bluuebunny/crossref_metadata_2025_split huggingface dataset:
Human amylin proteotoxicity impairs protein biosynthesis, and alters major cellular signaling pathways in the heart, brain and liver of humanized diabetic rat model in vivo
Authors: Ilaiwy Amro , Liu Miao , Parry Traci S. , Bain James R. , Muehlbauer Mike J. , Willis Monte S. , Despa Florin 
Published: June 2021

The 37 amino acid hormone Amylin is co‐secreted with insulin from β cells in the pancreas. In pre‐diabetic and obese humans, chronic amylin hyper‐secretion parallels the course of disease and is involved in the pathophysiology of beta cell destruction in the pancreas. In rats with transgenic expression of beta cell amylin (HIP), we have discovered that human amylin is prone to misfolding and has proteotoxic effects in vivo, resulting in the induction of cell death paralleling the pathophysiology of neurodegenerative disease. These misfolded proteotoxic amylin proteins are found to migrate to both the brain and heart to induce both neurologic deficits and cardiac dysfunction. In the present study, we use non‐targeted GC‐MS metabolomics analysis to investigate the metabolic consequences of amyloidogenic and cytotoxic amylin oligomers and diabetes in HIP heart, brain, liver, and plasma compared to wild type controls at 1 year of age. We identified that HIP hearts had 45 significantly altered metabolites by t‐test (p<0.05) compared to wildtype control hearts (0.1–34.3 fold different, N=8/group). Similarly, we identified 30 metabolites significantly different in the HIP brain by t‐test (p<0.05) compared to wildtype control brains (0.2–25.2 fold different (N=~10/group). HIP livers had 58 metabolites significantly altered by t‐test (p<0.05) compared to wildtype livers (0.01–99.4 fold different, N=~10/group. Pathway enrichment analysis identified a systemic alteration in protein biosynthesis in the heart and brain of HIP rats compared to wild type controls. Phenylalanine metabolism and aminoacyl‐tRNA biosynthesis were specifically decreased in heart and plasma. Tyrosine metabolism is affected across organs, including decreased tyrosine (heart), phenylalanine (heart, liver, brain), and increased fumarate (heart, liver, brain). Increased urea and urea cycle were identified in heart and liver. As protein degradation is a major up‐regulator of the urea cycle in human rat diabetic models, these findings suggest a broader connection between amylin, diabetes, protein catabolism, and effects on the urea cycle, which may contribute to the increased morbidity and mortality in diabetics at a multi‐system level beyond the effects on glucose metabolism.Support or Funding InformationThis work was supported by the National Institutes of Health (R01HL104129 to M.W.; R01HL118474 to F.D.), a Jefferson‐Pilot Corporation Fellowship (to M.W.), National Science Foundation (CBET 1357600 to F.D.), Alzheimer's Association (VMF‐15‐363458 to F.D.) and the Leducq Foundation (to M.W.).
Heat Stress Effects on the Kinetics of Olfactory Responses
Authors: Hagerty Samantha , Singletary Melissa , Globa Ludmila , Pustovyy Oleg , Morrison Edward E , Sorokulova Iryna , Vodyanoy Vitaly J 
Published: June 2021

Temperature is one of the most challenging stressors, affecting human and animal health. Extreme heat stress can damage the olfactory sensory neurons. In this work, we examined the effects of elevated temperature on the kinetic properties of rat olfactory sensory receptors in vitro by the recording of electroolfactogram (EOG) of the olfactory epithelium (OE) removed from the animals before and after the heat stress at 45 ºC for 25 minutes. EOG were evoked by an odorant mixture of ethyl butyrate, eugenol, and (+) and (−) carvone. The biochemical properties of the animal blood related to heat stress were characterized. Exposure of rats to high temperature resulted in a significant increase of body temperature. The mean body temperatures of rats before and immediately after heat stress were 36.7±0.07 ºC and 40.3 ±0.17 ºC, respectively. The kinetic properties of electrical responses to odorant were significantly changed in animals subjected to heat stress. The mean half‐rise (tr)and –decay times (td) of control OE were 328±11 and 660±20 ms, respectively. The rise and decay of EOG peak amplitude after heat stress were much faster, being reduced by 175 %, and 72 %, respectively. Heat stress did not result in a change of IL‐1β; IL‐6, TNF‐α, INF‐γ cytokines level. However, a significant increase of the IL‐10 level was found in rats exposed to heat. The level of lipopolysaccharides (LPS) was significantly increased in the serum of heat‐stressed animals compared to control animals. The concentration of free vesicles in animal blood increased after exposure to heat stress from (1.4±0.2)×106 to (3.8±0.3)×106 vesicles μl−1, indicating a faster conversion of erythrocytes into echinocytes. The kinetic properties found in this work are consistent with the kinetics of cultured mouse olfactory neurons 1. The effect of elevated temperature on the kinetic properties of olfactory receptors is also consistent with those seen in other neurons2–4. Detrimental effects of elevated temperatures on olfaction are shown in other animals5. The change in kinetic properties of olfactory receptors as a result of elevated temperature is consistent with those in other neurons2–4. Cytokines were found to cause neurodegeneration of the olfactory bulb6. We conclude that heat stress causes a strong irreversible modulation of olfactory responses.Support or Funding InformationSupported by grant from the National Institute of Standards and Technology: 70NANB14H324
High‐Fat Diet Induced Modulation of Glutamatergic Currents in Neurons of the Dorsal Motor Nucleus of the Vagus
Authors: Clyburn Courtney E. , Browning Kirsteen N. 
Published: June 2021

A high fat diet (HFD) has been shown to induce reactive gliosis in many areas of the central nervous system, including the brainstem. This gliosis, and particularly astrocyte activation, have been shown to modulate the properties of the synapse including synaptic strength. While we demonstrated previously that longer‐term exposure to a HFD affects synaptic transmission to neurons of the dorsal motor nucleus of the vagus (DMV) in rats, the effects of short‐term exposure have not been examined. The purpose of this study is to test the hypothesis that, following short periods of exposure to a HFD, astrocyte activation contributes to the modulation of synaptic transmission in the DMV.Whole cell patch clamp recordings of DMV neurons were made from thin (300mm) brainstem slices from Sprague‐Dawley rats 4–6 years of age. Rats were fed a control diet (14% kcal from fat) throughout the study, or a HFD (60% kcal from fat) for 3–7 days prior to experimentation. The effects of fluoroacetate (100μM), an astrocyte metabolism inhibitor, on glutamatergic miniature excitatory postsynaptic currents (mEPSCs) were examined.The short periods of exposure to HFD employed in the current study did not alter DMV neuronal properties. Since astrocytes are primarily responsible for glutamate uptake and clearance from the synapse, neurons were defined as responding to fluoroacetate if the drug induced a significant increase in mEPSC decay time. Accordingly, 7/13 HFD neurons responded to fluoroacetate, and in these neurons, both the amplitude and frequency of glutamatergic mEPSCs were decreased significantly (11.7 ± 0.85 pA in fluoroacetate vs 15.2 ± 0.85 pA in control; 0.5±0.09 vs 1.1±0.25 events per second; n=7; p<0.05 for both). In contrast, in control rats, neither the amplitude nor frequency of mEPSCs were affected by fluoroacetate, even in the 3/12 responding neurons (16.5 ± 0.55 pA vs 15.0 ± 0.1 pA; 0.8±0.25 vs 1.0±0.34 events per second; n=6; p>0.05 for both).This study suggests that even short periods of exposure to a HFD alter astrocyte activity that subsequently modulates synaptic transmission. Fluoroacetate‐induced alterations in both frequency and amplitude of glutamatergic synaptic events suggests that this modulation occurs both presynaptically and postsynaptically. Astrocytes are known to release glycine and D‐serine, which are essential co‐factors for the NMDA receptor. While the NMDA receptor appears not to be tonically active in the DMV under normal conditions, altered astrocyte function may contribute to the increase in glutamatergic mEPSC amplitude in HFD. In total, these results indicate that short‐term exposure to a high fat diet may alter the synaptic strength in the DMV, even in the absence of HFD‐induced weight gain or peripheral inflammation. These modulations of vagal circuitry may dysregulate gastrointestinal reflexes or disrupt gastric motility.Support or Funding InformationFunded by NIH 078364 and NSF IOS1148978
Poloxamer 188 Improves Autoresuscitation in Pigs with Severe Traumatic Hemorrhage
Authors: Martini Wenjun , Xia Hui , Dubick Michael A 
Published: June 2021

IntroductionPoloxamer 188 (P188) is a copolymer surfactant. Its protective effects against ischemic injury, cardiomyopathy, and intracerebral hemorrhage have been shown in studies from rats and mice. The underlying protective mechanisms are unclear. This study investigated its effects on blood volume in pigs after severe traumatic hemorrhage and hypotensive resuscitation.MethodsTwenty anesthetized and instrumented pigs were randomized into saline (n=10) and P188 (n=10) groups. Femur fracture was performed in each pig's left leg, followed by hemorrhage of 55% of estimated blood volume and 15 min shock period. Afterwards, pigs were resuscitated with small volume of saline (4ml/kg) or P188 (1.33 ml/kg of P188 200mg/ml, plus 2.67 ml/kg saline). Indocyanine green dye (5ml of 1mg/ml) was injected before femur and hemorrhage and 15 min after P188 administration with blood samples taken accordingly to determine changes of blood volume and Hct. Pigs were monitored for 6h or until death.ResultsAll baseline measurements are similar between the two groups. Femur and hemorrhage reduced mean arterial pressure to 54±6% of baseline values and reduced blood volume from 104±4 ml/kg to 67±4 ml/kg (both p<0.05) and reduced Hct from 31±1% to28±1% in the saline resuscitated group. Less reduction was observed with P188 resuscitation in blood volume (from 98±3 ml/kg to 74±3 ml/kg, p<0.05 compared to baseline and to saline values), with a consistent larger drop in Hct (31±1% to 24±1%, p<0.05 compared to baseline and to saline values). Survival time was similar between the saline (225±45 min) and P188 (235±78 min) groups.ConclusionsFollowing severe traumatic hemorrhage and small volume resuscitation in pigs, P188 improved autoresuscitation, but did not affect short term survival.Support or Funding InformationUS Army Medical Research and Materiel Command
Effects of Systemic Hypercapnia and Orexin on Gastric Motility and Respiration in Rats
Authors: Sherwood Jacob William , Landon Carol , Dean Jay 
Published: June 2021

The theory of pneumogastric ventilation predicts that systemic hypercapnia causes a primary pulmonary hypercapnic ventilatory response (HCVR) that is supplemented by a secondary gastric ventilatory response that work together to remove excess CO2 from the body. Gastric ventilation consumes arterialized CO2 during increased production and secretion of gastric acid. In the stomach lumen, CO2 is reconstituted and “ventilated” out through the esophagus, mixed in the oropharynx with pulmonary gas and “exhaled”. Activation of gastric ventilation occurs during CO2 retention in a hypercapnic environment or with alveolar hypoventilation such as COPD. Both pulmonary and gastric ventilatory responses are integrated and coordinated at the level of the caudal solitary complex (cSC), mediated in large part by the vagus nerve (Dean, 2011, Resp Physiol Neurobiol 175(2): 189–209). Central chemoreceptors in the cSC or stimulated by both CO2/H+ and orexin. Likewise, CO2/H+ and orexin stimulate pulmonary ventilation and gastric acid secretion. In fact, hypercapnia causes an increase in production of orexin, which helps maintain the HCVR during wakefulness (Nattie et al, 2010, J Appl Physiol 89: 153–162). Consistent with the theory of pneumogastric ventilation, we found that hypercapnia causes an acute decrease in gastric pH. We do not know, however, how hypercapnia affects gastric motility. Accordingly, we implanted male Sprague‐Dawley rats with the DSI 4‐ET Telemetry unit to measure ECG, respiratory rate via diaphragmatic EMG (dEMG), and gastric EMG (gEMG) to measure gastric motility. Following recovery from surgery, we then subjected them to step‐wise increases in ambient CO2 (30 min/step) starting with air, 5% CO2 in air, 10% CO2 in air, and recovery in air. We also tested the effects of orexin on gastric motility during normocapnia using a lateral tail vein IV injection of orexin‐A. Histamine was used as a positive control for gastric motility. Our findings show that in air, gEMG activity occurs roughly every 15 seconds with bursts lasting 3–4 seconds. Graded hypercapnia caused a graded decrease in the amplitude of periodic gEMG bursts (5% CO2) that stopped completely in 10% CO2. Recovery in air rapidly returns gEMG activity to normal. As expected, dEMG increased with increasing CO2. Similarly, orexin‐A causes an immediate decrease in gEMG activity. We postulate that CO2 activates cSC neurons causing vagally‐mediated relaxation of gastric smooth muscle and increase in gastric acid production to ventilate gastric CO2 during systemic hypercapnia.Support or Funding InformationONR N000141310405 & N000141612537
Episode Frequency Determines the Impact of Chronic Intermittent Hypoxia on Phrenic Long Term Facilitation
Authors: Gonzalez‐Rothi Elisa Janine , Perim Raphael Rodrigues , Tadjalli Arash , Simon Alec K , Ciesla Marissa , Mitchell Gordon S 
Published: June 2021

Acute intermittent hypoxia (AIH) elicits a form of spinal, phrenic motor plasticity known as phrenic long‐term facilitation (pLTF). Preconditioning with chronic intermittent hypoxia (CIH) as might be experienced during sleep disordered breathing, has conflicting effects on pLTF. For example, preconditioning with CIH consisting of 5 min hypoxic episodes with 5 min intervals (12 hours per night; 7 days) enhances AIH induced pLTF (Ling et al., 2001). Conversely, 8 hours of intermittent hypoxia consisting of 2 min episodes with 2 min intervals 16 hours prior to AIH abolishes pLTF through a mechanism that requires systemic inflammation and spinal p38 MAP kinase activation (Huxtable et al., 2015). We hypothesized that this differential response resulted from differences in the frequency hypoxic episodes (6 versus 15 per hour), versus the cumulative duration (1 versus 7 days) or timing (day versus night) of intermittent hypoxia. Thus, we compared the impact of intermittent hypoxia presented for 7 consecutive days, 8 hours per day (IH‐7). The three experimental groups were: 1) 5 min episodes of 10.5% O2 with 5 min normoxic intervals (6 episodes/hour, 8 hours/day, 7 days; IH‐7‐5min); 2) 2 min hypoxic episodes (10.5% O2) with 2 minute normoxic intervals (15 episodes/hour, 8 hours/day, 7 days; IH‐7‐2 min); and 3) naïve rats exposed to normoxia (21% O2; 8hrs/day, 7 days; sham). Neurophysiology experiments conducted 16 hours after the final day of IH‐7 enabled assessment of AIH‐induced phrenic and hypoglossal long‐term facilitation. In comparison with sham rats, rats preconditioned with IH‐7‐5 exhibited normal pLTF expression (45% baseline; p < 0.05). In rats preconditioned with IH‐7‐2, pLTF was abolished (7% baseline; p> 0.05). Mean arterial pressure was elevated in rats exposed to IH‐7‐2 (10mmHg), but not IH‐7‐5. Thus, the impact of CIH on pLTF and arterial blood pressure is highly dependent on the frequency of hypoxic episodes. An important transition in impact of CIH from pro‐plasticity to pro‐inflammatory/pathogenic (Dale et al., 2014) occurs between 6 and 15 episodes per hour, consistent with previous literature reports (Navarette‐Opazo et al., 2014).Support or Funding InformationSupported by: K12HD055929 (EGR), 1R01HL69084 (GSM); 1R01HL511198 (GSM)
Intraspinal microstimulation induced respiratory phase resetting
Authors: Sunshine Michael Daniel , Ganji Comron Nassar , Reier Paul J , Moritz Chet Thomas , Fuller David D 
Published: June 2021

Electrical stimulation of the spinal cord can activate somatic motor circuits after spinal cord injury. In particular, stimulation of the dorsal spinal cord has translated into clinical use due to the relatively low invasiveness. Modeling studies indicate that dorsal activation of motor pathways occurs through excitation of afferent projections to spinal motor pools. However, because spinal stimulation does not always allow for activation of discrete neuronal populations, off target effects are often observed. In ongoing studies, our group is investigating intraspinal microstimulation as a tool to activate respiratory motoneurons with possible application to spinal cord injury. Currently it is unclear if and how intraspinal stimulation will alter the pattern of respiratory output produced by the brainstem. However, activation of ascending respiratory‐related afferent fibers in cervical dorsal white matter or spinobulbar projections from cervical interneurons has the potential to modulate the respiratory pattern. Here we tested the hypothesis that intraspinal microstimulation in the dorsal but not ventral mid‐cervical spinal cord would rapidly alter the timing of inspiratory discharge. Diaphragm, external intercostal, and sternocleidomastoid electromyography activity was recorded in N=6 anesthetized and ventilated spinal intact adult rats. Following unilateral laminectomy from C2‐T1 a 10×2 grid was established by dividing the rostrocaudal exposed cord into ten sites with the two stimulus tracts located 0.5 and 1mm lateral to midline. A tungsten electrode was gradually advanced from the dorsal spinal surface to depth of 1800–2400μm with 10–90 μA currents (0.3 ms per phase, biphasic pulses) delivered every 600 μm. Dorsal stimulation (average simulation depth of 478 μm) resulted in an abrupt increase in respiratory rate (breaths per minute) at~13% of tested sites. Of the sites that triggered increases in respiratory rate, 54% were located at the dorsal surface (i.e., depths of 0 μm). These initial results indicate that intraspinal stimulation of the dorsal cervical spinal cord can trigger rapid changes in respiratory rate, presumably via activation of ascending pathways which innervate brainstem respiratory neurons.Support or Funding InformationFUNDING: 1R01NS080180‐01A1 (DDF), NICHD: T32‐HD043730 (MDS), Department of Defense W81XWH‐14‐1‐0625 (PJR)
High‐altitude Adaptation and Hypoxia Signaling in Deer Mice
Authors: Scott Graham R. , Ivy Catherine M. , Tate Kevin B. , Velotta Jonathan P. , Schweizer Rena M. , Cheviron Zachary A. 
Published: June 2021

The hypoxic and cold environment at high altitudes requires that endothermic animals sustain high rates of O2 consumption for both locomotion and thermogenesis while facing a diminished O2 supply. Recent evidence suggests that genes in the hypoxia inducible factor (HIF) pathway have been targeted by natural selection and have contributed to evolutionary adaptation to high altitudes in several species. Here, we examine the role of hypoxia signaling in high‐altitude adaptation in deer mice (Peromyscus maniculatus). Maximal O2 consumption (VO2max) in hypoxia is augmented in high‐altitude populations, underpinned by increases in pulmonary O2 extraction, arterial O2 saturation, cardiac output, and tissue O2 extraction compared to low‐altitude populations. Highlanders also maintain higher heart rates during deep hypoxia at rest. Associated with the population differences in physiology is extreme allele frequency variation in a non‐synonymous single nucleotide polymorphism in Epas1, the gene encoding HIF‐2α. Transcriptome scans indicate that these differences in Epas1 allele frequency stem from a history of spatially varying selection between high and low altitudes. RNA‐Seq measurements of gene expression in the left ventricle show that transcriptomic variation in HIF target genes is correlated to VO2max. Furthermore, comparisons of the hypoxia response between mice with different Epas1 genotypes (captured from an admixed population on the summit Mount Evans CO) show that the high‐altitude Epas1 allele is associated with higher heart rates in deep hypoxia, but that it has no association with variation in breathing or blood haemoglobin content. Our results therefore suggest that changes in hypoxia signaling contribute to high‐altitude adaptation in deer mice.Support or Funding InformationSupported by NSERC of Canada and the USA National Science Foundation
Mitochondria‐derived Small Non‐coding RNAs in Extreme Anoxia Tolerance
Authors: Riggs Claire Louise , Podrabsky Jason Earl 
Published: June 2021

Mitochondria are critical sensors of oxygen and play a major role in the regulation of the cellular response to oxygen deprivation. Understanding mitochondrial function during transitions into and out of anoxia in species that can tolerate anoxia may lend new insights into the role that mitochondria play in cellular homeostasis in response to fluctuating levels of oxygen. The objective of this study was to examine the potential role of small RNAs in long‐term vertebrate anoxia tolerance. Expression patterns of small RNAs were determined using RNAseq in the most anoxia tolerant vertebrate, embryos of the annual killifish Austrofundulus limnaeus. Anoxia tolerance varies during development in this species in a way that allows for the comparison of developmental stages with extreme anoxia tolerance to stages with a more typical vertebrate anoxia tolerance. Embryos of 4 different developmental stages were exposed to anoxia, followed by aerobic recovery, and small RNA expression was determined with Illumina RNAseq under aerobic conditions, anoxia, and during aerobic recovery. A large proportion of the differentially expressed small RNAs were found to be encoded in the mitochondrial genome. About 12% of the unique small RNAs identified were encoded within the mitochondrial genome, and around 20% of the highly differentially expressed RNAs in response to anoxia were mitochondrial in origin. Of the differentially expressed sequences mapping to the mitochondrial genome, small RNAs derived from mitochondrial tRNAs were particularly enriched, with sequences up‐regulated during anoxia and aerobic recovery from anoxia. These small RNAs of interest localize to anoxia sensitive tissues, such as the brain and heart, providing further evidence for a potential role in supporting anoxia tolerance. These same small RNAs have been detected in cell cultures derived from A. limnaeus embryos, by RNAseq and in situ hybridization. Cell culture expression patterns corroborated whole‐embryo sequence expression patterns. This work highlights a potential new class of small RNAs derived from the mitochondrial genome that may act to mediate and coordinate the physiological response to anoxia in this species. Further understanding the biology of these mitochondrially‐derived small RNAs and their role in anoxia tolerance may provide novel insight into combating cellular damage induced by heart attack and stroke, two lethal consequences of heart disease in humans.Support or Funding InformationNSF IOS 1354549; NSF GRFP DGE 1057604