Is there an influence of historical events on contemporary fish species richness in rivers? Comparisons between Western Europe and North America

Freshwater fish species richness on 132 West European and North American rivers is analysed using eleven variables related to contemporary ecology (nine) and history (two). This is done in order to examine the relative and joint effects of both historical and ongoing processes on the contemporary richness of these two regional fish faunas. Relationships are quantified by simple and stepwise multiple regression procedures. Species-area curves are presented for the fish faunas within both continents. We show that ecological factors statistically explain most of the variation in freshwater fish species richness for both continents. Effects of historical factors are shown to be statistically significant, but add only a little to the variance already explained by ecological factors. Our analyses further indicate that rivers (which flow directly into the ocean) support fewer species of fish than do similarly sized tributaries. The immigration-extinction hypothesis appears to provide a plausible explanation for this observed pattern. The fact that in our final model, a continental effect is still highly significant, leads us not to exclude the possibility of some other historical influences in generating different overall species richness levels on the two continents.     

Normalization references for Europe and North America for application with USEtox? characterization factors

Purpose

In life cycle impact assessment, normalization can be a very effective tool for the life cycle assessment practitioner to interpret results and put them into perspective. The paper presents normalization references for the recently developed USEtox? model, which aims at calculating globally applicable characterization factors. Normalization references for Europe and North America are determined, and guidance for expansions to other geographical regions is provided.

Materials and methods

The base years of the European and North American inventories are 2004 and 2002/2008, respectively. Emission data were extracted from two literature sources referring to each of the considered regions. The inventory for North America was adapted to avoid extrapolation of data from other regions and thus bring consistency with the emission inventory for Europe. In spite of different inventory assumptions, a similar coverage of substances was obtained for both regions with relatively high representation of metals and a number of organic compounds, mainly consisting of non-methane volatile organic compounds and pesticides. The two inventory sets were eventually characterized with the characterization factors (CFs) calculated with the version 1.0 of the USEtox? model and substance database; both interim and recommended CFs were used.

Results and discussion

Normalization references are provided for Europe and North America for the three USEtox? toxic impact categories; ratios between the normalization references for the two regions in all cases lie below a factor of 3. Causes for the observed discrepancies are found to be different inventory assumptions as well as variations in the type and intensity of actual emissions between the two regions. Additional causes are inventories that only cover a limited number of substances, and the characterization model, which can only provide interim factors for certain substances like metal compounds. Based on these causes and on a review of recent studies on normalization references, a list of substances to be prioritized when collecting emission data was built, demonstrating the importance of metals.

Conclusions

In the perspective of further refining the presented normalization references and of calculating new references for other regions, guidance is provided including a list of priority substances that should be considered when building emission inventories for normalization references.     

AMPK: a link between metabolism and reproduction?

5'AMP-activated protein kinase (AMPK) is a serine/threonine kinase that acts as a fuel gauge in regulating energy metabolism. It restores cellular ATP levels by switching on catabolic pathways and switching off anabolic pathways. Some evidence indicates that AMPK could be also implicated in reproductive functions such as granulosa cell steroidogenesis and nuclear oocyte maturation in several species. Some metabolic hormones such as leptin, resistin, adiponectin (three adipokines) and ghrelin may in part act through the AMPK signaling. These hormones are also involved in the control of the reproductive functions at the hypothalamus-pituitary-gonadal axis level in both male and female. Thus, AMPK could be one of the signaling pathways controlling the interactions between energy balance and reproduction. The reproductive system is tightly coupled with energy balance, and thereby metabolic abnormalities can lead to the development of some physiopathological situations such as the polycystic ovary syndrome (PCOS). Women with PCOS show altered fertility mostly associated with metabolic disorders such as insulin-resistance, hyperinsulinemia and/or dyslipidemia. Metformin, an insulin-sensitizer, is used for the treatment of women with PCOS. It restores subnormal fertility and energy balance. Recent studies show that AMPK is involved in the mechanism of action of metformin. Thus, it may be a therapeutic target. However, further investigations are necessary to elucidate the functions of AMPK in both metabolic and reproductive tissues.     

Myzostomida: a link between trochozoans and flatworms?

Myzostomids are obligate symbiotic invertebrates associated with echinoderms with a fossil record that extends to the Ordovician period. Due to their long history as host-specific symbionts, myzostomids have acquired a unique anatomy that obscures their phylogenetic affinities to other metazoans: they are incompletely segmented, parenchymous, acoelomate organisms with chaetae and a trochophore larva. Today, they are most often classified within annelids either as an aberrant family of polychaetes or as a separate class. We inferred the phylogenetic position of the Myzostomida by analysing the DNA sequences of two slowly evolving nuclear genes: the small subunit ribosomal RNA and elongation factor-1alpha. All our analyses congruently indicated that myzostomids are not annelids but suggested instead that they are more closely related to flatworms than to any trochozoan taxon. These results, together with recent analyses of the myzostomidan ultrastructure, have significant implications for understanding the evolution of metazoan body plans, as major characters (segmentation, coeloms, chaetae and trochophore larvae) might have been independently lost or gained in different animal phyla.     

An ecological map of Europe: why and how?

After a recall of the recent emergence of the great ecological problems on the scale of the European continent and of the privileged use of vegetation maps as an ecological tool, a cartographic synthesis of the main plant formations in Europe is submitted on the basis of a hierarchized and numerized nomenclature of the vegetation units. Examples of connections between vegetation and ecology, as suggested or facilitated by this map, are given: use of the monthly ombrothermic diagrams as a privileged tool, thermic limits of the boreal zone, indicative value of the Mediterranean xerothermic area, predictive models of the geographical shifts of the great ecosystems according to the expected climate changes.     

Smc5/6: a link between DNA repair and unidirectional replication?

Of the three structural maintenance of chromosome (SMC) complexes, two directly regulate chromosome dynamics. The third, Smc5/6, functions mainly in homologous recombination and in completing DNA replication. The literature suggests that Smc5/6 coordinates DNA repair, in part through post-translational modification of uncharacterized target proteins that can dictate their subcellular localization, and that Smc5/6 also functions to establish DNA-damage-dependent cohesion. A nucleolar-specific Smc5/6 function has been proposed because Smc5/6 yeast mutants display penetrant phenotypes of ribosomal DNA (rDNA) instability. rDNA repeats are replicated unidirectionally. Here, we propose that unidirectional replication, combined with global Smc5/6 functions, can explain the apparent rDNA specificity.     

Mitochondrial dysfunction: A potential link between neuroinflammation and neurodegeneration?

Dysfunctional mitochondria are thought to play a cardinal role in the pathogenesis of various neurological disorders, such as multiple sclerosis, Alzheimer’s disease, Parkinson’s disease and stroke. In addition, neuroinflammation is a common denominator of these diseases. Both mitochondrial dysfunction and neuroinflammatory processes lead to increased production of reactive oxygen species (ROS) which are detrimental to neurons. Therefore, neuroinflammation is increasingly recognized to contribute to processes underlying neurodegeneration. Here we describe the involvement of mitochondrial (dys)function in various neurological disorders and discuss the putative link between mitochondrial function and neuroinflammation.     

Antidiabetic pharmacology: a link between metabolic syndrome and neuro-oncology?

One of the main topics of the annual meeting of the American Society for Clinical Oncology in 2011 were the results presented on breast cancer chemotherapy and concomitant administration of the oral antidiabetic metformin. The overall agreement was that current evidence is just enough to dramatically change the clinical practice of oncology, and in our case, brain cancer treatment, and that further research is needed to address the relationship between diabetes, metabolism, insulin analogues and neoplasia. Still, it is very interesting to explore the potentially beneficial effects of metformin in glioma chemo/immunotherapy and wait for results in the clinic. In the current paper we present the cell and molecular aspects of the metabolic syndrome, metformin administration and cancer chemotherapy, with a special emphasis in neuro-oncology, since brain tumors are usually devastating diseases with an extremely high mortality within two years of diagnosis even when surgical, radiotherapeutic and chemotherapeutic interventions are applied.     

Visfatin: the missing link between intra-abdominal obesity and diabetes?

Human obesity-related diabetes and the accompanying metabolic disorders have been specifically linked to increased visceral adipose tissue mass. Understanding the differences in biology of the two human fat depots (visceral and subcutaneous) might hold the key to therapeutic strategies aimed at reducing obesity-induced insulin resistance and alleviating symptoms of the metabolic syndrome. Visfatin (pre-B-cell colony-enhancing factor, PBEF) is a novel adipokine that appears to be preferentially produced by visceral adipose tissue and has insulin-mimetic actions. Could this molecule hold the key to future treatments for type 1 and 2 diabetes? This article discusses the pros and cons of visfatin action and how it might affect future therapeutic strategies.     

CFTR: a missing link between exocrine and endocrine pancreas?

<正>Cystic fibrosis(CF),a life-shortening hereditary disease mainly afflicting people of Caucasian origins,is caused by loss-of-function mutations in the CFTR(Cystic Fibrosis Transmembrane conductance Regulator)gene,which encodes a phosphorylation-activated,but ATP-gated anion channel expressed primarily in epithelial cells.To date,nearly 2000 mutations have been identified as pathogenic,     

Axon-glial disruption: the link between vascular disease and Alzheimer's disease?

Vascular risk factors play a critical role in the development of cognitive decline and AD (Alzheimer's disease), during aging, and often result in chronic cerebral hypoperfusion. The neurobiological link between hypoperfusion and cognitive decline is not yet defined, but is proposed to involve damage to the brain's white matter. In a newly developed mouse model, hypoperfusion, in isolation, produces a slowly developing and diffuse damage to myelinated axons, which is widespread in the brain, and is associated with a selective impairment in working memory. Cerebral hypoperfusion, an early event in AD, has also been shown to be associated with white matter damage and notably an accumulation of amyloid. The present review highlights some of the published data linking white matter disruption to aging and AD as a result of vascular dysfunction. A model is proposed by which chronic cerebral hypoperfusion, as a result of vascular factors, results in both the generation and accumulation of amyloid and injury to white matter integrity, resulting in cognitive impairment. The generation of amyloid and accumulation in the vasculature may act to perpetuate further vascular dysfunction and accelerate white matter pathology, and as a consequence grey matter pathology and cognitive decline.     

Polyoxovanadates: The missing link between simple paramagnets and bulk magnets?

Oxovanadium clusters provide novel examples of large magnetic clusters, which may showin nuce the typical behavior of bulk magnetic materials.The paper reviews the magnetic properties of V₁₅, comprising fifteen oxovanadium(IV); V₁₄, comprising fourteen oxovanadium(IV); V₃₊₁, comprising three localized oxovanadium(IV), six localized oxovanadium(V), and one oxovanadium(IV) delocalized over three sites; V₄₊₂ and V₄₊₄ which comprise four localized and two and four delocalized oxovanadium(IV), respectively. The different observed magnetic behaviors are discussed on the basis of several models of different sophistication.     

Functional link between distal vasodilation and sleep-onset latency?

Thermoregulatory processes have long been implicated in initiation of human sleep. The purpose of this study was to evaluate the role of heat loss in sleep initiation, under the controlled conditions of a constant-routine protocol modified to permit nocturnal sleep. Heat loss was indirectly measured by means of the distal-to-proximal skin temperature gradient (DPG). A stepwise regression analysis revealed that the DPG was the best predictor variable for sleep-onset latency (compared with core body temperature or its rate of change, heart rate, melatonin onset, and subjective sleepiness ratings). This study provides evidence that selective vasodilation of distal skin regions (and hence heat loss) promotes the rapid onset of sleep.