ON THE COVER
Plainfin midshipman fish (Porichthys notatus) build nests in the rocky intertidal zone. Males (left) produce calls known as a “hums” to attract females (right) to their nest. Hums require repeated muscle contractions at a frequency of 70–100 Hz. Individual hums last for over an hour and accordingly require in excess of 360,000 muscle contractions in a single call. Nelson et al. determine how Ca2+ is handled during this remarkable performance. Photo credit: Margaret Marchaterre, Department of Neurobiology and Behavior, Cornell University. See page 127.
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Aalkjær and Nielsen discuss new data revealing the basis of acid–base transport in t-tubules of skeletal muscle.
Milestone in Physiology
JGP 100th Anniversary
Chiu and colleagues review the primary evidence for divergent activation mechanisms and unitary properties of Pannexin 1 channels.
The bacterial pyridine nucleotide uptake family of transporters mediates the uptake of B-type vitamins, but their transport mechanism is unknown. Jaehme et al. show that the PnuT thiamine transporter utilizes a facilitated diffusion mechanism and supports metabolic trapping of phosphorylated thiamine.
Sodium–calcium exchangers contribute to the generation of intracellular Ca2+ signals in numerous physiological processes. Shlosman et al. determine the ion stoichiometry of the only sodium–calcium exchanger of known atomic structure, revealing its functional similarity to mammalian exchangers.
Polyamine block of AMPA-type ionotropic glutamate receptors is attenuated by auxiliary proteins stargazin and cornichon-3. Brown et al. show that relief from block is due to enhanced blocker permeation and present a modified model of permeant channel block to account for their experimental findings.
Ca2+-dependent facilitation is a positive feedback mechanism that regulates Cav2.1 P/Q-type channels but not closely related Cav2.2 N-type channels. Thomas et al. identify the molecular determinants that distinguish the ability of Cav2.1 and Cav2.2 to undergo Ca2+-dependent facilitation.
NHE- and diffusion-dependent proton fluxes across the tubular system membranes of fast-twitch muscle fibers of the rat
The regulation of pH across the t-system membrane of skeletal muscle fibers is poorly understood. Using a sealed tubule preparation, Launikonis et al. reveal Na+/H+ exchange activity and characterize the properties of the diffusional and NHE proton fluxes across the t-system.
Malignant hyperthermia can result from mutations in the ryanodine receptor that favor anesthetic-induced Ca2+ release. Zullo et al. find that membrane potential modulates the effect of the volatile anesthetic halothane on skeletal muscle ryanodine receptors possessing the Y524S mutation.
The swimbladder muscle of the Pacific midshipman fish contracts up to 360,000 times in an hour while generating mating calls. Using experimental measurements and computational modeling, Nelson et al. reveal the Ca2+ handling that permits these superfast muscle fibers to sustain high-frequency calling.
Integrative model of coronary flow in anatomically based vasculature under myogenic, shear, and metabolic regulation
Coronary blood flows through a complex vasculature that is regulated by a number of physiological mechanisms, including myogenic, shear regulation, and metabolic control. Namani et al. describe a fully integrative and anatomically correct model that accurately predicts experimental observations.