Substrate Usage Research Articles

Biased movement drives local cryptic coloration on distinct urban pavements.

Explanations of how organisms might adapt to urban environments have mostly focused on divergent natural selection and adaptive plasticity. However, differential habitat choice has been suggested as an alternative. Here, we test for habitat choice in enhancing crypsis in ground-perching grasshoppers colonizing an urbanized environment, composed of a mosaic of four distinctly coloured substrates (asphalt roads and adjacent pavements). Additionally, we determine its relative importance compared to present-day natural selection and phenotypic plasticity. We found that grasshoppers are very mobile, but nevertheless approximately match the colour of their local substrate. By manipulating grasshopper colour, we confirm that grasshoppers increase the usage of those urban substrates that resemble their own colours. This selective movement actively improves crypsis. Colour divergence between grasshoppers on different substrates is not or hardly owing to present-day natural selection, because observed mortality rates are too low to counteract random substrate use. Additional experiments also show negligible contributions from plasticity in colour. Our results confirm that matching habitat choice can be an important driver of adaptation to urban environments. In general, studies should more fully incorporate that individuals are not only selective targets (i.e. selected on by the environment), but also selective agents (i.e. selecting their own environments).

A flexible self-charged power panel for harvesting and storing solar and mechanical energy

A flexible self-charged power panel is integrally designed and fabricated to simultaneously harvest solar and mechanical energy and convert and store in electric energy. The flexible amorphous silicon solar cell, the transparent triboelectric nanogenerator (TENG), and lithium (Li)-ion batteries are coherently integrated into one thin panel with the encapsulating materials, ethylene-tetra-fluoro-ethylene (ETFE) for the solar modules. The flexible self-charged power panel exhibits good performance to directly convert solar and mechanical energy into electricity that was directly stored in Li-ion battery without excessive energy loss. The integrated device also greatly minimizes the usage of current collectors, substrates and packaging materials. Moreover, such a power panel can compensate for the absence of solar cells and prolongs the time of energy supply and improve the energy density of the whole device.

Occurrence and nesting behavior of social wasps in an anthropized environment

Some effort had been made concerning the social biodiversity of wasps in Brazil; however, few approaches have been made relating to how this taxa have adapted their nesting behavior to anthropic mixed environments. Thus, the present work aimed to survey the occurrence of social wasps in an anthropic area and their relationship with different types of nesting substrates. Increasing the knowledge of social wasps in anthropic areas would allow us to develop strategies for their conservation and management. Twenty long-term surveys were made at the Universidade de São Paulo, Ribeirão Preto campus, São Paulo State. During the searches, we collected information about wasp species and nesting substrate. A total of 20 species of 8 genera were identified, and a total of 431 active colonies were registered. Epiponini was the richest in terms of species richness. On the other hand, Mischocyttarini was represented by more active colonies. Mischocyttarus cerberus had a remarkably greater number of colonies, which agreed with the idea of preference of anthropic environments by independent founding wasps. Nesting behavior was associated with eight substrate categories. We observed that some species might express certain plasticity regarding their nesting substrate usage, whereas some expressed certain specificity. Facing the increase in the actual urbanization process and, consequently, habitat loss, this type of study might contribute towards better understanding how these insects are affected by altered environment.

Development of Palm Fatty Acid Distillate-Containing Medium for Biosurfactant Production by Pseudomonas sp. LM19.

High production costs of biosurfactants are mainly caused by the usage of the expensive substrate and long fermentation period which undermines their potential in bioremediation processes, food, and cosmetic industries even though they, owing to the biodegradability, lower toxicity, and raise specificity traits. One way to circumvent this is to improvise the formulation of biosurfactant-production medium by using cheaper substrate. A culture medium utilizing palm fatty acid distillate (PFAD), a palm oil refinery by-product, was first developed through one-factor-at-a-time (OFAT) technique and further refined by means of the statistical design method of factorial and response surface modeling to enhance the biosurfactant production from Pseudomonas sp. LM19. The results shows that, the optimized culture medium containing: 1.148% (v/v) PFAD; 4.054 g/L KH2PO4; 1.30 g/L yeast extract; 0.023 g/L sodium-EDTA; 1.057 g/L MgSO4·7H2O; 0.75 g/L K2HPO4; 0.20 g/L CaCl2·2H2O; 0.080 g/L FeCl3·6H2O gave the maximum biosurfactant productivity. This study demonstrated that the cell concentration and biosurfactant productivity could reach up to 8.5 × 109 CFU/mL and 0.346 g/L/day, respectively after seven days of growth, which were comparable to the values predicted by an RSM regression model, i.e., 8.4 × 109 CFU/mL and 0.347 g/L/day, respectively. Eleven rhamnolipid congeners were detected, in which dirhamnolipid accounted for 58% and monorhamnolipid was 42%. All in all, manipulation of palm oil by-products proved to be a feasible substrate for increasing the biosurfactant production about 3.55-fold as shown in this study.

Chronic Urotensin-II Administration Improves Whole-Body Glucose Tolerance in High-Fat Diet-Fed Mice.

Urotensin-II (U-II) is an endogenous peptide agonist of a G protein-coupled receptor—urotensin receptor. There are many conflicting findings about the effects of U-II on blood glucose. This study aims to explore the effects of U-II on glucose metabolism in high-fat diet-fed mice. Male C57BL/6J mice were fed a 45% high-fat diet or chow diet and were administered U-II intraperitoneally for in vivo study. Skeletal muscle C2C12 cells were used to determine the effects of U-II on glucose and fatty acid metabolism as well as mitochondrial respiratory function. In this study, we found that chronic U-II administration (more than 7 days) ameliorated glucose tolerance in high-fat diet-fed mice. In addition, chronic U-II administration reduced the weight gain and the adipose tissue weight, including visceral, subcutaneous, and brown adipose tissue, without a significant change in blood lipid levels. These were accompanied by the increased mRNA expression of the mitochondrial thermogenesis gene Ucp3 in skeletal muscle. Furthermore, in vitro treatment with U-II directly enhanced glucose and free fatty acid consumption in C2C12 cells with increased aerobic respiration. Taken together, chronic U-II stimulation leads to improvement on glucose tolerance in high-fat diet-fed mice and this effect maybe closely related to the reduction in adipose tissue weights and enhancement on energy substrate utilization in skeletal muscle.

My branch is your branch: Talar morphology correlates with relative substrate size in platyrrhines at Tiputini Biodiversity Station, Ecuador

Given that most species of primates are predominantly arboreal, maintaining the ability to move among branches of varying sizes has presumably been a common selective force in primate evolution. However, empirical evaluations of the relationships between morphological variation and characteristics of substrate geometry, such as substrate diameter relative to an animal's body mass, have been limited by the lack of quantified substrate usage in the wild. Here we use recently published quantitative data to assess the relationships between relative substrate size and talar morphology in nine New World monkey species at the Tiputini Biodiversity Station, Ecuador. Within this sample, both fibular facet angle (the angle between the fibular facet and the trochlear rims) and body-mass-standardized area of the medial tibial facet decrease as average and maximum relative substrate size increases. Correlations between medial tibial facet area and relative substrate size are driven by the inclusion of callitrichids in this sample. Nevertheless, these findings strengthen the hypothesis that variation in fibular facet orientation and medial tibial facet area are functionally correlated with habitual degrees of pedal inversion. They also strengthen the notion that evolutionarily changing body mass could impact habitat geometry experienced by a lineage and thereby substantially impact major trends in primate morphological evolution. This study highlights the importance of empirical data on substrate use in living primates for inferring functional and evolutionary implications of morphological variation.

Phylogenetic Perspectives on Catarrhine Talo-Crural Joint Phenotypic Plasticity.

Previous investigations of the primate talo-crural joint (TCJ; specifically on the talus and distal tibia) have demonstrated that substrate preference significantly influences morphology, but this association is not necessarily found in subadults. This has been interpreted as the result of a plastic, behaviorally induced response of bone due to substrate use. In this investigation, we use geometric morphometric and phylogenetic comparative methods to investigate ontogenetic phenotypic plasticity in the catarrhine TCJ. Osteological specimens from four African hominoid and four cercopithecid species, divided into subadult and adult developmental stages based on molar eruption, formed the study group. We tested for phylogenetic signal in the shape of both the talar and tibial articular surfaces, at both developmental stages. We then used phylomorphospaces to examine the evolution of shape differences at each developmental stage for each element, and to determine if substrate usage is associated with shape in this phylogenetic context. A significant phylogenetic signal was found for both articular surfaces in subadults, but not adults. In phylomorphospace, both talar and tibial articular morphologies show an association with substrate preference in adults, but not in subadults. Our results provide confirmation of the significant effect of habitual substrate usage and the consequences of bone remodeling during ontogeny on the shape and presentation of the TCJ. These results also suggest caution when using adult talo-tibial shapes to evaluate phylogenetic relationships as TCJ morphology can be considered as a palimpsest, with substrate usage overwriting phylogenetic information in adult specimens. Anat Rec, 302:1977-1984, 2019. © 2019 American Association for Anatomy.

Exercise-Dependent Modulation of Bone Metabolism and Bone Endocrine Function: New Findings and Therapeutic Perspectives

Physical inactivity is the fourth leading cause of mortality worldwide; regardless of geographic location and income, it is a contributing risk factor to the other three causes. Physical activity is really a drug, a poly-pill; its “regular use” can reduce this risk throughout the activation of a plethora of responses in virtually all the body tissues. The beneficial effects of physical activity on cardiovascular function and hemodynamics are mainly mediated by skeletal muscle, adipose tissue and the immune system via the usage, delivery and distribution of metabolic substrates and improvement in inflammatory status. There is emerging evidence for exercise-dependent changes in bone metabolism as well; with improved bone quality, reduced fracture risk and increased bone endocrine function, the last of which modulates energy metabolism through its effects on pancreatic islet cells, skeletal muscle and adipose tissue. Bone endocrine function relies on the integration of biomechanical stimuli and endocrine signals from other organs and tissues. Here I review current concepts about exercise-dependent modulation of bone endocrine function and its beneficial effects on whole-body metabolism. Several molecular mechanisms have been identified that support this exercise-stimulated bone-mediated metabolic effect and, among these, Wnt signaling, fibroblast growth factor-23, bone morphogenic protein-7, osteocalcin, RANK/RANKL/OPG axis, and lipocalin-2 gave the largest evidences. In conclusion, beside the controversies surrounding technical aspects of the exercise, the efficacy of physical activity in preventing/treating metabolic and inflammatory dysfunctions also passes throughout the bone.

SUN-103 A Direct Comparison Of Metabolic Responses To Nad Repletion In C57bl/6j And C57bl/6n Diet-induced Obesity Mouse Models

Background and Aim:Supplementation with precursors of nicotinamide adenine dinucleotide (NAD) such as nicotinamide riboside (NR) was shown to be beneficial in preventing high fat diet- or age-induced metabolic dysfunction in mice. However, initial human studies investigating NR supplementation have shown little metabolic benefit in the mildly obese or elderly. A reason for lack of NR effects could be the use of mouse strains with underlying dysfunction such as being deficient in the mitochondrial NADPH generating nicotinamide nucleotide transhydrogenase (Nnt), as seen in C57BL/6J mice commonly used for NR studies. Here, we evaluated NR effectson whole-body energy metabolism and mitochondrial function in C57BL/6J and C57BL/6N, a strain with functional Nnt. Methods: Mice were fed a high fat diet (HFD, 60% fat) or standard chow ± supplementation of 3g/l NR in the drinking water for 8 weeks. Metabolic phenotype was determined by assessing body and organ weight, glucose tolerance, indirect calorimetry and measuring high resolution mitochondrial O2 flux in liver, skeletal muscle and heart. Results: Both strains developed mild obesity and impaired glucose tolerance. NR supplementation had a positive effect on fasting blood glucose and on energy expenditure of C57BL/6N mice on HFD, with lower overall energy expenditure than C57BL/6J mice. In both chow and HFD-fed C57BL/6J, not C57BL/6N mice, NR influenced substrate usage as determined by respiratory exchange ratio. Mitochondrial non-coupled O2 flux (1.4-fold, p<0.01, n=5) and citrate synthase activity (1.3-fold, p<0.05, n=7) were increased by NR supplementation specifically in heart muscle fibers of C57BL/6N, but not C57BL/6J mice on HFD. No significant effect on mitochondrial function was detected in the other tissues. Heart oxidative stress markers 4-hydroxynonenal and expression of NADPH oxidase 4 were significantly suppressed by NR only in C57BL/6N mice. The suppression of oxidative stress markers in C57BL/6N was associated with 2-fold upregulation of Nnt protein (p<0.01, n=5). Conclusion: NR can support mitochondrial function in diet-induced obesity, but its effect is influenced by mouse strain, possibly related to oxidative stress and Nnt function, in which augmenting NAD availability in the context of oxidative stress could be beneficial for the heart.The authors declare that there is no conflict of interest. AG, DMC, LO, RSF, YME, DN, DJH, DPL, CLD, CL, KK, GGL.This project was funded by the European Union H2020 grant EXNADMINA 705869 (AG and GGL), Wellcome Trust Senior Research Fellowship (GGL), University of Birmingham Research Development Award (AG) and Society for Endocrinology Early Career Grant (AG).

Substrates on the cuttings rooting of black pepper genotypes

The soil in the production of clonal seedlings of black pepper (Piper nigrum L.) contributes to fusarium and nematodes infestation in commercial crops, and thus the usage of alternative substrates might be a preventive control measure against these pathogens. The aim of this study was to investigate the rhizogenic behavior of the cultivars Bragantina, Iaçará and Guajarina of black pepper in different substrates. The experimental design was in randomized blocks in a 3x4 factorial design (cultivars: Bragantina, Iaçará and Guajarina x substrates: soil + organic compound (18%), vermiculite, carbonized rice hulls and commercial substrate), with four replications of 16 cuttings each. The evaluated characteristics were: survival (%); rooting (basal or nodal) (%); nodal rooting (%); basal rooting (%); number of nodal roots; number of basal roots; total number of roots; length of the largest nodal root (cm); basal root length (cm); nodal root volume (cm3); basal root volume (cm3); Total root volume (cm3); nodal root dry mass (mg); basal root dry mass (mg) and the total root dry mass (mg). There are differences within black pepper cultivars as to the characteristics related to the root system. The vermiculite substrate was the most suitable, and carbonized rice hull is not recommended for the adventitious rooting of cuttings of cultivars Bragantina, Iaçará and Guajarina.

Field-deployable measurements of free-living individuals to determine energy balance: fuel substrate usage through δ13C in breath CO2 and diet through hair δ13C and δ15N values

ABSTRACTCarbon isotopes of breath CO2 vary depending on diet and fuel substrate used. This study examined if exercise-induced δ13C-CO2 changes in substrate utilization were distinguishable from baseline δ13C-CO2 variations in a population with uncontrolled diet, and compared hair isotope values and food logs to develop an isotope model of diet. Study participants included nine women with diverse Body Mass Index (BMI), age, ancestry, exercise history, and diet. Breath samples were collected prior to and up to 12 h after a 5- or 10 K walk/run. Indirect calorimetry was measured with a smartphone-enabled mobile colorimetric device, and a field-deployable isotope analyzer measured breath δ13C-CO2 values. Diet was assessed by food logs and δ13C, δ15N of hair samples. Post-exercise δ13C-CO2 values increased by 0.54 ± 1.09‰ (1 sd, n = 9), implying enhanced carbohydrate burning, while early morning δ13C-CO2 values were lower than daily averages (p = 0.0043), indicating lipid burning during overnight fasting. Although diurnal δ13C-CO2 variation (1.90 ± 0.77‰) and participant baseline range (3.06‰) exceeded exercise-induced variation, temporal patterns distinguished exercise from dietary isotope effects. Hair δ13C and δ15N values were consistent with a new dietary isotope model. Notwithstanding the small number of participants, this study introduces a novel combination of techniques to directly monitor energy balance in free-living individuals.

Barrier engineering for HgCdTe unipolar detectors on alternative substrates

Delta-doped layers together with compositionally grading have been utilized to get nBn configurations for the HgCdTe material system in all the short-wave (SWIR), medium-wave (MWIR) and long-wave (LWIR) infrared bands. Shockley Read Hall (SRH), trap-assisted tunneling (TAT), Auger and radiative recombination mechanisms have been included in the analyses and strong suppression of SRH and TAT currents have been demonstrated with the designed structures. This methodology is especially useful when the carrier lifetime is limited due to alternative substrate usage. No degradation in photo-response has been observed as adjusting the valence band offset is quite flexible with the delta-doped nano-layers and the valence band barrier can be completely removed. Calculations have been performed for 1–3 μs lifetime targeting the alternative substrate applications and up to 60 degrees of increase in the operation has been shown to be possible.

Fatty acid amide hydrolase inhibitor (URB597) as a regulator of myocardial lipid metabolism in spontaneously hypertensive rats.

Pressure overload, which is typical of hypertension, is known to evoke alterations not only in the morphology of the heart but also in the preference of myocardial energetic substrates usage. Nowadays, the endocannabinoid system (ECS) serves as a potential therapeutic target for cardiovascular disorders and, simultaneously, affects whole body metabolism homeostasis. Therefore, an open question is whether ECS, apart from decreasing blood pressure, also affects cardiac muscle metabolism in hypertensive conditions. All experiments were conducted on a genetic model of primary hypertension i.e. spontaneously hypertensive rats (SHRs) and Wistar Kyoto rats (WKY) served as a normotensive control. ECS was chronically activated by 2-weeks intraperitoneal injections of fatty acid amide hydrolase (FAAH) inhibitor - URB597. Lipid analyses in the left ventricle and serum were based on ex vivo heart perfusion in Langendorff perfusion system, thin layer chromatography, and gas liquid chromatography. The total expression of selected proteins was determined using Western blot as well as immunohistochemical techniques. As expected, URB597 markedly reduced systolic as well as mean blood pressures in SHRs. Moreover, prolonged FAAH inhibition resulted in stimulation of 3H-palmitate uptake and incorporation into different lipid fractions in cardiomyocytes in the hypertensive as well as normotensive conditions. An increase in fatty acid oxidation caused by URB597 treatment was observed only in WKY rats, but not SHRs, and was accompanied by an elevation in peroxisome proliferator-activated receptor alpha (PPARα) and β-hydroxyacyl-CoA dehydrogenase (β-HAD) expressions. Chronic activation of ECS significantly upregulates palmitate uptake and its esterification but not oxidation in the SHR's myocardium.

Graphite decorated nano alumina (nano Al2O3@Cg): A versatile inorganic nano-promoter for the synthesis of 4-alkyl-5-methyl-1H-pyrazol-3-ols in aqueous media

A benign, simple, and efficient synthesis of 4-alkyl-5-methyl-1H-pyrazol-3-ols has been described in refluxing water through the four-component reaction of β-ketoesters, hydrazine hydrate, different aldehydes, and acetophenone derivatives in the presence of nano Al2O3@Cg, as a novel nanocatalyst. The new promoter has been prepared via a straightforward procedure and characterized by fourier transform infrared spectroscopy (FT-IR), energy-dispersive X-ray spectroscopy (EDAX), thermogravimetric analysis (TGA), field emission scanning electron microscopy (FESEM), and inductively coupled plasma atomic emission spectroscopy (ICP-AES) techniques. Utilizing water as the reaction medium, uncomplicated operational procedure, mild reaction conditions, application of a cost-effective, nontoxic, heterogeneous, easily available nanoscale inorganic-based catalyst, wide-range of substrates usage, and recovery and reusability of nano Al2O3@Cg catalyst within 4 runs without activity loss, are some highlighted features of the reported method.

Astrocyte support is important for the compensatory potential of the nigrostriatal system neurons during early neurodegeneration

Glial pathology precedes symptoms of Parkinson's disease and multiple other neurodegenerative diseases. Prolonged impairment of astrocytic functions could increase the vulnerability of dopaminergic neurons in the substantia nigra (SN), accelerate their degeneration and affect ability to compensate for partial degeneration at the presymptomatic stages of the disease. The aim of this study was to investigate the astrocyte depletion in the SN, its impact on the dopaminergic system functioning and multiple markers of energy metabolism during the early stages of neurodegeneration and compensation. We induced death of 30% of astrocytes by chronic infusion of fluorocitrate (FC) into the SN, simultaneously activating microglia response but sparing the dopaminergic neurons. The FC effect was reversible after toxin withdrawal. Dopaminergic neurons were killed by 6-hydroxydopamine causing transient locomotor disability, reversed with time showing compensatory potential. Death of astrocytes diminished the capability of the dopaminergic system to compensate for the degeneration of neurons and caused a local energy deprivation by decreasing lactate and glycogen amount. Studied markers suggest a shift in the usage of energy substrates, via increased glycogenolysis and glycolysis markers, ketone bodies availability and fatty acid transport in remaining cells. Peroxisome proliferator-activated receptor-gamma coactivator 1α (PGC-1alpha) and AMP-activated protein kinase (AMPK), the energy sensors, showed different regulation between the cell-types. Increased neuronal expression of carnitine palmitoyltransferase 1c could play a role in the adaptation to metabolic stress in response to glia dysfunction. Astrocyte energetic support is one of the essential factors for neuronal compensatory mechanisms of dopaminergic system and might have a leading role in the presymptomatic Parkinson's disease stages. OPEN SCIENCE BADGES: This article has received a badge for *Open Materials* because it provided all relevant information to reproduce the study in the manuscript. The complete Open Science Disclosure form for this article can be found at the end of the article. More information about the Open Practices badges can be found at https://cos.io/our-services/open-science-badges/.

Claw morphometrics in monitor lizards: Variable substrate and habitat use correlate to shape diversity within a predator guild.

Numerous studies investigate morphology in the context of habitat, and lizards have received particular attention. Substrate usage is often reflected in the morphology of characters associated with locomotion, and, as a result, claws have become well‐studied ecomorphological traits linking the two. The Kimberley predator guild of Western Australia consists of 10 sympatric varanid species. The purpose of this study was to quantify claw size and shape in the guild using geometric morphometrics, and determine whether these features correlated with substrate use and habitat. Each species was assigned a Habitat/substrate group based on the substrate their claws interact with in their respective habitat. Claw morphometrics were derived for both wild caught and preserved specimens from museum collections, using a 2D semilandmark analysis. Claw shape significantly separated based on Habitat/substrate group. Varanus gouldii and Varanus panoptes claws were associated with sprinting and extensive digging. Varanus mertensi claws were for shallow excavation. The remaining species’ claws reflected specialization for some form of climbing, and differed based on substrate compliance. Varanus glauerti was best adapted for climbing rough sandstone, whereas Varanus scalaris and Varanus tristis had claws ideal for puncturing wood. Phylogenetic signal also significantly influenced claw shape, with Habitat/substrate group limited to certain clades. Positive size allometry allowed for claws to cope with mass increases, and shape allometry reflected a potential size limit on climbing. Claw morphology may facilitate niche separation within this trophic guild, especially when considered with body size. As these varanids are generalist predators, morphological traits associated with locomotion may be more reliable candidates for detecting niche partitioning than those associated directly with diet.

Culture Medium Development for Microbial-Derived Surfactants Production-An Overview.

Surfactants are compounds that can reduce the surface tension between two different phases or the interfacial tension of the liquid between water and oil, possessing both hydrophilic and hydrophobic moieties. Biosurfactants have traits that have proven to be advantageous over synthetic surfactants, but these compounds do not compete economically with synthetic surfactants. Different alternatives increase the yield of biosurfactants; development of an economical production process and the usage of cheaper substrates during process have been employed. One of the solutions relies on the suitable formulation of a production medium by including alternative raw materials sourced from agro-wastes, hydrocarbons, or by-products of a process might help in boosting the biosurfactant production. Since the nutritional factors required will be different among microorganisms, the establishment of a suitable formulation for biosurfactant production will be challenging. The present review describes various nutrients and elements considered in the formulation of a production medium with an approach focusing on the macronutrient (carbon, nitrogen source, and C/N ratio), minerals, vitamins, metabolic regulators, and salinity levels which may aid in the study of biosurfactant production in the future.

Sweet Success: Metabolic Substrate Adaptations To Acute Hypoxia In The Naked Mole Rat (Heterocephalus Glaber)

Naked mole rats are among the most hypoxia‐tolerant mammals identified. This tolerance is partially achieved through their ability to coordinately reduce metabolic rates by &gt; 85% in acute hypoxia while staying warm and active in their hypoxic underground burrows. Our understanding of the physiological responses that enable their hypoxia‐tolerance is improving; however, the underlying molecular and biochemical mechanisms that support this remarkable energetic suppression are poorly understood. Of particular interest is a putative metabolic fuel substrate switch in hypoxia. Naked mole rats primarily metabolize lipids in normoxia, but carbohydrate metabolism may be favored in hypoxia because carbohydrate oxidation yields more energy per molecule of oxygen than does lipid oxidation. We hypothesized that naked mole rats switch to primarily glucose‐fueled metabolism in acute hypoxia and that the energetic needs of brain and heart are prioritized over those of other tissues. Furthermore, we predicted that heat production from brown adipose tissue, which is a glucose‐intensive process, would be turned off in hypoxia as an energy‐saving strategy. To test these hypotheses, we measured metabolic fuel usage and heat production in naked mole rats exposed to acute hypoxia (7% O2) using non‐invasive in vivo imaging techniques, including infrared thermography, magnetic resonance imaging (MRI), and positron emission tomography (PET). We found that glucose metabolism is markedly upregulated in heart and brain during acute hypoxia, but decreased in liver. Furthermore, heat generation from brown adipose tissue is entirely turned off in hypoxia and the naked mole rat body temperature drops to near or below ambient temperature, indicating that all endogenous heat production ceases in hypoxia. We conclude that naked mole rats maximize the energy/oxygen ratio in their metabolic fuel substrate usage and prioritize feeding the energetic needs of brain and heart over all other metabolic processes in hypoxia.Support or Funding InformationThis study was supported by an NSERC discovery grant to MEP, a CIHR grant to AJS, and CRC grants to MEP and AJS.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Glucose and lactate as metabolic constraints on presynaptic transmission at an excitatory synapse.

Synapses have high energy demands which increase during intense activity. We show that presynaptic terminals can utilise extracellular glucose or lactate to generate energy to maintain synaptic transmission. Reducing energy substrates induces a metabolic stress: presynaptic ATP depletion impaired synaptic transmission through a reduction in the number of functional synaptic vesicle release sites and a slowing of vesicle pool replenishment, without a consistent change in release probability. Metabolic function is compromised in many pathological conditions (e.g. stroke, traumatic brain injury and neurodegeneration). Knowledge of how synaptic transmission is constrained by metabolic stress, especially during intense brain activity, will provide insights to improve cognition following pathological insults. The synapse has high energy demands, which increase during intense activity. Presynaptic ATP production depends on substrate availability and usage will increase during activity, which in turn could influence transmitter release and information transmission. We investigated transmitter release at the mouse calyx of Held synapse using glucose or lactate (10, 1 or 0mm) as the extracellular substrates while inducing metabolic stress. High-frequency stimulation (HFS) and recovery paradigms evoked trains of EPSCs monitored under voltage-clamp. Whilst postsynaptic intracellular ATP was stabilised by diffusion from the patch pipette, depletion of glucose increased EPSC depression during HFS and impaired subsequent recovery. Computational modelling of these data demonstrated a reduction in the number of functional release sites and slowed vesicle pool replenishment during metabolic stress, with little change in release probability. Directly depleting presynaptic terminal ATP impaired transmitter release in an analogous manner to glucose depletion. In the absence of glucose, presynaptic terminal metabolism could utilise lactate from the aCSF and this was blocked by inhibition of monocarboxylate transporters (MCTs). MCT inhibitors significantly suppressed transmission in low glucose, implying that lactate is a presynaptic substrate. Additionally, block of glycogenolysis accelerated synaptic transmission failure in the absence of extracellular glucose, consistent with supplemental supply of lactate by local astrocytes. We conclude that both glucose and lactate support presynaptic metabolism and that limited availability, exacerbated by high-intensity firing, constrains presynaptic ATP, impeding transmission through a reduction in functional presynaptic release sites as vesicle recycling slows when ATP levels are low.

Microbial methanogenesis in the sulfate-reducing zone of sediments in the Eckernförde Bay, SW Baltic Sea

Abstract. Benthic microbial methanogenesis is a known source of methane in marine systems. In most sediments, the majority of methanogenesis is located below the sulfate-reducing zone, as sulfate reducers outcompete methanogens for the major substrates hydrogen and acetate. The coexistence of methanogenesis and sulfate reduction has been shown before and is possible through the usage of noncompetitive substrates by methanogens such as methanol or methylated amines. However, knowledge about the magnitude, seasonality, and environmental controls of this noncompetitive methane production is sparse. In the present study, the presence of methanogenesis within the sulfate reduction zone (SRZ methanogenesis) was investigated in sediments (0–30 cm below seafloor, cm b.s.f.) of the seasonally hypoxic Eckernförde Bay in the southwestern Baltic Sea. Water column parameters such as oxygen, temperature, and salinity together with porewater geochemistry and benthic methanogenesis rates were determined in the sampling area Boknis Eck quarterly from March 2013 to September 2014 to investigate the effect of seasonal environmental changes on the rate and distribution of SRZ methanogenesis, to estimate its potential contribution to benthic methane emissions, and to identify the potential methanogenic groups responsible for SRZ methanogenesis. The metabolic pathway of methanogenesis in the presence or absence of sulfate reducers, which after the addition of a noncompetitive substrate was studied in four experimental setups: (1) unaltered sediment batch incubations (net methanogenesis), (2) 14C-bicarbonate labeling experiments (hydrogenotrophic methanogenesis), (3) manipulated experiments with the addition of either molybdate (sulfate reducer inhibitor), 2-bromoethanesulfonate (methanogen inhibitor), or methanol (noncompetitive substrate, potential methanogenesis), and (4) the addition of 13C-labeled methanol (potential methylotrophic methanogenesis). After incubation with methanol, molecular analyses were conducted to identify key functional methanogenic groups during methylotrophic methanogenesis. To also compare the magnitudes of SRZ methanogenesis with methanogenesis below the sulfate reduction zone (&gt; 30 cm b.s.f.), hydrogenotrophic methanogenesis was determined by 14C-bicarbonate radiotracer incubation in samples collected in September 2013.SRZ methanogenesis changed seasonally in the upper 30 cm b.s.f. with rates increasing from March (0.2 nmol cm−3 d−1) to November (1.3 nmol cm−3 d−1) 2013 and March (0.2 nmol cm−3 d−1) to September (0.4 nmol cm−3 d−1) 2014. Its magnitude and distribution appeared to be controlled by organic matter availability, C / N, temperature, and oxygen in the water column, revealing higher rates in the warm, stratified, hypoxic seasons (September–November) compared to the colder, oxygenated seasons (March–June) of each year. The majority of SRZ methanogenesis was likely driven by the usage of noncompetitive substrates (e.g., methanol and methylated compounds) to avoid competition with sulfate reducers, as was indicated by the 1000–3000-fold increase in potential methanogenesis activity observed after methanol addition. Accordingly, competitive hydrogenotrophic methanogenesis increased in the sediment only below the depth of sulfate penetration (&gt; 30 cm b.s.f.). Members of the family Methanosarcinaceae, which are known for methylotrophic methanogenesis, were detected by PCR using Methanosarcinaceae-specific primers and are likely to be responsible for the observed SRZ methanogenesis.The present study indicates that SRZ methanogenesis is an important component of the benthic methane budget and carbon cycling in Eckernförde Bay. Although its contributions to methane emissions from the sediment into the water column are probably minor, SRZ methanogenesis could directly feed into methane oxidation above the sulfate–methane transition zone.