CYTOPLASMIC GRANULES 

 OF ASTROCYTES CULTIVATED IN VITRO 



KAZUO OGAWA 



Department of Anatomy, Kyoto University, School of Medicine, Kyoto, Japan 



It has been reported by Ogawa and Okamoto (K. Ogawa and M Okamoto: 

 Proc. llth Ann. Meet. Am. Histochem. Soc, }. Histochem. Cytochem., 

 in press, 1960) that cytoplasmic granules of cultured astrocytes are 

 extractable lipids containing unsaturated bonds and cholestérols, rather 

 than secreted mucopolysaccharides or mucoproteins as claimed by Lums- 

 den (C. E. Lumsden: In: W. F. Windle {ed.)f Biology of Neuroglia, 

 pp. 141-161, Springfield, 111., 1958). 



This is to report that the living astrocytes may be classified morpho- 

 logically into the following 3 major types: 



Type I. Fusiform astrocytes 



Type II. Astrophorous astrocytes 



Subdivision a) Oligodendro-astrocytes 



b) Standard astrocytes 



c) Multidendro-astrocytes 

 Type III. Membraniform astrocytes. 



Furthermore, cytoplasmic granules were observed in ail types of 

 astrocytes, although the amount of granules varies among the cell types. 

 Fusiform astrocytes and oligodendro-astrocytes are considered to be 

 ontogenically young astrocytes, and multidendro-astrocytes as well as 

 membraniform astrocytes, the latter being characterized by a membrane 

 attached to the processes, as rather older astrocytes. Standard astro- 

 cytes are characterized by having 5 to 6 moderately long processes 

 with a moderate number of branches. 



In addition, a lower activity of succinate-tetrazolium reductase, 

 indicating a lower rate of oxidative respiration, associated with thinner 

 and fewer mitochondria was observed in cytoplasmic areas with lipid 

 granules as compared to areas without granules. 



Further study on the metabolic rôle of lipid granules in astrocytes 

 cultivated in vitro is in progress. 



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