the humoral response. In the case of liposome-entrapped preparations, a 10 microg dose of antigen showed the optimum antibody response. Mice immunized with liposome containing RESA peptide(s)-CS.T3 conjugate along with polytuftsin showed the highest antibody levels in all the strains, whereas the RESA peptide(s) alone, adsorbed on alum or entrapped in liposomes, showed either poor or moderate antibody levels. The antibodies raised against liposome-entrapped preparations in both high-responder strain (SJL/J H-2s) and low-responder strain (FVB/J H-2q) showed 2 4-fold lower Kd values as compared to the alum adsorbed preparations, suggestive of high affinity antibodies. All the antigen preparations predominantly induced IgG2a and IgG2b isotype response, suggesting that the T-helper response involved is of the CD4 Thl type. The in vitro merozoite reinvasion inhibition assay showed 50-92% inhibition with sera raised against different antigen formulations. The highest percentage inhibition was observed with the RESA peptide-CS.T3 conjugate containing polytuftsin in liposomes. Thus, the incorporation of peptide antigens inside liposomes not only reduced the antigen dose by 5-fold but also elicited a high titre with high affinity antibodies and the inhibition of merozoites to RBC in vitro. Therefore, we conclude that the incorporation of these synthetic constructs in liposomes could be a useful strategy for the development of a subunit immunogen against malaria.

Adjuvants, Immunologic↗
PubMed1999

Cellular immune response to retinal S-antigen and interphotoreceptor retinoid-binding protein fragments in Eales' disease patients.

The role of retinal antigens in Eales' disease was studied in 24 patients and an equal number of healthy controls. Lymphocyte proliferative responses were tested in vitro against native S-antigen, its uveitopathogenic peptides (peptide M and peptide G), yeast histone H3 peptide and uveitopathogenic fragment of interphotoreceptor retinoid-binding protein (IRBP; R16) to establish their role in the pathogenesis of Eales' disease. Out of 24 Eales' disease patients, 6 showed significant proliferative response against S-antigen, its uveitogenic fragments or IRBP. None among the controls showed any response to any retinal antigen used in this study. There was no statistically significant difference in the response to purified protein derivative between patients and controls. These results suggest that retinal antigens may play a role in the etiopathogenesis of Eales' disease. An extraneous agent that could result in exposure of normally sequestered uveitopathogenic antigens of the immune system, leading to an exuberant immune response in the eye may initiate the disease.

Adolescent↗
PubMed1999

How many drug rehabilitation places are needed in prisons to reduce the risk of bloodborne virus infection?

Transmission of HIV and hepatitis B virus infection has been recognised in prisons, and injecting drug use is a major route of infection. Combined results of two pilot health care surveys showed that 47% of prisoners with a history of injecting drug use wanted help to give up class A drugs but only 11% of non-injecting drug users expressed a similar wish. It would therefore seem appropriate for prisons to estimate the number of inmates with a history of injecting drug use and provide drug rehabilitation places for half that number (47% rounded up). Data from three prisons in England and Scotland for which the numbers of drug rehabilitation places were known showed that they provided less than quarter of the minimum requirement based on this formula. The proportion of inmates with a history of injecting or of non-injecting drug use who want help to give up class A drugs requires further investigation in order to refine the needs formula.

Adult↗
PubMed1998

An apyrase from Mimosa pudica contains N5,N10-methenyl tetrahydrofolate and is stimulated by light.

An apyrase (NTP/NDPase) implicated in the response of Mimosa pudica to stimuli, such as touch, has been cloned, sequenced and expressed in Escherichia coli. While purifying and characterizing this enzyme, it was observed that a chromophore is associated with it, having absorption in the ultraviolet-A/blue region of the spectrum. The absorbance maximum of the chromophore, purified from the enzyme complex by gel filtration and HPLC, is around 350 nm. The chromophore has been identified as N5,N10-methenyl tetrahydrofolate (MTHF) by comparing the excitation and emission spectra of synthetic MTHF and the isolated cofactor, and by reconstitution of the enzyme complex with synthetic MTHF. Upon excitation with light (350 nm), an increase of apyrase activity was observed in the purified or reconstituted holoenzyme but not in the apoenzyme. The wavelength dependence of the light stimulation matched well with the fluorescence excitation spectra of the cofactor, MTHF. Possible implications of the results for signal transduction in M. pudica have been discussed.

Amino Acid Sequence↗
PubMed1998

Bis-cationic heteroaromatics as macrofilaricides: synthesis of bis-amidine and bis-guanylhydrazone derivatives of substituted imidazo[1,2-a]pyridines.

A series of guanylhydrazone, amidine, and hydrazone derivatives of 2-phenylimidazo[1,2-a]pyridine have been prepared and evaluated for macrofilarial activity against Acanthocheilonema viteae and Brugia pahangi in jirds. Compounds with 4',6-bis-substitution by cyclic guanylhydrazone groups show activity. 4',6-Bis-amidines show some activity but are more toxic; 4'- or 6-monosubstituted compounds are inactive. 2,6-Bis-substituted compounds lacking the phenyl ring are inactive. 4',6-Bis-substituted compounds having additional double bonds inserted between the heterocyclic ring and the phenyl ring or between the substituent and the ring system show reduced activity.

Amidines↗
PubMed1998

Is absence of pyruvate dehydrogenase complex in mitochondria a possible explanation of significant aerobic glycolysis by normal human leukocytes?

The oxygen consumption of leukocyte mitochondria of both healthy donors and leukemic patients was tested by using different respiratory substrates. The results indicate that pyruvate could not be utilized by mitochondria of normal leukocytes, whereas mitochondria of leukemic leukocytes could use pyruvate as a good respiratory substrate. A search for the possible presence of pyruvate dehydrogenase complex (PDC) in leukocytes indicates that this enzyme is apparently absent in mitochondria of normal leukocytes but is quite active in mitochondria of leukemic leukocytes. The absence of PDC in normal leukocyte mitochondria can explain the phenomenon of significant aerobic glycolysis that has been observed in normal leukocytes.

Acetyl Coenzyme A↗
PubMed1998

Use of guanylyl cyclase C for detecting micrometastases in lymph nodes of patients with colon cancer.

INTRODUCTION: Guanylyl cyclase C appears to be expressed only in colorectal cancer cells in extraintestinal tissues. Thus, guanylyl cyclase C may be useful as a marker to detect colorectal cancer micrometastases not detectable by histopathology in lymph nodes of patients. METHODS: Twelve patients with colon adenocarcinoma, Dukes Stages A through C2, and one patient with a tubulovillous adenoma were included in this study. Forty-two lymph nodes were collected from fresh surgical specimens, and each was examined by histopathology and reverse transcription followed by polymerase chain reaction using guanylyl cyclase C-specific primers. Histopathology identified colon cancer cells in 6 of 16 lymph nodes from five Dukes Stage C patients but not in lymph nodes from the patient with a tubulovillous adenoma, the Dukes Stage A patient, or six Dukes Stage B patients. Reverse transcription followed by polymerase chain reaction using guanylyl cyclase C-specific primers was performed on all 42 lymph nodes. RESULTS: Guanylyl cyclase C messenger RNA was not detected by reverse transcription followed by polymerase chain reaction in lymph nodes from the patient with the tubulovillous adenoma or the patient with Dukes Stage A colon carcinoma. Seven lymph nodes from Dukes Stage C patients revealed guanylyl cyclase C messenger RNA including six lymph nodes containing histopathologically confirmed metastases. Of significance, guanylyl cyclase C messenger RNA was detected in 6 of 21 lymph nodes from Dukes Stage B patients. Indeed, clinical staging of two patients could be upgraded from B to C using reverse transcription followed by polymerase chain reaction and guanylyl cyclase C-specific primers. CONCLUSION: Reverse transcription followed by polymerase chain reaction using guanylyl cyclase C-specific primers might be useful to more accurately assess micrometastases in lymph nodes of colorectal cancer patients undergoing disease staging.

Adenocarcinoma↗
PubMed1998

Thymopentin and splenopentin as immunomodulators. Current status.

Splenopentin (SP-5, Arg-Lys-Glu-Val-Tyr) and thymopentin (TP-5, Arg-Lys-Asp-Val-Tyr) are synthetic immunomodulating peptides corresponding to the region 32-34 of a splenic product called splenin (SP) and the thymic hormone thymopoietin (TP), respectively. TP was originally isolated as a 5-kDa (49-amino acids) protein from bovine thymus while studying effects of the thymic extracts on neuromuscular transmission and was subsequently observed to affect T cell differentiation and function. TP I and II are two closely related polypeptides isolated from bovine thymus. A radioimmunoassay for TP revealed a crossreaction with a product found in spleen and lymph node. This product, named splenin, differs from TP only in position 34, aspartic acid for bovine TP and glutamic acid for bovine splenin and it was called TP III as well. Synthetic pentapeptides (TP-5) and (SP-5), reproduce the biological activities of TP and SP, respectively. It is now evident that various forms of TPs were created by proteolytic cleavage of larger proteins during isolation. cDNA clones have been isolated for three alternatively spliced mRNAs that encodes three distinct human T cell TPs. The immunomodulatory properties of TP, SP, TP-5, SP-5 and some of their synthetic analogs reported in the literature have been briefly reviewed.

Adjuvants, Immunologic↗
PubMed1998

Mimosa pudica apyrase requires polysaccharide and Ca2+ for the activity.

Mimosa pudica Linn leaves with pulvini contain unique isoforms (I and II) of Apyrase enzyme (EC 3.6.1.5). The activity of isoform I depends on divalent cation Mn2+. This isoform is associated noncovalently with the polysaccharide, containing mainly of galactose and arabinose sugars. The apparent molecular mass of these 2 isoforms are 36 and 34 Kd respectively. The association of the polysaccharide with the isoform I has been found to be Ca2+ dependent which is endogenously present in this isoform. Removal of Ca2+ and polysaccharide from the enzyme (isoform I) leads to an inactivation. The enzyme activity can be restored when both Ca2+ and endogenous polysaccharide fraction were added at an optimal molar ratio of Ca2+:protein of 7:1. The endogenous polysaccharide can be replaced by the standard arabinogalactan. No other sugar or polysaccharide except the arabinogalactan can restore the apyrase activity. Calcium mediates a conformational change in the protein which helps in association of polysaccharide as evidenced from fluorometric and far UV-CD studies to restore the enzymic activity. Neither any interaction of the polysaccharide with the protein is detected in absence of Ca2+ nor the enzyme activity could be recovered under such condition.

Amylases↗
PubMed1998

The role of nitric oxide in the process of implantation in rats.

Nitric oxide (NO) plays an important role in cell signalling in many physiological systems, including reproduction. During pregnancy, oestrogen modulates uterine NO generation, and NO may play an intermediary role in the oestrogen-mediated effects on the uterus. Since oestrogen is actively involved in inducing endometrial receptivity to support the process of implantation, the role of NO in the process of implantation in rats was investigated. N omega-nitro-L-arginine methyl ester (L-NAME), an inhibitor of NO synthase (NOS), was administered in utero with or without sodium nitroprusside (SNP), a generator of NO, on different days during the preimplantation phase of gestation. The status of gestation in respect of implantation failure, endometrial receptivity and embryo development were assessed. L-NAME was administered at various doses (2-5 mg per uterine horn) and on different days of pregnancy (days 2-6 of pregnancy) to optimize the pregnancy terminating dose (absence of implantation site on day 8 of pregnancy) and the effective day of treatment. L-NAME led to failure of implantation when administered at 2.5 mg per uterine horn on day 3 of pregnancy. The characteristic preimplantation permeability changes in the uterus were significantly attenuated and embryo growth was retarded. The L-NAME-mediated effects were significantly reversed when SNP (100 micrograms) was co-administered with L-NAME. These findings suggest a role for NO in the process of implantation. The possible mechanism by which inhibition of the NO-NOS system may interfere with implantation is discussed.

Animals↗
PubMed1998

Experimental autoimmune uveitis as animal model for human posterior uveitis.

Uveitis is an intraocular inflammatory disease that mostly affects children and young adults. It is one of the major causes of blindness in young individuals in India and the world. It is responsible for about 10 per cent of total visual impairment. Unfortunately, etiological diagnosis is not evident in a majority of these patients. It is generally felt that autoimmune mechanism may be involved in so called 'idiopathic' cases which has led to search for the putative autoantigens in experimental animal models. It has been demonstrated that experimental autoimmune uveitis (EAU) can be elicited against several retinal proteins in rats, mice and sub-human primates. These include the S-antigen, a major protein on retinal photoreceptor cell, interphotoreceptor retinoid binding protein (IRBP) and several others. There are many similarities between clinical entities and the EAU, but the EAU differs from the clinical conditions in being self-limited, and requiring complete Freund's adjuvant for induction of the disease. The disease can be induced only in susceptible strains. Nevertheless, use of the EAU model has allowed for identification of disease causing epitopes of antigens and evaluation of disease modifying strategies which could be applied in clinical situations. There has been significant progress in this field, but still a lot more is required to be learnt to translate it into clinical practice.

Adult↗
PubMed1997

Cholecystokinin A and B receptors are differentially expressed in normal pancreas and pancreatic adenocarcinoma.

Cholecystokinin (CCK) plays an important role in pancreatic carcinogenesis. While human CCK-A and -B receptors have been fully characterized, their relative roles in human pancreatic adenocarcinoma remain unclear. Thus, expression of CCK-A and -B receptors in normal human pancreas, pancreatic adenocarcinomas, and other human extrapancreatic tissues and malignancies was examined, using reverse transcription followed by the polymerase chain reaction (RT-PCR). mRNA isolated from 15 normal pancreas specimens, 22 pancreatic adenocarcinomas, and 58 extrapancreatic tissues and tumors was subjected to RT-PCR using primers specific for human CCK-A and -B receptors. Expression of CCK-B receptors was detected in all tissues arising from pancreas and in most extrapancreatic tissues and tumors. In contrast, CCK-A receptors exhibited a more selective pattern of expression in gall bladder, intestine, brain, ovary, spleen, and thymus. Of significance, CCK-A receptors were expressed selectively in all pancreatic adenocarcinomas, but not in any normal pancreas specimens. In situ hybridization, using receptor-specific riboprobes, localized CCK-A receptor expression to ductal cells, the presumed origin of most human pancreatic adenocarcinomas. Southern blot analysis revealed no evidence of CCK-A receptor gene amplification or rearrangement in pancreatic adenocarcinomas. Because of its selective expression, the CCK-A receptor may serve as selective biomarker for pancreatic adenocarcinoma.

Adenocarcinoma↗
PubMed1997

Selenium salts and chromosome damage.

Sodium selenite and sodium selenate, fed by gavaging to age-matched male Swiss albino mice and observed after 24 h following a colchicine-fixative-air drying-Giemsa schedule, were found to induce chromosome breaks and spindle disturbances in bone marrow cells. The four concentrations used were fractions of LD50 and the effects were directly proportionate to the concentration of the chemical. Sodium selenite induced a slightly higher frequency of chromosomal aberrations than sodium selenate.

Animals↗
PubMed1997

Selective inhibition of mitochondrial respiration and glycolysis in human leukaemic leucocytes by methylglyoxal.

The effect of methylglyoxal on the oxygen consumption of mitochondria of both normal and leukaemic leucocytes was tested by using different respiratory substrates and complex specific artificial electron donors and inhibitors. The results indicate that methylglyoxal strongly inhibits mitochondrial respiration in leukaemic leucocytes, whereas, at a much higher concentration, methylglyoxal fails to inhibit mitochondrial respiration in normal leucocytes. Methylglyoxal strongly inhibits ADP-stimulated alpha-oxoglutarate and malate plus NAD+-dependent respiration, whereas, at a higher concentration, methylglyoxal fails to inhibit succinate and alpha-glycerophosphate-dependent respiration. Methylglyoxal also fails to inhibit respiration which is initiated by duroquinone and cannot inhibit oxygen consumption when the N,N,N', N'-tetramethyl-p-phenylenediamine by-pass is used. NADH oxidation by sub-mitochondrial particles of leukaemic leucocytes is also inhibited by methylglyoxal. Lactaldehyde, a catabolite of methylglyoxal, can exert a protective effect on the inhibition of leukaemic leucocyte mitochondrial respiration by methylglyoxal. Methylglyoxal also inhibits l-lactic acid formation by intact leukaemic leucocytes and critically reduces the ATP level of these cells, whereas methylglyoxal has no effect on normal leucocytes. We conclude that methylglyoxal inhibits glycolysis and the electron flow through mitochondrial complex I of leukaemic leucocytes. This is strikingly similar to our previous studies on mitochondrial respiration, glycolysis and ATP levels in Ehrlich ascites carcinoma cells [Ray, Dutta, Halder and Ray (1994) Biochem. J. 303, 69-72; Halder, Ray and Ray (1993) Int. J. Cancer 54, 443-449], which strongly suggests that the inhibition of electron flow through complex I of the mitochondrial respiratory chain and inhibition of glycolysis by methylglyoxal may be common characteristics of all malignant cells.

Adenosine Triphosphate↗