Sodium selectivity of Reissner's membrane epithelial cells

Background  

Sodium absorption by Reissner's membrane is thought to contribute to the homeostasis of the volume of cochlear endolymph. It was previously shown that the absorptive transepithelial current was blocked by amiloride and benzamil. The most commonly-observed target of these drugs is the epithelial sodium channel (ENaC), which is composed of the three subunits α-,β- and γ-ENaC. However, other less-selective cation channels have also been observed to be sensitive to benzamil and amiloride. The aim of this study was to determine whether Reissner's membrane epithelial cells could support parasensory K⁺ absorption via amiloride- and benzamil-sensitive electrogenic pathways.     

Indirect cues in selecting a hunting site in a sit‐and‐wait predator

Sit‐and‐wait predators use relatively simple rules for their decisions to choose and leave a patch, such as using the direct presence of prey to select a hunting site. However, the direct presence of prey can only be used when there is a highly visited patch in the proximity of the predator. Therefore, it is plausible that sit‐and‐wait predators also exploit indirect cues of prey presence and, consequently, use associative learning to select a hunting site. The present study tests for the role of associative learning in a sit‐and‐wait predator species for which the ecology is well understood: Misumena vatia Clerck crab spiders. An ecologically relevant scenario is used by selecting flower colour as the conditioned stimulus and prey presence as the unconditioned stimulus. The results provide no evidence that M. vatia crab spiders use the association between flower colour and food presence for selecting a hunting site. After a training phase of being exposed to a colourful artificial flower highly visited by bees, spiders select a hunting site independently of its colour during the testing phase. Investigations of similar scope and ecological relevance are required with other sit‐and‐wait predators to identify the conditions promoting the use of associative learning for foraging site selection when animals face an unpredictable food supply.     

Extrapyramidaler Kern und extrapyramidale Fasern im Accessorius und Hypoglossus

Zusammenfassung Die kleinen Zellen im Accessoriuskern und Hypoglossuskern, die in Form und Bau der Neben- und Mittelzelle Waldeyers im Rückenmark sehr nahe stehen, zeigen deutliche retrograde Veränderung nach der Durchtrennung des Accessorius bzw. Hypoglossus. Wir möchten dem-nach diese Zellen als extrapyramidalen Kern und die kleine markhaltige Faser im N. accessorius und hypoglossus als extrapyramidale Faser betrachten.