bluuebunny/crossref_metadata_2025 huggingface dataset:
Retromer involvement in trafficking of the calcium-activated K channel, KCa3.1
Authors: Hamilton Kirk , Logue Matthew , Chueng Tanya , Pilmore Elliot , Devor Daniel , McDonald Fiona
Published: May 2023

The intermediate-conductance Ca2+-activated K+ channel KCa3.1 ( KCNN4) regulates many physiological processes, including, water and electrolyte transport in polarised epithelia and vascular tone. Crucial for KCa3.1 function is the regulation of the number of channels at the plasma membrane. Even though, the mechanism of trafficking of KCa3.1 to and from the basolateral membrane (BLM) of epithelial cells has been advanced recently, there is opposing evidence suggesting that KCa3.1 is recycled back to the leading edge of migrating cells; while others have reported that KCa3.1 does not enter recycling endosomes, but is targeted for degradation. The highly conserved multi-protein complex Retromer has been demonstrated to regulate the membrane retrieval and recycling of many membrane-bound proteins, including ion channels. Using mass-spectrometry, it was reported that when VPS35, a core protein of the Retromer complex, was knocked-down, the membrane expression of KCa3.1 was reduced 1.4 fold in HeLa cells; suggesting a link between Retromer and trafficking of KCa3.1. In contrast, our data indicate KCa3.1 was not affected by knockdown of VPS35 in our FRT (Fischer rat thyroid)-KCa3.1 stable cell line. Here, we have examined other key components (sorting nexins SNX1, SNX4, SNX27; cargo binding proteins) of the Retromer complex to determine if those proteins aid in trafficking of KCa3.1 directly to the BLM. We conducted immunoblot and Ussing chamber experiments to examine the effects of knockdown of SNX 1, SNX2 or SNX27 on the BLM population of KCa3.1 and functional expression of the channel (K+current), respectively. Using our FRT-KCa3.1 cell line, we demonstrate knockdown of SNX1, SNX4 or SNX27 decreases KCa3.1 current. Further, we demonstrate knockdown of SNX4 or SNX27 decreases BLM expression of KCa3.1, consistent with the decrease in current observed.These data, along with our previous data, strongly indicate that the role of Retromer in the trafficking of KCa3.1 to the BLM of epithelial cells is quite dynamic. Reducing SNX4 or SNX27 have notable effects on trafficking of KCa3.1. While knockdown of SNX1 might affect the trafficking of KCa3.1 by altering other proteins of the Retromer complex.

This work was supported by the National Institutes of Health grants HL083060 and HL092157 to DCD, Lottery Health New Zealand (R-LHR-2019-101706) to FJM, Aim Fund grant to KLH, and the Department of Physiology, University of Otago.

This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
O-Mannosylation of alpha-dystroglycan is required to prevent stress-induced cardiac muscle fiber damage and heart failure
Authors: Hord Jeffrey , Anderson Mary , Prouty Sally , Melton Shelly , Weiss Robert , Campell Kevin
Published: May 2023

Mutations in glycosyltransferases involved in the O-mannosyl processing and formation of matriglycan on alpha-dystroglycan (αDG) constitute a subset of limb girdle muscular dystrophies referred to as dystroglycanopathies. Patients exhibit a range of cardiac phenotypes, including progressive disease leading to heart failure and acute events that can result in death. The goal of the present study was to investigate the factors that provoke heart pathology in a mouse model of dystroglycanopathy. We disrupted O-mannosylation of αDG in vivo by designing a striated muscle-specific protein O-mannosyltransferase 1 knockout mouse line. Hearts from conditional knockout mice appeared histologically and functionally similar to littermate controls up to 60-weeks-of-age. Acute pharmacological-induced contractile stress resulted in large patches of damaged cardiomyofibers and was associated with bradycardia, as determined by electrocardiography, in knockout mice twenty-four hours following the stressor. In hearts from littermate control mice, stress-induced cardiac muscle damage was limited to small patches or individual fibers and did not cause cardiac dysfunction. The contraction-induced cardiac muscle fiber damage observed in the knockout mice led to aberrant remodeling that developed into extensive ventricular fibrosis when examined twenty-eight days later, an effect that was not observed in control hearts. These data indicate that cardiomyopathy due to improper glycosylation of αDG can be instigated by a short-lived increase in workload.

Cardiovascular Institutional Research Fellowship -- National Institutes of Health (5T32HL007121-45); Paul D. Wellstone Muscular Dystrophy Specialized Research Center (1U54NS053672); Howard Hughes Medical Institute

This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Chronic intermittent hypoxia induces remodeling of sympathetic innervation in mouse heart (atria and ventricles)
Authors: Bizanti Ariege , Zhang Yuanyuan , Toledo Zulema , Bendowski Kohlton , Chen Jin , Cheng Zixi
Published: May 2023

Chronic intermittent hypoxia (CIH) is a commonly used model for sleep apnea, which constitutes a major risk factor for many cardiovascular diseases (CVD). Autonomic imbalance (sympathetic overactivity and parasympathetic withdrawal) is hypothesized to be a causal contributor of CIH-induced CVD. Previously, we showed that CIH reduced baroreflex control of heart rate and induced vagal cardiac motor neuronal death in the brainstem. CIH activates the central nervous system circuitry, which in turn enhances sympathetic outflow. However, whether CIH induces remodeling of the peripheral cardiac sympathetic innervation remains undetermined. Here, C57BL/6J male mice (2 months, n=7/group) were exposed to room air (RA, 21% O2) or CIH (alternating 21% and 5.7% O2, every 6 minutes, 10hr/day) for 8-10 weeks. Flat-mounts of their whole left and right atria, ventricles, and interventricular septum were prepared and immunohistochemically labeled for tyrosine hydroxylase (TH, a sympathetic postganglionic marker). Using confocal microscopy (or Zeiss M2 Imager) and a Neurolucida Digitization and Tracing system, we scanned and quantitively analyzed the sympathetic axon density in both the RA and CIH experimental groups. We found: 1) Several large TH-IR bundles entered the atria and ventricles and branched out into smaller bundles and eventually ramified into individual axons and their terminals that covered the entire atria, ventricles, and interventricular septum. 2) TH-IR neurons were observed in the intrinsic cardiac ganglia (ICG). Most TH-IR axons passed through the ICG and innervated the cardiac muscles, blood vessels, and fat cells. 3) CIH significantly remodeled the TH-IR axon innervation of the atria. Specifically, CIH significantly increased the density of TH-IR innervation at the sinoatrial (SA) node, the atrioventricular (AV) node, and the auricles (p <0.05, n=7). 4) CIH-induced TH-IR axon innervation structural remodeling (increased density and complexity) in the ventricles and interventricular septum. 5) TH-IR axon innervation will be integrated into 3D heart scaffold to provide a common coordinate framework for RA and CIH comparison. These results suggest that increased sympathetic innervation may further amplify the effects of enhanced CIH-induced central sympathetic drive to the heart. Along with our previous finding that CIH reduces parasympathetic control of the heart, our work supports the hypothesis that chronic autonomic imbalance underlies CIH-induced CVD.

This study was supported by NIH HEAL/SPARC U01 NS113867-01, NIH R15 R15HL137143-01A1, and UCF dissertation completion Fellowship.

This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Kv7 channel isoforms contribute to H2O2-mediated vasodilation in the ischemic heart after exercise training
Authors: Self Trevor , Heaps Cristine
Published: May 2023

Ischemic heart disease is a multifaceted pathological manifestation that continues to impose a significant burden on individuals and the healthcare system. As a potential therapeutic modality, exercise training has been reported to induce vascular adaptations that improve coronary perfusion in the compromised myocardium distal to coronary occlusion. Coronary arteriolar hydrogen peroxide (H2O2) production is enhanced after exercise training and contributes to improved vasodilation of arterioles supplying ischemic myocardium. Voltage-gated potassium (Kv) channels have been identified as significant contributors to resting membrane potential and enhanced vasodilation in ischemic models, yet specific isoforms remain elusive. Many Kv isoforms exhibit redox-sensitivity with Kv1-4 families being implicated in H2O2-mediated vasodilation in rodents and human. Based on these previous findings, we tested the hypothesis that redox-sensitive Kv isoforms contribute to exercise training-enhanced H­2O2-mediated dilation in arterioles of the ischemic heart. Yucatan miniature swine were surgically instrumented with an ameroid occluder around the left circumflex coronary artery, gradually inducing complete occlusion and creating a collateral-dependent vascular bed. Arterioles fed by the left anterior descending artery served as nonoccluded control vessels. Pigs were separated into two groups, one of which underwent a progressive exercise training regimen (treadmill run; 5 days/week for 14 weeks) and another that remained sedentary, limited to normal pen activity. Candidate Kv channel isoforms were pharmacologically targeted in tension myography studies of isolated coronary arterioles (~125 μm internal diameter) and whole-cell voltage clamp studies of arteriolar smooth muscle cells. Our findings revealed a significant role for the Kv7 family, specifically implicating Kv7.4 and Kv7.5, in H2O2-mediated vasodilation of the coronary microcirculation. We show that the contribution of Kv7 channel isoforms to vascular relaxation was eliminated by ischemia or exercise training in tension myography, although together, ischemia and exercise training restored a significant role for Kv7 channel isoforms. Interestingly, whole-cell voltage clamp recordings of isolated vascular smooth muscle cells revealed unaltered Kv7 channel currents among all treatment groups. With no observed changes in whole cell Kv7 currents after ischemia and/or exercise training, our data suggest that adaptations in a second messenger signaling pathway are driving the changes in channel contribution to H2O2-mediated vasodilation.

NIH RO1 HL139903

This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Spinal Afferent Innervation of the Rat Heart: Anterograde Tracing
Authors: Ma Jichao , Bizanti Ariege , Kwiat Andrew , Madas Jazune , Chen Jin , Cheng Zixi
Published: May 2023

Spinal afferent innervation of the heart regulates cardiac function. Understanding the precise distribution and morphology of spinal afferent nerves in the heart is crucial as remodeling of cardiac sensory innervation results in cardiovascular diseases. To specifically study the spinal afferent innervation of the heart, we injected tracer dextran biotin (DB) into the left DRG (C8-T3; 1.5 μl/each ganglion). Rats were allowed to recover for 14 days, then perfused through the left ventricle with 40°C PBS (1M phosphate-buffered saline, pH = 7.4). Tissues were then fixed by perfusion with 4% paraformaldehyde in 0.1M PBS (4°C, pH 7.4). After the perfusion, hearts were harvested, and the atria and ventricles were separated. Then, a cut was introduced along the interatrial septum to separate the left and right atrium, and DAB staining was performed. DB-labeled single spinal afferent axons in the flat-mounts of the left and right atria were traced using the Neurolucida system. We summarized our findings based on morphology, innervation area, and target of individual spinal afferent axons. 1) Morphological characteristics of single spinal afferent axons: DB-labeled single axons entered the atria and bifurcated into many branches with or without varicosities. Varicose branches which arose from a single axon traveled through the atria either in the same direction or a non-preferential direction. 2) Distinct regions received single spinal afferent axons include left and right auricles, the sinoatrial node, the atrioventricular node, left precaval vein, pulmonary veins, and the junction between the left atrium and pulmonary veins. Axons with different terminal structures could be found in all these regions. 3) Single afferent axons were identified on different targets: such as cardiac and smooth muscles, fat tissue, blood vessels, and intrinsic cardiac ganglia. Our work will provide a foundation for specific labeling of spinal afferent innervation of the heart.

This study was supported by NIH HEAL/SPARC U01 NS113867-01, NIH R15 R15HL137143-01A1, and UCF dissertation completion Fellowship.

This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Open-book, open-web versus closed-book, closed-web examinations in anatomy and physiology classes
Authors: Milam Lauren , Jimenez Xavier , Shaw Donald
Published: May 2023

Due to COVID and distance learning, a possible evaluation is open-book examinations. We tested the hypothesis that students taking open-book, open-web exams spend less time studying anatomy and physiology and would performed more poorly on critical thinking exam questions compared to students taking closed-book, closed-web exams. We tested the exam performance using different types of exam questions according to Bloom's taxonomy. As well, students that participated in the research submitted study journals that accounted for the time they spent studying for each exam. Data has been collected for both open-book, open-web and closed-book, closed-web sections over Exams #1, #2, #3, and Final. Data from Exams #1 and #2 for both sections has already been completely analyzed. Data from the open-book section had shown that students' exam performance over five different types of questions were descending as the level of difficult became more challenging in both Exams #1 and #2. Data from the closed-book section showed that as the level of difficult became more challenging, there was not a decline in performance on Exam #1 and there was a less steep decline in performance on Exam #2 than the open-book section. For both exams, there was a statistical significance between the study times of the sections as the average study times of the closed-book section was significantly greater than of that of the open-book section. These results suggest that students in the open-book section deal with challenging questions more poorly than the closed-book section while also studying significantly less than the closed-book, closed-web section. Moreover, the data for Exams #1 through Final of both sections has been collected and will be analyzed and included for further comparison.

This research was supported and funded by the Department of Biological Sciences at the University of Tennessee at Martin.

This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Impact of cannabidiol and lamotrigine on parameters of action potentials in sciatic nerves of frogs
Authors: Milam Lauren , Jimenez Xavier , Shaw Donald
Published: May 2023

Cannabidiol causes inhibitory effects on sodium channels, but its action on nerve impulses is not understood. Lamotrigine blocks the nerve impulses, however, it is not known if this action is of extracellular or intracellular origin. With the use of nerve chambers, we are hoping to elucidate this unknown mechanism. We hypothesize that these two chemicals may modify components of action potentials of nerve fibers in frogs. Action potential recording was made possible by the IWorx Data Quest system and a nerve chamber. Action potential data was analyzed by looking at two different components—the peaks of depolarization and the difference between the peak of depolarization and the nadir of repolarization. For every 50 minutes of recording, the data was divided into three clusters—before chemicals, after 10 minutes of treatment, and 30 minutes after treatment. In frogs, we found the high dosage (1.0 milligram/milliliter (mg/mL)) of cannabidiol had no effect on the maximum amplitude of depolarization among the three data clusters—saline, 10 minutes after cannabidiol, and 30 minutes after cannabidiol. The high dosage of cannabidiol also had no effect on the repolarization of action potentials when compared among the above three data clusters. In addition, in frogs we found the low dosage (0.1 mg/mL) of cannabidiol showed a significant difference in the maximum amplitude of depolarization when the saline data cluster was compared to the 10-minute cluster after cannabidiol cluster. Likewise, there was a significant difference on the repolarization of action potentials when the saline data cluster was compared to the 10-minute cluster after cannabidiol cluster and when the 10-minute cluster was compared to the 30-minute cluster after cannabidiol cluster. High dosage of lamotrigine showed a significant difference on the maximum amplitude of depolarization when the saline cluster was compared to the 10-minute cluster after lamotrigine on action potentials. Low dosage of lamotrigine data is currently being collected to be analyzed and presented cumulatively with all the data.

This research is being supported and funded by the Department of the Biological Sciences at the University of Tennessee at Martin.

This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Identifying the role of HSP70 co-chaperones in modulating sarcomeric proteostasis
Authors: Branscom Graham , Wagner Marcus , Day Sharlene
Published: May 2023

Background: Hypertrophic cardiomyopathy (HCM) is the most common genetically inherited cardiovascular disease that affects one in 500 people. Variants in MYBPC3 result in premature termination codons, ultimately causing haploinsufficiency in MyBP-C protein–a hallmark of familial HCM pathophysiology. Recent GWAS reports identify risk alleles for HCM that are concordant with left ventricular (LV) functional traits of decreased left ventricular chamber volumes and increased ejection fraction, and in contrast are protective alleles for dilated cardiomyopathy. Several of the top HCM risk alleles encode for co-chaperones of HSP70. However, how these co-chaperones directly modulate sarcomeric protein turnover and HCM pathophysiology is unknown. Hypothesis: We hypothesize that HSP70 co-chaperones identified by recent GWAS regulate contractility by affecting sarcomeric and Z-disc steady state expression. Methods and Results: Human induced pluripotent stem cell cardiomyocytes (hiPSC-CMs) were transduced with GFP-tagged adenovirus (AdV) expressing shRNA targeted against BAG3, DNAJC18, HSPB7, or scrambled shRNA (control) and transduction efficiency was assessed by flow cytometry for GFP expression. A >70% transduction efficiency was achieved with each viral construct (p<0.0001). Viral transduction and knockdown of HSP70 co-chaperone did not induce cellular toxicity. BAG3, DNAJC18, and HSPB7 were reduced by ≥50% at both the transcript and protein levels as measured via RT-qPCR and western blot. BAG3 KD reduced MyBP-C protein levels (p<0.0001) by 53%, along with most other profiled sarcomeric and Z-disk proteins (p<0.05). DNAJC18 had no significant effect on MyBP-C protein levels, but caused a decrease in tropomyosin (p<0.0001) and myosin light chain 3 (p<0.0001). HSPB7 KD increased MyBP-C protein levels (p<0.01) by 46%. Myosin (p<0.01), tropomyosin (p<0.05), and myosin light chain 2 (p<0.05) also showed increased expression upon HSPB7 knockdown. Conclusion: GWAS-identified HSP70 co-chaperones BAG3, DNAJC18, and HSPB7 regulate the steady state expression of sarcomeric and Z-disc proteins. Further studies will be needed to elucidate whether regulation is occurring at the transcription, translational, or posttranslational level, and whether therapeutic modulation of these co-chaperones can be leveraged to stabilize MyBP-C and other sarcomeric and Z-disc proteins in patients with familial HCM.

Institutional/internal grants

This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Transcriptional regulation of gastrointestinal solute transporters by growth hormone and cortisol in Atlantic salmon
Authors: Runiewicz Ellie , Richardson Sierra , Bradley Serena , Hall Daniel , McCormick Stephen , Breves Jason
Published: May 2023

To maintain hydromineral balance in marine habitats, teleost fishes drink ambient seawater to replace water that is passively lost to the external environment. Initially, the esophagus desalinates imbibed seawater to produce a fluid closer to the osmolality of plasma. This desalination enables the intestine to partake in fluid uptake through solute-linked transport processes. In parallel with gastrointestinal processes that support water balance, branchial ionocytes promote ion balance by actively extruding Na+ and Cl-. Despite growth hormone (Gh) and cortisol being firmly established as “seawater-adapting hormones” in euryhaline teleosts, it remains largely unknown how they regulate gastrointestinal processes. We therefore examined the responses of Atlantic salmon ( Salmo salar) parr implanted with ovine Gh (5 μg/g body weight), cortisol (10 μg/g body weight), or the combination of both hormones. We first determined that our implants were sufficient to elicit physiological responses by confirming that cortisol stimulated branchial Na+/K+-ATPase (NKA) activity. Cortisol also stimulated branchial Na+/K+/2Cl- cotransporter 1 ( nkcc1) and cystic fibrosis transmembrane regulator 1 gene expression, whereas the combination of Gh and cortisol stimulated nka-α1b expression. Of the two Na+/H+ exchangers (Nhes) proposed to underlie the removal of Na+ from the lumen of the esophagus, nhe2, but not nhe3 expression, was stimulated by cortisol. In the current model of how solute-linked water absorption occurs in teleost intestine, Na+ and Cl- enter into enterocytes via apical Nkcc2 prior to their basolateral exit via NKA and Clc-family Cl- channels. Water is absorbed from luminal fluid by enterocytes in a transcellular fashion via aquaporins (Aqps). The combination of cortisol and Gh stimulated the expression of intestinal nkcc2, nka-α1b, and nka-β1b in the anterior intestine whereas there were no effects on aqp1a, -1b, -8ab, or -10. Collectively, our data indicate that cortisol and Gh coordinate the expression of solute transporters in salmon esophagus and intestine in a fashion that supports hydromineral balance in marine habitats. Supported by the National Science Foundation (IOS-1755131 to J.P.B.).

National Science Foundation [IOS-1755131]

This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Assessing conversational oral communication in an undergraduate anatomy and physiology course
Authors: Brundage Cord
Published: May 2023

Effective oral communication is an important competency for scholars and health professionals. This is more traditionally assessed through orations and class presentation. Practically, graduates may be tasked with more instances of interpersonal and conversational oral communication. It is also difficult to assess student recall knowledge in prepared speeches and presentations. The Cal Poly Pomona institutional rubric for oral communication was adapted to be used in group discussions and one-on-one conversations. Evaluation criteria included central message, organization, language and delivery. Each criterion was evaluated on a 4-tier (0-3) mastery scale. The specific evaluation criteria area needing the most development was also noted. Undergraduate upper-division, anatomy and physiology students (n = 48) participated in five topic discussions in randomly assigned groups of 12 throughout the laboratory section of the course. The facilitator evaluated student oral communication skills using the adapted rubric throughout each discussion. At the end of the semester the same rubric was used to score responses to 5-prompts during a one-on-one oral examination with the instructor. This modified rubric was able to be used in real-time. Overall students demonstrated modestly higher scores in the discussions 1.952 +/- 0.36 than in the oral examinations 1.717 +/- 0.23. In both assessments the area of greatest need of development was language (56.6% - 68% of statements) followed by delivery (28% -37.6% of statements). During oral examinations the rubric was used while concurrently evaluating student content knowledge. Some students were consistent, while others scored at a range of levels. It remains to be determined whether student peak achievement or average performance are better indicators of competency. In either case this project highlighted the need to support student use of anatomy and physiology language to improve their conversational oral communication skills in that content area.

Cal Poly Pomona Office of Academic Programs

This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Intact endothelial cell autophagy mitigates outcomes of acute ischemic stroke
Authors: Mookherjee Sohom , Light Milo , Tandar Megan , Hill Nathan , Begaye Lori , Chaix Amandine , Denorme Frederik , Campbell Robert A. , Symons John David
Published: May 2023

Acute ischemic stroke (AIS) deprives cerebral artery endothelial cells (ECs) of nutrients which decreases mechanistic target of rapamycin complex 1 (mTORC1) activity to initiate autophagic flux. We tested the hypothesis that depletion of EC autophagy worsens tissue injury, and neurobehavioral and motor outcomes of AIS. First, using a gain of function approach, adult male C57Bl6 mice consumed standard diet that was not (control) or was supplemented with the mTORC1 inhibitor rapamycin (14 milligrams / kilogram chow). After 3-weeks, phosphorylated ribosomal S6 / total S6 was greater (p<0.05) in liver segments of rapamycin vs. control fed mice, indicating mTORC1 repression. All mice were challenged with transient middle cerebral artery occlusion (tMCAO, 60-minutes;) followed by reperfusion (R, 23 hours). AIS -induced infarct volume, neurobehavioral deficits, and motor dysfunction was less severe (p<0.05) in mice fed rapamycin-supplemented vs. control chow. Next, using a loss of function procedure, adult male C57Bl6 mice with intact EC autophagy-related protein 3 ( Atg3WT ) or inducible depletion of EC ATG3 ( Atg3EC-/- ) completed the AIS protocol. AIS increased (p<0.05) ATG3 colocalization with the EC marker VE-Cdh5 after 23 h R in ipsilesional (ischemic) vs. contralesional (non-ischemic) hemispheres of Atg3WT but not Atg3EC-/- mice. Neutrophil infiltration (flow cytometry), cell death (TUNEL), microglia (IBA-1) and astrocyte (GFAP) activation, and neurodegeneration (NeuN) were greater (p<0.05) in ischemic hemispheres of Atg3EC-/- vs. Atg3WT mice. Further, infarct volume was greater, and motor function (grip test, rotarod) and neurobehavioral performance (Y-maze, Bederson score, modified neurological severity score) were worse (p<0.05), in Atg3EC-/- vs. Atg3WT mice. These findings suggest that outcomes of AIS are: (i) better in response to mTORC1 inhibition but are (ii) exacerbated in response to EC autophagy depletion. To test whether intact EC autophagy is necessary for protection afforded by mTORC1 inhibition in the context of AIS, Atg3WT and Atg3EC-/- mice consumed rapamycin-supplemented chow for 3-weeks. In preliminary studies, AIS-induced infarct volume was less severe after rapamycin feeding in Atg3WT vs. Atg3EC-/- mice, underscoring the importance of EC autophagy. Initiating EC autophagic flux might be protective in the context of AIS by enabling: (i) recycling of damaged proteins; (ii) nutrient generation from degraded substrates; and / or (iii) arterial vasodilation for nutrient delivery.

Supported by R01HL141540 to JDS

This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Targeting LRP1 in a rodent cervical injury model to promote functional recovery
Authors: Sunshine Michael , Taylor Chase , Devine Caroline , Alilain Warren
Published: May 2023

Impairments following spinal cord injuries (SCI) are due to the primary trauma and secondary complications. Secondary complications include 1) degeneration of white matter tracts and 2) persistent neuroinflammation. Here we test a novel compound, NOVO-118 that is designed to mitigate these secondary complications in a rodent model of SCI. NOVO-118 is an antagonist of the low-density lipoprotein receptor regulated protein 1 (LRP1) which is expressed in all cell types in the central nervous system. Antagonism of LRP1 in neurons is implicated in promoting axon regeneration by reducing RhoA activation. Further, antagonism of LRP1 within microglia may reduce myelin uptake and mitigate the transition to their pro-inflammatory state. We hypothesize that LRP1, we can promote regeneration and mitigate neuroinflammation leading to functional recovery following cervical contusion SCI. As LRP1 is broadly expressed throughout many organ systems, we delivered NOVO-118 (or vehicle) to the intrathecal space above the lesion over a 30-day period after injury to mitigate off target effects. We measured the effect of NOVO-118 on ventilation and locomotor function using whole body plethysmography and open-field activity chambers. Behavioral assessments were performed pre-injury, 3, 7-, 14-, 21-, and 28-days post injury. Minute ventilation under normoxia was reduced in both groups at days 3 and 7 post injury which recovered towards pre-injury levels by day 14. The vehicle treated animals also had reduced minute ventilation during hypoxic challenge at days 3 and 14 post injury. However, the NOVO-118 treated rats were able to maintain pre-injury minute ventilation under hypoxic challenge at all time points. This suggests LRP1 as a new therapeutic target to promote recovery after SCI. Ongoing work is investigating the possible mechanisms through which NOVO-118 led to these functional improvements.

Novoron Bioscience (WJA, MDS), NIH NINDS R01NS101105 (WJA)

This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
At-home void training with spinal epidural stimulation in an individual with chronic spinal cord injury using advanced customized software
Authors: Hubscher Charles , Wang Siqi , Johnson Erik , Cooke Christa , Christie Breanne , Tenore Francesco , Harkema Susan
Published: May 2023

Bladder dysfunction is a highly prevalent quality of life issue in individuals with chronic spinal cord injury (SCI). The current study examined control of storage and emptying with neuromodulation in an SCI individual newly implanted with a spinal cord epidural stimulation (scES) electrode array. The goals of this pilot trial were 1) to enable dynamic human in-the-loop, sensor feedback, learning algorithm-controlled neuromodulation of micturition pathways in the home environment, and 2) to improve the transition from bladder storage to voiding in the home-setting by flexibly adjusting preset parameters in accordance with real-time physiological responses to bladder distention (e.g., sensations of fullness). Application of scES with a neurostimulator attached to a 16-electrode array was first examined in a controlled lab setting during filling cystometry by interactively identifying optimal stimulation parameters (cathode/anode configuration, stimulation frequency and amplitude) for storage and voiding. Efficacy was then tested in the lab for six-hour periods during natural bladder filling, followed by at-home use. The current report is on the first of four participants, a 40-year-old male T3 level of injury (AIS A) approximately 12 years post-injury, who entered the study having high filling pressures and low voiding efficiency. At-home daily training with scES (cohorts determined with prior in-lab mapping experiments) revealed effective storage at low fill pressure and efficient voiding, which improved over time. A major advantage of this system is afforded by the versatility of the multi-electrode array and technology advancements (STIMX) allowing for smooth transition from the storage to emptying phase, enabled by the ability to activate multiple spinal cord regions and associated functions with a single electrode placement and device using numerous cohorts simultaneously. Our next step is to develop a closed-loop, adaptive, real-time processing system that is used to automatically modulate epidural stimulation parameters based on acquired multi-modal sensor data.

Funding provided by NIH Roadmap Initiative - Office of Strategic Coordination, Other Transactions, SPARC Program Award # OT2OD024898, University of Louisville Hospital, and Medtronic Inc.

This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Forearm vascular conductance responses to rhythmic handgrip in young African American compared with Caucasian American women
Authors: Nyarko Ruby , Liu Randy , Dalve Ashlesha , Perez Justo , Appiah Crystal , Van Wagoner Tyler , Kaur Jasdeep
Published: May 2023

Non-Hispanic African American (AA) individuals have a disproportionately high prevalence, and mortality rate of cardiovascular disease (CVD) compared to other populations. Previous studies have demonstrated that even young, healthy AA individuals have blunted flow-mediated dilation, attenuated vasodilatory responses to pharmacological infusions and rhythmic handgrip exercise (RHG), as well as higher arterial stiffness and exaggerated peripheral vasoconstriction to isometric handgrip exercise and other non-exercise-stimuli compared to Caucasian-American (CA) individuals. These studies indicate that vascular alterations occur early on in life of AA individuals, potentially contributing to elevated risk of CVD in this racial group. However, these racial disparities in vascular function have almost exclusively been studied in men. Herein, we tested the hypothesis that, similar to young AA men, young AA women will exhibit an attenuated increase in forearm blood flow (FBF) and forearm vascular conductance (FVC) during rhythmic handgrip exercise (RHG) compared to age-matched CA women. Forearm blood flow (FBF; duplex Doppler ultrasound) and mean arterial pressure (MAP; finger photoplethysmography) were measured in young CA (n = 5) and AA (n = 5) women during rhythmic handgrip exercise performed at three workloads (15%, 30%, and 45% of maximal voluntary contraction (MVC)). FVC was calculated as FBF/MAP. Baseline FBF (CA: 66.0 ± 12.8 and AA: 61.6 ± 12.2 ml/min; mean ± SD, p = 0.30); FVC (CA: 0.8 ± 0.2 and AA: 0.7 ± 0.2 ml/min/mmHg; p = 0.16), MAP (CA: 82 ± 11 and AA: 88 ± 4 mmHg; p = 0.28), and MVCs (CA: 50 ± 4 and AA: 52 ± 5 kg; p = 0.35) were similar between the groups. Both groups exhibited intensity-dependent increases in FBF and FVC; however, contrary to our hypothesis, there were no race difference (mixed-model two-way ANOVA; FVC: race effect p = 0.18, intensity effect p < 0.0001, interaction p = 0.48). For instance, in response to RHG at 45%, CA had 384 ± 112% increase in FBF from baseline and AA had 499 ± 153% increase. Increase in FVC from baseline was 198 ± 76% for CA women and 314 ± 151% for AA women. MAP did not differ between the groups (e.g., ΔMAP at 45%; CA: 13 ± 11 vs AA: 9 ± 5, p = 0.41). These preliminary data suggest that the hyperemic response to rhythmic handgrip exercise in young African American women are similar to age-matched Caucasian-American women.

Supported byKinesiology and Health Education UT Austin Start-up Account 19-2635-91.

This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Does increasing insulin resistance in adolescence actively decrease cerebral perfusion to oral glucose tolerance test?
Authors: Khademi Motlagh Hedyeh , Wannebo Brett , Ward Aaron , Bowlin Shawn , Eldridge Marlowe , Wieben Oliver , Livett Timothy , Carrel Aaron , Hermann Bruce , Jones Jana , Schrage William
Published: May 2023

Background: Approximately 20% of American adolescents are obese, and nearly half demonstrate some form of insulin resistance (IR). Insulin acts as a metabolic hormone, a neurotrophic growth factor, and a vasodilator. Notably, adults with neurologic disease often exhibit IR and reduced cerebral blood flow (CBF). Adolescent brains are actively growing such that IR may negatively impact brain health in part due to lower brain perfusion. Specifically, given the role of insulin as a potential vasodilator, we hypothesized CBF would increase in response to a physiologic glucose-insulin surge, but this effect would lessen as IR level increased. Methods: Adolescents (n=11, 3 females, age=14.8±2 yr, BMI=24.7±7) taking no medications were studied. IR was estimated by calculating HOMA-IR using fasting glucose and insulin, spanning a spectrum of IR (excluding diabetes). Subjects completed a magnetic resonance imaging (MRI) study visit to assess cerebral perfusion using arterial spin labeling (ASL). Heart rate (HR), mean arterial pressure (MAP) and end tidal CO2 (ETCO2) were assessed at baseline and during oral glucose tolerance test (OGTT); ingesting 75g glucose in 296mL water (Trutol). Venous blood was sampled at baseline and 5, 10, 20, 30, 45, and 60 minutes post OGTT. Perfusion at peak plasma insulin was compared to baseline. Significance was determined using linear regression of change in perfusion (peak- baseline) versus HOMA-IR and set at p≤0.05. Results: Results are mean±SD. HR (p=0.9), MAP (p=0.22) and ETCO2 (p=0.75) were similar across HOMA-IR. MAP (p=0.44) and ETCO2 (p=0.15) did not change during OGTT at insulin peak. Peak insulin occurred at 44±13 min post OGTT (baseline: 8±4 vs. peak: 65±38 μU/mL, p=0.001). Glucose changed from 79±6 to 142±30 mg/dL at peak insulin (p=0.0005). There were no significant associations between HOMA-IR and changes in perfusion in gray matter (R2=0.06, p=0.43) and white matter (R2=0.07, p=0.13). There were no significant associations for the following regions: hippocampus, amygdala, thalamus, anterior and posterior insula, and precuneus (R2 all <0.2, p all >0.14). There was a trend toward negative regression in anterior cingulate gyrus (R2=0.25, p=0.11). Conclusions: These data suggest an OGTT does not acutely change brain perfusion at a global or regional level in adolescents, except possibly the anterior cingulate gyrus that is negatively impacted by increasing IR. The majority of present findings do not support our hypothesis that OGTT-mediated changes in cerebral perfusion are associated with IR in adolescents.

NIH R21HD097510

This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Brain Derived Neurotrophic Factor (BDNF) modifies endothelial Ca2+ signaling
Authors: Macarilla Christian , Choi Chung-Sik , Taylor Mark
Published: May 2023

BACKGROUND: Preventing or reversing endothelial dysfunction is essential for preserving vascular homeostasis and staving off vascular disease. Previous findings from our lab suggest that maintaining a distinct profile of calcium (Ca2+) signals along the endothelial network is crucial for sustaining normal vascular function and structure, and progressive restriction of dynamic Ca2+ signals under chronic low-flow conditions precedes impaired vasodilation and vascular remodeling. Brain Derived Neurotrophic Factor (BDNF) plays a key role in maintaining brain plasticity and has recently been implicated in cardiovascular health, perhaps through direct action on the endothelial TrkB receptors. The goal of this study was to determine whether BDNF might exert its effects by altering the endothelial Ca2+ signaling profile. METHODS: Using confocal imaging, we assessed endothelial Ca2+ in Cal-520-loaded open mouse carotid arteries. RESULTS: Two concentrations of Both BDNF (2.2M x 10-9 and 2.2M x 10-6) and the selective TrkB agonist LM22A-4 (4.8 x 10-9 and 4.8 x 10-6) increased Ca2+ dynamics beyond baseline; LM22A-4 increased frequency of events while BDNF increased the amplitude of events. TrKB receptor inhibition with the antagonist ANA-12 appeared to reduce TrkB dependent Ca2+ changes. These findings suggest that activation of the TrkB receptor alters Ca2+ dynamics in ex vivo carotid arteries. Future work will aim to elucidate the contribution of internal and external sources of Ca2+ and determine the role of shear stress in BDNF release.

This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Hypoxia-Evoked Spinal Adenosine Kinetics in Rats with Chronic Spinal Cord Injury
Authors: Seven Yasin Baris , Michaelson Alysha , Parikh Komal , Mitchell Gordon
Published: May 2023

Therapeutic acute intermittent hypoxia (tAIH) is emerging as a simple and effective means of improving motor function after spinal cord injury (SCI) and ALS. For example, daily AIH applied one-week after C2 spinal hemisection (C2Hx) improves breathing in rats. Unfortunately, studies using the same protocol with chronic cSCI (>8 weeks) report less robust recovery, except when the rats are pretreated with an adenosine 2A receptor antagonist. Pro-inflammatory conditions, such as those experienced after SCI, increase CNS extracellular adenosine concentrations. Guided by increased understanding of adenosinergic signaling mechanisms constraining AIH-induced phrenic motor plasticity, we aimed to determine real-time in vivo dynamics of extracellular adenosine in response to hypoxia in the ventral cervical spinal cord in intact and spinally injured rats. We used enzyme-immobilized micro-biosensors for real time enzymatic detection of extracellular adenosine in the mid-cervical spinal cord of intact rats and rats with chronic C2Hx (>8 weeks post-injury) during 5-min 13% O2, 1-min 9% O2 and 1-min 9% O2 + 4% CO2. Extracellular adenosine exhibits rapid kinetics with a time-constant of seconds, regardless of condition. Rats with chronic C2Hx were classified post hoc into 2 groups: normotensive (systolic blood pressure > 120 mmHg) and hypotensive (systolic blood pressure < 120 mmHg). Normotensive C2Hx rats had baseline adenosine levels comparable to intact rats; hypoxia-induced increases in adenosine were slightly reduced versus intact rats. On the other hand, hypotensive C2Hx rats had elevated baseline adenosine levels and almost completely diminished hypoxia-evoked adenosine increases. Hypercapnic hypoxia had minimal impact on adenosine levels during exposures, but lowered adenosine following each hypercapnic hypoxic episode. These results suggest that changes in cardiovascular hemodynamics in chronic SCI rats can alter basal tissue adenosine levels, possibly undermining the therapeutic efficacy of tAIH in the condition of chronic SCI. Further, hypercapnic hypoxia appears to minimize inhibitory effects of adenosine on tAIH-induced phrenic/diaphragm motor plasticity.

Supported by: NIH HL147554, HL148030 & OT2OD023854 and the University of Florida McKnight Brain Institute

This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
The effects of sucrose and arsenic on muscular insulin signaling pathway differ between gastrocnemius and quadriceps muscles
Authors: Pánico Pablo , Velasco Myrian , Salazar Ana María , Ostrosky-Wegman Patricia , Hiriart Marcia
Published: May 2023

Background: Muscle insulin resistance can originate from a sedentary lifestyle, hypercaloric diets or, the exposure to endocrine-disrupting pollutants such as arsenic. In skeletal muscle, insulin stimulates glucose uptake by translocating GLUT4 to the sarcolemma. This study aimed to evaluate the alterations induced by sucrose and arsenic exposure in vivo on the pathways involved in insulin-stimulated GLUT4 translocation in the quadriceps and gastrocnemius muscles. Methods: Male Wistar rats were treated with 20 % sucrose (S), 50 mg/L sodium arsenite (A), or both (A+S) in drinking water for 8 weeks. The intraperitoneal insulin tolerance (ITT) test was on the seventh week of treatment. Quadriceps and gastrocnemius muscles were obtained after overnight fasting or after 30 min of intraperitoneal insulin injection. We assessed changes in GLUT4 translocation to the sarcolemma by cell fractionation and abundance of the proteins involved in GLUT4 translocation by Western blot. Results: Male rats consuming S and A+S gained more weight than control and A-treated animals. Rats consuming S, A, and A+S developed insulin resistance assessed through ITT. Neither treatments nor insulin stimulation in the quadriceps produced changes in GLUT4 levels in sarcolemma and Akt phosphorylation. Conversely, A and A+S decreased protein expression of Tether containing Ubx domain for GLUT4 (TUG), and A alone increased calpain-10 expression. All treatments reduced this muscle's protein levels of VAMP2. Conversely, S and A-treatment increased basal GLUT4 levels in the sarcolemma of the gastrocnemius, while all treatments inhibited insulin-induced GLUT4 translocation. These effects correlated with lower basal levels of TUG and impaired insulin-stimulated TUG proteolysis. Moreover, animals treated with S had reduced capn10 protein levels in this muscle, while A and A+S inhibited insulin-induced Akt phosphorylation. Conclusion: Arsenic and sucrose act through different pathways to impair GLUT4 trafficking, and the effects differ between the quadriceps and gastrocnemius.

CONACYT-Fronteras #568492, DGAPA-PAPIIT-UNAM #IN20872 and DGAPA-PAPIIT-UNAM #IN205621

This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.