Limb proportions show developmental plasticity in response to embryo movement.

Animals have evolved limb proportions adapted to different environments, but it is not yet clear to what extent these proportions are directly influenced by the environment during prenatal development. The developing skeleton experiences mechanical loading resulting from embryo movement. We tested the hypothesis that environmentally-induced changes in prenatal movement influence embryonic limb growth to alter proportions. We show that incubation temperature influences motility and limb bone growth in West African Dwarf crocodiles, producing altered limb proportions which may, influence post-hatching performance. Pharmacological immobilisation of embryonic chickens revealed that altered motility, independent of temperature, may underpin this growth regulation. Use of the chick also allowed us to merge histological, immunochemical and cell proliferation labelling studies to evaluate changes in growth plate organisation, and unbiased array profiling to identify specific cellular and transcriptional targets of embryo movement. This disclosed that movement alters limb proportions and regulates chondrocyte proliferation in only specific growth plates. This selective targeting is related to intrinsic mTOR (mechanistic target of rapamycin) pathway activity in individual growth plates. Our findings provide new insights into how environmental factors can be integrated to influence cellular activity in growing bones and ultimately gross limb morphology, to generate phenotypic variation during prenatal development.

The role of embryo movement in the development of the furcula.

The pectoral girdle is a complex structure which varies in its morphology between species. A major component in birds is the furcula, which can be considered equivalent to a fusion of the paired clavicles found in many mammals, and the single interclavicle found in many reptiles. These elements are a remnant of the dermal skeleton and the only intramembranous bones in the trunk. Postnatally, the furcula plays important mechanical roles by stabilising the shoulder joint and acting as a mechanical spring during flight. In line with its mechanical role, previous studies indicate that, unlike many other intramembranous bones, furcula growth during development can be influenced by mechanical stimuli. This study investigated the response of individual aspects of furcula growth to both embryo immobilisation and hypermotility in the embryonic chicken. The impact of altered incubation temperature, which influences embryo motility, on crocodilian interclavicle development was also explored. We employed whole-mount bone and cartilage staining and 3D imaging by microCT to quantify the impact of rigid paralysis, flaccid paralysis and hypermobility on furcula growth in the chicken, and 3D microCT imaging to quantify the impact of reduced temperature (32-28 °C) and motility on interclavicle growth in the crocodile. This revealed that the growth rates of the clavicular and interclavicular components of the furcula differ during normal development. Total furcula area was reduced by total unloading produced by flaccid paralysis, but not by rigid paralysis which maintains static loading of embryonic bones. This suggests that dynamic loading, which is required for postnatal bone adaptation, is not a requirement for prenatal furcula growth. Embryo hypermotility also had no impact on furcula area or arm length. Furcula 3D shape did, however, differ between groups; this was marked in the interclavicular component of the furcula, the hypocleideum. Hypocleideum length was reduced by both methods of immobilisation, and interclavicle area was reduced in crocodile embryos incubated at 28 °C, which are less motile than embryos incubated at 32 °C. These data suggest that the clavicular and interclavicle components of the avian furcula respond differently to alterations in embryo movement, with the interclavicle requiring both the static and dynamic components of movement-related loading for normal growth, while static loading preserved most aspects of clavicle growth. Our data suggest that embryo movement, and the mechanical loading this produces, is important in shaping these structures during development to suit their postnatal mechanical roles.

Validating a Noninvasive Technique for Monitoring Embryo Movement In Ovo.

Avian embryos are a commonly used model system for developmental studies, but monitoring of physiological parameters such as heart rate (HR) and movement in ovo poses a challenge to researchers. These are also increasingly common research objectives for ecological and embryo behavior studies in oviparous species. We therefore explored the validity of a new digital egg-monitoring system for the noninvasive monitoring of these parameters. We tested the relationship between frequency-of-movement values gathered by digital monitoring and those gathered by the current standard method, which is comparatively invasive and requires egg windowing, and demonstrated that the digital monitoring method effectively distinguishes individual movements but cannot reliably monitor HR in actively motile embryos. We therefore provide recommendations for the appropriate use of this technique for avian physiologists. We also applied the digital monitoring method to reveal how frequency of movement varies throughout prenatal ontogeny in the chicken and showed that commonly used protocols in developmental studies can themselves alter motility; egg windowing and application of light modulate frequency of movement. Recent work has revealed the importance of embryo motility in regulating gene expression and cellular activity during developmental processes. Together with our data, this highlights the value of noninvasive monitoring methods and the importance of controlling for altered embryo motility/behavior in developmental studies.

The carbon footprint of acute care: how energy intensive is critical care?

OBJECTIVES: Climate change has the potential to threaten human health and the environment. Managers in healthcare systems face significant challenges to balance carbon mitigation targets with operational decisions about patient care. Critical care units are major users of energy and hence more evidence is needed on their carbon footprint. STUDY DESIGN: The authors explore a methodology which estimates electricity use and associated carbon emissions within a Critical Care Unit (CCU). METHODS: A bottom-up model was developed and calibrated which predicted the electricity consumed and carbon emissions within a CCU based on the type of patients treated and working practices in a case study in Cornwall, UK. RESULTS: The model developed was able to predict the electricity consumed within CCU with an error of 1% when measured against actual meter readings. Just under half the electricity within CCU was used for delivering care to patients and monitoring their condition. CONCLUSIONS: A model was developed which accurately predicted the electricity consumed within a CCU based on patient types, medical devices used and working practice. The model could be adapted to enable it to be used within hospitals as part of their planning to meet carbon reduction targets.

Mechanoadaptation of developing limbs: shaking a leg.

The proportion of total limb length taken up by the individual skeletal elements (limb proportionality), varies widely between species. These diverse skeletal forms have evolved to allow for a range of limb uses and they first emerge as the embryo develops, to achieve the characteristic skeletal architecture of each species. During this time, the developing skeleton experiences mechanical loading as a result of embryonic muscle contraction. The possibility that adaptation to such mechanical input may allow embryos to coordinate the appearance of skeletal design with their expanding range of movements has so far received little attention. This is surprising, given the critical role exerted by embryo movement in normal skeletal development; stage-specific in ovo immobilisation of embryonic chicks results in joint contractures and a reduction in longitudinal bone growth in the limbs. Epigenetic mechanisms allow for selective activation of genes in response to environmental signals, resulting in the production of phenotypic complexity in morphogenesis; mechanical loading of bone during movement appears to be one such signal. It may be that 'mechanosensitive' genes under regulation of mechanical input adjust proportionality along the bone's proximo-distal axis, introducing a level of phenotypic plasticity. If this hypothesis is upheld, species with more elongated distal limb elements will have a greater dependence on mechanical input for the differences in their growth, and mechanosensitive bone growth in the embryo may have evolved as an additional source of phenotypic diversity during skeletal development.

Cartilage to bone transitions in health and disease.

Aberrant redeployment of the 'transient' events responsible for bone development and postnatal longitudinal growth has been reported in some diseases in what is otherwise inherently 'stable' cartilage. Lessons may be learnt from the molecular mechanisms underpinning transient chondrocyte differentiation and function, and their application may better identify disease aetiology. Here, we review the current evidence supporting this possibility. We firstly outline endochondral ossification and the cellular and physiological mechanisms by which it is controlled in the postnatal growth plate. We then compare the biology of these transient cartilaginous structures to the inherently stable articular cartilage. Finally, we highlight specific scenarios in which the redeployment of these embryonic processes may contribute to disease development, with the foresight that deciphering those mechanisms regulating pathological changes and loss of cartilage stability will aid future research into effective disease-modifying therapies.

Geography of non-melanoma skin cancer and ecological associations with environmental risk factors in England.

BACKGROUND: This study investigates the geography of non-melanoma skin cancer (NMSC) in England, and ecological associations with three widespread environmental hazards: radon, arsenic and ultraviolet radiation from the sun. METHODS: Age-/sex-standardised registration rates of NMSC were mapped for local authority (LA) areas (n=326), along with geographical data on bright sunshine, household radon and arsenic. Associations between NMSC and environmental variables, adjusted for socio-economic confounders, were investigated. RESULTS: There was a substantial geographical variation in NMSC rates across English local authorities and between cancer registration regions. Forty percent of variance in rates was at registry region level and 60% at LA level. No association was observed between environmental arsenic and NMSC rates. Rates were associated with area-mean bright sunshine hours. An association with area-mean radon concentration was suggested, although the strength of statistical evidence was sensitive to model specification. CONCLUSION: The significant geographical variation across England in NMSC registration rate is likely to be partly, but not wholly, explained by registry differences. Findings tentatively support suggestions that environmental radon may be a risk factor for NMSC. Although NMSC is rarely fatal, it has significant implications for individuals and health services, and further research into NMSC geographical and environmental risk factors is warranted.