The retina of the frog was superfused with a Ringer solution containing impermeant "probe" cations and anions. Light-evoked concentration changes in these probe ions were measured in the subretinal space (SRS) with ion-selective microelectrodes. A decrease in probe ion concentration was found, and several observations suggest that this is caused by a light-evoked expansion of the SRS. The probe ion decrease was not seen in the isolated retina; thus, the pigment epithelial (PE) cells are important for its generation. Pharmacological studies suggest that K+ channels in the PE cells are important--perhaps the PE cells shrink in response to the light-evoked decrease in SRS [K+]. The light-evoked decrease of SRS volume may be important in the understanding of SRS solute concentrations, retina-PE adhesivity, photoreceptor-PE cell interactions, and the interphotoreceptor matrix.

No abstract

The genus Metacordyceps contains arthropod pathogens in Clavicipitaceae (Hypocreales) that formerly were classified in Cordyceps sensu Kobayasi et Mains. Of the current arthropod pathogenic genera of Hypocreales, the genus Metacordyceps remains one of the most poorly understood and contains a number of teleomorphic morphologies convergent with species of Cordyceps s.s. (Cordycipitaceae) and Ophiocordyceps (Ophiocordycipitaceae). Of note, the anamorph genera Metarhizium and Pochonia were found to be associated only with Metacordyceps and demonstrated to be phylogenetically informative for the clade. Several species of Cordyceps considered to have uncertain placements (incertae sedis) in the current taxonomic framework of clavicipitoid fungi were collected during field expeditions mostly in eastern Asia. Species reclassified here in Metacordyceps include Cordyceps atrovirens Kobayasi & Shimizu, Cordyceps indigotica Kobayasi & Shimizu, Cordyceps khaoyaiensis Hywel-Jones, Cordyceps kusanagiensis Kobayasi & Shimizu, Cordyceps martialis Speg., Ophiocordyceps owariensis Kobayasi, Cordyceps pseudoatrovirens Kobayasi & Shimizu and Ophicordyceps owariensis f. viridescens (Uchiy. & Udagawa) G.H. Sung, J.M. Sung, Hywel-Jones & Spatafora. Incorporation of these species in a multigene phylogenetic framework of the major clades of clavicipitoid fungi more than doubled the number of species in Metacordyceps and allowed for refinement of morphological concepts for the genus consistent with the phylogenetic structure. Based on these findings we then discuss evolution of this genus, subgeneric relationships, anamorph connections, and suggest additional species that should be confirmed for possible inclusion in Metacordyceps.

Natural polyphenols are major constituents of plant foods and herbs. Numerous studies have demonstrated that natural polyphenols inhibited amyloid formation and destabilized the preformed amyloid fibrils. However, the molecular mechanism for the antiamyloidogenesis of polyphenols is still unclear and remains to be further explored. In the present study, the preformed lysozyme fibrils were used as an in vitro model to study the disruptive effects of tea catechins on amyloid fibrils. Results showed that tea catechins induced the conversion of lysozyme fibrils to amorphous aggregates and inhibited fibril-induced hemolysis. Hydroquinone also showed disruptive effect on the fibrils, whereas phenol and two typical antioxidants, ascorbic acid and alpha-tocopherol, did not affect the fibrillar structure, suggesting that polyphenolic structure is essential for fibril deposition. Correlation analyses indicate that the fibril-depositing effects were related to both the antioxidative potency and hydrophobicity of tea catechins. These findings provide new evidence for comprehensive understanding of the interaction between natural polyphenols and amyloid fibrils.

Accumulating evidence has strongly suggested that amyloid fibrils of protein or peptide are cytotoxic. Fibrillar species appear to lead to disruption of cell membrane structures and thereby cause cell death. In this study, human erythrocytes were used as an in vitro model to examine the disruptive effect of lysozyme fibrils on the plasma membrane. Both the protofibrils and mature fibrils induced hemolysis and aggregation of erythrocytes. Treating ghost membranes with the fibrils resulted in aggregation of membrane proteins through intermolecular disulfide cross-linking. LC-ESI-MS/MS and Western blotting analysis showed that lysozyme fragments were incorporated into the aggregates of ghost membrane proteins, which suggested that thio-disulfide exchange among lysozyme and membrane proteins was triggered when the fibrils interacted with erythrocyte membranes. Metal-ion chelators, radical scavengers, and antioxidants had no effect on the amyloid-induced disulfide cross-linking. The exposure of interior hydrophobic residues and the increased level of solvent-accessible disulfides in the lysozyme fibrils are thought to be involved in membrane disruption. These results may unveil a novel pathway for the cytotoxicity of amyloid fibrils.