204 Colchicine 



colchicine, recovers. This leads often to pluripolar spindles, which 

 are considered to be an important factor counteracting the poly- 

 ploidizing action of the alkaloid. Recovery is incomplete, and chromo- 

 some coiuits demonstrated a great variability from cell to cell.^*^ 



Another peculiarity of the spindle of amphibian eggs is its asym- 

 metrical reactions towards the depolarization effects of colchicine. 

 The hypothesis has been put forward that this may be related to a 

 differential sensitivity of the centrosomes, whether of paternal or 

 maternal origin. ^^ 



Similar disturbances of development have been described in Rana 

 agilis^ and Bii^o vulgaris, where an apparent decrease of cellular res- 

 piration was observed.^" The exact relation between mitotic changes 

 and the abnormalities of later development, which will be related in 

 the next section, are most difficult to understand. A detailed de- 

 scription of the action of colchicine on the cleavage and early de- 

 velopment stages of the fish Oryzias latipes cannot possibly be svmi- 

 marized here, but should be consulted by embryologists interested in 

 chemically induced abnormal growth. ^9 



The changes described in the egg of Tiibifex, an invertebrate, are 

 remarkably similar to those reported in vertebrates. In 1:30,000 

 solutions of colchicine some eggs are able to divide twice. One of the 

 main effects is on cytoplasmic limits, which may disappear after hav- 

 ing been normally formed at telophase.^^ 



A relative resistance towards colchicine, changes in sensitivity re- 

 lated to developmental stages, the absence of polyploidy in the em- 

 bryos, and peculiar actions on cleavage are the main facts which at 

 this time emerge from a great amount of observations.-^- ^^ There is 

 no doubt that cytologists and embryologists have many more prob- 

 lems to solve and probably new types of colchicine effects to discover. 



8.1-2: Male gametes. There are surprisingly few data available 

 on the action of colchicine on spermatogenesis. In mice, aged 22 

 days, some arrested mitoses (or meioses?) have been reported in early 

 work.-^ In adult animals, colchicine brought evidence of nuclear and 

 cytological destruction. Arrested mitoses of spermatogonia in rats in- 

 jected with inore than 1.4 mg/kg of the drug have been described. 

 The spermatocytes did not appear to be altered, akhough 24 hours 

 after the injection the nixmber of metaphases Avas somewhat in- 

 creased. •''- 



Personal observations of the junior author (unpublished) are that 

 in the testes of mice injected 1.25 mg/kg, most of the spermatocytes 

 have no more spindle 24 hours later. Spermatogonia appear to be 

 unaltered, and the stages of meiosis are normal, as long as no spindle 

 activity is required. Many spermatids with vacuolated nuclei may be 

 observed, but this ]:)henomenon is a consequence of the general 



