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295 results on '"Fagan, Michael J."'

63. Morphological evolution of the mammalian jaw adductor complex

Author

Lautenschlager, Stephan, Gill, Pamela, Luo, Zhe‐Xi, Fagan, Michael J., and Rayfield, Emily J.

Subjects
Mammals, Vertebrate palaeontology, digestive, oral, and skin physiology, Original Articles, musculoskeletal evolution, Biological Evolution, mammalian evolution, digital reconstruction, vertebrate palaeontology, stomatognathic diseases, Jaw, stomatognathic system, Mammalian evolution, Masticatory Muscles, Digital reconstruction, Musculoskeletal evolution, Animals, Original Article, Cynodontia, Mesozoic
Abstract

The evolution of the mammalian jaw during the transition from non‐mammalian synapsids to crown mammals is a key event in vertebrate history and characterised by the gradual reduction of its individual bones into a single element and the concomitant transformation of the jaw joint and its incorporation into the middle ear complex. This osteological transformation is accompanied by a rearrangement and modification of the jaw adductor musculature, which is thought to have allowed the evolution of a more‐efficient masticatory system in comparison to the plesiomorphic synapsid condition. While osteological characters relating to this transition are well documented in the fossil record, the exact arrangement and modifications of the individual adductor muscles during the cynodont–mammaliaform transition have been debated for nearly a century. We review the existing knowledge about the musculoskeletal evolution of the mammalian jaw adductor complex and evaluate previous hypotheses in the light of recently documented fossils that represent new specimens of existing species, which are of central importance to the mammalian origins debate. By employing computed tomography (CT) and digital reconstruction techniques to create three‐dimensional models of the jaw adductor musculature in a number of representative non‐mammalian cynodonts and mammaliaforms, we provide an updated perspective on mammalian jaw muscle evolution. As an emerging consensus, current evidence suggests that the mammal‐like division of the jaw adductor musculature (into deep and superficial components of the m. masseter, the m. temporalis and the m. pterygoideus) was completed in Eucynodontia. The arrangement of the jaw adductor musculature in a mammalian fashion, with the m. pterygoideus group inserting on the dentary was completed in basal Mammaliaformes as suggested by the muscle reconstruction of Morganucodon oehleri. Consequently, transformation of the jaw adductor musculature from the ancestral (‘reptilian’) to the mammalian condition must have preceded the emergence of Mammalia and the full formation of the mammalian jaw joint. This suggests that the modification of the jaw adductor system played a pivotal role in the functional morphology and biomechanical stability of the jaw joint.

Published
2016

69. Stress, strain, and elasticity

Author

Postema, Michiel, Fagan, Michael J., Department of Physics and Technology [Bergen] (UiB), University of Bergen (UiB), University of Hull [United Kingdom], and Michiel Postema

Subjects
[SPI.MECA]Engineering Sciences [physics]/Mechanics [physics.med-ph], [SPI.MECA.SOLID]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Mechanics of the solides [physics.class-ph]
Abstract

International audience; The mathematical formulation of wave propagation in solids involves the use of the concepts and principles of 3-dimensional stress and strain analysis. Hence, we start by outlining these principles.

Published
2011
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84. A virtual approach to evaluate therapies for management of multiple myeloma induced bone disease.

Author

Ji, Bing, Genever, Paul G., and Fagan, Michael J.

Subjects
MULTIPLE myeloma, B cell lymphoma, OSTEOBLASTS, BONE diseases, DIPHOSPHONATES
Abstract

Multiple myeloma bone disease is devastating for patients and a major cause of morbidity. The disease leads to bone destruction by inhibiting osteoblast activity while stimulating osteoclast activity. Recent advances in multiple myeloma research have improved our understanding of the pathogenesis of multiple myeloma-induced bone disease and suggest several potential therapeutic strategies. However, the effectiveness of some potential therapeutic strategies still requires further investigation and optimization. In this paper, a recently developed mathematical model is extended to mimic and then evaluate three therapies of the disease, namely: bisphosphonates, bortezomib and TGF-β inhibition. The model suggests that bisphosphonates and bortezomib treatments not only inhibit bone destruction, but also reduce the viability of myeloma cells. This contributes to the current debate as to whether bisphosphonate therapy has an anti-tumour effect. On the other hand, the analyses indicate that treatments designed to inhibit TGF-β do not reduce bone destruction, although it appears that they might reduce the viability of myeloma cells, which again contributes to the current controversy regarding the efficacy of TGF-β inhibition in multiple myeloma-induced bone disease. © 2015 The Authors. International Journal for Numerical Methods in Biomedical Engineering published by John Wiley & Sons Ltd. [ABSTRACT FROM AUTHOR]

Published
2016
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