bluuebunny/crossref_metadata_2025 huggingface dataset:
NaV1.1 and NaV1.6 Play Unique and Essential Roles in Muscle Spindle Afferent Function in Adult Mice
Authors: Ortiz Serena , Espino Cyrrus , Griffth Theanne N. , Wilkinson Katherine A.
Published: May 2024

Voltage gated sodium channels (NaVs) are crucial for the generation and propagation of action potentials. There are 9 different isoforms found in mammals (NaV1.1-1.9), and NaV1.1, NaV1.6, and NaV1.7 are found in the muscle proprioceptors that sense muscle stretch, the muscle spindle afferents. This sensory information is critical for motor reflexes and the sense of body and limb position in space. We previously found that mice lacking one or both copies of NaV1.1 in peripheral sensory neurons displayed motor deficits, including intention tremors. Muscle spindle afferents in these mice also had unstable static stretch sensitivity but normal dynamic sensitivity, suggesting a specific deficit in the maintenance of proprioceptor excitability when the Piezo2 channel was likely to be closed (Espino, et al., 2022). We hypothesized that NaV1.6 would also be necessary for normal motor behavior and muscle spindle afferent function. We generated sensory neuron specific deletions of NaV1.6 by crossing NaV1.6fl/fl mice with mice expressing PirtCre (NaV1.6cko) and observed severe motor deficits on the open field and rotarod test only in NaV1.6cko (n=15) and not NaV1.6Het (n=12) mice compared to NaV1.6fl/fl controls (n=8). In contrast to mice lacking NaV1.1, we did not observe intention tremors. We used an ex vivo muscle nerve preparation consisting of the extensor digitorum longus muscle and peroneal branch of the sciatic nerve. The muscle was maintained at the length of maximal twitch contraction (Lo) and given a battery of 9 ramp-and-hold stretches (2.5, 5, and 7.5% Lo repeated 3 times each) and 16 sinusoidal vibrations (5-100 μm amplitude; 10-100 Hz frequency). Preliminary results include recordings from 18 adult mice of both sexes (NaV1.6fl/fl n=8; NaV1.6cko n=10). We were only able to find stretch sensitive responses in 3 of 10 NaV1.6cko mice, and those were severely impaired with firing rates less than 5 Hz. In contrast, we found robust slowly adapting responses to stretch in all 8 NaV1.6fl/fl mice. Only 1 of 10 NaV1.6cko mice had any firing in response to vibration, in contrast to the normal dynamic sensitivity observed in NaV1.6fl/fl and NaV1.1cko afferents. This suggests that NaV1.6 plays a critical role in initiating muscle spindle afferent transmission, whereas NaV1.1 is essential for maintaining proprioceptor excitability during static stretch. Future studies will determine whether loss of NaV1.7, which does not result in motor deficits, alters muscle spindle afferent function.

This work was supported by NIH Grant 5SC3GM127195 (KAW) a RISE Fellowship 5R25GM71381 (SO), NIH 5T32GM099608-10 and 1T32GM1144303-01A1 (CE).

This is the full abstract presented at the American Physiology Summit 2024 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.
Rapid Changes in Cerebrovascular Compliance During Vasovagal Syncope
Authors: Shoemaker Leena , Sajid Aleena , Schondorf Ronald , Shoemaker J. Kevin
Published: May 2024

Background: The rapid reduction in arterial blood pressure (ABP) during vasovagal syncope (VVS) is associated with a characteristic decline in diastolic cerebral blood velocity (CBV) and maintained systolic CBV as measured by transcranial Doppler. This increased pulsatility was originally considered to be indicative of a “dysfunctional” increase in cerebrovascular resistance (CVR). Conversely, it may be due to increased cerebrovascular compliance (Ci) that partially attenuates the cerebral effects of rapid hypotension. We tested the hypothesis that Ci supports CBV during pre-syncope in VVS. Method: Finger ABP and right middle cerebral artery blood velocity (MCAv) were recorded from 15 otherwise healthy patients (n = 11 female, 40 ± 16 years, 24.9 ± 4.0 kg/m2) at rest and during head-up tilt (80°, 5 to 28 min). Individual ABP and CBV waveforms of every second heartbeat during VVS were input into a modified Windkessel model to calculate Ci and CVR. MCAv pulsatility was determined as pulse amplitude (systolic MCAv-diastolic MCAv) and Pulsatility Index (Pi; pulse amplitude/mean MCAv). Linear mixed models assessed the contribution of Ci to changes in CBV and Pi. Within-subject mediation analysis investigated the possibility of Ci mediating the relation between blood pressure (i.e., mean ABP and pulse pressure, PP) and cerebrovascular pulsatility. Results: Diastolic and systolic ABP decreased progressively during presyncope, resulting in a nadir reduction of mean ABP of Δ24 ± 9 mmHg at end-tilt (all p ≤ 0.04 vs mid-tilt). Mean MCAv decreased by 22 ± 12% prior to end-tilt (p < 0.01 vs mid-tilt). CVR decreased progressively for 10s prior to end-tilt (p ≤ 0.04 vs mid-tilt). Pi increased significantly, with peak increases occurring at 4 s prior to end-tilt (77 ± 50%, p < 0.01 vs mid-tilt). The increase in Ci (307 ± 223%, p < 0.01 vs mid-tilt) significantly contributed to changes in MCAv (χ2 =10.6, p < 0.01) and Pi (χ2 = 4.9, p = 0.03). Correlations of PP and ABP with Pi were not significant. However, PP was related to MCAv pulse amplitude (total effect: b = 1.57) and Ci ( b = -0.01, both p < 0.01). Ci partially mediated (indirect effect: b = -0.78, p < 0.01) the direct relation between PP and MCAv pulse amplitude ( b = 0.79, p = 0.01). Conclusion: These data provide evidence that Ci attenuates the fall in CBV under conditions of falling PP. Cerebrovascular regulation in VVS appears to be functioning as in healthy populations. However, this regulation is not suffcient to preserve flow in the presence of such extreme and rapid reductions in ABP.

USRI — Western University, Natural Sciences and Engineering Research Council of Canada (NSERC, Grant No. RGPIN-2018-06255).

This is the full abstract presented at the American Physiology Summit 2024 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.
Role of L-type Ca2+ channels in the differential response to oxytocin of uteri from virgin and proven breeder rats
Authors: Pathare Riya , Sondgeroth Korie , Porta Maura
Published: May 2024

Introduction: The experience of pregnancy affects uterine function well beyond delivery. For instance, the likelihood of accelerated parturitions, spontaneous delivery, and risk of hemorrhage in future pregnancies is increased with parity. While epidemiological evidence for these phenomena is abundant, mechanistic explanations of these and other changes are still being investigated. We previously demonstrated that the response to oxytocin is more robust in the uteri of proven breeder rats and that T-type calcium channels, although slightly more expressed in proven breeder samples had a rather limited impact in this mechanism. Hypothesis: Here, we tested the hypothesis that voltage gated L-type calcium channels contribute more significantly than T-type calcium channels in the differential response to oxytocin in the myometrium from virgin (V) and proven breeder (PB) rats. Methods: V and PB non pregnant female 18-week-old rats were euthanized at proestrus. Uterine strips were suspended in a tissue bath containing Krebs solution (in mM, NaCl 117, KCl 4.7, NaHCO3 25, MgCl2 1.2, KH2PO4 1.2, CaCl2 2.5, glucose 11, pH= 7.4) at 37°C in 95% O2 and 5% CO2. Dose response curves to the L-type calcium channel blocker Verapamil (10E-8 to 10E-5 M) and dose responses to oxytocin in the presence of either 10 E-6 or 10E-5 Verapamil were recorded. Area under the curve, frequency, amplitude, and duration of contractions were measured. L-type channels expression was evaluated with qRT-PCR. T-tests and ANOVA two ways were used for statistical analysis. Results: Compared to control, both doses of Verapamil suppressed 100% of spontaneous and 50% of oxytocin-evoked contractility in V and PB samples. The maximal response to oxytocin was significantly stronger in PB than in V (p<0.001). Thus, blocking L-type Ca2+ channels does not alter the differential response to oxytocin observed in the absence of verapamil. The difference in Expression of the L-type calcium channel revealed a 2-fold increase in PB compared to V uteri. These findings closely align with oxytocin dose response data in the presence of the T-type calcium channels blocker Mibefradil and with the T-type channels expression. Conclusions: Neither L-type or T-type Ca2+ channels appear to be key players in the differential response to oxytocin of V and PB uteri. Instead, it is more likely that other elements of the intracellular calcium control are involved in this phenomenon.

Acknowledgements: This study was supported by a Kenneth Suarez Fellowship to RP and an MWU intramural fund to MP.

This is the full abstract presented at the American Physiology Summit 2024 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 local acidosis in hypothalamic vasopressin cell excitation during hypoxia
Authors: Shook Levi , Stern Javier E.
Published: May 2024

The supraoptic nucleus (SON) of the hypothalamus plays a key role in the regulation of fluid homeostasis through the synthesis and release of vasopressin (VP). In this population, VP release can occur at both dendritic and axonal sites, allowing for both localized and distal effects such as renal water retention and vasoconstriction. Recent work from our laboratory demonstrated an inverse neurovascular coupling (iNVC) response in which VP cell activation by acute salt loading resulted in dendritic release of VP, leading to localized vasoconstriction and hypoxia. Additionally, we demonstrated that the hypoxic milieu in turn potentiates VP cell activity and increases firing, suggesting that these mechanism constitutes a positive feedback loop that optimized VP activation in order to cope with the homeostatic challenge (Roy et al., Cell Reports 2021). Still, the biophysical mechanism by which the iNVC-hypoxia elicits increased firing in VP neurons has not yet been explored. We hypothesized that hypoxia-induced acidosis, via activation of acid sensitive ion channels (ASICs) (which are present in SON VP neurons; Ohbuchi et al in 2010) is a key mechanism contributing to VP cell excitation in the iNVC positive feedback loop. We investigated this with whole cell patch clamp electrophysiology using eGFP-VP transgenic rats. We recorded from identified SON VP cells and measured deflections in voltage as bath pH was changed from 7.25 to 6.3 (10 mins). Bath solution was either HCL-buffered artificial cerebrospinal fluid (aCSF) aerated with 95% O2/5% CO2 or HEPES-buffered solution (HBS). We observed an excitatory response to the decreases in pH in most SON VP cells recorded (68.75%, n = 11/16). These responses were reversible and, in many cases, repeatable following a second stimulation. To examine cell-type specificity, ongoing studies are focusing on comparing these responses to those obtained from oxytocin cells. Further, we plan to repeat these experiments in the presence of the ASIC-blocker amiloride and determine whether the hypoxia-induced excitatory effect during iNVC is indeed dependent on ASIC-channels. Together, our results support our hypothesis that tissue acidosis (likely via activation of ASIC-channels) contributes to the excitatory feedback loop evoked during salt-induced iNVC in VP neurons.

This abstract was supported by the National Heart Lung and Blood Institute of the National Institutes of Health [R01 HL162575-01 (J.E.S.)].

This is the full abstract presented at the American Physiology Summit 2024 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.
Glomerular Hemodynamics During Recovery from Renal Ischemia-Reperfusion Injury Addressed with Micropuncture in Rats
Authors: Thomson Scott , Vallon Volker
Published: May 2024

Objective: To establish the physical basis for low GFR in ischemic renal injury (IR) and determine whether abnormalities in GFR determinants persist after renal recovery. Method: IR was generated in male and female Wistar Froemter rats by clamping both renal pedicles for 60 minutes. Controls had same surgery without pedicle clamp. Glomerular hemodynamics were assessed by renal micropuncture (MP) after 1 day, 1 week, or 4 weeks. Single nephron GFR (SNGFR) was paired with tubular stop-flow (PSF) and free-flow pressure (PFF) in each nephron. Afferent Starling pressure (EFPa) is PSF-PFF. Glomerular capillary pressure (PGC) was computed from PSF, PFF and plasma oncotic pressure. ANOVA factors included IR, sex, time point and date of experiment (nested). Inter-nephron heterogeneity was extracted from normalized root-square difference between each data point and the mean for that animal. (total n=349 nephrons, 47 rats). Results:

[Formula: see text]

Summary and conclusion: The physical cause of low GFR in IR was low EFPa, which resulted from low PGC with normal PFF in all animals except 1. The injured kidney manifest elevated inter-nephron variability for all variables. Mean values for SNGFR and intra-renal pressures returned to normal in the “recovered” kidney, but variability between nephrons did not return to normal. Female rats had lower baseline SNGFR and PGC than males but the hemodynamic patterns during IR and renal recovery were not differentiable by sex (excluding one female outlier with high PFF). Despite “normal” GFR and PGC, the “recovered” kidney is not a “normal” kidney.

NIH NIDDK R01 132690.

This is the full abstract presented at the American Physiology Summit 2024 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.
Low Intensity Renal Ultrasound Exposure Reduces Systemic Inflammation Induced by LPS Challenge in Mice
Authors: Mathis Keisa W. , Dinh Viet Q. , Chaudhari Sarika K. , Young-Stubbs Cassandra M.
Published: May 2024

Low-intensity pulsed ultrasound (LIPUS), a procedure historically used to stimulate bone healing and tissue repair, activates the splenic cholinergic anti-inflammatory pathway and ultimately reduces circulating and tissue-specific pro-inflammatory cytokine release if applied to the kidney prior to renal ischemia/reperfusion injury. We questioned whether LIPUS would be effective in reducing the inflammatory response to lipopolysaccharide (LPS) if exposure occurred as pre- or post-treatment. We hypothesized that LIPUS exposure before an LPS challenge would suppress the subsequent inflammatory response in mice, and that LIPUS exposure after an LPS challenge would be similarly beneficial. Female C57BL/6J mice were randomized into Saline, LPS, LPS/Pre-treatment and LPS/Post-treatment groups at 15 weeks of age. Pre-treated mice were subjected to 20-minute LIPUS exposure while under anesthesia for five consecutive days. On the 6th day, mice were injected with LPS (1 mg/kg dissolved in saline, IP) or saline (100 μL). One hour after LPS injection, post-treated mice were exposed to LIPUS for 20 min. Three hours after LPS or saline injection, all mice were humanely euthanized, and plasma, spleen and kidney were harvested for analysis of proinflammatory cytokines associated with the response to LPS. LPS significantly increased plasma TNF-α (280±37 vs. 0.07±0.00 pg/mL), plasma IL-6 (96124±6688 vs. 425±181 pg/mL), splenic IL-6 (0.77±0.16 vs. 0.17±0.04 pg/μg of protein), and renal cortical IL-6 (0.50±0.07 vs. 0.01±0.00 pg/μg of protein) compared to saline-treated mice (all p<0.05). LIPUS pre-treatment significantly reduced plasma TNF-α (183±15 pg/mL) and plasma IL-6 (63656±8441 pg/mL), without altering splenic and renal cytokines in LPS-treated mice. LIPUS post-treatment lowered plasma IL-6 (47432 ± 1182 pg/mL). In conclusion, five days of LIPUS exposure prior to an LPS challenge effectively reduced circulating inflammatory mediators, while a single LIPUS exposure after an LPS challenge also successfully reduced systemic IL-6. These findings demonstrate the potential in using LIPUS as a therapeutic strategy for quelling acute inflammatory responses and warrant further investigation of its use as a therapy for chronic inflammatory diseases.

Studies funded by Department of Defense (LR210096) for KWM.

This is the full abstract presented at the American Physiology Summit 2024 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.
Prolonged Blue Light Exposure Does Not Elicit Adverse Changes to Physical Activity in Male Mice
Authors: Greenwood Sarah , Bowen Robert S.
Published: May 2024

Color plays a role in human and animal circadian rhythm patterns, behaviors, and emotional responses. Environments containing blue colors improve information storage in humans and reproductive success in animals; however, environments containing blue light influence behavioral and emotional responses in rodents and humans in adverse ways. Exposure to blue light alters sleeping patterns, induces the stress response, and elicits depressive behaviors. These initial responses then affect awake time functionality and productivity. Under normal physiological conditions, mice, when provided access to an in-cage running wheel, exhibit high levels of nocturnal physical activity behavior. It is unknown if this nocturnal behavior changes after prolonged blue light exposure. Therefore, this project's hypothesis is wheel running utilization decreases after exposure to blue light during the diurnal restful period in the normally nocturnal mouse. The purpose of this study was to expose mice to overhead blue LED lights during the daytime rest period and to examine nighttime physical activity patterns. Daily wheel running distance, duration, and speed monitoring in C57BL/6j male mice (n=12) occurred for 21 days. During the second week of the study, an experimental group (n=6) underwent blue light-emitting diode (LED) light exposure, and a control group (n=6) experienced white LED light exposure at the same intensity. The lights were on a 12-hour light/dark cycle at full brightness during the exposure period. Differences in wheel running distance, duration, and speed following exposure to blue LED light were assessed via individual two-way (group by phase of study) ANOVAs. Blue LED light exposure did not appear to affect average daily wheel running distance [F=0.42, p=0.57], duration [F=0.79, p=0.42], or speed [F=0.08, p=0.87]. Following exposure to blue LED light during the restful diurnal period, wheel running remained stable. This lack of effect indicates that mechanisms may exist to protect mice from the adverse effects associated with blue light exposure, especially as it pertains to participating in routine physical activity. These postulated mechanisms may allow robust participation in physical activity-related behaviors in these animals and represent a potential biological regulator that could aid in mitigating the adverse effects of blue light exposure experienced in humans.

All funding for this research was provided by the Union University Department of Biology.

This is the full abstract presented at the American Physiology Summit 2024 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.
Loss of Pnn in neurons regulates protein expression of genes involved in frontotemporal dementia and alters locomotor activities in mice
Authors: Leu Steve
Published: May 2024

The regulation of pre-mRNA alternative splicing in neurons is considered to be associated with neurodegeneration disease. In the present study, we applied an inducible neuron-specific gene depletion mouse model to determine whether the expression of Pnn, a mRNA splicing regulator, is involved in the induction of neurodegeneration. Six-weeks old male mice carrying CaMKII-CreERT2 gene cassette and Pnnflox/flox allele were injected with tamoxifen to induce the disruption of Pnn gene structure. In addition to histopathological and biochemical examination, brain MRI analysis and the observation on behavior alteration were also performed on mice with neuronal Pnn depletion. Locomotor activity measurement showed that the travel distance, ratio of moving/resting, central time, and central distance in neuronal Pnn-depleted mice were all higher than that in wild type mice since three months after induction of Pnn gene disruption. Moreover, the decrease in gripping force was observed in mice with neuronal Pnn depletion. MRI analysis further demonstrated that loss of Pnn in neurons leads to cerebral ventricular dilatation and hippocampal atrophy in 10-month-old mice. Mass spectrometry-based immuno-precipitation proteomics indicated the interaction between Pnn and frontotemporal dementia (FTD)-associated proteins, including TDP-43, FUS, and hnRNPA1. It is worth noting that both immunofluorescent stainings and Western blottings demonstrated the up-regulation of FTD-associated proteins in hippocampus and cerebral cortex of mice with neuronal Pnn depletion. However, the transcriptional level of genes involved in FTD were not altered by Pnn depletion. In conclusion, loss of Pnn in neurons leads to behavioral alteration in mice with regulating protein expression of genes involved in FTD, implying the involvement of Pnn deficiency in neurodegeneration.

This research was supported by Chang Gung Medical Research Program Grant (Grant number: CMRPG 8N0341-2).

This is the full abstract presented at the American Physiology Summit 2024 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.
Associations between Illicit ADHD Medication Use and Aspects of Mental Distress Among College Students
Authors: Bonventre Samantha , Taufman Kayla , Polis Jenna , Lin Julia , Patrissy Cara , Begdache Lina
Published: May 2024

The illicit use of Attention-Deficit Hyperactivity Disorder (ADHD) medication has become a prevalent issue on college campuses. Illicit ADHD medications are used without a medical prescription. The concern is that these medications are psychostimulants that may alter brain chemistry and affect the quality of brain maturity in individuals who do not need them medically, which potentially can affect mental health. An alarmingly high percent of reported illicit ADHD medication users are college aged students between the age of 18 and 22 years. Little is known about the effect of illicit ADHD medication use on mental well-being among college students. Thus, the purpose of the study was to assess the impact of illicit ADHD medication use on different aspects of mental distress among college students. The study collected 702 responses from undergraduate students at several US colleges and included self-reported data on illicit Adderall use, age and symptoms of mental distress. The anonymous survey was created in Google Forms. Mental distress was evaluated through The Kessler Psychological Distress Scale (K10). The data were analyzed in SPSS, Version 28.0, using Pearson’s Correlation Coeffcient. Of the 72.5% of the participants who reported using ADHD medication without a prescription, 71.4% reported academic reasons as their motivation for use. There is a positive correlation between feelings of worthlessness and illicit ADHD medication use (p<0.05). Age was negatively correlated with feelings nervous (p<0.01) and restless or fidgety (p<0.01). Additionally, a negative correlation was found between age and being able to do only half or less of what you would normally have been able to do (p<0.01). On the other hand, illicit ADHD medication use was negatively correlated with feeling that everything was an effort (p<0.05), as well feeling unable to work or carry out normal activities (p<0.01). Our results suggest that students who use ADHD medication illicitly are more likely to experience symptoms of mental distress. Interestingly, our findings propose that the younger the age of use, the higher the risk of mental distress.

We received no support or financial grants.

This is the full abstract presented at the American Physiology Summit 2024 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 Pkd1 enhances intestinal integrity and motility prior to accelerated kidney cyst growth
Authors: Sedaka Randee , Lovelady Caleb , Shinde Sejal , Hallit Emily , Yamaguchi Shinobu , Lee Goo , Maynard Craig
Published: May 2024

Autosomal dominant polycystic kidney disease (ADPKD) is the most common inherited kidney disorder, primarily caused by PKD1 germline mutations. Polycystin-1, PKD1’s encoded protein, is essential to maintain kidney epithelial cell integrity, but its role in the gut has yet to be determined. Considering macrophage infiltration precedes accelerated cyst growth in Pkd1 knockout ( Pkd1KO) mice, and the gut is the body’s largest reservoir of inflammatory cells, we hypothesized that loss of Pkd1 would weaken the intestinal epithelial cell barrier and mount an inflammatory response, potentially preceding kidney damage. Plasma, urine, kidney, and intestines were collected from 11-12 week old male and female conditional Pkd1KO (CAGG-creER; tamoxifen-induced at 5-6 weeks) and flox (control) mice. Plasma was used to measure intestinal permeability as well as monocyte chemoattractant protein-1 (MCP-1) and lipocalin-2 (LCN-2) concentration. Urine was utilized to assess kidney injury, while tissues were used for RT-PCR and histology. Pkd1KO mice had significantly elevated kidney-to-body weight ratio, cyst ratio, and expression of tubular injury markers kidney injury molecule 1 (Kim1) and Lcn2 compared to flox mice. Despite this cellular injury, kidney inflammatory gene expression and urine osmolality did not differ between genotypes. No overt morphological changes were observed in the ileum or colon, nor were there differences in expression of proinflammatory chemokines or cytokines in either tissue. Plasma abundance of MCP-1 and LCN-2 was similar between genotypes. Epithelial permeability in the small and large intestines was significantly decreased in Pkd1KO versus flox mice. Moreover, Pkd1KO mice had a significantly reduced whole gut transit time compared to flox mice. This corresponded with increases in colonic expression of epithelial integrity marker occludin and water channels aquaporin 4 and aquaporin 8 in Pkd1KO mice. Together, these data insinuate that loss of Pkd1 in the intestines leads to a tighter intestinal barrier accompanied by increased water channel expression and gut motility. These findings appear unrelated to inflammatory involvement in early PKD.

These studies were supported by NIH T32 DK007545 to RS, R01 DK132028 to TS, and R03 DK119717 to TS.

This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Spinal TNF-α receptor expression in a rodent model of respiratory motor neuron death
Authors: Lewis Ryan , Smith Catherine , Nichols Nicole
Published: May 2024

Intrapleural injection of cholera toxin B fragment conjugated to saporin (CTB-SAP) selectively kills respiratory motor neurons, and mimics aspects of neurodegenerative diseases including breathing deficits. In this model, phrenic long-term facilitation (pLTF) induced by acute intermittent hypoxia is enhanced following 7 days (d) of CTB-SAP vs. control rats, whereas pLTF in 28d CTB-SAP treated rats is comparable to pLTF in controls suggesting that the underlying mechanisms of plasticity at both time points differ. Inflammation is a hallmark of neurodegenerative diseases and is known to prevent pLTF. Furthermore, ketoprofen (NSAID) delivery attenuates pLTF in 7d CTB-SAP-treated rats, but enhances it in 28d CTB-SAP-treated rats; this suggests that inflammation contributes to pLTF in 7d CTB-SAP-treated rats, but undermines pLTF in 28d CTB-SAP-treated rats. In addition, cervical spinal inflammatory marker gene expression ( e.g., TNF-a) is increased in CTB-SAP rats, and pilot data suggest that soluble TNF receptor 1 (sTNFR1) inhibition differentially affects pLTF (Nichols and Smith , ibid). Thus, the goal of the current study is to investigate TNFR1 as a pharmacological target that can modulate inflammation to maximize pLTF and breathing in CTB-SAP rats. We hypothesized that C4 TNFR1 expression would be increased on phrenic motor neurons and glial cells of CTB-SAP rats vs. controls. To address this, we studied TNFR1 expression on phrenic motor neurons and glial cells using immunohistochemistry, confocal microscopy, and ImageJ analysis in male Sprague Dawley rats 7 and 28 days after intrapleural injection of: CTB-SAP or un-conjugated CTB and SAP (control); n=8/group. Our preliminary data (n=4/group) suggest that phrenic TNFR1 expression is increased in 7d CTB-SAP rats vs. controls (p<0.05), but is unaffected in 28d CTB-SAP rats vs. controls (p>0.05). Further data analysis is underway for phrenic as well as glial TNFR1 expression in CTB-SAP rats vs. controls. If C4 TNFR1 expression is increased, this would suggest that TNFR1 is a viable target for therapeutic intervention in CTB-SAP rats, and potentially in patients with breathing deficits due to respiratory motor neuron death.

NSF Computational Neuroscience grant, MU CVM COR grant, and Spinal Cord Injury & Disease Research Program grant.

This is the full abstract presented at the American Physiology Summit 2024 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.
Shared and Distinct Cellular and Molecular Landscapes of Cardiac Left Ventricle Injury in Three Models of Hypertension: Insights from Single-nucleus RNA Sequencing
Authors: Qiu Qiongzi , Liu Yong , Xue Hong , Liu Jing , Therani Bhavika , Usa Kristie , Huang Jing
Published: May 2024

High blood pressure is the leading risk factor of heart diseases, affecting millions of patients who remain hypertensive despite taking three or more anti-hypertensive medications. Understanding the cellular and molecular basis of heart damage at cell type-specific level in different types of hypertension is crucial for developing targeted therapies. In this study, we applied 10x Genomics' single-nucleus RNA sequencing (snRNA-seq) technology to cardiac left ventricle samples from three well-established hypertension models: C57BL/6 mice treated with Ang II, the Dahl salt-sensitive rat, and the spontaneous hypertensive rat, along with their respective controls. Our dataset included 166,489 nuclei from 18 samples across 9 experimental conditions. Our analysis revealed a shared set of cellular and molecular changes across these hypertensive models. For instance, we observed extracellular matrix remodeling in fibroblasts in salt-sensitive and spontaneous hypertension, as indicated by increased collagen production. Endothelial cells showed an increased proportion in all three models, and showed higher levels of injury based on expression patterns of increased proliferation and migration. Both AngII-induced and spontaneous hypertension showed cardiomyocyte dysfunction, affecting cardiac muscle contraction and ATP metabolic process. Notably, impaired ATP generation was a common response in AngII-induced hypertension, involving not only cardiomyocytes but also endothelial cells and fibroblasts. During the progression of salt-sensitive hypertension, a notable increase in inflammation occurred, marked by steadily increasing immune cell infiltration, eventually reaching a 1.5-fold increase in immune cells. T cells were particularly elevated during the high-salt diet and actively engaged in the CD45 signaling network in the late stage of spontaneous hypertension, where an elevated interaction between cardiomyocyte and endothelial cells through vascular endothelial growth factor was observed. In conclusion, the utilization of snRNA-seq identified shared and distinct cellular and molecular changes associated with left ventricular injury in various models of hypertension.

NIH grant HL149620.

This is the full abstract presented at the American Physiology Summit 2024 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.
Use and Perception of Peer Recommendations to Improve Study Skills in Undergraduate Anatomy and Physiology Courses
Authors: Brundage Cord
Published: May 2024

Student success data from students enrolled in an undergraduate anatomy and Physiology (A&P) course at the University of Wisconsin-La Crosse indicated that student performance closely correlated with the number of prior completed university semesters. Based on this data we hypothesized that some students may have gained (or use) study skills that may have contributed to their success. Students at the end of the term were asked to provide recommendations to future A &P students on how to be successful in the course. A total of 408 recommendations from 68 students were received and underwent inductive and then deductive coding. More than 50% of respondents encouraged group studying and frequent engagement with material. The ranked and coded list of recommendations was then provided to the entering student at the start of the new term. Entering students were subsequently polled to gauge perceptions/reactions to this information. 91% of entering A&P students (n = 73) responded that they valued receiving study recommendations at the start of the term 59% of which said they preferred having that information come from former students rather than the faculty. Following the 1st lecture examination these students completed an Ink Shedding activity in which they shared exam studying strategies with their peers. Of the 62 participants 80% both found the activity helpful and recommended it be incorporated into future semesters. Collectively this data supports the perceived value of offering study skill resources to upper division A&P students and a positive reaction to peer guidance. Student performance improved on embedded course assessments. This information has been used to further develop peer mentoring programs and resource collaboration within the A&P lecture and laboratory curriculum.

This research was supported by a UWL FY2023 Course Improvement Grant and a University of Wisconsin System IDEAS Alliance Curriculum Reform Grant.

This is the full abstract presented at the American Physiology Summit 2024 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.
Advanced Metrics and Early Predictors of Cardiogenic Shock
Authors: Shah Nisarg
Published: May 2024

Cardiogenic shock (CS) can be defined as a range of illnesses that describes a state where cardiac output, which is the blood volume ejected from the left ventricle every minute that leads to tissue perfusion of nutrients, is insuffcient in providing adequate oxygenation to the systemic circulation. The incidence of CS on admission has increased in recent years, with the six- and 12-month mortality rates remaining unchanged. The purpose of this literature review is to bring forth several parameters that have been utilized in the past 10 years to predict CS mortality. Further studies to implement these parameters in management algorithms, along with early screenings and advanced treatment options such as mechanical cardiac assist devices, can improve the mortality associated with CS. This literature-based review was conducted by evaluating current research focusing on the clinical presentation of CS and predictors of CS. PubMed served as the primary database for article retrieval due to access. Two searches were conducted: One for clinical presentations and advanced metrics for CS and another for early predictors for CS. Thirteen articles regarding clinical presentation and seven articles regarding early predictors were selected. Three tools/scores and five laboratory tests were identified that allowed clinicians to prognosticate outcomes in patients suffering from CS based on clinical and laboratory presentations. Examining these predictors will allow earlier intervention in the development of CS and potentially help lower the mortality rate of CS. The eventual creation of a scoring system that incorporates multiple metrics discussed in this review can provide the most accurate prognosis of CS, which can lead to more targeted interventions.

This is the full abstract presented at the American Physiology Summit 2024 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.
Studies on Membrane Potential and Ca2+ Oscillations in Rat Carotid Body Type I Cells
Authors: Kim Donghee , White Carl
Published: May 2024

Carotid body (CB) glomus cells sense changes in arterial O2 pressure (PO2) and pH, and adjust the secretory and carotid sinus nerve activity and ventilation to help maintain normal levels of blood PO2 and pH. Our recent studies showed that isolated CB cell clusters perfused with physiological buffer solution generate spontaneous Ca2+ oscillations at low frequency in normoxia. Mild and moderate levels of hypoxia (2-5%O2) and acidosis (pHo7.2-7.3) increased the frequency and amplitude of Ca2+ oscillations. Inhibitors of voltage-dependent Ca2+ channels and removal of external Ca2+ abolished Ca2+ oscillations, indicating that Ca2+ influx was critical for generating Ca2+ oscillations. To better understand the phenomenon of Ca2+oscillations in glomus cells, we examined the potential role of oscillations in cell membrane potential (Em) in CB cells in triggering Ca2+ influx and Ca2+ oscillations. Using the cell-attached patch configuration, we assessed cell Em by recording TASK single channels, because a linear relationship exists between TASK amplitude and cell Em. Recording of TASK in CB cells in normoxia showed that many CB cells exhibit oscillations in TASK amplitude, indicating the presence of spontaneous oscillations in cell Em. The oscillation frequency of cell Em was similar to that of Ca2+ oscillations. Oscillations in TASK single channel amplitude were blocked by nifedipine (Ca2+ channel antagonist), by removal of extracellular Ca2+, and by 2-APB (an inhibitor of ER Ca2+ channel and store-operated Ca2+ entry). Mild hypoxia increased the frequency of oscillations of TASK amplitude, indicating that mild hypoxia increased the frequency of cell Em oscillations. These findings suggest that cell Em oscillations (that open voltage-dependent Ca2+ channels and increase Ca2+ influx) are an integral component of the cellular signaling mechanism by which Ca2+ oscillations are produced in CB cells.

This work was funded by National Institutes of Health (NIH) grants to D.K. (HL111497) and C.W. (HL142906), and an award from Rosalind Franklin University of Medicine and Science.

This is the full abstract presented at the American Physiology Summit 2024 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.
Caloric Restriction Improves Hepatic Thyroid Hormone Signaling During Metabolic Syndrome
Authors: Jardines Eira , Cornejo Manuel , Nakano Daisuke , Nishiyama Akira , Ortiz Rudy
Published: May 2024

Thyroid hormone dysregulation has been associated with metabolic syndrome (MetS) risk factors: hypertension, atherogenic dyslipidemia, obesity, and glucose intolerance. Several pathways are regulated by thyroid hormones such as the insulin signaling pathway, lipid metabolism, and antioxidant production among others. Impairment of thyroid hormone production causes dysregulation of these pathways. Caloric restriction (CR) is a form of non-pharmaceutical approach that has been shown to ameliorate MetS cluster factor conditions. However, caloric restriction's effects on thyroid hormone signaling during MetS remains unclear. A cohort of 11-week-old Otsuka Long Evan Tokushima Fatty (OLETF) and lean-strain control Long Tokushima Evans Otsuka (LETO) rats were fed chow ad libitium for 4 weeks. At 15 weeks, the animals were fed a 50% CR diet (compared to their control) for 10 days and assigned to four groups: (1) LETO (n=14), (2) LETO CR (n=14), (3) OLETF (n=14), and (4) OLETF CR (n=14). After the CR period, 7 animals from each group were then refed at pre-CR levels for 7 days and assigned to four groups: (1) LETO (n=7), (2) LETO post-recovery (LETO PR; n=7), (3) OLETF (n=7), and (4) OLETF PR (n=7). Mean body mass decreased 12% and 14% in LETO and OLETF, respectively, during the CR period compared to their ad lib controls. Hepatic deiodinase 1 (Dio1) protein expression was reduced by 41% in the OLETF compared to LETO. Dio1 protein expression was increased by 150% during CR and 88% by PR in OLETF. Deiodinase 2 (Dio2) showed a decreasing trend in OLETF rats compared to LETO and an increasing trend in the OLETF CR group compared to its ad lib control. Both free (fT4) and total T4 (tT4) had increasing trends in OLETF compared to LETO. CR induced a decreasing trend in fT4 and tT4 in OLETF compared to ad lib OLETF controls. These findings demonstrate that caloric restriction induces changes in hepatic thyroid hormone signaling that can improve impaired metabolism induced by MetS.

Doctoral fellowship UC MEXUS-CONACYT 440553 National Institute on Minority Health and Health Disparities grant 9T37-MD001480 American Heart Association 23DIVSUP1066372.

This is the full abstract presented at the American Physiology Summit 2024 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.
Elevated blood pressure follows physiological body-water conservation
Authors: Marton Adriana , Rauh Manfred , Takase-Minegishi Kaoru , Saffari Seyed Ehsan , Lim Tzy Tiing , Wild Johannes , Nagel Armin
Published: May 2024

Background: Pre-clinical evidence suggests that blood pressure (BP) increase is part of an adaptive physiological body response designed to prevent under-hydration. This idea challenges established thinking that hypertension is caused by initial salt-driven over-hydration. We tested the hypothesis that this alternative view also holds true in humans. Methods: In a mechanistic study, we investigated the interrelation between daily Na+ and water intake, renal solute and water excretion, renal water conservation, and body Na+ balance with BP in 6 healthy men living in a controlled environment for 205 days. In an additional daily-life observational study we investigated the interrelation between BP and adaptive-physiological water and Na+ conservation in 108 Singaporeans. Results: In participants living under controlled conditions, BP increased when urine osmolality was high, and fluid intake or urine volume was low. This BP-increasing water conservation response was not caused by body Na+ retention. Similarly, participants living under daily-life conditions showed a BP-elevating adaptive body water conservation response with increased plasma solute concentration, increased plasma vasopressin levels, and reduced urine volume production due to reduced renal free-water excretion. Participants with higher BP relied on more urea and glucose solutes, but on less Na+ solutes, to maintain their hydration status. Participants with essential hypertension showed more pronounced adaptive-physiological water conservation. None of these hypertension-specific water conservation responses were accompanied by differences in 24-h Na+ excretion. Conclusions: BP increase in humans is part of a systemic body water conservation response that occurs largely independent of body Na+ balance.

The Mars500 Salt and Water Homeostasis Project was realized by grant support from the German Federal Ministry for Economics and Technology/DLR Forschung unter Weltraumbedingungen (50WB1624-50WB2024) and the Interdisciplinary Centre for Clinical Research (IZKF Junior Research Group 2), Friedrich-Alexander-University of Erlangen-Nuremberg to JT. The food products were donated by APETITO, Coppenrath und Wiese, ENERVIT, HIPP, Katadyn, Kellogg, Molda, and Unilever. The Sodium Storage in Singaporeans Project was realized with grant support from Duke NUS Medical School (Duke-NUS-KBrFA/2019/0026) to JT.

This is the full abstract presented at the American Physiology Summit 2024 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 Mitochondrial Targeted Ubiquinol (MitoQ) Improves Immune Cell Bioenergetics in Patients with Heart Failure with Preserved Ejection Fraction
Authors: Bohmke Natalie , Chavez Domenico , Abbate Antonio , Markley Roshanak , Carbone Salvatore , Kirkman Danielle
Published: May 2024

BACKGROUND: Heart failure with preserved ejection fraction (HFpEF) is a proinflammatory syndrome. Mitochondrial dysfunction that is characteristic of HFpEF could alter immunometabolism, attenuating the functional reserve of immune cells. In addition, immune cell mitochondrial respiration is a biomarker of systemic mitochondrial health. The aim of this study was to assess the impact of a chronic oral mitochondrial targeted ubiquinol (MitoQ) on the immune cell bioenergetic profile in patients with HFpEF. We hypothesized that MitoQ administration in patients with HFpEF, would improve mitochondrial respiration in peripheral blood mononuclear cells (PBMC’s). METHODS: In this double-blind, crossover trial 8 patients with a clinical diagnosis of HFpEF (6 female, 2 male; 6 African American/Black, 2 white; mean ± SEM, Age, 58±5 years; BMI, 37±1 kg/m2) received a 4 week oral dose of MitoQ (MTQ, 20 mg/day) and placebo (PLB) in random order separated by a 2 week wash out period. Following completion of each trial arm, a venous blood sample was obtained and PBMCs were isolated using density gradient centrifugation. High resolution respirometry coupled with modulators of cellular respiration was performed to obtain basal respiration, ATP-linked respiration, maximal respiration, and spare respiratory capacity of the immune cells. Paired samples t-tests were used to compare variables between conditions. RESULTS: MitoQ was safe, well tolerated, and compliance was high (MTQ, 99 ± 1%; PLB, 89±4%). Basal respiration (MTQ, 106.4 ± 11.5 pmol/min; PLB, 66.5±5.9 pmol/min; p=0.002), ATP-linked respiration (MTQ, 41.4± 16.9 pmol/min; PLB, 16.3±6.7 pmol/min; p=0.04), maximal respiration (MTQ, 323.9 ± 50.0 pmol/min; PLB, 65.4±23.1 pmol/min; p=0.01), spare respiratory capacity (MTQ, 217.5 ± 39.6 pmol/min; PLB, 149.6 ±18.2 pmol/min; p=0.02), were higher following MTQ compared to PLB. CONCLUSIONS: In patients with HFpEF, administration of a mitochondrial targeted ubiquinol improved the immune cell mitochondrial respiration capacity and effciency. An increase in spare respiratory capacity following MTQ reflects an improvement in functional reserve that would augment the ability to respond to an acute stressor. These findings have positive implications for the ability to target and improve mitochondrial function in patients with HFpEF. Future work should investigate if the observed improvements in immune cell mitochondrial function are mirrored in other tissues.

Supported by AHA 19CDA3474002.

This is the full abstract presented at the American Physiology Summit 2024 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.