The Glomerular Basement Membrane in Amyloidosis of the Mouse 



255 



Fig. 1. Low power view of several glomerular capillaries in 

 experimental amyloidosis. Arrows indicate nodular protru- 

 sions of the osmiophilic middle layer of the basement mem- 

 brane. i\ capillary lumen; b, cavity of Bowman's capsule. 

 Magnification 5000. 



Light microscopy showed an amyloidosis of almost 

 all glomcruh. With the periodic acid-silver reaction 

 the capillary wall stained black. The amyloid seemed 

 to be deposited within the space enclosed by the 

 capillary wall. 



Electron microscopy revealed hitherto unknown 

 changes of the basement membrane, in particular of 

 the osmiophilic middle layer. Measurements of the 

 basement membrane in normal mice confirm the 

 findings of Rhodin (18) and Yamada (21). The total 

 thickness of the basement membrane is 1200 A ± 

 117. The osmiophilic middle layer is 632 A ± 73 

 thick. The less osmiophilic inner and outer layers 

 are 273 A ±31 thick. In mice with amyloidosis the 

 basement membrane is thickened either continuously 

 or in wavy form (fig. 1). The total thickness is 2200 

 A ± 116. This increase in thickness is exclusively 

 due to a broadening of the osmiophilic middle layer 

 measuring 1557 A ± 107. The inner and outer less 

 osmiophilic layers are of the same thickness as in 

 normal animals. The difference of the means of the 

 osmiophilic middle layer in sick and normal mice is 

 significant on the 99 % level (Student's r-test). The 

 variance of the osmiophilic middle layer in mice 

 with amyloidosis is so much greater than in normal 



animals (95 "o level; Fisher's F-test) that it cannot 

 be explained as caused by chance alone.' This seems 

 to indicate that the increase in thickness of the 

 middle layer in mice with amyloidosis is caused by 

 a patiiological condition and therefore is varying 

 within relatively broad limits. 



Apart from the general increase in thickness local 

 protrusions of the middle laser in the shape of knots 

 or mushrooms were observed (fig. 2). These 

 nodular, sometimes hernia-like protrusions have a 

 height of 0.5-1.5 // and a width of 0.6 2.0 /<. They 

 were detected later also with the light microscope 

 on sections stained with the periodic acid silver 

 reaction (9). All the protrusions arc bulging exclu- 

 sively towards the cavity of Bowman's capsule. Fhis 

 could be conceived of as a morphological expression 

 of the decrease in pressure towards the cavity of 

 Bowman's capsule and of the direction of the filtra- 

 tion gradient. Sometimes several protrusions were 

 observed on the same capillary loop spaced closely 

 together. The inner and outer less osmiophilic layers 

 line the bulges of the middle layer and are of the 

 same thickness as in normal mice. The foot processes 

 are always in contact with the outer layer lining the 



^ For greatly appreciated help with the statistical evalua- 

 tion of the material we are much obliged to Dr. E. Olbrich, 

 Department of Histology and Embryology, Univ. of Inns- 

 bruck. 



Fig. 2. Glomerular capillary wall in experimental amyloid- 

 osis. C, capillary lumen \\ith fixed plasma protein particles; 

 P, protrusion of the osmiophilic middle layer in the shape of 

 a mushroom; O, oblique section through capillary wall. 

 Magnification 26,000. 



