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A ROTHSTEIN

Publications and source records attributed to A ROTHSTEIN.

At least 37 records · Page 2Linked to original sources
PubMed1960

The binding of mercury by the yeast cell in relation to changes in permeability.

Yeast cells exposed to mercuric chloride suffer irreversible damage to the membrane, resulting in a loss of potassium and cellular anions to the medium. The maximal loss of K(+), but not the time course of K(+) loss is related to the mercury concentration, the relationship following a normal curve on a graph of log-concentration versus effect. It is concluded that the response is all or none for individual cells, and that with increasing concentrations of metal, the threshold is exceeded in an increasing proportion of the cells. Parallel studies of the binding of mercury by the cells indicate two distinct phases, only one of which is associated with the physiological response. The binding process is relatively slow but reaches an equilibrium state. Desorption is markedly dependent on temperature. No simple stoichiometric relationship exists between the binding of mercury and the physiological response (K(+) loss).

Mercury↗
PubMed1960

The uptake of divalent manganese ion by mature normal human red blood cells.

At physiological pH and concentrations of Mn(++) in excess of 5 x 10(-4)M, study of the Mn(++) ion movement into human red cells is complicated by physicochemical alterations of the ion itself. At concentrations below 5 x 10(x4)M, the rate of uptake bears a linear relationship to the Mn(++) concentration. The permeability constant for inward movement of Mn(++) is 2.87 +/- 0.13 (S.E.) x 10(-9) cm./sec. The rate is not influenced by the addition of metabolic substrates such as glucose or adenosine or the metabolic inhibitors iodoacetate or fluoride. Co(++), Ca(++), and Mg(++) do not appear to compete with Mn(++) for entry, but at high concentrations relative to Mn(++), they reduce the rate of entry. Ca(++) is far more effective than Co(++) or Mg(++) in this regard. The permeability constant for outward Mn(++) movement is 1.38 +/- 0.21 (S.E.) x 10(-9) cm./sec., about half of that for entry. This slower rate of outward movement is consistent with the finding that 40 to 60 per cent of the Mn(++) taken up by the red cells is non-ultrafilterable. Less than 5 to 10 per cent of the Mn(++) appears to be bound to the stroma. It is concluded that entry and exit of Mn(++) is a process of passive diffusion involving no carriers, transport, or metabolic linkage.

Biological Transport↗
PubMed1959

An all-ornone response in thh release of potassium by yeast cells with methylene blue and other basic redox dyes.

Basic redox dyes, such as methylene blue, induce a loss of K(+) from yeast cells. The maximal loss, rather than the rate of loss, is related to the dye concentration, the response following a normal distribution on a plot of log-dose, versus percentage loss of K(+). This fact taken together with the observed correlation between K(+) loss and frequency of staining (as measured by microscopic observation), indicates that the response is all-or-none for individual cells. The response is produced by all the basic redox dyes tested (9), but by none of the acidic dyes (4). However, only the oxidized form of the dye is effective. Cations protect the cells from the basic dyes in a competitive manner, the bivalent cations (especially UO(2) (++)) being more effective than monovalent cations. It is suggested that the action of the dyes involves two steps, the first a binding to ribonucleic acid in the cell membrane (with competition from cations) and the second, an oxidation of neighboring sulfhydryl groups to the disulfide form. At a threshold level, unique for each cell, a generalized membrane breakdown occurs, resulting in the release of potassium and of other cytoplasmic constituents.

Cations, Monovalent↗
PubMed1958

The active transport of Mg++ and Mn++ into the yeast cell.

Certain bivalent cations, particularly Mg(++) and Mn(++), can be absorbed by yeast cells, provided that glucose is available, and that phosphate is also absorbed. The cation absorption is stimulated by potassium in low concentrations, but inhibited by higher concentrations. From the time course studies, it is apparent that the absorption rather than the presence of phosphate and the potassium is the important factor. Competition studies with pairs of cations indicate that binding on the surface of the cell is not a prerequisite to absorption. The absorption mechanism if highly selective for Mg(++) and Mn(++), as compared to Ca(++), Sr(++), and UO(2) (++), whereas the binding affinity is greatest for UO(2) (++), with little discrimination between Mg(++), Ca(++), Mn(++), and Sr(++). In contrast to the surface-bound cations which are completely exchangeable, the absorbed cations are not exchangeable. It is concluded that Mg(++) and Mn(++) are actively transported into the cell by a mechanism involving a phosphate and a protein constituent.

Biological Transport↗
PubMed1957

The active transport of phosphate into the yeast cell.

Phosphate can distribute in the cell wall space, but is not bound to an appreciable extent at the cell surface in non-metabolizing yeast. During metabolism of sugars, phosphate is actively transported into the yeast cell by a mechanism specifically involving glycolysis reactions. The movement of phosphate is in the inward direction only (no appreciable efflux), and it can proceed against a concentration gradient of 100 to 1. It is dependent on external phosphate concentrations in an asymptotic relationship, but is independent of the cellular orthophosphate concentration. The pH optimum for the phosphate uptake of 6.5 is shifted to the acid side by potassium. At certain values of pH a stimulation of 700 per cent by potassium can be observed. The nature of the effects of K(+) and H(+) are discussed.

Biological Transport↗