SARCOPLASMIC RETICULUM CA2+-UPTAKE AND CA2+-RELEASE ARE DEPRESSED FOLLOWING 90 MINUTES OF PROLONGED EXERCISE DURING NORMOXIA BUT NOT HYPOXIA.
Bibliographic record
Abstract
Exercise in hypoxia as compared to normoxia is known to reduce exercise tolerance. PURPOSE: In this study, we have attempted to determine the role of the sarcoplasmic reticulum (SR) in muscle function during prolonged exercise. METHODS: To examine the effect of hypoxia (14% O2) (H) on SR function during prolonged cycling, 7 male subjects cycled at a work rate corresponding to 50% VO2 peak in normoxia (21% O2) (N), for 90 min during N and H on different days. Oxalate supported Ca2+-uptake and SR Ca2+-release (20 mM 4-chloro-m-cresol) measurements were made using Indo-1, in vitro, from tissue extracted from the vastus lateralis. RESULTS: Exercise oxygen consumption was not altered (P > 0.05) between conditions during N compared with H (1447 ± 171, 1492 ± 191 ml O2-min−1). SR Ca2+-uptake (μmoles-g protein−1-min−1, X ± S.E.) was depressed (P < 0.05) following 90 min of cycling in N (385 ± 47) compared to rest (487 ± 74). However, SR Ca2+-uptake was not altered during H following 90 min of exercise H (463 ± 77 vs 422 ± 71). The early, rapid rate (Phase 1) of Ca2+-release (μmoles-g protein−1-min−1) was not altered by exercise (P < 0.05) or condition (P < 0.05) (Rest, 90 min; N: 1943 ± 200, 1969 ± 202; or H: 1909 ± 287, 2256 ± 300). An effect of exercise was observed following 90 min of cycling in the slower, more prolonged rate (Phase 2) of Ca2+-release (μmoles-g protein−1-min−1) in N (Rest, 90 min; 971 ± 134, 682 ± 95) but not H (981 ± 171, 810 ± 173). CONCLUSION: It is concluded that prolonged exercise results in structural alterations to the SR which act to depress SR Ca2+-uptake and SR Ca2+-release (Phase 2), measured in vitro, during N but not H. Supported by NSERC (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".