Citations

Background Patient admissions at a U.S. tertiary care hospital occur via the emergency department (ED), or transfer center. We aim to compare the clinical outcomes of patients admitted from the ED to admissions coordinated by the transfer center. Methods Admissions to Mayo Clinic Hospital, Rochester, MN, between July 2019 to June 2021 were identified in this retrospective study and categorized into two cohorts—transfer center and ED. The two cohorts were then matched for age, sex, admitting service, and Charlson Comorbidity Index. Univariate and multivariate analyses were performed to compare hospital length of stay (LOS), mortality, 30-day mortality, and 30-day readmissions between the two cohorts. Results 73,685 admissions were identified, of which 24,262 (33%) were transfer center admissions. In the matched cohorts (n = 19,093, each), in-hospital mortality (2.4% versus 1.9%), 30-day mortality (5.4% versus 3.9%), 30-day readmission (12.7% versus 7.2%), and LOS (6.4 days versus 5.1 days) were significantly higher (P < 0.001) among the admissions coordinated by transfer center. A higher palliative care consultation rate (9.4% versus 6.2%, P < 0.001), and a lower proportion of home discharges home (76.2% versus 82.5%, P < 0.001) among transfer center admissions was observed. Similar findings were noted in multivariate analysis, even when adjusting for LOS. Conclusions Transfer center admissions had higher in-hospital mortality, LOS, 30-day mortality, and 30-day readmission compared to ED admissions. This study also highlights new considerations for palliative care consultation before transfer acceptance, especially to avoid futile transfers. Additional studies analyzing factors behind the outcomes of transfer center admissions are required.

Abstract Purpose The Optimizing Performance Through Intrinsic Motivation and Attention for Learning (OPTIMAL) theory postulates that directing attention to the intended movement effect or outcome (external focus) is more effective than directing attention to the internal body motion or body part (internal focus). This study compared external versus internal focus of attention as novice students learned ultrasound-guided peripheral cannulation. The authors hypothesized that conditions promoting an external (vs internal) focus of attention would result in better performance on immediate and delayed (retention) testing. Method The authors conducted a randomized, experimental study from October 2022 to February 2023 comparing external and internal focus using ultrasound-guided peripheral venous cannulation followed by practice using an ultrasound training block. Undergraduate health science students performed 4 practice trials with instructions to focus on the needle tip (external focus) or their hands (internal focus), followed by immediate and delayed (retention) assessment 2 weeks later. The primary outcome was time to successful cannulation. Results were compared using Kaplan-Meier curves and parametric survival analysis regression (accelerated failure time) models. Results Seventy participants completed the immediate assessment. The external focus group completed successful cannulation a mean of 2.33 times faster (95% confidence interval [CI], 1.47–3.67; P &lt; .001) than those in the internal focus group (median time, 12.0 vs 29.5 seconds). Results also favored the external focus group during practice, with the external focus group successfully completing the task a mean of 1.83 times faster (95% CI, 1.04–3.21; P = .04) than the internal focus group. In the retention assessment, the external focus group successfully completed the task a mean of 2.37 times faster (95% CI, 1.19–4.74; P = .02) than the internal focus group. Conclusions External focus of attention compared with internal focus of attention improves medical motor skill learning in novice learners.

The diaphragm muscle (DIAm) as the major inspiratory pump is highly active. During breathing, fatigue resistant DIAm motor units are recruited that comprise type I and IIa fibers. Accordingly, these fibers have substantially higher mitochondrial volume density (MVD) and mitochondrial respiratory capacity (SDHmax) compared to more fatigable type IIx/IIb fibers. Cervical spinal cord injury disrupts descending inspiratory drive and markedly reduces eupneic activity of the DIAm. With C2 spinal cord hemisection (C2SH) DIAm activity on the ipsilateral side is reduced. Following a two-week period of C2SH, we found reduced MVD and SDHmax in type I and IIa DIAm fibers. As a result, we hypothesize that endurance of the DIAm is reduced. Female and male Sprague Dawley rats were used. EMG electrodes were placed in the left and right DIAm 3 days prior to C2SH surgery, and baseline recordings of eupneic DIAm activity were obtained in awake animals. The right C2 spinal cord was hemisected, and the extent of injury was confirmed by the absence of eupneic DIAm activity on the ipsilateral side while animals were anesthetized. Subsequently, DIAm EMG activity was recorded at 3, 7 and 14 days post C2SH. After two weeks, rats were anesthetized and the DIAm was excised. DIAm strips were cut and suspended in a tissue chamber containing Rees-Simpson solution maintained at 26oC, with thecostal margin clamped and the central tendon attached to a Cambridge Dual-Mode force/length transducer. DIAm strips were stimulated using platinum plate electrodes with supramaximal current (~250 mA) pulses (1 ms), and maximum specific force was determined at 75 Hz. The force-velocity relationship was then determined by systematically changing load, and maximum velocity (Vmax) was estimated based on curve fitting with the Hill-equation. Based on the force-velocity measurements peak power of the DIAm was calculated. Subsequently, the DIAm was repetitively stimulated and allowed to shorten at 30% maximum velocity (isovelocity approximating peak power output). Endurance of the DIAm was then determined as the duration that peak power output was sustained. Finally, the DIAm was rapidly frozen, and cross-sections were cut for fiber type and cross-sectional area (CSA) measurements. C2SH resulted in a marked decrease in eupneic DIAm EMG activity across the two-week period, which disproportionately affected type I and IIa DIAm fibers. However, there was no impact of C2SH on DIAm fiber type proportions or CSA. Following two-weeks C2SH, maximum specific force, Vmax, and peak power output of the DIAm were comparable between intact and injured sides. However, endurance of the DIAm was reduced on the injured side compared to the intact side. These results support our hypothesis that reduced activity of DIAm, reduces oxidative capacity of type I and IIa fibers and thereby reduces endurance. In clinical conditions such as mechanical ventilation DIAm activity is reduced and if maintained for longer periods of time this may affect DIAm endurance post weaning. Research supported by NIH grant: HL146114 (GCS). 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.

Maintaining pH is critical for proper cellular and organ function. To measure intracellular pH, we made a novel genetically encoded protein, pHire, that increases red fluorescence with increasing pH. Thus, pHire allows for the coupling of multiple fluorescent tags without spectral overlap. We have expressed pHire in mammalian epithelial cells, Drosophila, and mice. In this study, our goal was to characterize pHire’s spectral properties by expression in human cells (HEK293) and in E.coli. To biophysically characterize pHire, we made a maltose binding protein (MBP)-pHire fusion protein to purify from E.coli. Pelleting individual colony growths revealed pink bacterial pellets which fluoresced with mCherry filters. Rather than purifying the MBP-pHire protein, equal volumes of bacteria were permeabilized with nigericin and high K+ solution for pH 5 to 9. These aliquots were then used to gather the fluorescence excitation and emission spectra of pHire, allowing us to determine the excitation and emission peaks of pHire as a function of pH. Our results showed peaks at Ex579 nm and Em611 nm, or roughly mCherry. Pelleted bacteria could also be fixed in perfusion chambers, revealing the same calibration curve as in mammalian cells and flies. Next, stable HEK293-pHire cells were selected to assay acid-base transport using NH4Cl or CO2/HCO3− in perfusion experiments. These HEK-pHire cells have less fluorescence than MBP-pHire bacteria but show the same Ex/Em peaks. However, an in-frame ATG 5’ to pHire in a mouse (adding 23 amino acids), removed pHire pH-dependence and decreased bacterial fluorescent output. Together these results indicate that pHire is biophysically similar in cells tested but that unstructured N-terminal additions block pH-responses. Funding: R25-DK101405, R21-DK129897. 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.

Allergens derived from the fungus Alternaria alternata stimulate the release of multiple alarmins including ATP, IL-33 and DNA fragments from human bronchial epithelial cells (hBECs). Oxidative stress induced by Alternaria extract activates ATP release by opening voltage-dependent anion channels (VDAC-1) in the apical membrane and by stimulating exocytosis of ATP containing membrane vesicles. The present study shows that pretreatment of hBECs with K2P channel inhibitors prior to Alternaria exposure significantly increases the initial rate of ATP release and inhibition of ATP loading into membrane vesicles with bafilomycin A1 blocks the response. Furthermore, pretreatment with the K+ channel openers, EBIO (KCa3.1 channels), NS11021 (KCa1.1 channels) and pinacidil (KATP channels) each inhibited the bafilomycin A1-dependent component of ATP release, reducing the initial rate of ATP secretion by ~50%. K2P channel blockers caused depolarization whereas K+ channel openers produced hyperpolarization of the cell membrane. Additionally, K2P channel inhibitors also increased Alternaria-stimulated Ca2+ uptake into hBECs while K+ channel openers reduced the Alternaria response by ~50%. Imaging experiments involving visualization of fluorescently labeled MARCKS proteins in the apical membrane showed that treatment with Alternaria caused a significant decrease in fluorescence intensity, however pretreatment with K+ channel openers, but not K2P channel blockers, inhibited the effect. These results are consistent with recent findings showing that MARCKS proteins bind to the plasma membrane through an electrostatic association with PIP2 and that phosphorylation by PKC or membrane hyperpolarization following K+ channel activation disrupts this interaction resulting in MARCKS detachment from the membrane. MARCKS detachment uncouples the membrane from the actin cytoskeleton, facilitating vesicle docking, fusion and release of ATP. This study was supported by NIH grants (AI128729 and AI169530) to HK and SMO and by USDA-AES 0016134 to SMO. 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.

Succinate dehydrogenase (SDH) is a mitochondrial enzyme that serves a dual role in mitochondrial respiration: catalyzing the oxidation of succinate to fumarate in the tricarboxylic acid (TCA) cycle and transferring electrons from succinate to ubiquinone as complex II in the electron transport chain (ETC). SDH is composed of four subunits (SDHA-SDHD) and the loss of SDHB subunit, specifically, has been shown to increase oxidative stress. As a part of the catalytic core of the SDH complex, the SDHB subunit mediates electron transfer to ubiquinone. In human airway smooth muscle (hASM) cells with siRNA-mediated knockdown of SDHB, the maximum velocity of the SDH reaction (SDHmax) is decreased. Moreover, SDHB-knockdown leads to an increase in mitochondrial volume density, indicating a role of SDH in mitochondrial remodeling. However, the impact of SDHB-knockdown on mitochondrial dynamics has not been explored. Therefore, we hypothesize that SDHB-knockdown promotes mitochondrial fragmentation as part of mitochondrial remodeling in hASM cells. To investigate this hypothesis, bronchiolar tissue samples were collected in female and male patients undergoing lung surgery with no current history of smoking or respiratory diseases, the smooth muscle layer was dissected and hASM cells were dissociated. The targeted knockdown of SDHB was achieved by siRNA-mediated knockdown. Mitochondria in hASM cells were labeled with MitoTracker Green (200 nM) and imaged in 3D with a Z optical slice of 0.5 μm using an oil-immersion ×60/1.4 NA objective on a Nikon Eclipse A1 laser scanning confocal system. Optical slices were deconvolved to enhance contrast and the MitoTracker labeling was thresholded to create binary images, which were then reconstructed in 3D. From these images, the mitochondrial complexity index (MCI) was calculated to quantify the extent of fragmentation. To identify the signaling pathway involved in mitochondrial fragmentation, the expression and phosphorylation of dynamin-related protein 1 (DRP1) was quantified by Western blot. Mitochondrial fragmentation is associated with increased phosphorylation of DRP1 at Ser616 (pDRP1s616). Furthermore, mitophagy was assessed by determining the mitochondrial expression of PINK1 and the phosphorylation of Parkin at Ser65 (pParkinS65). Mitochondrial biogenesis was also evaluated through the expression of PGC1α, NRF1/2 and TFAM. Our results show that SDHB-knockdown increased mitochondrial fragmentation (reduced MCI) in hASM cells, and increased pDRP1s616 phosphorylation and its translocation to mitochondria. SDHB-knockdown also increased mitochondrial expression of PINK1 and pParkins65 phosphorylation indicating activation of mitophagy. We also confirmed that SDHB-knockdown increased expression of PGC1α, NRF1/2 and TFAM consistent with mitochondrial biogenesis. These findings unveil the mechanisms underlying SDHB-knockdown-mediated mitochondrial remodeling. Supported by NIH grant R01-HL157984 (GCS). 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.

Aging is a significant risk factor for cardiovascular disease and is known to be associated with an increase in vascular stiffness and decrease in sensitivity to NO mediated vasodilatation. However, the underlying mechanism for these changes in vascular function is unknown. Smooth muscle tone is known to be regulated by the expression and phosphorylation of both nonmuscle (NM) and smooth muscle (SM) myosin. NM and SM phosphorylation is regulated by the activity of myosin light chain kinase (MLCK) and MLC phosphatase. MLC phosphatase is a trimeric enzyme consisting of enzymatic, myosin targeting (MYPT1) and a 20kDa subunit of unknown function. Two isoforms of MYPT1 are produced by alternative mRNA splicing, which differ by the presence or absence of a COOH-terminal leucine zipper (LZ+/-), and the relative expression of LZ+/LZ- MYPT1 determines the sensitivity to NO mediated vasodilatation. We defined NM myosin expression using two-dimensional SDS PAGE and LZ+/LZ- MYPT1 expression using immunoblotting in aortic and tertiary mesenteric smooth muscle from 6mo and 24mo old Fischer344 rats. The data demonstrate that aging is associated with a significant decrease in the expression of both LZ+ MYPT1 and NM myosin. The reduction in LZ+ MYPT1 expression would both decrease the sensitivity to NO mediated smooth muscle dilatation and increase vascular tone, which is a hallmark of the vasculature in aging. On the other hand, the reduction in NM myosin would result in a decrease in vascular tone and could represent a compensatory mechanism to normalize blood pressure during aging. These data demonstrate that there are changes in the expression of smooth muscle regulatory and contractile proteins during aging and these changes in protein expression contribute to molecular mechanism for the decrease in sensitivity to NO mediated vasodilatation as well as the increase in vascular tone or the vascular dysfunction that occurs with aging. Supported by a Mayo CV Prospective Grant (FVB). 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.

Aging is associated with an increased incidence of cardiac dysfunction. We hypothesized that aging associated changes in cardiac regulatory and contractile proteins produce contractile dysfunction. We assessed regulatory and contractile protein expression as well as contractility in left ventricular cardiac muscle from Fischer F-344 rats at 6-, 18-, and 24-month of age. Age-related changes in the expression of β-MHC as well as the expression and phosphorylation of troponin I (TnI) and cardiac myosin binding C protein (MyBP-C) were assessed by Western blot. Aging was associated with an increase in the expression of β-MHC and the phosphorylation of both TnI at Ser23/24 and MyBP-C. Mechanical properties were assessed in Triton-X permeabilized anterior papillary muscle from the left ventricle from both 6- and 24-month old rats. In papillary muscle of 24-month old rats, there was a decrease in maximum Ca2+ activated force, Ca2+ sensitivity of force and the rate constant for force recovery after quick release (ktr). Additionally, cardiomyocytes were isolated from the left ventricle at 6-, 18-, and 24-month of age using a modified Langendorff system. Cardiomyocytes were then loaded with fura-2 AM to measure cytosolic calcium ([Ca2+]cyt) responses to electrical field stimulation (0.5 Hz). [Ca2+]cyt and contractile (sarcomere length shortening) responses to stimulation were simultaneously measured using an IonOptix system. In older cardiomyocytes, the amplitude of evoked [Ca2+]cyt responses was reduced while there was no difference in the kinetics of the [Ca2+]cyt transient. The extent of sarcomere length shortening as well as the rates of both shortening and relaxation were reduced. These results demonstrate that aging is associated with changes in the expression and phosphorylation of contractile and regulatory proteins, which produce changes in cardiac contractility. Supported by a Mayo CV Prospective Grant (FVB). 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.

This study aimed to investigate the impact of central α2-adrenergic mechanisms on arterial baroreflex control of sympathetic and cardiovagal outflow in healthy humans. R-R interval (ECG), blood pressure (brachial arterial catheter), and muscle sympathetic nerve activity (MSNA; peroneal microneurography) were measured in eight healthy participants (5 females; 28±7 years). Sympathetic action potentials (AP) were extracted from the filtered MSNA neurogram (continuous wavelet transform) during a 5-minute baseline (BSL) and an intravenous dexmedetomidine infusion consisting of a loading dose (LD; 10 minutes at 0.225 μg/kg/hr) and a maintenance dose (MD; ~0.15 μg/kg/hr). Sympathetic AP baroreflex threshold gain was measured as the slope of the linear relationship between AP discharge probability and diastolic blood pressure. The linear relationship between R-R interval and systolic blood pressure (sequence technique) quantified cardiovagal baroreflex gain. Mixed-effects analyses and post-hoc t-tests were performed. Data are reported as mean ± SD. Dexmedetomidine reset the baroreflex threshold operating points for all sympathetic AP clusters downwards to lower firing probabilities (cluster 4; BSL: 20±6, LD: 13±8, MD: 6±5%, both p<0.01 vs. BSL) and leftwards to lower diastolic pressures (BSL: 72±9, LD: 69±8, MD: 65±10 mmHg, both p<0.01 vs. BSL). Dexmedetomidine reduced baroreflex threshold gain for the subpopulation of medium-sized sympathetic APs (cluster 4; BSL: -6.5±2.0, LD: -2.6±1.6, MD: -2.0±0.7 %/mmHg, both p<0.01 vs. BSL). Dexmedetomidine did not affect baroreflex threshold gain of small (cluster 1; BSL: -1.9±1.1, LD: -1.3±1.6, MD: -1.1±0.8 %/mmHg, both P>0.88 vs. BSL) or large AP clusters (cluster 9; BSL: -0.8±0.4, LD: -0.8±1.0, MD: -0.2±0.7 %/mmHg, both P>0.98 vs. BSL). Dexmedetomidine reset the cardiovagal baroreflex to lower systolic pressures but did not affect R-R interval (BSL: 1035±261, LD: 1025±308, MD: 1005±292ms, Main effect P=0.45) or gain (BSL: 24±11, LD: 30±20, MD: 26±25 ms/mmHg, Main effect P=0.63). These findings suggest that central α2-adrenergic mechanisms differentially affect arterial baroreflex control of sympathetic and cardiovagal outflow in humans by minimally affecting cardiovagal baroreflex gain but strongly affecting the baroreflex gain for the subpopulation of medium-sized sympathetic APs. This work was supported by the Natural Sciences and Engineering Research Council of Canada (NSERC) and the National Institutes of Health (NIH). 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.

This study investigated the impact of integrated muscle sympathetic nerve activity (MSNA) discharge patterns on human neurocirculatory regulation. In 13 healthy females (42 ± 15 years), the transduction of integrated MSNA (peroneal microneurography) into mean arterial pressure (MAP; arterial catheter) was studied during an intravenous infusion of a nicotinic ganglionic antagonist (trimethaphan camsylate, 1-7 mg/min). Neurovascular transduction (signal averaging) was studied based on the overall response, burst sequence (singlet, doublet, and triplet+), and burst amplitude (binned into tertials: small, medium, and large bursts). Data (mean ± SD) are reported for a 10-minute baseline (BSL), the one-minute period at the midpoint of the trimethaphan infusion with integrated MSNA bursts (TM-Mid), and the last minute of trimethaphan infusion with integrated MSNA bursts (TM-Last). During BSL, the MAP transduction responses were greatest for triplets+ (singlets: 0.9 ± 0.2 mmHg, doublets: 2.0 ± 0.6 mmHg, triplet+: 2.6 ± 0.9 mmHg; P < 0.01) and large bursts (small: 1.0 ± 0.3 mmHg, medium: 1.7 ± 0.5 mmHg, large: 2.2 ± 0.7 mmHg; P < 0.01). Trimethaphan infusion reduced integrated MSNA burst frequency resulting in a greater proportion of singlets (BSL: 45 ± 18 %, TM-Mid: 75 ± 23 %, TM-Last: 94 ± 20 %; P < 0.01), a lower proportion of doublets, and a lower proportion of triplets+ (BSL: 23 ± 19 %, TM-Mid: 9 ± 18 %, TM-Last: 0 ± 0 %; P < 0.01). Trimethaphan infusion reduced integrated MSNA burst amplitude resulting in a greater proportion of small bursts (BSL: 33 ± 0.2 %, TM-Mid: 60 ± 26 %, TM-Last: 78 ± 37 %; P < 0.01), a lower proportion of medium bursts, and a lower proportion of large bursts (BSL: 34 ± 1 %, TM-Mid: 17 ± 26 %, TM-Last: 1 ± 5 %; P < 0.01). Trimethaphan-mediated changes in MSNA burst frequency and amplitude were associated with reduced overall MAP transduction responses (BSL: 1.6 ± 0.5 mmHg, TM-Mid: 0.5 ± 0.2 mmHg, TM-Last: 0.3 ± 0.3 mmHg; P < 0.01). Linear regression analyses demonstrated that the trimethaphan-mediated reduction in the proportion of large bursts ( β = 0.02 ± 0.008 mmHg/%, R2 = 0.13, P = 0.03) more strongly affected sympathetic neurovascular transduction responses than reductions in the proportion of triplet+ burst sequences (P = 0.91). These findings suggest that time varying MSNA discharge patterns, particularly variations in burst amplitude, support human neurocirculatory regulation. This work was supported by the National Institutes of Health and the Natural Sciences and Engineering Research Council of Canada. 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.