Evidence for a Functional Interaction between Integrins and G Protein-activated Inward Rectifier K+ Channels

Heteromultimeric G protein-activated inward rectifier K+ (GIRK) channels, abundant in heart and brain, help to determine the cellular membrane potential as well as the frequency and duration of electrical impulses. The sequence arginine-glycine-aspartate (RGD), located extracellularly between the first membrane-spanning region and the pore, is conserved among all identified GIRK subunits but is not found in the extracellular domain of any other cloned K+ channels. Many integrins, which, like channels, are integral membrane proteins, recognize this RGD sequence on other proteins, usually in the extracellular matrix. We therefore asked whether GIRK activity might be regulated by direct interaction with integrin. Here, we present evidence that mutation of the RGD site to RGE, particularly on the GIRK4 subunit, decreases or abolishes GIRK current. Furthermore, wild-type channels can be co-immunoprecipitated with integrin. The total cellular amount of expressed mutant GIRK channel protein is the same as the wild-type protein; however, the amount of mutant channel protein that localizes to the plasma membrane is decreased relative to wild-type, most likely accounting for the diminished GIRK current detected. GIRK channels appear to bind directly to integrin and to require this interaction for proper GIRK channel membrane localization and function

Falling Calcium Levels Are Harming Freshwater Animals

Crayfish are especially vulnerable to falling levels of calcium in eastern North American lakes. This poses a threat to the ecosystems in which crayfish and other crustaceans reside.York's Knowledge Mobilization Unit provides services and funding for faculty, graduate students, and community organizations seeking to maximize the impact of academic research and expertise on public policy, social programming, and professional practice. It is supported by SSHRC and CIHR grants, and by the Office of the Vice-President Research & Innovation. [email protected] www.researchimpact.c

EFFECT OF THE DOMAIN GEOMETRY ON THE EXISTENCE OF MULTIPEAK SOLUTIONS FOR AN ELLIPTIC PROBLEM

Abstract. In this paper, we construct multipeak solutions for a singularly perturbed Dirichlet problem. Under the conditions that the distance function d(x, ∂Ω) has k isolated compact connected critical sets T1,..., Tk satisfying d(x, ∂Ω) = cj = const., for all x ∈ Tj, mini̸=j d(Ti, Tj)> 2 max1≤j≤k d(Tj, ∂Ω), and the critical group of each critical set Ti is nontrivial, we construct a solution which has exactly one local maximum point in a small neighbourhood of Ti, i = 1,..., k. (1.1

What have we learned about ecological recovery from liming interventions of acid lakes in Canada and Italy?

The idea of launching another special issue of the Journal of limnology on Lake Orta was born in 2014, on the 25th anniversary of its liming intervention, during an International symposium on Lake Orta organized and hosted by the Pallanza Institute (http://www.ise.cnr.it/vb). The conference did not simply celebrate the past. While the liming of Lake Orta was undoubtedly a great national and international success, the speakers at the conference, instead sought to enlarge and deepen knowledge of patterns and mechanisms of lake ecosystem responses to the water quality improvements, or chemical recovery, that accompanied Lake Orta\u27s liming

Mechanisms underlying recovery of zooplankton in Lake Orta after liming

The goal of this study was to improve the understanding of the large-scale mechanisms underlying the recovery of the zooplankton of Lake Orta from historical contamination, following reduced input of ammonia and metals and the subsequent 1989/90 liming intervention. The industrial pollution had been severe and long-lasting (1929-1990). Zooplankton biodiversity has improved, but most of the new taxa appearing in our counts are rotifers, while many calanoids and the large cladoceran predators (Bythotrephes and Leptodora) that are common in the nearby Lake Maggiore, were still absent from Lake Orta 17 years after liming. To aid understanding of the large-scale mechanisms controlling changes in annual richness, we assessed the annual persistence (P) of Crustacea and Rotifera taxa as an estimator of whether propagules that survived introduction, as result of the natural recolonization process, also thrived. We found that the rate of introduction of zooplankton colonists and their persistence in the water column of Lake Orta changed from 1971 to 2007. New rotifer taxa appeared in the lake after the mid-1980s, when discharge of toxic substances decreased, but their annual persistence was low (P<0.5) until the turn of the century. The numerical values of rotifer and crustacean persistence in Lake Orta were unexpectedly high in 2001 and 2007 (0.55 and 0.72 for rotifers, 0.85 and 0.86 for crustacean, respectively), much higher than in limed lakes in Sudbury, Canada, and in adjacent Lake Maggiore. We hypothesize this could be related to the lack of Cladoceran predators and zooplanktivorous fish in the pelagic waters of Lake Orta

Past, present and future of the fish community of Lake Orta (Italy), one of the world\u27s largest acidified lakes

Since 1926, the fishes in Lake Orta, one of Italy\u27s deepest natural lakes, were heavily damaged by profundal hypoxia and acidification linked to oxidation of ammonia from industrial effluents and by industrial metal pollution. Of the original 28 fish species, only perch survived the lake\u27s contamination. Recently, the water quality of the lake has been largely restored by reductions in pollutant inputs, and a massive liming intervention. These interventions restored fish habitat, but it is unclear whether the recent fish reintroductions were successful, and the present status of the fish community is unknown. Here we reviewed the history of the Lake Orta fish assemblage. Using an extensive 2014 sampling campaign, we compared the present fish community to both its pre-pollution composition and to the assemblages of nearby un-polluted, but otherwise similar lakes, Lake Mergozzo and Lake Maggiore. While nearshore fish density now appears normal in lake Orta, the open water community remains impoverished both in numbers and in species. Epilimnetic and hypolimnetic benthic nets were dominated by perch and roach in all the three lakes, but the catch of pelagic nets differed among lakes. Perch (Perca fluviatilis), rudd (Scardinius erythrophthalmus) and brown trout (Salmo trutta) dominated in Lake Orta while shad (Alosa fallax lacustris) and coregonids (Coregonus spp.) were dominant in the open waters of the other two lakes, but missing from Lake Orta. Many fully or partially migratory species, including marble trout (Salmo trutta marmoratus), eel (Anguilla Anguilla) and barbel (Barbus plebejus) were also missing from Lake Orta, a consequence of their initial extirpation and blocked re-colonization routes along the River Strona. In comparison with both pre-pollution and contemporary reference data, the fish community of Lake Orta has not been rehabilitated. The recovery of the littoral community is complete, but cold water species such as burbot (Lota lota), Arctic charr (Salvelinus alpinus) and bullhead (Cottus gobio) are still lacking, as are the pelagic zooplanktivores European whitefish (Coregonus lavaretus) and shad, which dominate offshore communities in the reference lakes, as they did a century ago in Lake Orta. To propose priorities for fish community rehabilitation in Lake Orta, we categorized the conservation, ecological and fishing values of each missing fish species in the lake, and evaluated the cost and probability of success of the needed intervention for each species. This analysis indicated that rehabilitation of shad and European whitefish should receive highest priority

Long-term research to understand impact of perturbations on lakes: the example of Lake Maggiore

Perturbations linked to the direct and indirect impacts of human activities during the so-called Anthropocene, affect the structure and functioning of lake ecosystems to varying degrees. To understand the patterns and mechanisms of these anthropogenic effects and the extent to which they may drive irreversible changes in ecosystem services, long-term research is required. Studies on the long-term dynamics of plankton may be particularly useful for large and deep lakes whose overall productivity is dominated by pelagic processes. In the open-waters of such lakes, planktonic organisms link and interact with both abiotic and biotic compartments. Here we will analyze 60 years of data on the plankton of the large, deep, subalpine, Lake Maggiore, tracing changes in the pelagic food web which occurred during different phases of the lake\u27s recent evolution. We will document short- to- medium response times by different trophic levels, from microbes, to primary producers and secondary consumers. We will revisit results of past studies based on contemporary and paleolimnological studies and present new analyses to: i) identify any tipping points of the lake trophic evolution, ii) discern effects of recent climatic change, iii) quantify whether inter-annual variability has changed perhaps in responses to changes in thermal stratification regime and warming. By supplementing structural with functional descriptions of long term changes in phyto- and zooplankton communities, we aim to test competing mechanisms underpinning the decade-scale changes we observed