PubMed Health⌕ Search

Biomedical subjects

A ROTHSTEIN

Publications and source records attributed to A ROTHSTEIN.

At least 19 recordsLinked to original sources
PubMed1965

LOCALIZATION OF ERYTHROCYTE MEMBRANE SULFHYDRYL GROUPS ESSENTIAL FOR GLUCOSE TRANSPORT.

The reactions of three organic mercurial compounds, chlormerodrin, parachloromercuribenzoate (PCMB), and parachloromercuribenzenesulfonate (PCMBS) with intact red blood cells, hemolyzed red cells, hemoglobin solutions, and hemoglobin-free ghosts have been characterized. Both PCMB and PCMBS react with only 2 to 3 sulfhydryl groups per mole of hemoglobin in solution, whereas chlormerodrin reacts with 6 to 7. In hemoglobin-free ghosts, however, all three reagents react with a similar number of sulfhydryl groups, approximately 4 x 10(-17) moles per cell, or about 25 per cent of the total stromal sulfhydryl groups, which react with inorganic mercuric chloride. In the intact cell the membrane imposes a diffusion barrier; chlormerodrin and PCMB penetrate slowly, whereas PCMBS does not. Kinetic studies of chlormerodrin binding to intact cells reveal that the majority of stromal sulfhydryl groups is located inside the diffusion barrier, with only 1 to 1.5 per cent (or 1 to 1,400,000 sites per cell) located outside of this barrier. Reaction of PCMBS with intact cells is limited to this small fraction on the outer membrane surface. All three reagents are capable of inhibiting glucose transport in the red cell. With chlormerodrin and PCMBS it was demonstrated that the inhibition results from interactions with the sulfhydryl groups located on the outer surface of the membrane.

Biological Transport↗
PubMed1964

DISCRIMINATION BETWEEN ALKALI METAL CATIONS BY YEAST. I. EFFECT OF PH ON UPTAKE.

Extracellular pH markedly influences the ability of yeast cells to discriminate between K(+) and Na(+), with K(+) favored to a greater degree at low pH. Studies of the kinetics of uptake of individual alkali metal cations by fermenting yeast indicate three zones relative to pH. Between pH 6 and 8, H(+) has no effect. Below pH 4, H(+) competitively inhibits the transport of each cation. Between pH 4 and 6, H(+) acts kinetically as a predominantly non-competitive inhibitor. Both effects can be reversed by increasing the concentrations of cations. However, the concentrations required to reverse the competitive effect are considerably lower than those required to reverse the apparently non-competitive effect. It is suggested that H(+) and the alkali metal cations can combine with two sites, a transport or carrier site, and a second, non-transporting site that influences the maximal rate of transport. Because the non-competitive inhibitory effect of H(+) is considerably greater on the other cations than on K(+), the discrimination in favor of K(+) is increased severalfold at low pH, beyond that predicted on the basis of the relative affinities for the transport site.

Biological Transport↗
PubMed1963

Interactions of arsenate with the phosphate-transporting system of yeast.

Arsenate competes with phosphate for transport into the yeast cell. The affinity of the two substances for the transport system is about equal, but in mixtures the phosphate is taken up about twice as fast as arsenate, because the maximal transport rate for phosphate is about twice as high. In addition to the competitive effect, arsenate causes a continuous and irreversible inactivation of the transport system that can be characterized by first order kinetics. The rate of arsenate inactivation is slower in the presence of phosphate and the amount of arsenate taken up before complete block is established is also decreased. The inactivation of the transport system cannot be relieved by washing or by treatment with glucose and phosphate. The inactivation is not the result of an inhibition of metabolism.

Arsenates↗
PubMed1962

Interaction of mercury with human erythrocytes.

The binding of mercury to red blood cells was measured in terms of Hg(203) uptake and desorption. The significant features of the binding are: (a) rapid achievement of equilibrium (3 to 5 minutes); (b) release of a Hg-complexing material from the red cells themselves which distorts the binding curves at low concentrations of metal (2.5 x 10(-7) to 5.0 x 10(-6)M); (c) prevention of binding by cysteine, glutathione, penicillamine, and EDTA but not by imidazole or histidine; (d) binding of mercury in amounts up to 7 times the reduced glutathione concentration of the cells before combination with glutathione itself; (e) binding primarily to sulfhydryl groups of hemoglobin and to a small number of stromal sulfhydryl groups, but also to other non-sulfhydryl cellular ligands after saturation of the sulfhydryl groups. Associated with the binding is inhibition of glucose uptake, induction of loss of K(+), and decrease in osmotic fragility. These effects increase over the range of concentrations (1 x 10(-17) to 1 x 10(-15) moles of Hg/RBC) well below those that result in saturation of the cellular binding sites; above 1 x 10(-15) moles/RBC, the effects decrease as the cells become saturated.

Biological Transport↗