Metaplasticity at identified inhibitory synapses in Aplysia.

Synaptic plasticity is an important feature of neural networks involved in the encoding of information. In the analysis of long-term potentiation and long-term depression, several examples have emerged in which this plasticity is itself modulated. This higher-order form of plasticity has been referred to as 'metaplasticity', a modification of synapses reflected as a change in the ability to induce or maintain plasticity.

Determinants of apical membrane permeabilities of barrier epithelia.

Renal collecting duct and thick ascending limb, as well as stomach, exhibit strikingly low permeabilities to water and solutes. However, the apical membrane characteristics responsible for these unique permeabilities remain unknown. While the lipid composition of artificial membranes governs membrane permeability, exoplasmic and cytoplasmic leaflets of biological apical membranes exhibit striking asymmetries in lipid composition.

Apical membrane of the gastric parietal cell: water, proton, and nonelectrolyte permeabilities.

Gastric parietal cell apical membranes must protect the cell from the extremely low pH and wide variations in osmolality of the gastric juice. To characterize the permeability properties of gastric apical membranes, we have measured passive permeabilities to water, protons, NH3, and small nonelectrolytes of membrane vesicles derived from parietal cells of fasted animals and fed animals. Both preparations are known to be highly enriched in H+/K(+)-ATPase, the enzyme responsible for acidifying the gastric contents.