Inwardly rectifying potassium (K+) channels (Kir) in Müller cells, the dominant glial cells in the retina, are supposed to be responsible for the spatial buffering action of K+ions. The molecular properties and subcellular localization of Müller cell Kir channels in rat and rabbit retinas were examined by using electrophysiological, molecular biological, and immunostaining techniques. Only a single population of Kir channel activity, the properties of which were identical to those of KAB-2/Kir4.1 expressed in HEK293T cells, could be recorded from endfoot to the distal portion of Müller cells. Consistently, Northern blot,in situhybridization, and RT-PCR analyses indicated expression of Kir4.1 in Müller cells per se. The Kir4.1 immunoreactivity was distributed in clusters throughout Müller cell membrane. The Kir4.1 expression in Müller cells disappeared promptly after culturing. When the dissociated Müller cells were cultured on laminin-coated dishes in the presence of insulin, Kir4.1 immunoreactivity was detected in a clustered manner on the cell membrane. Because insulin and laminin exist in the surrounding of Müller cells in the retina, these substances possibly may be physiological regulators of expression and distribution of Kir4.1 in Müller cellsin vivo.

A new strategy for mixed biaryl synthesis has been developed using the hypervalent iodine(III) reagents. The unique reactivities of the sigma-heteroaryl iodine(III) intermediates generated in situ are the key element for the unusual metal catalyst-free transformations and strict control of the product selectivities.

Cochlear endolymph has a highly positive potential of approximately +80 mV. This so-called endocochlear potential (EP) is essential for hearing. Although pivotal roles of K+channels in the formation of EP have been suggested, the types and distribution of K+channels in cochlea have not been characterized. Because EP was depressed by vascular perfusion of Ba2+, an inhibitor of inwardly rectifying K+(Kir) channels, but not by either 4-aminopyridine or tetraethylammonium, we examined the expression of Kir channel subunits in cochlear stria vascularis, the tissue that is supposed to play the central role in the generation of positive EP. Of 11 members of the Kir channel family examined with reverse transcription-PCR, we could detect only expression of KAB-2 (Kir4.1) mRNA in stria vascularis. KAB-2 immunoreactivity was specifically localized at the basolateral membrane of marginal cells but not in either basal or intermediate cells. Developmental expression of KAB-2 in marginal cells paralleled formation of EP. Furthermore, deaf mutant mice (viable dominant spotting; WV/WV) expressed no KAB-2 in their marginal cells. These results suggest that KAB-2 in marginal cells may be critically involved in the generation of positive EP.

Immunolocalization of KAU-2 (Kir4

The hypervalent iodine-mediated C-C selective coupling of N-methanesulfonyl anilides with aromatic hydrocarbons has been developed. The first organocatalytic oxidative cross-biaryl-coupling was achieved by the catalyst control in defining specific 2,2'-diiodobiphenyls for the direct C-C bond formations.