Prion filament networks in [URE3] cells of Saccharomyces cerevisiae.

The [URE3] prion (infectious protein) of yeast is a self-propagating, altered form of Ure2p that cannot carry out its normal function in nitrogen regulation. Previous data have shown that Ure2p can form protease-resistant amyloid filaments in vitro, and that it is aggregated in cells carrying the [URE3] prion. Here we show by electron microscopy that [URE3] cells overexpressing Ure2p contain distinctive, filamentous networks in their cytoplasm, and demonstrate by immunolabeling that these networks contain Ure2p. In contrast, overexpressing wild-type cells show a variety of Ure2p distributions: usually, the protein is dispersed sparsely throughout the cytoplasm, although occasionally it is found in multiple small, focal aggregates. However, these distributions do not resemble the single, large networks seen in [URE3] cells, nor do the control cells exhibit cytoplasmic filaments. In [URE3] cell extracts, Ure2p is present in aggregates that are only partially solubilized by boiling in SDS and urea. In these aggregates, the NH(2)-terminal prion domain is inaccessible to antibodies, whereas the COOH-terminal nitrogen regulation domain is accessible. This finding is consistent with the proposal that the prion domains stack to form the filament backbone, which is surrounded by the COOH-terminal domains. These observations support and further specify the concept of the [URE3] prion as a self-propagating amyloid.

Some Parameters of Immune Status in Children before and after Cataract Extraction with Intraocular Lens Implantation.

An immunological study was performed in 71 children aged 6-15 years old. Twenty seven of these 71 patients have undergone surgery for congenital cataract, 23 - for traumatic cataract aspiration-irrigation with a posterior chamber intraocular lens implantation and 21 - for secondary intraocular lens implantation. The number of peripheral blood active T lymphocytes, CD4(+), CD8(+), HLA DR(+) lymphocytes and antibody response to lens (alpha-crystalline) and retina (S-antigen) proteins were determined. Tissue specific antibodies were revealed in cases of both increased and decreased T-cellular immunity parameters. Sensibilization to S-antigen at the background of HLA DR(+) lymphocytes increase and a decrease in other parameters of immunity that may be regarded as the autoimmune status was the most unfavorable prognostic sign. In these cases even after atraumatic surgery the risk of postoperative inflammation was rather high with development of chronicity.