Does low testosterone affect adaptive properties of adipose tissue in obese men?

Obesity and (pre)diabetes in males is associated with low serum testosterone and increased oestradiol levels. It is unknown whether these changes in sex steroids are part of a vicious circle resulting in an increase of risk for metabolic complications of obesity, or whether it presents merely an epiphenomenon. The risk for metabolic complications in obesity seems to be determined by adaptation and integrity of adipose tissue. It is unknown whether the typical changes in sex steroids seen in obese men are desirable or ominous with respect to these functions. However, it might be clinically relevant, as low serum testosterone can be treated, and well with different forms of interventional therapy. The present review provides a short summary on findings, obstacles and future research needed to gain better insight into consequences of changes in sex steroids for adaptation of adipose tissue in obese men.     

Does neonatal brain ischemia induce schizophrenia-like behavior in young adult rats?

Perinatal cerebral hypoxia represents a major cause of obstetric complications and the resulting transient oxygen deficiency might belong to early risk factors for schizophrenia. The aim of this study was to evaluate possible long-term behavioral changes induced by one hour of continuous bilateral common carotid artery occlusion in 12-day-old male rats. Post-ischemic behavioral disturbances were evaluated in social (play) behavior on postnatal day 22 (PND 22), open field test (PND 35 and 50) and prepulse inhibition of the acoustic startle reflex (PND 50). Transient ischemia in neonatal rats was not significantly altered in social dyadic interactions evaluated in pre-weaning pups, but resulted in enhanced locomotor activity in pubertal rats (PND 35) and impaired prepulse inhibition of the startle reflex in post-pubertal males (PND 50). These behavioral alterations suggest that perinatal hypoxic/ischemic insults may represent a risk factor for later manifestation of specific features relevant to schizophrenia in predisposed individuals.     

Does an increase in irradiance influence periphyton in a heavily-grazed woodland stream?

Summary Irradiance level and grazer density were manipulated in a factorial design to examine the relative effects of biotic and abiotic factors on periphyton biomass, productivity, and taxonomic structure in a heavily grazed, woodland stream. Irradiance levels were increased from 0.26 to 12.42 mol quanta/m²/d by placing metal halide lamps over the stream. The major grazer in this system was the prosobranch snail Elimia clavaeformis. Its densities were reduced from ca. 750 individuals/m² to near zero by raising platforms off the stream bottom. Experimental treatments were maintained for 48 days. Biomass-specific carbon fixation rates increased significantly in response to higher light levels, indicating that periphyton communities were light-limited at this time of year. However, positive effects of irradiance on areal-specific carbon fixation and biomass were detected only when grazer density was reduced. Basal cells of the chlorophyte Stigeoclonium dominated communities exposed either to low light or high grazing pressure. When light was increased and grazer density reduced, large or upright diatoms became more abundant. Results from this study indicated that limitation of periphyton photosynthesis could be mitigated by increasing the levels of an abiotic resource (light) to this system, but that periphyton biomass was controlled by biotic interactions.     

Does testosterone affect foraging behavior in male frogs?

During the breeding season, males often produce costly and extravagant displays or physical ornaments to attract females. Numerous studies have established that testosterone could directly influence the expression of certain sexual signals. However, few of these studies have focused on the indirect role that testosterone could play in modulating prey detection and visual performance to improve the foraging ability of males and hence their acquisition of nutritional resource. In the present study, we experimentally modified the testosterone levels of European tree frog males (Hyla arborea), staying in the natural range previously measured in the field, and we investigated the effect of testosterone on the foraging ability of individuals. Foraging capacities were measured on males placed in an arena with a virtual cricket moving on a computer screen. Our results demonstrated a significant effect of testosterone on the hunting behavior of H. arborea. We observed that testosterone reduced the orientation latency to virtual prey for supplemented males compared to controls. In addition, testosterone significantly increased the attack promptness of male frogs. Finally, our experiment did not demonstrate any impact of testosterone on male attack success.     

How well does a commercially available wearable device measure sleep in young athletes?

ABSTRACT

The validity of a commercially available wearable device for measuring total sleep time was examined in a sample of well-trained young athletes during night-time sleep periods and daytime naps. Participants wore a FitBit HR Charge on their non-dominant wrist and had electrodes attached to their face and scalp to enable polysomnographic recordings of sleep in the laboratory. The FitBit automatically detected 24/30 night-time sleep periods but only 6/20 daytime naps. Compared with polysomnography, the FitBit overestimated total sleep time by an average of 52 ± 152 min for night-time sleep periods, and by 4 ± 8 min for daytime naps. It is important for athletes and practitioners to be aware of the limitations of wearable devices that automatically detect sleep duration.     

Does a favourable change in the living conditions of young Kenyans affect their body (morphological) structure?

The aim of this study is to describe changes in the body structure of young Kenyans as a result of an upturn in the living conditions. The analyzed changes in their body build were caused by regular lifestyle and nutrition. The research material was male youth aged between 18 and 26. All those young men were students of a basic vocational school in Nairobi (Kenya). The first research was carried out in 1999 (n=121), the second one (n=302) exactly 12 months later and at the same institution. Changes in the body structure were studied on 31 individuals, who were examined twice. The examined parameters included: body height, body weight, chest circumference, waist circumference and thigh circumference. Information was also collected on the period a given student had stayed at that institution, his tribal membership, the number of children in his household and his number in the sequence of births in his family. Also the date of birth (at least the year) was of significance. All the examined men, whose body structure changes were analyzed, belonged to the Bantu language group. The studied individuals were at an age when growth had already finished. A more significant increase was observed in body weight, waist and thigh circumference. A regular schedule of activities and meals served in the dormitory resulted in body weight changes in 87% of those individuals, who were reexamined. As the basic reason for the observed changes one can regard the improvement in the level of nutrition, which was described by the examined individuals as "good".     

Does childhood experience of attention-deficit hyperactivity disorder symptoms increase sleep/wake cycle disturbances as measured with actigraphy in adult patients with bipolar disorder?

ABSTRACT

Childhood attention-deficit hyperactivity disorder (ADHD) is a common precursor of adult bipolar disorders (BD). Furthermore, actigraphy studies demonstrate that each disorder may be associated with abnormalities in sleep and activity patterns. This study investigates whether the presence or absence of self-reported childhood experiences of ADHD symptoms is associated with different sleep and activity patterns in adults with BD. A sample of 115 euthymic adult patients with BD was assessed for childhood ADHD symptoms using the Wender Utah Rating Scale (WURS) and then completed 21 days of actigraphy monitoring. Actigraphic measures of sleep quantity and variability and daytime activity were compared between BD groups classified as ADHD+ (n = 24) or ADHD? (n = 91), defined according to established cutoff scores for the WURS; then we examined any associations between sleep–wake cycle parameters and ADHD dimensions (using the continuous score on the WURS). Neither approach revealed any statistically significant associations between actigraphy parameters and childhood ADHD categories or dimensions. We conclude that the sleep and activity patterns of adult patients with BD do not differ according to their self-reported history of ADHD symptoms. We discuss the implications of these findings and suggest how future studies might confirm or refute our findings.     

Does predation result in adult sex ratio skew in a sexually dimorphic insect genus?

Theory proposes that sexually dimorphic, polygynous species are at particularly high risk of sex-biased predation, because conspicuous males are more often preyed upon compared to females. We tested the effects of predation on population sex ratio in a highly sexually dimorphic insect genus (Hemideina). In addition, introduction of a suite of novel mammalian predators to New Zealand during the last 800 years is likely to have modified selection pressures on native tree weta. We predicted that the balance between natural and sexual selection would be disrupted by the new predator species. We expected to see a sex ratio skew resulting from higher mortality in males with expensive secondary sexual weaponry; combat occurs outside refuge cavities between male tree weta. We took a meta-analytic approach using generalized linear mixed models to compare sex ratio variation in 58 populations for six of the seven species in Hemideina. We investigated adult sex ratio across these populations to determine how much variation in sex ratio can be attributed to sex-biased predation in populations with either low or high number of invasive mammalian predators. Surprisingly, we did not detect any significant deviation from 1 : 1 parity for adult sex ratio and found little difference between populations or species. We conclude that there is little evidence of sex-biased predation by either native or mammalian predators and observed sex ratio skew in individual populations of tree weta is probably an artefact of sampling error. We argue that sex-biased predation may be less prevalent in sexually dimorphic species than previously suspected and emphasize the usefulness of a meta-analytic approach to robustly analyse disparate and heterogeneous data.     

Does the timing of attainment of maturity influence sexual size dimorphism and adult sex ratio in turtles?

The attainment of sexual maturity has been shown to affect measures of sexual size dimorphism (SSD) and adult sex ratios in several groups of vertebrates. Using data for turtles, we tested the model that sex ratios are expected to be male‐biased when females are larger than males and female‐biased when males are larger than females because of the relationship of each with the attainment of maturity. Our model is based on the premise that the earlier‐maturing sex remains smaller, on average throughout life, and predominates numerically unless the sexes are strongly affected by differential mortality, differential emigration, and immigration, or biased primary sex ratios. Based on data for 24 species in seven families, SSD and sex ratios were significantly negatively correlated for most analyses, even after the effect of phylogenetic bias was removed. The analyses provide support for the model that SSD and adult sex ratios are correlated in turtles as a result of simultaneous correlation of each with sexual differences in attainment of maturity (bimaturism). Environmental sex determination provides a possible mechanism for the phenomenon in turtles and some other organisms. © 2014 The Authors. Biological Journal of the Linnean Society published by John Wiley & Sons Ltd on behalf of The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 112 , 142–149.     

Does sun glare increase antipredator behaviour in prey?

As the sun gradually lowers over the horizon, prey species with more sun in their eyes should have more difficulty in visually monitoring their surroundings for threats and thus experience a higher predation risk. In a unique setting, I could examine changes in antipredator behaviour in a prey species, the semipalmated sandpiper Calidris pusilla, facing attacks by peregrine falcons Falco peregrinus, which originated from the general direction of the lowering sun. I predicted gradual changes in antipredator behaviour as sun glare becomes more problematic later in the day. As the day progressed, sandpipers occurred in sparser groups when the sun glared but not when clouds obscured the sun, suggesting that fewer individuals engaged in risky foraging. Pecking rate and foraging success decreased later in the day when the sun glared but not otherwise implying an increase in vigilance at the expense of foraging. When more sun hit their eyes, sandpipers also moved faster suggesting increased skittishness. The sun glare effect might be relevant to any species foraging in open areas not only when the sun sets but also when it rises especially if predators can target prey species at these vulnerable times. The temporal gradient in predation risk that the sun glare effect creates might thus apply broadly and have important consequences for antipredator vigilance, foraging efficiency, and habitat use.     

Is sleep apnea underdiagnosed in adult patients with osteogenesis imperfecta? –a single-center cross-sectional study

Background

Patients with Osteogenesis imperfecta (OI) suffer from increased bone fracture tendency generally caused by a mutation in genes coding for type I collagen. OI is also characterized by numerous co-morbidities, and recent data from questionnaire studies suggest that these may include increased risk for sleep apnea, a finding that lacks clinical evidence from cohort studies. In this cross-sectional study, 25 adults with OI underwent clinical otorhinolaryngology examination as well as overnight polysomnography to address the question. The participants were aged between 19 and 77?years, and ten of them had mild clinical OI phenotype, seven had a moderately severe phenotype, and eight had a severe phenotype.

Results

We found obstructive sleep apnea (apnea hypopnea index ≥5/h) in as many as 52% of the OI patients in the cohort. Unexpectedly, however, no correlation was present between sleep apnea and daytime sleepiness, experienced bodily pain, severity of OI, Mallampati score, or neck circumference.

Conclusions

Seeing that the usual predictors showed no association with occurrence of sleep apnea, we conclude that obstructive sleep apnea may easily be left as an undetected disorder in individuals with OI. Recurrent nocturnal hypoxia due to episodes of apneas can even affect bone metabolism, thereby further aggravating bone fragility in patients with OI.

     

The association between endogenous testosterone level and behavioral flexibility in young men – Evidence from stimulus-outcome reversal learning

The capacity to flexibly adapt responding to unexpected changes in the environment is crucial for survival. Several neurotransmitters have been implicated in stimulus-outcome reversal learning. Yet, it remains an open question whether inter-individual differences in the neuroactive hormone testosterone may also be related to this type of behavioral flexibility. In this study we assessed the association between endogenous testosterone level and reversal learning in young healthy men. We used an observer reversal learning task, in which subjects viewed computer-based decisions between two stimuli, of which one was currently rewarded while the other one was punished. Contingencies reversed unpredictably every 5–9 trials. Subjects had to indicate the current outcome association before the actual outcome was revealed. In the trial following an unexpected reversal either the same stimulus from the reversal (experienced reversal), or its alternative, for which the reversal had not yet been shown (inferred reversal), could be chosen by the computer, and subjects had to adapt responding accordingly. We found that testosterone predicted better post-reversal performance. This correlation was strongest in the more difficult inferred reversal condition, particularly in impulsive individuals. Collectively, these data support the view that endogenous testosterone may enhance behavioral flexibility in men, particularly when working memory demand is high and subjects have to update several stimulus-outcome contingencies at the same time. It remains to be further elucidated whether this testosterone effect was achieved through an interaction with dopaminergic transmission or through direct interplay with androgen receptors in the brain regions implicated in reversal learning.     

Does attractiveness in men provide clues to semen quality?

The psychological mechanisms underlying attractiveness judgements in humans are thought to be evolved adaptations for finding a high quality mate. The phenotype-linked fertility hypothesis proposes that females obtain reliable information on male fertility from male expression of sexual traits. A previous study of Spanish men reported that facial attractiveness was positively associated with semen quality. We aimed to determine whether this effect was widespread by examining a large sample of Australian men. We also extended our study to determine whether cues to semen quality are provided by components of attractiveness: masculinity, averageness and symmetry. Each male participant was photographed and provided a semen sample that was analyzed for sperm morphology, motility and concentration. Two independent sets of women rated the male photographs for attractiveness, and three further sets of 12 women rated the photographs for masculinity, symmetry or averageness. We found no significant correlations between semen quality parameters and attractiveness or attractive traits. Although male physical attractiveness may signal aspects of mate quality, our results suggest that phenotype-linked cues to male fertility may not be general across human populations.     

Does forest fragmentation cause an increase in forest temperature?

Forest fragmentation is considered by many to be a primary cause of the current biodiversity crisis. The underlying mechanisms are poorly known, but a potentially important one is associated with altered thermal conditions within the remaining forest patches, especially at forest edges. Yet, large uncertainty remains about the effect of fragmentation on forest temperature, as it is unclear whether temperature decreases from forest edge to forest interior, and whether this local gradient scales up to an effect of fragmentation (landscape attribute) on temperature. We calculated the effect size (correlation coefficient) of distance from forest edge on air temperature, and tested for differences among forest types surrounded by different matrices using meta-analysis techniques. We found a negative edge-interior temperature gradient, but correlation coefficients were highly variable, and significant only for temperate and tropical forests surrounded by a highly contrasting open matrix. Nevertheless, it is unclear if these local-scale changes in temperature can be scaled up to an effect of fragmentation on temperature. Although it may be valid when considering “fragmentation” as forest loss only, the landscape-scale inference is not so clear when we consider the second aspect of fragmentation, where a given amount of forest is divided into a large number of small patches (fragmentation per se). Therefore, care is needed when assuming that fragmentation changes forest temperature, as thermal changes at forest edges depend on forest type and matrix composition, and it is still uncertain if this local gradient can be scaled up to the landscape.     

Does a universal sleep education programme improve the sleep habits of primary school children?

Sleep and Biological Rhythms - While a number of studies have evaluated sleep education programmes for adolescents and for parents of very young children, there is much less research available on...     

Does tree diversity increase wood production in pine forests?

Recent experimental advances on the positive effect of species richness on ecosystem productivity highlight the need to explore this relationship in communities other than grasslands and using non-synthetic experiments. We investigated whether wood production in forests dominated by Aleppo pine (Pinus halepensis) and Pyrenean Scots pine (Pinus sylvestris) differed between monospecific and mixed forests (2-5 species) using the Ecological and Forest Inventory of Catalonia (IEFC) database which contains biotic and environmental characteristics for 10,644 field plots distributed within a 31,944 km(2) area in Catalonia (NE Spain). We found that in Pyrenean Scots pine forests wood production was not significantly different between monospecific and mixed plots. In contrast, in Aleppo pine forests wood production was greater in mixed plots than in monospecific plots. However, when climate, bedrock types, radiation and successional stage per plot were included in the analysis, species richness was no longer a significant factor. Aleppo pine forests had the highest productivity in plots located in humid climates and on marls and sandstone bedrocks. Climate did not influence wood production in Pyrenean Scots pine forests, but it was highest on sandstone and consolidated alluvial materials. For both pine forests wood production was negatively correlated with successional stage. Radiation did not influence wood production. Our analysis emphasizes the influence of macroenvironmental factors and temporal variation on tree productivity at the regional scale. Well-conducted forest surveys are an excellent source of data to test for the association between diversity and productivity driven by large-scale environmental factors.     

Does biodiversity increase spatial stability in plant community biomass?

We tested the hypothesis that biodiversity decreases the spatial variability of biomass production between subplots taken within experimental grassland plots. Our findings supported this hypothesis if functional diversity (weighted Rao's Q ) was considered. Further analyses revealed that diversity in rooting depth and clonal growth form were the most important components of functional diversity stabilizing productivity. Using species or functional group richness as diversity measures there was no significant effect on spatial variability of biomass production, demonstrating the importance of the biodiversity component considered. Moreover, we found a significant increase in spatial variability of productivity with decreasing size of harvested area, suggesting small-scale heterogeneity as an important driver. The ability of diverse communities to stabilize biomass production across spatial heterogeneity may be due to complementary use of spatial niches. Nevertheless, the positive effect of functional diversity on spatial stability appears to be less pronounced than previously reported effects on temporal stability.