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.

Characterization of phosphate transport in Streptomyces granaticolor.

Transport of inorganic phosphate in Streptomyces granaticolor was characterized in two growth stages; kinetic parameters were determined and two transport systems were found in both stages, with the following values: KT1 = 0.06 mM, Jlim1 = 0.95 nmol min-1 (mg DS)-1, and KT2 = 1.

Cell volume regulation in Claviceps fusiformis. An animal-type Na,K-ATPase operating in a fungus?

Claviceps fusiformis, an ergot pathogen of pearl millet, was equilibrated in media without and with 0.1 mM ouabain (g-strophantin). Highly significant effects of ouabain on the contents of sodium ions and water were found, suggesting that an active transport of sodium ions, similar to that in animal cells, regulates the cell volume of the fungus.

Ba2+ ions hyperpolarize algal cell membrane and enhance plasmalemma resistance without affecting ion and water contents.

Culturing the fresh-water alga Hydrodictyon reticulatum for 9 days in the presence of 0.2 and 0.4 mmol/l Ba2+ increases the membrane potential about twice and the plasmalemma resistance 5-10 times without having any significant effect on the cell contents of water and Na+, K+ and Cl- ions.

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.

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.

Cell volume maintenance and regulation in kidney tissues of various vertebrates.

Ouabain-sensitive and ouabain-insensitive mechanisms are shown to participate to a different extent in the cell volume maintenance in kidney tissues of various vertebrates. The ouabain-insensitive mechanisms predominate in the lamprey and in fresh-water fishes, whereas in the flounder, representing sea fishes, there is a complete predominance of the ouabain-sensitive mechanism. In the rabbit kidney cortex tissue the two systems play a comparable role.

Effect of a sudden and a slow concentration increase in plasma urea on its concentration in some tissues of the dog and rat.

The urea concentration in the renal cortex ([RC]) of pentobarbital-anaesthetized dogs was 5.71 times higher than the plasma concentration ([P]); the liver ([L]) and the skeletal muscle ([SM]) concentrations were the same as ([P]). Rapid infusion of 20% urea (1 g/kg b.

Some characteristics of urea accumulation in the renal cortex tissue of rats and dogs.

The urea concentration in the renal cortex ([RC]), liver ([L]) and skeletal muscle ([SM]) of non-diuretic Wistar rats was measured chemically and after an i.m. injection of 14C-urea and was compared with the plasma urea concentration ([P]).

Cell water content in carp kidney tissue slices as influenced by various osmotic agents.

Determination of water content in the surviving kidney tissue of the carp (Cyprinus carpio) is a convenient method for studying epithelial cell volume regulation under the influence of various osmotic agents and inhibitors. Artificial media of abnormal tonicities were used both as a purely experimental tool and as an attempt to model the behaviour of the tissue under extreme (physiological or pathological) conditions. In a medium hypertonic with mannitol the inhibition of the sodium-potassium pump by ouabain does not change the water content of the tissue (the same as in normal Krebs-Henseleit saline).

Ouabain-insensitive mechanism of cell volume maintenance in the carp kidney.

1) An ouabain-insensitive mechanism of cell volume maintenance, similar to that operating in the kidney tissue of mammals and in epithelial cells of the frog urinary bladder, has been demonstrated in the kidney tissue of carp (Cyprinus carpio)--there is no significant swelling even after 4-hour incubation with 10(-4) mol/l-1 ouabain. 2) The mechanism is not affected by 2-hour incubation with sodium in the saline replaced with tris or choline and, unlike in rabbit kidney cortex, cannot be inhibited by alkaline pH. 3) Neither a contractile mechanism sensitive to cytochalasin B, nor transport of divalent cations could be shown to be involved in this ouabain-insensitive cell volume maintenance in the carp kidney tissue.

Effect of Mercurascan on sodium transport in frog skin and bladder.

The authors studied the effect of Mercurascan (MSC) (a hydroxy- mercury derivative of fluorescein) on electrical parameters, namely potential difference (P.D.) and short circuit current (S.

Absence of a thyroxine effect on the sodium content in the frog urinary bladder.

As a contribution to the discussion whether in vitro thyroxine effects occur at all on anuran epithelial membranes it has been shown that thyroxine 10(-6) and 10(-4) M) produces neither a detectable change in the content of ions and water in the tissue of the urinary bladder of Rana temporaria, nor a change in the oxygen consumption of the bladder or skin of this frog species.

Muscosal and serosal effects of insulin on ion contents of the frog urinary bladder.

When applied in vitro at the serosal border of the bladder of Rana temporaria insulin (1.7.10(-5) M) brings about a decrease in the tissue sodium content, suggesting a stimulation of the pump extruding sodium ions from epithelial cells.