Showing papers by "Matthew B. Grisham published in 1983"

Myeloperoxidase-dependent effect of amines on functions of isolated neutrophils.

Abstract: Isolated neutrophilic leukocytes were incubated with primary amines and related nitrogenous compounds. Stimulation of neutrophil oxygen (O2) metabolism with phorbol myristate acetate or opsonized zymosan resulted in production of hydrogen peroxide (H2O2), myeloperoxidase-catalyzed oxidation of chloride (C1-) to hypochlorous acid (HOC1), and the reaction of HOC1 with the added compounds to yield nitrogen-chlorine (N-C1) derivatives. Formation of N-C1 derivatives of low lipid solubility resulted in accumulation of the derivatives in the extracellular medium. These oxidizing agents were identified and measured on the basis of their absorption spectra and their ability to oxidize 5-thio-2-nitrobenzoic acid to the disulfide form. The yield of N-Cl derivatives was in the order: taurine greater than Tris greater than spermidine greater than spermine greater than glucosamine greater than putrescine greater than guanidinoacetate. Accumulation of N-C1 derivatives was also observed in the absence of added amines, owing to the reaction of HOC1 with endogenous taurine and other amines that were released from the cells into the medium. In the presence of compounds that yield lipophilic N-C1 derivatives, little or no accumulation of oxidizing agents was observed. Instead, these compounds inhibited the accumulation of N-C1 derivatives that was obtained with taurine, and their effect was competitive with taurine. Inhibition was in the order: methylamine greater than ethanolamine greater than phenylethylamine greater than p-toluenesulfonamide greater than ammonia greater than guanidine. Formation of lipophilic N-C1 derivatives also resulted in inhibition of O2 uptake and glucose metabolism. Inhibition was prevented by adding catalase to eliminate H2O2, dapsone to inhibit myeloperoxidase, taurine to compete for reaction with HOC1, or compounds that are rapidly oxidized by HOC1 or N-C1 derivatives, to reduce these oxidizing agents. The results indicate that: (a) formation of N-C1 derivatives that do not penetrate biological membranes can protect leukocytes against the cytotoxicity of HOC1 and lipophilic N-C1 derivatives, and (b) formation of membrane-permeable N-C1 derivatives in the absence of target cells or readily oxidized substances results in oxidative attack by the N-C1 derivatives on leukocyte components and inhibition of leukocyte functions.

The cytoplasmic malate dehydrogenase in neoplastic tissues; presence of a novel isoenzyme?

Abstract: Malate dehydrogenase (MDH, EC 1.1.1.37) catalyzes the reversible reduction of oxaloacetate to malate in the presence of NADH. In eukaryotic cells the enzyme is generally found to be present as two distinct isoenzymes; one form is present in the cellular cytosol and the other is present exclusively in the mitochondria. These 2 isoenzymes form part of a shuttle system (the malate-aspartate shuttle) that functions as the major mechanism for the transportation of reducing equivalents between the cytosol and the mitochondria. As part of our ongoing studies on the mechansim of action and metabolic function of the malate dehydrogenases (Bernstein et al. 1978; Bernstein & Everse, 1978; Bernstein & Grisham 1978), we recently investigated the kinetic properties of the 2 isoenzymes present in rat Novikoff hepatoma tissues. These studies were initiated to evaluate whether or not the enzymes in the malate-asparate shuttle of tumour tissues are structurally and functionally identical to those of normal tissues. Fresh tumour or liver was homogenized with a glass tissue homogenizer in 0.1 M potassium phosphate buffer, pH 7.5, containing 0.25M sucrose. The homogenate was centrifuged for 10 min at 10,000 g to remove tissue debris. The supernatant was then centrifuged for 30 min at 20,000 g to obtain a high-speed supernatant that contained the cytoplasmic enzymes. The supernatantant did not contain any isocitrate dehydrogenase activity or transhydrogenase activity and was therefore judged to be free of mitochondrial enzymes. This high-speed supernatant was used without further fractionation for the determination of the cytoplasmic MDH