Evidence that actin and myosin are involved in the poleward flux of tubulin in metaphase kinetochore microtubules of crane-fly spermatocytes
Bibliographic record
Abstract
We studied the effects of various drugs on the poleward flux of tubulin in kinetochore microtubules in metaphase-I crane-fly spermatocytes. We used as a measure of tubulin flux a 'gap' in acetylation of kinetochore microtubules immediately poleward from the kinetochore; the 'gap' is caused by a time lag between incorporation of new tubulin subunits at the kinetochore and subsequent acetylation of those subunits as they flux to the pole. We confirmed that the 'gap' is due to flux by showing that the 'gap' disappeared when cells were treated briefly with the anti-tubulin drug nocodazole, which decreases microtubule dynamics. The 'gap' disappeared when cells were treated for 10 minutes with anti-actin drugs (cytochalasin D, latrunculin B, swinholide A), or with the anti-myosin drug 2,3-butanedione 2-monoxime. The 'gap' did not disappear when cells were treated with the actin stabilizing drug jasplakinolide. We studied whether these drugs altered spindle actin. We used fluorescent phalloidin to visualize spermatocyte F-actin, which was associated with kinetochore spindle fibers as well as the cell cortex, the contractile ring and finger-like protrusions at the poles. Spindle F-actin was no longer seen after cells were treated with cytochalasin D, swinholide A or a high concentration of latrunculin B, whereas a low concentration of latrunculin B, which did not completely remove the 'gap', caused reduced staining of spindle actin. Neither 2,3-butanedione 2-monoxime nor jasplakinolide altered spindle actin. These data suggest that an actomyosin mechanism drives the metaphase poleward tubulin flux.
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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) | 0.001 | 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".