Changes in muscle activation,oxygenation, and morphology following a fatiguing repetitive forward reaching task in young adult males and females

We sought to evaluate sex-specific 1) muscle activation patterns, hemodynamics, and swelling responses to short-cycle repetitive fatigue; 2) relationships between muscular responses and perceived fatigability. Asymptomatic participants (N = 26, 13 females) completed a repetitive pointing task until 8/10 on the Borg CR10 scale. Upper trapezius (UT), supraspinatus (SUPRA), and biceps brachii (BIC) muscle activation, activation variability (CV), median power frequency (MdPF) and thickness, and UT oxygenation were recorded. Males had higher BIC CV, UT and SUPRA MdPF, and UT and BIC thickness. Longer time to fatigue-terminal was correlated to greater SUPRA activation increase (ρ = 0.624) and BIC MdPF decrease (ρ = -0.674) in males, while in females it was correlated to greater (ρ = -0.657) and lower (ρ = 0.683) decrease of SUPRA and BIC CV, respectively. Male’s greater increase in SUPRA thickness correlated to greater increase in UT thickness and tissue oxygenation index, and to lower increase of UT deoxyhemoglobin. Females’ greater decrease of SUPRA MdPF correlated to greater decrease of UT MdPF, while greater UT activation increase was related to lower UT thickness increase. Results suggest that despite comparable time to fatigue-terminal, males have greater force-generating capacity and neuromuscular reliance on recruitment and excitation rates, while females have greater reliance on activation variability. Further, there are relationships between hemodynamic and swelling patterns in males, while there are relationships between activation and swelling patterns in females. Although there were no differences in experimental task-induced changes, there are sex-specific relationships between muscular patterns and perceived fatigability, which may help explain sex-specific mechanisms of musculoskeletal disorders.     

Estimation of Fine-Scale Recombination Intensity Variation in the <Emphasis Type="Italic">white–echinus</Emphasis> Interval of <Emphasis Type="Italic">D. melanogaster</Emphasis>

Accurate assessment of local recombination rate variation is crucial for understanding the recombination process and for determining the impact of natural selection on linked sites. In Drosophila, local recombination intensity has been estimated primarily by statistical approaches, by estimating the local slope of the relationship between the physical and genetic maps. However, these estimates are limited in resolution and, as a result, the physical scale at which recombination intensity varies in Drosophila is largely unknown. Although there is some evidence suggesting as much as a 40-fold variation in crossover rate at a local scale in D. pseudoobscura, little is known about the fine-scale structure of recombination rate variation in D. melanogaster. Here we experimentally examine the fine-scale distribution of crossover events in a 1.2-Mb region on the D. melanogaster X chromosome using a classic genetic mapping approach. Our results show that crossover frequency is significantly heterogeneous within this region, varying approximately 3.5-fold. Simulations suggest that this degree of heterogeneity is sufficient to affect levels of standing nucleotide diversity, although the magnitude of this effect is small. We recover no statistical association between empirical estimates of nucleotide diversity and recombination intensity, which is likely due to the limited number of loci sampled in our population genetic data set. However, codon bias is significantly negatively correlated with fine-scale recombination intensity estimates, as expected. Our results shed light on the relevant physical scale to consider in evolutionary analyses relating to recombination rate and highlight the motivations to increase the resolution of the recombination map in Drosophila.     

Cortisol and behavioral responses to enrichment in military working dogs

Our objective was to compare the effects of two schedules of enrichment exposure, a distributed (high frequency) and regular regime versus a mass (low frequency) and irregular regime, on the cortisol and behavioral responses of 14 kennelled military working dogs. The enrichment experiences were exercise coupled with human contact. Both groups of dogs were exposed to approximately the same total amount of enrichment per week for a total of 7 weeks. The distributed and regular regime (DRR) furnished enrichment for 20-min intervals three to four times a day every weekday; the mass and irregular regime (MIR) randomly furnished enrichment for 16 or 24 continuous hours 1 day out of 5. Our data show that: (1) cortisol concentrations of DRR dogs significantly decreased between the first and the last week of observations; this was not the case in MIR dogs; (2) at the 7th week DRR dogs had lower cortisol concentrations than did MIR dogs; (3) all dogs in each group exhibited stereotypies. Our results suggest that MIR dogs underwent a decline in welfare throughout the experiment, whereas DRR dogs appeared to undergo a period of acute stress at the beginning of their training that resolved over 7 weeks. This study suggests that the welfare of kennelled dogs, particularly military working dogs, is affected among other factors by schedules of exercise and contact with people.     

The combined effect of SNP-marker and phenotype attributes in genome-wide association studies

The last decade has seen rapid improvements in high-throughput single nucleotide polymorphism (SNP) genotyping technologies that have consequently made genome-wide association studies (GWAS) possible. With tens to hundreds of thousands of SNP markers being tested simultaneously in GWAS, it is imperative to appropriately pre-process, or filter out, those SNPs that may lead to false associations. This paper explores the relationships between various SNP genotype and phenotype attributes and their effects on false associations. We show that (i) uniformly distributed ordinal data as well as binary data are more easily influenced, though not necessarily negatively, by differences in various SNP attributes compared with normally distributed data; (ii) filtering SNPs on minor allele frequency (MAF) and extent of Hardy–Weinberg equilibrium (HWE) deviation has little effect on the overall false positive rate; (iii) in some cases, filtering on MAF only serves to exclude SNPs from the analysis without reduction of the overall proportion of false associations; and (iv) HWE, MAF and heterozygosity are all dependent on minor genotype frequency, a newly proposed measure for genotype integrity.     

A comparison of two methods for assessing critical flicker fusion frequency in hens

This paper compared two general methods for assessing critical fusion frequency in hens (gallus gallus domesticus). The first method was a conditional discrimination procedure with the stimuli presented successively. The second was a two-alternative forced-choice procedure with the stimuli presented simultaneously. It was found that both methods of stimulus presentation gave comparable results suggesting that either method is useful when investigating psychophysics in animals. The results also show that hens’ critical fusion frequency is considerably higher than that of humans which may account for hens’ inability to recognise images presented on standard computer or television monitors.     

斜纹夜蛾种群控制的研究概况

斜纹夜蛾Spodoptera litura(Fabricius)是重要的农业害虫之一。为了控制斜纹夜蛾,使农作物免受危害,前人研究了化学防治、杀虫灯和性诱捕器诱杀、植物诱集和驱避、转基因抗虫品种以及生物防治对其种群控制作用。化学防治在压制斜纹夜蛾种群暴发、减轻农作物遭受损失方面作出了巨大贡献,但日益增强的抗药性、农药残留造成的环境污染、对天敌的杀伤和人畜安全的影响等问题不断受到关注,人们开始对该害虫的一些新的治理策略进行了探讨。在这些无公害的控制技术中,植物诱集和生物防治是2种值得提倡的有效措施。不少植物源提取物和昆虫生长调节剂对斜纹夜蛾幼虫具有极好的效果,是值得研发的2种新型生物制剂。香芋和蓖麻等诱集作物对斜纹夜蛾有较好的诱集效果,如果能将作物诱集和释放天敌昆虫或病原微生物制剂结合,使之成为一套有效的生态控制体系,将可现实斜纹夜蛾种群的持续控制。     

应用高剂量/庇护所策略管理Bt作物抗性的三个基本假设：综述与展望

目前, 抗虫转基因作物的抗性管理方法主要是高剂量/庇护所策略。该策略的有效性取决于3个基本的假设条件：（1）抗虫转基因作物（Bt作物）表达出高剂量的杀虫蛋白, 该剂量使得靶标害虫对Bt杀虫蛋白的抗性表现型为功能性完全隐性或近于完全隐性, 进而使得Bt作物可以杀死几乎所有的抗性杂合个体和所有的敏感性个体;（2）靶标害虫种群的Bt抗性基因起始频率处于很低的水平;（3）源自转基因作物田和非转基因作物田(庇护所)的成虫在田间随机混合并交配。这3个假设必须同时满足, 缺一不可。本文就这3个假设的理论基础和经验研究的进展进行了综合论述, 并着重讨论了随机交配假设的最新研究进展以及今后的研究方向和方法。     

Genetic heterogeneity in regional populations of Quebec—Parental lineages in the Gaspe Peninsula

Stable colonization of the Gaspe Peninsula by Europeans started in the middle of the 18th century at the time of the British conquest of New France. The earliest settlers were Acadians, escaping British deportation policies, followed by Loyalists from the US, who preferred to remain under British rule after the Declaration of Independence. In the 19th century, the developing fishing industry attracted French Canadians from the St. Lawrence Valley and newcomers from Europe including Channel Islanders from Jersey and Guernsey. We analyzed parental lineages of the self‐declared descendants of these four groups of settlers by mtDNA D‐loop sequencing and Y‐chromosome genotyping and compared them with French, British, and Irish samples. Their representation in terms of haplotype frequency classes reveals different signatures of founder effects, such as a loss of rare haplotypes, modification of intermediate frequency haplotypes, reduction in genetic diversity (seen in Acadians), but also enrichment by admixture. Parental lineages correlate with group identity. Descendants of early settlers, Acadians and Loyalists, preserved their identity more than those of French Canadian and Channel Islander “latecomers.” Although overall genetic diversity among Gaspesians is comparable with their European source populations, F_ST analysis indicated their greater differentiation. Distinct settlement history, a limited number of founders and relative genetic isolation contributed to the regionalization of the Quebec gene pool that appears less homogenous than usually anticipated. Am J Phys Anthropol, 2009. © 2009 Wiley‐Liss, Inc.     

Somatostatin: A Novel Substrate and a Modulator of Insulin-Degrading Enzyme Activity

Insulin-degrading enzyme (IDE) is an interesting pharmacological target for Alzheimer's disease (AD), since it hydrolyzes β-amyloid, producing non-neurotoxic fragments. It has also been shown that the somatostatin level reduction is a pathological feature of AD and that it regulates the neprilysin activity toward β-amyloid.In this work, we report for the first time that IDE is able to hydrolyze somatostatin [k_cat (s^− 1) = 0.38 (± 0.05); K_m (M) = 7.5 (± 0.9) × 10^− 6] at the Phe6-Phe7 amino acid bond. On the other hand, somatostatin modulates IDE activity, enhancing the enzymatic cleavage of a novel fluorogenic β-amyloid through a decrease of the K_m toward this substrate, which corresponds to the 10-25 amino acid sequence of the Aβ(1-40). Circular dichroism spectroscopy and surface plasmon resonance imaging experiments show that somatostatin binding to IDE brings about a concentration-dependent structural change of the secondary and tertiary structure(s) of the enzyme, revealing two possible binding sites. The higher affinity binding site disappears upon inactivation of IDE by ethylenediaminetetraacetic acid, which chelates the catalytic Zn²⁺ ion. As a whole, these features suggest that the modulatory effect is due to an allosteric mechanism: somatostatin binding to the active site of one IDE subunit (where somatostatin is cleaved) induces an enhancement of IDE proteolytic activity toward fluorogenic β-amyloid by another subunit. Therefore, this investigation on IDE-somatostatin interaction contributes to a more exhaustive knowledge about the functional and structural aspects of IDE and its pathophysiological implications in the amyloid deposition and somatostatin homeostasis in the brain.