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American Journal of Physiology. Regulatory, Integrative and Comparative Physiology

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https://www.readbyqxmd.com/read/28515081/flexible-ammonia-handling-strategies-using-both-cutaneous-and-branchial-epithelia-in-the-highly-ammonia-tolerant-pacific-hagfish
#1
Alexander M Clifford, Alyssa M Weinrauch, Susan L Edwards, Michael P Wilkie, Greg G Goss
Hagfish consume carrion, potentially exposing them to hypoxia, hypercarbia, and high environmental ammonia (HEA). We investigated branchial and cutaneous ammonia handling strategies by which Pacific hagfish (Eptatretus stoutii) tolerate and recover from high ammonia loading. Hagfish were exposed to HEA (20 mmol L(-1)) for 48 h to elevate plasma total ammonia (TAmm) levels before placement into divided chambers for a 4 h recovery period in ammonia-free seawater where ammonia excretion (JAmm) was measured independently in the anterior and posterior compartments...
May 17, 2017: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
https://www.readbyqxmd.com/read/28515080/effect-of-resistance-exercise-under-conditions-of-reduced-blood-insulin-on-ampk%C3%AE-ser485-491-inhibitory-phosphorylation-and-ampk-pathway-activation
#2
Kohei Kido, Takumi Yokokawa, Satoru Ato, Koji Sato, Satoshi Fujita
Insulin stimulates skeletal muscle glucose uptake via activation of the protein kinase B/Akt (Akt) pathway. Recent studies suggest that insulin down-regulates AMP-activated protein kinase (AMPK) activity via Ser485/491 phosphorylation of the AMPK α-subunit. Thus, lower blood insulin concentrations may induce AMPK signal activation. Acute exercise is one method to stimulate AMPK activation; however, no study has examined the relationship between blood insulin levels and acute resistance exercise-induced AMPK pathway activation...
May 17, 2017: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
https://www.readbyqxmd.com/read/28515079/impact-of-acetaminophen-consumption-and-resistance-exercise-on-extracellular-matrix-gene-expression-in-human-skeletal-muscle
#3
Shivam H Patel, Andrew C D'Lugos, Erica R Eldon, Donald Curtis, Jared M Dickinson, Chad C Carroll
Acetaminophen (APAP) given during chronic exercise reduces skeletal muscle collagen and cross-linking in rats. We propose that the effect of APAP on muscle ECM may, in part, be mediated by dysregulation of the balance between matrix metalloproteinases (MMPs) and tissue inhibitors of MMPs (TIMPs). The purpose of this study was to evaluate the impact of APAP consumption during acute resistance exercise (RE) on several regulators of the ECM in human skeletal muscle. In a double-blinded, placebo-controlled, randomized cross-over design, recreationally active men (n=8, 25±2yr) performed two trials of knee extension...
May 17, 2017: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
https://www.readbyqxmd.com/read/28490452/role-of-endothelial-nitric-oxide-in-control-of-peripheral-vascular-conductance-during-muscle-metaboreflex-activation
#4
Danielle Senador, Jasdeep Kaur, Alberto Alvarez, Hanna W Hanna, Abhinav C Krishnan, Yasir H Altamimi, Donal S O'Leary
Muscle metaboreflex activation during submaximal dynamic exercise, increases arterial pressure primarily via increases in cardiac output as there is little systemic vasoconstriction. Indeed, in normal animals we have often shown a small, but significant, peripheral vasodilation during metaboreflex activation, which is mediated, at least in part, by release of epinephrine and activation of vascular β2 receptors. We tested whether this vasodilation is in part due to increased release of nitric oxide caused by the rise in cardiac output eliciting endothelium-dependent flow-mediated vasodilation...
May 10, 2017: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
https://www.readbyqxmd.com/read/28490451/evidence-for-intraventricular-secretion-of-angiotensinogen-and-angiotensin-by-the-subfornical-organ-using-transgenic-mice
#5
Khristofor Agassandian, Justin L Grobe, Xuebo Liu, Marianna Agassandian, Anthony P Thompson, Curt D Sigmund, Martin D Cassell
Direct intracerebroventricular injection of angiotensin II causes increases in blood pressure, salt and water intake, presumably mimicking an effect mediated by an endogenous mechanism. The subfornical organ (SFO) is a potential source of cerebrospinal fluid (CSF) angiotensin-I (Ang-I) and angiotensin-II (Ang-II), and thus we hypothesized that the SFO has a secretory function. Endogenous levels of angiotensinogen (AGT) and renin are very low in the brain. We therefore examined the immunohistochemical localization of angiotensin peptides and AGT in the SFO, and AGT in the CSF in two transgenic models over-expressing either human AGT (A+ mice), or both human AGT and human renin (SRA mice) in the brain...
May 10, 2017: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
https://www.readbyqxmd.com/read/28490450/sedentary-conditions-and-enhanced-responses-to-gaba-in-the-rvlm-role-of-the-contralateral-rvlm
#6
Maryetta D Dombrowski, Patrick J Mueller
A sedentary lifestyle is a major risk factor for cardiovascular disease, and both conditions are associated with overactivity of the sympathetic nervous system. Ongoing discharge of sympathetic nerves is regulated by the rostral ventrolateral medulla (RVLM), which in turn is modulated by the primary excitatory and inhibitory neurotransmitters glutamate and γ-amino-butyric acid (GABA), respectively. We reported previously that sedentary conditions enhance GABAergic modulation of sympathoexcitation in the RVLM, despite overall increased sympathoexcitation...
May 10, 2017: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
https://www.readbyqxmd.com/read/28490449/enhanced-insulin-secretion-and-insulin-sensitivity-in-young-lambs-with-placental-insufficiency-induced-intrauterine-growth-restriction
#7
Leticia E Camacho, Xiaochuan Chen, William W Hay, Sean W Limesand
Intrauterine growth restriction (IUGR) is associated with persistent metabolic complications, but information is limited for IUGR infants. We determined glucose-stimulated insulin secretion (GSIS) and insulin sensitivity in young lambs with placental insufficiency-induced IUGR. Lambs with hyperthermia-induced IUGR (n=7) were compared to control lambs (n=8). GSIS was measured at 8±1 days of age, and at 15±1 days body weight-specific glucose utilization rates were measured with radiolabeled D-glucose during a hyperinsulinemic-euglycemic clamp (HEC)...
May 10, 2017: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
https://www.readbyqxmd.com/read/28490448/intermittent-hypoxia-training-blunts-cerebrocortical-presenilin-1-overexpression-and-amyloid-%C3%AE-accumulation-in-ethanol-withdrawn-rats
#8
Myoung-Gwi Ryou, Robert T Mallet, Daniel B Metzger, Marianna E Jung
Abrupt cessation of chronic alcohol consumption triggers signaling cascades that harm vulnerable brain regions and produce neurobehavioral deficits. We have demonstrated that a program of intermittent, normobaric hypoxia training (IHT) in rats prevents neurobehavioral impairment resulting from abrupt ethanol withdrawal (EW). Moreover, EW induced expression of stress-activated protein kinase p38 and presenilin 1 (PS1), the γ-secretase component that produces the neurotoxic amyloid-β (Aβ) peptides, Aβ40 and Aβ42...
May 10, 2017: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
https://www.readbyqxmd.com/read/28468942/sex-specific-effects-of-stress-on-metabolic-and-cardiovascular-disease-are-women-at-a-higher-risk
#9
Margaret O Murphy, Analia S Loria
Cardiovascular disease (CVD) has traditionally been viewed as a male disease; however, the relative risk for obesity and hypertension morbidity and mortality, major risk factors for CVD, is higher for women in the United States. Emerging epidemiological data strongly supports stressful experiences as a modifiable risk factor for obesity, insulin resistance and heart disease in women at all ages. Therefore, primary prevention of these diseases may be associated with both identifying and increasing the knowledge regarding the gender-differences in emotional functioning associated with physiological responses to stress...
May 3, 2017: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
https://www.readbyqxmd.com/read/28450279/autophagy-upregulates-pro-renin-receptor-expression-via-reduction-of-p62-sqstm1-and-activation-of-erk1-2-signaling-pathway-in-podocytes
#10
Caixia Li, Helmy M Siragy
Autophagy plays a major role in podocytes health and disease. P62, also known as Sequestosome-1, is a marker for autophagic activity and is required for the formation and degradation of ubiquitnated protein by autophagy. Knockout of p62 enhanced extracellular signal-regulated kinases (ERK1/2) activity. (Pro)renin receptor (PRR) is expressed in podocytes where it contributes to the homeostasis of these cells. The influence of autophagy on (Pro)renin receptor (PRR) expression is unknown. We hypothesized that in podocytes, upregulation of autophagic activity increases PRR expression via reduction of p62 and stimulation of ERK1/2 signaling pathway...
April 27, 2017: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
https://www.readbyqxmd.com/read/28438765/longitudinal-characterization-of-renal-proximal-tubular-markers-in-normotensive-and-preeclamptic-pregnancies
#11
Elisabeth Codsi, Vesna D Garovic, Maria L Gonzalez-Suarez, Natasa Milic, Kristi S Borowski, Carl H Rose, Norman P Davies, Kianoush Kashani, John C Lieske, Wendy M White
Glomerular damage is common in preeclampsia (PE), but the extent and etiology of tubular injury are not well understood. The aim of this study was to evaluate tubular injury in patients with PE and to assess whether it predates clinical disease. We performed a prospective cohort study of 315 pregnant women who provided urine samples at the end of the second trimester and at delivery. This analysis included women who developed PE (n=15), gestational hypertension (GH) (n=14), and normotensive controls (NC) (n=44)...
April 24, 2017: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
https://www.readbyqxmd.com/read/28438764/neurogenic-hypertension-and-the-secret-of-respiration
#12
Benedito H Machado, Daniel B Zoccal, Davi J A Moraes
In spite of recent advances on the knowledgement of the neural control of cardiovascular function, the cause of sympathetic overactivity in neurogenic hypertension remains unknown. Studies from our laboratory point out that rats submitted to chronic intermittent hypoxia (CIH), an experimental model of neurogenic hypertension, present changes in the central respiratory network that impact the pattern of sympathetic discharge and the levels of arterial pressure. In addition to the fine coordination of respiratory muscle contraction and relaxation, essential for O2 and CO2 pulmonary exchanges, neurons of the respiratory network are precisely connected to the neurons controlling the sympathetic activity in the brainstem...
April 24, 2017: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
https://www.readbyqxmd.com/read/28438763/the-performing-animal-causes-and-consequences-of-body-remodelling-and-metabolic-adjustments-in-red-knots-facing-contrasting-thermal-environments
#13
François Vézina, Alexander R Gerson, Christopher G Guglielmo, Theunis Piersma
Using red knots (Calidris canutus) as a model, we determined how changes in mass and metabolic activity of organs relate to temperature-induced variation in metabolic performance. In cold-acclimated birds, we expected large muscles and heart, improved oxidative capacity and lipid transport, and we predicted that this would explain variation in maximal thermogenic capacity (Msum). We also expected larger digestive and excretory organs in these birds and predicted that this would explain variation in basal metabolic rate (BMR)...
April 24, 2017: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
https://www.readbyqxmd.com/read/28438762/etb-receptor-contribution-to-vascular-dysfunction-in-postmenopausal-women
#14
Megan M Wenner, Kelly N Sebzda, Andrew V Kuczmarski, Ryan T Pohlig, David G Edwards
Endothelin-1 (ET-1) contributes to age-related endothelial dysfunction in men via the ETA receptor. However, there are sex differences in the ET-1 system, and ETB receptors are modulated by sex hormones. The purpose of this study was to test the hypothesis that ETB receptors contribute to impaired vasodilatory function in postmenopausal women (PMW). We measured flow-mediated dilation (FMD) using ultrasound, and cutaneous nitric oxide-mediated vasodilation during local heating (42°C) via laser Doppler flowmetry in 18 young (YW; 22±1 years) and 16 PMW (56±1 years)...
April 24, 2017: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
https://www.readbyqxmd.com/read/28438761/improved-skeletal-muscle-ca-2-regulation-in-vivo-following-contractions-in-mice-overexpressing-pgc-1%C3%AE
#15
Hiroaki Eshima, Shinji Miura, Nanami Senoo, Koji Hatakeyama, David C Poole, Yutaka Kano
In skeletal muscle, resting intracellular Ca(2+) concentration ([Ca(2+)]i) homeostasis is exquisitely regulated by Ca(2+) transport across the sarcolemmal, mitochondrial and sarcoplasmic reticulum (SR) membranes. Of these three systems, the relative importance of the mitochondria in [Ca(2+)]i regulation remains poorly understood in in vivo skeletal muscle. We tested the hypothesis that the capacity for Ca(2+) uptake by mitochondria is a primary factor in determining [Ca(2+)]i regulation in muscle at rest and following contractions...
April 24, 2017: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
https://www.readbyqxmd.com/read/28438760/use-of-the-hyperinsulinemic-euglycemic-clamp-to-assess-insulin-sensitivity-in-guinea-pigs-dose-response-partitioned-glucose-metabolism-and-species-comparisons
#16
Dane M Horton, David A Saint, Julie A Owens, Kathryn L Gatford, Karen L Kind
The guinea pig is an alternate small animal model for the study of metabolism, including insulin sensitivity. However, only one study to date has reported the use of the hyperinsulinemic-euglycemic clamp (HEC) in anaesthetized animals in this species, and the dose-response has not been reported. We therefore characterized the dose-response curve for whole-body glucose uptake using recombinant human insulin in the adult guinea pig. Inter-species comparisons with published data showed species differences in maximal whole body responses (guinea pig ≈ human < rat < mouse), and the insulin concentrations at which half-maximal insulin responses occurred (guinea pig > human ≈ rat > mouse)...
April 24, 2017: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
https://www.readbyqxmd.com/read/28404583/acute-hypoxia-activates-neuroendocrine-but-not-pre-sympathetic-neurons-in-the-paraventricular-nucleus-of-the-hypothalamus-differential-role-of-nitric-oxide
#17
K Max Coldren, De-Pei Li, David D Kline, Eileen M Hasser, Cheryl M Heesch
Hypoxia results in decreased arterial PO2, arterial chemoreflex activation, and compensatory increases in breathing, sympathetic outflow, and neuroendocrine secretions, including increased secretion of vasopressin (AVP), corticotropin releasing hormone (CRH), adrenocorticotropin hormone (ACTH), and corticosterone. In addition to a brainstem pathway including the nucleus tractus solitarius (nTS) and the rostral ventrolateral medulla (RVLM), medullary pathways to the paraventricular nucleus of the hypothalamus (PVN) contribute to chemoreflex responses...
April 12, 2017: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
https://www.readbyqxmd.com/read/28404582/histone-deacetylase-activity-modulates-exercise-induced-skeletal-muscle-plasticity-in-zebrafish-danio-rerio
#18
Alec Izaac Marcus Simmonds, Frank Seebacher
Aerobic exercise has a positive impact on animals by enhancing skeletal muscle function and locomotor performance. Responses of skeletal muscle to exercise involve changes in energy metabolism, calcium handling, and the composition of contractile protein isoforms, which together influence contractile properties. Histone deacetylases (HDAC) can cause short-term changes in gene expression, and may thereby mediate plasticity in contractile properties of skeletal muscle in response to exercise. The aim of this project was to determine (in zebrafish, Danio rerio) the traits that mediate inter-individual differences in sustained and sprint performance, and to determine whether inhibiting class I and II HDACs mediates exercise-induced changes in these traits...
April 12, 2017: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
https://www.readbyqxmd.com/read/28404581/maternal-and-postnatal-high-fat-diet-consumption-programs-energy-balance-and-hypothalamic-melanocortin-signaling-in-nonhuman-primate-offspring
#19
Elinor L Sullivan, Heidi M Rivera, Cadence A True, Juliana G Franco, Karalee Baquero, Tyler A Dean, Jeanette C Valleau, Diana L Takahashi, Tim Frazee, Genevieve Hanna, Melissa A Kirigiti, Leigh Ann A Bauman, Kevin L Grove, Paul Kievit
Maternal high-fat diet (HFD) consumption during pregnancy decreased fetal body weight and impacted development of hypothalamic melanocortin neural circuitry in nonhuman primate offspring. We investigated whether these impairments during gestation persisted in juvenile offspring and examined the interaction between maternal and early postnatal HFD consumption. Adult dams consumed either a control diet (CTR, 15% calories from fat) or a high saturated-fat diet (HFD, 37% calories from fat) during pregnancy. Offspring were weaned onto a CTR or HFD at approximately 8 months of age...
April 12, 2017: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
https://www.readbyqxmd.com/read/28404580/effects-of-face-head-and-whole-body-cooling-during-passive-heat-stress-on-human-somatosensory-processing
#20
Hiroki Nakata, Mari Namba, Ryusuke Kakigi, Manabu Shibasaki
We herein investigated the effects of face/head and whole body cooling during passive heat stress on human somatosensory processing recorded by somatosensory-evoked potentials (SEPs) at C4' and Fz electrodes. Fourteen healthy subjects received a median nerve stimulation at the left wrist. SEPs were recorded at normothermic baseline (Rest), when esophageal temperature had increased by ~1.2 °C (Heat stress: HS) during passive heating, face/head cooling during passive heating (face/head cooling: FHC), and after HS (whole body cooling: WBC)...
April 12, 2017: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
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