Showing papers in "Journal of Anatomy in 2019"

New insights into the development of the human cerebral cortex

Abstract: The cerebral cortex constitutes more than half the volume of the human brain and is presumed to be responsible for the neuronal computations underlying complex phenomena, such as perception, thought, language, attention, episodic memory and voluntary movement. Rodent models are extremely valuable for the investigation of brain development, but cannot provide insight into aspects that are unique or highly derived in humans. Many human psychiatric and neurological conditions have developmental origins but cannot be studied adequately in animal models. The human cerebral cortex has some unique genetic, molecular, cellular and anatomical features, which need to be further explored. The Anatomical Society devoted its summer meeting to the topic of Human Brain Development in June 2018 to tackle these important issues. The meeting was organized by Gavin Clowry (Newcastle University) and Zoltan Molnar (University of Oxford), and held at St John's College, Oxford. The participants provided a broad overview of the structure of the human brain in the context of scaling relationships across the brains of mammals, conserved principles and recent changes in the human lineage. Speakers considered how neuronal progenitors diversified in human to generate an increasing variety of cortical neurons. The formation of the earliest cortical circuits of the earliest generated neurons in the subplate was discussed together with their involvement in neurodevelopmental pathologies. Gene expression networks and susceptibility genes associated to neurodevelopmental diseases were discussed and compared with the networks that can be identified in organoids developed from induced pluripotent stem cells that recapitulate some aspects of in vivo development. New views were discussed on the specification of glutamatergic pyramidal and γ-aminobutyric acid (GABA)ergic interneurons. With the advancement of various in vivo imaging methods, the histopathological observations can be now linked to in vivo normal conditions and to various diseases. Our review gives a general evaluation of the exciting new developments in these areas. The human cortex has a much enlarged association cortex with greater interconnectivity of cortical areas with each other and with an expanded thalamus. The human cortex has relative enlargement of the upper layers, enhanced diversity and function of inhibitory interneurons and a highly expanded transient subplate layer during development. Here we highlight recent studies that address how these differences emerge during development focusing on diverse facets of our evolution.

Bioengineering the microanatomy of human skin.

Abstract: Recreating the structure of human tissues in the laboratory is valuable for fundamental research, testing interventions, and reducing the use of animals. Critical to the use of such technology is the ability to produce tissue models that accurately reproduce the microanatomy of the native tissue. Current artificial cell‐based skin systems lack thorough characterisation, are not representative of human skin, and can show variation. In this study, we have developed a novel full thickness model of human skin comprised of epidermal and dermal compartments. Using an inert porous scaffold, we created a dermal construct using human fibroblasts that secrete their own extracellular matrix proteins, which avoids the use of animal‐derived materials. The dermal construct acts as a foundation upon which epidermal keratinocytes were seeded and differentiated into a stratified keratinised epithelium. In‐depth morphological analyses of the model demonstrated very close similarities with native human skin. Extensive immunostaining and electron microscopy analysis revealed ultrastructural details such as keratohyalin granules and lamellar bodies within the stratum granulosum, specialised junctional complexes, and the presence of a basal lamina. These features reflect the functional characteristics and barrier properties of the skin equivalent. Robustness and reproducibility of in vitro models are important attributes in experimental practice, and we demonstrate the consistency of the skin construct between different users. In summary, a new model of full thickness human skin has been developed that possesses microanatomical features reminiscent of native tissue. This skin model platform will be of significant interest to scientists researching the structure and function of human skin.

Intermediate progenitors and Tbr2 in cortical development

Abstract: In developing cerebral cortex, intermediate progenitors (IPs) are transit amplifying cells that specifically express Tbr2 (gene: Eomes), a T-box transcription factor. IPs are derived from radial glia (RG) progenitors, the neural stem cells of developing cortex. In turn, IPs generate glutamatergic projection neurons (PNs) exclusively. IPs are found in ventricular and subventricular zones, where they differentiate as distinct ventricular IP (vIP) and outer IP (oIP) subtypes. Morphologically, IPs have short processes, resembling filopodia or neurites, that transiently contact other cells, most importantly dividing RG cells to mediate Delta-Notch signaling. Also, IPs secrete a chemokine, Cxcl12, which guides interneuron and microglia migrations and promotes thalamocortical axon growth. In mice, IPs produce clones of 1-12 PNs, sometimes spanning multiple layers. After mitosis, IP daughter cells undergo asymmetric cell death in the majority of instances. In mice, Tbr2 is necessary for PN differentiation and subtype specification, and to repress IP-genic transcription factors. Tbr2 directly represses Insm1, an IP-genic transcription factor gene, as well as Pax6, a key activator of Tbr2 transcription. Without Tbr2, abnormal IPs transiently accumulate in elevated numbers. More broadly, Tbr2 regulates the transcriptome by activating or repressing hundreds of direct target genes. Notably, Tbr2 'unlocks' and activates PN-specific genes, such as Tbr1, by recruiting Jmjd3, a histone H3K27me3 demethylase that removes repressive epigenetic marks placed by polycomb repressive complex 2. IPs have played an important role in the evolution and gyrification of mammalian cerebral cortex, and TBR2 is essential for human brain development.

Ageing of the somatosensory system at the periphery: age-related changes in cutaneous mechanoreceptors

Abstract: Decline of tactile sensation associated with ageing depends on modifications in skin and both central and peripheral nervous systems. At present, age-related changes in the periphery of the somatosensory system, particularly concerning the effects on mechanoreceptors, remain unknown. Here we used immunohistochemistry to analyse the age-dependent changes in Meissner's and Pacinian corpuscles as well as in Merkel cell-neurite complexes. Moreover, variations in the neurotrophic TrkB-BDNF system and the mechanoprotein Piezo2 (involved in maintenance of cutaneous mechanoreceptors and light touch, respectively) were evaluated. The number of Meissner's corpuscles and Merkel cells decreased progressively with ageing. Meissner's corpuscles were smaller, rounded in morphology and located deeper in the dermis, and signs of corpuscular denervation were found in the oldest subjects. Pacinian corpuscles generally showed no relevant age-related alterations. Reduced expression of Piezo2 in the axon of Meissner's corpuscles and in Merkel cells was observed in old subjects, as well was a decline in the BDNF-TrkB neurotrophic system. This study demonstrates that cutaneous Meissner's corpuscles and Merkel cell-neurite complexes (and less evidently Pacinian corpuscles) undergo morphological and size changes during the ageing process, as well as a reduction in terms of density. Furthermore, the mechanoprotein Piezo2 and the neurotrophic TrkB-BDNF system are reduced in aged corpuscles. Taken together, these alterations might explain part of the impairment of the somatosensory system associated with ageing.

Are endocasts good proxies for brain size and shape in archosaurs throughout ontogeny

Abstract: Cranial endocasts, or the internal molds of the braincase, are a crucial correlate for investigating the neuroanatomy of extinct vertebrates and tracking brain evolution through deep time. Nevertheless, the validity of such studies pivots on the reliability of endocasts as a proxy for brain morphology. Here, we employ micro‐computed tomography imaging, including diffusible iodine‐based contrast‐enhanced CT, and a three‐dimensional geometric morphometric framework to examine both size and shape differences between brains and endocasts of two exemplar archosaur taxa – the American alligator (Alligator mississippiensis) and the domestic chicken (Gallus gallus). With ontogenetic sampling, we quantitatively evaluate how endocasts differ from brains and whether this deviation changes during development. We find strong size and shape correlations between brains and endocasts, divergent ontogenetic trends in the brain‐to‐endocast correspondence between alligators and chickens, and a comparable magnitude between brain–endocast shape differences and intraspecific neuroanatomical variation. The results have important implications for paleoneurological studies in archosaurs. Notably, we demonstrate that the pattern of endocranial shape variation closely reflects brain shape variation. Therefore, analyses of endocranial morphology are unlikely to generate spurious conclusions about large‐scale trends in brain size and shape. To mitigate any artifacts, however, paleoneurological studies should consider the lower brain–endocast correspondence in the hindbrain relative to the forebrain; higher size and shape correspondences in chickens than alligators throughout postnatal ontogeny; artificially ‘pedomorphic’ shape of endocasts relative to their corresponding brains; and potential biases in both size and shape data due to the lack of control for ontogenetic stages in endocranial sampling.

Fascia thickness, aging and flexibility: is there an association?

Abstract: The morphology of the connective tissue may play an important role in locomotor mechanics. Recent research has revealed an association between increased fascia thickness and reduced joint flexibility in patients with chronic pain. The present study aimed to examine the relationship of both factors in healthy individuals, additionally testing the hypothesis that older subjects display a higher fascia thickness. Young (n = 18, 22 ± 1 years) and old (n = 17, 69 ± 4 years) healthy females were recruited for a quasi-experimental, cross-sectional trial. All participants underwent standardized ultrasound-based thickness measurements of the deep fasciae of the trunk and lower limb. Flexibility was assessed using sit and reach testing (hamstring extensibility) and the Schober test (lumbar flexion and extension). Systematic between-group differences of fascia thickness and variable associations (i.e. fascia thickness and flexibility) were detected using non-parametric data analyses. Young adults exhibited higher fascia thickness of the anterior and posterior lower leg, anterior thigh and abdominal wall (+12.3-25.8%, P < 0.05). Conversely, older participants showed higher thickness in the lumbar spine (+40.0-76.7%, P < 0.05). Correlations of both body mass and fascia thickness (τ = 0.45-0.75, P < 0.05), as well as flexibility and fascia thickness (τ = 0.38-0.42, P < 0.05) were found. Age-related changes in fascia thickness may be a contributing factor of restrictions in joint range of motion. Further study delineating the cause-effect triangle of body mass index, flexibility and fascia thickness is necessary.

New insights into a spectrum of developmental malformations related to mTOR dysregulations: challenges and perspectives

Abstract: In recent years the role of the mammalian target of rapamycin (mTOR) pathway has emerged as crucial for normal cortical development. Therefore, it is not surprising that aberrant activation of mTOR is associated with developmental malformations and epileptogenesis. A broad spectrum of malformations of cortical development, such as focal cortical dysplasia (FCD) and tuberous sclerosis complex (TSC), have been linked to either germline or somatic mutations in mTOR pathway-related genes, commonly summarised under the umbrella term ‘mTORopathies’. However, there are still a number of unanswered questions regarding the involvement of mTOR in the pathophysiology of these abnormalities. Therefore, a monogenetic disease, such as TSC, can be more easily applied as a model to study the mechanisms of epileptogenesis and identify potential new targets of therapy. Developmental neuropathology and genetics demonstrate that FCD IIb and hemimegalencephaly are the same diseases. Constitutive activation of mTOR signalling represents a shared pathogenic mechanism in a group of developmental malformations that have histopathological and clinical features in common, such as epilepsy, autism and other comorbidities. We seek to understand the effect of mTOR dysregulation in a developing cortex with the propensity to generate seizures as well as the aftermath of the surrounding environment, including the white matter.

The medial pulvinar: function, origin and association with neurodevelopmental disorders.

Abstract: The pulvinar is primarily referred to for its role in visual processing. However, the 'visual pulvinar' only encompasses the inferior and lateral regions of this complex thalamic nucleus. The remaining medial portion (medial pulvinar, PM) establishes distinct cortical connectivity and has been associated with directed attention, executive functions and working memory. These functions are particularly impaired in neurodevelopmental disorders, including schizophrenia and attention deficit and hyperactivity disorder (ADHD), both of which have been associated with abnormal PM architecture and connectivity. With these disorders becoming more prevalent in modern societies, we review the literature to better understand how the PM can participate in the pathophysiology of cognitive disorders and how a better understanding of the development and function of this thalamic nucleus, which is most likely exclusive to the primate brain, can advance clinical research and treatments.

Three-dimensional analysis of shape variations and symmetry of the fibula, tibia, calcaneus and talus.

Abstract: The bones forming the talocrural joint (TCJ) and subtalar joint (STJ) are often assumed to be bilaterally symmetric. Therefore, the contralateral limb (i.e. the fibula, tibia, calcaneus and talus) is used as a template or an intra-subject control in clinical and research practice. However, the validity of the symmetry assumption is controversial, because insufficient information is available on the shape variations and bilateral (a)symmetry of the fibula, tibia, calcaneus and talus. Using three-dimensional spatially dense sampled representations of bone shapes extracted from bilateral computed tomography scans of 66 individuals (55 male, mean age: 61 ± 10 years; 11 female, mean age: 53 ± 15 years), we analyzed whether: (i) similar shape patterns exist in the left and right bones of the same type; (ii) gender has an effect on bone shape variations; (iii) intra-subject shape variation is smaller than that of inter-subject for a given shape variance direction. For the first set of analyses, all left and right instances of the same type of bone were considered as two separate groups, and statistically compared with each other on multiple aspects including group location (central tendency), variance-covariance scale (dispersion) and orientation (covariance structure) using distance-based permutational tests. For the second and third sets of analyses, all left and right bones of the same type were pooled into one group, and shape variations in the TCJ and STJ bones were extracted using principal component analysis. The effects of gender on age-adjusted bone shape differences were assessed using an analysis of covariance. Moreover, intra-class correlation was employed to evaluate intra- and inter-subject bone shape variations. For each bone type, both sides had similar shape patterns (Ppermutational -values > 0.05). After Bonferroni adjustment, gender led to shape differences, which were mainly in the lateral and medial condyles of the tibia (P = 0.003), the length and height of the calcaneus (P < 0.001), the posterior and anterior talar articular surfaces of the calcaneus (P = 0.001), and in the posterior aspect of the talus (P = 0.001). Intra-subject shape variations in the tibial tuberosity together with the diameter of the tibia, and the curvature of the fibula shaft and the diameter of the fibula were as high as those of inter-subject. This result suggests that the shape symmetry assumption could be violated for some specific shape variations in the fibula and tibia.

Challenges in creating dissectible anatomical 3D prints for surgical teaching.

Abstract: Three-dimensional (3D) printing, or additive manufacturing, is now a widely used tool in pre-operative planning, surgical teaching and simulator training. However, 3D printing technology that produces models with accurate haptic feedback, biomechanics and visuals for the training surgeon is not currently available. Challenges and opportunities in creating such surgical models will be discussed in this review paper. Surgery requires proper tissue handling as well as knowledge of relevant anatomy. To prepare doctors properly, training models need to take into account the biomechanical properties of the anatomical structures that will be manipulated in any given operation. This review summarises and evaluates the current biomechanical literature as it relates to human tissues and correlates the impact of this knowledge on developing high fidelity 3D printed surgical training models. We conclude that, currently, a printer technology has not yet been developed which can replicate many of the critical qualities of human tissue. Advances in 3D printing technology will be required to allow the printing of multi-material products to achieve the mechanical properties required.

Extraordinary grip strength and specialized myology in the hyper-derived hand of Perodicticus potto?

Abstract: Previous behavioral reports of the African lorisid, Perodicticus potto, have speculated that these animals have an extraordinary grip strength. This ability is hypothesized to be facilitated by a range of anatomical features within the forelimb, ranging from the presence of a retia mirabilia in its wrist to the hyper-abduction of its pollex. Despite numerous behavioral reports, however, this claim of extraordinary grip strength has not been empirically substantiated. This study quantifies the physiological cross-sectional area of the digital flexor muscles within P. potto. These data are compared with a broad primate sample, including several similarly sized strepsirrhines. Contrary to expectation, we found that P. potto actually has relatively below-average digital flexor PCSA. However, we identified other myological characteristics in the upper limb of P. potto that were unexpected, including the largest brachioradialis muscle (an elbow flexor) among our primate sample, and - despite P. potto having only a vestigial second digit - an independent digital extensor indicis that is absent in almost a quarter of our primate sample.

Sublaminar organization of the human subplate: developmental changes in the distribution of neurons, glia, growing axons and extracellular matrix.

Abstract: The objective of this paper was to collect normative data essential for analyzing the subplate (SP) role in pathogenesis of developmental disorders, characterized by abnormal circuitry, such as hypoxic-ischemic lesions, autism and schizophrenia. The main cytological features of the SP, such as low cell density, early differentiation of neurons and glia, plexiform arrangement of axons and dendrites, presence of synapses and a large amount of extracellular matrix (ECM) distinguish this compartment from the cell-dense cortical plate (CP; towards pia) and large fiber bundles of external axonal strata of fetal white matter (towards ventricle). For SP delineation from these adjacent layers based on combined cytological criteria, we analyzed the sublaminar distribution of different microstructural elements and the associated maturational gradients throughout development, using immunocytochemical and histological techniques on postmortem brain material (Zagreb Neuroembryological Collection). The analysis revealed that the SP compartment of the lateral neocortex shows changes in laminar organization throughout fetal development: the monolayer in the early fetal period (presubplate) undergoes dramatic bilaminar transformation between 13 and 15 postconceptional weeks (PCW), followed by subtle sublamination in three 'floors' (deep, intermediate, superficial) of midgestation (15-21 PCW). During the stationary phase (22-28 PCW), SP persists as a trilaminar compartment, gradually losing its sublaminar organization towards the end of gestation and remains as a single layer of SP remnant in the newborn brain. Based on these sublaminar transformations, we have documented developmental changes in the distribution, maturational gradients and expression of molecular markers in SP synapses, transitional forms of astroglia, neurons and ECM, which occur concomitantly with the ingrowth of thalamo-cortical, basal forebrain and cortico-cortical axons in a deep to superficial fashion. The deep SP is the zone of ingrowing axons - 'entrance (ingrowth) zone'. The process of axonal ingrowth begins with thalamo-cortical fibers and basal forebrain afferents, indicating an oblique geometry. During the later fetal period, deep SP receives long cortico-cortical axons exhibiting a tangential geometry. Intermediate SP ('proper') is the navigation and 'nexus' sublamina consisting of a plexiform arrangement of cellular elements providing guidance and substrate for axonal growth, and also containing transient connectivity of dendrites and axons in a tangential plane without radial boundaries immersed in an ECM-rich continuum. Superficial SP is the axonal accumulation ('waiting compartment') and target selection zone, indicating a dense distribution of synaptic markers, accumulation of thalamo-cortical axons (around 20 PCW), overlapping with dendrites from layer VI neurons. In the late preterm brain period, superficial SP contains a chondroitin sulfate non-immunoreactive band. The developmental dynamics for the distribution of neuronal, glial and ECM markers comply with sequential ingrowth of afferents in three levels of SP: ECM and synaptic markers shift from deep to superficial SP, with transient forms of glia following this arrangement, and calretinin neurons are concentrated in the SP during the formation phase. These results indicate developmental and morphogenetic roles in the SP cellular (transient glia, neurons and synapses) and ECM framework, enabling the spatial accommodation, navigation and establishment of numerous connections of cortical pathways in the expanded human brain. The original findings of early developmental dynamics of transitional subtypes of astroglia, calretinin neurons, ECM and synaptic markers presented in the SP are interesting in the light of recent concepts concerning its functional and morphogenetic role and an increasing interest in SP as a prospective substrate of abnormalities in cortical circuitry, leading to a cognitive deficit in different neurodevelopmental disorders.

Myoarchitectural disarray of hypertrophic cardiomyopathy begins pre-birth.

Abstract: Myoarchitectural disarray – the multiscalar disorganisation of myocytes, is a recognised histopathological hallmark of adult human hypertrophic cardiomyopathy (HCM). It occurs before the establishment of left ventricular hypertrophy (LVH) but its early origins and evolution around the time of birth are unknown. Our aim is to investigate whether myoarchitectural abnormalities in HCM are present in the fetal heart. We used wild‐type, heterozygous and homozygous hearts (n = 56) from a Mybpc3‐targeted knock‐out HCM mouse model and imaged the 3D micro‐structure by high‐resolution episcopic microscopy. We developed a novel structure tensor approach to extract, display and quantify myocyte orientation and its local angular uniformity by helical angle, angle of intrusion and myoarchitectural disarray index, respectively, immediately before and after birth. In wild‐type, we demonstrate uniformity of orientation of cardiomyocytes with smooth transitions of helical angle transmurally both before and after birth but with traces of disarray at the septal insertion points of the right ventricle. In comparison, heterozygous mice free of LVH, and homozygous mice showed not only loss of the normal linear helical angulation transmural profiles observed in wild‐type but also fewer circumferentially arranged myocytes at birth. Heterozygous and homozygous showed more disarray with a wider distribution than in wild‐type before birth. In heterozygous mice, disarray was seen in the anterior, septal and inferior walls irrespective of stage, whereas in homozygous mice it extended to the whole LV circumference including the lateral wall. In conclusion, myoarchitectural disarray is detectable in the fetal heart of an HCM mouse model before the development of LVH.

Astrogliogenesis in human fetal brain: complex spatiotemporal immunoreactivity patterns of GFAP, S100, AQP4 and YKL-40.

Abstract: The astroglial lineage consists of heterogeneous cells instrumental for normal brain development, function and repair. Unfortunately, this heterogeneity complicates research in the field, which suffers from lack of truly specific and sensitive astroglial markers. Nevertheless, single astroglial markers are often used to describe astrocytes in different settings. We therefore investigated and compared spatiotemporal patterns of immunoreactivity in developing human brain from 12 to 21 weeks post conception and publicly available RNA expression data for four established and potential astroglial markers - GFAP, S100, AQP4 and YKL-40. In the hippocampal region, we also screened for C3, a complement component highly expressed in A1-reactive astrocytes. We found diverging partly overlapping patterns of the established astroglial markers GFAP, S100 and AQP4, confirming that none of these markers can fully describe and discriminate different developmental forms and subpopulations of astrocytes in human developing brain, although AQP4 seems to be the most sensitive and specific marker for the astroglial lineage at midgestation. AQP4 characterizes a brain-wide water transport system in cerebral cortex with regional differences in immunoreactivity at midgestation. AQP4 distinguishes a vast proportion of astrocytes and subpopulations of radial glial cells destined for the astroglial lineage, including astrocytes determined for the future glia limitans and apical truncated radial glial cells in ganglionic eminences, devoid of GFAP and S100. YKL-40 and C3d, previously found in reactive astrocytes, stain different subpopulations of astrocytes/astroglial progenitors in developing hippocampus at midgestation and may characterize specific subpopulations of 'developmental astrocytes'. Our results clearly reflect that lack of pan-astrocytic markers necessitates the consideration of time, region, context and aim when choosing appropriate astroglial markers.

Comparative multi-scale hierarchical structure of the tail, plantaris, and Achilles tendons in the rat.

Abstract: Rodent tendons are widely used to study human pathologies such as tendinopathy and repair, and to address fundamental physiological questions about development, growth, and remodeling. However, how the gross morphology and multi-scale hierarchical structure of rat tendons, such as the tail, plantaris, and Achilles tendons, compare with that of human tendons are unknown. In addition, there remains disagreement about terminology and definitions. Specifically, the definitions of fascicle and fiber are often dependent on diameter sizes, not their characteristic features, and these definitions impair the ability to compare hierarchical structure across species, where the sizes of the fiber and fascicle may change with animal size and tendon function. Thus, the objective of the study was to select a single species that is commonly used for tendon research (rat) and tendons with varying mechanical functions (tail, plantaris, Achilles) to evaluate the hierarchical structure at multiple length scales using histology, SEM, and confocal imaging. With the exception of the specialized rat tail tendon, we confirmed that in rat tendons there are no fascicles and the fiber is the largest subunit. In addition, we provided a structurally based definition of a fiber as a bundle of collagen fibrils that is surrounded by elongated cells, and this definition was supported by both histologically processed and unprocessed samples. In all rat tendons studied, the fiber diameters were consistently between 10 and 50 μm, and this diameter range appears to be conserved across larger species. Specific recommendations were made highlighting the strengths and limitations of each rat tendon as a research model. Understanding the hierarchical structure of tendon can advance the design and interpretation of experiments and development of tissue-engineered constructs.

Fabella prevalence rate increases over 150 years, and rates of other sesamoid bones remain constant: a systematic review

Abstract: The fabella is a sesamoid bone located behind the lateral femoral condyle. It is common in non‐human mammals, but the prevalence rates in humans vary from 3 to 87%. Here, we calculate the prevalence of the fabella in a Korean population and investigate possible temporal shifts in prevalence rate. A total of 52.83% of our individuals and 44.34% of our knees had fabellae detectable by computed tomography scanning. Men and women were equally likely to have a fabella, and bilateral cases (67.86%) were more common than unilateral ones (32.14%). Fabella presence was not correlated with height or age, although our sample did not include skeletally immature individuals. Our systematic review yielded 58 studies on fabella prevalence rate from 1875–2018 which met our inclusion criteria, one of which was an outlier. Intriguingly, a Bayesian mixed effects generalized linear model revealed a temporal shift in prevalence rates, with the median prevalence rate in 2000 (31.00%) being ~ 3.5 times higher than that in 1900 (7.64%). In all four countries with studies before and after 1960, higher rates were always found after 1960. Using data from two other systematic reviews, we found no increase in prevalence rates of 10 other sesamoid bones in the human body, indicating that the increase in fabella prevalence rate is unique. Fabella presence/absence is due to a combination of genetic and environmental factors: as the prevalence rates of other sesamoid bones have not changed in the last 100 years, we postulate the increase in fabella prevalence rate is due to an environmental factor. Namely, the global increase in human height and weight (due to improved nutrition) may have increased human tibial length and muscle mass. Increases in tibial length could lead to a larger moment arm acting on the knee and on the tendons crossing it. Coupled with the increased force from a larger gastrocnemius, this could produce the mechanical stimuli necessary to initiate fabella formation and/or ossification.

Glia to neuron ratio in the posterior aspect of the human spinal cord at thoracic segments relevant to spinal cord stimulation.

Abstract: Spinal cord stimulation (SCS) applied between T8 and T11 segments has been shown to be effective for the treatment of chronic pain of the lower back and limbs. However, the mechanism of the analgesic effect at these medullary levels remains unclear. Numerous studies relate glial cells with development and maintenance of chronic neuropathic pain. Glial cells are electrically excitable, which makes them a potential therapeutic target using SCS. The aim of this study is to report glia to neuron ratio in thoracic segments relevant to SCS, as well as to characterize the glia cell population at these levels. Dissections from gray and white matter of posterior spinal cord segments (T8, T9, intersection T9/T10, T10 and T11) were obtained from 11 human cadavers for histological analyses. Neuronal bodies and glial cells (microglia, astrocytes and oligodendrocytes) were immunostained, microphotographed and counted using image analysis software. Statistical analyses were carried out to establish significant differences of neuronal and glial populations among the selected segments, between the glial cells in a segment, and glial cells in white and gray matter. Results show that glia to neuron ratio in the posterior gray matter of the human spinal cord within the T8-T11 vertebral region is in the range 11 : 1 to 13 : 1, although not significantly different among vertebral segments. Glia cells are more abundant in gray matter than in white matter, whereas astrocytes and oligodendrocytes are more abundant than microglia (40 : 40 : 20). Interestingly, the population of oligodendrocytes in the T9/T10 intersection is significantly larger than in any other segment. In conclusion, glial cells are the predominant bodies in the posterior gray and white matter of the T8-T11 segments of the human spinal cord. Given the crucial role of glial cells in the development and maintenance of neuropathic pain, and their electrophysiological characteristics, anatomical determination of the ratio of different cell populations in spinal segments commonly exposed to SCS is fundamental to understand fully the biological effects observed with this therapy.

Cranial anatomy of the early cynodont Galesaurus planiceps and the origin of mammalian endocranial characters

Abstract: The cranial anatomy of the early non-mammalian cynodont Galesaurus planiceps from the South African Karoo Basin is redescribed on the basis of a computed tomographic reconstruction of the skull. Previously, little was known about internal skull morphology and the nervous and sensory system of this taxon. The endocranial anatomy of various cynodonts has been intensively studied in recent years to understand the origin of mammalian characters in the nasal capsule, brain and ear. However, these studies have focused on only a few taxa, the earliest of which is another Early Triassic cynodont, Thrinaxodon liorhinus. Galesaurus is phylogenetically stemward of Thrinaxodon and thus provides a useful test of whether the mammal-like features observed in Thrinaxodon were present even more basally in cynodont evolution. The cranial anatomy of G. planiceps is characterized by an intriguing mosaic of primitive and derived features within cynodonts. In contrast to the very similar internal nasal and braincase morphology of Galesaurus and Thrinaxodon, parts of the skull that seem to be fairly conservative in non-prozostrodont cynodonts, the morphology of the maxillary canal differs markedly between these taxa. Unusually, the maxillary canal of Galesaurus has relatively few ramifications, more similar to those of probainognathian cynodonts than that of Thrinaxodon. However, its caudal section is very short, a primitive feature shared with gorgonopsians and therocephalians. The otic labyrinth of Galesaurus is generally similar to that of Thrinaxodon, but differs in some notable features (e.g. proportional size of the anterior semicircular canal). An extremely large, protruding paraflocculus of the brain and a distinct medioventrally located notch on the anterior surface of the tabular, which forms the dorsal border of the large parafloccular lobe, are unique to Galesaurus among therapsids with reconstructed endocasts. These features may represent autapomorphies of Galesaurus, but additional sampling is needed at the base of Cynodontia to test this.

A reappraisal and revision of the numbering of the pharyngeal arches

Abstract: The pharyngeal arches are a prominent and significant feature of vertebrate embryos. These are visible as a series of bulges on the lateral surface of the embryonic head. In humans, and other amniotes, there are five pharyngeal arches numbered 1, 2, 3, 4 and 6; note the missing '5'. This is the standard scheme for the numbering of these structures, and it is a feature of modern anatomy textbooks. In this article, we discuss the rationale behind this odd numbering, and consider its origins. One reason given is that there is a transient 5th arch that is never fully realized, while another is that this numbering reflects considerations from comparative anatomy. We show here, however, that neither of these reasons has substance. There is no evidence from embryology for a '5th' arch, and the comparative argument does not hold as it does not apply across the vertebrates. We conclude that there is no justification for this strange numbering. We suggest that the pharyngeal arches should simply be numbered 1, 2, 3, 4 and 5 as this would be in keeping with the embryology and with the general numbering of the pharyngeal arches across the vertebrates.

Evaluating osteological ageing from digital data

Abstract: Age at death estimation of human skeletal remains is one of the key issues in constructing a biological profile both in forensic and archaeological contexts. The traditional adult osteological methods evaluate macroscopically the morphological changes that occur with increasing age of specific skeletal indicators, such as the cranial sutures, the pubic bone, the auricular surface of the ilium and the sternal end of the ribs. Technologies such as computed tomography and laser scanning are becoming more widely used in anthropology, and several new methods have been developed. This review focuses on how the osteological age-related changes have been evaluated in digital data. First, the 3D virtual copies of the bones have been used to mimic the appearance of the dry bones and the application of the traditional methods. Secondly, the information directly extrapolated from CT scans has been used to assess qualitatively or quantitatively the changes of the trabecular bones, the thickness of the cortical bones, and to perform morphometric analyses. Lastly, the most innovative approach has been the mathematical quantification of the changes of the pelvic joints, calculating the complexity of the surface. The importance of new updated reference datasets, created thanks to the use of CT scanning in forensic settings, is also discussed.

Physiological in vitro sacroiliac joint motion: a study on three-dimensional posterior pelvic ring kinematics.

Abstract: The sacroiliac joint (SIJ) is a well-known source of low back and pelvic pain, of increasing interest for both conservative and surgical treatment. Alterations in the kinematics of the pelvis have been hypothesized as a major cause of SIJ-related pain. However, definitions of both the range and the extent of physiological movement are controversial, and there are no clear baseline data for pathological alterations. The present study combined a novel biomechanical setup allowing for physiological motion of the lumbosacral transition and pelvis without restricting the SIJ movement in vitro, combined with optical image correlation. Six fresh human pelvises (81 ± 10 years, three females, three males) were tested, with bodyweight-adapted loading applied to the fifth lumbar vertebra and both acetabula. Deformation at the lumbopelvises was determined computationally from three-dimensional image correlation data. Sacroiliac joint motion under the loading of 100% bodyweight primarily consisted of a z-axis rotation (0.16°) and an inferior translation of the sacrum relative to the ilium (0.32 mm). Sacroiliac joint flexion-extension rotations were minute (< 0.02°). Corresponding movements of the SIJ were found at the lumbosacral transition, with an anterior translation of L5 relative to the sacrum of -0.97 mm and an inferior translation of 0.11 mm, respectively. Moreover, a flexion of 1.82° was observed at the lumbosacral transition. Within the innominate bone and at the pubic symphysis, small complementary rotations were seen around a vertical axis, accounting for -0.10° and 0.11°, respectively. Other motions were minute and accompanied by large interindividual variation. The present study provides evidence of different SIJ motions than reported previously when exerted by physiological loading. Sacroiliac joint kinematics were in the sub-degree and sub-millimeter range, in line with previous in vivo and in vitro findings, largely limited to the sagittal rotation and an inferior translation of the sacrum relative to the ilium. This given physiological loading scenario underlines the relevance of the lumbosacral transition when considering the overall motion of the lumbopelvis, and how relatively little the other segments contribute to overall motion.

The moment arms of the muscles spanning the glenohumeral joint: a systematic review

Abstract: The moment arm of a muscle represents its leverage or torque-producing capacity, and is indicative of the role of the muscle in joint actuation. The objective of this study was to undertake a systematic review of the moment arms of the major muscles spanning the glenohumeral joint during abduction, flexion and axial rotation. Moment arm data for the deltoid, pectoralis major, latissimus dorsi, teres major, supraspinatus, infraspinatus, subscapularis and teres minor were reported when measured using the geometric and tendon excursion methods. The anterior and middle sub-regions of the deltoid had the largest humeral elevator moment arm values of all muscles during coronal- and scapular-plane abduction, as well as during flexion. The pectoralis major, latissimus dorsi and teres major had the largest depressor moment arms, with each of these muscles exhibiting prominent leverage in shoulder adduction, and the latissimus dorsi and teres major also in extension. The rotator cuff muscles had the largest axial rotation moment arms regardless of the axial position of the humerus. The supraspinatus had the most prominent elevator moment arms during early abduction in both the coronal and scapular planes as well as in flexion. This systematic review shows that the rotator cuff muscles function as humeral rotators and weak humeral depressors or elevators, while the three sub-regions of the deltoid behave as substantial humeral elevators throughout the range of humeral motion. The pectoralis major, latissimus dorsi and teres major are significant shoulder depressors, particularly during abduction. This study provides muscle moment arm data on functionally relevant shoulder movements that are involved in tasks of daily living, including lifting and pushing. The results may be useful in quantifying shoulder muscle function during specific planes of movement, in designing and validating computational models of the shoulder, and in planning surgical procedures such as tendon transfer surgery.

Calibration of life history traits with epiphyseal closure, dental eruption and bone histology in captive and wild red deer.

Abstract: The study of skeletochronology and bone tissue as a record of information on ontogenetic stages and events is widely used for improving the knowledge about life histories (LHs) of extinct and extant vertebrates. Compared with dinosaurs and extant reptiles, mammalian bone histology has received little attention. Here, we calibrate for the first time bone and dental age with histological bone characteristics and LH stages in ontogenetic series of red deer. We rely on known LHs of different aged individuals of captive Cervus elaphus hippelaphus from Austria to correlate epiphyseal closure, dental eruption pattern, bone growth marks and bone tissue patterns in femora and tibiae, and of wild Cervus elaphus hispanicus from Spain. Our data show that females (of both subspecies) attain skeletal maturity earlier than males. At this moment, epiphyseal closure (in femora and tibiae) and dental eruption are complete and long bones start to deposit an external fundamental system. The results also show that the attainment of reproductive maturity in red deer occurs slightly before skeletal maturity.

Variation in the spatial distribution of erector spinae activity during a lumbar endurance task in people with low back pain.

Abstract: © 2019 Anatomical Society This study aimed to investigate the spatial distribution and redistribution of lumbar erector spinae (ES) activity during a lumbar extension endurance task in pain-free participants and how this is modified in people with low back pain (LBP). High density surface electromyography (HDEMG) was recorded using 13 × 5 electrode grids placed over the lumbar ES in 13 LBP and 13 control participants while completing an Ito test to task failure. The root mean square of the HDEMG signals was computed, a topographical map of the EMG amplitude generated and the centre of the activity (centroid) determined throughout the task. The centroid of the EMG amplitude map was systematically more cranial (F = 6.09, P = 0.022) for the LBP participants compared with the control subjects. Regression analysis showed that the extent of redistribution of ES activity was associated with longer endurance. These results show that LBP participants utilised a different motor strategy to perform the endurance task, characterised by greater activation of more cranial regions of the ES and less redistribution of ES activity throughout the task. This study provides new insight into the functional activation of the lumbar ES and how it is modified when people have pain.

Potential biomarkers of the mature intervertebral disc identified at the single cell level.

Abstract: Intervertebral disc (IVD) degeneration and trauma is a major socio-economic burden and the focus of cell-based regenerative medicine approaches. Despite numerous ongoing clinical trials attempting to replace ailing IVD cells with mesenchymal stem cells, a solid understanding of the identity and nature of cells in a healthy mature IVD is still in need of refinement. Although anatomically simple, the IVD is comprised of heterogeneous cell populations. Therefore, methods involving cell pooling for RNA profiling could be misleading. Here, by using RNA in situ hybridization and z proportion test, we have identified potential novel biomarkers through single cell assessment. We quantified the proportion of RNA transcribing cells for 50 genetic loci in the outer annulus fibrosus (AF) and nucleus pulposus (NP) in coccygeal bovine discs isolated from tails of four skeletally mature animals. Our data reconfirm existing data and suggest 10 novel markers such as Lam1 and Thy1 in the outer AF and Gli1, Gli3, Noto, Scx, Ptprc, Sox2, Zscan10 and LOC101904175 in the NP, including pluripotency markers, that indicate stemness potential of IVD cells. These markers could be added to existing biomarker panels for cell type characterization. Furthermore, our data once more demonstrate heterogeneity in cells of the AF and NP, indicating the need for single cell assessment by methods such as RNA in situ hybridization. Our work refines the molecular identity of outer AF and NP cells, which can benefit future regenerative medicine and tissue engineering strategies in humans.

The effect of automated landmark identification on morphometric analyses.

Abstract: Morphometric analysis of anatomical landmarks allows researchers to identify specific morphological differences between natural populations or experimental groups, but manually identifying landmarks is time-consuming. We compare manually and automatically generated adult mouse skull landmarks and subsequent morphometric analyses to elucidate how switching from manual to automated landmarking will impact morphometric analysis results for large mouse (Mus musculus) samples (n = 1205) that represent a wide range of 'normal' phenotypic variation (62 genotypes). Other studies have suggested that the use of automated landmarking methods is feasible, but this study is the first to compare the utility of current automated approaches to manual landmarking for a large dataset that allows the quantification of intra- and inter-strain variation. With this unique sample, we investigated how switching to a non-linear image registration-based automated landmarking method impacts estimated differences in genotype mean shape and shape variance-covariance structure. In addition, we tested whether an initial registration of specimen images to genotype-specific averages improves automatic landmark identification accuracy. Our results indicated that automated landmark placement was significantly different than manual landmark placement but that estimated skull shape covariation was correlated across methods. The addition of a preliminary genotype-specific registration step as part of a two-level procedure did not substantially improve on the accuracy of one-level automatic landmark placement. The landmarks with the lowest automatic landmark accuracy are found in locations with poor image registration alignment. The most serious outliers within morphometric analysis of automated landmarks displayed instances of stochastic image registration error that are likely representative of errors common when applying image registration methods to micro-computed tomography datasets that were initially collected with manual landmarking in mind. Additional efforts during specimen preparation and image acquisition can help reduce the number of registration errors and improve registration results. A reduction in skull shape variance estimates were noted for automated landmarking methods compared with manual landmarking. This partially reflects an underestimation of more extreme genotype shapes and loss of biological signal, but largely represents the fact that automated methods do not suffer from intra-observer landmarking error. For appropriate samples and research questions, our image registration-based automated landmarking method can eliminate the time required for manual landmarking and have a similar power to identify shape differences between inbred mouse genotypes.

Metacarpal trabecular bone varies with distinct hand-positions used in hominid locomotion.

Abstract: Trabecular bone remodels during life in response to loading and thus should, at least in part, reflect potential variation in the magnitude, frequency and direction of joint loading across different hominid species. Here we analyse the trabecular structure across all non-pollical metacarpal distal heads (Mc2-5) in extant great apes, expanding on previous volume of interest and whole-epiphysis analyses that have largely focused on only the first or third metacarpal. Specifically, we employ both a univariate statistical mapping and a multivariate approach to test for both inter-ray and interspecific differences in relative trabecular bone volume fraction (RBV/TV) and degree of anisotropy (DA) in Mc2-5 subchondral trabecular bone. Results demonstrate that whereas DA values only separate Pongo from African apes (Pan troglodytes, Pan paniscus, Gorilla gorilla), RBV/TV distribution varies with the predicted loading of the metacarpophalangeal (McP) joints during locomotor behaviours in each species. Gorilla exhibits a relatively dorsal distribution of RBV/TV consistent with habitual hyper-extension of the McP joints during knuckle-walking, whereas Pongo has a palmar distribution consistent with flexed McP joints used to grasp arboreal substrates. Both Pan species possess a disto-dorsal distribution of RBV/TV, compatible with multiple hand postures associated with a more varied locomotor regime. Further inter-ray comparisons reveal RBV/TV patterns consistent with varied knuckle-walking postures in Pan species in contrast to higher RBV/TV values toward the midline of the hand in Mc2 and Mc5 of Gorilla, consistent with habitual palm-back knuckle-walking. These patterns of trabecular bone distribution and structure reflect different behavioural signals that could be useful for determining the behaviours of fossil hominins.

Validity and reliability of a freehand 3D ultrasound system for the determination of triceps surae muscle volume in children with cerebral palsy.

Abstract: This study assessed the validity, intra-rater and inter-rater reliability of segmentation of in vivo medial gastrocnemius (MG), lateral gastrocnemius (LG) and soleus (SOL) muscle volume measurement using a single sweep freehand 3D ultrasound (3DUS) in children with cerebral palsy (CP). The MG, LG and SOL of both limbs of 18 children with CP (age 8 years 4 months ± 1 year 10 months, 11 males, unilateral CP = 9, bilateral CP = 9, Gross Motor Functional Classification System I = 11, II = 7) were scanned using freehand 3DUS and magnetic resonance imaging (MRI). All freehand 3DUS and MRI images were segmented and volumes rendered by two raters. Validity was assessed using limits of agreement method. Intra-rater and inter-rater reliability was assessed using intra-class correlation (ICC), coefficient of variance (CV) and minimal detectable change (MDC). Freehand 3DUS overestimated muscle volume of the MG and LG by 0.98 and 0.99, respectively, for all muscles. ICCs for inter-rater reliability of the segmentation process for freehand 3DUS and MRI volumes were > 0.96 and 0.98, respectively, for all muscles. MDCs for single rater freehand 3DUS and MRI were < 4.0 mL (14%) and 3.2 mL (11%), respectively, in all muscles. Freehand 3DUS is a valid and reliable method for the measurement of lower leg muscle volume that can be measured with a single sweep in children with CP in vivo. It can be used as an alternative to MRI for the detection of clinically relevant changes in calf muscle volume as the result of growth and interventions.

Three-dimensional structure of efferent and epididymal ducts in mice.

Abstract: The aim of the present study was to clarify the detailed morphology of efferent and epididymal ducts in adult mice using three-dimensional (3D) analysis. We reconstructed efferent and epididymal ducts in three adult mice using serial paraffin sections and high-performance 3D reconstruction software to draw the core lines of all ducts. By comparing the 3D core lines with the histological features in serial sections, we obtained detailed information on the gross characteristics of the ducts and identified the duct divisions accurately. The intra-testicular rete testis penetrated the tunica albuginea at one place and turned into the extra-testicular rete testis, which branched once or twice to give rise to four efferent ducts within 0.5 mm from the tunica albuginea. As these ducts approached the epididymis, they converged into one again and changed abruptly into the initial segment (IS) of the epididymis. The average length from the tunica albuginea to the IS was 19.7 ± 3.1 mm. In one mouse, we found four additional efferent ducts diverging from the common region with blind ends. The epididymal duct was a single highly convoluted duct with no branch and an average length of 767 ± 26 mm. By dividing the epididymal duct into five regions based on its cytological features and periodic acid-Schiff stainability, we calculated the length and diameter of individual regions accurately. Furthermore, we clearly showed locations of the connective tissue septa that divide the head epididymis into several segments. The epididymal duct followed a complicated, winding path within each segment while drawing a large spiral overall along the circumference of the epididymis. Sometimes the direction of this spiral reversed between adjacent segments. The present study revealed the detailed 3D structures of efferent and epididymal ducts in adult mice.

Upper molar morphology, homologies and evolutionary patterns of chinchilloid rodents (Mammalia, Caviomorpha).

Abstract: Chinchilloidea are a clade of caviomorph rodents that includes seven living species, the Dinomyidae Dinomys branickii, the Chinchillidae Lagostomus maximus, two species of Chinchilla and three species of Lagidium. In addition, two extinct families are traditionally considered chinchilloids - Neoepiblemidae and Cephalomyidae. The phylogeny of the Chinchilloidea has so far not been well established and is based on partial analyses. Studying the anatomy and ontogeny of extinct and extant taxa, we propose homologies for the upper molars of Chinchilloidea for which these homologies have not been previously proposed: that is the Chinchillidae Prolagostomus, Lagostomus, Lagidium and Chinchilla, and the Neoepiblemidae Neoepiblema and Phoberomys. We identify patterns of occlusal simplification within Chinchilloidea and evaluate its importance in an evolutionary context. A phylogenetic analysis recovered Dinomyidae, Chinchillidae and Neoepiblemidae as clades. 'Cephalomyidae' have not been not recovered as a monophyletic group and 'cephalomyids' are closely related to Neoepiblemidae. Branisamys is not included within the Dinomyidae and appears to be a basal chinchilloid.