Biomedical subjects
Publications and source records attributed to R Nandakumar.
Using 13.8 fb(-1) of data collected at or just below the Upsilon(4S) with the CLEO detector, we report the result of a search for the flavor changing neutral current process D0-->gammagamma. We observe no significant signal for this decay mode and determine 90% confidence level upper limits on the branching fractions B(D0-->gammagamma)/B(D0-->pi(0)pi(0))<0.033 and B(D0-->gammagamma)<2.9 x 10(-5).
Using the combined CLEO II and CLEO II.V data sets of 9.1 fb(-1) at the Upsilon(4S), we measure properties of psi mesons produced directly from decays of the B meson, where "B" denotes an admixture of B+, B-, B0, and B;(0), and "psi" denotes either J/psi(1S) or psi(2S). We report first measurements of psi polarization in B-->psi(direct)X: alpha(psi(1S))=-0.30(+0.07)(-0.06)+/-0.04 and alpha(psi(2S))=-0.45(+0.22)(-0.19)+/-0.04. We also report improved measurements of the momentum distributions of psi produced directly from B decays, correcting for measurement smearing. Finally, we report measurements of the inclusive branching fraction for B-->psiX and B-->chi(c1)X.
In e(+)e(-) collisions using the CLEO detector, we have studied the decay of the D0 to the final state K(0)(S)pi(+)pi(-) with the initial flavor of the D0 tagged by the decay D(*+)-->D0pi(+). We use the Dalitz technique to measure the resonant substructure in this final state and clearly observe ten different contributions by fitting for their amplitudes and relative phases. We observe a K(*)(892)(+)pi(-) component which arises from doubly Cabibbo suppressed decays or D0-D0; mixing.
We report on a search for charmless hadronic B decays to the three-body final states K(0)(S)h(+)pi(-), K(+)h(-)pi(0), K(0)(S)h(+)pi(0) (h(+/-) denotes a charged pion or kaon), and their charge conjugates, using 13.5 fb(-1) of integrated luminosity produced near sqrt[s]=10.6 GeV, and collected with the CLEO detector. We observe the decay B-->K0pi(+)pi(-) with a branching fraction (50(+10)(-9)(stat.)+/-7(syst.))x10(-6) and the decay B-->K(*+)(892)pi(-) with a branching fraction (16(+6)(-5)(stat.)+/-2(syst.))x10(-6).
Pseudomonas fluorescens (two native strains, one collection strain and their strain mixtures in all possible combinations) when applied through seed, seedling dip, soil and on leaf significantly reduced the tomato spotted wilt virus (TSWV) disease. In P. fluorescens-treated plants, the peroxidase and phenylalanine ammonia-lyase activity increased. Accumulation of phenolic compounds and lignin were shown to be increased in the P. fluorescens-treated plants. Isoperoxidase native PAGE indicated that the peroxidase isoforms in tomato plants induced by fluorescent pseudomonads were different from the control plants; this suggests that the general phenylpropanoid pathway is probably stimulated in tomato plants treated which in turn led to significant reduction in TSWV.
AIMS: To purify and characterize an extracellular alpha-glucosidase from Trichoderma viride capable of inactivating a host-specific phytotoxin, designated RS toxin, produced by the rice sheath blight pathogen, Rhizoctonia solani Kühn. METHODS AND RESULTS: The host-specific RS toxin was purified from both culture filtrates (culture filtrate toxin, CFTox) and R. solani-inoculated rice sheaths (sheath blight toxin, SBTox). Sodium dodecyl sulphate-polyacrylamide gel electrophoresis analyses of extracellular proteins, purified from a biocontrol fungus T. viride (TvMNT7) grown on SBTox and CFTox separately, were carried out. The antifungal activity of the purified high molecular weight protein (110 kDa) was studied against RS toxin as well as on the sclerotial germination and mycelial growth of R. solani. Enzyme assay and Western blot analysis with the antirabbit TvMNT7 110-kDa protein indicated that the protein was an alpha-glucosidase. The 110-kDa protein was highly specific to RS toxin and its Michaelis-Menten constant value was 0.40 mmol l-1 when p-nitrophenyl alpha-D-glucopyranoside was used as the substrate. The isoelectric point of the protein was 5.2. N-terminal sequencing of the alpha-glucosidase protein showed that its amino acid sequence showed no homology with other known alpha-glucosidases. CONCLUSION: This appears to be the first report of the purification and characterization of an alpha-glucosidase capable of inactivating a host-specific toxin of fungal origin. The alpha-glucosidase is specific to RS toxin and is different from the known alpha-glucosidases. SIGNIFICANCE AND IMPACT OF THE STUDY: As RS toxin could be inactivated by the microbial alpha-glucosidase enzyme, isolation of the gene that codes for the enzyme from T. viride and transfer of the gene to rice plants would lead to enhanced resistance against sheath blight pathogen by inactivation of RS toxin.
A procedure for the enhanced lysis of mucous producing psychrotrophic gram positive bacteria for subsequent enzyme studies is described. An initial washing of bacterial cells with Tween 80 was found to improve the degree of cell disruption in subsequent sonication or grinding with glass beads, resulting in about 20-200% increase in total soluble protein content. However, in terms of lactate dehydrogenase (LDH) activity present in the lysate, pretreatment with Tween 80 was more effective in combination with grinding, especially in the highly mucous producing strain GY11. The type of surfactant used in the pretreatment procedure before grinding strongly influenced the percentage lysis of tested strains, both in terms of released soluble protein and enzyme activity. Zymograms of LDH and glutamate dehydrogenase (GDH) activity present in the lysates also very well supported the results obtained by total protein and enzyme activity measurements.
A monoclonal-antibody-based, sequential competitive-flow-injection immunoassay system in expanded-bed mode has been developed for the determination of nisin. The system allows the determination of nisin in the presence of suspended particles without any significant interference, illustrating its potential for on-line monitoring of fermentation processes or the analysis of food matrices. The dose response range of the system when operated in expanded-bed mode was 6-90 microM. The detection limit under packed-bed conditions was 3 microM. The results correlated well with the results from conventional ELISA in the analysis of samples of processed cheese. When milk samples, fermentation samples and buffer were spiked with nisin, the mean recoveries were 86% for milk samples, 96% for fermentation samples and 98% for buffer solution.
The rice sheath blight pathogen, Rhizoctonia solani, produces a toxin designated as RS-toxin, a carbohydrate compound containing mainly alpha-glucose and mannose. Different microflora were tested for RS-toxin inactivation. Isolates of Trichoderma viride inactivated this toxin when it was provided as the sole food source, and these isolates reduced the severity of toxin-induced symptoms and electrolyte leakage from rice cells. The best-performing isolate, TvMNT7, produced two extracellular proteins of 110 and 17 kDa. The high molecular mass protein was shown to have alpha-glucosidase activity. The purified 110 kDa protein was able to reduce RS-toxin activity.
A high-expression plasmid, pKSGHE3-1, containing the salt-tolerant glutaminase (EC 3.5.1.2) from marine bacterium Micrococcus luteus K-3 was constructed. pKSGHE3-1 was made by inserting the DNA fragment (1.43 kb) containing the structural gene synthesized by polymerase chain reaction into the downstream region of the tac promoter of expression vector pKK223-3. The translational start codon was located 10 bases downstream of the Shine-Dalgarno sequence (AGGA) of pKK223-3. Escherichia coli JM109 transformed with pKSGHE3-1 exhibited more than 190-fold higher glutaminase activity than M. luteus K-3 under optimal culture conditions. The enzyme was purified to homogeneity through three column chromatography steps with a final yield of 17.1%. The recombinant enzyme showed the same enzymatic properties, including salt tolerance, as those of M. luteus K-3. This glutaminase expression system allows the production of sufficient quantities of glutaminase for basic structure-function studies including chemical modification and future X-ray crystallization analysis.
A microbial biosensor based on immobilised psychrotrophic yeast Yarrowia lipolytica integrated to FIA for the determination of middle chain alkanes was developed. The system responded very well to middle chain alkanes even at low operational temperatures down to +5 degrees C. The maximum sensitivity was obtained at 15 degrees C. A linear relationship was observed between the sensor response and dodecane concentration up to 100 microM.
A simple, economical and rapid affinity chromatography procedure with dyes as the ligand has been described for the one-step purification of a cold-adapted lactate dehydrogenase. Non-specific elution of Procion blue H-ERD-modified Sepharose yielded homogeneous preparations of lactate dehydrogenase both in column based procedures and in batch wise operations. Low operational temperatures resulted in the enhanced binding of the enzyme to the blue dye. The dissociation constants of the enzyme-dye complexes were 7.2 +/- 0.2 microM and 11.2 +/- 0.2 microM at 5 degrees C and 20 degrees C respectively.
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Isolated native nonrheumatic tricuspid valve endocarditis rarely is described in the absence of intravenous drug use, intracardiac catheters, or cardiac anomalies. We diagnosed tricuspid valve endocarditis in two elderly nonaddicted patients with recurrent pulmonary infiltrates, anemia, and microscopic hematuria that occurred during several months and was caused by Gemella morbillorum and Candida glabrata, respectively. We have reviewed 27 other cases of nonaddicted patients with tricuspid valve endocarditis from the literature and discussed etiology, clinical characteristics, and outcome. Mean age was 53.5 years (range, 22 to 74 years old), and 72% had underlying medical conditions. Staphylococcus oureus, Streptococcus bovis, and candida species were the causative organisms in 70% of the cases. Average duration of infection before diagnosis was 9.3 months. We conclude that isolated tricuspid valve endocarditis in nonaddicted patients occurs mainly in the middle-aged and older persons, mimicking chronic illness and community-acquired pneumonia. In the absence of a history of intravenous drug use, diagnostic delays are common. We suggest that right-sided endocarditis must be considered in any patient with the "Tricuspid Syndrome," consisting of recurrent pulmonary events, anemia, and microscopic hematuria. Careful evaluation of prior medical records and clinical course can be very helpful. Echocardiography and serial blood cultures provide the key to diagnosis.
To examine whether children (mean age 34 months) can fast map and extend novel action labels to actions for which they do not already have names, the comprehension of familiar and novel verbs was tested using colored drawings of Sesame Street characters performing both familiar and unfamiliar actions. Children were asked to point to the character "verbing," from among sets of 4 drawings. With familiar words and actions, children made correct choices 97% of the time. With novel action words, children performed at levels mostly significantly above chance, selecting a previously unlabeled action or another token of a just-names action. In a second, control experiment children were asked to select an action from among the same sets of 4 drawings, but they were not given a novel action name. Here children mainly demonstrated performance at levels not significantly different from chance, showing that the results from the main experiment were attributable to the presence of a word in the request. Results of these studies are interpreted as support for the availability of principles to ease verb acquisition.
BACKGROUND: Helicobacter pylori infection has been implicated in the development of encephalopathy in chronic liver disease (CLD); this is possibly due to increased production of ammonia by the action of bacterial urease on urea in the gastric lumen. AIM: To evaluate whether H. pylori eradication in patients with CLD affects arterial ammonia levels. METHODS: Forty-six patients with CLD (40 alcoholic, 6 post hepatitis B; Child's class A 7, B 17, C 22) and 36 patients with symptoms of acid-peptic disease (APD) underwent gastrointestinal endoscopy and biopsy; gastric biopsies were evaluated for H. pylori status using rapid urease test and histology. H. pylori-positive subjects received quadruple-drug eradication therapy for 2 weeks. Fasting arterial plasma ammonia levels were estimated before and after eradication of H. pylori. RESULTS: H. pylori infection was present in 21 of 46 (45.7%) patients with CLD and 23 of 36 (63.9%) with APD. At baseline, mean (SD) ammonia levels were higher in the CLD group (97.4 [10.9] versus 81.3 [7.7] mcg/dL in the APD group; p = 0.0001), irrespective of H. pylori status. Amongst patients with liver disease, arterial ammonia levels were similar in the H. pylori-positive and -negative patients (94.1 [9.7] and 100.2 [11.3] mcg/dL, respectively); however, ammonia levels were higher in patients in Child's class C (102.7 [11.4] mcg/dL/dL) than in those in class A (88.4 [1.6] mcg/dL; p < 0.002) or B (94.1 [9.7] mcg/dL; p < 0.002). In patients with APD, ammonia levels were higher in H. pylori-positive patients (85.3 [6.4] versus 74.1 [3.3] mcg/dL; p < 0.001). After eradication of H. pylori infection, ammonia levels decreased to 88.4 (10.0) mcg/dL in CLD and 76.7 (4.8) mcg/dL in APD (p = 0.001 as compared to baseline). There was no difference in post-eradication ammonia levels between Child's classes. CONCLUSION: Levels of arterial blood ammonia are higher in CLD than in APD, and correlate with severity of liver disease. H. pylori eradication was associated with reduction in arterial ammonia levels in patients with CLD.
There are few reports of skeletal infections in patients with cirrhosis. We present two such cases, both with alcoholic liver disease, seen over a period of one year. The first, a 46-year-old man, presented as pyrexia of unknown origin, and was found to have pyogenic discitis; he responded to antibiotic and surgery. The second, a 42-year-old man, presented with chest wall abscess and was diagnosed to have tubercular osteomyelitis; he expired despite treatment with non-hepatotoxic anti-tubercular drugs.
We report a 32-year-old man with acute myeloid leukemia presenting as obstructive jaundice. Imaging revealed dilated common bile duct with abrupt narrowing at the lower end, distended gall bladder, and dilated intrahepatic biliary radicles. In addition he had a mass lesion in the urinary bladder. On evaluation he was found to have the eosinophilic variant of M4 subtype acute myeloid leukemia. He expired before chemotherapy could be instituted.