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American Journal of Physiology. Regulatory, Integrative and Comparative Physiology

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https://www.readbyqxmd.com/read/29995459/models-of-intermittent-hypoxia-and-obstructive-sleep-apnea-molecular-pathways-and-their-contribution-to-cancer
#1
Imre Hunyor, Kristina M Cook
Obstructive sleep apnea (OSA) is common and linked to a variety of poor health outcomes. A key modulator of this disease is nocturnal intermittent hypoxia. There is striking epidemiological evidence that patients with OSA have higher rates of cancer and cancer mortality. Small animal models demonstrate an important role for systemic intermittent hypoxia in tumor growth and metastasis, yet underlying mechanisms are poorly understood. Emerging data indicates that intermittent hypoxia activates the hypoxic response and inflammatory pathways in a manner distinct from chronic hypoxia...
July 11, 2018: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
https://www.readbyqxmd.com/read/29995458/differential-influence-of-vitamin-c-on-the-peripheral-and-cerebral-circulation-following-diving-and-exposure-to-hyperoxia
#2
Otto F Barak, Kresimir Caljkusic, Ryan L Hoiland, Philip N Ainslie, Stephen R Thom, Ming Yang, Pavle Jovanov, Zeljko Dujic
We examined if the diving-induced vascular changes in the peripheral and cerebral circulation could be prevented by oral antioxidant supplementation. Fourteen divers performed a single SCUBA dive to 18 msw for 47 mins. Twelve of the divers participated in a follow-up study involving breathing 60% oxygen at ambient pressure for 47 mins. Prior to both studies, participants ingested vitamin C (2g/day) or a placebo capsule for six days. After two-week washout, the study was repeated with the different condition...
July 11, 2018: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
https://www.readbyqxmd.com/read/29995457/the-impact-of-age-on-the-development-of-fatigue-during-large-and-small-muscle-mass-exercise
#3
Joshua C Weavil, Thomas J Hureau, Taylor S Thurston, Simranjit K Sidhu, Ryan S Garten, Ashley D Nelson, Chris J McNeil, Russell S Richardson, Markus Amann
AIM: To examine the impact of aging on neuromuscular fatigue following cycling (CYC; large active muscle mass) and single-leg knee-extension (KE; small active muscle mass) exercise. METHODS: Eight young (25±4years) and older (72±6years) participants performed CYC and KE to task-failure at a given relative intensity (80% of peak power output). The young also matched CYC and KE workload and duration of the old (iso-work comparison). Peripheral- and central-fatigue were quantified via pre/post-exercise decreases in quadriceps twitch-torque (∆Qtw, electrical femoral nerve stimulation) and voluntary activation (∆VA)...
July 11, 2018: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
https://www.readbyqxmd.com/read/29995456/mef2-as-upstream-regulator-of-the-transcriptome-signature-in-human-skeletal-muscle-during-unloading
#4
Eric Rullman, Rodrigo Fernandez-Gonzalo, Igor B Mekjavić, Thomas Gustaffsson, Ola Eiken
Our understanding of skeletal muscle structural and functional alterations during unloading has increased in recent decades, yet the molecular mechanisms underpinning these changes have only started to be unraveled. The purpose of the current investigation was to assess changes in skeletal muscle gene expression after 21 days of bed rest, with a particular focus on predicting upstream regulators of muscle disuse. Additionally, the association between differential microRNA expression and the transcriptome signature of bed rest were investigated...
July 11, 2018: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
https://www.readbyqxmd.com/read/29975567/directional-sensitivity-of-dynamic-cerebral-autoregulation-in-squat-stand-maneuvers
#5
Ronney B Panerai, Sam C Barnes, Mintu Nath, Naomi Ball, Thompson G Robinson, Victoria J Haunton
Dynamic cerebral autoregulation (CA), the transient response of cerebral blood flow (CBF) to rapid changes in arterial blood pressure (BP), is usually modelled as a linear mechanism. We tested the hypothesis that dynamic CA can display non-linear behavior resulting from differential efficiency dependent on the direction of BP changes. CBF velocity (CBV, transcranial Doppler), heart rate (HR, 3-lead ECG), continuous BP (Finometer) and end-tidal CO2 (capnograph) were measured in 10 healthy young subjects during 15 squat-stand maneuvers (SSM) with a frequency of 0...
July 5, 2018: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
https://www.readbyqxmd.com/read/29975566/folic-acid-supplementation-improves-vascular-endothelial-function-yet-not-skin-blood-flow-during-exercise-in-the-heat-in-patients-with-heart-failure
#6
Bryce Nicholas Balmain, Ollie Jay, Norman R Morris, Glenn Malcolm Stewart, Kenji Shiino, Amelia J McFarland, Rohan Jayasinghe, Jonathan Chan, Surendran Sabapathy
Heart failure (HF) patients are susceptible to heat strain during exercise, secondary to blunted skin blood flow (SkBF) responses which may be explained by impaired nitric oxide (NO)-dependent vasodilation. Folic acid improves vascular endothelial function and SkBF through NO-dependent mechanisms in healthy older individuals and cardiovascular disease patients. We examined the effect of folic acid supplementation (5 mg/d for 6wk) on vascular function (brachial artery flow-mediated dilation [FMD]), and SkBF responses (cutaneous vascular conductance [CVC]) during 60-min of exercise at a fixed metabolic heat production (300 ẆHprod ) in a 30{degree sign}C environment in ten HF (New York Heart Association Class I-II) patients and ten healthy controls (CON)...
July 5, 2018: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
https://www.readbyqxmd.com/read/29975565/cardiovascular-responses-to-cold-and-submaximal-exercise-in-patients-with-coronary-artery-disease
#7
Rasmus I P Valtonen, Antti Kiviniemi, Heidi E Hintsala, Niilo R I Ryti, Tuomas Kenttä, Heikki V Huikuri, Juha Perkiömäki, Craig G Crandall, Wouter David van Marken-Liechtenbelt, Markku Alen, Hannu Rintamäki, Matti Mäntysaari, Arto Hautala, Jouni J K Jaakkola, Tiina Maria Ikaheimo
INTRODUCTION: Regular year-round exercise is recommended for patients with coronary artery disease (CAD). However, the combined effects of cold and moderate sustained exercise, both known to increase cardiac workload, on cardiovascular responses are not known. We tested the hypothesis that cardiac workload is increased and evidence of ischemia would be observed during exercise in the cold in patients with CAD. METHODS: Sixteen men (59.3{plus minus}7.0 years, mean{plus minus}SD), with stable CAD underwent each four 30-min exposures in a randomized order: seated rest and moderate-intensity exercise (walking, 60-70% of HRmax) performed at +22{degree sign}C and -15{degree sign}C...
July 5, 2018: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
https://www.readbyqxmd.com/read/29949411/purinergic-plasticity-within-petrosal-neurons-in-hypertension
#8
Davi J A Moraes, Melina P da Silva, Pedro F Spiller, Benedito H Machado, Julian F R Paton
The carotid bodies are peripheral chemoreceptors and contribute to the homeostatic maintenance of arterial levels of O2 , CO2 and [H+ ]. They have attracted much clinical interest recently because of the realisation that aberrant signalling in these organs is associated with several pathologies including hypertension. Herein, we describe data suggesting that sympathetic overactivity in neurogenic hypertension is, at least in part, dependent on carotid body tonicity and hyperreflexia that is related to changes in the electrophysiological properties of chemoreceptive petrosal neurons...
June 27, 2018: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
https://www.readbyqxmd.com/read/29949410/oleoylethanolamide-modulates-glucagon-like-peptide-1-receptor-agonist-signaling-and-enhances-exendin-4-mediated-weight-loss-in-obese-mice
#9
Jacob D Brown, Danielle McAnally, Jennifer E Ayala, Melissa A Burmeister, Camilo Morfa, Layton Smith, Julio E Ayala
Long-acting glucagon-like peptide-1 (GLP1) receptor (GLP1R) agonists (GLP1RA), like Exendin-4 (Ex4), promote weight loss. Based on a newly-discovered interaction between GLP1 and oleoylethanolamide (OEA), we tested whether OEA enhances GLP1RA-mediated anorectic signaling and weight loss. We analyzed the effect of GLP1+OEA and Ex4+OEA on canonical GLP1R signaling and other proteins/pathways that contribute to the hypophagic action of GLP1RA (AMPK, Akt, mTOR and glycolysis). We demonstrate that OEA enhances canonical GLP1R signaling when combined with GLP1 but not with Ex4...
June 27, 2018: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
https://www.readbyqxmd.com/read/29949409/exercise-cardiac-magnetic-resonance-imaging-a-feasibility-study-and-meta-analysis
#10
Rhys I Beaudry, Thomas Jake Samuel, Jing Wang, Wesley J Tucker, Mark J Haykowsky, Michael D Nelson
Cardiac stress testing improves detection and risk assessment of heart disease. Magnetic resonance imaging (MRI) is the clinical gold-standard for assessing cardiac morphology and function at rest; however, exercise MRI has not been widely adapted for cardiac assessment due to imaging and device limitations. Commercially available MR ergometers, together with improved imaging sequences, have overcome many previous limitations, making cardiac stress MRI more feasible. Here, we aimed to demonstrate clinical feasibility, and establish the normative, healthy response to supine exercise MRI...
June 27, 2018: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
https://www.readbyqxmd.com/read/29949408/absent-increase-in-vertebral-artery-blood-flow-during-l-arginine-infusion-in-hypertensive-men
#11
Lauro C Vianna, Igor A Fernandes, Thales C Barbosa, Tatiana G Amaral, Natalia Galito Rocha, Niels H Secher, Antonio Claudio Lucas da Nóbrega
Endothelial dysfunction is observed in the peripheral vasculature of hypertensive patients, but it is unclear how the cerebral circulation is affected. More specifically, little is known about the impact of human hypertension on vertebral artery (VA) endothelial function. This study evaluated whether the endothelial function of the VA is impaired in hypertensive men. For 13 male hypertensive subjects (46{plus minus}3 years) and 8 age-matched male controls (46{plus minus}4 years), blood pressure (photoplethysmography), VA and common carotid (CC) blood flow (duplex ultrasound) were determined at rest and during 30-min of intravenous L-arginine (30-g, a precursor of nitric oxide) or isotonic saline infusion...
June 27, 2018: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
https://www.readbyqxmd.com/read/29949407/alterations-in-dietary-sodium-intake-affects-cardiovagal-baroreflex-sensitivity
#12
Matthew C Babcock, Michael S Brian, Joseph Charles Watso, David G Edwards, Sean D Stocker, Megan M Wenner, William B Farquhar
High dietary sodium intake has been linked to alterations in neurally mediated cardiovascular function, but the effects of high sodium on cardiovagal baroreflex sensitivity (cBRS) in healthy adults are unknown. PURPOSE: To determine whether high dietary sodium alters cBRS and heart rate variability (HRV), and whether acute intravenous (IV) sodium loading similarly alters cBRS and HRV. METHODS: High dietary sodium (300 mmol/day, 7 days) was compared to low sodium (20 mmol/day, 7 days; randomized) in 14 participants (age: 38{plus minus}4 yrs, BMI: 23{plus minus}1 kg/m2 , 7 women)...
June 27, 2018: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
https://www.readbyqxmd.com/read/29924632/heat-shock-protein-72-regulates-hepatic-lipid-accumulation
#13
Ashley E Archer, Robert S Rogers, Alex T Von Schulze, Joshua L Wheatley, E Matthew Morris, Colin S McCoin, John P Thyfault, Paige C Geiger
Induction of the chaperone Heat Shock Protein 72 (HSP72) through heat treatment, exercise, or overexpression improves glucose tolerance and mitochondrial function in skeletal muscle. Less is known about HSP72 function in the liver where lipid accumulation can result in insulin resistance and Nonalcoholic Fatty Liver Disease (NAFLD). The purpose of this study was 1) to determine whether weekly in vivo heat treatment (HT) induces hepatic HSP72 and improves glucose tolerance in rats fed a high-fat diet (HFD) and 2) to determine the ability of HSP72 to protect against lipid accumulation and mitochondrial dysfunction in primary hepatocytes...
June 20, 2018: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
https://www.readbyqxmd.com/read/29924631/effects-of-postweaning-calorie-restriction-on-accelerated-growth-and-adiponectin-in-nutritionally-programmed-microswine-offspring
#14
Elizabeth A DuPriest, Baoyu Lin, Philipp Kupfer, Kaiu Sekiguchi, Amruta Bhusari, Alexandra Quackenbush, Almir Celebic, Terry K Morgan, Jonathan Q Purnell, Susan Pound Bagby
Poor prenatal development followed by rapid childhood growth conveys greater cardiometabolic risk in later life. Microswine offspring exposed to perinatal maternal protein restriction (MPR; "low protein offspring", LPO) grow poorly in late-fetal/neonatal stages. After weaning to ad libitum (AL) diet, LPO-AL exhibit accelerated growth and fat deposition rates with low adiponectin mRNA despite low-normal body fat and small intra-abdominal adipocytes. We examined effects of caloric restriction (CR) on growth and metabolic status in LPO and normal protein offspring (NPO) randomized to AL or CR diets from weaning...
June 20, 2018: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
https://www.readbyqxmd.com/read/29897824/the-risk-of-cardiovascular-disease-end-stage-renal-disease-and-stroke-in-post-partum-women-and-their-fetuses-after-a-hypertensive-pregnancy
#15
Mark W Cunningham, Babbette D LaMarca
Women with hypertensive pregnancy complications are at greater risk of developing cardiovascular disease (CVD), metabolic diseases, stroke, and end-stage renal disease later in life. Pregnancy complications not only effect the mother's long-term health, but also the health of the fetus immediately after delivery and into adulthood. The health of the fetus until adulthood can be influenced by developmental programming, in which the fetus is exposed to insults that will ultimately affect the growth of the offspring and increase the offspring's risk of developing hypertension, coronary heart disease, metabolic disease, and chronic kidney disease in adulthood...
June 13, 2018: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
https://www.readbyqxmd.com/read/29897823/preoptic-area-cooling-increases-the-sympathetic-outflow-to-brown-adipose-tissue-bat-and-bat-thermogenesis
#16
Mazher Mohammed, Christopher J Madden, Kim J Burchiel, Shaun F Morrison
Modest cold exposures are likely to activate autonomic thermogenic mechanisms due to activation of cutaneous thermal afferents, whereas central thermosensitive neurons set the background tone on which this afferent input is effective. In addition, more prolonged or severe cold exposures that overwhelm cold defense mechanisms would directly activate thermosensitive neurons within the central nervous system. Here, we examined the involvement of the canonical brown adipose tissue (BAT) sympathoexcitatory efferent pathway in the response to direct local cooling of the preoptic area (POA) in urethane-chloralose anesthetized rats...
June 13, 2018: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
https://www.readbyqxmd.com/read/29897822/energy-compensation-in-response-to-aerobic-exercise-training-in-overweight-adults
#17
Kyle D Flack, Kelsey Elise Ufholz, LuAnn K Johnson, John S Fitzgerald, James N Roemmich
BACKGROUND: Weight loss from exercise is often less than expected. Putative compensatory mechanisms may limit exercise-induced reductions in body fat and might be proportional to exercise energy expenditure. PURPOSE: To determine compensation (difference between accumulated exercise energy expenditure and changes in body tissue energy stores) and compensatory responses to 1500 or 3000 kcal/week of exercise energy expenditure. METHODS: Overweight to obese (n=36) sedentary men and women were randomized to groups expending 300 or 600 kcal/exercise session, 5 days/week, for 12 weeks...
June 13, 2018: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
https://www.readbyqxmd.com/read/29897821/microvascular-adaptations-to-resistance-training-are-independent-of-load-in-resistance-trained-young-men
#18
Tanya M Holloway, Robert W Morton, Sara Y Oikawa, Sean McKellar, Steven K Baker, Stuart M Phillips
Resistance training promotes microvasculature expansion; however, it remains unknown how different resistance training programs contribute to angiogenesis. Thus, we recruited experienced resistance trained participants and determined the effect of 12 wk of either high-repetition/low-load or low-repetition/high-load resistance training performed to volitional fatigue on muscle microvasculature. Twenty men performed either a high-repetition (20-25 repetitions, 30-50% of 1RM; n=10) or a low-repetition (8-12 repetitions, 75-90% of 1RM; n=10) resistance training program...
June 13, 2018: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
https://www.readbyqxmd.com/read/29897820/time-course-of-changes-in-maternal-left-ventricular-function-during-subsequent-pregnancy-in-women-with-a-history-of-gestational-hypertensive-disorders
#19
Michinari Hieda, Jeung-Ki Yoo, Dan-Dan Sun, Yoshiyuki Okada, Rosemary S Parker, Monique A Roberts-Reeves, Beverley Adams-Huet, David B Nelson, Benjamin D Levine, Qi Fu
Women with a history of gestational hypertensive disorders (GHD) are at increased risk for developing perinatal cardiovascular complications (e.g., gestational hypertension, preeclampsia, etc.) in subsequent pregnancies. The underlying mechanisms remain uncertain, but impaired maternal left ventricular function may be one contributing factor for these complications. We evaluated the time course of changes in left ventricular function before, during and after pregnancy in women with prior GHD. Sixteen women with a history of GHD (the high-risk group), and 25 women without such a history (controls) were enrolled...
June 13, 2018: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
https://www.readbyqxmd.com/read/29897819/lesion-of-the-ovlt-markedly-attenuates-chronic-deoxycorticosterone-acetate-doca-salt-hypertension-in-the-rat
#20
John P Collister, David B Nahey, Rochelle Hartson, Charles E Wiedmeyer, Christopher T Banek, John W Osborn
Lesions of the anteroventral third ventricle (AV3V region) are known to prevent many forms of experimental hypertension, including mineralocorticoid (DOCA-salt) hypertension in the rat. However, AV3V lesions include the organum vasculosum of the lamina terminalis (OVLT), portions of the median preoptic nucleus, as well as efferent fibers from the subfornical organ (SFO), thereby limiting the ability to define the individual contribution of these structures to the prevention of experimental hypertension. Having previously reported that the SFO does not play a significant role in the development of DOCA-salt hypertension, the present study was designed to test the hypothesis that the OVLT is necessary for DOCA-salt hypertension in the rat...
June 13, 2018: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
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