Ornithopods are an extinct group of dinosaurs that were particularly abundant and diverse in the Cretaceous of the Iberian Peninsula, and whose abundance in the Maestrazgo Basin has allowed numerous taxa to be identified over the last decade. Many of these fossil remains are still taxonomically indeterminate and require a more detailed study on both a macroscopic and microscopic scale. In this contribution, an osteohistological analysis is carried out on a partial skeleton-composed of five incomplete vertebrae, two dorsal ribs, an ischium, a fibula, and a tibia-found in the province of Aliaga (Teruel, NE Spain). We identified a progressive slowdown in tissue apposition and a variation in the type of growth marks generated in every bone, allowing a more precise identification of the ontogenetic stage of the specimen as a subadult individual. The skeletochronological correlation between the different elements also suggests that the specimen reached sexual maturity at around seven years of age and died between nine and twelve years of age. Likewise, the usefulness of the three-front model is proven for the first time in an ornithopod dinosaur, as a tool for analysing the histology expressed by the different bone elements of a single specimen and inferring their skeletochronological potential. Comparison with other ornithopod taxa reveals the great variability that each bone element shows depending on the taxon analysed, which prevents us from determining a single element suitable for studying the skeletochronology of any ornithopod taxon.
Changes in the microstructure of the aortic wall precede the progression of various aortic pathologies, including aneurysms and dissection. Current clinical decisions with regards to surgical planning and/or radiological intervention are guided by geometric features, such as aortic diameter, since clinical imaging lacks tissue microstructural information. The aim of this proof-of-concept work is to investigate a non-invasive imaging method, diffusion tensor imaging (DTI), in ex vivo aortic tissue to gain insights into the microstructure. This study examines healthy, aneurysm and a type B chronic dissection aortae, via DTI. DTI-derived metrics, such as the fractional anisotropy, mean diffusivity, helical angle and tractography, were examined in each morphology. The results from this work highlighted distinct differences in fractional anisotropy (healthy, 0.24 ± 0.008; aneurysmal, 0.19 ± 0.002; dissected, 0.13 ± 0.006) and a larger variation in the helical angle in the dissected aorta compared to healthy (39.28 ± 11.93° vs. 26.12 ± 4.60°, respectively). These differences were validated by histological characterisation. This study demonstrates the sensitivity of DTI to pathological changes in aortic tissue, highlighting the potential of this methodology to provide improved clinical insight.
Tendon injuries and disorders associated with mechanical tendon overuse are common musculoskeletal problems. Even though tendons play a central role in human movement, the intrinsic healing process of tendon is very slow. So far, it is known that tendon cell activity is supported by several interstitial cells within the tendon. However, the interplay between the tendon and the adjacent muscle for tendon regeneration and development processes has not been fully investigated. Here, we tested whether factors released from muscle derived myogenic cells (myoblasts) enhance tenogenic progressions of human tendon derived cells (tendon fibroblasts) using two-dimensional (2D) culture model and a three-dimensional (3D)-engineered tendon construct culture model, which mimics tendon regeneration and development. The conditioned media from myoblasts and unconditioned media as control were applied to tendon fibroblasts. In 2D, immunofluorescence analysis revealed increased collagen type I expressing area and increased migration potential when conditioned media from myoblasts were applied. In the 3D-engineered human tendon construct model, wet weight, diameter, and cross-sectional area of the tendon constructs were increased in response to the application of conditioned media from myoblasts, whereas the collagen density was lower and mechanical function was reduced both at the functional level (maximum stiffness) and the material level (maximum stress and modulus). These results indicate that myoblast-derived factors extend collagen expressing area and enhance migration of tendon fibroblasts, while factors involved in the robustness of extra-cellular matrix deposition of tissue-engineered tendon constructs are lacking. Our findings suggest that adjacent muscle affects the signaling interplay in tendons.
We have read with great interest the paper published by the Journal of Anatomy [244(5), 2024, 861-872] on Is human height based on a Lucas sequence relationship between the foot height, tibial length, femur length and upper body length? by Paley et al. The authors show that foot height, tibial length, femur length and upper body length follow a generalized Lucas sequence. Our letter demonstrates that their result is indeed stronger, as their data follow the original, homogeneous Lucas sequence.
The importance of interactions between neighbouring rapidly growing tissues of the head during development is recognised, yet this competition for space remains incompletely understood. The developing structures likely interact through a variety of mechanisms, including directly genetically programmed growth, and are mediated via physiological signalling that can be triggered by structural interactions. In this study, we aimed to investigate a different but related potential mechanism, that of simple mechanical plastic deformation of neighbouring structures of the head in response to soft tissue expansion during human postnatal ontogeny. We use computational modelling and normative real-world data to evaluate the potential for mechanical deformation to predict early postnatal cranial shape changes in humans. We test some aspects of the spatial packing hypothesis applied to the growing brain and masticatory muscles, and their effects on the cranium, with a particular focus on the basicranium and face. A simple finite element model of an early postnatal human cranium, brain and masticatory muscles was created from CT and MRI. Growth of the brain and muscles was simulated using a tissue expansion material. The effect of the expanding soft tissues on the cranium was assessed using geometric morphometrics, comparing the baseline model to simulation results, and also to normative cranial shape data collected from neonatal MRI (0-4 months of age). Findings revealed that cranial shape changes present in the normative sample were consistent with cranial base flexion and were largely allometric (size-linked). Simulation of brain expansion produced broadly similar shape changes of the basicranium with most growth occurring in the cranial vault, while masticatory muscle expansion produced smaller and more widespread changes throughout the cranium. When simulated together, expansion of the masticatory muscles exerted a constraining effect on the results of brain expansion. Our findings that the simple growth simulations were able to mimic biological growth suggest that the relationship between regions of the developing head may be partly structural within the first few months of postnatal ontogeny in humans.
The analysis of incremental marks in the enamel, dentine and cementum of extant and extinct species provides important information about the rate and pattern of tooth growth, which permits inferences about key life history traits. Traditionally, such research has mainly focused on primates, while other mammalian groups have remained relatively unexplored. In some cases, this has led to the misidentification of incremental markings and the miscalculation of dental growth parameters in non-primate taxa, which has highlighted the importance of obtaining more reliable comparative frameworks. Here, we partially fill this gap by providing a detailed analysis of the dental microstructure in the extant giraffe Giraffa camelopardalis. We specifically studied the histology of the different cusps (i.e. protoconid, metaconid, hypoconid, entoconid and hypoconulid) of two first lower molars and two third lower molars with different degree of wear to identify the different incremental markings and to calculate dental growth parameters such as daily secretion rate and enamel formation front angle for each cusp and tooth. Our results show that incremental markings in enamel were more apparent as compared to those in dentine and/or cementum and have permitted a deeper analysis of the former tissue. Enamel laminations, which had a daily periodicity, were the most common incremental lines in all teeth. Supradaily Retzius lines and subdaily cross-striations and laminations were also recognised in dental enamel, revealing multiple secretory pulses of the ameloblasts in the giraffe. Generally, values of enamel growth parameters (i.e. daily secretion rate and enamel formation front angle) obtained for the first lower molar were comparable to those reported for closely related taxa, while those calculated for the third lower molar present a higher degree of variation that may be linked to differences in general somatic rates of growth. Nevertheless, enamel growth parameters were highly variable within each tooth, suggesting caution when making general (palaeo)biological inferences from dental histology. The giraffe dentine and cementum also register incremental lines. In the dentine, most of these features were classified as daily von Ebner's lines and their counting and measurement revealed values of secretion rates that agree with those previously reported in other artiodactyls. The age calculated from the incremental lines in the dental cementum matches that deduced from dental wear, suggesting that the counting of yearly lines in this tissue is a reliable tool to estimate individual age in giraffids. This study further suggests ways to refine future analyses of dentine and cementum and sets the stage for dental palaeohistology of extinct giraffids and closely related ungulates for which life history information is still unknown.
The primary weight-bearing structure of the proximal femur, trabecular bone, has a complex three-dimensional architecture that was previously difficult to comprehensively display. This study examined the spatial architecture of trabecular struts in the coronal, sagittal, and horizontal sections of the proximal femur using 21 cases prepared with P45 sectional plasticization. The primary compressive strut (PCS) exhibited a "mushroom-like" shape with upper and lower parts. The lower part extended from the medial inferior cortical bone of the femoral neck to the central region of the femoral head, while the upper part radiated from the epiphyseal line to the subchondral cortical bone of the femoral head. The secondary compressive strut (SCS), originated below the distal end of the PCS, ran diagonally upward, and intersected with the secondary tensile strut (STS) within the greater trochanter. The primary tensile strut (PTS) comprised anterior (aPTS) and posterior (pPTS) components originating from the anterior- and posterior-superior cortical bone of the femoral neck. These converged, entered the femoral head, intersected with the PCS beneath the epiphyseal line, forming a dense trabecular center, and terminated at the subchondral cortical bone below the fovea of the femoral head. The secondary tensile strut (STS) originated from the cortical bone around the lower edge of the greater trochanter, converging upwards and medially to terminate at the superior cortical bone of the femoral neck. The trabecular system of the proximal femur consists of two subsystems: one between the femoral head and neck, and another between the femoral neck and shaft. The head-neck system comprises intersecting PCS, aPTS, and pPTS, facilitating stress transmission. The neck-shaft system features intersecting STS and SCS, enabling stress transmission between these regions. These independent systems are separated by Ward's triangle. The findings of this study offer anatomical guidance for the improvement of internal fixation methods, orthopedic implants, and the design of surgical robots.
Notosuchia were a successful lineage of Crocodyliformes that achieved a remarkable diversity during the Cretaceous of Gondwana, particularly in South America. Although paleohistology has expanded our knowledge of the paleobiology of notosuchians, several clades of this lineage remain poorly understood in this aspect. Here we help to address this gap by conducting the first histological analysis of appendicular bones of a peirosaurid. To increase our knowledge about growth dynamics and examine intraeskeletal and interspecific histological variation, we analyze the microstructure of a tibia, fibula, phalanx, fragment of ornamented element (possible osteoderm or skull bone) and a possible long bone of an individual assigned to Peirosauridae indet. (MAU-Pv-437). The peirosaurid studied here appears to have reached sexual but not somatic maturity and the minimum age inferred from appendicular bones results in a lower estimated than the age inferred from osteoderms in a previous study on the same individual. The cortical bone in MAU-Pv 437 is formed by vascularized parallel fibered bone/lamellar bone which indicates that this individual experienced a moderate growth rate. This indicates different growth dynamics from what has been observed for other notosuchians specimens, suggesting a lack of a uniform growth pattern for this clade.
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：