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Variations in the rate of mitosis in normal and colchicine‐treated tadpoles of Rana pipiens and Amblystoma jeffersonianum
Author(s) -
Mills Katharine Olive
Publication year - 1939
Publication title -
journal of morphology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.652
H-Index - 74
eISSN - 1097-4687
pISSN - 0362-2525
DOI - 10.1002/jmor.1050640107
Subject(s) - salamander , biology , rana , hatching , colchicine , mitosis , anaphase , epidermis (zoology) , larva , amphibian , metaphase , anatomy , andrology , zoology , botany , microbiology and biotechnology , ecology , genetics , cell cycle , medicine , cell , gene , chromosome
Study of the epidermis of Rana pipiens and Amblystoma jeffersonianum showed no variations in the mitotic rate that were correlated with the age expressed in hours after hatching or with the time of day at which the tadpoles were fixed. The average mitotic index of the epidermis during the first day of larval life was 1.88 in the frog and 1.02 in the salamander. This was correlated with the earlier developmental stage at which the frog hatched. Colchicine in concentrations above 5 × 10 −4 M. in the frog and above 2.5 × 10 −3 M. in the salamander arrested almost all mitoses at metaphase. Inhibition was incomplete after treatment with concentrations of 1.25 × 10 −4 M. in the frog and 5 × 10 −4 M. in the salamander. Severe injury was characterized by the presence of vacuolated cells with deeply stained inclusions, similar to cells found after x‐radiation. Cells continued to enter the prophase at the normal rate. The accumulation of metaphases during the first 4 hours of colchicine treatment indicated a mitotic period of about 80 minutes in the frog. During subsequent periods the expected accumulation of metaphases did not occur. It was concluded that the arrested metaphases either degenerated or passed into a resting stage without passing through anaphase.