l62 



H. HOLTER 



The first important observation that ought to be mentioned in this 

 connection was made by Rose [25] who in a strain of HeLa cells by means 

 of a time-lapse film demonstrated that certain granules, which he called 

 " micro-kinetospheres ", actively make contact with newly ingested pino- 

 cytosis vacuoles, and fuse with them. He assumes that by this process 

 certain enzymes are injected into the vesicles, and that this is a necessary 

 condition for the later shrinkage and change in refraction index of the 

 vesicles which he observes. Rose himself suggests that the microkineto- 

 spheres might be identical with the lysosomes. 



Alkaline 

 Phosphata 



lII!'''^''^1ilBlFS'^'"'"''''''"'^ 



^^/cf 



•.'oxidative •■/TTiVa' • ■ ■" • • • • . /77\ 



pM05P«OBYl.ATI0N,*vV^ '^^ . ' •..i?*^^^^*^^' <^ . V^^ 



Fig. 4. Diagrammatic representation of a cell in the proximal convolution of 

 the rat kidney. (After NovikofF [18].) Micropinocytosis vacuoles (p) are shown 

 forming at the ends of the canalicular structures (c) extending into the cell between 

 adjacent microvilli (mv) of the brush border. These are shown fusing into larger 

 vacuoles (v), which are transformed into lysosomes (L). Other abbreviations are: 

 A, oxidized substrate; ADP, adenosine diphosphate; AH2, reduced substrate; 

 Al'P, adenosine triphosphate; ATPase, adenosine triphosphatase; BM, basement 

 membrane; E, endothelial cell of blood capillary; GA, Golgi apparatus; N, 

 nucleus; and Pi, orthophosphate. 



Lysosomes were detected and named by deDuve and his coworkers 

 [10] who have shown them to be the carriers of a whole array of 

 hydrolytic enzymes and who assume that they are the main instruments 

 of intracellular digestion. Rose's interpretation, that pre-existing lysosomes 

 by fusion convey digestive enzymes to the pinocytic vesicles is certainly a 

 very tempting one. It conflicts, however, to a certain degree with another 

 point of view according to which the pinocytic vesicles are transformed 

 into lysosomes. This point of view is held by Straus [29] who studied the 

 uptake of peroxidase, a protein marked by its enzymic activity, and des- 



