A distinct subfraction of Aß is responsible for the high-affinity Pittsburgh compound B-binding site in Alzheimer's disease brain.

The positron emission tomography (PET) ligand (11) C-labeled Pittsburgh compound B (PIB) is used to image ß-amyloid (Aß) deposits in the brains of living subjects with the intent of detecting early stages of Alzheimer's disease (AD). However, deposits of human-sequence Aß in amyloid precursor protein transgenic mice and non-human primates bind very little PIB. The high stoichiometry of PIB:Aß binding in human AD suggests that the PIB-binding site may represent a particularly pathogenic entity and/or report local pathologic conditions. In this study, (3) H-PIB was employed to track purification of the PIB-binding site in > 90% yield from frontal cortical tissue of autopsy-diagnosed AD subjects. The purified PIB-binding site comprises a distinct, highly insoluble subfraction of the Aß in AD brain with low buoyant density because of the sodium dodecyl sulfate-resistant association with a limited subset of brain proteins and lipids with physical properties similar to lipid rafts and to a ganglioside:Aß complex in AD and Down syndrome brain. Both the protein and lipid components are required for PIB binding. Elucidation of human-specific biological components and pathways will be important in guiding improvement of the animal models for AD and in identifying new potential therapeutic avenues. A lipid-associated subpopulation of Aß accounts for the high-affinity binding of Pittsburgh compound B (PIB) in Alzheimer's disease brain. Mass spectrometry of the isolated PIB-binding site from frontal cortex identified Aß peptides and a set of plaque-associated proteins in AD but not age-matched normal brain. The PIB-binding site may represent a particularly pathogenic entity and/or report local pathologic conditions.

Development, in vitro testing, and clinical use of a 3.5 mm-diameter zirconia abutment.

The use of small-diameter implants is indicated when small missing teeth have to be replaced, especially in esthetic zones. Nevertheless, the small diameter can pose a limiting factor with respect to what materials can be used for the final crown. In most cases, full-ceramic crowns in combination with a ceramic abutment are usually the material of choice for final reconstructions. To date, based on mechanical considerations, a 3.5 mm implant diameter has been a contraindication for using ceramic abutments. The authors describe here the development, in vitro testing, and clinical use of a zirconium abutment with a 3.5 mm diameter. The advantages of this small-diameter zirconia abutment include a minimum platform height that offers optimal prosthetic flexibility, and an accurate transfer of the implant position on to the master model. Furthermore, a precise rotational orientation for single-tooth restorations, optimal mechanical stability, and optimal fatigue resistance can be achieved. The microgap is minimized and protection against overload is afforded. In the reported case, high patient satisfaction was achieved due also to an esthetically pleasing final result.