Browsing by Author "Campos, EO"

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    A major portion of synaptic basal lamina acetylcholinesterase is detached by high salt- and heparin-containing buffers from rat diaphragm muscle and Torpedo electric organ
    (1998) Casanueva, OI; García-Huidobro, T; Campos, EO; Aldunate, R; Garrido, J; Inestrosa, NC
    Collagen-tailed asymmetric acetylcholinesterase (AChE) forms are believed to be anchored to the synaptic basal lamina via electrostatic: interactions involving proteoglycans. However, it was recently found that in avian and rat muscles, high ionic strength or polyanionic buffers could not detach AChE: from cell-surface clusters and that these buffers solubilized intracellular non-junctional asymmetric AChE rather than synaptic: forms of the enzyme. In the present study, asymmetric AChE forms were specifically solubilized by ionic buffers from sg synaptic basal! lamina-enriched fractions, largely devoid of intracellular material, obtained from the electric organ of Torpedo californica and the end plate regions of rat diaphragm muscle, Furthermore, foci of AChE activity were seen to diminish in size, number, and staining intensity when the rat synaptic basal lamina-enriched preparations were treated with the extraction buffers, Pn the case of Torpedo, almost all the AChE activity was removed from the pure basal lamina sheets. We therefore conclude that a major portion of extracellular collagen-tailed AChE is extractable from rat and Torpedo synaptic basal lamina by high ionic strength and heparin buffers,;although some non-extractable AChE activity remains associated with the junctional regions.
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    Induction of settlement and metamorphosis of the scallop Argopecten purpuratus Lamarck by excess K+ and epinephrine
    (1999) Martinez, G; Aguilera, C; Campos, EO
    Settlement and metamorphosis of marine invertebrate larvae is known to be triggered by specific environmental cues. Neuroactive compounds, particularly some monoamines, have been implicated in this process, and depolarization of receptor cell membranes has been suggested to occur as a response to them. An increase of extracellular K+ in seawater has been used as an effective inducer of these processes for some species. This study describes work designed to assay effects of epinephrine and excess K+ as inducers of settlement and metamorphosis of larvae of the scallop Argopecten purpuratus. Epinephrine and excess K+ increased the percentages of settlement, metamorphosis, and survival of these larvae. Responses were dose-dependent, with a maxima under 10(-5) M (epinephrine) and 10 mM (K+). In the case of epinephrine, the responses did not vary significantly with the time of exposure. An analysis of size and energy content of larvae induced to metamorphosis by the different methods showed that larvae induced with epinephrine produced postlarvae that were significantly smaller in size and energetically weaker than postlarvae produced using excess K+ or no added exogenous inducer.
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    Prostaglandins and reproduction of the scallop Argopecten purpuratus
    (1999) Martínez, G; Mettifogo, L; Lenoir, R; Campos, EO
    In order to learn about factors that influence the reproductive cycle of marine bivalves, the levels of prostaglandins (PGs) PGE(2) and PGF(2 alpha) were measured during gametogenesis in the functional hermaphrodite scallop, Argopecten purpuratus. The PGs, in extracts of gonads of these scallops, were measured by radioimmunoassay techniques on different days after an induced spawning. To verify that gametogenesis was taking place during the experimental time, each time scallops were sampled, gonadal maturation was examined by gonadal index and by qualitative and quantitative histological analysis. Quantitative analysis involved oocyte size frequency distributions and determination of cross-sectional area occupied by mature sperm. The experiment was run twice, once in winter and once in spring. A linear decrease of both PGs was detected in male and female portions of the gonads as the maturation of these proceeded. In the spring experiment, this decrease was detected in both gonadal portions, but in the winter experiment, it was detected only for the male portion and not for the female one. The histological analysis of the gonads showed that in winter, the female gametes did not mature, although the male gametes did. These results are indicative of an inverse relationship between gonadal maturity and PG levels. J. Exp. Zool. 284:225-231, 1999. (C) 1999 Wiley-Liss, Inc.
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    Stable complexes involving acetylcholinesterase and amyloid-β peptide change the biochemical properties of the enzyme and increase the neurotoxicity of Alzheimer's fibrils
    (1998) Alvarez, A; Alarcón, R; Opazo, C; Campos, EO; Muñoz, FJ; Calderón, FH; Dajas, F; Gentry, MK; Doctor, BP; De Mello, FG; Inestrosa, NC
    Brain acetylcholinesterase (AChE) forms stable complexes with amyloid-beta peptide (A beta) during its assembly into filaments, in agreement with its colocalization with the A beta deposits of Alzheimer's brain. The association of the enzyme with nascent A beta aggregates occurs as early as after 30 min of incubation. Analysis of the catalytic activity of the AChE incorporated into these complexes shows an anomalous behavior reminiscent of the AChE associated with senile plaques, which includes a resistance to low pH, high substrate concentrations, and lower sensitivity to AChE inhibitors. Furthermore, the toxicity of the AChE-amyloid complexes is higher than that of the A beta aggregates alone. Thus, in addition to its possible role as a heterogeneous nucleator during amyloid formation, AChE, by forming such stable complexes, may increase the neurotoxicity of A beta fibrils and thus may determine the selective neuronal loss observed in Alzheimer's brain.