Competition for endogenous and exogenous nutrients between Sporobolomyces roseus and Cochliobolus sativus

Sporobolomyces roseus reduced conidial germination of Cochliobolus sativus on glass slides covered with a thin layer (0.1 mm) of water agar or Czapek Dox agar by ca. 60 and 99%, respectively. On wheat flag leaves S. roseus reduced conidial germination by ca. 15% but reduced germ tube length by ca. 48%. However, cell-free aqueous diffusates collected from water agar slides and leaves with and without S. roseus showed no differential effect on Co. sativus when bioassayed on water agar slides. Diffusates from Czapek Dox agar with S. roseus reduced conidial germination by 46% when compared with the nutrient-rich diffusate from Czapek Dox agar alone. Although this demonstrated the ability of the yeasts to reduce the amount of exogenous nutrients, this did not account for the 99% reduction found in the presence of S. roseus. When Co. sativus was separated from S. roseus on Czapek Dox agar by two layers of cellophane, the reduction was the same and maintained for at least 3 days. If Co. sativus was removed from S. roseus by transferring the upper cellophane sheet to a glass slide, germination was restored, indicating that the yeasts formed also a continuous drain of endogenous nutrients from the conidia. A steady supply of amino acids and (or) glucose to Czapek Dox agar slides with S. roseus and Co. sativus could only partially overcome the antagonistic interaction.

Ein Verfahren zur elektronenmikroskopischen Untersuchung von Gewebekulturen im Wuchsverband

An improved method for the electron microscopic study of sectioned tissue cultures of human brain tumors is based on commercial perforated cellophane sheets upon which the cells are grown. Specimens are fixed with buffered osmium tetroxide, imbedded horizontally in Metacrylate or Vestopal without separating them from the cellophane sheet and the monolayer cut in sections of 500 A.Electron micrographs show a very good preservation of intracellular and intercellular structures.

The adsorption of direct dyes on cellulose

The dyeing of cellulose with direct dyes has been studied in detail by Neale and his collaborators, and a quantitative theory to account for the effect of dye and electrolyte concentration on the adsorption equilibrium has been developed by Hanson, Neale & Stringfellow (1935). More recently, a slightly different theory has been described by Willis, Warwicker, Standing & Urquhart (1945), supported by a very full examination of the adsorption of Chrysophenine G on cellophane sheet. The two theories are based on common postulates and differ mainly in the mathematical development and the simplifying assumptions which are adopted. Both assume that the direct dyes exist in solution as fully dissociated salts of the type Na z D, and that of all the ions present only the dye anions are specifically adsorbed at the cellulose/water interface. The distribution of all other ions is determined by the need for electrical neutrality in any finite volume of the system. Hanson et al . divide the dyeing system into two parts, namely, the aqueous solution contained within the fibre and the external solution, and proceed to apply the laws of membrane equilibrium to the distribution of ions between these two parts of the solution.