Left hemispheric dominance during auditory processing in a noisy environment

Background  

In daily life, we are exposed to different sound inputs simultaneously. During neural encoding in the auditory pathway, neural activities elicited by these different sounds interact with each other. In the present study, we investigated neural interactions elicited by masker and amplitude-modulated test stimulus in primary and non-primary human auditory cortex during ipsi-lateral and contra-lateral masking by means of magnetoencephalography (MEG).     

A simple synthesis of four stereoisomers of roseoside and their inhibitory activity on leukotriene release from mice bone marrow-derived cultured mast cells

Four stereoisomers of roseoside (vomifoliol glucosides) were synthesized using glucose as a chiral resolving reagent. The four synthetic stereoisomers exhibited inhibitory activity on leukotriene release from mouse bone marrow-derived cultured mast cells (BMCMC). The (6S)-isomers of roseoside were about twice as active as (6R)-isomers.     

Three-dimensional colocalization analysis of plasma-derived apolipoprotein B with amyloid plaques in APP/PS1 transgenic mice

Parenchymal accumulation of amyloid-beta (Aβ) is a hallmark pathological feature of Alzheimer’s disease. An emerging hypothesis is that blood-to-brain delivery of Aβ may increase with compromised blood–brain barrier integrity. In plasma, substantial Aβ is associated with triglyceride-rich lipoproteins (TRLs) secreted by the liver and intestine. Utilizing apolipoprotein B as an exclusive marker of hepatic and intestinal TRLs, here we show utilizing an highly sensitive 3-dimensional immuno-microscopy imaging technique, that in APP/PS1 amyloid transgenic mice, concomitant with substantially increased plasma Aβ, there is a significant colocalization of apolipoprotein B with cerebral amyloid plaque. The findings are consistent with the possibility that circulating lipoprotein-Aβ contributes to cerebral amyloidosis.     

High Rate of N2 Fixation by East Siberian Cryophilic Soil Bacteria as Determined by Measuring Acetylene Reduction in Nitrogen-Poor Medium Solidified with Gellan Gum

For evaluating N₂ fixation of diazotrophic bacteria, nitrogen-poor liquid media supplemented with at least 0.5% sugar and 0.2% agar are widely used for acetylene reduction assays. In such a soft gel medium, however, many N₂-fixing soil bacteria generally show only trace acetylene reduction activity. Here, we report that use of a N₂ fixation medium solidified with gellan gum instead of agar promoted growth of some gellan-preferring soil bacteria. In a soft gel medium solidified with 0.3% gellan gum under appropriate culture conditions, bacterial microbiota from boreal forest bed soils and some free-living N₂-fixing soil bacteria isolated from the microbiota exhibited 10- to 200-fold-higher acetylene reduction than those cultured in 0.2% agar medium. To determine the N₂ fixation-activating mechanism of gellan gum medium, qualitative differences in the colony-forming bacterial components from tested soil microbiota were investigated in plate cultures solidified with either agar or gellan gum for use with modified Winogradsky''s medium. On 1.5% agar plates, apparently cryophilic bacterial microbiota showed strictly distinguishable microbiota according to the depth of soil in samples from an eastern Siberian Taiga forest bed. Some pure cultures of proteobacteria, such as Pseudomonas fluorescens and Burkholderia xenovorans, showed remarkable acetylene reduction. On plates solidified with 1.0% gellan gum, some soil bacteria, including Luteibacter sp., Janthinobacterium sp., Paenibacillus sp., and Arthrobacter sp., uniquely grew that had not grown in the presence of the same inoculants on agar plates. In contrast, Pseudomonas spp. and Burkholderia spp. were apparent only as minor colonies on the gellan gum plates. Moreover, only gellan gum plates allowed some bacteria, particularly those isolated from the shallow organic soil layer, to actively swarm. In consequence, gellan gum is a useful gel matrix to bring out growth potential capabilities of many soil diazotrophs and their consortia in communities of soil bacteria.In 1967, Schöllhorn and Burris discovered that nitrogenase from an N₂-fixing rhizobium of soybean can reduce acetylene to produce ethylene (C₂H₄) (32), a reaction analogous to the conversion of the natural substrate N₂ into ammonia. Shortly afterwards, it was shown that this acetylene reduction activity parallels N₂ reduction by nitrogenase (13), and since then, acetylene reduction assays have been widely used in the evaluation of biological N₂ fixation. An acetylene reduction assay is generally performed under the following conditions: precultured bacterial cells are suspended into N-free or -deficient liquid medium containing a carbon source, usually d-glucose or d-mannitol (35) at 0.5 to 2.0%, and exposed for 24 h or less at a representative room temperature, e.g., 25°C (2). However, this method is not applicable to free-living, microaerobic N₂-fixing bacteria, which have been regarded as notoriously difficult to culture. To solve this problem, Döbereiner and her group developed a soft gel method (7), which used 0.2% agar as a gel matrix for the medium. Due to a vertical gradient of dissolved oxygen concentrations, these microaerobes formed a thin layer at the particular depth of the medium that contained an ideal level of dissolved oxygen (10). Also, significant activities in acetylene reduction assays were observed for N₂-fixing microaerobes, particularly those from the rhizoplane of monocotyledonous crop plants (e.g., Azospirillum and Herbaspirillum spp.) (1, 9, 40). To date, these soft gel media solidified with 0.2% agar have been widely used as the most basic method for the screening of free-living or difficult-to-culture N₂-fixing bacteria (2, 16).In an agar composed of soft gel, however, the layer formation of highly transparent colony-forming bacteria is often obscured and is more difficult to observe than comparable layer formation in water due to the higher turbidity of the agar gel, and some members of the soil bacterial community do not show any positive response in acetylene reduction assays under these conditions. These drawbacks to the usage of agar as a soft gel matrix delayed the recognition that free-living N₂ fixers make a potent contribution to the support of ecosystems under adverse soil conditions. Hashidoko et al. developed an improved soft gel medium for growth of N₂-fixing bacteria in 2002 (15). In their study, 0.2% agar was replaced with 0.3% gellan gum, a bacterial extracellular polysaccharide (EPS) produced by Sphingomonas elodea (a synonym of Sphingomonas paucimobilis) ATCC 31461 (12, 17, 18). Initially, gellan gum was used for the purpose of preparing a highly transparent soft gel medium that was better for culturing microaerobic N₂-fixing rhizobacteria. It had other favorable physical properties: when 0.3% gellan gum containing Winogradsky''s mineral mixture was autoclaved, the medium remained in a liquid form over a period of several hours while cooling to room temperature. Even after the gellan gum had been solidified, the soft gel was easily liquefied upon mechanical agitation. The liquefied medium was able to resolidify after a short period of time, so it was easy to uniformly disperse inoculants into the soft gel medium. The outstanding transparency (14) and other properties of this gel matrix enable easy visualization of transparent colony-forming N₂-fixing bacteria and also allow observation of their responses to various concentrations of dissolved oxygen and cell motilities (15).In many preliminary experiments, nitrogen-poor gellan gum media allowed high growth of diazotrophs, but this study was needed to compare gellan gum with agar as a gel matrix for N₂ fixation. Because Siberian boreal forest soils have been noted for their low N₂-fixing capability (3), we first cultured bacterial microbiota from the eastern Siberian Taiga forest bed in gellan gum medium. A quantitative comparison of N₂ fixation behaviors of free-living soil bacteria was attempted to investigate gellan gum as a potential N₂ fixation-promoting soft gel matrix. We here first report on the efficacy of gellan gum as a soft gel matrix for monitoring acetylene reduction by the use of free-living N₂-fixing soil bacteria.     

Genetic and Molecular Basis of Individual Differences in Human Umami Taste Perception

Umami taste (corresponds to savory in English) is elicited by L-glutamate, typically as its Na salt (monosodium glutamate: MSG), and is one of five basic taste qualities that plays a key role in intake of amino acids. A particular property of umami is the synergistic potentiation of glutamate by purine nucleotide monophosphates (IMP, GMP). A heterodimer of a G protein coupled receptor, TAS1R1 and TAS1R3, is proposed to function as its receptor. However, little is known about genetic variation of TAS1R1 and TAS1R3 and its potential links with individual differences in umami sensitivity. Here we investigated the association between recognition thresholds for umami substances and genetic variations in human TAS1R1 and TAS1R3, and the functions of TAS1R1/TAS1R3 variants using a heterologous expression system. Our study demonstrated that the TAS1R1-372T creates a more sensitive umami receptor than -372A, while TAS1R3-757C creates a less sensitive one than -757R for MSG and MSG plus IMP, and showed a strong correlation between the recognition thresholds and in vitro dose - response relationships. These results in human studies support the propositions that a TAS1R1/TAS1R3 heterodimer acts as an umami receptor, and that genetic variation in this heterodimer directly affects umami taste sensitivity.     

Increased Stathmin1 Expression in the Dentate Gyrus of Mice Causes Abnormal Axonal Arborizations

Pituitary adenylate cyclase-activating polypeptide (PACAP) is involved in multiple brain functions. To clarify the cause of abnormal behavior in PACAP deficient-mice, we attempted the identification of genes whose expression was altered in the dentate gyrus of PACAP-deficient mice using the differential display method. Expression of stathmin1 was up-regulated in the dentate gyrus at both the mRNA and protein levels. PACAP stimulation inhibited stathmin1 expression in PC12 cells, while increased stathmin1expression in neurons of the subgranular zone and in primary cultured hippocampal neurons induced abnormal arborization of axons. We also investigated the pathways involved in PACAP deficiency. Ascl1 binds to E10 box of the stathmin1 promoter and increases stathmin1 expression. Inhibitory bHLH proteins (Hes1 and Id3) were rapidly up-regulated by PACAP stimulation, and Hes1 could suppress Ascl1 expression and Id3 could inhibit Ascl1 signaling. We also detected an increase of stathmin1 expression in the brains of schizophrenic patients. These results suggest that up-regulation of stathmin1 in the dentate gyrus, secondary to PACAP deficiency, may create abnormal neuronal circuits that cause abnormal behavior.     

Multiple attractors in host-parasitoid interactions: coexistence and extinction

This paper considers the dynamics of a two-dimensional discrete-time model for host-parasitoid interactions, and shows that the model has two attractors: the fixed point where two species coexist and a boundary cycle where the parasitoid is absent. The analysis with the Liapunov exponent confirms that this kind of bistability is common in this model. The generality of this phenomenon in host-parasitoid interactions is also discussed.     

Isolation and characterization of an anaerobic dehydrodivanillin-degrading bacterium.

A novel, strictly anaerobic, gram-negative, non-spore-forming, fusiform, rod-shaped bacterium having high dehydrodivanillin (DDV)-degrading activity was isolated from cow ruminal fluid. This strain degraded a range of six main lignin-related compounds such as DDV, ferulic acid, dehydrodiisoeugenol, guaiacoxyacetic acid, vanillin, and veratrylglycerol-beta-guaiacyl ether to the extent of 14 to 83% within 2 days under strictly anaerobic conditions. As DDV degradation intermediates, three aromatic compounds (dehydrodivanillic acid, vanillic acid, and 5-carboxyvanillic acid) and two alicyclic compounds (cyclohexanecarboxylic acid and cyclohexanol) were detected by thin-layer, high-performance liquid, and gas chromatography and mass spectrometry. The addition of 1% glucose and peptone in a synthetic medium stimulated growth of the strain but slowed down DDV degradation. The presence of 0.1% yeast extract increased both cell growth and DDV degradation. The growth yield in defined medium was 151.5 g (dry weight) of cells per mol of DDV utilized. Characterization of the strain indicated that it was distinct from known Fusobacterium and Clostridium species. The bacterium was easily induced to form protoplasts after treatment with either penicillin or lysozyme. The frequencies of protoplast formation and regeneration in the strain were 94 and 18%, respectively.     

Intergeneric protoplast fusion between Fusobacterium varium and Enterococcus faecium for enhancing dehydrodivanillin degradation.

Intergeneric protoplast fusion between Fusobacterium varium (Pcs Glu+) and Enterococcus faecium (Pcr Glu-) was performed under strictly anaerobic conditions to improve dehydrodivanillin (DDV) degradation. The fusion frequency obtained from the selective medium (Pc+ Glu-) was about 0.9 X 10(-5) to 1.3 X 10(-5). The seven fusants isolated were all gram-negative anaerobes with rod shapes like that of F. varium and with main phenotypical properties of cocci like those of E. faecium such as esculin and starch hydrolysis, milk clotting, and lactate production. Five fusants showed enhanced DDV degradation activities that were 2 to 4 times higher than those of parental strains. Genetic relatedness between a fusant (FE7) and the parents was estimated by DNA-DNA Southern blot hybridization with 32P-labeled chromosomal DNA fragments of F. varium and E. faecium as respective probes. The fusant FE7 presented a very high cross-hybridization with both probes, indicating a high DNA homology between the fusant and both parental strains. Almost all the fusants obtained here have stably kept the properties described above for about 2 years. These results suggest that intergeneric gene transfer takes place through protoplast fusion and that the fusants that were obtained are stable recombinants.     

Anaerobic reduction of ferulic acid to dihydroferulic acid by Wolinella succinogenes from cow rumen

Summary Ferulic acid(FA)-modifying microflora from the rumen of cows were acclimated in an FA-containing medium, in which aromatic compounds (dihydroferulic acid, homovanillic acid, carboxymethylphenol and vanillic acid) and volatile fatty acids (acetic, butyric and isobutyric) were detected by gas chromatography and mass spectrometry. An anaerobic curved bacterium was isolated from the rumen microflora. This bacterium was characterized and identified as Wolinella succinogenes according to the method of Holdeman et al. (1977). It could only reduce FA to dihydroferulic acid in the absence of hydrogen acceptors such as nitrate or fumarate and under strictly anaerobic conditions. FA-reducing ability of the bacterium was inhibited to some extent at FA concentrations greater than 5 mM. The FA was reduced more effectively at pH values of 7.0–7.2 than at 6.8 and the reduction was enhanced by the addition of an Ruminococcus albus' culture supernatant.