Aging Influences The Modulation Of Reflex Cutaneous Vasodilation During Passive Whole-body Heating
Bibliographic record
Abstract
Reflex cutaneous vasodilation during whole-body heating is attenuated in healthy older adults compared to their younger counterparts. This is partly due to reduced nitric oxide (NO) bioavailability at the cutaneous end-organ level. While oxidative stress can reduce NO bioavailability in human skin, the particular reactive oxygen species (ROS) sources responsible for reflex cutaneous vasodilation modulation in older adults remain unclear. PURPOSE: To determine the potential roles of NADPH oxidase, xanthine oxidase, and superoxide anions in modulating reflex cutaneous vasodilation during passive heating in young and older adults. METHODS: Cutaneous vascular conductance (CVC), normalized to maximum vasodilation (%CVCmax), was assessed in 10 young (n = 5 females; mean [SD]: 22 [4] years) and 8 older adults (n = 4 females; 64 [5] years) at 5 dorsal forearm sites treated with 1) Ringer’s solution (control), 2) 10 mM ascorbate (non-specific antioxidant), 3) 10 μM tempol (superoxide dismutase mimetic), 4) 100 μM apocynin (NADPH oxidase inhibitor), or 5) 10 μM allopurinol (xanthine oxidase inhibitor), via intradermal microdialysis. Local skin sites were set to 34 °C, with rectal temperature of ~37.0 °C throughout 90 min of rest. Participants were then immersed in a warm water bath ~40 °C to clamp rectal temperature at ~38.5 °C for 60 min. RESULTS: For young adults there was only a significant main effect of heating (p < 0.001) such that %CVCmax was elevated above baseline after 60 min of heating for both young and older adults (p < 0.001). As with older, there was a significant heating by treatment site interaction (p = 0.044). Further, cutaneous vasodilator responses at ascorbate (+8%CVCmax [2,15], p = 0.011), apocynin (+8%CVCmax [1,15], p = 0.016), and allopurinol (+9%CVCmax [2,16], p = 0.007) treated sites were elevated from control after 60 min of heating, but not for tempol (+5%CVCmax [2,12], p = 0.212). CONCLUSION: ROS other than superoxide derived from NADPH oxidase, xanthine oxidase, and potentially other ascorbate-sensitive sources, attenuate reflex cutaneous vasodilation in healthy older adults, but not young adults. These findings shed new light on the specific ROS pathways that modulate age-related cutaneous microvascular function. FUNDING: Natural Sciences and Engineering Research Council of Canada
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".