Influence of acclimation temperature on the osmotic regulation and survival of rainbow trout (Salmo gairdneri) rapidly transferred from fresh water to sea water

Certain physiological responses of two groups of rainbow trout acclimated at 10 and 17°C to a sudden change in salinity were investigated in order to determine the most appropriate temperature for direct transfer in salt water. Plasma osmolarities of fish acclimated at 17°C increased at a much faster rate following transfer and approached a much higher value than that reached by the fish acclimated at 10°C. The same was apparent for body tissue dehydration. Haematocrit values, the number of red blood cells, as well as red cell volume showed no significant difference between the two groups of fish for most of the experimental period. The larger increases in plasma osmotic pressure and tissue dehydration observed at 17°C are discussed in connection with the physiological adjustments accompanying higher temperature acclimation.     

Celiac-related properties of chemically and enzymatically modified gluten proteins

The effects of chemical (acid-heating treatment) and enzymatic (microbial transglutaminase, TGase) modification (deamidation) of gluten proteins on their physicochemical and celiac disease-related properties were studied. Ammonia release, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and sample solubility analyses were employed to check the extent of gluten modification. Among different treatments achieved, the acid-heating treatment performed at 90 degrees C for 3 h induced gluten deamidation, paralleling an increase of gluten solubility without relevant proteolysis. Changes in the immunoreactivity of celiac IgA anti-gliadin antibodies (AGAs) to modified gluten proteins were detected by using a competitive indirect enzyme-linked immunosorbent assay method. Chemical deamidation by acid-heating treatment of gluten lowered IgA-AGA immunoreactivity. IgA-AGA immunoreactivity to gliadins was increased when they were submitted to TGase-catalyzed deamidation. The acid-heating treatment of gluten reduced its cytotoxic activity on human colon adenocarcinoma LoVo cell line. These results showed that chemical deamidation of gluten may be envisaged as a way to lower the potential risk for celiac people due to widespread use of gluten as a food additive.     

Edge effects and trampling in boreal urban forest fragments – impacts on the soil microbial community

Fragmentation of forest ecosystems increases the proportion of edge habitat and is accompanied by a change in plant species composition. The recreational use of urban forests leads to decreased vegetation cover and the formation of paths, and thus, to fragmentation at small scales. We studied the impacts of forest and path edge effects on the soil microbial community structure (by using the phospholipid fatty acid (PLFA) method) and microbial activity (measured as basal respiration) in 34 mesic boreal urban forest fragments in Finland. We sampled the humus layer 1) from the forest edge into the interior (0–80 m), and 2) at different distances from paths. Microbial community structure was only slightly affected by the forest edge but differences were found between distances of 0–10 m and over 50 m from the edge. These changes correlated with changes in soil pH. Although changes in the microbial community structure were not pronounced, microbial biomass and activity were 30–45% lower at the first 20 m into the forest fragments, due to a low moisture content of the humus near the edge. The decreased microbial activity detected at forest edges implies decreased litter decomposition rates, and thus, a change in ecosystem nutrient cycling. The microbial community structure differed between paths and surrounding areas and correlated with changes in soil pH. Paths also supported approximately 25–30% higher microbial biomass with a transition zone of at least 1 m from the path edge. Path associated disturbances (mainly alterations in vegetation and soil pH) were reflected in the soil microbial community structure up to 1.5 m from the paths.     

Breeding for herbicide resistance using molecular and cellular techniques

Summary The costs associated with yield testing cause maize (Zea mays L.) breeders to search for ways to maximize testing efficiency. The objective of this study was to select individual locations, or a group of locations as preliminary testing sites for yield evaluation of maize hybrids within FAO 600 maturity zone in Yugoslavia. Yield data for 12 locations obtained for the period 1975 to 1984 were used. The predictive potential of the site was judged by the correlations between location means and overall mean (r>0.95), linear regression of locations means on overall mean (b>1.0) and percentage of the 10% overall highest yielding hybrids selected by 10% selection intensity at each location, or at the group of locations (I_s>80%). Also factors as average location yield (x) and variation in individual location yield during the period of 10 years (CV) were related to the predictive potential of the site. Differences among locations in all criteria were found. Average yielding locations had higher values of estimators of predictive ability of overall performance than low yielding locations. None of individual locations satisfied all requested criteria. Five locations with highest values for each individual criterion were selected and all possible two, three, four and five-location combinations among them studied. Combinations of two locations could be used for very preliminary screening of hybrids by applying mild selection intensity. A more accurate prediction of overall one-year performance requires an evaluation of hybrids in a minimum of three, but frequently four, selected locations. However, for precise estimation of over-year hybrid performance, testing the hybrids at selected locations in more than one year is necessary.     

The Impact of Roads on the Redistribution of Plants and Associated Arthropods in a Hyper-Arid Ecosystem

The construction of vehicular roads likely affects the distribution of natural resources. Although the effects of roads on different ecosystem aspects have been extensively studied, studies in arid and, particularly, in hyper-arid ecosystems are scarce. In drylands, where water is the main limiting factor, the effect of roads on the redistribution of water may have strong subsequent effects on the ecosystem, especially when roads cross natural water flow paths. To fill this knowledge gap, we studied the effects of a road that runs across a slope on the distribution of plants and animals in a hyper-arid environment. Changes in shrub cover, below and above the road, were quantified by remote sensing and image classification, while plant-associated arthropods were vacuum-sampled from shrub canopies and from open (inter-shrub) areas. We found that the spatial distribution of shrubs, a vital resource facilitating many other organisms, was affected by the road, with an increase in the shrub cover immediately above the road and a decrease below it. Arthropod abundance generally followed shrub cover, but the exact pattern depended on the specific group sampled. While some arthropod groups (e.g., aphids, parasitic wasps and barklice) thrived under the disturbed conditions above the road, other arthropod groups (e.g., mites and true bugs) were less abundant in the disturbed patches. Our results highlight the strong effects of human-made structures on the distribution of flora and fauna in arid ecosystems.     

Comparative studies on body composition of rainbow trout (Salmo gairdneri R.) in relation to type of diet and growth rate

Three populations of rainbow trout (mean initial live weight 40 g) were fed experimentally under almost the same conditions for 49 weeks. The aim of the experiment was the examination of the changes in the relative proportions of the major whole body constituents (water, protein, fat and ash) in relation to type and amount of diet and growth rate. Two pelleted dry diets (A and B) and one mixed diet (C) were used. The amount of food given daily to the fish in the case of diets A and B was continuously based on fish body weight and water temperature. The population which received diet C (raw material and pelleted dry food) was fed on maximum ratio. Sampling was carried out approximately every two months. After 25 weeks, and besides the regular sampling, fish were sampled from each population and analyses were made on their fillets. The same analyses were also carried out. on fillets and whole body material on a sample of wild fish, of almost the same age, fed on a variety of food organisms in a stream near the experimental tanks. When the results are expressed in terms of dry weight, the analyses of whole body material showed that ash content remained fairly constant in all populations throughout the experimental time. Further, with increasing body weight and age the percentages of water and protein decreased and the percentage of fat content increased in all populations and especially in fish fed on diet C which appeared to have the maximum growth rate and final mean body weight. Similarly, fish fed on diet B, which showed the lowest growth rate and final mean body weight, had low changes in the major body constituents throughout the experimental period. The lowest and the most regular rate in the changes of these parameters appeared in fish fed on diet A which also had a sufficient growth rate and mean final body weight. Analyses of the fillets for the three different types of food used have different results. The analysed wild fish had the highest percentage of water content and, expressing the results in terms of dry weight, the highest percentage of ash and protein content, while they appeared to have the lowest percentage of fat content, on both whole body material and fillets.Since the three types of diets used in this experiment gave three different growth rates, as well as three different body compositions of the reared trout, it is suggested from the present results that the relative proportions and changes of the four body constituents and effects on the growth rate of trout are strongly affected by the type of food.