Altered Ribonucleotide Reductase Activity inDrug-Resistant Mammalian Cells Detected by an AssayProcedure for Intact Cells
Bibliographic record
Abstract
Hydroxyurea, an antitumor drug which specifically inhibits ribonucleotide reductase, has been used as a selective agent to obtain single-step and double-step drug-resistant cell lines altered in reductase activity. Using an assay procedure developed for analyzing enzyme activity in intact cells a variety of novel changes in the properties of the enzyme activity was detected in the drug-resistant lines. Differences in cellular levels of enzyme activity, changes involving pyrimidine and purine substrate Km values, and altered enzyme sensitivity to hydroxyurea were found using the in vivo assay procedure. These changes could account for the drug-resistant phenotypes. The assay technique which is described in this report is easy to perform, can accurately determine enzyme activity in as few as 5 X 10(6) cells grown conveniently on the surface of a single tissue culture plate, and is a valuable quick screening method for identifying cells altered in different aspects of ribonucleotide reductase activity.
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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) | 0.001 | 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 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.001 |
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".