Effect of acute sympathetic nervous system activation on flow-mediated dilation of brachial artery
Bibliographic record
Abstract
We tested the hypothesis that flow-mediated dilation (FMD) of the brachial artery would be impaired by acute increases in sympathetic nervous system activity (SNA) in models where similar peak shear stress stimulus was achieved by varying the duration of forearm muscle ischemia. Eleven healthy young men were studied under four different conditions, each with its own control: lower body suction (LBS), cold pressor test (CPT), mental arithmetic task (MAT), and activation of muscle chemoreflex (MCR). The duration of ischemia before observation of FMD by ultrasound imaging was 5 min each for control, LBS, and CPT; 3 min for MAT; and 2-min for MCR. Peak shear rate was not different between control and any of the SNA conditions, although total shear in the first minute was reduced in MAT. MCR was the only condition in which brachial artery vasoconstriction was observed before forearm occlusion [4.38 (SD 0.53) vs. control 4.60 (SD 0.53) mm, P < 0.05]; however, diameter increased to the same absolute value as that of the control, so the percent FMD was greater for MCR [9.85 (SD 2.33) vs. control 5.29 (SD 1.50)%]. Blunting of the FMD response occurred only in the CPT model [1.51 (SD 1.20)%]. During SNA, the increase in plasma cortisol from baseline was significant only for MCR; the increase in plasma norepinephrine was significant for MCR, LBS, and CPT; and the increase in epinephrine was significant only for MCR. These results showed that the four models employed to achieve increases in SNA had different effects on baseline brachial artery diameter and that blunted FMD is not a general response to increased SNA.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 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 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 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".