Faculty Bibliography

This study compares three commonly used tests to detect organic mental disorders: the Mini-Mental State (MMS), Cognitive Capacity Screening Examination (CCSE), and Tachistoscope (T-Scope). Ninety-seven medical-surgical inpatients at the Mount Sinai Hospital referred for psychiatric consultation had a Missouri Mental Status Examination performed by a psychiatrist who also rated the patients' organic mental disorder as 'none,' 'mild,' 'moderate,' or 'severe.' The CCSE, MMS, and T-Scope, respectively, showed: sensitivity--0.54, 0.52, 0.68; specificity--0.85, 0.76, 0.79; and positive predictive value--0.83, 0.74, 0.79. False negatives occurred more often among those patients with mild organic mental disorders with all instruments (p = 0.05), while the T-Scope could not be administered in 27% of the patients. Screening instruments with increased acceptability, sensitivity, and specificity need to be developed to identify a potentially life-threatening disorder

The ability of intact human red cells to scavenge extracellularly generated H2O2 and O2-, and to prevent formation of hydroxyl radicals and hypochlorous acid has been examined. Red cells inhibited oxidation of ferrocytochrome c by H2O2. Cells treated with aminotriazole no longer inhibited, indicating that protection was almost entirely due to intracellular catalase. Contribution by the GSH system was slight, and apparent only with low H2O2 concentrations when catalase was inhibited by aminotriazole. The cells were about a quarter as efficient at inhibiting cytochrome c oxidation as an equivalent concentration of purified catalase. No inhibition of O2(-)-dependent reduction of ferricytochrome c or nitroblue tetrazolium was observed, although extracted red cell superoxide dismutase inhibited nitroblue tetrazolium reduction at one fortieth the concentration of that in the cells. Red cells efficiently inhibited deoxyribose oxidation by hydroxyl radicals generated from H2O2, O2- and Fe(EDTA), and myeloperoxidase-dependent oxidation of methionine to methionine sulfoxide by stimulated neutrophils. Most of the red cell inhibition of hydroxyl radical production, and all the inhibition of methionine oxidation, was prevented by blocking intracellular catalase with aminotriazole. Thus red cells are able to efficiently scavenge H2O2, but not O2-, produced in their environment, and to inhibit formation of hydroxyl radicals and hypochlorous acid. They may therefore have an important role in extracellular antioxidant defense.

The neuroexcitotoxin kainate has been used as a selective lesioning agent to model the etiology of a number of neurodegenerative disorders. Although excitotoxins cause susceptible neurons to undergo prolonged or repeated depolarization, the proximate metabolic pathology responsible for neuronal necrosis has remained elusive. We report here that kainate-induced death of cerebellar neurons in culture is prevented by inhibiting the enzyme xanthine oxidase, a cellular source of cytotoxic superoxide radicals (O2-.). Moreover, neurons are also protected from excitotoxin-induced death by the addition to the culture medium of either superoxide dismutase or mannitol, which scavenge superoxide and hydroxyl radicals, respectively, or serine protease inhibitor, which forestalls formation of xanthine oxidase. These findings indicate that excitotoxin-induced neuronal degeneration is mediated by superoxide radicals generated by xanthine oxidase, a mechanism partially analogous to that proposed for tissue damage seen upon reperfusion of ischemic tissues.

The spectral modifications in the absorption and emission properties of merocyanine 540 have been evaluated in solvents of varying dielectric constants. The fluorescence behavior of dye in solutions of low dielectric constant has offered a possibility for monitoring the micropolarity of sialoganglioside micelles in aqueous solutions. Our results demonstrate that sialic acid residues markedly influence the aggregation properties of gangliosides in solution as well as the nature of dye binding to the micellar structures.

The oxidative reactivities of four tryptophan metabolites in the kynurenine pathway were examined as a potential mechanism for their reported neurotoxicities and carcinogenicities. Neither quinolinic acid, a neurotoxin, nor its monocarboxylic analogue, picolinic acid, auto-oxidized over a wide pH range. However, 3-hydroxyanthranilic acid (3-HAT), a carcinogen, readily auto-oxidized and the reaction rate increased exponentially with increasing pH. 3-HAT auto-oxidation likely involves two steps: auto-oxidation of 3-HAT to the semiquinoneimine (anthranilyl radical) which oxidizes to the quinoneimine, followed by condensation and oxidation reactions to yield a second carcinogen, cinnabarinic acid. 3-HAT auto-oxidation to cinnabarinate required molecular oxygen and generated superoxide radicals and H2O2. Superoxide dismutase (SOD) accelerated 3-HAT auto-oxidation 4-fold, probably by preventing back reactions between superoxide and either the anthranilyl radical or the quinoneimine formed during the initial step of auto-oxidation. Catalase did not accelerate 3-HAT auto-oxidation, but it did prevent destruction of cinnabarinate by H2O2. Interconversion between oxyhemoglobin and methemoglobin occurred during 3-HAT auto-oxidation, although neither form of hemoglobin altered rates of 3-HAT auto-oxidation. Mn2+, Mn3+ and Fe3+-EDTA did not directly catalyze cinnabarinate formation in the absence of O2, but they did accelerate cinnabarinate formation under aerobic conditions

Phenylhydrazine-induced oxidative damage in red cells results in increased binding of merocyanine 540, a fluorescence probe sensitive to changes in lipid packing. Fluorescence polarization studies with diphenylhexatriene did not reveal major changes in order parameters both in intact red cells and lysates treated with phenylhydrazine. These fluorescence studies indicate that major changes are observed in membrane lipids. Analytical studies of membrane phospholipids revealed a significant decrease in phosphatidylethanolamine. The results of the fluorescence and lipid studies, taken in association with our previously reported findings on spectrin and other cytoskeletal protein degradation in red cells exposed to phenylhydrazine, suggests that degradation of cytoskeleton membrane proteins is also responsible for changes in the lipid bilayer surface of the red cell membrane.

1,4-Naphthoquinone-2-potassium sulphonate (NQKS) undergoes an autoxidation reaction in aqueous solution under physiological conditions to produce 3-hydroxy-1,4-naphthoquinone-2-potassium sulphonate (NQKS-OH). Intermediates of dioxygen reduction, superoxide radicals, hydrogen peroxide and hydroxyl radicals, are also detected. The kinetics of the autoxidation of NQKS show a first order dependence on NQKS and hydroxide ion concentration and a zeroth order dependence on oxygen concentration. For the rate equation r = -d[O2]/dt = kappa obs., [NQKS] [-OH], kappa obs. = (6.4 +/- 0.6) X 10(2) M-1s-1 at 37 degrees C. Hydroxide ion attack on NQKS appears to be the rate determining step. The reaction may be conveniently described as a 'hydrolytic autoxidation'. The hydrolytic autoxidation of NQKS occurs in NQKS-treated red blood cells; the hydroxylated quinone NQKS-OH is produced and hydroxyl radical formation is stimulated. The importance of this reaction in NQKS-induced oxidative stress in red blood cells is discussed. The hydrolytic autoxidation of quinones bearing one or more unsubstituted (hydrogen) positions on the quinone centre is a novel mechanism by which such quinones may induce oxidative stress in cellular systems.

The effects of phenylhydrazine on intact red cells and on red cell ghost membrane proteins were studied by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). In intact red cells 1 mM phenylhydrazine induced a marked decrease in intensity of the alpha- and beta-bands of spectrin without the formation of high molecular weight materials. Phenylhydrazine was also responsible for cross-linking of hemoglobin, which is apparent by the appearance of two new broad bands on the gel. Membrane glycoproteins were unaffected. Electrophoretic patterns of cytoskeletal proteins from phenylhydrazine-treated red cells obtained on two-dimensional SDS-polyacrylamide gels and stained with Coomassie blue or fluorescently labeled with monobromobimane indicated the presence of a new band between bands 4.2 and 5 at 60-65 kilodaltons (K). An immunoelectrophoretic blotting procedure utilizing polyclonal IgG antibodies for alpha- and beta-spectrin of the red cell cytoskeletal proteins revealed that the band observed at 60-65 K in the two-dimensional SDS-PAGE studies reacted with the antibodies. The presence or absence of glucose in the incubation medium and modification of oxyhemoglobin to met- or carboxyhemoglobin in the red cells did not protect the phenylhydrazine-mediated degradation of the major cytoskeletal proteins. Metal chelators and antioxidants had no effect on membrane protein changes. Ghost red cell proteins did not undergo changes at 1 mM phenylhydrazine in the presence or absence of hemoglobin, although at 5 mM phenylhydrazine the appearance of a faint high molecular weight band was observed. These results indicate that spectrin degradation without significant polymerization can be induced by phenylhydrazine.

Hydroxypyruvaldehyde is a substrate for the red cell glyoxalase system. It was metabolized by glyoxalase I with reduced glutathione to S-glyceroyl glutathione which was subsequently enzymatically hydrolyzed to reduced glutathione and glycerate by glyoxalase II. There was a competing spontaneous reaction of hydroxypyruvaldehyde with oxygen, which produced hydrogen peroxide, inducing oxidative metabolism in hydroxypyruvaldehyde-treated red cells. The incubation of red cells with hydroxypyruvaldehyde produced a stimulation in the flux of glucose oxidized through the hexose monophosphate shunt pathway, a stimulation in lactate production with a decrease in pyruvate production in the Embden-Meyerhoff pathway, an oxidation of reduced pyridine nucleotides and reduced glutathione to their oxidized cogeners, and changes in the oxidative status of hemoglobin. Overall, the majority of hydroxypyruvaldehyde consumption in red cell suspensions appeared to occur via non-oxidative routes, e.g. glyoxalase and/or 2-ketoaldehyde dehydrogenase, and non-enzymic protein binding. Although the observed oxidative metabolism induced by hydroxypyruvaldehyde in red cells was not severe (reduced glutathione levels in hydroxypyruvaldehyde-treated red cells were ca. 80% of the control values in untreated cells), the oxidative effects may be important in red cell ageing processes.

Studies of the ability of Plasmodium falciparum to grow in vitro in the red blood cells of subjects with certain beta-thalassemia syndromes are often difficult to interpret because of the known inhibitory effect of an elevated cellular content of human fetal hemoglobin (HbF). P falciparum therefore was cultured in vitro in the erythrocytes of subjects with hemoglobin H (HbH) disease and various other alpha-thalassemia genotypes that are unaccompanied by increased levels of HbF. Growth of the malaria parasite was markedly retarded in HbH red blood cells, when compared with growth in blood from normal control subjects. No consistent impairment of growth was seen in the erythrocytes of subjects having deletion of only one or two alpha-globin genes. These results indicate that erythrocytes with a severe thalassemia phenotype provide a less hospitable growth environment for P falciparum than normally hemoglobinized red blood cells, even in the absence of increased levels of HbF.