Associations between Level and Change in Physical Function and Brain Volumes

Background

Higher levels of fitness or physical function are positively associated with cognitive outcomes but the potential underlying mechanisms via brain structure are still to be elucidated in detail. We examined associations between brain structure and physical function (contemporaneous and change over the previous three years) in community-dwelling older adults.

Methodology/Principal Findings

Participants from the Lothian Birth Cohort 1936 (N=694) underwent brain MRI at age 73 years to assess intracranial volume, and the volumes of total brain tissue, ventricles, grey matter, normal-appearing white matter, and white matter lesions. At ages 70 and 73, physical function was assessed by 6-meter walk, grip strength, and forced expiratory volume. A summary ‘physical function factor’ was derived from the individual measures using principal components analysis. Performance on each individual physical function measure declined across the three year interval (p<0.001). Higher level of physical function at ages 70 and 73 was associated with larger total brain tissue and white matter volumes, and smaller ventricular and white matter lesion volumes (standardized β ranged in magnitude from 0.07 to 0.17, p<0.001 to 0.034). Decline in physical function from age 70 to 73 was associated with smaller white matter volume (0.08, p<0.01, though not after correction for multiple testing), but not with any other brain volumetric measurements.

Conclusions/Significance

Physical function was related to brain volumes in community-dwelling older adults: declining physical function was associated with less white matter tissue. Further study is required to explore the detailed mechanisms through which physical function might influence brain structure, and vice versa.     

The invasion-associated type III system of Salmonella typhimurium directs the translocation of Sip proteins into the host cell

The ability of Salmonella typhimurium to interact with host cells is largely dependent on the function of a type III protein-secretion system encoded at centisome 63 of its chromosome. We have shown here that two targets of this protein-secretion system, SipB and SipC, are translocated into cultured intestinal Henle-407 cells. Translocation required the function of the type III secretion apparatus, as an S. typhimurium strain carrying a mutation in invA , which encodes an essential component of this system, failed to translocate the Sip proteins. Null mutations in the genes encoding SipB, SipC or SipD, prevented protein translocation, indicating that these proteins are involved in the translocation process. In contrast, mutations in sipA and sptP , which also encode secreted proteins, did not interfere with the translocation of SipC, indicating that only a subset of targets of the type III secretion system act as translocases. Externally or internally localized bacteria could direct protein translocation into Henle-407 cells as this process occurred in the presence of cytochalasin D at a concentration that prevented bacterial entry, or in the presence of gentamicin added shortly after bacterial internalization at a concentration that killed extracellular Salmonella . These results indicate that protein translocation into host cells may be a universal function of all type III secretion systems.     

PINK1 Phosphorylates MIC60/Mitofilin to Control Structural Plasticity of Mitochondrial Crista Junctions

1. Download high-res image (208KB)
2. Download full-size image

     

Lignocellulosic residues: Biodegradation and bioconversion by fungi

The ability of fungi to degrade lignocellulosic materials is due to their highly efficient enzymatic system. Fungi have two types of extracellular enzymatic systems; the hydrolytic system, which produces hydrolases that are responsible for polysaccharide degradation and a unique oxidative and extracellular ligninolytic system, which degrades lignin and opens phenyl rings. Lignocellulosic residues from wood, grass, agricultural, forestry wastes and municipal solid wastes are particularly abundant in nature and have a potential for bioconversion. Accumulation of lignocellulosic materials in large quantities in places where agricultural residues present a disposal problem results not only in deterioration of the environment but also in loss of potentially valuable material that can be used in paper manufacture, biomass fuel production, composting, human and animal feed among others. Several novel markets for lignocellulosic residues have been identified recently. The use of fungi in low cost bioremediation projects might be attractive given their lignocellulose hydrolysis enzyme machinery.     

Roseovarius albus sp. nov., a new Alphaproteobacterium isolated from the Mediterranean Sea

Strain 4SM10^T, an aerobic marine, Gram-negative, heterotrophic and non pigmented bacterium isolated from seawater from Vinaroz in Castellón, Spain, was characterized using a polyphasic approach. Analysis of the 16S rRNA gene sequence placed the strain within the Roseobacter clade in the family Rhodobacteraceae. Phylogenetic analyses also showed that strain 4SM10^T forms a stable clade with species of the genus Roseovarius, being related to Roseovarius nubinhibens ISM^T and Roseovarius aestuarii SMK-122^T at 97.5 and 97.4 % 16S rRNA sequence similarity, respectively. Average Nucleotide Identity (ANI) values, determined as a measure of overall genomic resemblance, confirmed that strain 4SM10^T does not belong to the same species as R. aestuarii CECT 7745^T and Roseovarius nubinhibens CECT 7750^T displaying ANI values well below the 95 % boundary for genomic species. Strain 4SM10^T requires Na⁺ plus a divalent cation (either Mg²⁺ or Ca²⁺) to grow, reduces nitrate to nitrite and uses a large number of amino acids and organic acids (but no carbohydrates) as sole carbon sources. Enzymatic activities displayed in API ZYM tests are alkaline phosphatase, leucine arylamidase and acid phosphatase. The major cellular fatty acids were identified as C_18:1 ω7c and/or C_18:1 ω6c (67.1 %). The DNA G+C content was determined to be 54.27 mol%. Based on the genotypic and phenotypic data obtained, the name Roseovarius albus sp. nov. is proposed for this novel taxon, with the type strain 4SM10^T (=CECT 7450^T = KCTC 22653^T).     

Metabolic stasis in an ancient symbiosis: genome-scale metabolic networks from two Blattabacterium cuenoti strains,primary endosymbionts of cockroaches

Background

Cockroaches are terrestrial insects that strikingly eliminate waste nitrogen as ammonia instead of uric acid. Blattabacterium cuenoti (Mercier 1906) strains Bge and Pam are the obligate primary endosymbionts of the cockroaches Blattella germanica and Periplaneta americana, respectively. The genomes of both bacterial endosymbionts have recently been sequenced, making possible a genome-scale constraint-based reconstruction of their metabolic networks. The mathematical expression of a metabolic network and the subsequent quantitative studies of phenotypic features by Flux Balance Analysis (FBA) represent an efficient functional approach to these uncultivable bacteria.

Results

We report the metabolic models of Blattabacterium strains Bge (iCG238) and Pam (iCG230), comprising 296 and 289 biochemical reactions, associated with 238 and 230 genes, and 364 and 358 metabolites, respectively. Both models reflect both the striking similarities and the singularities of these microorganisms. FBA was used to analyze the properties, potential and limits of the models, assuming some environmental constraints such as aerobic conditions and the net production of ammonia from these bacterial systems, as has been experimentally observed. In addition, in silico simulations with the iCG238 model have enabled a set of carbon and nitrogen sources to be defined, which would also support a viable phenotype in terms of biomass production in the strain Pam, which lacks the first three steps of the tricarboxylic acid cycle. FBA reveals a metabolic condition that renders these enzymatic steps dispensable, thus offering a possible evolutionary explanation for their elimination. We also confirm, by computational simulations, the fragility of the metabolic networks and their host dependence.

Conclusions

The minimized Blattabacterium metabolic networks are surprisingly similar in strains Bge and Pam, after 140 million years of evolution of these endosymbionts in separate cockroach lineages. FBA performed on the reconstructed networks from the two bacteria helps to refine the functional analysis of the genomes enabling us to postulate how slightly different host metabolic contexts drove their parallel evolution.

     

Study of the volatile compounds produced by Debaryomyces hansenii NRRL Y-7426 during the fermentation of detoxified concentrated distilled grape marc hemicellulosic hydrolysates

The volatile compounds produced by Debaryomyces hansenii NRRL Y-7426 during the fermentation of detoxified concentrated distilled grape marc hemicellulosic hydrolysates was analysed by GC?CMS. Thirty-five compounds corresponding to ten groups of volatile compounds: terpenes, higher alcohols, C₆ alcohols, aldehydes, volatile acids, acetates, ethyl esters, volatile phenols, sulphur compounds and hydrocarbons were identified. The supplementation with commercial nutrients increased the concentration of 2-phenylethanol, a commercial flavour and fragrance compound, with a rose-like odour, employed in cosmetics and food industries; and other positive compounds to the aroma such as terpenes and ethyl esters. Non-supplemented media produced the highest content in higher alcohols, volatile acids, sulphur compounds and in the majority of hydrocarbons detected, meanwhile supplementation with vinasses hardly produced volatile compounds. Only four volatile compounds contributed directly to the aroma according to the OAVs values higher than 1. Finally, a PCA analysis allowed accounting for 100?% of the variance.     

The Dark Recovery Rate in the Photocycle of the Bacterial Photoreceptor YtvA Is Affected by the Cellular Environment and by Hydration

We report thermal recovery kinetics of the lit state into the parental dark state, measured for the blue light-sensing photoreceptor YtvA inside overexpressing E. coli and B. subtilis bacterial cells, performed for the wild type and several mutated proteins. Recovery was followed as a recovery of the fluorescence, as this property is only found for the parental but not for the photochemically generated lit state. When cells were deposited onto a microscope glass plate, the observed thermal recovery rate in the photocycle was found ca. ten times faster in comparison to purified YtvA in solution. When the E. coli or B. subtilis colonies were soaked in an isotonic buffer, the dark relaxation became again much slower and was very similar to that observed for YtvA in solution. The observed effects show that rate constants can be tuned by the cellular environment through factors such as hydration.     

The Stenopodainae (Hemiptera,Heteroptera) of Argentina

In Argentina, 10 genera and 33 species of Stenopodainae (Hemiptera: Reduviidae) have been recorded. Diagnoses of the genera, subgenera and species are given, and an illustrated key to genera is provided. Six species are new records for Argentina and an additional seven species represent new records for provinces.