Calcium spark properties in ventricular myocytes are altered in aged mice
Bibliographic record
Abstract
This study determined whether whole cell Ca(2+) transients and unitary sarcoplasmic reticulum (SR) Ca(2+) release events are constant throughout adult life or whether Ca(2+) release is altered in aging ventricular myocytes. Myocytes were isolated from young adult (approximately 5 mo old) and aged (approximately 24 mo old) mice. Spontaneous Ca(2+) sparks and Ca(2+) transients initiated by field stimulation were detected with fluo-4. All experiments were conducted at 37 degrees C. Ca(2+) transient amplitudes were reduced, and Ca(2+) transient rise times were abbreviated in aged cells stimulated at 8 Hz compared with young adult myocytes. Furthermore, the incidence and frequency of spontaneous Ca(2+) sparks were markedly higher in aged myocytes compared with young adult cells. Spark amplitudes and spatial widths were similar in young adult and aged myocytes. However, spark half-rise times and half-decay times were abbreviated in aged cells compared with younger cells. Resting cytosolic Ca(2+) levels and SR Ca(2+) stores were assessed by rapid application of caffeine in fura-2-loaded cells. Neither resting Ca(2+) levels nor SR Ca(2+) content differed between young adult and aged cells. Thus increased spark frequency in aging cells was not attributable to increased SR Ca(2+) stores. Furthermore, the decrease in Ca(2+) transient amplitude was not due to a decrease in SR Ca(2+) load. These results demonstrate that alterations in fundamental SR Ca(2+) release units occur in aging ventricular myocytes and raise the possibility that alterations in Ca(2+) release may reflect age-related changes in fundamental release events rather than changes in SR Ca(2+) stores and diastolic Ca(2+) levels.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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".