Reinvestigations of the Spindle Body and Related Problems II. Effects of cycloheximide upon the development of kinetochore fibers studied in the pollen mitosis of Ornithogalum virens in vivo

• Published in: CYTOLOGIA Vol. 37; no. 1; pp. 143 - 154
• Main Authors: Niitsu, Tsuneyoshi, Hanaoka, Akio, Uchiyama, Kazuko
• Format: Journal Article
• Language: English
• Published: Japan Mendel Society, International Society of Cytology 1972
• ISSN: 0011-4545; 1348-7019
• DOI: 10.1508/cytologia.37.143

By applying the synchronous mitotic cycle in the pollen grains of Ornithogalum virens (n=3) cultured in vitro, the effect of cycloheximide on the kinetochore fiber development has been studied morphologically as well as quantitatively. 1. Cycloheximide of 1 ppm did not suppress mitosis completely but a delay in the mitotic process appeared, especially when entering metaphase. 2. The arrested mitotic cells prior to metaphase will enter mitotic activity with the termination of the cycloheximide treatment. Their delay in entering metaphase corresponded exactly to the duration time of the cycloheximide treatment during which period the kinetochore fiber development and the sister kinetochore separation had been suppressed. The chromosomes at arrested metaphase showed skipairs. 3. The mitotic cells in anaphase at the beginning of the treatment showed no effect of the drug and proceeded normally to further mitotic stages. 4. By the suppression of the kinetochore fiber development by cycloheximide treatment, the kinetochore substance may be confirmed to be a kind of protein which is synthesized at the kinetochore site in prometaphase. 5. The quantitative analysis of both the frequency curves and also of the duration time of the mitotic stages indicate the absence of kinetochore fiber in prometaphase. These were generally believed to be present in fixed preparations.