72 Colchicine 



A fully formed nietajihasic spindle was reduced by weaker concen- 

 trations than those necessary for anaphase. Specific concentrations 

 applied to the fully formed metaphasic spindle led directly to a star 

 metaphase (cf. Chapter 2) . These stars formed by treated metaphases 

 persisted for five or six hours. Dining this time the Brownian move- 

 ment shown by the mitochondria was actively increasing. While 

 the activity of the protoplasmic material was increasing, the meta- 

 phasic spindle fibers were being reduced. 



With finther reduction of concentrations and with application to 

 metaphase, no obvious reduction of the spindle was obtained. This 

 concentration (2.5 X 1^^"" ^^) l^'^^' 'i'> effect on anaphase, but produced 

 a slight retardation of the spindle at metaphase. Yet this same con- 

 centration applied to earlier stages, the prophase, induced visible and 

 truly inhibiti\e effects. No visible changes were observed at full meta- 

 phase by the concentration 1.9 X 1^^"" ^^• 



Pro-metaphase, an earlier stage than metaphase, responded (Fig. 

 3.2/-/>) innnediately to a strength (2.5 X 10 "^ ^^) t^^^t was without 

 detectaijle action at anaphase. The s])indlc formed at late proj)hase 

 was innnediately reduced, and the chromosomes scattered in the cyto- 

 plasm: a typical exploded metaphase. Doses without inliuence at 

 anaphase and with only slight effectiveness at metaphase were totally 

 effective at pro-metaphase, or late prophase (Fig. 3.2r-e) . 



Reduction to a concentration of 1.9 X 10 ^' M, effective at meta- 

 phase and now ajDplied at prophase, created the star meta])hase. 

 Under these conditions, sexeral focal j^oints for the star remained after 

 treatment (Fig. 3.2/,g) . Hence, this concentration usually led to 

 the multiijle star metai)hase (Fig 3.2/) . The particular concentra- 

 tion inducing stars was effective only at prophase. Now, compare the 

 difference between an effective concentration at projihase, .2 X 10" M, 

 with the concentration required to reduce the anaphasic spindle,-" 

 25 X 10'*^ M. The difference is significant. 



Since, as one approaches interphase from anaphase, corresjjond- 

 ingly weaker concentrations are recjuired, it becomes a point ol in- 

 terest to note requirements for detectable results at interphase, or 

 resting stage, or even late telophase. The concentration ^vas raised to 

 1 ()()() X 10 '■' M before any changes were noticed, and then the toxic 

 action as well as pycnotic changes were the only results obtained. 

 From all these tests there appears to l)e a critical point in ilie nntoiic 

 cycle when spindle fibers can be reduced with a minimum toncenira- 

 tion.-'" That stage is late prophase and pro-metaphase. 



f hree important conclusions were reached:-" (1) Effectiveness in 

 destroying the spindle or interference with its further develoj^mcnt 

 depends upon concentration; the greater the concentration, tlu 

 greater the effectiveness upon the spindle, within certain limits. (2) 



