Paramecium caudatumの大核 : II.分裂に伴う核構造の変化
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概要
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The present paper deals with the results of cytological studies on the structural changes of the macronucleus in a vegetative cell cycle of Paramecium caudatum, with special reference to the coiling cycle of the chromatin element. For this study stocks KA6 and K_32 of variety 12 were mainly used. The results obtained are summarized as follows. 1. The division cycle of the macronucleus is divided, for the time being, into three stages as follow; interphase (resting stage), predivision stage, and division stage. Onset of the predivision stage is characterized by the beginning of micronuclear division, and the micronucleus reaches metaphase or anaphase just before the initiation of macronuclear division. 2. The chromatin elements in the early interphase consist of unformly Feulgen positive threads which are observed throughout the entire cycle of cell division. Paired threads generally observed in the interphase are derived from the two stranded spiral in the end of the preceding division stage, and the uncoiling of the spirals seems to take place in the early interphase. 3. In the interphase, the threads show beaded appearances. The beading may represent the twisted condition of the chromonema. In the later interphase, the threads gradually shorten to show clearly spiral structures. The parallel arrangement in the paired threads is observed at this time. 4. The chromatin threads in the predivision stage of the macronucleus become shorter and more condensed, and the paired arrangement of the threads becomes more distinct. The chromatin threads of the macronucleus at the predivision stage are longer than the micronuclear metaphase chromosomes of the same animal. 5. The division stage may be divided into two phases, elongation and constriction. The chromatin threads in the early elongation phase are left still in a condensed condition. In the constriction phase, the spiral of the threads is gradually uncoiled, but the two stranded spiral condition can be established distinctly at the terminal portions. 6. The chromatin threads in the macronucleus is called "macronuclear chromosomes" in this study basing on the structure and the duplication cycle described above. 7. The nuclear mambrane and the nucleoli persist throughout the entire stage of division. The small nucleoli are associated with the terminal portions of the macronuclear chromosomes, and it is probable that they are formed of particular portions of the chromosomes.
- 社団法人日本動物学会の論文
- 1961-03-15
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