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Biomedical subjects

S Srinivasan

Publications and source records attributed to S Srinivasan.

At least 19 recordsLinked to original sources
PubMed2007

Analysis of nitrite reductase (nirK and nirS) genes and cultivation reveal depauperate community of denitrifying bacteria in the Black Sea suboxic zone.

Chemical profiles of the Black Sea suboxic zone show a distribution of nitrogen species which is traditionally associated with denitrification, i.e. a secondary nitrite maximum associated with nitrate depletion and a N(2) gas peak. To better understand the distribution and diversity of the denitrifier community in the Black Sea suboxic zone, we combined a cultivation approach with cloning and sequencing of PCR-amplified nitrite reductase (nirS and nirK) genes. The Black Sea suboxic zone appears to harbour a homogeneous community of denitrifiers. For nirK, over 94% of the sequences fell into only three distinct phylogenetic clusters, and for nirS, a single closely related sequence type accounted for 91% of the sequences retrieved. Both nirS and nirK genes showed a dramatic shift in community composition at the bottom of the suboxic zone, but overall, nirK-based community composition showed much greater variation across depths compared with the highly uniform distribution of nirS sequences throughout the suboxic zone. The dominant nirK and nirS sequences differed at the amino acid level by at least 17% and 8%, respectively, from their nearest database matches. Denitrifying isolates recovered from the suboxic zone shared 97% 16S rRNA gene sequence similarity with Marinobacter maritimus. Analysis of the recently discovered nirS gene from the anammox bacterium Candidatus'Kuenenia stuttgartiensis' revealed that mismatches with commonly used primers may have prevented the previous detection of this divergent sequence.

Bacteria↗
PubMed2006

Glial cell line-derived neurotrophic factor-mediated enteric neuronal survival involves glycogen synthase kinase-3beta phosphorylation and coupling with 14-3-3.

Glial cell line-derived neurotrophic factor (GDNF) promotes the growth and survival of enteric neurons, but the mechanisms involved are poorly understood. GDNF is known to promote the survival of enteric neurons through activation of the PI3-Kinase/Akt signaling pathway. We investigated the role of glycogen synthase kinase-3beta (GSK-3beta) in enteric neuronal survival, and the ability of GDNF to regulate the activity of GSK-3beta using primary rat embryonic enteric neurons. GDNF, through activation of the PI3-kinase pathway enhanced the phosphorylation of GSK-3beta at its N-terminal serine-9 residue, and promoted the association of GSK-3beta with 14-3-3. Transfection of a constitutively active S9A-GSK-3beta mutant prevented the survival effects of GDNF, whereas a dominant negative GSK-3beta construct prevented GDNF withdrawal-induced cell death. Increased GSK-3beta activity was associated with an increase in tau phosphorylation. Thus, GDNF promotes enteric neuronal survival by modulating GSK-3beta and its downstream target tau. Inhibitors of GSK-3beta activity may have therapeutic potential in improving enteric neuronal survival.

14-3-3 Proteins↗
PubMed2006

Endocapsular iris reconstruction implants for acquired iris defects: a clinical study.

PURPOSE: To report the clinical efficacy, safety, and long-term follow-up data on the use of endocapsular iris reconstruction implants (IRIs) during cataract surgery in patients with acquired iris defects. METHODS: Single centre, retrospective, noncomparative, interventional case series. Five eyes of four patients with acquired iris defects and visually significant cataracts underwent clear cornea phacoemulsification and intraocular lens (IOL) implantation combined with insertion of endocapsular IRI. Data on the best-corrected visual acuity (BCVA), degree of preoperative and postoperative glare, photophobia, surgical complications, and long-term implant stability were analysed. RESULTS: In all patients, IRI were successfully placed within the capsular bag during cataract surgery. There were no intraoperative or postoperative complications. Mean follow-up period was 29 months (range, 16-42). BCVA, subjective glare, and photophobia improved in all five eyes. Desired anatomic results were achieved in all of them. CONCLUSIONS: In patients with acquired iris defects, implantation of endocapsular IRI during cataract surgery appears to be a safe and effective procedure. At a mean time gate of 29 months, both IOLs and IRI appeared to remain stable within the capsular bag.

Adult↗
PubMed2006

Determination of the Pu240/Pu239 ratio by alpha spectrometry using the WinALPHA program.

The isotopic ratio of 240Pu to 239Pu is an important parameter in identifying the origin of plutonium in a given radioactive sample. High-resolution mass spectrometry is generally accepted as an accurate technique for determining this ratio, but this is a very costly method. Alternatives to this method are alpha- and gamma-spectrometry studies but the problem with these low-cost method lies with the analysis of the spectrum. Recently, Noy et al. [2004. Nucl. Instrum. Methods in Phys. Res. A 525, 522-528] developed a computer program code called WinALPHA to quantitatively analyze the alpha spectrum; the program is available from the IAEA website. In this paper, we report the results obtained from the analysis of the alpha spectrum of plutonium from power bearing product samples from power reactor fuel reprocessing plant using the WinALPHA program. The results are found to be in good agreement (within 1-2%) with results from mass spectrometry.

Journal Article↗
PubMed2006

Shell Vial Culture assay for the rapid diagnosis of Japanese encephalitis, West Nile and Dengue-2 viral encephalitis.

BACKGROUND: Encephalitis caused by flaviviruses, Japanese encephalitis virus (JEV) and West Nile virus (WNV) is responsible for significant morbidity and mortality in many endemic countries. Dengue-2 (Den-2) virus is a recent addition to the list of encephalitogenic viruses, after its Central Nervous System (CNS) invasion capability has been established. There is a wide array of laboratory tools that have helped us not only in the diagnosis of these conditions but also in understanding their pathogenesis and pathology. However, there are no reports of Shell Vial Culture (SVC), a centrifuge enhanced tissue culture assay that has revolutionized viral culturing in terms of rapidity and sensitivity being optimized for these flaviviral encephalitic conditions. The present study is an attempt to standardize and evaluate the usefulness of SVC for the laboratory diagnosis of JE, WN and Den-2 encephalitis cases and to compare it with Indirect Immunofluorescence (IIF) technique that detects cell associated virus antigen. Analysis of the various clinical parameters with respect to viral etiology has also been carried out. RESULTS: Pediatric patients constituted the major group involved in the study (92%). Etiological diagnosis of viral encephalitis could be established in twenty nine (58%) patients. JE encephalitis was the commonest with 19 (39%) cases being positive followed by, WN (9 cases-18%) and Den-2 (one case). IIF test could detect antigens of JE, WN and Den-2 viruses in 16(32%), 7(14%) and 1 case respectively. Shell vial culture assay picked up all cases that were positive by IIF test. In addition, SVC assay could detect 3 and 2 more cases of JE and WN encephalitis respectively, that were negative by the IIF test. CONCLUSION: Shell vial culture is a rapid and efficient tool for the etiological diagnosis of JE, WN and Den-2 encephalitis cases. Early, prompt collection, transport and processing of the CSF samples, would make SVC a better method for the rapid diagnosis of these flaviviral infections.

Adolescent↗
PubMed2006

Outcome of scorpion sting envenomation after a protocol guided therapy.

OBJECTIVE: Scorpion sting (SS) envenomation is a life threatening emergency in children, though not so severe in adults. Attempt to develop protocol using prazosin and dobutamine and few other drugs to treat SS. METHODS: Children aged 0-13 years with a history of scorpion sting were studied. Clinical features, complications, drug therapy and outcome of the cases for the period 1992-97(N = 186) was collected by the authors and also from the medical records department (RETROSPECTIVE GROUP). Cases treated during 1997-2000 (N = 198) as per the protocol were recorded as PROSPECTIVE GROUP. All the cases were observed for at least for 24 hours. Cases coming within 4 hours of a sting were given a dose of Prazosin (30 mic.gm/Kg/dose) and were observed. Those who came after 4 hours & were asymptomatic received only symptomatic treatment. Cases with signs of envenomation received Prazosin every 6 hourly till recovery. Cases having acute pulmonary edema (APE) were treated with dobutamine and sodium nitroprusside drip. Complicated cases were monitored in PICU as per the protocol. RESULT: Complications associated with excessive parasympathetic and sympathetic stimulation were observed. Myocarditis was observed due to the toxin and excessive catecholamine, which complicated in left ventricular failure (LVF) and APE. Nearly half of the children with acute myocarditis developed APE. Death was mainly due to myocarditis and APE, with or without encephalopathy. Mortality was high in children who received steroid and antihistaminics outside and who came late (> 4 hours). CONCLUSION: Complication rate remained almost same in both the groups. There was a significant reduction in overall mortality (P = < 0.0155) and in deaths associated with APE (P = < 0.0001) after the protocol guided therapy. There was also a reduction in mortality in encephalopathy group though not statistically significant. This treatment protocol and aggressive management of APE reduced the mortality due to SS significantly.

Adolescent↗
PubMed2006

Glycogen synthase kinase 3beta and Alzheimer's disease: pathophysiological and therapeutic significance.

Alzheimer's disease (AD) is a neurodegenerative disorder associated with cognitive and behavioral dysfunction and is the leading cause of dementia in the elderly. Several studies have implicated molecular and cellular signaling cascades involving the serine-threonine kinase, glycogen synthase kinase beta(GSK-3beta) in the pathogenesis of AD. GSK-3beta may play an important role in the formation of neurofibrillary tangles and senile plaques, the two classical pathological hallmarks of AD. In this review, we discuss the interaction between GSK-3beta and several key molecules involved in AD, including the presenilins, amyloid precursor protein, tau, and beta-amyloid. We identify the signal transduction pathways involved in the pathogenesis of AD, including Wnt, Notch, and the PI3 kinase/Akt pathway. These may be potential therapeutic targets in AD.

Alzheimer Disease↗
PubMed2006

Risk factors and associated problems in the management of infections with methicillin resistant Staphylococcus aureus.

PURPOSE: It is necessary to define the problem of methicillin resistant Staphylococcus aureus (MRSA) in every hospital to evolve control strategies. The objectives of this study were to determine factors influencing the persistence of MRSA in patients with hospital acquired infection and to identify alternate cost effective antibiotics. METHODS: A six month study was carried out for 50 patients with MRSA infection. Treatment modalities and risk factors were determined by a preset protocol. Minimum inhibitory concentration of commonly used antibiotics was determined. RESULTS: The risk factors were prolonged postoperative morbidity, prior antibiotic therapy and emergency admissions. Seventy percent of the isolates were from postoperative cases undergoing emergency surgeries. Isolation was highest during the second week of hospital stay. Emergency admissions had a significantly higher chance of early isolation. Prior treatment with multiple antibiotics in 38% was found to be another major risk factor. Ofloxacin was seen to be efficacious in a small percentage of cases. Rifampicin in combination with ofloxacin and clindamycin were found to be other good alternatives. Ofloxacin was found to be the cheapest and vancomycin the most expensive, for a full course of treatment. CONCLUSIONS: Minimizing risk factors and attention to alternate cost effective combination therapy may ease the problem of management of infections with MRSA.

Anti-Bacterial Agents↗
PubMed2006

Feeding of infants and young children in tsunami affected villages in Pondicherry.

The study was conducted to identify the problems related to feeding of children post tsunami in four villages in Pondicherry. Data were collected from 100 randomly chosen families who had an infant or a young child below 3 years of age during Tsunami. Informants were the mothers. In the population studied, 30% mothers did not exclusively breast feed for 6 months; 58% bottle fed their children and 51% fed their infants with commercial formula. The occurrence of diarrhea was three times higher among children who were fed with free breast milk substitutes (BMS) than in those who were not fed with the same. Those populations, wherein a pre-existing tradition of artificial feeding is present, infants are at further risk during a crisis situation like Tsunami. Breast feeding practices need strengthening even in routine conditions to tackle a disaster rather than intervention after the disaster.

Age Factors↗
PubMed2005

Epitaxial deposition of calcium oxalate on uric acid rich stone matrix is induced by a 29 kDa protein.

BACKGROUND: Association of macromolecules particularly the role of proteins in urolithiasis has been studied for last few centuries, but still a complete profile of stone matrix proteins that mediate co-precipitation of uric acid and calcium oxalate has not been characterized. We isolated and characterize proteins from uric acid rich stone matrix, which have oxalate binding activity. METHODS: Matrix proteins were isolated from uric acid rich stone matrix using EDTA as a demineralizing agent. The radiolabelled solubilized proteins were fractionated with increasing ionic concentration by DEAE cellulose column chromatography to identify the oxalate binding protein. It was purified using Sephadex G-200 column chromatography. Amino acid composition was determined and monoclonal antibody was produced against the oxalate binding uric acid rich stone matrix protein. Urinary uric acid binding proteins were isolated from stone formers urine, their oxalate binding activity assayed and cross reactivity with the produced monoclonal antibody were checked using ELISA and Western blotting. RESULTS: Matrix on DEAE column chromatography elution yielded 3 protein peaks and they were named as fraction I, II and III among which fraction I had higher oxalate binding activity which was further purified with Sephadex G-200 column which yielded 2 protein peaks designated as Ia and Ib. Fraction Ib with molecular weight 29 kDa exhibited the maximum oxalate binding activity. Forty percent of this 29 kDa protein is comprised of basic amino acids. Monoclonal antibody (IgG1) was produced against the 29 kDa stone matrix protein. Urinary uric acid binding proteins were isolated from stone formers, 4 protein peaks were obtained named as fraction I to IV. Among them, fraction IV having molecular weight of approximately 29 kDa cross reacted up to 85.6% with 29 kDa stone matrix protein. Moreover, urinary 29 kDa protein exhibited oxalate binding activity of 94.16 +/- 6.08 pmol/mg protein at pH 5.5. CONCLUSION: The 29 kDa protein isolated from uric acid rich stone matrix and urine are one and the same, thereby insinuating that 29 kDa protein might play a major role in epitaxial deposition of calcium oxalate over uric acid core, consequently favoring the lithogenic events like uric acid and calcium oxalate nucleation, aggregation and retention.

Animals↗
PubMed2005

Mixed ligand copper(II) complexes of phenanthroline/bipyridyl and curcumin diketimines as DNA intercalators and their electrochemical behavior under Nafion and clay modified electrodes.

The mode of binding of copper(II) mixed ligand complexes of phen/bpy and Knoevenagel condensate of curcumin (4-salicylidene-1,7-bis(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione) and 4-X-anilines with herring sperm DNA has been investigated using spectral and electrochemical techniques in Tris-HCl buffer pH 7.1. On titration with DNA, usual hypochromism and unusual (large) red shift (30-35 nm) for some of these complexes were observed in their absorption spectra of intense intraligand (IL) pi-pi* transition around 420 nm. Variations in the absorbance due to their interaction with DNA on time scale were also investigated, under fixed concentrations of complex and DNA. On interaction with DNA, the quasi-reversible CuII/I redox couple slightly improves its reversibility with considerable decrease in current intensity. The intercalation of these copper complexes into the DNA base pairs was also investigated by gel retardation assay method. All the experimental results indicate that the phen mixed copper(II) complexes intercalate more effectively into the DNA base pairs than their bpy counterparts. Significant differences in the redox behavior of these copper(II) complexes under electrochemically modified GC electrodes with Nafion and K10 Montmorillonite clay have also been investigated and discussed.

2,2'-Dipyridyl↗
PubMed2005

Synthesis and bioactivity of some new N-aryl/alkyl/cyclohexyl-N'-(2,3-dihydro-2-oxo-4H-benz[e][1,3,2]oxazaphosphorin-2-yl) ureas.

Several new substituted oxazaphosphorinyl urea derivatives of the type RR'P(O)NHC(O)NHR'' were synthesized from alpha-(3-chloro-4-fluoroanilino)-o-cresol by reaction with chlorides of aryl/alkyl/cyclohexyl carbamidophosphoric acids in the presence of triethylamine at 0-50 degrees C. Their significant insecticidal and antimicrobial activity and promotion of Rhizobium bacteria growth in the soil without effect on the host tissue suggests their possible commercial application as ecofriendly pesticides and antimicrobial agents.

Alternaria↗
PubMed2005

Helicobacter pylori and recurrent pain abdomen.

OBJECTIVE: Pain abdomen is a common problem in childhood. Many factors i.e., organic changes in the gut, psychological and environment contribute to recurrent pain abdomen (RAP) in children. Helicobacter pylori infects children very early in childhood and stays indefinitely in the gut without its eradication. It may be responsible for pain abdomen and peptic ulcers in children. This study was done to assess the HP status in children with RAP diagnosed and evaluate the effects of eradication of HP infection in them. METHODS: 76 children were included in the study. RESULT: Out of 76 children studied 14.8% had evidence of a secondary cause for pain abdomen and responded to appropriate therapy. 65.45% of children who had undergone UGIE, had evidence of HP infection in the upper gastrointestinal tract. Most of these children responded to HP eradication therapy by becoming free of abdominal pain after the eradication therapy with OCA or OMA regimen. We could not do repeated endoscopies in all of them to prove the eradication due to parents' refusal and this is the main drawback of this study. CONCLUSION: However, in view of clinical response to HP eradication therapy in almost all the cases, we strongly advocate this therapy for those children with RAP, in whom HP infection of the upper gastrointestinal tract can be established beyond doubt.

Abdominal Pain↗