bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Impact of Nitrate Supplementation on the Peripheral Chemoreceptor Reflex to Hypoxia in Older Adults
Authors: Bock Josh , Limberg Jacqueline , Hughes William , Kruse Nicholas , Ueda Ken‐ichi , Casey Darren 
Published: November 2023

Peripheral chemoreceptors located within the carotid bodies activate cardiorespiratory reflexes in response to hypoxia. Carotid body chemoreceptor activity has been shown to be enhanced in conditions such as congestive heart failure, hypertension, and possibly aging. Nitric oxide (NO) has been proposed as an inhibitory modulator of carotid body chemosensitivity in response to hypoxia. Additionally, NO bioavailability is often reduced with cardiovascular risk factors such as aging. In the present study, we tested the hypothesis that increasing NO bioavailability via dietary nitrate (NO3) supplementation would reduce cardiorespiratory responses to hypoxia in older adults. A double‐blind, randomized, placebo‐controlled, cross‐over study design was used to evaluate minute ventilation (VE) and heart rate (HR) responses to acute hypoxia in 7 older adults (66±2 years; 5M/2F) before and after 4 weeks of NO3 supplementation (beetroot powder) and placebo (beetroot powder devoid of NO3). On each study visit, subjects underwent two separate isocapnic hypoxic tests (self‐regulating, partial rebreathing system with 10% O2). Subjects remained on 10% O2 until SpO2 reached ≤80%. The hypoxic exposures were separated by a 15‐minute washout period with the subjects breathing room air. VE, HR, and SpO2 were continuously monitored throughout each hypoxic exposure. Data were grouped together using a 7‐breath average with the slope of the linear regression line for each dependent variable (VE and HR) versus SpO2 serving as a measure of peripheral chemosensitivity. The slopes for the two hypoxia tests on each study visit were averaged and used for statistical comparisons. On study day one (true baseline) acute hypoxia increased both VE and HR (P<0.05 for both). Four weeks of NO3 supplementation reduced the hypoxic ventilatory response (−0.16 ± −0.05 vs. −0.06 ± −0.03 L/minute/%SpO2, P<0.05), whereas no change was observed following the placebo phase of the study (−0.14 ± −0.07 vs. −0.14 ± −0.08 L/minute/%SpO2, P=0.67). Additionally, the heart rate responses to acute hypoxia were also reduced following NO3 supplementation (−0.49 ± −0.08 vs. −0.30 ± −0.05 beats/minute/%SpO2, P<0.05), but not with placebo (−0.54 ± −0.11 vs. −0.45 ± −0.08 beats/minute/%SpO2, P=0.21). Our preliminary findings suggest that supplementation of NO3 to boost NO bioavailability in older adults blunts the cardiorespiratory responses to hypoxia. Future studies should examine the therapeutic potential of NO3 in patient populations exhibiting exaggerated peripheral chemosensitivity.Support or Funding InformationResearch supported by Neogenis Inc.
Acute intermittent hypoxia (AIH) and continuous hypoxia increase augmented breaths and efferent splanchnic sympathetic nerve activity in conscious rats
Authors: Coldren Kevin Max , Hasser Eileen , Heesch Cheryl 
Published: November 2023

Previously we reported an intensity dependent effect of continuous hypoxia to increase minute ventilation and augmented breaths (high amplitude spikes in plethysmography traces). Lesion of catecholaminergic neurons projecting to the PVN attenuated ventilatory responses to hypoxia, suggesting an important role for the PVN. Recent immunohistochemistry experiments revealed that pre‐sympathetic neurons in the PVN were activated by acute intermittent hypoxia (AIH, 5 bouts, 3 min 10% O2, separated by 5 min of 21% O2) but not by continuous 10% or 8% O2 (2 hr). Current experiments in chronically instrumented conscious rats evaluated the functional effects of continuous 8% O2 (2 hr, n = 5) and AIH (n = 5) on mean arterial pressure (MAP), heart rate (HR) and integrated efferent splanchnic sympathetic nerve activity (int. SSNA). Effects of AIH on diaphragm EMG were determined in a separate group of rats (n=9). Continuous 8% O2: Qualitatively similar to previous data using 10% O2, 2 hr continuous 8% O2 resulted in a sustained decrease in MAP (baseline = 112 ±3; 2 hr 8% O2 = 86 ± 2 mmHg) and an initial increase in HR from baseline (334 ± 6 beats/min) to 424 ± 26 beats/min at 5 min. Within 5 min of exposure to 8% O2, int SSNA increased (+258 ±22%) and remained elevated at 2 hrs (+179±92%). MAP, HR, and int SSNA returned towards control levels within 10 min after return to normoxia (21% O2). Acute Intermittent Hypoxia: MAP, HR, and diaphragm EMG were measured in 9 conscious rats previously instrumented with telemetry probes. AIH bouts increased MAP (e.g. AIH5= +7±1 mmHg), HR (e.g. AIH5= +83±8 beats/min), integrated diaphragm EMG amplitude (e.g. AIH5= +25±7%), and frequency of regular breathing (e.g. AIH5= +49±7 breaths/min). Similar to responses with continuous hypoxia, regularly spaced augmented breaths (high amplitude diaphragm EMG) were evident during bouts of AIH (e.g. AIH5= 3±1/min). In a separate group of chronically instrumented conscious rats (n =5), MAP, HR and SSNA were monitored during the AIH protocol. Similar to telemetry data, bouts of hypoxia increased MAP (e.g. AIH5= +8±2 mmHg) and HR (e.g. AIH5= +75±7 beats/min). In addition SSNA increased during hypoxic bouts (e.g. AIH5= +183±38 % from baseline). Interestingly, it appears that regularly spaced large bursts in SSNA occurred at a frequency (e.g. AIH5 =3±0/min) similar to the frequency of high amplitude bursts that were observed in diaphragm EMG in telemetry experiments. Combined with immunohistochemistry findings, we conclude that activation of pre‐sympathetic neurons in the PVN could possibly contribute directly to the increased SSNA during AIH, but activation of SSNA during continuous hypoxia (8% O2) appears to be mediated by pathways distinct from the PVN.Support or Funding InformationFunded by NIH HL 98602.
Expression of adrenergic alpha 1 receptor subtypes in magnocellular, pre‐autonomic and medial parvocellular regions of the paraventricular nucleus of the hypothalamus (PVN): Effects of acute intermittent hypoxia
Authors: Heesch Cheryl Miller , Coldren Kevin Max , Barr Stacy 
Published: November 2023

Catecholaminergic inputs to magnocellular, pre‐autonomic, and medial parvocellular neuroendocrine cells in the PVN may participate in activation of these neurons during chemoreflex stimulation. Current experiments evaluated the effects of acute intermittent hypoxia (AIH, 3 min 10% O2, separated by 5 min) on regional expression of alpha1 adrenergic receptor subtypes within the PVN. Spinally projecting PVN neurons were pre‐labeled in rats by prior IML injections of Fluorogold (2%,180 nl bilateral) to aid in visual identification of pre‐autonomic regions of the PVN. Conscious rats were exposed to AIH, while normoxic control rats (N) were exposed to changes in gas flow over the same times, but O2 concentration remained at 21%. One hour later, rats were deeply anesthetized, brains were removed, and the forebrains sectioned (10 μm) on a cryostat. Laser Capture Microscopy (LCM) was used to capture magnocellular, pre‐autonomic and medial parvocellular neurons in the PVN. RNA was isolated, cDNA synthesized and, using target specific primers, expression of mRNA for alpha 1 adrenergic receptor subtypes, 1a, 1b, and 1d and the reference gene GAPDH was evaluated by real time RT‐PCR. Capture of cell populations enriched for specific regions of the PVN was verified by high relative expression of mRNA for vasopressin in the magnocellular (1±0.55) compared to the medial (0.05±0.01) and pre‐autonomic regions (0.13±0.1), and high relative expression of glucocorticoid receptor mRNA in the medial (1±0.33) versus the magnocellular (0.16±0.03) and pre‐autonomic regions (0.09±0.02). Expression of the three alpha 1 receptor subtypes was not changed by AIH in pre‐autonomic and magnocellular regions of the PVN. In the medial parvocellular region, AIH decreased expression of alpha 1d receptors (N= 1±0.35; AIH = 0.28±0.06), while expression of alpha 1a and alpha 1b receptor subtypes remained unchanged. Using Fos‐IR as an index of neuronal activation, immunohistochemistry experiments found that, compared to continuous hypoxia (2 hr, 10% O2), activation of CRH‐IR neurons in the medial parvocellular region of the PVN was significant but modest in rats exposed to AIH (continuous hypoxia = 28±6%; AIH = 7±1%). It is possible that downregulation of adrenergic alpha 1d receptors in the medial parvocellular region during AIH limits excitation of these neurons.Support or Funding InformationFunded by Univ. MO Research Board to CMH and NIH HL 98602.
Tumor Necrosis Factor Alpha Increases Excitability in Subfornical Organ Neurons
Authors: Simpson Nick J , Ferguson Alastair V 
Published: November 2023

Tumor necrosis factor‐alpha (TNFα) is a pro‐inflammatory cytokine implicated in cardiovascular diseases involving hypertension. It has been shown that TNFα−/− mice do not develop angiotensin II‐induced hypertension, although the mechanism for this is unknown. Recent studies suggest that the subfornical organ (SFO) is critical for TNFα's hypertensive effects. We therefore used patch clamp techniques to examine both acute and longer term effects of TNFα's on the excitability of dissociated SFO neurons. It was found that bath application of 500 pM TNFα induced acute depolarizations in 58% (n = 11/19) of SFO neurons tested (mean depolarization of 6.7 ± 0.8 mV, n = 11). TNFα's acute effects were concentration‐dependent with depolarizing effects observed on SFO neurons at 50 pM (44%, mean depolarization of 6.8 ± 1.0 mV, n = 7/16), and 500fM (22%, mean depolarization of 3.1 ± 0.4 mV, n = 2/9). SFO neurons incubated with TNFα for 24 hours at 575 pM showed increased action potential frequency compared to control SFO neurons (3.7 ± 1.3 Hz, TNFα, n = 7, 0.4 ± 0.2 Hz, control, n = 7, p < 0.05, Student's t‐test). Additionally, TNFα incubation reduced the action potential threshold relative to control (rheobase = 5.5 ± 0.7 pA, TNFα, n = 6, rheobase = 12 ± 1.8 pA, control, n = 6, p < 0.01, Student's t‐test). Furthermore, TNFα incubation was found to increase the magnitude of transient Na+ currents (INa) compared to control (2.7 ± 0.2 nA, TNFα, n = 12, 1.7 ± 0.1 nA, control, n = 15, p < 0.001, Student's t‐test). Lastly, it was observed that TNFα incubation shifted the activation of voltage‐gated Na+ channels to a more hyperpolarized state (V1/2 = −34.5 ± 0.8 mV, TNFα, n = 12, V1/2 = −30.2 ± 1.2 mV, control, n = 11, p < 0.001, Student's t‐test). These data suggest that TNFα is increasing the acute and long‐term excitability in SFO neurons, and this long‐term effect is influenced by INa modulation.Support or Funding InformationCIHR
Effect of Monoamine Reuptake Inhibitors on Seizures in DBA/1 Mice
Authors: Ahamed Hassan A. , Kim Yu Jaung , Bravo Eduardo , Richerson George B. 
Published: November 2023

BackgroundDBA/1 mice suffer from audiogenic seizures that lead to wild running, clonic seizures, tonic hind‐limb extension, and eventually seizure induced respiratory arrest (S‐IRA). The use of the selective serotonin reuptake inhibitor (SSRI) fluoxetine has been shown to prevent DBA/1 mice from having S‐IRA and tonic seizures. In the present study we use fluoxetine and the more selective agent escitalopram to determine the role serotonin reuptake plays in seizure protection in DBA/1 mice.HypothesisHigh doses of fluoxetine and escitalopram have the ability to completely protect DBA/1 mice from audiogenic seizures.MethodsAt postnatal day 21 – 24, DBA/1 mice were subjected to audiogenic seizure priming for 3 – 5 days in order to induce ~100% seizure susceptibility. After they were primed, mice were subjected to a drug dosing scheme that consisted of 0 (vehicle), 1, 3, 10, 30 or 100 mg/kg of fluoxetine in a 10% DMSO and saline solution or escitalopram in a saline solution – at the same doses. Mice were then subjected to an audiogenic stimulus (≥106 dB) 30 minutes after drug injection. The stimulus was given for 60 seconds and mice were monitored for convulsions and S‐IRA. For those mice that developed S‐IRA, a mini‐ventilator was used to resuscitate them. If a mouse survived, it was given a week for the drug to clear, then randomized to another dosing group.ResultsAt 100 mg/kg of fluoxetine, DBA/1 mice were completely protected from audiogenic seizures (n = 6 of 6). These mice displayed no evidence of seizures. It was found that all other doses were unable to protect mice from seizures and S‐IRA, except for one mouse at 1 mg/kg (n = 29 of 30). Some DBA/1 mice that received 100 mg/kg as their first dose and allowed to live, developed spontaneous seizures and eventually died 4 – 6 days after injection (n = 2 of 2). At 100 mg/kg of escitalopram, there was a lower success rate relative to fluoxetine; at this dose, escitalopram completely protected some mice (n = 2 of 6), blocked tonic‐clonic seizures (n = 1 of 6), and had no effect on tonic‐clonic + S‐IRA (n = 3 of 6). At lower doses, escitalopram was completely ineffective at stopping seizures and always led to tonic‐clonic seizures + S‐IRA (n = 20 of 20).ConclusionsDBA/1 mice were protected from audiogenic seizures at 100 mg/kg of fluoxetine. Escitalopram, does not have as strong of an anticonvulsive effect suggesting that fluoxetine may have off‐target effects that are responsible for its more powerful anticonvulsive properties. It was seen, however, that in some cases DBA/1 mice developed spontaneous seizures after exposure to a high dose of fluoxetine.Support or Funding InformationSupported by a STRIDE fellowship from the American Physiological Society and a grant from the National Heart, Lung and Blood Institute.
Differential expression of VEGF isoforms and receptors in the phrenic motor nucleus of end‐stage SOD‐1G93A mutant rats
Authors: Satriotomo Irawan , Mitchell Gordon S. 
Published: November 2023

Amyotrophic lateral sclerosis (ALS) is a devastating motor neuron disease causing paralysis and death from respiratory failure. Despite major loss of phrenic motor neurons (PMN) In a rodent model of familial ALS (SOD1G93A rats), breathing capacity is maintained until late in disease progression (Nichols, et al., 2013). Thus, compensatory respiratory plasticity preserves breathing capacity despite progressive respiratory motor neuron cell death. Vascular endothelial growth factor (VEGF), often regarded as an angiogenic factor, also plays a pivotal role in neuroprotection and neuroplasticity. VEGF‐A and VEGF receptor 2 (VEGFR‐2) are expressed in PMN of naïve rats, and intrathecal VEGF‐A injections induce long‐lasting phrenic motor facilitation (Dale‐Nagle et al., 2011). Little is known concerning in the expression of different VEGF isoforms or their corresponding receptors in PMN, or changes in their expression with motor neuron disease. Since VEGF may play a key role in compensating for respiratory motor neuron loss, we investigated expression of multiple VEGF isoforms (A, B, C, D, E) and receptor subtypes (VEGFR‐1/Flt‐1, VEGFR‐2/KDR/Flk‐1, VEGFR‐3) in the phrenic motor nucleus of end‐stage SOD1G93A rats (20% decrease from peak body mass). We utilized immunohistochemistry to label different VEGF isoforms and receptors within neurons (NeuN positive), astrocytes (GFAP positive) and microglia (OX‐42 positive). Presumptive phrenic motor neurons expressed VEGF‐A, with minimal or no expression of VEGF‐B, ‐C, ‐D, and ‐E. These neurons expressed all VEGF receptors (1, 2 and 3). On the other hand, reactive astrocytes expressed all VEGF isoforms and VEGF receptors 1 and 2, but not VEGFR‐3. Interestingly, activated microglia expressed only VEGF‐B, ‐C and ‐D, but not VEGF‐A or ‐E; microglia expressed VEGFR‐1 and VEGFR‐2, but not VEGFR‐3. In conclusion, multiple VEGF isoforms and receptors are differentially expressed among different cells types of the phrenic motor nucleus of SOD‐1 mutant rats. Increased VEGF expression in glial cells neighboring motor neurons may confer neuroprotection, or help surviving motor neurons compensate for the loss of their neighbors during diseases progression. However, knowledge of the specific role(s) played by different VEGF isoforms/receptors in ALS is lacking.Support or Funding InformationSupported by McKnight Brain Institute
Transient receptor potential ankyrin 1 channel in regulating emotion, learning and memory, cognition, and social behavior of mice
Authors: Lee Hsueh‐Te , Lee Kuan‐I , Lin Hui‐Ching , Lee Tzong‐Shyuan 
Published: November 2023

The transient receptor potential ankyrin 1 (TRPA1) channel is a non‐selective cation channel that helps regulate inflammatory pain sensation and nociception and the development of inflammatory diseases. However, the potential role of the TRPA1 channel and the underlying mechanism in brain functions are not fully resolved. In this study, we demonstrated that genetic deletion of the TRPA1 channel in mice or pharmacological inhibition of its activity increased neurite outgrowth. In vivo study in mice provided evidence of the TRPA1 channel as a negative regulator in hippocampal functions; functional ablation of the TRPA1 channel in mice enhanced hippocampal functions, as evidenced by less anxiety‐like behavior and enhanced fear‐related or spatial learning and memory, and novel location recognition as well as social interactions. However, the TRPA1 channel appears to be a prerequisite for motor function; functional loss of the TRPA1 channel in mice led to axonal bundle fragmentation, downregulation of myelin basic protein and decreased mature oligodendrocyte population in the brain, for impaired motor function. The TRPA1 channel may play a crucial role in neuronal development and oligodendrocyte maturation and be a potential regulator in emotion, cognition, learning and memory, and social behavior.Support or Funding InformationMinistry of Science and Technology, R.O.C.
Cellular dynamics of tissue fusion in craniofacial development and orofacial clefting
Authors: Bush Jeffrey O. , Kim Seungil , Hagan Bronwyn 
Published: November 2023

Tissue fusion is a process common to the formation of multiple organs and often involves the removal of an intervening epithelial seam between two separate embryonic prominences. Tissue fusion is particularly important during craniofacial development for the proper formation of the intact upper lip and primary palate and the formation of the intact secondary palate and failure of these processes leads to cleft lip or cleft palate respectively. Whereas formation of the lip involves fusion of the medial nasal process with the lateral nasal and maxillary processes, the secondary palate forms by fusion of the secondary palatal shelves; in both cases an intervening epithelial seam must be removed for confluence of the structure. Although apoptosis is thought to be involved in tissue fusion during both processes, direct functional evidence of this is limited and the importance of apoptosis relative to other cellular behaviors is unknown. Further, the relationship between contact of the embryonic primordia and the initiation of cellular behaviors that drive palate fusion is currently unknown. Here I will discuss our recent studies utilizing mouse genetics and live imaging approaches to determine cellular mechanisms of tissue fusion during craniofacial development.Support or Funding InformationThis work was supported by grant R01DE025877 from the NIH/NIDCR.
Vimentin Regulates Activation of the NLRC4 Inflammasome
Authors: Cheng Yuan , Davis Jennifer , Lu Ziyan , Gates Khalilah , Coates Bria , Ridge Karen 
Published: November 2023

NLRC4 inflammasome activation and subsequent maturation of IL‐1β has been implicated in inflammation and acute lung injury (ALI). Cellular inflammation involves two signals. The first signal is either a pathogen‐associated molecular pattern (PAMP) or damage‐associated molecular pattern (DAMP) which activates toll‐like‐receptors (TLR) which causes the NF‐κB induction of pro‐IL‐1β. The second signal, mediated by bacterial flagellin, involves formation of a NLRC4 inflammasome which activates caspase‐1 and maturation of IL‐1β. We have used a flagellin (fliC) strain of Pseudomonas aeruginosa (PAO1) to activate the NLRC4 inflammasome. Previously it was shown that vimentin expression was involved in NLRP3 inflammasome activation. We hypothesized that vimentin is important in the NLRC4 inflammatory response and that the absence of vimentin would reduce hallmarks of lung inflammation. To determine the role of vimentin in the NLRC4 inflammatory pathway, wild‐type (WT) and vimentin‐knockout (Vim−/−) mice were subjected to a lethal dose of PAO1, which induces both pro‐inflammatory cytokine expression and induces a systemic inflammatory response that is associated with significant mortality. Wild‐type mice displayed about a 2‐fold increase in mortality compared with Vim−/− mice. Vim−/− mice had a median survival of more than 40 h, whereas WT animals had a median survival of 20 h. Histopathological examination showed that the lungs of PAO1‐treated WT mice had severe alveolar damage, characterized by interstitial edema, and more fluid and debris in the airspace than the PAO1‐treated Vim−/− mice. WT mice exposed to PAO1 exhibited an increase in wet‐to‐dry lung weight ratio and total protein concentration in the bronchoalveolar lavage fluid (BALF), whereas Vim−/− mice failed to exhibit such an increase. PAO1 induces rapid production and release of pro‐inflammatory cytokines and chemokines, which are sufficient to induce lung inflammation and ALI in mice and humans. When WT and Vim−/− mice were exposed to PAO1 for 6 h, significantly more caspase‐1 and IL‐1β were found in BALF from WT mice than in Vim−/− mice. PAO1 mediated markers that are NLRC4‐independent, such as tumor necrosis factor α (TNF‐α), were not affected by the loss of vimentin. Additionally, whole lung homogenates prepared from WT and Vim−/− mice exposed to PAO1 had increased levels of pro‐IL‐1β protein. These data suggest that vimentin is not involved in the TLR‐mediated NF‐κB activation and upregulation of pro‐IL‐1β. Rather, vimentin is required for the second step in for PAO1‐induced activation of caspase‐1 and maturation of IL‐1β via the NLRC4 inflammasome.Support or Funding InformationThis work was supported by National Heart, Lung, and Blood Institute (HL128194; HL071643)