Search PubMed⌕ Search

Biomedical subjects

C R Ross

Publications and source records attributed to C R Ross.

At least 73 records · Page 4Linked to original sources
PubMed1983

Effect of cephaloridine on the transport of organic ions in dog kidney plasma membrane vesicles.

The cephalosporin antibiotics cephaloridine and cefazolin were examined for their effects on the transport of a prototype anion, [3H]p-aminohippurate (PAH) and a prototype cation, N1-[3H] methylnicotinamide (NMN) in basolateral membrane vesicles and brush border membrane vesicles (BBMV). Cefazolin inhibited transport of 50 microM PAH in both membranes and had no effect on transport of 50 microM NMN transport. Under identical conditions, cephaloridine, a zwitterion, inhibited PAH transport in both membranes and NMN transport in BBMV but not in basolateral membrane vesicles. Cephaloridine was less effective than cefazolin in inhibiting PAH transport in BBMV. The results demonstrate the organic transport systems in the basolateral membrane vesicles differ from those in the BBMV. Furthermore, a zwitterionic drug can interact with both systems in the BBMV. An explanation for the intracellular accumulation of cephaloridine is presented.

Aminohippuric Acids↗
PubMed1983

Na+ gradient-dependent p-aminohippurate (PAH) transport in rat basolateral membrane vesicles.

The relationship between the transmembrane Na+ gradient and p-aminohippurate (PAH) transport was examined in isolated rat basolateral membrane vesicles. A 100 mM Na+ gradient (o leads to i) accelerated the influx of 50 microM [3H]PAH whereas similar gradients of choline+, K+, or Li+ did not. The sodium effect was not due to a diffusion potential. The Na+ gradient (o leads to i) decreased the apparent Michaelis constant for PAH from 0.167 +/- 0.016 to 0.054 +/- 0.016 mM and increased the maximum flux rate from 116.00 +/- 13.50 to 427.34 +/- 98.96 pmol/mg/min. An "overshoot" of [3H]PAH influx (159 +/- 4% of the equilibrium value) could be demonstrated only in the presence of a Na+ gradient (o leads to i) plus an opposing gradient of unlabeled PAH (i leads to o). These results suggest that PAH transport and the Na+ gradient are functionally related. A model for cellular uptake of PAH by a Na+ gradient-dependent anion exchange mechanism is presented.

Aminohippuric Acids↗
PubMed1981

Mechanisms of organic cation transport in kidney plasma membrane vesicles: 2. delta pH studies.

The active step in the renal secretion of the organic cation N1-methylnicotinamide has been proposed to be the translocation across the luminal membrane. The presence of a H+:N1-methylnicotinamide antiport system has been found in luminal membrane vesicles isolated from dog kidney cortex but not in the antiluminal membrane. The conclusion reached is that N1-methylnicotinamide secretion is "secondarily active" and is driven by a proton gradient (urine to cell). The ph gradient in turn is created by the Na+:H+ antiport which is present in the luminal membrane. Therefore, two functionally linked antiport systems supply the energy for the active secretion of cationic drugs.

Animals↗
PubMed1980

Mechanisms of organic cation transport in kidney plasma membrane vesicles: 1. Countertransport studies.

Transport for organic cations has been described in both luminal and antiluminal membranes. The two transport systems difer from one another on the basis of kinetic parameters and countertransport. By using N1-[3H]methylnicotinamide as the indication cation, a series of organic cations (which were known to be secreted) were tested for their capacity to stimulate countertransport. The phenomenon of countertransport was symmetrical in that it was observed for both influx and efflux in both membranes. However, under appropriate conditions, certain organic cations were effective in producing "uphill" transport of N1-[3H]methylnicotinamide in the luminal membrane and the effect was limited to that membrane exclusively. Detailed analysis of countertransport in the luminal membrane showed quantitative differences in the maximal stimulation produced by the various cations: giving rise to the relationship that the concentration of organic cation which gave one-half maximal N1-[3H]methylnicotinamide countertransport approximated its affinity constant. The data were interpreted to suggest that all the members of the organic cation series tested are translocated across the luminal membrane by the same carrier but that they are moved at different rates.

Animals↗
PubMed1980

Experimental transmission of Syphacia muris among rats, mice, hamsters and gerbils.

Rats infected with Syphacia muris were allowed to cohabit with uninfected Mongolian gerbils, Syrian hamsters and mice. These uninfected animals subsequently became infected with Syphacia muris and when were removed and allowed to cohabit with uninfected rats. Syphacia muris was readily transmitted back to the rat from the gerbil, hamster and mouse. Transmission of Syphacia muris to the gerbil and hamster expands the host range of this parasite.

Animals↗
PubMed1979

Isolation of luminal and antiluminal membranes from dog kidney cortex.

Luminal (brush border) and antiluminal (basal-lateral) membranes were isolated from canine renal cortex. The enzyme marker for luminal membrane, alkaline phosphatase was enhanced 19-fold and the antiluminal enzyme marker, (Na+ + K+)-ATPase, was enhanced 22-fold in their respective membrane preparation, while the amount of cross contamination was minimal. Contamination of these preparations by enzyme markers for lysosomes, endoplasmic reticulum and mitochondria was also low. Routinely, more than 50 mg membrane protein was isolated for each membrane. Electron micrographs showed that the membranes were uniform in size, appearance, and vesicular in nature. An examination of the orientation of these membranes showed that 76.5% of the antiluminal membranes and 86% of the luminal membranes were right-side out.

Animals↗
PubMed1979

Transport of organic ions in renal cortical luminal and antiluminal membrane vesicles.

Based upon saturability, kinetic analysis and specific inhibition, specific transport for the organic anion, p-aminohippurate was found in isolated luminal and antiluminal membrane vesicles from dog kidney cortex. The transport for organic anions in the two membranes differed from one another on the basis of kinetic parameters ((Km, Vmax and Ki for probenecid) and counterflow phenomenon (only the antiluminal membrane displayed the capacity to accelerate the exchange of p-aminohippurate). Also described is specific transport for the organic cation N1 methylnicotinamide in each membrane. The luminal and antiluminal transport of N1-methylnicotinamide are distinguished from one another by kinetic parameters (Km, Vmax and Ki for Darstine) and counterflow data (counterflow of N1-methylnicotinamide was observed only in the luminal membrane). The results are discussed in view of a proposed model to explain transepithelial transport of these organic ions.

Animals↗
PubMed1976

Transport of organic cations and anions by choroid plexus.

The accumulation of organic cations and anions by the isolated rabbit choroid plexus was measured and the results were considered in comparison to in vivo measurements of transport using the ventriculocisternal perfusion technique also in rabbits. The accumulation in vitro of 3H-p-aminohippurate (PAH) and 14C-N1-methylnicotinamide (NMN) was shown to be organic anion and cation specific and dependent upon oxidative metabolism since tissue/medium ratios were reduced by competitive inhibitors including dibenamine and mepiperphenidol for cation transport and probenecid for anion transport and were also reduced by cyanide and dinitrophenol. Rabbits pretreated with chlorpromazine and anesthetized with pentobarbital were perfused lateral ventricle to cisterna magna with artificial cerebrospinal fluid containing inulin, 3H-PAH and 14C-NMN. Ratios of concentrations of these substances in the perfusate to those infused were calculated. Significant reductions in the ratios for PAH and NMN compared to unulin were obtained when low rates of perfusion, 40mul/min, were employed with low concentrations of PAH (2 mug/ml) and NMN (0.2 mug/ml). Probenecid (10(-3)M) specifically increased the ratio for PAH without affecting the NMN ratios. Mepiperhenidol (10(-o) M) blocked NMN transport but no PAH. The data and calculated clearances indicate that these prototype anions and cations may be actively transported out of cerebrospinal fluid, but for cations only at a low rate.

Aminohippuric Acids↗
PubMed1975

Nicotinamide adenine dinucleotide phosphate-malic enzyme of rat liver. Purification, properties, and immunochemical studies.

Rat liver malic enzyme (EC 1.1.1.40) was purified from livers of rats fasted and refed a high sucrose diet containing 1% desiccated thyroid powder. The purification was accomplished by a six-step procedure. The specific activity of the purified enzyme was increased 181-fold above that of the initial high speed supernatant of liver extracts. Slight additional purification of malic enzyme was achieved with preparative disc electrophoresis. The specific activities of the purified rat liver malic enzyme from the least two steps were between 28.0 and 30.5 units per mg of protein. Homogeneity of the purified enzyme was determined by disc and starch gel electrophoresis as well as sedimentation velocity and sedimentation equilibrium studies. The molecular weight and S20, w values of rat liver malic enzyme are 268,000 and 10.2, respectively. Amino acid analysis based on milligram of protein hydrolyzed yielded higher amounts of leucine and glutamic acid but lower quantities of alanine and voline per subunit than the corresponding Escherichia coli enzyme...

Amino Acids↗
PubMed1975

Reversible inhibition of (Na+ + K+)-ATPase with a cardiac glycoside.

The effect of a semisynthetic cardiac glycoside, Actinogen (Ay22241), on Na+ + K+ - ATPase was studied. Ay22241 was found to be as an effective inhibitor of the enzyme as ouabain, Ay22241 inhibition was a time dependent process and was completely reversible. While ouabain inhibition was also time dependent, it was only partially reversible. This reversibility with Ay22241 should make it a useful tool in studying the mode of action of cardiac glycosides.

Adenosine Triphosphatases↗
PubMed1975

Renal excretion of N'1-methylnicotinamide in the rat.

The renal excretion of N'1-methylnicotinamide (NMN) was studied in the rat. Renal clearance experiments clearly demonstrated that: 1) NMN is secreted; 2)a tubularmaximum (Tm), 7 mumol/min per kg, could be reached; and 3)NMN secretion is inhibitedby a competitive inhibitor, mepiperphenidol. In free-flow micropuncture experiments, animals were infused with plasma concentrations of NMN ABOVE Tm; the TF/P NMNto TF/P inblin ratio for proximal and distal samples was 2.34 and 2.28, respectively, indicating that NMN is secreted in the proximal tubules and is not secreted orreabsorbed in the distal tubules. This finding was further confirmed by intratubularmicroinjections of ['14C]NMN into rats. In diuretic animals approxiamately 10%of the NMN injected into early proximal tubules was reabsorbed, but no reabsorption could be detected after distal injections. The nondiuretic animals showed no significant reabsorption of NMN. It was concluded that NMN transport is a carrier-mediated process and that reabsorption, if it occurs, plays only a minor role.

Absorption↗
PubMed1975

Binding of N1-methylnicotinamide and p-aminohippuric acid to a particulate fraction from dog kidney.

The active secretion of organic ions by the kidney may be described by the following models: 1)binding to a carrier protein and 2) a translocation process across the membrane. The feasibility of such a model was tested by measuring binding of either an organic cation, N1-methylnicotinamide (NMN) or an organic anion p-aminohippuric acid (PAH) to particulate material obtained from dog renal cortex tissue. The method employed was one in which the bound and free forms of the ligand were separated by centrifugation through a gel matrix. Binding of NMN and PAH was found to be tissue specific. In addition, binding was pH, time, temperature, protein-concentration and ligand-concentration dependent. Saturation of binding for either ligand was observed at concentrations greater than 50 mM, suggesting low affinity. Interestingly, a positive cooperative effect was observed for binding of either NMN or PAH to the particulate material. Although binding was associated only with particulate material, the binding proteins were released from the membrane system(s) by treatment with the nonionic detergent Lubrol WX. These studies show that NMN and PAH binding share many features in common but that the two processes are independent of each other. The results are consistent with, but do not prove, the model.

Aminohippuric Acids↗