Browsing by Author "Soto, C"

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    Acetylcholinesterase accelerates assembly of amyloid-beta-peptides into Alzheimer's fibrils: Possible role of the peripheral site of the enzyme
    (1996) Inestrosa, N.C.; Alvarez, A; Perez, CA; Moreno, RD; Vicente, M; Linker, C; Casanueva, OI; Soto, C; Garrido, J
    Acetylcholinesterase (AChE), an important component of cholinergic synapses, colocalizes with amyloid-beta peptide (A beta) deposits of Alzheimer's brain. We report here that bovine brain AChE, as well as the human and mouse recombinant enzyme, accelerates amyloid formation from wild-type A beta and a mutant A beta peptide, which alone produces few amyloid-like fibrils. The action of AChE was independent of the subunit array of the enzyme, was not affected by edrophonium, an active site inhibitor, but it was affected by propidium, a peripheral anionic binding site ligand. Butyrylcholinesterase, an enzyme that lacks the peripheral site, did not affect amyloid formation. Furthermore, AChE is a potent amyloid-promoting factor when compared with other A beta-associated proteins. Thus, in addition to its role in cholinergic synapses, AChE may function by accelerating A beta formation and could play a role during amyloid deposition in Alzheimer's brain.
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    Dispersal and extrapolation on the accuracy of temporal predictions from distribution models for the Darwin's frog
    (2017) Uribe, D; Soto, C; Valenzuela, A; Bizama, G; Simonetti Zambello, Javier; Pliscoff, Patricio
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    Extracellular matrix regulates the amount of the beta-amyloid precursor protein and its amyloidogenic fragments
    (1996) Bronfman, FC; Soto, C; Tapia, L; Tapia, V; Inestrosa, NC
    We have studied the influence of the extracellular matrix (ECM) on the amount of beta-amyloid precursor protein (APP) and C-terminal amyloid-bearing fragments in 3T3 fibroblasts. After incubation with ECM components, the cellular APP content of 3T3 cells changed. Besides, different substrata including collagen, fibronectin, laminin, vitronectin, and heparin, determined changes in the amount of a C-terminal 22 kDa-fragment. The regulation of amyloidogenic fragments by the ECM was transient; in fact, when 3T3 cells were plated on tissue culture dishes coated with collagen or vitronectin, maximal levels of the 22 kDa fragment were observed 12 h after plating; in the presence of fibronectin, the maximum level of the amyloidogenic fragment was obtained 36 h after plating. These results indicate that the ECM modulates in a transient way the generation of APP-derived polypeptides containing the amyloid-beta-peptide (A beta). The ECM does not have a generalized effect on 3T3 fibroblasts, because no significant differences in cell attachment, growth rate, whole-cell polypeptide pattern, beta(1) integrin and a-tubulin levels were observed on cells grown on various matrix proteins. Laminin, collagen, and heparin also influence the level of an amyloidogenic fragment of 35 kDa in Neuro 2A neuronal cells, without a significant change in the neuronal marker acetylcholinesterase. In this case, however, a long-lasting response to ECM molecules was observed. These observations provide evidence that ECM molecules influence APP biogenesis, including the generation of amyloidogenic fragments containing the A beta peptide. Our studies might prove significant to understand the localized increment of beta-amyloid deposition in selected areas of the brain of Alzheimer's patients. (C) 1996 Wiley-Liss, Inc.
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    Voltammetric study of the redox chemistry of 2,3-dihydroxy-quinoxaline and its zinc complexes in non-aqueous medium
    (PERGAMON-ELSEVIER SCIENCE LTD, 1998) Bodini, ME; del Valle, MA; Copia, GE; Soto, C
    The electrochemical behaviours of 2,3-dihydroxy-quinoxaline (2,3-DH(2)Qx) and the complex species formed with zinc(II) have been studied in non-aqueous media. Using dimethylsulphoxide or N,N-dimethylformamide as solvents the monoanion of the ligand is obtained quantitatively after reduction of one of the hydroxylic protons. The reduction potential for the hydroxylic proton is -1.93 V vs S.C.E. in DMSO and -1.68 V vs S.C.E. in DMF, reflecting the different donor number of the solvents. If acetonitrile is used, the simultaneous reduction of both hydroxylic protons is observed. The oxidation to the semiquinone is observed at -0.12 V us S.C.E. in DMSO and DMF whereas it appears at -0.02 V us S.C.E. in acetonitrile.