bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of traumatic brain injury on blood pressure regulation and cardio-renal function in rats
Authors: Lorenz John , Sakthivel Srikumaran , Lorenz Suzanne , Nieman Michelle
Published: May 2023

Traumatic Brain Injury (TBI) affects around 68 million people worldwide annually. While the neurologic effects of TBI have been extensively studied, potential effects on the autonomic nervous system have received less attention, despite clinical observations of autonomic dysfunction. We therefore sought to develop a rat model of repeated traumatic brain injury to examine the effects on cardiovascular and renal regulation, and we hypothesized that TBI would result in autonomic dysregulation of cardio-renal function. TBI was induced in male rats (250-300 gBW) under brief isoflurane anesthesia by dropping a 245g weight from a height of 1-1.5 meters onto the mid-sagittal area of the skull while the rat was suspended on a perforated tear-away platform. In the first series of experiments, blood pressure was measured continuously by telemetry over a two-week period, while rats were subjected to three successive injuries, each separated by 48 hours (repeated TBI, rTBI). Mean blood pressure was found to increase by about 7 mmHg following the third TBI (104.0 ± 1.1 to 111.0 ± 1.3 mmHg; p < 0.001, n=9). Though mild, the elevation in blood pressure was highly consistent, occurring in all of the injured rats. There were no correlate changes in heart rate observed in these rats. We then sought to examine the underlying causes of these blood pressure changes. Balance studies were performed using metabolic cages to examine salt and water intake and output before and during rTBI. Though intake of food and water were slightly affected by rTBI, no measurable effect of rTBI was observed on salt and water balance in these rats. We next measured cardiac function in anesthetized rats following rTBI and found no significant differences in any major contractile variables (LV systolic pressure, dP/tmax, dP/dtmin). In a final series of experiments, we evaluated renal blood flow during step-wise reductions in renal perfusion pressure using an aortic clamp and found that, while blood flow autoregulation was not impaired in rTBI rats, baseline renal blood flow was mildly reduced in injured rats compared to uninjured controls (3.44 ± 0.16 vs 3.94 ± 0.05 mL/min/gKW). In summary, we have generated a rat model of repeated traumatic brain injury that results in a consistent elevation of resting arterial blood pressure. Speculation that these observed changes may result from autonomic dysregulation remains to be investigated.

University of Cincinnati College of Medicine Innovation Seed Grant

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.
Cardio-centric hemodynamic management with and without adjuvant ethyl nitrite improves mean arterial pressure in rodents with chronic high-thoracic traumatic spinal cord injury
Authors: Duffy Jennifer , Hoiland Ryan , Wearing Oliver , Erskine Erin , Kwon Brian , West Christopher
Published: May 2023

Objective: Traumatic spinal cord injury (SCI) causes an initial injury followed by a protracted phase of spinal cord tissue hypoxia. This tissue hypoxia contributes to secondary injury, leading to worse motor and cardio-autonomic outcomes in the chronic setting. No neuroprotective agents to mitigate secondary injury have been identified as efficacious in clinical trials. However, we have demonstrated that taking a cardio-centric approach to hemodynamic management following SCI by augmenting cardiac output and mean arterial pressure (MAP) with the b1-adrenoceptor agonist dobutamine (DOB), and further coupling DOB infusion with the inhalation of ethyl nitrite (ENO), an S-nitrosylating agent, is associated with improved spinal cord oxygenation in the acute phase post-SCI. Aim: To determine the influence of a cardio-centric approach to hemodynamic management with adjuvant ENO inhalation following SCI on long term outcomes. We hypothesized that treatment with DOB and ENO in the acute phase following SCI would mitigate secondary injury and improve cardiovascular outcomes in the chronic setting. Methods. A total of 34 male Wistar rats underwent a T3 contusion injury (300 kdyn) and were assigned into 4 treatment groups: control (n=6), ENO (n=6), DOB (n=12), and combined DOB and ENO (n=10). At 11-weeks post-SCI, a locomotor assessment was conducted using the Basso, Beattie and Bresnahan (BBB) locomotor rating scale. At 12-weeks post-SCI, rodents were anesthetized with intravenous urethane (2.44±0.50 g/kg) and instrumented with a solid-state pressure transducer in the carotid artery to measure MAP. Results. We observed a higher MAP in both DOB (113.6 ± 11.4 mmHg; p = 0.030) and ENO+DOB (116.7 ± 14.6 mmHg; p=0.013) treated groups when compared with controls (94.65 ± 11.62 mmHg). The MAP of ENO treated animals (91.6 ± 7.3 mmHg; P= 0.97) was not different from controls. No differences in BBB scores were found between DOB (15.17 ± 4.49), ENO+DOB (13.95 ± 3.86), ENO (12.5 ± 2.5) and control (11.8 ± 2.7)(P=0.29). Collectively, these data suggest that DOB treatment, alone or in combination with ENO, improves systemic hemodynamics in the chronic high-thoracic SCI setting

US Department of Defense, ICORD Seed Grant, Craig H. Neilsen Foundation

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.
Glucocorticoid excess and insulin resistance in aged spontaneously hypertensive rats/stroke-prone
Authors: Lansdell Theresa , Hernaiz-Ojeda Angel , Lewis Ally , Dorrance Anne
Published: May 2023

Vascular diseases cause chronic cerebral hypoperfusion and neuronal injury and are the second most common cause of dementia. A significant cause of chronic cerebral hypoperfusion is hypertension. Insulin resistance is an important risk factor for hypertension. Aside from age, insulin resistance is also the most important risk factor for the development of dementia. While Insulin resistance is considered an important risk factor for the development of hypertension and dementia, little consideration has been given to the idea that hypertension could initiate insulin resistance and fuel a destructive cycle that hastens dementia. We hypothesized that hypertension initiates insulin resistance through sustained activation of the hypothalamic-pituitary-adrenal axis. To test this hypothesis, we measured corticosterone and the expression of steroid biosynthetic genes in six-month-old spontaneously hypertensive rat/stroke-prone (SHRSP) and normotensive Sprague Dawley (SD) rats. To measure glycemic control, rats were subjected to glucose tolerance and insulin tolerance tests. SHRSP were hypertensive and cognitively impaired. SHRSPs had increased corticosterone compared to SD (Male SD vs. SHRSP: 167±29 pg/g vs.1091±166 pg/g, P<0.0001; Female SD vs. SHRSP: 134±19 pg/g vs. 376±47 pg/g, P=0.0017). Adrenal CYP11B1 mRNA expression was increased in SHRSP (Males 14.44±1.44, P=0.0009; Females 710±59, P=0.0016). STARD1 mRNA expression provided a marker of HPA negative feedback. Male SHRSPs had decreased STARD1 mRNA expression (0.56±0.09, P = 0.0217). However, female SHRSPs had increased STARD1 mRNA expression (12.5± 2.25, P=0.0028). Female, but not male, SHRSPs had increased fasting blood glucose, decreased fasting insulin, and reduced rates of glucose clearance (SD vs. SHRSP: 73±6 vs. 92±4 mg/dL glucose, P=0.0045; 33±2.0 vs. 12±5 pmol/L insulin, P=0.0111; AUC 185±37 vs. 279±27 mg/dL/h, P=0.0368). When fasting rats were challenged with insulin, both male and female SHRSPs had decreased clearance of glucose compared to SDs (Male SD vs. SHRSP AUC 87 ± 2 vs. 58 ± 4 mg/dL/h, P< 0.0001, Female SD vs. SHRSP AUC 82 ± 2 vs. 68 ± 3 mg/dL/h, P=0.0007). These results indicate that hypertension is associated with impaired HPA function and insulin resistance, with female SHRSP succumbing faster to hyperglycemia than males.

Alzheimer's Association Research 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.
Intestinal epithelial ZO-2 is critical for downregulation of injury-induced proliferation after mucosal repair is complete
Authors: Abtahi Shabnam , Chanez-Paredes Sandra , Rincon-Cruz Lorena , Nandivada Prathima , Hunziker Walter , Turner Jerrold
Published: May 2023

Zonula occludens-2 (ZO-2), encoded by TJP2, is a multi-domain scaffolding protein that recruits claudin proteins to tight junctions. In MDCK cells, Tjp2 knockdown inhibits Hippo signaling pathway and activates Yap/Taz. In humans, TJP2 mutations within the region that mediates claudin binding are associated with cholestasis that is exacerbated by defects in bile acid conjugation. Similarly, liver-specific Tjp2 knockout mice are phenotypically normal but hypersensitive to bile-acid induced cholestatic disease. We sought to determine whether ZO-2 has similar protective functions in intestinal epithelia. Like humans with TJP2 mutations, intestinal epithelial-specific Tjp2-knockout in mice did not induce spontaneous gut disease. There was, however, increased epithelial proliferation, mucosal hyperplasia, and Yap/Taz activation. Nuclear activated Yap was increased 1.9±0.1-fold in Tjp2 knockout enterocytes relative to wild type. In hepatocytes, bile acid stress elicited liver disease. We therefore asked if intestinal epithelial Tjp2 knockout increased mucosal injury induced by systemic T cell activation, TLR3 activation (poly I:C injection), or irradiation. In contrast to hepatocytes lacking ZO-2, intestinal epithelial ZO-2 deletion accelerated proliferation and repair. However, unlike wildtype mice, intestinal epithelial proliferation remained increased in Tjp2 knockout mice after repair was complete and mitotic activity had returned to baseline in wildtype mice. This phenotype is intrinsic to epithelial cells, as Tjp2 knockout enteroids excessive proliferation and formed complex cysts with exuberant budding. These data indicate that ZO-2 is a critical regulator of proliferative homeostasis within the intestinal epithelium and suggest that ZO-2 loss may contribute to dysregulated growth of intestinal neoplasms.

Supported by: National Institutes of Health grants R01DK61931 and R01DK068271

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.
A low-dose pemetrexed-cisplatin combination regimen induces significant nephrotoxicity in mice compared with pemetrexed or cisplatin alone
Authors: Iwhiwhu Samson , Kumar Ravi , Afolabi Jeremiah , Adebiyi Adebowale
Published: May 2023

Pemetrexed is a cytostatic agent used to treat solid tumors and autoimmune diseases. Pemetrexed exerts its antineoplastic activity by multitargeted disruption of folate-dependent processes that mediate cell replication. Pemetrexed is now combined with cisplatin to treat non-small cell lung cancer and malignant mesothelioma. Cisplatin nephrotoxicity is well-established. Recent evidence in humans suggests that pemetrexed monotherapy can cause kidney injury. However, the mechanisms of pemetrexed-induced kidney injury remain unclear. Whether pemetrexed-cisplatin combination chemotherapy exacerbates nephrotoxicity is also unknown. In this study, we investigated acute kidney injury (AKI) in mice administered a low-dose regimen of pemetrexed or cisplatin alone and compared it with a pemetrexed-cisplatin combination. C57BL/6J (8-10 weeks old) male mice were randomly divided into four groups and administered (intraperitoneally) the experimental drugs solubilized in Captisol (sulfobutylether-b-cyclodextrin). Group 1 received Captisol (excipient control), Group 2 pemetrexed (10 mg/kg), Group 3 cisplatin (1 mg/kg), and Group 4 pemetrexed (10 mg/kg) plus cisplatin (1 mg/kg). The mice were treated every other day for two weeks, three times per week. Transdermal glomerular filtration (GFR) measurement was performed on the third day after the last treatment, followed by a necropsy. Whereas body weight changes and kidney-to-body weight ratio were comparable in the control vs. pemetrexed or cisplatin alone group, these indices were significantly increased in the pemetrexed-cisplatin combination group. There was a relative decrease in the GFR of mice treated with pemetrexed or cisplatin alone and in the pemetrexed-cisplatin combination. However, only mice treated with cisplatin and pemetrexed-cisplatin combination showed a significant reduction in GFR. There were trends of increases in the plasma or urinary levels of AKI biomarkers, including blood, urea nitrogen (BUN), creatinine, neutrophil gelatinase-associated lipocalin (NGAL), and cystatin C in control vs. pemetrexed or cisplatin alone. Renal lipid peroxidation and DNA damage were comparable in control vs. pemetrexed or cisplatin alone. However, the mice administered with a combination of pemetrexed and cisplatin showed amplified lipid peroxidation, proteinuria, and AKI. These findings indicate that combining pemetrexed and cisplatin promotes considerable kidney damage at individual doses that do not cause significant nephrotoxicity. Hence, patients treated with pemetrexed-cisplatin combination chemotherapy should be monitored closely for AKI.

Disclosure of Funding: NIH: R01 HL151735-01.

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.
Sleeping while diving: seals at sea drift in and out of sleep at depth
Authors: Kendall-Bar Jessica , Williams Terrie , Costa Daniel
Published: May 2023

In mammals, sleep is critical and ubiquitous. However, in marine mammals that spend months or entire lifetimes at sea, sleep can limit access to air and foraging opportunities and leave animals vulnerable to predation. Large, deep-diving northern elephant seals (Mirounga angustirostris) travel thousands of kilometers and spend up to 7 months at sea in search of food. We posited that combined demands to feed and avoid predators would strongly restrict aquatic sleep in seals. We built a portable, non-invasive system to simultaneously monitor electroencephalogram (EEG), electrocardiogram (ECG), three-dimensional motion, and swimming behavior. EEG activity of 13 young (< 3-years-old) female northern elephant seals (N = 5 in the lab, N = 8 in the wild [N = 3 at sea]) revealed that total sleep time was indeed strongly restricted at sea compared to on land (> 6-fold difference; 10.8 ± 3.0 h/day on land, 1.7 ± 0.7 h/day at sea). Seals at sea slept during short naps (< 20 min) while resting on the ocean floor (64-249 m deep) or drifting through the water column (82-377 m deep). REM sleep in mammals co-occurs with sleep paralysis. Our data support the presence of sleep paralysis through a persistent supine inversion (belly-up posture) whenever the seal was in REM (100% of REM sleep in the open ocean). Unexpectedly, elephant seals at sea exhibited a large proportion of REM sleep (29.1 ± 4.3% of at-sea total sleep time), compared to aquatic sleep in captive Caspian seals, harp seals, walruses, and fur seals (11%, 6%, 5%, and 1% respectively). This suggests that sleep at depth allows seals to drift safely in and out of sleep paralysis. However, time for sleep is limited by near-constant foraging to support high energetic demands due to their large body size. The extreme flexibility in sleep duration exhibited by northern elephant seals is unprecedented among mammals – approaching that which is observed in migrating birds. These insights into sleep for a large, highly mobile marine mammal can contribute to our understanding of sleep’s function and pathology across mammals, including humans.

Funding: NSF Graduate Resesarch Fellowship, Laurel Clark Sea to Space Physiology Research Grant, ARCS Fellowship, Sooy Graduate Fellowship, National Geographic Early Career Grant, Special Research Grant – UC Santa Cruz, Joint Industry Project (JIP2207-23) [DPC], Office of Naval Research (Grants # N00014-08-1-1195 [DPC], N00014-18-1-2822 [DPC], N00014-00-1-0880 [DPC], N00014-03-1-0651 [DPC], N00014-08-1-1195 [DPC], N00014-20-1-2762 [TMW], N00014-19-1-2178 [TMW])

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.
High glucose-stimulated secretion of Semaphorin-3G by proximal tubule cells inhibits angiogenesis in peritubular endothelial cells
Authors: Caceres Paulo
Published: May 2023

Hyperglycemia in the diabetic kidney causes tubular and microvascular abnormalities that eventually lead to kidney damage. Given the close association between the proximal tubule and peritubular capillaries, a thorough understanding of their interaction could help identify mechanisms of diabetic kidney disease. Microvascular abnormalities are known to occur in diabetic patients and animal models. Despite known growth factors produced by the proximal tubule that could potentially target neighboring endothelial cells, it is not well understood whether the proximal tubule regulates angiogenesis. Here we propose that the proximal tubule secretes Semaphorin-3G (Sema3G), an anti-angiogenic protein. We hypothesize, that high glucose stimulates Sema3G secretion by proximal tubule cells and inhibits angiogenesis in peritubular endothelial cells.To study the role of secreted Sema3G, we collected the conditioned media from cultured polarized proximal tubule cells (RPTEC cell line) where we silenced Sema3G via lentivirus-delivered shRNAs. To study angiogenesis, we developed primary cultures of mouse kidney peritubular endothelial cells and analyzed angiogenesis via tubulogenesis assays in matrigel.We observed that the basolateral conditioned medium from RPTEC cells stimulated angiogenesis of peritubular endothelial cells in matrigel over 8 hours (p<0.01). However, RPTEC cells pre-grown on high glucose (25 mM) lost this ability. The apical media did not have any effect. To identify a potential proximal tubule anti-angiogenic factor, we measured release of Sema3G from polarized RPTEC cells. We found that RPTEC cells secreted Sema3G basolaterally and high glucose stimulated this by 5.5-fold. (p<0.01). Next, we tested the anti-angiogenic potential of Sema3G in peritubular endothelial cells. While adding recombinant Sema3G (200ng/ml) produced a modest inhibition (28%, p<0.05) of baseline peritubular endothelial cell angiogenesis, instead it completely blocked the stimulatory effect of a dose-response treatment (50–100ng/ml) with the potent angiogenic factor VEGF (p<0.01). Finally, to test the role of endogenous proximal tubule Sema3G, we silenced Sema3G via lentivirus-delivered shRNA in RPTEC cells. We then collected the conditioned medium from cells on normal or high glucose and performed angiogenesis assays. We found that silencing Sema3G in RPTEC cells on high glucose restored the ability of the conditioned medium to stimulate peritubular endothelial angiogenesis.We conclude that RPTEC proximal tubule cells secrete Sema3G, which is stimulated by high glucose, and this anti-angiogenic factor inhibits angiogenesis in mouse peritubular endothelial cells.

Henry Ford Hospital, American Heart Association

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.
Endothelial Estrogen Receptor Beta Deletion Augments Endothelial Function in High Fat Diet Fed-Female Mice
Authors: Sharma Neekun , Ramirez-Perez Francisco , Betancourt-Cortes Edgar , Power Gavin , Lazo-Fernandez Yoskaly , Martinez-Lemus Luis Alejandro , Padilla Jaume , Manrique Camila
Published: May 2023

Arterial stiffening and endothelial dysfunction are key contributors to the development and progression of cardiovascular disease (CVD) in women with obesity. Estrogen actions in the vasculature, mainly mediated via estrogen receptor alpha (ERα), result in enhanced endothelial function, lowered arterial stiffness and decreased blood pressure. However, these vasculoprotective effects seem to be abrogated in obesity. The role that estrogen receptor beta (ERβ) plays in maintaining vascular health in females is not well-characterized and previous studies have pointed toward an inhibitory effect of ERβ signaling on the ERα mediated vascular relaxation. Therefore, the present investigation is aimed at examining the role of endothelial cell (EC) ERβ on endothelial function and arterial stiffness in a model of obesity. EC-ERβKO female mice (ERβ double floxed VE cadherin-Cre+) and their respective littermates (ERβ double floxed Cre-) were fed control chow or a high fat diet (60%) starting at 12 weeks of age for 16 weeks. All reported differences are significant at p<0.05. HFD feeding resulted in significant weight gain in the EC-ERβKO and control groups. Neither, HFD nor EC ERβ deletion impacted blood pressure. As expected, HFD feeding resulted in aortic stiffening in the control cohort. Conversely, ERβ deletion in EC tended (P=0.06) to ameliorate aortic stiffening associated with HFD feeding. After euthanasia and using pressure myography, we also determined ex vivo mesenteric artery vasomotor function and stiffness by measuring flow-mediated dilation (FMD), vascular responses to insulin (INS), sodium nitroprusside (SNP), and the passive mechanical properties of the arterial wall, respectively. Sixteen weeks of HFD resulted in blunted FMD responses only in the control cohort. INS-induced vasodilation was enhanced in the EC-ERβKO group fed HFD. Vasomotor responses to SNP (i.e. endothelial independent) were similar among groups. Contrary to our findings in the aorta, EC ERβ deletion resulted in increased incremental modulus of elasticity (increased stiffness) in mesenteric arteries. Collectively, these findings suggest that deletion of EC ERβ in the setting of obesity enhances endothelial vasodilatory function with a variable impact on arterial stiffening that is dependent on the vascular bed examined. Further studies are needed to delineate the interactions between ERβ and ERα in the endothelium, and their impact in the pathogenesis of CVD in women with obesity and insulin resistance.

Funding supported by R01 HL142770 (CM-A).

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 “microbiome-gut-brain axis” in Alzheimer's disease and its role in neurocognitive decline
Authors: Loew Ethan , Sallis Benjamin , Tracy Matthew , Haran John , McCormick Beth
Published: May 2023

Alzheimer’s disease (AD) is a progressive neurocognitive disease characterized by amyloid beta plaques and neurofibrillary tangles in the brain along with inflammation both in the brain and systemically. This has led to the theory of microbial communities or infections as being causative in the development of neuroinflammation as well as immunosenescence and inflamm-aging seen in AD. Our own research has demonstrated a decreased abundance of anti-inflammatory taxa and an increased abundance of pro-inflammatory taxa in the gut microbiome of AD patients. However, it is unclear how the AD microbiome exerts effects on the central nervous system. To address this gap in knowledge we have performed gut microbiome profiling, analysis of immune cell populations in serum, blood cytokine profiling, and cognitive assessments of AD older adults at 90-day intervals. In our early data collected from this ongoing study we have observed changes in B-cell populations with an increased abundance of class-switched B-cells in older adults with greater levels of cognitive impairment. We have further demonstrated that colonization of mice with the microbiome of AD older adults promotes B-cell class-switching when compared with cognitively impaired older adults without AD. Additionally, we have discovered a loss of phytoestrogen-metabolizing bacteria such as Adlercreutzia equolifaciens among AD older adults with rapidly progressing dementia. Phytoestrogens have been previously identified in protecting the intestinal epithelium from oxidative stress and epithelial permeability. Our preliminary studies have suggested that that the phytoestrogen (s)-equol, produced by A. equolifaciens, confers resistance to epithelial damage in the setting of bacterial lipopolysaccharide. Thus, we hypothesize that Adlercreutzia equolifaciens and similar phytoestrogen-metabolizing bacteria maintain epithelial homeostasis in the setting of inflammation while a gain of pro-inflammatory taxa in AD leads to intestinal barrier disruption, increased antigen presentation, immune cell dysregulation, and ultimately cognitive decline. This continuing work aims to further establish the connection between AD related neurocognitive decline, the microbiome, and immune system.

This research was funded by grant numbers R01DK125407, R01AG067483, and 5T32A1007349-31 from the National Institutes of Health

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.
Representing connectivity circuits in autonomic physiology: the SPARC map of organ innervation
Authors: Gillespie Tom , Martone Maryann
Published: May 2023

The Stimulating Peripheral Activity to Relieve Conditions (SPARC) program is a NIH-funded consortium to improve the understanding of how the autonomic nervous system (ANS) interacts with end organs and the central nervous system. A major goal of SPARC is to use this knowledge to develop the next generation of neuromodulator devices as effective disease therapies. To support neuromodulation planning, the routes of ANS neuron populations (as well as those populations conveying visceral sensing) are to be mapped in terms of the anatomical structures where they pass through or terminate. Such a map would also serve as an organizing scaffold for (i) a growing SPARC repository of electrophysiology recordings and molecular assay data, as well as (ii) the computational simulation of the effect of neural stimulation on any relevant point on the CNS or ANS. The resulting SPARC map represents connectivity as a network of conduits, and is known as the SPARC Connectivity Knowledge Base of the Autonomic Nervous System (SCKAN). SCKAN contains explicit knowledge about CNS-ANS-end organ circuitry derived from SPARC data and scientific literature, in a form that supports computational reasoning. All connections are annotated with standard reference SPARC vocabularies allowing us to integrate datasets that are annotated to the same annotation standard. Circuits on the map represent details of ANS connectivity associated with a particular organ, e.g., bladder control, defensive breathing, modulation of peristalsis or cardiac inotropy/chronotropy. These circuits are created through interviews with SPARC investigators, anatomical experts and the scientific literature. They contain detailed representations of neuron populations giving rise to ANS connections, including mappings of the locations of cell bodies, dendrites, axon segments and synaptic endings. Circuits are modeled using ApiNATOMY, a knowledge model and tool suite specifically created to represent biological connectivity. Furthermore, these detailed circuits are supplemented with general knowledge on connectivity between CNS nuclei, ANS ganglia, nerves, and end organs derived from the scientific literature. To facilitate extracting this knowledge from the literature and maintaining relevance over time, we developed a Natural Language Processing (NLP) pipeline, which extracts connectivity relationships between unique anatomical structures within a sentence from the scientific literature. SCKAN is being used to create a queryable visual atlas of ANS circuitry through the SPARC portal.

SPARC Funding: NIH Common Fund, NIH Office of the Director, Award OT2 OD030541

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 interplay between iron regulation and ferroptosis cell death signaling
Authors: Garcia Jorge , Chapa Xavier , Javadov Sabzali
Published: May 2023

Iron is an important ion that is mainly involved in different aspects of cellular metabolism. Normally, iron homeostasis is regulated by storage and transport proteins that help stabilize and facilitate transport throughout the body. Transferrin is the main iron transport protein in the blood; it transports ferric iron (Fe3+) from absorption sites to different tissue cells via endocytosis upon interacting with the transferrin receptor. In the cell, in addition to the cytoplasm, mitochondria are heavily involved in iron metabolism. The excess of labile (free unbound) iron in the cell can undergo the Fenton reaction to further enhance ROS production inevitably leading to cell death through apoptosis and/or ferroptosis. Ferroptosis is a new type of cell death that is mediated by iron-dependent lipid peroxidation and is associated with a myriad of diseases such as cardiovascular and neurodegenerative diseases, and cancer, among others. Mitochondria are involved in ferroptotic cell death signaling, nevertheless, the exact mechanisms underlying the contribution of mitochondria to ferroptotic signaling remain unknown. This study was performed to elucidate the effects of iron on cell viability and mitochondrial function in cardiomyocytes. H9c2 cardiomyocytes were cultured in the presence/absence of ferric ammonium citrate (FAC, 200 and 400 μM), tert-butyl hydroxide (TBH, 10 and 100 μM), and deferoxamine (DFO, 200 and 400 μM) individually and in combination. Cell death was quantified by the lactate dehydrogenase (LDH) activity in the culture media whereas mitochondrial function was estimated by changes in the mitochondrial membrane potential measured by using TMRM, a potential-sensitive fluorescent dye. Our results show that TBH at low concentrations or FAC at both low and high concentrations did not induce cell death. However, FAC at high concentration (400 μM) in combination with TBH (10 μM) significantly increased cell death. Additionally, DFO alone induced cell death, demonstrating the importance of maintaining iron balance in cellular media. In conclusion, this study demonstrated that the detrimental effects of iron (FAC) on cell viability are increased in the presence of oxidative stress (TBH) in H9c2 cardiomyocytes.

This study was supported by the National Institutes of Health (Grant R16GM145390).

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.
Reactive hyperemia acutely decreases peripheral arterial stiffness
Authors: Jackson Ronald , Lima Natalia , Sherman Sara , Clifford Philip
Published: May 2023

Previous studies have shown that peripheral arterial stiffness can be reduced acutely by exercise, mechanical compression, and heat. Since reactive hyperemia elicits large increases in conduit artery blood flow similar to the other maneuvers, it may have similar effects on peripheral arterial stiffness. However, the effect of reactive hyperemia on peripheral arterial stiffness has not been investigated. We tested the hypothesis that reactive hyperemia would acutely decrease peripheral arterial stiffness as measured by pulse wave velocity (PWV). Seven healthy young adults (4 women; age: 30 ±4 years; mean±SD) were included in this study. Brachial to radial PWV was measured by placing pulse tonometer’s simultaneously over the brachial and radial arteries. Reactive hyperemia was performed using a rapid-release cuff positioned on the right upper arm, inflated to 220 mmHg and sustained for 5 min. Arterial blood pressure was continuously monitored via photoplethysmography beat by beat on the middle finger of the contralateral hand. Measurements were made before cuff inflation and at 5, 15, and 30 min after cuff release. At baseline before cuff inflation, brachial to radial PWV was 10.8 ±1.6 m/sec. PWV decreased (p<0.05) to 8.7 ± 1.8 m/sec at 5 min. PWV was not different from baseline (p>0.05) at 15 min (10.8 ± 2.7 m/sec) or at 30 min (10.1 ± 3.3 m/sec). Mean arterial pressure (MAP) was not significantly different (p>0.05) across time points. The results show that reactive hyperemia produces an acute reduction in brachial to radial PWV. However, the reduction was not long lasting. This was a local response not confounded by arterial pressure changes. The large increase in conduit artery blood flow or trapped metabolites may provide a potential mechanism.

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.
Developmental changes in cardiac composition before and after birth in sheep
Authors: Vasquez Reyes Kaylee-Abril , Louey Samantha , Jonker Sonnet
Published: May 2023

Introduction: The myocardium is made up of many elements that each play an important role in heart function. The contractile cardiomyocytes proliferate prenatally, and become terminally differentiated in the weeks leading up to birth. Despite a loss of ~ 1/3 of the cardiomyocytes about 1 week before birth, the hearts continue to increase in size (Jonker et al., 2015). At birth, the demands on the cardiovascular system change, which may affect the relative cellular makeup of the myocardium. In this study, we determined the fractional composition of the myocardium in four different ages around the time of birth. Methods: Hearts, arrested in diastole, were collected from control fetal (135d and 142d gestational age; dGA; term is 147d) and newborn (1d and 5d postnatal age; PN) lambs. Sections of left ventricle were fixed (4% paraformaldehyde), paraffin embedded and stained (Masson’s Trichrome). Images (400x) were analyzed by unbiased sampling (grid system, FIJI) to classify according to these categories: cardiomyocyte cell body, cardiomyocyte nucleus, blood vessel lumen, blood vessel wall, collagen, non-collagen connective tissue. All values are represented as percent of total area (±SD). Groups (n=3-4 each age) were compared by 1-way ANOVA followed, if indicated, by Tukey's multiple comparisons test. Males and females were both represented in each age (135dGA, 143dGA, 1dPN, 5dPN: n=1/2, 2/2, 3/1, 2/1, respectively). Results: The average area composed of cardiomyocyte for all groups was 81.7 ± 7.4%, and did not differ between ages. The average area composed of vasculature for all groups was 8.6 ± 5.2%, and did not change with age. Connective tissue area was 3-fold greater at 1dPN (8.5 ± 3.6%) than 143dGA (2.8 ± 1.2%, P<0.05) and 5dPN (2.5 ± 0.8%, P<0.05). This was not due to more collagen, which did not differ between ages. Further analysis of the cardiomyocyte fraction indicated that the nucleus was 60% larger (compared to total myocyte area) at 1dPN (P<0.04; in advancing age order: 18.2 ± 3.3%, 14.2 ± 1.0%, 26.3 ± 4.9%, 17.1 ± 1.8%). Conclusion: Our preliminary analysis indicates little change in the cellular composition of the left ventricle myocardium, save for a transient increase in connective tissue area and larger nuclei per cardiomyocyte area 1 day after birth. A change in glycogen after birth could be a factor that leads to increased cardiomyocyte nuclear area per cytoplasm and increased relative fraction of connective tissue.

This study was funded by NIH NHLBI R01HL142483. KAVR was funded by a NIH supplement to R01HL142483.

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 response of fetal sheep cardiomyocytes to intralipid infusion
Authors: Iverson Kaliyah , Loey Samantha , Jonker Sonnet
Published: May 2023

Introduction: The developing heart undergoes changes in metabolic substrates parallel with perinatal developmental stages. The preferred substrates for fetal hearts are carbohydrates, which transitions to a preference for fatty acids postnatally. The underdevelopment of lipid metabolism mechanisms in preterm infants cause imbalances or dysfunction in uptake, cellular processing, and storage of fatty acids; and increase the risks for long term cardiovascular and metabolic diseases. It is unknown whether the heart can process fatty acids before birth, and how it affects cardiomyocyte growth. The aim of this study was to determine the effects of Intralipid infusion on fetal sheep cardiac myocyte growth. We hypothesized that the size of cardiomyocytes would remain unchanged, however we expected an increase in maturity. Methods: Intralipid 20® was infused into instrumented fetal sheep (IL, 0.4 ml/kg/hr for 8 days, n=4F/7M); the contralateral twin received saline at a comparable rate (CON, n=7F/4M). Hearts were collected at 133 days gestational age (dGA; term is 147 dGA), and enzymatically dissociated, then myocytes fixed in paraformaldehyde. The length and width were measured in 100 myocytes using a wet mount, under calibrated light microscopy (40x, Zeiss Axiophot), and analyzed with Image Pro 6.3. Nucleation was determined in 500 cells; percentage binucleation is a surrogate measure of maturation. Data are presented as mean ± standard deviation. Groups were compared by t-test. Results: Body weight (IL, 4.2 ± 0.6 vs. CON, 4.1 ± 0.6kg) and heart weight (IL, 29.9 ± 4.1 vs. CON, 27.2 ± 4.6g) were not different between the lipid and control fetuses. Interim results indicate no differences in length or diameter in cardiomyocytes of the left and right ventricle (IL, N=3-7; CON, N=7-9). We found no differences in cardiomyocyte length in the septum, but Intralipid (N=10) increased the diameter of mononucleated (+12%, P=0.016) and binucleated (+11%, P=0.012) myocytes (vs. CON, N=7). In the septum, Intralipid treatment increased binucleation (P<0.02; 69.2 ± 8.0% vs 60.8 ± 9.7%). In the RV, increased binucleation was only a tendency (P<0.06; 70.7 ± 6.4% vs 60.8 ± 9.9%; IL n=6). Binucleation was unaffected in the LV (67.1 ± 9.9%). Summary/Conclusion: The increase in diameter of fetal cardiomyocytes in the septum could reflect different regional regulation of growth to the infused intralipid. Interestingly, parallels could be made between the septal hypertrophy described in offspring from diabetic mothers.

This study is funded by NIH R01HL146997 and R01HL142483. KI is funded by a NIH supplement to R01HL142483.

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.
Influence of Hydration Status and Plasma Copeptin on Ambulatory Blood Pressure in Healthy Young Adults
Authors: Jeong Soolim , Barnett Alex , Linder Braxton , Tharpe McKenna , Hutchison Zach , Culver Meral , Nichols Olivia , Fuller-Rowell Thomas , Watso Joseph , Robinson Austin
Published: May 2023

BACKGROUND: Adequate hydration is essential for regulating various physiological systems and may influence blood pressure (BP). Hypohydration is linked with elevated copeptin (surrogate of arginine vasopressin), which is associated with elevated cardiovascular disease risk. However, there is limited information on the influence of hydration and copeptin on ambulatory BP measures in young adults. Therefore, we sought to investigate associations between hydration, copeptin, and ambulatory BP. METHODS: We studied 41 participants (19 M/22 F, 24 White/17 Black, age 21±1 years, body mass index 26±5 kg/m2, screening BP 111± 10/67±8 mmHg; Mean ± SD) who provided a 24-hour urine sample. We measured urine specific gravity (USG), urine osmolality (OSM), and plasma copeptin as biomarkers of hydration. We used ambulatory BP monitoring (Suntech Oscar2) to assess BP during daytime (1000-2000) and nighttime (0000-0600). Our primary outcomes were plasma copeptin (pmol/L) and night-to-day BP dip ratio (nighttime/daytime BP) in dehydrated (USG >1.020 or OSM >800 mOsm/kg) vs euhydrated participants. Statistical procedures included Student’s t-tests and Mann-Whitney U tests. We also used Spearman’s rho correlation (controlling for BMI, sex, and race). We set α at ≤0.05. RESULTS: Copeptin concentration was elevated in dehydrated compared with euhydrated participants (USG: 6.6±2.9 vs 4.3±2.0 pmol/L, p<0.005; OSM: 6.6±2.7 vs 4.1±2.0 pmol/L, p<0.001). After controlling for BMI, sex, and race, copeptin was associated with USG (rho=0.44, p=0.005) and OSM (rho=0.51, p=0.001). Systolic and diastolic BP dip ratios did not differ by hydration status for either USG or OSM ( ps>0.179). Additionally, adjusted BP dip ratios were not correlated with OSM or USG ( ps>0.149). Plasma copeptin was not associated with BP dip ratios ( ps>0.155) but was associated with absolute nocturnal systolic (rho=-0.34, p=0.036) and diastolic BP dip (rho=-0.33, p=0.041). When we split participants by low and high copeptin concentration (median split), higher copeptin was associated with a lower (i.e., worse) systolic BP dip ratio (0.87±0.06 vs 0.90±0.06, p=0.048) and lower absolute nocturnal systolic and diastolic BP dip ( ps<0.01). CONCLUSIONS: Hydration biomarkers were correlated with plasma copeptin, but not ambulatory BP. The significance of our findings are that higher copeptin was associated with blunted nocturnal BP dipping in younger adults, which could predispose them to increased future cardiovascular disease risk.

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.
Dysregulation of hepatic microcirculatory function and tissue oxygenation in a rodent model of sleep apnea
Authors: Marcus Noah , Gadkari Priyanka , Smith Carter , Highum Aubrey , Gerritts Raina , Madigan Benjamin , Harbeck Katherine , Lei Ryan , Schwartz Kelsey , Lang James , Clayton Sarah
Published: May 2023

Sleep apnea (SA) is highly prevalent in patients with non-alcoholic fatty liver disease (NAFLD). The pathophysiology of NAFLD is incompletely understood however hemodynamic dysregulation and tissue hypoxia are hypothesized to play important roles. SA is associated with vascular and autonomic dysfunction however its effects on hepatic hemodynamic control have not been explored. We hypothesized that exposure to an experimental model of SA (CIH) would result in exaggerated reductions in hepatic perfusion (HP) and tissue PO2 (HPO2) during intermittent asphyxia (IA) and that these changes would be exacerbated by ovariectomy (OVX). Female Sprague Dawley rats (n=4-6 per group) were exposed to CIH or sham for 8h/d for 14 days. At the conclusion of CIH or sham, HP and HPO2 responses to IA (ten episodes FiO2 10%, FiCO2 3%, 30s each) were measured under anesthesia. Data was analyzed using ANOVA or unpaired t-tests. IA normoxic HP and PO2 was significantly decreased relative to pre-AIH in all groups, but HP was markedly lower in OVX-CIH vs sham or CIH (p<0.05). Reduction in HP during the hypoxic portion of IA was greater in CIH and OVX-CIH than sham (p<0.05) but was not different between the two CIH groups. HPO2 decreased to a greater extent in CIH v. sham during the hypoxic portion of IA (p<0.05). In conclusion, 14 days of CIH causes dysregulation of hepatic hemodynamics and tissue PO2 and loss of female sex steroid hormones may exacerbate these changes. Our findings identify a potential role of SA in the pathophysiology of NAFLD.

DMU Mentored Student Research Program

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.
Spontaneous Cardiac Baroreflex Sensitivity in Young, Healthy Black and White Adults: Influence of Race and Sex
Authors: Taherzadeh Ziba , Garza Nicole , Skow Rachel , Young Benjamin , Nandadeva Damsara , Stephens Brandi , Grotle Ann-Katrin , Fadel Paul
Published: May 2023

Background: Black (BL) individuals living in the United States are more likely to develop hypertension and cardiovascular disease compared to their White (WH) counterparts. However, studies investigating racial differences in blood pressure regulation and baroreflex sensitivity (BRS) are limited and have reported equivocal results. Furthermore, despite BL females also having a high prevalence of hypertension and cardiovascular disease, sex differences are often not considered. Additionally, baroreflex effectiveness index (BEI) is a newer measure used to estimate baroreflex function, yet studies have not examined the influence of sex or race on BEI. Therefore, the purpose of this project was to investigate the effects of both race and sex on cardiac BRS and BEI. We hypothesized that BL individuals would have lower cardiac BRS and BEI than WH individuals. Methods: We studied 88 young healthy adults, 28 BL males (21 ± 3 years; mean ± SD), 17 WH males (24 ± 4 years), 15 BL females (21 ± 3 years), and 28 WH females (23 ± 4 years). Heart rate (ECG) and beat-to-beat arterial blood pressure (finger photoplethysmography) were continuously recorded during a five-minute resting baseline. Cardiac BRS was measured using the Sequence Method, by identifying the gain of the relationship between systolic blood pressure and RRI from sequence(s) of three or more consecutive heartbeats in which systolic blood pressure and RRI change in the same direction. BEI was quantified by baroreflex-driven ramps relative to all systolic blood pressure ramps. Results: Cardiac BRS was significantly higher in BL individuals (31 ± 15 ms/mmHg) compared to WH individuals (25 ± 11 ms/mmHg; main effect of race, p = 0.02). Interestingly, post hoc comparisons revealed that this was only true within the males (p = 0.03), but not females (p = 0.63). However, there was no difference in cardiac BRS between males and females (main effect of sex, p = 0.35) and no interaction between sex and race (p = 0.27). There were also no effects of race (p = 0.65) or sex (p = 0.15) on BEI. Conclusion: These preliminary data suggest that, in contrast to our hypothesis, young BL individuals have higher cardiac BRS compared to WH individuals; an effect that is only present in males. In contrast, BEI was not influenced by race or sex. Collectively, our findings do not suggest that lower cardiac BRS plays a major role in the higher prevalence of cardiovascular disease in BL individuals.

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.