bluuebunny/crossref_metadata_2025 huggingface dataset:
Viability changes in human neutrophils and monocytes following exposure to toxin extracted from Aphanizomenon flos-aquae
Authors: Barton L. L. , Foster E. W. , Johnson G. V.
Published: May 2010

An in vitro method for detecting toxin produced by Aphanizomenon flos-aquae is described. This procedure is more sensitive than the mouse toxicity test and is based on viability changes in human leukocytes.
A simple method for studying chemotaxis using sustained release of attractants from inert polymers
Authors: Langer R. , Fefferman M. , Gryska P. , Bergman K.
Published: May 2010

Chemotaxis of the bacterium Escherichia coli and the planarian Dugesia dorotocephala toward a variety of substances impregnated in sustained-release polymers has been demonstrated. Tests were carried out in soft agar and in aqueous medium with highly consistent results. The simplicity of this method may make it particularly useful for rapid qualitative screening of new wild-type and mutant strains of bacteria for chemotaxis toward nonmetabolites. The cost, ease of fabrication, and the facility with which they can be utilized in test systems suggest that these sustained-release vehicles will provide a new and general method of creating concentration gradients to study chemotaxis.
Peptidoglycan turnover during growth recovery after chloramphenicol treatment in a Dap− Lys− mutant of Bacillus megaterium
Authors: Fréhel Claude , Chastellier Chantal de , Ryter Antoinette
Published: May 2010

The study of diaminopimelic acid (DAP) incorporation and turnover during growth recovery in chloramphenicol-treated (CMP-treated) Bacillus megaterium cells showed that two kinds of turnover occurred. A low acid-soluble turnover appeared as soon as growth resumed in bacteria labeled before the CMP treatment and at the middle of the first generation in those labeled during the treatment. The acid-insoluble turnover appeared only at the beginning of the second generation of growth resumption in bacteria labeled before CMP addition and at the beginning of the third generation in those labeled during the CMP treatment. The acid-soluble release observed during the period of cell wall thinning is too low to account for the decrease of the wall thickness and the acid-insoluble loss appears after this period.When bacteria were transferred into partially spent medium instead of fresh culture medium the acid-insoluble release started to appear half a generation sooner. Electron microscopic observations showed that in this case, large scales detached from the cell wall. This activity of wall degradation was not observed when the partially spent medium was previously heated for 10 min at 100 °C.The persistence of a thick wall on cell ends during the first generation does not reflect an absence of growth sites because their labeling on autoradiographs is high. Rather, it seems to be due to a low lytic activity at the poles.
Free-living and symbiotic characteristics of chlorate resistant mutants of Rhizobium japonicum
Authors: Vasconcelos Laura de , Miller Llonas , Neyra Carlos A.
Published: May 2010

This work investigated the usefulness of chlorate resistance as a method for the selection of nitrate reductase negative (NR−) strains from Rhizobium japonicum (61A76) and evaluated the symbiotic characteristics of these strains. Chlorate resistant strains were selected from populations seeded on CS 7 agar containing 10 or 20 mM KClO3 and incubated in 2% air – 98% N2–CO2 (95:5).Over 200 resistant strains were isolated, 58% of which lacked the dissimilatory nitrate reductase. In 12 selected isolates, some strains had also lost the assimilatory nitrate reductase, but all retained hydrogenase activity.Chlorate resistant strains inoculated to soybean seedlings were equal to or better than the parent strain in terms of nodule mass and acetylene reduction. Those strains lacking both assimilatory and dissimilatory nitrate reductase showed the best symbiotic characteristics, suggesting that chlorate resistance in R. japonicum could be a useful method for the selection of strains with superior nitrogen-fixing characteristics.
Induction of sclerotialike mycelium in axenic cultures of Claviceps purpurea producing clavine alkaloids
Authors: Pažoutová Sylvie , Řeháček Zdeněk , Voříšek Josef
Published: May 2010

Aggregates of sclerotialike (SL) cells, present normally among filamentous sphacelial hyphae of submerged cultures of Claviceps purpurea strain 129 synthesizing clavine alkaloids, may represent an adaptation to unfavorable environmental conditions. Their formation can be induced by dyes (acriflavine, toluidine blue, fluorescein, basic fuchsin, ethidium bromide, and methylene blue). A treatment of the original strain with ethyl methanesulphonate yielded five mutants with stable SL phenotypes. Electron microscopy was used to illustrate the morphogenetic processes in mutant strains and the fragmentation of SL clusters to arthrospores.
The effect of rhizobiophages on populations of Rhizobium trifolii in the root zone of clover plants
Authors: Barnet Yvonne M.
Published: May 2010

The effect of rhizobiophages CT3 and CT4 on Rhizobium trifolii SU91 and SU36, respectively, was examined. These phage-susceptible strains were used, either singly or paired with a competing phage-resistant type as inoculum for Trifolium subterraneum plants growing in vitro in agar medium. Addition of bacteriophage to single strain experiments produced no significant effects on total bacterial numbers, nodulation, or plant dry weight. However, when phages were added to the paired inocula, significant decreases in counts of the susceptible strain were observed, frequently accompanied by a rise in numbers of the resistant type. An increase in the proportion of ineffective variants of the susceptible rhizobia was also observed, although plant dry weights and nodule numbers were not altered. These effects were dependent only upon a difference in phage susceptibility of the bacteria and were obtained even when the competing strain was only partially resistant and a relatively poor competitor.
Interactions between Lugol's fixative and ethylene in the acetylene-reduction assay for nitrogenase activity in lake water
Authors: Leonardson Lars
Published: May 2010

Lugol's solution is a practical and efficient fixative for the acetylene-reduction assay of nitrogenase activity in aquatic organisms. Correction must be made, however, for the solubility of ethylene in the liquid phase and reactions between Lugol's solution and ethylene. With a vapor phase – liquid phase volume ratio of 1.9:1, the mean solubility of ethylene in mixtures of lake water and Lugol's solution was 7.2%. No correlation was found between ethylene solubility and the concentration of Lugol's solution. Storage of fixed samples for more than 1 day before gas chromatographic analysis resulted in increased loss of ethylene from the vapor phase; the loss amounted to ca. 18% after 3 days. Higher losses were noted at higher concentrations of Lugol's solution. Most probably these effects were caused by iodine addition to ethylene, as indicated by the consumption of ethylene by iodine – potassium iodide solutions. The reaction was catalyzed by the rubber septa of the incubation vessels when the septa were in contact with the liquid phase. Loss of ethylene decreased with increased concentration of phytoplankton because the organisms absorbed iodine. By using a standardized technique and determining ethylene solubility and reaction patterns between ethylene and the mixture of water and Lugol's solution, it is possible to correct for the loss of ethylene.
Studies of the structure–function relationships of Neurospora crassa pyruvate kinase: interaction with blue dextran – Sepharose and Cibacron blue 3G-A
Authors: Kapoor M. , O'Brien M. D.
Published: May 2010

Blue dextran – Sepharose and Cibacron blue 3G-A interact with pyruvate kinase of Neurospora crassa. The enzyme is readily released from the substituted Sepharose column by elution with 0.17 M potassium phosphate buffer (pH 7.9), or 2 mM fructose 1,6-diphosphate (FDP), but not with either of the substrates, ADP and phosphoenolpyruvate (PEP), at 2 mM. Cibacron blue 3G-A is a noncompetitive inhibitor of pyruvate kinase with respect to both substrates. It appears to compete with the allosteric effector, FDP, for binding to the enzyme surface. A lack of elution of the enzyme from the immobilized blue dextran matrix by adenine nucleotides and the absence of a difference spectrum in the 650- to 700-nm range suggest that a "dinucleotide-fold" substructure is not implicated in the dye binding sites on pyruvate kinase. The interaction of Cibacron blue 3G-A and this enzyme can be followed fluorometrically; incremental addition of the dye to the enzyme solution results in a progressive decrease in the fluorescence of surface tryptophanyl residues. The quenching of fluorescence of exposed aromatic groups is subject to reversal following addition of FDP to the pyruvate kinase – Cibacron blue complex.
The perpetuation of orthomyxoviruses and paramyxoviruses in Canadian waterfowl
Authors: Hinshaw V. S. , Webster R. G. , Turner B.
Published: May 2010

A longitudinal survey of viruses in feral ducks from 1976 to 1978 in the Vermillion area of Alberta, Canada, has shown that influenza A viruses and paramyxoviruses are present year after year in these apparently healthy ducks. Influenza viruses were isolated most frequently each year from mallards, pintails, and blue-winged teals, but were not restricted to these species. During the 3-year survey, 1262 influenza viruses were isolated from 4827 ducks, revealing the high incidence of influenza infection, a finding which contrasts with the very low incidence found in ducks during migration through Tennessee.Many different influenza A viruses were detected in the ducks, including 27 different combinations of hemagglutinin and neuraminidase subtypes. These viruses encompass all but one of the known hemagglutinin and neuraminidase subtypes. The virus subtypes in the ducks varied from year to year; however, 6 of these 27 subtypes were present every year. The predominant subtype changed from Hav7Neq2 in 1976–1977 to Hav6N2 in 1978. Antigenic comparisons of current and previous Hav6 viruses isolated from ducks, turkeys, and a shearwater showed that antigenic drift occurs in avian influenza viruses.Paramyxoviruses occur in the Canadian ducks at a much lower frequency than influenza viruses; in 3 years, 69 paramyxoviruses were isolated and included two types: lentogenic NDV and Duck/Mississippi/75.These longitudinal studies indicate that the feral ducks in the study area of Canada are a perpetual reservoir of diverse influenza A viruses and paramyxoviruses.
Antibodies to snowshoe hare virus of the California group in the horse population in Nova Scotia
Authors: McFarlane B. L. , Embree J. E. , Embil J. A. , Rozee K. R. , Weste J. B. , Artsob H. , Spence L.
Published: May 2010

A large number of North American equine samples were tested for the California group of arboviruses (CAL). Of 861 equine sera tested by hemagglutination inhibition using the snowshoe hare virus as an antigen, 106 (12.3%) were positive. Neutralization tests confirmed antibodies to this virus in 72 of the positive sera. This study provides evidence of CAL activity in the domestic animal population of Nova Scotia.
Comparative studies of nitrogen-fixing bacteria associated with grasses in Israel with Azospirillum brasilense
Authors: Nur Israel , Okon Yaacov , Henis Yigal
Published: May 2010

Free-living, dinitrogen-fixing bacteria associated with roots of grasses were isolated from several locations in Israel. Bacteria with characteristics similar to those of Azospirillum were isolated from Cynodon dactylon roots and were compared with Azospirillum brasilense from Brasil (Sp-7) and from California (Cd). Colonies of the Israeli isolates were yellow and consisted of curved rods, 0.5–0.6 μm in diameter with polar flagella, whereas colonies of A. brasilense were pink (Sp-7) and red (Cd) and the cells were 1.0–1.1 μm in diameter with polar flagella. Ultraviolet absorption spectra of soluble c and membrane-bound c and b cytochromes were similar in all isolates. When grown in semisolid agar medium with or without ammonium chloride all isolates formed a growth zone below the surface. However, they grew best under aerobic conditions in liquid medium containing NH4Cl. All isolates could use salts of malate and lactate, arabinose, and galactose, but not mannitol, as sole carbon sources; they did not need biotin to shorten their lag phase. One Israeli isolate was capable of growing and fixing nitrogen with glucose as a sole carbon source. The Israeli isolates formed aggregates above pH7.6 in liquid or semisolid medium and were capable of reducing nitrate to nitrogen gas under anaerobic conditions.
Presence of spiroplasma-inhibitory substances in plant tissue extracts
Authors: Liao C. H. , Chen T. A.
Published: May 2010

Plant tissue extracts prepared from corn, periwinkle, celery, and lettuce contain substance(s) which are inhibitory for spiroplasma growth in culture media. The inhibition titer, measured as the highest dilution of plant extracts which block spiroplasma growth, is inversely proportional to the spiroplasma concentration used for testing. At a concentration of 104 cells/mL, the growth of four spiroplasma isolates investigated (corn stunt spiroplasma, Spiroplasma citri, honey bee spiroplasma, and Bermuda grass (Cynodon dactylon) spiroplasma) was suppressed by the addition of corn and periwinkle extracts up to dilutions of 1/160 and 1/1280, respectively. Spiroplasmas remained viable in extract-supplemented media for at least 5 days and continued to multiply shortly after the plant extract was removed. These results suggest that (1) the inhibitory action of plant extracts is spiroplasmastatic, and (2) inhibitory factors may temporarily bind to cytoplasmic membrane and subsequently suppress the process of cell replication. The anti-mycoplasma activity was greatly reduced when the extract was placed in boiling water for 10 min or at 37 °C for 5 days. No loss of activity was detected when the extract was kept at −20 or 4 °C for 5 days.
Reconstitution of rubella hemagglutinin on liposomes
Authors: Trudel Michel , Ravaoarinoro Madeleine , Payment Pierre
Published: May 2010

The hemagglutinin of rubella virus has been purified by differential centrifugation through a sucrose density gradient after disruption of purified virus with Tween 80 – ether. The purified isolated hemagglutinin was then adsorbed on liposomes which had been prepared by mixing lecithin and dicetyl phosphate in a 3.5:1 molar ratio. The complex of hemagglutinin adsorbed on the virosomes had a higher sedimentation rate, enabling their separation from free hemagglutinin. It was thus possible to obtain a pure preparation of virosomes by rate zonal centrifugation in a sucrose density gradient containing 0.5 M NaCl. Immunoelectron microscopy showed aggregation of these virosomes with a rubella immune antiserum; this would suggest that the HA subunits are oriented in the same way as on the whole virus.
Stable isotope fractionation by Clostridium pasteurianum. 3. Effect of SeO32– on the physiology and associated sulfur isotope fractionation during SeO32– and SeO42– reductions
Authors: Harrison G. I. , Laishley E. J. , Krouse H. R.
Published: May 2010

Increased [Formula: see text] concentration reduced H2S evolution from [Formula: see text] during whole cell and cell-free extract reductions by Clostridium pasteurianum. H2S production from [Formula: see text] was completely inhibited by [Formula: see text] in stationary phase cells. Generation times increased with greater [Formula: see text] concentration, the increase with 1 mM[Formula: see text] being a factor of 2.5 for 1 mM[Formula: see text], and over 3 for 1 mM[Formula: see text] reductions. In vitro and in vivo experiments with proposed intermediates of the [Formula: see text] reduction pathway show that [Formula: see text] inhibited both the [Formula: see text] to [Formula: see text] and [Formula: see text] to S2− reaction sequences with the latter being more pronounced in growth experiments. Both extracts and whole cells reduced [Formula: see text], to Se0 but Se0 granules were not found in the cell's cytoplasm. The formation of [Formula: see text] by an extracellular chemical mechanism appears not to have occurred in these experiments. Increased [Formula: see text] concentration had the effect of compressing the isotopic release pattern for H2S along the H2S production axis and did not significantly alter the maximum and mimimum values of δ34S. Thus, inhibition by [Formula: see text] limited the conversions of sulfur species without altering the isotopic selectivity of rate-controlling steps in the pathway.
Plasmid detection in a bacteriocinogenic strain of Clostridium perfringens
Authors: Li A. W. , Krell P. J. , Mahony D. E.
Published: May 2010

Bacteriocinogenic Clostridium perfringens, strain 28, harboured plasmid DNA detectable by dye-buoyant density-gradient centrifugation. This plasmid DNA was absent from an ultraviolet light cured variant which had simultaneously lost its immunity and ability to produce bacteriocin. Agarose gel electrophoresis of the plasmid DNA revealed at least six bands but denaturation experiments suggested three plasmids occurring in more than one conformation. Electron microscopy revealed three major size distributions of circular DNA of molecular weights 1,5.6, and 7.1 megadaltons. Some evidence suggests that the 5.6 megadalton plasmid may control bacteriocin 28 production.
Sporulation de Entomophthora obscura Hall & Dunn en culture liquide
Authors: Latgé J. P.
Published: May 2010

Growth and production of azygospores of Entomophthora obscura were studied through batch cultures in media containing glucose, or vegetable oil, and yeast extract. In media containing 3% glucose and 1% yeast extract, an 8-h lag phase occurred and sporulation began only at the 40th hour of culture; spore maturation lasted 4 days in average. Young mycelial stages were characterized by high nucleic acid and protein but low lipid concentrations. During sporogenesis stages, the quantity of lipids and chitin increased and the concentration of total polyosides (chitin excluded) was lower in comparison with the mycelial stages. Sporulation was induced by means of medium starvation in carbon and (or) nitrogen. The only sporulation inhibitor which allowed considerable growth was sodium fluoroacetate. [Translated by the journal]
Changes in the outer cell wall of Rhizobium during development of root nodule symbiosis in soybean
Authors: Bal Arya K. , Shantharam S. , Verma D. P. S.
Published: May 2010

Treatment of soybean root nodule tissue with a nonionic detergent, Nonidet P-40, after aldehyde fixation, results in a selective solubilization of membranes. The cell wall membrane of bacteroids and of free-living Rhizobium is resistant to this treatment. Fragments of "extra" membrane present inside the membrane envelope enclosing the bacteroids are also resistant to the detergent and are morphologically similar to the outer membrane of the cell wall of Rhizobium grown in broth culture. These observations, along with electrophoretic profiles of detergent resistant membranes from nodules, free-living Rhizobium, and isolated nodule bacteroids, suggest that the Rhizobium cell wall membrane undergoes significant changes during establishment of the root nodule symbiosis.
Sulfur isotope fractionation by Proteus vulgaris and Salmonella heidelberg during the reduction of thiosulfate
Authors: McCready R. G. L. , Grinenko V. A. , Krouse H. R.
Published: May 2010

Proteus vulgaris metabolized thiosulfate to H2S. The amount evolved and its sulfur isotope composition identified it solely with sulfane sulfur. In contrast. Salmonella heidelberg sequentially reduced the sulfane sulfur of S2O32− with slight enrichment of the evolved sulfide in 32S and then reduced the sulfonate sulfur of S2O32− with large isotopic selectivities and an inverse isotopic fractionation pattern. The inverse isotope fractionation pattern for the H2S derived from the sulfonate sulfur was almost identical to that observed during the reduction of high concentrations of sulfite by S. heidelberg.
Purification and properties of the periplasmic hydrogenase from Desulfovibrio desulfuricans
Authors: Glick Bernard R. , Martin William G. , Martin Stanley M.
Published: May 2010

The periplasmic hydrogenase of Desulfovibrio desulfuricans was isolated and purified. Cells were washed with Tris–EDTA and the enzyme precipitated from the wash with ammonium sulfate. Absorption chromatography on DEAE and hydroxyapatite yielded the enzyme at better than 95% purity as judged by gel electrophoresis. The hydrogenase catalyzed the production of more than 9000 μmol H2/min mg protein−1 from reduced methyl viologen at 37 °C. It is very stable and resists inactivation by heat (50% activity remained after 5 min in air at 65 °C) and by enzyme inhibitors (except N-ethylmaleimide and potassium ferricyanide). After storage in air at 4 °C for 1 month no activity was lost. The enzyme activity is sensitive to ionic environmental changes. With methyl viologen the optimum pH was 5.5 but with p-xylene polymeric viologen the optimum was about pH 7 but less sharp. The molecular weight was 47 × 103 (± 2 × 103), 52 × 103(± 2 × 103), and 56 × 103 (± 2 × 103) by SDS –gel electrophoresis, gel chromatography, and sedimentation equilibrium, respectively, and the isoelectric point was at pH 6.0. The enzyme consists of one polypeptide chain terminated at the amino end by proline. This enzyme might be useful in the production of hydrogen from water and solar energy.
Yersinia enterocolitica: observations on some growth characteristics and response to selective agents
Authors: Schiemann D. A.
Published: May 2010

A broth medium which provided for optimum growth of Yersinia enterocolitica was formulated. In this medium Y. enterocolitica grew best at pH 7.6–7.9 and 32 °C with a generation time of 33–39 min depending upon the strain. Examination of various chemicals as potential selective agents in an agar medium showed a high tolerance for surface-active agents, but cetrimide, 4-nitrophenol, potassium tellurite, and sodium azide were inhibitory at very low concentrations. Irgasan was tolerated at concentrations inhibitory to some other Enterobacteriaceae. Minimum inhibitory concentrations for 57 antibacterial agents tested against 18 strains suggested that carbenicillin, novobiocin, and SCE-129 (cefsulodin) might serve as useful agents for selective isolation of Y. enterocolitica.
Plasmid-borne resistance to ultraviolet light and phage in Streptococcus faecalis ssp. zymogenes
Authors: Frazier Marsha L. , Zimmerman Leonard N.
Published: May 2010

A plasmid of molecular weight 38.5 × 106 that is found in a number of enterococci and carries genetic markers for lysin production was found also to carry genes for resistance to bacteriophage SFL1 as well as to ultraviolet light.
Behaviour of mixed populations of halophilic bacteria in continuous cultures
Authors: Rodriguez-Valera F. , Ruiz-Berraquero F. , Ramos-Cormenzana A.
Published: May 2010

Two main physiological groups of bacteria are known which are adapted to high saline environments, moderate and extreme halophiles. In order to clarify some aspects of the competition between these two groups in their natural habitats, continuous cultures were used to provide a changing spectrum of conditions of salt concentration, temperature, and nutrient concentration (dilution rate). The effects of these parameters on natural solar saltern populations were studied. Complex media were used to increase the range of competing microorganisms. Nineteen strains of halophilic bacteria were isolated and studied with respect to their growth response at different salt concentrations. The temperature seemed to be the decisive factor within the range of salt concentrations studied (20–30%, w/v), the moderate halophiles being favored by low temperatures. Within this group, motile, gram-negative rods, and spiral forms were the predominant morphological types. In general, microorganisms that showed high growth rates in batch cultures predominated in continuous cultures with high dilution rates (high nutrient concentrations); those that grew slowly in batch cultures predominated in cultures with low dilution rates.
Catabolism of 3-O-methyl-D-glucopyranose by Cryptococcus laurentii
Authors: Bhanot Pradeep , Brown Robert G.
Published: May 2010

When Cryptococcus laurentii is grown on 3-O-methyl-D-glucopyranose (3-O-MeGlc), two metabolic products are methanol and an extracellular mannan. Hydrolysis of the mannan produced during growth on 3-O-MeGlc labelled with 14C in the 1 or 6 position yields mannose with retention of the labelling pattern in the carbon chain. O-Methyl-labelled substrate yields radioactive methanol. Three possible mechanisms of O-demethylation are ether cleavage, peroxidase attack, and β-elimination. The latter mechanism was shown to be the most likely through the use of double-labelled (3H and 14C) 3-O-MeGlc.
MARKOV APPROACH FOR PREDICTIVE MODELING AND PERFORMANCE EVALUATION OF A THERMAL POWER PLANT
Authors: GUPTA SORABH , TEWARI P. C.
Published: May 2010

The present paper deals with the opportunities for the availability predictive modeling of a thermal plant using Markov process and probabilistic approach. These opportunities will be identified by evaluation of a predictive model to be built for the steam generation system of a thermal power plant. This feasibility study covers two areas: development of a predictive model and evaluation of performance with the help of developed model. The present system under study consists of five subsystems with three feasible states: full working, reduced capacity working and failed. After drawing transition diagram, differential equations are generated and then a probabilistic simulated predictive model using Markov approach has been developed considering some assumptions. Availability matrix for each subsystem is also developed, which provide various availability levels. On the basis of this study, performance of each subsystem of steam generation system is evaluated and then maintenance decisions are made for subsystems.
MCVM: MONTE CARLO MODELING OF PHOTON MIGRATION IN VOXELIZED MEDIA
Authors: LI TING , GONG HUI , LUO QINGMING
Published: May 2010

The Monte Carlo code MCML (Monte Carlo modeling of light transport in multi-layered tissue) has been the gold standard for simulations of light transport in multi-layer tissue, but it is ineffective in the presence of three-dimensional (3D) heterogeneity. New techniques have been attempted to resolve this problem, such as MCLS, which is derived from MCML, and tMCimg, which draws upon image datasets. Nevertheless, these approaches are insufficient because of their low precision or simplistic modeling. We report on the development of a novel model for photon migration in voxelized media (MCVM) with 3D heterogeneity. Voxel crossing detection and refractive-index-unmatched boundaries were considered to improve the precision and eliminate dependence on refractive-index-matched tissue. Using a semi-infinite homogeneous medium, steady-state and time-resolved simulations of MCVM agreed well with MCML, with high precision (~100%) for the total diffuse reflectance and total fractional absorption compared to those of tMCimg (< 70%). Based on a refractive-index-matched heterogeneous skin model, the results of MCVM were found to coincide with those of MCLS. Finally, MCVM was applied to a two-layered sphere with multi-inclusions, which is an example of a 3D heterogeneous media with refractive-index-unmatched boundaries. MCVM provided a reliable model for simulation of photon migration in voxelized 3D heterogeneous media, and it was developed to be a flexible and simple software tool that delivers high-precision results.
EFFECTS OF NAAG AND MPEP ON RAT CORTICAL SPREADING DEPRESSION
Authors: WANG ZHEN , LUO WEIHUA , SUN XIAOLI , LI PENGCHENG , CHEN SHANGBIN , LUO QINGMING
Published: May 2010

Cortical spreading depression (CSD) is a pathophysiological phenomenon. There are sufficient evidences to prove that CSD plays an important role in some neurological disorders. However, exact mechanisms of its initiation and propagation are still unclear. Previous studies showed that glutamate receptors could be concerned with CSD, but those studies were mostly performed oriented to ionotropic glutamate receptors (iGluRs). There is relatively little report about effects of metabotropic glutamate receptors (mGluRs) on CSD. Here, we applied optical intrinsic signal imaging (OISI) combined with direct current (DC) potential recording to examine influences of some mGluRs antagonist (or agonist) on CSD propagation in rat's brain, to indirectly validate actions of some mGluRs on CSD. We found that N-acetyl-L-aspartyl-L-glutamate (NAAG, an agonist at mGluR3) inhibited the propagation of CSD, and the inhibition was gradually developed with time. However, 6-methyl-2-phenylethynyl-pyridine (MPEP, an antagonist of mGluR5) did not produce any significant alterations with the CSD propagation. Our findings suggest that mGluR3 could play an important role in the CSD propagation, but the activity of mGluR5 was comparatively weak. These findings can help to understand the propagation mechanism of CSD, and consider the therapy of some neurological diseases involved with CSD.
Diffusion-Controlled Glow Discharge Pressure Extended by the Multi-Dual Microhollow Cathode Configuration for Flat Lighting
Authors: Hwang Hyeon Seok , Park Ki Wan , Song Kie Moon , Lee Se Jong , Baik Hong Koo
Published: May 2010

We investigated pure Xe discharge primarily as a source of vacuum ultraviolet for discharge lamps, using a multi-dual hollow cathode. One of the problems associated with the discharge properties of Xe gas is its easy constriction. We prevented the problem by using an electrode configured as a multi-dual microhollow cathode. This result originated from auxiliary charge particles generated in a lamp discharge space and less variation of electron generation rate, which reduced thermal instability and as a result sequentially suppressed the constriction of Xe discharge. Furthermore, we observed that a six-channel flat-panel lamp could be driven with a pulse power supply.
EFCOSS
Authors: Rasch Arno , Bücker H. Martin
Published: May 2010

An interactive software environment is proposed that combines numerical simulation codes with optimization software packages in an automated and modular way. It simplifies the experimentation with varying objective functions for common optimization problems such as parameter estimation and optimal experimental design that are frequently encountered in computational science and engineering. The design philosophy takes into consideration the need for derivatives of potentially large-scale simulation codes via automatic differentiation as well as distributed computing in a heterogenous environment via CORBA.
Algorithm 903
Authors: Celledoni Elena , Zanna Antonella
Published: May 2010

We present two algorithms and their corresponding Fortran routines for the exact computation of free rigid body motions. The methods use the same description of the angular momentum part

m

by Jacobi elliptic functions, and suitably chosen frames for the attitude matrix/quaternion
Q
/
q
, respectively. The frame transformation requires the computation of elliptic integrals of the third kind. Implementation and usage of the routines are described, and some examples of drivers are included. Accuracy and performance are also tested to provide reliable numerical results.
Mesh colors
Authors: Yuksel Cem , Keyser John , House Donald H.
Published: May 2010

The coloring of 3D models using 2D or 3D texture mapping has well-known intrinsic problems, such as mapping discontinuities and limitations to model editing after coloring. Workarounds for these problems often require adopting very complex approaches. Here we propose a new technique, called mesh colors, for associating color data directly with a polygonal mesh. The approach eliminates problems deriving from using a map from texture space to model space. Mesh colors is an extension of vertex colors where, in addition to keeping color values on each vertex, they are also kept on edges and faces. Like texture mapping, the approach allows higher texture resolution than model resolution, but at the same time it guarantees one-to-one correspondence between the model surface and the color data, and eliminates discontinuities. We show that mesh colors integrate well with the current graphics pipeline and can be used to generate very high-quality textures.
Santa Claus
Authors: Welch Peter H. , Pedersen Jan B.
Published: May 2010

With the commercial development of multicore processors, the challenges of writing multithreaded programs to take advantage of these new hardware architectures are becoming more and more pertinent. Concurrent programming is necessary to achieve the performance that the hardware offers. Traditional approaches present concurrency as an
advanced
topic: they have proven difficult to use, reason about with confidence, and scale up to high levels of concurrency. This article reviews
process-oriented design
, based on Hoare's algebra of Communicating Sequential Processes (CSP), and proposes that this approach to concurrency leads to solutions that are manageable by novice programmers; that is, they are easy to design and maintain, that they are scalable for complexity,
obviously correct
, and relatively easy to verify using formal reasoning and/or model checkers. These solutions can be developed in conventional programming languages (through CSP libraries) or specialized ones (such as occam-π) in a manner that directly reflects their formal expression. Systems can be developed without needing specialist knowledge of the CSP formalism, since the supporting mathematics is burnt into the tools and languages supporting it. We illustrate these concepts with the
Santa Claus problem
, which has been used as a challenge for concurrency mechanisms since 1994. We consider this problem as an example control system, producing external signals reporting changes of internal state (that model the external world). We claim our occam-π solution is
correct-by-design
, but follow this up with formal verification (using the FDR model checker for CSP) that the system is free from deadlock and livelock, that the produced control signals obey crucial ordering constraints, and that the system has key liveness properties.
Performance of large low-associativity caches
Authors: Dube Parijat , Zhang Li , Daly David , Bivens Alan
Published: May 2010

While it is known that lowering the associativity of caches degrades cache performance, little is understood about the degree of this effect or how to lessen the effect, especially in very large caches. Most existing works on cache performance are simulation or emulation based and there is a lack of analytical\ models characterizing performance in terms of different configuration parameters such as line size, cache size, associativity and workload specific parameters. We develop analytical models to study performance of large cache architectures by capturing the dependence of miss ratio on associativity and other configuration parameters. While high associativity may decrease cache misses, for very large caches the corresponding increase in hardware cost and power may be significant. We use our models as well as simulation to study different proposals for reducing misses in low associativity caches, specifically, address space randomization and victim caches. Our analysis provides specific detail on the impact of these proposals, and a clearer understanding of why they do or do not work.
Energy efficient management of two cellular access networks
Authors: Marsan Marco Ajmone , Meo Michela
Published: May 2010

In this paper we evaluate the energy saving that can be achieved with the energy-aware cooperative management of the cellular access networks of two operators offering service over the same area. We evaluate the amount of energy that can be saved by using both networks in high traffic conditions, but switching off one of the two during the periods when traffic is so low that the desired quality of service can be obtained with just one network. When one of the two networks is off, its customers are allowed to roam over the one that is on. Several alternatives are studied, as regards the switch-off pattern: the one that balances the switch-off frequencies, the one that balances roaming costs, the one that balances energy savings, and the one that maximizes the amount of saved energy. Our results indicate that a huge amount of energy can be saved, and suggest that, to reduce energy consumption, new cooperative attitudes of the operators should be encouraged with appropriate incentives, or even enforced by regulation authorities.
Affinity, lateral mobility, and clustering contribute independently to β2-integrin-mediated adhesion
Authors: Yu Tao , Wu Xing , Gupta Kiran B. , Kucik Dennis F.
Published: May 2010

Affinity changes and avidity modulation both contribute to activation of β2-integrin-mediated adhesion, an essential, early step in inflammation. Avidity modulation, defined as an increase in adhesiveness independent of integrin conformational changes, might be due to integrin clustering, motion, or both. Increased integrin diffusion upon leukocyte activation has been demonstrated, but whether it is proadhesive in itself, or just constitutes a mechanism for integrin clustering, remains unclear. To understand the proadhesive effects of integrin affinity changes, clustering, and motion, an experimental system was devised to separate them. Clustering and integrin motion together were induced by cytochalasin D (CD) without inducing high-affinity; integrin motion could then be frozen by fixation; and high affinity was induced independently by Mn2+. Adhesion was equivalent for fixed and unfixed cells except following pretreatment with CD or Mn2+, which increased adhesion for both. However, fixed cells were less adhesive than unfixed cells after CD, even though integrin clustering was similar. A simple explanation is that CD induces both clustering and integrin motion, fixation then stops motion on fixed cells, but integrins continue to diffuse on unfixed cells, increasing the kinetics of integrin/ICAM-1 interactions to enhance adhesion. Affinity changes are then independent of, and additive to, avidity effects.
Cloning and identification of tissue-specific expression of KCNN4 splice variants in rat colon
Authors: Barmeyer Christian , Rahner Christoph , Yang Youshan , Sigworth Frederick J. , Binder Henry J. , Rajendran Vazhaikkurichi M.
Published: May 2010

KCNN4 channels that provide the driving force for cAMP- and Ca2+-induced anion secretion are present in both apical and basolateral membranes of the mammalian colon. However, only a single KCNN4 has been cloned. This study was initiated to identify whether both apical and basolateral KCNN4 channels are encoded by the same or different isoforms. Reverse transcriptase-PCR (RT-PCR), real-time quantitative-PCR (RT-QPCR), and immunofluorescence studies were used to clone and identify tissue-specific expression of KCNN4 isoforms. Three distinct KCNN4 cDNAs that are designated as KCNN4a, KCNN4b, and KCNN4c encoding 425, 424, and 395 amino acid proteins, respectively, were isolated from the rat colon. KCNN4a differs from KCNN4b at both the nucleotide and the amino acid level with distinct 628 bp at the 3′-untranslated region and an additional glutamine at position 415, respectively. KCNN4c differs from KCNN4b by lacking the second exon that encodes a 29 amino acid motif. KCNN4a and KCNN4b/c are identified as smooth muscle- and epithelial cell-specific transcripts, respectively. KCNN4b and KCNN4c transcripts likely encode basolateral (40 kDa) and apical (37 kDa) membrane proteins in the distal colon, respectively. KCNN4c, which lacks the S2 transmembrane segment, requires coexpression of a large conductance K+channel β-subunit for plasma membrane expression. The KCNN4 channel blocker TRAM-34 inhibits KCNN4b- and KCNN4c-mediated86Rb (K+surrogate) efflux with an apparent inhibitory constant of 0.6 ± 0.1 and 7.8 ± 0.4 μM, respectively. We conclude that apical and basolateral KCNN4 K+channels that regulate K+and anion secretion are encoded by distinct isoforms in colonic epithelial cells.
Protection of cisplatin cytotoxicity by an inactive cyclin-dependent kinase
Authors: Hodeify Rawad , Megyesi Judit , Tarcsafalvi Adel , Safirstein Robert L. , Price Peter M.
Published: May 2010

Cisplatin cytotoxicity is dependent on cyclin-dependent kinase 2 (Cdk2) activity in vivo and in vitro. A Cdk2 mutant (Cdk2-F80G) was designed in which the ATP-binding pocket was altered. When expressed in mouse kidney cells, this protein was kinase inactive, did not inhibit endogenous Cdk2, but protected from cisplatin. The mutant was localized in the cytoplasm, but when coexpressed with cyclin A, it was activated, localized to the nucleus, and no longer protected from cisplatin cytotoxicity. Cells exposed to cisplatin in the presence of the activated mutant had an apoptotic phenotype, and endonuclease G was released from mitochondria similar to that mediated by endogenous Cdk2. But unlike apoptosis mediated by wild-type Cdk2, cisplatin exposure of cells expressing the activated mutant did not cause cytochrome c release or significant caspase-3 activation. We conclude that cisplatin likely activates both caspase-dependent and -independent cell death, and Cdk2 is required for both pathways. The mutant-inactive Cdk2 protected from both death pathways, but after activation by excess cyclin A, caspase-independent cell death predominated.
Hypoxic regulation of erythropoiesis and iron metabolism
Authors: Haase Volker H.
Published: May 2010

The kidney is a highly sensitive oxygen sensor and plays a central role in mediating the hypoxic induction of red blood cell production. Efforts to understand the molecular basis of oxygen-regulated erythropoiesis have led to the identification of erythropoietin (EPO), which is essential for normal erythropoiesis and to the purification of hypoxia-inducible factor (HIF), the transcription factor that regulates EPO synthesis and mediates cellular adaptation to hypoxia. Recent insights into the molecular mechanisms that control and integrate cellular and systemic erythropoiesis-promoting hypoxia responses and their potential as a therapeutic target for the treatment of renal anemia are discussed in this review.
Epigenetic alterations in aging
Authors: Gonzalo Susana
Published: May 2010

Aging is a multifaceted process characterized by genetic and epigenetic changes in the genome. The genetic component of aging received initially all of the attention. Telomere attrition and accumulation of mutations due to a progressive deficiency in the repair of DNA damage with age remain leading causes of genomic instability. However, epigenetic mechanisms have now emerged as key contributors to the alterations of genome structure and function that accompany aging. The three pillars of epigenetic regulation are DNA methylation, histone modifications, and noncoding RNA species. Alterations of these epigenetic mechanisms affect the vast majority of nuclear processes, including gene transcription and silencing, DNA replication and repair, cell cycle progression, and telomere and centromere structure and function. Here, we summarize the lines of evidence indicating that these epigenetic defects might represent a major factor in the pathophysiology of aging and aging-related diseases, especially cancer.
The Spatial Profile of Macaque MT Neurons Is Consistent With Gaussian Sampling of Logarithmically Coordinated Visual Representation
Authors: Kumano Hironori , Uka Takanori
Published: May 2010

Neurons in extrastriate visual areas have large receptive fields (RFs) compared with those in primary visual cortex (V1), suggesting extensive spatial integration. To examine the spatial integration of neurons in area MT, we modeled the RFs of MT neurons based on a symmetrical (Gaussian) integration of V1 outputs and tested the model using single-unit recording in two fixating macaque monkeys. Because visual representation in V1 is logarithmically compressed along eccentricity, the resulting RF model is log-Gaussian along the radial axis in polar coordinates. To test the log-Gaussian model, the RF of each neuron was mapped on a 5 × 5 grid using a small patch of random dots drifting at the preferred velocity of the neuron. The majority of MT neurons had RFs with a steeper slope near the fovea and a shallower slope away from the fovea. Among various two-dimensional Gaussian models fitted to the RFs, the log-Gaussian model provided the best description. The fitted parameters revealed that the range of sampling by MT neurons has no systematic relationship with eccentricities, consistent with a recent study for V4 neurons. Our results suggest that MT neurons integrate inputs from constant-sized patches of V1 cortex.
Attractor-Map Versus Autoassociation Based Attractor Dynamics in the Hippocampal Network
Authors: Colgin Laura L. , Leutgeb Stefan , Jezek Karel , Leutgeb Jill K. , Moser Edvard I. , McNaughton Bruce L. , Moser May-Britt
Published: May 2010

The autoassociative memory model of hippocampal field CA3 postulates that Hebbian associations among external input features produce attractor states embedded in a recurrent synaptic matrix. In contrast, the attractor-map model postulates that a two-dimensional continuum of attractor states is preconfigured in the network during development and that transitions among these states are governed primarily by self-motion information (“path-integration”), giving rise to the strong spatial characteristic of hippocampal activity. In this model, learned associations between “coordinates” on the attractor map and external cues can result in abrupt jumps between states, in the case of mismatches between the current input and previous associations between internal coordinates and external landmarks. Both models predict attractor dynamics, but for fundamentally different reasons; however, the two models are not a priori mutually exclusive. We contrasted these two models by comparing the dynamics of state transitions when two previously learned environmental shapes were morphed between their endpoints, in animals that had first experienced the environments either at the same location, or at two different locations, connected by a passageway through which they walked. As predicted from attractor-map theory, the latter animals expressed abrupt transitions between representations at the midpoint of the morph series. Contrary to the predictions of autoassociation theory, the former group expressed no evidence of attractor dynamics during the morph series; there was only a gradual transition between endpoints. The results of this critical test thus cast the autoassociator theory for CA3 into doubt and indicate the need for a new theory for this structure.