著者

Kikuo Chishima

出版者

Editorial Board of Okajimas Folia Anatomica Japonica

雑誌

Okajimas Folia Anatomica Japonica (ISSN:0030154X)

巻号頁・発行日

vol.24, no.3, pp.149-186_9, 1952 (Released:2012-09-24)

参考文献数

101

被引用文献数

3 3

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(1) In this paper the origin of the so-called primordial germ cell and the histogenesis of the gonad in chick embryo are described with special reference to the differentiation of erythrocytes.(2) Erythrocytes in the gonad of chick embryos show transitional phases into several kinds of formed elements of the gonad such as small lymphoid cell, " fat-laden cell ", fibroblast or connective tissue cell, eosinophilic granulocyte and mesenchymal cell-B, according to, (a)the cellular environment, where the erythrocytes are localized or remain stagnant, and (b) with the lapse of time.(3) The differential potencies of erythro c yte were recognized by means of the following experiments, viz. (i) blood cell culture, (ii)gonad implantation and (iii) wound inducing experiment with testis.(4) Gonad primordium in early embryonal stage is in dire c t contact with erythrocytes contained in the subcardinal vein and revehent vein, and some of these erythrocytes adhere to the gonad and show transitional phases into gonadal elements.(5) So-called primordial germ cells with very low value of mitotic index show no reliable evidence of genetic continuity with oögonia or spermatogonia; on the contrary, they arise, most probably, from the incorporation (fusion) with many of the mesenchymal elements of the germinal epithelium in situ, and further the germinal epithelial cells show transitions from the erythrocytes.(6) There are three d i fferent modes, from which the sex-cord may be formed. The first is from the germinal epithelium which is a derivative from the blood layer (since 8-9 day of incubation). In this case there can be found no evidence of local intensive proliferation of the epithelial elements, on the contrary, migration and differentiation of erythrocytes can be clearly demonstrable. The second mode is formation from the condensation and differentiation of erythrocytes migrated into the interstices of the gonad. The third mode is the transformation and rearrangement of mesonephric elements.(7) Asymmetrical development of the embryonic g o nad in the female chick is due to the lack of first and second modes of sex-cord formation of the right ovary. The right ovary, consequently retregresses by the hatching time according to the degeneration of the right mesonephros.(8) There is no evidence that the otigonia composed of ovigerous 180 K. Chishima layer of the left ovary are produced by mitotic proliferation of their own kind. Their characteristic nuclear features, resembling the prophase of mitosis, are not true mitotic figures.(9) So-called "cluster of fat-laden cells " show transitional phases from cluster of erythrocytes that have migrated into the inter stices of the medullar region.(10) Distend e d medullary cords are derived from the degeneration of the medullary cords and of the " cluster of fat-laden cells ".(11) Rete cords are transitional portions of the mes o nephric tissues into the gonad.