The formation of neurotoxic aggregates by amyloid-β peptide (Aβ) is considered to be a key step in the onset of Alzheimer's disease. It is widely accepted that oligomers are more neurotoxic than amyloid fibrils in the aqueous-phase aggregation of Aβ. Membrane-mediated amyloidogenesis is also relevant to the pathology, although the relationship between the aggregate size and cytotoxicity has remained elusive. Here, aggregation processes of Aβ on living cells and cytotoxic events were monitored by fluorescence techniques. Aβ formed amyloids after forming oligomers composed of ≈10 Aβ molecules. The formation of amyloids was necessary to activate apoptotic caspase-3 and reduce the ability of the cell to proliferate; this indicated that amyloid formation is a key event in Aβ-induced cytotoxicity.

The study was conducted to evaluate the meat texture, muscle proximate composition, lipid class composition, and collagen content of cultured amberjack and to compare these parameters with those of the yellowtail. Our results showed that the meat texture of cultured amberjack was tougher and had a lower degree of seasonality than that of cultured yellowtail. Muscle lipid and collagen content also varied in the two fish species over the study period. Meat breaking strength was not correlated with any of the muscle constituents, indicating that variations in the meat texture of cultured amberjack was not directly influenced by the changes in the muscle biochemical constituents.

Both peptides were a-helical in dry state and gradually transitioned to intramolecular and then to intermolecular b-sheet upon exposure to vapor. The onset of b-sheet formation was delayed in AbpE but proceeded rapidly once triggered. AbpE inhibited the transition of Ab to intermolecular b-sheet structure, while Ab shifted the structure of AbpE towards more b-turn and less intermolecular b-sheet structure. Thus, each peptide inhibits intermolecular b-sheet formation in the other. This may explain the increased toxicity of oligomeric Ab þ AbpE peptide combinations as fibrils are less toxic. Additionally, the rapid formation and retention of b-turn structure in AbpE may facilitate its increased toxicity.