EIKCTKON MICKOSCOPY 



dense l^odies in the basal parts of the epi- droplets are formed in the apical parts of the 



thelial cells of the proximal convoluted tu- cells, where there are no mitochondria, prob- 



bulos when very small amounts of the hor- ably from the vacuoles or from enzyme-pro- 



mone were given. Wlien larger doses were ducing granules (cytosomes). An occasional 



used, extremely dense small granules were fusion between a mitochondrion and a drop- 



foiuid in the basement membranes of the let may take place if they are located close 



tubular epithelium. The authors presumed to each other. A primary accumulation of 



that these granules were precipitations of protein inside the mitochondria is not prob- 



calcium salts. In the apical parts of the epi- able. 



thelial cells of the proximal convoluted tu- Policard et at. (1957) produced lesions in 

 bules large bodies were formed, which had the epithelial cells of the proximal convo- 

 a xery low density and were PAS -positive, luted tubules in rats by injecting a colloidal 

 The.y increased in size and occasionally filled solution of 5 per cent sodium silicate in the 

 the larger part of the cells. In the basal parts peritoneum. The brush border was partly 

 of the cells the number of mitochondria was destroyed and in cells with more severe dam- 

 decreased, probably because several of them age the apical parts of the cells were cut off 

 had developed into the above-mentioned and ejected into the tubular lumen. The 

 electron-dense bodies. The tubular lumina basal infoldings of the cell membrane disap- 

 were filled by the same PAS-positive sub- peared. The mitochondria were large and 

 stance as is seen in the tubular epithelium, pale with vacuoles or a severely changed 

 The formation of concrements probably inner structure. 



started by the precipitation of calcium salts Rouiller and Modtjabai (1958) perfused a 



in this substance. Electron microscopy of the sodium-free 5 per cent solution of glucose 



concrements showed a structure quite similar through the peritoneal cavity of rabbits. The 



to that of apatite crystals. Similar observa- cells of the proximal convoluted tubules 



tions have been made by this author in showed a marked increase in size and were 



biops3^ specimens from patients with hyper- very pale in the light microscope, as is ob- 



parathyroidism and renal calcifications. served in human subjects which have been 



Rhodin (1954) first studied the effect of treated with large intravenous infusions of, 



intraperitoneal injections of egg white on the for instance, dextran. Electron microscopy 



proximal tubular epithelium in mice. There showed an extremely low contrast in the cy- 



were no changes in the appearance of the toplasm of some cells of the proximal convo- 



brush border. In the apical parts of the cells luted tubules and very large and numerous 



there was increased vacuolization. Large vacuoles inside or between the cells. The api- 



opaque bodies were found in the cytoplasm cal part of the cells were partly destroyed 



corresponding to the hyaline droplets seen and ejected into the tubular lumen. The 



by light microscopy. Inside these bodies were mitochondria w^ere few^ and small. According 



remnants of double membranes. The author to the authors, these changes were due to an 



concluded that these bodies developed from increased content of water in the tubular 



the mitochondria during resorption of pro- cells. In some mitochondria were accumula- 



tein as previously described by Oliver (1948) tions of small dark granules, which were re- 



and others. garded by authors as evoked by the resorp- 



These observations were confirmed by tion of glucose. Similar changes were induced 



Miller and Sitte (1955) and by Gansler and in mice by Yolac (1959) with sucrose. 



Rouiller (1956). According to Miller (1959), The tubular lesions in potassium-depleted 



the association between the hyaline droplets rats were studied by Tauxe et al. (1957), and 



and the mitochondria is only secondary. The Muehrcke and Bonting (1958). There were 



214 



