Origin of the forward-going "backward" wave
(Source: Journal of Applied Physiology)
Source: Journal of Applied Physiology - November 22, 2017 Category: Physiology Authors: Tyberg, J. V., Burrowes, L. M., Shrive, N. G., Wang, J.-J. Tags: VIEWPOINT Source Type: research
Effects of anti-inflammatory (NSAID) treatment on human tendinopathic tissue
In conclusion, there was no indication that short-term ibuprofen treatment affects gene expression in human chronic tendinopathic tendon or leads to any clear changes in tendon pain or function.
NEW & NOTEWORTHY Nonsteroidal anti-inflammatory drugs are widely used in the treatment of tendinopathy, but little is known of the effects of these drugs on tendon tissue. We find that 1 wk of ibuprofen treatment has no effect on gene expression of collagen and related growth factors in adult human tendinopathic tendon in vivo (in spite of relatively low levels of variation in gene expression), suggesting that tendinopathic cel...
Source: Journal of Applied Physiology - November 22, 2017 Category: Physiology Authors: Heinemeier, K. M., Ohlenschlaeger, T. F., Mikkelsen, U. R., Sonder, F., Schjerling, P., Svensson, R. B., Kjaer, M. Tags: RESEARCH ARTICLE Source Type: research
UBC-Nepal Expedition: acute alterations in sympathetic nervous activity do not influence brachial artery endothelial function at sea level and high altitude
Evidence indicates that increases in sympathetic nervous activity (SNA), and acclimatization to high altitude (HA), may reduce endothelial function as assessed by brachial artery flow-mediated dilatation (FMD); however, it is unclear whether such changes in FMD are due to direct vascular constraint, or consequential altered hemodynamics (e.g., shear stress) associated with increased SNA as a consequence of exposure to HA. We hypothesized that 1) at rest, SNA would be elevated and FMD would be reduced at HA compared with sea-level (SL); and 2) at SL and HA, FMD would be reduced when SNA was acutely increased, and elevated w...
Source: Journal of Applied Physiology - November 22, 2017 Category: Physiology Authors: Tymko, M. M., Tremblay, J. C., Steinback, C. D., Moore, J. P., Hansen, A. B., Patrician, A., Howe, C. A., Hoiland, R. L., Green, D. J., Ainslie, P. N. Tags: RESEARCH ARTICLE Source Type: research
Measuring high-altitude adaptation
High altitudes (>8,000 ft or 2,500 m) provide an experiment of nature for measuring adaptation and the physiological processes involved. Studies conducted over the past ~25 years in Andeans, Tibetans, and, less often, Ethiopians show varied but distinct O2 transport traits from those of acclimatized newcomers, providing indirect evidence for genetic adaptation to high altitude. Short-term (acclimatization, developmental) and long-term (genetic) responses to high altitude exhibit a temporal gradient such that, although all influence O2 content, the latter also improve O2 delivery and metabolism. Much has been learned con...
Source: Journal of Applied Physiology - November 22, 2017 Category: Physiology Authors: Moore, L. G. Tags: REVIEW Source Type: research
Epigenomics and human adaptation to high altitude
Over the past decade, major technological and analytical advancements have propelled efforts toward identifying the molecular mechanisms that govern human adaptation to high altitude. Despite remarkable progress with respect to the identification of adaptive genomic signals that are strongly associated with the "hypoxia-tolerant" physiological characteristics of high-altitude populations, many questions regarding the fundamental biological processes underlying human adaptation remain unanswered. Vital to address these enduring questions will be determining the role of epigenetic processes, or non-sequence-based features of...
Source: Journal of Applied Physiology - November 16, 2017 Category: Physiology Authors: Julian, C. G. Tags: REVIEW Source Type: research
Human cerebral blood flow control during hypoxia: focus on chronic pulmonary obstructive disease and obstructive sleep apnea
The brain is a vital organ that relies on a constant and adequate blood flow to match oxygen and glucose delivery with the local metabolic demands of active neurons. Thus exquisite regulation of cerebral blood flow (CBF) is particularly important under hypoxic conditions to prevent a detrimental decrease in the partial pressure of oxygen within the brain tissues. Cerebrovascular sensitivity to hypoxia, assessed as the change in CBF during a hypoxic challenge, represents the capacity of cerebral vessels to respond to, and compensate for, a reduced oxygen supply, and has been shown to be impaired or blunted in a number of co...
Source: Journal of Applied Physiology - November 16, 2017 Category: Physiology Authors: Beaudin, A. E., Hartmann, S. E., Pun, M., Poulin, M. J. Tags: REVIEW Source Type: research
On the existence of a central respiratory oxygen sensor
A commonly held view that dominates both the scientific and educational literature is that in terrestrial mammals the central nervous system lacks a physiological hypoxia sensor capable of triggering increases in lung ventilation in response to decreases in Po2 of the brain parenchyma. Indeed, a normocapnic hypoxic ventilatory response has never been observed in humans following bilateral resection of the carotid bodies. In contrast, almost complete or partial recovery of the hypoxic ventilatory response after denervation/removal of the peripheral respiratory oxygen chemoreceptors has been demonstrated in many experimental...
Source: Journal of Applied Physiology - November 16, 2017 Category: Physiology Authors: Gourine, A. V., Funk, G. D. Tags: REVIEW Source Type: research
Acute oxygen sensing by the carotid body: from mitochondria to plasma membrane
Maintaining oxygen homeostasis is crucial to the survival of animals. Mammals respond acutely to changes in blood oxygen levels by modulating cardiopulmonary function. The major sensor of blood oxygen that regulates breathing is the carotid body (CB), a small chemosensory organ located at the carotid bifurcation. When arterial blood oxygen levels drop in hypoxia, neuroendocrine cells in the CB called glomus cells are activated to signal to afferent nerves that project to the brain stem. The mechanism by which hypoxia stimulates CB sensory activity has been the subject of many studies over the past 90 years. Two discrete mo...
Source: Journal of Applied Physiology - November 16, 2017 Category: Physiology Authors: Chang, A. J. Tags: REVIEW Source Type: research
Determinants of hypoxia-inducible factor activity in the intestinal mucosa
The intestinal mucosa is exposed to fluctuations in oxygen levels due to constantly changing rates of oxygen demand and supply and its juxtaposition with the anoxic environment of the intestinal lumen. This frequently results in a state of hypoxia in the healthy mucosa even in the physiologic state. Furthermore, pathophysiologic hypoxia (which is more severe and extensive) is associated with chronic inflammatory diseases including inflammatory bowel disease (IBD). The hypoxia-inducible factor (HIF), a ubiquitously expressed regulator of cellular adaptation to hypoxia, is central to both the adaptive and the inflammatory re...
Source: Journal of Applied Physiology - November 16, 2017 Category: Physiology Authors: Fagundes, R. R., Taylor, C. T. Tags: REVIEW Source Type: research
Oxygen metabolism and innate immune responses in the gut
Epithelial cells of the mucosa provide a first line of defense to prevent the inappropriate translocation of luminal antigens, and therefore contribute significantly to nonspecific innate immunity. In the gastrointestinal (GI) tract, barrier is provided by multiple components of the mucosa, including mucus production, epithelial junctional complexes, and the production of antimicrobial molecules. In recent years, it is better appreciated that tissue oxygen metabolism is key to homeostasis in the mucosa. The intestine, for example, maintains a low baseline Po2 level due to high rates of metabolism, countercurrent blood flow...
Source: Journal of Applied Physiology - November 16, 2017 Category: Physiology Authors: Colgan, S. P., Campbell, E. L. Tags: REVIEW Source Type: research
The hypoxia-adenosine link during inflammation
Hypoxic tissue conditions occur during a number of inflammatory diseases and are associated with the breakdown of barriers and induction of proinflammatory responses. At the same time, hypoxia is also known to induce several adaptive and tissue-protective pathways that dampen inflammation and protect tissue integrity. Hypoxia-inducible factors (HIFs) that are stabilized during inflammatory or hypoxic conditions are at the center of mediating these responses. In the past decade, several genes regulating extracellular adenosine metabolism and signaling have been identified as being direct targets of HIFs. Here, we discuss th...
Source: Journal of Applied Physiology - November 16, 2017 Category: Physiology Authors: Bowser, J. L., Lee, J. W., Yuan, X., Eltzschig, H. K. Tags: REVIEW Source Type: research
Walking economy is predictably determined by speed, grade, and gravitational load
The metabolic energy that human walking requires can vary by more than 10-fold, depending on the speed, surface gradient, and load carried. Although the mechanical factors determining economy are generally considered to be numerous and complex, we tested a minimum mechanics hypothesis that only three variables are needed for broad, accurate prediction: speed, surface grade, and total gravitational load. We first measured steady-state rates of oxygen uptake in 20 healthy adult subjects during unloaded treadmill trials from 0.4 to 1.6 m/s on six gradients: –6, –3, 0, 3, 6, and 9°. Next, we tested a second set...
Source: Journal of Applied Physiology - November 13, 2017 Category: Physiology Authors: Ludlow, L. W., Weyand, P. G. Tags: RESEARCH ARTICLE Source Type: research
Severe energy deficit upregulates leptin receptors, leptin signaling, and PTP1B in human skeletal muscle
This study shows that the skeletal muscle leptin receptors and their corresponding signaling cascade are upregulated in response to a severe energy deficit, contributing to increase maximal fat oxidation. The responses are more prominent in the arm muscles than in the legs but partly blunted by whey protein ingestion and high volume of exercise. This occurs despite an increase of protein tyrosine phosphatase 1B protein expression, a known inhibitor of insulin and leptin signaling. (Source: Journal of Applied Physiology)
Source: Journal of Applied Physiology - November 13, 2017 Category: Physiology Authors: Perez-Suarez, I., Ponce-Gonzalez, J. G., de La Calle-Herrero, J., Losa-Reyna, J., Martin-Rincon, M., Morales-Alamo, D., Santana, A., Holmberg, H.-C., Calbet, J. A. L. Tags: RESEARCH ARTICLE Source Type: research
Acute effects of long-acting bronchodilators on small airways detected in COPD patients by single-breath N2 test and lung P-V curve
In conclusion, bronchodilators reduce the heterogeneity of peripheral airway mechanical properties and the extent of their closure, with minor effects on critical closing pressure. This should lessen the risk of small-airway damage and positively affect gas exchange.
NEW & NOTEWORTHY This is the first study investigating in stable chronic obstructive pulmonary disease patients the acute effects of two long-acting bronchodilators, a β-agonist and a muscarinic antagonist, on peripheral airways using simultaneous lung pressure-volume curve and single-breath N2 test. By lessening airway mechanical property heterogenei...
Source: Journal of Applied Physiology - November 13, 2017 Category: Physiology Authors: Pecchiari, M., Santus, P., Radovanovic, D., D'Angelo, E. Tags: RESEARCH ARTICLE Source Type: research
Short-term arrival strategies for endurance exercise performance at moderate altitude
For sea level-based endurance athletes who compete at moderate and high altitudes, many are not logistically able to arrive at altitude weeks before the event to fully acclimatize. For those who can only arrive at altitude the night before competition, we asked if there is a physiological and performance advantage in reducing altitude exposure time to 2 h before competition. On three separate visits, 10 cyclists completed overnight laboratory exposures of: 1) a 14-h exposure to normobaric hypoxia (16.2% O2, simulating 2,500 m; 14H), 2) a 12-h exposure to normoxia, then a 2-h hypoxic exposure (2H), and 3) a 14-h exposure to...
Source: Journal of Applied Physiology - November 13, 2017 Category: Physiology Authors: Foss, J. L., Constantini, K., Mickleborough, T. D., Chapman, R. F. Tags: RESEARCH ARTICLE Source Type: research
