bluuebunny/crossref_metadata_2025_split huggingface dataset:
Species Differences in Gastrointestinal Tract Glucose Transporters between Rainbow Trout (Oncorhynchus mykiss) and Nile Tilapia (Oreochromis niloticus)
Authors: Subramaniam Marina , Weber Lynn P , Ching John C , Enns Cole B , Kilgour Alyssa B , Drew Murray D , Loewen Matthew E 
Published: November 2023

Metabolic differences in omnivore and carnivore glucose homeostasis are well established. However, differences in the gastrointestinal glucose transporers have not been well characterized. Here we assess the differences in electrogenic transport of D‐glucose along different sections of the intestine between Rainbow trout (Oncorhynchus mykiss), a carnivorous fish and Nile tilapia (Oreochromis niloticus), an omnivorous fish in Ussing chambers. The kinetics of glucose transport in pyloric caeca and midgut of trout were similar to the sodium‐dependent glucose transporter isoform 1 (SGLT1) in mammals, and the kinetics in colon resembled mammalian SGLT2. In contrast to trout, the kinetics in all three intestinal sections in tilapia resembled mammalian SGLT2. In addition, SGLT1 and SGLT2 inhibitors further confirm the locations of glucose transporters. In conclusion, trout has two types of SGLTs, a high affinity, low capacity transporter in pyloric caeca and midgut, and a low affinity, high capacity transporter in the colon. Tilapia has only one type of SGLT throughout the gut, which is a low affinity, high capacity transporterSupport or Funding InformationNSERC ‐ CRDPJ: 446912‐13 to LPW, MEL & MDD
Aquatic hypercapnia and aerial excretion of CO2 in air‐breathing fishes
Authors: Jew Corey , Thomsen Mikkel , Bayley Mark , Hicks James W 
Published: November 2023

The notion that bimodal breathers (animals that breathe both air and water) obtain O2 from the air and exhale CO‐2 into the water has been well established in the literature. However, while the majority of supporting experiments tested animals maintained in hypoxic water, freshwater systems that bimodal breather inhabit have been reported to be hypercapnic as well. Data from 3 air‐breathing fishes show that when in hypercapnic water, excretion of CO2 into the air does increase, but the majority of CO2 is still released into the water. To maintain a downward diffusion gradient for CO2 from the gills to the water, a high blood PCO2 must also be sustained. Our data suggest in aquatic hypercapnia, air‐breathing fish are unable regulate blood PCO2 below that of the water. This is likely due to low ventilation at the air‐breathing organ and high surface area contact with water at the gills.Support or Funding InformationSociety for Experimental Biology, American Physiological Society
Glycogen synthesis from lactate in skeletal muscle of the painted turtle in vitro.
Authors: Wang Dongying , Hill Craig A. , Grombka‐Murphy Caitlan E. , Fisher Jonathon S. , Warren Daniel E. , Nguyen Karena 
Published: November 2023

Painted turtles (Chrysemys picta) can accumulate lactate loads approaching 200 mM while over wintering in ice‐covered ponds, a feat achieved, in part, because of large glycogen stores in the liver and skeletal muscle. Mammals cannot directly synthesize glycogen from lactate in muscle and rely on liver Cori cycling for this purpose. To investigate the potential for gluconeogenesis from lactate in skeletal muscle in this species, turtles were made anoxic for 24 hours at 20°C to deplete skeletal muscle glycogen. Bundles of iliofibularis muscle were isolated and incubated in HEPES or CO2/HCO3− buffered solutions for 8 hours to determine the dependence of glycogen repletion on the buffering system at 20°C. Bundles were also incubated for 4 hours in solutions containing L‐[14C(U)]‐lactate with varying concentrations of glucose and lactate, and then analyzed for the amount of 14C that was oxidized or incorporated into muscle glycogen. Muscle glycogen synthesis required the presence of CO2 and HCO3−. The rates of 14C‐lactate oxidation and 14C‐incorporation into glycogen were independent of extracellular glucose, but dependent on extracellular lactate concentrations. The involvement of PEPCK, a key enzyme in gluconeogenesis, was also assessed using the specific inhibitor, 3‐mercaptopicolinic acid (MPA). 100 μM MPA inhibited 40% of the 14C‐incorporation into muscle glycogen when added to lactate incubations. To confirm the specificity of MPA on turtle PEPCK, enzyme assays were carried out with liver tissue homogenate. 100 μM MPA inhibited 86% of cytosolic PEPCK activity and 61% of mitochondrial PEPCK activity. This work confirms that the skeletal muscle mass of the turtle is important in the direct metabolism of lactate and provides additional support for the hypothesis that in situ skeletal muscle gluconeogenesis is the norm among vertebrates, rather than the exception.Support or Funding InformationThis study was funded by a National Institutes of Health R15 awarded to DEW.
Oxygen uptake efficiency slope in patients with metabolic syndrome and obstructive sleep apnea
Authors: Carvalho Jefferson Cabral , Cepeda Felipe Xerez , Rodrigues Sara , Dutra‐Marques Akothirene Cristhina Brisolla , Toschi‐Dias Edgar , Rondon Maria Urbana Pinto Brandão , Alves Maria‐Janieire Nazaré Nunes , Braga Ana Maria Fonseca Wanderley , Lorenzi‐Filho Geraldo , Trombetta Ivani Credidio 
Published: November 2023

Patients with metabolic syndrome (MetS) and obstructive sleep apnea (OSA) have increased cardiovascular risk. Besides decreased peak oxygen consumption peak (VO2peak), the decreased on Oxygen uptake efficiency slope (OUES) during cardiopulmonary exercise testing (CPET) can be used as a marker submaximal of worst prognosis. Therefore, we tested the hypotheses that: 1) OUES is decreased in MetS patients and the association of MetS; 2) OSA causes further decreased on OUES; and 3) The MetS risk factors are associated with OUES. Seventy eight MetS sedentary patients (ATP‐III) without the use of drugs were divided into: MetS+OSA (n=39, 50±1 yrs) and MetS‐OSA (n=33, 45±1 yrs). A control group (C; n=21, 46±1 yrs) was also studied. OSA was determined by apnea/hypopnea index (AHI>15events/h‐polysomnography). The OUES was obtained through the CPET by linear regression analysis of the relation between relative oxygen uptake (ml/kg/min) and the logarithm of VE (l/min), from the 1st min up to maximum effort (OUES100%). Besides, we analyzed the OUES in relation to lean mass body (LMB) (OUES100% LMB). The LMB was obtained by bioimpedance. The MetS+OSA and MetS‐OSA were similar, and both presented lower levels than C regarding OUES100% (25.3± 0,8, 25.3±0,9 and 32.3± 1,7 ml/kg/min/log, respectively p<0.001). Similar results were found to OUES100% LMB (36.8± 1.0, 38.2± 1.1 and 44.2± 2.7 ml/kg/min/log, p=0.003) and to VO2peak (21.7±0.9 vs. 21.8± 0.7 vs. 28±1.4 ml/kg/min, p<0.001). MetS groups have similar MetS risk factors and in body mass index (BMI) and greater than C. Regarding LMB, no difference was observed among groups. Further analysis showed that there were no association between the MetS risk factors or apnea/hypopnea index with OUES. Only BMI was associated with OUES 100% (r=−0,31, p=0.002). MetS patients have impaired cardiorespiratory efficiency during exercise independently of the presence of OSA. The excess body fat seems to be the main cause of this impairment in MetS patients.Support or Funding InformationThis study was supported by Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP# 2011/17533‐6 ) and, in part, by Fundação Zerbini. Jefferson C Carvalho was supported by Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, Felipe X Cepeda was supported by FAPESP# 2015/03274‐0,Sara Rodrigues was supported by FAPESP# 2013/15323‐0, Akothirene CB Dutra‐Marques was supported by Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, Edgar Toschi‐Dias was supported by FAPESP# 2013/07651‐7.
A novel model of weightlifting in mice: Signaling and gene transcription responses in skeletal muscle
Authors: Cui Di , Lewellen Bevan , Wilson Rebecca , Zhang Mei , Yan Zhen 
Published: November 2023

Resistance exercise promotes skeletal muscle hypertrophy, prevents muscle atrophy and improves muscle function. However, despite the significant biological and clinical relevance we still have a poor understanding of the molecular and cellular mechanisms. A critical barrier is the lack of an appropriate animal model of resistance training. We have developed a novel weightlifting cage for mice to perform squat like movements against weight and subjected adult wild type mice (C57BL/6) to an acute bout of weightlifting (WL; n = 4) using sedentary mice as control (CON; n = 3). Following 3 days of acclimatization in the cage, mice in the WL group were allowed to perform weightlifting against 150% of their body weight overnight during the dark cycle (12 hrs). Immediately following the dark cycle, all the mice were sacrificed, and skeletal muscle, liver and heart tissues were harvested for RNA and protein analyses. Mice in the WL group pushed 419±83 times overnight. Semi‐quantitative RT‐PCR showed 3‐fold increase of tumor necrosis factor receptor superfamily, member 12 (Tnfrsf12a or Fn14) mRNA and 2‐fold increase of down syndrome critical region gene 1 (Dscr1) mRNA with no change in TNF‐related weak inducer of apoptosis (Tweak) mRNA in gastrocnemius muscle. Western blot analysis no significant changes in 5′ AMP‐activated protein kinase (AMPK), phospho‐AMPK (p‐AMPKThr172), protein kinase B (Akt), p‐AKTSer473 and cleaved Notch1 proteins. Therefore, we have developed a novel model of resistance exercise and confirmed that weightlifting results in increased Fn14 and Dscr1 mRNA in recruited skeletal muscle. This novel weightlifting cage may be used as a model of resistant exercise for future research.Support or Funding InformationChina Scholarship Council Fund (201506140108)
Power Reserve at the Limit of Ramp‐incremental Exercise is Affected by Incrementation Rate
Authors: Davies Matthew J , Benson Alan P , Birch Karen M , Rossiter Harry B , Ferguson Carrie 
Published: November 2023

The mechanisms that bring about task failure during exercise in which VO2max is attained remain poorly understood. A fundamental question is whether maximum voluntary power declines to the point at which it no longer exceeds the requirements of the exercise task (i.e. no power reserve). We recently demonstrated that there was no power reserve at the limit of tolerance (LoT) of ramp‐incremental (RI) cycle ergometry, but that the central and peripheral contributions to performance fatigue (PF; i.e. the decline in maximal voluntary power) were widely heterogeneous amongst individuals. As the kinetics of central and peripheral limitations to power generation are likely to be influenced by the kinetics of the task, we aimed to determine the influence of ramp‐incrementation rate on the power reserve at the LoT.Using an instantaneous switch from cadence‐independent to isokinetic cycling, peak isokinetic power (PISO, measured at 80 rpm for 6 s) was measured at baseline, and at the LoT of 3 maximal RI exercise tests (LoT PISO). Ramp‐incrementation rates of 10, 25 and 50 W·min−1 (RI‐10, RI‐25 and RI‐50, respectively) were performed in seven healthy participants (mean ± SD; 27 ± 6 yr; 174 ± 9 cm; 72 ± 10 kg; 5 m, 2 f). Breath‐by‐breath pulmonary gas exchange was measured throughout all protocols.Baseline PISO was not different amongst the three RI protocols (732 ± 140, 739 ± 143, and 737 ± 144 W for RI‐10, RI‐25 and RI‐50, respectively; p > 0.05). VO2max at LoT was within the normal day‐to‐day variation (< 7 %) across the three RI protocols (mean: 3.69 ± 0.74 L·min−1); however, flywheel power requirement at LoT increased with ramp rate (RI‐10: 270 ± 38; RI‐25: 318 ± 43; RI‐50: 354 ± 52 W; p < 0.05). PF was 313 ± 135, 346 ± 129, 380 ± 139 W for RI‐10, RI‐25 and RI‐50, respectively (p > 0.05), with LoT PISO decreasing to 54 ± 12 % of baseline PISO. Thus at LoT, PISO was greater than flywheel power in RI‐10 (p < 0.05), but was not different from flywheel power in RI‐25 and RI‐50 (p > 0.05).At the limit of ramp‐incremental exercise in which VO2max is attained, the absence of a power reserve in RI‐25 and RI‐50 is consistent with the notion that exercise intolerance occurs when maximal evocable power equals the power required by the task. However, our data indicate that, while there was considerable fatigue during RI‐10, the decline in PISO was insufficient to limit the exercise, thus other mechanisms were contributory to the exercise limitation in this slow ramp condition. This suggests that the mechanisms that precipitate task failure at VO2max are plastic in young healthy subjects, and dependent on the kinetics of the task.
X‐irradiation and Simulated Microgravity affects Rat Weight, Food Intake, Insulin and Paw Pressure Pain Threshold
Authors: Chowdhury Parimal , Akel Nisreen , Parsian Azmat‐Jamshidi , Griffin Robert , Yadlapalli Jai , Dobretsov Maxim 
Published: November 2023

The aim of this study is to examine various physiological measurements in response to range of space‐like radiation doses in a NASA‐validated rodent model of simulated microgravity.MethodsFour groups of rats (6 rats per group), control (CON), irradiated (IR), irradiated plus hindlimb suspended (IR+HLS) and suspended (HLS), were used in the study and maintained for two consecutive weeks. IR and IR+HLS groups were exposed to five sessions of X‐ray irradiation (0.5 Gy each, at 3–4 days intervals; cumulative dose 1.2 Gy). Body weights, food and water intakes, pressure pain thresholds and random blood plasma insulin levels were measured.ResultsCompared to CON, weight gain was slowed by about 25% in IR animals and by 50% in HLS and IR+HLS groups. IR acutely decreased food consumption by 20%‐50% when compared to pre‐exposure levels. Effect of HLS on food consumption (15% decrease) was evident during first day of post‐suspension. HLS but not IR resulted in deep tissue hyperalgesia (45% decreases in PPT) and a 40%–60% decrease in plasma insulin levels.Summary and ConclusionsThese observations suggest that exposure to IR may contribute to space flight‐associated anorexia and weight loss. However exposure to microgravity and lower limb disuse appear to be associated with complications. These include insulinopenia, deep tissue hyperalgesia and the muscle atrophy in addition to weight loss and, from our previous studies, bone degenerative effects.Support or Funding InformationSupported by a grant from Arkansas Space Grant Consortium
Are Inert Gases Inert? Hyperbaric Nitrogen and Hyperoxia Stimulate Singlet O2 Production in Solitary Complex Neurons of the Dorsocaudal Medulla in Rat Brain Slices
Authors: Roberts Teryn , Dean Jay B. 
Published: November 2023

InertGas Narcosis (IGN, or N2 Narcosis) at hyperbaric pressure is alimiting factor in US Naval diving operations; however, little is known aboutthe mechanisms underlying this CNS disorder. It has been hypothesized that inertgases such as N2 interact with O2 at hyperbaric pressureto form collision complexes that generate singlet oxygen (1O2). If true then 1O2 maycontribute, in part, to onset of IGN. Accordingly, we predict that hyperbaric nitrogen (HBN2) willinteract with O2‐sensitive neurons in the caudal solitary complex(cSC) to generate 1O2. The goals of this study were to 1)develop an in vitro system for measuring 1O2 productionin real time in the mammalian CNS; 2) determine the effect of hyperoxia (0.4→0.95 atmospheres absolute, ATA) on 1O2production at normobaric pressure; and 3) determine the effect of HBN2(up to 6.6ATA N2) on 1O2 production duringhyperoxia (0.95ATA O2). The fluorescent probe Singlet Oxygen SensorGreen (SOSG) was used to detect 1O2 production in thebrain slices of rat medulla oblongata (P16‐40, male/female, 400μm, 30–36°C). Fluorescence intensity of cSC neurons was measured at 1–2.5min intervalsand correlated with 1O2 production using one of two NikonTE2000 inverted microscopes; one microscope was automated for use inside asealed hyperbaric chamber (MWP=85psig). Confocalimaging indicated that SOSG reaction product during excitation was confined tothe soma, proximal processes and fibers. Results show that increasing pO2 from 0.4 to 0.95 ATA increased the rate of 1O2 production. Ascorbate (1–4mM),an inhibitor of 1O2, decreased the rate of 1O2production in control O2 and hyperoxia in a dose‐dependent manner. Exposure to HBN2 (0.25ATA/min) at maximum depth (10 min) followed by decompression (0.5ATA/min) back to sea level caused a post‐dive transientincrease in 1O2 that lasted at least 10min. These findings demonstrate 1O2 can be measured in CNS neurons in brain slices using SOSG and that 1O2production is stimulated by normobaric hyperoxia. Additionally, exposure to HBN2 increases 1O2 production but not untilde compression. This suggests that 1O2production is activated by compression to at least 6.6ATA N2, decompression or both. Thus, we postulate that 1O2 generated subsequent to exposure to HBN2 may contribute to IGN and decompression sickness.Support or Funding InformationONR Undersea Medicine
Prolonged Adenosine Triphosphate Infusion & Exercise Hyperemia
Authors: Shepherd John Roger Alden , Joyner Michael J. , Dinenno Frank A , Curry Timothy B , Ranadive Sushant M 
Published: November 2023

Adenosine triphosphate (ATP) is postulated to be a major exercise related vasodilating metabolite. In humans, ATP infusion mimics exercise hyperemia. However, it remains unknown whether ATP can evoke the prolonged vasodilation seen during exercise. Therefore we tested two hypotheses during a three‐hour intra‐arterial infusion of a high dose of ATP (20 μgrams ·100 mL forearm vol−1·min−1): (1) skeletal muscle blood flow would wane over time (tachyphalaxis); (2) exercise hyperemic responses during ATP administration would be blunted compared to baseline. Nine healthy young participants (25 ± 1 years) performed seven rhythmic handgrip exercise bouts (20% of maximum), two during saline (control) and five during 180 minutes of continuous ATP infusion. Forearm vascular conductance (FVC; ml min−1 (100 mmHg) −1) and percent (%) change from control were calculated. Five minutes of ATP infusion resulted in a 710% increase in FVC (4.8±0.3 vs 35.0±1.9 ml min−1 *100 mmHg −1, P<0.05). FVC did not wane over time with values of 35.0±1.9 and 36±2.6 ml min−1 (100 mmHg) −1 (P>0.05) seen prior to the exercise bouts at 5 vs 150 minutes respectively. With superimposed exercise FVC increased from 35.0±1.9 to 49.6±2.2 ml min−1 *100 mmHg −1 at five minutes and 36.0±2.6 to 54.5±1.1 at 150 min (P<0.05). Our findings demonstrate (1) ATP vasodilation is sustained over time without tachyphalaxis; (2) vasodilator responses to exercise during high dose ATP infusion remain intact. This latter finding questions the extent to which ATP is obligatory for exercise hyperemia.Support or Funding InformationThis research was supported by National Institutes of Health Research Grants HL‐119337 and by CTSA UL1 TR000135. The Caywood Professorship via the Mayo Foundation also supported this research.
Tempol Augments the Blunted Cutaneous Microvascular Thermal Reactivity in Healthy Young African Americans
Authors: Hurr Chansol , Patik Jordan C , Christmas Kevin M. , Brothers R. Matthew 
Published: November 2023

African Americans (AA) have a higher risk for a variety of cardiovascular and metabolic diseases including hypertension, stroke, peripheral artery disease, and type 2 diabetes mellitus when compared with Caucasian Americans (CA). While this elevated risk is multifactorial impaired vascular endothelial function is a contributing factor. In this study, we hypothesized that cutaneous hyperemic response to a standard local heating protocol is reduced in young AA when compared with CA. We further hypothesized that tempol (a superoxide dismutase mimetic) would increase this cutaneous vasodilatory response to local heating in AA. Microdialysis fibers were randomly assigned to receive 1) lactated Ringer's solution (Control), 2) 10 mM ascorbic acid, or 3) 10 μM 4‐hydroxy‐2,2,6,6‐tetramethylpiperidine‐1‐oxyl (Tempol) at a rate of 2.0 μl/min. Cutaneous vascular conductance (CVC) was calculated as red blood cell flux divided by mean arterial pressure. All CVC data were presented as a percentage of maximal CVC (%CVCmax) that was determined by maximal cutaneous vasodilation induced by 44 °C plus sodium nitroprusside administration. Twenty‐four (12 AA, 12 CA) young (23 ± 4 years of age) and healthy (body mass index (24.3 ± 2.8 kg/m2) subjects participated in the study. At the Control site, there were no differences between groups for baseline %CVCmax during resting without heat (P = 0.275). During 33 °C, there were still no differences in %CVCmax between groups (P = 0.107); however, %CVCmax at 39 °C was lower in AA when compared with CA (P < 0.001). At the ascorbic acid site, there were no differences between groups for both baseline %CVCmax during resting without heat (P = 0.549) and %CVCmax during 33 °C (P = 0.120); however, %CVCmax at 39 °C was attenuated in AA relative to CA (P < 0.001). At tempol site, there were no differences between groups for all phases including baseline CVC during resting without heat (P = 0.791), %CVCmax during 33 °C (P = 0.550), and %CVCmax at 39 °C (P = 0.948). These data suggest that 1) cutaneous vasodilation in response to local heating is blunted in AA relative to CA. 2) in AA, elevated O2− generation attenuates cutaneous vasodilation when heat is directly applied to the skin.Support or Funding InformationInstitutional start‐up funds from The University of Texas at Austin