ヒキガエル初期幼生の細胞數に關する研究 : I.測定法及び核の分布状態について
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概要
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Total cell counts were made on the larvae of Bufo unlgaris from the blastula stage to the tailbud stage. Camera lucida drawings of each serial section were divided into several parts according to their distribution density of the nucleus (nuclear density). Surface area of each part was measured by weighing and then multiplied by corresponding density. Sum of the cell number of each section was again summed up throughout the whole length. As the variation is relatively small in the posterior portion, there the procedure was made every 2ed to 10th section. Observed nuclear density C was corrected to the true value C_0 by a formula C=C_0 (1+90% d/D), where d is mean maximal diameter of the nucleus and D the thickness of a section. Although the accuracy of these laborious measurements is not very high (±15% error is unavoidable), it may be stated that the increase in cell number is steep during gastrulation (20, 000 to 140, 000) and afterwards it is markedly slackened (140, 000 to 300, 000). Some fundamental properties of the nuclear density of various embryonic parts were discussed. In the tail-bud stage, the nuclear density is determined regardless of the germinal layers by a field, whose gradient is chiefly directed from outer side to the center (centripetal gradient), while dorso-ventral and cephalo-caudal gradients are negligibly small. It was observed in sections of trunk region at tail-bud stage, density decreases to the direction of the depth R, in a manner expressed by a single parabolic formula. From the analogy of these properties with the oxygene distribution in the respiring spherical cell calculated by RASHEVSKY (1938), the author proposed a hypothesis, that the nuclear density is determined by the respiratory activities of the embryonic parts. Presumed high asphyxia of the major part in the early larva will explain the strong resistance to emetine, the toxic action of which is thought to appear when adequately dehydrogenated (SIRAKAMI '52 in press).
- 社団法人日本動物学会の論文
- 1952-07-15
著者
関連論文
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