CYTOGENETIC ANALYSIS 473 



Pretreatments 



Mitotic arrest and hypotonicity. — Samples of solid, transplantable tumors may be 

 readily obtained for arrested mitoses, following the procedures outlined by Bayreuther 

 and Klein. 64 These workers employed a small volume of 10 per cent alcohol in dis- 

 tilled water, given intraperitoneally as a means of dilating the vascular network about 

 tumor implants for greater penetration of the colchicine solution subsequently ad- 

 ministered (0.5 ml. of a 0.025 per cent solution of colchicine, followed by sacrificing 

 after 90 minutes) . Generally, actively proliferating cells of solid implants {in situ) are 

 to be found peripherally, where vascularization assures rapid colchicinization. Similar 

 procedures may be employed with cheek-pouch implants of both species of laboratory 

 hamsters in which vascularization is known to be extensive. 411 If the cheek pouch is 

 used, colchicine may be administered intraperitoneally or locally into the cheek pouch, 

 following light anesthesia with ether. When ascites tumor cells are to be pretreated 

 with colchicine, a dose of 0.17 ml. of a 0.006 per cent solution of colchicine per 10 g. 

 body weight provides the maximum number of mitoses. Levan presents a con- 

 venient conversion table for injections in vivo. 780 



To harvest carcinomas and papillomas in rabbits, Palmer 989 injected colchicine- 

 saline (5 per cent) at a dose rate of 0.0012 mg./g. body weight intravenously for 9-12 

 hours. Hungerford employed a colchicine dosage of 5 x 10 ~ 7 M for six hours to 

 arrest primary murine fibroblasts (unpublished). Makino and Sasaki 842 arrested 

 mitoses in cultures from various species with a 20-50 x 10 ~ 8 M solution of colchicine 

 two to five hours prior to trypsinizing and centrifuging. D. K. Ford and his col- 

 laborators 390, 391 utilized a similar schedule, except that fixation with 3:1 enabled 

 lengthier storage of fixed cells. 



The striking resistance of the Syrian or golden hamster, Mesocricetus auratus, to 

 colchicine is a topic of increasing interest as this species is utilized more extensively for 

 research. 874, u " Harnois 521 has noted that the bone marrow of the Syrian hamster 

 displays numerous c-metaphases after three hours, following treatment with 20 mg. of 

 colchicine/ 100 g. body weight. Earlier, Orsiniand Pansky 970 characterized the natural 

 resistance of this species to an endemic alkaloid. 



Exposures in vitro of fibroblasts derived from Syrian hamsters to colchicine are 

 proportionally resistant. Harnois calculated an optimum number of c-metaphases 

 among pulmonary derivatives of Syrian hamster at a colchicine concentration of 

 10 ~ 4 M. The optimal concentration for cells from the Chinese hamster similarly 

 derived was 10 ~ 6 M. Thus, Harnois concluded that cells of the Syrian hamster were 

 100 times more resistant to colchicine when compared to the Chinese hamster. This 

 resistance is species specific and may be increased in vitro by means of incubating 

 Syrian hamster cells in the presence of a relatively low dosage of colchicine added to 

 the nutrient medium. It should be mentioned that mitoses of the Chinese or striped- 

 back hamster, Cricetulus griseus, are equally sensitive to colchicine, as are the cells of 

 most rodents, primates, and ungulates. Dosages prescribed for colchicine-sensitive 

 species are equally effective for tissues of the Chinese hamster given both in vivo and 



