Fatty acids increase paracellular absorption of aluminium across Caco-2 cell monolayers

Passive paracellular absorption, regulated by tight junctions (TJs), is the main route for absorption of poorly absorbed hydrophilic substances. Surface active substances, such as fatty acids, may enhance absorption of these substances by affecting the integrity of TJ and increasing the permeability. It has been suggested that aluminium (Al) absorption occurs mainly by the paracellular route. Herein, we investigated if physiologically relevant exposures of fully differentiated Caco-2 cell monolayers to oleic acid and docosahexaenoic acid (DHA), which are fatty acids common in food, increase absorption of Al and the paracellular marker mannitol. In an Al toxicity test, mannitol and Al absorption through Caco-2 cell monolayers were similarly modulated by Al concentrations between 1 and 30 mM, suggesting that absorption of the two compounds occurred via the same pathways. Exposure of Caco-2 cell monolayers to non-toxic concentrations of Al (2 mM) and ¹⁴C-mannitol in fatty acid emulsions (15 and 30 mM oleic acid, 5 and 10 mM DHA) caused a decreased transepithelial electrical resistance (TEER). Concomitantly, fractional absorption of Al and mannitol, expressed as percentage of apical Al and mannitol retrieved at the basolateral side, increased with increasing dose of fatty acids. Transmission electron microscopy was applied to assess the effect of oleic acid on the morphology of TJ. It was shown that oleic acid caused a less structured morphology of TJ in Caco-2 cell monolayers. Taken together our findings indicate that fatty acids common in food increase the paracellular intestinal absorption of Al. These findings may influence future risk assessment of human Al exposure.     

Enhanced stability of alcohol dehydrogenase by non-covalent interaction with polysaccharides

Non-covalent interaction of alcohol dehydrogenase with polysaccharides was studied using three neutral and three anionic polysaccharides. The process of interaction of alcohol dehydrogenase with gum Arabic was optimized with respect to the ratio of enzyme to gum Arabic, pH, and molarity of buffer. Alcohol dehydrogenase–gum Arabic complex formed under optimized conditions showed 93 % retention of original activity with enhanced thermal and pH stability. Lower inactivation rate constant of alcohol dehydrogenase–gum Arabic complex within the temperature range of 45 to 60 °C implied its better stability. Half-life of alcohol dehydrogenase–gum Arabic complex was higher than that of free alcohol dehydrogenase. A slight increment was observed in kinetic constants (K _m and V _max) of gum Arabic-complexed alcohol dehydrogenase which may be due to interference by gum Arabic for the binding of substrate to the enzyme. Helix to turn conversion was observed in complexed alcohol dehydrogenase as compared to free alcohol dehydrogenase which may be responsible for observed stability enhancement.     

Using heterozygosity–fitness correlations to study inbreeding depression in an isolated population of white‐tailed deer founded by few individuals

A heterozygosity–fitness correlations (HFCs) may reflect inbreeding depression, but the extent to which they do so is debated. HFCs are particularly likely to occur after demographic disturbances such as population bottleneck or admixture. We here study HFC in an introduced and isolated ungulate population of white‐tailed deer Odocoileus virginianus in Finland founded in 1934 by four individuals. A total of 422 ≥ 1‐year‐old white‐tailed deer were collected in the 2012 hunting season in southern Finland and genotyped for 14 microsatellite loci. We find significant identity disequilibrium as estimated by g₂. Heterozygosity was positively associated with size‐ and age‐corrected body mass, but not with jaw size or (in males) antler score. Because of the relatively high identity disequilibrium, heterozygosity of the marker panel explained 51% of variation in inbreeding. Inbreeding explained approximately 4% of the variation in body mass and is thus a minor, although significant source of variation in body mass in this population. The study of HFC is attractive for game‐ and conservation‐oriented wildlife management because it presents an affordable and readily used approach for genetic monitoring that allowing identification of fitness costs associated with genetic substructuring in what may seem like a homogeneous population.     

A rare sugar xylitol. Part I: the biochemistry and biosynthesis of xylitol

The rare sugar xylitol is a five-carbon polyol (pentitol) that has beneficial health effects. Xylitol has global markets and, therefore, it represents an alternative to current dominant sweeteners. The research on microbial reduction of d-xylose to xylitol has been focused on metabolically engineered Saccharomycess cerevisiae and Candida strains. The Candida strains have an advantage over the metabolically engineered S. cerevisiae in terms of d-xylose uptake and maintenance of the intracellular redox balance. Due to the current industrial scale production of xylitol, it has become an inexpensive starting material for the production of other rare sugar. The first part of this mini-review concentrates on the biochemistry of xylitol biosynthesis and the problems related to intracellular redox balance.     

Genetic population structure, queen supersedure and social polymorphism in a social Hymenoptera

In social insects, the emergence of multiple queening is linked to changes in a suite of traits such as the reproductive life span of queens, mating patterns and population structure. We investigated queen turnover, colony longevity, spatial distribution patterns and genetic differentiation in a population of the socially polymorphic ant Formica fusca. Genetic differentiation between the social forms was absent, and mating patterns were similar in the two forms. The spatial distribution of single- and multi-queen colonies indicated an absence of colony reproduction by budding in both colony types. However, the rate of queen supersedure was high in multi-queen colonies and absent in single-queen ones. The social structure of colonies remained stable across years, but colony mortality did not differ between the two social forms. These results imply that differences between social types may appear and persist also in sympatry, and that these differences may occur in some traits, but not others, despite the presence of homogenizing gene flow.     

Seasonal differences between moose and roe deer in ability to digest browse

The digestive capacity of free-living moose Alces alces (L.) and roe deer Capreolus capreolus (L.) for four plant species was studied with in vitro technique. Moose were found to digest all species better than roe deer. Individual variations were also smaller for moose. In moose the level of digestibility was the same both summer and winter, while roe deer shot in winter digested winter samples of bilberry Vaccinium myrtillus L. and to some extent Scots pine Pinus silvestris L. better than did summer roe deer. This was taken as evidence for a seasonal adaptation in the roe deer rumen. Digestibility of the plant material studied showed a strong negative correlation to the fiber content. The results are discussed in relation to winter problems for roe deer and possible food competition between moose and roe deer.     

Diversity surveys and evolutionary relationships of aoxB genes in aerobic arsenite-oxidizing bacteria

A new primer set was designed to specifically amplify ca. 1,100 bp of aoxB genes encoding the As(III) oxidase catalytic subunit from taxonomically diverse aerobic As(III)-oxidizing bacteria. Comparative analysis of AoxB protein sequences showed variable conservation levels and highlighted the conservation of essential amino acids and structural motifs. AoxB phylogeny of pure strains showed well-discriminated taxonomic groups and was similar to 16S rRNA phylogeny. Alphaproteobacteria-, Betaproteobacteria-, and Gammaproteobacteria-related sequences were retrieved from environmental surveys, demonstrating their prevalence in mesophilic As-contaminated soils. Our study underlines the usefulness of the aoxB gene as a functional marker of aerobic As(III) oxidizers.     

Floristic diversity patterns in the White Carpathians biosphere reserve,Czech Republic

The flora of the White Carpathians, a mountain range in the south-east of the Czech Republic, is documented by about 485,000 records of vascular plant occurrences collected since the mid-19^th century. A total of 1299 species recorded in 93 grid cells of 2.8 × 3.1 km were used for an analysis of spatial patterns of floristic diversity in the White Carpathians. Multivariate statistical techniques such as ordination and classification were used to reveal the main gradients in floristic composition and species richness, and measured environmental data and Ellenberg indicator values were used to assess underlying environmental factors. There is a striking floristic contrast between the western and eastern part of the study area, which is associated with differences in climate, mean altitude, topographic heterogeneity measured as altitudinal range, and land use. The western part is characterised by thermophilous, continental and calcicolous species of open habitats. In contrast, the more forested eastern part along the state border with Slovakia and the north-eastern part of the area are characterised by acidophilous species with higher moisture requirements. This pattern is consistent with the established phytogeographical division of the Czech Republic into the phytogeographical regions of Thermophyticum and Mesophyticum. The further division of the area into four regions, based on classified grid data, is also similar to the current division into phytogeographical districts, except for the Javorníky district. There are two distinct hot spots of species richness, in the western and the extreme north-eastern part. A poorer flora was found in landscapes with intensive agriculture. Species richness is associated with different environmental factors than species composition, namely with soil types and land-use categories. Alien species are more common in areas with a higher incidence of arable land and built-up areas, and less common in areas dominated by grasslands and forests.     

p38 mitogen-activated protein kinase and mitogen-activated protein kinase-activated protein kinase 2 (MK2) signaling in atrophic and hypertrophic denervated mouse skeletal muscle

Background

p38 mitogen-activated protein kinase has been implicated in both skeletal muscle atrophy and hypertrophy. T317 phosphorylation of the p38 substrate mitogen-activated protein kinase-activated protein kinase 2 (MK2) correlates with muscle weight in atrophic and hypertrophic denervated muscle and may influence the nuclear and cytoplasmic distribution of p38 and/or MK2. The present study investigates expression and phosphorylation of p38, MK2 and related proteins in cytosolic and nuclear fractions from atrophic and hypertrophic 6-days denervated skeletal muscles compared to innervated controls.

Methods

Expression and phosphorylation of p38, MK2, Hsp25 (heat shock protein25_rodent/27_human, Hsp25/27) and Hsp70 protein expression were studied semi-quantitatively using Western blots with separated nuclear and cytosolic fractions from innervated and denervated hypertrophic hemidiaphragm and atrophic anterior tibial muscles. Unfractionated innervated and denervated atrophic pooled gastrocnemius and soleus muscles were also studied.

Results

No support was obtained for a differential nuclear/cytosolic localization of p38 or MK2 in denervated hypertrophic and atrophic muscle. The differential effect of denervation on T317 phosphorylation of MK2 in denervated hypertrophic and atrophic muscle was not reflected in p38 phosphorylation nor in the phosphorylation of the MK2 substrate Hsp25. Hsp25 phosphorylation increased 3-30-fold in all denervated muscles studied. The expression of Hsp70 increased 3-5-fold only in denervated hypertrophic muscles.

Conclusions

The study confirms a differential response of MK2 T317 phosphorylation in denervated hypertrophic and atrophic muscles and suggests that Hsp70 may be important for this. Increased Hsp25 phosphorylation in all denervated muscles studied indicates a role for factors other than MK2 in the regulation of this phosphorylation.