Osmotic Environment Research Articles

Osmotic Environments during Fetal Development of Dogfish, Mustelus canis (Mitchill) and Squalus acanthias Linnaeus, and Some Comparisons with Skates and Rays

Osmotic Environments during Fetal Development of Dogfish, Mustelus canis (Mitchill) and Squalus acanthias Linnaeus, and Some Comparisons with Skates and Rays

THE ENZYMATIC RESPONSE OF ASTROCYTES TO VARIOUS IONS IN VITRO.

The effect of environmental ion concentration on the enzyme activity of astrocytes was investigated in tissue cultures of rat cerebral cortex. It was found that the oxidative enzymatic activity (succinic dehydrogenase, DPN-diaphorase, and several other enzymes) of astrocytes depended on the concentration of NaCl in the environment. This response was not specific for NaCl, but was also elicited by MgCl(2) and LiCl; the response was less consistent, and often questionable for KCl. However, only NaCl could elicit enzymatic changes in astrocytes at concentrations known to be present in a living organism. Astrocytes were the only cells which responded this way; it appeared that the foot-plates were particularly involved in the response since increase of enzyme activity occurred earlier in the foot-plates than in the perikarya. It was concluded that astrocytes are metabolically involved in the maintenance of the ionic and osmotic environment of the central nervous system, particularly in regard to the active transport of sodium.

Spermine as a protective agent against osmotic lysis.

PREVIOUS studies have revealed a close relationship between the growth requirement of Pasteurella tularensis and Neisseria perflava for spermine or allied polyamines and their marked osmotic fragility1,2. The susceptibility of those bacteria to the osmotic environment is manifested by leakage of cell material, rapid decay of respiratory ability and a sharp decline of viability following their brief exposure to distilled water. In the case of P. tularensis the osmotic cell damage is largely prevented by microgram amounts of spermine. On the other hand, the dependence of N. perflava on spermine as an essential growth factor in a chemically defined medium can be eliminated by proper adjustment of its tonicity.

Use of high molecular weight solutes in the study of isolated intracellular structures.

DURING a study of red algal plastids (‘rhodoplasts’) in vitro, some facts came to light which may have general interest in a study of isolated cell components. Sugars, such as sucrose, are the substances commonly used for the maintenance of the osmotic environment for isolated cellular components1.