Progression of programmed cell death in tobacco BY‐2 cells is delineated by specific changes in de novo and salvage synthesis of purine nucleotides
Bibliographic record
Abstract
Alterations in the pattern of purine nucleotide synthesis and degradation 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 purine nucleotides was estimated by following the metabolic fate of the [8‐14C]5‐aminoimidazole‐4‐carboxamide‐1‐β‐d‐ribofuranoside (AICAR), the salvage synthesis was investigated using [8‐14C]adenine and adenosine, and the degradation pathway was studied by following the incorporation of [8‐14C]inosine. The results indicated that specific changes in purine metabolism occurred during the death programme of tobacco cells. During the early phases of PCD, increases in the salvage activity of adenine and adenosine were observed, and these were related to the high activity of the two major salvage enzymes: adenine phosphoribosyltransferase (APRT) and adenosine kinase (ARK). During the following stages, a large fraction of purine nucleotide was also produced through the de novo pathway, suggesting a tight regulation between salvage and de novo synthesis. These changes were strictly associated with PCD, as they did not occur if NO or hydrogen peroxide was increased individually, or if actinomycin, which inhibits the death programme, was added to the medium in the presence of NO and hydrogen peroxide. These changes in purine nucleotide synthesis represent an early metabolic switch which may be needed to ensure the proper execution of all the high‐energy demand processes characteristic of the death programme.
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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".