SUMMARY Acute right ventricular (RV) hypertension and failure occur clinically. In this study we examined the mechanism of RV failure. Adult dogs were studied acutely under anesthesia; dogs were instrumented for measurement of pressures and right coronary artery blood flow. Myocardial blood flow and cardiac output were determined with radionuclide-labeled microspheres, and the presence of ischemia was determined by biochemical analysis of ventricular biopsies. RV hypertension was produced by constricting the pulmonary artery and was increased until RV failure occurred, as evidenced by decreased aortic pressure and cardiac output and increased RV end-diastolic pressure. With increasing RV systolic pressure, RV myocardial blood flow failed to increase in proportion to demand. At the onset of RV failure, there was no reactive hyperemia of right coronary flow compared with control, indicating the absence of further coronary vascular reserve; biochemical analysis demonstrated that the RV free wall was ischemic; the LV free wall was not. Infusion of phenylephrine raised aortic pressure and hence, myocardial perfusion pressure; RV failure reversed as shown by decreased RV end-diastolic pressure and increased cardiac output and RV systolic pressure; reactive hyperemia of right coronary flow was restored and the biochemical indexes of ischemia were reversed, demonstrating that ischemia is the cause of failure in acute RV hypertension.RIGHT VENTRICULAR (RV) HYPERTENSION and consequent RV failure occur acutely in diseases such as pulmonary embolism. In 1936, Fineberg and Wiggers suggested that the right ventricle could not generate adequate pressure to overcome the resistance of the obstructed pulmonary vasculature, but they did not define the mechanisms.' Salisbury2 demonstrated that RV failure could be improved by aortic constriction; his work suggests that myocardial perfusion may influence the ability of the right ventricle to pump against increased afterload, but he did not measure coronary blood flow.

The proximal component of the talo-crural joint, the tibia, was compared, using geometric morphometrics, in 240 specimens from 10 extant taxa to identify differences in shape and the factors influencing them. The specimens were laser scanned, digitally reconstructed, and landmarked. Regression analysis was used to evaluate tibial shape, and significant amounts of shape variation among taxa were due to body mass, tibial size, superfamily, and substrate preference in the whole tibia, as well as, separate analysis of the distal tibial articular facets, and the medial malleolar facet. The most important factor for whole tibial shape was tibial robusticity, which closely correlated with body mass. However, substrate preference was also a significant factor in tibial shape and independent from body mass. Substrate preference was also the most important factor defining distal articular morphology. Principal components analysis and pairwise permutation tests were used to compare differences in morphology among taxa. Nearly all were significantly different in overall tibial shape, and distal morphology. Shape and presentational morphology associated with body mass, tibial size, superfamily, and substrate preference were identified, along with the similarities and differences among individual taxa. These were visualized by TPS deformation of an exemplar surface. Relationships among these factors were assessed with their dot-product. Results demonstrated that size significantly influenced proximal presentation, while substrate preference influenced articular morphology. Anat Rec, 294:217-230, 2011. V V C 2010 Wiley-Liss, Inc.

The distal component of the talo-crural joint, the talus, was compared, using geometric morphometrics, in 219 specimens from nine extant taxa to identify differences in shape and the factors influencing them. The specimens were laser scanned, digitally reconstructed, and landmarked. The whole talus, proximal and distal articular facet subgroups were analyzed using Generalized Procrustes analysis, linear regression, principal component analysis, analysis of percent variance, dot-product vector analysis, and pair-wise permutation tests to evaluate shape, and were visualized by TPS deformation of an exemplar surface. Significant percentages of shape variation among taxa were due to body mass, talar size, superfamily, and substrate preference. Shape and presentational morphology associated with these factors were documented, along with the similarities and differences among individual taxa. Nearly all taxa were significantly different in overall, proximal and distal shapes. The most important factors influencing whole talar shape were log centroid size and substrate preference. Substrate preference was also the most important factor defining proximal articular morphology and unrelated to other factor such as mass, while distal articular morphology was influenced by superfamily (head angle and shape). Results demonstrated that substrate preference and superfamily significantly influenced distal presentation, while substrate preference influenced proximal articular shape. Anat Rec, 296:877-890, 2013. V C 2013 Wiley Periodicals, Inc.

Objectives: The primate talus is known to have a shape that varies according to differences in locomotion and substrate use. While the modern human talus is morphologically specialized for bipedal walking, relatively little is known on how its morphology varies in relation to cultural and environmental differences across time.Here we compare tali of modern human populations with different subsistence economies and lifestyles to explore how cultural practices and environmental factors influence external talar shape. Materials and Methods:The sample consists of digital models of 142 tali from 11 archaeological and post-industrial modern human groups. Talar morphology was investigated through 3D (semi)landmark based geometric morphometric methods.Results: Our results show distinct differences between highly mobile huntergatherers and more sedentary groups belonging to a mixed post-agricultural/industrial background. Hunter-gatherers exhibit a more "flexible" talar shape, everted posture, and a more robust and medially oriented talar neck/head, which we interpret as 171:456-469.wileyonlinelibrary.com/journal/ajpa reflecting long-distance walking strictly performed barefoot, or wearing minimalistic footwear, along uneven ground. The talus of the post-industrial population exhibits a "stable" profile, neutral posture, and a less robust and orthogonally oriented talar neck/head, which we interpret as a consequence of sedentary lifestyle and use of stiff footwear.Discussion: We suggest that talar morphological variation is related to the adoption of constraining footwear in post-industrial society, which reduces ankle range of motion. This contrasts with hunter-gatherers, where talar shape shows a more flexible profile, likely resulting from a lack of footwear while traversing uneven terrain.We conclude that modern human tali vary with differences in locomotor and cultural behavior.footwear, Homo sapiens, subsistence strategies, talus