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PubMed1991

Use of pig hepatocytes to study the inhibition of monoamine oxidase by furazolidone.

Primary cultures of pig hepatocytes were used to examine the irreversible inhibition of monoamine oxidase (MAO), which has been observed in tissues of a number of different animal species after oral treatment with furazolidone. The rapid biotransformation of the MAO substrate p-tyramine by intact cells could effectively and irreversibly be inhibited with the known MAO inhibitors iproniazid and clorgyline. Incubation of cells with beta-hydroxyethylhydrazine and also 3-amino-2-oxazolidinone, which were previously proposed as the metabolites of furazolidone responsible for the in vivo effect, resulted in an irreversible inhibition of the MAO activity. Incubation of cells with furazolidone also resulted in a dose-related inhibition, but this effect was completely reversible on withdrawal of the drug. A similar MAO inhibition was observed after treatment of cells with nitrofurazone and furaltadone but not with nitrofurantoin. The results obtained with intact cells were confirmed by studies with 13,000 g pellets of homogenates made from cells preincubated for 24 hr with the compounds, which showed an irreversible inhibition in the case of iproniazid and 3-amino-2-oxazolidinone, but not in the case of furazolidone. The present study shows that hepatocytes are capable of transforming 3-amino-2-oxazolidinone, but not furazolidone itself, into a potent irreversible type of MAO inhibitor.

Animals↗
PubMed1986

An evaluation of Aquaphor Gauze dressing in burned children.

Aquaphor Gauze was evaluated as a dressing for skin graft donor sites, for partial thickness burn injuries and for split thickness skin grafts. Control dressings consisted of: fine mesh gauze for skin graft donor sites. silver sulphadiazine (Silvadene) on coarse mesh gauze for the partial thickness burns, and nitrofurazone cream (Furacin) on fine mesh gauze for the skin grafts. The Aquaphor Gauze was found to be inferior to the fine mesh gauze for donor site dressings. No statistically significant difference was identified between Aquaphor Gauze and controls for the treatment of partial thickness burns. As a dressing for skin grafts the Aquaphor Gauze was significantly superior to the control dressing as measured by graft take and reduced patient pain. We would recommend that Aquaphor Gauze be used as a dressing for skin grafts where the risk of infection is not excessive.

Adolescent↗
PubMed1989

Susceptibility of Pseudomonas and Staphylococcus wound isolates to topical antimicrobial agents: a 10-year review and clinical evaluation.

A 10-year review of Ps. aeruginosa and Staph. aureus susceptibility to various topical agents is presented. Susceptibility testing was performed using the agar well diffusion (AWD) method. A reduction in microbial growth to numbers less than 10(5) per gram of tissue in the wound, measured by quantitative biopsy, was compared with predicted susceptibility test results. In this measurement of clinical efficacy, silver sulphadiazine and mafenide acetate compared most favourably with AWD results, 83 per cent and 82 per cent respectively. However, nitrofurazone only reduced bacterial counts to less than 10(5) per gram 42 per cent of the time when an inhibition zone was present. Hydrogen peroxide solution (1 per cent) was 100 per cent effective by the AWD test, but no relationship to clinical efficacy could be shown. Minimal inhibitory concentration (MIC) data for gentamicin sulphate was compared to AWD and showed a positive relationship of greater than 80 per cent for both organisms. The AWD test has been a useful aid in the decision-making process for the choice of topical agent by providing data which eliminates agents inappropriate for use.

Administration, Topical↗
PubMed2005

Quantitative determination of four nitrofuran metabolites in meat by isotope dilution liquid chromatography-electrospray ionisation-tandem mass spectrometry.

A confirmatory method based on isotope dilution liquid chromatography-tandem mass spectrometry (LC-MS/MS) has been developed for the low-level determination of residues of four nitrofuran veterinary drugs in meat, e.g., furazolidone, furaltadone, nitrofurantoin, and nitrofurazone. The procedure entails an acid-catalysed release of protein-bound metabolites, followed by their in situ conversion into the 2-nitrobenzaldehyde (NBA) imine-type derivatives. Liquid-liquid extraction and clean-up on a polymeric solid phase extraction cartridge are then performed before LC-MS/MS analysis by positive electrospray ionisation (ESI) applying multiple reaction monitoring of three transition reactions for each compound. Reliable quantitation is obtained by using one deuterated analogue per analyte (d4-NBA derivative) as internal standard (IS). Validation of the method in chicken meat was conducted following the European Union (EU) criteria for the analysis of veterinary drug residues in foods. The decision limits (CCalpha) were 0.11-0.21 microg/kg, and the detection capabilities (CCbeta) 0.19-0.36 microg/kg, thus below the minimum required performance limit (MRPL) set at 1 microg/kg by the EU. The method is robust and suitable for routine quality control operations, and more than 200 sample injections were performed without excessive pollution of the mass spectrometer or loss of LC column performance.

Chromatography, Liquid↗
PubMed2005

Determination of nitrofuran metabolites in poultry muscle and eggs by liquid chromatography-tandem mass spectrometry.

The use of nitrofurans in food-producing animals has been banned in EU. Detection of the protein-bound nitrofuran metabolites is the best approach to evaluate their utilization. A fast, sensitive and reliable LC-MS-MS method is presented to analyze simultaneously the metabolites of four commonly used nitrofuran drugs, furazolidone, furaltadone, nitrofurazone and nitrofurantoin. The sample clean up was performed by a single liquid-liquid extraction step, after a hydrolysis and derivatisation process. Separation of the molecules was performed by liquid chromatography in a C18 column (100 mmx2.1 mm, 4 microm) at room temperature. The quantitative and confirmatory determination of these metabolites was performed by multiple reactions monitoring (MRM). Limits of quantification of 0.5 ngg(-1) were achieved and the total analysis was accomplished in 5 min. This protocol has been applied to identify contaminated samples of poultry muscle and egg products.

Animals↗
PubMed2002

Synthesis of some new biologically active thiadiazolotriazinones--part III.

4-Amino-6-arylmethyl/tert-butyl-3-mercapto-1,2,4-triazin-5(4H)-ones (1) were condensed with arylfuroic acids (2) to yield 7-(5-aryl-2-furyl)-3-arylmethyl/tert-butyl-4H-1,3,4-thiadiazolo[2,3-c]-1,2,4-triazin-4-ones (3). The newly synthesized compounds exhibited antibacterial activity comparable to that of nitrofurazone. In addition, two compounds displayed in vitro antitumor activity with moderate growth inhibition against a panel of 60 tumor cell lines.

Anti-Infective Agents↗
PubMed1990

On-line combination of dialysis and column-switching liquid chromatography as a fully automated sample preparation technique for biological samples. Determination of nitrofuran residues in edible products.

The potential of dialysis coupled on-line with trace enrichment by column-switching high-performance liquid chromatography as an automated sample treatment technique in drug residue analysis has been investigated. The nitrofuran veterinary drugs furazolidone, nitrofurazone, nitrofurantoin and furaltadone were used as model compounds. Critical parameters, i.e., dialyser dimensions, air segmentation, dialysis time, flow-rates and enrichment column breakthrough, were evaluated. Depending on the analytical purpose, the technique can be set up in either a highly sensitive or a high-speed mode. High dialysis efficiencies (greater than 85%) can be obtained in a stopped-flow dialysis of only 3 min. Aqueous biological sample volumes (eggs, meat, milk) of 100 microliters to 4 ml can be injected with only sample treatment. A routine monitoring method for residues of nitrofuran drugs in edible products was set up. A 4-ml sample was dialysed in a pulsed mode with an efficiency of about 30% and concentrated on a short C18 column. Recoveries compared with standards were 75-85% (coefficient of variation 2-7%). Limits of determination ranged from 1 to 10 micrograms/kg. At this concentration level, ca. 30 samples can be monitored per day.

Animals↗
PubMed2001

Determination of the metabolites of nitrofuran antibiotics in animal tissue by high-performance liquid chromatography-tandem mass spectrometry.

A LC-MS-MS method is presented to analyse simultaneously the metabolites of four nitrofuran antibacterial agents, furazolidone, furaltadone, nitrofurazone and nitrofurantoin in animal muscle tissue. Sample clean-up and analyte enrichment was performed by solid-phase extraction (SPE) with a polystyrene sorbent following combined hydrolysis of the protein-bound drug metabolites and derivatisation of the homogenised tissue with 2-nitrobenzaldehyde. Limits of detection of 0.5-5 ng g(-1) tissue and limits of determination of 2.5-10 ng g(-1) tissue were achieved using electrospray ionisation in positive mode. Analyte identification and quantification was performed according to EU guidelines, using multiple reaction monitoring (MRM) with one precursor ion and two product ions as identifiers. The use of an internal standard in combination with the simplified sample preparation led to a sensitive and reliable analysis method. The yield of the derivatisation reaction was between 66 and 74% and the recovery of SPE reached 92-105% for all values between 10 and 500 ng g(-1). The developed analytical protocol has been applied to contaminated tissue samples of furazolidone- and furaltadone-treated pigs and allowed unequivocal identification and quantification of the metabolites.

Animals↗
PubMed2002

Salmonella typhimurium mutagenicity tester strains that overexpress oxygen-insensitive nitroreductases nfsA and nfsB.

We have designed and constructed a series of plasmids that contain the major and/or minor Escherichia coli nitroreductase genes, nfsA and nfsB, in different combinations with R plasmid mucA/B genes and the Salmonella typhimurium OAT gene. The plasmid encoded gene products are necessary for both the metabolic activation of a range of structurally diverse nitrosubstituted compounds, and for mutagenic translation bypass. Introduction of these plasmids into S. typhimurium TA1538 and TA1535 has created several new tester strains which exhibit an extremely high mutagenic sensitivity and a broad substrate specificity towards a battery of nitrosubstituted test compounds that included 4-nitroquinoline-1-oxide (4-NQO), nitrofurazone (NF), 1-nitropyrene (1-NP), 2-nitronaphthalene (2-NN), 2-nitrofluorene (2-NF), and 1,6-dinitropyrene (1,6-DNP). Our studies show that the nfsA gene encodes a product that is extremely effective in the metabolic activation of a range of structurally diverse nitrosubstituted compounds. Several of the new tester strains are more than two orders of magnitude more sensitive to nitrosubstituted compounds than the Ames tester strains TA100 or TA98. In addition to enhancing mutagenic sensitivity, plasmids encoding both metabolic and mutagenesis functions on a single plasmid provide considerable flexibility for future mechanistic studies or tester strain development, in which it may be necessary to introduce additional plasmids containing different antibiotic resistance markers.

Bacterial Proteins↗
PubMed1997

Targeted disruption of the gene encoding the classical nitroreductase enzyme in Salmonella typhimurium Ames test strains TA1535 and TA1538.

The gene encoding the 'classical nitroreductase' (CNR) of Salmonella typhimurium was disrupted. In this manner, cnr null mutant derivatives of strains TA1535 and TA1538 were constructed, and named YG7131 and YG7127, respectively. In both strain backgrounds, cnr gene disruption reduced nitrofurazone-reductase activity. This reduction almost completely eliminated the nitroreductase activity of strain TA1538. In contrast, the nitroreductase activity of strain TA1535 was much higher than that in TA1538. In this background, cnr gene disruption resulted in a reduction in nitroreductase activity by a similar absolute amount as in TA1538, but representing only about one-quarter of the original activity of TA1535. The results suggest that S. typhimurium has originally at least two distinct nitroreductases, one of which is already deficient in strain TA1538; the CNR is present in both TA1535 and TA1538. Also, these two strains (including their derivatives, TA98 and TA100) are not isogenic with regard to nitroreductase activity. After the introduction of plasmid pKM101, the sensitivities of the strains YG7132 and YG7128, the cnr-null mutants of TA98 and TA100, respectively, against several nitro compounds were compared with those of the conventional cnr-deficient strains TA98NR and TA100NR and the wild-type strains TA98 and TA100. The mutagenicities of 2-nitrofluorene and 1-nitropyrene in YG7132 or TA98NR were ten-fold lower than those of the compounds in TA98. Similarly, the mutagenicity of 2-(2-furyl)-3-(5-nitro-2-furyl) acrylamide in strain YG7128 or TA100NR was substantially lower than that of the compound in TA100. However, the mutagenicity of 2-nitronaphthalene in YG7128 was between those observed with TA100 and TA100NR, suggesting that a nitroreductase in S. typhimurium other than CNR is involved in the metabolic activation of this compound. The cnr gene of S. typhimurium positively hybridized with DNA at 13 min on the E. coli chromosome where the nfsB and nfnB genes of E. coli are mapped. These results suggest that the cnr gene of S. typhimurium is a counterpart of the nfsB and nfnB genes of E. coli, and that the newly constructed cnr-deletion strains are useful to assess the role of nitroreductases in the metabolic activation of mutagenic nitro compounds.

Blotting, Southern↗
PubMed1990

Bandages and topical agents.

Bandages are included in the regimen of therapy of superficial wounds. Bandages have varying functions depending upon the type of wound to which they are applied. When bandaging recently inflicted open wounds, the primary bandage layer may be dry-to-dry, wet-to-dry, or wet-to-wet, depending upon the type of tissue and exudate present on the wound. These bandages aid in debriding and cleansing a wound. The secondary layer of such bandages serves primarily to absorb material from the wound, and the tertiary bandage layer serves to hold the other bandage layers in place. Once an open wound is well into the repair stage of healing, an occlusive bandage may be considered to help enhance epithelialization of the wound. Bandages for wounds associated with compound fractures must include some form of fixation for the fracture. Other types of bandages are designed to (1) cover closed wounds, (2) provide pressure over a wound, and (3) relieve pressure over wounds or impending wounds. Bandages for closed wounds provide protection and allow for absorption of exudate that may be present. Pressure bandages are used to control minor hemorrhage, edema, and excess granulation tissue. With impending decubital ulcers, actual decubital ulcers, or repaired decubital ulcers, it is necessary to have a bandage designed to relieve pressure over the lesion. Many substances have been described for topical application to wounds. This section presents information on some substances available to or commonly used by veterinarians. It includes information on the wound lavage solutions chlorhexidine diacetate, povidone-iodine, hydrogen peroxide, and sodium hypochlorite solutions. Topical antibacterial agents are used to help prevent wound infection. The triple antibiotics, silver sulfadiazine, nitrofurazones, and gentamicin sulfate are some commonly used antibacterial agents. Hydrophilic agents are used to diffuse fluids through the wound tissues to bathe the tissues from the inside. Dry starch copolymer flakes and dextran polymer beads are two substances that help bathe the wound with the body's own fluids. Other topical medications are used to selectively act upon various wound tissues and exudates to aid in cleansing the wound; these include organic acid preparations and enzymatic debriding agents. In addition, a live yeast-cell derivative has been described for enhancing tissue oxygen consumption, epithelialization, and collagen synthesis in wounds.

Administration, Topical↗
PubMed2003

Mechanism of metronidazole-resistance by isolates of nitroreductase-producing Enterococcus gallinarum and Enterococcus casseliflavus from the human intestinal tract.

Enterococcus casseliflavus and Enterococcus gallinarum strains resistant to metronidazole, nitrofurantoin and nitrofurazone were isolated from fecal samples of a patient with recurrent ulcerative colitis treated with metronidazole. Unlike other metronidazole-resistant bacteria, these strains produced nitroreductase but metabolized metronidazole to compounds that could not be detected by liquid chromatography with UV or mass spectral analysis. Metronidazole-susceptible Clostridium perfringens grew equally well in spent cultures of Enterococcus spp. incubated with or without metronidazole. These data indicate that the nitroreductases produced by these Enterococcus strains did not activate metronidazole to bactericidal metabolites and these bacteria may reduce the effectiveness of metronidazole. We have indirect evidence for an alternative pathway that results in metronidazole resistance. These strains of enterococcus had nitroreductase so resistance should not have occurred.

Chromatography, High Pressure Liquid↗
PubMed2000

Evaluation of in-vivo wound healing activity of Hypericum patulum (Family: hypericaceae) leaf extract on different wound model in rats.

The methanol extract of Hypericum patulum Thumb. leaves were investigated for the evaluation of their wound healing potential on different experimental models of wounds in rats. The methanol extract of leaves (HPM), in the form of an ointment with two different concentrations (5% and 10% w/w ointment of leaf extract in simple ointment base) was evaluated for wound healing potential in an excision wound model and an incision wound model in rats. Both concentrations of the methanol extract ointment showed significant responses in both the wound types tested when compared with the control group. The effect produced by the extract ointment, in terms of wound contracting ability, wound closure time, regeneration of tissues at wound site, tensile strength of the wound and histopathological characteristics were comparable to those of a standard drug nitrofurazone ointment.

Administration, Topical↗
PubMed2004

Analysis of matrix-bound nitrofuran residues in worldwide-originated honeys by isotope dilution high-performance liquid chromatography-tandem mass spectrometry.

A sensitive and selective isotope dilution liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESIMS/MS) method is presented for the simultaneous analysis of the metabolites of four nitrofuran veterinary drugs, that is, furazolidone, furaltadone, nitrofurantoin, and nitrofurazone, in honey samples. The method entails a combined hydrolysis of protein-bound drug metabolites and derivatization of the resulting metabolites with 2-nitrobenzaldehyde (NBA) during an overnight incubation, followed by a liquid-liquid extraction and a cleanup on a polymeric solid-phase extraction cartridge. Mass spectral acquisition is carried out in the positive ion mode by applying multiple reaction monitoring (MRM) of three diagnostic transition reactions for each analyte under survey. A reliable quantification is obtained by the use of one deuterated analogue per analyte (NBA-d(4) derivative). The method has been validated in honey according to the European Union criteria for the analysis of veterinary drug residues in food. Expressed in underivatized nitrofuran metabolite concentrations, the decision limits (CCalpha) ranged within 0.07-0.46 microg/kg, and the detection capabilities (CCbeta) were within 0.12-0.56 microg/kg. The method has been successfully applied in a survey of honeys of various geographical origins, showing that furazolidone is the main nitrofuran antibiotic administered to treat bacterial diseases of bees.

Chromatography, High Pressure Liquid↗
PubMed2005

Liquid chromatography-tandem mass spectrometry for the determination of protein-bound residues in shrimp dosed with nitrofurans.

An analytical method was developed for the determination of bound residues of the nitrofuran drugs furazolidone, nitrofurazone, furaltadone, and nitrofurantoin with a sensitivity of 1 ppb in shrimp. In this procedure, shrimp tissue is prewashed with solvents followed by overnight acid hydrolysis, during which the side chains of the bound residues are released and simultaneously derivatized with 2-nitrobenzaldehyde. After liquid-liquid extraction cleanup, the derivatives are detected and quantitated using liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) with an atmospheric pressure chemical ionization interface. The method was validated using control shrimp fortified with each side-chain analyte at 1, 2, and 4 ppb. Method accuracies were >80% with coefficients of variation of <20% for all four analytes. Tissues from dosed shrimp were assayed to demonstrate the effectiveness of the method for recovering bound residues of nitrofurans. In shrimp dosed with nitrofurans, nitrofurantoin exhibited the lowest level of bound residues.

Animals↗
PubMed1982

Structure/activity relationships for the enhancement by electron-affinic drugs of the anti-tumour effect of CCNU.

Using a regrowth-delay assay, we investigated structure/activity relationships for the enhancement by electron-affinic agents of the anti-tumour effect of the nitrosourea CCNU against the KHT sarcoma in C3H mice. A series of neutral 2-nitroimidazoles similar in electron affinity but varying in octanol/water partition coefficient (PC) over 4 orders of magnitude (0.016- greater than 200, Misonidazole = 0.43) were examined at a fixed dose of 2.5 mmol/kg. A parabolic (quadratic) dependence of activity on log PC was observed. Analogues more hydrophilic than misonidazole (MISO) were inactive as were those with very high PCs (greater than 20). Those with PC 0.43--20 were usually more active than MISO, some considerably so. The fairly lipophilic 5-nitroimidazoles nimorazole and metronidazole (METRO) had similar activity to MISO, despite their reduced electron affinity. Two basic 2-nitroimidazoles more efficient as radiosensitizers in vitro likewise showed activity comparable to MISO. We also investigated several agents more electron-affinic than MISO, including some non-nitro compounds. Most were inactive at maximum tolerated doses, but nitrofurazone showed reasonable activity. Sensitizer dose-response curves were obtained for MISO, METRO and two of the most effective agents, benznidazole (Ro 07-1051) and Ro 07-1902. The two latter agents were both considerably more active than MISO at low doses (0.1--0.9 mmol/kg). These studies indicate that the structural features of electron-affinic agents responsible for the enhancement of KHT tumour response to CCNU, are quite different from those affecting radiosensitization, lipophilicity being particularly important. The microsomal enzyme-inhibitor SKF 525A increased the anti-tumour effect of CCNU, suggesting inhibition of CCNU metabolism as one possible mechanism contributing to chemosensitization by lipophilic electron-affinic agents in mice.

Animals↗
PubMed2004

Semicarbazide is a minor thermal decomposition product of azodicarbonamide used in the gaskets of certain food jars.

Evidence is presented for the first time showing that semicarbazide (SEM) is a minor thermal decomposition product of the blowing agent azodicarbonamide (ADC). A novel direct analytical method based on liquid chromatography electrospray ionization tandem mass spectrometry (LC-ESIMS/MS) has been developed to determine SEM in foamed polyvinyl chloride (PVC) seals of metal lids, as well as in commercially available ADC. The direct LC-MS/MS method for gaskets entails extraction of the gaskets in hot water, addition of ((15)N(2)(13)C)-SEM as internal standard, and injection of an aliquot directly into the LC-MS system, achieving good sensitivity (S/N = 348 for 2 ng injected on-column) and monitoring three characteristic mass transitions (m/z 76-->31; 76 -->44; 76-->59). Semicarbazide can be detected in thermally treated ADC, reaching up to 0.93 mmol mol(-1) at 220 degrees C, as determined by the direct LC-MS/MS method. This new method is also compared to the classical derivatization method using 2-nitrobenzaldehyde (2-NBA) that is routinely employed to determine SEM as an indicator of the usage of the antimicrobial drug nitrofurazone, the use of which is not authorized in the European Union (EU). Both methods revealed proportional results, with approx. 3-fold higher levels recorded by the direct SEM approach, probably due to differences in the extraction procedures used. A limited survey of plastic seals from used press twist and twist-off metal lids on food jars (non-foamed and foamed) revealed levels of SEM ranging from 2 to 8689 microg kg(-1)(average = 1593 microg kg(-1), n= 57 determinations).

Azo Compounds↗
PubMed2000

In vitro susceptibility of Escherichia coli strains isolated from diarrhoeic dairy calves to 15 antimicrobial agents.

The in vitro activities of 15 antimicrobial agents against 195 strains of Escherichia coli isolated from dairy calves affected by neonatal diarrhoea were determined. Of these strains 137 produced one or more potential virulence factors (F5, F41, F17, cytotoxic necrotizing factor, verotoxin and the eae gene), but the remaining 58 strains did not produce any of these factors. The overall percentage of resistant strains to streptomycin, tylosin and tetracycline was very high (above 65%). A high level of resistance (from 23 to 50%) to ampicillin, neomycin, kanamycin, spectinomycin, chloramphenicol, sulphadimethoxine and trimethoprim was also detected. The E. coli strains were very susceptible (89-95%) to apramycin and gentamicin and highly susceptible (99-100%) to polymyxin B, florfenicol and nitrofurazone. Some significant differences (P < 0.05) in the frequencies of resistance to some of the antimicrobials tested and in the rates of multi-drug resistance among the strains producing potential virulence factors and non-fimbriated, non-toxigenic, eae-negative strains were found. Most of the strains showed multi-resistance: 76.9% of the isolates were resistant to at least two antibiotics, 67.7% were resistant to at least four antibiotics and 50.3% were resistant to at least six antibiotics.

Animals↗