In vivo skin elastography with high-definition optical videos
biomechanical properties; Dermatology; Dermatology; mechanical properties; optical flow; skin elastography; strain image; suction cup; tissue; tissue abnormality; visualization
Background/aims Continuous measurements of biomechanical properties of skin provide potentially valuable information to dermatologists for both clinical diagnosis and quantitative assessment of therapy. This paper presents an experimental study on in vivo imaging of skin elastic properties using high-definition optical videos. The objective is to (i) investigate whether skin property abnormalities can be detected in the computed strain elastograms, (ii) quantify property abnormalities with a Relative Strain Index (RSI), so that an objective rating system can be established, (iii) determine whether certain skin diseases are more amenable to optical elastography and (iv) identify factors that may have an adverse impact on the quality of strain elastograms. Methods There are three steps in optical skin elastography: (i) skin deformations are recorded in a video sequence using a high-definition camcorder, (ii) a dense motion field between two adjacent video frames is obtained using a robust optical flow algorithm, with which a cumulative motion field between two frames of a larger interval is derived and (iii) a strain elastogram is computed by applying two weighted gradient filters to the cumulative motion data. Results Experiments were carried out using videos of 25 patients. In the three cases presented in this article (hypertrophic lichen planus, seborrheic keratosis and psoriasis vulgaris), abnormal tissues associated with the skin diseases were successfully identified in the elastograms. There exists a good correspondence between the shape of property abnormalities and the area of diseased skin. The computed RSI gives a quantitative measure of the magnitude of property abnormalities that is consistent with the skin stiffness observed on clinical examinations. Conclusions Optical elastography is a promising imaging modality that is capable of capturing disease-induced property changes. Its main advantage is that an elastogram presents a continuous description of the spatial variation of skin properties on the pixel level that would otherwise be impossible with other sensors. Its value will be further enhanced when used with a point-wise measuring device such as a cutometer that yields absolute elasticity values.
Zhang Y; Brodell R T; Mostow E N; Vinyard C J; Marie H
Skin Research and Technology
2009
2009-08
Journal Article
<a href="http://doi.org/10.1111/j.1600-0846.2009.00351.x" target="_blank" rel="noreferrer noopener">10.1111/j.1600-0846.2009.00351.x</a>
Food Mechanical Properties in Three Sympatric Species of Hapalemur in Ranomafana National Park, Madagascar
Anthropology; bamboo lemur; diet; evolution; Evolutionary Biology; fracture-toughness; genus cebus; hardness; macaca-fascicularis; mechanical properties; morphology; patterns; primates
We investigated mechanical dietary properties of sympatric bamboo lemurs, Hapalemur g. griseus, H. aureus, and H. (Prolemur) simus, in Ranomafana National Park, Madagascar. Each lemur species relies on bamboo, though previous behavioral observations found that they specialize on different parts of a common resource (Tan: Int J Primatol 20 [1999] 547-566; Tan: PhD dissertation [2000] State University of New York, Stony Brook). On the basis of these earlier behavioral ecology studies, we hypothesized that specialization on bamboo is related to differences in mechanical properties of specific parts. We quantified mechanical properties of individual plant parts from the diets of the bamboo lemur species using a portable tester. The diets of the Hapalemur spp. exhibited high levels of mechanical heterogeneity. The lemurs, however, could be segregated based on the most challenging (i.e., mechanically demanding) foods. Giant bamboo culm pith was the toughest and stiffest food eaten, and its sole lemur consumer, H. simus, had the most challenging diet. However, the mechanical dietary properties of H. simus and H. aureus overlapped considerably. In the cases where lemur species converged on the same bamboo part, the size of the part eaten increased with body size. Plant parts that were harvested orally but not necessarily masticated were the most demanding, indicating that food preparation may place significant loads on the masticatory apparatus. Finally, we describe how mechanical properties can influence feeding behavior. The elaborate procurement processes of H. simus feeding on culm pith and H. griseus and H. aureus feeding on young leaf bases are related to the toughnesses of protective coverings and the lemurs' exploitation of mechanical vulnerabilities in these plants. Am J Phys Anthropol 139:368-381, 2009. (C) 2008 Wiley-Liss, Inc.
Yamashita N; Vinyard C J; Tan C L
American Journal of Physical Anthropology
2009
2009-07
Journal Article
<a href="http://doi.org/10.1002/ajpa.20992" target="_blank" rel="noreferrer noopener">10.1002/ajpa.20992</a>
Mechanical properties of foods used in experimental studies of primate masticatory function
biomechanical analysis; elastic modulus; etectromyography; fracture-toughness; fracture-toughness; genus cebus; jaw; lateral pterygoid muscle; macaca-fascicularis; mandibular symphysis; masseter force; mechanical properties; movement; old-world monkeys; periodontal mechanoreceptive afferents; Zoology
In vivo studies, of jaw-muscle behavior have been integral factors in the development of our current understanding of the primate masticatory apparatus. However, even though it has been shown that food textures and mechanical properties influence jaw-muscle activity during mastication, very little effort has been made to quantify the relationship between the elicited masticatory responses of the subject and the mechanical proper-ties of the foods that are eaten. Recent work on human mastication highlights the importance of two mechanical properties-toughness and elastic modulus (i.e., stiffness)-for food breakdown during mastication. Here we provide data on the toughness and elastic modulus of the majority of foods used in experimental studies of the nonhuman primate masticatory apparatus. Food toughness ranges from approximately 56.97Jm(-2) (apple pulp) to 4355.45 Jm(-2) (prune pit). The elastic modulus of the experimental foods ranges from 0.07 MPa for gummy bears to 346 MPa for popcorn kernels. These data can help researchers studying primate mastication select among several potential foods with broadly similar mechanical properties. Moreover, they provide a framework for understanding how jaw-muscle activity varies with food mechanical properties in these studies.
Williams S H; Wright B W; Den Truong V; Daubert C R; Vinyard C J
American Journal of Primatology
2005
2005-11
Journal Article
<a href="http://doi.org/10.1002/ajp.20189" target="_blank" rel="noreferrer noopener">10.1002/ajp.20189</a>
Preference and consequences: A preliminary look at whether preference impacts oral processing in non-human primates
Anthropology; bitter taste; cebus-apella; chewing behavior; electromyography; Evolutionary Biology; fallback foods; Feeding; Food mechanical properties; Food preference; hardness; mastication; mechanical properties; model foods; muscle; patterns; texture
Non-human primates demonstrate food preferences much like humans. We have little insight, however, into how those preferences impact oral processing in primates. To begin describing this relationship, we conducted a preliminary analysis measuring food preference in two tufted capuchins (Cebus apella) and comparing ranked preference to physiological variables during chewing of these foods. Food preference was assessed for each monkey across 12 foods, including monkey biscuits and 11 foods consumed by humans (e.g., various fruits and nuts). Animals chose from randomized pairs of foods to generate a ranked scale across the 12 foods. Contemporaneous with preference testing, electromyographic (EMG) activity was measured for the jaw-closing muscles to assess oral physiology during chewing of these foods. As expected, these capuchins exhibited clear preferences among these 12 foods. Based on their preferences, we identified sets of preferred and non-preferred brittle (i.e., almond versus monkey chow) and ductile (i.e., dates and prunes versus apricots) foods for physiological comparisons that broadly control variation in food mechanical properties (FMPs). As expected, oral physiology varied with FMPs in each animal. Within brittle and ductile groupings, we observed several significant differences in chewing cycle length and relative muscle activation levels that are likely related to food preference. These differences tended to be complex and individual specific. The two capuchins chewed non-preferred apricots significantly faster than preferred dates and prunes. Effect sizes for preference were smaller than those for FMPs, supporting the previous focus on FMPs in primate dietary research. Although preliminary, these results suggest that food preference may influence oral physiology in non-human primates. The prospect that this relationship exists in monkeys raises the possibility that a link between food preference and oral processing in humans may be based on shared tendencies with non-human primates, such as aversion to bitter items or preference for sweet foods. (C) 2016 Elsevier Ltd. All rights reserved.
Vinyard C J; Thompson C L; Doherty A; Robl N
Journal of Human Evolution
2016
2016-09
Journal Article
<a href="http://doi.org/10.1016/j.jhevol.2016.07.001" target="_blank" rel="noreferrer noopener">10.1016/j.jhevol.2016.07.001</a>
The role of mineral in the storage of elastic energy in turkey tendons
age; Biochemistry & Molecular Biology; Chemistry; collagen; crosslinks; mechanical properties; Polymer Science; tissue
Mammals elastically store energy in leg and foot tendons during locomotion. In the turkey, much of the force generated by the gastrocnemius muscle is stored as elastic energy during tendon deformation and not within the muscle. During growth, avian tendons mineralize in the portions distal to the muscle and show increased tensile strength and modulus as a result. The purpose of this study was to evaluate the viscoelastic behavior of turkey tendons and self-assembled collagen fiber models to determine the molecular basis for tendon deformation. The stress-strain behavior of tendons and self-assembled collagen fibers was broken into elastic and viscous components. The elastic component was found to be to a first approximation independent of source of the collagen and to depend only on the extent of cross-linking. In the absence of cross-links the elastic component of the stress was found to be negligible for self-assembled type I collagen fibers. In the presence of cross-links the behavior approached that found for mineralized turkey tendons. The elastic constant for turkey tendon was shown to be between 5 and 7.75 GPa while it was about 6.43 Gpa for self-assembled collagen fibers aged for 6 months at 22 degreesC. The viscous component for mineralized turkey tendons was about the same as that of self-assembled collagen fibers aged for 6 months, a result suggesting that addition of mineral does not alter the viscous properties of tendon. It is concluded that elastic energy storage in tendons involves direct stretching of the collagen triple-helix, nonhelical ends, and cross-links between the molecules and is unaffected by mineralization. Furthermore, it is hypothesized that mineralization of turkey tendons is an efficient means of preserving elastic energy storage while providing for increased load-bearing ability required for locomotion of adult birds.
Silver F H; Christiansen D; Snowhill P B; Chen Y; Landis W J
Biomacromolecules
2000
2000
Journal Article
<a href="http://doi.org/10.1021/bm9900139" target="_blank" rel="noreferrer noopener">10.1021/bm9900139</a>
Mechanobiology of force transduction in dermal tissue
3-dimensional collagen lattices; age-related-changes; bullous pemphigoid antigen; collagen; Dermatology; epidermal growth-factor; extracellular-matrix; fibrils; gap junctions; guinea-pig skin; human-skin fibroblasts; increases inositol trisphosphate; integrins; mechanical properties; mechanochemical transduction; protein-kinase-c; secondary messengers; skin; smooth-muscle cells
Background/aims: The influence of mechanical forces on skin has been examined since 1861 when Langer first reported the existence of lines of tension in cadaver skin. Internal tension in the dermis is not only passively transferred to the epidermis but also gives rise to active cell-extracellular matrix and cell-cell mechanical interactions that may be an important part of the homeostatic processes that are involved in normal skin metabolism. The purpose of this review is to analyse how internal and external mechanical loads are applied at the macromolecular and cellular levels in the epidermis and dermis. Methods: A review of the literature suggests that internal and external forces applied to dermal cells appear to be involved in mechanochemical transduction processes involving both cell-cell and cell-extra-cellular matrix (ECM) interactions. Internal forces present in dermis are the result of passive tension that is incorporated into the collagen fiber network during development. Active tension generated by fibroblasts involves specific interactions between cell membrane integrins and macromolecules found in the ECM, especially collagen fibrils. Forces appear to be transduced at the cell-ECM interface via re-arrangement of cytoskeletal elements, activation of stretch-induced changes in ion channels, cell contraction at adherens junctions, activation of cell membrane-associated secondary messenger pathways and through growth factor-like activities that influence cellular proliferation and protein synthesis. Conclusions: Internal and external mechanical loading appears to affect skin biology through mechanochemical transduction processes. Further studies are needed to understand how mechanical forces, energy storage and conversion of mechanical energy into changes in chemical potential of small and large macromolecules may occur and influence the metabolism of dermal cells.
Silver F H; Siperko L M; Seehra G P
Skin Research and Technology
2003
2003-02
Journal Article
<a href="http://doi.org/10.1034/j.1600-0846.2003.00358.x" target="_blank" rel="noreferrer noopener">10.1034/j.1600-0846.2003.00358.x</a>
Trabecular Bone Structure in the Mandibular Condyles of Gouging and Nongouging Platyrrhine Primates
Anthropology; architecture; biomechanics; bone; callithrix-jacchus; callitrichids; cancellous; cortical bone; elastic principal directions; Evolutionary Biology; femoral-head; fossil record; iterative selection method; jaw functional morphology; marmosets; mechanical properties; tamarins; temporomandibular-joint
The relationship between mandibular form and biomechanical function is a topic of significant interest to morphologists and paleontologists alike. Several previous studies have examined the morphology of the mandible in gouging and nongouging primates as a means of understanding the anatomical correlates of this feeding behavior. The goal of the current study was to quantify the trabecular bone structure of the mandibular condyle of gouging and nongouging primates to assess the functional morphology of the jaw in these animals. High-resolution computed tomography scan data were collected from the mandibles of five adult common marmosets (Callithrix jacchus), saddle-back tamarins (Saguinus fuscicollis), and squirrel monkeys (Saimiri sciureus), respectively, and various three-dimensional morphometric parameters were measured from the condylar trabecular bone. No significant differences were found among the taxa for most trabecular bone structural features. Importantly, no mechanically significant parameters, such as bone volume fraction and degree of anisotropy, were found to vary significantly between gouging and nongouging primates. The lack of significant differences in mechanically relevant structural parameters among these three platyrrhine taxa may suggest that gouging as a habitual dietary behavior does not involve significantly higher loads on the mandibular condyle than other masticatory behaviors. Alternatively, the similarities in trabecular architecture across these three taxa may indicate that trabecular bone is relatively unimportant mechanically in the condyle of these primates and therefore is functionally uninformative. Am J Phys Anthropol 141:583-593, 2010. (C) 2009 Wiley-Liss, Inc.
Ryan T M; Colbert M; Ketcham R A; Vinyard C J
American Journal of Physical Anthropology
2010
2010-04
Journal Article
<a href="http://doi.org/10.1002/ajpa.21178" target="_blank" rel="noreferrer noopener">10.1002/ajpa.21178</a>