Alterations in pyrimidine nucleotide metabolism as an early signal during the execution of programmed cell death in tobacco BY-2 cells
Bibliographic record
Abstract
Changes in pyrimidine metabolism were investigated during programmed cell death (PCD) of tobacco BY-2 cells, induced by a simultaneous increase in the endogenous levels of nitric oxide (NO) and hydrogen peroxide. The de novo synthesis of pyrimidine nucleotides was estimated by following the metabolic fate of the (14)C-labelled orotic acid, whereas the rates of salvage and degradation pathways were studied by measuring the respective incorporation of (14)C-labelled uridine and uracil under different treatments. Nucleic acid metabolism was also examined using labelled thymidine as a marker. The results show that specific alterations in the balance of pyrimidine nucleotide synthesis, which include a decreased rate of salvage activity of uracil and uridine and increased salvage activity of thymidine, represent a metabolic switch that establishes proper cellular conditions for the induction of PCD. In particular, a reduction in the utilization of uracil for salvage products occurs very early during PCD, before the appearance of typical cytological features of the death programme, thus representing an early metabolic marker for PCD. These changes are strictly associated with PCD, since they do not occur if NO or hydrogen peroxide are increased individually, or if actinomycin, which inhibits the death programme, is added into the medium in the presence of NO and hydrogen peroxide. The possible roles of these fluctuations in pyrimidine metabolism on the cellular nucleotide pool are discussed in relation to the induction of cell death.
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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) | 0.000 | 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".