BDNF VAL66MET polymorphism and memory decline across the spectrum of Alzheimer's disease

The brain-derived neurotrophic factor (BDNF) Val66Met (rs6265) polymorphism has been shown to moderate the extent to which memory decline manifests in preclinical Alzheimer's disease (AD). To date, no study has examined the relationship between BDNF and memory in individuals across biologically confirmed AD clinical stages (i.e., Aβ+). We aimed to understand the effect of BDNF on episodic memory decline and clinical disease progression over 126 months in individuals with preclinical, prodromal and clinical AD. Participants enrolled in the Australian Imaging, Biomarkers and Lifestyle (AIBL) study who were Aβ + (according to positron emission tomography), and cognitively normal (CN; n = 238), classified as having mild cognitive impairment (MCI; n = 80), or AD (n = 66) were included in this study. Cognition was evaluated at 18 month intervals using an established episodic memory composite score over 126 months. We observed that in Aβ + CNs, Met66 was associated with greater memory decline with increasing age and were 1.5 times more likely to progress to MCI/AD over 126 months. In Aβ + MCIs, there was no effect of Met66 on memory decline or on disease progression to AD over 126 months. In Aβ + AD, Val66 homozygotes showed greater memory decline, while Met66 carriers performed at a constant and very impaired level. Our current results illustrate the importance of time and disease severity to clinicopathological models of the role of BDNF Val66Met in memory decline and AD clinical progression. Specifically, the effect of BDNF on memory decline is greatest in preclinical AD and reduces as AD clinical disease severity increases.     

Morphological clues to genetic species: multivariate analysis of greater Galago sibling species

Several studies conducted in diverse fields indicate the presence of a genetic discontinuity within the taxon Galago crassicaudatus E. Geoffroy--the thick-tailed bushbaby. One of these areas is morphology. This contribution details a statistical analysis of skull material classified under this taxon in order 1) to confirm the objective existence of two morphotypes, and 2) to investigate the characters that allow the skull types to be distinguished. Emphasis is placed on multivariate techniques, although univariate and bivariate techniques are included where they are felt to be appropriate. All statistical analyses point to the reality of the morphological discontinuity between the groups. This is true even when size considerations have been reduced by rescaling the data. The results support separation of the populations at a specific level: G. crassicaudatus and G. garnettii. In addition, the structural changes observed in the two taxa--including an increase in overall size in G. crassicaudatus--are indicative of a divergence in preferred habitats: G. garnettii is adapted to more mesic environmental conditions, and to a softer, less fibrous diet than is its more robust sibling.     

A Phylogenetic Analysis of Human Syntenies Revealed by Chromosome Painting in Euarchontoglires Orders

To search for cytogenetic signatures that can help to clarify evolutionary affinities among the five orders within the Euarchontoglires clade, we focused on associations of conserved syntenic blocks that have been accumulated in the karyotypes of Primates (Strepsirhini and Haplorhini), five families of Rodentia, Scandentia (Tupaia belangeri), Dermoptera (Galeopterus variegatus) and Lagomorpha (Oryctolagus cuniculus). We examined available chromosome painting data to identify conserved chromosomes and chromosomal segments, and syntenic associations likely to have characterized the ancestral eutherian karyotype. The data set includes 161 characters that have been subjected to a concatenated analysis using maximum parsimony (MP) and Bayesian inference (BI). The phylogenetic pattern recovered is generally consistent with reconstructions based on molecular and morphological data (particularly with respect to higher systematic groupings), but there are several anomalies (e.g., in the position of the lagomorphs). Both MP and BI topologies have weak statistical support, as a consequence of the high number of autapomorphic and homoplastic character states that have evolved during the history of the clade. The vast majority of derived associations are located on the terminal portions of the branches, and very few can be identified to support deeper divergences in the tree, indicating that chromosomal structures are far more fluid that was previously recognized. The high levels of homoplasy reflected in our data suggest that the number of possible syntenic character states is limited by chromosomal structures, and the same associations occur repeatedly.     

Female-biased Sex Ratios in the Neotropical Treehopper Umbonia ataliba (Homoptera: Membracidae)

The authors report and explain female-biased sex ratios in the neotropical treehopper Umbonia ataliba Homoptera: Membracidae at Monteverde, Costa Rica. Umbonia ataliba mothers semelparously oviposit egg masses into host-plant branches, make feeding holes, and guard the eggs and the nymphs until the young moult to become adults. At adulthood, offspring sex ratios are female-biased, with families having, on average, one male per 3.17 females (SD = 0.149, n = 48). The female bias does not appear to be explained by the hypothesis that males are more difficult to raise to independence: males are smaller than females, males have a shorter development time, males do not require disproportionately more feeding holes, and males do not experience higher mortality in families that are unprotected from parasites and predators, rather, females die more often in protected families. Thus females, not males, may be more difficult to raise to independence. The authors investigated whether increases in the size of males and females increased the fitness of either sex disproportionately, but found no relationship between size and fitness for either sex. We found evidence that local-mate competition conditions and inbreeding occur. Mating occurs at the natal site and nearly all copulations take place between siblings (99.3 %, n = 153 copulations). Most females (mean proportion of females = 0.65, SD = 0.33, n = 7 families) copulate with their male siblings prior to dispersing; whether the unmated proportion copulates later is unknown. This paper suggests that the numerical bias reflects an investment bias favoured under selection by inbreeding and local-mate competition conditions.     

Biosecurity for Translocations: Cirl Bunting (Emberiza cirlus), Fisher’s Estuarine Moth (Gortyna borelii lunata), Short-Haired Bumblebee (Bombus subterraneus) and Pool Frog (Pelophylax lessonae) Translocations as Case Studies

Exposure to parasites in conservation translocations increases the risks to recipient and translocated populations from disease, and therefore there has been interest in implementing biosecurity methods. Using four case examples we described how biosecurity was applied in practical translocation scenarios prior to and during a translocation and also post-release. We implemented biosecurity, including quarantine barriers, at specific points in the translocation pathway where hazards, identified by the disease risk analysis, had the potential to induce disease. Evidence that biosecurity protected translocated and recipient populations, included an absence of mortality associated with high-risk non-native parasites, a reduction in mortality associated with endemic parasites, the absence of high-risk pathogenic parasites, or associated diseases, at the destination; and the apparent absence of diseases in closely related species at the destination site. The biosecurity protocols did not alter the level or duration of translocated species confinement and therefore probably did not act as a stressor. There is a monetary cost involved in biosecurity but the epidemiological evidence suggests that conservation translocation managers should carefully consider its use. Breakdowns in quarantine have occurred in human hospitals despite considerable investment and training for health professionals, and we therefore judge that there is a need for training in the objectives and maintenance of quarantine barriers in conservation translocations. Biosecurity protocols for conservation translocations should be continually updated in response to findings from disease risk analysis and post-release disease surveillance and we recommend further studies to evaluate their effectiveness.