The Experts below are selected from a list of 4110 Experts worldwide ranked by ideXlab platform
Fred Spoor - One of the best experts on this subject based on the ideXlab platform.
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comparative anatomy of the middle ear Ossicles of extant hominids introducing a geometric morphometric protocol
Journal of Human Evolution, 2016Co-Authors: Alexander Stoessel, Philipp Gunz, Romain David, Fred SpoorAbstract:The presence of three interconnected auditory Ossicles in the middle ear is a defining characteristic of mammals, and aspects of ossicle morphology are related to hearing sensitivity. However, analysis and comparison of Ossicles are complicated by their minute size and complex three-dimensional shapes. Here we introduce a geometric morphometric measurement protocol for 3D shape analysis based on landmarks and semilandmarks obtained from μCT images and apply it to Ossicles of extant hominids (great apes and humans). We show that the protocol is reliable and reproducible over a range of voxel resolutions, and captures even subtle shape differences. Using this approach it is possible to distinguish the hominid taxa by mean shapes of their malleus and incus (p < 0.01). The stapes appears less diagnostic, although this may in part be related to the small sample size available. Using ancestral state estimation, we show that, within hominids, Homo sapiens is derived with respect to its malleus (short manubrium, long corpus, head anterior-posterior flattened, articular facet shape), incus (wide intercrural curvature, long incudal processes, articular facet shape) and stapes (high stapes with kidney-shaped footplate). H. sapiens also shows a number of plesiomorphic shape traits whereas Gorilla and Pan possess a number of autapomorphic characteristics. The Pongo Ossicles appear to be close to the plesiomorphic hominid condition. The malleus shows little difference in size among hominids, and allometry is thus of little importance. In contrast, the incus and stapes are more variable in size, and their shape is more strongly related to size differences. Although the form-function relationships in the middle ear are not fully understood, some aspects of ossicle morphology suggest that interspecific differences in hearing capacities are present among hominids. Finally, the results of this study provide a comparative framework for morphometric studies analyzing Ossicles of extinct hominids, with a bearing on taxonomy, phylogeny and auditory function.
Janhenning Dirks - One of the best experts on this subject based on the ideXlab platform.
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morphology shape variation and movement of skeletal elements in starfish asterias rubens
Journal of Anatomy, 2019Co-Authors: Lena Schwertmann, Oliver Focke, Janhenning DirksAbstract:Starfish (order: Asteroidea) possess a complex endoskeleton composed of thousands of calcareous Ossicles. These Ossicles are embedded in a body wall mostly consisting of a complex collagen fiber array. The combination of soft and hard tissue provides a challenge for detailed morphological and histological studies. As a consequence, very little is known about the general biomechanics of echinoderm endoskeletons and the possible role of ossicle shape in enabling or limiting skeletal movements. In this study, we used high-resolution X-ray microscopy to investigate individual ossicle shape in unprecedented detail. Our results show the variation of ossicle shape within Ossicles of marginal, reticular and carinal type. Based on these results we propose an additional classification to categorize Ossicles not only by shape but also by function into 'connecting' and 'node' Ossicles. We also used soft tissue staining with phosphotungstic acid successfully and were able to visualize the ossicle ultrastructure at 2-μm resolution. We also identified two new joint types in the aboral skeleton (groove-on-groove joint) and between adambulacral Ossicles (ball-and-socket joint). To demonstrate the possibilities of micro-computed tomographic methods in analyzing the biomechanics of echinoderm skeletons we exemplarily quantified changes in ossicle orientation for a bent ray for ambulacral Ossicles. This study provides a first step for future biomechanical studies focusing on the interaction of Ossicles and soft tissues during ray movements.
Kun Lv - One of the best experts on this subject based on the ideXlab platform.
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a novel auditory Ossicles membrane and the development of conductive hearing loss in dmp1 null mice
Bone, 2017Co-Authors: Kun Lv, Haiyang Huang, Xing Yi, Mark E Chertoff, Chaoyuan Li, Baozhi Yuan, Robert J Hinton, Jian Q FengAbstract:Abstract Genetic mouse models are widely used for understanding human diseases but we know much less about the anatomical structure of the auditory Ossicles in the mouse than we do about human Ossicles. Furthermore, current studies have mainly focused on disease conditions such as osteomalacia and rickets in patients with hypophosphatemia rickets, although the reason that these patients develop late-onset hearing loss is unknown. In this study, we first analyzed Dmp1 lac Z knock-in auditory Ossicles (in which the blue reporter is used to trace DMP1 expression in osteocytes) using X-gal staining and discovered a novel bony membrane surrounding the mouse malleus. This finding was further confirmed by 3-D micro-CT, X-ray, and alizarin red stained images. We speculate that this unique structure amplifies and facilitates sound wave transmissions in two ways: increasing the contact surface between the eardrum and malleus and accelerating the sound transmission due to its mineral content. Next, we documented a progressive deterioration in the Dmp1 -null auditory ossicle structures using multiple imaging techniques. The auditory brainstem response test demonstrated a conductive hearing loss in the adult Dmp1 -null mice. This finding may help to explain in part why patients with DMP1 mutations develop late-onset hearing loss, and supports the critical role of DMP1 in maintaining the integrity of the auditory Ossicles and its bony membrane.
Kelly E Oquin - One of the best experts on this subject based on the ideXlab platform.
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two three loci control scleral ossicle formation via epistasis in the cavefish astyanax mexicanus
PLOS ONE, 2017Co-Authors: Anastasia Lyon, Amanda K Powers, Joshua B Gross, Kelly E OquinAbstract:The sclera is the protective outer layer of the eye. In fishes, birds, and reptiles, the sclera may be reinforced with additional bony elements called scleral Ossicles. Teleost fish vary in the number and size of scleral Ossicles; however, the genetic mechanisms responsible for this variation remain poorly understood. In this study, we examine the inheritance of scleral Ossicles in the Mexican tetra, Astyanax mexicanus, which exhibits both a cave morph and a surface fish morph. As these morphs and their hybrids collectively exhibit zero, one, and two scleral Ossicles, they represent a microcosm of teleost scleral ossicle diversity. Our previous research in F2 hybrids of cavefish from Pachon cave and surface fish from Texas suggested that three genes likely influence the formation of scleral Ossicles in this group through an epistatic threshold model of inheritance, though our sample size was small. In this study, we expand our sample size using additional hybrids of Pachon cavefish and Mexican surface fish to (1) confirm the threshold model of inheritance, (2) refine the number of genes responsible for scleral ossicle formation, and (3) increase our power to detect quantitative trait loci (QTL) for this trait. To answer these three questions, we scored surface fish and cavefish F2 hybrids for the presence of zero, one, or two scleral Ossicles. We then analyzed their distribution among the F2 hybrids using a chi-square (χ2) test, and used a genetic linkage map of over 100 microsatellite markers to identify QTL responsible for scleral ossicle number. We found that inheritance of scleral Ossicles follows an epistatic threshold model of inheritance controlled by two genes, which contrasts the three-locus model estimated from our previous study. Finally, the combined analysis of hybrids from both crosses identified two strong QTL for scleral ossicle number on linkage groups 4.2 and 21, and a weaker QTL on linkage group 4.1. Scleral ossification remains a complex trait with limited knowledge of its genetic basis. This study provides new insight into the number and location of genes controlling the formation of scleral Ossicles in a teleost fish species.
Ivan Martin - One of the best experts on this subject based on the ideXlab platform.
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engineering of a functional bone organ through endochondral ossification
Proceedings of the National Academy of Sciences of the United States of America, 2013Co-Authors: Celeste Scotti, Adam Papadimitropoulos, Elia Piccinini, Atanas Todorov, Andrea Barbero, Hitoshi Takizawa, Paul Bourgine, Markus G Manz, Ivan MartinAbstract:Embryonic development, lengthening, and repair of most bones proceed by endochondral ossification, namely through formation of a cartilage intermediate. It was previously demonstrated that adult human bone marrow-derived mesenchymal stem/stromal cells (hMSCs) can execute an endochondral program and ectopically generate mature bone. Here we hypothesized that hMSCs pushed through endochondral ossification can engineer a scaled-up ossicle with features of a “bone organ,” including physiologically remodeled bone, mature vasculature, and a fully functional hematopoietic compartment. Engineered hypertrophic cartilage required IL-1β to be efficiently remodeled into bone and bone marrow upon subcutaneous implantation. This model allowed distinguishing, by analogy with bone development and repair, an outer, cortical-like perichondral bone, generated mainly by host cells and laid over a premineralized area, and an inner, trabecular-like, endochondral bone, generated mainly by the human cells and formed over the cartilaginous template. Hypertrophic cartilage remodeling was paralleled by ingrowth of blood vessels, displaying sinusoid-like structures and stabilized by pericytic cells. Marrow cavities of the Ossicles contained phenotypically defined hematopoietic stem cells and progenitor cells at similar frequencies as native bones, and marrow from Ossicles reconstituted multilineage long-term hematopoiesis in lethally irradiated mice. This study, by invoking a “developmental engineering” paradigm, reports the generation by appropriately instructed hMSC of an ectopic “bone organ” with a size, structure, and functionality comparable to native bones. The work thus provides a model useful for fundamental and translational studies of bone morphogenesis and regeneration, as well as for the controlled manipulation of hematopoietic stem cell niches in physiology and pathology.
