Experimental Physiology最新文献

Optical coherence tomography (OCT) enables visualization and quantification of the cutaneous microvasculature, yet no study has compared responses to distinct forms of heating in humans. We hypothesized that local skin heating (LH) would evoke larger responses in microvascular diameter, velocity, flow and density than passive whole-body heating (PH) or heated exercise (HE), and that HE responses would exceed PH. Twelve healthy young adults completed four interventions: baseline (33°C; BL), LH, PH (seated) and HE (ergometer cycling) in a climatic chamber (50 min, 40°C, 50% relative humidity). OCT was used to quantify microvascular variables immediately after each intervention. Microvascular responses differed across conditions (P < 0.001). LH induced the largest responses in all OCT indices (all P < 0.001): diameter (67 µm), velocity (195 µm s^-1), flow (687 picolitres s^-1) and density (56.0%), compared with BL (42 µm, 106 µm s^-1,154 picolitres s^-1 and 26.6%, respectively), PH (45 µm, 99 µm s^-1, 165 picolitres s^-1 and 34.4%, respectively) and HE (49 µm, 105 µm s^-1, 208 picolitres s^-1 and 34.5%, respectively). Although the diameter response was higher after HE (P = 0.046), no differences were documented for PH and HE relative to 33°C BL for other OCT measures (all P > 0.05). Comparable responses were observed between PH and HE across all variables (all P > 0.05). Local heating elicited substantially greater increases in all OCT-derived microvascular metrics compared with PH and HE. Although both PH and HE activate the cutaneous microvasculature, neither stimulus approaches the magnitude of response achieved with local heating. These findings demonstrate that OCT provides quantifiable insights into the distinct ways in which the skin microvasculature responds to different heat exposures.

Elastin insufficiency is associated with structural differences in the large elastic arteries and cerebral artery dysfunction. However, previous studies have not assessed potential sex differences in cerebrovascular function. We measured cerebral blood flow (CBF) using arterial spin labeling MRI at rest and in response to hypercapnia challenge (cerebrovascular responsiveness, CR) in middle-aged and old elastin haploinsufficient (Eln^+/-) and wild-type (Eln^+/+) mice. We also assessed neuroinflammation by microglia and astrocyte cell counts. We found that Eln^+/- mice had a significantly lower resting CBF in the cerebral cortex compared with Eln^+/+ mice, with similar non-significant trends in the hippocampus and thalamus. In contrast, the Eln^+/- mice had an intact hypercapnic response, resulting in better CR compared with Eln^+/+ in hippocampus, with a similar trend in the cerebral cortex. Sex did not impact CBF or CR. We found that Eln^+/- mice had lower hippocampal volume compared with Eln^+/+ mice. Glia cell counts were highly dependent on brain region, with Eln^+/- mice having more microglia in the cerebral cortex, but fewer astrocytes in the hippocampus compared with Eln^+/+ mice. While sex also impacted glial cell counts, we found no interactions between sex and Eln genotype. Our results demonstrate that elastin haploinsufficiency results in lower resting CBF, but greater CR.

This study examined whether consuming a (poly)phenol-rich food before strenuous muscle-damaging exercise can modify post-exercise markers of inflammation and oxidative stress. Using a double-blinded, randomised, placebo-controlled, between-subjects design, 26 recreationally active males (n = 15) and females (n = 11) consumed higher-(poly)phenol (H-POL) foods (dates, dark chocolate, pomegranate; 285.1 mg/day) or lower-(poly)phenol foods (L-POL) (cereal bar, milk chocolate, sports drink; 88.3 mg/day) for 3 days before, and then 30 min before, strenuous exercise (100 drop jumps, 50 squat jumps). A range of blood markers associated with inflammation (total and differential leukocytes, interleukin (IL)-6, IL-10, IL-1β, IL-2, IL-4, IL-12, tumour necrosis factor-alpha (TNF-α), interferon-gamma (IFN-γ), monocyte chemoattractant protein-1 (MCP-1), granulocyte colony-stimulating factor), and oxidative stress (glutathione peroxidase (GPX), 4-hydroxynonenal (4-HNE), and urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG)) were quantified pre, immediately post, 1 and 2 h post-exercise. One hundred and nineteen plasma (poly)phenol metabolites were measured pre, immediately post and 1 h post-exercise. Total plasma (poly)phenol concentrations were greater in the H-POL vs. L-POL intervention, peaking 1 h post-exercise (H-POL: 239.5 ± 87.8 µM vs. L-POL 58.9 ± 33.8 µM; P < 0.001). There were interaction effects for IL-10 and TNF-α but no differences with post hoc tests. Urinary 8-OHdG excretion was higher in H-POL vs L-POL (condition effect; P < 0.001), whereas erythrocytes GPX activity was higher in the L-POL vs. H-POL (condition effect; P < 0.001). A (poly)phenol food intervention before exercise increased total plasma (poly)phenol concentrations but had limited and inconsistent effects on markers of inflammation and oxidative stress in the 2 h after strenuous exercise.

Human thermal perception involves complex and dynamic interactions between peripheral input and central neural regulation. However, the spatial and temporal characteristics of brain responses to different cold exposure scenarios remain poorly understood. In this study, we combined traditional analysis with AI-based anomaly detection to examine electroencephalographic (EEG) responses across five stages of cold exposure in 20 healthy participants, including baseline, cold exposure, wind stimulation, adaptation and recovery. Alpha-band power analysis revealed 14 EEG channels with significant stage-dependent differences, primarily located in the right hemisphere across frontal, central and parietal regions. Shapley additive explanations (SHAP)-based feature importance scores further validated stage-specific channels, identifying F8, T8 and CP6 for cold exposure, T7 for wind stimulation, T8 for adaptation, and F8 and CP6 for recovery. Time-frequency analysis revealed early spectral responses within 1 s for cold exposure and recovery, and within 2 s for wind stimulation, while AI anomaly detection estimated later latencies of 2.201∼2.735 s, highlighting the distinct sensitivities of each method. These results reveal right-lateralized, stage-specific brain activations, and demonstrate the complementary value of traditional and AI methods in decoding thermal responses.

Marathon open-water swimming presents extreme thermophysiological challenges, particularly in cold environments. This case report describes continuous core temperature data from a solo crossing of New Zealand's Foveaux Strait, an infamously cold (13°C -14°C), turbulent open-water swim. A 52-year-old male swimmer (body mass index, 27.9 kg m^-2; body fat, 18%) completed the 37 km swim in 9 h 52 min under standard marathon swimming rules (no wetsuit). Core temperature (measured via an ingestible thermometer pill) decreased rapidly after immersion, falling from 37.9°C to <35.0°C within 50 min. The swimmer reached a nadir of 33.88°C at 2 h 42 min and remained hypothermic for more than half of the swim (total, 369 min). Despite this, he displayed no overt cognitive or motor impairment, completed the swim unaided and did not experience an after-drop post-immersion. This case highlights the remarkable thermoregulatory tolerance of a cold-adapted endurance swimmer.

Although various medical devices are available for the purpose of heat therapy, their effect on muscle temperature remains unclear. This study compared the effects of a water-perfused suit (WPS), short-wave diathermy (SWD) and hot-water immersion (HWI) on muscle, core and skin temperatures, along with perceived thermal discomfort. Ten healthy volunteers (four males and six females) were exposed to WPS, SWD or HWI for 1 h on three occasions, separated by 3-7 days, in a counterbalanced order. Muscle temperature increased with all devices (P < 0.0001, partial η² = 0.55) but was lower after WPS in comparison to both SWD (P = 0.00656) and HWI (P = 0.00949). Core temperature was higher with HWI than with WPS (P ≤ 0.0104) and SWD (P ≤ 0.0213) from 20 min onwards. Although the average skin temperature over the thigh was lower with SWD than with HWI (P = 0.007, -1.2 [-2.0; -0.4]°C), the maximal local skin temperature was higher with SWD than with HWI (P = 0.0153, -0.7 [-1.4; -0.2]°C). Thermal discomfort was higher during HWI than during WPS (P ≤ 0.0159) and SWD (P ≤ 0.0130). In conclusion, only SWD and HWI increased muscle temperatures. SWD was able to increase local muscle temperatures comfortably, but the effects were localized. HWI can increase both peripheral and central temperatures easily, but the associated increases in core temperature might lead to hyperthermia-induced discomfort.

Long-duration spaceflight represents an extreme challenge, triggering adaptive responses including spaceflight-associated neuro-ocular syndrome, characterized by diminished visual acuity and ocular changes, which is a significant health risk for Mars missions. Concurrently, spacefarers experience brain adaptations, including ventricular expansion and CSF redistribution; however, the integrative physiological mechanisms linking these brain-eye responses remain unestablished. We applied automated morphometric analysis to investigate brain-eye relationships using high-resolution MRI data from terrestrial control subjects and spacefarers, conducting correlation analysis between third ventricle volume and ocular parameters. Analysis revealed significant baseline correlations between third ventricle volume and multiple ocular parameters in healthy control subjects, including globe dimensions, optic nerve sheath volume, optic nerve length and retro-orbital width. Following spaceflight, adaptations occurred: optic nerve sheath volume increased by 11.93 ± 6.07 mm³ (right) and 27.22 ± 8.74 mm³ (left), and optic nerves lengthened by 0.38 mm (right) and 0.47 mm (left). The baseline analysis showed that multiple orbital structures were correlated with third ventricle volume, whereas longitudinal change analysis revealed selective associations: only globe changes were correlated with third ventricle expansion. This study demonstrates structure-specific brain-eye relationships consistent with CSF-mediated coupling as a mechanism underlying spaceflight-associated neuro-ocular syndrome during the cranial microgravity response. Following spaceflight, third ventricle expansion is correlated selectively with globe changes, while dissociating from optic nerve sheath and retro-orbital adaptations, providing quantitative evidence that microgravity creates differential biomechanical effects across orbital compartments. This supports CSF compartmentalization and the limited intracranial volume expansion (cranial ceiling effect) as underlying mechanisms. The findings illuminate the limits of brain elastic tissue expansion during intracranial fluid accumulation in astronauts.

Altitude training enhances haematological adaptations and endurance at sea level, typically requiring exposure to ∼2500 m altitude for 3-4 weeks. Emerging evidence suggests that low-dose carbon monoxide (CO) inhalation might mimic hypoxia and might be used by elite athletes. In this study, we examine whether periodic low-dose CO exposure can replicate the live-high, train-low model in well-trained individuals, focusing primarily on haematological and performance effects of CO exposure, with haematological markers commonly used to interpret haemoglobin mass changes discussed as exploratory. Eight well-trained individuals (four males and four females) participated in a randomized crossover study. They completed two training blocks of 4 weeks at sea level: one with CO inhalation (INCO) to simulate live-high, train-low and one with ambient air as a control (AIR), separated by a 6 month washout. Haematological variables, in vivo muscle oxidative capacity and performance metrics were assessed before and after each intervention. After INCO, haemoglobin mass (p = 0.018; +53.6 ± 10.8 g. vs. +0.8 ± 11.8 g), red blood cell volume (p = 0.032; +156.6 ± 66.7 mL vs. -65.1 ± 50.7 mL) and blood volume (p = 0.036; +240.4 ± 120.5 mL vs. -208.3 ± 167.5 mL) increased significantly compared with AIR. INCO significantly reduced immature reticulocytes (p = 0.04), but muscle oxidative capacity and performance metrics remained unchanged. These findings suggest that daily low-dose CO exposure at sea level over 4 weeks enhanced haematological adaptations more than standard training but did not affect muscle oxidative capacity or performance.