Exposure systems for bioelectromagnetic experiments

One of the most interesting questions in bioelectromagnetics is why there is a difference between results of experiments performed in various labs in “identical” conditions. One of the possible reasons is the difference of investigated objects, especially while performing experiments in vivo. However, the authors, as engineers, would like to focus readers’ attention on the technical aspects of exposure systems, especially the presence and role of mutual interaction between biological objects under test (OUT) and the exposure system, the interactions between the objects, the role of polarization, the similarity of real exposure to that applied in experiments etc. All these factors may alter the results of experiments and lead to false conclusions.     

TrackBeam, a simple tool for estimating potential exposure to the solar beam underneath tree canopies

A simple tool, TrackBeam, for rapid in situ estimates of potential exposure to the solar beam of objects underneath tree canopies is presented, tested and demonstrated to be useful in insect conservation studies. The tool can be used whenever accurate data on sun exposure is of use e.g., in ecological studies of saproxylic insects. TrackBeam draws upon the principles behind the analysis of hemispherical photographs but its use is much less dependent on the weather at the time of sampling. It may be used for detecting canopy openings in directions corresponding to the solar path. Based on this, periods of time with potential beam exposure and/or the proportion of sky that is not obscured by canopy for objects such as dead wood may be estimated. The results of using TrackBeam compares well between operators and with the corresponding results of analysed hemispherical photographs. Results are presented which show that TrackBeam was successfully used to characterise the habitat light requirements of the saproxylic beetle Melanotus castanipes (Coleoptera: Elateridae).     

Attachment Behavior of Shewanella putrefaciens onto Magnetite under Aerobic and Anaerobic Conditions

In this study, batch experiments were used to characterize attachment behavior of Shewanella putrefaciens strain 200R to ferrihydrite and magnetite. Attachment was quantified in batch experiments with a 0.01 M NaNO ₃ solution as a function of pH (ranging from 3 to 10), sorbed anion (PO₄ ^{3 ?} ), and growth conditions (aerobic vs. anaerobic). Electrophoretic mobility data was collected for S. putrefaciens cells and magnetite grains and used as a means to interpret the role of electrostatic interaction in attachment studies. Little difference in attachment behavior was observed as a function of growth conditions or surface treatments. The exception was at pH ranging from 2 to 4, under anaerobic conditions, where increased attachment was measured on magnetite surfaces with sorbed PO₄ ^{3 ?} . This increased attachment was attributed to development of Fe-PO₄ surface complexes or secondary mineral phases, resulting in altered surface interactions between cell and mineral surfaces. Attachment was irreversible and increased with time under anaerobic conditions even under elevated pH conditions unfavourable to electrostatic interactions between cells and mineral surfaces. These results suggest that electrophoretic mobility data in this system is not a good predictor of attachment behavior, while surface charge development via protonation and deprotonation of surface functional groups is consistent with experimental attachment data. In this study, S. putrefaciens appears to utilize polymers or pili to remain attached to Fe-oxides and this process may facilitate Fe reduction on these surfaces. Results from this study underscore the need for quantitative bulk measurements of microbial attachment to accurately predict partitioning of dissimilatory iron reducing bacteria between solution and solid phases.     

假结核耶尔森氏菌中Phd-Doc毒素-抗毒素系统的功能鉴定

【背景】毒素-抗毒素系统在微生物体内广泛存在,在微生物对抗外界不良环境方面发挥重要作用。【目的】以模式细菌假结核耶尔森氏菌(Yersinia pseudotuberculosis,Yptb)为材料,探究其编码的Phd-Doc毒素-抗毒素系统的作用机制和生物学功能。【方法】通过生物信息学方法预测Yptb中编码的Phd-Doc毒素-抗毒素系统,通过毒性分析、基因表达分析及蛋白相互作用对其进行鉴定;通过抗生素胁迫、氧胁迫、生物被膜形成等实验研究Phd-Doc在体内发挥的生物学功能。【结果】生物信息学分析鉴定出一对Phd-Doc毒素-抗毒素系统,发现二者共转录且相互作用;毒素蛋白Doc能够引起大肠杆菌形态发生变化并抑制其生长,抗毒素蛋白Phd能中和Doc的毒性;Phd-Doc毒素-抗毒素系统具有自调控抑制效应;phd-doc的缺失对Yptb自身的生长无影响,而且毒素蛋白Doc在野生型Yptb内过表达并未显示毒性;phd-doc在转录水平上响应了抗生素胁迫和氧胁迫,其中,对氯霉素胁迫最为敏感,但并不影响Yptb的生长;同时,Phd-Doc能够影响Yptb的生物被膜形成能力。【结论】Yptb中Phd-Doc毒素-抗毒素系统的功能鉴定对于更好地了解在多变的外部环境下微生物的定殖和响应机制具有重要意义。     

The relationship between co-exposure to multiple heavy metals and liver damage

BackgroundThe impact of heavy metal exposure on human health has attracted widespread attention of researchers, and the impact of heavy metal exposure on liver function has also been confirmed, however, more attention is paid to the impact of single or two heavy metal exposures, and most epidemiological studies focus on heavy metal pollution areas. In this study, rural residents in non-heavy metal-contaminated areas in Northwest China were selected as the research objects to explore the comprehensive effects of co-exposure to multiple heavy metals on the liver, which can provide certain reference and support for related research.ObjectivesThis study used a Bayesian nuclear machine model (BKMR) to evaluate the relationship between exposure to heavy metal mixtures and indicators of liver function in a population in rural Northwest China.ResultsExposure to higher concentrations of metal mixtures was positively correlated with total bilirubin, direct bilirubin, and aspartate aminotransferase, and negatively correlated with alanine aminotransferase, with Pb contributing the most to indicators of liver function. We also observed a possible interaction of Cd with other heavy metals in the effect of heavy metal mixtures on DB levels.ConclusionsConcurrent exposure to higher concentrations of heavy metal mixtures (Cr, Co, Cd, and Pb) in rural China was associated with indicators representing poor liver function, of which the effect of lead on liver function should be focused. More prospective epidemiological studies and animal experiments need to be carried out to determine this relationship and possible mechanism.     

Effects of environmental heterogeneity on species diversity and composition of terrestrial bryophyte assemblages in tropical montane forests of southern Ecuador

Background: Most studies on tropical bryophytes deal with epiphytic species. This is the first ecological study of tropical forests that focuses specifically on terrestrial bryophytes.

Aim: To investigate the differences between slope and ridge environments in upper montane forests of southern Ecuador in terms of species diversity (richness, abundance), species composition and life forms of terrestrial bryophytes.

Methods: We used Non-metric Multidimensional Scaling (NMDS) to group bryophyte relevés by study location, habitat type and exposure class. Species indicator values were calculated and compared for different habitats.

Results: In total, 140 species were recorded, the majority being liverworts. NMDS analyses and Mantel correlations clearly separated between slope and ridge relevés, and between sunny and shaded microhabitats on ridges. Bryophyte life forms also showed different distribution patterns in slope and in ridge habitats. Mosses were more prominent in sunny than in shaded microhabitats.

Conclusions: Environmental differentiation between ridges and slopes, and small-scale variation in microclimatic conditions caused by differences in exposure, were stronger predictors of species richness and composition than geographical distance between study sites.     

Interplay between stress response genes associated with attention‐deficit hyperactivity disorder and brain volume

The glucocorticoid receptor plays a pivotal role in the brain's response to stress; a haplotype of functional polymorphisms in the NR3C1 gene encoding this receptor has been associated with attention‐deficit hyperactivity disorder (ADHD). The serotonin transporter (5‐HTT) gene polymorphism 5‐HTTLPR is known to influence the relation between stress exposure and ADHD severity, which may be partly because of its reported effects on glucocorticoid levels. We therefore investigated if NR3C1 moderates the relation of stress exposure with ADHD severity and brain structure, and the potential role of 5‐HTTLPR. Neuroimaging, genetic and stress exposure questionnaire data were available for 539 adolescents and young adults participating in the multicenter ADHD cohort study NeuroIMAGE (average age: 17.2 years). We estimated the effects of genetic variation in NR3C1 and 5‐HTT, stress exposure and their interactions on ADHD symptom count and gray matter volume. We found that individuals carrying the ADHD risk haplotype of NR3C1 showed significantly more positive relation between stress exposure and ADHD severity than non‐carriers. This gene–environment interaction was significantly stronger for 5‐HTTLPR L‐allele homozygotes than for S‐allele carriers. These two‐ and three‐way interactions were reflected in the gray matter volume of the cerebellum, parahippocampal gyrus, intracalcarine cortex and angular gyrus. Our findings illustrate how genetic variation in the stress response pathway may influence the effects of stress exposure on ADHD severity and brain structure. The reported interplay between NR3C1 and 5‐HTT may further explain some of the heterogeneity between studies regarding the role of these genes and hypothalamic–pituitary–adrenal axis activity in ADHD.     

Shell fighting and competition between two hermit crab species in Panama

Summary This article is a study of shell fighting between two intertidal hermit crab species in Panama. Laboratory results showed some cases of high exchange frequencies between Calcinus obscurus and Clibanarius albidigitus when the former occupied poor-quality shells. Exchange frequencies varied considerably between collecting sites, and were always low when the defending Clibanarius came from Venado Beach. Shell exchange frequencies estimated from field experiments were similar to those obtained in the laboratory. Observations on relative shell sizes occupied by both species in areas of sympatry and allopatry failed to provide clear evidence that Calcinus reduced the shell size of Clibanarius or that Clibanarius increased the shell size occupied by Calcinus. Results obtained here differ from those obtained in previous studies (Abrams 1980; Bertness 1981a, b), and these differences are discussed. Although shell fighting may be an important component of the interaction of these species, it is likely that roughly 90% of the competition experienced by each species is intraspecific.     

Grazing dynamics in intertidal rockpools: Connectivity of microhabitats

Differences between rockpool and emergent rock communities are often attributed to their contrasting physical conditions. However, differences in grazing pressure between rockpools and open rock could also exert an important structuring role. Greater densities and/or the lack of tidal constraints on foraging may allow grazing intensity to be greater in rockpools. Here, wax discs were deployed to compare grazing intensity between rockpool and emergent rock habitats at each of three tidal heights on a moderately exposed shore in SW England. Grazing intensity was then examined in relation to herbivore density. Grazing intensity in pools was twice that on emergent rock, despite a lower density of herbivores in the rockpools. Of these herbivores, patellid limpets are the dominant grazers on rocky shores throughout the NE Atlantic and are recognised to have a major role in structuring intertidal communities. Thus, subsequent experiments focussed on the influence of limpets in determining the differences in consumer pressure between rockpools and emergent rock. Three alternative explanations were considered: (1) the effect of continuous immersion on grazing intensity in rockpools; (2) differences in limpet species abundance between the two habitats; (3) movement of limpets from emergent rock into pools to feed. The level of grazing pressure exerted by Patella ulyssiponensis (Gmelin), the predominant species living constantly immersed in rockpools, was similar to that of P. vulgata (Linnaeus) which is predominantly found on emergent rock. P. vulgata were observed moving from emergent rock into rockpools during high tide. Manipulative experiments confirmed that these foraging excursions resulted in a 2-fold increase in grazing intensity in the pools. Grazing activity of P. vulgata in rockpools was not consistent between sites and may be influenced by differences in wave exposure and/or the abundance of microbial resources. Elevated consumer pressure in rockpools may be an important factor influencing algal assemblages and probably explains the predominance of grazer resistant-species in these pools.     

Biomineralization of Middle Rare Earth Element Samarium in Yeast and Bacteria Systems

Microorganisms play an important role in the mineralization of heavy metals in different environments. Previous studies have reported the phosphate mineralization of light (Ce) and heavy (Yb) rare earth elements with yeast. However, little is known about differences in the biomineralization process of middle rare earth elements (including Sm, Eu, Gd, Tb and Dy) by yeast and bacteria. We carried out a series of experiments to compare the sorption process of Sm by Saccharomyces cerevisiae (yeast), Pseudomonas fluorescens (gram-negative bacteria) and Bacillus subtilis (gram-positive bacteria) in initial pH 3, 4 and 5 solutions. The concentrations of Sm in exposure solutions decreased as a function of exposure time in all three systems, which revealed the accumulation of Sm by cells. In both yeast and bacteria systems, Sm(III) was mineralized to monazite(Sm) phase particles on cell surfaces at 5 days of exposure after a short-term adsorption process. In these three systems, nano-sized Sm phosphate formed more quickly on cell surfaces with higher pH exposure solutions. The formation of precipitation on bacterial cell surfaces was faster than in yeast. There were no significant differences in the sorption process of Sm between the two bacteria Pseudomonas fluorescens and Bacillus subtilis.     

Absence of morningness alleles in non-European populations

ABSTRACT

In spite of suspected circadian differences between different ancestral groups, most human studies have used individuals of European descent. This also applies to three recent genome-wide association studies (GWAS), which pinpointed a number of chronotype loci. We investigated the distribution of these hits in different 1000 Genomes populations. We found 6 out of the 41 alleles previously identified by GWAS in European participants (in the genes RGS16, PER2 and AK5 and between the genes APH1A and CA14) to be absent from some non-European population groups. This highlights the need for ancestral diversity in circadian research and may reflect differences affecting the phenotype of individuals of East Asian ancestry.     

小麦隐匿柄锈菌与小麦互作不同阶段的基因差异表达分析

[目的]小麦叶锈病是影响小麦生产主要病害之一,其病原菌新小种的出现和劣势小种上升为优势小种导致抗病品种的抗病性不断被克服.小麦隐匿柄锈菌与小麦互作不同阶段差异表达谱分析对于揭示该病菌致病的分子机制,进而有效防控小麦叶锈病具有重要意义.[方法]利用转录组分析小麦隐匿柄锈菌致病生理小种与感叶锈病小麦品种MuTcLr19亲和...     

Molecular Modelling of Protein-Nucleic Acid Interactions

Abstract

Computer modeling techniques to study the interaction of proteins with nucleic acids are presented. The methods utilize information from genetic and chemical modification experiments and macromolecular structural constraints. These techniques, in addition to computer model building procedures and theoretical energy calculations, are illustrated for the study of the lac and cro repressor-operator systems. Our predicted interactions between lac and its operator agree with those recently reported for lac based upon sequence alignment with the cro repressor. Several molecular models of the putative helical segment of cro interacting with its OR3 operator are presented. These models are reflective of intermediate conformations experienced by the repressor in recognition of the operator sequence. The results of our studies are further discussed in terms of the design of short peptides interacting with nucleic acid sequences and the evolutionary requirements in establishing these repressor interactions.     

Neisseria gonorrhoeae effectively blocks HIV‐1 replication by eliciting a potent TLR9‐dependent interferon‐α response from plasmacytoid dendritic cells

Clinical and epidemiological research provides evidence for a positive correlation between Neisseria gonorrhoeae infection and HIV transmission; however, mechanistic studies examining this relationship have yielded conflicting results. To explore this interaction, we exposed ex vivo cultured peripheral blood cells from acute HIV⁺ individuals to N. gonorrhoeae. Unexpectedly, we observed a profound inhibition in HIV‐1 replication in the ex vivo cultures, and this was recapitulated when peripheral blood mononuclear cells (PBMCs) from healthy donors were co‐infected with HIV‐1 and N. gonorrhoeae. Next, we established that gonococcal‐infected PBMCs liberated a soluble factor that effectively blocked HIV‐1 replication. Cytokine analyses and antibody blocking experiments revealed that the type I interferon, interferon‐α (IFNα), was expressed upon exposure to N. gonorrhoeae and was responsible for the inhibition of HIV‐1. Intracellular staining, TLR9‐blocking and cell depletion‐based studies demonstrated that the IFNα was elicited by plasmacytoid dendritic cells (pDCs) in a TLR9‐dependent manner. The pDC response to N. gonorrhoeae was unexpected given pDCs more established role in innate defence against intracellular pathogens, suggesting this may be a bacterial immune evasion strategy. In the context of HIV, this overcomes the virus's otherwise effective avoidance of the interferon response and represents a previously unrecognized intersection between these two sexually transmitted pathogens.     

Contribution of lead in soil to children’s lead burden,an update

Abstract

Blood lead levels in children in the USA have dropped dramatically since lead in food, air and drinking water was reduced. In inner cities and older residential areas, increased lead exposure may still be a problem because of dilapidated housing with high lead paint levels. In these areas, at mining sites and around smelters lead levels in soil may be very high. A review of many studies indicates that lead in soil or mine tailings does not make a meaningful contribution to lead absorption by children. The contribution of lead in soil to overall exposure, if any, lies within the variation of the analytical method for blood lead measurements. The results of exposure studies in the pediatric population reviewed in this article do not support exposure predictions for children under 6 years of age based on the US EPA Integrated Exposure Uptake Biokinetic Model (using default parameters or using results obtained with in vitro digestion models). They also do not support predictions based on the percent of solubility of lead in soil (accessibility studies).     

Notes on Shetland lichens: I

ABSTRACT

Background: According to modern coexistence theory, ecologically similar species can coexist if fitness differences between them are small, or niche differences between them are large. However, these predictions have not been tested extensively in real systems and are difficult to examine in traits-based studies.

Aims: The aim of our study was, by using the carnivorous pitcher plant genus Nepenthes as a model system, to examine (1) species growth ranks as a proxy for fitness; (2) modern coexistence theory at a geographical scale; (3) evidence for pitcher trait-mediated resource partitioning between sympatric Nepenthes species.

Methods: We used growth ranks, obtained from a survey of experienced Nepenthes nursery owners, as a proxy for fitness. Multivariate pitcher-, vegetative- or combined-trait distances, computed from morphometric-trait data from the literature were used as proxies for niche differences. Data on global Nepenthes species-pair sympatry was modelled against these fitness and niche differences.

Results: Niche and growth rate differences were positively and negatively correlated with sympatry, respectively, as expected from theory.

Conclusion: Our results agree with theory and suggest that fitness differences can be approximated from average species growth. Prey- and microhabitat-resource partitioning, operating through divergent pitcher and vegetative traits respectively, are likely mechanisms that stabilise the coexistence of sympatric Nepenthes species.     

Plasma-transforming growth factor-alpha expression in residents of an arseniasis area in Taiwan

Abstract

Epidemiological studies have demonstrated an association between long-term exposure to inorganic arsenic and the related adverse effects such as cancers, skin lesions, and vascular diseases. Although several hypotheses have been proposed for the mechanism of arsenic-induced pathogenesis, it remains imperfectly understood. Recent studies have suggested that alterations in growth signal transduction pathways, particularly involving transforming growth factor-alpha (TGF-alpha), may be important. Immunoassays were used to determine the plasma levels of TGF-alpha and epidermal growth factor receptor (EGFR), which is the receptor for TGF-alpha, in residents of an arseniasis area of Taiwan in relation to their estimated cumulative arsenic exposure from drinking water. No relationship between arsenic exposure and EGFR was found. However, among the high cumulative exposure group (>6 ppm-years), levels of plasma TGF-alpha (25.5±38.2 pg ml^?1) and the proportion of individuals with TGF-alpha over-expression (29.4%) were significantly higher (p<0.05) than normal, healthy unexposed controls (8.1±5.6 pg ml^?1, 8.6%, respectively). There was a significant linear trend between cumulative arsenic exposure and the prevalence of plasma TGF-alpha over-expression after adjusting for age and sex (p=0.019). The results suggest that plasma TGF-alpha expression may be a useful biomarker when detecting adverse effects on arsenic exposed population.     

Effects of pulsed electromagnetic fields on learning and memory abilities of STZ-induced dementia rats

Introduction: Recent studies have shown that pulsed electromagnetic field (EMF) has therapeutic potential for dementia, but the associated neurobiological effects are unclear. This study aimed to determine the effects of pulsed EMF on Streptozotocin (STZ)-induced dementia rats.Methods: Forty Sprague-Dawley rats were randomly allocated to one of the four groups: (i) control, (ii) normal saline injection (sham group), (iii) STZ injection (STZ group) and (iv) STZ injection with pulsed EMF exposure (PEMF, 10 mT at 20 Hz) (STZ + MF group). Morris water maze was used to assess the learning and memory abilities. Insulin growth factors 1 and 2 (IGF-1 and IGF-2) gene expression were determined by quantitative PCR. Results: The results showed that the mean escape latency in STZ-induced dementia rats was reduced by 66% under the exposure of pulsed EMF. Compared with the STZ group, the swimming distance and the time for first crossing the platform decreased by 55 and 41.6% in STZ + MF group, respectively. Furthermore, the IGF-2 gene expression significantly increased compared to that of the STZ group. Conclusions: Our findings indicate that the pulsed EMF exposure can improve the ability of learning and memory in STZ-induced dementia rats and this effect may be related to the process of IGF signal transduction, suggesting a potential role for the pulsed EMF for the amelioration of cognition impairment.     

Geographic variation for elaiosome–seed size ratio and its allometric relationship in two closely related Corydalis species

Abstract

Background: Elaiosomes serve as a reward for seed-dispersing ants. The size of the elaiosome and the elaiosome–seed mass (ESM) ratio are expected to affect seed dispersal, whilst seed size affects the establishment of seedlings. Elaiosomes and seeds can undergo independent change, thus variation in these traits may arise through heterogeneous selection for seedling establishment and for dispersal. Only a few studies have examined intraspecific variation in these traits.

Aims: The aim of this study was to determine if the ratio of elaiosome–seed mass was different in two co-occurring congeneric plant species (Corydalis intermedia and C. solida). Under the hypothesis that the ESM ratio affected diaspore attractiveness to ants, the allometric relationship between elaiosome and seed mass was used to infer how selection by ants may shape the diaspore.

Methods: Seed and elaiosome mass were measured in fruits collected from central and marginal populations of the two plant species. The allometric relationship between seed and elaiosome mass was obtained using major axis regression. In situ cafeteria experiments estimated the removal rate of diaspores by ants.

Results: Intra- and interspecific variation in diaspore traits were found. The selfing C. intermedia produced heavier seeds and elaiosomes than the outcrossing C. solida. Ants removed more diaspores from C. intermedia where both species were present. A slope larger than one characterised the allometric relationship between elaiosome and seed mass in both species. This slope was twice as steep in the central populations of C. intermedia compared to marginal ones.

Conclusions: Results indicate that in C. intermedia elaiosome mass must increase more than proportionally with increasing seed mass for the diaspore to remain attractive to ants. The direction of interspecific differences suggests that a plant-mating system may affect selection for dispersal.     

Apocynin: a potent NADPH oxidase inhibitor for the management of atrial fibrillation

Abstract

Oxidative stress in atrial tissue may be causally related to atrial fibrillation as suggested by clinical and animal studies. Reactive oxygen species (ROS) are known to play a key role in fibrosis and the induction of after-depolarization and triggered activity. Therefore, suppressing oxidative stress may have a potential beneficial role in the management of atrial fibrillation. Since increased NADPH oxidase activity is shown to play a key role in generation of ROS in atrial tissue and in atrial fibrillation, our proposed strategy to target upstream inhibition of ROS production by inhibition of NADPH oxidase activity may provide a novel approach to prevent atrial fibrillation recurrences. We hypothesize that apocynin could be effective against atrial fibrillation, by virtue of its potent inhibitory effect of a major oxidative system (i.e. NADPH oxidase) combined with its demonstrated anti-inflammatory, antifibrotic and antihypertensive effects which partially are driven from its antioxidant property. Atrial fibrillation is known to be initiated by the interaction of these multiple factors.