Energetic Resources Research Articles

Plant virus infection influences bottom-up regulation of a plant-aphid-parasitoid system

Plant viruses strongly influence the physiology of their host plants and phytophagous insect vectors, thereby affecting ecological interactions between them. Despite the important role of natural enemies on insect vector control and thus on virus dissemination, the influence of plant viruses on the third trophic level received little attention. We investigated how infection of the plant Camelina sativa (Brassicaceae) by the Turnip yellows virus (TuYV) influenced the host plant, an aphid vector (Myzus persicae) and an aphid parasitoid (Aphidius colemani) through bottom-up effects on the physiology of the three trophic levels. We also considered the behavioural responses of A. colemani towards infected and control (uninfected) plant-aphid complexes. Highlighting the importance of virus infection on bottom-up regulation of tri-trophic systems, TuYV infection resulted in (1) decreased photosynthetic activity and biomass in C. sativa, (2) an improvement of some aphid fitness parameters important for population dynamics and virus dissemination (i.e. better nymphal survival and shorter pre-reproductive period), but (3) a decrease in some other aphid parameters (i.e. lower body size and quantity of stored energetic resources), which probably explained (4) the decrease in several fitness-related traits (i.e. body size, fecundity and lipid content) in parasitoids developing in aphids reared on infected plants. Female parasitoids showed similar attraction towards control and infected plants, and similar attack and rejection rates towards control and virus-infected aphids. Our results suggest that in agroecosystems, virus presence may reduce parasitoid abundance and consequently biological control of aphid vectors, impacting virus dissemination and plant damage.

Mitochondrial proteostasis as a shared characteristic of slowed aging: the importance of considering cell proliferation.

Proteostasis is one of the seven "pillars of aging research" identified by the Trans-NIH Geroscience Initiative and loss of proteostasis is associated with aging and age-related chronic disease. Accumulated protein damage and resultant cellular dysfunction are consequences of limited protein repair systems and slowed protein turnover. When relatively high rates of protein turnover are maintained despite advancing age, damaged proteins are more quickly degraded and replaced, maintaining proteome fidelity. Therefore, maintenance of protein turnover represents an important proteostatic mechanism. However, measurement of protein synthesis without consideration for cell proliferation can result in an incomplete picture, devoid of information about how new proteins are being allocated. Simultaneous measurement of protein and DNA synthesis provides necessary mechanistic insight about proteins apportioned for newly proliferating cells versus for somatic maintenance. Using this approach with a number of murine models of slowed aging shows that, compared to controls, energetic resources are directed more toward somatic maintenance and proteostasis, and away from cell growth and proliferation. In particular, slowed aging models are associated with heightened mechanisms of mitochondrial proteostatic maintenance. Taking cell proliferation into account may explain the paradoxical findings that aging itself and slowed aging interventions can both be characterized by slower rates of protein synthesis.

Roles and Mechanistic Bases of Glucocorticoid Regulation of Avian Reproduction.

To maximize fitness, organisms must invest energetic and nutritional resources into developing, activating, and maintaining reproductive physiology and behavior. Corticosterone (CORT), the primary avian glucocorticoid, regulates energetic reserves to meet metabolic demands. At low (baseline) plasma levels, CORT activates avian mineralocorticoid receptors and may stimulate lipid mobilization, foraging activity, and feeding behavior. During stress in birds, elevated plasma CORT also stimulates glucocorticoid receptors and may promote glycemia, lipolysis, and proteolysis. Furthermore, CORT orchestrates physiological and behavioral adjustments to perceived threats. While many avian studies demonstrate effects of CORT on reproduction, few studies have elucidated the mechanisms, including receptor activation and site(s) of action, which underlie these effects. Even fewer studies have investigated how low and elevated plasma CORT regulates energetic reserves to meet the metabolic demands of reproduction. Here, we propose several hypotheses to clarify the direct and indirect effects of CORT on avian reproductive physiology and behavior. In addition, we emphasize the need for new manipulative studies involving alterations of endogenous plasma CORT levels and/or food availability to elucidate how CORT regulates the energetic demands of reproduction.

Predicting Life-History Trade-Offs with Whole-Organism Performance.

Whole-organism performance traits are key intermediaries between the organism and the environment. Because performance traits are energetically costly to both build and maintain, performance will compete with other life-history traits over a limited pool of acquired energetic resources at any given time, potentially leading to trade-offs in performance expression. Although these trade-offs can have important implications for organismal fitness we currently lack a conceptual framework for predicting both where trade-offs might be expected, and which traits may be especially prone to trade-offs with other fitness-related life-history traits. We propose such a framework based on an estimate of the energetic requirements of locomotion in vertebrates, the ecological cost of transport. By analyzing existing data on mammalian energetic budgets and life-history, we found that species with higher costs of locomotion also tended to be those with "slow" life histories that invest relatively less in current reproduction than "fast" life-history species. We discuss the potential implications of ectothermy for masking such relationships, and how this framework might be expanded upon in the future.

Occludin regulates glucose uptake and ATP production in pericytes by influencing AMP-activated protein kinase activity

Energetic regulation at the blood-brain barrier is critical for maintaining its integrity, transport capabilities, and brain demands for glucose. However, the underlying mechanisms that regulate these processes are still poorly explored. We recently characterized the protein occludin as a NADH oxidase and demonstrated its influence on the expression and activation of the histone deacetylase SIRT-1. Because SIRT-1 works in concert with AMP-activated protein kinase (AMPK) (AMPK), we investigated the impact of occludin on this metabolic switch. Here we show that in blood-brain barrier pericytes, occludin promotes AMPK expression and activation, influencing the expression of glucose transporters GLUT-1 and GLUT-4, glucose uptake, and ATP content. Furthermore, occludin expression, AMP-dependent protein kinase activity, and glucose uptake were altered under inflammatory (TNFα) and infectious (HIV) conditions. We also show that pericytes share glucose and mitochondria with astrocytes, and that occludin levels modify the ability of pericytes to share those energetic resources. In addition, we demonstrate that murine mitochondria can be transferred from live brain microvessels to energetically impaired human astrocytes, promoting their survival. Our findings demonstrate that occludin plays an important role in blood-brain barrier pericyte metabolism by influencing AMPK protein kinase activity, glucose uptake, ATP production, and by regulating the ability of pericytes to interact metabolically with astrocytes.

Transcriptional Control of the Lateral-Flagellar Genes of Bradyrhizobium diazoefficiens.

Bradyrhizobium diazoefficiens, a soybean N2-fixing symbiont, possesses a dual flagellar system comprising a constitutive subpolar flagellum and inducible lateral flagella. Here, we analyzed the genomic organization and biosynthetic regulation of the lateral-flagellar genes. We found that these genes are located in a single genomic cluster, organized in two monocistronic transcriptional units and three operons, one possibly containing an internal transcription start site. Among the monocistronic units is blr6846, homologous to the class IB master regulators of flagellum synthesis in Brucella melitensis and Ensifer meliloti and required for the expression of all the lateral-flagellar genes except lafA2, whose locus encodes a single lateral flagellin. We therefore named blr6846 lafR (lateral-flagellar regulator). Despite its similarity to two-component response regulators and its possession of a phosphorylatable Asp residue, lafR behaved as an orphan response regulator by not requiring phosphorylation at this site. Among the genes induced by lafR is flbTL , a class III regulator. We observed different requirements for FlbTL in the synthesis of each flagellin subunit. Although the accumulation of lafA1, but not lafA2, transcripts required FlbTL, the production of both flagellin polypeptides required FlbTL Moreover, the regulation cascade of this lateral-flagellar regulon appeared to be not as strictly ordered as those found in other bacterial species.IMPORTANCE Bacterial motility seems essential for the free-living style in the environment, and therefore these microorganisms allocate a great deal of their energetic resources to the biosynthesis and functioning of flagella. Despite energetic costs, some bacterial species possess dual flagellar systems, one of which is a primary system normally polar or subpolar, and the other is a secondary, lateral system that is produced only under special circumstances. Bradyrhizobium diazoefficiens, an N2-fixing symbiont of soybean plants, possesses dual flagellar systems, including the lateral system that contributes to swimming in wet soil and competition for nodulation and is expressed under high energy availability, as well as under requirement for high torque by the flagella. The structural organization and transcriptional regulation of the 41 genes that comprise this secondary flagellar system seem adapted to adjust bacterial energy expenditures for motility to the soil's environmental dynamics.

Seasonal Patterns of Variation in Steroid Plasma Levels and Immune Parameters in Anurans from Brazilian Semiarid Area.

Elevated androgens and glucocorticoids displayed by males during the reproductive season have been proposed to mediate a possible trade-off between reproduction and immunocompetence. Anurans living in arid and semiarid environments display a strong seasonal reproduction, which could accentuate the variation in physiological, immunological, and behavioral parameters. We studied covariation between steroid plasma levels, morphometric variables associated with body condition and immunity, leukocyte profile, parasite load, and response to an immunological challenge across different phases of the annual life-history cycle of three anuran species from a Brazilian semiarid area. Our results showed a seasonal pattern of covariation among leukocyte parameters, kidney mass, and steroid plasma levels, with higher values measured during the reproductive season, particularly when males were sampled during calling activity. Moreover, these anurans showed a stronger response to an immunological challenge during the reproductive period. The immunosuppression during the dry period was particularly evident for the species that aestivate, indicating that the availability of energetic resources might be an important factor determining seasonal variation in inflammatory response. Intensity of the helminth infection was associated with eosinophil count but showed a more complex pattern with regard to androgens levels. These data emphasize that variations in the intensity of helminth infection might be more closely related to specific aspects of the immune response than to the general seasonal patterns of variation in steroid plasma levels, total circulating leukocytes, and inflammatory response.

Colony adaptive response to simulated heat waves and consequences at the individual level in honeybees (Apis mellifera)

Since climate change is expected to bring more severe and frequent extreme weather events such as heat waves, assessing the physiological and behavioural sensitivity of organisms to temperature becomes a priority. We therefore investigated the responses of honeybees, an important insect pollinator, to simulated heat waves (SHW). Honeybees are known to maintain strict brood thermoregulation, but the consequences at the colony and individual levels remain poorly understood. For the first time, we quantified and modelled colony real-time activity and found a 70% increase in foraging activity with SHW, which was likely due to the recruitment of previously inactive bees. Pollen and nectar foraging was not impacted, but an increase in water foragers was observed at the expense of empty bees. Contrary to individual energetic resources, vitellogenin levels increased with SHW, probably to protect bees against oxidative stress. Finally, though immune functions were not altered, we observed a significant decrease in deformed wing virus loads with SHW. In conclusion, we demonstrated that honeybees could remarkably adapt to heat waves without a cost at the individual level and on resource flow. However, the recruitment of backup foraging forces might be costly by lowering the colony buffering capacity against additional environmental pressures.

Long-term profiles of work-related rumination associated with leadership, job demands, and exhaustion: A three-wave study

ABSTRACTThis study extends previous research on recovery from work stress by investigating the role of qualitative job demands and leadership in employees’ work-related rumination (WRR). The long-term development of WRR was examined from a person-centred approach across 22 months. Drawing on the stressor-detachment framework and conservation of resources theory, we investigated whether different WRR profiles could be understood in terms of levels of and changes in quantitative, cognitive, and emotional job demands, several aspects of supervisory leadership, and exhaustion that was expected to result from the impeded energy restoration process. A three-wave questionnaire study was conducted among Finnish municipal employees in heterogeneous occupations. Factor mixture modelling was used to identify latent classes (i.e. subgroups of participants with similar mean levels and mean-level changes) of WRR. The results indicated five distinct classes of WRR. Participants in the higher WRR classes reported higher levels of job demands, less supervisor fairness, and more abusive supervision. In the decreasing class, WRR decreased concurrently with decreasing job demands. Exhaustion showed considerable congruence with WRR both between and within persons. The findings are discussed from the point of view of a loss cycle concerning energetic psychological resources and difficulties in goal attainment.

Planning of Renewable Generation in Distribution Systems Considering Daily Operating Periods

This paper presents an optimization approach for planning of renewable generation in energy distribution systems. The considered generations are based on wind turbines and photovoltaic panels. The objective is to determine the optimal placement of the renewable distributed generation aiming at minimizing the investment and operational costs in a long term planning. The proposed approach represents the stochastic behavior of the renewable resources by handling historical data to determine the wind and photovoltaic capacity factors. The method for obtaining such factors considers the daily load periods, which allows representing the availability of the energetic resources in different periods. The optimization method is based on the bioinspired metaheuristic known as artificial immune system. Two systems of the literature and practical wind and solar data from Brazil are used to assess the proposed approach.

Shorebird stopover habitat decisions in a changing landscape

ABSTRACTTo examine how habitat use by sandpipers (Calidrisspp.; Baird's sandpipers, dunlin, least sandpipers, pectoral sandpipers, semipalmated sandpipers, stilt sandpipers, and white‐rumped sandpipers) varies across a broad suite of environmental conditions, we conducted surveys at wetlands throughout the spring migratory period in 2013 and 2014 in 2 important stopover regions: the Rainwater Basin (RWB) in Nebraska, USA, and the Prairie Pothole Region (PPR) in South Dakota, USA. Because providing adequate energetic resources for migratory birds is a high priority for wetland management, we also measured invertebrate abundance at managed wetlands in the RWB to determine how food abundance influences the occupancy and abundance of sandpipers on wetlands throughout the migratory period. To quantify habitat use, we surveyed wetlands every 7–10 days in both regions and visually estimated wetland attributes. Our results indicate that invertebrate abundance predicted occupancy, but not abundance, of sandpipers at wetlands in the RWB. The wetland vegetation characteristics that predict sandpiper occupancy are similar in both regions, but wetlands in the PPR support a higher abundance of sandpipers than wetlands in the RWB. Our results suggest that sandpipers make stopover decisions that balance local and regional wetland conditions. Managers should maintain the cues (i.e., mudflat) and ecological conditions beyond invertebrate abundance that predict sandpiper habitat use to successfully provide resources for sandpipers during migratory stopover if that is a goal of wetland management. © 2017 The Wildlife Society.

Knowledge of and Attitudes Toward Alcoholism Among Church Leaders in Saint Vincent/Grenadines

Saint Vincent and the Grenadines (SVG) is an Eastern Caribbean country with a high rate of alcohol use disorders (AUDs) but inadequate community mental health resources to address them. This study examined SVG clergy’s potential role in community alcohol interventions. We recruited clergy through a chain referral method. We gathered data through 30 semi-structured interviews and qualitatively coded interview transcripts for themes relevant to the topic of alcoholism. We found that SVG church leaders have considerable knowledge regarding alcoholism on both personal and societal levels. The church leaders’ consistent concern about drinking problems in their communities and their commitment to community outreach suggest they are an energetic resource that should be utilized in future AUD interventions. However, their impact may be hampered by theological divisions, the perception that drinking problems only affect non-church members, non-church members’ possible reluctance to seek help from churches, and a misinformed approach to tackling drinking.

Knowledge of and Attitudes Toward Alcoholism among Church Leaders in Saint Vincent/Grenadines

Saint Vincent and the Grenadines (SVG) is an Eastern Caribbean country with a high rate of alcohol use disorders (AUDs) but inadequate community mental health resources to address them. This study examined SVG clergy’s potential role in community alcohol interventions. We recruited clergy through a chain referral method. We gathered data through 30 semi-structured interviews and qualitatively coded interview transcripts for themes relevant to the topic of alcoholism. We found that SVG church leaders have considerable knowledge regarding alcoholism on both personal and societal levels. The church leaders’ consistent concern about drinking problems in their communities and their commitment to community outreach suggest they are an energetic resource that should be utilized in future AUD interventions. However, their impact may be hampered by theological divisions, the perception that drinking problems only affect non-church members, non-church members’ possible reluctance to seek help from churches, and a misinformed approach to tackling drinking.

The regulation of transcriptional repression in hypoxia

A sufficient supply molecular oxygen is essential for the maintenance of physiologic metabolism and bioenergetic homeostasis for most metazoans. For this reason, mechanisms have evolved for eukaryotic cells to adapt to conditions where oxygen demand exceeds supply (hypoxia). These mechanisms rely on the modification of pre-existing proteins, translational arrest and transcriptional changes. The hypoxia inducible factor (HIF; a master regulator of gene induction in response to hypoxia) is responsible for the majority of induced gene expression in hypoxia. However, much less is known about the mechanism(s) responsible for gene repression, an essential part of the adaptive transcriptional response. Hypoxia-induced gene repression leads to a reduction in energy demanding processes and the redirection of limited energetic resources to essential housekeeping functions. Recent developments have underscored the importance of transcriptional repressors in cellular adaptation to hypoxia. To date, at least ten distinct transcriptional repressors have been reported to demonstrate sensitivity to hypoxia. Central among these is the Repressor Element-1 Silencing Transcription factor (REST), which regulates over 200 genes. In this review, written to honor the memory and outstanding scientific legacy of Lorenz Poellinger, we provide an overview of our existing knowledge with respect to transcriptional repressors and their target genes in hypoxia.

Pioneering developments of marine renewable energy in Australia

The history of ocean renewable energy developments in Australia is reviewed. A layperson’s description of the physical operating principle is given for the main classes of technology that have been tested in Australian waters. The Australian marine domain possesses among the world’s most energetic wave-energy resources, driven by powerful mid-latitude westerly winds. The northern coast of Western Australia has tidal ranges significant on a global scale, and some geographical features around the continent have local tidal resonances. The East Australian Current, one of the world’s major western boundary currents, runs along the eastern Australian seaboard, offering potential for ocean-current energy. Sea-water temperatures in the tropical north-east of Australia may permit ocean thermal energy conversion. While this abundance of resources makes Australia an ideal location for technology development, the population is highly concentrated in a few large cities, and transmission infrastructure has developed over a century to supply cities from traditional power plants. Several wave-power developments have resulted in demonstration of deployments in Australian waters, three of which have been grid connected. Trials of tidal devices have also occurred, while other classes of ocean renewable energy have not yet been trialled. The prospects for marine renewable energy in Australia are discussed including non-traditional applications such as coastal protection and energy export.

The choreography of the chemical defensome response to insecticide stress: insights into the Anopheles stephensi transcriptome using RNA-Seq

Animals respond to chemical stress with an array of gene families and pathways termed “chemical defensome”. In arthropods, despite many defensome genes have been detected, how their activation is arranged during toxic exposure remains poorly understood. Here, we sequenced the transcriptome of Anopheles stephensi larvae exposed for six, 24 and 48 hours to the LD50 dose of the insecticide permethrin to monitor transcriptional changes of defensome genes across time. A total of 177 genes involved in insecticide defense were differentially expressed (DE) in at least one time-point, including genes encoding for Phase 0, I, II, III and antioxidant enzymes and for Heat Shock and Cuticular Proteins. Three major patterns emerged throughout time. First, most of DE genes were down-regulated at all time-points, suggesting a reallocation of energetic resources during insecticide stress. Second, single genes and clusters of genes turn off and on from six to 48 hours of treatment, showing a modulated response across time. Third, the number of up-regulated genes peaked at six hours and then decreased during exposure. Our results give a first picture of how defensome gene families respond against toxicants and provide a valuable resource for understanding how defensome genes work together during insecticide stress.

Does increased salinity influence the competitive outcome of two producer species?

Within the context of global climate changes, it is expected that low-lying coastal freshwater ecosystems will face seawater intrusion with concomitant increase in salinity levels. Increased salinity may provoke disruption of competitive relationships among freshwater species. However, species may be capable of acclimating to salinity, which, in turn, may influence the resilience of ecosystems. Accordingly, this work aimed at assessing the effects of multigenerational exposure to low levels of salinity in the competitive outcome of two species of green microalgae: Raphidocelis subcapitata and Chlorella vulgaris. To attain this, three specific objectives were delineated: (1) compare the toxicity of natural seawater (SW) and NaCl (as a surrogate of SW) to the two microalgae, (2) determine the capacity of the two microalgae species to acclimate to low salinity levels, and (3) assess the influence of exposure to low salinity levels in the competitive outcome of the two microalgae. Results revealed SW to be slightly less toxic than NaCl for the two microalgae. The EC25,72h for growth rate was 4.63 and 10.3mScm-1 for R. subcapitata and 6.94 and 15.4mScm-1 for C. vulgaris, respectively for NaCl and SW. Both algae were capable of acclimating to low levels of salinity, but C. vulgaris seemed to acclimate faster than R. subcapitata. When exposed in competition, under control conditions, the growth rates of C. vulgaris were lower than those of R. subcapitata. However, C. vulgaris was capable of acquiring competitive advantage equaling or surpassing the growth rate of R. subcapitata with the addition of NaCl or SW, respectively. The multigenerational exposure to low levels of salinity influenced the competitive outcome of the two algae both under control and salinity exposure. These results suggest that long-term exposure to low salinity stress can cause shifts in structure of algae communities and, therefore, should not be neglected since algae are at the basis of food web constituting important energetic resources to higher trophic levels.

Resource depletion in an electric vehicle powertrain using different LCA impact methods

The growing demand for electric vehicles entails an increased consumption of critical energetic and non-energetic abiotic resources, necessary for an optimal performance of the vehicle. The depletion of these resources and the future availability to meet their demand appears to be a potential limitation for the expansion of the electrified vehicle industry. The goal of this study is to perform a detailed life cycle analysis, including manufacturing, use and disposal, of key components of EV powertrains, identifying materials and processes responsible for abiotic depletion impact. This study also investigates the sensitivity of the results to the choice of Life Cycle Assessment (LCA) impact methods. For this, a LCA is performed on an integrated electric drive, by considering seven impact methods. Results show that energetic resources consumption generate the largest impact, followed by metals and lastly by mineral resources. The consumption of electricity in each life cycle is a crucial factor in the generation of total impact. There are agreements among methods on the materials and processes contributing the most to depletion, given the differences in approach used by each impact method.

Resource Recovery from Wastewater by Biological Technologies: Opportunities, Challenges, and Prospects.

Limits in resource availability are driving a change in current societal production systems, changing the focus from residues treatment, such as wastewater treatment, toward resource recovery. Biotechnological processes offer an economic and versatile way to concentrate and transform resources from waste/wastewater into valuable products, which is a prerequisite for the technological development of a cradle-to-cradle bio-based economy. This review identifies emerging technologies that enable resource recovery across the wastewater treatment cycle. As such, bioenergy in the form of biohydrogen (by photo and dark fermentation processes) and biogas (during anaerobic digestion processes) have been classic targets, whereby, direct transformation of lipidic biomass into biodiesel also gained attention. This concept is similar to previous biofuel concepts, but more sustainable, as third generation biofuels and other resources can be produced from waste biomass. The production of high value biopolymers (e.g., for bioplastics manufacturing) from organic acids, hydrogen, and methane is another option for carbon recovery. The recovery of carbon and nutrients can be achieved by organic fertilizer production, or single cell protein generation (depending on the source) which may be utilized as feed, feed additives, next generation fertilizers, or even as probiotics. Additionlly, chemical oxidation-reduction and bioelectrochemical systems can recover inorganics or synthesize organic products beyond the natural microbial metabolism. Anticipating the next generation of wastewater treatment plants driven by biological recovery technologies, this review is focused on the generation and re-synthesis of energetic resources and key resources to be recycled as raw materials in a cradle-to-cradle economy concept.

An update on the global stressors and constraints affecting Daphnia populations in large Chilean Patagonian lakes (39-51°S)

The zooplankton communities in Chilean Patagonian lakes (39-51°S) are characterized by the low presence of daphniid cladocerans, i.e., under conditions of the usual native oligotrophy and, thus, low mineral concentrations. Nevertheless, from some northern Patagonian lakes (39-41°S) a marked abundance of daphniids has been reported. According to the literature, as well as evidence from field observations, the main causes of such marked changes in the local zooplankton assemblages would be changes in phytoplankton quantity and quality, providing increased energetic resources for the zooplankton communities. Such energetic resources might decrease the stress effects of low calcium concentrations, as calcium constitutes an essential nutrient for caparace formation in Daphniidae; in addition, energetic expenses needed to perform vertical migrations due to fish predation and exposure to natural ultraviolet radiation can better be provided for. This is a markedly different situation compared to North Patagonian lakes, where daphniid abundance and number of species are related only to phytoplankton quantity and quality in term of phosphorus/nitrogen molar ratio.