Biology subjects

Daley, M. A.

Publications and source records attributed to Daley, M. A..

5 recordsLinked to original sources

bioRxiv2026

Sociality, diurnal temperature range and isothermality: Significant determinants of mass-independent resting metabolic rate in subterranean African mole-rats (Superfamily Bathyergidae)

Animals exhibit a diverse range of sociality from the strictly solitary to the highly social. Different forms of sociality have evolved in response to ecological constraints and selective habitat pressures, which are governed by the energetic and fitness costs to an individual. Uniquely among mammals, the clade of African mole-rats (Bathyergidae and Heterocephalidae) covers three distinct life-history forms of sociality: solitary, social and eusocial species. This variety in social structure makes them a model clade to study how metabolic traits vary between different forms of sociality. Resting metabolic rates (RMR) of seven African mole-rat species, ranging from solitary to eusocial, were measured using open-flow respirometry. Results were combined with published data, enabling the inclusion and statistical analysis of 16 species in total. We identified distinct allometric scaling of RMR, with eusocial species exhibiting a considerably greater rise in RMR with increases in body mass. This is likely attributable to reproductive and behavioural divisions of labour, and mass-dependent colony roles in eusocial species. Phylogenetically-informed analyses further identified that sociality, in addition to select bioclimatic traits - diurnal temperature range ({degrees}C) and isothermality (%) - significantly explain variation in the mass-independent RMR of African mole-rats. These findings elucidate, for the first time, that sociality can be a determinant of RMR, and calls for further study to identify the wider significance of sociality on mammalian metabolism, as well as exploring the allometric scaling of metabolic rate with respect to mammalian sociality.

physiology↗

bioRxiv2025

Long-term, age-associated activity quantification in the DE50-MD dog model of Duchenne muscular dystrophy (DMD)

Animal models with a clinically relevant phenotype remain important for robust evaluation of novel therapeutics for the fatal, X-linked genetic disorder, Duchenne Muscular Dystrophy (DMD). Demonstration of functional improvement is crucial for both patients and regulatory authorities. DMD is associated with a decline in musculoskeletal function with progressive paresis, muscle atrophy and fibrosis: phenotypic features that are also seen in the DE50-MD canine model of DMD. Here we investigate non-invasive methods to quantify changes in activity and behaviour in DE50-MD dogs, using collar-based, tri-axial accelerometers. We measured activity in affected DE50-MD male dogs (3-8 per age point) and littermate wild-type (WT) male controls (3-13 per age point) at monthly intervals from 3 to 18 months of age using Axivity-AX3 accelerometers attached ventrally on each dogs collar. Data were recorded for 48 hours while dogs remained in their kennels with outside runs following their normal routine. Acceleration vector magnitudes were used to derive various activity indicators over a 24-hour period. Mixed model analyses were used to examine differences between affected and WT groups at different ages. DE50-MD dogs activity indicators were significantly higher for % time spent at rest (p<0.001) and significantly lower for all other activity indicators (all p<0.05), when compared to age-matched WT dogs. Sample size calculations reveal that these non-invasive and objective biomarkers offer significant promise for preclinical testing of therapeutics in this model of DMD. Our approach reveals opportunities for cross-model standardisation of activity monitoring methods, applicable to both research and companion animal settings. Summary statementThe DE50-MD dog model of Duchenne muscular dystrophy shows significant age-associated reduction in activity quantified through non-invasive, wearable accelerometers. Activity metrics tested show promise for objective assessment of activity patterns for preclinical trials.

neuroscience↗

bioRxiv2024

Neural Networks Estimate Muscle Force in Dynamic Conditions Better than Hill-type Muscle Models

Hill-type muscle models are widely used, even though they do not accurately represent certain muscle mechanics. We explored neural networks to develop new muscle models. We trained neural networks to estimate muscle force from activation, muscle length, and muscle velocity. Training data was recorded using sonomicrometry, electromyography, and a tendon buckle on two muscles of guinea fowl. First, we compared the neural network to a Hill-type muscle model, using the same data for network training and model optimization. Second, we trained neural networks on large datasets, in a more realistic machine learning scenario. We found that neural networks generally yielded higher coefficients of determination and lower errors than Hill-type muscle models. Our neural networks performed better when estimating forces on the muscle used for training, but on another bird, than on a different muscle of the same bird, which could be explained by inaccuracies in activation and force scaling. We extracted forcelength and force-velocity relationships from the trained neural networks and found that both effects were underestimated and that both relationships were not replicated well outside of the training data distribution. We discuss suggested experimental designs to collect suitable training data and conclude that neural networks could provide an accurate alternative to Hill-type muscle models, particularly for modeling dynamic muscle behavior that is prevalent in faster movements, given a suitable training dataset, while scaling of the training data should be comparable between muscles and animals. SummaryNeural networks predict muscle forces more accurately than Hill-type muscle models, particularly under dynamic conditions. However, they struggle to replicate the force-length and force-velocity relationships well.

bioengineering↗

bioRxiv2023

Linking in vivo muscle dynamics to in situ force-length and force-velocity reveals that guinea fowl lateral gastrocnemius operates at shorter than optimal lengths

Force-length (F-L) and force-velocity (F-V) properties characterize skeletal muscles intrinsic properties under controlled conditions, and it is thought that these properties can inform and predict in vivo muscle function. Here, we map dynamic in vivo operating range and mechanical function during walking and running, to the measured in situ F-L and F-V characteristics of guinea fowl (Numida meleagris) lateral gastrocnemius (LG), a primary ankle extensor. We use in vivo patterns of muscle tendon force, fascicle length, and activation to test the hypothesis that muscle fascicles operate at optimal lengths and velocities to maximize force or power production during walking and running. Our findings only partly support our hypothesis: in vivo LG velocities are consistent with optimizing power during work production, and economy of force at higher loads. However, LG does not operate at lengths on the force plateau ({+/-}5% Fmax) during force production. LG length was near L0 at the time of EMG onset but shortened rapidly such that force development during stance occurred almost entirely on the ascending limb of the F-L curve, at shorter than optimal lengths. These data suggest that muscle fascicles shorten across optimal lengths in late swing, to optimize the potential for rapid force development near the swing-stance transition. This may provide resistance against unexpected perturbations that require rapid force development at foot contact. We also found evidence of passive force rise (in absence of EMG activity) in late swing, at lengths where passive force is zero in situ, suggesting that dynamic history dependent and viscoelastic effects may contribute to in vivo force development. Direct comparison of in vivo work loops and physiological operating ranges to traditional measures of F-L and F-V properties suggests the need for new approaches to characterize dynamic muscle properties in controlled conditions that more closely resemble in vivo dynamics.

physiology↗

bioRxiv2019

Tuning of feedforward control enables stable muscle force length dynamics after loss of autogenic proprioceptive feedback

Animals must integrate feedforward, feedback and intrinsic mechanical control mechanisms to maintain stable locomotion. Recent studies of guinea fowl (Numida meleagris) revealed that the distal leg muscles rapidly modulate force and work output to minimize perturbations in uneven terrain. Here we probe the role of reflexes in the rapid perturbation response of muscle by studying the effects of proprioceptive loss. We induced bilateral loss of autogenic proprioception in the lateral gastrocnemius muscle (LG) using self-reinnervation. We compared ankle kinematics and in vivo muscle dynamics in birds with reinnervated LG and intact LG. Reinnervated and intact muscles exhibit similar force-length dynamics, with rapid changes in work to stabilize running obstacle terrain. Reinnervated LG exhibits 23ms earlier steady-state activation, consistent with feedforward tuning of activation phase to compensate for lost proprioception. Modulation of force duration is impaired in rLG, confirming the role of reflex feedback in regulating force duration in intact muscle.

physiology↗