ELECTRON MICKOSCOI'Y 



normal kidneys that the sHt-pores between 

 the foot processes are the filtration pores 

 postulated by Pappenhcimer (1955). It could 

 therefore be expected that in cases where the 

 foot process organization was impaired, filtra- 

 tion should also be low. As pointed out by 

 Farquhar et al. (1957a, c), Vernier et al. 

 (1958a) and Rhodin (1959), this is not the 

 case in familial nephrosis or lipide nephrosis. 

 On the contrary, a decreased renal function 

 was observed in cases with subacute glomer- 

 ulonephritis where the foot processes were 

 intact. 



The problem has been discussed by Berg- 

 strand (1959) on the basis of investigations 

 in amyloidosis and diabetic glomerulosis. 

 According to this author, changes in filtration 

 rate cannot with certainty be correlated to 

 changes of the capillary wall. A severe reduc- 

 tion in filtration fraction, on the other hand, 

 is most probably a sign of an increased re- 

 sistance to filtration through the capillary 

 walls. This was observ^ed in most of his cases 

 and he concluded from the electron micro- 

 scopical observations that the most probable 

 cause of the decrease in filtration fraction 

 was a thickening of the basement membrane, 

 perhaps associated with a change of its 

 ultrastructure, which could not be demon- 

 strated with certainty with the present tech- 

 niques. Bergstrand presumes that the filtra- 

 tion pores in the normal capillary wall are 

 localized in the basement membrane. The 

 same opinion has been expressed by Sitte 

 (1959). 



Other attempts to solve the problem have 

 been made by studying the passage of very 

 small particles through the glomerular capil- 

 lary wall. Farquhar and Palade used ferritin 

 molecules, Latta and Maunsbach thorotrast, 

 and Vernier silver-labeled protein molecules. 

 These studies were performed both in normal 

 and nephrotic animals. The authors observed 

 a very rapid passage of particles with a diam- 

 eter less than 75 AU, whereas larger particles, 

 abo\'e all thorotrast, were retained in the 

 bloodstream. No changes of structure could 



be observed in the basement membrane when 

 particles were passing through. No definite 

 conclusions could thus be drawn about the 

 morphological Imsis of glomerular ultrafiltra- 

 tion. 



REFERENCES 



1. AsHWOBTH, C. T., "Ultrastructural Aspects 



of Renal Patho-Physiology," Tex. Rep. 

 Biol. Med., 17, 60-72 (1959a). 



2. AsHWORTH, C. T. AND Grollman, A., "Elec- 



tron Microscopy in Experimental Hyperten- 

 sion," A.M.A. Arch. Path., 68, 148-153 

 (1959b). 



3. Bencosme, S. a., Stone, R. S., Latta, H., 



AND Madden, S. C. "Acute Reactions with 

 Collagen Production in Renal Glomeruli of 

 Rats as Studied Electron Microscopically," 

 y. UUrastr. Res., 3: 171-185 (1959). 



4. Bergstrand, A., "The Morphological Basis 



for the Filtration Process in the Glomeruli," 

 Acta Chir. Suppl. 245, 336-342 (1959). 



5. Bergstrand, A. and Bucht, H., "Electron 



Microscope Investigation on Biopsy Mate- 

 rial frum Patients with Renal Diseases: A 

 Case of Subacute Glomerulonephritis," 

 Proc. Stockholm Conference on Electron 

 Microscopy, 256-258, 1956. 



6. Bergstrand, A. and Bucht, H., "Electron 



Microscopic Investigations on the Glomeru- 

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 Glomerulosclerosis)," Lab. Invest., 6, 293- 

 300 (1957). 



7. Bergstrand, A. and Bucht, H., "Anatomy 



of the Glomerulus as Observed in Biopsy 

 Material from Young and Healthy Human 

 Subjects," Z. Zellforsch., 48, 51-73 (1958). 



8. Bergstrand, A. and Bucht, H., "Electron 



Microscopic Observations on Renal Amyloi- 

 dosis," (1959a) (to be published). 



9. Bergstrand, A. and Bucht, H., "The Glo- 



merular Lesions of Diabetes Mellitus and 

 Their Electron-Microscope Appearances," 

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10. Bergstrand, A., Friberg, L., Mendel, L., 



and Odeblad, E., "Localization of Subcu- 

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 Ultrastruct. Res., 3: 238, 1959. 



11. Bergstrand, A. and Ericsson, J., "Electron 



Microscopic Investigation on the Anatomy 

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 Healthy Human Subjects," (1959) (To be 

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12. Bohle, A., Sitte, H., and Miller, F., "Elek- 



216 



