Redox activity ofHydrodictyon reticulatum plasmalemma vesicles.

Plasmalemma vesicles with preserved redox activity were prepared from nets ofHydrodictyon reticulatum. Since the walls are mechanically very resistant, a combination of partial cell-wall enzyme digestion and ultrasonic homogenization had to be used for the disruption of cells. To isolate the plasma-membrane-enriched microsomal fraction separation in an aqueous two-phase polymer system was found to be most suitable.

Effects of mannitol hypertonicity on water and ion contents in the alga Hydrodictyon reticulatum.

Long-term effects of mannitol hypertonicity on the water and ion contents in the fresh-water alga Hydrodictyon reticulatum were studied. The cells did not behave as osmometers and a closer examination suggested that wall elasticity was related to the medium tonicity and that the rate of sodium extrusion from the cells depended on the wall (turgor) pressure.

The plasmalemma redox system of a fresh-water alga and membrane electrical parameters.

In order to learn more details about the plasmalemma redox system in the alga Hydrodictyon reticulatum the electrophysiological characteristics of the plasma membrane as influenced by artificial electron acceptors were estimated. Ferricyanide anion as well as TTF+ depolarized the membrane potential, the effect being more marked in the dark than in the light. In the presence of ferricyanide the membrane resistance in the light was decreased by about 29% on the average, in the dark it remained unchanged.

Effects of amiloride on the transport of sodium and other ions in the alga Hydrodictyon reticulatum.

The diuretic amiloride, an almost specific inhibitor of sodium transport in animal cells and tissues, appears to produce a number of effects in the alga Hydrodictyon reticulatum. At 1 mmol/l concentration it markedly reduces the influx of sodium ions (but not their active outflux), the influxes of potassium, chloride as well as of bicarbonate ions, and causes a profound decrease in the plasmalemma membrane potential. This plurality of inhibitory effects suggests that individual transport processes in the alga are mutually coupled.

Parallel pathways of potassium transport in the alga Hydrodictyon reticulatum. Effects of calcium.

Inflow of potassium ions into the alga Hydrodictyon reticulatum is reduced in the dark, the reduction being accompanied by a change in the selectivity pattern with respect to alkali metal ions, observed in competition experiments and evaluated by the gnostic analysis as described by Kovanic. This suggests that in the light a special mechanism of potassium uptake with a characteristic selectivity is switched on. This mechanism can be also suppressed by too high (2 mmol/l) or too low (EGTA) concentration of calcium ions in the medium.