Role of water temperature in the regulation of water intake.

Performed 3 experiments on small groups (n = 2-6) of thirsty Carworth female albino rats. Cool water suppressed water intake. The suppression was apparent from the 1st min of drinking. Suppression occurred for both short (20-min) and long (100-min) daily drinking sessions, and occurred whether the water was available from a sipper tube or a bowl. When cellular hydration was delayed by giving Ss isotonic saline instead of water, the suppression by cooling was enhanced. Cool-water suppression of water intake appears to be a short-latency satiety mechanism that anticipates cellular and extracellular hydration. (27 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

River-Ice Ecology.?II: Biological Aspects

River ice is an integral and important component of the flow regime in cold-regions environments. As demonstrated in a companion paper, it can significantly affect many of the hydrologic, geomorphic, and chemical characteristics of a river. Building on such a physical template, this paper reviews the related biological effects at all stages of winter ice cover, including the period of autumn cooling, initial freeze-up, main winter, and breakup. Special focus is placed on the role of ice in seasonal movements and avoidance behavior of fish and benthic organisms, the creation of unique in-channel and riparian habitats, the modification of aquatic and floodplain vegetation, and some river-ecology theories, including disturbance ecology and flood-pulse theory. Included is a comprehensive reference list, the most complete ever assembled on this subject.     

Fowl adenovirus recombinant expressing VP2 of infectious bursal disease virus induces protective immunity against bursal disease

The right hand end Nde I fragment 3 (90.8-100 map units) of the fowl adenovirus serotype 10 (FAV-10) was characterised so as to allow the location of an insertion site for recombinant vector construction. Infectious bursal disease virus (IBDV) VP2 gene from the Australian classical strain 002/73, under the control of the FAV-10 major late promoter/leader sequence (MLP/LS) was inserted into a unique Not I site that was generated at 99.5 map units. This recombinant virus was produced without deletion of any portion of the FAV-10 genome. When administered to specific pathogen free (SPF) chickens intravenously, intraperitoneally, subcutaneously or intramuscularly, it was shown that the FAV-10/VP2 recombinant induced a serum VP2 antibody response and protected chickens against challenge with IBDV V877, an intermediate virulent classical strain. Birds were not protected when the recombinant was delivered via the conjunctival sac.     

Inhibition of mouse acetylcholinesterase by fasciculin: crystal structure of the complex and mutagenesis of fasciculin

Animal models of autoimmune diseases have been instrumental in advancing our understanding of autoimmunity in humans. Collagen-induced arthritis in mice is an autoimmune disease model of rheumatoid arthritis, which is MHC class II restricted and CD4 T cell dependent. To better understand the fundamental role of T cells in arthritis, we have generated a transgenic mouse carrying the rearranged Valpha11.1 and Vbeta8.2 TCR chain genes isolated from a type II collagen (CII)-specific T cell hybridoma. Cell surface analysis indicated that Vbeta8.2 chain was expressed on the surface of nearly all peripheral T cells. Analysis of T cell subsets in transgenic mice revealed a profound skewing in peripheral T cells towards the CD4 population. Although peripheral T cells were not tolerant to CII and responded to CII stimulation in vitro, transgenic mice did not develop spontaneous arthritis. However, a rapid onset of arthritis with severe clinical signs was detected in transgenic mice after immunization with CII in complete Freund's adjuvant. Histological analysis of inflamed joints showed a great resemblance to arthritic joints in man. This unique transgenic mouse model provides valuable insights into the mechanism of arthritis and into potential specific immune interventions.     

E-cadherin expression can alter the specificity of gap junction formation

Specificity of gap junction formation produces communication compartments, groups of cells joined to each other by gap junctions (homologous communication) but more rarely to cells in adjacent compartments (heterologous communication). Specificity of junction formation can be studied in mixed cultures of different cell types. In these model systems, compartmentation is often associated with sorting out, a process that produces separate domains of the different cells. The borders of the physically distinct domains correlate with the functional boundaries of the communication compartments. Compartments have also been observed in vivo where they are believed to play a role in separating groups of cells following different differentiation pathways. Two classes of cell surface molecule, connexins and cell adhesion molecules, are candidates for a role in the control of specificity. A representative of each class appears to be necessary for gap junction formation and both are expressed in a tissue specific manner. We have shown that mixed cultures of rat epithelial (BRL) cells and rat (BICR) fibroblasts show specificity, form communication compartments and sort out. Both cell types express the same connexin (connexin 43) but different cell adhesion molecules (BRL, P-cadherin and 125-kDa N-cadherin; BICR, 140-kDa N-cadherin). Transfection of both cell types with E-cadherin results in a 10-fold increase in heterologous communication. These data suggest that E-cadherin plays a role in the control of specificity of gap junction formation.     

A review of hydroecological results of the Northern River Basins Study,Canada. Part 1. Peace and Slave rivers

During the early 1990s a multi‐component research programme was initiated by the Northern River Basins Study (NRBS) in Canada to answer the question: How does and how could flow regulation affect the aquatic ecosystem? Research focused on the major headwaters of the Mackenzie River, the Peace and Slave rivers, which became regulated in 1968 by the W.A.C. Bennett Dam in the Rocky Mountains. The lack of knowledge about the hydroecology of large northern rivers as well as a paucity of data for this relatively isolated basin required that studies be undertaken to assess how flow regulation had modified the physical template of this system. Research focused on quantifying the regulation effects on the flow regime, ice conditions, fluvial geomorphology and riparian vegetation of the Peace and Slave rivers and the Slave River Delta. Results of the NRBS studies indicate that regulation of the Peace River has shifted the pattern of seasonal flows and damped flow extremes creating a less variable annual regime. Increased winter releases from the reservoir have virtually eliminated the formation of a complete winter ice cover for a significant distance below the dam and delayed ice‐cover formation farther downstream. Higher ice levels that accompany increased winter flows are thought to affect the frequency and magnitude of ecologically important ice‐induced floods that occur during the spring. Although more difficult to link solely to the effects of flow regulation, pronounced morphologic and vegetation changes have been observed along the Peace River, including channel narrowing via the abandonment of secondary/backwater channels and in‐channel shoaling along the lower reaches. Vegetation succession has been especially evident on abandoned bar surfaces. Morphological changes were also observed in the Slave River Delta, particularly along the ecologically sensitive outer margin of the delta. Copyright © 2002 Environment Canada. Published by John Wiley & Sons, Ltd.     

Effects of projected climate on the hydrodynamic and sediment transport regime of the lower Athabasca River in Alberta,Canada

The potential effects of climate change on the hydrodynamic and sediment transport regime of the lower Athabasca River (LAR) in Alberta, Canada, is investigated. Future climate projections for the region suggest a potential increase in mean air temperature and precipitation by about 2.8–7.1 °C and 8–25%, respectively, by the end of this century. Implications of these climatic changes on the hydrologic regime of the LAR are found to be significant with spring flows expected to increase by about 11–62% and 26–71% by the end of the century for a moderate and high emissions scenarios respectively with corresponding decreases in summer flows. The effects of such changes are examined using the MIKE‐11 hydrodynamic and sediment transport modelling system with inflow boundary conditions corresponding to the changing hydro‐climatic regime. The results suggest that there will be an overall increase in flow velocity, water level, and suspended sediment concentration and transport for most seasons except in the summer months when there may be some decreases. The projected changes in suspended sediment concentration will result in an overall increase in mean annual sediment load in the LAR and to the Peace Athabasca Delta by over 50% towards the latter part of this century (2080s) compared with the 1980s base‐line period. Implications of such potential changes in the transport characteristics of the river system to the mobilization and transport of various chemical constituents and their effects on the region's aquatic ecosystems are subjects of other ongoing investigations.     

Restoring Ice-jam Floodwater to a Drying Delta Ecosystem

Abstract

Overbank flooding is essential to the ecological health of riparian landscapes, particularly river deltas. One of the world's largest freshwater deltas, the Peace-Athabasca Delta (PAD) in northern Canada, has experienced a series of wetting and drying cycles because of inter-annual variations in flooding. Recent research has found that most of the major floods affecting this system are produced by spring ice jams. For approximately two decades, however, the combination of climatic and flow-regulation effects precluded significant ice-jam flooding of the PAD. Resultant drying caused major changes to the ecology of the delta and led to the evaluation of a number of methods to restore water flows. Since most of delta is contained within a national park (Wood Buffalo National Park), a major goal was to employ non-structural measures. Hence, in an effort to manage the water problems of this delta, the final report of a multi-agency “Northern River Basins Study” made the recommendation that the spring flow-release strategy of the upstream hydro electric reservoir be modified to increase the probability of ice-jam flooding near the PAD. This was to be conducted in years when downstream hydrometeorological conditions (snowpack magnitude and ice-cover strength) appeared conducive to ice-jam formation. Such favourable conditions developed in the spring of 1996, a natural ice jam began to develop, and regulated flows were increased to assist in potential flooding. As a result, the PAD experienced its first major flood in over 20 years. This paper reviews the hydrometeorological conditions that led to the ice-jam formation, compares the conditions to historical events, analyzes the spatial extent of the flood, and evaluates the effectiveness of the flow release.