Elastic tethers remain functional during anaphase arrest in partially-lysed crane-fly spermatocytes: a possible approach for studying mitotic tethers
Bibliographic record
Abstract
ABSTRACT Mitotic tethers connect partner telomeres of all segregating anaphase chromosomes in all animal cells that have been tested, as detected by laser-cutting chromosome arms during anaphase and seeing that the arm fragments move rapidly across the equator to their partner chromosome moving to the opposite pole, telomere moving towards telomere. Tethers exert anti-poleward forces on the poleward separating telomeres, but tether elasticity (that produces the backwards forces) diminishes during anaphase: as determined by the behavior of arm fragments; short tethers (early anaphase) are elastic, long tethers (late anaphase) are not elastic, and medium-length tethers transition between the two states. We developed a procedure in which the tethers still functioned after we partially-lysed anaphase crane-fly spermatocytes. The partial lysis consistently arrested chromosome movements, after which the tethers moved the chromosomes backwards, potentially allowing the elastic tethers to be studied biochemically. To ensure that tether function was not altered by the partial cell-lysis procedure, we compared backward chromosome movements in partially-lysed cells with arm fragment movements in control cells. In the partially-lysed cells the backward chromosomal movements had characteristics identical to those of arm fragments in non-lysed (control) cells. In particular, in both control and partially-lysed cells shorter tethers caused backward movements more often than did longer tethers; shorter tethers caused backward movements over greater fractional distances (of the tether) than did longer tethers; and velocities of the backwards movements were the same for tethers of different lengths. We also compared the effects of Calyculin A (an inhibitor of Protein Phosphatase1) in control versus in partially-lysed cells. Calyculin A (CalA) added to control cells in early anaphase blocks dephosphorylation, thereby maintaining tether elasticity throughout anaphase: after the chromosomes reach the poles they move backwards when the usual poleward forces are reduced. Partial lysis preserves this tether functionality: after partial lysis of CalA-treated cells the chromosomes move backward and reach the partner telomeres at even very long tether lengths. We conclude that partial cell-lysis arrests anaphase chromosome poleward movement but does not affect tether function.
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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".