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L P Solomonson

Publications and source records attributed to L P Solomonson.

53 records · Page 3Linked to original sources
PubMed1981

Cardiac sodium, potassium-adenosine triphosphatase as a possible site of adriamycin-induced cardiotoxicity.

Adriamycin ws tested as a possible inhibitor of cardiac sodium-potassium-activated adenosine triphosphatase (Na-K-ATPase). At concentrations of 10(-4) M and lower, Adriamycin had no effect upon either ouabain-sensitive (Na-K-ATPase) or ouabain-insensitive adenosine triphosphatase activity in homogenates and microsomal fractions of cardiac tissue from several different species. Adriamycin inhibited adenosine triphosphatase activity at a concentration of 10(-3) M, but this was due to the inhibition of ouabain-insensitive adenosine triphosphatase rather than to inhibition of Na-K-ATPase. Under no condition was an inhibition of Na-K-ATPase activity by Adriamycin observed. These conditions included preincubation of the enzyme with Adriamycin, chelation of Ca2+, addition of reduced nicotinamide adenine dinucleotide phosphate, and variation of buffer and pH. It was concluded that Na-K-ATPase is not a likely site of Adriamycin-induced cardiotoxicity.

Adenosine Triphosphatases↗
PubMed1980

Action of Corn and Rice-inactivating Proteins on a Purified Nitrate Reductase from Chlorella vulgaris.

When nitrate reductase (NR) purified from Chlorella was incubated with NR-inactivating proteins purified from corn roots and rice cell suspension cultures or with trypsin there was a loss in NADH-NR and NADH cytochrome c reductase (NADH-CR) activities with time whereas the reduced methylviologen NR (MV-NR) remained active. When NADH-NR and NADH-CR activities were inactivated completely by the incubation with corn protein, the major protein band obtained by polyacrylamide gel electrophoresis shifted from an R(F) value of 0.12 to an R(F) of 0.25 and reduced MV-NR activity moved to the new position on the gel. When NADH-NR and NADH-CR activities were partially inactivated by the corn protein, NADH-NR activity was detected in an intermediate position (R(F) value of 0.18). Incubation with trypsin also caused a change in the NR protein migration pattern (R(F) value of 0.20). This protein band also had reduced MV-NR activity. Thus, the corn inactivator degrades NR in a fashion similar to but not identical with trypsin. The incubation of NR with rice inactivating protein resulted in a loss of NADH-NR but had no effect on the migration of NR protein or on the reduced MV-NR activity or mobility suggesting that the rice protein binds to Chlorella NR.

Journal Article↗
PubMed1980

Uridine uptake inhibition in Novikoff hepatoma cells by perturbants of intracellular Ca2+ and K+ levels.

The rate of uptake of uridine into the acid-soluble fraction of Novikoff hepatoma cells is inhibited by low concentrations of the ionophores A23187 and gramicidin and other perturbants of intracellular cation levels. Inhibition of uridine uptake by A23187 is dependent on Ca2+ and is reduced by serum and high levels of Mg2+. The effectiveness of A23187 is dependent on the Ca2+/Mg2+ ratio rather than the absolute concentration of either ion. Inhibition of uridine uptake by gramicidin is not significantly affected by serum or divalent cations. Other effectors of monovalent cation flux such as ouabain and valinomycin also inhibit uridine uptake. These results indicate that net uptake of uridine may be influenced by intracellular levels of certain monovalent and divalent inorganic cations.

Animals↗
PubMed1976

Changes in (Na+ + K+)-ATPase activity of Ehrlich ascites tumor cells produced by alteration of membrane fatty acid composition.

The fatty acid composition of plasma membrane derived from Ehrlich ascites tumor cells was altered in vivo by changing the dietary lipid of the tumor-bearing mice. The activity of (sodium + potassium)-adenosinetriphosphatase ((Na+ + K+ATPase), in partially purified plasma membranes, was measured ass a function of temperature. Arrhenius plots of the data were biphasic. Striking differences, dependent on the membrane fatty acid composition, were observed in the transition temperature and in the energies of activation below the transition temperature. The transition temperatures for the (Na+ + K+)-ATPase of plasma membrane derived from tumor cells grown in mice fed a regular chow diet containing a mixture of fatty acids (PMC), a 16% sunflower oil diet (PMSU), or a 4% tristearin diet (PMTS) were 20, 21, and 13.5 degrees C, respectively...

Adenosine Triphosphatases↗
PubMed1975

Reduced nicotinamide adenine dinucleotide-nitrate reductase of Chlorella vulgaris. Purification, prosthetic groups, and molecular properties.

NADH:nitrate reductase (EC 1.6.6.1) from Chlorella vulgaris has been purified 640-fold with an over-all yield of 26% by a combination of protamine sulfate fractionation, ammonium sulfate fractionation, gel chromatography, density gradient centrifugation, and DEAE-chromatography. The purified enzyme is stable for more than 2 months when stored at minus 20 degrees in phosphate buffer (pH 6.9) containing 40% (v/v) glycerol. After the initial steps of the purification, a constant ratio of NADH:nitrate reductase activity to NADH:cytochrome c reductase and reduced methyl viologen:nitrate reductase activities was observed. One band of protein was detected after polyacrylamide gel electrophoresis of the purified enzyme. This band also gave a positive stain for heme, NADH dehydrogenase, and reduced methyl viologen:nitrate reductase. One band, corresponding to a molecular weight of 100, 000, was detected after sodium dodecyl sulfate polyacrylamide gel electrophoresis. The enzyme contains FAD, heme, and molybdenum in a 1:1:0.8 ratio. One "cyanide binding site" per molybdenum was found. No non-heme-iron or labile sulfide was detected. From a dry weight determination of the purified enzyme, a minimal molecular weight of 152, 000 per molecule of heme or FAD was calculated. An s20, w of 9.7 S for nitrate reductase was found by the use of sucrose density gradient centrifugation and a Stokes radius of 89 A was estimated by gel filtration techniques. From these values, and the assumption that the partial specific volume is 0.725 cc/g, a molecular weight of 356, 000 was estimated for the native enzyme. These data suggest that the native enzyme contains a minimum of 2 molecules each of FAD, heme, and molybdenum and is composed of at least three subunits.

Binding Sites↗
PubMed1975

Purification of NADH-Nitrate Reductase by Affinity Chromatography.

ASSIMILATORY NITRATE REDUCTASE (NADH: nitrate oxidoreductase, EC 1.6.6.1) from Chlorella vulgaris has been purified to electrophoretic homogeneity with an overall yield of 60% by a procedure that utilizes blue dextran-agarose as an affinity column. Nitrate reductase binds to blue dextran and is not eluted in the presence of high ionic strength buffer but is rapidly eluted in the presence of mumolar concentrations of NADH.

Journal Article↗
PubMed1972

Nitrate Reductase and Chlorate Toxicity in Chlorella vulgaris Beijerinck.

A study of the growth-inhibiting effect of chlorate on the Berlin strain of Chlorella vulgaris Beijerinck provided complete confirmation of the theory of chlorate toxicity first proposed by Aberg in 1947. Chlorate was toxic to the cells growing on nitrate, and relatively nontoxic to the cells growing on ammonium. The latter cells contained only 0.01 as much NADH-nitrate reductase as the nitrate-grown cells. Chlorate could substitute for nitrate as a substrate of the purified nitrate reductase with Km = 1.2 mm, and V(max) = 0.9V(max) for nitrate. Bromate, and to a much smaller extent, iodate, also served as alternate substrates. Nitrate is a reversible competitive inhibitor of chlorate reduction, which accounts for the partial reversal, by high nitrate concentrations, of the observed inhibition of cell growth by chlorate. During the reduction of chlorate by NADH in the presence of purified nitrate reductase, there was a progressive, irreversible inhibition of the enzyme activity, presumably brought about by the reduction product, chlorite. Both the NADH-nitrate reductase activity and the associated NADH-cytochrome c reductase activity were inactivated to the same extent by added chlorite. The spectral properties of the cytochrome b(557) associated with the purified enzyme were not affected by chlorite. The inactivation of the nitrate reductase by chlorite could account for the toxicity of chlorate to cells grown on nitrate, though the destruction of other cell components by chlorite or its decomposition products cannot be excluded.

Journal Article↗