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Biomedical subjects

A Thakur

Publications and source records attributed to A Thakur.

At least 55 records · Page 3Linked to original sources
PubMed1999

Familial resemblance in humoral immune response to defined and crude Schistosoma mansoni antigens in an endemic area in Brazil.

This study addressed whether the humoral immune response to crude and defined Schistosoma mansoni antigens aggregates within families. The sample included 155 siblings from 42 nuclear families in Brazil. Sera examined by ELISA for antibody isotypes reactive to defined schistosome antigens and crude schistosome antigens (soluble adult worm antigen preparation and soluble egg antigen) demonstrated that there was a difference in sibling-pair correlations between defined and crude S. mansoni antigens. In contrast to the finding with crude antigens, egg-positive sibling pairs showed significant familial resemblance for all IgG subclasses and IgE to adult-stage antigens Smp20.8 and Smp50. Only the IgE and IgG4 isotypes showed familial resemblance to the egg-stage antigen, Smp40. Egg-negative sibling pairs showed significant familial resemblance only for IgE and IgG4 to Smp40. That both the IgE and IgG4 response to defined S. mansoni antigens showed familial resemblance is interesting in light of the converging evidence for the role of IgE and IgG4 in human susceptibility and resistance to reinfection.

Adolescent↗
PubMed1999

Port-wine-stain (nevus flammeus), congenital Becker's nevus, café-au-lait-macule and lentigines: phakomatosis pigmentovascularis type Ia--a new combination.

A 16-year-old male had brown macules in a geographic pattern with increased terminal hair on the back and dusky red partially blanchable non progressing macules on his left thigh since birth. Clinical diagnoses of Becker's nevus and port-wine-stain were made and confirmed histopathologically. In addition, he had multiple lentigines on the face and trunk and a single café-au-lait-macule on his chest.

Adolescent↗
PubMed1998

Chemotactic activity of tears and bacteria isolated during adverse responses.

Inflammatory processes are characterized by the dynamic influx of leukocytes. This leukocyte recruitment and activation is thought to be initiated by chemical signals including chemotactic factors. This study was designed to investigate the chemotactic activity in different tear types and bacteria isolated during adverse responses to contact lens wear. Chemotactic activity was determined by quantitating in vitro neutrophil migration using a microchemotaxis chamber. Results demonstrated that tears collected immediately after 8 hours sleep (P<0.001) and tears collected during adverse responses (P<0.001) showed significantly higher chemotactic activity compared to reflex tears. Specific neutralizing antibodies to IL-8, LTB4 and C5a were added to closed eye and adverse response tears. Pre-incubation of closed eye tears with antibodies to IL-8 showed a significant reduction in chemotactic activity (P<0.0001), whereas a significant reduction of PMN migration in adverse response tears was observed after pre-treatment with antibodies to LTB4 (P<0.0001). However no difference in chemotactic activity was observed after incubation with antibody to C5a or irrelevant antibody. Dot blots demonstrated that closed eye tears contained approximately 150 ng ml-1 IL-8 and adverse response tears contained 2 ng ml-1 IL-8. Most Gram negative bacteria isolated from contact lenses caused directed migration of PMNs. Addition of neutralizing antibody to LPS significantly abrogated the chemotactic activity of bacterial cells (P<0.001). Our findings provide evidence that IL-8 during eye closure, and bacterial chemotactic substances and LTB4 during contact lens induced adverse responses, are responsible for the recruitment of PMNs.

Chemotaxis, Leukocyte↗
PubMed1998

Cytokine and lipid inflammatory mediator profile of human tears during contact lens associated inflammatory diseases.

Contact lens induced acute red eye (CLARE) and contact lens induced peripheral ulcer (CLPU) are among the most common contact lens induced inflammatory reactions. Both CLARE and CLPU are characterized by corneal infiltration which indicates the presence of chemoattractants and other inflammatory mediators. The aim of this study was to characterize the cytokine and chemotactic lipid inflammatory mediator profile in the tears of people experiencing CLARE or CLPU. Cytokines IL-1 beta, IL-6, IL-8, GM-CSF and LTB4 in tears were measured by antibody sandwich and competition inhibition enzyme-linked immunosorbent assays (ELISA). Platelet activating factor-like activity was measured by a degranulation assay by measuring the release of labelled serotonin from platelets. The functional role GM-CSF and chemoattractants were determined by flow cytometry and chemotaxis. Increased levels of cytokines and chemoattractants were detected in both CLARE and CLPU tears. CLPU tears showed increased levels of LTB4 (P = 0.002) and PAF-like activity (P = 0.047) whereas CLARE tears showed increased levels of GM-CSF (P = 0.002). IL-8 (P < 0.05). LTB4 (P = 0.002) and PAF-like activity (P = 0.047) compared to control tears. Flow cytometric analysis revealed that incubation of PMN with CLARE tears increased the number of IgA receptors indicating that the GM-CSF in CLARE tears was active. Combinations of suboptimal concentrations (which were found in CLARE and CLPU tears) of IL-8 with either LTB4 or PAF significantly (P < 0.0001) enhanced the chemotactic activity for PMN compared to their individual effects. Our data highlight the possible pathophysiological roles of these inflammatory mediators in leukocyte recruitment and activation during ocular inflammatory responses. The results suggests that GM-CSF, IL-8 and LTB4 are active during corneal pathology and LTB4 or IL-8 may maintain the contact lens induced PMN response in vivo.

Acute Disease↗
PubMed1998

The proinflammatory cytokines and arachidonic acid metabolites in human overnight tears: homeostatic mechanisms.

The tear film plays an important role in the defense of the external ocular surface. During sleep a number of changes take place, including increased production and release of various inflammatory mediators. We have studied the hypothesis that closed-eye tears contain proinflammatory cytokines and lipid inflammatory mediators, which serve to recruit polymorphonuclear leukocytes (PMNs) and regulate the function of PMNs and IgA during sleep. We investigated interleukin-1beta, interleukin-6, interleukin-8, monocyte chemotactic protein 1, granulocyte-macrophage colony stimulating factor (GM-CSF), leukotriene B4 (LTB4), and platelet activating factor (PAF) in open and closed-eye tears of normal healthy subjects. Results showed that IL-6, IL-8, GM-CSF, LTB4, and PAF were present in high levels in closed-eye tears compared to open-eye tears. Closed-eye tears were able to recruit neutrophils, with maximal recruitment after 8 hr of sleep, suggesting that chemokine IL-8 and the lipid chemoattractant LTB4 were active. Flow cytometric analysis revealed that incubation of neutrophils with closed-eye tears up-regulated the surface expression of IgA receptor, indicating that the GM-CSF in tears was functionally active. Up-regulation of cytokines and the lipid inflammatory mediator LTB4 during eye closure are noteworthy, as each of these cytokines has an established role in initiation and amplification of the inflammatory response. IL-8 and LTB4 may act as potent chemoattractants and activators for PMNs, whereas IL-6 and GM-CSF potentiate the secretion and function of IgA and enhance neutrophil responsiveness to proinflammatory agonists.

Adult↗
PubMed1998

Interactions between Candida species and platelets.

Candida spp. are able to cause disseminated disease in immunocompromised patients. This study examined the interactions of Candida spp. with platelets, complement and polymorphonuclear leucocytes (PMNLs). With the exception of C. albicans, all other Candida spp., including a C. albicans strain previously classified as C. stellatoidia, aggregated human platelets at a ratio of yeast cells: platelets of 1:80. Usually, those species and strains that aggregated platelets were either killed or prevented from growing in platelet-rich plasma indicating that the aggregation released microbicidal or microbistatic substances that were active against Candida spp. All Candida spp. were resistant to attack by complement in 50% serum. However, all species activated complement as determined by the presence of C3 fragments on their surface, in particular a 195-kDa fragment corresponding to C3c, two fragments at 67 and 40 kDa corresponding to iC3b, and a 33-kDa fragment corresponding to C3d. When strains were tested for their ability to stimulate the release of pro-inflammatory substances from platelets and PMNLs, it was found that most strains stimulated PMNLs to release interleukin(IL)-8 but not IL-1beta or leucotriene B4. The ability of C. albicans to evade complement-mediated killing and not to aggregate platelets may contribute to the survival of this species in the blood during vascular infections.

Anticoagulants↗
PubMed1998

Effect of tear secretory IgA on chemotaxis of polymorphonuclear leucocytes.

PURPOSE: The aim of the present study was to examine the effect of tear and purified colostrum secretory IgA (sIgA) on polymorphonuclear leucocyte (PMN) chemotaxis. METHODS: The chemotactic effect of tear and purified sIgA for PMN was studied using a modified Boyden chamber. Tears treated with anti-human IgA, complement-inactivated tears and albumin were used as controls. RESULTS: The data indicate that both tear and purified sIgA are highly chemotactic for PMN. Anti-sIgA antibodies reduced the chemotactic effect of closed-eye tears (34%) and tear collected during ocular inflammation. CONCLUSION: The massive recruitment of PMN in tears during sleep may be partially attributed to the increased levels of tear sIgA. This may play an important role in protecting the eye against bacterial infection.

Chemotaxis, Leukocyte↗
PubMed1997

Presence of inflammatory mediators in the tears of contact lens wearers and non-contact lens wearers.

The present studies have demonstrated the levels of N-methyl histamine in tears from normal physiological states, pathological states and contact lens wear. Histamine was significantly increased in closed eye tears compared with both open and reflex tears. Tears from other ocular conditions had low levels of histamine except for environmental hypersensitivity, which contained significantly elevated levels compared to normal tear types. Interestingly, tears from asymptomatic contact lens wearers had significant levels of histamine whereas tears from contact lens adverse events had lower levels, possibly reflecting a change in histamine metabolism.

Analysis of Variance↗
PubMed1997

Modulation of cytokine production from an EpiOcular corneal cell culture model in response to Staphylococcus aureus superantigen.

The present study investigated the hypothesis that Staphylococcus aureus enterotoxin B (SEB) produces epithelial cell death and releases inflammatory cytokines that produce stromal infiltration during contact lens induced peripheral ulceration. Epithelial cells were incubated with different doses of SEB for various time periods. Culture supernatants were assayed for cytokines IL-1 beta, IL-6 and chemotactic agents IL-8 and LTB4 SEB induced the production of IL-1 beta and IL-8. Epithelial cells exposed for longer periods (48 h) with low concentrations of SEB produced significantly higher levels (P < 0.02) of IL-1 beta and IL-8 (P < 0.05) compared to a 24 h exposure. SEB did not induce the production of IL-6 and LTB4.

Cell Death↗
PubMed1997

Complement and complement regulatory proteins in human tears.

PURPOSE: The complement system is part of the innate defense system of the body, and it contributes to inflammatory conditions. The current study examined tears for the presence of complement components, the activity of the components, and the presence of regulatory components. METHODS: The significance of a functional complement system in tears was examined in four ways. First, the presence and concentration of complement components in tear samples (open-eye, closed-eye, and reflex tears) was examined by sandwich enzyme-linked immunosorbent assay. Second, the presence of an active pathway in each tear type was established by supplementation of complement-deficient sera. Third, Western blotting of tear samples was used to determine whether complement components were activated in tears. Fourth, the presence of regulatory components was examined by enzyme-linked immunosorbent assay and by the inhibition of the ability of tears to supplement deficient sera. RESULTS: Components C1q, C3, factor B, C4, C5, and C9 were detected in closed-eye tears. Only C3, factor B, and C4 were detected in open-eye and reflex tears. Tears were able to supplement complement-deficient sera, indicating that the components were in an active state. Complement components C3, factor B, C4, and C9 were activated in closed-eye tears. The regulatory protein decay-accelerating factor was found only in closed-eye tears. Lactoferrin, another regulatory protein present in all tear types, was shown to inhibit complement-mediated red blood cell lysis, although the inhibition by closed-eye tear lactoferrin was reduced compared to that isolated from other tear types. CONCLUSIONS: This study has demonstrated that the complement system in tears was functionally active and that the concentration of all components was increased greatly in closed-eye tears. In spite of the presence of regulatory proteins, proteins of the complement cascade in tears were shown to be activated.

Blinking↗
PubMed1997

Exchange transfusion in septic neonates with sclerema: effect on immunoglobulin and complement levels.

OBJECTIVE: To study the effect of exchange transfusion (ET) on the levels of immunoglobulins (Ig) and C3 in neonatal sepsis with sclerema. DESIGN: Randomized controlled trial in a referral neonatal unit of a teaching hospital. SUBJECTS: Consecutive culture positive septic neonates with sclerema were enrolled and were randomized to undergo ET (study group, n = 20) or no ET (controls, n = 20). RESULTS: Mortality was 50% in the study group and 95% in controls. Gram negative organisms accounted for 85% in study group and 90% in controls. IgG, IgA and IgM levels rose significantly while C3 levels did not show significant rise 12-24 hours after ET. Ig and C3 levels did not change significantly in the controls. CONCLUSION: ET with fresh whole blood in septicemic newborns with sclerema improves survival, particularly in the more premature group and significantly enhances, IgG, IgA and IgM levels.

Bacteremia↗
PubMed1996

Role of T-cell subsets in protection, delayed type of hypersensitivity and granuloma formation during Yersinia enterocolitica infection in mice.

Studies were undertaken with (C57BL/6 x DBA/2) B6D2 F1 mice as a prototype of a strain resistant to Y. enterocolitica. The growth of Y. enterocolitica in liver and spleen following intravenous infection was determined. Restriction of growth of Y. enterocolitica in the spleen and liver started, when a delayed type of hypersensitivity (DTH) became elicitable. Mice were treated with monoclonal antibodies (mAb) specific to T-cell surface markers; injection of these antibodies leads to marked depletion of the specific T-cell subset. After selective in vivo depletion the three characteristic T-cell mediated phenomena, DTH, anti-bacterial protection and granuloma formation were investigated. DTH to Y. enterocolitica soluble antigen was abolished in mice treated with anti-Thy1.2 or anti-CD4 mAbs, while anti-CD8 mAbs had no effect. The elimination of bacteria from the spleens of infected animals was inhibited by the application of either anti-Thy1.2 or anti-CD8 mAbs, while anti-CD4 mAbs had a marginal effect on anti-bacterial protection. The accelerated development of mononuclear cell foci in the liver of immune mice was also inhibited by the application of anti-CD4 and anti-CD8 mAbs. Thus, it appears that specific T-lymphocytes play an important role in murine Yersiniosis. The present model is valuable for the investigation of the cellular immune response to this important enteric pathogen.

Animals↗
PubMed1996

Detection of antibody to C-carbohydrate of group A streptococci with enzyme-treated whole bacterial cells as antigen for ELISA.

Antibody to specific cell-wall carbohydrate of group A streptococci in human sera was determined by enzyme-linked immunosorbent assay (ELISA) with enzyme-treated whole cells and purified group A carbohydrate (ACHO) as antigens. The optimal concentration of enzyme-treated whole bacterial cells to coat wells was 2 x 10(8) cells/ml and for purified ACHO antigen the optimal concentration was 1 microgram/ml. Sera from patients with acute rheumatic fever and acute glomerulonephritis were screened for the presence of C-carbohydrate antibodies. Patients with acute post-streptococcal complications showed significantly higher titres of antibody when compared with normal healthy individuals. ELISA results were also compared with purified ACHO as an antigen; this showed a highly significant correlation (r = 0.73). Results showed that measurement of the anti-ACHO antibody by ELISA with enzyme-treated whole cells can be a useful, reliable and simple method for serological diagnosis of group A infection and sequelae.

Antibodies, Bacterial↗
PubMed1996

Type-specific antibodies to purified streptococcal M proteins from potentially rheumatogenic M-types in patients with rheumatic fever and rheumatic heart disease.

This study was designed to identify the predominant serotypes of group A streptococci (GAS) responsible for rheumatic fever (RF) and rheumatic heart disease (RHD) in India. RF and RHD sera were screened for antibodies to M proteins retrospectively against known rheumatogenic M types and M types isolated from patients with acute RF. All GAS strains isolated from four patients with acute RF in a short outbreak of RF, were identical - serum opacity factor (SOF) negative, T-pattern 3/13 B3264 and M-non-typable. Because of this, M protein was isolated from only one of these four M-non-typable strain (S-399). This was done by limited pepsin digestion and purification by ion-exchange chromatography on DEAE-Sephadex, followed by gel filtration. Purified M protein was found to be homologous on SDS-PAGE (mol.wt 20 kDa), immunogenic in rabbits and to retain its antigenic structure. This purified M protein from an M-non-typable strain (pep-MNT) was used as an antigen to screen RF and RHD sera retrospectively by ELISA for the prevalence of the M-non-typable GAS strain. The prevalence of the M-non-typable strain was compared with that of the known rheumatogenic M types. Results suggest that the M-non-typable strain could be a provisional new rheumatogenic M type in India and could be a candidate for a multivalent M-protein vaccine to control RF and RHD.

Adolescent↗
PubMed1996

Expression and characterization of glutathione peroxidase activity in the human blood fluke Schistosoma mansoni.

Antioxidants may play an important role in immune evasion by schistosome parasites. Previous studies have focused on the roles of superoxide dismutase and glutathione S-transferase. In the present study, glutathione peroxidase (GPX) activity was measured in different fractions of worm extracts from several developmental stages of Schistosoma mansoni. The enzyme activity was shown to be developmentally regulated, with higher specific activities being found in the tegument-enriched Nonidet P-40 extract of adult worms (the stage least susceptible to immune killing) than in the larval stages (which are most susceptible to immune elimination). In all extracts tested, the activity against cumene hydroperoxide, even when glutathione S-transferase activity was removed, was higher than that for hydrogen peroxide. The expression of GPX cDNA in pGEX-2T by bacteria produced a 50-kDa fusion protein and a 32-kDa truncated protein. The latter was due to termination at the internal UGA codon that codes for selenocysteine. GPX activity was detected in the recombinantly produced GPX but not with Sj26-glutathione S-transferase from the vector. Mutating the TGA codon to TGT produced a full-length product, GPXm (19 kDa), that was used to produce 19 monoclonal antibodies. Anti-GPXm monoclonal antibodies recognized a 19-kDa molecule in adult-worm extract which, upon removal by immunoprecipitation, resulted in the loss of over 90% of the GPX activity, suggesting that a single form of GPX exists in the schistosome.

Animals↗
PubMed1996

Usefulness of ELISA using antigen A60 in serodiagnosis of neurotuberculosis.

Anti-mycobacterial antibody to A60 antigen were quantified in the sera and cerebrospinal fluid (csf) samples of one hundred patients of neurotuberculosis and twenty non-tubercular controls by immunoenzymatic (ELISA) assay. Sixty three patients (63%) had "significant" antibody titres in serum and/or CSF samples. In contrast, none of the samples from the control group showed this level of antibody concentration. The evaluation of this assay in tuberculoma (group A, 79 cases) vis-a-vis tubercular meningitis or TBM (group B, 21 patients) revealed significant antibody levels in the former 46 (58.2%) in comparison to 17 (77.3%) in the latter group. A positive relationship was observed in the titres of anti-mycobacterial antibodies in serum and in CSF both in cases of tuberculoma and TBM. This study indicates the utility of A60 antigen ELISA assay in categorising these patients into tubercular aetiology specially in the absence of bacteriological isolation from CSF which still remains the gold standard diagnostic criterion.

Antibodies, Bacterial↗