In this Issue
May 15, 2016; volume 120, issue 10
- Age-related differences in plasma BDNF levels after prolonged bed rest
Blood concentrations of brain-derived neurotrophic factor (BDNF) increase after 14 days of bed rest in older but not younger people, and may indicate that the aging brain is less resistant to acute stresses, and increases in BDNF could represent the protective response to the acute stress of bed rest.
- Vitamin D3 intake modulates diaphragm but not peripheral muscle force in young mice
In vitro force data from a peripheral leg muscle [extensor digitorum longus (EDL)] as well as diaphragm (DIA) force from an older group of mice (12 wk old) were included. Additional markers of muscle anabolism and catabolism were also included. The data confirm that vitamin D modifies DIA force in young mice, suggesting a role for vitamin D in DIA development.
- Intestinal and sublingual microcirculation are more severely compromised in hemodilution than in hemorrhage
This study showed that in the systemic hyperdynamic state of hemodilution, intestinal and sublingual microcirculation were more severely compromised than in hemorrhage. Consequently, the decreased ability to increase O2 extraction could result from microcirculatory shunting, and not from failure in O2 dissociation from Hb. Despite the severe villi hypoperfusion, tissue Pco2 was normal, which could be ascribed to CO2 clearance in the deeper intestinal layers.
- Chronic in vivo or acute in vitro resveratrol attenuates endothelium-dependent cyclooxygenase-mediated contractile signaling in hypertensive rat carotid artery
These experiments were designed to investigate the under-studied role of resveratrol (RSV) in affecting COX and TP receptor-mediated endothelium-dependent contraction that can contribute to endothelial dysfunction. The data demonstrate for the first time that both chronic in vivo RSV treatment and acute in vitro RSV exposure can attenuate endothelium-dependent contraction and that this attenuating effect can occur in the arterial wall not only by suppressing PG production via AMPK but also by inhibiting TP receptor activity.
- Living altitude influences endurance exercise performance change over time at altitude
This study adds new practical information for endurance athletes, coaches, and sport physiologists on the best living altitude and acclimatization time for altitude training before an endurance competition taking place at altitude. We recommend that endurance athletes competing acutely at a low altitude (1,780 m) acclimatize by living at that altitude and not higher. Athletes choosing to live at a higher altitude may need longer acclimatization time to minimize performance decrements at altitude.
- Short-term aerobic exercise training improves gut peptide regulation in nonalcoholic fatty liver disease
Nonalcoholic fatty liver disease (NAFLD) is the most common liver-related disease. Exercise is widely prescribed as treatment, but the mechanism is unknown. We examined the effects of exercise on gut peptides [peptide tyrosine tyrosine (PYY) and glucagon-like peptide-1 (GLP-1)] in patients with clinically diagnosed NAFLD. Prior to training, those with NAFLD exhibited elevated fasting plasma PYY and GLP-1, and the response to glucose ingestion was abnormal. Exercise reduced fasting GLP-1 and normalized the glucose-stimulated response of both hormones.
- Increased ventilatory variability and complexity in patients with hyperventilation disorder
It has been hypothesized but never proven that hyperventilation disorder results from an abnormality of respiratory control. We show that well-defined patients suffering from hyperventilation disorder (permanent hypocapnia during a cardiopulmonary exercise test) are characterized by increased variability of their resting ventilation due to increased ventilatory complexity with stable ventilatory-chemoresponsiveness interactions. We hypothesize that this submissive hypocapnia may be related to central nervous system sensitization.
- Chronic intermittent hypoxia alters ventilatory and metabolic responses to acute hypoxia in rats
Our study addresses the controversy of whether chronic exposure to intermittent hypoxia enhances ventilatory chemosensitivity. We quantified hypoxic chemosensitivity in conscious rats using a novel method, which unlike most previously published approaches, was able to uncover key effects of prolonged intermittent hypoxia on both metabolic and ventilatory responses to acute hypoxia. We propose that hypoxic chemosensitivity is indeed enhanced by intermittent hypoxia and thus is a potentially important contributor to sleep disordered breathing in humans.
HIGHLIGHTED TOPIC | Analogs of Microgravity: Space Research without Leaving the Planet
- WISE 2005: Aerobic and resistive countermeasures prevent paraspinal muscle deconditioning during 60-day bed rest in women
Aerobic and resistive exercise that promotes musculoskeletal loading through the spine may be beneficial during prolonged spaceflight to mitigate the effects of microgravity and maintain cross-sectional area and strength of the lumbar paraspinal muscles.
- Motor control of landing from a countermovement jump in simulated microgravity
For the first time, the mechanism of landing from a jump is investigated in weightlessness with simulated gravity conditions (1-0.2 g). Even if this environment is far from the usual Earth's gravitational field, humans adjust their motor command to the task constraints. Kinetic, kinematic, and electromyographic observations enlarge the knowledge of the plasticity of the human motor system for the exploration of Moon, Mars, and other planets with different gravity.
- Effect of acute hypercapnia during 10-day hypoxic bed rest on posterior eye structures
Horizontal 10-day bed rest, followed by acute hypercapnia and hypoxia, resulted in morphological changes of posterior eye structures measured by optical coherence tomography. Bed rest caused an increase in the thickness of the choroidal layer. Hypoxia and hypercapnia caused an increase in the thickness of the retinal nerve fiber layer (RNFL). It appears that the increase in the choroidal layer is affected predominantly by a hydrostatic, and the RNFL by a vasoactive, effect.
HIGHLIGHTED TOPIC | Molecular Adaptations to Exercise, Heat Acclimation, and Thermotolerance
- Rapid cooling after acute hyperthermia alters intestinal morphology and increases the systemic inflammatory response in pigs
This study used pigs, a more advanced phylogenic model, to provide physiological support for the idea that rapid cooling may be detrimental to the pathophysiology of hyperthermia in humans. It was determined that rapid cooling to promote acute hyperthermia recovery directly resulted in intestinal morphological changes associated with greater damage and increased the systemic inflammatory response.
- Cytosolic calcium transients are a determinant of contraction-induced HSP72 transcription in single skeletal muscle fibers
The activating factors for contraction-induced HSP72 transcription in skeletal muscle remain unclear. The present study utilizes single skeletal muscle fibers to demonstrate that the intermittent cytosolic Ca2+ transient that occurs with skeletal muscle depolarization provides a sufficient stimulus to activate HSP72 transcription. Metabolic or mechanical factors associated with fatigue and cross-bridge cycling likely play a more limited role.