bluuebunny/crossref_metadata_2025_split huggingface dataset:
Numbers of pH‐sensitive K+ channel‐immunoreactive neurons are reduced in CO2‐insensitive Brown Norway rats in select brainstem nuclei associated with central respiratory chemoreception (1092.8)
Authors: Martino P , Olesiak S , Riley D , Neumueller S , Forster H , Hodges M 
Published: June 2021

Brown Norway (BN) rats display an extremely low hypercapnic ventilatory response (HCVR) compared to other strains such as the Dahl S (SS) rat. Multiple pH‐sensitive potassium (K+) channels are expressed within multiple brainstem chemosensory nuclei and may contribute to CO2‐H+ detection/signaling in chemosensitive neurons. Herein we tested the hypothesis that there are selective reductions in the numbers of neurons expressing pH‐sensitive Kv1.4, Kir 2.3, and TASK‐1 K+ channels in the chemosensory nucleus of the solitary tract (NTS) but not in the pre‐Botzinger Complex (pre‐BötC), nucleus ambiguus (NA) or hypoglossal nucleus (XII) of BN but not SS rats. Medullary sections (25 µm) from male and female BN (n=14) and SS (n=15) rats were stained with cresyl violet or primary antibodies targeting KV1.4, Kir2.3, or TASK‐1 and the numbers of K+ channel‐immunoreactive (‐ir) neurons were quantified. There was little difference among female and male rats within each strain in all nuclei studied. However, within the NTS there were significantly fewer Kir2.3, (47.46% ± 1.83%; TASK‐1 57.46% ± 2.17%; and Kv1.4 64.11% ± 1.6% observed in BN rats as compared to SS rats. In contrast, the numbers of K+ channel‐ir neurons did not significantly (P< 0.05) differ within the NA and the hypoglossal nucleus, with some significant (P < 0.05) differences observed in the Medullary Raphe and the pre‐Botzinger complex. Fewer pH sensitive K+ channel‐immunoreactive neurons is evidence that at least partly explains the lower hypercapnic response in BN rats compared to that in SS rats.Grant Funding Source: Supported by the Department of Veterans Affairs and NIH HL25739
Lemur tyrosine kinase‐2, a novel regulator of androgen receptor signaling in prostate cancer (1095.1)
Authors: Shah Kalpit , Bradbury Neil 
Published: June 2021

Androgens and the androgen receptor play essential roles in the development and progression of prostate cancer, which claims roughly around 28,000 lives every year. Contemporary reports have demonstrated that the stability and sensitivity of the androgen receptor can be manipulated through alteration in kinases activity. Recent Genome Wide Analysis Studies argues that a decrease in gene expression of Lemur Tyrosine Kinase 2 (LMTK2) is associated with an increased risk of prostate cancer. We show that manipulation of LMTK2 levels in the prostate adenocarcinoma cell line, LNCaP, markedly affects the expression of androgen dependent genes. Moreover, loss of LMTK2 leads to reduced androgen receptor degradation, enhancing the ability of androgen to activate their target genes. Furthermore, in vivo Proximity Ligation Assays and Co‐immunoprecipiation assay shows that the androgen receptor and LMTK2 are binding partners in LNCaP cells. Using a combination of biochemical, molecular and cellular approaches, our work defines a novel cellular pathway for the androgen receptor regulation in prostate adenocarcinoma cells; pharmacologic manipulation of such regulation will provide innovative and more effective therapies for the treatment of patients with prostate cancer.Grant Funding Source: NIH
Targeting glucagon‐like peptide‐1 and α2 adrenergic receptor combination using GLP‐1/yohimbine to achieve β‐cell specific targeting and therapy (1095.19)
Authors: Ananthakrishnan Kameswari , Weber Craig , Hart Nathaniel , Vagner Josef , Limesand Sean , Lynch Ronald 
Published: June 2021

Coupling multiple receptor binding domains into a single molecule enhances ligand binding affinity, and if the domains target different receptors, only cells expressing the complementary receptor combination will bind this agent. Pancreatic β‐cells express Glucagon Like Peptide‐1 (GLP‐1R) and α2Adrenergic Receptors (α2AR) that, as a combination, are relatively unique to the β‐cell. Moreover, activation of GLP‐1R and α2AR inversely affect β‐cell signaling. We propose that linking GLP‐1 to Yohimbine (Yhb; α2AR antagonist) may provide an agent with enhanced affinity, β‐cell specificity and possibly unique therapeutic potential. Using microscopy, we established that GLP‐1/Yhb bound to β‐cells with high affinity at nM concentrations and was rapidly internalized. In cells where either GLP‐1R or α2AR were knocked down (using siRNA), binding of GLP‐1/Yhb was significantly reduced (蠄 half of cells with both receptors), demonstrating specificity. Over a range of concentrations (0.01 – 5 nM ), GLP‐1/Yhb had similar activity as monomeric GLP‐1 for increasing cAMP production. Conversely, measurement of Glucose Stimulated Insulin Secretion (GSIS) showed that, at both 1nM and 100 nM, GLP‐1/Yhb potentiates GSIS more than GLP‐1 alone. Thus, due to its specificity for β‐cells and positive impact on β‐cell function, bivalent agents like GLP‐1/Yhb may provide a unique approach for successful β‐cell specific targeting and therapy.Grant Funding Source: Supported by: Juvenile Diabetes Research Foundation and American Diabetes Association
Rescue of the disrupted enamel phenotype in Slc4a4‐null mice using explant organ culture maintained in a living host kidney capsule (1098.8)
Authors: Wen Xin , Kurtz Ira , Paine Michael 
Published: June 2021

Slc4a4 encodes the electrogenic sodium base transporter NBCe1 that is involved in transcellular base transport and pH regulation during amelogenesis. Patients with mutations in the SLC4A4 gene and NBCe1‐/‐ mice present with dysplastic enamel, amongst other pathologies. Loss of NBCe1 function leads to local abnormalities in enamel matrix pH regulation and also results in systemic acidemic blood pH due to defecting renal bicarbonate absorption. Whether local changes in enamel pH/base transport and/or a decrease in systemic pH are the cause of the abnormal enamel phenotype is currently unknown. In the present study we addressed this question by explanting fetal wild‐type and Slc4a4‐null mandibles into healthy host kidney capsules to study enamel formation in the absence of systemic acidemia. Mandibular E11.5 explants from NBCe1‐/‐ mice, maintained in host kidney capsules for 70 days, resulted in teeth with enamel and dentin with morphological and mineralization properties similar to cultured NBCe1+/+ mandibles grown under identical conditions. Despite the capacity of ameloblasts to dynamically modulate the local pH of the enamel matrix, at least in the NBCe1‐/‐ mice, the cause of the enamel phenotype appears primarily to be due to abnormalities in systemic pH. Extrapolating these data to humans, our findings suggest that in patients with NBCe1 mutations, correction of the systemic metabolic acidosis at a sufficiently early time point may lead to amelioration of enamel abnormalities.Grant Funding Source: NIH
Histamine enhances Syrian hamster hippocampal neuronal activity at low levels of synaptic excitation (1100.11)
Authors: Malins Kevin , Hamilton Jock , Horowitz John , Horwitz Barbara 
Published: June 2021

Previous work showed that histamine (HA) infused into hippocampi excited CA1 pyramidal neurons and lengthened hibernation bouts by 50%. However, HA effectiveness in increasing CA1 pyramidal neuron excitability at low levels of synaptic stimulation (mirroring that when entering torpor) is unknown. We tested the hypotheses that HA modulation of Syrian hamster CA1 pyramidal neurons: increased evoked response amplitude (ERA) to threshold level voltages, persisted at temperatures below 37°C, and involved H2 receptors. We measured CA1 ERAs in response to Schaffer collateral stimulation ranging from near‐maximal saturation (“max”) to below threshold levels at 30°C (n=14) and 20°C (n=17). Addition of 10µM HA to the perfusate increased near‐threshold stimulation ERAs [Taking the max response before HA as 100%, near‐threshold ERAs increased from 2.7% to 12.9% at 30°C (P<0.01), and from 2.5% to 20.7% at 20°C (P<0.001)]. These HA‐mediated increases in ERAs decreased as stimulation intensity approached max. Cimetidine (H2 antagonist; 20 µM) blocked the HA‐mediated ERA increase in 8 of 8 slices stimulated at 50‐75% of saturation. Data support our hypotheses, showing HA enhanced responses near threshold at both 30°C and 20°C, and that HA enhancement was mediated via H2 receptors. Data are consistent with the proposal that HA may modulate a low‐level hippocampal signal to the ascending arousal system to prolong torpor.Grant Funding Source: Supported by UC Davis Provost's Undergraduate Fellowship to KJM
Metabolic signatures in overwintering raccoon dogs (Nyctereutes procyonoides) (1101.13)
Authors: Niiranen Laura , Mäkelä Kari , Thalmann Olaf , Saarela Seppo , Herzig Karl‐Heinz 
Published: June 2021

The raccoon dog (RD) is a Eurasian dog‐like mammal with a peculiar wintering strategy. It is the only member of the family canidae that can spend cold winters in an inactive state. Our objective was to investigate the molecular signatures regulating energy homeostasis during the crucial phases of seasonal adaptation in RD (autumnal fattening and winter fasting). We analyzed several key regulators of metabolism /food intake on the transcription levels from RD hypothalamus (orexigenic: NPY, orexin‐2 receptors (OX2R) and anorexigenic: POMC, leptin receptors (LepR)) and from the RD plasma (leptin, insulin, ghrelin, peptide YY, GIP, interleukin 8, MCP‐1). The 10‐week winter fasting period had no significant effect on the analyzed mRNA expression levels in the hypothalamus. Plasma peptides and cytokines were also not significantly different. In contrast, autumnal fattening decreased the expression of hypothalamic OX2R (p=0,002) and also LepR (p=0,006). Plasma leptin was increased in the autumnal fattening phase (p=0,027). In conclusion, our results indicate that RD is well adapted to long periods of fasting. In autumnal fattening we observed a seasonal downregulation of hypothalamic OX2R and LepR in contrast to the increased leptin plasma levels. These lower levels of LepR during the autumnal fattening phase enable the animals to increase their food intake in spite of the inhibitory action of the circulating leptin.Grant Funding Source: Supported in part by the Academy of Finland
Chronic effects of fibroblast growth factor 21 on whole body and liver metabolism in a natural animal model of increased adiposity (1101.7)
Authors: Samms Ricardo , Murphy Michelle , Barrett Perry , Coskun Tamer , Paul Emmerson , Adams Andrew , Kharitonenkov Alexi , Tsintzas Kostas , Ebling Ebling 
Published: June 2021

This study aimed to investigate the effect of chronic treatment with the liver and fat‐derived hormone FGF21 on whole body and liver energy metabolism in Siberian hamsters in their seasonally fat state. Recombinant FGF21 (1 mg/kg/day) or saline (vehicle) were continuously infused for 14 days via subcutaneous, osmotic mini‐pumps. Body weight, ependymal white adipose tissue and hepatic triglyceride content were reduced (P<0.05) by 7%, 24% and 47% respectively in animals treated with FGF21. Whole body daily energy expenditure and fat oxidation increased (P<0.01) by 9% and 75% respectively. After FGF21 treatment, liver pyruvate dehydrogenase complex (PDC) activation, a key regulator of glucose oxidation, was reduced (P<0.05) by 35%, with a concomitant 30% increase (P<0.05) in long‐chain acylcarnitine accumulation reflecting enhanced fatty acid flux through β‐oxidation. There was an increase (P <0.05) in protein abundance of PGC1α and of two of its targets; PDK4, a molecular inhibitor of PDC, and pACC, which would increase fat oxidation. These findings suggest that FGF21‐induced upregulation of hepatic PGC1α mediates the shift in energy utilization from carbohydrate to fat. This mechanism serves to couple the FGF21‐induced modulation in nutrient flux to its known anti‐steatotic effect, and may contribute to increased energy expenditure and ultimately weight lossGrant Funding Source: BBSRC
The importance of decreased Cl‐ channel activity in preventing K+‐induced force depression at the onset of muscle activity (1102.17)
Authors: Higgins Amanda , Renaud Jean‐Marc 
Published: June 2021

Interstitial [K+] reaches 10‐12 mM even in non‐fatiguing muscle activity. At low stimulation frequencies (1‐90 Hz) and 37°C, peak force is potentiated at these [K+], and force depression in mouse EDL muscle occurs only when [K+] exceeds 13 mM. Partial decreases in Cl‐ channel activity allows for force recovery at elevated [K+] while complete block of Cl‐ channel activity worsens the K+‐induced force depression. The objective of this study was to determine the optimal level of Cl‐ channel activity or conductance (GCl). Increasing K+ from 4.7 (control) to 13 mM reduced peak force by 75%. Subsequent exposure to 9‐AC, a ClC‐1 Cl‐ channel blocker, allowed for an increase in force being 25%, 26% and 43% at 6.5, 10 and 20 µM 9‐AC, respectively. At 40 and 100 µM 9‐AC, the force increases were smaller, being 15% and 9%, respectively; i.e., an optimum effect was observed at 20 µM 9‐AC. Interestingly, at 20 µM 9‐AC, the GCl is expected to be about 30% of the normal GCl at rest. More importantly, there is evidence for a 70% decrease in GCl at the onset of a muscle activity. We therefore suggest that this decrease in GCl at the onset of exercise play a critical role in preventing K+, which rapidly reaches 10‐12 mM, to depress membrane excitability and force generation and in fact maintain the K+‐induced force thereby improving muscle performance.Grant Funding Source: CIHR
Effects of lipopolysaccharide‐induced systemic inflammation on the contractile properties of the fast twitch extensor digitorum longus muscle in mice (1102.19)
Authors: Mandawe Remie , Wilkinson Katherine 
Published: June 2021

Chronic sepsis, which includes a large inflammatory response, leads to muscle wasting, decreased muscle contractile forces and an increase in fatigability (Lanone, et al., 2005; Rossignol, et al., 2008). The effects of lower levels of systemic inflammation on muscle contractile properties have not been well studied. We tested the hypothesis that contractile properties of skeletal muscles are altered by lower levels of systemic inflammation using an in vitro adult mouse extensor digitorum longus muscle preparation. We tested the response to inflammation caused by a high dose of lipopolysaccharide (LPS; 7.5 x 10^5 Endotoxin Units/ kg IP 18 hrs before sacrifice; n=6) with or without a 1 month exposure to low LPS (7.5 x 104 EU/kg; 2/wk, n=4). Controls were given a saline injection 18 hrs before sacrifice (n=6). Twitch and tetanic contractions were induced by bath electrodes and a 10 min fatigue test (.5 ms pulse width, 60 Hz, 350 ms train at supramaximal voltage every 3 s) was performed. Muscle contractile properties including time to peak contraction, half‐relaxation time and fatigue index (40th train tension/maximal tetanic tension) were not significantly different from control values following high LPS, even when it was preceded by a month of low LPS. Future studies will increase the sample size and confirm that LPS‐induced systemic inflammation at our doses does not alter contractile properties.Grant Funding Source: Supported by a CSUPERB President's Commission Fellowship (RGM) and a CSUPERB New Investigator (KAW)
Angiotensin II type 2 receptor regulates skeletal myoblast differentiation: implications for treatment of cachexia and skeletal muscle wasting (1102.34)
Authors: Yoshida Tadashi , Delafontaine Patrice 
Published: June 2021

Patients with advanced congestive heart failure (CHF) or chronic kidney disease (CKD) often have increased angiotensin II (Ang II) levels and cachexia. Ang II infusion in rodents causes sustained skeletal muscle wasting and decreases muscle regenerative potential through Ang II type 1 receptor (AT1R)‐mediated signaling, likely contributing to the development of cachexia in CHF and CKD. However, the potential role of Ang II type 2 receptor (AT2R) signaling in skeletal muscle physiology is unknown. We found that AT2R expression was robustly increased in regenerating skeletal muscle after cardiotoxin (CTX)‐induced muscle injury in vivo and differentiating myoblasts in vitro, suggesting that the increase in AT2R played an important role in regulating myoblast differentiation and muscle regeneration. To determine the potential role of AT2R in muscle regeneration, we infused C57BL/6 mice with AT2R antagonist PD123319 (PD, 30 mg/kg/d) during CTX‐induced muscle regeneration. PD reduced the size of regenerating myofibers (727.5±54.6 and 516.0±37.0 µm2 in sham and PD, respectively, p<0.05) and the myoblast differentiation marker myogenin and eMyHC expression (56.9% and 40.2% decrease in PD, respectively. p<0.01). In cultured myoblasts, AT2R knockdown by siRNA suppressed myogenin expression and myoblast differentiation via upregulation of phospho‐ERK, and ERK inhibitor U0126 treatment completely blocked the effect of AT2R knockdown. On the other hand, AT2R agonist CGP42112 (CGP, 1 µg/kg/min) infusion in C57BL/6 mice potentiated CTX injury‐induced myogenin and eMyHC expression (44.5% and 79.1% increase in CGP, respectively, p<0.05) and increased the size of regenerating myofibers (784.3±32.1 and 981.1±65.2 µm2 in sham and CGP, respectively. p<0.05). These data indicate that AT2R signaling positively regulates myoblast differentiation and potentiates skeletal muscle regenerative potential, providing a new therapeutic target in wasting disorders such as CHF and CKD.Grant Funding Source: Supported by NIH/NHLBI (R01HL080682 and R01HL070241) and NIH/NIGMS (P20GM103629).
Aspirin ingestion does not alter the onset or slope of local sweat rate during whole‐body passive heat stress (1104.12)
Authors: Carter Stephen J. , Herron Robert L. , Akers S. Zeb , Collins Ann B. , Wingo Jonathan E. 
Published: June 2021

Aspirin ingestion does not alter the onset or slope of local sweat rate during whole‐body passive heat stressStephen J. Carter, Robert L. Herron, S. Zeb Akers, Ann B. Collins, Jonathan E. Wingo. Department of Kinesiology, The University of Alabama, Tuscaloosa, AL 35487Aspirin (acetylsalicylic acid; ASA) is a commonly prescribed over‐the‐counter drug. As a fever suppressant ASA may interfere with normal hypothalamic‐mediated temperature regulation. We sought to determine if varying doses of ASA would alter the onset and slope (i.e., sensitivity) of local sweat rate during whole‐body passive heating. Seven healthy men (mean ± SD; 28 ± 3 y) completed a counter‐balanced design to compare ASA treatments (single dose of non‐enteric coated 325‐mg ASA vs. 4 days of 81‐mg ASA) to a control trial. A 10 day washout period was given between ASA treatments. Participants were physically active, free from cardiovascular disease and refrained from vigorous physical activity 24 h prior to testing. Upon arrival, participants were outfitted with a heart rate monitor, rectal thermocouple, 6 skin thermocouples, and a ventilated capsule placed on the dorsal forearm to measure local sweat rate via capacitance hygrometry. To raise mean body temperature (Tb) participants rested supine while hot water (~49 °C) circulated through a tube‐lined suit. Body heating ensued until participants reached a 1.0 °C increase above baseline Tb. ASA did not affect Tb at baseline (P=0.14). The onset and slopes were unaffected by ASA use (P=0.33 and P=0.87, respectively). Additionally, ASA treatments did not alter peak sweat output (P=0.87). Aspirin ingestion did not appear to affect sweat responses in this cohort of men.
Central angiotensin AT2‐receptor blockade affects thermoregulation and running performance in rats (1104.16)
Authors: Pimentel Alan , Rezende Edson , Gomes Thales , Coimbra Cândido , Leite Laura 
Published: June 2021

The aim of the study was to verify the effect of central angiotensin II AT2 receptor blockade in thermoregulatory responses during exercise in rats. Internal (Tb) and skin tail (Ttail) temperatures were measured in Wistar rats while they were running until fatigue (18 m.min‐¹, 5% inclination) after intracerebroventricular injection of 2µL of PD 123319 (PD; AT2 angiotensin II receptor antagonist; 10 µg) or 0.15 M NaCl (SAL) (n=7/each). Total time of exercise until fatigue (TTE) and workload (W) were determined. Rats treated with PD had an increase of 17% and 20% in TTE and W, respectively, in comparison with SAL animals (p<0.05). During exercise, Tb enhanced in both group, however, no difference was seen between treatments. On the other hand, following the first 15 minutes of exercise, Ttail variation was superior in PD rats until fatigue (3.1 ± 1,5 °C Sal vs. 4.9 ± 1,2 °C PD, p<0.05). Moreover, the increased Ttail at fatigue shown by PD‐rats directly correlated with their enhanced TTE (r = 0.82, P < 0.01). The data shows that AT2 receptor blockade improves heat balance during exercise due to better ability to dissipate heat, which contributes to enhanced exercise performance.Grant Funding Source: FAPEMIG, CNPq and CAPES
Thermoregulatory responses to heat stress and hypoxia (1104.19)
Authors: Low David , Bailey Thomas , Jones Helen 
Published: June 2021

The aim of this study was to examine the thermoregulatory responses to combined heat stress and hypoxia. Seven healthy male subjects (22±3 yr, 80±11 kg, 180±7 cm), dressed in a water‐perfused suit, underwent moderate passive heating (Δ core temperature ~0.8 °C) on 2 separate occasions. In 1 trial subjects breathed normoxic air (NORMOXIA) and in the other subjects breathed balanced 13% O2 air (HYPOXIA). Skin blood flow (SkBF; laser Doppler flowmetry), expressed as cutaneous vascular conductance (CVC; flux/blood pressure), and local sweat rate (SR; capacitance hygrometry) were recorded on the forearm. Core (Tcore; intestinal pill) and local skin temperatures (Tsk), as well as blood pressure (BP; automated sphygmomanometry and digital photoplethysmography), heart rate (HR; ECG) oxygen saturation (SpO2; pulse oximetry) were also monitored. Tcore and mean body temperature (Tbody) thresholds for heat stress‐induced elevations in SkBF and SR, as well as the SkBF/SR: Tcore/Tbody slopes were calculated. At normothermic baseline HYPOXIA reduced SpO2 (98±1 vs 90±6 %, P<0.01) and slightly elevated forearm SkBF (9±6 vs 13±12 % CVC max, P=0.10) and HR (67±10 vs 74±7 beats.min‐1, P<0.01). Tcore (37.0±0.3 vs 37.0±0.3 °C, P=0.30) was unchanged. During heating the forearm SkBF Tcore threshold (36.9±0.3 vs 37.0±0.2 °C, P=0.30) and the forearm SR Tbody threshold (36.7±0.3 vs 36.7±0.2 °C, P=0.90) were not different between trials. The forearm SkBF:Tcore slope was slightly reduced during HYPOXIA (1.04±1.17 vs 0.59±1.19 CVC units·°C, P=0.07) whereas the forearm SR:Tbody slope (0.17±0.09 vs 0.22±0.11 ml.cm2.min‐1·°C, P=0.04) was increased by HYPOXIA. These results indicate that moderate hypoxia does not affect central thermoregulatory function but alters peripheral thermoregulatory effector function via blunted skin blood flow and accentuated sweating slopes possibly via baseline hypoxia‐induced cutaneous vasodilation.Grant Funding Source: European Commission FP7