Biomedical subjects
N Wilkins
Publications and source records attributed to N Wilkins.
Inhibition of Na+-H+ exchange by N,N'-dicyclohexylcarbodiimide in isolated rat renal brush border membrane vesicles.
The inactivation of rat renal brush border membrane Na+-H+ exchange by the covalent carboxylate reagent N,N'-dicyclohexylcarbodiimide (DCCD) was studied by measuring 1 mM Na+ influx in the presence of a pH gradient (pHi = 5.5; pHo = 7.5) and H+ influx in the presence of a Na+ or Li+ gradient ([Na+]i = 150 mM; [Na+]o = 1.5 mM). In the presence of DCCD, the rate of Na+ uptake decreased exponentially with time and transport inhibition was irreversible. At all DCCD concentrations the loss of activity was described by a single exponential, consistent with one critical DCCD-reactive residue within the Na+-H+ exchanger. Among several carbodiimides the most hydrophobic carbodiimide, DCCD, was also the most effective inhibitor of Na+-H+ exchange. With 40 nmol of DCCD/mg of protein, at 20 degrees C for 30 min, 75% of the amiloride-sensitive 1 mM Na+ uptake was inhibited. Neither the equilibrium Na+ content nor the amiloride-insensitive Na+ uptake was significantly altered by the treatment. The Na+-dependent H+ flux, measured by the change in acridine orange absorbance, was also decreased 80% by the same DCCD treatment. If 150 mM NaCl, 150 mM LiCl, or 1 mM amiloride was present during incubation of the brush border membranes with 40 nmol of DCCD/mg of protein, then Li+-dependent H+ flux was protected 50, 100, or 100%, respectively, compared to membranes treated with DCCD in the absence of Na+-H+ exchanger substrates. The combination of DCCD and an exogenous nucleophile, e.g. ethylenediamine and glycine methyl ester, increased Na+-dependent H+ flux in the presence of 80 nmol of DCCD/mg of protein, compared to the transport after DCCD treatment alone. These findings suggest that the Na+-H+ exchanger contains a single carboxylate residue in a hydrophobic region of the protein, and the carboxylate and/or a nearby endogenous nucleophilic group is critical for exchange activity.
The law. 5. The juvenile offender.
Explore the source record for details and available documents.
Information requirements for HMOs: the planning function.
With estimates for 1993 indicating that HMO enrollment will reach 50 million nationwide, it is apparent that HMOs have successfully overcome the obstacles they faced to gain acceptance as a valid part of the healthcare industry. However, the most crucial challenge is still being faced--effective information management.
MedCenters Health Plan case study.
This case history will describe how the planning department at MedCenters Health Plan, a large multidisciplinary group practice in Minneapolis, Minn, uses its information system to support decision making.
The medical profession in Jamaica in the post-emancipation period.
Explore the source record for details and available documents.
HIV / AIDS and the informal sector.
Explore the source record for details and available documents.