Hybridization and Back-Crossing in Giant Petrels (Macronectes giganteus and M. halli) at Bird Island,South Georgia,and a Summary of Hybridization in Seabirds

Hybridization in natural populations provides an opportunity to study the evolutionary processes that shape divergence and genetic isolation of species. The emergence of pre-mating barriers is often the precursor to complete reproductive isolation. However, in recently diverged species, pre-mating barriers may be incomplete, leading to hybridization between seemingly distinct taxa. Here we report results of a long-term study at Bird Island, South Georgia, of the extent of hybridization, mate fidelity, timing of breeding and breeding success in mixed and conspecific pairs of the sibling species, Macronectes halli (northern giant petrel) and M. giganteus (southern giant petrel). The proportion of mixed-species pairs varied annually from 0.4–2.4% (mean of 1.5%), and showed no linear trend with time. Mean laying date in mixed-species pairs tended to be later than in northern giant petrel, and always earlier than in southern giant petrel pairs, and their breeding success (15.6%) was lower than that of conspecific pairs. By comparison, mixed-species pairs at both Marion and Macquarie islands always failed before hatching. Histories of birds in mixed-species pairs at Bird Island were variable; some bred previously or subsequently with a conspecific partner, others subsequently with a different allospecific partner, and some mixed-species pairs remained together for multiple seasons. We also report the first verified back-crossing of a hybrid giant petrel with a female northern giant petrel. We discuss the potential causes and evolutionary consequences of hybridization and back-crossing in giant petrels and summarize the incidence of back-crossing in other seabird species.     

Site-specific chlorophyll reference conditions for lakes in Northern and Western Europe

The Water Framework Directive (WFD) requires EU Member States to assess the “ecological status” of surface waters. As a component of ecological status, many European countries are developing a classification scheme for chlorophyll concentrations as a measure of phytoplankton biomass. The chlorophyll classification must be based on the degree of divergence of a water body from an appropriate baseline or ‘reference condition’. This article describes the development of a series of regression models for predicting reference chlorophyll concentrations on a site-specific basis. For model development, a large dataset of European lakes considered to be in reference condition, 466 lakes in total, was assembled. Data were included from 12 European countries, but lakes from Northern and Western Europe dominated and made up 92% of all reference lakes. Data have been collated on chlorophyll concentration, altitude, mean depth, alkalinity, humic type, surface area and geographical region. Regression models were developed for estimating site-specific reference chlorophyll concentrations from significant predictor ‘typology’ variables. Reference chlorophyll concentrations were found to vary along a number of environmental gradients. Concentrations increased with colour and alkalinity and decreased with lake depth and altitude. Forward selection was used to identify independent explanatory variables in regression models for predicting site-specific reference chlorophyll concentrations. Depth was selected as an explanatory variable in all models. Alkalinity was included in models for low colour and humic lakes and altitude was included in models for low colour and very humic lakes. Uncertainty in the models was quite high and arises from errors in the data used to develop the models (including natural temporal and spatial variability in data) and also from additional explanatory variables not considered in the models, particularly nutrient concentrations, retention time and grazing. Despite these uncertainties, site-specific reference conditions are still recommended in preference to type-specific reference conditions, as they use the individual characteristics of a site known to influence phytoplankton biomass, rather than adopt standards set to generally represent a large population of lakes of a particular type. For this reason, site-specific reference conditions should result in reduced error in ecological status classifications, particularly for lakes close to typology boundaries.     

Point-of-care measurements reveal release of purines into venous blood of stroke patients

Purinergic Signalling - Stroke is a leading cause of death and disability. Here, we examine whether point-of-care measurement of the purines, adenosine, inosine and hypoxanthine, which are...     

Platelet glycoprotein IIb-IIIa-like proteins mediate endothelial cell attachment to adhesive proteins and the extracellular matrix

The adherence of human umbilical vein endothelial (HUVE) cells to adhesive matrix proteins was examined to determine if cell attachment and spreading were mediated by the glycoprotein (GP) IIb-IIIa complex on endothelial cells. The HUVE cells adhered well to glass slides that had been coated with fibronectin, vitronectin, fibrinogen, or von Willebrand factor but failed to adhere to albumin-coated or to uncoated slides. The HUVE cell attachment and spreading on vitronectin, fibrinogen, and von Willebrand factor were greatly inhibited by a GP IIb-IIIa monoclonal antibody (7E3). In contrast, HUVE cell attachment to fibronectin was not inhibited by 7E3 but was inhibited by a fibronectin-receptor antibody (alpha GP140), which had no effect on cell attachment to the other adhesive proteins. The 7E3 antibody, but not alpha GP140, disrupted HUVE cell monolayers by detaching cells from their naturally occurring extracellular matrix. These data indicate that platelet GP IIb-IIIa-like proteins mediate the adherence of HUVE cells to specific adhesive proteins and to the extracellular matrix.     

Prions adhere to soil minerals and remain infectious

An unidentified environmental reservoir of infectivity contributes to the natural transmission of prion diseases (transmissible spongiform encephalopathies [TSEs]) in sheep, deer, and elk. Prion infectivity may enter soil environments via shedding from diseased animals and decomposition of infected carcasses. Burial of TSE-infected cattle, sheep, and deer as a means of disposal has resulted in unintentional introduction of prions into subsurface environments. We examined the potential for soil to serve as a TSE reservoir by studying the interaction of the disease-associated prion protein (PrP(Sc)) with common soil minerals. In this study, we demonstrated substantial PrP(Sc) adsorption to two clay minerals, quartz, and four whole soil samples. We quantified the PrP(Sc)-binding capacities of each mineral. Furthermore, we observed that PrP(Sc) desorbed from montmorillonite clay was cleaved at an N-terminal site and the interaction between PrP(Sc) and Mte was strong, making desorption of the protein difficult. Despite cleavage and avid binding, PrP(Sc) bound to Mte remained infectious. Results from our study suggest that PrP(Sc) released into soil environments may be preserved in a bioavailable form, perpetuating prion disease epizootics and exposing other species to the infectious agent.     

Suicide and Social Change in China

Using recently available data from China's Disease Surveillance Points system, we estimate that there are over 300,000 suicides in China per year; this makes suicide one of the most important causes of death in the country and makes the suicide rate in China one of the highest in the world. Moreover, the pattern of suicides in China is quite different than in other parts of the world – there are more completed suicides among females than males and rural rates are three-fold urban rates. The lack of reliable suicide data prior to 1987 makes it difficult to determine whether the rates are currently rising, falling, or staying constant. However, reports of suicides in the Chinese press and case studies conducted by the authors suggest (but do not prove) that the high rates of suicide currently experienced are related to the social changes that have occurred with the economic reforms (which started in 1978). Another possible explanation for the high rates of suicide is the large numbers of persons with depressive illness in China who remain untreated. Single-cause models of suicide (i.e., social factors or mental illness) do not do justice to the complexity of the processes involved and, therefore, do not provide useful information about the etiology and prevention of suicide in China or elsewhere. We describe our own dynamic model of suicide that includes five interacting factors which, we believe, collectively determine the suicide rates in a community.     

Novel splice variants derived from the receptor tyrosine kinase superfamily are potential therapeutics for rheumatoid arthritis

Introduction  

Despite the advent of biological therapies for the treatment of rheumatoid arthritis, there is a compelling need to develop alternative therapeutic targets for nonresponders to existing treatments. Soluble receptors occur naturally in vivo, such as the splice variant of the cell surface receptor for vascular endothelial growth factor (VEGF) – a key regulator of angiogenesis in rheumatoid arthritis. Bioinformatics analyses predict that the majority of human genes undergo alternative splicing, generating proteins – many of which may have regulatory functions. The objective of the present study was to identify alternative splice variants (ASV) from cell surface receptor genes, and to determine whether the novel proteins encoded exert therapeutic activity in an in vivo model of arthritis.     

Dating of divergences within the Rattus genus phylogeny using whole mitochondrial genomes

The timing and order of divergences within the genus Rattus have, to date, been quite speculative. In order to address these important issues we sequenced six new whole mitochondrial genomes from wild-caught specimens from four species, Rattus exulans, Rattus praetor, Rattus rattus and Rattus tanezumi. The only rat whole mitochondrial genomes available previously were all from Rattus norvegicus specimens. Our phylogenetic and dating analyses place the deepest divergence within Rattus at approximately 3.5 million years ago (Mya). This divergence separates the New Guinean endemic R. praetor lineage from the Asian lineages. Within the Asian/Island Southeast Asian clade R. norvegicus diverged earliest at approximately 2.9Mya. R. exulans and the ancestor of the sister species R. rattus and R. tanezumi subsequently diverged at approximately 2.2Mya, with R. rattus and R. tanezumi separating as recently as approximately 0.4Mya. Our results give both a better resolved species divergence order and diversification dates within Rattus than previous studies.     

Sporicidal Activity of Sodium Hypochlorite at Subzero Temperatures

Sodium hypochlorite was an excellent disinfectant at low temperatures. With the addition of ethylene glycol to prevent freezing, hypochlorite solutions at low free available chlorine concentrations, were effective against Bacillus subtilis var. niger spores from 0 to -40 C. The effectiveness of this decontaminant was influenced by temperature, pH, and concentration, with pH 7.2 the optimum for decontamination at all temperatures and concentrations.