bluuebunny/crossref_metadata_2025 huggingface dataset:
Intracellular polyol accumulation by yeastlike fungi of the genera Geotrichum and Endomyces in response to water stress (NaCl)
Authors: Luxo Cristina , Nobre M. Fernanda , Costa Milton S. da
Published: May 2010

The growth and intracellular accumulation of polyhydroxy alcohols (polyols) were studied in 10 yeastlike fungi of the genera Geotrichum and Endomyces in media with and without the addition of NaCl. The specific growth rate of all strains decreased when the NaCl concentration in the medium was higher than 0.25 M, and no growth occurred at concentrations higher than 1.50 M. High-performance liquid chromatography showed that mannitol was the main polyol accumulated during the late exponential and stationary phases of growth in media without added NaCl. In the presence of 0.75 or 1.0 M NaCl these organisms, with the exception of Geotrichum penicillatum IGC 3460, accumulated high levels of arabinitol (arabitol) as a compatible solute; mannitol was detected in trace amounts only in the late stationary phase of some strains. Geotrichum penicillatum IGC 3460, however, accumulated mannitol instead of arabinitol in response to an increase of NaCl in the growth medium. In this organism, the substitution of arabinitol for glucose in the growth medium did not affect the accumulation of mannitol.Key words: polyol, osmoregulation, Geotrichum, Endomyces.
Erratum: Effects of oxytetracycline, oxolinic acid, and flumequine on bacteria in an artificial marine fish farm sediment
Authors: Hansen Pia K. , Lunestad Bjørn T. , Samuelsen Ole B.
Published: May 2010

Oxytetracycline, oxolinic acid, and flumequine are at present the most frequently used antibacterial agents in the treatment of marine farmed fish in Norway. These substances are supplied with the food pellets and a substantial amount ends up in the sediment under the net pens. The effects of these antibacterial agents on the microbial community in a sediment were experimentally examined in tanks containing sediment to which was added either oxytetracycline, oxolinic acid, or flumequine, and supplied with a constant water flow. During the first 20 days of the experiment, approximately one-third of the antibacterial agents disappeared from the sediments. During the next 165 days another 25% vanished. There were elevated numbers of bacteria resistant to oxytetracycline and oxolinic acid a few days after the start of the experiment. The resistance that developed to oxytetracycline was higher and longer lasting than that to oxolinic acid and flumequine. Of the quinolones, flumequine seemed least disposed to induce resistance. The number of bacteria in all treated sediments decreased to 50–67% of the numbers in the control sediment 2 days after medication. Seven days after medication the sulfate reduction rates in the treated sediments were reduced to less than 10% of the rates found in the control. This effect lasted at least 29 days, but after 70 days the inhibition of the sulfate reduction in the treated sediments had disappeared.Key words: antibacterial agents, sediment, bacterial resistance, sulfate reduction.
Effect of temperature on succinate transport by an arctic and a temperate strain of rhizobia
Authors: Bigwaneza Pierre C. , Prévost Danielle , Bordeleau Lucien M. , Antoun Hani
Published: May 2010

The effect of temperature on the succinate transport system was studied in the arctic Rhizobium strain N31 (isolated from Astragalus alpinus) and in the temperate strain SM2 (isolated from Onobrychis viciifolia). Only one inducible succinate transport system was found in the two strains as indicated by the linear Eadie–Hofstee plot obtained at 10, 15, and 25 °C. The transport of succinate was not affected by arsenate, but was inhibited by carbonyl cyanide m-chlorophenylhydrazone, KCN, and iodoacetate, implying an active process, a proton motive force, and essential sulfhydryl groups in the system. At 25 °C the apparent Km and Vmax values observed were 6.7 and 7.4 μM and 40.8 and 27.9 nmol∙min−1∙mg protein−1 for strains N31 and SM2, respectively. Similar kinetic parameters for succinate transport at 25 °C were obtained with the cells of both strains grown at 10 or 25 °C. However, when transport was measured at 10 °C the Km and Vmax values obtained with strain SM2 were higher for cells cultured at 10 °C than for those cultured at 25 °C, suggesting that this temperate strain might be more affected by low growth temperature than the arctic strain N31. The succinate transport systems in the two strains were affected by temperature in a similar fashion, as indicated by similar Arrhenius plots of Vmax showing a discontinuity at 20 °C and by comparable apparent energy of activation values. These observations suggest that the cold adaptation of strain N31 is not related to a cold adaptation of the succinate carrier.Key words: arctic, Rhizobium, succinate, symbiosis, transport.
Characterization of the cell wall of Butyrivibrio species
Authors: Hespell R. B. , Kato K. , Costerton J. W.
Published: May 2010

Most Butyrivibrio strains have been isolated from the gastrointestinal tract of animals and have been classified as Butyrivibrio fibrisolvens. A few strains isolated from human feces are designated as Butyrivibrio crossatus, the other species in this genus. Butyrivibrio fibrisolvens strains are anaerobic, curved rods that produce butyrate, but numerous studies have shown that these strains display considerable variations in phenotypic properties and heterogeneity in DNA relatedness. Although over 60 strains have been characterized in these respects, the cell wall structure of only a few strains has been studied. In this study, cell wall related properties of 12 strains representative of five DNA relatedness groups were examined. All strains were very sensitive to penicillin and other antibiotics that interfere with cell wall synthesis. Although an occasional resistant strain was found, most strains were sensitive to a variety of protein synthesis antibiotics that included aminoglycosides and tetracycline. In contrast, all strains were highly resistant to nalidixic acid. Peptidoglycans were isolated from seven B. fibrisolvens strains and Lachnospira multiparus. Compositional analyses indicated molar ratios of 0.7:2:2:1:0.8 for muramic acid, glucosamine, alanine, glutamic acid, and diaminopimelic acid, respectively, in all peptidoglycans, which also showed a low degree of cross-linking. A trichloroacetic acid extractable galactosamine-containing polysaccharide copurified with the Butyrivibrio peptidoglycans. Electron microscopy of thin sections showed all strains to possess a Gram-positive type of cell wall that was atypically thin (12–18 nm). Most strains also displayed external (surface) polysaccharide layers. Cytoplasmic inclusions and granules were evident in many strains and were composed of polysaccharides, on the basis of cell composition analyses. The findings that Butyrivibrio strains have overall similarities in cell wall properties, but differences in DNA relatedness, suggest that these organisms should be classified as several more species in the same genus or family.Key words: Butyrivibrio fibrisolvens, Butyrivibrio crossatus, cell wall, peptidoglycan, ruminal bacteria.
Compétition entre souches de Rhizobiaceae: mise en évidence de différents modes d'adhésion sur les racines de soja
Authors: Dolhem-Biremon C. , Mary P. , Tailliez R.
Published: May 2010

Adhesion of 11 Rhizobiaceae strains on soybean roots was investigated. Whether these strains were able or not to nodulate soybean, they were found to adhere to these roots. Bacterial concentration above 1 × 1010 cells∙mL−1 was necessary to saturate root surfaces. Homologues and heterologous strains were used in mixed inoculation with Bradyrhizobium japonicum G49 StrR, used as reference strain in low number. Competition for adhesion was obtained at saturating concentrations of competitive strains. Only partial inhibition (< 55%) of the G49 StrR strain adhesion in the presence of heterologous strains was obtained, suggesting the occurrence of two modes of G49 StrR strain adhesion on the host roots: (i) a nonspecific adhesion of the B. japonicum and (ii) a specific adhesion of the B. japonicum or of strain G49 StrR. With homologous strains, inhibition of G49 StrR strain adhesion indicated a different competitive behavior between the four strains used belonging to the two DNA homology groups. Thus, the existence of species-specific recognition for all strains of B. japonicum, on soybean roots, remains to be confirmed.Key words: Rhizobiaceae, soybean, competition, adhesion, root.
The possible involvement of a fatty acyl thioesterase in the termination of the synthesis of fatty acids in a psychrophilic bacterium, Vibrio sp. strain ABE-1
Authors: Morita Naoki , Okuyama Hidetoshi
Published: May 2010

In Vibrio sp. strain ABE-1, very long chain fatty acids with up to 30 carbon atoms were synthesized in vitro in the form of acyl-acyl carrier protein by a fatty acid synthetase that had been prepared from the cytosol fraction precipitated between 55 and 75% saturation with ammonium sulfate. In contrast, fatty acids with 10–18 carbon atoms, which are the usual acyl components in this bacterium, were synthesized in vitro when the unfractionated cytosol fraction was used as the source of catalytic activity. When partially purified fatty acid synthetase was used together with a subfraction that had been prepared from the cytosol fraction precipitated between 0 and 55% saturation with ammonium sulfate, 16-carbon fatty acids were recovered as the dominant free fatty acids, and fatty acids with more than 20 carbon atoms were not synthesized in vitro. Acyl-acyl carrier proteins and acyl-CoAs with 16-carbon fatty acids were preferentially hydrolyzed when this subfraction was used as the source of catalytic activity. These results suggest that (a) fatty acyl thioesterase(s) with high specificity for acyl-acyl carrier proteins with 16-carbon fatty acids regulate(s) acyl chain length. This activity could explain the high levels of 16-carbon fatty acids in this bacterium.Key words: acyl chain length regulation, fatty acyl thioesterase, acyl-ACP, fatty acid synthetase, psychrophilic bacteria, Vibrio sp.
Cell interactions of Listeria monocytogenes L forms and peritoneal exudative cells in rats
Authors: Mihailova L. , Markova N. , Radoucheva T. , Veljanov D. , Radoevska S.
Published: May 2010

Listeria monocytogenes 4b and its forms without cell walls (L forms of a protoplastic type) were used to study in vivo interactions with host cells. Samples of peritoneal lavage fluid were obtained from rats intraperitoneally inoculated at intervals between 1 and 15 days after challenge, for scanning electron microscopic, bacteriological, biochemical, and cytometrical investigations. Scanning electron microscopic examination revealed continuous adhesion of L forms on the macrophage surface up to 15 days after inoculation. The persistence of the L forms within the peritoneal cavity was also shown bacteriologically at all sample times, while the parental bacterial forms were isolated from the peritoneal cavity up to 7 days after challenge. The total count of peritoneal exudative cells determined by automated flow peroxidase cytometry peaked on the 15th day in animals infected with parental forms, while in animals infected with L forms the peak was lower and the macrophage population was predominant. The glycolytic and acid phosphatase activity of peritoneal exudative cells was two times higher in rats infected with L forms as compared with rats infected with the L. monocytogenes parental forms on the 3rd day after challenge. An understanding of the nature of the interactions between L forms of L. monocytogenes and peritoneal exudative cells found in vivo could be used to establish the influence of L forms on host cellular defense mechanisms.Key words: Listeria monocytogenes, L forms, peritoneal exudative cells, electron microscopy.
Competition for nodule occupancy of introduced Bradyrhizobium japonicum strain SMGS1 in French soils already containing Bradyrhizobium japonicum strain G49
Authors: Pinochet X. , Arnaud F. , Cleyet-Marel J. C.
Published: May 2010

The competitiveness of Bradyrhizobium japonicum strains G49 and SMGS1 was first studied in the greenhouse in sterilized sand, with or without added soil. Strain SMGS1 was more competitive than strain G49 with soybean (Glycine max L.) cultivar Labrador but the two strains showed equivalent competitiveness with cultivar Kingsoy. When soil was added, nodule occupancy of strain G49 was only 22% with this cultivar. In field experiments, conducted over 2 years in soils already containing strain G49 (1.5 × 103 to 4.0 × 104 cells/g of soil), nodule occupancy of inoculated strain SMGS1 ranged from 20 to 90%. Nodule occupancy was 3–22% higher when inoculation was done by peat seed coating or with liquid inoculation in the row than with peat-coated clay microgranulars. Nodule occupancy was also dependent on the physiological state of the inoculated cells. When an inoculum stored at 28 °C for 1 year was used at the same viable cell rate, nodule occupancy of strain SMGS1 was 4–20% lower than with a recently made inoculum. Pot experiments with soil from field experiments carried out in the 1st year showed that the inoculated strain continued forming nodules without further inoculation, with a recovery rate equivalent to that of field experiment in the previous year.Key words: Bradyrhizobium japonicum, interstrain competition, inoculation technology, ELISA, field trials.
Homology between the genes of octopine catabolism of Rhizobium meliloti A3 and corresponding genes from the Ti plasmid
Authors: Bergeron Janique , Beaulieu Carole , Levesque Roger C. , Kondorosi Adam , Dion Patrice
Published: May 2010

The ability to catabolize crown-gall opines is found in Agrobacterium tumefaciens and various types of nonagrobacteria. Among the 75 Rhizobium meliloti strains tested in this work, 6 utilized the opines octopine and octopinic acid as the sole carbon and nitrogen source. From a genomic library of one of these six strains, R. meliloti A3, a clone conferring the octopine catabolism (Occ) phenotype was identified and named pJMA. A different Occ clone, which had been obtained from R. meliloti Rm41, did not hybridize with clone pJMA from strain A3. However, some fragments of clone pJMA hybridized to a 20-kilobase KpnI fragment containing the Ti plasmid genes of octopine catabolism (occ genes) from A. tumefaciens 15955. Shorter probes carrying the octopine permease genes or part of the octopine oxidase and ornithine cyclodeaminase genes from A. tumefaciens also hybridized with pJMA. The R. meliloti DNA carried by pJMA was localized to a megaplasmid of the wild-type strain A3. Thus, it appears possible that genes represented on the Occ clone from strain A3 share a common origin with the corresponding genes from the Ti plasmid.Key words: Rhizobium meliloti, Agrobacterium tumefaciens, octopine catabolism.
Detection of Escherichia coli by the nutrient agar plus 4-methylumbelliferyl β-D-glucuronide (MUG) membrane filter method
Authors: Shadix Lois C. , Dunnigan Michele E. , Rice Eugene W.
Published: May 2010

A two-step membrane filter procedure was evaluated to determine the ability to differentiate Escherichia coli from other coliform bacteria recovered from water. M-Endo LES agar incubated at 35 °C for 24 ± 2 h was used as the initial isolation medium. Membranes containing coliform colonies were transferred to nutrient agar plus 4-methylumbelliferyl β-D-glucuronide (MUG) and incubated for an additional 4 h at 35 °C. Escherichia coli colonies were distinguished by fluorescence when viewed under a long-wavelength ultraviolet light. A total of 119 MUG-positive colonies were isolated from 15 water sources, of which 115 (96.6%) were identified as E. coli. An examination of 182 pure culture environmental E. coli isolates revealed that 167 isolates (91.8%) exhibited fluorescence on the nutrient agar plus MUG medium. Survivors of E. coli cultures exposed to chlorination were also capable of producing a positive MUG reaction.Key words: membrane filtration, 4-methylumbelliferyl β-D-glucuronide (MUG), Escherichia coli, water.
Reconstitution of glucose uptake and chemotaxis in Pseudomonas aeruginosa glucose transport defective mutants
Authors: Sly Laura M. , Worobec Elizabeth A. , Perkins Richard E. , Phibbs Jr. Paul V.
Published: May 2010

Wild-type glucose uptake and glucose chemotaxis activities were restored in glucose transport defective Pseudomonas aeruginosa strains PFB360 and PFB362 after introduction of plasmid pPZ129, containing a 1.1-kilobase DNA fragment that is essential for the expression of the P. aeruginosa periplasmic glucose binding protein. The restoration of glucose uptake and chemotaxis to wild-type levels in these strains was also achieved by reconstitution with cold-shock fluid and purified glucose binding protein isolated from P. aeruginosa PA01 wild-type strain H103 grown in conditions resulting in the induction of the high-affinity glucose transport system. Glucose uptake was determined by whole cell uptake and shock fluid binding of D-[U-14C]glucose, using standard filter binding assays. Positive chemotaxis towards glucose was assessed by capillary assays using 10 mM glucose, the amount required for optimal chemotaxis, and judged by plating capillary contents accumulated after 30 min.Key words: glucose-binding protein, Pseudomonas aeruginosa, glucose transport, chemotaxis.
Immunohistochemical studies on localization of the extracellular polysaccharide produced by Xanthomonas oryzae pv. oryzae in infected rice leaves
Authors: Watabe M. , Yamaguchi M. , Kitamura S. , Horino O.
Published: May 2010

An antibody reacting with extracellular polysaccharide from Xanthomonas oryzae pv. oryzae was used to detect the extracellular polysaccharide in infected leaf tissues of rice plants (Oryzae sativa cv. IR24) by immunofluorescence and immunoelectron microscopy. Using extracellular polysaccharide as a hapten and bovine serum albumin as a carrier, an extracellular polysaccharide – bovine serum albumin conjugate was prepared. After a rabbit was immunized against the conjugate, an antibody reacting with extracellular polysaccharide from X. oryzae pv. oryzae was isolated and purified. Using ELISA, the antibody was capable of detecting extracellular polysaccharide at concentrations above 0.1 μg/mL. Immunofluorescent antibody staining of infected rice leaves showed that extracellular polysaccharide produced by X. oryzae pv. oryzae was distributed in both xylem vessels and transverse veins but not in either sieve tubes or mesophyll tissues. This demonstrates that the distribution of extracellular polysaccharide coincided with that of bacteria in the infected leaf tissues. Immunoelectron microscopy showed that localization of extracellular polysaccharide was restricted to the area close to bacterial cells. The amount of extracellular polysaccharide may not be enough to plug xylem vessels of rice leaves infected with X. oryzae pv. oryzae.Key words: anti extracellular polysaccharide antibody, Xanthomonas oryzae pv. oryzae, immunofluorescent microscopy, immunoelectron microscopy, rice plant.
The expression of potential colonization factors of yeasts isolated from fish during different growth conditions
Authors: Vázquez-Juárez Ricardo , Ascencio F. , Andlid T. , Gustafsson L. , Wadström T.
Published: May 2010

Three strains, Rhodotorula rubra, Rhodotorula glutinis, and Candida zeylanoides, isolated from fish, were tested for the expression of putative tissue colonization factors. All strains were able to bind collagen type I, fibronectin, and laminin to various degrees after growing on various solid and broth media, while the binding to collagen type IV was sparse under all conditions tested. For the three strains tested, a very low cell surface hydrophobicity was shown for growth on various solid and broth media. Mostly, the strains also expressed a negatively charged surface. Extracellular protease activity using different substrates was shown for all three strains. Furthermore, two properties related to iron scavenging, i.e., binding of lactoferrin and production of siderophores, were also tested. For the three strains a capacity to bind lactoferrin as well as a capacity to excrete siderophores were demonstrated. Since these different properties have been correlated to virulence and to the capacity of colonization in other organisms, we address the question of whether the expression of these properties in yeasts could contribute to colonization in fish.Key words: marine yeasts, fish colonization.
Characterization of cellulase-free xylanases from the newly isolated Bacillus sp. strain BP-23
Authors: Blanco A. , Pastor F. I. J.
Published: May 2010

A Bacillus strain with xylanase activity has been isolated. Maximum xylanase production was obtained when the strain was cultured in media supplemented with birchwood xylan or rice straw; production was repressed by glucose and xylose. The optimal temperature and pH for xylanase activity were 45–50 °C and 5.5–7.5, respectively. Crude xylanase was highly stable at a wide range of pH values, retaining 100% of the activity after 24 h of incubation at 37 °C in buffer at pH 10.0. Analysis by polyacrylamide gel electrophoresis and zymogram techniques showed four xylanase activity bands with apparent molecular masses of 32, 48, 61, and 66 kDa. The most active of them (molecular mass 32 kDa) apparently corresponded to a xylanase with an isoelectric point (pI) of 9.3 in isoelectrofocusing gels developed as zymograms. Four other bands with xylanase activity were detected at pIs of 7.7, 5.6, 5.0, and 4.5. Analysis for carboxymethylcellulase activity revealed that only the band of 48 kDa and the band with a pI of 7.7 showed hydrolytic activity against the cellulosic substrate.Key words: Bacillus sp., xylanase, isolation.
Kinetic studies of unmodified individual Escherichia coli β-galactosidase molecules in free solution
Authors: Craig Douglas B. , Haslam Allison M. , Coombs Jennifer M.L. , Nichols Ellert R.
Published: May 2010

Assays were performed on individual Escherichia coli β-galactosidase molecules at 2 different concentrations of the substrate DDAO-β-d-galactoside using a free zone capillary electrophoresis–based protocol with an in-laboratory–constructed instrument utilizing laser-induced fluorescence detection. In a typical run, 2 enzyme molecules were injected into the capillary. They were separated from each other by a brief period of electrophoresis and incubated on the capillary in the presence of the substrate. They were then mobilized on the capillary into a zone of substrate at a different concentration, re-incubated, and the product peaks mobilized past the detector . The relative change in activity as the concentration was increased differed between molecules, suggesting differences in Km. In a different experiment, the capillary was filled with on average 13 enzyme molecules per run, incubated, and the activities of the individual molecules determined. The shapes of the distribution curves of single molecule activities obtained at different concentrations of the substrate resorufin-β-d-galactoside were indistinguishable, suggesting a homogeneous Km. To explain why individual enzyme molecules behaved as if they were heterogeneous with respect to Km but the population behaved as if it were homogeneous, theoretical Michaelis–Menten curves were constructed. The curves for populations with heterogeneous Km values were found to be indistinguishable from that of a homogeneous population.
Drug resistance is affected by colocalization of P-glycoproteins in raft-like structures unexpected in eggshells of the nematodeHaemonchus contortus
Authors: Riou Mickaël , Guégnard Fabrice , Sizaret Pierre-Yves , Le Vern Yves , Kerboeuf Dominique
Published: May 2010

In nematodes as in other eukaryotes, there is increasing evidence that drug resistance depends on both changes in the drug cellular targets and in nonspecific mechanisms, involving cellular detoxification by efflux pumps. In vertebrates, P-glycoproteins (Pgp) are membrane efflux pumps responsible for the elimination of xenobiotic agents, especially drugs. We previously reported the presence of Pgp pumps in eggshells and cuticles of the nematode Haemonchus contortus. Eggshells and cuticles are different from cell membranes, in particular they include a chitin layer. Nevertheless these structures present some common biological features with cell membranes and play a role in xenobiotic transport. Pgp activity has been shown to depend on the lipid environment and, in particular, on the cholesterol content in both vertebrate and nematode models. In vertebrates, Pgp is in part located in membrane cholesterol-enriched microdomains, the rafts. We describe here, for the first time, lipid microdomains in eggshells that could correspond with raft-like structures (RLSs). Moreover, a large proportion of the Pgp was shown to colocalize with these RLSs. The functional consequences of the colocalization for xenobiotic transport and thus drug resistance in nematodes were analyzed and compared with results obtained in vertebrates. An understanding of such mechanisms is crucial in overcoming the failure of drug treatments due to the development of resistance.
Structure determination ofStreptococcus suisserotype 2 capsular polysaccharide
Authors: Van Calsteren Marie-Rose , Gagnon Fleur , Lacouture Sonia , Fittipaldi Nahuel , Gottschalk Marcello
Published: May 2010

The capsular polysaccharide (CPS) of Streptococcus suis serotype 2 was isolated, purified, chemically modified, and characterized. Sugar and absolute configuration analyses of the CPS gave the following composition: d-Gal, 3; d-Glc, 1; d-GlcNAc, 1; d-Neu5Ac, 1; l-Rha, 1. Sialic acid was found to be terminal, and the CPS was quantitatively desialylated by mild acid hydrolysis. The CPS was also submitted to periodate oxidation followed by borohydride reduction and Smith degradation. Sugar and methylation analysis,1H and13C nuclear magnetic resonance, and mass spectrometry of the native CPS or of its specifically modified products allowed to determine the repeating unit sequence: [4)[Neu5Ac(α2–6)Gal(β1–4)GlcNAc(β1–3)]Gal(β1–4)[Gal(α1–3)]Rha(β1–4)Glc(β1-]n. The backbone sequence was found to be identical to that of Streptococcus agalactiae or group B Streptococcus (GBS) type VIII and Streptococcus pneumoniae type 23F. The S. suis CPS shares the sequence Neu5Ac-Gal-GlcNAc-Gal in common with GBS types Ia, Ib, II, III, and IV CPSs but differs from them by the presence of rhamnose and the fact that sialic acid is 2,6- rather than 2,3-linked to the following Gal. A correlation between the S. suis CPS sequence and genes of the serotype 2 cps locus encoding putative enzymes responsible for the biosynthesis of the repeating unit was tentatively established.
Palmitoylation of prohibitin at cysteine 69 facilitates its membrane translocation and interaction with Eps 15 homology domain protein 2 (EHD2)
Authors: Ande Sudharsana Rao , Mishra Suresh
Published: May 2010

Plasma membrane translocation of specific cytosolic proteins plays an important role in cell signaling pathways. We have recently shown that prohibitin (PHB) , a protein present in the plasma membranes of various cell types, interacts with Eps 15 homology domain protein 2 (EHD2), a lipid raft protein. However, the mechanism involved in membrane translocation of PHB is not known.We report that PHB undergoes palmitoylation at cysteine 69 (Cys69), and that this palmitoylation is required for PHB's membrane translocation. Furthermore, we demonstrate that membrane translocation of PHB facilitates tyrosine phosphorylation and its interaction with EHD2. Thus, the palmitoylation and membrane translocation of PHB and its interaction with EHD2 may play a role in cell signaling.
Derivation of human embryonic stem cell lines after blastocyst microsurgery
Authors: Meng Guoliang , Liu Shiying , Li Xiangyun , Krawetz Roman , Rancourt Derrick E.
Published: May 2010

Embryonic stem cells (ESCs) are derived from the inner cell mass (ICM) of the blastocyst. Because of their ability to differentiate into a variety of cell types, human embryonic stem cells (hESCs) provide an unlimited source of cells for clinical medicine and have begun to be used in clinical trials. Presently, although several hundred hESC lines are available in the word, only few have been widely used in basic and applied research. More and more hESC lines with differing genetic backgrounds are required for establishing a bank of hESCs. Here, we report the first Canadian hESC lines to be generated from cryopreserved embryos and we discuss how we navigated through the Canadian regulatory process. The cryopreserved human zygotes used in this study were cultured to the blastocyst stage, and used to isolate ICM via microsurgery. Unlike previous microsurgery methods, which use specialized glass or steel needles, our method conveniently uses syringe needles for the isolation of ICM and subsequent hESC lines. ICM were cultured on MEF feeders in medium containing FBS or serum replacer (SR). Resulting outgrowths were isolated, cut into several cell clumps, and transferred onto fresh feeders. After more than 30 passages, the two hESC lines established using this method exhibited normal morphology, karyotype, and growth rate. Moreover, they stained positively for a variety of pluripotency markers and could be differentiated both in vitro and in vivo. Both cell lines could be maintained under a variety of culture conditions, including xeno-free conditions we have previously described. We suggest that this microsurgical approach may be conducive to deriving xeno-free hESC lines when outgrown on xeno-free human foreskin fibroblast feeders.
Effect of sex steroid hormones on brain edema, intracranial pressure, and neurologic outcomes after traumatic brain injury
Authors: Shahrokhi Nader , Khaksari Mohammad , Soltani Zahra , Mahmoodi Mehdi , Nakhaee Nouzar
Published: May 2010

Recent studies have reported that estrogen and progesterone have a neuroprotective effect after traumatic brain injury (TBI); however, the mechanism(s) for this effect have not yet been elucidated. The aim of the present study was to investigate the role of sex steroid hormones on changes in brain edema, intracranial pressure (ICP), and cerebral perfusion pressure (CPP) after TBI in ovariectomized (OVX) rats. In this study, 50 female rats were divided into 5 groups: control (intact), sham, and 3 TBI groups consisting of vehicle, estrogen (1 mg/kg), and progesterone (8 mg/kg). TBI was induced by the Marmarou method, and the hormones were injected i.p. 30 min after TBI. ICP was measured in the spinal cord, and CPP was calculated by subtracting the mean arterial pressure (MAP) from ICP. The results revealed that brain water content after TBI was lower (p < 0.001) in the estrogen and progesterone groups than in the vehicle group. After trauma, ICP was significantly higher in TBI rats (p < 0.001). The ICP in the estrogen and progesterone groups decreased at 4 and 24 h after TBI compared with vehicle (p < 0.001 and p < 0.05, respectively). The CPP in the estrogen and progesterone groups increased after 24 h compared with vehicle (p < 0.001). Also after TBI, the neurological score (veterinary coma scale) was significantly higher than vehicle at 1 h (p < 0.01) and 24 h (p < 0.001) in the group treated with estrogen. In conclusion, pharmacological doses of estrogen and progesterone improved ICP, CPP, and neurological scores after TBI in OVX rats, which implies that these hormones play a neuroprotective role in TBI.
Cytotoxicity and apoptosis induced by a new podophyllotoxin glucoside in human hepatoma (HepG2) cells
Authors: Liu Yanfeng , Zhao Changqi , Li Hongxing , Yu Miao , Gao Jiali , Wang Lei , Zhai Yonggong
Published: May 2010

4-Demethylepipodophyllotoxin 7′-O-β-d-glucopyranoside (4′ DPG), a new podophyllotoxin glucoside with a chemical structure similar to that of 4-demethylpicropodophyllotoxin 7′-O-β-d-glucopyranoside (4DPG), was isolated from the rhizomes of Sinopodophyllum emodi (Wall.) Ying (Berberidaceae). Like 4DPG and etoposide (VP-16), 4′ DPG displayed dose- and time-dependent cytotoxic effects in HepG2 cells. Flow cytometric analysis demonstrated the presence of apoptotic cells and DNA fragmentation after HepG2 cells were exposed to 4′ DPG (1 µmol/L). In addition, 4′ DPG-driven apoptotic events were associated with upregulation of Bax and downregulation of Bcl-2. These results suggest that 4′ DPG has prominent cytotoxic activity and induces apoptosis by increasing the ratio of Bax to Bcl-2 in HepG2 cells.
Bidirectional communication between oocytes and follicle cells: ensuring oocyte developmental competence
Authors: Kidder Gerald M. , Vanderhyden Barbara C.
Published: May 2010

Female fertility is determined to a large extent by the quality (developmental competence) of the oocyte as reflected in its ability to undergo meiosis, be fertilized, and give rise to a healthy embryo. Growth of the mammalian oocyte is coordinated with that of the follicle that encloses it by the actions of signals that pass in both directions between the germline and somatic components. This review summarizes what is known about the roles played by 2 different modes of intrafollicular signalling in oogenesis: paracrine factors activating receptors on the opposite cell type, and direct sharing of small molecules throughout the follicle via gap junction channels. Recent evidence indicates that these 2 modes of signalling interact to regulate oocyte growth and granulosa cell proliferation and that defects in either can contribute to female infertility.
Comparison of the novel HK-2 human renal proximal tubular cell line with the standard LLC-PK1 cell line in studying drug-induced nephrotoxicity
Authors: Gunness Patrina , Aleksa Katarina , Kosuge Kazuhiro , Ito Shinya , Koren Gideon
Published: May 2010

Established cell lines are widely used as in vitro models in toxicology studies. The choice of an appropriate cell line is critical when performing studies to elucidate drug-induced toxicity in humans. The porcine renal proximal tubular cell line LLC-PK1 is routinely used to study the nephrotoxic effects of drugs in humans. However, there are significant interspecies differences in drug pharmacokinetics and pharmacodynamics. The objective of this study was to determine whether the human renal proximal tubular cell line HK-2 is an acceptable model to use when performing in vitro toxicity studies to predict effects in humans. We examined 2 nephrotoxic agents, ifosfamide (IFO) and acyclovir, that exhibit different clinical nephrotoxic patterns. HK-2 cells metabolized IFO to its nephrotoxic metabolite, chloroacetaldehyde (CAA). Acyclovir induced a concentration-dependent decrease in HK-2 cell viability, suggesting that acyclovir may induce direct insult to renal proximal tubular cells. The results support clinical pathology data in humans and suggest that HK-2 cells are a suitable model to use in in vitro toxicity studies to determine drug-induced nephrotoxicity in humans.
CRISIS-INDUCED INTERMITTENCY IN HAMILTONIAN SYSTEMS
Authors: GRETE PATRICK , MARKUS MARIO
Published: May 2010

In this paper, we consider compact, invariant sets in Hamiltonian systems in order to extend the concept of crisis to such systems. We focus on crisis-induced intermittency in several systems where two invariant sets merge, obtaining scaling laws for the residence times and for the probability distribution decay as a function of a critical parameter. The connection to hitherto known crisis-induced intermittency in dissipative systems is discussed.
OUTPUT FEEDBACK CONTROL OF UNIFIED CHAOTIC SYSTEMS BASED ON FEEDBACK PASSIVITY
Authors: SANGPET TEERAWAT , KUNTANAPREEDA SUWAT
Published: May 2010

Recently, the concept of feedback passivity-based control has drawn attention to chaos control. In all existing papers, the implementations of passivity-based control laws require the system states for feedback. In this paper, a passivity-based control law which only requires the knowledge of the system output is proposed. Simulation results are provided to show the effectiveness of the proposed solution.
ON OPTIMUM PUPIL FIELDS WITH MAXIMUM ELECTRIC FIELD COMPONENT IN FOCUS
Authors: URBACH H. P. , PEREIRA S. F. , BROER D. J.
Published: May 2010

The field in the entrance pupil of a high NA lens can be optimized such that, for given incident power, the electric field component in a given direction in the focal point is maximum. If the field component is chosen parallel to the optical axis, the longitudinal component is maximized and it is found that the optimum longitudinal component is narrower than the Airy spot. We discuss how this can be used to obtain higher resolution in photolithography when a resist is used that is sensitive to only the longitudinal component. We describe a proposition for realizing such resist.
DENSITY OF STATES AND LASING THRESHOLD IN DYE-DOPED CHOLESTERIC LIQUID CRYSTALS
Authors: BLINOV L. M.
Published: May 2010

As the complex transmission coefficient for a Fabry–Perot dielectric plate is well-known, the density of states (DOS) approach by J. Bendickson et al. [Phys. Rev. E53, 4107 (1996)] was applied to the plate and a formula was found for the spectrum of its threshold gain for lasing from the dye-doped plate. Next, the dispersion relation and the spectrum of the threshold gain was discussed for the infinite helical cholesteric liquid crystal (CLC). Then the DOS approach was applied to the non-absorbing CLC layers having finite, different thickness. The threshold gain spectra were calculated and dependences were found of the minimum threshold gain on the layer thickness and the optical anisotropy of the material. Finally, the results of the DOS analytical technique were compared with numerical calculations based on the precise solutions of the Maxwell equations and, in such a way, the DOS technique has been proven. The contribution of the dye absorption was discussed separately. The experimental data presented in the paper are in good agreement with the threshold gain calculations.
BRILLOUIN–RAMAN MULTI-WAVELENGTH LASER COMB GENERATION BASED ON Bi-EDF BY USING DUAL-WAVELENGTH IN DISPERSION COMPENSATING FIBER
Authors: SHAHI S. , HARUN S. W. , NORIZAN S. F. , MOGHADDAM M. R. A. , AHMAD H.
Published: May 2010

A multi-wavelength Brillouin fiber laser (BFL) is demonstrated by using dual-wavelength fiber in a 7.7 km dispersion compensating fiber (DCF) that is incorporated in a 49 cm Bismuth erbium-doped fiber laser. The BFL operates in C-band, which is shifted by 0.08 nm and amplified by a Raman pump (RP). The threshold power for BP pumps and the Raman pump is achieved at 7 dBm and around 35 mW, respectively. The exclusive and practical benefits of using reduced high nonlinear Bismuth-erbium doped fiber ( Bi-EDF ) in implementing a four-wave mixing (FWM) method for multi-wavelengths Brillouin fiber laser (BFL) applications are experimentally demonstrated. Coupled interactions of Brillouin, Raman, and FWM scattering explain the unique feature of proposed configuration.
RECENT PROGRESS ON PARAMETRIC GENERATION OF MONOCHROMATIC THz PULSES
Authors: DING YUJIE J. , JIANG YI , XU GUIBAO , ZOTOVA IOULIA B.
Published: May 2010

We review our recent progress on power scaling of THz pulses generated from several nonlinear-optical crystals. By using a high-resistivity GaP crystal, we have significally increased the output peak power to as high as 722 W. By stacking three GaP wafers, we have further increased the highest output peak power to 2.36 kW. On the other hand, by using CO2 laser pulses, we have obtained the average output power of 260 μW. We have also used these laser pulses to scale up the output power for the THz pulses to 29.8 μW by stacking GaAs wafers. Indeed, by stacking up to ten wafers, we have increased the output power by a factor of 160. Finally, by using ultrafast laser pulses, we have achieved record-high output powers for the THz pulses generated from multi-period periodically-poled LiNbO3 crystals based on a backward configuration. The highest output power measured by us so far is 10.7 μW.
Superior <110>-Directed Electron Mobility to <100>-Directed Electron Mobility in Ultrathin Body (110) n-Type Metal–Oxide–Semiconductor Field-Effect Transistors
Authors: Shimizu Ken , Saraya Takuya , Hiramoto Toshiro
Published: May 2010

The direction dependence of electron mobility in (110) n-type metal–oxide–semiconductor field-effect transistor (MOSFET) with an extremely thin silicon-on-insulator (SOI) has been studied. It is newly found that the electron mobility in the <110> direction surpasses that in the <100> direction with SOI thickness of 3.2 nm, which is opposite to the trend observed in bulk n-type MOSFET. The physical origins of this phenomenon can be attributed to the non-parabolicity in the two-fold valley.
Optical Properties of Laser-Irradiated ZnO Nanoparticles in 2-Propanol
Authors: Takahashi Shoutarou , Hasuike Yuhei , Noguchi Atsushi , Tsuge Takeharu , Ishikawa Masamichi , Odawara Osamu , Wada Hiroyuki
Published: May 2010

We investigate the effects of laser irradiation on the optical properties of ZnO nanoparticles in an organic solvent. ZnO nanoparticles are synthesized using normal precipitation methods in 2-propanol. Irradiating the nanoparticles in the solvent with unreacted reactants, which is colloidal solution without purification after the preparation, results in a reduction in the green luminescence, which is related to the number of surface oxygen defects, and an increase in the ultraviolet luminescence, which is related to the crystallinity of ZnO. Irradiation does not, however, significantly alter the nanoparticle diameter. Conversely, irradiation of purified (reactant-free) ZnO nanoparticles in the solvent does not change the ZnO photoluminescence intensity. We conclude that laser irradiation of the ZnO nanoparticles dispesed with reactants reduces the number of surface defects on the ZnO nanoparticles. Without the reactants, laser irradiation of the ZnO nanoparticles in the solvent does not modify the surface defects concentration, nor does it increase the crystallinity.
Analytical Model for Obtaining the Ionization Rate Ratio of Mesa InAlAs Avalanche Photodiodes
Authors: Nakata Takeshi , Kasahara Kenichi , Makita Kikuo
Published: May 2010

We proposed a new analytical model to extract the effective ionization rate ratio k from the measured multiplication noise of Avalanche photodiodes (APDs). In this model, k was expressed as a function of the multiplication factor M. We extracted the effective k of the mesa-structured InAlAs APDs using this model. A measurement system that consisted of a low-noise differential preamplifier was developed for this purpose, leading to the measurements of the noise data, particularly in the region where it was small. APD noise data could be fitted to the curve based on this new analytical model better than with other analytical models over the wide range of M. The effective k in the region where M was small became appropriate using this model. The quantum efficiency of the APDs was also found to be reasonable compared with the results obtained using the other analytical models.
Solubilization of Single-Walled Carbon Nanotubes Using Ozone Generated by Dielectric Barrier Discharge
Authors: Sun Wei , Khaled Usama , Tomita Hironari , Li Zhenyu , Imasaka Kiminobu , Suehiro Junya
Published: May 2010

This paper describes effects of ozone (O3) concentration on water-solubility of single-walled carbon nanotubes (SWCNTs). Ozone was generated by dielectric barrier discharge (DBD) in atmospheric air with the maximum concentration of 220 ppm. Water solubility of ozone-treated SWCNTs, which was evaluated by optical absorbance of the SWCNT suspension, increased with ozone treatment time and reached the maximum in 60 min. The dispersed SWCNTs suspension was stable even after two months of the ozone treatment. Fourier transform infrared (FTIR) spectroscopy and Raman spectra analysis revealed that SWCNTs surface was functionalized with chemical group such as –COO- after the ozone treatment. The longer ozone treatment introduced more functional groups and decreased zeta potential of the SWCNT surface, which improved water-solubility of the SWCNTs due to electrostatic repulsion force between them. It was also found that the ozone treatment induced morphological changes of SWCNTs.
Reaction Kinetics in the Rapid Oxide Growth on Si(001)-(2×1) Probed with Reflectance Difference Spectroscopy
Authors: Ohno Shin-ya , Ochiai Toshiyuki , Morimoto Masahiro , Suzuki Takanori , Shudo Ken-ichi , Tanaka Masatoshi
Published: May 2010

We investigated the NO adsorption process on Si(001)-(2×1) and the oxygen adsorption process on potassium-covered Si(001)-(2×1) by reflectance difference spectroscopy (RDS). In both cases, the time courses that deviated from a simple Langmuirian kinetics could not be well fitted with a single exponential function, indicating the involvement of two different processes. In NO adsorption, a highly coordinated nitrogen adsorption site (N≡Si3) might play a role in the initial reaction process, producing an inhomogeneous strain on the first layer of oxynitride. In potassium-assisted oxidation, a sudden decrease in RD intensity just after oxygen exposure is associated with a reaction of oxygen with a potassium film, and the subsequent oxidation is slightly enhanced by the potassium–oxygen complex.
Generalized Gradient Approximation +U Study for Metallization Mechanism of Niobium-Doped Anatase Titanium Dioxide
Authors: Orita Nozomi
Published: May 2010

I investigated the metallization mechanism of niobium(Nb)-doped anatase titanium dioxide (TiO2). There are recent calculations for Nb-doped TiO2 using the local density approximation (LDA) or generalized gradient approximation (GGA) method. I performed GGA+U calculations to solve the problem. The obtained band gap and the defect state are expected to be improved by the GGA+U method. I calculated the electronic structures of undoped, one-Nb-doped, and two-Nb-doped TiO2 per supercell. It was found that metallization is caused not by Mott transition with an overlap between the impurity and conduction bands but by the direct doping of an excess electron of Nb to the hybridized bands consisting mainly of Ti and Nb d-orbitals.
Variation of Electrostatic Discharge Robustness Induced by the Surface Morphology of High Power Light-Emitting Diodes
Authors: Yang Shih Chun , Lin Pang , Fu Han Kuei , Wang Chien Ping , Chen Tzung Te , Lee An Tse , Huang Sheng Bang , Chu Mu Tao
Published: May 2010

The capability of high-power nitride-based light-emitting diodes (HPLED) to withstand electrostatic discharge (ESD) is very important key index due to the horizontal structure of the insulating property of the sapphire substrate. Accordingly, the investigation of ESD failure mechanisms is a beneficial topic. However, it is difficult to real-time monitor the damage caused by the ESD stress because it occurred in a very short period. Before the series ESD stress, atomic force microcopy (AFM) and conductive AFM (C-AFM) were applied to explore the correlation between surface morphology and electrical properties of LED chips. Furthermore, after the series ESD stress, transmission electron microscopy (TEM) was used to investigate the failure modes and compare to the distribution of the surface current observed by C-AFM. These findings suggest that the V-shaped defect and surface morphology are strong correlate to the endurance of ESD stress.