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F. HAGUENAU AND K. H. HOLLMANN 



trgastoplasm 

 (organized) 



Endoplasmic 

 reticulum 



RNP-granules 

 'nbosomes' 



Fig. I. 



It is the relationship, if any, between one form and the other, in par- 

 ticular that of "organized ergastoplasm" to RNP-granules which is not 

 clear and that we will now consider in the mammary gland and specially 

 in its cancers. 



I. Ergastoplasm in the normal mammary gland 



Classic cytologists long ago discovered ergastoplasm in the mammary 

 gland and described the strongly basophilic filaments present in great 

 amount at the basis of the secretory cell [3, 4] and Fig. 2(0). This baso- 

 philia disappears under the action of ribonuclease and the reaction is 

 greater during the first phase of the secretory cycle. It then decreases to 

 appear again with reconstitution of the alveolar cells. The various changes 

 occurring in ergastoplasm are also easily followed in the fluorescent 

 microscope after acridine orange staining. 



In the electron microscope, development of the ergastoplasm during 

 the lactation period is remarkable (Fig. 2(b)). Its order and ultrastructure 

 are characteristic. Ribonucleoprotein particles are regularly arranged at 

 the surface of the membrane system of the endoplasmic reticulum which 

 itself is organized in parallel lamellae (Figs. 3 and 4). This "organization" 

 in parallel array is one of the essential features of the ergastoplasm at that 

 stage. Only when ergastoplasm is found in this "organized" form does 

 elaboration of milk occur. 



The ultrastructural details of the secretion have been described in two 

 recent studies in the rat [5] and in the mouse [6]. 



It has been shown that milk secretion in these species is made up of at 

 least two morphologically distinct elements probably corresponding to 

 protein secretion for the one and to lipid secretion for the other. The topo- 

 graphical relationship between lipid secretion and definite cell organelles 

 is still under discussion while on the contrary, formation of protein granules 

 appears clearly related to the Golgi complex. Indeed it is exclusively in 



