抄録
The brown fat tissue which has been studied for a long time is well developed in hibernating animals. The present paper was undertaken to learn more about the embryological development and the histochemical patterns according to the developmental stages of the interscapular brown fat tissue. In addition, the white fat tissue was studied histochemically. The rat embryos of the Wister strain and 3-day young rat were used. The sections were stained with hematoxylin eosin for the histological examination and were stained with PAS, Feulgen reaction, methyl green pyronin, mercuric bromphenol blue, Sudan black B, spirit blue and Baker’s phospholipid staining for the histochemical purpose. The results are as follows: The embryonal spread of the interscapular brown fat anlage is much wider in range than what has been reported by other investigators. The anlage cells develop from the mesenchymal cell surrounding the specific blood vessels in the 17.5 mm-long embryo. They have several cytoplasmic processes and a characteristic nucleus. In the 18 mm-long embryo, the cell islets aggregate into a lobule and the cells begin to have small fat vacuoles. At the end of the intrauterine life, the anlage cells take on a plurivacuolar appearance. The anlage of the white fat cell is seen first in the cervical subcutaneous region of the 36 mm long embryo. However, it takes a different developmental process histologically and histochemically from that of the brown fat cells. In the histochemical studies, it is most conspicuous that the PAS and methyl green pyronin staining reactions decrease suddenly at the end of the intrauterine life. Moreover, the Feulgen reaction and Sudan black B staining reaction decrease slightly at the same time. Other staining reactions show no marked changes throughout the developmental process. These phenomena seem to suggest that the great alteration in the components of the chemical substances within the brown fat cells occurs at the end of the intrauterine life. For example, we can expect that the fat droplets can be derived from the polysaccharides.
