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Quadriceps muscle power and optimal shortening velocity are inversely related to angiotensin converting enzyme activity in older men
<p>This dataset corresponds to the article titled "Quadriceps muscle power and optimal shortening velocity are inversely related to angiotensin converting enzyme activity in older men"</p>
Data from: The foot is more than a spring: human foot muscles perform work to adapt to the energetic requirements of locomotion
The foot has been considered both as an elastic mechanism that increases the efficiency of locomotion by recycling energy, as well as an energy sink that helps stabilize movement by dissipating energy through contact with the ground. We measured the activity of two intrinsic foot muscles, Flexor Digitorum Brevis (FDB) and Abductor Hallucis (AH), as well as the mechanical work performed by the foot as a whole and at a modelled plantar muscle tendon unit (MTU) to test whether these passive mechanics are actively controlled during stepping. We found that the underlying passive visco-elasticity of the foot is modulated by the muscles of the foot, facilitating both dissipation and generation of energy depending on the mechanical requirements at the center of mass (COM). Compared to level-ground stepping, the foot dissipated and generated an additional –0.2 J/kg and 0.10 J/kg (both P < 0.001) when stepping down and up a 26 cm step respectively, corresponding to 21 % and 10 % of the additional net work performed by the leg on the COM. Of this compensation at the foot, the plantar MTU performed 30 % and 89 % the work for step downs and step ups respectively. This work occurred early in stance and late in stance for stepping down respectively, when the activation levels of FDB and AH were increased between 69 % - 410 % compared to level steps (all P < 0.001). These findings suggest that the energetic function of the foot is actively modulated by the intrinsic foot muscles and may play a significant role in movements requiring large changes in net energy such as stepping on stairs or inclines, accelerating, decelerating, and jumping.
Data from: Gut evolution in early Cambrian trilobites and the origin of predation on infaunal macroinvertebrates: evidence from muscle scars in Mesolenellus.
Trilobites are particularly common Cambrian fossils, but their trophic impact on the rapidly evolving marine ecosystems of that time is difficult to assess, due to uncertainties on how diverse their feeding habits truly were. Gut anatomy might help to constrain inferences on trilobite feeding ecology, but preservation of digestive organs is exceedingly rare. Muscle scars on the glabella, known as 'frontal auxiliary impressions' (FAIs), have been interpreted as evidence of the evolution of a pouch-like organ with powerful extrinsic muscles (i.e. a crop) in some trilobites. Here we describe FAIs in Mesolenellus hyperboreus from Cambrian Stage 4 strata of North Greenland, which represents the oldest example of such structures and their first report in the Suborder Olenellina. Mesolenellus FAIs suggest that the crop in trilobites was clearly differentiated from the rest of the digestive tract, and essentially located under a hypertrophied glabellar frontal lobe. Reviews of the digestive anatomy of trilobite sister-taxa and the glabellar morphology of the oldest-known trilobites suggest that the gut of the trilobite ancestor was an essentially simple tract (i.e. no well-differentiated crop) flanked laterally by numerous midgut glands. A crop first evolved in the Cambrian in groups like olenelloids and (later) paradoxidoids. Using ichnological evidence, we hypothesize that the emergence of olenelloids yields evidence for the evolution of predatory inclinations in a group of arthropods originally dominated by surface-deposit-feeders. By allowing the exploitation of a rapidly developing food source, infaunal animals, the diversification of feeding strategies in trilobites might partially explain their unparalleled evolutionary success.
Data from: Evolutionary design of a flexible, seasonally migratory, avian phenotype: why trade gizzard mass against pectoral muscle mass?
Migratory birds undergo impressive body remodelling over the course of an annual cycle. Prior to long-distance flights, red knots (Calidris canutus islandica) reduce gizzard mass while increasing body mass and pectoral muscle mass. Although body mass and pectoral muscle mass are functionally linked via their joint effects on flight performance, gizzard and pectoral muscle mass are thought to be independently regulated. Current hypotheses for observed negative within-individual covariation between gizzard and pectoral muscle mass in free-living knots are based on a common factor (e.g., migration) simultaneously affecting both traits, and/or protein limitation forcing allocation decisions. We used diet manipulations to generate within-individual variation in gizzard mass and test for independence between gizzard and pectoral muscle mass within-individuals outside the period of migration and under conditions of high protein availability. Contrary to our prediction, we observed a negative within-individual covariation between gizzard and pectoral muscle mass. We discuss this result as a potential outcome of an evolved mechanism underlying body remodelling associated with migration. Although our proposed mechanism requires empirical testing, this study echoes earlier calls for greater integration of studies of function and mechanism, and in particular, the need for more explicit consideration of the evolution of mechanisms underlying phenotypic design.
Up-regulation of sarcoplasmic reticulum function protects skeletal muscle against cytoplasmic calcium overload during hibernation in ground squirrels
<p>We investigated the potential mechanism of the SR in maintenance of calcium (Ca<sup>2+</sup>) homeostasis of slow-twitch muscle (soleus, SOL), fast-twitch muscle (extensor digitorum longus, EDL) and mixed muscle (gastrocnemius, GAS) in hibernating ground squirrels (<i>Spermophilus dauricus</i>). Results showed that cytosolic and SR Ca<sup>2+</sup> concentrations in distinct skeletal muscle fibers increased and decreased during late torpor, respectively, but both returned to summer-active levels during early torpor. Ryanodine receptor1 (RyR1) and sarco/endoplasmic reticulum Ca<sup>2+</sup> ATPase isoform 1 (SERCA1) protein expression increased during hibernation. Up-regulation factors of SERCA activity: Phospholamban phosphorylation increased in the SOL and GAS, β-adrenergic receptor-2 protein expression increased in the GAS, and calmodulin kinase-2 phosphorylation increased in the SOL during hibernation. Down-regulation factors of SERCA activity: Sarcolipin and SERCA1 co-localization decreased in the EDL and GAS. These data suggest that SERCA activity in skeletal muscle fibers increases likely during hibernation. FKBP12/calsequestrin1 (negative regulatory factors of RyR1) and RyR1 co-localization decreased in the GAS, indicating that the RyR1 channel opening probability increased during hibernation. Dihydropyridine receptors protein expression and its co-localization with RYR1 decreased during hibernation prompts that the contractility of skeletal muscle was weakened. Protein expression of Ca<sup>2+</sup>-binding proteins calsequestrin1 and calmodulin increased indicating that the ability of intracellular free calcium binding increased during whole hibernation period. These findings confirm that the release, uptake, and binding of free Ca<sup>2+</sup> in the SR were enhanced in different skeletal muscles during hibernation. Up-regulation of muscular sarcoplasmic reticulum function protects skeletal muscle fibers against cytoplasmic calcium overload during hibernation in ground squirrels.We investigated the potential mechanism of the SR in maintenance of calcium (Ca<sup>2+</sup>) homeostasis of slow-twitch muscle (soleus, SOL), fast-twitch muscle (extensor digitorum longus, EDL) and mixed muscle (gastrocnemius, GAS) in hibernating ground squirrels (<i>Spermophilus dauricus</i>). Results showed that cytosolic and SR Ca<sup>2+</sup> concentrations in distinct skeletal muscle fibers increased and decreased during late torpor, respectively, but both returned to summer-active levels during early torpor. Ryanodine receptor1 (RyR1) and sarco/endoplasmic reticulum Ca<sup>2+</sup> ATPase isoform 1 (SERCA1) protein expression increased during hibernation. Up-regulation factors of SERCA activity: Phospholamban phosphorylation increased in the SOL and GAS, β-adrenergic receptor-2 protein expression increased in the GAS, and calmodulin kinase-2 phosphorylation increased in the SOL during hibernation. Down-regulation factors of SERCA activity: Sarcolipin and SERCA1 co-localization decreased in the EDL and GAS. These data suggest that SERCA activity in skeletal muscle fibers increases likely during hibernation. FKBP12/calsequestrin1 (negative regulatory factors of RyR1) and RyR1 co-localization decreased in the GAS, indicating that the RyR1 channel opening probability increased during hibernation. Dihydropyridine receptors protein expression and its co-localization with RYR1 decreased during hibernation prompts that the contractility of skeletal muscle was weakened. Protein expression of Ca<sup>2+</sup>-binding proteins calsequestrin1 and calmodulin increased indicating that the ability of intracellular free calcium binding increased during whole hibernation period. These findings confirm that the release, uptake, and binding of free Ca<sup>2+</sup> in the SR were enhanced in different skeletal muscles during hibernation. Up-regulation of muscular sarcoplasmic reticulum function protects skeletal muscle fibers against cytoplasmic calcium overload during hibernation in ground squirrels.</p>
Data from: Obesity-induced decreases in muscle performance are not reversed by weight loss
BACKGROUND/OBJECTIVES: Obesity can affect muscle phenotypes, and may thereby constrain movement and energy expenditure. Weight loss is a common and intuitive intervention for obesity, but it is not known whether the effects of obesity on muscle function are reversible by weight loss. Here we tested whether obesity-induced changes in muscle metabolic and contractile phenotypes are reversible by weight loss. SUBJECTS/METHODS: We used zebrafish (Danio rerio) in a factorial design to compare energy metabolism, locomotor capacity, muscle isometric force and work-loop power output, and myosin heavy chain (MHC) composition between lean fish, diet-induced obese fish, and fish that were obese and then returned to lean body mass following diet restriction. RESULTS: Obesity increased resting metabolic rates (Po0.001) and decreased maximal metabolic rates (P = 0.030), but these changes were reversible by weight loss, and were not associated with changes in muscle citrate synthase activity. In contrast, obesity-induced decreases in locomotor performance (P = 0.0034), and isolated muscle isometric stress (P = 0.01), work-loop power output (Po0.001) and relaxation rates (P = 0.012) were not reversed by weight loss. Similarly, obesity-induced decreases in concentrations of fast and slow MHCs, and a shift toward fast MHCs were not reversed by weight loss. CONCLUSION: Obesity-induced changes in locomotor performance and muscle contractile function were not reversible by weight loss. These results show that weight loss alone may not be a sufficient intervention.
Data from: A splice mutation in the PHKG1 gene causes high glycogen content and low meat quality in pig skeletal muscle
Glycolytic potential (GP) in skeletal muscle is economically important in the pig industry because of its effect on pork processing yield. We have previously mapped a major quantitative trait loci (QTL) for GP on chromosome 3 in a White Duroc × Erhualian F2 intercross. We herein performed a systems genetic analysis to identify the causal variant underlying the phenotype QTL (pQTL). We first conducted genome-wide association analyses in the F2 intercross and an F19 Sutai pig population. The QTL was then refined to an 180-kb interval based on the 2-LOD drop method. We then performed expression QTL (eQTL) mapping using muscle transcriptome data from 497 F2 animals. Within the QTL interval, only one gene (PHKG1) has a cis-eQTL that was colocolizated with pQTL peaked at the same SNP. The PHKG1 gene encodes a catalytic subunit of the phosphorylase kinase (PhK), which functions in the cascade activation of glycogen breakdown. Deep sequencing of PHKG1 revealed a point mutation (C>A) in a splice acceptor site of intron 9, resulting in a 32-bp deletion in the open reading frame and generating a premature stop codon. The aberrant transcript induces nonsense-mediated decay, leading to lower protein level and weaker enzymatic activity in affected animals. The mutation causes an increase of 43% in GP and a decrease of>20% in water-holding capacity of pork. These effects were consistent across the F2 and Sutai populations, as well as Duroc × (Landrace × Yorkshire) hybrid pigs. The unfavorable allele exists predominantly in Duroc-derived pigs. The findings provide new insights into understanding risk factors affecting glucose metabolism, and would greatly contribute to the genetic improvement of meat quality in Duroc related pigs.
Data from: The roles of joint tissues and jaw muscles in palatal biomechanics of the Savannah monitor (Varanus exanthematicus) and their significance for cranial kinesis
Many vertebrates exhibit cranial kinesis, or movement between bones of the skull other than at the jaw joint. Many kinetic species possess a particular suite of features to accomplish this movement, including flexible cranial joints and protractor musculature. Whereas the skeletal anatomy of these kinetic systems is well understood, how these joints are biomechanically loaded, how different soft tissues affect joint loading and kinetic capacity, and how the protractor musculature loads the skull remain poorly understood. Here we developed a Finite Element Model of the savannah monitor, Varanus exanthematicus, a modestly kinetic lizard, to better elucidate the roles of soft tissue in mobile joints and protractor musculature on cranial loading. We described the 3D resultants of jaw muscles and histology of palatobasal, otic and jaw joints. We tested the effects of joint tissue types, bite point, and muscle loads to evaluate the biomechanical role of muscles have on the palate and braincase. We found the jaw muscles have significant mediolateral components and resultants that can impart stability across palatocranial joints. We found articular tissues affect the magnitude of strains experienced across the palatobasal and otic joints. We found that without protractor muscle loading, the palate, quadrate and braincase experience higher strains suggesting this muscle helps insulate the braincase and palatoquadrate from high loads. Finally, we found the cross-sectional properties of the bones of Varanus exanthematicus is well suited for performing under torsional loads. These findings suggest that torsion may be a significant driver in the evolution of cranial kinesis in lepidosaurs.
Data from: The arrangement of possible muscle fibres in the Ediacaran taxon Haootia quadriformis
Haootia quadriformis from Newfoundland, Canada, is one of the most unusual impressions of a soft-bodied macro-organism yet described from the late Ediacaran Period. Interpreted as a metazoan of cnidarian grade, the body impression of H. quadriformis possesses features interpreted as fibrous structures that represent possible evidence for muscular tissue. Evidence both in support of and against a relationship between H. quadriformis and the Staurozoa, one of the cnidarian groups to which Haootia was compared in Liu et al., is outlined by Miranda et al.. Our intention in our original paper was to illustrate the staurozoan body plan for comparative purposes, rather than suggest homology or direct ancestry. Nevertheless, fresh insights from workers with expertise in the biology of extant cnidarians are welcomed.
Data from: Vamorolone trial in Duchenne muscular dystrophy shows dose-related improvement of muscle function
Objective: We carried out first-in-patient studies of vamorolone, a first-in-class dissociative steroidal anti-inflammatory drug, in Duchenne muscular dystrophy. Methods: An open-label, multiple-ascending dose study of vamorolone was conducted in 48 boys with Duchenne muscular dystrophy (4 to <7 years, steroid-naïve). Dose levels were 0.25, 0.75, 2.0 and 6.0 mg/kg/day using an oral suspension formulation (12 boys/dose level; 1/3rd to 10x glucocorticoid dose in DMD). Results: Over a 24-week treatment period, oral administration of vamorolone at all doses tested was safe and well-tolerated. The 2.0 mg/kg/day dose group met the primary efficacy outcome of improved muscle function (time to stand; 24 weeks vamorolone treatment versus natural history controls), without evidence of most adverse effects of glucocorticoids. Significant dose-responsive improvements in 10 meter run/walk, and six-minute walk test were observed for 2.0 and 6.0 mg/kg/day dose groups. The morbidity of most concern to many chronic glucocorticoid users, bone loss, was not seen with vamorolone at any dose, as evidenced by serum osteocalcin. Biomarker outcomes for adrenal suppression and insulin resistance were also less impacted in vamorolone-treated DMD patients, relative to published studies of glucocorticoid therapy. Conclusions: Vamorolone demonstrated both efficacy and a reduction in adverse effects in DMD patients compared to traditional glucocorticoids in a 24-week, open-label study. Vamorolone has potential to replace chronic glucocorticoids in many disorders where side effects detract from patient quality of life. Classification of Evidence: This study provides Class II evidence that certain dosages of vamorolone are well tolerated and effective in improving muscle function in DMD.
Data from: Anthropogenic changes in sodium affect neural and muscle development in butterflies
The development of organisms is changing drastically because of anthropogenic changes in once-limited nutrients. Although the importance of changing macronutrients, such as nitrogen and phosphorus, is well-established, it is less clear how anthropogenic changes in micronutrients will affect organismal development, potentially changing dynamics of selection. We use butterflies as a study system to test whether changes in sodium availability due to road salt runoff have significant effects on the development of sodium-limited traits, such as neural and muscle tissue. We first document how road salt runoff can elevate sodium concentrations in the tissue of some plant groups by 1.5–30 times. Using monarch butterflies reared on roadside- and prairie-collected milkweed, we then show that road salt runoff can result in increased muscle mass (in males) and neural investment (in females). Finally, we use an artificial diet manipulation in cabbage white butterflies to show that variation in sodium chloride per se positively affects male flight muscle and female brain size. Variation in sodium not only has different effects depending on sex, but also can have opposing effects on the same tissue: across both species, males increase investment in flight muscle with increasing sodium, whereas females show the opposite pattern. Taken together, our results show that anthropogenic changes in sodium availability can affect the development of traits in roadside-feeding herbivores. This research suggests that changing micronutrient availability could alter selection on foraging behavior for some roadside-developing invertebrates.
Life history predicts flight muscle phenotype and function in birds
<p>1. Functional traits are the essential phenotypes that underlie an organism's life history and ecology. Although biologists have long recognized that intraspecific variation is consequential to an animals' ecology, studies of functional variation are often restricted to species-level comparisons, ignoring critical variation within species. In birds, interspecific comparisons have been foundational in connecting flight muscle phenotypes to species-level ecology, but intraspecific variation has remained largely unexplored.</p> <p>2. We asked how age- and sex-dependent demands on flight muscle function are reconciled in birds. The flight muscle is an essential multifunctional organ, mediating a large range of functions associated with powered flight and thermoregulation. These functions must be balanced over an individual's lifetime.</p> <p>3. We leveraged within- and between-species comparisons in a clade of small passerines (<em>Tarsiger</em> bush-robins) from the eastern edge of the Qinghai-Tibet Plateau. We integrated measurements of flight muscle physiology, morphology, behavior, phenology, and environmental data, analyzing trait data within a context of three widespread, adaptive life-history strategies – sexual dichromatism, age and sex-structured migration, and delayed plumage maturation. This approach provides a framework of the selective forces that shape functional variation within and between species.</p> <p>4. We found more variation in flight muscle traits within species than has been previously described between species of birds under 20 g. This variation was associated with the discovery of mixed muscle fiber types (i.e. both fast glycolytic and fast oxidative fibers), which differ markedly in their physiological and functional attributes. This result is surprising given that the flight muscles of small birds are generally thought to contain only fast oxidative fibers, suggesting a novel ecological context for glycolytic muscle fibers in small birds. Within each species, flight muscle phenotypes varied by age and sex, reflecting the functional demands at different life-history stages and the pressures that individuals face as a result of their multi-class identity (i.e. species, age, and sex).</p> <p>5. Our findings reveal new links between avian physiology, ecology, behavior, and life history, while demonstrating the importance of demographic-dependent selection in shaping functional phenotypic variation. </p>
Data from: Rapid evolution of larval life history, adult immune function and flight muscles in a poleward moving damselfly
Although a growing number of studies have documented the evolution of adult dispersal-related traits at the range edge of poleward-expanding species, we know little about evolutionary changes in immune function or traits expressed by nondispersing larvae. We investigated differentiation in larval (growth and development) and adult traits (immune function and flight-related traits) between replicated core and edge populations of the poleward-moving damselfly Coenagrion scitulum. These traits were measured on individuals reared in a common garden experiment at two different food levels, as allocation trade-offs may be easier to detect under energy shortage. Edge individuals had a faster larval life history (growth and development rates), a higher adult immune function and a nearly significant higher relative flight muscle mass. Most of the differentiation between core and edge populations remained and edge populations had a higher relative flight muscle mass when corrected for latitude-specific thermal regimes, and hence could likely be attributed to the range expansion process per se. We here for the first time document a higher immune function in individuals at the expansion front of a poleward-expanding species and documented the rarely investigated evolution of faster life histories during range expansion. The rapid multivariate evolution in these ecological relevant traits between edge and core populations is expected to translate into changed ecological interactions and therefore has the potential to generate novel eco-evolutionary dynamics at the expansion front.
Data from: A functional regulatory variant of MYH3 influences muscle fiber-type composition and intramuscular fat content in pigs
Muscle development and lipid accumulation in muscle critically affect meat quality in livestock. Yet, the underlying genetic factors for myofiber-type specification and intramuscular fat (IMF) accumulation remain to be elucidated. Using two independent intercrosses between Western breeds and Korean native pigs (KNPs) and a joint linkage-linkage disequilibrium analysis, we here identified a 488.1-kb region on porcine chromosome 12 that affects both reddish meat color (a*) and IMF. In this critical region, only the MYH3 gene, encoding myosin heavy chain 3, was found to be preferentially overexpressed in the skeletal muscle in KNPs. Subsequently, MYH3-transgenic mice demonstrated that this gene controls both myofiber-type specification and adipogenesis in skeletal muscle. We discovered a structural variant in the promotor/regulatory region of MYH3 for which Q allele carriers exhibited significantly higher values of a* and IMF than q allele carriers. Furthermore, chromatin immunoprecipitation and co-transfection assays showed the structural variant in the 5'-UTR of MYH3 abrogated binding of the myogenic regulatory factors (MYF5, MYOD, MYOG, and MRF4). The allele distribution of the MYH3 among worldwide pig populations indicated that the MYH3 Q allele is of Asian origin and likely predates domestication. In conclusion, we identified a functional regulatory sequence variant in the porcine MYH3 that provides novel insights into the genetic basis of the regulation of myofiber type ratios and associated changes in IMF in pigs. The MYH3 variant can play an important role to improve pork quality in current breeding programs.
Data from: Muscle-tendon mechanics explain unexpected effects of exoskeleton assistance on metabolic rate during walking
The goal of this study was to gain insight into how ankle exoskeletons affect the behavior of the plantarflexor muscles during walking. Using data from previous experiments, we performed electromyography-driven simulations of musculoskeletal dynamics to explore how changes in exoskeleton assistance affected plantarflexor muscle–tendon mechanics, particularly for the soleus. We used a model of muscle energy consumption to estimate individual muscle metabolic rate. As average exoskeleton torque was increased, while no net exoskeleton work was provided, a reduction in tendon recoil led to an increase in positive mechanical work performed by the soleus muscle fibers. As net exoskeleton work was increased, both soleus muscle fiber force and positive mechanical work decreased. Trends in the sum of the metabolic rates of the simulated muscles correlated well with trends in experimentally observed whole-body metabolic rate (R2=0.9), providing confidence in our model estimates. Our simulation results suggest that different exoskeleton behaviors can alter the functioning of the muscles and tendons acting at the assisted joint. Furthermore, our results support the idea that the series tendon helps reduce positive work done by the muscle fibers by storing and returning energy elastically. We expect the results from this study to promote the use of electromyography-driven simulations to gain insight into the operation of muscle–tendon units and to guide the design and control of assistive devices.
Data from: Primary dermal fibroblasts and pectoralis muscle show similar patterns of oxidative stress in tropical and temperate birds despite differing life-histories
<p><span>Tropical birds have a "slower pace of life," with lower rates of whole-animal metabolism, smaller metabolically active organs, and lower cellular metabolic rates than their temperate counterparts. Oxidative stress is a physiological mechanism that may dictate differing life-histories such as those found between tropical and temperate birds. <span>Oxygen is required to make ATP, resulting in the production of reactive oxygen species (ROS)</span>. If left unchecked, ROS can structurally alter proteins, induce mutations in DNA, and damage structural lipids. To combat accumulating oxidative damage, organisms have evolved an elaborate and costly antioxidant system that serves to sequester ROS before they wreak cellular havoc. We examined whether oxidative stress would differ between tropical and temperate birds. We used isolated primary dermal fibroblasts and pectoralis muscle tissue for measurements. We measured four aspects of oxidative stress in primary fibroblasts – reduced glutathione (GSH) concentration, ROS production, mitochondrial content, and lipid peroxidation (LPO) damage. We found no significant differences in the four variables between temperate and tropical birds.. In muscle tissue, we measured catalase (CAT), superoxide dismutase (SOD) glutathione peroxidase (GPx) activity, peroxyl and hydroxyl scavenging capacity, and LPO damage. We found that peroxyl scavenging capacity was significantly higher in tropical birds compared with temperate birds. </span></p>
Data from: Muscle–spring dynamics in time-limited, elastic movements
Muscle contractions that load in-series springs with slow speed over a long duration do maximal work and store the most elastic energy. However, time constraints, such as those experienced during escape and predation behaviours, may prevent animals from achieving maximal force capacity from their muscles during spring-loading. Here, we ask whether animals that have limited time for elastic energy storage operate with springs that are tuned to submaximal force production. To answer this question, we used a dynamic model of a muscle–spring system undergoing a fixed-end contraction, with parameters from a time-limited spring-loader (bullfrog: Lithobates catesbeiana) and a non-time-limited spring-loader (grasshopper: Schistocerca gregaria). We found that when muscles have less time to contract, stored elastic energy is maximized with lower spring stiffness (quantified as spring constant). The spring stiffness measured in bullfrog tendons permitted less elastic energy storage than was predicted by a modelled, maximal muscle contraction. However, when muscle contractions were modelled using biologically relevant loading times for bullfrog jumps (50 ms), tendon stiffness actually maximized elastic energy storage. In contrast, grasshoppers, which are not time limited, exhibited spring stiffness that maximized elastic energy storage when modelled with a maximal muscle contraction. These findings demonstrate the significance of evolutionary variation in tendon and apodeme properties to realistic jumping contexts as well as the importance of considering the effect of muscle dynamics and behavioural constraints on energy storage in muscle–spring systems.
Data from: Mitochondrial membranes in cardiac muscle from Antarctic notothenioid fishes vary in phospholipid composition and membrane fluidity
Antarctic notothenioid fishes are highly stenothermal, yet their tolerance for warming is species-dependent. Because a body of literature points to the loss of cardiac function as underlying thermal limits in ectothermic animals, we investigated potential relationships among properties of ventricular mitochondrial membranes in notothenioids with known differences in both cardiac mitochondrial metabolism and organismal thermal tolerance. Fluidity of mitochondrial membranes was quantified by fluorescence depolarization for the white-blooded Chaenocephalus aceratus and the red-blooded Notothenia coriiceps. In these same membranes, lipid compositions and products of lipid peroxidation, the latter of which can disrupt membrane order, were analyzed in both species and in a second icefish, Pseudochaenichthys georgianus. Mitochondrial membranes from C. aceratus were significantly more fluid than those of the more thermotolerant species N. coriiceps (P < .0001). Consistent with this, ratios of total phosphatidylethanolamine (PE) to total phosphatidylcholine (PC) were lower in membranes from both species of icefishes, compared to those of N. coriiceps (P < .05). However, membranes of N. coriiceps displayed a greater unsaturation index (P < .0001). No differences among species were found in membrane products of lipid peroxidation. With rising temperatures, greater contents of PC in mitochondrial membranes from ventricles of icefishes are likely to promote membrane hyperfluidization at a lower temperature than for cardiac mitochondrial membranes from the red-blooded notothenioid. We propose that physical and chemical properties of the mitochondrial membranes may contribute to some of the observed differences in thermal sensitivity of physiological function among these species.
Processed data from "Human and rat skeletal muscle single-nuclei multi-omic integrative analyses nominate causal cell types, regulatory elements, and SNPs for complex traits"
<p>This is the processed data from our manscript "Human and rat skeletal muscle single-nuclei multi-omic integrative analyses nominate causal cell types, regulatory elements, and SNPs for complex traits"</p>
Processed data from "Human and rat skeletal muscle single-nuclei multi-omic integrative analyses nominate causal cell types, regulatory elements, and SNPs for complex traits"
<p>This is the processed data from our manscript "Human and rat skeletal muscle single-nuclei multi-omic integrative analyses nominate causal cell types, regulatory elements, and SNPs for complex traits"</p>
ScienceDex guides
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These curated guides explain access requirements, typical timelines, costs, and reuse considerations for widely used research datasets.
Allen Brain Atlas
Allen Brain Atlas is an Allen Institute collection of brain map atlases, datasets, APIs, and analysis tools covering mouse, human, and non-human primate brain resources.
Annotated Behaviour and Observability Dataset (ABODe)
ABODe is a University of Edinburgh DataShare dataset for behavior classification in group-housed mice using home-cage video, identities, bounding boxes, ground-plate positions, and annotator labels.
DANDI Archive for NWB datasets
DANDI is a BRAIN Initiative archive for publishing and sharing neurophysiology data, including electrophysiology, optophysiology, and behavioral data packaged as NWB and related standards.
International Brain Laboratory public data
The International Brain Laboratory public data releases expose standardized mouse decision-making experiments, including Neuropixels recordings, widefield calcium imaging, behavior, and session metadata accessed through the ONE API.
OpenNeuro
OpenNeuro is a free, open platform for sharing neuroimaging datasets, with public search, dataset pages, and download paths for web, S3, DataLad, and the OpenNeuro CLI.