両生類卵形成過程の研究 : VIII. ウシガエル卵母細胞における核由来物質の行動

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Electron microscopic studies of very early bullfrog oocytes reveal cylindrical structures of about 150mμ un cross-sectional diameter with a linearly continuous central core 35mμ in diameter. They project from aggregated masses of nuage material presumably formed by the transannular passage of granules of about 300A in diameter on the lateral loops of lampbrush chromosomes. In the oocytes of about 100-150μ in diameter, the core-containing cylinders are observed most frequently solitary or in tangled or parallel clusters in the peripheral ooplasm facing the region of nuclear envelope through which the transannular passage of the nuclear material occur. When the diameter of the oocytes increases from 150μ to 200μ the cylinders are often observed to be intimately associated with mitochondria. During subsequent growth of oocytes, the cylinders undergo ultrastructural changes and transform into polysome clusters retaining their original rod shaped profiles and their association with mitochondria. Just about at the time when polysome clusters can be detected, the number of mitochondria distributed rather scarcely in the ooplasm begins to increase very rapidly and clumps of mitochondria are formed. A hypothesis is presented on the basis of the time sequence of these events, and the relevant ultrastructural observations are reported here. The hypothesis suggests that the cylindrical structures may contain messenger ribonucleic acids in a masked form which direct the synthesis of those proteins necessary for the proliferation of the mitochondria in very early oocytes of this species.
1971-03-15

両生類卵形成過程の研究 : VIII. ウシガエル卵母細胞における核由来物質の行動

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