Long-lasting potassium channel inactivation in myoepithelial fibres is related to characteristics of swimming in diphyid siphonophores.

Diphyid siphonophores swim using bursts of propulsive jets, which are produced by contractions of a monolayer of subumbrellar myoepithelial fibres lining the nectophore. This swimming behaviour is characterised by successive increases in the force generating the jets during the initial jets of the burst. Action potentials that generate the contractions propagate throughout the myoepithelial layer: both their amplitude and duration successively increase during the first part of the burst.

Excitation-contraction coupling in skeletal and caudal heart muscle of the hagfish Eptatretus burgeri Girard.

Hagfishes are regarded as the most primitive living craniates. Excitation-contraction (E-C) coupling mechanisms were studied in skeletal and caudal heart muscle fibres of the hagfish Eptatretus burgeri. In white (fast) skeletal muscle fibres from the musculus tubulatus, force generation in response to electrical stimulation was maintained in nominally Ca(2+) free artificial seawater (ASW) (0Ca(2+)-ASW) containing 10 mmol l(-1) Co(2+) (a blocker of Ca(2+) currents).