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American Journal of Physiology. Regulatory, Integrative and Comparative Physiology

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https://www.readbyqxmd.com/read/29791205/physiologic-hyperinsulinemia-caused-by-acute-hyperglycemia-minimizes-renal-sodium-loss-by-direct-action-on-the-kidney
#1
Debra L Irsik, Michael W Brands
This study used acute, renal-artery insulin infusion in conscious rats to test the hypothesis that hyperinsulinemia attenuates glucose-induced natriuresis by a direct renal mechanism. We reported previously that hyperinsulinemia was required to prevent ad libitum eating or an acute glucose bolus from causing excessive renal sodium loss. Rats were instrumented with renal artery, aortic, and femoral vein catheters and DSI blood pressure telemeters and were housed in metabolic cages. Insulin was clamped chronically at normal levels in two groups (irV and irI) by administering streptozotocin and then infusing insulin iv...
May 23, 2018: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
https://www.readbyqxmd.com/read/29791204/role-of-adenosine-signaling-in-coordinating-cardiomyocyte-function-and-coronary-vascular-growth-in-chronic-fetal-anemia
#2
Lowell Davis, James Musso, Divya Soman, Samantha Louey, Jonathan William Nelson, Sonnet S Jonker
Fetal anemia causes rapid and profound changes in cardiac structure and function, stimulating proliferation of the cardiac myocytes, expansion of the coronary vascular tree, and impairing early contraction and relaxation. While HIF-1α is sure to play a role, adenosine, a metabolic byproduct that increases coronary flow and growth, is implicated as a major stimulus for these adaptations. We hypothesized that genes involved in myocardial adenosine signaling would be up-regulated in chronically anemic fetuses, and that calcium handling genes would be down-regulated...
May 23, 2018: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
https://www.readbyqxmd.com/read/29791203/short-term-thermoneutral-housing-alters-glucose-metabolism-and-markers-of-adipose-tissue-browning-in-response-to-a-high-fat-diet-in-lean-mice
#3
Zachary Stephen Clayton, Carrie E McCurdy
Systemic insulin resistance and glucose intolerance occur with as little as 3 days of a high-fat diet (HFD) in mice and humans; the mechanisms that initiate acute insulin resistance are unknown. Most laboratories house mice at 22{degree sign}C, which is below their thermoneutral temperature (~30{degree sign}C). Cold stress has been shown to increase white adipose tissue (WAT) browning, alter lipid trafficking and impair immune function, while energy intake and expenditure decrease with increasing ambient temperature; importantly, dysregulation of these parameters have been strongly linked to obesity-induced insulin resistance...
May 23, 2018: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
https://www.readbyqxmd.com/read/29768036/greater-reductions-in-fat-preferences-in-calhm1-than-cd36-knockout-mice
#4
Anthony Sclafani, Karen Ackroff
Several studies indicate an important role of gustation in intake and preference for dietary fat. The present study compared fat preference deficits produced by deletion of CD36, a putative fatty acid taste receptor, and CALHM1, an ion channel responsible for release of the ATP neurotransmitter used by taste cells. Naïve CD36 knockout (KO) mice displayed reduced preferences for soybean oil emulsions (Intralipid) at low concentrations (0.1-1%) compared to wildtype (WT) mice in 24 h/day two-bottle tests. CALHM1 KO mice displayed even greater Intralipid preference deficits compared to WT and CD36 KO mice...
May 16, 2018: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
https://www.readbyqxmd.com/read/29768035/microgravity-induced-ocular-changes-are-related-to-body-weight
#5
Jay C Buckey, Scott D Phillips, Allison P Anderson, Ariane B Chepko, Veronique Archambault-Leger, Jiang Gui, Abigail M Fellows
On Earth, tissue weight generates compressive forces that press on body structures and act on the walls of vessels throughout the body. In microgravity tissues no longer have any weight and tissue compressive forces are lost, suggesting individuals who weigh more may show greater effects from microgravity exposure. One unique effect of long-duration microgravity exposure is the spaceflight-associated neuro-ocular syndrome (SANS) which can present with globe flattening, choroidal folds, optic disc edema, and a hyperopic visual shift...
May 16, 2018: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
https://www.readbyqxmd.com/read/29741932/to-hypertrophy-and-beyond-myostatin-and-its-association-to-intermuscular-adipose-tissue-with-exercise-and-aging
#6
Kevin Andrew Murach
No abstract text is available yet for this article.
May 9, 2018: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
https://www.readbyqxmd.com/read/29741931/arginase-up-regulation-and-enos-uncoupling-contribute-to-impaired-endothelium-dependent-vasodilation-in-a-rat-model-of-intrauterine-growth-restriction
#7
Isabelle Grandvuillemin, Christophe Buffat, Farid Boubred, Edouard Lamy, Julien Fromonot, Philippe Charpiot, Stephanie Simoncini, Florence Sabatier, Françoise Dignat-George, Anne-Christine Peyter, Umberto Simeoni, Catherine Yzydorczyk
Individuals born after intrauterine growth restriction (IUGR) are at increased risk of developing cardiovascular diseases in adulthood, notably hypertension (HTN). Alterations in the vascular system, particularly impaired endothelium-dependent vasodilation, may play an important role in long-term effects of IUGR. Whether such vascular dysfunction precedes HTN has not been fully established in individuals born after IUGR. Moreover, the intimate mechanisms of altered endothelium-dependent vasodilation remain incompletely elucidated...
May 9, 2018: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
https://www.readbyqxmd.com/read/29741930/highly-sensitive-index-of-cardiac-autonomic-control-based-on-time-varying-respiration-derived-from-ecg
#8
Pierre Gilfriche, Laurent M Arsac, Yannick Daviaux, Jaime Diaz-Pineda, Brice Miard, Olivier Morellec, Jean-Marc André
Frequency-domain indices of Heart Rate Variability (HRV) have been used as a marker of sympathovagal balance. However, they have been shown to be degraded by inter-individual or task-dependent variability, and especially breathing frequency. The study introduces a new method for analyzing respiratory (vagally) mediated Heart Rate Variability, to better assess subtle variations in sympathovagal balance, using ECG information. We evaluated the sensitivity of our new method comparatively to classic HRV analyses with cognitive workload...
May 9, 2018: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
https://www.readbyqxmd.com/read/29741929/is-activation-of-human-brown-adipose-tissue-a-viable-target-for-weight-management
#9
Kara L Marlatt, Kong Y Chen, Eric Ravussin
To date, human studies show that BAT contributes a small, yet highly variable amount to overall energy expenditure. No studies have shown a decrease in body weight with cold-induced BAT activation, and existing pharmacologic studies suggest that BAT activation via the sympathetic nervous system may result in increased heart rate and systolic blood pressure. Furthermore, even though the amount and/or activity of BAT have been shown to vary with seasons, such variation does not seem to be translated into weight changes...
May 9, 2018: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
https://www.readbyqxmd.com/read/29718700/relationship-between-intermuscular-adipose-tissue-infiltration-and-myostatin-before-and-after-aerobic-exercise-training
#10
Adam R Konopka, Christopher A Wolff, Miranda K Suer, Matthew P Harber
Intermuscular adipose tissue (IMAT) is associated with impaired skeletal muscle contractile and metabolic function. Myostatin and downstream signaling proteins such as cyclin-dependent kinase 2 (CDK2) contribute to the regulation of adipose and skeletal muscle mass in cell culture and animals models but this relationship remains incompletely understood in humans. The purpose of this study was to determine if the infiltration of IMAT was associated with skeletal muscle myostatin and downstream proteins before and after 12-weeks of aerobic exercise training (AET) in healthy older women (OW; 69{plus minus}2y), older men (OM; 74{plus minus}3y) and young men (YM; 20{plus minus}1y)...
May 2, 2018: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
https://www.readbyqxmd.com/read/29718699/effect-of-a-melanocortin-type-2-receptor-mc2r-antagonist-on-the-corticosterone-response-to-hypoxia-and-acth-stimulation-in-the-neonatal-rat
#11
Adam J Goldenberg, Ashley L Gehrand, Emily Waples, Mack Jablonski, Brian Hoeynck, Hershel Raff
The adrenal stress response in the neonatal rat shifts from ACTH-independent to ACTH-dependent between postnatal days 2 (PD2) and 8 (PD8). This may be due to an increase in an endogenous, bioactive, non-immunoreactive ligand to the MC2R. GPS1574 is a newly described MC2R antagonist that we have shown to be effective in vitro. Further experimentation with GPS1574 would allow better insight into this seemingly ACTH-independent steroidogenic response in neonates. We evaluated the acute corticosterone response to hypoxia or ACTH injection following pretreatment with GPS1574 (32 mg/kg) or Vehicle for GPS1574 in PD2, PD8, and PD15 rat pups...
May 2, 2018: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
https://www.readbyqxmd.com/read/29718698/placental-ischemia-stimulated-t-helper-17-cells-induce-preeclampsia-associated-cytolytic-natural-killer-cells-during-pregnancy
#12
Corbin A Shields, Maggie McCalmon, Tarek Ibrahim, Dakota L White, Jan Michael Williams, Babbette D LaMarca, Denise C Cornelius
Previous studies have demonstrated that T-helper 17 cells (TH 17s) and cytolytic NK cells (cNKs) are increased in women with preeclampsia (PE). In this study, we investigated the role of placental ischemia-stimulated TH 17s to induce cNKs in pregnancy. We further assessed the role of TH 17-mediated oxidative stress to facilitate cNK activation in pregnancy by treating with the SOD mimetic tempol. CD4+ /CD25- cells were isolated from reduced uterine perfusion pressure (RUPP) rats and differentiated into TH 17 cells in vitro...
May 2, 2018: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
https://www.readbyqxmd.com/read/29718697/znt2-is-critical-for-lysosome-acidification-and-biogenesis-during-mammary-gland-involution
#13
Olivia C Rivera, Stephen R Hennigar, Shannon L Kelleher
Mammary gland involution is a tightly regulated process of tissue remodeling by which a lactating mammary gland reverts to the pre-pregnant state, and is characterized by the most profound example of regulated epithelial cell death in normal tissue. Defects in the execution of involution are associated with lactation failure and breast cancer. Initiation of mammary gland involution requires upregulation of lysosomal biogenesis and acidification to activate lysosomal-mediated cell death (LCD); however, specific mediators of this initial phase of involution are not well-described...
May 2, 2018: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
https://www.readbyqxmd.com/read/29718696/electrical-excitability-of-roach-rutilus-rutilus-ventricular-myocytes-effects-of-extracellular-k-temperature-and-pacing-frequency
#14
Ahmed Badr, El-Sabry Abu-Amra, Mohamed Farag El-Sayed, Matti Vornanen
Exercise, capture and handling stress in fishes can elevate extracellular K+ concentration ([K+ ]o ) with potential impact on heart function. Therefore, effects of [K+ ]o on excitability of ventricular myocytes of winter-acclimatized roach (Rutilus rutilus) (4{plus minus}0.5{degree sign}C) were examined at different temperatures and pacing rates. Frequencies corresponding to in vivo heart rates at 4{degree sign}C (0.37Hz), 14{degree sign}C (1.16Hz) and 24{degree sign}C (1.96Hz) had no effect on excitability of myocytes...
May 2, 2018: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
https://www.readbyqxmd.com/read/29693432/phosphodiesterase-pde-4b-knock-out-prevents-skeletal-muscle-atrophy-in-rats-with-burn-injury
#15
Ambikaipakan Balasubramaniam, Sulaiman Sheriff, Lou Ann Friend, J Howard James
PDE4-cAMP pathway plays a predominant role in mediating skeletal muscle proteolysis in burn injury. The present investigations to determine the PDE4 isoform(s) involved in this action revealed that burn injury increased the expression of rat skeletal muscle PDE4B mRNA by 6-fold, but had little or no effect on expression of other PDE4 isoforms. These observations led us to study the effects of burn in PDE4B KO-rats. As reported by us previously, burn injury significantly increased EDL muscle total and myofibrillar proteolysis in WT-rats, but there were no significant effects on either total or myofibrillar protein breakdown in EDL muscle of PDE4B KO-rat with burn injury...
April 25, 2018: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
https://www.readbyqxmd.com/read/29693431/maximum-heart-rate-does-not-limit-cardiac-output-at-rest-or-during-exercise-in-the-american-alligator-alligator-mississippiensis
#16
William Joyce, Ruth M Elsey, Tobias Wang, Dane A Crossley Nd
In most vertebrates, increases in cardiac output result from increases in heart rate (fH ) with little or no change in stroke volume (Vs), and maximum cardiac output (Q̇) is typically attained at or close to maximum fH . We therefore tested the hypothesis that increasing maximum fH may increase maximum Q̇. To this end, we investigated the effects of elevating fH with right atrial pacing on Q̇ in the American alligator (Alligator mississippiensis) at rest and whilst swimming. During normal swimming, Q̇ increased entirely by virtue of a tachycardia (29 {plus minus} 1 to 40 {plus minus} 3 beats min-1 ) whilst Vs remained stable...
April 25, 2018: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
https://www.readbyqxmd.com/read/29693430/editorial-focus-interrogating-the-central-melanocortin-system-choosing-the-right-model
#17
Gina L C Yosten
No abstract text is available yet for this article.
April 25, 2018: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
https://www.readbyqxmd.com/read/29693429/ergogenic-effects-of-beetroot-juice-supplementation-during-severe-intensity-exercise-in-obese-adolescents
#18
Letizia Rasica, Simone Porcelli, Mauro Marzorati, Desy Salvadego, Alessandra Vezzoli, Fiorenza Agosti, Alessandra De Col, Gabriella Tringali, Andrew M Jones, Alessandro Sartorio, Bruno Grassi
Previous studies showed a higher O2 cost of exercise, and therefore a reduced exercise tolerance, in obese patients during constant work rate (CWR) exercise compared to healthy subjects. Among the ergogenic effects of dietary nitrate (NO3 -) supplementation in sedentary healthy subjects, a reduced O2 cost and enhanced exercise tolerance have often been demonstrated. The aim of this study was to evaluate the effects of beetroot juice supplementation, rich in NO3 -, on physiological variables associated with exercise tolerance in obese adolescents...
April 25, 2018: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
https://www.readbyqxmd.com/read/29668326/effects-of-aging-and-exercise-training-on-leg-hemodynamics-and-oxidative-metabolism-in-the-transition-from-rest-to-steady-state-exercise-role-of-cgmp-signaling
#19
Peter Piil, Tue Smith Jørgensen, Jon Egelund, Nicolai Rytter, Lasse Gliemann, Jens Bangsbo, Ylva Hellsten, Michael Nyberg
Aging is associated with slower skeletal muscle O2 uptake (VO2 ) kinetics; however, the mechanisms underlying this effect of age are unclear. Also, the effects of exercise training in elderly on the initial vascular and metabolic response to exercise remain to be elucidated. We measured leg hemodynamics and oxidative metabolism in the transition from rest to steady state exercise engaging the knee-extensor muscles in young (n=15, 25{plus minus}1 years) and older (n=15, 72{plus minus}1 years) subjects before and after a period of aerobic high-intensity exercise training...
April 18, 2018: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
https://www.readbyqxmd.com/read/29668325/is-cushing-mechanism-a-dynamic-blood-pressure-stabilizing-system-insights-from-granger-causality-analysis-of-spontaneous-blood-pressure-and-cerebral-blood-flow
#20
Saqib Saleem, Paul D Teal, Connor A Howe, Michael M Tymko, Philip N Ainslie, Yu-Chieh Tzeng
Blood pressure regulation is widely recognised as being integral to the control of end-organ perfusion but it remains unclear whether end-organ perfusion also plays a role in driving changes in blood pressure (BP). A randomized and placebo controlled study design was followed to examine the feedback relationships between very-low-frequency fluctuations in BP and cerebral blood flow (CBF) in humans under placebo treatment and α1-adrenergic blockade. To determine the causal relations among haemodynamic variables, BP, middle cerebral artery blood velocity (MCAv), and end-tidal CO2 time-series were decimated, low-pass filtered (<0...
April 18, 2018: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
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