bluuebunny/crossref_metadata_2025 huggingface dataset:
Cigarette smoke causes RV dysfunction and cardiac fibroblast proliferation (1090.8)
Authors: O'Connell Kelly , Vang Alex , Sakhatskyy Pavlo , Lu Qing , Rounds Sharon , Choudhary Gaurav
Published: June 2021

Chronic obstructive pulmonary disease (COPD) is frequently associated with right ventricular (RV) dysfunction. Cigarette smoke (CS) is the leading cause of COPD. Male AKR mice subjected to CS for 6 weeks recapitulate the RV dysfunction seen in patients with COPD but without pulmonary hypertension (PH). Mice exposed to CS had reduced tricuspid annular plane systolic excursion (TAPSE) suggesting decreased RV function compared to mice exposed to room air (RA) (1.1±0.1 vs. 0.8±0.1, respectively, P<0.05). Collagen content was increased in the RV of CS‐exposed mice, compared to RA (11.3±0.7 vs. 9.0±0.7, respectively, P<0.05). In primary isolated cardiac fibroblasts (CF) exposed to 10% CS extract for 24 hours, proliferation was increased by ~2‐fold (normalized cell count of 1.97±0.15 vs. 1.0±0.0, respectively, P<0.01). CF proliferation was unaffected by the inhibition of reactive oxygen species or aldehydes but was significantly reduced by mecamylamine, an inhibitor of nicotinic acetylcholine receptors (nAChR). Further, nicotine (200‐600nM) dose‐dependently increased CF proliferation. Additionally, exposure to CS extract or nicotine significantly increased PKCalpha expression in CF and increased expression of the activated form of the mitogen activated protein kinase, ERK1/2. These data suggest that nicotine in CS causes CF proliferation that may be mediated by nAChRs, PKCalpha and ERK signaling.
Selective knockout of acid α‐glucosidase GAA gene expression in the medulla alters breathing (1091.3)
Authors: Fuller David , Elmallah Mai Kamal , Ross Heather , Cerreta Anthony , Corti Manuela , Smith Barb , Poirier Amy , Mandel Ronald , Byrne Barry
Published: June 2021

Pompe disease results from gene mutations in GAA ‐ an enzyme necessary to degrade lysosomal glycogen. Hypoventilation is a hallmark feature historically attributed to Pompe‐associated muscle pathology but the contribution of brain to this deficit is unclear. In ongoing experiments, we are using a Cre‐Lox recombination approach to knockout (KO) the GAA gene in medullary respiratory neurons while leaving somatic muscle expression unaltered. AAV vectors driving Cre recombinase were injected into the ventrolateral medulla of C57Bl/6 mice in which exons 4‐8 of the GAA gene were floxed with loxP sites. Whole body plethysmography was used to assess breathing patterns at 1‐2 months post‐injection during baseline (21% O2) and respiratory challenge (7% CO2, 21% O2). During baseline conditions at 2 months, AAV‐Cre injected mice had increased ventilation compared to saline injected mice (P<0.05). However, during respiratory challenge at 2 months, the AAV‐Cre group had a reduced ventilatory response (P<0.05). These preliminary results demonstrate that medullary GAA KO can alter breathing. Our working hypothesis is that neuronal glycogen accumulation leads to dysfunction in medullary networks, and the increased baseline breathing indicates a compensatory response to ongoing neuropathology. The blunted hypercapnic ventilatory response may reflect an inability to fully compensate for the ongoing neuropathology.

Grant Funding Source: Funding: Parker B. Francis Fellowship (MKE), 1R21NS081431‐01 (DDF, BJB)
vGluT2 is necessary for rostroventrolateral medullary catecholaminergic neurons to drive respiration and parasympathetic activity (1091.4)
Authors: Holloway Ben , Abbott Steve , Viar Ken , Guyenet Patrice
Published: June 2021

Catecholaminergic neurons located in the rostroventrolateral medulla (CA‐RVLM) contribute to sympathetic, parasympathetic, and neuroendocrine responses and are activated by hypotension, hypoglycemia, hypoxia, infection, pain, and psychological stress. Most CA‐RVLM express vGluT2, and work on slices suggests they release glutamate but the significance of vGluT2 in these neurons in vivo is unestablished. To investigate the role of vGluT2 in CA‐RVLM in vivo, we crossed floxed vGluT2 mice with dopamine‐β‐hydroxylase (DβH) Cre mice, creating mice with vGluT2 selectively deleted from DβH neurons (cKO mice). We then injected a Cre‐dependent AAV2 that expresses channelrhodopsin fused to mCherry into the RVLM of cKO or control mice. In both experimental and control groups, photostimulation activated the channelrhodopsin+ CA‐RVLM. Photostimulation of CA‐RVLM in control mice increased respiratory rate in conscious mice and efferent vagal nerve activity in anesthetized mice, while in cKO mice, photostimulation had no affect on respiratory rate or efferent vagal nerve activity. Thus, vGluT2 is necessary for CA‐RVLM neurons to activate respiration and increase vagal nerve activity.

Grant Funding Source: Supported by NIH HL28785 and HL74011 to PGG, and American Heart Association 11post7170001 to SBGA
Optogenetic stimulation of adrenergic C1 neurons in rat produces arousal from sleep, sighs and increases breathing frequency (1091.5)
Authors: Burke Peter , Abbott Steven , Hodges Walter , Viar Kenneth , Coates Melissa , Stornetta Ruth , Guyenet Patrice
Published: June 2021

Acute hypoxia causes hyperventilation, sighs and arousal from sleep. The role of C1 neurons in mediating hypoxia counter‐regulation in a behaving animal remains untested. We determined sufficiency by optogenetic methods. Channelrhodopsin‐2 was selectively introduced into C1 neurons of Tyrosine Hydroxylase Cre‐driver rats (Cre/0) with a Cre‐dependant adeno‐associated viral vector (AAV2 DIO‐EF1alpha‐ChR2‐EYFP). Sleep stages were identified from EEG and neck EMG recordings. Breathing was measured using whole body plethysmography and blood pressure by telemetry. During non‐rapid eye movement sleep (nREM), unilateral photostimulation of C1 neurons produced arousal in 84 ± 4% of trials and sighs in 68 ± 7% of trials and increased respiratory frequency by 26 ± 5 bpm (n=5). During quiet awake states, C1 stimulation also caused sighs and increased breathing rate. This increase in breathing by C1 stimulation was occluded by hypoxia (12% O2), but not hypercapnia (6% CO2), despite the significantly higher basal ventilation under hypercapnia. This evidence suggests that the C1 neurons that activate breathing are themselves activated by hypoxia and drive the ventilatory response and arousal from sleep.

Grant Funding Source: NIH (HL28785, HL74011)
Minocycline prevents the attenuated acute hypoxic ventilatory response and changes in brainstem neurochemistry following neonatal sustained hypoxia exposure (1092.11)
Authors: MacFarlane Peter , Mayer Catherine
Published: June 2021

Sustained hypoxia (SH) exposure uniquely during the end of the second postnatal week of life (postnatal (P) age 11‐15) attenuates the acute hypoxic ventilatory response (HVR) in rats. In the current study, we investigated whether the microglia inhibitor minocycline would be protective against the SH‐induced attenuation of the HVR and changes in brainstem neurochemistry. Neonatal rats were exposed to SH (11% O2, 5 days) starting at P11 and received an i.p. injection of minocycline (25mg/kg) or saline midway into the exposure period; plethysmography and measurements of brainstem immunoreactivity for Iba1 and 5‐HT were performed the day after SH ended (P16). SH exposure attenuated the HVR, increased Iba1 and decreased 5‐HT immunoreactivity in the nTS compared normoxia raised rats. Minocycline prevented the SH‐induced attenuated HVR including the changes in nTS Iba1 and 5‐HT immunoreactivity. We speculate that brainstem microglia may be involved in SH‐induced changes in brainstem neurochemistry leading to a 5‐HT‐induced modification of the mechanisms mediating the acute HVR. These data share several similarities to Sudden Infant Death Syndrome victims including evidence of impaired (cardio)‐respiratory control, brainstem gliosis, and serotonergic deficits associated with a vulnerability to an environmental stressor.
GAL‐160 increases CO2 chemosensitivity and reverses opioid‐induced respiratory depression in rats (1092.14)
Authors: Baby Santhosh , Ideo Courtney , Mardirosian Saro , Peng Sean , Golder Francis , MacIntyre D.
Published: June 2021

OIRD may result, at least in part, from decreased CO2 chemosensitivity. Previously, we reported that GAL‐021 administered IV reverses OIRD and increases CO2 chemosensitivity in rats. GAL‐021 IV has now been shown to attenuate OIRD in humans. Here we report on GAL‐160, an orally bioavailable analog of GAL‐021. In conscious rats, OIRD was induced with morphine (10 mg/kg, IV) and was evident as respiratory acidosis and hypoxemia using arterial blood gas analysis. GAL‐160 (0.03 ‐ 0.3 mg/kg/min X 30 min IV infusion) dose‐dependently reversed the effects of morphine on breathing. The effects on CO2 chemosensitivity were evaluated in urethane anesthetized rats following biphasic IV infusion of GAL‐160 (0.005 mg/kg/min X 15 min + 0.003 mg/kg/min X 60 min and 0.01 mg/kg/min X 15 min + 0.006 mg/kg/min X 60 min): regimens that do not stimulate ventilation. Minute volume was measured using tracheal spirometry at three levels of PaCO2: baseline (eucapnia), and +10 and +20 mmHg above baseline. CO2 chemosensitivity was calculated as the slope of the hypercapnic ventilatory responses. GAL‐160 increased CO2 chemosensitivity in the higher dose group (slope before GAL‐160: 10 ± 2; after GAL‐160: 16 ± 2 ml/min/mmHg) but not the lower dose group (before GAL‐160: 11 ± 2; after GAL‐160: 11 ± 2 ml/min/mmHg). These results demonstrate that GAL‐160 can reverse OIRD possibly by increasing CO2 chemosensitivity.
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
Rac1 as a potential candidate for improved insulin sensitivity following exercise (1095.5)
Authors: Sheikh Shabnam
Published: June 2021

It has long been known that physical exercise alleviates insulin resistance in diabetes. While several mechanisms of action have been explored, a clear signaling pathway has yet to be determined. One possible candidate for involvement is Rac1, a rho GTPase. Downstream of PI3K, Rac1 is involved in actin remodeling in the context of GLUT4 translocation and is activated in response to both insulin and exercise. Although Rac1 is active during exercise, the duration of activation following exercise is yet to be determined and may be critical in the post‐exercise improvements in insulin stimulated glucose uptake. The goal of my project is two‐fold. First, I plan to investigate the duration of Rac1 activation following exercise. Secondly, I plan to investigate Rac1’s role in the insulin/exercise signaling pathway by examining potential upstream and downstream proteins. Experiments will be conducted in vitro, using differentiated C2C12 murine skeletal muscle cells and electrical stimulation will be used in place of exercise to stimulate contraction. Cells will be cultured in normal media or in glucolipotoxicity media to mimic diabetes. Following electrical stimulation, active Rac1 levels will be measured at varying time points to determine length of Rac1 activation. In addition, to map out the Rac1 signaling pathway, various proteins will be blocked and downstream activity will be measured to determine the pathway. Results will be discussed once obtained.
Protective effects of lower dose of melatonin on TNFα‐induced type II collagen loss in primary cultured chondrocytes (1096.1)
Authors: Kim Joo‐Heon , Hong Yunkyung , Choi Jeonghyn , Hong Yonggeun
Published: June 2021

Type II collagen (COL2A1) is a major component of cartilage, and its loss is a main characteristic of osteoarthritis.The purpose of this study is to elucidate effects of melatonin on TNFa‐mediated extracellular matrix degradation in vitro. TNFaexposure for 24 hr induced reduction of cell viability with severe loss of COL2A1, but not proteoglycan, which was restored by lower dose of melatonin. Concomitantly, active MMP‐13 was decreased in melatonin‐treated cells. Calcitonin‐gene related peptide (CGRP) was also co‐treated with TNFa on chondrocytes. Although cell viability was higher in co‐treatment with CGRP than TNFa only, COL2A1 loss induced by MMP13 was augmented in combined treatment. However, proteoglycan and COL2A1 content were elevated by lower concentration of melatonin on TNFa and CGRP‐treated cells. There were upregulation of Bax and downregulation of Bcl‐2 in DMSO‐vehicle, leading to marked increase of Bax/Bcl‐2 ratio. It was significantly attenuated by melatonin at concentration of 1uM or 1nM, but not 1mM. Melatonin 1mM alone treatment without TNFa and CGRP induced alteration of cellular morphology, reduction of cell viability, and attenuation of COL2A1, indicating detrimental effect of high dose of melatonin on chondrocyte physiology.We suggest that lower dose ofmelatoninmay protect TNFa‐mediated catalytic response in primary cultured chondrocytes.
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
Molecular regulation of adiposity in a migrant, the gray catbird (1100.1)
Authors: Corder Keely , Russell David , Huss Janice , Schaeffer Paul
Published: June 2021

Prior to their migration, birds make physiological and behavioral adjustments to quickly accumulate fat stores to fuel their journey. The majority of these fat stores are utilized during their long‐distance flights. However, birds often complete vernal migrations with residual fat, which may be detrimental due to impaired flight behavior and increased predation risk, thus return to lean body composition is also rapid. This need for swift and substantial changes in a bird’s physiology marks migration as a unique life history stage emphasizing phenotypic flexibility, defined as intra‐individual and reversible phenotypic transformations. Specific mechanisms directing stage transitions of adiposity in migrating birds are largely unknown. This study aims to characterize the role of peroxisome proliferator‐activated receptors (PPARs) in migratory adiposity of the gray catbird (Dumetella carolinensis). PPARs are a family of nuclear receptors involved in mammalian energy metabolism and are highly conserved in our study species. We find evidence of PPAR involvement in migratory adiposity with a coordinated increased rate of glycerol release from adipose tissue, a downstream PPAR process, during periods of migration compared to non‐migratory stages. These data support further investigation into PPAR target gene expression experiments, and advance our understanding of the regulation of stage transitions associated with migratory adiposity.
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
Serotonin modulates the heart rate through 5‐HT2 receptor activation in Drosophila larvae (1100.7)
Authors: Stacy Audra , Majeed Zana , Cooper Robin
Published: June 2021

Serotonin, 5‐HT, plays various roles in the fruit fly, Drosophila melanogaster. Previous studies have shown that 5‐HT modulates the heart rate in third instar larvae. However, 5‐HT receptor subtypes that mediate 5‐HT action in larval cardiac tissue has not yet been determined. In this study, various 5‐HT agonists and antagonists were employed to determine which 5‐HT receptor subtypes are responsible for the positive chronotropic effect by 5‐HT. The pharmacological results demonstrate that a 5‐HT2B agonist significantly increases the heart rate; however, 5‐HT1A, 5‐HT1B, and 5‐HT7 agonists do not have a significant effect on the heart rate. Furthermore, 5‐HT2 antagonist, ketanserin, markedly reduces the positive chronotropic effect of 5‐HT in a dose‐response manner. Furthermore, we employed genetic approaches to confirm the pharmacological results. For this propose, we used RNA interference (RNAi) line to knock down 5‐HT2ADro and also used 5‐HT2ADro and 5‐HT2BDro insertional mutation lines. The results show that 5‐HT2ADro or 5‐HT2BDro receptors mutation reduces the response of heart to 5‐HT. Given these results, we conclude that 5‐HT2 receptors activation are involved in the action of 5‐HT on the heart rate in the larval stage.
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
The metabolic determinant underlying the rate of energy use during prolonged fasting for the diamondback watersnake, Nerodia rhombifer (1101.4)
Authors: Larkin Matthew , Secor Stephen
Published: June 2021

During prolonged bouts of fasting, tissues and organs lose mass as a function of their metabolic expenditure and differences in the allocation of endogenous energy. We previously observed considerable variation in the rate at which individual diamondback watersnakes (Nerodia rhombifer) lose body and fat mass during extended fasts. It has also been found that these snakes exhibit variation in their standard metabolic rate (SMR). We therefore hypothesized that individual variation in SMR is responsible for the observed variation in body mass and body fat loss with fasting. Predictably, snakes with relatively high SMR would metabolize fat stores at a greater rate (therefore loss body mass faster) than snakes that possess relatively low SMR. We explored the causal relationships between SMR and body and fat loss during extended bouts of fasting for the diamondback watersnake by examining variation in SMR and differential loss of body, fat, and organ mass over six months of fasting. Baseline SMR and body mass was measured from 55 snakes and organ masses from 10 snakes. For each following month, 5 snakes were dissected, with 10 snakes sampled on the 6th month. SMR of individuals was measured at 2‐month intervals. On average snakes lost 0.1 grams of fat per day while fasting, with a 5‐fold range in daily fat loss among snakes. After 5 months of fasting, variation in body fat loss ranged from 25% to 90%. There was a 2.5‐fold variation in SMR among these same individuals. As predicted, snakes with higher SMR experienced a greater rate of body fat loss. We have demonstrated that basal rates of metabolism can significant determine rates of body fat loss and therefore impact an individual’s capacity to survive long episodes of fasting.
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 loss

Grant 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).
Body position does not affect respiratory sinus arrhythmia magnitude (1103.4)
Authors: Abrosimova Marie , Baden Jeff , Day Trevor
Published: June 2021

Body position does not affect respiratory sinus arrhythmia magnitude Respiratory sinus arrhythmia (RSA) is the normal fluctuation in heart rate in phase with respiration. Instantaneous heart rate (IHR) increases with inspiration and decreases with expiration. The mechanisms underlying RSA are unclear, but some evidence suggests that central brainstem mechanisms drive RSA, independent of afferent feedback. Cardiac loading associated with inspiration or gravity may also trigger the Bainbridge reflex, although the contribution of this reflex is unclear in humans. We investigated the effects of incremental increases in inspired volume on RSA magnitude during both 45° head‐up and head‐down tilt (HUT, HDT). Six healthy subjects were positioned on a tilt table and instrumented with ECG to measure IHR (60/period) and a pnuemotachometer to measure respiratory volumes. Following a forced vital capacity (FVC) measurement, subjects were coached to breathe 30 consecutive breaths at each inspiratory volume of 10, 15, 20, 25 and 30% of FVC using a computer screen for visual feedback. The average RSA magnitude of the middle 10 breaths of each trial was plotted against the inspired volume, and linear regression was performed. The increase in RSA magnitude with inspired volume was highly linear in HUT and HDT (R2>0.9), but the mean slopes were not different between positions. We have determined a range of inspired volumes that generate a linear RSA magnitude response. Further, our data demonstrate that gravity‐dependent cardiac loading does not influence RSA magnitude associated with increases in inspired volume.
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 stress

Stephen J. Carter, Robert L. Herron, S. Zeb Akers, Ann B. Collins, Jonathan E. Wingo. Department of Kinesiology, The University of Alabama, Tuscaloosa, AL 35487

Aspirin (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
Aerobic fitness affects noradrenergic involvement in cutaneous vasoconstriction to local and whole body cooling (1104.8)
Authors: Miller James , Hodges Gary
Published: June 2021

We investigated the effect of aerobic fitness on the adrenergic involvement during local and reflex cutaneous vasoconstriction (VC) in response to local cooling (LC) and whole body skin cooling (WBC). In 8 sedentary and 8 aerobically‐trained subjects skin blood flow (SkBF) was measured using laser‐Doppler flowmetry. Local skin temperature (Tloc) and whole body skin temperature (Tsk) were controlled with cooler/heater probe holders and water perfused suits, respectively. Microdialysis was used to administer yohimbine and propranolol (YP) to antagonise α‐ and β‐receptors, and BIBP to antagonise Y1‐receptors. Ringer’s was perfused at control sites. Part 1 investigated the effect of aerobic fitness on VC responses to LC (Tloc 34 to 24°C). Trained participants exhibited a greater vasoconstrictor response to LC compared to sedentary participants at control sites (P 0.05). YP treatment reduced the VC in both groups (P < 0.05). Part 2 examined reflex VC to WBC (Tsk 34 to 30.5°C). Again, well‐trained subjects presented greater VC in response to WHC compared to sedentary subjects (P < 0.05), but not under conditions of adrenergic blockade. Sedentary individuals display an impaired VC response to LC and WBC when compared to well aerobically‐trained individuals. These data suggest that aerobic training can improve cutaneous VC responses and this is mediated via adrenergic function.
Thermal effect induced by anandamide is dissociated of locomotor and feeding behavior (1105.5)
Authors: Lima Paulo , Machado Frederico , Coimbra Cândido
Published: June 2021

The endocannabinoid system has an important role on thermal control and modulates behaviors that may affect the body temperature (Tb), such as locomotion and food intake (FI). In order to test whether changes on Tb induced by anandamide (AEA) are related with behavioral changes, rats received an i.c.v. injection of AEA (0.1, 1.0 and 10.0 μg) and vehicle. Total FI was daily weighted, and both Tb and spontaneous locomotor activity (SLA) were simultaneous and continuously recorded. AEA induced increase on Tb without changes on SLA and FI. For all doses tested, the Tb average at post‐injection period was higher than pre‐injection period. Higher termal effect was verified by 10.0 μg of AEA, starting within the first hour post‐injection, being maintained for 8 hours after treatment. At the first hour, a dose‐dependent thermal effect was observed (r = 0.953; p<0.05). Hypoactivity was verified only for 1.0 μg of AEA. As expected, both Tb and SLA values at dark phase were always higher than at light phase with a positive correlation between them (r = 0.834, p<0.001), however this correlation was inverted (r = ‐0.852, p<0.01) after 10.0 μg of AEA. In summary, our results suggest that brain AEA induces increase of Tb, and this effect may occur independently of changes in both locomotion and FI. Moreover, it is possible that hypolocomotion induced by AEA could be an adaptive response due to increased Tb.

Grant Funding Source: CNPQ, Capes and Fapemig
Aging is associated with slowed vasodilator kinetics in dynamically contracting muscle: role of nitric oxide (1106.10)
Authors: Casey Darren , Walker Branton , Ranadive Sushant , Joyner Michael
Published: June 2021

We tested the hypothesis that aging would be associated with slowed vasodilator kinetics in contracting muscle in part due to a reduced nitric oxide (NO) bioavailability. Young (n=10; 24 ± 2 yr) and older (n=10; 67 ± 2 yr) adults performed rhythmic forearm exercise (4 min each) at 10, 20 and 30% of max during saline infusion (control) and NO synthase (NOS) inhibition. Brachial artery diameter and velocities were measured using Doppler ultrasound. Forearm vascular conductance (FVC) was calculated for each duty cycle (1s contraction/2s relaxation) from blood flow (ml/min) and blood pressure (mmHg) and fit with a monoexponential model. The main parameters derived from the model were the amplitude (Amp) of the FVC response and the number of duty cycles for FVC to change 63% of the steady‐state amplitude (τFVC). Under control conditions 1) the Amp of the response at 20 and 30% MVC was lower in older (240 ± 24 and 319 ± 33 ml/min/100mmHg) compared to young adults (338 ± 45 and 462 ± 52 ml/min/100mmHg; P < 0.05) and 2) τFVC was slower in older (10 ± 1, 13 ± 1 and 15 ± 1 duty cycles) compared to young (6 ± 1, 9 ± 1 and 11 ± 1 duty cycles) adults at all intensities (P < 0.05). NOS inhibition blunted the Amp and slowed the τFVC in young, at all intensities (10 ± 2, 12 ± 1 and 16 ± 2 duty cycles; P < 0.05), whereas it did not change in older adults. Our data indicate that the vasodilator kinetics in exercising muscle are altered with aging likely due to blunted NO signaling.

Grant Funding Source: Supported by NIH grants HL105467 (DPC), HL46493 (MJJ) and by CTSA UL1 TR000135