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At least 19 recordsLinked to original sources
PubMed1978

The mechanism of the mutagenic action of hydroxylamine XIII. Reversion of phage MS2 amber mutants in the presence of hydroxylamines.

The replication of the phage MS2 in the presence of either hydroxylamine (HA) or O-methylhydroxylamine (OMHA) (mutagenesis in vivo) results in an increase in the reversion frequency of two amber mutations in the maturation protein. When acting on the extracellular phage (mutagenesis in vitro) the mutagens do not affect the reversion frequency. The most probable mode of mutagenic action of the hydroxylamines on the vegetative MS2 phage involves the enzymic formation of modified precursors and their incorporation into RNA.

Coliphages↗
PubMed1978

The mechanism of the mutagenic action of hydroxylamine XII. Phenotypic suppression of amber mutants of phage T7 by hydroxylamine and O-methylhydroxylamine.

The reproduction of phage T7 in the presence of hydroxylamine (HA) (mutagenesis in vivo) results in the phenotypic suppression of some amber mutants. The presence of O-methylhydroxylamine (OMHA) results in a similar effect, indicating a similar mechanism for the action of the two compounds. Since the rate of reaction of mutagen with nucleoside residues under these conditions in negligibly low, one of the most plausible explanations of this effect is the enzymic formation of modified precursors and their incorporation into bacterial tRNAs or phage-induced RNA.

Coliphages↗
PubMed1977

Activation of guanylate cyclase in cerebral cortex of rat by hydroxylamine.

Hydroxylamine actived guanylate cyclase in particulate fraction of cerebral cortex of rat. Activation was most remarkable in crude mitochondrial fraction. When the crude mitochondrial fraction was subjected to osmotic shock and fractionated, guanylate cyclase activity recovered in the subfractions as assayed with hydroxylamine was only one-third of the starting material. Recombination of the soluble and the particulate fractions, however, restored guanylate cyclase activity to the same level as that of the starting material. When varying quantities of the particulate and soluble fractions were combined, enzyme activity was proportional to the quantity of the soluble fraction. Heating of the soluble or particulate fraction at 55 degrees for 5 min inactivated guanylate cyclase. The heated particulate fraction markedly activated guanylate cyclase activity in the native soluble fraction, while the heated soluble fraction did not stimulate enzyme activity in the particulate. The particulate fraction preincubated with hydroxylamine at 37 degrees for 5 min followed by washing activated guanylate cyclase activity in the soluble fraction in the absence of hydroxylamine. Further fractionation of the crude mitochondrial fraction revealed that the factor(s) needed for the activation by hydroxylamine is associated with the mitochondria. The mitochondrial fraction of cerebral cortex activated guanylate cyclase in supernatant of brain, liver, or kidney in the presence of hydroxylamine. The mitochondrial fraction prepared from liver or kidney, in turn, activated soluble guanylate cyclase in brain. Activation of guanylate cyclase by hydroxylamine was compared with that of sodium azide. Azide activated guanylate cyclase in the synaptosomal soluble fraction, while hydroxylamine inhibited it. The particulate fraction preincubated with azide followed by washing did not stimulate guanylate cyclase activity in the absence of azide. The activation of guanylate cyclase by hydroxylamine is not due to a change in the concentration of the substrate GTP, Addition of hydroxylamine did not alter the apparent Km value of guanylate cyclase for GTP. Guanylate cyclase became less dependent on manganese in the presence of hydroxylamine. Thus the activation of guanylate cyclase by hydroxylamine is due to the change in the Vmax of the reaction.

Animals↗
PubMed1977

Stimulation of guanylate cyclase by sodium nitroprusside, nitroglycerin and nitric oxide in various tissue preparations and comparison to the effects of sodium azide and hydroxylamine.

Sodium nitroprusside, nitroglycerin, sodium azide and hydroxylamine increased guanylate cyclase activity in particulate and/or soluble preparations from various tissues. While sodium nitroprusside increased guanylate cyclase activity in most of the preparations examined, the effects of sodium azide, hydroxylamine and nitroglycerin were tissue specific. Nitroglycerin and hydroxylamine were also less potent. Neither the protein activator factor nor catalase which is required for sodium azide effects altered the stimulatory effect of sodium nitroprusside. In the presence of sodium azide, sodium nitroprusside or hydroxylamine, magnesium ion was as effective as manganese ion as a sole cation cofactor for guanylate cyclase. With soluble guanylate cyclase from rat liver and bovine tracheal smooth muscle the concentrations of sodium nitroprusside that gave half-maximal stimulation with Mn2+ were 0.1 mM and 0.01 mM, respectively. Effective concentrations were slightly less with Mg2+ as a sole cation cofactor. The ability of these agents to increase cyclic GMP levels in intact tissues is probably due to their effects on guanylate cyclase activity. While the precise mechanism of guanylate cyclase activation by these agents is not known, activation may be due to the formation of nitric oxide or another reactive material since nitric oxide also increased guanylate cyclase activity.

Animals↗
PubMed1979

Equivalence of microbiological and hydroxylamine methods of analysis for ampicillin dosage forms.

Ampicillin formulations were assayed by microbiological and hydroxylamine methods to determine whether thehydroxylamine analytical method is a suitable substitute for the microbiological method. Paired assay results by the 2 analytical methods were obtained on different strengths of tablet, capsule, and suspension, formulations containing ampicillin and ampicillin degradation compounds. Several statistical tests were used to assess the equivalence of the paired assay results. The data analyses indicate that the hydroxylamine method is a suitable substitute for the microbiological method for potency assays and stability studies of ampicillin formulations. The hydroxylamine method yielded slightly higher assay results than the microbiological method for severely degraded formulations.

Ampicillin↗
PubMed1977

Mutagenesis of lambda phage: 5-bromouracil and hydroxylamine.

Mutagenesis by 5-bromouracil of lambda phage to clear plaque formers does not depend on the recA function of the host E. coli cell or on the red function of the phage. Pretreatment of the host cells with ultraviolet light does not affect bromouracil mutagenesis of the adsorbed phage. Mutagenesis by hydroxlamine to clear plaque formers takes place at a high level in recA- host cells, and is not changed by preirradiation of of rec+ (wild type) hosts with ultraviolet light. Thus, bromouracil and hydroxylamine appear to mutate lambda phage by a process which differs from that responsible for ultraviolet mutagenesis. Two characteristics of bromouracil mutagenesis--the nonlinear dependence of the number of mutants on bromouracil incorporation, and a high frequency of heterozygotes--fit in with Rydberg's (1977) picture of bromouracil mutagenesis as a consequence of base mispairing, with mismatch repair removing the mutations at low incorporation of the analog.

Bromouracil↗
PubMed1977

Cellular content of the Krebs cycle keto acids in yeasts grown on different nitrogen sources, including hydroxylamine.

The cellular pool of Krebs cycle keto acids was followed as a function of growth in three yeasts. The keto acids were analyzed as silylated methoximes by quantitative gas chromatography with capillary glass columns. The 2-oxoglutaric acid content was strikingly high in the hydroxylamine (HA)-tolerant, HA-utilizing Endomycopsis lipolytica when compared to that in the nitrate-utilizing yeast Cryptococcus albidus and Saccharomyces cerevisiae, requiring fully reduced nitrogen for growth. The content of E. lipolytica increased throughout the log phase to maxima of about 200-250 microgram per g dry weight in HA and ammonia media. These amounts are 20-25 times greater than those attained in the two other yeasts. The cellular content of pyruvic acid was at a maximum early in the log phase, amounting to 50-70 microgram per g dry weight for all yeasts. The oxalacetic acid content never exceeded 9 microgram per g dry weight in any of the yeasts. Oximeformation, for which keto acid production is a prerequisite, is discussed as part of the HA-tolerance.

Ammonium Sulfate↗
PubMed1979

Hydroxylamine sensitivity and salt tolerance in screening and identifying mycobacteria.

Hydroxylamine sensitivity offered no advantage over p-nitrobenzoic acid in distinguishing between tubercle bacilli and other (opportunist and non-significant) mycobacteria. It was of limited use in identification procedures. Salt tolerance assisted in the identification of strains which may be Mycobacterium triviale and M. chelonei var borstelense.

Bacteriological Techniques↗
PubMed1979

Highly purified hydroxylamine oxidoreductase derived from Nitrosomonas europaea. Some physicochemical and enzymatic properties.

Hydroxylamine oxidoreductase [EC 1.7.3.4] of Nitrosomonas europaea was purified to an electrophoretically homogeneous state and some of its properties were studied. The molecular weight of the enzyme as determined by gel filtration on Sephadex G150 and by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate is 175,000-180,000, while the minimum molecular weight per heme determined from the dry weight and heme content is 17,500. The enzyme is a C-type cytochrome; its reduced form shows absorption peaks at 418 (gamma peak), 521 (beta peak), 553 (alpha peak), and 460 nm (due to an unidentified chromophore). Although the alpha peak at 553 nm has a shoulder at 559 nm, the enzyme does not posses protoheme or a cytochrome b subunit. It seems likely that the enzyme molecule possess heme c molecules in different states. The enzyme reacts rapidly with various eukaryotic cytochromes c, but does not react with "bacterial-type" cytochromes c. Although the enzyme does not react with cytochrome c-552 (N. europaea), another C-type cytochrome of the organism, cytochrome c-554 (N. europaea) acts as an electron acceptor for the enzyme.

Cyanides↗
PubMed1977

Oxidation of aliphatic hydroxylamines in aqueous solutions.

The effects of pH, buffer constituents, duration of storage, presence of air, heavy metal ions, extracting solvents and various additives and cofactors on the aerial oxidation of some aliphatic primary and secondary hydroxylamines were investigated. Copper ions were particularly effective catalysts of the oxidation reaction. Conditions to minimize this transformation are described.

Chelating Agents↗
PubMed1977

Derivatization to stabilize some aliphatic primary hydroxylamines for g.l.c. analysis.

By appropriate choice of trimethylsilylating and trifluoroacetylating reagents and organic solvents for extraction, stable derivative of aliphatic primary hydroxylamines metabolites, N-hydroxyphentermine, N-hydroxychlorphentermine, N-hydroxymexiletene, N-hydroxyphenethylamine, N-hydroxyamphetamine, and N-hydroxy-3,4-dimethoxyamphetamine, were obtained and examined by g.l.c. analysis without decomposition and without interference from the parent drug or other metabolic products.

Amines↗
PubMed1975

Separation of two L-glutamine-hydroxylamine glutamyltransferases from rat liver.

The purification of glutamine synthetase (GS) from rat liver demonstrates that a small portion of glutamine-hydroxylamine-glutamyltransferase activity (GT) remains associated with GS activity (GT(S)). As GS is purified from the water extract, the ratio between GT(S) activity (GT(T)) is left to be extracted by KC1 from the pellet and, on further purification, appears to be independent of GS activity. Subtle differences in pH optimum, substrate requirement and reaction rates on addition of cofactors and amino acids in vitro and in responses to hormonal stimuli in vivo indicate that the glutamine transfer reaction may be catalyzed by two distinguishable proteins; only the minor component may be identical to GS.

Acyltransferases↗
PubMed1978

The role of chloride ion in photosystem II. I. Effects of chloride ion on photosystem II electron transport and on hydroxylamine inhibition.

1. Chloroplasts washed with Cl--free, low-salt media (pH 8) containing EDTA, show virtually no DCMU-insensitive silicomolybdate reduction. The activity is readily restored when 10 mM Cl- is added to the reaction mixture. Very similar results were obtained with the other Photosystem II electron acceptor 2,5-dimethylquinone (with dibromothymoquinone), with the Photosystem I electron acceptor FMN, and also with ferricyanide which accepts electrons from both photosystems. 2. Strong Cl--dependence of Hill activity was observed invariably at all pH values tested (5.5--8.3) and in chloroplasts from three different plants: spinach, tobacco and corn (mesophyll). 3. In the absence of added Cl- the functionally Cl--depleted chloroplasts are able to oxidize, through Photosystem II, artificial reductants such as catechol, diphenylcarbazide, ascorbate and H2O2 at rates which are 4--12 times faster than the rate of the residual Hill reaction. 4. The Cl--concentration dependence of Hill activity with dimethylquinone as an electron acceptor is kinetically consistent with the typical enzyme activation mechanism: E(inactive) + Cl- in equilibrium E . Cl- (active), and the apparent activation constant (0.9 mM at pH 7.2) is unchanged by chloroplast fragmentation. 5. The initial phase of the development of inhibition of water oxidation in Cl--depleted chloroplasts during the dark incubation with NH2OH (1/2 H2SO4) is 5 times slower when the incubation medium contains Cl- than when the medium contains NH2OH alone or NH2OH plus acetate ion. (Acetate is shown to be ineffective in stimulating O2 evolution).

Anions↗