Effects of acute hypoxia on the adenylate cyclase and evans blue transport of brain microvessels

Kinetic parameters of the albumin transport were measured during and after an acute hypoxic insult evoked in newborn piglets by experimental bilateral pneumothorax. Adenylate cyclase activity was determined in the cerebral microvessels isolated by ultracentrifugation from different stages of brain damage. A decrease of the adenylate cyclase activity was observed in the cerebral microvessels of animals with acute hypoxic condition. However, the adenylate cyclase activity was found to be increased significantly in the microvessels during recirculation.

The activation of adenylate cyclase in the microvessel wall may be of pathogenetic importance in the development of vasogenic brain oedema.     

The development and standardization of an ELISA for ovalbumin determination in influenza vaccines

A double antibody sandwich enzyme-linked immunosorbent assay (ELISA) for the detection of ovalbumin in influenza vaccines has been developed and standardized. Commercially available reagents were used. ELISA was compared to single radial immunodiffusion (SRD) and immunoelectro-osmophoresis (IEOP) techniques. The detection limit by ELISA was 0.5 ng/ml. This method was found to be at least 1000 times more sensitive than SRD and at least 200 times more sensitive than IEOP. It was concluded that ELISA is a specific, sensitive and reproducible method for the determination of the small amounts of ovalbumin found as an impurity in unconcentrated influenza vaccines.     

Site dependent time optimization of protein synthesis with special regard to accuracy

The efficiency of protein synthesis is determined by its rate, accuracy, and energy consumption. With the energy consumption fixed, we optimize the system with respect to time and accuracy. Using an analytic model for a simple system and computer simulations for more complex systems, where also the possibility of errors is included, we demonstrate how different parts of the messenger RNA influence the protein production rate differently. The first part of the coding sequence is of major importance, since the availability of empty initiation sites is crucial, and queuing back to that region may interfere with initiation. The elongation rate at different positions depends on codon usage, on the concentrations of substrate and co-factors, and on the kinetic rate constants, including those of the proofreading branch(es). Ribosomal proofreading is a time consuming process and by allowing for more errors in the beginning of a protein, it is possible to increase the production rate of that protein. We calculate the mean translation time per functioning protein for various translation accuracies, and discuss the different strategies open to living cells.     

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.