Nathan Jeffery | University of Liverpool (original) (raw)

Papers by Nathan Jeffery

Scientific Reports 9, 2019

Reconstructions of habitual activity in past populations and extinct human groups is a primary go... more Reconstructions of habitual activity in past populations and extinct human groups is a primary goal of paleoanthropological research. Muscle attachment scars (entheses) are widely considered as indicators of habitual activity and many attempts have been made to use them for this purpose. However, their interpretation remains equivocal due to methodological limitations and a paucity of empirical data supporting an interaction between systematic muscle forces and entheseal morphology. We have recently addressed the first issue with precise three-dimensional measuring protocols and rigorous multivariate analysis focusing on the patterns among different entheses rather than comparing each entheseal structure separately. In a previous study, the resulting entheseal correlations reflected synergistic muscle groups that separated individuals according to their lifelong occupational activities. Here we address the second issue by applying this methodology to existing micro-computed tomography data from rats that have undergone muscle stimulation under experimental conditions. In contrast to previous animal studies, we relied on blind analytical procedures across two research institutions and controlled for most factors of interindividual variability. Results demonstrated that the multivariate associations among different entheseal surfaces can directly reflect repetitive muscle recruitment and provide essential information on muscle use. Entheses are the areas of the bone where muscles, tendons, or ligaments attach 1,2. They represent the only direct evidence of the musculotendinous system on skeletal remains 2 and are thought to broadly reflect muscular activity. As such, entheses have been used in attempts to reconstruct past habitual physical activity among past human populations and extinct hominin species 3-5. Some of these studies 5-8 rely on entheseal changes describing osteo-phytic or osteolytic traits within the broader area of muscle attachment, which can potentially be pathological 5,7,9. By contrast, research focusing on variation in the entire entheseal morphology 10-19 typically relies on the assumption that entheses vary in size and shape with changes of biomechanical load, according to Wolff 's law 20 and to more recent paradigms of bone re-modeling before and during adulthood 21,22. However, it has been demonstrated that the etiology underlying both aspects of entheseal variability (entheseal changes and entire enthesis morphology) is deeply multi-factorial, involving complex interactions among biological age, body size, sexual dimorphism, physical activity, population history, systemic factors (genes, nutrition and hormones), as well as pathology 4,5,9. Detecting correlates of muscular activity through this maelstrom has been hindered in previous studies by important methodological design flaws, such as low or untested measuring precision 23 , lack of rigorous multivariate statistical approaches 16,24 , and disregard for important compounding variables such as old age and body size 4,9,25. To address some of these issues, we recently presented a repeatable method for quantifying the three-dimensional (3D) surface areas of human hand entheses and multivariate analysis of the resulting measurements 15,16. By focusing on the multivariate correlations among different entheses rather than on the morphology of individual entheses, we found that patterns within the human hand reflect two fundamental muscle synergy groups associated with power versus precision grasping movements 15. We subsequently applied the method to

Over the past two decades, the development of methods for visualizing and analysing specimens dig... more Over the past two decades, the development of methods for visualizing and analysing specimens digitally, in three and even four dimensions, has transformed the study of living and fossil organisms. However, the initial promise that the widespread application of such methods would facilitate access to the underlying digital data has not been fully achieved. The underlying datasets for many published studies are not readily or freely available, introducing a barrier to verification and reproducibility, and the reuse of data. There is no current agreement or policy on the amount and type of data that should be made available alongside studies that use, and in some cases are wholly reliant on, digital morphology. Here, we propose a set of recommendations for minimum standards and additional best practice for three-dimensional digital data publication, and review the issues around data storage, management and accessibility.

The masticatory apparatus amongst closely related carnivoran species raises intriguing questions ... more The masticatory apparatus amongst closely related carnivoran species raises intriguing questions about the interplay between allometry, function, and phylogeny in defining interspecific variations of cranial morphology. Here we describe the gross structure of the jaw adductor muscles of several species of canid, and then examine how the muscles are scaled across the range of body sizes, phylogenies, and trophic groups. We also consider how the muscles are accommodated on the skull, and how this is influenced by differences of endocranial size. Data were collected for a suite of morphological metrics, including body mass, endocra-nial volume, and muscle masses and we used geometric morphometric shape analysis to reveal associated form changes. We find that all jaw adductor muscles scale isometrically against body mass, regardless of phylogeny or trophic group, but that endocranial volume scales with negative allometry against body mass. These findings suggest that head shape is partly influenced by the need to house isometrically scaling muscles on a neurocranium scaling with negative allometry. Principal component analysis suggests that skull shape changes, such as the relatively wide zygomatic arches and large sagittal crests seen in species with higher body masses, allow the skull to accommodate a relative enlargement of the jaw adductors compared with the endocranium. Anat Interspecific differences of Carnivoran skull shape are dependent on numerous factors, most notably phylogeny, dietary function and allometry with the relative importance of each depending on the group of species under investigation. Here, we attempt to resolve the relative importance of allometry and diet in determining cranial morphology among one particularly widespread and varied carnivoran family, the canids. We aim to account for phy-logeny and determine how labile the musculoskeletal morphology of the wild canid head is by combining advances in imaging with conventional dissection and more advanced computational methods such as geometric morphometrics.

Advances in Phylogeny, Functional Morphology and Development, 2015

Journal of Anatomy

Rodents are defined by a uniquely specialized dentition and a highly complex arrangement of jaw-c... more Rodents are defined by a uniquely specialized dentition and a highly complex arrangement of jaw-closing muscles. Finite element analysis (FEA) is an ideal technique to investigate the biomechanical implications of these specializations, but it is essential to understand fully the degree of influence of the different input parameters of the FE model to have confidence in the model’s predictions. This study evaluates the sensitivity of FE models of rodent crania to elastic properties of the materials, loading direction, and the location and orientation of the models’ constraints. Three FE models were constructed of squirrel, guinea pig and rat skulls. Each was loaded to simulate biting on the incisors, and the first and the third molars, with the angle of the incisal bite varied over a range of 45 . The Young’s moduli of the bone and teeth components were varied between limits defined by findings from our own and previously published tests of material properties. Geometric morphometri...

Journal of …, Jan 1, 2011

We illustrate here microCT images in which contrast between muscle and connective tissue has been... more We illustrate here microCT images in which contrast between muscle and connective tissue has been achieved by means of staining with iodine. Enhancement is shown to be dependent on the concentration of iodine solution (I2KI), time in solution and specimen size. Histological examination confirms that the arrangement of individual muscle fibres can be visualised on the enhanced microCT images, and that the iodine accumulates in themuscle fibres in preference to the surrounding connective tissues.We explore the application of this technique to describe the fibrous structure of skeletal muscle, and conclude that it has the potential to become a non-destructive and cost-effective method for investigating muscle fascicle architecture, particularly in comparative morphological studies.

Osteoarthritis and Cartilage, 2015

Osteoarthritis and Cartilage, 2013

resolution cartilage T1r maps (In plane resolution ¼ 0.2 mm2) clearly show better classification ... more resolution cartilage T1r maps (In plane resolution ¼ 0.2 mm2) clearly show better classification of multiple cartilage layers at 7T compared to 3T . Pixel profile of T1r values on the high-resolution map showed a monotonic increase from deep to superficial zone (w36 to 55 ms) at 7T while profile obtained at 3T were highly noisy . These preliminary data clearly shows advantage of T1r mapping in term of high resolution at 7T. Evaluation of other potential advantage of T1r mapping at 7T requires a detailed study on patients with cartilage pathologies. Comparison of results from 7T using global and localized shim reveal that with localized shim volume around cartilage and setting of reference frequency and voltage corresponding to this volume, B0 and B1 inhomogeneity artifacts were mitigated. In this study SAR was well within scanner set limits. Conclusions: In conclusion, increased SNR at 7T MRI can be exploited to obtain high-resolution T1r maps of in vivo human knee cartilage in a clinically relevant time and SAR constraints, which provides the ability to characterize cartilage molecular integrity with enhanced accuracy and precision. Fig. 1. A single slice high resolution T1r (ms) map of in vivo human knee patella cartilage overlaid on anatomical image from 7T (A) and 3T (B).

Sagittal fractures of the first phalanx are a common, potentially catastrophic injury in racehors... more Sagittal fractures of the first phalanx are a common, potentially catastrophic injury in racehorses. These fractures are often linked to an acute, one time, biomechanical event; however, recent evidence implies that chronic exposure to stress can lead to the accumulation of bony changes that affect the structural integrity of the bone and increase the likelihood of fracture. The aim of the study was to compare variations of two common metrics of bone adaptation – subchondral bone density and thickness across the proximal articular surface of the first phalanx in Thoroughbred horses that (1) raced but never experienced a first phalanx fracture (Raced Control); (2) raced and had experienced fracture of the contralateral first phalanx (Contralateral to Fracture); (3) had never raced or experienced a first phalanx fracture (Unraced Control). A total of 22 first phalangeal bones were sampled post-mortem and imaged using micro-computed tomography calibrated for mineral density measures. Measurements of volumetric subchondral bone mineral density and thickness were taken from images at five sites from medial to lateral, in three coronal planes (25, 50 and 75% dorsal-palmar). At each of the 15 sites, measurements were repeated and averaged across 10 adjacent micro-computed tomography slices of bone, spanning 0.75 mm. The magnitude and variance of these measurements were compared between sites and between cohorts with non-parametric statistical tests. Across the proximal osteochondral surface of the first phalanx, the pattern of subchondral bone volumetric bone mineral density and thickness varied with each coronal section studied. The subchondral bone thickness was greater for the central and dorsal coronal sections, compared with the palmar section. For the race-fit groups (Raced Control and Contralateral to Fracture), the highest volumetric bone mineral density was in the central sagittal groove. The volumetric bone mineral density was significantly greater in the sagittal groove in the central coronal section in the raced than the unraced group. The Contralateral to Fracture group demonstrated significantly greater variance of volumetric bone mineral density compared with the Raced Control and Unraced Control (P < 0.0001), with no difference in variance noted between the Raced Control and Unraced Control groups. There was a small (R rank = 0.3) but significant correlation between subchondral bone volumetric bone mineral density and thickness in the Contralateral to Fracture group (P = 0.005). The findings demonstrate that differences exist in subchondral bone volumetric bone mineral density and thickness across the proximal osteochondral surface of the equine first phalanx in horses with different training histories. The findings also demonstrate that the subchondral bone of the sagittal groove of the equine first phalanx adapts to race-training in the race-fit groups (Raced Control and Contralateral to Fracture) with an increase in volumetric bone mineral density relative to unraced controls. Within the race-trained groups, the Contralateral to Fracture bones had a greater variance of volumetric bone mineral density, suggesting that stress-induced bone adaptation had become more erratic, potentially contributing to the aetiology of sagittal fractures of the first phalanx in the Thoroughbred racehorse.

Early bone development may have a significant impact upon bone health in adulthood. Bone mineral ... more Early bone development may have a significant impact upon bone health in adulthood. Bone mineral density (BMD) and bone mass are important determinants of adult bone strength. However, several studies have shown that BMD and bone mass decrease after birth. If early development is important for strength, why does this reduction occur? To investigate this, more data characterizing gestational, infant, and childhood bone development are needed in order to compare with adults. The aim of this study is to document early vertebral trabecular bone development, a key fragility fracture site, and infer whether this period is important for adult bone mass and structure. A series of 120 vertebrae aged between 6 months gestation and 2.5 years were visualized using microcomputed tomography. Spherical volumes of interest were defined, thresholded, and measured using 3D bone analysis software (BoneJ, Quant3D). The findings showed that gestation was characterized by increasing bone volume fraction whilst infancy was defined by significant bone loss (≈2/3rds) and the appearance of a highly anisotropic trabecular structure with a predominantly inferior-superior direction. Childhood development progressed via selective thickening of some trabeculae and the loss of others; maintaining bone volume whilst creating a more anisotropic structure. Overall, the pattern of vertebral development is one of gestational overproduction followed by infant "sculpting" of bone tissue during the first year of life (perhaps in order to regulate mineral homeostasis or to adapt to loading environment) and then subsequent refinement during early childhood. Comparison of early bone developmental data in this study with adult bone volume values taken from the literature shows that the loss in bone mass that occurs during the first year of life is never fully recovered. Early development could therefore be important for developing bone strength, but through structural changes in trabecular microarchitecture rather than bone mass.

Structural and functional trade-offs are integral to the evolution of the mammalian skull and its... more Structural and functional trade-offs are integral to the evolution of the mammalian skull and its development. This paper examines the potential for enlargement of the masticatory musculature to limit the size of the endocranial cavity by studying a myostatin-deficient mouse model of hypermuscularity (MSTN−/−). The study tests the null prediction that the larger MSTN−/− mice have larger brains compared with wild-type (WT) mice in order to service the larger muscles. Eleven post-mortem MSTN−/− mice and 12 WT mice were imaged at high resolution using contrast enhanced micro-CT. Masticatory muscle volumes (temporalis, masseter, internal and external pterygoids) and endocranial volumes were measured on the basis of two-dimensional manual tracings and the Cavalieri principle. Volumes were compared using Kruskal–Wallis and Student's t-tests. Results showed that the masticatory muscles of the MSTN−/− mice were significantly larger than in the WT mice. Increases were in the region of 17–36% depending on the muscle. Muscles increased in proportion to each other, maintaining percentages in the region of 5, 10, 21 and 62% of total muscle volume for the external ptyergoid, internal pterygoid, temporalis and masseter, respectively. Kruskal–Wallis and t-tests demonstrated that the endocranial volume was significantly larger in the WT mice, approximately 16% larger on average than that seen in the MSTN−/− mice. This comparative reduction of MSTN−/− endocranial size could not be explained in terms of observer bias, ageing, sexual dimorphism or body size scaling. That the results showed a reduction of brain size associated with an increase of muscle size falsifies the null prediction and lends tentative support to the view that the musculature influences brain growth. It remains to be determined whether the observed effect is primarily physical, nutritional, metabolic or molecular in nature.

High density mineralised protrusions (HDMP) from the tidemark mineralising front into hyaline art... more High density mineralised protrusions (HDMP) from the tidemark mineralising front into hyaline articular cartilage (HAC) were first described in Thoroughbred racehorse fetlock joints and later in Icelandic horse hock joints. We now report them in human material. Whole femoral heads removed at operation for joint replacement or from dissection room cadavers were imaged using magnetic resonance imaging (MRI) dual echo steady state at 0.23 mm resolution, then 26-lm resolution high contrast X-ray microtomography, sectioned and embedded in polymethylmethacrylate, blocks cut and polished and re-imaged with 6-lm resolution X-ray microtomography. Tissue mineralisation density was imaged using backscattered electron SEM (BSE SEM) at 20 kV with uncoated samples. HAC histology was studied by BSE SEM after staining block faces with ammonium triiodide solution. HDMP arise via the extrusion of an unknown mineralisable matrix into clefts in HAC, a process of acellular dystrophic calcification. Their formation may be an extension of a crack self-healing mechanism found in bone and articular calcified cartilage. Mineral concentration exceeds that of articular calcified cartilage and is not uniform. It is probable that they have not been reported previously because they are removed by decalcification with standard protocols. Mineral phase morphology frequently shows the agglomeration of many fine particles into larger concretions. HDMP are surrounded by HAC, are brittle, and show fault lines within them. Dense fragments found within damaged HAC could make a significant contribution to joint destruction. At least larger HDMP can be detected with the best MRI imaging ex vivo.

Foot and Ankle Surgery, 2006

Little is know about the effects of the changing body weight on the juvenile skeleton and to what... more Little is know about the effects of the changing body weight on the juvenile skeleton and to what extent it can explain the phenotypic variability observed in human joint morphology. The talus occupies a pivotal position and must sustain and distribute the weight of the body without deformation and whilst remaining a functional biomechanical unit. It is hypothesized that the talus exhibits morphological plasticity of its articular surfaces in order to adapt to the increases in body weight associated loading over ontogeny. Objectives: To explore plasticity in talar articular facet morphology during development in response to increases in body weight. Method: Tali from juvenile archaeological remains from 8 to 18 years of age were cast, then laser scanned and homologous landmark data were acquired by a novel method and utilized in 3D geometric morphometric analysis. Femur length was used as a proxy for individual body weights. Results: Changes in shape and orientation of three talar articular facets was observed over ontogeny. Principle components 1, 2, 3 and 5 correlated significantly with increases in body weight. Conclusions: Talar articular surface morphology is plastically adaptive to changes in body weight over ontogeny. A framework of normal ontogenetic changes over the juvenile period is provided for practitioners.

Journal of anatomy, 2013

The mouse has been the dominant model organism in studies on the development, genetics and evolut... more The mouse has been the dominant model organism in studies on the development, genetics and evolution of the mammalian skull and associated soft-tissue for decades. There is the potential to take advantage of this well studied model and the range of mutant, knockin and knockout organisms with diverse craniofacial phenotypes to investigate the functional significance of variation and the role of mechanical forces on the development of the integrated craniofacial skeleton and musculature by using computational mechanical modelling methods (e.g. finite element and multibody dynamic modelling). Currently, there are no detailed published data of the mouse masticatory musculature available. Here, using a combination of micro-dissection and non-invasive segmentation of iodine-enhanced micro-computed tomography, we document the anatomy, architecture and proportions of the mouse masticatory muscles. We report on the superficial masseter (muscle, tendon and pars reflecta), deep masseter, zygomaticomandibularis (anterior, posterior, infraorbital and tendinous parts), temporalis (lateral and medial parts), external and internal pterygoid muscles. Additionally, we report a lateral expansion of the attachment of the temporalis onto the zygomatic arch, which may play a role in stabilising this bone during downwards loading. The data presented in this paper now provide a detailed reference for phenotypic comparison in mouse models and allow the mouse to be used as a model organism in biomechanical and functional modelling and simulation studies of the craniofacial skeleton and particularly the masticatory system.

Journal of anatomy, 2013

Iodine potassium iodide (I2KI) solution can be employed as a contrast agent for the visualisation... more Iodine potassium iodide (I2KI) solution can be employed as a contrast agent for the visualisation of soft tissue structures in micro-computed tomography studies. This technique provides high resolution images of soft tissue non-destructively but initial studies suggest that the stain can cause substantial specimen shrinkage. The degree of specimen shrinkage, and potential deformation, is an important consideration when using the data for morphological studies. Here we quantify the macroscopic volume changes in mouse skeletal muscle, cardiac muscle and cerebellum as a result of immersion in the common fixatives 10% phosphate-buffered formal saline, 70% ethanol and 3% glutaraldehyde, compared with I2KI staining solution at concentrations of 2, 6, 10 and 20%. Immersion in the I2KI solution resulted in dramatic changes of tissue volume, which were far larger than the shrinkage from formalin fixation alone. The degree of macroscopic change was most dependent upon the I2KI concentration, with severe shrinkage of 70% seen in solutions of 20% I2KI after 14 days' incubation. When using this technique care needs to be taken to use the lowest concentration that will give adequate contrast to minimise artefacts due to shrinkage.

The vestibulo-ocular reflex is the system of compensatory ocular movements in response to stimula... more The vestibulo-ocular reflex is the system of compensatory ocular movements in response to stimulation of the kinetic labyrinth seen in all vertebrates. It allows maintenance of a stable gaze even when the head is moving. Perhaps the simplest influence on the VOR is the spatial orientation of the planes of the semicircular canals relative to the extraocular muscles. It is hypothesized that the extraocular muscles are in parallel alignment with their corresponding semicircular canals in order to reduce the amount of neural processing needed and hence keep reflex times to a minimum. However, despite its obvious importance, little is known of this spatial arrangement. Moreover, nothing is known about any ontogenetic changes in the relative orientations of the extraocular muscles and semicircular canals. The morphologies of fetal and adult specimens of Homo sapiens were examined using magnetic resonance (MR) images. Three-dimensional co-ordinate data were taken from the images and used to calculate vector equations of the extraocular muscles and planes of best fit for the semicircular canals. The relative orientations of the muscles and canals were then calculated from the vectors and planes. It was shown that there are significant correlations between both the anterior and lateral semicircular canals and their corresponding extraocular muscles during ontogeny. In the case of the lateral canal with the medial rectus, the lateral canal with the lateral rectus, and the anterior canal with the inferior oblique, the trend is towards, though never reaching, alignment, whereas the anterior canal and the superior rectus muscle move out of alignment as age increases. Furthermore, it was noted that none of the six muscle-canal pairs is in perfect alignment, either during ontogeny or in adulthood. It was also shown that the three semicircular canals are not precisely orthogonal, but that the anterior and posterior canals form an angle of about 858, while the anterior and lateral canals diverge by 1008. Overall, it was shown that there is significant reorientation of the extraocular muscles and semicircular canals during ontogeny, but that, in most cases, there is little realignment beyond the fetal period. J. Morphol. 268:878-890, 2007Morphol. 268:878-890, . 2007 Wiley-Liss, Inc.

Scientific Reports 9, 2019

Reconstructions of habitual activity in past populations and extinct human groups is a primary go... more Reconstructions of habitual activity in past populations and extinct human groups is a primary goal of paleoanthropological research. Muscle attachment scars (entheses) are widely considered as indicators of habitual activity and many attempts have been made to use them for this purpose. However, their interpretation remains equivocal due to methodological limitations and a paucity of empirical data supporting an interaction between systematic muscle forces and entheseal morphology. We have recently addressed the first issue with precise three-dimensional measuring protocols and rigorous multivariate analysis focusing on the patterns among different entheses rather than comparing each entheseal structure separately. In a previous study, the resulting entheseal correlations reflected synergistic muscle groups that separated individuals according to their lifelong occupational activities. Here we address the second issue by applying this methodology to existing micro-computed tomography data from rats that have undergone muscle stimulation under experimental conditions. In contrast to previous animal studies, we relied on blind analytical procedures across two research institutions and controlled for most factors of interindividual variability. Results demonstrated that the multivariate associations among different entheseal surfaces can directly reflect repetitive muscle recruitment and provide essential information on muscle use. Entheses are the areas of the bone where muscles, tendons, or ligaments attach 1,2. They represent the only direct evidence of the musculotendinous system on skeletal remains 2 and are thought to broadly reflect muscular activity. As such, entheses have been used in attempts to reconstruct past habitual physical activity among past human populations and extinct hominin species 3-5. Some of these studies 5-8 rely on entheseal changes describing osteo-phytic or osteolytic traits within the broader area of muscle attachment, which can potentially be pathological 5,7,9. By contrast, research focusing on variation in the entire entheseal morphology 10-19 typically relies on the assumption that entheses vary in size and shape with changes of biomechanical load, according to Wolff 's law 20 and to more recent paradigms of bone re-modeling before and during adulthood 21,22. However, it has been demonstrated that the etiology underlying both aspects of entheseal variability (entheseal changes and entire enthesis morphology) is deeply multi-factorial, involving complex interactions among biological age, body size, sexual dimorphism, physical activity, population history, systemic factors (genes, nutrition and hormones), as well as pathology 4,5,9. Detecting correlates of muscular activity through this maelstrom has been hindered in previous studies by important methodological design flaws, such as low or untested measuring precision 23 , lack of rigorous multivariate statistical approaches 16,24 , and disregard for important compounding variables such as old age and body size 4,9,25. To address some of these issues, we recently presented a repeatable method for quantifying the three-dimensional (3D) surface areas of human hand entheses and multivariate analysis of the resulting measurements 15,16. By focusing on the multivariate correlations among different entheses rather than on the morphology of individual entheses, we found that patterns within the human hand reflect two fundamental muscle synergy groups associated with power versus precision grasping movements 15. We subsequently applied the method to

Over the past two decades, the development of methods for visualizing and analysing specimens dig... more Over the past two decades, the development of methods for visualizing and analysing specimens digitally, in three and even four dimensions, has transformed the study of living and fossil organisms. However, the initial promise that the widespread application of such methods would facilitate access to the underlying digital data has not been fully achieved. The underlying datasets for many published studies are not readily or freely available, introducing a barrier to verification and reproducibility, and the reuse of data. There is no current agreement or policy on the amount and type of data that should be made available alongside studies that use, and in some cases are wholly reliant on, digital morphology. Here, we propose a set of recommendations for minimum standards and additional best practice for three-dimensional digital data publication, and review the issues around data storage, management and accessibility.

The masticatory apparatus amongst closely related carnivoran species raises intriguing questions ... more The masticatory apparatus amongst closely related carnivoran species raises intriguing questions about the interplay between allometry, function, and phylogeny in defining interspecific variations of cranial morphology. Here we describe the gross structure of the jaw adductor muscles of several species of canid, and then examine how the muscles are scaled across the range of body sizes, phylogenies, and trophic groups. We also consider how the muscles are accommodated on the skull, and how this is influenced by differences of endocranial size. Data were collected for a suite of morphological metrics, including body mass, endocra-nial volume, and muscle masses and we used geometric morphometric shape analysis to reveal associated form changes. We find that all jaw adductor muscles scale isometrically against body mass, regardless of phylogeny or trophic group, but that endocranial volume scales with negative allometry against body mass. These findings suggest that head shape is partly influenced by the need to house isometrically scaling muscles on a neurocranium scaling with negative allometry. Principal component analysis suggests that skull shape changes, such as the relatively wide zygomatic arches and large sagittal crests seen in species with higher body masses, allow the skull to accommodate a relative enlargement of the jaw adductors compared with the endocranium. Anat Interspecific differences of Carnivoran skull shape are dependent on numerous factors, most notably phylogeny, dietary function and allometry with the relative importance of each depending on the group of species under investigation. Here, we attempt to resolve the relative importance of allometry and diet in determining cranial morphology among one particularly widespread and varied carnivoran family, the canids. We aim to account for phy-logeny and determine how labile the musculoskeletal morphology of the wild canid head is by combining advances in imaging with conventional dissection and more advanced computational methods such as geometric morphometrics.

Advances in Phylogeny, Functional Morphology and Development, 2015

Journal of Anatomy

Rodents are defined by a uniquely specialized dentition and a highly complex arrangement of jaw-c... more Rodents are defined by a uniquely specialized dentition and a highly complex arrangement of jaw-closing muscles. Finite element analysis (FEA) is an ideal technique to investigate the biomechanical implications of these specializations, but it is essential to understand fully the degree of influence of the different input parameters of the FE model to have confidence in the model’s predictions. This study evaluates the sensitivity of FE models of rodent crania to elastic properties of the materials, loading direction, and the location and orientation of the models’ constraints. Three FE models were constructed of squirrel, guinea pig and rat skulls. Each was loaded to simulate biting on the incisors, and the first and the third molars, with the angle of the incisal bite varied over a range of 45 . The Young’s moduli of the bone and teeth components were varied between limits defined by findings from our own and previously published tests of material properties. Geometric morphometri...

Journal of …, Jan 1, 2011

We illustrate here microCT images in which contrast between muscle and connective tissue has been... more We illustrate here microCT images in which contrast between muscle and connective tissue has been achieved by means of staining with iodine. Enhancement is shown to be dependent on the concentration of iodine solution (I2KI), time in solution and specimen size. Histological examination confirms that the arrangement of individual muscle fibres can be visualised on the enhanced microCT images, and that the iodine accumulates in themuscle fibres in preference to the surrounding connective tissues.We explore the application of this technique to describe the fibrous structure of skeletal muscle, and conclude that it has the potential to become a non-destructive and cost-effective method for investigating muscle fascicle architecture, particularly in comparative morphological studies.

Osteoarthritis and Cartilage, 2015

Osteoarthritis and Cartilage, 2013

resolution cartilage T1r maps (In plane resolution ¼ 0.2 mm2) clearly show better classification ... more resolution cartilage T1r maps (In plane resolution ¼ 0.2 mm2) clearly show better classification of multiple cartilage layers at 7T compared to 3T . Pixel profile of T1r values on the high-resolution map showed a monotonic increase from deep to superficial zone (w36 to 55 ms) at 7T while profile obtained at 3T were highly noisy . These preliminary data clearly shows advantage of T1r mapping in term of high resolution at 7T. Evaluation of other potential advantage of T1r mapping at 7T requires a detailed study on patients with cartilage pathologies. Comparison of results from 7T using global and localized shim reveal that with localized shim volume around cartilage and setting of reference frequency and voltage corresponding to this volume, B0 and B1 inhomogeneity artifacts were mitigated. In this study SAR was well within scanner set limits. Conclusions: In conclusion, increased SNR at 7T MRI can be exploited to obtain high-resolution T1r maps of in vivo human knee cartilage in a clinically relevant time and SAR constraints, which provides the ability to characterize cartilage molecular integrity with enhanced accuracy and precision. Fig. 1. A single slice high resolution T1r (ms) map of in vivo human knee patella cartilage overlaid on anatomical image from 7T (A) and 3T (B).

Sagittal fractures of the first phalanx are a common, potentially catastrophic injury in racehors... more Sagittal fractures of the first phalanx are a common, potentially catastrophic injury in racehorses. These fractures are often linked to an acute, one time, biomechanical event; however, recent evidence implies that chronic exposure to stress can lead to the accumulation of bony changes that affect the structural integrity of the bone and increase the likelihood of fracture. The aim of the study was to compare variations of two common metrics of bone adaptation – subchondral bone density and thickness across the proximal articular surface of the first phalanx in Thoroughbred horses that (1) raced but never experienced a first phalanx fracture (Raced Control); (2) raced and had experienced fracture of the contralateral first phalanx (Contralateral to Fracture); (3) had never raced or experienced a first phalanx fracture (Unraced Control). A total of 22 first phalangeal bones were sampled post-mortem and imaged using micro-computed tomography calibrated for mineral density measures. Measurements of volumetric subchondral bone mineral density and thickness were taken from images at five sites from medial to lateral, in three coronal planes (25, 50 and 75% dorsal-palmar). At each of the 15 sites, measurements were repeated and averaged across 10 adjacent micro-computed tomography slices of bone, spanning 0.75 mm. The magnitude and variance of these measurements were compared between sites and between cohorts with non-parametric statistical tests. Across the proximal osteochondral surface of the first phalanx, the pattern of subchondral bone volumetric bone mineral density and thickness varied with each coronal section studied. The subchondral bone thickness was greater for the central and dorsal coronal sections, compared with the palmar section. For the race-fit groups (Raced Control and Contralateral to Fracture), the highest volumetric bone mineral density was in the central sagittal groove. The volumetric bone mineral density was significantly greater in the sagittal groove in the central coronal section in the raced than the unraced group. The Contralateral to Fracture group demonstrated significantly greater variance of volumetric bone mineral density compared with the Raced Control and Unraced Control (P < 0.0001), with no difference in variance noted between the Raced Control and Unraced Control groups. There was a small (R rank = 0.3) but significant correlation between subchondral bone volumetric bone mineral density and thickness in the Contralateral to Fracture group (P = 0.005). The findings demonstrate that differences exist in subchondral bone volumetric bone mineral density and thickness across the proximal osteochondral surface of the equine first phalanx in horses with different training histories. The findings also demonstrate that the subchondral bone of the sagittal groove of the equine first phalanx adapts to race-training in the race-fit groups (Raced Control and Contralateral to Fracture) with an increase in volumetric bone mineral density relative to unraced controls. Within the race-trained groups, the Contralateral to Fracture bones had a greater variance of volumetric bone mineral density, suggesting that stress-induced bone adaptation had become more erratic, potentially contributing to the aetiology of sagittal fractures of the first phalanx in the Thoroughbred racehorse.

Early bone development may have a significant impact upon bone health in adulthood. Bone mineral ... more Early bone development may have a significant impact upon bone health in adulthood. Bone mineral density (BMD) and bone mass are important determinants of adult bone strength. However, several studies have shown that BMD and bone mass decrease after birth. If early development is important for strength, why does this reduction occur? To investigate this, more data characterizing gestational, infant, and childhood bone development are needed in order to compare with adults. The aim of this study is to document early vertebral trabecular bone development, a key fragility fracture site, and infer whether this period is important for adult bone mass and structure. A series of 120 vertebrae aged between 6 months gestation and 2.5 years were visualized using microcomputed tomography. Spherical volumes of interest were defined, thresholded, and measured using 3D bone analysis software (BoneJ, Quant3D). The findings showed that gestation was characterized by increasing bone volume fraction whilst infancy was defined by significant bone loss (≈2/3rds) and the appearance of a highly anisotropic trabecular structure with a predominantly inferior-superior direction. Childhood development progressed via selective thickening of some trabeculae and the loss of others; maintaining bone volume whilst creating a more anisotropic structure. Overall, the pattern of vertebral development is one of gestational overproduction followed by infant "sculpting" of bone tissue during the first year of life (perhaps in order to regulate mineral homeostasis or to adapt to loading environment) and then subsequent refinement during early childhood. Comparison of early bone developmental data in this study with adult bone volume values taken from the literature shows that the loss in bone mass that occurs during the first year of life is never fully recovered. Early development could therefore be important for developing bone strength, but through structural changes in trabecular microarchitecture rather than bone mass.

Structural and functional trade-offs are integral to the evolution of the mammalian skull and its... more Structural and functional trade-offs are integral to the evolution of the mammalian skull and its development. This paper examines the potential for enlargement of the masticatory musculature to limit the size of the endocranial cavity by studying a myostatin-deficient mouse model of hypermuscularity (MSTN−/−). The study tests the null prediction that the larger MSTN−/− mice have larger brains compared with wild-type (WT) mice in order to service the larger muscles. Eleven post-mortem MSTN−/− mice and 12 WT mice were imaged at high resolution using contrast enhanced micro-CT. Masticatory muscle volumes (temporalis, masseter, internal and external pterygoids) and endocranial volumes were measured on the basis of two-dimensional manual tracings and the Cavalieri principle. Volumes were compared using Kruskal–Wallis and Student's t-tests. Results showed that the masticatory muscles of the MSTN−/− mice were significantly larger than in the WT mice. Increases were in the region of 17–36% depending on the muscle. Muscles increased in proportion to each other, maintaining percentages in the region of 5, 10, 21 and 62% of total muscle volume for the external ptyergoid, internal pterygoid, temporalis and masseter, respectively. Kruskal–Wallis and t-tests demonstrated that the endocranial volume was significantly larger in the WT mice, approximately 16% larger on average than that seen in the MSTN−/− mice. This comparative reduction of MSTN−/− endocranial size could not be explained in terms of observer bias, ageing, sexual dimorphism or body size scaling. That the results showed a reduction of brain size associated with an increase of muscle size falsifies the null prediction and lends tentative support to the view that the musculature influences brain growth. It remains to be determined whether the observed effect is primarily physical, nutritional, metabolic or molecular in nature.

High density mineralised protrusions (HDMP) from the tidemark mineralising front into hyaline art... more High density mineralised protrusions (HDMP) from the tidemark mineralising front into hyaline articular cartilage (HAC) were first described in Thoroughbred racehorse fetlock joints and later in Icelandic horse hock joints. We now report them in human material. Whole femoral heads removed at operation for joint replacement or from dissection room cadavers were imaged using magnetic resonance imaging (MRI) dual echo steady state at 0.23 mm resolution, then 26-lm resolution high contrast X-ray microtomography, sectioned and embedded in polymethylmethacrylate, blocks cut and polished and re-imaged with 6-lm resolution X-ray microtomography. Tissue mineralisation density was imaged using backscattered electron SEM (BSE SEM) at 20 kV with uncoated samples. HAC histology was studied by BSE SEM after staining block faces with ammonium triiodide solution. HDMP arise via the extrusion of an unknown mineralisable matrix into clefts in HAC, a process of acellular dystrophic calcification. Their formation may be an extension of a crack self-healing mechanism found in bone and articular calcified cartilage. Mineral concentration exceeds that of articular calcified cartilage and is not uniform. It is probable that they have not been reported previously because they are removed by decalcification with standard protocols. Mineral phase morphology frequently shows the agglomeration of many fine particles into larger concretions. HDMP are surrounded by HAC, are brittle, and show fault lines within them. Dense fragments found within damaged HAC could make a significant contribution to joint destruction. At least larger HDMP can be detected with the best MRI imaging ex vivo.

Foot and Ankle Surgery, 2006

Little is know about the effects of the changing body weight on the juvenile skeleton and to what... more Little is know about the effects of the changing body weight on the juvenile skeleton and to what extent it can explain the phenotypic variability observed in human joint morphology. The talus occupies a pivotal position and must sustain and distribute the weight of the body without deformation and whilst remaining a functional biomechanical unit. It is hypothesized that the talus exhibits morphological plasticity of its articular surfaces in order to adapt to the increases in body weight associated loading over ontogeny. Objectives: To explore plasticity in talar articular facet morphology during development in response to increases in body weight. Method: Tali from juvenile archaeological remains from 8 to 18 years of age were cast, then laser scanned and homologous landmark data were acquired by a novel method and utilized in 3D geometric morphometric analysis. Femur length was used as a proxy for individual body weights. Results: Changes in shape and orientation of three talar articular facets was observed over ontogeny. Principle components 1, 2, 3 and 5 correlated significantly with increases in body weight. Conclusions: Talar articular surface morphology is plastically adaptive to changes in body weight over ontogeny. A framework of normal ontogenetic changes over the juvenile period is provided for practitioners.

Journal of anatomy, 2013

The mouse has been the dominant model organism in studies on the development, genetics and evolut... more The mouse has been the dominant model organism in studies on the development, genetics and evolution of the mammalian skull and associated soft-tissue for decades. There is the potential to take advantage of this well studied model and the range of mutant, knockin and knockout organisms with diverse craniofacial phenotypes to investigate the functional significance of variation and the role of mechanical forces on the development of the integrated craniofacial skeleton and musculature by using computational mechanical modelling methods (e.g. finite element and multibody dynamic modelling). Currently, there are no detailed published data of the mouse masticatory musculature available. Here, using a combination of micro-dissection and non-invasive segmentation of iodine-enhanced micro-computed tomography, we document the anatomy, architecture and proportions of the mouse masticatory muscles. We report on the superficial masseter (muscle, tendon and pars reflecta), deep masseter, zygomaticomandibularis (anterior, posterior, infraorbital and tendinous parts), temporalis (lateral and medial parts), external and internal pterygoid muscles. Additionally, we report a lateral expansion of the attachment of the temporalis onto the zygomatic arch, which may play a role in stabilising this bone during downwards loading. The data presented in this paper now provide a detailed reference for phenotypic comparison in mouse models and allow the mouse to be used as a model organism in biomechanical and functional modelling and simulation studies of the craniofacial skeleton and particularly the masticatory system.

Journal of anatomy, 2013

Iodine potassium iodide (I2KI) solution can be employed as a contrast agent for the visualisation... more Iodine potassium iodide (I2KI) solution can be employed as a contrast agent for the visualisation of soft tissue structures in micro-computed tomography studies. This technique provides high resolution images of soft tissue non-destructively but initial studies suggest that the stain can cause substantial specimen shrinkage. The degree of specimen shrinkage, and potential deformation, is an important consideration when using the data for morphological studies. Here we quantify the macroscopic volume changes in mouse skeletal muscle, cardiac muscle and cerebellum as a result of immersion in the common fixatives 10% phosphate-buffered formal saline, 70% ethanol and 3% glutaraldehyde, compared with I2KI staining solution at concentrations of 2, 6, 10 and 20%. Immersion in the I2KI solution resulted in dramatic changes of tissue volume, which were far larger than the shrinkage from formalin fixation alone. The degree of macroscopic change was most dependent upon the I2KI concentration, with severe shrinkage of 70% seen in solutions of 20% I2KI after 14 days' incubation. When using this technique care needs to be taken to use the lowest concentration that will give adequate contrast to minimise artefacts due to shrinkage.

The vestibulo-ocular reflex is the system of compensatory ocular movements in response to stimula... more The vestibulo-ocular reflex is the system of compensatory ocular movements in response to stimulation of the kinetic labyrinth seen in all vertebrates. It allows maintenance of a stable gaze even when the head is moving. Perhaps the simplest influence on the VOR is the spatial orientation of the planes of the semicircular canals relative to the extraocular muscles. It is hypothesized that the extraocular muscles are in parallel alignment with their corresponding semicircular canals in order to reduce the amount of neural processing needed and hence keep reflex times to a minimum. However, despite its obvious importance, little is known of this spatial arrangement. Moreover, nothing is known about any ontogenetic changes in the relative orientations of the extraocular muscles and semicircular canals. The morphologies of fetal and adult specimens of Homo sapiens were examined using magnetic resonance (MR) images. Three-dimensional co-ordinate data were taken from the images and used to calculate vector equations of the extraocular muscles and planes of best fit for the semicircular canals. The relative orientations of the muscles and canals were then calculated from the vectors and planes. It was shown that there are significant correlations between both the anterior and lateral semicircular canals and their corresponding extraocular muscles during ontogeny. In the case of the lateral canal with the medial rectus, the lateral canal with the lateral rectus, and the anterior canal with the inferior oblique, the trend is towards, though never reaching, alignment, whereas the anterior canal and the superior rectus muscle move out of alignment as age increases. Furthermore, it was noted that none of the six muscle-canal pairs is in perfect alignment, either during ontogeny or in adulthood. It was also shown that the three semicircular canals are not precisely orthogonal, but that the anterior and posterior canals form an angle of about 858, while the anterior and lateral canals diverge by 1008. Overall, it was shown that there is significant reorientation of the extraocular muscles and semicircular canals during ontogeny, but that, in most cases, there is little realignment beyond the fetal period. J. Morphol. 268:878-890, 2007Morphol. 268:878-890, . 2007 Wiley-Liss, Inc.