Uncoupling protein-2 prevents neuronal death and diminishes brain dysfunction after stroke and brain trauma

Whereas uncoupling protein 1 (UCP-1) is clearly involved in thermogenesis, the role of UCP-2 is less clear. Using hybridization, cloning techniques and cDNA array analysis to identify inducible neuroprotective genes, we found that neuronal survival correlates with increased expression of Ucp2. In mice overexpressing human UCP-2, brain damage was diminished after experimental stroke and traumatic brain injury, and neurological recovery was enhanced. In cultured cortical neurons, UCP-2 reduced cell death and inhibited caspase-3 activation induced by oxygen and glucose deprivation. Mild mitochondrial uncoupling by 2,4-dinitrophenol (DNP) reduced neuronal death, and UCP-2 activity was enhanced by palmitic acid in isolated mitochondria. Also in isolated mitochondria, UCP-2 shifted the release of reactive oxygen species from the mitochondrial matrix to the extramitochondrial space. We propose that UCP-2 is an inducible protein that is neuroprotective by activating cellular redox signaling or by inducing mild mitochondrial uncoupling that prevents the release of apoptogenic proteins.     

Effects of the herbivorous minnow,southern redbelly dace (<Emphasis Type="Italic">Phoxinus erythrogaster</Emphasis>), on stream productivity and ecosystem structure

We used field and mesocosm experiments to measure effects of southern redbelly dace (Phoxinus erythrogaster), a grazing minnow, on stream ecosystem structure and function. Ecosystem structure was quantified as algal filament length, algal biomass, size distribution of particulate organic matter (POM), algal assemblage structure, and invertebrate assemblage structure, whereas ecosystem function was based on gross and net primary productivity. Our experiments showed that moderate densities of Phoxinus temporarily reduced mean algal filament length and mean size of POM relative to fishless controls. However, there was no detectable effect on algal biomass or ecosystem primary productivity. Several factors could explain the lack of effect of Phoxinus on primary productivity including increased algal production efficiency in grazed treatments or increased grazing by other organisms in fishless treatments. The inability of Phoxinus to reduce algal biomass and system productivity contrasts with experimental results based on other grazing minnows, such as the central stoneroller (Campostoma anomalum), and questions the generality of grazer effects in stream ecosystems. However, environmental venue and the spatial and temporal scale of ecosystem measurements can greatly influence the outcome of these experiments. Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users. The experiments described herein comply with the current laws of the country in which the experiments were performed.     

Spatial Variation in δ15N and δ13C Isotopes in the San Juan River, New Mexico and Utah: Implications for the Conservation of Native Fishes

Synopsis Spatial patterns of resource use by small-bodied fishes in the San Juan River were examined using stable isotopes. Using δ¹⁵N of fishes as an index of trophic position, our data suggest both native and non-native fishes primarily consumed macro-invertebrates. The δ¹³C of these fishes further suggested a detritus-based food web, from which most species fed on chironomids in low-velocity habitats. A two-way ANOVA revealed a significant interaction between trophic level of fish species and longitudinal position in the river. This interaction was primarily attributed to a decline in trophic level of non-native red shiner Cyprinella lutrensis, relative to other species, in upstream reaches of the river. In addition, ANCOVA results suggest trophic position of fishes was dependent on channel type (primary vs. secondary), as there was less variability in resource use in secondary channels. These data provided a spatial framework of trophic interactions that can be used to predict the outcome of management actions. Overall, we confirmed high overlap in resource used between native and non-native fishes. However, spatial variation in trophic interactions both longitudinally and laterally in the river present a challenge to resource managers attempting to managing entire river systems.     

Effects of Barriers and Thermal Refugia on Local Movement of the Threatened Leopard Darter, Percina pantherina

Local, short-term dispersal by the U.S. federally-threatened leopard darter, Percina pantherina, was examined in the field and in the laboratory to assess the possible effects of natural versus man-made barriers on movement. Mark-resight studies were conducted in two summers at sites in the Glover River (southeastern Oklahoma, U.S.A.). At one site, patches of 'preferred' habitat were separated by a natural riffle; at the other site, by a low-water road crossing with culverts. At the Natural Riffle site, darters moved downstream across the riffle, but also moved upstream into deeper water when water temperatures exceeded 29°C in the `preferred' habitat. Use of deeper, cooler waters by this species in late summer suggests that thermal refugia may be important habitats for the long-term management of leopard darters. At the Road Crossing site, all documented movement was in a downstream direction, and at least two darters traversed culverts in the low-water bridge. Laboratory studies of movement across several types of culverts suggested that culverts significantly decrease the probability of movement among habitat patches.     

Bombyx mori silk fibroin liquid crystallinity and crystallization at aqueous fibroin-organic solvent interfaces.

A banded morphology has been observed for Bombyx mori silk fibroin films obtained from an aqueous hexane interface; the period of the banding is approximately 1 microm. Morphology and diffraction from different regions of the banded structure suggest that it is a free surface formed by a cholesteric liquid crystal. Truncated hexagonal lamellar crystallites of B. mori silk fibroin have been observed in films formed in the surface excess layer of fibroin at the interface between aqueous fibroin and hexane or chloroform. Based on initial crystallographic evidence, a three-fold helical conformation has been ascribed to the fibroin chains within the crystals. The chain conformation and crystalline habit appear to be similar to the silk III structure previously observed at the air-water interface (Valluzzi R, Gido SP. Biopolymers 1997;42:705-717; Valluzzi R, Gido S, Zhang W, Muller W, Kaplan D. Macromolecules 1996;29:8606-8614) but the crystalline packing is different. Diffraction data obtained for the crystallites are similar to diffraction behavior for a collagen-like model peptide. Diffraction patterns obtained from crystallized regions of the banded morphology can be indexed using the same unit cell as the hexagonal lamellar crystallites. Surfactancy of fibroin and subsequent aggregation and mesophase formation may help to explain the liquid crystallinity reported for silk, which is long suspected to play a role in the biological silk spinning process (Valluzzi R, Gido SP. Biopolymers 1997;42:705-717; Willcox, P. J.; Gido, SP, Muller W, Kaplan DL. Macromolecules 1996:29:5106-5110; Magoshi J, Magoshi Y, Nakamura S. In: Kaplan D, Adams W, Farmer B, Viney C, editors, Mechanism of Fiber Formation of Silkworm. Washington, DC: American Chemical Society 1994:292-310; Magoshi J, Magoshi Y, Nakamura S. J Appl Polym Sci Appl Polym Symp 1985;41:187-204; Magoshi J, Magoshi Y, Nakamura S. Polym Commun 1985;26:309.).     

Predictability of littoral-zone fish communities through ontogeny in Lake Texoma,Oklahoma-Texas,USA

Synopsis We sampled larval, juvenile and adult fishes from littoral-zone areas of a large reservoir (Lake Texoma, Oklahoma-Texas) (1) to characterize environmental factors that influenced fish community structure, (2) to examine how consistent fish–environment relationships were through ontogeny (i.e., larval vs. juvenile and adult), and (3) to measure the concordance of larval communities sampled during spring to juvenile and adult communities sampled at the same sites later in the year. Larval, juvenile and adult fish communities were dominated by Atherinidae (mainly inland silverside, Menidia beryllina) and Moronidae (mainly juvenile striped bass, Morone saxatilis) and were consistently structured along a gradient of site exposure to prevailing winds and waves. Larval, juvenile and adult communities along this gradient varied from atherinids and moronids at highly exposed sites to mostly centrarchids (primarily Lepomis and Micropterus spp.) at protected sites. Secondarily, zooplankton densities, water clarity, and land-use characteristics were related to fish community structure. Rank correlation analyses and Mantel tests indicated that the spatial consistency and predictability of fish communities was high as larval fishes sampled during spring were concordant with juvenile and adult fishes sampled at the same sites during summer and fall in terms of abundance, richness, and community structure. We propose that the high predictability and spatial consistency of littoral-zone fishes in Lake Texoma was a function of relatively simple communities (dominated by 1–2 species) that were structured by factors, such as site exposure to winds and waves, that varied little through time.     

Phase behavior and hydration of silk fibroin

The osmotic stress method was applied to study the thermodynamics of supramolecular self-assembly phenomena in crystallizable segments of Bombyx mori silkworm silk fibroin. By controlling compositions and phases of silk fibroin solution, the method provided a means for the direct investigation of microscopic and thermodynamic details of these intermolecular interactions in aqueous media. It is apparent that as osmotic pressure increases, silk fibroin molecules are crowded together to form silk I structure and then with further increase in osmotic pressure become an antiparallel beta-sheet structure, silk II. A partial ternary phase diagram of water-silk fibroin-LiBr was constructed based on the results. The results provide quantitative evidence that the silk I structure must contain water of hydration. The enhanced control over structure and phase behavior using osmotic stress, as embodied in the phase diagram, could potentially be utilized to design a new route for water-based wet spinning of regenerated silk fibroin.     

Comparative riverscape genetics reveals reservoirs of genetic diversity for conservation and restoration of Great Plains fishes

We used comparative landscape genetics to examine the relative roles of historical events, intrinsic traits and landscape factors in determining the distribution of genetic diversity of river fishes across the North American Great Plains. Spatial patterns of diversity were overlaid on a patch‐based graphical model and then compared within and among three species that co‐occurred across five Great Plains watersheds. Species differing in reproductive strategy (benthic vs. pelagic‐spawning) were hypothesized to have different patterns of genetic diversity, but the overriding factor shaping contemporary patterns of diversity was the signature of past climates and geological history. Allelic diversity was significantly higher at southern latitudes for Cyprinella lutrensis and Hybognathus placitus, consistent with northward expansion from southern Pleistocene refugia. Within the historical context, all species exhibited lowered occupancy and abundance in heavily fragmented and drier upstream reaches, particularly H. placitus; a pelagic‐spawning species, suggesting rates of extirpation have outpaced losses of genetic diversity in this species. Within most tributary basins, genetically diverse populations of each species persisted. Hence, reconnecting genetically diverse populations with those characterized by reduced diversity (regardless of their position within the riverine network) would provide populations with greater genetic and demographic resilience. We discuss cases where cross‐basin transfer may be appropriate to enhance genetic diversity and mitigate negative effects of climate change. Overall, striking similarities in genetic patterns and in response to fragmentation and dewatering suggest a common strategy for genetic resource management in this unique riverine fish assemblage.     

River network architecture,genetic effective size and distributional patterns predict differences in genetic structure across species in a dryland stream fish community

Dendritic ecological network (DEN) architecture can be a strong predictor of spatial genetic patterns in theoretical and simulation studies. Yet, interspecific differences in dispersal capabilities and distribution within the network may equally affect species’ genetic structuring. We characterized patterns of genetic variation from up to ten microsatellite loci for nine numerically dominant members of the upper Gila River fish community, New Mexico, USA. Using comparative landscape genetics, we evaluated the role of network architecture for structuring populations within species (pairwise F_ST) while explicitly accounting for intraspecific demographic influences on effective population size (N_e). Five species exhibited patterns of connectivity and/or genetic diversity gradients that were predicted by network structure. These species were generally considered to be small‐bodied or habitat specialists. Spatial variation of N_e was a strong predictor of pairwise F_ST for two species, suggesting patterns of connectivity may also be influenced by genetic drift independent of network properties. Finally, two study species exhibited genetic patterns that were unexplained by network properties and appeared to be related to nonequilibrium processes. Properties of DENs shape community‐wide genetic structure but effects are modified by intrinsic traits and nonequilibrium processes. Further theoretical development of the DEN framework should account for such cases.     

Ecosystem Processes Performed by Unionid Mussels in Stream Mesocosms: Species Roles and Effects of Abundance

Unionid mussels are a guild of freshwater, sedentary filter-feeders experiencing a global decline in both species richness and abundance. To predict how these losses may impact stream ecosystems we need to quantify the effects of both overall mussel biomass and individual species on ecosystem processes. In this study we begin addressing these fundamental questions by comparing rates of ecosystem processes for two common mussel species, Amblema plicata and Actinonaias ligamentina, across a range of abundance levels and at two trophic states (low and high productivity) in stream mesocosms. At both low and high productivity, community respiration, water column ammonia, nitrate, and phosphorus concentrations, and algal clearance rates were all linearly related to overall mussel biomass. After removing the effects of biomass with ANCOVA, we found few differences between species. In a separate series of experiments, nutrient excretion (phosphorus, ammonia, and molar N:P) and biodeposition rates were only marginally different between species. For the species studied here, functional effects of unionids in streams were similar between species and linearly related to biomass, indicating the potential for strong effects when overall mussel biomass is high and hydrologic residence times are long.