Effects of external saccharides on cell wall properties and ion transport inHydrodictyon reticulatum.

Various saccharides, when present at osmotically insignificant concentrations in growth media, were tested as to their effects on the cell walls of the green algaHydrodictyon reticulatum, manifesting themselves in differences in cell water and ion contents. BothD: -xylose andD: -mannose reduce the cell water content andD: -galactose does occasionally the same but onlyD: -xylose reduces significantly the intracellular sodium concentration, presumably by forming steric hindrances at the outlets of the sodium pumps at the outer surface of the cell membrane. No significant effects of eitherL: -arabinose orD: -arabinose on the cell water and ion contents were found.

Non-osmotic effects of external sugars on the cell water content and transport of cations across the plasmalemma inHydrodictyon reticulatum.

Saccharides added to the cultivation medium influence the properties of the cell wall of the strictly autotrophic green algaHydrodictyon reticulatum, most probably in such a way that they interfere with the processes of growth and repair of microfibrils. Natural monosaccharides (glucose, fructose, galactose, mannose, sucrose, cellobiose, raffinose) reduce the cell water content, increase the intracellular concentration mostly of both potassium and sodium cations and reduce the ohmic resistance of the cell membrane.

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.

Osmosis: membranes impermeable and permeable for solutes, mechanism of osmosis across porous membranes.

A mathematical description is presented of osmotic flows across both ideally semipermeable membranes and membranes permeable not only for the solvent but also for the solute. The principles of thermodynamics of irreversible processes used for the description are given and illustrated on the example of electroosmosis. Modern ideas about the physical basis of osmotic pressure on porous membranes are discussed and an experiment is described that models the processes of osmosis on a macroscopic level.

[Determination of chlorine levels in Presept, a modern disinfectant].

Presept (containing sodium dichloroisocyanurate as active component) was shown to be an excellent analytical reagent superior to classical Chloramine T and Chloramine B. Potentiometric titration of potassium ferrocyanide was found to be most suitable for estimation of chlorine content in Presept solutions. The presence of serum albumin can block or reverse the oxidation of ferrocyanide completely, whereas that of a detergent is of little importance.