Stimulative effect of 2,3-diphosphoglycerate on methemoglobin reduction by ascorbic acid

Summary The reduction of methemoglobin by ascorbic acid was accelerated by the presence of 2,3-diphosphoglycerate     

Stimulation of methemoglobin reduction by selenium: a comparative study with erythrocytes of various animals

The extent of stimulation of methemoglobin (metHb) reduction by selenite depends upon the level of reduced glutathione (GSH) in the erythrocytes. The reason for the species difference in the effect of selenite was discussed with respect to species differences in the GSH levels in erythrocytes.     

Stimulation of methemoglobin reduction by selenium: A comparative study with erythrocytes of various animals

Summary The extent of stimulation of methemoglobin (metHb) reduction by selenite depends upon the level of reduced glutathione (GSH) in the erythrocytes. The reason for the species difference in the effect of selenite was discussed with respect to species differences in the GSH levels in erythrocytes.     

Methemoglobin in hypoxic rats

Methemoglobin levels have been found to vary with altitude and to shift the hemoglobin-oxygen dissociation curve. In this study, hematocrits and methemoglobin levels were monitored in rats exposed to hypoxia (420 torr absolute) for various intervals. Hematocrits gradually increased throughout the period of hypoxia, while methemoglobin levels rose by 12 h, peaked at 24 h and returned to control level by day 6. These data, in the context of other work, suggest that increased methemoglobin is important in acclimation to hypoxia.     

Relationship between the pentose phosphate shunt and methemoglobin reductase activity in human erythrocytes: Effect of aging on methemoglobin reductase activity.

The increase in methemoglobin reductase activity in human erythrocytes upon incubation with inosine, phosphate, pyruvate occurs only in the presence of methylene blue. No difference in activity of the methemoglobin reductases was observed between enzyme extracts of fresh cells and aged cells.     

Relationship between the pentose phosphate shunt and methemoglobin reductase activity in human erythrocytes: Effect of aging on methemoglobin reductase activity

Summary The increase in methemoglobin reductase activity in human erythrocytes upon incubation with inosine, phosphate, pyruvate occurs only in the presence of methylene blue. No difference in activity of the methemoglobin reductases was observed between enzyme extracts of fresh cells and aged cells.     

Comparison of human adult and fetal hemoglobin: Aminophenol-induced methemoglobin formation

Summary Human fetal hemoglobin was more susceptible to methemoglobin formation in the presence of aminophenols than was adult hemoglobin. This was due to the intrinsic properties of the proteins rather than the presence of methemoglobin reductases.This work was supported by a grant from the National Institute of General Medical Sciences GM-17184.     

Protective effect of selenite on nitrite toxicity.

Selenite was found to decrease nitrite-induced mortality in a dose-dependent manner. Its effect seems to be due to its action in reducing methemoglobin formed by nitrite.     

Protective effect of selenite on nitrite toxicity

Summary Selenite was found to decrease nitrite-induced mortality in a dose-dependent manner. Its effect seems to be due to its action in reducing methemoglobin formed by nitrite.     

Effect of iron and hemoproteins on hydrogen peroxide-supported styrene oxidation to styrene oxide

Summary Fe²⁺, Fe³⁺ and their complexes with EDTA and hemin, methemalbumin and methemoglobin were active catalyzers of H₂O₂ supported styrene oxidation to styrene oxide. Methemoglobin was the most active compound; its peroxidative activity was comparable to that of cytochrome P-450 in liver microsomes of phenobarbital-treated rats. Cumene hydroperoxide supported styrene oxidation with methemoglobin and microsomal hemoproteins and was found to be more efficient than H₂O₂.This work was supported by C.N.R. (National Research Council) contract No. 79.03197.04.     

Methemoglobin formation and reduction in relation to hemoglobin oxygen affinity

Summary It is suggested that although the high oxygen affinity hemoglobin (Hb LR) (143(H21)HisGln) with stabilization of R quaternary conformation is not more susceptible to the oxidizing effect of nitrites in vitro, in an in vivo situation where hemoglobin is partly deoxygenated, it might be more susceptible to methemoglobin formation due to higher oxidation and lower reduction rate.Supported by NIH grant No. 5 RO1 AM 20181-02 and VA grant No. 5455-002.Acknowledgments. The technical assistance of Ms Carol A. Perry is highly appreciated.     

Auto-oxidation of hemoglobin in plasma

Summary The rate of auto-oxidation of human hemoglobin to methemoglobin was measured in plasma at 37°C. Halflives of hemoglobin were found to be 20 h, 12 h and 7 h at the oxygen tensions of 126, 57 and 23 mm Hg, respectively.     

Functional properties of lyophilized hemoglobin in the presence of amino acids after 13 months of conservation

Summary Four lyophilisates of hemoglobin, each protected by an amino acid salt, were conserved for 13 months. The determinations carried out (oxyhemoglobin, methemoglobin, p50, Hill's number, and visible spectrum) demonstrated that the hemoglobin had retained its functional properties.     

Auto-oxidation of hemoglobin in plasma.

The rate of auto-oxidation of human hemoglobin to methemoglobin was measured in plasma at 37 degrees C. Half-lives of hemoglobin were found to be 20 h, 12 h and 7 h at the oxygen tensions of 126, 57 and 23 mm Hg, respectively.     

Binding of antimalarial drugs to hemozoin fromPlasmodium berghei

Summary Chloroquine, quinacrine and mefloquine bind toPlasmodium berghei hemozoin, hemin, heme, protoporphyrin IX and protease digested methemoglobin. This binding may be the basis for drug accumulation and action in the parasite.Acknowledgments. We thank the World Health Organization, the National Research Council of Thailand and Mahidol University for financial support. Dr Prapin Wilairat's suggestions are appreciated.     

The detection of superoxide anion from the reaction of oxyhemoglobin and phenylhydrazine using EPR spectroscopy.

The low temperature EPR spectrum of a quickly reacted mixture of oxyhemoglobin and phenylhydrazine was studied. With the use of a computer, the spectral contribution of methemoglobin in the region of g = 2 was subtracted. The remaining spectrum was that of an axial free radical (g perpendicular = 2.00, g parallel = 2.06) having the magnetic parameters of superoxide anion. In the presence of superoxide dismutase, this axial radical was not seen, confirming that superoxide anion is indeed generated by the reaction.     

Spectral properties of methemoglobins prepared by the action of sodium nitrite and potassium ferricyanide

Summary Methemoglobin was prepared by the addition of sodium nitrite or potassium ferricyanide to oxy or deoxyhemoglobin. The spectral properties of these methemoglobins were studied before and after extensive dialysis. It is shown that the methemoglobin formed by sodium nitrite has substantial spectral differences in visible and Soret band compared to that formed by potassium ferricyanide. These differences are proportional to the excess of sodium nitrite only. This suggests that both methemoglobins are similar compounds.Supported by NIH grant No. 5R01AM 20181-03 and VA grant No. 5455-003.Acknowledgments. The technical assistance of Ms Carol A. Perry and the secretarial assistance of Ms Wanda Stewart are highly appreciated.     

The detection of superoxide anion from the reaction of oxyhemoglobin and phenylhydrazine using EPR spectroscopy

Summary The low temperature EPR spectrum of a quickly reacted mixture of oxyhemoglobin and phenylhydrazine was studied. With the use of a computer, the spectral contribution of methemoglobin in the region of g=2 was subtracted. The remaining spectrum was that of an axial free radical (g=2.00, g=2.06) having the magnetic parameters of superoxide anion. In the presence of superoxide dismutase, this axial radical was not seen, confirming that superoxide anion is indeed generated by the reaction.The portion of this investigation carried out at the Albert Einstein College of Medicine was supported in part by US Public Health Service Research Grant HL-93399 from the Heart and Lung Institute and by National Institute Contract Nol-CP-55606 to J.P. This is communication No. 378 from the Joan and Lester Avnet Institute of Molecular Biology.Predoctoral fellow in the Medical Scientist Training Program (United States Public Health Service Grant 5-TO-5-GM 01669-12) at the New York University School of Medicine.Recipient of a grant-in-aid from the New York Heart Association.     

Local reduction in physics

A conventional wisdom about the progress of physics holds that successive theories wholly encompass the domains of their predecessors through a process that is often called “reduction.” While certain influential accounts of inter-theory reduction in physics take reduction to require a single “global” derivation of one theory׳s laws from those of another, I show that global reductions are not available in all cases where the conventional wisdom requires reduction to hold. However, I argue that a weaker “local” form of reduction, which defines reduction between theories in terms of a more fundamental notion of reduction between models of a single fixed system, is available in such cases and moreover suffices to uphold the conventional wisdom. To illustrate the sort of fixed-system, inter-model reduction that grounds inter-theoretic reduction on this picture, I specialize to a particular class of cases in which both models are dynamical systems. I show that reduction in these cases is underwritten by a mathematical relationship that follows a certain liberalized construal of Nagel/Schaffner reduction, and support this claim with several examples. Moreover, I show that this broadly Nagelian analysis of inter-model reduction encompasses several cases that are sometimes cited as instances of the “physicist׳s” limit-based notion of reduction.     

Reduction redux

Putnam's criticisms of the identity theory attack a straw man. Fodor's criticisms of reduction attack a straw man. Properly interpreted, Nagel offered a conception of reduction that captures everything a physicalist could want. I update Nagel, introducing the idea of overlap, and show why multiple realization poses no challenge to reduction so construed.