Pushing the limit: masticatory stress and adaptive plasticity in mammalian craniomandibular joints
TL;DR: It is argued that a critical component of current and future research on adaptive plasticity in the skull, and especially cranial joints, should employ a multifaceted characterization of a functional system, one that incorporates data on myriad tissues so as to evaluate the role of altered load versus differential tissue response on the anatomical, cellular and molecular processes that contribute to the strength of such composite structures.
Abstract: Excessive, repetitive and altered loading have been implicated in the initiation of a series of soft- and hard-tissue responses or ;functional adaptations' of masticatory and locomotor elements. Such adaptive plasticity in tissue types appears designed to maintain a sufficient safety factor, and thus the integrity of given element or system, for a predominant loading environment(s). Employing a mammalian species for which considerable in vivo data on masticatory behaviors are available, genetically similar domestic white rabbits were raised on diets of different mechanical properties so as to develop an experimental model of joint function in a normal range of physiological loads. These integrative experiments are used to unravel the dynamic inter-relationships among mechanical loading, tissue adaptive plasticity, norms of reaction and performance in two cranial joint systems: the mandibular symphysis and temporomandibular joint (TMJ). Here, we argue that a critical component of current and future research on adaptive plasticity in the skull, and especially cranial joints, should employ a multifaceted characterization of a functional system, one that incorporates data on myriad tissues so as to evaluate the role of altered load versus differential tissue response on the anatomical, cellular and molecular processes that contribute to the strength of such composite structures. Our study also suggests that the short-term duration of earlier analyses of cranial joint tissues may offer a limited notion of the complex process of developmental plasticity, especially as it relates to the effects of long-term variation in mechanical loads, when a joint is increasingly characterized by adaptive and degradative changes in tissue structure and composition. Indeed, it is likely that a component of the adaptive increases in rabbit TMJ and symphyseal proportions and biomineralization represent a compensatory mechanism to cartilage degradation that serves to maintain the overall functional integrity of each joint system. Therefore, while variation in cranial joint anatomy and performance among sister taxa is, in part, an epiphenomenon of interspecific differences in diet-induced masticatory stresses characterizing the individual ontogenies of the members of a species, this behavioral signal may be increasingly mitigated in over-loaded and perhaps older organisms by the interplay between adaptive and degradative tissue responses.
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1,217 citations
TL;DR: In this article, the authors highlight recent advances in X-ray microcomputed tomography (microCT) as applied to materials, specifically advances made since the first materials microCT review appeared in Internati...
Abstract: This review highlights recent advances in X-ray microcomputed tomography (microCT) as applied to materials, specifically advances made since the first materials microCT review appeared in Internati...
470 citations
TL;DR: Novel findings in biomedicine and developments in imaging and computer technologies are beginning to provide a vision of future innovations in the diagnostics and therapeutics of TMJ disorders, and the identification and use of local or systemic biomarkers to diagnose disease or monitor improvements in therapy.
Abstract: Because their etiologies and pathogenesis are poorly understood, temporomandibular joint (TMJ) diseases are difficult to diagnose and manage. All current approaches to treatments of TMJ diseases are largely palliative. Definitive and rational diagnoses or treatments can only be achieved through a comprehensive understanding of the etiologies, predisposing factors, and pathogenesis of TMJ diseases. While much work remains to be done in this field, novel findings in biomedicine and developments in imaging and computer technologies are beginning to provide us with a vision of future innovations in the diagnostics and therapeutics of TMJ disorders. These advances include the identification and use of local or systemic biomarkers to diagnose disease or monitor improvements in therapy; the use of imaging technologies for earlier and more sensitive diagnostics; and the use of biomedicine, biomimetics, and imaging to design and manufacture bioengineered joints. Such advances are likely to help to customize and enhance the quality of care we provide to patients with TMJ disorders.
218 citations
Journal Article•
TL;DR: The data suggest that myostatin has direct effects on the proliferation and differentiation of osteoprogenitor cells, and that hisostatin antagonists and inhibitors are likely to enhance both muscle mass and bone strength.
Abstract: Myostatin (GDF-8) is a member of the transforming growth factor-beta (TGF-β) superfamily that is highly expressed in skeletal muscle, and myostatin loss-of-function leads to doubling of skeletal muscle mass. Myostatin-deficient mice have been used as a model for studying muscle-bone interactions, and here we review the skeletal phenotype associated with altered myostatin signaling. It is now known that myostatin is a key regulator of mesenchymal stem cell proliferation and differentiation, and mice lacking the myostatin gene show decreased body fat and a generalized increase in bone density and strength. The increase in bone density is observed in most anatomical regions, including the limbs, spine, and jaw, and myostatin inhibitors have been observed to significantly increase bone formation. Myostatin is also expressed in the early phases of fracture healing, and myostatin deficiency leads to increased fracture callus size and strength. Together, these data suggest that myostatin has direct effects on the proliferation and differentiation of osteoprogenitor cells, and that myostatin antagonists and inhibitors are likely to enhance both muscle mass and bone strength.
195 citations
TL;DR: The osteological correlates and inferred soft tissue anatomy of the jaw muscles and relevant neurovasculature in the temporal region of the dinosaur head are presented to provide the anatomical foundation necessary for future analyses of skull function and evolution in an important vertebrate clade.
Abstract: Jaw muscles are key components of the head and critical to testing hypotheses of soft-tissue homology, skull function, and evolution. Dinosaurs evolved an extraordinary diversity of cranial forms adapted to a variety of feeding behaviors. However, disparate evolutionary transformations in head shape and function among dinosaurs and their living relatives, birds and crocodylians, impair straightforward reconstructions of muscles, and other important cephalic soft tissues. This study presents the osteological correlates and inferred soft tissue anatomy of the jaw muscles and relevant neurovasculature in the temporal region of the dinosaur head. Hypotheses of jaw muscle homology were tested across a broad range archosaur and sauropsid taxa to more accurately infer muscle attachments in the adductor chambers of non-avian dinosaurs. Many dinosaurs likely possessed m. levator pterygoideus, a trait shared with lepidosaurs but not extant archosaurs. Several major clades of dinosaurs (e.g., Ornithopoda, Ceratopsidae, Sauropoda) eliminated the epipterygoid, thus impacting interpretations of m. pseudotemporalis profundus. M. pseudotemporalis superficialis most likely attached to the caudoventral surface of the laterosphenoid, a trait shared with extant archosaurs. Although mm. adductor mandibulae externus profundus and medialis likely attached to the caudal half of the dorsotemporal fossa and coronoid process, clear osteological correlates separating the individual bellies are rare. Most dinosaur clades possess osteological correlates indicative of a pterygoideus ventralis muscle that attaches to the lateral surface of the mandible, although the muscle may have extended as far as the jugal in some taxa (e.g., hadrosaurs, tyrannosaurs). The cranial and mandibular attachments of mm adductor mandibulae externus superficialis and adductor mandibulae posterior were consistent across all taxa studied. These new data greatly increase the interpretive resolution of head anatomy in dinosaurs and provide the anatomical foundation necessary for future analyses of skull function and evolution in an important vertebrate clade.
148 citations
Cites background from "Pushing the limit: masticatory stre..."
...Finally, feeding behavior and connective tissue adaptive plasticity are major factors involved in the structure and function of jaw muscles and the skull (Ravosa et al., 2007)....
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References
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TL;DR: Fibrocartilage is a dynamic tissue that disappears when the tendons are rerouted surgically and can be maintained in vitro when discs of tendon are compressed, but at some locations fibrocartilaginous is a sign of pathology.
Abstract: Where tendons and ligaments are subject to compression, they are frequently fibrocartilaginous. This occurs at 2 principal sites: where tendons (and sometimes ligaments) wrap around bony or fibrous pulleys, and in the region where they attach to bone, i.e. at their entheses. Wrap-around tendons are most characteristic of the limbs and are commonly wider at their point of bony contact so that the pressure is reduced. The most fibrocartilaginous tendons are heavily loaded and permanently bent around their pulleys. There is often pronounced interweaving of collagen fibres that prevents the tendons from splaying apart under compression. The fibrocartilage can be located within fascicles, or in endo- or epitenon (where it may protect blood vessels from compression or allow fascicles to slide). Fibrocartilage cells are commonly packed with intermediate filaments which could be involved in transducing mechanical load. The ECM often contains aggrecan which allows the tendon to imbibe water and withstand compression. Type II collagen may also be present, particularly in tendons that are heavily loaded. Fibrocartilage is a dynamic tissue that disappears when the tendons are rerouted surgically and can be maintained in vitro when discs of tendon are compressed. Finite element analyses provide a good correlation between its distribution and levels of compressive stress, but at some locations fibrocartilage is a sign of pathology. Enthesis fibrocartilage is most typical of tendons or ligaments that attach to the epiphyses of long bones where it may also be accompanied by sesamoid and periosteal fibrocartilages. It is characteristic of sites where the angle of attachment changes throughout the range of joint movement and it reduces wear and tear by dissipating stress concentration at the bony interface. There is a good correlation between the distribution of fibrocartilage within an enthesis and the levels of compressive stress. The complex interlocking between calcified fibrocartilage and bone contributes to the mechanical strength of the enthesis and cartilage-like molecules (e.g. aggrecan and type II collagen) in the ECM contribute to its ability to withstand compression. Pathological changes are common and are known as enthesopathies.
705 citations
"Pushing the limit: masticatory stre..." refers background in this paper
...…organization and associates strongly with water and proteoglycans, important for tissues subjected to compression, tension and shear, such as the symphyseal FC pad and TMJ articular cartilage (Mizoguchi et al., 1996; Pirttiniemi et al., 1996; Benjamin and Ralphs, 1998; Tanaka et al., 2000)....
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Book•
01 Jan 1989
TL;DR: Wozencraft et al. as discussed by the authors studied the behavioral development of terrestrial Carnivores, including the role of odour in the social lives of these animals, and compared the behavior of Hyenas and giant pandas in the Tangjiahe Reserve, China.
Abstract: An Introduction to the Carnivora.- I Behavior.- 1 Acoustic Communication by Fissiped Carnivores.- 2 The Role of Odor in the Social Lives of Carnivores.- 3 Behavioral Development of Terrestrial Carnivores.- 4 The Comparative Behavioral Ecology of Hyenas: The Importance of Diet and Food Dispersion.- 5 Intraspecific Variation in Canid Social Systems.- 6 The Mating Tactics and Spacing Patterns of Solitary Carnivores.- 7 Carnivore Group Living: Comparative Trends.- II Ecology.- 8 The Feeding Ecology of Giant Pandas and Asiatic Black Bears in the Tangjiahe Reserve, China.- 9 Adaptations for Aquatic Living by Carnivores.- 10 Ecological Constraints on Predation by Large Felids.- 11 The Advantages and Disadvantages of Small Size to Weasels, Mustela Species.- 12 Basal Rate of Metabolism, Body Size, and Food Habits in the Order Carnivora.- 13 Patterns of Energy Output during Reproduction in Carnivores.- III Evolution.- 14 Locomotor Adaptations by Carnivores.- 15 Carnivore Dental Adaptations and Diet: A Study of Trophic Diversity within Guilds.- 16 The Physiology and Evolution of Delayed Implantation in Carnivores.- 17 Molecular and Biochemical Evolution of the Carnivora.- 18 The Phylogeny of the Recent Carnivora.- 19 Fossil History of the Terrestrial Carnivora.- Appendix: Classification of the Recent Carnivora.- W. Chris Wozencraft.- Species and Subject Index.
679 citations
TL;DR: The current revival of morphology is heralded by a flourish of studies in functional anatomy with the general result being a renewed focus of interest in the problem of organic form.
Abstract: The current revival of morphology is heralded by a flourish of studies in functional anatomy with the general result being a renewed focus of interest in the problem of organic form. Recent morphological studies are characterized by considerations of the functional properties of structure and of the interrelationships between the structure and the environment of the organism although the traditional considerations of pure morphological description and of the phylogenetic change of morphological form are not ignored. These studies have established a broader base for morphological inquiry and have permitted a far better understanding, albeit largely theoretical, of all factors influencing the observable shape of morphological features. It may be possible, in the near future, to partition these factors and to determine the influence of function, of surrounding structures, of phylogeny, and so forth in the molding of anatomical features. The importance of functional anatomy in the recent upsurge of morphological studies is eclipsed by its basic contribution to a deeper appreciation of biological adapta-
642 citations
TL;DR: The effects of mechanical loading on cartilage and the resulting chondrocyte-mediated biosynthesis, remodeling, degradation, and repair of this tissue are focused on.
Abstract: Recent studies suggest that there are multiple regulatory pathways by which chondrocytes in articular cartilage sense and respond to mechanical stimuli, including upstream signaling pathways and mechanisms that may lead to direct changes at the level of transcription, translation, post-translational modifications, and cell-mediated extracellular assembly and degradation of the tissue matrix. This review focuses on the effects of mechanical loading on cartilage and the resulting chondrocyte-mediated biosynthesis, remodeling, degradation, and repair of this tissue. The effects of compression and tissue shear deformation are compared, and approaches to the study of mechanical regulation of gene expression are described. Of particular interest regarding dense connective tissues, recent experiments have shown that mechanotransduction is critically important in vivo in the cell-mediated feedback between physical stimuli, the molecular structure of newly synthesized matrix molecules, and the resulting macroscopic biomechanical properties of the tissue.
631 citations
"Pushing the limit: masticatory stre..." refers background in this paper
...…that alter tissue proliferation, composition and function as a response to induced degeneration of the cartilage matrix (Mizoguchi et al., 1996; Pirttiniemi et al., 1996; Grodzinsky et al., 2000; Honda et al., 2000; Lee et al., 2000; Huang et al., 2003; Kim et al., 2003; Wong and Carter, 2003)....
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...Lastly, changes in expression of type I and type II collagen vary in response to joint loads, further supporting the hypothesis that mechanotransduction signals changes in gene expression that alter tissue proliferation, composition and function as a response to induced degeneration of the cartilage matrix (Mizoguchi et al., 1996; Pirttiniemi et al., 1996; Grodzinsky et al., 2000; Honda et al., 2000; Lee et al., 2000; Huang et al., 2003; Kim et al., 2003; Wong and Carter, 2003)....
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TL;DR: The ecomorphological hypotheses that morphology, performance capability, ecology and behavior have evolved synchronously have been confirmed using the Anolis lizards of Jamaica and Puerto Rico.
Abstract: Studies of ecomorphology–the relationship among species between morphology and ecology–contain two implicit and rarely tested hypotheses: (1) that morphological differences among species result in differences in performance capability at ecologically relevant tasks, which, in turn, produce differences in behavior and ecology; and (2) that morphology, performance capability, ecology and behavior have evolved synchronously. I tested these hypotheses using the Anolis lizards of Jamaica and Puerto Rico. I measured morphological and performance variables on recently caught lizards. Movement, display rate and microhabitat measurements were made on lizards observed in the field. Body size explained most of the variation in morphology and performance ability, but was not correlated with the ecological or behavioral variables. When the effect of body size is removed from the morphological and performance variables, the ecomorphological hypotheses were confirmed. Species that were similar morphologically were also ...
614 citations
"Pushing the limit: masticatory stre..." refers background in this paper
...In doing so, such analyses of the biological role of a feature or system directly address one or more facets of the important inter-relationships among behavior, morphology, performance, fitness and evolution, information critical for understanding ontogenetic and interspecific variation in character-state transformations (Bock and von Walhert, 1965; Losos, 1990; Wainwright and Riley, 1994; Lauder, 1995)....
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...…of the important inter-relationships among behavior, morphology, performance, fitness and evolution, information critical for understanding ontogenetic and interspecific variation in character-state transformations (Bock and von Walhert, 1965; Losos, 1990; Wainwright and Riley, 1994; Lauder, 1995)....
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...…and other investigations is to analyze, under naturalistic conditions, the range of behaviors an organism employs with a given morphology as well as the role of adaptive plasticity in fine-tuning the fit between form and behavior during an organism’s lifespan (Grant and Grant, 1989; Losos, 1990)....
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...A common goal of these and other investigations is to analyze, under naturalistic conditions, the range of behaviors an organism employs with a given morphology as well as the role of adaptive plasticity in fine-tuning the fit between form and behavior during an organism’s lifespan (Grant and Grant, 1989; Losos, 1990)....
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