Cover picture: Freeze-fracture scanning electron microscopy images of testicular tissue samples from adult and juvenile mice (postnatal day 7), respectively. Adult seminiferous tubules display complex epithelial structures at various spermatogenic cycle stages and fully developed lumina, whereas immature cords are smaller solid structures composed of only Sertoli cells and spermatogonia (see Research Article by Fleck et al., 253–271).
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ClC-K2 is present on the basolateral membrane of kidney epithelial cells, but little is known about its single channel properties. Pinelli et al. record unitary ClC-K2 currents from intercalated cells of mouse connecting tubules and investigate their regulation by voltage, pH, Cl−, and Ca2+.
Phospholipids are required to bind to two distinct sites on the inward rectifier potassium channel for maximal efficacy. Lee et al. show that a membrane-associating tryptophan residue in the second site can mimic the effect of phospholipid binding and cause a conformational change to reveal the primary binding site.
For the aquaporins, selectivity to water is ensured to a large extent by an arginine filter within the pore of the channel. Carpentier et al. find that selectivity to silicon is also controlled by this filter but with the involvement of additional residues that are within or close to the pore.
Male germ cell development takes place within the testes of mammals, but little is known about its regulation. Fleck et al. record from spermatogonia and Sertoli cells, both in vitro and in situ, and find evidence for P2X4- and P2X7-mediated ATP-gated currents as well as a Ca2+-activated BK conductance.