The use of Silver-stained “Comets” to Visualize DNA Damage and Repair in Normal and Xeroderma pigmentosum Fibroblasts After Exposure to Simulated Solar Radiation
Bibliographic record
Abstract
The alkaline and neutral comet assays have been widely used to assess DNA damage and repair in individual cells after in vivo or in vitro exposure to chemical or physical genotoxins. Cells processed under neutral conditions generate comets primarily from DNA double strand breaks, whereas under alkaline conditions, comets arise from DNA single and double strand breaks and alkali-labile lesions. A modified version of the alkaline comet assay, as described here, used silver stain to visualize the comets and a Gelbond base to facilitate the manipulation and processing of samples. To demonstrate how these modifications improve the assay, fibroblasts derived from both normal and Xeroderma pigmentosum (Xp) individuals were exposed to simulated solar radiation and the resulting DNA damage and repair evaluated and compared with results from the relevant literature. Comets from normal fibroblasts reached their maximum length at about an hour after irradiation. Dose-dependent increases in comet length were observed up to at least 360 mJ/cm2. In contrast, comet lengths from repair deficient Xp fibroblasts were shorter than normal cells reflecting their reduced capacity to generate single strand breaks by the excision of DNA dimers. For incubation times of more than 1 h, comet lengths from normal fibroblasts underwent a time-dependent decrease, supporting the contention that this change was related to the ligation step in the DNA repair process. These changes were compatible with the model of DNA damage and repair established by others for ultraviolet radiation.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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 teacher head, 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".