In this Issue
January 2017; volume 122, issue 1
EDITORIAL | Cores of Reproducibility in Physiology
REVIEW | Cores of Reproducibility in Physiology
RESEARCH ARTICLES | Aging and Exercise
- Resistance training with instability is more effective than resistance training in improving spinal inhibitory mechanisms in Parkinson’s disease
Patients with Parkinson’s disease (PD) have motor dysfunction. Spinal inhibitory mechanisms are important for modulating both supraspinal motor commands and sensory feedback at the spinal level. Resistance training with instability was more effective than resistance training in increasing the levels of presynaptic inhibition and disynaptic reciprocal inhibition of lower limb at rest of the patients with PD, reaching the average values of the healthy controls.
- Habitual aerobic exercise does not protect against micro- or macrovascular endothelial dysfunction in healthy estrogen-deficient postmenopausal women
This is the first study to demonstrate that habitual aerobic exercise may not protect against age/menopause-related whole forearm microvascular endothelial dysfunction in healthy nonobese estrogen-deficient postmenopausal women, consistent with recent findings regarding macrovascular endothelial function. This is in contrast to what is observed in healthy middle-aged and older aerobic exercise-trained men.
- Neuromuscular electrical stimulation prior to presleep protein feeding stimulates the use of protein-derived amino acids for overnight muscle protein synthesis
Neuromuscular electrical stimulation (NMES) as well as presleep dietary protein ingestion represent effective strategies to stimulate muscle protein synthesis rates. Here we demonstrate that in older men after a day of bed rest, the application of NMES prior to presleep protein feeding stimulates the use of dietary protein-derived amino acids for overnight muscle protein synthesis by 18% compared with presleep protein feeding only.
- Obesity, type 2 diabetes, and impaired insulin-stimulated blood flow: role of skeletal muscle NO synthase and endothelin-1
Although impairments in endothelial signaling are hypothesized to reduce insulin-stimulated blood flow in type 2 diabetes (T2D), human studies examining these links are limited. We provide the first measures of nitric oxide synthase and endothelin-1 expression from skeletal muscle tissue containing native microvessels in individuals with and without T2D before and during insulin stimulation. Higher basal skeletal muscle expression of endothelin-1 and reduced endothelial nitric oxide phosphorylation (peNOS)/eNOS may contribute to reduced insulin-stimulated blood flow in obese T2D patients.
- Effect of increased and maintained frequency of speed endurance training on performance and muscle adaptations in runners
Ten speed endurance training (SET) sessions improved short-term exercise capacity and 10-km performance, which was followed by further improved short-term exercise capacity, but unchanged 10-km performance after 20 SET sessions performed with either high frequency (4 per 8 days) or continued low frequency (2 per 8 days) in trained runners. The further gain in short-term exercise capacity was associated with changes in muscle expression of proteins of importance for the development of fatigue.
- Flow velocity is relatively uniform in the coronary sinusal venous tree: structure-function relation
A hemodynamic model is developed in the entire coronary sinusal venous tree of the swine heart. A key finding is that the coronary sinusal venous system complies with the area preservation rule for efficient venous return while the coronary arterial tree obeys the minimum energy hypothesis. This model can also serve as a physiological reference state to test various therapeutic rationales through the venous route.
- A pilot study examining the impact of exercise training on skeletal muscle genes related to the TLR signaling pathway in older adults following hip fracture recovery
These pilot data demonstrate that 3 mo of exercise training in older adults recovering from hip fracture surgery was able to mitigate skeletal muscle gene expression related to inflammation and ceramide metabolism while also improving surgical limb lean tissue, strength, and physical function.
- Intermittent parathyroid hormone administration attenuates endothelial dysfunction in old rats
We have demonstrated that intermittent parathyroid hormone administration can rescue age-related vascular dysfunction by improving endothelial-dependent dilation in the aorta of older rodents. This demonstrates a novel potential benefit of parathyroid hormone administration in aging.
- Nasal high-flow therapy reduces work of breathing compared with oxygen during sleep in COPD and smoking controls: a prospective observational study
Nasal high-flow (NHF) therapy can support ventilation in patients with chronic obstructive pulmonary disease during sleep by decreasing the work of breathing and improving CO2 levels. On the other hand, oxygen supplementation corrects hypoxemia, but it produces only a minimal reduction in work of breathing and is associated with increased CO2 levels. Therefore, NHF can be a useful method to assist ventilation in patients with increased respiratory mechanical loads.
- Relationship between obstructive sleep apnea and endogenous carbon monoxide
Endogenous carbon monoxide (CO) levels are recognized to be a surrogate marker of oxidative stress. No study has evaluated both exhaled and blood CO at the same time in obstructive sleep apnea (OSA) patients. Here we provide evidence that exhaled CO levels positively correlated with hypoxia during sleep in OSA patients, but blood CO levels did not, and that continuous positive airway pressure therapy significantly decreased exhaled CO levels in the OSA group, but did not significantly affect blood CO.
- Central and peripheral responses to static and dynamic stretch of skeletal muscle: mechano- and metaboreflex implications
Different modalities of passive stretching administration (dynamic or static) in combination with circulatory cuff occlusion may reduce or amplify the mechano- and metaboreflex. We showed a reduced mechanoreflex response to static compared with dynamic stretching. The lack of increase in central hemodynamics during the combined mechano- and metaboreflex stimulation implicates marginal interactions between these two pathways.
- Renal sympathetic denervation attenuates hypertension and vascular remodeling in renovascular hypertensive rats
The effects of renal sympathetic denervation (RSD) on hypertension, cardiac function, vascular fibrosis, and renal apoptosis were studied in the 2K1C rat model. Results showed that RSD attenuated hypertension, improved vascular remodeling, and reduced vascular fibrosis through decreased sympathetic activity in the 2K1C rat model, but it did not change the kidney size, renal apoptosis, or renal caspase-3 expression. These results could suggest possible clinical efficacy of RSD for renovascular hypertension.
- Rates of performance loss and neuromuscular activity in men and women during cycling: evidence for a common metabolic basis of muscle fatigue
Although men and women differed considerably in their absolute cycling performances, there was no sex difference in the metabolically based exponential time constant that described the performance-duration relationship. Similarly, the fatigue-induced increases in neuromuscular activity were not different between the sexes when compared from a metabolic perspective. These data suggest that men and women have similar rate-limiting mechanisms for short-duration dynamic exercise that are determined by the extent the exercise is supported by anaerobic metabolism.
- Effect of hypohydration on thermoregulatory responses in men with low and high body fat exercising in the heat
This is the first known investigation to compare thermoregulatory responses to exercise heat stress between men with high and low body fat (BF) in a physiologically uncompensable environment while simultaneously examining the confounding influence of hydration status. Both groups demonstrated similar sweating and cutaneous vasodilatory responses when euhydrated, despite vast differences in rectal temperature. Furthermore, in contrast to low BF, individuals with high BF demonstrated similar increases in core body temperature when either euhydrated or hypohydrated.
- Effect of sodium nitrite on local control of contracting skeletal muscle microvascular oxygen pressure in healthy rats
Ischemic conditions as diverse as chronic heart failure (CHF) and frostbite inflict tissue damage via inadequate O2 delivery. Herein we demonstrate that direct application of sodium nitrite enhances the O2 supply-O2 demand relationship, raising microvascular O2 pressure in healthy skeletal muscle. This therapeutic action of nitrite-derived nitric oxide occurred without inducing systemic hypotension and has the potential to relieve focal ischemia and preserve tissue vitality by enhancing O2 delivery.
- Nondestructive cryomicro-CT imaging enables structural and molecular analysis of human lung tissue
The described micro-CT cryostage provides a novel way to study the three-dimensional lung structure preserved without the effects of fixatives while enabling subsequent studies of the cellular matrix composition and gene expression. This approach will, for the first time, enable researchers to study structural changes of lung tissues that occur with disease and correlate them with changes in gene or protein signatures.
- The effect of obesity on the contractile performance of isolated mouse soleus, EDL, and diaphragm muscles
The effect of obesity on isolated muscle function is surprisingly underresearched. The present study is the first to examine the effects of obesity on isolated muscle performance using a method that more closely represents real-world muscle function. This work uniquely establishes a muscle-specific profile of mechanical changes in relation to underpinning mechanisms. These findings may be important to understanding the negative cycle of obesity and in designing interventions for improving weight status.
- Aerobic exercise in humans mobilizes HSCs in an intensity-dependent manner
Here we demonstrate for the first time that mobilization of hematopoietic stem cells (HSC) through exercise is intensity dependent, with the greatest mobilization occurring immediately after high-intensity exercise. As well, we show that exercise is a general stimulus for mobilization: increases in specific HSC populations are reliant on general mononuclear cell mobilization. Finally, we demonstrate no differences in mobilization between groups with different aerobic fitness.
- Nasal high flow reduces dead space
Clearance of expired air in upper airways by nasal high flow (NHF) can be extended below the soft palate and de facto causes a reduction of dead space. Using scintigraphy, the authors found a relationship between NHF, time, and clearance. Direct measurement of CO2 and O2 in the trachea confirmed a reduction of rebreathing, providing the actual data on inspired gases, and this can be used for the assessment of other forms of respiratory support.
- Single passive leg movement-induced hyperemia: a simple vascular function assessment without a chronotropic response
Using the single passive leg movement (PLM) technique, a variant of the vascular function assessment PLM, we have identified a novel peripheral vascular assessment method that is more easily performed than PLM, which, by not evoking potentially confounding central hemodynamic responses, may be more useful clinically.
- A translational cellular model to study the impact of high-frequency oscillatory ventilation on human epithelial cell function
Traditionally, large-animal models are used to analyze the impact of clinical ventilators on lung cellular function. In our dual-chamber model, we interface high-frequency oscillatory ventilation (HFOV) directly with airway cells to study the effects of HFOV independently and combined with hyperoxia. Therefore, it is possible to study the preclinical impact of interventional factors without the high cost of animal models, thus reducing staff, time, as well as animal sparing.
VIEWPOINTS | Aging and Exercise
- Commentaries on Viewpoint: A time for exercise: the exercise windowTHE OPTIMAL EXERCISE TIMING “WINDOW” DEPENDS ON THE OUTCOMECOMMENTARY ON VIEWPOINT: A TIME FOR EXERCISE: THE EXERCISE WINDOWCOMMENTARY ON VIEWPOINT: A TIME FOR EXERCISE: THE EXERCISE WINDOWCOMMENTARY ON VIEWPOINT: A TIME FOR EXERCISE: THE EXERCISE WINDOWCOMMENTARY ON VIEWPOINT: A TIME FOR EXERCISE: THE EXERCISE WINDOWEXERCISE STRATEGIES TO IMPROVE POSTPRANDIAL METABOLIC CONTROL: MORE TO BE DONECOMMENTARY ON VIEWPOINT: A TIME FOR EXERCISE: THE EXERCISE WINDOWDOES THE “EXERCISE WINDOW” WORK IN TYPE 1 DIABETES?COMMENTARY ON VIEWPOINT: A TIME FOR EXERCISE: THE EXERCISE WINDOW
- Commentaries on Viewpoint: “Tighter fit” theory—physiologists explain why “higher altitude” and jugular occlusion are unlikely to reduce risks for sports concussion and brain injuriesFROM MONRO AND KELLIE TO MOUNTAINS AND CONCUSSION; THE SCIENCE OF SLOSHEXPLANATION OF BRAIN PHYSIOLOGY TO ENHANCE UNDERSTANDING OF THE “TIGHTER FIT” THEORYCOMMENTARY ON VIEWPOINT: “TIGHTER FIT” THEORY—PHYSIOLOGISTS EXPLAIN WHY “HIGHER ALTITUDE” AND JUGULAR OCCLUSION ARE UNLIKELY TO REDUCE RISKS FOR SPORTS CONCUSSION AND BRAIN INJURIESCOMMENTARY ON VIEWPOINT: “TIGHTER FIT” THEORY—PHYSIOLOGISTS EXPLAIN WHY “HIGHER ALTITUDE” AND JUGULAR OCCLUSION ARE UNLIKELY TO REDUCE RISKS FOR SPORTS CONCUSSION AND BRAIN INJURIESALL’S SWELL WITH THE BRAIN; ON THE SIGNIFICANCE OF BLOOD-BRAIN BARRIER DISRUPTION IN HYPOXIA