Pigments,Parasites and Personalitiy: Towards a Unifying Role for Steroid Hormones?

A surging interest in the evolution of consistent trait correlations has inspired research on pigment patterns as a correlate of behavioural syndromes, or "animal personalities". Associations between pigmentation, physiology and health status are less investigated as potentially conserved trait clusters. In the current study, lice counts performed on farmed Atlantic salmon Salmo salar naturally infected with ectoparasitic sea lice Lepeophtheirus salmonis showed that individual fish with high incidence of black melanin-based skin spots harboured fewer female sea lice carrying egg sacs, compared to less pigmented fish. There was no significant association between pigmentation and lice at other developmental stages, suggesting that host factors associated with melanin-based pigmentation may modify ectoparasite development to a larger degree than settlement. In a subsequent laboratory experiment a strong negative correlation between skin spots and post-stress cortisol levels was revealed, with less pigmented individuals showing a more pronounced cortisol response to acute stress. The observation that lice prevalence was strongly increased on a fraction of sexually mature male salmon which occurred among the farmed fish further supports a role for steroid hormones as mediators of reduced parasite resistance. The data presented here propose steroid hormones as a proximate cause for the association between melanin-based pigmentation and parasites. Possible fundamental and applied implications are discussed.     

Genome wide AFLP markers support cryptic species in Coniophora (Boletales)

Numerous fungal morphospecies include cryptic species that routinely are detected by sequencing a few unlinked DNA loci. However, whether the patterns observed by multi-locus sequencing are compatible with genome wide data, such as amplified fragment length polymorphisms (AFLPs), is not well known for fungi. In this study we compared the ability of three DNA loci and AFLP data to discern between cryptic fungal lineages in the three morphospecies Coniophora olivacea, Coniophora arida, and Coniophora puteana. The sequences and the AFLP data were highly congruent in delimiting the morphotaxa into multiple cryptic species. However, while the DNA sequences indicated introgression or hybridization between some of the cryptic lineages the AFLP data did not. We conclude that as few as three polymorphic DNA loci was sufficient to recognize cryptic lineages within the studied Coniophora taxa. However, based on analyses of a few (three) sequenced loci the hybridization could not easily be distinguished from incomplete lineage sorting. Hence, great caution should be taken when concluding about hybridization based on data from just a few loci.     

The effect of stimulation therapy and donepezil on cognitive function in Alzheimer¿s disease. A community based RCT with a two-by-two factorial design

ABSTRACT: BACKGROUND: Progressive neurodegeneration in Alzheimer's disease (AD) induces cognitive deterioration, and there is controversy regarding the optimal treatment strategy in early AD. Stimulation therapy, including physical exercise and cholinesterase inhibitors are both reported to postpone cognitive deterioration in separate studies. We aimed to study the effect of stimulation therapy and the additional effect of donepezil on cognitive function in early AD. METHOD: DESIGN: A two-by-two factorial trial comprising stimulation therapy for one year compared to standard care to which a randomized double-blinded placebo controlled trial with donepezil was added. SETTING: Nine rural municipalities in Northern Norway. PARTICIPANTS: 187 participants [greater than or equal to]65 years with a recent diagnosis of mild or moderate AD were included in the study of which 146 completed a one-year follow-up. INTERVENTIONS: In five municipalities the participants received stimulation therapy whereas participants in four received standard care. All participants were randomised double-blinded to donepezil or placebo and tested with three different cognitive tests four times during the one-year study period. MAIN OUTCOME: Changes in MMSE sum score. SECONDARY OUTCOME: Changes in ADAS-Cog and Clock Drawing Test. RESULTS: MMSE scores remained unchanged amongst AD participants receiving stimulation therapy and those receiving standard care. The results were consistent for ADAS-Cog and Clock Drawing Test. No time trend differences were found during one-year follow-up between groups receiving stimulation therapy versus standard care or between donepezil versus placebo. CONCLUSION: In rural AD patients non-pharmacological and pharmacological therapy did not improve outcome compared with standard care but all groups retained cognitive function during one year follow-up. Other studies are needed to confirm these results. ClinicalTrials.gov (Identifier: NCT00443014). EudraCT database (no 2004-002613-37). KEYWORDS: Alzheimer's disease. Symptomatic treatment. Postponement of cognitive deterioration.     

A heterogeneous computing environment to solve the 768-bit RSA challenge

In December 2009 the 768-bit, 232-digit number RSA-768 was factored using the number field sieve. Overall, the computational challenge would take more than 1700 years on a single, standard core. In the article we present the heterogeneous computing approach, involving different compute clusters and Grid computing environments, used to solve this problem.     

Crystal Structure of Lymnaea stagnalis AChBP Complexed with the Potent nAChR Antagonist DHβE Suggests a Unique Mode of Antagonism

Nicotinic acetylcholine receptors (nAChRs) are pentameric ligand-gated ion channels that belong to the Cys-loop receptor superfamily. These receptors are allosteric proteins that exist in different conformational states, including resting (closed), activated (open), and desensitized (closed) states. The acetylcholine binding protein (AChBP) is a structural homologue of the extracellular ligand-binding domain of nAChRs. In previous studies, the degree of the C-loop radial extension of AChBP has been assigned to different conformational states of nAChRs. It has been suggested that a closed C-loop is preferred for the active conformation of nAChRs in complex with agonists whereas an open C-loop reflects an antagonist-bound (closed) state. In this work, we have determined the crystal structure of AChBP from the water snail Lymnaea stagnalis (Ls) in complex with dihydro-β-erythroidine (DHβE), which is a potent competitive antagonist of nAChRs. The structure reveals that binding of DHβE to AChBP imposes closure of the C-loop as agonists, but also a shift perpendicular to previously observed C-loop movements. These observations suggest that DHβE may antagonize the receptor via a different mechanism compared to prototypical antagonists and toxins.     

Population dynamics in changing environments: the case of an eruptive forest pest species

In recent decades we have seen rapid and co‐occurring changes in landscape structure, species distributions and even climate as consequences of human activity. Such changes affect the dynamics of the interaction between major forest pest species, such as bark beetles (Coleoptera: Curculionidae, Scolytinae), and their host trees. Normally breeding mostly in broken or severely stressed spruce; at high population densities some bark beetle species can colonise and kill healthy trees on scales ranging from single trees in a stand to multi‐annual landscape‐wide outbreaks. In Eurasia, the largest outbreaks are caused by the spruce bark beetle, Ips typographus (Linnaeus), which is common and shares a wide distribution with its main host, Norway spruce (Picea abies Karst.). A large literature is now available, from which this review aims to synthesize research relevant for the population dynamics of I. typographus and co‐occurring species under changing conditions. We find that spruce bark beetle population dynamics tend to be metastable, but that mixed‐species and age‐heterogeneous forests with good site‐matching tend to be less susceptible to large‐scale outbreaks. While large accumulations of logs should be removed and/or debarked before the next swarming period, intensive removal of all coarse dead wood may be counterproductive, as it reduces the diversity of predators that in some areas may play a role in keeping I. typographus populations below the outbreak threshold, and sanitary logging frequently causes edge effects and root damage, reducing the resistance of remaining trees. It is very hard to predict the outcome of interspecific interactions due to invading beetle species or I. typographus establishing outside its current range, as they can be of varying sign and strength and may fluctuate depending on environmental factors and population phase. Most research indicates that beetle outbreaks will increase in frequency and magnitude as temperature, wind speed and precipitation variability increases, and that mitigating forestry practices should be adopted as soon as possible considering the time lags involved.     

Conserving small and fragmented populations of large mammals: Non-invasive genetic sampling in an isolated population of Asian elephants in Nepal

The Terai is one of the world's most spectacular landscapes, encompassing parts of Nepal and northern India. This area used to harbour large and continuous populations of charismatic species like elephants, tigers and rhinoceros. However, recent habitat fragmentation reduced these populations into small, partially or completely isolated remnants. The largest of these fragments in Nepal is the Bardia National Park. Here, the elephant population was functionally extinct in the early 1970s and -80s, but was rescued by a considerable number of immigrants in 1994. In order to assess population size, sex ratio, age structure, and levels of genetic variation, we carried out non-invasive genetic sampling, using elephant dung as the source of DNA. A capture-mark-recapture estimate of population size suggested that there were 57 individuals in the study area, which agrees well with field observations. Notably, a strongly male-biased sex ratio was evident among sub-adult individuals. This observation suggests the presence of sub-adult immigrants in the population, which was supported by formal migrant detection analysis. Genetic variation was quite high and the evidence for male immigrants suggests that there are good prospects for maintenance of genetic diversity. A decade ago a large-scale project was initiated in the Terai region to link remaining populations of large mammals through dispersal corridors. The program is basically founded on the assumption that habitat fragments are isolated with little or no migration between them. Our results indicate that this may not be the case, at least not for the Asian elephant in western Nepal, which therefore reduces the alleged extinction risk from genetic erosion and stochastic demographic events.