The cellular prion protein and its role in Alzheimer disease

The cellular prion protein (PrP^C) is a membrane-bound glycoprotein especially abundant in the central nervous system (CNS). The scrapie prion protein (PrP^Sc, also termed prions) is responsible of transmissible spongiform encephalopathies (TSE), a group of neurodegenerative diseases which affect humans and other mammal species, although the presence of PrP^C is needed for the establishment and further evolution of prions.The present work compares the expression and localization of PrP^C between healthy human brains and those suffering from Alzheimer disease (AD).In both situations we have observed a rostrocaudal decrease in the amount of PrP^C within the CNS, both by immunoblotting and immunohistochemistry techniques. PrP^C is higher expressed in our control brains than in AD cases. There was a neuronal loss and astogliosis in our AD cases. There was a tendency of a lesser expression of PrP^C in AD cases than in healthy ones. And in AD cases, the intensity of the expression of the unglycosylated band is higher than the di- and monoglycosylated bands.With regards to amyloid plaques, those present in AD cases were positively labeled for PrP^C, a result which is further supported by the presence of PrP^C in the amyloid plaques of a transgenic line of mice mimicking AD.The work was done according to Helsinki Declaration of 1975, and approved by the Ethics Committee of the Faculty of Medicine of the University of Navarre.Key words: cellular prion protein, Alzheimer disease, transgenic mice     

Immunogold-silver staining and epipolarized light microscopic detection of phosphoenolpyruvate carboxykinase and glycogen phosphorylase in rat liver

The subcellular distribution of enzymes related to carbohydrate metabolism was determined in sections of paraformaldehyde fixed and polyethylene glycol-1540-embedded rat liver and in cryostat sections. For this purpose, goat anti-rat phosphoenolpyruvate carboxykinase (PEPCK) serum and rabbit anti-rat glycogen phosphorylase (GP) serum were used as primary antibodies to localize the corresponding antigens. The primary antibodies were localized by 5 nm colloidal gold labeled secondary antibodies (either rabbit anti-goat IgG for PEPCK or goat anti-rabbit IgG for GP), and the gold particles were enhanced by silver staining using appropriate development reagents. The silver enhanced gold particles were detected by epipolarized light microscopy. PEPCK and GP immunoreactive molecules were found only in glycogen-containing areas of the cytosome of hepatocytes, and not in other cells. No immunocytochemical staining of hepatocytes was found when normal serum replaced the primary antibody in the procedures. Visio-Bond semithin (0.35–1.0 m) sections provided higher resolution for subcellular immunostaining of PEPCK and GP than cryosections of 10 m. Epipolarized light microscopy provided detection at high sensitivity of the gold-labeled antibody, and combined with transmitted light, allowed simultaneous visualization of the tissue morphology.