Microrépartition des populations de truite commune (Salmo trutta L.) de juvenile de saumon atlantique (Salmo salar L.) et des autres espès préntes dans la partie haute du Scorff (Bretagne)

Resume Une étude de la microrártition de la population de truite commune (Salmo trutta L.) et du juvénile de Saumon atlantique (Salmo salar L.) associée aux autres espès préntes est effectuée en fin d'été dans la partie amont du Scorff (distance source-estuaire 65 km).La population de saumon est composée uniquement d'individus d'âge 0⁺ alors que les truites ont entre 0⁺ et 3⁺ ans avec une majorité pour la classe d'âge des 1⁺ an. La densité de saumon augmente avec la vitesse de courant (r = 0,99) et la taille de la granulométrie du substrat. Un habitat trés favorable à l'espèce se caractérise par une faible profondeur (> 23 cm), une vitesse de courant élevée (61 cm/ s) et un substrat caillouteux. 75,4% de la population est recensée en plein courant.L'effet rive, est particulièrement important pour la truite quelque soit son âge (80,1%). L'absence de la truite 0⁺ du faciés à courant élevé et sa localisation près des berges dans les zones courantes (41 cm/ s) peu profondes entraînent une ségrégation spatiale avec le saumon de même âge. La truite d'au moins un an est présente dans des milieux plus profonds (27 cm) à vitesse de courant nulle à moyenne (< 28 cm/ s). L'effet rive est renforcée par la présence de nombreux courants en berge.Parmi les espéces d'accompagnement, le chabot a la distribution la plus large. La loche et la lamproie de Planer sont les espéces les plus abondantes et ont des densités très élevées dans des secteurs caractéristiques.L'ensemble de ces résultats est discuté en liaison avec les premières observations concernant la distribution de ces espèces sur le cours principal du Scorff.

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We describe the microdistribution of populations of Brown Trout (Salmo trutta L.) and of juvenile atlantic Salmon (Salmo salar L.) in the upstream part of the Scorff river (Brittany) at the end of summer.The Salmon population was composed of one age classe (0⁺) only while Trout age varied from 0⁺ to 3⁺ years, with a majority in age class 1⁺. Salmon density increased with current velocity (r = 0.99) and the nature of the substratum. A very favorable habitat for this species was characterized by reduced depth (< 23 cm), a high current velocity (61 cm s ¹) and a stony substrate. The largest part of the population (74%) was localized in the centre of the running open water.A bank effect was particularly important for brown trout, irrespective of age (80.1%). The trout 0⁺ is absent from shallow rifles and its presence in the few deep running water areas (41 cm s^–1) along the banks involved a spatial segregation with salmon 0⁺. The trout of one year and older were localized in deeper habitats (27 cm) with zero to medium current velocity (< 28 cm s^–1). The bank effect was intensified by the presence of many overhangs along the bank.Among the secondary species, sculpin had the widest distribution, but Stone-loach and brook lamprey were the most abundant species and reached high densities in characteristic areas.

     

Deanol Affects Choline Metabolism in Peripheral Tissues of Mice

Abstract: The enzymatic hydrolysis of UDP-galactose in rat and calf brain was studied. The hydrolysis occurs in two steps: The first is the conversion of UDP-galactose to galactose-1-phosphate catalyzed by nucleotide pyrophosphatase (EC 3.6.1.9), and the second is the conversion of the latter to free galactose by alkaline phosphatase (EC 3.1.3.1). The overall conversion has a pH optimum of 9.0, but there is considerable activity at pH 7.4, which is the optimum for UDP-galactose:ceramide galactosyltransferase in the synthesis of cerebrosides. Preparations from cytosol from calf brain cerebellum or stem that were enriched in UDP-galactose hydrolytic activity inhibit cerebroside synthesis under conditions optimal for the synthesis. Microsome-rich and nuclear debris fractions contain the highest apparent specific activity among the subcellular fractions studied. Hydrolysis of UDP-galactose occurs in all areas of brain, brainstem having the highest activity. The apparent specific activity in jimpy mouse brain homogenate is nearly twice as high as in the control brain homogenate.     

Comparison of phosphorus distribution and cycling between adjacent native semidesert shrub and cultivated grass-dominated ecosystems

Summary P concentrations at several soil profile depths and for various plant parts were monitored over most of one year in adjacent native semidesert shrub and cultivated crested wheatgrass ecosystems. When multiplied by appropriate soil bulk densities and phytomass values, it was possible to calculate P mineralomasses in these two ecotessera. Knowledge of new to old growth ratios allowed estimation of P turnover. Although there was greater P in the vegetation of the native stand, the tissues lived longer and decomposed less rapidly than those in the grass stand that has been established in a portion of the original shrub dominated semidesert. The grass stand showed higher net primary productivity and had a much higher fraction of phytomass that is consumable by livestock. There was thus, at least a five-fold greater turnover of P in the tilled and seeded system. The introduced grasses are also withdrewing more P from the soil reserves. Whether nutrient export from the systems could lead to long-term declines in productivity will require further monitoring and experimental effort.     

Emergence of blackflies (Diptera: Simuliidae) from a small forested stream in Ontario

Three species of blackflies were found in emergence-trap samples taken overa period of 8 months from a second-order, forested, cold-stenothermal stream in southern Ontario. The emergence phenologies of the two common species, Prosimulium mixtum and Stegopterna mutata, are described and compared with their phenologies in other streams in North America. Hypotheses are presented for the poor faunal diversity and prolonged emergence of the two species in the stream studied. Emergence data are used to describe the pupal distribution in the stream.Wing-length measurements showed a distinct dimorphism in P. mixtum: females were larger than males. Adult size (except of P. mixtum females) varied among sampling sites in the stream and, in the case of S. mutata, this variation was time dependent.     

Indoleamine 2,3-Dioxygenase Tissue Distribution and Cellular Localization in Mice: Implications for Its Biological Functions

Earlier studies have suggested that indoleamine 2,3-dioxygenase (IDO) has a wide tissue distribution in mammals. However, detailed information on its cellular localization and also the levels of expression in various tissues is still scarce. In the present study, we sought to determine the cellular localization of IDO and also to quantify the level of its expression in various mouse tissues by using the branched DNA signal amplification assay, Western blotting, and immunohistochemical staining. The highest levels of constitutive IDO expression were found to be selectively present in the caput of epididymis, except for its initial segment. IDO expression was also detected inside the luminal compartment and even in the stereocilia within this region. In the prostate, high levels of IDO were selectively expressed in the capsular cells. In addition, high levels of IDO expression were also selectively detected in certain types of cells in the placenta, spleen, thymus, lung, and digestive tract. Notably, the morphological features of most of the positively stained cells in these organs closely resembled those of antigen-presenting cells. Based on the tissue distribution and cellular localization characteristics of IDO, it is hypothesized that its expression may serve two main functions: one is to deplete tryptophan in an enclosed microenvironment (such as in the epididymal duct lumen) to prevent bacterial or viral infection, and the other is to produce bioactive tryptophan catabolites that would serve to suppress T-cell–mediated immune responses against self-antigens, fetal antigens, or allogeneic antigens, in different situations. (J Histochem Cytochem 58:17–28, 2010)