Biomedical subjects

D Chandra

Publications and source records attributed to D Chandra.

At least 19 recordsLinked to original sources

PubMed2006

GABAA receptor alpha 4 subunits mediate extrasynaptic inhibition in thalamus and dentate gyrus and the action of gaboxadol.

The neurotransmitter GABA mediates the majority of rapid inhibition in the CNS. Inhibition can occur via the conventional mechanism, the transient activation of subsynaptic GABAA receptors (GABAA-Rs), or via continuous activation of high-affinity receptors by low concentrations of ambient GABA, leading to "tonic" inhibition that can control levels of excitability and network activity. The GABAA-R alpha4 subunit is expressed at high levels in the dentate gyrus and thalamus and is suspected to contribute to extrasynaptic GABAA-R-mediated tonic inhibition. Mice were engineered to lack the alpha4 subunit by targeted disruption of the Gabra4 gene. alpha4 Subunit knockout mice are viable, breed normally, and are superficially indistinguishable from WT mice. In electrophysiological recordings, these mice show a lack of tonic inhibition in dentate granule cells and thalamic relay neurons. Behaviorally, knockout mice are insensitive to the ataxic, sedative, and analgesic effects of the novel hypnotic drug, gaboxadol. These data demonstrate that tonic inhibition in dentate granule cells and thalamic relay neurons is mediated by extrasynaptic GABAA-Rs containing the alpha4 subunit and that gaboxadol achieves its effects via the activation of this GABAA-R subtype.

Animals↗

PubMed2006

Highly purified CD44+ prostate cancer cells from xenograft human tumors are enriched in tumorigenic and metastatic progenitor cells.

CD44 is a multifunctional protein involved in cell adhesion and signaling. The role of CD44 in prostate cancer (PCa) development and progression is controversial with studies showing both tumor-promoting and tumor-inhibiting effects. Most of these studies have used bulk-cultured PCa cells or PCa tissues to carry out correlative or overexpression experiments. The key experiment using prospectively purified cells has not been carried out. Here we use FACS to obtain homogeneous CD44(+) and CD44(-) tumor cell populations from multiple PCa cell cultures as well as four xenograft tumors to compare their in vitro and in vivo tumor-associated properties. Our results reveal that the CD44(+) PCa cells are more proliferative, clonogenic, tumorigenic, and metastatic than the isogenic CD44(-) PCa cells. Subsequent molecular studies demonstrate that the CD44(+) PCa cells possess certain intrinsic properties of progenitor cells. First, BrdU pulse-chase experiments reveal that CD44(+) cells colocalize with a population of intermediate label-retaining cells. Second, CD44(+) PCa cells express higher mRNA levels of several 'stemness' genes including Oct-3/4, Bmi, beta-catenin, and SMO. Third, CD44(+) PCa cells can generate CD44(-) cells in vitro and in vivo. Fourth, CD44(+) PCa cells, which are AR(-), can differentiate into AR(+) tumor cells. Finally, a very small percentage of CD44(+) PCa cells appear to undergo asymmetric cell division in clonal analyses. Altogether, our results suggest that the CD44(+) PCa cell population is enriched in tumorigenic and metastatic progenitor cells.

Animals↗

PubMed2006

Prepatent detection of Fasciola gigantica infection in bovine calves using metacercarial antigen.

Metacercarial antigen of Fasciola gigantica was evaluated for early immunodiagnosis of experimental bovine fasciolosis using ELISA and Western blot. In ELISA, the experimental F. gigantica infection was detected as early as 2 weeks post-infection (WPI). The gradual increasing trend of antibody level was observed from 2 to 7 WPI, followed by a plateau, which was maintained up to 14 WPI. In Western blot, sera from experimentally infected calves recognized one distinct polypeptide of 21 kDa in fractionated metacercarial antigen as early as 10th day post infection. From 2 WPI, more polypeptide bands were reacting. Recognition of these protein bands persisted till the end of the experiment (14 WPI). Cattle sera collected from the field showed 34.5% seroprevalence of fasciolosis by ELISA using MAg. Comparative immunoblot studies of metacercarial antigen with anti-Gigantocotyle explanatum and anti-Paramphistomum epiclitum sera revealed that 21 and 25 kDa polypeptides of metacercarial antigen did not cross-react with any of these sera and appear to be unique to F. gigantica and having the desirable qualities of early and specific immunodiagnosis.

Animals↗

PubMed2005

Cathepsin L cysteine proteinase in the diagnosis of bovine Fasciola gigantica infection.

Cathepsin L cysteine proteinase from Fasciola gigantica was evaluated for its potential in the early prepatent detection of this helminth infection in bovine calves. Five cross-bred bovine calves were experimentally infected with 400 metacercariae/calf and evaluated for anti-cathepsin L antibody response. F. gigantica infection in these calves could be detected 4 weeks post-infection using an ELISA, dipstick ELISA and Western blotting with 100% sensitivity. The antigen was also used to detect F. gigantica field infection in cattle, by screening 256 sera of these animals by an ELISA, which demonstrated an overall infection rate of 26.95%. Preliminary studies showed that F. gigantica cathepsin L cysteine proteinase does not cross-react with Paramphistomum epiclitum, Gigantocotyle explanatum and hydatid cyst antigens. However, extensive studies on the cross-reactivity of this antigen with related helminth parasites of cattle and buffaloes are required, before this antigen can be considered suitable for immuno-diagnosis of fasciolosis in these ruminants.

Animals↗

PubMed2004

Detection of circulating 54 kDa antigen in sera of bovine calves experimentally infected with F. gigantica.

The antibody response and circulating antigen levels in bovine calves, infected experimentally with Fasciola gigantica, were monitored using enzyme-linked immunoelectrotransfer blot (EITB) and sandwich ELISA, respectively. By EITB, the infected calves' sera recognized the polypeptides in the range of 54-58 kDa as early as 2 weeks post-infection. By 12th week post-infection, the lower two polypeptides of 12 and 8 kDa had disappeared. In sandwich ELISA, the circulating 54 kDa and whole worm antigen of F. gigantica were detected in the sera samples of infected calves as early as 2 weeks post-infection and persisted until the end of experiment (26th week PI). The 54 kDa antigen of F. gigantica appears to be specific and possesses promising immunodiagnostic potential for early prepatent diagnosis of bovine fasciolosis.

Animals↗

PubMed2004

An allele-specific polymerase chain reaction assay for the differentiation of members of the Anopheles culicifacies complex.

Anopheles culicifacies, the principal vector of malaria in India, is a complex of five cryptic species which are morphologically indistinguishable at any stage of life. In view of the practical difficulties associated with classical cytotaxonomic method for the identification of members of the complex, an allele-specific polymerase chain reaction (ASPCR) assay targeted to the D3 domain of 28S ribosomal DNA was developed. The assay discriminates An. culicifacies species A and D from species B, C and E. The assay was validated using chromosomally identified specimens of An. culicifacies from different geographical regions of India representing different sympatric associations. The assay correctly differentiates species A and D from species B, C and E. The possible use of this diagnostic assay in disease vector control programmes is discussed.

Alleles↗

PubMed2004

Atypical haemolytic uraemic syndrome as a complication of induction chemotherapy for acute lymphoblastic leukaemia.

This report describes a case of fatal haemolytic uraemic syndrome (HUS) developing in a child with acute lymphoblastic leukaemia (ALL) during induction chemotherapy. The aetiology in this case is uncertain but it may have resulted from treatment with L-asparaginase or vincristine. The possibility of HUS during induction chemotherapy for ALL should be considered early on in the treatment regimen, if clinical signs and symptoms suggest this diagnosis, so that appropriate treatment can be instituted.

Antineoplastic Combined Chemotherapy Protocols↗

PubMed2003

Recurrent paroxysmal cold haemoglobinuria in a 3-year-old child: a case report.

We present the case of a 3-year-old girl who presented on two separate occasions, eight months apart, with typical features of paroxysmal cold haemoglobinuria (PCH). On each occasion, she suffered malaise and fever with dark urine following an upper respiratory tract infection. She developed severe anaemia and required transfusion of red cells on both occasions, although each time she made a quick recovery. She was found to be direct antiglobulin test-positive with anti-C3d, and agglutination was observed on the blood film. A biphasic Donath-Landsteiner antibody was demonstrated. The specificity of the antibody was not identified, although it was not anti-P. As far as we are aware, recurrence of acute PCH in a child has not been previously reported in the literature.

Agglutination Tests↗

PubMed2002

Modulation of radiation-induced changes in the xanthine oxidoreductase system in the livers of mice by its inhibitors.

The xanthine oxidoreductase (XOD) system, which consists of xanthine dehydrogenase (XDH) and xanthine oxidase (XO), is one of the major sources of free radicals in biological systems. The XOD system is present predominantly in the normal tissues as XDH. In damaged tissues, XDH is converted into XO, the form that generates free radicals. Therefore, the XO form of the XOD system is expected to be found mainly in radiolytically damaged tissue. In this case, XO may catalyze the generation of free radicals and potentiate the effect of radiation. Inhibition of the XOD system is likely to attenuate the detrimental effects of ionizing radiation. We have examined this possibility using allopurinol and folic acid, which are known inhibitors of the XOD system. Swiss albino mice (7-8 weeks old) were given single doses of allopurinol and folic acid (12.5-50 mg/kg) intraperitoneally and irradiated with different doses of gamma radiation at a dose rate of 0.023 Gy/s. The XO and XDH activities as well as peroxidative damage and lactate dehydrogenase (LDH) were determined in the liver. An enhancement of the activity of XO and a simultaneous decrease in the activity of XDH were observed at doses above 3 Gy. The decrease in the ratio XDH/XO and the unchanged total activity (XDH + XO) suggested the conversion of XDH into XO. The enhanced activity of XO may potentiate radiation damage. The increased levels of peroxidative damage and the specific activity of LDH in the livers of irradiated mice supported this possibility. Allopurinol and folic acid inhibited the activities of XDH and XO, decreased their ratio (XDH/XO), and lowered the levels of peroxidative damage and the specific activity of LDH. These results suggested that allopurinol and folic acid have the ability to inhibit the radiation-induced changes in the activities of XDH and XO and to attenuate the detrimental effect of this conversion, as is evident from the diminished levels of peroxidative damage and the decreased activity of LDH.

Allopurinol↗

PubMed2002

Gabapentin and lamotrigine in Indian patients of partial epilepsy refractory to carbamazepine.

52 patients (25 males and 27 females) suffering from refrectory partial seizures, of not more than two years duration and on carbamazepine monotherapy were enrolled in this study. Patients were randomly put on gabapentin (19 males and 8 females) or lamotrigine (6 males and 19 females) as add on therapy. The efficacy of the drugs was assessed by the seizure frequency, pattern of seizures and seizure free interval. The safety was evaluated from the biochemical investigations and the adverse effects observed or reported by the patients during the course of the study. The average frequency of basal partial seizures was 6.26+3.86 and 5.04+2.47 which decreased significantly (p<. 001) after 12 weeks of add on therapy to 1.75+2.16. and 1.68+2.94 in the GBP and LTG group respectively. However, there was no significant difference between the two drugs after 12 weeks of add on therapy. The PCB (primary change in basal seizure frequency) values decreased to -72+34.92 and -76.22+29.68 in the GBP and LTG group respectively. The difference in these two groups was not significant. The responder rate was 77.7% and 92% respectively in GBP and LTG group respectively. GBP was found to be more effective in partial seizures with secondarily generalization while LTG was effective in all subtypes of partial seizures. The abnormal scalp EEG was recorded in 33.3% (9 of 27 patients) in GBP group and 40 %( 10 of 25 patients) in LTG group and it did not revert to normal in 33.3% and 40% of patients in either of groups (GBP/LTG). Minor side effects which were self limiting were noticed in 80% in groups I and 74% were groups II.

Acetates↗

PubMed2001

Structural and kinetic modifications of aldose reductase by S-nitrosothiols.

Modification of aldose reductase (AR) by the nitrosothiols S-nitroso-N-acetyl penicillamine (SNAP) and N-(beta-glucopyranosyl)-N(2)-acetyl-S-nitrosopenicillamide (glyco-SNAP) resulted in a 3-7-fold increase in its k(cat) and a 25-40-fold increase in its K(m) for glyceraldehyde. In comparison with the native protein, the modified enzyme was less sensitive to inhibition by sorbinil and was not activated by SO(2-)(4) anions. The active-site residue, Cys-298, was identified as the main site of modification, because the site-directed mutant in which Cys-298 was replaced by serine was insensitive to glyco-SNAP. The extent of modification was not affected by P(i) or O(2), indicating that it was not due to spontaneous release of nitric oxide (NO) by the nitrosothiols. Electrospray ionization MS revealed that the modification reaction proceeds via the formation of an N-hydroxysulphenamide-like adduct between glyco-SNAP and AR. In time, the adduct dissociates into either nitrosated AR (AR-NO) or a mixed disulphide between AR and glyco-N-acetylpenicillamine (AR-S-S-X). Removal of the mixed-disulphide form of the protein by lectin-column chromatography enriched the preparation in the high-K(m)-high-k(cat) form of the enzyme, suggesting that the kinetic changes are due to the formation of AR-NO, and that the AR-S-S-X form of the enzyme is catalytically inactive. Modification of AR by the non-thiol NO donor diethylamine NONOate (DEANO) increased enzyme activity and resulted in the formation of AR-NO. However, no adducts between AR and DEANO were formed. These results show that nitrosothiols cause multiple structural and functional changes in AR. Our observations also suggest the general possibility that transnitrosation reactions can generate both nitrosated and thiolated products, leading to non-unique changes in protein structure and function.

Aldehyde Reductase↗

PubMed2001

Metabolic regulation of aldose reductase activity by nitric oxide donors.

Regulation of aldose reductase (AR), a member of the aldo-keto reductase superfamily, by nitric oxide (NO) donors was examined. Incubation of human recombinant AR with S-nitrosoglutathione (GSNO) led to inactivation of the enzyme and the formation of an AR-glutathione adduct. In contrast, incubation with S-nitroso-N-acetyl penicillamine (SNAP) or N-(beta-D-glucopyranosyl)-SNAP (GlycoSNAP) led to an increase in enzyme activity which was accompanied by the direct nitrosation of the enzyme and the formation of a mixed disulfide with the NO-donor. To examine in vivo modification, red blood cells (RBC) and rat aortic vascular smooth muscle cells (VSMC) were incubated with 1 mM GSNO or SNAP. Exposure of VSMC to SNAP and GSNO for 2 h at 37 degrees C led to approximately 71% decrease in the enzyme activity with DL-glyceraldehyde as the substrate. Similarly, exposure of RBC in 5 mM glucose to NO-donors for 30 min at room temperature, followed by increasing the glucose concentration to 40 mM, resulted in >75% decrease in the formation of sorbitol. These investigations indicate that NO and/or its bioactive metabolites can regulate cellular AR, leading to either activation (by nitrosation) or inactivation (by S-thiolation).

Aldehyde Reductase↗

PubMed2001

Modulation of glyoxalase, glutathione S-transferase and antioxidant enzymes in the liver, spleen and erythrocytes of mice by dietary administration of fenugreek seeds.

There is a growing interest in understanding the biological effect of time-tested folk medicinal plants. In the present work, the effect of dietary administration of fenugreek seeds on the glyoxalase system and antioxidant enzymes as well as levels of glutathione (GSH) have been examined in different tissues of mice. Swiss albino mice were fed with diet containing powdered fenugreek for 4 weeks. The mode and magnitude of effect was found to depend on the dose of fenugreek and type of tissue. The diet containing 1 and 2% of fenugreek enhanced the specific activity of gly I, whereas 5 and 10% inhibited its activity in the liver. However, on the other hand, the specific activity of gly II decreased continuously with dose. Dietary administration of fenugreek seeds resulted in an increase of GSH levels and the glutathione S-transferase (GST) activity in the liver. Fenugreek (1 and 2%) showed no appreciable change in superoxide dismutase (SOD) and catalase. However, 5 and 10% doses of fenugreek supplementation inhibited their activities. In the case of spleen, a significant change in gly I was observed only at 10% fenugreek. In addition, a significant increase was also observed with GSH levels. Fenugreek treatment up to 5% showed a small but consistent increase in erythrocytes. In the case of GST, the activity enhanced with dose. Significant elevation of catalase activity was observed with a 10% dose of fenugreek. The significance and relevance of these findings are suggested in relation to mechanistic aspects.

Animals↗

PubMed2001

Radiation induced oxidative stress: II studies in liver as a distant organ of tumor bearing mice.

Since the radiation dose tolerance of normal tissues/organs away from the site of tumor influences the success of radiation therapy of cancer, and antioxidant status is likely to be one of the factors to determine the tolerance; the radioresponse of antioxidant enzymes has been examined in the liver as a representative distant organ in the tumor-bearing mice. Swiss albino male mice (7-8 weeks old) with Ehrlich solid tumor in the thigh pad were irradiated with different doses of gamma-radiation (0-9 Gy) at a dose rate of 0.0153 Gy/s and the specific activities of enzymes involved in the free radical metabolism were determined in the liver. Except GST, the activities of SOD, DTD and Gly I as well as the GSH content were found to be higher in the liver of tumor-bearing mice compared to the non-tumor bearing mice. The catalase activity progressively decreased with dose in both the groups of mice. However, the activity was relatively higher in the liver of tumor- bearing mice than the control. Thus, the radioresponse of antioxidant enzymes seemed to be significantly different in the liver of tumor-burdened mice compared to controls. The enhanced activities might be due to relatively more damage caused by radiation. The higher levels of NO* and peroxidative damage in the liver of tumor-bearing mice probably suggest this possibility. These findings of the present work might have some serious implications as the increased radiation-damage of the distant normal organs (due to tumor burden) is likely to adversely affect the therapeutic gain.

Animals↗

PubMed2001

A comparative study of cervical cytology, colposcopy and PCR for HPV in female sex workers in Singapore.

This study examined the prevalence of human papillomavirus (HPV) infection in a cohort of female sex workers in Singapore. HPV infection was diagnosed by clinical examination, Papanicolaou (Pap) smears, histology and polymerase chain reaction (PCR). One hundred and eighty-seven female sex workers who came for their routine medical screening were enrolled into the study. PCR was positive for HPV in 27 (14.4%), 20 of these had a single HPV type detected, while 7 had multiple types of HPV detected. The most common HPV types identified were types 16, 58 and 18. In conclusion, HPV infection is moderately prevalent among sex workers as tested by PCR, but routine screening with Pap smears does not appear to be a sensitive method of diagnosis for HPV infection.

Adult↗

PubMed2001

Effect of fluvoxamine and N-methyl-D-aspartate receptor antagonists on shock-induced depression in mice.

We have earlier demonstrated that NMDA receptor antagonists possess antidepressant effect and also they show a synergism with imipramine. The present study attempts to investigate whether NMDA receptor antagonists also interact with selective serotonin reuptake inhibitors. The study was conducted in albino mice using shock-induced depression model. The mice were placed on a grid floor and shock delivered were of 2 sec duration with a 9 sec interval for 1 h. Twenty four hours later depression was measured by an open field test followed by a forced swimming test. Presentation of inescapable foot shock significantly reduced ambulation (from 159.50 +/- 5.42 to 80.50 +/- 4.61) and rearing (from 22.10 +/- 2.15 to 11.30 +/- 1.32) in the open field arena and increased immobility duration in the forced swimming test (from 82.20 +/- 3.51 to 158.90 +/- 4.61). Pretreatment with fluvoxamine, MK-801, ketamine and the combination of fluvoxamine with either of the NMDA antagonists antagonised shock-induced depression. Haloperidol and ketanserin pretreatment modified the effect of these agents. These findings suggest an interaction of NMDA receptor antagonists with fluvoxamine, and an involvement of brain dopaminergic and tryptaminergic mechanisms in the behavioural suppression observed after inescapable foot shock.

Animals↗

PubMed2000

Receptor-interacting protein 140 directly recruits histone deacetylases for gene silencing.

Receptor-interacting protein 140 (RIP140) encodes a histone deacetylase (HDAC) inhibitor-sensitive repressive activity. Direct interaction of RIP140 with HDAC1 and HDAC3 occurs in vitro and in vivo as demonstrated in co-immunoprecipitation and glutathione S-transferase pull-down experiments. The HDAC-interacting domain of RIP140 is mapped to its N-terminal domain, between amino acids 78 and 303 based upon glutathione S-transferase pull-down experiments. In chromatin immunoprecipitation assays, it is demonstrated that histone deacetylation occurs at the chromatin region of the Gal4 binding sites as a result of Gal4 DNA binding domain-tethered RIP expression. The immunocomplexes of RIP140 from cells transfected with RIP140 and HDAC are able to deacetylate histone proteins in vitro. This study presents the first evidence for RIP140 as a negative coregulator for nuclear receptor actions by directly recruiting histone deacetylases and categorizes RIP140 as a novel negative coregulator that is able to directly interact with HDACs.

Adaptor Proteins, Signal Transducing↗

PubMed2000

Comparative bioavailability of two formulations of azithromycin.

AIM: To compare the bioequivalence of two brands of azithromycin capsules in healthy male volunteers for regulatory purpose. METHOD: A single oral dose of 500 mg of either test (Panacea Biotec Ltd.) or reference (Pfizer India Ltd.) preparation of azithromycin was administered to 12 volunteers in double blind randomised cross over fashion. Serum levels of azithromycin were analysed using microbiological assay. The pharmacokinetic parameters studied were Cmax, Tmax, AUC, t1/2, Ke, CL and MRT. In vitro dissolution tests were conducted for both the preparations and compared with in vivo absorption. RESULTS: The mean peak serum azithromycin concentration of 0.516 +/- 0.008 microgram/ml was observed at 2.33 +/- 0.22 h with test brand and was similar to that of reference brand with Cmax of 0.494 +/- 0.011 microgram/ml at 2.71 +/- 0.26 h. The statistical difference between all the other paharmacokinetic parameters were insignificant. CONCLUSION: Both the brands of azithromycin can be considered to be bioequivalent on the basis of results obtained.

Adolescent↗