Purification and characterization of glutathione reductase from Scots pine needles

Changes in the excitability of the liverwort Conocephalum conicum L. caused by inhibitors of ionic channels and phosphorylation uncouplers, were examined. Action potentials were triggered by electrical and light stimuli. Tetraethylammonium chloride, an inhibitor of K⁺ channels, completely blocked the ability to generate action potentials. Excitability also disappeared under the influence of MnCl₂ and LaCl₃, inhibitors of Ca²⁺ channels. The participation of Ca²⁺ and K⁺ in the electrogenesis of action potentials in C. conicum is discussed. Treatment with phosphorylation uncouplers induced a gradual disappearance of the metabolic component of the resting potential. It was accompanied by some series of excitations, numbering from several to over a dozen impulses characterized by decreasing amplitudes, after which the organism became totally unexcitable. Dicyclohexylcarbodiimide an inhibitor of H⁺-ATPase, also caused depolarization of the transmembrane potential and disappearance of excitability. The results indicated the participation of a metabolic component in the generation of action potentials in C. conicum .     

Mammalian FMRF-NH2-like peptide in rat pituitary: Decrease by osmotic stimulus

Previous studies with the Brattleboro rat suggested a possible interaction at the pituitary level between AVP and the neuropeptide, F-8-F-NH₂. In order to test this hypothesis, we studied the effect of various osmotic stimuli on neurohypophyseal F-8-F-NH₂. In rats drinking 2% NaCl solution for two days, neural lobe AVP and F-8-F-NH₂ levels were equally reduced by 87%. After maximal depletion, pituitary levels of F-8-F-NH₂ and AVP rebounded in parallel when normal drinking water was reintroduced. Pituitary stalk transection depleted neurohypophyseal F-8-F-NH₂. The results of this study suggest that neurohypophyseal F-8-F-NH₂ originates from the hypothalamus and, furthermore, is coreleased along with AVP in response to hyperosmotic stimuli.