Diversity at the Subcellular Level and Its Significance 153 



the blood plasma (Common et al., 1948; Schjeide and Urist, 1956) 

 and the liver cell approximates in its fine structure that of the hen. 

 Among other things, the ER increases approximately two- to threefold 

 (Figs. 12A, 12B ) . Here again, the pattern of organization remains 

 much the same, with cisternae of the ER associated with mitochon- 

 drial surfaces; only the number of cisternae increases, which implies 

 a corresponding increase in volume of the system and the area of its 

 surface. 



It is evident from the foregoing that some of the diversity encoun- 

 tered at subcellular levels is controlled by extracellular factors, or 

 factors of extracellular origin. Less dramatic are of course the natural 

 variations that accompany the normal function. When, for example, 

 a muscle fiber contracts, there are well-known alterations in the struc- 

 ture of the fibrils; equally impressive but less well-known changes 

 appear in the fine structure of the sarcoplasmic reticulum. The general 

 pattern of organization shown by the SR of the relaxed fiber persists 

 along with the sarcomeric organization of the fibrils, but the details 

 of fine structure of the system are radically and characteristically 

 altered (Franzini and Porter, unpublished observations). 



A better documented example is provided by the liver cell and its 

 response to plasmapheresis. It has been repeatedly noted (Stenram, 

 1953; Lagerstedt, 1949; Glinos. 1958 I that when an animal is deprived 

 of plasma proteins through repeated bleedings (and return of cells) 

 the distribution of the basophilic material (the ergastoplasm) in the 



FIG. 11 A. Parts of two secretory cells of the normal mouse seminal vesicle. The 

 basal pole <6p) is at the lower right, the apical (ap) at the upper left. The 

 cytoplasm is filled with long profiles of the rough ER (rer) or ergastoplasm, with 

 their long axes oriented parallel to the long axis of the cell. The larger spherical 

 vesicles toward the apical pole are part of the Golgi complex. 



The pattern of organization shown by the endoplasmic reticulum in these cells 

 is characteristic of this tissue in the normal mouse and also in mice given exog- 

 enous testosterone. Obviously the cisternae tend to enwrap the nucleus except at 

 the basal pole. The irregular inside dimensions of the cisternae may reflect uneven 

 accumulations of synthesized material. The limiting membranes of these cisternae 

 are typically indistinct and densely packed with ribosomes. The total surface for 

 ribosome association is relatively enormous (Deane and Porter. 1960). (Courtesy 

 of Helen W.Deane.) Magnification: 10,200 X. 



FIG. 11B. Epithelial cells of the mouse seminal vesicle as they appear two weeks 

 after castration. They have obviously lost height and are not now tall and columnar 

 as in Fig. 11A. Basal and apical poles are indicated. The change in volume and 

 height is reflected in. and is possibly due to a great reduction in the amount of 

 ergastoplasm. The profiles of cisternae are still evident. The pattern of organization 

 shown by these is the same as in the normal animal; only the long dimensions 

 and total surface area have diminished. Magnification: 10.200 X. 



