LYSOSOMES, A NKW GROIP Ol' CVl'OPLASM IC PAKTICLES I43 



LYSOSOME-LIKI. PAKTICLES IN OTIIHR TISSUES 



Kidney. It has long been known that the parenteral administration of some 

 proteins, as of a number ot colloidal dyes, causes the appearance of characteristic 

 droplets in the brush-border cells of the convoluted tubules. Early work on these 

 droplets has been reviewed by Cierard and (Wordier (37) and more recently by 

 Rather (74). They have been extensively studied by Zollinger ( 106) and by 

 Oliver and his co-workers (70, 71, 61), and with the aid of electron microscopy 

 by Rhodin (79) and by Gansler and Rouiller (36), who have also demonstrated 

 the presence of smaller bodies of a similar type (big granules and microbodies) 

 in the kidneys of untreated animals. Most authors believe that the droplets 

 originate from mitochondria and are involved in the reabsorption of proteins and 

 other substances from the lumen of the tubules. 



According to Kretchmer and Dickerman (56), kidney droplets retain their 

 characteristic shape after disruption of the cells and are recovered with the nu- 

 clear and mitochondrial fractions after differential centrifugation. Straus (92) 

 has succeeded in purifying these bodies by a combination of filtration and cen- 

 trifugation procedures; he has also shown that droplets of smaller size could be 

 isolated from normal rat kidneys. His purified preparations had low cytochrome 

 oxidase and succinic dehydrogenase activities (easily accounted for by a contamina- 

 tion with mitochondria) and a high content in acid phosphatase as well as sig- 

 nificant autolytic (catheptic?) activity (92). After publication of the work on the 

 hepatic lysosomes, Straus (93) was able to show that in addition to acid phos- 

 phatase, the droplet fractions contain the acid nucleases, ^-glucuronidase and 

 cathepsin, all concentrated 10- to 15-fold with respect to the original homogenates. 

 He also found that these enzymes are not fully active in fresh preparations and 

 are activated by exposure to hypotonic media (94). A close kinship between the 

 kidney droplets and the hepatic lysosomes was thus clearly established. 



The droplets isolated by Straus vary enormously in size, from o.i to 5 microns. 

 Some therefore are smaller, others larger, than mitochondria, and this indicates 

 that a size intermediate between those of mitochondria and microsomes may not 

 be a necessary characteristic of lysosomes in other tissues. Like the liver particles, 

 the droplets appear to be denser than mitochondria and of a darker color. Al- 

 though purified preparations have not been examined in the electron microscope, 

 it is possible that the three size-groups distinguished by Straus correspond ap- 

 proximately to the microbodies, big granules and hyaline droplets observed by 

 the electron microscopists (89, 79, 36). Like the dense bodies in liver, these 

 formations appear to be surrounded by a single membrane and have a dense in- 

 terior. On the few pictures available in the literature, they seem to be less poly- 

 morphic, to show an internal cavity only exceptionally, and to be devoid of the 

 ferritin-like granules seen in most hepatic bodies. Thus these granules may not 

 be a constant feature of lysosomes. This may also be true in liver, since particles 



