Design and function of superfast muscles : new insights into the physiology of skeletal muscle

First published online as a Review in Advance on October 24, 2005. (Some corrections may occur before final publication online and in print)Author Posting. © Annual Reviews, 2005. This article is posted here by permission of Annual Reviews for personal use, not for redistribution. The definitive version was published in Annual Review of Physiology 68 (2006): 22.1-22.29, doi:10.1146/annurev.physiol.68.040104.105418.Superfast muscles of vertebrates power sound production. The fastest, the swimbladder muscle of toadfish, generates mechanical power at frequencies in excess of 200 Hz. To operate at these frequencies, the speed of relaxation has had to increase approximately 50-fold. This increase is accomplished by modifications of three kinetic traits: (a) a fast calcium transient due to extremely high concentration of sarcoplasmic reticulum (SR)-Ca2+ pumps and parvalbumin, (b) fast off-rate of Ca2+ from troponin C due to an alteration in troponin, and (c) fast cross-bridge detachment rate constant (g, 50 times faster than that in rabbit fast-twitch muscle) due to an alteration in myosin. Although these three modifications permit swimbladder muscle to generate mechanical work at high frequencies (where locomotor muscles cannot), it comes with a cost: The high g causes a large reduction in attached force-generating cross-bridges, making the swimbladder incapable of powering low-frequency locomotory movements. Hence the locomotory and sound-producing muscles have mutually exclusive designs.This work was made possible by support from NIH grants AR38404 and AR46125 as well as the University of Pennsylvania Research Foundation

The Putative Liquid-Liquid Transition is a Liquid-Solid Transition in Atomistic Models of Water

We use numerical simulation to examine the possibility of a reversible liquid-liquid transition in supercooled water and related systems. In particular, for two atomistic models of water, we have computed free energies as functions of multiple order parameters, where one is density and another distinguishes crystal from liquid. For a range of temperatures and pressures, separate free energy basins for liquid and crystal are found, conditions of phase coexistence between these phases are demonstrated, and time scales for equilibration are determined. We find that at no range of temperatures and pressures is there more than a single liquid basin, even at conditions where amorphous behavior is unstable with respect to the crystal. We find a similar result for a related model of silicon. This result excludes the possibility of the proposed liquid-liquid critical point for the models we have studied. Further, we argue that behaviors others have attributed to a liquid-liquid transition in water and related systems are in fact reflections of transitions between liquid and crystal

Institutional effects on nurses’ working conditions: a multi-group comparison of public and private non-profit and for-profit healthcare employers in Switzerland

Background: In response to the need for competitive recruitment of nurses resulting from the worldwide nursing shortage, employers need to attract and retain nurses by promoting their competitive strengths in their working conditions (WCS) and by addressing their competitive weaknesses. This study investigated workplace differences between public hospitals (PuHs), private for-profit hospitals (PrHs), socio- medical institutions (SOMEDs), home care services (HCs), private medical offices (PrOs) and non-profit organisations (NPOs), helping to provide a foundation for competition-oriented institutional employer branding and to increase transparency in the labour market for nurses. Methods: Data from the Swiss Nurses at Work study of the career paths of 11 232 nurses who worked in Switzerland between 1970 and 2014 were subjected to secondary analysis, assessing the effect of institutional characteristics on self-reported determinants of job satisfaction (such as WCS) using multivariate linear regression and post hoc tests with Bonferroni-adjusted significance levels. Principal component analysis was used to reduce the number of WCS in the original study. Results: Nurses at PuHs and PrHs were less likely to experience autonomy, flexibility of work hours and participation in decision-making than those at other workplaces. Although PuHs were rated higher than PrHs in terms of satisfaction with salary and advancement opportunities, they were associated with more alienating work factors, such as stress and aggression. SOMED workplaces were significantly more often associated with alienating conditions and low job satisfaction, but were rated higher than the other institutions in terms of participation in decision-making. The nurses’ ratings implied that PrO workplaces were more likely to offer a mild work environment, social support and recognition than other institutions, but that advancement opportunities were limited. NPO workplaces were associated with the highest degree of autonomy, flexibility, participation, recognition, organisational commitment and job satisfaction. In these respects, HC and NPO workplaces received similar ratings, although the HC workplaces were associated with a significantly lower organisational commitment and significantly lower job satisfaction. Conclusions: Due to their structural characteristics, NPOs, SOMEDs and HCs can attract nurses seeking greater self-determination, PuHs can attract career-oriented nurses, and PrOs and PrHs are likely to attract nurses through offering less-stressful working conditions

International Consensus Statement on Rhinology and Allergy: Rhinosinusitis

Background: The 5 years since the publication of the first International Consensus Statement on Allergy and Rhinology: Rhinosinusitis (ICAR‐RS) has witnessed foundational progress in our understanding and treatment of rhinologic disease. These advances are reflected within the more than 40 new topics covered within the ICAR‐RS‐2021 as well as updates to the original 140 topics. This executive summary consolidates the evidence‐based findings of the document. Methods: ICAR‐RS presents over 180 topics in the forms of evidence‐based reviews with recommendations (EBRRs), evidence‐based reviews, and literature reviews. The highest grade structured recommendations of the EBRR sections are summarized in this executive summary. Results: ICAR‐RS‐2021 covers 22 topics regarding the medical management of RS, which are grade A/B and are presented in the executive summary. Additionally, 4 topics regarding the surgical management of RS are grade A/B and are presented in the executive summary. Finally, a comprehensive evidence‐based management algorithm is provided. Conclusion: This ICAR‐RS‐2021 executive summary provides a compilation of the evidence‐based recommendations for medical and surgical treatment of the most common forms of RS