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PubMed1996

Effect of superoxide dismutase mimics on radical adduct formation during the reaction between peroxynitrite and thiols--an ESR-spin trapping study.

We have reexamined the formation and reactions of radicals formed from peroxynitrite (ONOO-)-mediated oxidation of glutathione (GSH), L-cysteine (Cys), N-acetyl-D,L-penicillamine (NAP), and sodium bisulfite (NaHSO3). Sulfur-centered and superoxide union radicals were trapped using 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) and the radical adducts were analyzed by electron spin resonance (ESR) spectroscopy. The following sulfur-centered radicals were detected: glutathionyl radical (GS') from GSH, L-cysteinyl radical ('Scys) from L-cysteine, N-acetyl-D,L-penicillamine thiyl radical ('SNAP) from NAP, and sulfite anion radical (SO3-.) from NaHSO3. Additionally the formation of the hydroxyl radical adduct of DMPO (DMPO/'OH) was observed. DMPO/'OH formation was totally inhibited by low-molecular-weight superoxide dismutase (SOD) mimics. This suggests that DMPO/'OH was formed from the decay of the superoxide radical adduct of DMPO. In the presence of SOD mimics, the DMPO-sulfur-centered adducts were more persistent, suggesting that O2-. is partially responsible for the instability of DMPO-thiyl adducts. Sulfur-centered radicals formed during oxidation of thiols and sulfite by peroxynitrite react with ammonium formate to form the carbon dioxide anion radical (CO2-.). We conclude that sulfur-centered radicals produced from the oxidation of thiols and sulfite by peroxynitrite arise from a hydroxyl-radical-independent mechanism. Biological implications of peroxynitrite-mediated oxidation of thiols as well as the use of SOD mimics in biological spin-trapping are discussed.

Cyclic N-Oxides↗
PubMed1983

Proton translocation during denitrification by a nitrifying--denitrifying Alcaligenes sp.

A heterotrophic nitrifying Alcaligenes sp. from soil was grown as a denitrifier on nitrate and subjected to oxidant pulse experiments to ascertain the apparent efficiencies of proton translocations during O2 and nitrogen-oxide respirations. With endogenous substrate as the reducing agent the leads to H+/2e- ratios, extrapolated to zero amount of oxidant per pulse, were 9.4, 3.7, 4.3 and 3.5 for O2, nitrate, nitrite and N2O, respectively. The value for O2 and those for the N-oxides are, respectively, somewhat larger and smaller than corresponding values for Paracoccus denitrificans. None of the three permeant ions employed with the Alcaligenes sp. (valinomycin-K+, thiocyanate and triphenylmethylphosphonium) was ideal for all purposes. Thiocyanate provided highest ratios for O2 but abolished the oxidant pulse response for nitrate and N2O. Valinomycin was slow to penetrate to the cytoplasmic membrane and relatively high concentrations were required for optimal performance. Triphenylmethylphosphonium enhanced passive proton permeability and diminished proton translocation at concentrations required to realize the maximal oxidant pulse response.

Alcaligenes↗
PubMed1990

Determination of intracellular buffer values after metabolic inhibition by fluoride and nitrilotriacetic acid.

Non-bicarbonate buffer values have been analysed in homogenates of squid mantle muscle and toad gastrocnemius muscle using the PCO2 equilibration technique. Homogenate metabolism was inhibited by the addition of potassium fluoride and nitrilotriacetic acid. After an initial change in the concentration of organic phosphates a new metabolic equilibrium was achieved which was insensitive to pH changes during PCO2 variations. Inaccurate measurements of homogenate buffer values could, thereby, be prevented. The accumulation of inorganic phosphate during the initial metabolic shift caused an increase in homogenate buffer values. Levels of unbound inorganic phosphate, which are effective in buffering, were estimated by enzymatic analysis in homogenate ultrafiltrates. Based on the evaluation of apparent dissociation constants pK', and buffer values for fluoride and inorganic phosphate, the non-bicarbonate, non-phosphatei (i: inorganic) buffer value of the tissue was calculated. The level of free inorganic phosphate in the resting tissue was considered for an estimate of the intracellular non-bicarbonate buffer value under control conditions.

Adenosine Diphosphate↗
PubMed1988

On the glutamate transport through cell envelope vesicles of Halobacterium halobium.

Glutamate uptake by envelope vesicles of Halobacterium halobium was measured. Previous authors showed that the glutamate uptake needs the illumination as well as Na+ gradient across the membrane. The latter is considered to be the driving force for the uptake. No satisfactory explanation for the necessity of the illumination has not been given. We found that in the absence of Cl- in the medium, only Na+ gradient was enough to induce the glutamate uptake, i.e. no illumination was needed. Glutamate uptake was measured with various strains of H. halobium. We found that the envelope vesicles prepared from strains containing no bacteriorhodopsin showed the glutamate uptake in the dark and in the presence of Cl- in the medium provided only that Na+ gradient is imposed.

Cell Membrane↗
PubMed2002

Severe anemia after gastrointestinal hemorrhage in a Jehovah's Witness: new treatment strategies.

OBJECTIVE: Management of severe anemia in a critically ill Jehovah's Witness is challenging. In the past, conservative therapy was the only option available to the practitioner. Recently, new interventional treatment strategies have become available, including human and bovine hemoglobin substitutes and high-dose recombinant human erythropoietin. DESIGN: Case report. SETTING: Intensive care unit in a quaternary care center. PATIENT: A patient with severe, life-threatening anemia caused by gastrointestinal hemorrhage who refused all blood products on religious grounds. INTERVENTION: Bovine hemoglobin substitute and high-dose recombinant human erythropoietin. CASE STUDY: A 50-yr-old Jehovah's Witness presented with massive upper gastrointestinal hemorrhage; initial hemoglobin was 3.5 g/dL. Endoscopy revealed a prepyloric ulcer, and hemorrhage control was achieved by epinephrine injections into the peri-ulcer mucosa. Despite control of hemorrhage, the patient became hemodynamically unstable. A total of 7 units of a bovine hemoglobin-based oxygen carrying compound (HBOC-201) was administered to enhance the patient's oxygen delivery. High-dose recombinant human erythropoietin was administered daily (500 units/kg). Hemoglobin levels were initially maintained and then slowly increased to a maximum of 7.6 g/dL on day 24 of therapy. CONCLUSION: This case demonstrates that the concurrent administration of hemoglobin-based oxygen carriers and recombinant human erythropoietin in severe, life-threatening anemia (hemoglobin, 3.5 g/dL) was associated with patient survival and a significant increase in hemoglobin to 7.6 g/dL, without the administration of allogeneic blood. Hemoglobin-based oxygen carriers can adequately serve as initial therapy to maintain tissue oxygen delivery while awaiting the maximal effect of recombinant erythropoietin on bone marrow red blood cell production. High-dose recombinant human erythropoietin offers these patients the best chance for normalization of hematocrit and survival in the long term.

Anemia↗
PubMed1986

Interactions between clay minerals and siderophores affect the respiration of Histoplasma capsulatum.

The reduction in the respiration of Histoplasma capsulatum in broth culture caused by montmorillonite appeared to be the result, in part, of the interference by the clay with the iron nutrition of the fungus. This interference was apparently the result of the adsorption by the clay of the iron-transporting siderophore (deferricoprogen B) produced by the fungus, as the reduction in respiration was partially alleviated by the addition of foreign siderophores. Neither kaolinite nor attapulgite (palygorskite) appeared to adsorb significant amounts of the siderophores, probably because of the low cation exchange capacity and specific surface area of kaolinite and the inaccessibility of adsorption sites in the fibrous attapulgite. These observations, in addition to the adhesion of montmorillonite to the hyphae, suggest mechanisms that may explain the discrete geographic distribution of this fungus, which is pathogenic to humans and which has been isolated essentially only from soils that do not contain montmorillonite.

Adsorption↗
PubMed1971

New quantitative, qualitative, and confirmatory media for rapid analysis of food for Clostridium perfringens.

A selective and differential medium, Shahidi-Ferguson Perfringens agar (SFP agar), and a confirmatory medium, lactose-motility agar (LM agar), were developed for the enumeration and identification of Clostridium perfringens in foods. These media provide a rapid, specific, and direct diagnosis of C. perfringens. SFP agar contains sodium metabisulfite and ferric ammonium citrate to demonstrate H(2)S production and egg yolk to demonstrate lecithinase production by C. perfringens. On SFP agar, C. perfringens produces black colonies, 2 to 3 mm in diameter, surrounded by zones of opaque precipitate. The typical colonies are confirmed on LM agar. Enumeration and identification are completed within 48 hr. All of the ingredients of SFP agar are stable to heat and storage conditions. SFP agar also contains two antibiotics, kanamycin and polymyxin B, which are inhibitory to many bacteria commonly occurring in foods. A comparative study of SFP agar and noninhibitory media showed that SFP agar did not inhibit any of the 16 strains of C. perfringens tested. Recovery of C. perfringens added to foods averaged 90.6% for SFP agar as compared with 69.8% for sulfite polymyxin-sulfadiazine (SPS) agar (BBL) and 60.2% for SPS agar (Difco). The colonies on the SFP agar, were much larger and were consistently black. Of 464 food samples tested, C. perfringens was found in 27 samples with SFP agar and in 5 samples with SPS agar (Difco), with a recovery ratio considerably higher on SFP agar. SFP agar is a more specific presumptive medium for the enumeration of C. perfringens and in conjunction with LM agar should save considerable time, effort, and materials toward the final identification of the species.

Agar↗
PubMed2006

Zinc phthalocyanine/magnetic fluid complex: a promising dual nanostructured system for cancer treatment.

In this study we evaluated the photophysical, photochemical properties of the zinc phthalocyanine/ magnetic fluid (ZnPC/MF) complex in liposomal medium. As a result of the present investigation we propose the liposome-encapsulated ZnPC/MF complex as a very promising nanostructured device for cancer treatment. The spectroscopy characterization and the in vitro dark toxicity of both ZnPC and ZnPC/MF complex in Hank's and in liposomal medium are reported. Our findings revealed that the spectroscopic properties of the ZnPC associated or not with MF presented little differences and are very close to what one expects from an ideal photosensitizer compound. Indeed, the ZnPC/MF complex in liposomal medium presented lower dark toxicity compared to the ZnPC/MF complex in Hank's, strongly supporting the use of the former for cancer treatment.

Animals↗
PubMed1988

Control of respiration in non-phosphorylating mitochondria is shared between the proton leak and the respiratory chain.

We measured the relationship between rate of respiration and membrane potential in isolated mitochondria titrated with malonate (to inhibit the electron transport chain) or with uncoupler (to increase the proton conductance of the inner membrane). We used the flux control summation and connectivity theorems of metabolic control theory to calculate the control over non-phosphorylating respiration exerted by the respiratory chain (and associated reactions) and by the leak of protons across the inner membrane. At 37 degrees C the flux control coefficient of the leak over respiration was 0.66; the flux control coefficient of the chain over respiration was 0.34. At 25 degrees C the values were 0.75 and 0.25 respectively. We argue that the basis for previous conclusions that all the control is exerted by the proton leak under similar conditions is invalid.

Animals↗
PubMedDate not supplied

Reactive oxygen scavenger effect of pyrimidines, benzotriazoles and related compounds.

Free radicals and reactive oxygen metabolites have been implicated as important pathologic mediators in many clinical disorders and diseases. An efficient method of detecting the free radical scavenger effect is through xanthine oxidase (XO) inhibition. The inhibition efficiency on XO has been detected as the rate of uric acid production, which has max 295 nm. Sulfasalazine showed potent inhibiting activity on XO (IC50 = 25.11 microM; Ki = 50.88 microM) and induced a mixed-type (non-competitive-uncompetitive) inhibition of the substrate xanthine. 2-mercapto-4(3H)-quinazolinone (16) and 2-mercaptopyrimidine (4) displayed inhibiting activity on XO with IC50 = 98.71 and 136.14 microM, while apparent inhibition constants (Ki) were 158.38 and 62.46 microM, respectively. However benzotriazoles showed weak inhibitory effect. The spin-trapping method with 5,5-dimethyl-1-pyrroline N-oxide (DMPO) by electron spin resonance (ESR) detected the presence of O2-* and OH*. It showed that the percentage inhibition for formation of DMPO-OOH for 2-mercapto-pyrimidine and sulfasalazine were 64.78 and 35.09, but for hydroxylation were 49.51, 38.55, 37.29 for 2-mercapto-4(3H)-quinazolinone, sulfasalazine and 2-mercaptopyrimidine at 500 microM, respectively.

Electron Spin Resonance Spectroscopy↗
PubMed2006

Carcinogenicity classification of vanadium pentoxide and inorganic vanadium compounds, the NTP study of carcinogenicity of inhaled vanadium pentoxide, and vanadium chemistry.

It is argued that, because of inherent weaknesses in design and procedure, the U.S. National Toxicology Program study of the carcinogenicity of inhaled vanadium pentoxide does not provide adequate evidence to support the classification by regulatory authorities of vanadium pentoxide as a Group 2B (possible) human carcinogen. The extension by one regulatory authority of the carcinogenicity classification for vanadium pentoxide to cover all vanadium compounds is also questioned. Such an extension implies that the toxic effect of some unknown vanadium species is more powerful than that of any oxygen species generated from the oxygen atoms in vanadium pentoxide, and that vanadium in any form can be converted in vivo to an undefined toxic species. There is no experimental or theoretical basis supporting this hypothesis. For oxygen-containing compounds like vanadium pentoxide, there is a need for some form of toxicity classification related to their oxygen content since it is likely to be the most reactive component of such compounds. For all particulates, such as those of crystalline vanadium pentoxide, the special toxicity of particulates, and especially nanoparticles, also needs separate consideration and classification.

Aerosols↗