鶏の下垂体前葉のCephalic lobe, Caudal lobe相互に於ける細胞型の一部交流の原因について

抄録

It has been demonstrated by many investigators (RAHN, '39 and others) that anterior pituitary of fowls is devided into two lobes-cephalic and caudal, and the cellular constituents of these regions are quite intrinsic respectively. But, in most cases, some mutual mingling of the cells or cell clusters of two lobes has been often seen. WINGSTRAND ('51) has also recognized such a case of mixing materials of different origin. The authors suggest that essential causes of the mingling may be supposed inview of the developmental facts described below.
1) In chick embryo of 3-day 20-hour of incubation, there is seen a process at the dorsal wall of Rathke's pouch. This is undoubtedly Bruni's " di verticolo medio " because of the existence of a mass of cells (ATWELL'S "entodermal buds ") between the tip of the process and the anterior end of the notochord. While, immediately above the "diverticolo medio " is also found another process separated distinctly by ventral longitudinal furrow ("primary furrow" of the authors) from the latter (Figs. 1, 6). None of the investigators as yet described this process, so that, for convenience of description, we call this hitherto undescribed process as "dorsal process". The process has a distinct lumen which is continuous with the lumen of the original Rathke's pouch. Furthermore, this process lies apparently in the upper half of Rathke's pouch (aboral lobe) being separated by the constriction of the pouch from the lower half (oral lobe), in which " diverticolo medio " is situated demarcating the boundary (constriction) between two lobes. About 4-day 5-hour to 5-day of incubation, the "secondary furrow " has appeared along the dorsal border of the " dorsal process " at which the division of the upper half of the pouch occurs. As a result of this, a smaller part of the upper pouch including "dorsalprocess" is sunk down to join the lower half. (Figs. 2, 7, 8)
From the fact above described, it is apparent that in early developmental stages of incubation (3-day 20-hour to 5-day) a part of the compornent of the aboral lobe (future caudal lobe) of Rathke's pouch is separated from the parts of the "dorsal process" and participates in formation of the oral lobe of the pouch. It is obviously recognized by the works of RAHN ('39), WILSON ('52) and others that the cellular differentiation of the anterior pituitary of the chick embryo occurs earlier than we expect. Furthermore, WILSON observed the fact that cephalic region of the pars distalis after 7-day of incubation contains a few of the caudal chromophiles. These facts coincide quite well with the authors' description.
2) At the peried of about 9 to 10-day of incubation, translocation has taken place in a part of the Rathke's pouch. In consequence of this, the oral lobe is transferred antero-dorsally, and is now bent at about right angle in the point of the constriction between two lobes. However, the grade of translocation of the lower part of the oral lobe is not so conspicuous as that of the upper one. Especially, near the portion of the attachment of epithelial stalk that grade is most inconspicuous. Thus, as will be seen in Fig. 3, there is often seen a case in which a cell cord of the oral lobe (cephalic lobe) has been extending over far from the boundary constriction of two lobes and joining to the ventral border of the aboral lobe (caudal lobe). Although there is some variation among the materials, the same figure is often seen in the case of the adult gland. (Figs. 4, 5).
All these observations lead to the suggestion thas the essential factors inducing the cellular mingling of both the lobes of the anterior pituitary of the fowl are due to the developmental facts above described.