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ToxB greatly reduces recognizable actin cables and actin patches. Untreated biological cells contain concentrated cortical structures, especially in buds, whereas treated biological cells show only weak diffuse staining even at ten times the exposure. The disappearance concerns actin filament organization and detectable F-actin, not necessarily destruction of the actin protein itself. actin monomer sequestration could leave substantial total actin present while eliminating most visible polymer.

Loss of actin cables should impair directed secretory-vesicle delivery and polarized cell growth; loss of actin patches should impair actin-dependent endocytosis. Disruption of the actomyosin machinery can also compromise cytokinesis. The rounded, poorly polarized appearance is consistent with these effects, but the images do not independently measure secretion, division rate or viability. A vehicle control and equal-exposure images are needed for quantitative fluorescence comparison; a longer exposure is useful for finding residual structures but prevents direct comparison of the displayed brightnesses.

The detectable cytoskeleton effect is substantially reversible after washout. Depolarized actin patches reappear first, reaching roughly 85% of biological cells near 20 minutes. Polarized actin patches subsequently increase to about 80%, while detectable actin cables recover later, reaching roughly 70–75% by the end of the time course. This argues against irreversible destruction of all cellular capacity to assemble actin.

Recovery is not instantaneous, and the population measurements do not prove that every previously treated biological cell recovers. Nor do they distinguish reuse of the existing actin pool from a contribution of new protein synthesis. A time-matched vehicle culture and a continuously treated culture would separate washout-dependent recovery from changes caused by handling or time alone. Reversibility of visible structures also does not by itself establish recovery of every physiological function.

Both structures turn over rapidly, with visible actin cables disappearing faster than actin patches under these conditions. Cable-positive biological cells fall from about 80% to essentially none within roughly two minutes. Polarized actin patches disappear over several minutes, while a transient depolarized-patch population persists before nearly all actin patches are lost by the end of the treatment time course.

Because ToxB binds actin monomers rather than existing actin filaments, a straightforward explanation is continuing normal disassembly without adequate replacement from assembly-competent actin monomers. The disappearance therefore reveals dynamic maintenance of structures that can look static in a fixed image. It does not show that the drug directly severs actin cables. Percentages of biological cells above a visibility threshold are not exponential decay curves for the lifetimes of individual actin filaments: cable thickness, staining sensitivity, actin monomer access and secondary loss of polarity can all affect the apparent timing. An analogous monomer-sequestering inhibitor established rapid yeast actin turnover in the classical study by Kathryn R. Ayscough and colleagues.^[ref]

actin patches can re-form, and can become polarized, before detectable actin cables return. Depolarized actin patches are abundant around 20 minutes after washout, when the cable curve remains essentially zero. By roughly 40 minutes many biological cells already have polarized actin patches, still with almost no visible actin cables. Thus a strict requirement for an already established visible cable network in patch assembly or initial patch polarization is inconsistent with these population data.

The converse is not demonstrated: actin cables recover only after actin patches have returned, so this experiment cannot establish that actin cables assemble independently of actin patches. It also cannot exclude sparse or very short actin filaments below the cable-detection threshold. The percentages do not follow the same individual biological cells, and temporal order alone does not prove a direct molecular dependence. The strongest conclusion is the one-way independence actually resolved by the graph, rather than complete mutual independence.

actin patches initially return in a depolarized distribution and then become concentrated at a growth pole. The depolarized fraction peaks near 20 minutes and subsequently falls as the polarized fraction rises. Patch assembly therefore recovers before normal spatial organization is restored.

A plausible cellular interpretation is recovery from disrupted trafficking and growth polarity, followed by establishment of a bud-associated growth site and renewed polarized secretion and endocytosis. Continued cell-cycle progression can also redistribute actin patches as biological cells grow and prepare to divide. The graph alone does not show that all biological cells pass synchronously through one particular cell-cycle stage, or that the recovered pole is the same pole used before treatment. Time-lapse imaging of the same biological cells and a bud or cell-cycle marker would distinguish restoration of an old site from selection of a new one.