Respiration characteristics in temperate rainforest tree species differ along a long-term soil-development chronosequence

We measured the response of dark respiration (R_d) to temperature and foliage characteristics in the upper canopies of tree species in temperate rainforest communites in New Zealand along a soil chronosequence (six sites from 6 years to 120,000 years). The chronosequence provided a vegetation gradient characterised by significant changes in soil nutrition. This enabled us to examine the extent to which changes in dark respiration can be applied across forest biomes and the utility of scaling rules in whole-canopy carbon modelling. The response of respiration to temperature in the dominant tree species differed significantly between sites along the sequence. This involved changes in both R_d at a reference temperature (R₁₀) and the extent to which R_d increased with temperature (described by E_o, a parameter related to the energy of activation, or the change in R_d over a 10°C range, Q₁₀). Site averaged E_o ranged from 44.4 kJ mol^–1 K^–1 at the 60-year-old site to 26.0 kJ mol^–1 K^–1 at the oldest, most nutrient poor, site. Relationships between respiratory and foliage characteristics indicated that both the temperature response of respiration (E_o or Q₁₀) and the instantaneous rate of respiration increased with both foliar nitrogen and phosphorus content. The ratio of photosynthetic capacity (Whitehead et al. in Oecologia 2005) to respiration (A_max/R_d) attained values in excess of 15 for species in the 6- to 120-year-old sites, but thereafter decreased significantly to around five at the 120,000-year-old site. This indicates that shoot carbon acquisition is regulated by nutrient limitations in the retrogressing ecosystems on the oldest sites. Our findings indicate that respiration and its temperature response will vary according to soil age and, therefore, to soil nutrient availability and the stage of forest development. Thus, variability in respiratory characteristics for canopies should be considered when using models to integrate respiration at large spatial scales.     

The dark phase improves genetic discrimination for some high throughput mouse behavioral phenotyping

Dark-phase testing has previously been shown by others to improve the outcome of some 'classical' behavior test situations. However, the importance of such ethological correctness and the effect of the light/dark cycle on high throughput behavioral testing situations such as 'mutant vs. wild type' and 'screening', are less or unknown, respectively. These testing situations differ from the 'classical' in that they are designed primarily to discriminate between genetically different mice rather than provide a detailed assessment of ability or psychosocial state. Here we test the hypotheses that dark-phase testing affects the outcome of high throughput behavioral tests and that dark-phase testing improves discrimination between genetically distinct mice (C57BL/6J, 129S1/SvImJ and B6129F1) using high throughput behavioral tests. Our results demonstrate that, although all successful tests showed some effect of phase, only the SHIRPA primary screen, open-field test and motor learning on the rotarod showed improved strain discrimination in the dark phase. Surprisingly, the social interaction test did not show a clear benefit to either phase, and interestingly, the tail-flick test discriminated strains better in the light phase. However, since the preponderance of our data shows that dark-phase testing improves, or does not affect, strain discrimination, we conclude that for these strains and tests, dark-phase testing provided superior outcomes. If discrimination is not achieved in the dark phase, then light phase-testing would be undertaken.     

Post-embryonic photoreceptor development and dark/light adaptation in the spittle bug Philaenus spumarius (L.) (Homoptera, Cercopidae)

The aims of this paper have been to describe (1) the general structure of the compound eye of the spittle bug Philaenus spumarius, (2) the eye's post-embryonic development, (3) photomechanical changes upon dark/light adaptation in the eye, and (4) how leaving the semi-aquatic foam bubble and turning into an adult affects the organization of the eye. Spittle bugs, irrespective of size or sex, possess apposition type compound eyes. The eye's major components (i.e. facet, cornea, cone and rhabdom) grow rather isometrically from the smallest nymph to the adult. Photomechanical changes can occur during both nymphal and adult phases and manifest themselves through pigment granules and mitochondria migrating to and away from the rhabdom, and rhabdom diameters varying with time of day and ambient light level. When a nymph transforms into an adult, its compound eyes’ dorsoventral axes widen, facet diameters increase, facet shapes turn from circular to pentagonal and hexagonal, the cornea thickens and the rhabdoms become thinner. The agile adults, free from the foam that surrounds the nymphs, can be expected to need their vision more than the nymphs, and the changes in eye structure do, indeed, indicate that the adults have superior visual acuity. A thicker cornea in the adults reduces water loss and protects the compound eye from mechanical and light-induced damage: protection given to the nymphs by their foam bubbles.     

Analysis of human tissues using Energy Dispersive X Ray Fluorescence – Dark matrix determination for the application to cancer research

BackgroundX ray Fluorescence has been essayed as a suitable technique for the elemental quantification of trace element in human tissues, namely comparison of normal and cancerous tissue. However, accurate results depend on a robust quantification approach, namely correct evaluation of the samples’ dark matrix.MethodsIn order to determine the most suitable dark matrix composition for the quantification of such samples using the Fundamental Parameter approach, we have measured several Certified Reference Materials and essayed different dark matrix compositions to achieve the most accurate results. The resulting dark matrix was then applied to normal and tumor ovarian and prostate tissue samples, and the obtained results were compared with the ones obtained with a comparative method using external standard calibration curves.ResultsUsing a dark matrix composed of 10 % - H, 22 % - C, 3 % - N and 60 % - O yielded the best compromise in accuracy for the light and heavy elements. For the reduced sample size and conditions of this study, for both organs, the concentrations of transition metals decrease in tumor tissues, while the concentration of lighter elements, P and Cl, increases. On the other hand, there are elements that showed different behavior between the two types of tissue, namely Zn and S, that increase in prostate tumor tissue and decrease in ovarian tissue.ConclusionAn increase in precision was one of the improvements found with the newly developed method, as the FP-approach contemplates matrix effects and the influence of other elements in the analytes’ quantification. Additionally, the determined dark matrix can be employed in any tissue analysis application by means of EDXRF.     

Arabidopsis thaliana model system reveals a continuum of responses to root endophyte colonization

We surveyed the non-mycorrhizal model plant Arabidopsis thaliana microscopically for its ability to form dark septate endophyte (DSE) symbioses in field, greenhouse, and laboratory studies. The laboratory studies were also used to estimate host growth responses to 34 Periconia macrospinosa and four Microdochium sp. isolates. Consistent with broad host range observed in previous experiments, field-, greenhouse-, and laboratory-grown A. thaliana were colonized by melanized inter- and intracellular hyphae and microsclerotia or chlamydospores indicative of DSE symbiosis. Host responses to colonization were variable and depended on the host ecotype. On average, two A. thaliana accessions (Col-0 and Cvi-0) responded negatively, whereas one (Kin-1) was unresponsive, a conclusion consistent with our previous analyses with forbs native to the field site where the fungi originate. Despite the average negative responses, examples of positive responses were also observed, a conclusion also congruent with earlier studies. Our results suggest that A. thaliana has potential as a model for more detailed dissection of the DSE symbiosis. Furthermore, our data suggest that host responses are controlled by variability in the host and endophyte genotypes.     

The dark side of coloration: Ecogeographical evidence supports Gloger's rule in American marsupials

Geographical distribution of color phenotypes and associations with ecological predictors remains poorly understood. An important geographic pattern concerning this topic is Gloger's rule, which predicts the increase of pigmentation in endothermic animals from cold and dry to warm and wet environments. Didelphid marsupials exhibit a variety of color patterns, ranging from light and dark uniform to more complex colorations. However, surprisingly little is known about the adaptive significance of dark coloration in this singular group of mammals. Using a phylogenetic comparative approach, we investigated whether coloration in different body regions of didelphids (i.e., dorsum and face) is associated with variables representing heat and humidity of the environment, as predicted by Gloger's rule. We demonstrated that Gloger's rule explains the interspecific color variation in American marsupials, especially when considering the facial region. Thus, dark coloration was more frequent among didelphid species occupying warm and wet environments than cold and dry environments. We also discuss the selective forces that can potentially explain coat color variation in didelphid marsupials, including camouflage, pathogen resistance, and pleiotropy hypotheses.     

Ectomycorrhizal root tips harbor distinctive fungal associates along a soil nitrogen gradient

A diverse range of fungi associate with ectomycorrhizal (EcM) root tips, however, their identity and the biotic and abiotic filters structuring these communities remain unknown. We employed a metabarcoding approach to characterize fungal communities associating with the EcM root tips of Quercus rubra along a natural soil nitrogen gradient. EcM communities and ectomycorrhizal associated fungi (EcAF) were tightly linked across the breadth of the soil gradient. Notably, EcAF communities were primarily shaped by the morphological attributes of EcM communities, particularly the relative abundance of EcM taxa forming rhizomorphic hyphae. Edaphic properties (soil C:N and net N mineralization) exerted minimal influence, suggesting a strong role of biotic interactions in EcAF community assembly. The presence of plants forming ericoid mycorrhizal associations also shapes the prevalence of ericoid mycorrhizal fungi associating with EcM root tips. Overall, EcAF communities were dominated by helotialean fungi, ericoid mycorrhizal fungi, dark septate endophytes, and the white-rot fungi Mycena.     

AMBER LENSES TO BLOCK BLUE LIGHT AND IMPROVE SLEEP: A RANDOMIZED TRIAL

All light is not equal: blue wavelengths are the most potent portion of the visible electromagnetic spectrum for circadian regulation. Therefore, blocking blue light could create a form of physiologic darkness. Because the timing and quantity of light and darkness both affect sleep, evening use of amber lenses to block blue light might affect sleep quality. Mood is also affected by light and sleep; therefore, mood might be affected by blue light blockade. In this study, 20 adult volunteers were randomized to wear either blue-blocking (amber) or yellow-tinted (blocking ultraviolet only) safety glasses for 3?h prior to sleep. Participants completed sleep diaries during a one-week baseline assessment and two weeks' use of glasses. Outcome measures were subjective: change in overall sleep quality and positive/negative affect. Results demonstrated that sleep quality at study outset was poorer in the amber lens than the control group. Two- by three-way ANOVA revealed significant (p?<?.001) interaction between quality of sleep over the three weeks and experimental condition. At the end of the study, the amber lens group experienced significant (p?<?.001) improvement in sleep quality relative to the control group and positive affect (p?=?.005). Mood also improved significantly relative to controls. A replication with more detailed data on the subjects' circadian baseline and objective outcome measures is warranted. (Author correspondence: jphelps@samhealth.org)     

欧洲黑蜂和新疆黑蜂越冬期抗氧化酶活性及相关基因表达分析

以欧洲黑蜂和新疆黑蜂为研究对象,比较和分析两个蜂种在越冬条件下抗氧化酶活性和抗氧化能力相关基因表达的变化规律,探究二者在越冬期的抗氧化酶功能及其基因表达特征。本试验测定了蜂群损失率和饲料消耗量等越冬性能指标以及总抗氧化能力（T-AOC）、超氧化物歧化酶（T-SOD）和过氧化氢酶（CAT）等抗氧化酶的酶活力值,并采用实时荧光定量PCR方法检测SOD、CAT、Grx1、MsrA和Vg基因等抗氧化酶功能基因的表达情况。结果显示,欧洲黑蜂和新疆黑蜂的蜂群损失率和饲料消耗率分别为32.86%、32.91%和23.41%、23.91%。在抗氧化酶活性变化规律方面,两个蜂种的T-AOC酶活力呈逐步升高趋势;T-SOD酶活力呈先下降再升高的趋势,在越冬中期达到最低值;CAT酶活力呈先升高再降低又再升高的趋势;在抗氧化功能相关基因的mRNA表达方面,两个蜂种的SOD基因和CAT基因的表达在越冬中期达到最低值;Grx1基因的表达在越冬后期急剧升高,达到峰值;MsrA基因的表达呈先降低后升高的趋势;Vg基因的表达在越冬的中前期呈逐渐升高趋势。结果表明,在低温逆境条件下,两个蜂种体内的抗氧化酶系统可能发挥了重要的防御作用,存在一定的耐寒适应机制,其中越冬中期可能是酶活性变化和基因表达的发生显著变化的特殊阶段。本试验的研究为揭示蜜蜂体内抵御低温应答机制研究提供新线索,也为深入研究蜜蜂耐寒分子机制和抗寒蜂种的选育提供基础数据。     

Biohydrogen production in alkalithermophilic conditions: Thermobrachium celere as a case study

In the present work the hydrogenesis in the anaerobic alkalithermophilic bacterium Thermobrachium celere was studied. The impact of several factors on hydrogen production during glucose fermentation was investigated in batch conditions. The optimal hydrogen production occurred at pH_67 °C 8.2 with phosphate buffer concentration of 50 mM. Hydrogen yield reached the highest value of 3.36 mol H₂/mol glucose when the partial pressure in the gas headspace was reduced. Supplementation of nitrogen sources and iron affected hydrogen production. Under optimized conditions, the maximum H₂ accumulation and H₂ production rate were estimated to be respectively 124.3 mmol H₂/l culture and 20.7 mmol H₂/l/h. Considering the efficient and rapid hydrogen evolution, and the ability to grow in extreme environments, T. celere might be a good candidate for biohydrogen production in open (non-sterile) bioprocess system.