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M Fox

Publications and source records attributed to M Fox.

At least 289 records · Page 16Linked to original sources
PubMed1974

Intestinal transport of weak electrolytes. Evidence in favor of a three-compartment system.

A study has been made of the transmural fluxes of benzoic, phenylacetic, and pentanoic acids, benzylamine, hexylamine, and D-amphetamine across rat jejunum incubated in vitro. The M to S fluxes of the weak acids were greater than their corresponding S to M fluxes, and the S to M fluxes of the weak bases were larger than their M to S fluxes. These patterns of asymmetric movements were observed when the transmural electrical potential difference was clamped at 0 mV, and when the pH values of the mucosal and serosal fluids were identical. The effects of a weak acid on the fluxes of other weak electrolytes were qualitatively similar when the effector weak acid was added to the mucosal fluid, and when it was added to the serosal fluid. But the effects of a weak base on the fluxes of other weak electrolytes were dependent upon its location, and the interactions observed when the effector weak base was added to the mucosal fluid were qualitatively different than those seen when it was added to the serosal fluid. The interactions between weak electrolytes could readily be explained in terms of the function of a system of three compartments in series, in which the pH of the intermediate compartment is greater than that of the bulk phases. But these observations could not be explained in terms of an analogous system involving an intermediate compartment of low pH, or in terms of a carrier mediated system. The transport function of the three-compartment system can be described in the form of an equation, and it is found that a pH difference of less than 0.5 unit may explain our observations on weak electrolyte transport.

Amines↗
PubMed1973

A transferable "resistance factor" from in vitro cultured MDMS-resistant Yoshida sarcoma cells.

Cells of the methylene dimethanesulphonate-(MDMS)-resistant Yoshida sarcoma cell line contain a low molecular weight "resistance factor" which is present in the culture medium of these cells and may be utilized by MDMS-sensitive Yoshida sarcoma cells either by co-culturing the two cell lines or by culturing the MDMS-sensitive Yoshida cells in a medium containing 20% used medium of MDMS-resistant Yoshida cells or in the presence of dialysed medium from resistant cells. The "resistance factor" does not inactivate the drug itself or its metabolites, and it has no influence on the sensitivity of the cells if added after MDMS treatment. Twenty-four hours seems to be enough time for the transfer of the resistance factor, but its effect on whole populations decreases within 24 hours of ceasing the supply. The relationship between these findings and the known phenomena of metabolic co-operation are discussed.

Agar↗