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S Bala

Publications and source records attributed to S Bala.

At least 19 recordsLinked to original sources
PubMed1995

HIV infection suppresses type 1 lymphokine and IL-12 responses to Toxoplasma gondii but fails to inhibit the synthesis of other parasite-induced monokines.

Individuals infected with Toxoplasma gondii normally develop resistance to the parasite, resulting in an asymptomatic chronic infection. In AIDS patients, this resistance is lost leading to reactivation of infection and development of encephalitis. To characterize the cytokine response of T. gondii-infected individuals, PBMC were cultured in vitro in the presence or absence of crude tachyzoite Ags (STAg). When stimulated with STAg, PBMC from T. gondii-infected donors, but not controls, produced high levels of Type 1 lymphokines (IL-2 and IFN-gamma) as well as the monokine IL-12, in the absence of detectable Type 2 lymphokines (IL-4 and IL-5). In contrast, cells of individuals from both groups produced high levels of IL-1, IL-6, and TNF-alpha when exposed to the same Ag preparation. By using highly purified elutriated cells, we demonstrated that monocytes are a major source of these monokines. The above findings were further expanded by analyzing the cytokine responses induced by STAg in PBMC from patients co-infected with T. gondii and HIV. Our results demonstrate that parasite-specific IL-2 and IFN-gamma responses are greatly impaired even before AIDS development, as is IL-12 synthesis by PBMC from HIV-infected individuals stimulated with STAg. In contrast, the release of IL-6 and TNF-alpha triggered by STAg is either not affected or augmented during HIV infection.

AIDS-Related Opportunistic Infections↗
PubMed1993

Studies on antimutagenic effects of guava (Psidium guajava) in Salmonella typhimurium.

The water and chloroform extracts of guava were tested for their antimutagenicity. The water extract was effective in inactivating the mutagenicity of direct-acting mutagens, e.g., 4-nitro-o-phenylenediamine, sodium azide, and the S9-dependent mutagen, 2-aminofluorene, in the tester strains of Salmonella typhimurium. The chloroform extract was inactive. Autoclaving of the water extract for 15 min did not reduced its activity appreciably. The enhanced inhibitory activity of the extracts on pre-incubation suggests the possibility of desmutagens in the extracts. Besides ascorbic acid and citric acid, the major constituents of the extracts, the role of other antimutagenic factors in the extracts cannot be ruled out.

Antimutagenic Agents↗
PubMed1993

Copper repletion restores the number and function of CD4 cells in copper-deficient rats.

Dietary copper deficiency decreases the number of splenic CD4 cells and mitogen-induced generation of interleukin-2 activity and DNA synthesis in cultures of splenic mononuclear cells. To determine the reversibility of these defects, Cu-deficient rats were fed a Cu-adequate diet for either 4, 7 or 11 d before preparation of cell cultures. Serum and hepatic concentrations of Cu attained 87 and 75%, respectively, of the control level after 4 d of dietary repletion. In contrast, interleukin-2 activity and [3H]thymidine incorporation in splenic cell cultures treated with T-cell mitogens were significantly greater than in cultures from Cu-deficient rats after 7, but not 4, d of dietary Cu repletion. The number of splenic CD4 cells was also greater after 7 d of dietary supplementation with Cu. Changes in the relative percentage and function of T-helper cells were highly correlated with one another and with hepatic Cu concentration. These observations indicate that an inadequate supply of dietary Cu reversibly suppresses the maturation and function of splenic T-helper cells.

Animals↗
PubMed1993

Detection of genome specific monomorphic loci in Bos taurus and Bubalus bubalis with oligodeoxyribonucleotide probe.

A synthetic oligodeoxyribonucleotide probe (OAT36) comprising nine repeats of 5'GACA 3' and several enzymes were used to analyse cow, (Bos taurus) and buffalo (Bubalus bubalis) genomes and a number of monomorphic loci were detected in both the species. Different animals from the same species showed an almost 'similar' monomorphic hybridization pattern but animals from two separate species showed a different 'genome specific' pattern. The overall hybridization with any enzyme and probe combination was found to be unique to one species. This forms the basis of genome specific hybridization which is substantiated by our zoo-blot hybridization studies. The evolutionary aspect of these loci in the context of sequence polymorphisms is discussed.

Animals↗
PubMed1992

Isolation of exfoliated colonic epithelial cells, a novel, non-invasive approach to the study of cellular markers.

Human stool is a heterogeneous mixture of non-digestible food residues, bacteria, cells exfoliated from the gastrointestinal mucosa and other secretory products. We have demonstrated that fresh human stools dispersed in a buffered saline solution can be fractionated over Percoll/BSA gradients to yield 9 discrete bands of cells in the density range of rho 1.033 to 1.139 and which could be further purified over Histopaque 1077. Enzyme-linked immunoassays (ELISA) for colon-specific antigen (CSA) and cytokeratins (CK) were positive. Western blot analysis showed the presence of 3 cytokeratin bands in the 40-kDa to 60-kDa range suggestive of cytokeratins 8, 18, and 19. Fluorescence flow-cytometric analysis of these cells using antibodies against CSA, CK, the blood-group antigens, carcinoembryonic antigen (CEA), non-mucus-secreting columnar-epithelium-specific MAb PR1A3, and to mucus-secreting colonic-epithelium-specific MAb PR5D5 showed varying degrees of reactivity. Expression of the blood-group phenotype suggests that cells from the proximal half of the colon had survived the transit, since in the adult expression of this marker is limited to cells from the proximal region of the colon. In this report we demonstrate the feasibility of studying, non-invasively, cell-specific markers on exfoliated cells isolated from stools. The evidence strongly suggests that almost all the cells are of colonic origin.

Antigens, Neoplasm↗
PubMed1992

Copper deficiency reversibly impairs DNA synthesis in activated T lymphocytes by limiting interleukin 2 activity.

The essentiality of adequate copper (Cu) nutriture for normal T-cell function in laboratory and domestic animals is well established. However, specific biochemical roles of Cu in the maturation and activation of T cells have not been defined. Previous work showed that when cultures of splenic mononuclear cells (MNCs) from Cu-deficient rats were exposed to T-cell mitogens, DNA synthesis was markedly reduced despite normal up-regulation of interleukin 2 (IL-2) receptors, transferrin receptors, and class II major histocompatibility complex molecules. In the present study, IL-2 activity in PHA-treated cultures of MNCs from Cu-deficient rats was 40-50% that of controls as determined by bioassay. Addition of rat IL-2 to phytohemagglutinin-treated cultures of MNCs from Cu-deficient rats increased blastogenic activity to control levels, demonstrating that Cu deficiency does not inhibit transition of quiescent cells to the competence phase of the activation process. Moreover, supplementation of MNC cultures from Cu-deficient rats with physiological levels of Cu enhanced IL-2 activity and DNA synthesis in response to phytohemagglutinin. These data indicate that IL-2 activity in cultures of activated splenic T lymphocytes from Cu-deficient rats is insufficient for optimal blastogenesis.

Animals↗
PubMed1992

A synthetic oligonucleotide probe (5'TTCCA 3')n uncovers a male specific hybridization pattern in the human genome.

A pentanucleotide motif 5'TTCCA3', originating from a 3.4 kb repeat fraction (DYZ1)1, is organized tandemly in the human genome. This motif is abundantly present on the long arm of the human Y (band Yq12) chromosome and is separated by Hae III digestion of male genomic DNA. We have developed a 20 base synthetic oligonucleotide probe, termed OAT20Y, comprising four repeat units of 5'TTCCA3', that uncovers a male-specific hybridization pattern in the human genome. The probe is highly sensitive, since less that 1 micrograms of DNA was sufficient to obtain visible signals after hybridization. Our results on discrimination of sex by using OAT20Y with several amniotic fluid samples was in accordance with clinical data. OAT20Y was found to be specific to the human genome as it did not hybridize with DNA of any non-human species. In addition to sexing human embryos in conjunction with severe X-linked genetic diseases, the probe may be useful in ascertaining the origin of tissues or blood samples in forensic cases.

Amniotic Fluid↗
PubMed1992

Effects of copper deficiency on T-cell mitogenic responsiveness and phenotypic profile of blood mononuclear cells from swine.

The effect of dietary copper deficiency on T-cell mitogenic responsiveness and phenotypic profile of blood mononuclear cells (MNC) in weaned pigs was examined. Outbred, weaned pigs were fed a semipurified diet containing adequate (6.4 mg/kg of body weight) or deficient (0.8 mg/kg) amounts of Cu. Pigs fed the low Cu diet for 10 weeks had markedly decreased concentrations of Cu in liver and plasma, and hypertrophic hearts. In vitro reactivity of MNC from Cu-deficient pigs to phytohemagglutinin and concanavalin A was significantly suppressed. This functional impairment was not associated with a decrease in the percentage of T cells, CD4 or CD8 cell subsets, or B cells. Expression of SLA-DQ and SLA-DR class II major histocompatibility complex (MHC) antigens was increased by Cu deficiency, the former significantly. Unlike rodents, in which inadequate Cu nutriture induces functional T cell deficiency that is associated with a decrease in the CD4 T-cell subset, swine fed inadequate Cu diets for 10 weeks had no changes in MNC subsets yet clearly manifested functional impairment of T-cell responses.

Animals↗
PubMed1992

Antimutagenic activity of Terminalia chebula (myroblan) in Salmonella typhimurium.

Antimutagenicity of water and chloroform extracts of dried myroblan Terminalia chebula was determined against two direct acting mutagens, sodium azide and 4-nitro-o-phenylenediamine (NPD) in strains TA100 and TA1535, and TA97a and TA98 of Salmonella typhimurium respectively and S9-dependent mutagen 2-aminofluorene (2-AF) in TA97a, TA98 and TA100 strains. Water extract reduced NPD as well as 2-AF induced his+ revertants significantly but did not have any perceptible effect against sodium azide included his+ revertants in TA100 and TA1535 strains of S. typhimurium. The pre-incubation studies, where the extract was incubated at 37 degrees C for 30 min with the said mutagen prior to plating, enhanced the inhibitory effect. Autoclaving the water extract reduced the inhibitory effect but the reduction in the effect was not significant. No inhibitory effect was observed in any of the strains and against any of the test mutagens with chloroform extract.

Chloroform↗
PubMed1991

Alterations in splenic lymphoid cell subsets and activation antigens in copper-deficient rats.

Rats were nursed by dams fed a diet containing adequate (6 micrograms/g) or deficient (0.6 micrograms/g) Cu during the lactation period and weaned to the same diet. Splenic mononuclear cells were isolated and the phenotypic profile determined by flow cytometry after immunolabelling with monoclonal antibodies to cell surface markers. Total splenic mononuclear cell yield and the relative percentage and absolute number of T-cells and the CD4+ (helper) and CD8+ (cytotoxic) T-subsets were decreased in Cu-deficient male rats. The relative percentage, but not the absolute numbers, of splenic B-cells and macrophages was increased by Cu deficiency. The percentage of splenic mononuclear cells from male rats that expressed interleukin-2 receptors and transferrin receptors in vivo was increased by Cu deficiency. In contrast, dietary Cu deficiency did not affect the yield and phenotypic profile of splenic mononuclear cells in female rats. Reactivity of splenic mononuclear cells to T-cell mitogens was decreased in Cu-depleted male and female rats. However, mitogen-induced increases in levels of interleukin-2 receptor and transferrin receptor were similar in cultures of splenic mononuclear cells obtained from control rats and rats subjected to restricted dietary intake of Cu only during the postlactation period. Thus, decreased mitogenic blastogenesis on exposure of cells from Cu-deficient rats does not reflect a nonspecific impairment of cellular activation.

Animals↗
PubMed1990

Determinants of OmpF porin antigenicity and structure.

Sixty-six murine hybridomas raised to Escherichia coli B/r porin were used to identify and differentiate the epitopes of this outer membrane protein. Anti-porin monoclonal antibodies (mAb) were raised against outer membrane fragments, purified native trimeric porin (trimer), and purified sodium dodecyl sulfate-denatured monomeric porin (monomer). Immunochemical and flow cytometric methods identified five distinct cell surface-exposed determinants on OmpF. The peptide composition of porin epitopes was determined by analysis of mAb reactivity with cyanogen bromide-generated peptide fragments. Four of 43 anti-monomer mAb reacted with surface exposed sites on OmpF, defining epitopes that consist of residues within CNBr peptides d2, d3, and B. The anti-porin mAb panel was also used to evaluate changes in porin antigenic structure in strains with short ompF deletions. Flow cytometric experiments indicated that despite changes in porin permeability, little if any alteration of surface epitopes occurred in these strains. Western immunoblot analysis of the mutant porins showed loss of reactivity with numerous mAb, which was caused by changes in three spatially distinct epitopes at residues 108-111, 118-123, and 124-129. Our findings indicate that in these ompF mutants the residues responsible for altering porin permeability are not exposed on the cell surface, but are buried within the tertiary structure of the protein. One of these regions, which is apparently involved in the determination of channel permeability characteristics, is conserved among 15 of 16 different porin molecules which were screened with the anti-OmpF mAb panel.

Amino Acid Sequence↗
PubMed1989

Antimutagenicity of some citrus fruits in Salmonella typhimurium.

The antimutagenic effect of 10 citrus fruit juices was observed against the mutagenicity of N-nitro-o-phenylenediamine (NPD) in TA97a and sodium azide in TA100 tester strains of Salmonella typhimurium using the Ames test. It was noticed that the juices of all these fruits reduced significantly the NPD and sodium azide induced revertant colonies. The inhibitory activity was enhanced if the mutagen and juice were co-incubated for about 30 min at 37 degrees C prior to performing the mutagenicity assay. Dilution with distilled water led to the reduction in the inhibitory activity. The antimutagenic activity of synthetic ascorbic acid or citric acid or combined ascorbic acid and citric acid was also seen. But the results with fruit juices tempted us to believe that in addition to ascorbic acid and citric acid, the presence of other factor(s) possessing antimutagenic properties cannot be ruled out.

Azides↗
PubMed1987

Albumin concentration in human amniotic fluid from normal pregnancies.

The present study is an attempt to estimate the albumin concentration in the human amniotic fluid of normal pregnancy. The study has been conducted from 12th to 20th week and from 30th to 43rd weeks of gestation. The results revealed a characteristic gestational profile with an increase in the concentration with the advancement of pregnancy from the 12th till the 20th week and an inverse relationship between the albumin level and the gestational age after the 30th week till term. The relationship between the albumin levels and the order of pregnancy indicated that the albumin concentration was not influenced by the birth order.

Albumins↗