In this Issue
February 2017; volume 122, issue 2
- Blood pressure reduction after gastric bypass surgery is explained by a decrease in cardiac output
The reason for the decrease in blood pressure (BP) in the first weeks after gastric bypass surgery remains to be elucidated. We show that the reduction in BP following surgery is caused by a decrease in cardiac output. In addition, the maximal ascending slope in systolic blood pressure decreased suggesting a reduction in left ventricular contractility and cardiac workload. These findings help to understand the physiological changes following surgery and are relevant in light of the increased risk of heart failure in these patients.
- The effect of alternate-day caloric restriction on the metabolic consequences of 8 days of bed rest in healthy lean men: a randomized trial
Alternate-day caloric restriction without overall energy reduction does not ameliorate the metabolic impairment induced in lean men by 8 days of bed rest.
- Pulmonary vascular collagen content, not cross-linking, contributes to right ventricular pulsatile afterload and overload in early pulmonary hypertension
The present study found an important role for collagen content, but not collagen cross-linking, in the pulsatile right ventricular (RV) afterload, which is correlated with RV hypertrophy. These results uncover a new collagen-mediated mechanical mechanism of RV dysfunction in early pulmonary hypertension progression. Furthermore, our results suggest that measures and metrics of pulsatile hemodynamics such as pulse pressure and pulse wave velocity are potentially important to cardiovascular mortality in patients with pulmonary hypertension.
- Castration alters protein balance after high-frequency muscle contraction
In the absence of androgens, markers of autophagy were elevated, and these could not be normalized by muscle contractions. In the fasted state, REDD1 was identified as a potential contributor to autophagy in noncontracted muscle, whereas phosphorylation of ULK1 may contribute to this process in the contracted muscle. In the refed state, markers of autophagy remain elevated in both noncontracted and contracted muscles, but the relationship with REDD1 and ULK1 (Ser757) no longer existed.
- Tendon collagen synthesis declines with immobilization in elderly humans: no effect of anti-inflammatory medication
In elderly humans, 2 wk of inactivity reduces tendon collagen protein synthesis, while tendon stiffness and modulus are only marginally reduced, and NSAID treatment does not affect this. This indicates that mechanical loading is important for maintenance of tendon collagen turnover and that changes in collagen turnover induced by short-term immobilization may only have minor impact on the internal structures that are essential for mechanical properties in elderly tendons.
- A mechanistic physicochemical model of carbon dioxide transport in blood
This study is the first to incorporate a mechanistic model of chloride-bicarbonate exchange between the erythrocyte and plasma into a full physicochemical model of the carriage of carbon dioxide in blood. The mechanistic nature of the model allowed a theoretical study of the quantitative significance for carbon dioxide transport of carbamino compound formation; the putative binding of chloride to deoxygenated hemoglobin, and the chloride (Hamburger) shift.
- Unique cytokine and chemokine responses to exertional heat stroke in mice
Immune modulators called cytokines are released following extreme hyperthermia leading to heat stroke. It is not known whether exercise in hyperthermia, leading to exertional heat stroke, influences this response. Using a mouse model of exertional heat stroke, we discovered a rapid accumulation of interleukin-6 and other cytokines involved in immune cell trafficking. This response may comprise a protective mechanism for early induction of cell survival and tissue repair pathways needed for recovery from thermal injury.
- Adrenodemedullation activates the Ca2+-dependent proteolysis in soleus muscles from rats exposed to cold
Although many effects of the sympathetic nervous system on muscle physiology are known, the role of catecholamines in skeletal muscle protein metabolism has been scarcely studied. We suggest that catecholamines released from adrenal medulla may be of particular importance for restraining the activation of the Ca2+-dependent proteolysis in soleus muscles during acute cold exposure. This finding helps us to understand the adaptive changes that occur in skeletal muscle protein metabolism during cold stress.
- State-dependent and -independent effects of dialyzing excitatory neuromodulator receptor antagonists into the ventral respiratory column
The two major findings are as follows: 1) during unilateral dialysis of 50 mM atropine into the ventral respiratory column to block excitatory muscarinic receptor activity, a compensatory increase in other neuromodulators was state independent, but the ventilatory response appears to be state dependent; and 2) the hypothesis that absence of decreased V̇i and f during unilateral dialysis of excitatory receptor antagonists was due to compensation by the contralateral VRC was not supported by findings herein.
- Transspinal direct current stimulation modulates migration and proliferation of adult newly born spinal cells in mice
Our results indicate that transspinal direct current stimulation (tsDCS) affects the migratory pattern and proliferation of adult newly born spinal cells, a cell population which has been implicated in learning and memory. In addition, our results suggest a potential mechanism of action regarding the functional effects of applying direct current. Thus tsDCS may represent a novel method by which to manipulate the migration and cell number of adult newly born cells and restore functions following brain or spinal cord injury.
- Vascular function and endothelin-1: tipping the balance between vasodilation and vasoconstriction
Endothelin-1 (ET-1) is recognized as the body’s most potent endogenous vasoconstrictor, but the impact of this peptide on vascular function is not well understood. The present study revealed that the intra-arterial administration of ET-1 impaired both microvascular and conduit vessel function of the leg in young, healthy, humans. Studies employing vascular testing in patient cohorts that experience a disease-related increase in ET-1 should thus exercise caution, as ET-1 clearly impairs vascular function.
- Sex-based difference in Achilles peritendinous levels of matrix metalloproteinases and growth factors after acute resistance exercise
In this investigation we utilized microdialysis of the peritendinous Achilles to evaluate potential differences between men and women in tendon production of key regulators of extracellular matrix remodeling. We demonstrate that a modest sex-specific difference exists in peritendinous levels of several key extracellular matrix modulators after an acute bout of resistance exercise.
- Divergent outcomes of fructose consumption on exercise capacity of rats: friend or foe
The evidence that short-term fructose intake potentiates exercise capacity by nitric oxide-mediated mechanisms yields an optimal fructose feeding frame in which beneficial effects of fructose have been acquired while detrimental effects have not yet been manifested. This highlights the significance of exercise physiology in providing constructive regimens to improve physical performance.
- Hemodynamic response to muscle reflex is abnormal in patients with heart failure with preserved ejection fraction
This study provides evidence that diastolic function is important for normal hemodynamic responses during activation of the muscle metaboreflex in humans. Moreover, it demonstrates that diastolic impairment leads to hemodynamic consequences that are similar to those provoked by systolic heart failure. In both cases the target blood pressure is obtained mainly by means of exaggerated vasoconstriction than by a flow-mediated mechanism.
- Effect of acute aerobic exercise and histamine receptor blockade on arterial stiffness in African Americans and Caucasians
African Americans are at greater risk for developing cardiovascular disease than Caucasians. We are the first to show that young and healthy African Americans exhibit greater central blood pressure, elevated brachial stiffness, and local carotid arterial stiffness after an acute bout of submaximal exercise compared with Caucasians, which may contribute to their higher risk of cardiovascular disease. Furthermore, African Americans exhibit attenuated vasodilator response compared with Caucasians.
- Role of calpain in eccentric contraction-induced proteolysis of Ca2+-regulatory proteins and force depression in rat fast-twitch skeletal muscle
Calpain-dependent proteolysis is one of the contributing factors to muscle damage that occurs with eccentric contraction (ECC). It is unclear, however, whether calpains account for proteolysis of Ca2+-regulatory proteins in in vivo muscles subjected to ECC. Here, we provide evidence that dihydropyridine receptor and junctophilin, but not ryanodine receptor and sarcoplasmic reticulum Ca2+-ATPase, undergo calpain-dependent proteolysis.
- Confidence in the curve: Establishing instantaneous cost mapping techniques using bilateral ankle exoskeletons
We are presenting novel subject-specific metabolic cost landscape confidence analyses. These confidence analyses can greatly improve experimental design, intersubject analysis, and the comparison of landscape mapping protocols. We validated these methods by mapping subject-specific metabolic cost landscapes using bilateral ankle exoskeletons and are presenting the first full study using instantaneous cost mapping techniques to optimally tune an assistive robotic device.
- Commentaries on Viewpoint: Human skeletal muscle wasting in hypoxia: a matter of hypoxic dose?INFLUENCE OF THE BETWEEN-SUBJECTS AND BETWEEN-HYPOXIC CONDITIONS VARIABILITY IN OXIDATIVE STRESSSKELETAL MUSCLE WASTING IN HYPOXIA; A MATTER OF ALTITUDECOMMENTARY ON VIEWPOINT: HUMAN SKELETAL MUSCLE WASTING IN HYPOXIA: A MATTER OF HYPOXIC DOSE?A DOSE OF 5,000 KM·H OF SEVERE HYPOXIA (AT > 5,000 m ALTITUDE) IS PROBABLY REQUIRED TO INDUCE SKELETAL MUSCLE WASTING IN HUMANSA LESSER MUSCLE HYPERTROPHIC RESPONSE TO RESISTANCE TRAINING BELOW THE HYPOXIC DOSE OF 5,000 KM·HCOMMENTARY ON VIEWPOINT: HUMAN SKELETAL MUSCLE WASTING IN HYPOXIA: A MATTER OF HYPOXIC DOSE?COMMENTARY ON VIEWPOINT: HUMAN SKELETAL MUSCLE WASTING IN HYPOXIA: A MATTER OF HYPOXIC DOSE?
- Commentaries on Viewpoint: Anemia contributes to cardiovascular disease through reductions in nitric oxideCOMMENTARY ON VIEWPOINT: ANEMIA CONTRIBUTES TO CARDIOVASCULAR DISEASE THROUGH REDUCTIONS IN NITRIC OXIDECAN EXERCISE IN HYPOXIA ALLEVIATE NO-DEPENDENT DETRIMENTAL EFFECTS OF ANEMIA?COMMENTARY ON VIEWPOINT: ANEMIA CONTRIBUTES TO CARDIOVASCULAR DISEASE THROUGH REDUCTIONS IN NITRIC OXIDE