bluuebunny/crossref_metadata_2025 huggingface dataset:
Untangling purinergic regulation through the stellate ganglion
Authors: Bussey Carol , Davis Harvey , Bogart Emma , Paterson David , Paton Julian
Published: May 2023

Sympathetic nerve overactivity is a key contributor to cardiovascular diseases, and related morbidity and mortality. Denervation of the stellate ganglion has been explored as a therapeutic strategy for heart failure, but there is a need for targeted, non-invasive approaches. Upregulation of P2X3 purinergic receptors in stellate ganglia of Spontaneously Hypertensive (SHR) compared to Wistar rats (16-week-old), revealed by RNASeq transcriptional profiling, leads us to hypothesize that purinergic signalling may play a role in the excessive sympathetic drive to the heart in cardiovascular disease.Cardiac effects of stellate ganglion purinergic stimulation were investigated in the working heart-brainstem preparation of Wistar rats (4-5 week old). Microinjection of ATP (100ng) directly into the right stellate ganglion increased heart rate (Wistar 13±6 Δbpm, n=6; SHR 25±8 Δbpm, n=2). This tachycardia was attenuated by either systemic P2X3 inhibition with AF-353 (Wistar 2±2 Δbpm, n=4), or abolished by denervation of the cardiac sympathetic nerve emanating from the stellate ganglion. However, bradycardic responses were also observed (Wistar -24 ± 12 bpm, n=5), likely indicating contrasting signalling by purinergic components such as adenosine.These findings were echoed in isolated post-ganglionic sympathetic neurones from the stellate ganglia of Wistar rats (4-6 weeks), wherein ATP evoked a significant increase (Median; 0.21) in [Ca2+]i as measured by Fura-2AM imaging (n=15, Wilcoxon matched-pairs test; p<0.0001) with a high degree of variability suggestive of responding and non-responding cells. This ATP-induced calcium transient was inhibited by specific P2X3 receptor antagonism with either NF-10 or AF-130.Further, immunofluorescence analysis shows clustering of neurones expressing P2X3 within the stellate ganglion.Stellate ganglion P2X3 purinergic receptors contribute to cardiac chronotropic regulation, with apparent heterogeneity in neuronal expression and differential purinergic responses. P2X3 receptor overexpression is likely to contribute to cardiac sympathetic overactivity and hypertension, making them a promising novel therapeutic target.

Funding: Support provided by Health Research Council of New Zealand.

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.
Dynamic homeostatic plasticity within cerebellar circuitry
Authors: Han Victor , Han Victor , Zhang Yueping , Magnus Gerhard
Published: May 2023

The cerebellum has proved useful as a model system due to its uniform modular organization and explicit physiological significance of input and output signals. The cerebellum of the mormyrid fish provides a special opportunity to directly determine how single PCs affect their target cells. Such an approach is nearly impossible in mammals.In this study of the mormyrid cerebellum, a Purkinje cell and its target cell were simultaneously patch-recorded in a slice preparation, as focal stimuli were used to activate the PC's parallel fibers (PFs) or single climbing fiber (CF). Upon establishment of synaptic connection between two PCs or a PC-DCN cell pair, three signals – PF responses in both cells and the synaptic inhibition from the pre- to the post-synaptic cell – were recorded as controls, followed by the conventional manipulations of pairing PF and CF inputs to induce long-term potentiation (LTP) or depression (LTD) at parallel fiber synapses onto the presynaptic cell. Then, the three signals are recorded again and contrasted with the controls.Surprisingly, we found that after PF-LTP was induced in the presynaptic cell, the synaptic inhibition from the same cell to the postsynaptic cell was significantly attenuated; conversely, after PF-LTD was induced in the presynaptic cell, the synaptic inhibition from same cell to postsynaptic cell was significantly enhanced. These results indicate that synaptic plasticity at input synapses of the mormyrid Purkinje cell are not simply conveyed to the same cell’s output synapses, as assumed in conventional theories of motor learning, but rather that the strength of a PC’s output synapses onto its target cells is up- and downregulated following LTD and LTP, respectively, at the same cell’s input synapses. We hypothesize that the runaway nature of Hebbian plasticity in a central neural network is buffered in an online fashion by changes generated by negative feedback at the same neuron’s output synapse, a phenomenon which we have termed dynamic homeostatic plasticity.

National Science Foundation, Grant/Award Number: 1929489 to VZH

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.
Using Supplemental Instruction through the EMPOWER Program to Increase Diversity in STEM Fields
Authors: King Adrienne , Wright Christa
Published: May 2023

The underrepresentation of women and racial minorities in science, technology, engineering and math (STEM) fields is of national concern. Despite recent increases, females continue to be underrepresented in math, physical science, and engineering related fields compared to their male counterparts. There is also evidence showing a troubling inequity trend in enrollment of most graduate and all post graduate degrees in STEM fields. These factors ultimately impact the workforce with women less likely than men with similar degrees to actually be employed in these fields, constituting 23% of the science and engineering labor force and only 10 % of employed physicists. Well-structured interventions are needed to support African American women in overcoming barriers to increase their representation in STEM. What is Needed to Make a Difference? Extracurricular instruction in the form of supplemental educational programming is needed to identify, engage and retain African American female students to ensure their level of post-secondary education STEM success and beyond. The R25 Summer Research Education Program is designed to support education activities that complement and or enhance the training of a workforce to meet the nation’s biomedical, behavioral, and clinical research needs. Methods: The Engaging Multidisciplinary Professional Opportunities for Women in Environmental Research (EMPOWER) program was created to address the diversity in STEM. This summer research experience program was developed to educate high school science teachers in tandem with outstanding African American and Hispanic women from metro Atlanta high schools in the research approaches and competencies required for a deeper understanding of how to measure and assess environmental exposures, including air and water in the urban environment and link them to health effects. Results/Discussion: Students and teachers participated in a four-week summer program. The primary objectives of EMPOWER were two-fold including:1) Enhance teaching capacity within the sciences and assist in the development of public and environmental health curriculum along with in class activities intended to promote interest in STEM. 2) Provide African-American and LatinX women opportunities to engage in faculty lead research projects, obtain hands-on training in tandem with professional and soft skill development. EMPOWER’s major contribution will be to continue to enhance STEM education in high schools leading to higher quality post-secondary opportunities and greater workforce diversity.

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.
Sex differences in the relationship between physical activity levels and cerebral pulsatility
Authors: Gaynor-Metzinger Sarean Harmoni , Fico Brandon , Moir M. , Miller Kathleen , Corkery Adam , Pearson Andrew , Loggie Nicole , Howery Anna , Rowley Howard , Rivera-Rivera Leonardo , Johnson Kevin , Johnson Sterling , Wieben Oliver , Barnes Jill
Published: May 2023

BACKGROUND: Greater cerebral blood flow pulsatility, measured as pulsatility index (PI), has recently been under investigation as a risk factor for cognitive impairment and neurodegenerative diseases. Furthermore, physical activity (PA), which has been associated with improved cognitive function and holds therapeutic effects for cardiovascular function, may be linked with lower cerebral pulsatility, especially in postmenopausal women (PMW). PURPOSE: To investigate the relationship between PA and PI in PMW and determine if these relationships are maintained in age-matched men. We hypothesized that there would be an inverse relationship between PA and PI in PMW, and that this relationship would diminish in age-matched men. METHODS: Fifty-two healthy PMW (age 63 ± 4 years) and 25 age-matched men (63 ± 4 years) were recruited for this study. PA was self-reported via the Godin Questionnaire (Godin Score) and using the metabolic equivalent to exercise in minutes per week (MET-Min). Cerebral blood flow was measured through the internal carotid arteries (ICAs), middle cerebral arteries (MCAs), and the basilar artery using 4D Flow MRI. PI was calculated as (maximum flow – minimum flow)/mean flow. RESULTS: There were no significant differences in PA between groups via Godin Score (PMW: 37 ± 21 vs. Men 37 ± 13, p = 1.00) or MET-Min (PMW: 1586 ± 901 vs. Men: 1831 ± 901, p = 0.28). When combined, there was a significant inverse association between MET-Min and basilar PI (r = -0.24, p = 0.04). In PMW, there was a trend for greater MET-Min to be associated with lower basilar PI (r = -0.24, p = 0.08), however this trend was not observed in men (r = -0.25, p = 0.25). Interestingly, in men, there was a significant positive association between MET-Min and MCA PI (r = 0.46, p = 0.03). There were no significant associations observed between PA and ICA PI. CONCLUSION: Greater PA may be linked to lower PI in PMW, but not in in age-matched men. The influence of regular physical activity on cerebral PI may be specific to certain cerebral vessels.

This study was funded by the Virginia Horn Henry Research Grant, NIH grant (AG070469-01), and the Wisconsin Alzheimer's Disease Research Center (P30-AG062715).

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.
Restoration of cardiac metabolic flexibility by glutathione in ecstasy-treated male Wistar rats is dependent of circulating testosterone and xanthine oxidase/uric acid/caspase 3 modulations
Authors: Ajayi Ayodeji , Akhigbe Roland , Aborisade Solomon , Ajayi Oluwatobi , Hamed Moses
Published: May 2023

Introduction and objectives: The abuse of ecstasy as a recreational drug is widespread, despite its complications such as cardiac injury and dyslipidaemia. Till date, the involvement of testosterone and xanthine oxidase (XO)/ uric acid (UA)/ caspase 3 signaling in ecstasy-induced cardiac injury and dysmetabolism is yet to be reported. The possible effect of glutathione in ecstasy-induced cardiac injury is also yet to be documented. Hence, this study was designed to evaluate the involvement of circulating testosterone and XO/UA/caspase 3 pathway in ecstasy-induced cardiac injury and dysmetabolism. Also, the effect of glutathione in ecstasy-induced cardiac injury was explored. Methods: Forty eight male Wistar rats were randomly distributed into six groups (n= 8). The control rats received distilled water, glutathione-treated rats received 15 mg/kg of glutathione, low dose ecstasy-treated (LDE) and high dose ecstasy-treated (HDE) rats received 5 mg/kg and 15 mg/kg of ecstasy respectively, LDE + glutathione-treated rats received 15 mg/kg of glutathione and 5 mg/kg of ecstasy, and HDE + glutathione-treated rats received 15 mg/kg of glutathione and 15 mg/kg of ecstasy via gavage for 8 weeks. Results: Ecstasy significantly increased the relative cardiac mass, but did not significantly alter the body weight gain and absolute cardiac mass. It also caused increased mean arterial pressure, diastolic pressure, heart rate, PR interval, and QT interval. In addition, it led to insulin resistance and improved β-cell function, increased fasting levels of insulin and plasma and cardiac lactate, lactate dehydrogenase, creatinine kinase, troponin I and T, C-reactive protein, total cholesterol, triglycerides, LDL-C, lipid peroxidation, TNF-α, IL-1β, IL-6, and NF-kB levels. These alterations were accompanied by increased plasma and cardiac levels of XO, UA, and caspase 3, reduced circulating testosterone, glutathione content, and glucose-6- phosphate dehydrogenase, and distortion of cardiac histo-architecture. However, glutathione administration averted ecstasy-driven cardiac injury and metabolic derangement. Conclusions: Taken together, these findings infer that ecstasy induces defective cardiac metabolic flexibility, which is associated with upregulation of XO/UA/caspase 3 signaling and downregulation of circulating testosterone and glutathione defense mechanisms. Also, these results indicate that glutathione alleviates ecstasy-induced cardiac metabolic inflexibility by suppressing XO/UA/caspase 3 signaling and enhancing circulating testosterone and glutathione defense mechanisms.

Self funded

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.
Effect of Age on Maximal Heart Rate in Spinal Cord Injury
Authors: Hamner J. , Picard Glen , Taylor J. Andrew
Published: May 2023

Objective: To determine whether there is a generalizable relationship between maximal heart rate (HR), age, and injury level in individuals with spinal cord injury (SCI). Methods: Retrospective analysis of aerobic capacity testing (VO2max) of 80 individuals with SCI. Hybrid (arms and legs) functional electrical stimulation (FES) rowing was used as the exercise modality, and multiple objective criteria of a maximal effort had to be achieved so that peak HRs approximated maximal in this population. The relationship between age, maximal HR, and injury level was examined with regression and analysis of covariance, with injury level as a continuous and categorical variable (thoracic vs. cervical). Results: The traditional age-related decline in maximal heart rate is largely preserved (Regression: Maximal HR = 204 – Age, r = -0.63, p < 0.001) in persons with thoracic (n = 42), but not cervical (n = 38), level SCI. There was no effect of sex, motor completeness, or aerobic capacity on this relation in those with thoracic SCI. Individuals with a cervical SCI have a reduced maximal heart rate (136 ± 18 bpm) and does not change with age (p = 0.23). Maximal heart in cervical SCI was not predictable from factors such as age, time since injury, weight, and injury level. Conclusion: Age-predicted maximal heart rate may be suitable for exercise testing and prescription for those with thoracic injuries but should not be used in the cervical spinal cord injured population.

This work was supported by NIH grants R01 HL117037 R21 HD088891 and ACL NIDILRR grant 90SI5021.

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.
Lack of concordance between estimates of sympathetic transduction in humans
Authors: Taylor J , Hamner Jason , Draghici Adina
Published: May 2023

The transduction of sympathetic nervous outflow into arterial vasoconstriction is critical for blood pressure homeostasis. Hence, there is an emerging field of sympathetic transduction to study human health and disease. Much of this work examines sympathetic transduction in response to spontaneous bursts of sympathetic activity. For these analyses, the dependent variable can be beat-by-beat changes in either systemic pressure (‘neurohemodynamic)’ or regional vascular conductance (‘neurovascular’). However, few studies have explored the concordance between changes in these two relations within individuals. Hypoxia induces increased sympathetic activity that is not accompanied by increased blood pressure; therefore, sympathetic transduction would seem to be altered. We assessed both ‘neurohemodynamic’ and ‘neurovascular’ sympathetic transduction during normoxia and sustained hypoxia (~80% SpO2) in young healthy individuals (N=7). Because hypoxia also induces tachycardia and tachypnea, we also assessed transduction(s) as a function of time rather than beat and after filtering out respiratory effects. Hypoxia induced significant (p<0.10) changes in heart rate (60+/-2 vs. 78+/-4 beats/min), respiration (5.8+/-0.3 vs. 8.7+/-1.2 L/min), and sympathetic activity (1431+/-256 vs.2066+/-470 aiu/min), but not in diastolic blood pressure (73+/-2 vs. 76+/-2 mmHg) or leg blood flow (11+/-1 vs. 11+/-1 cm/sec). This resulted in greater ‘neurohemodynamic’ (p<0.01) but no change in ‘neurovascular’ (p=0.94) sympathetic transduction. However, transduction(s) assessed as a function of time and after respiratory filtering demonstrated no effect on ‘neurohemodynamic’ (p=0.24) with a reduced ‘neurovascular’ (p=0.10) sympathetic transduction. These findings indicate that beat-by-beat systemic and regional estimates for transduction from spontaneous bursts of sympathetic activity may not reflect the linear relationship between sympathetic nervous outflow transduced into arterial vasoconstriction for blood pressure homeostasis. In addition, physiologic confounders, such as changes or differences in chronotropic and/or ventilatory state can exert profound influences on the estimated sympathetic transduction(s) and so should be considered if these analyses are to be pursued.

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 acute removal of metformin induces mitochondrial remodeling and increases mitochondrial respiration
Authors: Bubak Matthew , Davidyan Arik , O'Reilly Colleen , Doidge Stephen , Britton Steven , Koch Lauren , Miller Benjamin
Published: May 2023

Metformin is a candidate to slow biological aging and extend healthspan, as it reduces the risk of morbidity and mortality in people with type 2 diabetes. However, it is not clear how metformin impacts individuals absent of chronic disease. This unknown is important to answer before prescribing metformin to healthy individuals to prolong the healthspan. It has been shown that metformin creates an inefficiency in energy transfer by accumulating within the mitochondria. Therefore, we hypothesized that the effects of metformin on healthspan are context specific; beneficial in the context of low energy demand/mitochondrial capacity but detrimental in the context of high energy demand/mitochondrial capacity. To test this hypothesis, we used 18-month, male rats selectively bred for low and high treadmill running capacity (LCR/HCR) as models of low and high intrinsic mitochondrial function. For both HCR and LCR, we used high-resolution respirometry (Oroboros O2K) on skeletal muscles from controls (CON), 4 weeks of metformin-treatment (MET), 4 weeks of metformin-treatment with a 48-hour metformin washout (MET-WO), and 48-hour washout with metformin added back to the respirometry chamber (MET-WO-SPIKE). A week prior to sacrifice, we labeled the rats with deuterium oxide to assess protein turnover as an indicator of mitochondrial remodeling. In gastrocnemius muscle, the HCR MET-WO had greater Complex I (CI), CI+Complex II (CII), and maximal respiration (MaxR) (115 ± 23, 164 ± 38, 157 ± 35 pmol/(s✕mg), respectively) compared to the CON (70 ± 24, p = 0.02, 114 ± 32, p = 0.01, 115 ± 40 pmol/(s✕mg), p = 0.04, respectively), and MET (63 ± 54, p = 0.007, 90 ± 50, p < 0.001, 91 ± 48 pmol/(s✕mg), p = 0.002, respectively). The HCR MET-SPIKE group had greater CII (83 ± 33 pmol/(s✕mg)) and MaxR (86 ± 35 pmol/(s✕mg)) compared to the MET (p = 0.007 and p = 0.002, respectively). In the soleus, MET-WO (4.15 ± 0.33%/day) had greater mitochondrial fractional synthesis rates (FSRs) compared to MET (3.12 ± 0.62%/day, p = 0.001) in the HCRs. In the LCRs, MET-WO (4.61 ± 0.42%/day) had greater FSRs compared to CON (p < 0.001, 3.07 ± 0.67%/day) and MET (3.12 ± 0.61%/day, p = 0.001). In the tibialis anterior, MET-WO (3.47 ± 0.80%/day) had greater FSRs compared to the MET (2.41 ± 0.47%/day, p = 0.04) within the HCRs with no differences in the LCR. These data show that metformin reduces mitochondrial respiration in HCR rats but not in LCR rats. The presence of metformin produced a greater subsequent response in HCR compared to LCR as shown by its acute removal revealing metformin-induced mitochondrial remodeling.

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.
Heart rate fragmentation in renovascular hypertensive rats
Authors: Silva Thais , Buzinari Tereza , Silva Carlos , Castania Jaci , Salgado Helio , Silva Luiz , Fazan Jr Rubens
Published: May 2023

Although rapid oscillations of the heart rate (HR) are attributed to vagal modulation of the heart, a pattern of ultra-rapid HR variation has been named heart rate fragmentation (HRF). It is a recently proposed approach to evaluate sino-atrial instability characterized by the presence of numerous inflections points in a series of successive values of cardiac intervals. HRF is increased in aging and coronary diseases. Hypertension markedly alters HRV indices and might affect HRF as well. This study aimed to investigate the HRF in renovascular hypertension in rats. Wistar rats were anesthetized, and hypertension was surgically induced by partial constriction of the left renal artery with a silver clip with a 0.2 mm gap. In one kidney one clip (1K1C) hypertension model, the contralateral kidney was removed. In two kidneys one clip (2K1C) model, the contralateral kidney was kept intact. Sham-operated control rats underwent to same surgical procedures without receiving the clip around the renal artery. After 45 days (2K1C) or 60 days (1K1C), animals were instrumented with a catheter into the femoral artery, and on the following day, their arterial pressure (AP) was directly recorded without the effect of anesthesia. For HRF analysis, pulse interval (PI) series were generated and transformed into a sequence of symbols “-1,” “0,” or “1” when the difference between successive PI values (transitions) was negative, zero, or positive, respectively. Following, sequences of 4 consecutive symbols were classified according to the number of transitions. The total percentage of inflection points (PIP) and the percentage of sequences with zero (W0), one (W1), two (W2), or three (W3) inflection points were quantified. As expected, the arterial pressure increased in both groups of hypertension rats compared to control counterparts. All HRF indices were found similar in 1K1C hypertensive rats compared to their control counterparts. Nevertheless, in 2K1C hypertensive rats HRF was found to be lower than normotensive controls (PIP: 64±7 vs. 79±1% and W2: 30±1 vs. 39±1% in 2K1C and normotensive controls, respectively). In conclusion, high blood pressure itself does not affect HRF, although, depending on the model of hypertension used, HRF can be markedly impaired. The interpretation of these findings is challenging, and the high levels of angiotensin in the 2K1C model may affect cardiac pacemaker cells, making their action potentials more stable than unstable. However, the specific mechanisms by which this could happen still need to be studied.

Funding Sources: FAPESP, CAPES and CNPq

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 beta-hydroxybutyrate on mitigating uric acid-induced changes in muscle cell mitochondrial bioenergetics
Authors: Larson John , Remund Nicole , Saito Erin , Warren Cali , Bikman Benjamin
Published: May 2023

Uric acid accumulates in the body in disease states and aggravates myriad pathologies, including joint pain, insulin resistance, and more. The mediating mechanisms of uric acid-induced disruption is via alterations in inflammatory status and direct effects on mitochondrial function, including disrupted respiration. Interestingly, the ketone beta-hydroxybutyrate (bHB) tends to have the opposite effects. In part, the relevance for this project is borne from the available evidence that indicates ketogenic diets tend to increase uric acid, while paradoxically improving metabolic outcomes, including mitochondrial function. Accordingly, the purpose of this work was to evaluate the competing effects of uric acid (UA) and bHB on mitochondrial bioenergetics in muscle cells. C2C12 muscle cells treated with UA (500 μM) tended to manifest reduced mitochondrial respiration across all conditions, particularly in a basal state (glutamate+malate), compared with control. In contrast, bHB (5mM) maintained respiration at normal levels throughout. The combination of bHB with UA increased respiration levels above UA alone, suggesting a protective effect. Future analyses will further phenotype the effects of these treatments on the production of reactive oxygen species and activation of inflammatory pathways.

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.
Hybrid Rat Diversity Program (HRDP): A renewable rat resource for systems genetics
Authors: Dwinell Melinda , Takizawa Akiko , Malloy Lynn , Tutaj Monika , Schilling Rebecca , Geurts Aron , Kwitek Anne
Published: May 2023

Rats are a major model for studying complex disease mechanisms, behavioral phenotypes, environmental factors, and for drug development and discovery. Inbred rat strains control for genetic background and allow for repeated, reproducible molecular, cellular, and whole animal phenotyping. Genetic susceptibility to disease, sensitivity to environmental elements, and pharmacogenomics are critical components of the concepts of precision medicine. The Hybrid Rat Diversity Program (HRDP) is a renewable rat resource that combines the power of genetic stability through inbred strains, power for genomic mapping strategies through genetic diversity and recombinant inbred strains, and strength in an animal model that mirrors many human disease traits. The HRDP was designed to include 96 inbred rat strains with genomic and physiological diversity to maximize power to detect specific genetic loci associated with complex traits while maximizing the genetic diversity among strains. The 96-strain panel consists of 33 genetically diverse inbred strains and two panels of recombinant inbred panels: FEXL/LEXF (33 strains, Japan) and HXB/BXH (30 strains, Czech Republic). Currently, 85% of the classic inbred and 68% of the RI strains are available for experiments. Whole genome sequencing of 89 unique strains have been sequenced. Strain specific variants are available at the Rat Genome Database through the HRPD Portal, the strain pages, and genomic tools. RNA sequencing of kidney, thymus, and muscle for the classic inbred strains are underway. The HRDP will provide a genetically stable population of rat strains with fully sequenced genomes, transcriptomes for brain and liver, and general phenotypic characterization to be used for systems genetic studies and fine mapping of complex traits.

National Institutes of Health, Office of the Director, R24OD024617

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.
Microglia Senescence Mediates Inflammation in the Hypothalamus of High-Fat Diet Induced Obese Mice
Authors: Plakkot Bhuvana , Di Agostino Ashley , Balasubramanian Priya , Subramanian Madhan
Published: May 2023

Hypothalamus is a major regulatory center in the brain responsible for various homeostasis processes. Distinct neurons and glial cells, including microglia support the cardiovascular functions in the hypothalamus. An important cardiovascular regulatory nucleus in the hypothalamus is the Paraventricular Nucleus (PVN). Previous studies from our laboratory showed evidence for cellular senescence in the PVN. Senescence is a state of irreversible growth arrest in proliferating cells, which has been implicated in several neurodegenerative diseases. Microglia, is the resident macrophage cells of the brain that can phagocytose and initiate local inflammatory responses. Upon chronic inflammatory signaling, microglia lose its phagocytic property and enters a state of activation and proliferation. We analyzed hypothalamus from young adult mice fed with either chow (6 kcal% fat) or High Fat Diet (HFD; 60 kcal% fat) for a period of 16 weeks. Cell sorting of activated microglia using a benchtop microfluidic cell sorter revealed an increase in activated microglia in the hypothalamus after chronic HFD feeding. Microglial activation has been associated with promotion of a senescence phenotype and induction of inflammation through senescence associated secretory phenotype (SASP). To investigate this, we analyzed senescence markers in the hypothalamus. Real-time PCR revealed elevated senescent markers p53, p21 and p16, along with a significant increase (P<0.05) in SASP factors such as IL1β, MCP1 and TNFα in the HFD group compared to controls. Immunofluorescence studies confirmed the presence of senescent Iba1+ microglial cells in the PVN of HFD mice compared to their chow counterparts. Taken together, these findings suggest that senescent microglia could play a central role in the hypothalamic inflammation in HFD-induced obesity and targeting microglia will help in developing novel preventive and treatment strategy for obesity associated cardiovascular diseases.

National Heart, Blood and Lung Institute grant R15HL148844; American Heart Association Institutional Research Enhancement Award – 959725.

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.
Neuromuscular coupling of obligatory respiratory muscles to inspiratory pressure is reduced in dystrophic (mdx) mice
Authors: Maxwell Michael , O' Halloran Ken
Published: May 2023

Neuromuscular coupling (NMC) is a recognised clinical index of inspiratory muscle function which reflects the efficiency of conversion of neural activation to inspiratory pressure. Duchenne muscular dystrophy (DMD) is characterised by respiratory insufficiency culminating in respiratory failure. We investigated inspiratory pressure generating capacity and electrical activation of obligatory inspiratory muscles in X-linked muscular dystrophy ( mdx) mice, to evaluate NMC of diaphragm, external intercostal and parasternal intercostal to inspiratory pressure across a range of behaviours in early established to late progressive disease.In urethane anaesthetised mice (1.7 g/kg i.p.), inspiratory pressure was recorded via a pressure transducer positioned in the thoracic oesophagus. Diaphragm EMG activity was recorded using needle electrodes. Studies were performed in male wildtype (WT) and mdx mice at 4, 8, 12 and 16 months old. Recordings were made at baseline and during sustained tracheal occlusion to task failure, defined as an inability to sustain peak pressure. Peak pressure was determined from the average of five successive peak efforts at the maximum response. The corresponding peak inspiratory EMG activities were determined. Two factor (age x genotype) analysis of variance was performed.Obligatory muscle EMG activities were significantly lower in mdx mice from 4 months of age. Peak inspiratory pressure was significantly greater in mdx at 4 months of age. At 8 months, peak inspiratory pressure was equivalent between WT and mdx followed by a significant decrease in peak inspiratory pressure in 12- and 16-month-old mdx. NMC was lower in mdx mice across the ventilatory and non-ventilatory range, emerging early in dystrophic disease.Reduced NMC of obligatory muscles to inspiratory pressure in mdx mice reveals a greater reliance on accessory muscles to support respiratory performance in dystrophic disease. Remarkably, this burden is adequately accommodated in early disease with a preserved capacity to generate peak inspiratory pressure. We reason that the loss of compensation afforded by accessory muscles to peak inspiratory pressure generation underpins the emergence of respiratory compromise in advanced disease. Our results may have implications for the understanding and treatment of DMD.

Funded by Science Foundation Ireland SFI/19/6628 INSPIRE DMD.

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 expression of mechano-stimulated Ca2+ transport pathways in kidney organoid tubules
Authors: Carrisoza-Gaytan Rolando , Gupta Navin , Hiratsuka Ken , Kroll Katharina , Morizane Ryuji , Lewis Jennifer , Satlin Lisa
Published: May 2023

Kidney organoids derived from human pluripotent stem cells exhibit glomerular- and tubular-like structures. As the technology for culturing organoids advances, the goal of promoting terminal differentiation demands that priority be given to characterization of their physiological function. To begin to functionally phenotype organoids, we examined mechano-induced changes in intracellular Ca2+ concentration ([Ca2+]i) and signaling pathways in tubules isolated from maturing organoids. We found that tubules microdissected from organoids cultured under static conditions and exposed to basolateral Yoda1 (5 μM), an activator of the mechanosensitive Ca2+ permeable channel Piezo1, exhibited an increase in [Ca2+]i of increasing magnitude with advancing days in culture (Carrisoza-Gaytan et al., ASN, 2021). This observation suggests that organoids undergo a developmental increase in the abundance and/or activity of Piezo1 and /or maturation of signal transduction pathways mediating this response with advancing days (d) in culture.To begin to examine these possibilities, transcript expression levels of the putative mechanosensor PIEZO1 and Ca2+ transport proteins TRPV4 and PMCA1 (plasma membrane Ca2+ ATPase) were measured in organoids (n=3-6) cultured for 8, 21, 35 and 49 d by RT-qPCR. ACTB (encoding β-actin) and GAPDH transcript expression were included as housekeeping genes. Abundance of Piezo1 and TRPV4 channel protein expression was studied by immunofluorescence (IF) and confocal microscopy in organoids (n=3) at 21 and 49 d in culture.RT-qPCR demonstrated an increase in PIEZO1 (28.1±2.0 fold, p≤ 0.05), TRPV4 (5.3±0.8 fold, p≤ 0.01) and PMCA1 (1.8±0.1 fold, p≤ 0.05) between 8 and 49 d in culture when normalized to GAPDH expression; we found that ACTB expression also increased with organoid maturation (1.9±0.1 fold, p≤ 0.01) when normalized to GAPDH expression during this interval. IF labeling of organoid cryosections revealed an increase in apical Piezo1 (3.2±0.6 fold, p≤ 0.001) and TRPV4 (1.5±0.1 fold, p≤ 0.05) in tubular structures at 49 vs 21 d in culture.These results demonstrate a developmental increase in molecular expression and cell localization of Ca2+ transport proteins responsible for the transduction of external mechanical stimuli into intracellular Ca2+ signals in organoids cultured over time.

UC2DK126023 (JAL, LS, RM); DP2 DK133821 (RM); R01 DK038470 (LMS); R01 DK129285 (LMS); P30 DK079307 (LMS)

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.
Piezo1 regulates expression of BK and TRPV4 channels in mouse cortical collecting duct (CCD)
Authors: Carattino Francisco , Mutchler Stephanie , Dalghi Marianela , Apodaca Gerard , Satlin Lisa , Kleyman Thomas , Carrisoza-Gaytan Rolando
Published: May 2023

Within the CCD, an acute increase in tubular fluid flow rate (TFFR) leads to an immediate high amplitude increase in [Ca2+]i, due to release of IP3-sensitive internal Ca2+ stores coupled to extracellular Ca2+ entry at the basolateral membrane in both principal (PC) and intercalated (IC) cells therein (Liu et al., 2003, 2005, 2007). This is followed by a decay in [Ca2+]i to a sustained plateau elevation due, at least in part, to luminal Ca2+ entry through TRPV4 (Berrout et al., 2012). This flow-induced increase in [Ca2+]i is necessary for BK channel-mediated flow induced K+ secretion (FIKS) in the microperfused mammalian CCD. We generated a mouse with IC-specific targeted deletion of the mechanosensitive Ca2+ permeable channel, Piezo1, which is expressed on the basolateral membranes of PCs and ICs in the mouse CCD (Dalghi et al., 2019). Microperfused CCDs isolated from these IC-PIEZO1-KO mice fed a high K (HK, 5% K+) diet and subject to an increase in TFFR did not exhibit either a peak or plateau elevation in [Ca2+]i in response to flow, and FIKS was eliminated. The absence of FIKS and the plateau elevation in [Ca2+] during sustained flow in the CCDs of KO mice led us to examine whether BK and TRPV4 channel expression was impacted by deletion of PIEZO1.Indirect immunofluorescence (IF) staining was performed to examine expression and localization of the BK and TRPV4 channels in PCs and ICs of IC-PIEZO1-KO mice. Whole cell and apical + subapical fluorescence intensities in cryosections were analyzed using LAS X software from a total of 3 male and 3 female control mice and 3 male and 3 female IC-PIEZO1-KO mice fed HK diet x 10d.IF analysis showed reduced whole cell BKα expression in ICs of both male (p≤0.05) and female (p≤0.01) IC-PIEZO1-KO mice. We also saw reduced BKα expression in PCs from female but not male KOs. In addition, ICs in female but not male KO mice had reduced whole cell TRPV4 expression vs. controls (p≤0.01). Also, whole cell expression of TRPV4 in PCs from female KO mice was reduced vs. female controls (p≤0.01). The ratio of apical-to-whole cell expression of BKα was similar in PCs and ICs of KO and control mice. Male, but not female, KO mice had modestly reduced apical TRPV4 expression in PCs vs. controls (p≤0.01). Piezo1 plays a role in the regulation of BK and TRPV4 channel expression in CCDs. In addition, sex differences exist in whole cell expression of these channels in response to IC-selective deletion of PIEZO1.

R01 DK038470 (TK, LMS); R01 DK129285 (TK, LMS); P30 DK079307 (TK)

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.
Chimeric constructs confer the human CFTR chloride channel with the properties of mouse CFTR
Authors: Sheppard David , Cai Zhiwei , Lea-Smith David , Stevenson Barbara , Doherty Ann , Davidson Heather , Porteous David , Boyd A
Published: May 2023

Mouse cystic fibrosis transmembrane conductance regulator (CFTR) differs from human CFTR in several important respects: altered gating pattern distinguished by prolonged residence in a sub-conductance state, reduced single-channel conductance and strong inward rectification. Transfer of the regulatory (R) domain of mouse CFTR to human CFTR was without effect, whereas transfer of both nucleotide-binding domains (NBDs) endowed human CFTR with greatly prolonged channel openings without conferring human CFTR with the sub-conductance state, single-channel conductance and inward rectification of mouse CFTR. We therefore hypothesised that the membrane-spanning domains (MSDs) determine these differences between human and mouse CFTR. To test this idea, we constructed the human-mouse CFTR (hmCFTR) chimeras hmTM1-6, hmTM7-12 and hmTM1-6:TM7-12 containing MSD1, MSD2 and MSD1+2 of mouse CFTR on a human CFTR background and studied them in excised inside-out membrane patches from transiently transfected CHO cells. For single-channel studies, we used a large Cl- concentration gradient ([Cl-]i, 147 mM; [Cl-]e, 10 mM) and clamped voltage at –50 mV, whereas for macroscopic studies, we used symmetrical Cl--rich solutions. All intracellular solutions contained PKA (75 nM) and ATP (1 mM) to activate and sustain CFTR activity; temperature was 37 °C. The three hmCFTR chimeras possessed a gating pattern intermediate between human and mouse CFTR. Both the single-channel conductance and open probability of the full open-state decreased in the rank order: human CFTR > hmTM7-12 > hmTM1-6 ≥ hmTM1-6:TM7-12 (n = 5-10). Like human CFTR, hmTM7-12 rarely transitioned to sub-conductance states, whereas hmTM1-6 sojourned to multiple sub-conductance states and hmTM1-6:TM7-12 resided in a tiny sub-conductance state resembling that of mouse CFTR. Human CFTR Cl- currents exhibited weak inward rectification, whereas those of mouse CFTR strongly inwardly rectified. Transfer of both MSDs of mouse CFTR to human CFTR in the chimeras hmTM1-6:TM7-12 reproduced the strong inward rectification of mouse CFTR (n = 4). Interestingly, the inward rectification of hmTM1-6 closely resembled that of mouse CFTR, whereas that of hmTM7-12 was intermediate between human and mouse CFTR (n = 6-9). Taken together, our data demonstrate that sequences from both MSDs specify the gating, conduction and rectification properties of CFTR with sequences from MSD1 playing a dominant role in determining the different rectification behaviour of human and mouse CFTR.

Supported by the Biotechnology and Biological Sciences Research Council and Cystic Fibrosis Trust.

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.
Investigating the Role of Neurovascular Coupling on Brain Function and Health
Authors: Larios Alyssa , Gu Chenghua
Published: May 2023

The brain consumes a disproportionate amount of energy, receiving 20% of the total cardiac output despite accounting for only 2% of the body’s weight. While total cerebral perfusion is homeostatically held constant, the neurovascular network dynamically modulates regional blood flow to deliver more nutrient-rich blood to highly active brain areas. Activity-dependent focal increases in cerebral blood flow, or neurovascular coupling (NVC), ensure that energy delivery is commensurate with neuronal metabolic demands. It is widely thought that neurovascular coupling is critical for normal brain function, as neurons lack energy stores and may require increases in oxygen or glucose delivery from the blood supply to fuel signaling operations that consume high levels of ATP. However, it is unknown which features of neuronal signaling are supported by NVC, if any. We are investigating this important question by using a genetic mouse model with NVC specifically impaired. This study will reveal new insights on how NVC supports normal brain function and health.

HHMI, NHLBI NIH

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.
Effects of volumetric muscle loss injury on contractile function, and bone structure and functional capacity in male C57BL/6J mice
Authors: Schifino Albino , Cooley Marion , Zhong Roger , Heo Junwon , Hoffman Daniel , Warren Gordon , Greising Sarah , Call Jarrod
Published: May 2023

Skeletal muscles and bones are structurally and functionally linked, such that bone strength is primarily determined the frequency and magnitude of the mechanical strain derived from muscular contractions. Volumetric muscle loss (VML) injury results in a significant loss of muscle tissue and a non-recoverable loss of muscle strength. However, the extent to which limbs that sustain a VML injury have associated changes to bone structure and functional capacity is unknown. This study’s objective was to investigate whether VML injury affects the adjacent tibial bone structure and functional capacity in adult male C57BL/6J mice. At 12 weeks of age, mice (n=14) underwent a unilateral VML injury (4mm diameter muscle biopsy) to the left hindlimb plantar flexor muscles, while the right limbs served as uninjured controls. At 20 weeks of age (2 months post-VML injury), mice were bilaterally tested for in vivo peak-isometric plantarflexion torque. Post-mortem analyses of tibial bone structure and mechanical properties was assessed via μCT and 3-point bending tests, respectively, at the mid-diaphysis. Statistical analyses were performed between injured and uninjured limbs via paired t-test, with an α-level of 0.05. At 2 months post-injury, VML-injured limbs had significantly less gastrocnemius muscle mass (28%), and peak-isometric torque (35%) as compared to uninjured limbs (p<0.001). Tibial bone strength, as measured by ultimate load, demonstrated a trend in VML-injured limbs to be 3% lower than that in uninjured limbs (p=0.055). Most notably, the cross-sectional moment of inertia (CSMI), the principal structural determinant of the bone’s ultimate load was 9% smaller in VML-injured limbs as compared to uninjured limbs (p=0.035). Additional structural changes in cortical bone were detected: notably, less cortical bone thickness (4.5%), volume (6.6%), and cross-sectional area (4.9%) in VML-injured limbs as compared to the uninjured limb (p≤ 0.025). Bone-to-muscle functional ratio (i.e., ultimate load:peak-isometric torque) was 38% greater in VML-injured limbs compared to uninjured limbs (p<0.001) indicating the deficits in muscle far outweigh that of bone at 2 months post-injury. Future research directions include determining if more time post-VML injury has a greater effect on bone ultimate load and exploring the extent to which the uninjured limbs in VML-injured mice experience compensatory or related changes to bone structure and function.

W81XWH-20-1-0885 to JAC and SMG

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.