Biodegradation of pyridine by freely suspended and immobilized Pimelobacter sp.

Freely suspended and Ca-alginate-immobilized cells of Pimelobacter sp. were used for degradation of pyridine. When the pyridine concentration was up to 2 g l^–1, freely suspended cells completely degraded pyridine regardless of the initial cell concentrations used. However, when the pyridine concentration increased to 4 g l^–1, the initial cell concentration in freely suspended cell culture should be higher than 1.5 g dry cell weight l^–1 for complete degradation of pyridine. In addition, a freely suspended cell culture with a high initial cell concentration resulted in a high volumetric pyridine-degradation rate, suggesting the potential use of immobilized cells for pyridine-degradation. When the immobilized cells were used for pyridine-degradation, neither specific pyridine-degradation rate nor tolerance against pyridine was improved. However, a high volumetric pyridine-degradation rate in the range 0.082–0.129 g l^–1 hr^–1 could be achieved by the immobilized cells because of the high cell concentration. Furthermore, when the immobilized cells were reused in degrading pyridine at a concentration of 2–4 g l^–1 they did not lose their pyridine-degrading activity for 2 weeks. Taken together, the data obtained here showed the feasibility of using immobilized cells for pyridine-degradation.     

Isolation of a phospholipase A1-producing microorganism

A bacterium which has phospholipase A₁ activity was isolated from soil. It is aerobic, motile, oxidase-negative and has flagella. The G+C content of the DNA was 58.1 mol%. The major isoprenoids of cell was were Q-8 and MK-8. The main cellular fatty acids were saturated straight chain (n-16) and cyclic (17:) fatty acids. Based on its morphological, physiological and chemotaxonomic characteristics, this organism was placed in the genusSerratia. Nutritional factors affecting enzyme production were explored. Xylose and ammonium sulfate were the best carbon and nitrogen sources, respectively. Ferrous ions exerted a considerable positive effect on enzyme production. The optimal pH and temperature for phospholipase A₁ production were 7.0 and 30°C, respectively.     

Anti-apoptotic mechanism of silkworm hemolymph in HeLa cell apoptosis

Silkworm hemolymph (SH) was found to exhibit anti-apoptotic activities in mammalian and insect cell systems. An anti-apoptotic mechanism of SH was investigated in a staurosporine-induced HeLa cell using flow cytometry, caspase assay, Immunoblot, and Immunochemistry. The addition of 5% SH to the medium resulted in lower intracellular activities of caspase-3 and caspase-9 after 0.6 μM of staurosporine treatment; however, SH did not directly inhibit the activities of those enzymes. This suggests SH inhibits the event upstream of these caspase activation steps, such as mitochondrial level events. We found from Immunoblot and Immunochemistry that cytochrome c release from the mitochondria was blocked by SH. SH also inhibited Bax translocation to the mitochondria. On the contrary, SH did not block the apoptosis when Bax is not involved in promoting apoptosis. With these results, we propose that SH protects mitochondria from apoptosis signal via blocking Bax translocation, and the subsequent apoptotic events are then inhibited. The inhibition of apoptosis using SH and its components may lead to new approaches for the minimization of cell death during commercial animal cell cultures.     

Photoluminescence imaging of europium (III)‐doped γ‐Al2O3 nanofiber structures

Aluminium oxide (Al₂O₃) has widely been used for catalysts, insulators, and composite materials for diverse applications. Herein, we demonstrated if γ‐Al₂O₃ was useful as a luminescence support material for europium (Eu) (III) activator ion. The hydrothermal method and post‐thermal treatment at 800°C were employed to synthesize Eu(III)‐doped γ‐Al₂O₃ nanofibre structures. Luminescence characteristics of Eu(III) ions in Al₂O₃ matrix were fully understood by taking 2D and 3D‐photoluminescence imaging profiles. Various sharp emissions between 580 to 720 nm were assigned to the ⁵D₀→⁷F_J (J = 0, 1, 2, 3, 4) transitions of Eu(III) activators. On the basis of X‐ray diffraction crystallography, Auger elemental mapping and the asymmetry ratio, Eu(III) ions were found to be well doped into the γ‐Al₂O₃ matrix at a low (1 mol%) doping level. A broad emission at 460 nm was substantially increased upon higher (2 mol%) Eu(III) doping due to defect creation. The first 3D photoluminescence imaging profiles highlight detailed understanding of emission characteristics of Eu(III) ions in Al oxide‐based phosphor materials and their potential applications.     

A multilevel mixed effects varying coefficient model with multilevel predictors and random effects for modeling hospitalization risk in patients on dialysis

For patients on dialysis, hospitalizations remain a major risk factor for mortality and morbidity. We use data from a large national database, United States Renal Data System, to model time-varying effects of hospitalization risk factors as functions of time since initiation of dialysis. To account for the three-level hierarchical structure in the data where hospitalizations are nested in patients and patients are nested in dialysis facilities, we propose a multilevel mixed effects varying coefficient model (MME-VCM) where multilevel (patient- and facility-level) random effects are used to model the dependence structure of the data. The proposed MME-VCM also includes multilevel covariates, where baseline demographics and comorbidities are among the patient-level factors, and staffing composition and facility size are among the facility-level risk factors. To address the challenge of high-dimensional integrals due to the hierarchical structure of the random effects, we propose a novel two-step approximate EM algorithm based on the fully exponential Laplace approximation. Inference for the varying coefficient functions and variance components is achieved via derivation of the standard errors using score contributions. The finite sample performance of the proposed estimation procedure is studied through simulations.     

The cucumber mosaic virus 1a protein regulates interactions between the 2b protein and ARGONAUTE 1 while maintaining the silencing suppressor activity of the 2b protein

The cucumber mosaic virus (CMV) 2b viral suppressor of RNA silencing (VSR) is a potent counter-defense and pathogenicity factor that inhibits antiviral silencing by titration of short double-stranded RNAs. It also disrupts microRNA-mediated regulation of host gene expression by binding ARGONAUTE 1 (AGO1). But in Arabidopsis thaliana complete inhibition of AGO1 is counterproductive to CMV since this triggers another layer of antiviral silencing mediated by AGO2, de-represses strong resistance against aphids (the insect vectors of CMV), and exacerbates symptoms. Using confocal laser scanning microscopy, bimolecular fluorescence complementation, and co-immunoprecipitation assays we found that the CMV 1a protein, a component of the viral replicase complex, regulates the 2b-AGO1 interaction. By binding 2b protein molecules and sequestering them in P-bodies, the 1a protein limits the proportion of 2b protein molecules available to bind AGO1, which ameliorates 2b-induced disease symptoms, and moderates induction of resistance to CMV and to its aphid vector. However, the 1a protein-2b protein interaction does not inhibit the ability of the 2b protein to inhibit silencing of reporter gene expression in agroinfiltration assays. The interaction between the CMV 1a and 2b proteins represents a novel regulatory system in which specific functions of a VSR are selectively modulated by another viral protein. The finding also provides a mechanism that explains how CMV, and possibly other viruses, modulates symptom induction and manipulates host-vector interactions.     

Detoxification of hydrogen peroxide maintains the water transport activity in figleaf gourd (Cucurbita ficifolia) root system exposed to low temperature

The figleaf gourd ( Cucurbita ficifolia Bouché) root system has the ability to take up water and nutrients at low soil temperatures, and in the present paper, we attempt to reveal some of the molecular mechanisms behind this low-temperature tolerance. Exposure of figleaf gourd root system to low temperature induced accumulation of H₂O₂ along the plasma membrane but not in the cytoplasm. H⁺-ATPase (EC 3.6.1.35) activity of isolated root plasma membranes and root hydraulic conductivity ( Lp_r ) were largely insensitive to externally applied H₂O₂. However, using bromocresol purple, it was shown that the acidification of the medium surrounding the root was strongly inhibited with low temperature- and H₂O₂-treated roots. Addition of catalase (EC 1.11.1.6) to the root medium during low-temperature exposure led to a recovery of H⁺-efflux along the root surface and increased Lp_r , demonstrating the importance of an H₂O₂ detoxification system in the root cells. Additional evidence for an increased Lp_r was obtained by the Fenton reaction wherein a warming of the solution increased the activity of the detoxification system. All available evidence suggests that the ability of figleaf gourd root system to maintain a low level of H₂O₂ in the cytoplasm and to detoxify reactive oxygen species is related to the maintenance of water transport activity at low temperatures.     

Structural and functional insights into intramolecular fructosyl transfer by inulin fructotransferase

Inulin fructotransferase (IFTase), a member of glycoside hydrolase family 91, catalyzes depolymerization of beta-2,1-fructans inulin by successively removing the terminal difructosaccharide units as cyclic anhydrides via intramolecular fructosyl transfer. The crystal structures of IFTase and its substrate-bound complex reveal that IFTase is a trimeric enzyme, and each monomer folds into a right-handed parallel beta-helix. Despite variation in the number and conformation of its beta-strands, the IFTase beta-helix has a structure that is largely reminiscent of other beta-helix structures but is unprecedented in that trimerization is a prerequisite for catalytic activity, and the active site is located at the monomer-monomer interface. Results from crystallographic studies and site-directed mutagenesis provide a structural basis for the exolytic-type activity of IFTase and a functional resemblance to inverting-type glycosyltransferases.     

Synthesis, biological evaluation and structural determination of beta-aminoacyl-containing cyclic hydrazine derivatives as dipeptidyl peptidase IV (DPP-IV) inhibitors

Inhibitors of dipeptidyl peptidase IV (DPP-IV) have been shown to be effective treatments for type 2 diabetes. A series of beta-aminoacyl-containing cyclic hydrazine derivatives were synthesized and evaluated as DPP-IV inhibitors. One member of this series, (R)-3-amino-1-(2-benzoyl-1,2-diazepan-1-yl)-4-(2,4,5-trifluorophenyl)butan-1-one (10f), showed potent in vitro activity, good selectivity and in vivo efficacy in mouse models. Also, the binding mode of compound 10f was determined by X-ray crystallography.