A Protective Cap Does Not Alter Rectal or Skin Temperature Responses During Simulated Occupational Work in the Heat

Heat tolerance testing (HTT), an essential component of return-to-activity guidelines following exertional heat injury (EHI), assesses tolerance to standardized conditions with rectal temperature (T rec ) and heart rate (HR) thresholds defining heat tolerant (HT) and intolerant (HI). Purpose: To compare sex-based differences in HTT classification before (pre) and after (post) heat acclimation (HA). Methods: 40 healthy participants without history of EHI (18M/22F, mean±SD, 23±4 years old) completed an HTT (120min at 5km·hr -1 , 2%grade) before and after five days of repeated exercise in (40°C, 40% relative humidity) categorized as isothermal (exercise intensity adjusted to maintain T rec at 38.5-39.5°C for 60min) exercise-HA. Results: We observed females to have lower body surface area (BSA; 1.7±0.1 vs. 2.0±0.2m 2 , p<0.001), body mass (59.5±5.4 vs. 79.5±10.1 kg, p<0.001), height (164.2±5.7 vs. 179.1±7.6cm, p<0.001), [Formula: see text]O 2 max (44.5±5.1 vs. 51.5±5.7 mL·min -1 ·kg -1 , p<0.001), and vVo2max (8.0±1.0 vs. 9.3±1.1 mph, p<0.001). Across criteria, 51.1% of participants were HI pre (66.7%F/52.6%M), improving to 23.6%HI post (28.6%F/10.5%M), potentially reflecting an elevated false positive rate. The best-performing criterion was a plateau in rectal temperature during the last 60min (ΔT rec 60) ≥0.45°C improving from 15%HI pre-HA (9.5%F vs. 21.1%M) to 10%HI post (9.5%F vs. 10.5%M), indicating effective thermoregulation in both sexes. The most stringent criterion ΔT rec 60≥0.25°C & HR≥120 bpm & T rec ≥38.2°C), classified 90%HI pre (100%F/78.9%M) and 67.5%HI post (76.2%F/57.9%M). The probability of heat tolerance (PHT) criterion, which includes a borderline category (BHT), showed 60% HI and 15% BHT pre (66.7%F/52.6%M HI, 19%F/10.5%M BHT) and 20%HI and 12.5%BHT post (28.6%F/10.5%M HI, 9.5%F/15.8 %M BHT). The T rec ≥38.5°C criterion showed a significant improvement, with 40%HI pre (42.9%F vs. 36.8%M) reducing to 7.5%HI post (9.5%F vs. 5.3%M). The HR≥150bpm criterion significantly improved with 37.6%HI pre (61.9%F vs. 10.5%M) reducing to 5.0%HI post (9.5%F vs. 0.0%M). The thermal circulatory ratio (TCR) at 120 minutes classified 50%HI pre (71.4%F vs. 26.3%M) and 15%HI post (23.8%F vs. 5.3%M). TCR at 60min (T60) similarly classified 65%HI pre (85.7%F vs. 42.1%M) and 40%HI post (46.9%F vs. 15.8%M), illustrating that females have higher HR for given T rec than males at both timepoints. Physiologically, females had higher resting HR (80±14 vs. 71±12bpm, p=0.046), pre-exercise resting HR (92±18 vs. 84±10bpm, p=0.007) and T rec (37.03±0.44 vs. 36.8±0.35°C, p=0.012) than males, and lower BSA adjusted whole body sweat loss (0.76±0.25 vs. 0.88±0.22L·m -2 , p=0.020). Conclusion: HA improves HT, but guidelines still misclassify participants pre- and post-HA, disproportionately affecting females, reflecting the inadequacy of criteria developed without female participants. DOD BA200299 This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.

Introduction: Greater heat-related health risks are a direct consequence of global warming. These risks are precipitated by physiological heat strain, specifically an increase in core temperature and heart rate, and sweating-induced dehydration. Older adults face greater heat-related heath risks, especially amongst those living with chronic health conditions. To our knowledge, limited research has explored the effect of health status on physiological strain of older adults during environmental heat exposure. Objectives: The objective of this study is to compare physiological heat strain between healthy older adults, older adults with risk factors for chronic diseases, and older adults living with chronic disease during exposure to a hot and humid environment with short bouts of light exercise to simulate activities of daily living. We hypothesized that physiological heat strain would be greatest for adults living with chronic disease, followed by those living with risk factors compared to healthy older adults. Methods: Seven healthy older adults (60-74 years, 5 females), 23 adults living with ≥1 risk factor according to the harmonized definition of metabolic syndrome (61-88 years, 6 females), and 10 older adults living with ≥1 non-communicable chronic disease (61-84 years, 2 females) were exposed to a 38°C environment with 60% humidity in an environmental chamber for 4 hours. To induce energy expenditure associated with activities of daily living (~3.5 METs), participants performed 10 minutes of light exercise (treadmill walking or cycling) every hour. Participants could drink water served at 15°C ad libitum. Rectal temperature and heart rate were measured continuously. Dehydration was calculated as the difference between pre- and post-exposure nude body mass (post-void) relative to pre-exposure nude body mass. Data are presented as mean ± standard deviation. Results: During the 4 hours of heat exposure, rectal temperature increased by 0.4 ± 0.3°C in healthy older adults, 0.5 ± 0.3°C in those living with at least 1 risk factor, and by 0.5 ± 0.4°C in older adults living with chronic disease. Heart rate increased by 11 ± 6 bpm in healthy older adults, 15 ± 7 bpm in those living with at least 1 risk factor, and by 9 ± 4 bpm in older adults living with chronic disease. Dehydration was 0.3 ± 1.0% in healthy older adults, 0.7 ± 0.8% in those living with at least 1 risk factor, and 0.8 ± 0.7% in older adults living with chronic disease. Conclusion: During exposure to hot/humid heat that integrates light exercise to simulate activities of daily living, these preliminary results suggest that thermal and cardiac strain do not differ markedly as a function of health status amongst older adults. However, older adults living with at last 1 risk factor or those living with chronic disease seem to experience greater dehydration. The clinical consequences of these differences remains to be determined. Canadian Institutes of Health Research This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.

PurposeTo investigate the influence of shorter, more frequent rest breaks during simulated work (outdoor mining) in the heat on physical performance and psychophysiological responses.MethodsOn separate days, thirteen males undertook two 225 min simulation trials in the afternoon (12.00–3.45 pm) including 180 min of treadmill walking at a constant rate of perceived exertion of 11 (or ‘light’) on the 6–20 Borg scale in a heat chamber (37 °C, 40% RH), interspersed with 45 min of rest breaks in an air-conditioned room (22 °C, 35% RH). Rest breaks in the current practice (CP) trial occurred at 1.00 and 2.30 pm (30 min and 15 min, respectively), while in the experimental (EXP) trial were at 1.00 (15 min), 1.45, 2.25 and 3.05 pm (10 min each).ResultsTotal distance covered was not different (p = 0.086) between CP (12,858 ± 2207 m) and EXP (12,094 ± 2174 m). Heart rate, thermal sensation and thermal comfort were significantly higher at 120–180 min (all p < 0.05) in CP compared to EXP. Moderate- to large-effect sizes (Hedge’s g) between trials were also found at 120–180 min for core temperature (g = 0.50 and 0.99, respectively). No differences were found between trials for cognitive performance, perceived fatigue, urine specific gravity, or total water intake (p > 0.05).ConclusionShorter, more frequent rest breaks have little impact on physical performance, thermal strain and exercise-related sensations. Current practices should remain in place until further studies can be conducted on an actual mine site during summer where outdoor workers perform their work duties.

The coronavirus 2019 (COVID-19), caused by severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2- 2), is highly contagious and has disastrous healthcare systems worldwide. Medical personnel are at a high risk of becoming infected with viruses; therefore, knowing what personal protective equipment (PPE) to use in each situation is critical. Furthermore, elective clinics and operations have been reduced to redirect the workforce to the acute specialties battling the outbreak; proper differentiation between patients who require immediate care and those who can be seen over the phone or whose treatment can be postponed is thus critical. Because Iran was one of the first and worst-affected countries, the Iranian Ministry of Health and Education has issued particular recommendations based on consensual best practices and, where available, literature. Only emergency surgical procedures are indicated, and all patients should be examined at least twice before surgery (on days 4 and 2). Procedures for positive patients should be postponed until the nasopharyngeal swab test is negative. Filtering facepiece 3 (FFP3) and/or powered air-purifying respirator (PAPR) devices, goggles, full-face visor, double gloves, water-resistant gowns, and protective caps are all required if the procedure is critical to the patient's survival. It is advised that negative patients utilize at most minuscule an FFP2 mask. Drills should never be used because they enhance the aerosolization of potentially infectious mucous particles. The manipulation of the dura should be minimized due to the probable neurotropism of SARS-CoV-2. We will be able to deal with the evolving and intricate implications of this new pandemic only through generally agreed-upon protocols and coordination.

We herein present a 40-year-old female physician who was diagnosed with idiopathic intracranial hypertension (IIH) 4 years ago. In the last years, the patient was in remission without any medications. Since the onset of COVID-19 pandemic, she has been stressfully working in the high-risk area, therefore using personal protective equipment (N95 mask, protective clothing, goggles, and protective cap) during the day for extended periods. Her headaches recurred and the patient was diagnosed with a relapse of IIH; acetazolamide and afterward topiramate were initiated, with diet treatment. Symptomatic metabolic acidosis, which is otherwise a rare side effect of the IIH treatment and not seen in her first attack even with higher doses, developed during the follow-up, presenting with shortness of breath and chest tightening. The emerging problems of IIH diagnosis and management during the COVID-19 pandemic will be discussed.

Prolonged heat exposure increases acute kidney injury (AKI) risk likely due to renal oxidative stress and inflammation. However, the effect of occupational heat stress (OHS) and the modifying role of hydration on renal oxidative stress and inflammation is unknown. This study tested the hypothesis that compared to fluid restriction ad libitum drinking consistent with OHS recommendations will attenuate renal oxidative stress and inflammation during simulated OHS. In a randomized, crossover design, 13 healthy adults (5 women) completed two 2 h OHS simulations consisting of of 8 circuits of treadmill walking (10 min) and rowing (5 min) at an oxygen uptake of 1.2 L/min in a wet bulb globe temperature of 33.1±0.2°C. In the drinking trial (Drink), subjects were provided 237 mL of a non-caloric sport drink (Gatorade Zero) every 15 min and drank ad libitum. In the fluid restriction trial (NoDrink), no fluid was provided. Rectal temperature and body weight were recorded. Urine and blood samples were collected pre-, post- and 1 h post- exposure. Inflammatory (monocyte chemotactic protein-1, MCP-1) and oxidative stress (thioredoxin 1, TRX-1) markers were measured in urine and serum, and fractional excretion (FE) was calculated. AKI risk was quantified as the product of urine insulin-like growth factor-binding protein 7 and urine tissue inhibitor of metalloproteinase 2 ([IGFBP7•TIMP-2]). Data are presented as mean ± SD. Peak rectal temperature was not different between trials (Drink: 38.5±0.4°C, NoDrink: 38.6±0.4°C, p=0.346). Percent changes in body weight were lower in Drink (1.3±0.8% vs. 2.8±0.9%, p&lt;0.001). FETRX-1 was elevated at post- (0.50±0.00%) compared to pre- (0.36±0.00%, p=0.011) and 1 h post- (0.29±0.13%, p=0.011). FEMCP-1 was elevated at post- (1.25±0.18%) compared to pre- (1.02±0.17%, p=0.006) but not 1 h post- (1.27±0.03%, p&gt;0.999). FETRX-1 and FEMCP-1 did not change significantly between trials (trial x time: p³0.622). [IGFBP7•TIMP-2] was higher at 1 h post- (17.5±1.0 (ng/mL)2/1000) compared to pre- (0.2±0.1 (ng/mL)2/1000, p&lt;0.001) and post- (1.1±0.4 (ng/mL)2/1000, p&lt;0.001) but did not differ between trials (trial x time: p=0.556). Peak changes in [IGFBP7•TIMP-2] were not significantly correlated with peak changes in FETRX-1 (r=0.126, p=0.557) or FEMCP-1 (r=0.292, p=0.166) and were correlated with peak changes in serum MCP-1 (r=0.714, p&lt;0.001) but not serum TRX-1 (r=0.227, p=0.286). Two hours of simulated OHS increased renal inflammation (FEMCP-1), oxidative stress (FETRX-1), and AKI risk ([IGFBP7•TIMP-2]), while ad libitum drinking did not modify FEMCP-1, FETRX-1, or [IGFBP7•TIMP-2]. Lack of correlations between peak changes in [IGFBP7•TIMP-2] and FEMCP-1, FETRX-1, or serum TRX-1, but the strong positive correlation with peak serum MCP-1 suggests a role for systemic inflammation in OHS induced AKI risk. NCT05458843 Funding: R01OH011528. 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.

Napping is one strategy that may assist night shiftworkers to cope with sleepiness and fatigue. However, one potential disadvantage of napping is that awakening from naps is disturbed by sleep inertia, which has also been found to impair performance and/or mood, transiently. The authors examined the effects of the timing and length of a night-shift nap on sleep inertia in a laboratory setting. Twelve male university students (mean ± SD: 21.6 ± 2.8 yrs) participated in this 3-day experiment, during which included a simulated night shift (22:00–08:00 h) and subsequent day (11:30–17:30 h) and night sleep (00:00–07:00 h). The simulated night shift was designed to include one of five (four nap/one no-nap) conditions. The napping conditions differed by their timing and duration: 00:00–01:00 h (Early 60 min; E60), 00:00–02:00 h (Early 120 min; E120), 04:00–05:00 h (Late 60 min; L60), 04:00–06:00 h (Late 120 min; L120). Participants completed all the experimental conditions in a counterbalanced order. Rectal temperature (RT) was recorded throughout the simulated shift and polysomnography (PSG) was recorded during the nap period. Immediately before and after each nap, participants were required to complete a visual analogue scale (VAS) to assess sleepiness and a visual vigilance test (VVT). During the simulated night shift, a set of tasks (an English transcription task, a performance test battery, and a break) was repeated hourly, except during the periods of napping. For each nap condition, the VAS and VVT (reaction time [RT]; lapses >5 s) results were analyzed by two-way, repeated-measures analysis of variance (ANOVA) (nap [nap versus no-nap] × time point [pre-nap versus post-nap]). PSG and RT data were analyzed with one-way repeated-measures ANOVA. Marginally significant interactions were observed for RTs and lapses in VVT for the L60 nap condition (p = .071 and p = .070, respectively). However, those effect sizes were moderate (partial η2 = 0.266, 0.268, respectively). Post hoc analyses showed significantly longer RTs (p < .05) and more lapses (p < .05) following the L60 nap compared with no nap. In contrast, there was no significant difference in sleepiness between the L60, or any of the other nap conditions, and the no-nap condition. Our findings suggest the effect of sleep inertia on VVT performance was profound in the L60 condition, although no significant effects on sleepiness were self-reported by VAS. The dissociation between performance and sleepiness might reflect an unstable state where participants cannot perceive decline in their performance. The present findings are significant in terms of occupational safety; the practical implication is that great care is needed when taking a 1-h nap between 04:00 and 05:00 h on the night shift. (Author correspondence: kubo@h.jniosh.go.jp)

Chronobiological investigations into core temperature during and after exercise can involve ambulatory measurements of intestinal temperature during actual competitions, esophageal temperature measurements in laboratory simulations, or rectal temperature, which can be measured in both the field and laboratory. These sites have yet to be compared during both morning and afternoon exercise and subsequent recovery. At 08∶00 and 17∶00 h, seven recreationally active males exercised at 70% peak oxygen uptake for 30 min and then recovered passively for 30 min. During the experiment, esophageal, rectal, intestinal, and skin temperatures, plus sweat loss, heart rate, and ratings of perceived exertion (RPE), were monitored. We found that the diurnal variation in intestinal temperature responses (0.45±0.32°C; mean±SD) was significantly larger compared with rectal (0.33±0.24°C) and, particularly, esophageal temperature responses (0.21±0.20°C; p= 0.019). This reflected a greater difference of 0.25–0.40°C between the esophagus and the other two sites in the afternoon, compared to inter‐site differences of only 0.13–0.16°C in the morning. Diurnal variation was small for skin temperature, heart rate, sweat loss, and RPE responses during exercise (p>0.05). Our data suggest that the relative differences between intestinal, rectal, and esophageal temperature during exercise and subsequent recovery depend on time of day to the extent that inferences from studies on experimental and applied chronobiology will be affected.

The seasonal changes in oxygen consumption, rectal temperature, and skin temperature in response to a 1-hr nude exposure to 14.1 C were measured once monthly in six subjects between October and February. The same measurements were obtained in another group nude exposed 8 hr daily to a chamber temperature of 13.5 C. Shivering decreased as a result of the seasonal and chamber cold exposure ( P &lt; 0.01). Heat production also decreased as a result of both types of exposure ( P &lt; 0.05) but never decreased to basal values. Skin temperature in the seasonal group exhibited no change, whereas a small fall occurred in the chamber group ( P &lt; 0.05). Although no rectal temperature change was demonstrated in the seasonal group, there was a significant fall in the rectal temperature in the chamber group. After the period of chamber and seasonal cold acclimatization, both groups were subjected to 21 days of heat acclimatization followed by another cold-response measurement. In both groups the changes induced by winter exposure and chamber exposure were not influenced by heat exposure. Since previous studies have demonstrated the lack of influence of cold exposure on heat acclimatization, it is concluded that heat and cold acclimatization are not mutually exclusive and can exist simultaneously in man. Note: (With the Technical Assistance of D. R. Johnston, F. W. Jacks, and W. Rawlings) Submitted on October 6, 1961

Six Angus steers (319 +/- 8.5 kg) were assigned to one of two groups (hot or cold exposure) of three steers each, and placed into two environmental chambers initially maintained at 16.5-18.8 degrees C air temperature (Ta). Cold chamber Ta was lowered to 8.4 degrees C, while Ta within the hot chamber was increased to 32.7 degrees C over a 24-h time period. Measurements included respiration rate, and air and body (rectal and skin) temperatures. Skin temperature was measured at shoulder and rump locations, with determination of sweat rate using a calibrated moisture sensor. Rectal temperature did not change in cold or hot chambers. However, respiration rate nearly doubled in the heat (P < 0.05), increasing when Ta was above 24 degrees C. Skin temperatures at the two locations were highly correlated (P < 0.05) with each other and with Ta. In contrast, sweat rate showed differences at rump and shoulder sites. Sweat rate of the rump exhibited only a small increase with Ta. However, sweat rate at the shoulder increased more than four-fold with increasing Ta. Increased sweat rate in this region is supported by an earlier report of a higher density of sweat glands in the shoulder compared to rump regions. Sweat rate was correlated with several thermal measurements to determine the best predictor. Fourth-order polynomial expressions of short-term rectal and skin temperature responses to hot and cold exposures produced r values of 0.60, 0.84, and 0.98, respectively. These results suggest that thermal inputs other than just rectal or skin temperature drive the sweat response in cattle.

Background: In the United States over 10% of all neonates are born premature (less than 37 weeks gestational age) and many face complications, such as necrotizing enterocolitis (NEC). NEC is the most deadly gastrointestinal disease in preterm neonates with up to 50% mortality. Survivors face life-long complications. NEC is a multifactorial disease caused by 1) intestinal immaturity, including a poorly developed physical barrier between luminal contents and the rest of the body; 2) an exaggerated immune response; and 3) intestinal dysbiosis, which together can result in irreparable damage to the intestine. Since there is no cure for NEC, prevention is the best strategy. Enhancing our understanding of intestinal epithelial cell (IEC) barrier regulation during early development will provide novel therapeutic targets to prevent NEC. Published evidence indicates roles for the RNA-binding protein insulin-like growth factor 2 mRNA binding protein 1 (IMP1) in intestinal development, barrier function, and intestinal repair. Sequencing data from the inflamed tissue of a NEC patient indicates that IMP1 is down-regulated relative to uninflamed tissue. Notably, roles for IMP1 in NEC are not defined. Emerging evidence suggests that mucus complexity, governed by enzymes such as Qsox1, impacts intestinal barrier function and inflammation susceptibility. This study aimed to define the role of IMP1 in NEC pathogenesis using a model of NEC-like intestinal injury in mice with IEC-specific Imp1 overexpression or Imp1 loss. Hypothesis: IMP1 expression is protective in a mouse model of NEC-like intestinal injury. Methods: All studies are OHSU IACUC-approved. This study used: wild-type (WT, control), Imp1 IEC-knockout ( VillinCre;Imp1 fl/fl ; Imp1 Δ IEC ), and Imp1 IEC-overexpression ( VillinCre;lslFLAG-Imp1 OE ; Imp1 IEC-OE ) mice. At post-natal day 4 mice of both sexes were randomly assigned to control or NEC groups. The control mice remained with the dam. NEC was induced with the well-established experimental NEC-like intestinal injury model. Mice were separated from the dam and maintained for 72 hours in an incubator. Pups were gavage-fed NEC formula (mixture of infant formula, puppy replacer, 1:10 dilution of bacteria derived from a premature infant with NEC, and 2.5 ug/g body weight of lipopolysaccharide) every 3 hours from 7am-10pm. Twice daily the pups were exposed to hypoxia (5% oxygen). After 72 hours, tissue was collected for histology, gene, and protein expression analyses. Survival was assessed with Kaplan-Meier curves. Total RNA sequencing was performed using the NovaSeq S4. The mucus and tissue barrier were evaluated by immunofluorescence staining for mucin 2, mucus lectins, occludin, and E-cadherin. Statistical analyses were performed using 2-way ANOVA with Tukey’s test for multiple comparisons and the Mantel-Cox log-rank test for survival analysis. Results: The NEC model induces pneumatosis, histological damage, and a significant up-regulation of inflammatory cytokine gene expression Lcn2 and Il1 b in all three genotypes, p &lt;0.05, n=5-15. Despite damage, Imp1 IEC-OE mice survive 2-times better than WT or Imp1 Δ IEC mice (survival for WT: 27.8%, n=36; Imp1 Δ IEC : 31.6%, n=19; Imp1 IEC-OE : 60%, n=10 mice, p&lt;0.05). RNA-sequencing data indicates that Imp1 IEC-OE mice significantly up-regulate expression of the disulfide catalyst Qsox1 (In NEC: WT: 1077 ± 94.6, Imp1 Δ IEC : 1017 ± 12.75, Imp1 IEC-OE : 1446 ± 45.73, p=0.003 vs WT and p=0.002 vs Imp1 Δ IEC ). Conclusion: Our data suggest that Imp1 expression enhances survival in a mouse model of NEC and promotes expression of a disulfide catalyst Qsox1, which may promote mucus maturation and protect the neonatal small intestine. NIH K01DK129401, R01HD097367, the Gerber Foundation, the OHSU Knight Cancer Institute This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.

Glomeruli number and glomerular volume are indicators of kidney health and chronic kidney disease (CKD) progression. Low nephron number is predictive of the development of CKD, and increased glomerular volume is associated with hyperfiltration and hypertension. Accurate estimates of glomeruli number are necessary for relating whole body GFR to single nephron GFR (SNGFR) which is an important parameter for mathematical modeling of transport along the nephron. In addition, previous studies had observed larger volumes and greater SNGFR in juxtamedullary glomeruli compared to cortical glomeruli. To enable routine estimation of cortical glomerular density and the size of cortical and juxtamedullary glomeruli, we optimized a cost- and time-effective method for labeling and imaging glomeruli in mouse models. Mice were injected with Alexa fluor 647 conjugated wheat germ agglutinin (WGA-647; 0.5 mg) intracardially. After 4 minutes circulation time, kidneys were perfusion fixed and harvested. Kidneys were sectioned at the midline at 600 µm up to 999 µm and cleared with ethyl cinnamate. Cross sections were imaged on Leica Sp8 with either 10x or 25x objective and 15 µm z-step size. This method enabled visualization of perfused glomerular capillaries and kidney vasculature. The cortical region was identified based on autofluorescence (488 nm laser). Individual glomeruli were identified and counted by automated 3D segmentation in Python. The diameters of individual glomeruli were measured in higher magnification images using Leica LAS X software. Juxtamedullary glomeruli were identified as those within the inner third of the cortex, nearest the medulla. On average, juxtamedullary glomeruli had larger diameters compared to cortical glomeruli. However, the extent of WGA-647 perfusion within individual glomeruli varied along the interlobular vessels. Including heparin (500 U/L) in the WGA-647 injection resulted in better filling or perfusion of glomeruli, especially in the superficial cortex, and as a result the estimated average glomerular diameter increased. In future, this methodology will be applied to compare cortical glomerular density and average glomerular volume in male and female mice and in genetic kidney disease models. National Institutes of Health T32 DK007052, R01 DK125049, U54 DK137329 This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.

Introduction: Skeletal muscle regeneration is an energy-demanding process that relies on mitochondria to generate ATP. While healthy skeletal muscle fibers have organized interfibrillar mitochondrial networks organizing architecture segregated into columns along the Z-line of the myofiber, regenerating fibers exhibits altered mitochondrial networks that span several sarcomeres. Despite links between muscle regeneration and altered mitochondrial dynamics and biogenesis, the role of specific cells in remodeling these networks remains unclear. Because muscle stem cells (MuSCs) play a critical role in muscle regeneration, we explored the relationship between MuSCs and mitochondria in regenerating muscle fibers. Methods: To induce muscle regeneration, we used the hindlimb ischemia mouse model of peripheral artery disease (PAD) and the mdx mouse model of Duchenne’s muscular dystrophy (DMD). Furthermore, transgenic reporter mice such as Pax7-tdTomato, H2B-EGFP, and mitoDendra2 were used to mark MuSCs, track nuclei, and label mitochondria, respectively. Fluorescently labeled MuSCs were also transplanted into BaCl 2 -injured muscle to elucidate their behavior and interactions throughout muscle regeneration. Immunofluorescence, single fiber staining, and biochemical assays from harvested muscles were performed for data analysis. Results: Following injury, a significant increase in the number of endogenous MuSCs was observed 7 days post-injury compared to contralateral control, while a dramatic increase in the fusion of MuSCs into myofibers was noted at days 14 and 28. Interestingly, all fused myofibers at days 14 and 28 displayed central nucleation, a hallmark of regeneration that fusion of the MuSC is critical for myofiber regeneration. Primary MuSCs from H2B-EGFP reporter mice were isolated and transplanted into the injured muscle to determine the origin of the centrally located myonuclei. In myofibers where the transplanted MuSCs had fused, centrally located myonuclei were GFP + , indicating their origin from MuSCs. Surprisingly, regenerating muscle fibers isolated from the mitoDendra2 mouse model exhibited high densities of mitochondrial content near the centrally located myonuclei. To evaluate whether MuSCs contribute to producing these central myonuclei near mitochondria, primary MuSCs isolated from mitoDendra2 reporter mice were transplanted into mdx mice. Fused myofibers indeed exhibited high Dendra2 + mitochondrial density between central nuclei along with a restoration of the mitochondrial network. Finally, we also observed a change in myogenic potential and mitochondrial respiration after transplanting MuSCs that have been preconditioned to enhance mitochondrial biogenesis. SIGNIFICANCE RELEVANCE: Overall, these data indicate that MuSC-derived myonuclei synthesize new mitochondria to generate the bioenergetics for myofiber regeneration after muscle injury. This relationship between MuSCs and myofiber mitochondria provides a basis for MuSC-derived mitochondrial transplantation as a therapeutic approach for muscular diseases associated with mitochondrial dysfunction. Acknowledgements: This work was supported by the NIH R01AR080169, R01AG072309, VA Merit Award I02RX005009 (to YCJ) This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.

objective: WDR77, a component of 20S PRMT5 containing a methyltransferase complex, can modify certain arginines in several splicosome Sm proteins and histones to dimethylarginine, which may play a role in transcriptional regulation. Studies have shown that the expression level of WDR77 plays a role in many systemic cancers such as non-small cell lung cancer, prostate cancer and ovarian cancer, and is positively correlated with poor prognosis of most cancers. However, WDR77 has not been studied in detail in glioma, and its biological significance in glioma has not been fully clarified. This study focused on glioma and explored the characterization and prognostic value of WDR77 in glioma, aiming to explore the role of WDR77 in glioma and its feasibility as a potential prognostic factor, so as to guide the clinical treatment of glioma in order to improve the prognosis of patients. Methods: In this study, the role of WDR77 in glioma and its feasibility as a potential prognostic factor were studied by bioinformatics analysis. In this study, transcriptome gene expression profiles and clinical data of 1018 glioma patients were collected from the Chinese glioma Genome Atlas Database (CGGA). The target gene WDR77 was selected from the candidate genes after four-layer analysis filtering (including survival analysis filtering, independent prognostic analysis filtering, ROC curve filtering and clinical correlation analysis filtering). Differential expression analysis, survival analysis, independent prognosis analysis, ROC curve analysis and clinical correlation analysis of the target gene WDR77 were performed to explore the feasibility of WDR77 as a potential prognostic factor for glioma. Then, immunoinfiltration analysis, co-expression analysis and GSEA analysis of the target gene WDR77 were performed to explore the role and mechanism of WDR77 in glioma. Results: WDR77 is significantly overexpressed in gliomas, which is associated with poor prognosis in gliomas (including GBM and LGG), and leads to shorter overall survival in LGG patients (HR =2.8, P =8.9 e-08). WDR77 was an independent prognostic factor for glioma (HR=2.110; 95%CI=1.700 – 2.618; P &lt;0.001), WDR77 had good prognostic accuracy (AUC values for 1-year, 3-year, and 5-year overall survival were 0.710, 0.761, and 0.799, respectively). WDR77 was positively correlated with regulatory pathways such as regulatory T cell differentiation and macrophage differentiation, and with immune cell infiltration such as CD4 + T cells (r=0.523, P =8.78e-35) and macrophages (r=0.509, P =1.36e-32). Conclusion: WDR77 is a novel molecular marker that can be used as an independent prognostic factor for human glioma, and the high expression of WDR77 suggests a poor prognosis for glioma. WDR77 may be a potential immunotherapeutic target for human glioma, and WDR77 affects the occurrence and development of glioma through multiple molecular pathways. National Clinical Key Specialty Project Foundation ; Shanxi Scholarship Council of China;Lvliang City high-level scientific and technological talents development project This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.

The Special Master’s Program at Georgetown University Medical Center (GUMC SMP) is a one year academic enhancement MS program that prepares students for future success in medical school. Its curriculum covers about half of the material in the first year basic science curriculum of Georgetown’s School of Medicine, supplemented with complementary graduate courses. GUMC SMP students attend the relevant basic science lectures with first year medical students (M1), are assessed by completing the same multiple choice questions used for their M1 counterparts and are graded against the M1 average to determine grades for corresponding SMP medical courses. In 2015, a second campus, the Georgetown Downtown SMP (GTDT), was opened that follows the same curriculum, but with all material delivered in a fully “flipped” manner. The GTDT students' average undergraduate GPA and MCAT scores are not different from the GUMC SMP students, whereas the average GPAs of SMP students are significantly lower than GPAs of their M1 peers (3.2 vs 3.7 in M1 class). The GTDT students review the lecture capture (LC) recordings of medical (or graduate) lectures on their own time and attend 2-4 hrs of class time four days per week during which the GTDT instructor provides active learning sessions to reinforce the material. The current research expands on our earlier findings, by evaluating the GTDT cohort performance in six medical physiology exams and three medical gross anatomy (GA) exams over the past five years compared to GUMC SMP peers and M1 students. Using the Student’s t test with the Bonferroni correction for multiple comparisons, significance level was designated at p&lt;0.05. Our results indicate that the GTDT students continued to outperform their GUMC SMP counterparts in all exams, reaching statistical significance in three out of six medical physiology exams and three out of three medical GA exams. The GTDT students also had higher average scores than their peer M1 students on five out of six medical physiology exams, reaching significance in three out of the six M1 exams. GTDT averages were higher than M1 students on GA exams, but differences did not reach statistical significance. The higher GTDT performance is most likely attributable to the students being actively engaged in flipped learning in all classroom sessions. Additionally, GTDT students’ responses to anonymous polling showed that they felt the active learning exercises were beneficial to their overall learning and their long-term retention of the material. Overall, our results continue to validate the successful use of the active learning environment in medical education, confirm its successful use in the GTDT program, and suggest that the flipped learning modality results in overall better learning outcomes in a rigorous medical curriculum. Georgetown University This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.