Figure 3-19. Electron Micrograph Showing Submicroscopic Structure of 

 Plastid in a Three-Week-Old Etiolated Barley Leaf. Note concentric arrange- 

 ment of the grana lamellae. Approximately 37,OOOx. (From von Wettstein, 

 D., 1959. "Developmental Changes in Chloroplasts and Their Genetic Con- 

 trol," in "Developmental Cytology," D. Rudnick (Ed.), Ronald Press, New 

 York, N. Y., Fig. 1, p. 150. Courtesy of Dr. D. von Wettstein. Forest Re- 

 search Institute, Stockholm, Sweden.) 



LYSOSOMES 



The term "lysosomes" was originated by deDuve and group (1955) 

 to designate a class of subcellular particles which, on the basis of cen- 

 trifugation studies, were deduced to be the cell sites of specific hydrolytic 

 enzymes. These enzymes (so-called "lysosomal hydrolases") included 

 acid phosphatase, ribonuclease, deoxyribonuclease, cathepsin, and /3-glu- 

 curonidase. Uricase, and possibly catalase and D-amino oxidase, was also 

 considered by these workers as attached either to the lysosomes or to 

 particles of similar nature (deDuve, 1959). Electron microscope exami- 

 nation of isolated liver fractions rich in the above-mentioned hydrolases 

 by Novikoflf, Beaufay, and deDuve (1956) revealed the presence of a 

 group of particles which were morphologically distinct from the mito- 

 chondria and the microsomes. These particles, termed "dense bodies," 



46 / CHAPTER 3 



