HYPORENINEMIC HYPOALDOSTERONISM COMPLICATING PRIMARY AUTONOMIC INSUFFICIENCY
aldosterone; angiotensin; biosynthesis; failure; functional-significance; General & Internal Medicine; idiopathic orthostatic hypotension; pathogenesis; prostacyclin; prostaglandin system; renin
Polsky F I; Roque D; Hill P E
Western Journal of Medicine
1993
1993-08
Journal Article
n/a
Mandibular corpus bone strain in goats and alpacas: Implications for understanding the biomechanics of mandibular form in selenodont artiodactyls
adductor muscle force; Anatomy & Morphology; bone strain; functional-significance; jaw; macaca-fascicularis; mandibles; mandibular corpus; mastication; masticatory biomechanics; morphology; movements; stress; symphyseal fusion
The goal of this study is to clarify the functional and biomechanical relationship between jaw morphology and in vivo masticatory loading in selenodont artiodactyls. We compare in vivo strains from the mandibular corpus of goats and alpacas to predicted strain patterns derived from biomechanical models for mandibular corpus loading during mastication. Peak shear strains in both species average 600-700 mu epsilon on the working side and approximately 450 mu epsilon on the balancing side. Maximum principal tension in goats and alpacas is directed at approximately 30 degrees dorsocaudally relative to the long axis of the corpus on the working side and approximately perpendicular to the long axis on the balancing side. Strain patterns in both species indicate primarily torsion of the working-side corpus about the long axis and parasagittal bending and/or lateral transverse bending of the balancing-side corpus. Interpretation of the strain patterns is consistent with comparative biomechanical analyses of jaw morphology suggesting that in goats, the balancing-side mandibular corpus is parasagittally bent whereas in alpacas it experiences lateral transverse bending. However, in light of higher working-side corpus strains, biomechanical explanations of mandibular form also need to consider that torsion influences relative corpus size and shape. Furthermore, the complex combination of loads that occur along the selenodont artiodactyl mandibular corpus during the power stroke has two implications. First, added clarification of these loading patterns requires in vivo approaches for elucidating biomechanical links between mandibular corpus morphology and masticatory loading. Second, morphometric approaches may be limited in their ability to accurately infer masticatory loading regimes of selenodont artiodactyl jaws.
Williams S H; Vinyard C J; Wall C E; Hylander W L
Journal of Anatomy
2009
2009-01
Journal Article
<a href="http://doi.org/10.1111/j.1469-7580.2008.01008.x" target="_blank" rel="noreferrer noopener">10.1111/j.1469-7580.2008.01008.x</a>
Cross-sectional bone distribution in the mandibles of gouging and non-gouging platyrrhini
bone biomechanics; callithrix-jacchus; cross-sectional geometry; form; functional-significance; iterative selection method; jaw functional morphology; load resistance; macaca-fascicularis; mandibular corpus; morphology; new-world monkeys; primates; stress; tree gouging; Zoology
Recent morphometric analyses have led to dissimilar conclusions about whether the jaws of tree-gouging primates are designed to resist the purportedly large forces generated during this biting behavior. We further address this question by comparing the cross-sectional geometry of the mandibular corpus and symphysis in tree-gouging common marmosets (Callithrix jacchus) to nongouging saddleback tamarins (Saguinus fuscicollis) and squirrel monkeys (Saimiri sciureus). As might be expected, based on size, squirrel monkeys tend to have absolutely larger cross-sectional areas at each tooth location sampled, while saddleback tamarins are intermediate, followed by the smaller common marmosets. Similarly, the amount and distribution of cortical bone in squirrel monkey jaws provides them with increased ability to resist sagittal bending (I (xx) ) and torsion (K) in the corpus as well as coronal bending (I (xx) ) and shearing in the symphysis. However, when the biomechanical parameters are scaled to respective load arm estimates, there are few significant differences in relative resistance abilities among the 3 species. A power analysis indicates that we cannot statistically rule out subtle changes in marmoset jaw form linked to resisting loads during gouging. Nevertheless, our results correspond to studies in vivo of jaw loading, field data, and other comparative analyses suggesting that common marmosets do not generate relatively large bite forces during tree gouging. The 3 species are like most other anthropoids in having thinner bone on the lingual than on the buccal side of the mandibular corpus at M-1. The similarity in corporal shape across anthropoids supports a hypothesized stereotypical pattern of jaw loading during chewing and may indicate a conserved pattern of mandibular growth for the suborder. Despite the overall similarity, platyrrhines may differ slightly from catarrhines in the details of their cortical bone distribution.
Vinyard C J; Ryan T M
International Journal of Primatology
2006
2006-10
Journal Article
<a href="http://doi.org/10.1007/s10764-006-9083-7" target="_blank" rel="noreferrer noopener">10.1007/s10764-006-9083-7</a>
Comparative analysis of masseter fiber architecture in tree-gouging (Callithrix jacchus) and nongouging (Saguinus oedipus) callitrichids
Anatomy & Morphology; arboreal guenons; bite force; cross-sectional area; dental; elastic energy-storage; functional-significance; internal architecture; masticatory apparatus; microwear; occlusal force; rhesus-monkeys
Common marmosets (Callithrix jacchus) and cotton-top tamarins (Saguinus oedipus) (Callitrichidae, Primates) share a broadly similar diet of fruits, insects, and tree exudates. Common marmosets, however, differ from tamarins by actively gouging trees with their anterior teeth to elicit tree exudate flow. During tree gouging, marmosets produce relatively large jaw gapes, but do not necessarily produce relatively large bite forces at the anterior teeth. We compared the fiber architecture of the masseter muscle in tree-gouging Callithrix jacchus (n = 10) to riongouging Saguinus oedipus (n = 8) to determine whether the marmoset masseter facilitates producing these large gapes during tree gouging. We predict that the marmoset masseter has relatively longer fibers and, hence, greater potential muscle excursion (i.e., a greater range of motion through increased muscle stretch). Conversely, because of the expected trade-off between excursion and force production in muscle architecture, we predict that the cotton-top tamarin masseter has more pinnate fibers and increased physiological cross-sectional area (PCSA) as compared to common marmosets. Likewise, the S. oedipus masseter is predicted to have a greater proportion of tendon relative to muscle fiber as compared to the common marmoset masseter. Common marmosets have absolutely and relatively longer masseter fibers than cotton-top tamarins. Given that fiber length is directly proportional to muscle excursion and by extension contraction velocity, this result suggests that marmosets have masseters designed for relatively greater stretching and, hence, larger gapes. Conversely, the cotton-top tamarin masseter has a greater angle of pinnation (but not significantly so), larger PCSA, and higher proportion of tendon. The significantly larger PCSA in the tamarin masseter suggests that their masseter has relatively greater force production capabilities as compared to marmosets. Collectively, these results suggest that the fiber architecture of the common marmoset masseter is part of a suite of features of the masticatory apparatus that facilitates the production of relatively large gapes during tree gouging. (C) 2004 Wiley-Liss, Inc.
Taylor A B; Vinyard C J
Journal of Morphology
2004
2004-09
Journal Article
<a href="http://doi.org/10.1002/jmor.10249" target="_blank" rel="noreferrer noopener">10.1002/jmor.10249</a>