Important discoveries and demonstrations in the Burton and Taylor Paper:1) That wrinkle length is linearly proportional to the strength of force exerted. (Which significantly improves the usefulness of the technique, even more than...
2) the increased sensitivity and...
3) greater consistency produced by UV irradiation, combined with benzene side chains, instead of all methyl side chains. (Because benzene absorbs UV light, but methyl groups don't.
4) Comparison of distances of particle displacement along the axis of a force(On the order of three micrometers) in contrast to the length of compression wrinkles(on the order of twenty micrometers) demonstrates an approximately seven fold
greater resolving power of the rubber wrinkling technique, as compared with gel displacement methods (That are sold under the name of "Traction Force Microscopy" TFM, that are sold by a company in Boston, which has a patent on that method, although it was invented by someone else. (Invented in 1970, ten years before publication of the rubber wrinkling method, 1980).
5) The same forces exerted on the inside surface of the plasma membrane are also exerted on rubber surfaces in contact with the outer surface of the plasma membrane. (This need not have been true, is somewhat surprising, and one should consider the possibility of the following:
6) There could easily be variations in this transmission of forces through the plasma membrane. For example, lack of force transmitted in one area would be mistaken for lack of force exerted inside the cell. Thus spatial and time differences in rubber distortion could be misinterpreted as localized differences and changes in force exertion, which might either remain constant or vary in some other pattern or sequence. This is not considered.
Also not considered by Burton and Taylor:
7) By what mechanism do actin and myosin get displaced to the furrow site? They don't notice that the pattern of wrinkles in the cover photograph indicates that these are compression wrinkles (of shearing forces exerted toward the furrow location) rather than tension wrinkles caused by constriction of the furrow itself.
7 1/2) Their results can (and, I think, should) be regarded as proving the rather unpopular theory that the means by which actin fibers accumulate and align at the furrow site is by actin (already assembled into fibers in the cell cortex) being pulled by the force of its own contractility, toward the equator.
7 2/3) Most researchers on this subject reject that theory and believe that the contractile ring is formed by localized self assembly (polymerization) of actin and myosin.
8) Although the directions of the forces exerted are a key variable, this paper does not discuss or explain how the actin in the equator is caused to contract much more strongly (at least twenty times as strong) in the circumferential direction as compared with very weak contraction transversely across the width of the cleavage furrow.
9) Surface curvatures are not discussed, although the ratio of curvatures (in the circumferential axis as compared with the longitudinal axis) is about one to twenty, and this ratio determines how anisotropic the contractility needs to be.
10) All published versions of the equatorial stimulation theory postulate that this induced strengthening (that is focused on the middle areas of the cells) also spreads to the polar areas of the cell surface. Indeed, the stimulatory signal is postulated to be emitted by the poles of the mitotic spindle. The stimulation is supposed to overlap at the equator, where the furrow will form. Therefore, one should be surprised to find evidence of no contractility near the poles. But that is what Burton and Taylor observed. I think they should have commented on this paradox.
[Please understand that Nature editors rewrite much of what you submit, and especially that they remove any parts that they consider unnecessary. Furthermore, when you are writing for Nature, you need to reduce what you say to the smallest possible word count. In High School, it seemed difficult to write an assigned thousand word essay. When writing scientific papers, the difficulty is to reduce your deathless prose to no more than 1,500 words, with a 200 word introduction, or to 3,000 words etc. I have spent many days counting words, and editing manuscripts down exactly a journal's maxima. Thus, Burton and Taylor had to edit out many complexities of which they were perfectly aware, and others were removed by editors and referees. I was not one of the two referees on this paper, but I should have been.]