Alkali-metal ions in the metabolism of Bact. lactis aerogenes . I. Experiments on the uptake of radioactive potassium, rubidium and phosphorus

(This paper has been printed in full in Proceedings B, 138, 219) By the use as tracers of 42 K, 86 Rb and 32 P it has been shown that in the metabolism of Bact. lactis aerogenes ladis aerogenes ( a ) the alkali-metal ion enters the cell during oxidation of the carbon substrate (glucose, succinic acid, acetic acid) whether or not a nitrogen source is provided so that growth occurs; in either event the alkali-metal ion subsequently leaves the cell again; ( b ) if the pH is lowered the maximum uptake of the cation by the functioning cell is raised, although increased hydrion concentration first causes displacement of alkali-metal ions from resting cells. ( c ) in the early stages of growth, or of glucose oxidation without growth, the flow into the cell of alkali cations and of phosphate anions takes place in a parallel way.

On the ultra-violet absorption of crystalline preparations of vitamin B 1

Evidence has been produced by several workers tending to support the view that vitamin B 1 possesses an ultra-violet absorption band with a maximum at about 260 mμ. Bowden and snow (1932) stated that the preparation studied by them possessed such a band, which disappeared simultaneously with the vitamin activity on irradiation with monochromatic light of wave-length 25 mμ. The absorption curve published by Windaus et al . (1931) for their preparations also showed a maximum near 260 mμ. Heyroth and Loufbarrow (1932) have studied a large number of preparations of varying vitamin activity, and have shown that much of their ultra-violet absorption can be attributed to inactive purine and pyrimidine derivatives. Nevertheless, they conclude that there is a significant correlation between absorption at 260 mμ and biological activity (see also Ohdake, 1932). It is therefore somewhat surprising that the preparations recently made at Oxford (Kinnersley, O'Brien and Peters (1932-1933), which can claim to be the most potent yet produced, have their maximum absorption at a definitely different wave-length, namely 245-9 muμ, while at 260 mμ their absorption curves only show a barely perceptible hump, protruding from the steeply descending portion of the main band. An attempt to connect this discrepancy with a possible effect of hydrion concentration on the wave-length of the maximum led to the discovery of a curious phenomenon.

Intracellular hydrion concentration studies. V.-Colorimetric p H of malignant cells in tissue culture

The microinjection of the relatively small of mammalian tissues offers considerable difficulties, the chief of which is some means of knowing whether the cell in still alive after the injection. Usually deterioration of the cell is made evident by easily recognisable morphological changes, but this is not always the case. The best criterion so far encountered for the injection of solutions of dyes is the restriction of the color to the cell injection. This is more difficult to judge with dyes, especially those basic in nature, which easily penetrate cells from without. In such cases special pains must be taken to prevent spilling into the medium during the time that the pipette is being brought into the cell to be injected. Fortunately, the Clark and Lubs indicators are sodium salts of acid dyes, and most of these penetrate living cells, either very slowly or not at all. The consequence is that a small amount accidentally spilled about the cells quickly fades away by diffusion into the surrounding medium and does not disturb the procedure of injection. When once a solution of an acid dye is injected into a cell, the acquired colour persists for an appreciable length of time. Up to the present, the injection of cells of somatic tissues has always been followed, generally within 5 to 15 minutes, by observable signs of cytolysis. This is accompanied, and frequently preceded, by a fading out of the colour of the injected dye. From these observations it has been assumed that the cell is alive as long as the indicator is still within the cell injected. This assumption is supported by experiments on marine ova (Needham, 1926), for they have been demonstrated to be alive while retaining the colour of the injected indicator both in the cytoplasm and in the nucleus (Chambers and Pollack, 1927).