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PubMed1999

Thiomicrospira chilensis sp. nov., a mesophilic obligately chemolithoautotrophic sulfuroxidizing bacterium isolated from a Thioploca mat.

A new member of the genus Thiomicrospira, which utilizes thiosulfate as the electron donor and CO2 as the carbon source, was isolated from a sediment sample dominated by the filamentous sulfur bacterium Thioploca. Although the physiological properties investigated are nearly identical to other described species of the genus, it is proposed that strain Ch-1T is a member of a new species, Thiomicrospira chilensis sp. nov., on the basis of differences in genotypic characteristics (16S rRNA sequence, DNA homology, G + C content). Strain Ch-1T was highly motile with a slight tendency to form aggregates in the stationary growth phase. The organism was obligately autotrophic and strictly aerobic. Nitrate was not used as an electron acceptor. Chemolithoautotrophic growth was observed with thiosulfate, tetrathionate, sulfur and sulfide. The isolate was not able to grow heterotrophically. Growth of strain Ch-1T was observed between pH 5.3 and 8.5 with an optimum at pH 7.0. The temperature range for growth was between 3.5 and 42 degrees C; the optimal growth temperature was between 32 and 37 degrees C. The mean maximum growth rate on thiosulfate was 0.4 h-1. This is the second Thiomicrospira species described that has a rod-shaped morphology; therefore discrimination between vibrio-shaped Thiomicrospira and rod-shaped Thiobacilli is no longer valid.

Base Composition↗

PubMed1994

The utilization of thiocyanate as a nitrogen source by a heterotrophic bacterium: the degradative pathway involves formation of ammonia and tetrathionate.

A Gram-negative soil bacterium (isolate 26B) has been shown to utilize up to 100 mM thiocyanate as a source of nitrogen when supplied with glucose as the source of carbon and energy. During growth of isolate 26B with thiocyanate as the source of nitrogen, no ammonia, nitrate, nitrite, cyanide, cyanate, sulfate, sulfite, sulfide or carbonyl sulfide was detected in the growth medium. Growth of the bacterium on 14C-labelled thiocyanate (1.6 microCi) and glucose, yielded 14C-labelled carbon dioxide (0.9 microCi). The addition of 2.9 mM thiocyanate to a bacterial suspension in phosphate buffer (50 mM, pH 7.4) resulted in the utilization of 2.1 mM thiocyanate and the production of 2.0 mM ammonia. This activity was inducible and only occurred after growth of the bacterium with thiocyanate as the source of nitrogen. Tetrathionate (0.7 mM) was detected in the medium after the utilization of thiocyanate (2.4 mM) by a suspension of the bacterium in phosphate buffer, and thiosulfate (1.0 mM) was detected as an intermediate. The addition of sulfide or thiosulfate to the bacterial suspension also resulted in the formation of tetrathionate. The utilization of both of these compounds appeared to be constitutive. A pathway for thiocyanate utilization by isolate 26B is proposed which involves the hydrolysis of thiocyanate to produce cyanate and sulfide. The cyanate then undergoes further hydrolysis to form ammonia and carbon dioxide. The sulfide is ultimately oxidized to tetrathionate via a pathway which includes thiosulfate.

Ammonia↗

PubMed2005

Thiomicrospira arctica sp. nov. and Thiomicrospira psychrophila sp. nov., psychrophilic, obligately chemolithoautotrophic, sulfur-oxidizing bacteria isolated from marine Arctic sediments.

Two psychrophilic, chemolithoautotrophic, sulfur-oxidizing bacteria were isolated from marine Arctic sediments sampled off the coast of Svalbard with thiosulfate as the electron donor and CO(2) as carbon source. Comparative analysis of 16S rRNA gene sequences suggested that the novel strains, designated SVAL-D(T) and SVAL-E(T), represent members of the genus Thiomicrospira. Further genotypic (DNA-DNA relatedness, DNA G+C content) and phenotypic characterization revealed that the strains represent members of two novel species. Both organisms are obligately autotrophic and strictly aerobic. Nitrate was not used as an electron acceptor. Chemolithoautotrophic growth was observed with thiosulfate, tetrathionate and sulfur. The temperature limits for growth of both strains were between -2 degrees C and 20.8 degrees C, with optima of 11.5-13.2 degrees C (SVAL-E(T)) and 14.6-15.4 degrees C (SVAL-D(T)), which is about 13-15 degrees C lower than the optima of all other recognized Thiomicrospira species. The maximum growth rate on thiosulfate at 14 degrees C was 0.14 h(-1) for strain SVAL-E(T) and 0.2 h(-1) for strain SVAL-D(T). Major fatty acids of SVAL-D(T) are C(16 : 1), C(18 : 0) and C(16 : 0), and those of SVAL-E(T) are C(16 : 1), C(18 : 1), C(16 : 0) and C(14 : 1). Cells of SVAL-D(T) and SVAL-E(T) are rods, like those of their closest relatives. To our knowledge the novel strains are the first psychrophilic, chemolithoautotrophic, sulfur-oxidizing bacteria so far described. The names Thiomicrospira arctica sp. nov. and Thiomicrospira psychrophila sp. nov. are proposed for SVAL-E(T) (=ATCC 700955(T)=DSM 13458(T)) and SVAL-D(T) (=ATCC 700954(T)=DSM 13453(T)), respectively.

Arctic Regions↗

PubMed2006

Thiomicrospira halophila sp. nov., a moderately halophilic, obligately chemolithoautotrophic, sulfur-oxidizing bacterium from hypersaline lakes.

Enrichments at 2 M NaCl and pH 7.5-8, with thiosulfate or sulfide as electron donor, inoculated with sediments from hypersaline chloride-sulfate lakes of the Kulunda Steppe (Altai, Russia) resulted in the domination of two different groups of moderately halophilic, chemolithoautotrophic, sulfur-oxidizing bacteria. Under fully aerobic conditions with thiosulfate, bacteria belonging to the genus Halothiobacillus dominated while, under microaerophilic conditions, a highly motile, short vibrio-shaped phenotype outcompeted the halothiobacilli. Three genetically and phenotypically highly similar vibrio-shaped isolates were obtained in pure culture and one of them, strain HL 5(T), was identified as a member of the Thiomicrospira crunogena cluster by 16S rRNA gene sequencing. The new isolates were able to grow with thiosulfate as electron donor within a broad salinity range from 0.5 to 3.5 M NaCl with an optimum at 1.5 M and within a pH range from 6.5 to 8.5 with an optimum at pH 7.5-7.8. Comparative analysis of ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) gene sequences demonstrated that strain HL 5(T) possessed two genes, cbbL-1 and cbbL-2, of the form I RuBisCO and a cbbM gene of the form II RuBisCO, similar to the other members of the Thiomicrospira crunogena cluster. On the basis of phenotypic and genetic comparison, the new halophilic isolates are proposed to be placed into a novel species, Thiomicrospira halophila sp. nov. (type strain HL 5(T)=DSM 15072(T)=UNIQEM U 221(T)).

Bacterial Typing Techniques↗

PubMed2006

SoxV transfers electrons to the periplasm of Paracoccus pantotrophus - an essential reaction for chemotrophic sulfur oxidation.

The soxVW genes are located upstream of the sox gene cluster encoding the sulfur-oxidizing ability of Paracoccus pantotrophus. SoxV is highly homologous to CcdA, which is involved in cytochrome c maturation of P. pantotrophus. SoxV was shown to function in reduction of the periplasmic SoxW, which shows a CysXaaXaaCys motif characteristic for thioredoxins. From strain GBOmegaV, which carries an Omega-kanamycin-resistance-encoding interposon in soxV, and complementation analysis it was evident that SoxV but not the periplasmic SoxW was essential for lithoautotrophic growth of P. pantotrophus with thiosulfate. However, the thiosulfate-oxidizing activities of cell extracts from the wild-type and from strain GBOmegaV were similar, demonstrating that the low thiosulfate-oxidizing activity of strain GBOmegaV in vivo was not due to a defect in biosynthesis or maturation of proteins of the Sox system and suggesting that SoxV is part of a regulatory or catalytic system of the Sox system. Analysis of DNA sequences available from different organisms harbouring a Sox system revealed that soxVW genes are exclusively present in sox operons harbouring the soxCD genes, encoding sulfur dehydrogenase, suggesting that SoxCD might be a redox partner of SoxV. No complementation of the ccdA mutant P. pantotrophus TP43 defective in cytochrome c maturation was achieved by expression of soxV in trans, demonstrating that the high identity of SoxV and CcdA does not correspond to functional homology.

Cytochrome c Group↗

PubMed1991

Ethylene Promotes Elongation Growth and Auxin Promotes Radial Growth in Ranunculus sceleratus Petioles.

Submergence induces elongation in the petioles of Ranunculus sceleratus L., after a rise in endogenous ethylene levels in the tissue. Petioles of isolated leaves also elongate 100% in 24 hours when treated with ethylene gas, without a change in the radius. Application of silver thiosulfate, aminoethoxyvinylglycine (AVG), abscisic acid (ABA), or methyl jasmonate inhibits this elongation response. Gibberellic acid treatment promotes ethylene-induced elongation, without an effect on the radius. Indoelastic acid (IAA) induces radial growth in the petioles, irrespective of the presence or absence of added ethylene. High concentrations of IAA will also induce elongation growth, but this is largely due to auxin-induced ethylene synthesis; treatment with silver thiosulfate, AVG, ABA, or methyl jasmonate inhibit this auxin-promoted elongation growth. However, the radial growth induced by IAA is not affected by gibberellic acid, and not specifically inhibited by ABA, methyl jasmonate, silver thiosulfate, or AVG. These results support the idea that petiole cell elongation during "accommodation growth" can be separated from radial expansion. The radial expansion may well be regulated by IAA. However, effects of high levels of IAA are probably anomalous, since they do not mimic normal developmental patterns.

Journal Article↗

PubMed2001

The shxVW locus is essential for oxidation of inorganic sulfur and molecular hydrogen by Paracoccus pantotrophus GB17: a novel function for lithotrophy.

The shxVW genes of Paracoccus pantotrophus were identified to be essential for lithotrophic oxidation of sulfur and hydrogen. shxV predicts a membrane protein which is 42% identical to CcdA of P. pantotrophus essential for cytochrome c biogenesis. shxW predicts a periplasmic thioredoxin. Disruption of shxV by an Omega-kanamycin interposon disabled the resulting mutant GB(Omega)V to grow with thiosulfate or molecular hydrogen and to express ShxW while cytochrome c formation was not affected. Mixotrophic growth with succinate and thiosulfate of strain GB(Omega)V revealed 2% of the thiosulfate-dependent oxygen uptake rate as compared to the wild-type while antigens of proteins essential for sulfur oxidation were present in both strains. Mixotrophic growth of strain GB(Omega)V with succinate and molecular hydrogen revealed neither hydrogenase activity nor antigens. Complementation analysis with plasmid pBHP6 carrying the shxVW genes revealed the wild-type phenotype of strain GB(Omega)V(pBHP6).

Antigens, Bacterial↗

PubMed1993

Long-lasting allergic patch test reaction caused by gold.

Allergic contact dermatitis caused by gold is rare, and only isolated cases have been reported. Patch testing with gold may cause a long-lasting reaction. The purpose of this study is to describe a well-studied case of gold allergy caused by dental gold crowns. A gold-sensitized patient and a non-sensitized control subject were examined using patch tests, immunohistochemistry, electron microscopy and blast transformation reactions. Sodium thiosulfate, auranofin and sodium thiomalate gave positive patch test reactions. Immunohistochemistry and electron microscopy were performed from biopsies taken from allergic patch test reactions caused by gold sodium thiosulfate 1 day and 17 days after applying the patches, from normal skin and from a 17-day-old allergic patch test reaction caused by ammonium persulfate. Down-regulation had taken place by 17 days in the allergic ammonium persulfate reaction, but not in the 17-day allergic gold test reaction. The patient reacted to all but one of the gold-induced blast transformation tests, sodium chloroaurate being non-inductive. The non-sensitized control subject did not exhibit any reactions. In conclusion, gold sodium thiosulfate, gold sodium thiomalate and auranofin can be used as patch test substances for gold allergy, though long-lasting allergic patch test reactions may develop. In vitro gold salt induced blast transformation is an alternative test for gold allergy. The slow down-regulation of the allergic patch test reactions needs to be studied further.

Crowns↗

PubMed2004

Bone marrow chemoprotection without compromise of chemotherapy efficacy in a rat brain tumor model.

Thiol chemoprotective agents can reduce chemotherapy side effects, but clinical use is limited due to concerns of impaired chemotherapeutic efficacy. We evaluated whether an optimized bone marrow chemoprotection regimen impaired the efficacy of enhanced chemotherapy against rat brain tumors. Nude rats with intracerebral human lung carcinoma xenografts were treated with carboplatin, melphalan, and etoposide phosphate delivered intra-arterially with osmotic blood-brain barrier disruption (n = 8/group). Thiol chemoprotection was N-acetyl-L-cysteine (1000 mg/kg) 60 min before chemotherapy and/or sodium thiosulfate (8 g/m(2)) 4 and 8 h after chemotherapy, when the blood-brain barrier is reestablished. Blood counts were obtained before treatment on day 3 and at sacrifice on day 9. N-acetylcysteine serum clearance half-life was 9 to 11 min. Pretreatment with N-acetylcysteine combined with delayed administration of sodium thiosulfate protected against toxicity toward total white cells, granulocytes, and platelets (P = 0.0016). Enhanced chemotherapy reduced intracerebral tumor volume to 4.3 +/- 1.0 mm(3) compared with 29.1 +/- 4.1 mm(3) in untreated animals (P < 0.0001). Tumor volume was 3.7 +/- 0.6 mm(3) in rats that received N-acetylcysteine before and sodium thiosulfate after chemotherapy. The data indicate the efficacy of enhanced chemotherapy for rat brain tumors was not affected by thiol chemoprotection that provided excellent protection for hematological toxicity. Negative interactions of thiols with antitumor efficacy were avoided by temporal and spatial separation of chemoprotectants and chemotherapy.

Acetylcysteine↗

PubMed1991

Relationship between hydrogen consumption, dehalogenation, and the reduction of sulfur oxyanions by Desulfomonile tiedjei.

Resting-cell suspensions of Desulfomonile tiedjei consumed H2 with 3-chloro-, 3-bromo-, and 3-iodobenzoate as electron acceptors with rates of 0.50, 0.44, and 0.04 mumol h-1 mg-1, respectively. However, benzoate and 3-fluorobenzoate were not metabolized by this bacterium. In addition, H2 uptake was at least fourfold faster when sulfate, sulfite, or thiosulfate was available as the electron acceptor instead of a haloaromatic substrate. When sulfite and 3-chlorobenzoate were both available for this purpose, the rate of H2 uptake by D. tiedjei was intermediate between that obtained with either electron acceptor alone. Hydrogen concentrations were reduced to comparably low levels when either 3-chlorobenzoate, sulfate, or sulfite was available as an electron acceptor, but significantly less H2 depletion was evident with benzoate or nitrate. Rates of 3-chlorobenzoate dechlorination increased from an endogenous rate of 14.5 to 17.1, 74.0, 81.1, and 82.3 nmol h-1 mg-1 with acetate, pyruvate, H2, and formate, respectively, as the electron donors. Sulfite and thiosulfate inhibited dehalogenation, but sulfate and NaCl had no effect. Dehalogenation and H2 metabolism were also inhibited by acetylene, molybdate, selenate, and metronidazole. Sulfite reduction and dehalogenation were inhibited by the same respiratory inhibitors. These results suggest that the reduction of sulfite and dehalogenation may share part of the same electron transport chain. The kinetics of H2 consumption and the direct inhibition of dehalogenation by sulfite and thiosulfate in D. tiedjei cells clearly indicate that the reduction of sulfur oxyanions is favored over aryl dehalogenation for the removal of reducing equivalents under anaerobic conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

Bacteria, Anaerobic↗

PubMed2001

Microbial thiocyanate utilization under highly alkaline conditions.

Three kinds of alkaliphilic bacteria able to utilize thiocyanate (CNS-) at pH 10 were found in highly alkaline soda lake sediments and soda soils. The first group included obligate heterotrophs that utilized thiocyanate as a nitrogen source while growing at pH 10 with acetate as carbon and energy sources. Most of the heterotrophic strains were able to oxidize sulfide and thiosulfate to tetrathionate. The second group included obligately autotrophic sulfur-oxidizing alkaliphiles which utilized thiocyanate nitrogen during growth with thiosulfate as the energy source. Genetic analysis demonstrated that both the heterotrophic and autotrophic alkaliphiles that utilized thiocyanate as a nitrogen source were related to the previously described sulfur-oxidizing alkaliphiles belonging to the gamma subdivision of the division Proteobacteria (the Halomonas group for the heterotrophs and the genus Thioalkalivibrio for autotrophs). The third group included obligately autotrophic sulfur-oxidizing alkaliphilic bacteria able to utilize thiocyanate as a sole source of energy. These bacteria could be enriched on mineral medium with thiocyanate at pH 10. Growth with thiocyanate was usually much slower than growth with thiosulfate, although the biomass yield on thiocyanate was higher. Of the four strains isolated, the three vibrio-shaped strains were genetically closely related to the previously described sulfur-oxidizing alkaliphiles belonging to the genus Thioalkalivibrio. The rod-shaped isolate differed from the other isolates by its ability to accumulate large amounts of elemental sulfur inside its cells and by its ability to oxidize carbon disulfide. Despite its low DNA homology with and substantial phenotypic differences from the vibrio-shaped strains, this isolate also belonged to the genus Thioalkalivibrio according to a phylogenetic analysis. The heterotrophic and autotrophic alkaliphiles that grew with thiocyanate as an N source possessed a relatively high level of cyanase activity which converted cyanate (CNO-) to ammonia and CO2. On the other hand, cyanase activity either was absent or was present at very low levels in the autotrophic strains grown on thiocyanate as the sole energy and N source. As a result, large amounts of cyanate were found to accumulate in the media during utilization of thiocyanate at pH 10 in batch and thiocyanate-limited continuous cultures. This is a first direct proof of a "cyanate pathway" in pure cultures of thiocyanate-degrading bacteria. Since it is relatively stable under alkaline conditions, cyanate is likely to play a role as an N buffer that keeps the alkaliphilic bacteria safe from inhibition by free ammonia, which otherwise would reach toxic levels during dissimilatory degradation of thiocyanate.

Alkalies↗

PubMed1970

Utilization of glucose in heterotrophic media by Thiobacillus intermedius.

The growth yield of Thiobacillus intermedius is greater in glucose-yeast extract or glucose-casein hydrolysate broth than in comparable media without glucose. The quantity of glucose utilized in the glucose-supplemented media is much greater than the increase in cell yield observed relative to the unsupplemented media. Addition of glucose to cell-free extracts of glucose-yeast extract or glucose-casein hydrolysate grown cells results in the reduction of endogenous cytochrome c. Thus, in these media, glucose serves as a source of energy. This is in contrast to thiosulfate-glucose broth in which glucose provides only cell carbon. The presence of thiosulfate in glucose-casein hydrolysate broth results in a marked decrease in glucose consumption. Cytochrome c in extracts of cells grown in this medium is not reduced by glucose addition. The data suggest that thiosulfate prevents the utilization of glucose for energy generation. The final growth yield in glucose-casein hydrolysate broth is directly proportional to the initial glucose concentration, although not all the glucose was utilized even at the lowest concentration tested. This effect may be due to an inefficient glucose transport in this organism.

Caseins↗

PubMed1999

Detoxification of hydrogen sulfide and methanethiol in the cecal mucosa.

Colonic bacteria liberate large quantities of the highly toxic gases hydrogen sulfide (H(2)S) and methanethiol (CH(3)SH). The colonic mucosa presumably has an efficient means of detoxifying these compounds, which is thought to occur through methylation of H(2)S to CH(3)SH and CH(3)SH to dimethylsulfide (CH(3)SCH(3)). We investigated this detoxification pathway by incubating rat cecal mucosal homogenates with gas containing H(2)S, CH(3)SH, or CH(3)SCH(3). Neither CH(3)SH nor CH(3)SCH(3) was produced during H(2)S catabolism, whereas catabolism of CH(3)SH liberated H(2)S but not CH(3)SCH(3). Thus, H(2)S and CH(3)SH are not detoxified by methylation to CH(3)SCH(3). Rather, CH(3)SH is demethylated to H(2)S, and H(2)S is converted to nonvolatile metabolites. HPLC analysis of the homogenate showed the metabolite to be primarily thiosulfate. Analysis of cecal venous blood obtained after intracecal instillation of H(2)(35)S revealed that virtually all absorbed H(2)S had been oxidized to thiosulfate. The oxidation rate of H(2)S by colonic mucosa was 10,000 times greater than the reported methylation rate. Conversion to thiosulfate appears to be the mechanism whereby the cecal mucosa protects itself from the injurious effects of H(2)S and CH(3)SH, and defects in this detoxification possibly could play a role in colonic diseases such as ulcerative colitis.

Animals↗

PubMed1985

Influence of the bacterial flora of the gut on sulfur amino acid degradation. A study of patients with bacterial overgrowth before and during treatment with oxytetracycline or metronidazole.

The urinary excretion of sulfur amino acids and their main degradation products was determined in 10 patients with bacterial overgrowth during treatment with oxytetracycline or metronidazole. A normal excretion of total sulfur and inorganic sulfate was found during treatment with both antibiotics, indicating a normal intake, uptake, and oxidation of sulfur amino acids to inorganic sulfate. Irrespective of type of antibiotic given, a normalization of the increased ester sulfate excretion was found, favoring the opinion that both the aerobic and anaerobic flora of the gut contribute to the formation of sulfate esters. The cystathioninuria found in patients with bacterial overgrowth was normalized only by treatment with metronidazole. Both antibiotics resulted in a reduced excretion of taurine and thiosulfate, but especially for thiosulfate, the effect of metronidazole treatment was more pronounced. The results suggest that the bacterial flora of the gut, such as anaerobes, may be of importance in the formation of thiosulfate in the human body.

Adult↗

PubMed2003

Antidotal treatment of cyanide poisoning.

Cyanide poisoning may result from different exposures: residential fires, industrial accidents, drug and plant intoxication. Clinical features include coma, respiratory arrest and cardiovascular collapse. The biological hallmark is lactic acidosis. A plasma lactate concentration > or = 10 mmol/L in fire victims without severe burns and > or = 8 mmol/L in pure cyanide poisoned patients is a sensitive and specific indicator of cyanide intoxication. Many antidotes are available and efficient. However, therapeutic strategies are still debated. Our objective was to compare conventional treatments to hydroxocobalamin. This article reviews the literature on cyanide poisoning treatment. Conventional treatment of cyanide poisoning includes decontamination, supportive and specific treatment. Decontamination should be adapted to the route of poisoning and never postpone supportive treatment. Basic life support includes immediate administration of high flow of oxygen, airway protection and cardiopulmonary resuscitation. Advanced life support includes mechanical ventilation, catecholamine and sodium bicarbonate infusion. Supportive treatment is efficient but does not modify the time course or the body burden of cyanide. Numerous antidotes are available. Oxygen counteracts efficiently cyanide action at the mitochondrial level. Sodium thiosulfate, methemoglobin forming agents and cobalt compounds act efficiently by complexing or transforming cyanide into non-toxic stable derivatives. However, regarding the main clinical condition of cyanide poisoning, i.e. smoke inhalation, we should take into account not only the efficiency of antidotes but also their safety. Sodium thiosulfate is both efficient and safe, but acts with delay. Methemoglobin-forming agents are potent, but due to the transformation of hemoglobin into methemoglobin, they impair tissue delivery of oxygen. Experimental data showed increased mortality in carbon monoxide- and cyanide-poisoned rats treated with these agents. Cobalt EDTA and hydroxocobalamin are efficient and act immediately. Cobalt EDTA is more potent on a molar basis; however, numerous side effects limit its use to evidenced cyanide poisoning. In a prospective study, hydroxocobalamin appeared safe in fire victims with or without cyanide poisoning. The only reported side effect was a red coloration of skin and urine. In conclusion, antidotes are beneficial in cyanide poisoning. In suspected cyanide-poisoned patients, we recommend the use of hydroxocobalamin as first-line antidote, owing to its safety. In massive cyanide poisoning, due to the limited potency of hydroxocobalamin, continuous infusion of sodium thiosulfate should be associated.

Antidotes↗

PubMedDate not supplied

[Formation of paramagnetic nitrosyl complexes of non heme iron in animals with participation of nitric oxide from exogenous and endogenous sources].

It was found that thiosulfate has a stabilizing effect on exogenous and endogenous dinitrosyl-iron complexes in mice treated with bacterial lipopolysaccharide. It was assumed that thiosulfate protects dinitrosyl-iron complexes from the destructive influence of superoxide and peroxinitrite whose enhanced synthesis, together with the synthesis of nitric oxide, is initiated in mice by the lipopolysaccharide. For the first time, the formation of dinitrosyl-iron complexes was demonstrated, which occurs with the participation of nitric oxide generated enzymatically via the L-arginine-dependent pathway. The injection of exogenous dinitrosyl-iron complexes with thiosulfate, which, together with diethyldithiocarbamate, provide the formation of exogenous mononitrosyl iron-diethyldithiocarbamate complexes, made it possible to use the ABC method, which markedly enhances the efficiency of scavenging of endogenous nitric oxide in mice treated with lipopolysaccharides.

Animals↗

PubMed1981

Effect of various compounds on the reaction of tris-(2-chloroethyl)amine with ribonucleic acid in vitro and on its toxicity in mice.

The effect of tris-(2-chloroethyl)-amine (HN-3) on RNA and DNA was investigated spectrophotometrically. The shift in the absorbance spectrum caused by the addition of HN-3 was used to test a variety of compounds for their ability to inhibit RNA alkylation. The effect of HN-3 on the activity of several enzymes was also investigated. The activities of ribonuclease A, desoxyribonuclease I, acetylcholinesterase, diaphorase, glutathione reductase, adenosine desaminase, glyoxalase I, 3-hydroxyacyl-CoA-dehydrogenase, xanthine oxidase, glucose-6-phosphate dehydrogenase, hexokinase and the microsomal N-oxygenation of aniline were not changed by HN-3, whereas the activity of cytochrome-c-reductase exhibited a dose dependent diminution in the presence HN-3. Of 105 compounds tested only 14, namely, sodium thiosulfate, dithioxanthine, thiosalicylic acid, 1,2,4-triazole-5-thiol, 2-thiocytosine, 2-thiohistadine, 2,3-dithiosuccinic acid, thioglycolic acid, 3-mercapto-D-valine,6-amino-2-thiouracil, thionicotine amide, dithiothreitol, sodium sulfite, and ergothioneine prevented the alkylation of RNA. All of them also reacted with HN-3 in absence of RNA. No correlation was found between the reaction constant of the reaction compound:HN-3 in the absence of RNA and the concentration of the compound which inhibited RNA alkylation by 50%. The compounds which were effective in vitro were also tested in mice for their ability to reduce HN-3 toxicity in vivo. Only sodium thiosulfate, d-penicillamine, and dithiosuccinic acid were effective. A 3.9fold increase in the LD50 of HN-3 was achieved in mice treated with sodium thiosulfate 3330 mg/kg i.p., a 1.7fold with 2125 mg dithiosuccinic acid/kg, and a 2fold increase with 2500 mg/kg d-penicillamine. The compound tested was injected i.p. 0.5 to 1 min after the s.c. injection of HN-3.

Alkylating Agents↗

PubMed1993

Thermally perturbed rhodanese can be protected from inactivation by self-association.

A fluorescence-detected structural transition occurs in the enzyme rhodanese between 30-40 degrees C that leads to inactivation and aggregation, which anomalously decrease with increasing protein concentration. Rhodanese at 8 micrograms/ml is inactivated at 40 degrees C after 50 min of incubation, but it is protected as its concentration is raised, such that above 200 micrograms/ml, there is only slight inactivation for at least 70 min. Inactivation is increased by lauryl maltoside, or by low concentrations of 2-mercaptoethanol. The enzyme is protected by high concentrations of 2-mercaptoethanol or by the substrate, thiosulfate. The fluorescence of 1,8-anilinonaphthalene sulfonate reports the appearance of hydrophobic sites between 30-40 degrees C. Light scattering kinetics at 40 degrees C shows three phases: an initial lag, a relatively rapid increase, and then a more gradual increase. The light scattering decreases under several conditions; at increased protein concentration; at high concentrations of 2-mercaptoethanol; with lauryl maltoside; or with thiosulfate. Aggregated enzyme is inactive, although enzyme can inactivate without significant aggregation. Glutaraldehyde cross-linking shows that rhodanese can form dimers, and that higher molecular weight species are formed at 40 degrees C but not at 23 degrees C. Precipitates formed at 40 degrees C contain monomers with disulfide bonds, dimers, and multimers. We propose that thermally perturbed rhodanese has increased hydrophobic exposure, and it can either: (a) aggregate after a rate-limiting inactivation; or (b) reversibly dimerize and protect itself from inactivation and the formation of large aggregates.

Disulfides↗