Excessive Na+/H+ Exchange in Disruption of Dendritic Na+ and Ca2+ Homeostasis and Mitochondrial Dysfunction following in Vitro Ischemia

Neuronal dendrites are vulnerable to injury under diverse pathological conditions. However, the underlying mechanisms for dendritic Na⁺ overload and the selective dendritic injury remain poorly understood. Our current study demonstrates that activation of NHE-1 (Na⁺/H⁺ exchanger isoform 1) in dendrites presents a major pathway for Na⁺ overload. Neuronal dendrites exhibited higher pH_i regulation rates than soma as a result of a larger surface area/volume ratio. Following a 2-h oxygen glucose deprivation and a 1-h reoxygenation, NHE-1 activity was increased by ∼70–200% in dendrites. This elevation depended on activation of p90 ribosomal S6 kinase. Moreover, stimulation of NHE-1 caused dendritic Na⁺_i accumulation, swelling, and a concurrent loss of Ca²⁺_i homeostasis. The Ca²⁺_i overload in dendrites preceded the changes in soma. Inhibition of NHE-1 or the reverse mode of Na⁺/Ca²⁺ exchange prevented these changes. Mitochondrial membrane potential in dendrites depolarized 40 min earlier than soma following oxygen glucose deprivation/reoxygenation. Blocking NHE-1 activity not only attenuated loss of dendritic mitochondrial membrane potential and mitochondrial Ca²⁺ homeostasis but also preserved dendritic membrane integrity. Taken together, our study demonstrates that NHE-1-mediated Na⁺ entry and subsequent Na⁺/Ca²⁺ exchange activation contribute to the selective dendritic vulnerability to in vitro ischemia.     

Potential respiration is a better respiratory predictor than biomass in young Artemia salina

These experiments test whether respiration can be predicted better from biomass or from potential respiration, a measurement of the mitochondrial and microsomal respiratory electron transport systems. For nearly a century Kleiber's law or a similar precursor have argued the importance of biomass in predicting respiration. In the last decade, a version of the Metabolic Theory of Ecology has elaborated on Kleiber's Law adding emphasis to the importance of biomass in predicting respiration. We argue that Kleiber's law works because biomass packages mitochondria and microsomal electron transport complexes. On a scale of five orders of magnitude we have shown previously that potential respiration predicts respiration as well as biomass in marine zooplankton. Here, using cultures of the branchiopod, Artemia salina and on a scale of less than 2 orders of magnitude, we investigated the power of biomass and potential respiration in predicting respiration. We measured biomass, respiration and potential respiration in Artemia grown in different ways and found that potential respiration (Ф) could predict respiration (R), both in µlO₂ h⁻¹ (R = 0.924Φ + 0.062, r² = 0.976), but biomass (as mg dry mass) could not (R = 27.02DM + 8.857, r² = 0.128). Furthermore the R/Ф ratio appeared independent of age and differences in the food source.     

Zinc-induced Neurotoxicity Mediated by Transient Receptor Potential Melastatin 7 Channels

Transient receptor potential melastatin 7 (TRPM7) channels are novel Ca²⁺-permeable non-selective cation channels ubiquitously expressed. Activation of TRPM7 channels has been shown to be involved in cellular Mg²⁺ homeostasis, diseases caused by abnormal magnesium absorption, and in Ca²⁺-mediated neuronal injury under ischemic conditions. Here we show strong evidence suggesting that TRPM7 channels also play an important role in cellular Zn²⁺ homeostasis and in Zn²⁺-mediated neuronal injury. Using a combination of fluorescent Zn²⁺ imaging, small interfering RNA, pharmacological analysis, and cell injury assays, we show that activation of TRPM7 channels augmented Zn²⁺-induced injury of cultured mouse cortical neurons. The Zn²⁺-mediated neurotoxicity was inhibited by nonspecific TRPM7 blockers Gd³⁺ or 2-aminoethoxydiphenyl borate, and by knockdown of TRPM7 channels with small interfering RNA. In addition, Zn²⁺-mediated neuronal injury under oxygen-glucose deprivation conditions was also diminished by silencing TRPM7. Furthermore, we show that overexpression of TRPM7 channels in HEK293 cells increased intracellular Zn²⁺ accumulation and Zn²⁺-induced cell injury, while silencing TRPM7 by small interfering RNA attenuated the Zn²⁺-mediated cell toxicity. Thus, TRPM7 channels may represent a novel target for neurological disorders where Zn²⁺ toxicity plays an important role.     

Fuzzy-Sets Approach to Noise Impact Assessment (7 pp)

Background, Aims and Scope Noise impacts are rarely assessed in Life Cycle Assessment (LCA), probably due to lack of data, to the difficulty of setting up an appropriate assessment method including relevant uncertainties and vagueness and to their site-dependent nature. The evaluation, as well as for odour, cultural and aesthetic impacts, seems to be closely related to human judgements and perception based. Although fuzzy-sets have been developed for this purpose since the late '60s and their usefulness has been proven by successful applications, noise impact assessment approaches have been essentially crisp so far. The aim of this paper is to present a method for noise impact assessment based on fuzzy sets with an application to a simple example. Methods The fuzzy noise impact assessment involves: 1) the quality assessment of the site concerned by the noise impact before the occurrence of noise emissions; quality is expressed by a crisp (i.e. non-fuzzy) function depending on variables (the so-called 'primitives'), which are relevant for the evaluation (e.g. the population density, the type of land use,...); 2) the fuzzy representation of the primitives, e.g. their evaluation by means of linguistic variables (such as 'the population density is high') and by fuzzy numbers; 3) the fuzzy representation of the quality, by fuzzifying the crisp function defined in 1) and 4) the fuzzy representation of the noise impact. In the example, the noise impacts of three processes of coal mining and combustion are assessed. Results and Discussion The application example proved the operationability of the method. Primitives and noise impact assessment results are represented by fuzzy numbers and intervals that are more informative than crisp numbers for the interpretation of results The quality and impact assessment results obtained seem to be coherent with the nature of the processes involved and of the variables characterizing them. Conclusion and Outlook Fuzzy intervals and numbers could be more informative and closer to human judgements and perceptions than crisp numbers are, thus improving the pertinence and the interpretation of the results. Despite the increase in sophistication and the fact that the representation of the variables involved in calculations should be developed further (e.g. on the basis of consensus gained in an expert panel), the fuzzy approach seems to be promising for the assessment of noise impacts in LCA.     

Environmental Impacts of Wild Caught Cod and Farmed Salmon - A Comparison with Chicken (7 pp)

Goal, Scope and Background The objective of this study was to assess environmental impacts of Norwegian cod fishing and salmon farming and compare these with chicken farming in order to find reference levels for environmental performance and identify problem areas and potentials for improvements. Methods A Life Cycle Screening following the production of 0.2 kg fillets as a functional unit through the respective food chains is performed for all 3 products. The analysis is partly quantitative and qualitative focusing on energy use, antifouling and land use impacts. Case studies are performed to investigate potentials for improvements within the fisheries and aquaculture industry. Results and Conclusions It can be concluded that the fishing phase for the cod and the feeding phase for both salmon and chicken dominate for all environmental impacts considered. Chicken is most energy effective followed by salmon and cod, which are almost on the same level. The area of sea floor affected by bottom trawling is around 100 times larger than the land area needed to produce the chicken feed for production of the 0.2 kg fillet. - The case studies show potentials for improvement of environmental performance, both for salmon farming and cod fishing, especially when it comes to energy use. The environmental impacts on the sea floor imposed by bottom trawling are not fully explored, but based on the precautionary principle a reasonable conclusion is that bottom trawls with less impact on the sea floor should be developed. Recommendation and Perspective LCA methods have initially been developed for land based industrial applications. More effort should be given to adapt these to fishing applications in order to obtain more accurate assessment of environmental impacts from seafood products. It is recommended to put more emphasis in finding improved indicators for impacts imposed by over-fishing, fuel emission from combustion at sea, use of antifouling and seafloor ecosystem disturbance.     

The Impact of the Weed Chrysanthemoides monilifera ssp. rotundata on Coastal Leaf Litter Invertebrates

In coastal areas of Australia, there are extensive infestations of the environmental weed Chrysanthemoides monilifera ssp. rotundata (bitou bush). This study looked at the impact of long-term infestations on the abundance and assemblage composition of leaf litter invertebrates. Assemblages were compared in weed infested and native shrublands along the New South Wales coastline over 12 months. The total abundance was not significantly reduced in the weedy habitat but the abundance of mites, thrips, spiders, ants, and centipedes was reduced at many sites. The invertebrate assemblages also differed between habitats, with the C. monilifera supporting a lower diversity of beetles. However, the millipedes, amphipods, earthworms, pseudoscorpions and isopods appeared to respond positively to the invasion, occurring in higher abundance and detected more frequently in the weedy areas. This has been partially attributed to a change in microclimate within the C. monilifera infestations. It is generally moister and darker, which these invertebrates tend to prefer. Secondly, C. monilifera produces less leaf litter of higher quality, and possibly higher palatability than the native sclerophyllous vegetation, which may encourage species that consume litter.     

Have the Harmful Effects of Introduced Rats on Islands been Exaggerated?

Introduced rats are now being eradicated from many islands. Increasingly, these eradications are contested by activists claiming moral, legal, cultural, historic or scientific reasons and poorly documented evidence of effects. We reviewed the global literature on the effects of rats on island flora and fauna. We then used New Zealand as a case study because of its four-decade history of rat eradications and many detailed and innovative studies of how rats affect native species. These include use of exclosures, local manipulations of rat populations, video surveillance, and measurements of responses following eradications. The most intensive studies have been on the Pacific rat (Rattus exulans), a small South-East Asian species spread by Polynesians throughout the Pacific. These and the more recently introduced Norway rat (R. norvegicus) and ship (roof) rat (R. rattus) suppress some forest plants, and are associated with extinctions or declines of flightless invertebrates, ground-dwelling reptiles, land birds, and burrowing seabirds. On islands off France, Norway rats are also implicated in declines of shrews. Globally, ship rats were associated with declines or extinctions of the largest number of indigenous vertebrate species (60), including small mammals such as deer mice and bats. Effects of rats on forest trees and seabird populations are sufficiently pervasive to affect ecosystem structure and function. However, the data are patchy. Deficiencies in our knowledge would be reduced by documenting distribution and abundance of indigenous species before and after eradications. Comprehensive measurements of the responses of indigenous species to rat eradications would enable the development of testable models of rat invasion effects.     

Relationship between oral impacts on daily performance and chewing ability among independent elders residing in Daejeon City, Korea

doi: 10.1111/j.1741‐2358.2011.00504.x
Relationship between oral impacts on daily performance and chewing ability among independent elders residing in Daejeon City, Korea Objective: The aim of this study was to assess the association between oral health‐related quality of life (OHRQoL) measured by the oral impacts on daily performances (OIDP) inventory and chewing ability. Methods: The cluster sampling method was used to select a sample of 634 socially active independent community‐dwelling elders. An oral examination was conducted and a questionnaire was implemented. After bivariate comparisons, a multivariable two‐level logistic model was developed for the dichotomous OIDP indicator using the generalised linear mixed model. Results: The mean age of the participants was 74 years and 56.6% were women. Eight percent were edentulous, and the mean number of teeth was 17.7. Overall, 39.3% of participants had one or more oral impacts on daily performance. Elders with chewing ability of 0–49, 50–74 and 75–99% were approximately 120, 20 and seven times more likely to have oral impacts compared with those with full chewing ability, respectively. Elders reporting their oral health as ‘fair’ or ‘better’ were 68% less likely to have oral impacts than those with poor or very poor self‐reported oral health. Conclusion: Among independent elders, amelioration of chewing ability including delivery of appropriate prosthodontic care might independently contribute to improving OHRQoL of elders by improving their physical, psychological and social wellbeing.     

Efflux permease CgAcr3-1 of Corynebacterium glutamicum is an arsenite-specific antiporter

Resistance to arsenite (As(III)) by cells is generally accomplished by arsenite efflux permeases from Acr3 or ArsB unrelated families. We analyzed the function of three Acr3 proteins from Corynebacterium glutamicum, CgAcr3-1, CgAcr3-2, and CgAcr3-3. CgAcr3-1 conferred the highest level of As(III) resistance and accumulation in vivo. CgAcr3-1 was also the most active when everted membranes vesicles from Escherichia coli or C. glutamicum mutants were assayed for efflux with different energy sources. As(III) and antimonite (Sb(III)) resistance and accumulation studies using E. coli or C. glutamicum arsenite permease mutants clearly show that CgAcr3-1 is specific for As(III). In everted membrane vesicles expressing CgAcr3-1, dissipation of either the membrane potential or the pH gradient of the proton motive force did not prevent As(III) uptake, whereas dissipation of both components eliminated uptake. Further, a mutagenesis study of CgAcr3-1 suggested that a conserved cysteine and glutamate are involved in active transport. Therefore, we propose that CgAcr3-1 is an antiporter that catalyzes arsenite-proton exchange with residues Cys129 and Glu305 involved in efflux.     

Humans alter habitat selection of birds on ocean‐exposed sandy beaches

Aim Resource‐selection functions (RSFs) can quantify and predict the density of animal populations across heterogeneous landscapes and are important conservation tools in areas subject to human disturbance. Sandy beach ecosystems have comparatively low habitat heterogeneity and structural relief in the intertidal zone, but intense human use. We aimed to develop predictive RSFs for birds on ocean‐exposed sandy beaches at two spatial scales, 25 ha (local scale) and 250 ha (landscape scale), and to test whether habitat selection of birds that commonly use the surf–beach–dune interface is influenced by the rates of human activities. Location Moreton and North Stradbroke Island, eastern Australia. Methods Avifauna and human activities were mapped on three sandy beaches covering 79 km of coastline for 15 months. Habitat characteristics of the surf–beach–dune interface were derived from remote sensing and ground surveys. RSFs were developed for 12 species of birds at two spatial scales: 25 ha (local scale) and 250 ha (landscape scale). Results  At local (25 ha) and landscape scales (250 ha), dune dimensions and the extent and type of vegetation structure were important predictors of bird density. Adding the frequency of human activities improved the predictive power of RSFs, suggesting that habitat selection of birds on beaches is modified by human use of these environments. Human activities occurred mostly in the mid‐ to lower intertidal zone of the beach, overlapping closely with the preferred habitats of Silver Gulls (Larus novaehollandiae), Pied Oystercatchers (Haematopus longirostris), Red‐capped Plovers (Charadrius ruficapillus) and endangered Little Terns (Sternula albifrons). Main conclusions In addition to demonstrating the appropriateness of RSFs to the surf–beach–dune interface, our results stress the need for systematic conservation planning for these ecosystems, where ecological values have traditionally been subsidiary to the maintenance of sand budgets and erosion control.