Single channel properties of neuronal nicotinic ACh receptors in stratum radiatum interneurons of rat hippocampal slices

The single channel properties of neuronal nicotinic ACh receptors (nAChRs) were investigated in outside-out patches from CA1 stratum radiatum interneurons from thin slices of rat hippocampus.The application of ACh (10 μm to 1 mm) induced the opening of observable single channel currents with two distinct current levels, which corresponded to conductance levels of 38 ± 3 and 62 ± 2 pS. The 38 pS channel was observed in 10 % (n = 260) of patches, whereas the 62 pS channel was observed in 4 % of patches; these two channel types were most often observed independently.The α7-selective nAChR antagonist methyllycaconitine (MLA; 50 nm) reduced the open probability of the 38 pS channel by 73 %. In contrast, the 62 pS channel was unaffected by MLA, but instead was blocked by dihydro-β-erythroidine (DHβE; 10 μm), a broad spectrum nAChR antagonist.These data suggest that rat hippocampal CA1 stratum radiatum interneurons in the slice possess at least two different types of functional nAChRs, an α7-containing subtype with a single channel conductance of 38 pS, and a non-α7 subtype with a single channel conductance of 62 pS

Diversity in the Globally Distributed Diatom Genus <i>Chaetoceros</i> (Bacillariophyceae): Three New Species from Warm-Temperate Waters

<div><p><i>Chaetoceros</i> is one of the most species rich, widespread and abundant diatom genera in marine and brackish habitats worldwide. It therefore forms an excellent model for in-depth biodiversity studies, assessing morphological and genetic differentiation among groups of strains. The global <i>Chaetoceros lorenzianus</i> complex presently comprises three species known to science. However, our recent studies have shown that the group includes several previously unknown species. In this article, 50 strains, mainly from high latitudes and from warm-temperate waters, were examined morphologically and genetically and the results compared with those of field studies from elsewhere. The strains clustered into five groups, two of which are formed by <i>C</i>. <i>decipiens</i> Cleve and <i>C</i>. <i>mitra</i> (Bailey) Cleve, respectively. Their species descriptions are emended based on samples collected close to the type localities. The three other groups are formed by new species, <i>C</i>. <i>elegans</i> sp. nov., <i>C</i>. <i>laevisporus</i> sp. nov. and <i>C</i>. <i>mannaii</i> sp. nov. Characters used to distinguish each species are: orientation of setae, shape and size of the apertures, shape, size and density of the poroids on the setae and, at least in some species, characters of the resting spores. Our aim is to cover the global species diversity in this complex, as correct species delineation is the basis for exploring biodiversity, distribution of organisms, interactions in the food web and effects of environmental changes.</p></div

<i>Chaetoceros decipiens</i>.

<p>Strain D10, SEM (A–C) and TEM (D). A: Solitary cell with silica fringes. B: Intercalary cells with overlapping silica membrane (arrow). C: Detail of fused seta bases, silica membrane and fringes on the mantle (arrowhead). D: Rows of poroids on the mantle. A and B scale bars, 10 μm. C and D scale bars, 2 μm.</p

<i>Chaetoceros mannaii</i> sp. nov.

<p>LM (A and B), SEM (C and E) and TEM (D and F); strain N1. A: Straight chain showing seta divergence and constrictions (arrows) between the mantle and the girdle. B: Oval valve face. C and D: Intercalary cells, with ear-like structures (arrowheads in D) at the bases of setae in heavily silicified frustule. E and F: Terminal valves, with ear-like structures at the seta bases (arrowheads in E) and distinct constriction above the ring (arrowheads in F). A scale bar, 20 μm. B–F scale bars, 5 μm.</p

<i>Chaetoceros decipiens</i>.

<p>LM (A and B), TEM (C, D, H-J) and SEM (E-G). A-E: Seta structure of lectotype MIC5366 (A), strains P14B3B (B) and D10 (C–E), showing the 4–6 sided seta with poroids and small spines. F: Terminal valve with fringes (arrowheads); strain D10. G: Silica warts on the basal ring of the mantle; strain D10. H: Annulus, costae and poroid pattern on intercalary valve; strain P10E5. I: Terminal valve showing rimoportula without external process (arrowhead); strain D10. J: Girdle bands; strain D10. A and B scale bars, 10 μm. C–J scale bars, 2 μm.</p

LM of <i>Chaetoceros elegans</i> sp. nov.

<p>Strain YL7. A: Chain view displaying seta divergence in the apical plane. B: Solitary cell. C: Chain view demonstrating large apertures and chloroplasts. D: End of chain showing constrictions (arrows) between the mantle and the girdle, and V-shaped protrusion (arrowhead) located centrally on terminal valve. A and B scale bars, 50 μm. C and D scale bars, 20 μm.</p

<i>Chaetoceros elegans</i> sp. nov.

<p>LM (C), TEM (A, B, H) and SEM (D–G). A and B: Overlapping ear-like structures (arrows) and small gap between the crossing bases of sibling setae in strain YL7. C: Terminal seta with partly visible poroids in LM; strain YL7. D and E: Seta structure showing elongated poroids (D, strain Ch12A1) and tear-shaped poroids (E, strain M1) and F and G: Detail of setae poroids; strain Ch12A1 (F) and strains MC785 (G). H: Girdle band; strain YL7. All scale bars are 2μm, except 10 μm in C.</p