The answer to the Image Quiz from 7/21/12 is that panel B shows diffuse effacement of foot processes.
The picture shows and EM of a glomerular capillary loop at high power. Panel A is normal, but what does panel B show?
Podocyte foot process effacement is characteristic of proteinuric renal diseases. In minimal change nephrotic syndrome (MCNS) foot processes are diffusely effaced whereas the extent of effacement varies in focal segmental glomerulosclerosis (FSGS). I suggest reading an excellent commentary by Pierre Ronco published in JCI in 2007 about the potential role of foot processes in proteinuria.Also worth reading is an excellent article by Barisoni et al published in CJASN in 2007. I am reproducing an image from this paper - see on the right.