The Advantage of Sex in the RNA Virus φ6

When laboratory populations of the RNA bacteriophage 6 are subjected to intensified genetic drift, they experience a decline in fitness. These experiments demonstrate that the average effect of mutations is deleterious, and they are used to suggest that Muller's ratchet can operate in these viruses. However, the operation of Muller's ratchet does not alone guarantee an advantage of sex. When 6 populations were subjected to a series of bottlenecks of one individual and then crossed, the measured advantage of sex was not significant. To determine whether a small sample size, as opposed to allelism or another explanation, can account for the negative result, we repeated the 6 experiments by crossing a larger set of populations. We found that bottlenecked populations of 6 could recover fitness through mutations. However, hybrids produced by crossing the populations recovered an additional amount over the contribution of mutations. This additional amount, which represents an advantage of sex to 6, was determined to be significantly greater than zero. These results provide indirect support for an advantage of sex through Muller's ratchet. However, we also use our experimental design and results to propose an alternative to Muller's ratchet as a model for the evolution of sex.     

Epistasis: Obstacle or Advantage for Mapping Complex Traits?

Identification of genetic loci in complex traits has focused largely on one-dimensional genome scans to search for associations between single markers and the phenotype. There is mounting evidence that locus interactions, or epistasis, are a crucial component of the genetic architecture of biologically relevant traits. However, epistasis is often viewed as a nuisance factor that reduces power for locus detection. Counter to expectations, recent work shows that fitting full models, instead of testing marker main effect and interaction components separately, in exhaustive multi-locus genome scans can have higher power to detect loci when epistasis is present than single-locus scans, and improvement that comes despite a much larger multiple testing alpha-adjustment in such searches. We demonstrate, both theoretically and via simulation, that the expected power to detect loci when fitting full models is often larger when these loci act epistatically than when they act additively. Additionally, we show that the power for single locus detection may be improved in cases of epistasis compared to the additive model. Our exploration of a two step model selection procedure shows that identifying the true model is difficult. However, this difficulty is certainly not exacerbated by the presence of epistasis, on the contrary, in some cases the presence of epistasis can aid in model selection. The impact of allele frequencies on both power and model selection is dramatic.     

Structural Advantage of Sugar Beet α-Glucosidase to Stabilize the Michaelis Complex with Long-chain Substrate

The α-glucosidase from sugar beet (SBG) is an exo-type glycosidase. The enzyme has a pocket-shaped active site, but efficiently hydrolyzes longer maltooligosaccharides and soluble starch due to lower K_m and higher k_cat/K_m for such substrates. To obtain structural insights into the mechanism governing its unique substrate specificity, a series of acarviosyl-maltooligosaccharides was employed for steady-state kinetic and structural analyses. The acarviosyl-maltooligosaccharides have a longer maltooligosaccharide moiety compared with the maltose moiety of acarbose, which is known to be the transition state analog of α-glycosidases. The clear correlation obtained between log K_i of the acarviosyl-maltooligosaccharides and log(K_m/k_cat) for hydrolysis of maltooligosaccharides suggests that the acarviosyl-maltooligosaccharides are transition state mimics. The crystal structure of the enzyme bound with acarviosyl-maltohexaose reveals that substrate binding at a distance from the active site is maintained largely by van der Waals interactions, with the four glucose residues at the reducing terminus of acarviosyl-maltohexaose retaining a left-handed single-helical conformation, as also observed in cycloamyloses and single helical V-amyloses. The kinetic behavior and structural features suggest that the subsite structure suitable for the stable conformation of amylose lowers the K_m for long-chain substrates, which in turn is responsible for higher specificity of the longer substrates.     

Vibrio sp. DSM 14379 Pigment Production—A Competitive Advantage in the Environment?

The ability to produce several antibacterial agents greatly increases the chance of producer’s survival. In this study, red-pigmented Vibrio sp. DSM 14379 and Bacillus sp., both isolated from the same sampling volume from estuarine waters of the Northern Adriatic Sea, were grown in a co-culture. The antibacterial activity of the red pigment extract was tested on Bacillus sp. in microtiter plates. The MIC₅₀ for Bacillus sp. was estimated to be around 10⁻⁵ mg/L. The extract prepared form the nonpigmented mutant of Vibrio sp. had no antibacterial effect. The pigment production of Vibrio sp. was studied under different physicochemical conditions. There was no pigment production at high or low temperatures, high or low salt concentrations in peptone yeast extract (PYE) medium, low glucose concentration in mineral growth medium or high glucose concentration in PYE medium. This indicates that the red pigment production is a luxurious good that Vibrio sp. makes only under favorable conditions. The Malthusian fitness of Bacillus sp. in a co-culture with Vibrio sp. under optimal environmental conditions dropped from 4.0 to −7.6, which corresponds to three orders of magnitude decrease in the number of CFU relative to the monoculture. The nonpigmented mutant of Vibrio sp. in a co-culture with Bacillus sp. had a significant antibacterial activity. This result shows that studying antibacterial properties in isolation (i.e. pigment extract only) may not reveal full antibacterial potential of the bacterial strain. The red pigment is a redundant antibacterial agent of Vibrio sp.     

Is That Me or My Twin? Lack of Self-Face Recognition Advantage in Identical Twins

Despite the increasing interest in twin studies and the stunning amount of research on face recognition, the ability of adult identical twins to discriminate their own faces from those of their co-twins has been scarcely investigated. One’s own face is the most distinctive feature of the bodily self, and people typically show a clear advantage in recognizing their own face even more than other very familiar identities. Given the very high level of resemblance of their faces, monozygotic twins represent a unique model for exploring self-face processing. Herein we examined the ability of monozygotic twins to distinguish their own face from the face of their co-twin and of a highly familiar individual. Results show that twins equally recognize their own face and their twin’s face. This lack of self-face advantage was negatively predicted by how much they felt physically similar to their co-twin and by their anxious or avoidant attachment style. We speculate that in monozygotic twins, the visual representation of the self-face overlaps with that of the co-twin. Thus, to distinguish the self from the co-twin, monozygotic twins have to rely much more than control participants on the multisensory integration processes upon which the sense of bodily self is based. Moreover, in keeping with the notion that attachment style influences perception of self and significant others, we propose that the observed self/co-twin confusion may depend upon insecure attachment.     

No Own-Age Advantage in Children’s Recognition of Emotion on Prototypical Faces of Different Ages

We test whether there is an own-age advantage in emotion recognition using prototypical younger child, older child and adult faces displaying emotional expressions. Prototypes were created by averaging photographs of individuals from 6 different age and sex categories (male 5–8 years, male 9–12 years, female 5–8 years, female 9–12 years, adult male and adult female), each posing 6 basic emotional expressions. In the study 5–8 year old children (n = 33), 9–13 year old children (n = 70) and adults (n = 92) labelled these expression prototypes in a 6-alternative forced-choice task. There was no evidence that children or adults recognised expressions better on faces from their own age group. Instead, child facial expression prototypes were recognised as accurately as adult expression prototypes by all age groups. This suggests there is no substantial own-age advantage in children’s emotion recognition.     

Does Hypothermic Treatment Provide an Advantage After Spinal Cord Injury Until Surgery? An Experimental Study

We compared the effects of early and late stage hypothermia treatment after spinal cord injury. Five groups each consisting of seven rats were included in this study. In Group 1a (Clip applied-non-treatment group) and Group 1b (Clip applied-treated group) the spinal cords were harvested 1 h after the injury. In Group 2a (clip applied, non-treated group) and Group 2b (clip applied-treated group) the injured segments were harvested 24 h after injury. Group 3 was designed as the sham-operated group. The significantly lower levels of TBARS and GSH-Px in Group 2a, as compared with Group 1b suggests that the hypothermia was effective in the early stage of treatment (P < 0.05). In contrast, TBARS and GSH-Px levels were significantly increased at the 24 h timepoint following treatment (P < 0.05).Short-term systemic hypothermia reduces lipid peroxidation in the early stages after spinal cord injury. This beneficial effect disappears 24 h following systemic hypothermic treatment.     

Hardy–Weinberg Disequilibrium of the IL-18 C?607A SNP Suggesting Selective Advantage of Heterozygotes

Interleukin-18 (IL-18) plays a key role in autoimmune, inflammatory, and infectious diseases. The IL-18 gene contains a C to A single nucleotide polymorphism (SNP) at position -607 (C-607A) within the promoter region, which was found to affect the promoter activity and subsequently the protein level of IL-18. We investigated this SNP in a group of healthy Singaporeans and found that CA was the most common genotype and the C allele was more prevalent than the A allele, which was not always the case in other ethnic groups. In addition, Singaporean Chinese were significantly different from Singaporean Indians in both allelic and genotypic distributions. Furthermore, significant deviations from Hardy-Weinberg equilibrium of this SNP were found in all three ethnic groups studied (Chinese, Indians, and Malays) and also in other published literature, suggesting that heterozygotes of this IL-18 C-607A SNP may have certain selective advantages.     

"Good Is Up” Is Not Always Better: A Memory Advantage for Words in Metaphor-Incompatible Locations

Four experiments examined whether memory for positive and negative words depended on word location and vertical hand movements. Cognitive processing is known to be facilitated when valenced stimuli are presented in locations that are congruent with the GOOD is UP conceptual metaphor, relative to when they are presented in incongruent locations. In both free recall and recognition tasks, we find a memory advantage for words that had been studied in metaphor incongruent locations (positive down, negative up). This incongruity advantage depends on the location of words during encoding, but no evidence was found to suggest that other spatial associations, such as the vertical position of the hand at encoding or word location during retrieval, affect memory. The results indicate that metaphors, like schemas, categories, and stereotypes, can influence cognition in complex ways, producing variable outcomes across different tasks.     

DHA Supplemented in Peptamen Diet Offers No Advantage in Pathways to Amyloidosis: Is It Time to Evaluate Composite Lipid Diet?

Numerous reports have documented the beneficial effects of dietary docosahexaenoic acid (DHA) on beta-amyloid production and Alzheimer's disease (AD). However, none of these studies have examined and compared DHA, in combination with other dietary nutrients, for its effects on plaque pathogenesis. Potential interactions of DHA with other dietary nutrients and fatty acids are conventionally ignored. Here we investigated DHA with two dietary regimes; peptamen (pep+DHA) and low fat diet (low fat+DHA). Peptamen base liquid diet is a standard sole-source nutrition for patients with gastrointestinal dysfunction. Here we demonstrate that a robust AD transgenic mouse model shows an increased tendency to produce beta-amyloid peptides and amyloid plaques when fed a pep+DHA diet. The increase in beta-amyloid peptides was due to an elevated trend in the levels of beta-secretase amyloid precursor protein (APP) cleaving enzyme (BACE), the proteolytic C-terminal fragment beta of APP and reduced levels of insulin degrading enzyme that endoproteolyse beta-amyloid. On the contrary, TgCRND8 mice on low fat+DHA diet (based on an approximately 18% reduction of fat intake) ameliorate the production of abeta peptides and consequently amyloid plaques. Our work not only demonstrates that DHA when taken with peptamen may have a tendency to confer a detrimental affect on the amyloid plaque build up but also reinforces the importance of studying composite lipids or nutrients rather than single lipids or nutrients for their effects on pathways important to plaque development.