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PubMed2000

Porphyrin and phthalocyanine antiscrapie compounds.

The transmissible spongiform encephalopathies (TSEs) are fatal, neurodegenerative diseases for which no effective treatments are available. The likelihood that a bovine form of TSE has crossed species barriers and infected humans underscores the urgent need to identify anti-TSE drugs. Certain cyclic tetrapyrroles (porphyrins and phthalocyanines) have recently been shown to inhibit the in vitro formation of PrP-res, a protease-resistant protein critical for TSE pathogenesis. We now report that treatment of TSE-infected animals with three such compounds increased survival time from 50 to 300%. The significant inhibition of TSE disease by structurally dissimilar tetrapyrroles identifies these compounds as anti-TSE drugs.

Animals↗
PubMed1981

Ability of Neisseria gonorrhoeae, Neisseria meningitidis, and commensal Neisseria species to obtain iron from transferrin and iron compounds.

The ability of Neisseria species to use iron compounds and to compete with iron-binding proteins was examined with deferrated defined medium and the iron chelator deferoxamine. All Neisseria species were able to assimilate a variety of ferric and ferrous iron salts. They were not able to efficiently solubilize an inorganic iron salt such as ferric nitrate, but were able to use iron chelated by citrate, oxalacetate, pyrophosphate, or nitrilotriacetate. Each of the 95 Neisseria isolates examined was able to use hemin as a sole source of iron, and most, but not all, of the isolates were able to obtain iron from hemoglobin. Heated human serum stimulated growth of all gonococci, meningococci, and some commensal Neisseria species in iron-deficient medium. All gonococci and meningococci were able to scavenge iron from 25% saturated transferrin, whereas most commensal organisms were inhibited by this iron-binding protein. The ability to compete with transferrin was specific, since partially saturated conalbumin was bacteriostatic for all Neisseria species. Although the pathogenic Neisseria species were able to compete more efficiently with transferrin for iron than were the nonpathogenic Neisseria species, no correlation was observed between the virulence of different strains or colony types of gonococci and the ability to scavenge iron in vitro from transferrin or other chelators.

Blood↗
PubMed1994

Influence of primers containing cupric ion on bonding of dentin treated with phosphoric acid.

A primer containing cupric [Cu (II)] ions that promoted the interfacial initiation of polymerization from dentin surfaces was studied. Bovine dentin surfaces were treated with 10% phosphoric acid, then with a Cu primer consisting of aqueous 35% 2-hydroxyethyl methacrylate (HEMA) containing 0.03% cupric salt, and finally bonded with 4-META/MMA-PMMA resin initiated with oxidized tributylborane (TBBO). The use of the Cu primer resulted in a mean bond strength of 12.5 MPa compared with 3.8 MPa without the primer and 6.3 MPa using a 35% HEMA primer without Cu. The Cu primer produced a bond strength of 13.5 MPa even without 4-META in the resin system. Use of the Cu primer should simplify the bonding procedure since enamel and dentin can be etched simultaneously with 10% phosphoric acid.

Acid Etching, Dental↗
PubMed2001

Degradation of p-hydroxyphenylacetic acid by photoassisted Fenton reaction.

The chemical decomposition of p-hydroxyphenylacetic acid, a phenolic pollutant present in agro-industrial plant effluents, has been investigated by means of the Fenton's reaction and the photoassisted Fenton's reaction, the so-called photo-Fenton system. The degradation levels achieved have been compared to those obtained by applying other Advanced Oxidation Processes, such as the combination UV/H2O2. The optimum pH to carry out the decomposition of this organic compound by either Fenton or photo-Fenton systems was found to be pH = 3. The presence of buffers such as phosphate impedes these processes due to the formation of ferric complexes. A reaction mechanism, which allows calculating the contribution of the radical reaction to the global process, has been proposed. According to this mechanism, the dominant way of degradation of p-hydroxyphenylacetic acid is through its reaction with the OH radicals originated in the photolysis of H2O2 and, especially, in the Fenton's reaction.

Carcinogens↗
PubMed1983

A rapid and sensitive paper electrophoresis assay for the detection of microbial siderophores elicited in solid-plating culture.

A rapid and sensitive assay for the detection of microbial siderophores (iron-binding compounds) is described. Nine representative fungal and bacterial cultures including Ustilago sphaerogena, Penicillium sp., Fusarium roseum, Rhodotorula pilimanae, Bacillus subtilis W 23, Bacillus subtilis W 168, Bacillus megaterium, Azotobacter vinelandii OP, and Escherichia coli B, were nutritionally stressed for iron by sequential transfers on iron-deficient solid-plating media. In response to Fe-stress conditions, the microorganisms excreted siderophore compounds into the extracellular solid culture medium. The solid agar matrix effectively concentrated and restricted the migration of the siderophore compounds to the region immediately adjacent to colonial growth. Agar-block samples from this region were removed and placed at the origin of an electrophoresis paper strip. The resultant absorbed material from the agar-block sample was subjected to high-voltage paper electrophoresis which separated the siderophore compounds by size and molecular net charge. Phenolic acid ("catechol")-type siderophores were detected by fluorescence under uv light. Hydroxamic acid-type siderophores were visualized by spraying the electrophoretogram with ferric iron solution.

Bacteria↗
PubMed2004

Isolation and structural characterization of siderophores, madurastatins, produced by a pathogenic Actinomadura madurae.

Madurastatins Al (1), A2 (2) and A3 (3), novel pentapeptides that were acylated with salicylic acid at the N-terminus, were isolated from the culture broth of a pathogenic Actinomadura madurae IFM 0745 strain. These structures were mainly determined by 2D NMR and MS/MS spectral techniques. The strain produced simultaneously madurastatins B1 (4) and B2 (5) consisting of Ser and salicylic acid moieties. Compounds 1 and 4 had an antibacterial activity against Micrococcus luteus, indicating that the presence of the aziridine ring is essential for such activity. Because 1 has a strong affinity with ferric ion due to the presence of two hydroxamic acids and a salicylic acid, it is considered to be a siderophore that is a low molecular weight iron chelater. The production of siderophores may be one of the characteristics of pathogenic microorganisms.

Actinobacteria↗
PubMed2006

MR contrast agents, the old and the new.

Magnetic resonance (MR) contrast agents are increasingly being used to help detect and characterize various neoplastic, inflammatory and functional abnormalities. The extracellular, non-specific contrast agents gadolinium chelates are by far the most widely used. Over the past few years a number of MR organ specific contrast agents have been introduced. MRI contrast agents are generally safe and well tolerated. The present review summarizes the properties, main characteristics and imaging applications of commercially available compounds as well as safety of these agents in normal and high-risk patients.

Contrast Media↗
PubMed1999

Transition metal ion complexes with associates of porphyrin bound to a hydrophobic-hydrophilic copolymer.

The interaction of dimeric forms of meso-tetraphenylporphine with Mn2+ as well as the interaction of associated forms of meso-tetra(p-aminophenyl)porphine bound to a hydrophobic-hydrophilic copolymer with Mn2+ and Fe3+ were studied by absorption, luminescence, Raman, and EPR spectroscopies. Both dimeric and associated forms of these porphyrins produced Mn2+ complexes. Manganese ions in these complexes undergo clusterization, which is accompanied by transformation of the six-line EPR signal of Mn2+ into a broad single-line signal. The EPR signal of Mn2+ in these clusters is characterized by a g-factor value typical of a free electron with half-width DeltaHpp = 50 mT. The interaction of the two-component complex with Fe3+ produces a donor-acceptor complex. The electronic spectrum of the donor-acceptor complex contains a broad band with a maximum at 760 nm. The molar extinction coefficient of the complex at 760 nm is 9.1.104 M-1.cm-1, and the rate constant for its formation is Kdac = (3.9 +/- 0.6).106 M-1. The constants for Mn2+ binding to the organic compounds used in this work were also determined.

Ferric Compounds↗
PubMedDate not supplied

Certain phosphate compounds in the erythrocytes of patients with primary hyperlipidaemia.

The investigations were carried out in 30 patients with primary hyperlipidaemia (hypercholesterolaemia, hypertriglyceridaemia and mixed form). The serum total cholesterol and triglycerides, and in the erythrocytes the levels of AMP, ADP, ATP, ATP complex with Fe, MP, HDP and DGP were determined. Twenty blood donors served as a control group. The obtained results showed a statistically highly significant rise in ADP concentration in all investigated subgroups of hyperlipidaemic subjects, and a non-significant quantitative shift of other determined phosphate compounds.

Adenosine Diphosphate↗
PubMed1998

Attenuation of iron-nitrilotriacetate (Fe-NTA)-mediated renal oxidative stress, toxicity and hyperproliferative response by the prophylactic treatment of rats with garlic oil.

Iron nitrilotriacetate (Fe-NTA) is a potent nephrotoxic agent. In this communication we show that Fe-NTA-mediated nephrotoxicity is diminished by 1 wk of oral daily pretreatment of male albino Wistar rats with garlic oil given by gavage at 50 or 100 mg/kg body weight/ml corn oil. Intraperitoneal Fe-NTA treatment at a dose level of 9 mg Fe/kg body weight/10 ml enhances renal microsomal lipid peroxidation and hydrogen peroxide generation which are accompanied by a decrease in the activities of renal antioxidant enzymes (e.g. catalase, glutathione peroxidase, glutathione reductase and glutathione S-transferase), and a depletion in the level of renal glutathione. Parallel to these changes, a sharp increase in blood urea nitrogen and serum creatinine has been observed. In addition, Fe-NTA treatment also enhances renal ornithine decarboxylase (ODC) activity and increases [3H]thymidine incorporation into renal DNA. Prophylactic treatment of animals with garlic oil before the administration of Fe-NTA resulted in the diminution of Fe-NTA mediated injury. The enhancement of renal lipid peroxidation and hydrogen peroxide generation was decreased. In addition, there was recovery of glutathione depletion and inhibition of the activities of antioxidant enzymes. Similarly, in animals given the higher dose of garlic oil (100 mg/kg body weight) the enhanced blood urea nitrogen and serum creatinine levels, which are indicative of renal injury, showed a reduction of about 30% and 40%, respectively, in comparison with the group treated with Fe-NTA alone. Pretreatment with garlic oil also ameliorated the Fe-NTA-mediated induction of ODC activity and enhancement of [3H]thymidine incorporation into DNA in a dose-dependent manner. Our data suggest that garlic oil is a potent chemopreventive agent and may suppress Fe-NTA-induced nephrotoxicity.

Administration, Oral↗
PubMedDate not supplied

Effects of pre-soaked retraction cords on the microcirculation of the human gingival margin.

In the direct treatment of cervical lesions and to improve the impression-making procedure prior to fabricating indirect restorations, exposure of the gingival sulcus and control of hemorrhage or gingival fluid seepage are a prerequisite. For gingival displacement, cords impregnated with medicaments are widely used. In this investigation, the authors first studied in vitro the time course of fluid absorption by retraction cords immersed in test solutions. Thereafter, in a clinical trial, they examined the microcirculatory responses of the gingival margin after subgingival insertion and removal of retraction cords pre-soaked in solutions containing saline, AlCl3, Fe2(SO4)3 or epinephrine. Blood flow was recorded using laser Doppler technique. Blood perfusion fell markedly upon inserting the retraction cord, and this response was invariably present with all the compounds tested. After five-minutes, the decrease became less apparent with cords that were impregnated with physiological saline, AlCl3 or Fe2(SO4)3. Removing the cord elicited a prompt, marked and sustained increase in gingival microcirculation. However, removal of the cord impregnated with 0.1% epinephrine failed to reverse the decreased perfusion, and blood flow to the gingival margin remained low over an additional 20-minute observation. The results of this study indicate that with the exception of epinephrine, all retraction substances tested produced gingival hyperemia for operative procedures. Only epinephrine exhibited sustained vasoconstrictor response. It is anticipated that using laser Doppler flowmetry may be a suitable technique to evaluate the appropriate concentration of epinephrine that would elicit topical vasoconstriction.

Absorption↗
PubMed1994

A role for Thr 252 in cytochrome P450cam oxygen activation.

Molecular dynamics simulations of the ferrous dioxygen bound form of wild type cytochrome P450cam were performed and the results analyzed to reveal the time-dependent interactions of T252 with surrounding residues as well as with bound oxygen. The results indicate a time-dependent bimodal interaction of T252 with both G248 and the terminal oxygen of the bound dioxygen. The hydrogen bonding interaction of T252 with these two moieties is "anticorrelated" in the sense that the breaking of the T252-G248 hydrogen bond is concurrent with formation of the T252-dioxygen interaction. These simulations support the probability of a role of T252 in stabilization of the initial dioxygen bound complex and promotion of subsequent formation of compound I previously indicated by several experimental studies.

Binding Sites↗
PubMed1983

Formation of hydroxyl radicals from hydrogen peroxide and iron salts by superoxide- and ascorbate-dependent mechanisms: relevance to the pathology of rheumatoid disease.

1. Superoxide and hydrogen peroxide are formed by activated phagocytes and react together in the presence of iron salts to form the hydroxyl radical, which attacks hyaluronic acid. Ascorbic acid also interacts with hydrogen peroxide and iron salts to form hydroxyl radical in a reaction independent of superoxide. Since iron salts, ascorbate and activated phagocytes are present in the rheumatoid joint, experiments were designed to see whether ascorbate-dependent or superoxide-dependent formation of hydroxyl radicals would be more important in vivo. 2. In the present study, addition of ascorbate to a superoxide-generating system at concentrations of 100 mumol/l provoked a superoxide-independent formation of hydroxyl radicals for a short period. Lower concentrations of ascorbate did not do this. It is therefore suggested that the superoxide-dependent reaction is probably more important. 3. It is further suggested that destruction of ascorbate by oxygen radicals formed by activated phagocytes accounts for the previously reported low concentrations of this compound in the serum and synovial fluid of rheumatoid patients.

Arthritis, Rheumatoid↗
PubMed1986

Enhancement of misonidazole cytotoxicity by iron.

The toxicity of misonidazole (MISO) to hypoxic Chinese hamster ovary (CHO) cells in serum-free medium is enhanced by Fe(III)-EDTA. Enhancement of MISO cytotoxicity by a factor of 1.6 was seen with 2 microM Fe(III)-EDTA, while 200 microM Fe(III)-EDTA results in sensitization by a factor of 2.0. Treatment of CHO cells with the iron chelator desferal resulted in protection against the hypoxic cytotoxicity in MISO (approximate protection factor of 2.5 with 100 microM desferal). Similar results were obtained with Chinese hamster V79 cells. Fe(III)-EDTA also enhanced binding of [2-14C] MISO to cellular macromolecules while desferal decreased binding of MISO to cellular macromolecules. These results suggest that iron plays an important role in the reductive metabolism of MISO and that modification of the intracellular metal ion status may be a useful approach to modulating the biological effect of nitro compounds.

Animals↗
PubMed2006

Reclassification of Thermoterrabacterium ferrireducens as Carboxydothermus ferrireducens comb. nov., and emended description of the genus Carboxydothermus.

Similarities in phylogeny and metabolic properties between the type species of two monospecific genera of thermophilic anaerobic bacteria, Carboxydothermus hydrogenoformans and Thermoterrabacterium ferrireducens, and analysis of their recently available 16S rRNA gene sequences warranted clarification of their taxonomic positions. We have determined that the value of DNA-DNA hybridization between the type strains is 53 %. Additional physiological studies revealed that C. hydrogenoformans Z-2901(T) is capable of Fe(III) reduction with H(2) as an electron donor and ferrihydrite as an electron acceptor. T. ferrireducens JW/AS-Y7(T) is able to grow and utilize CO with ferrihydrite as an electron acceptor without hydrogen or acetate production. We therefore reclassify Thermoterrabacterium ferrireducens as Carboxydothermus ferrireducens comb. nov. (type strain JW/AS-Y7(T)=DSM 11255(T)=VKM B-2392(T)). The description of the genus Carboxydothermus is emended to include such important physiological properties as growth on organic compounds and capacity for Fe(III) reduction.

Carbon Monoxide↗
PubMedDate not supplied

[The nitrosophenol system of iron metabolism regulation in actinomycetes].

Iron-containing o-nitrosophenol compounds have been isolated from 64 strains of microorganisms of 18 species. The analysis of author's and published data allowed to divide iron-containing microbial compounds into two physiological groups: ferri-ionophores, i. e. compounds participating in active iron transfer, and those immobilizing iron at increase in its content in medium up to 10(-4)-10(-2) M. O-nitrosophenol pigments were found to belong to the latter group. A scheme of participation of o-nitrosophenol compounds in regulation of iron metabolism in actinomycetes has been proposed.

Biological Transport↗
PubMed1978

Mössbauer study of cytochrome c2 from Rhodospirillum rubrum. Sign of the product gxgygz of some low spin ferric heme proteins.

We have studied cytochrome c2 from Rhodospirllum rubrum with Mössbauer spectroscopy and electron paramagnetic resonance. The Mössbauer data on the ferric protein, taken in external magnetic fields up to 50 kG, were analyzed within the framework of the ligand field model commonly used to evaluate low-spin ferric heme compounds. The data analysis shows that the determinant of the electronic g-tensor, i.e. the product gxgygz, is positive for cytochrome c2. We have reanalyzed published Mössbauer data of some low-spin ferric heme proteins with respect to the sign of the g-tensor determinant. We find that gxgygz is also positive for the cytochromes c, bs, and P-450, and for chloroperoxidase.

Cytochrome c Group↗
PubMed1997

Spectroscopic and enzymatic characterization of the active site dinuclear metal center of calcineurin: implications for a mechanistic role.

The active site of bovine brain calcineurin contains an Fe3+-Zn2+ dinuclear metal center. Replacement of Zn2+ with Fe2+ yields a mixed valence Fe3+-Fe2+ center that exhibits a characteristic EPR signal that can be used as a convenient spectroscopic probe of the active site. Addition of product phosphate to both the Fe3+-Fe2+ and Fe3+-Zn2+ forms of calcineurin led to perturbations of the respective EPR signals, indicating that phosphate affects the environment of the paramagnetic centers. Anaerobic titrations of the iron-substituted Fe3+-Fe2+ enzyme with dithionite resulted in a gradual loss of activity toward pNPP that paralleled the loss of intensity of the EPR signal of the mixed valence diiron center. During dithionite reduction, an EPR resonance with g approximately 12 appeared. The intensity of this resonance increased when the spectrum was recorded in a parallel mode cavity and was therefore attributed to a paramagnetic center with integer spin. Oxidation of the Fe3+-Fe2+ cluster to the diferric state by hydrogen peroxide also led to a loss of activity. These results indicate that the mixed valence oxidation state represents the catalytically competent form of the cluster. The dependence of the enzyme activity on the redox state of the cluster has implications for a mechanistic role.

Aniline Compounds↗