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Considerable controversy exists concerning the origin and composition of Alzheimer neurofibrillary tangles (ANT) and of paired helical filaments (PHF), the abnormal cytoplasmic fibers which ultrastructurally are the major components of ANT. Thus far, the unusual solubility properties of PHF have hindered the analysis of ANT. A new procedure is presented for isolating purified PHF which are soluble in the presence of sodium dodecyl sulfate. The purification protocol involves differential and rate zonal centrifugation, treatment with the detergents sarcosyl and sulfobetain 3–14, and sonication. The isolated PHF from Alzheimer disease/senile dementia of the Alzheimer type (7 cases) and Down's syndrome (one case) have been characterized structurally by negative-stain electron microscopy, biochemically by PAGE, and immunologically by both the ELISA technique and Western blot analysis using a monoclonal antibody prepared against ANT. Distinct polypeptides were shown to be associated with this structure and not seen in preparations from young and age-matched normal brains.

Nerve ending particles isolated from prenatal and postnatal rats by means of density-gradient centrifugation in a ficoll medium actively incorporated [32P]-orthophosphate into nucleotides, phosphoproteins and phospholipids. This process requires Mg2+; is dependent on malate plus pyruvate but not glucose, and is inhibited by dinitrophenol, gramicidin, oligomycin, azide, p-chloromercuribenzoate, CaCl2 but not iodoacetate. It was concluded that the metabolic energy at the synapse is derived largely from the mitochondria of the synaptic complex rather than from its cytoplasm. Thin-layer chromatography and paper electrophoresis revealed that the metabolically active phospholipids, namely phosphatidic acid, phosphatidyl inositol and the polyphosphoinositides which were found to be tightly bound to the phosphoprotein fraction, contained more than 90% of the total radioactivity but constituted less than 9% of the total phospholipids. The highest phosphoprotein and phospholipid content of the nerve endings (expressed in μmoles P/mg nerve ending protein) as well as maximal 32P-incorporation occurred just prior to and continued into the stage when functional changes are formed. It is suggested that an increase in the amount of enzymatic activity coupled with an increase in the permeability of the synaptosomal membrane to inorganic phosphate and other metabolites could trigger the rapid morpho-biochemical and functional changes observed in rat brain during this period of development. A simple density-gradient withdrawing device for the isolation of the submitochondrial particles after density-gradient centrifugation of the conventional mitochondrial fraction was described.