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PubMed2003

The activities of antioxidant nutrients in human plasma depend on the localization of attacking radical species.

The oxidation of endogenous antioxidant nutrients in human plasma was determined to examine their activities against free radicals generated in the aqueous and lipid compartments of plasma. Free radicals were induced at a constant rate in the aqueous compartment by the hydrophilic radical generator, 2,2'-azobis-(2-amidinopropane)dihydrochloride (AAPH; 10-20 mmol/L) and in the lipid compartment by the lipophilic radical generator, 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile) (MeO-AMVN; 1-2 mmol/L). The depletion of endogenous plasma antioxidant nutrients (lutein, cryptoxanthin, beta-carotene, lycopene, alpha-tocopherol, ascorbic acid, uric acid) was determined after incubation with either AAPH or MeO-AMVN at 37 degrees C using HPLC. The oxidation of the aqueous and lipid compartments of plasma was selectively monitored by a fluorimetric method using either the hydrophilic probe, 2',7'-dichlorodihydrofluorescein (DCFH) or the lipophilic probe, 4,4-difluoro-5-(4-phenyl-1,3-butadienyl)-4-bora-3a, 4a-diaza-s-indacene-3-undecanoic acid (BODIPY 581/591). When plasma was incubated with AAPH, the rates of consumption of the antioxidant nutrients were as follows: ascorbic acid > alpha-tocopherol > uric acid > lycopene > lutein > cryptoxanthin > beta-carotene. When plasma was incubated with MeO-AMVN, alpha-tocopherol and carotenoids were depleted at similar rates and ahead of the major water-soluble antioxidants. Our study indicates that the antioxidant nutrients present in both the lipid and aqueous compartments can remove free radicals generated in plasma, and their activity depends on the localization of the attacking radical species.

Amidines↗
PubMed1987

Circular dichroism of poly(dG-dC) modified by the carcinogens N-methyl-4-aminoazobenzene or 4-aminobiphenyl.

Poly(dG-dC) was modified to different extents by the carcinogens 4-aminobiphenyl (ABP) or N-methyl-4-aminoazobenzene (MAB). HPLC analysis of the enzymatically hydrolyzed modified polymers indicates that more than 90% of the ABP and 81% of the MAB modification occurs at the C8 position of guanine. The conformational changes of the unmodified and modified polymers were studied as a function of ethanol and magnesium ion concentrations by the use of circular dichroism (CD). The modified polymers show a CD inversion pattern similar to that of the salt-induced B to Z transition of poly(dG-dC). Both of the modified polymers require less salt or ethanol than the unmodified polymer for the inversion of the spectra. The amount of ethanol or magnesium needed to induce the inverted CD spectrum is inversely proportional to the percentage of bound ABP or MAB. These data indicate that ABP and MAB can enhance conversion from B to Z conformation in alternating purine-pyrimidine sequences.

Aminobiphenyl Compounds↗
PubMed2003

The intestinal anti-inflammatory activity of UR-12746S on reactivated experimental colitis is mediated through downregulation of cytokine production.

BACKGROUND: UR-12746S (dersalazine sodium) is cleaved by colonic bacteria delivering the PAF antagonist UR-12715 and 5-ASA. This study describes the anti-inflammatory activity of UR-12746S in an experimental model of reactivated colitis and its effects on cytokine production. METHODS: Rats were initially rendered colitic by a colonic instillation of 10 mg of trinitrobenzenesulphonic acid (TNBS) dissolved in 0.25 ml of 50 % ethanol, and colitis was reactivated two weeks after by a second administration of the same dose of TNBS. Two groups of colitic rats received UR-12746S (25 and 50 mg/kg daily, p.o.) and colonic damage was evaluated every week for 4 weeks. Different biochemical markers of colonic inflammation were assayed: MPO activity and cytokine (IL-1beta and TNFalpha) levels. Also, the in vitro effects of UR-12715 and 5-ASA on cytokine production were assayed. RESULTS: UR-12746S showed anti-inflammatory effect in reactivated colitis in rats, as evidenced by a significant reduction in MPO activity. Both doses of UR-12746S decreased IL-1beta production, while only the highest dose assayed inhibited TNFalpha production. In vitro studies revealed that UR-12715 or 5-ASA (from 10(-6) to 10(-4) M) inhibited IL-8 production (30-40%) in HT-29 cells when incubated with LPS. This inhibitory effect was enhanced when both compounds were administered simultaneously at 10(-4) M. In addition, UR-12715 inhibited IL-1beta or TNFalpha production in THP-1 or U937 cells, respectively, when these cells were stimulated by PMA and LPS; whereas 5-ASA only showed a weak effect in inhibiting IL-1beta production. CONCLUSION: UR-12746S was able to prevent relapse in experimental colitis and inhibition of proinflammatory cytokine production participates in the intestinal anti-inflammatory activity exerted by this compound.

Aminosalicylic Acids↗
PubMed2004

Influence of a long-chain alkane on the photoinduced nematic-isotropic transition.

We investigated the phenomenon of photoinduced nematic-isotropic (N-I) transition for different concentrations of a long-chain alkane, viz., octadecane (OD), and a host liquid crystalline material having a small quantity (4.5 mol %) of a photoactive azo compound. As expected, the N-I transition temperature diminishes with increasing concentration of OD. Data of time-resolved measurements of the dielectric constant through both the UV-activated trans-cis transformation and the thermal back relaxation process are presented. With increasing concentration of OD, although the response time for the former process increases slightly by less than a factor of 2, the thermal back relaxation shows a greater increase by more than an order of magnitude. As a possible explanation for this surprising result, we discuss an argument based on the structural incompatibility of the constituents of the system investigated.

Journal Article↗
PubMed1980

Structure-staining relationships in histochemistry and biological staining. I. Theoretical background and a general account of correlation of histochemical staining with the chemical structure of the reagents used.

A description is given of the choice, rationale and calculation of several numerical coefficients for describing the chemical structures of staining reagents such as dyestuffs, enzyme substrates, diazonium and tetrazolium salts. Using such coefficients, structure-staining correlations may be made for many staining systems. Examples include the structural correlations of the quantitative affinity measurements of the staining of chromatin with basic dyes, the tetrazolium salts for use as visualizing agents in enzyme histochemistry, and the use of bis-azo compounds as acid or basic dyes, or as fat stains. The value of such structure-staining correlation models for assisting the rational selection and design of new histochemical reagents, and for understanding old reagents and procedures, is discussed.

Chemical Phenomena↗
PubMed1998

Contact dermatitis due to 2,2'-azobis(2-amidinopropane) dihydrochloride: an outbreak in production workers.

2,2'-azobis(2-amidinopropane) dihydrochloride (AAPH) is an azo compound which has been used as a radical chain initiator. The purpose of this study was to confirm contact sensitivity to AAPH in individuals who were engaged in the production of AAPH, and presented with prolonged eczematous eruptions mainly on exposed areas. Patch testing was carried out with AAPH (1 and 5% aq.) on 8 patients and 6 healthy volunteers who had never been exposed to this chemical. All patients showed a strong positive patch test reaction to this agent, while all control subjects showed negative results. Because this chemical has recently been used for studies on the oxidation of biological materials, not only production workers in the chemical industry but also medical researchers should avoid prolonged exposure to this agent.

Adult↗
PubMed1999

Biotransformation of 2,4,6-trinitrotoluene with Phanerochaete chrysosporium in agitated cultures at pH 4.5.

The biotransformation of 2,4,6-trinitrotoluene (TNT) (175 microM) by Phanerochaete chrysosporium with molasses and citric acid at pH 4.5 was studied. In less than 2 weeks, TNT disappeared completely, but mineralization (liberated 14CO2) did not exceed 1%. A time study revealed the presence of several intermediates, marked by the initial formation of two monohydroxylaminodinitrotoluenes (2- and 4-HADNT) followed by their successive transformation to several other products, including monoaminodinitrotoluenes (ADNT). A group of nine acylated intermediates were also detected. They included 2-N-acetylamido-4,6-dinitrotoluene and its p isomer, 2-formylamido-4, 6-dinitrotoluene and its p isomer (as acylated ADNT), 4-N-acetylamino-2-amino-6-nitrotoluene and 4-N-formylamido-2-amino-6-nitrotoluene (as acetylated DANT), 4-N-acetylhydroxy-2,6-dinitrotoluene and 4-N-acetoxy-2, 6-dinitrotoluene (as acetylated HADNT), and finally 4-N-acetylamido-2-hydroxylamino-6-nitrotoluene. Furthermore, a fraction of HADNTs were found to rearrange to their corresponding phenolamines (Bamberger rearrangement), while another group dimerized to azoxytoluenes which in turn transformed to azo compounds and eventually to the corresponding hydrazo derivatives. After 30 days, all of these metabolites, except traces of 4-ADNT and the hydrazo derivatives, disappeared, but mineralization did not exceed 10% even after the incubation period was increased to 120 days. The biotransformation of TNT was accompanied by the appearance of manganese peroxidase (MnP) and lignin-dependent peroxidase (LiP) activities. MnP activity was observed almost immediately after TNT disappearance, which was the period marked by the appearance of the initial metabolites (HADNT and ADNT), whereas the LiP activity was observed after 8 days of incubation, corresponding to the appearance of the acyl derivatives. Both MnP and LiP activities reached their maximum levels (100 and 10 U/liter, respectively) within 10 to 15 days after inoculation.

Biodegradation, Environmental↗
PubMed1979

Production of a mutagen from ponceau 3R by a human intestinal anaerobe.

Ponceau 3R was reduced in vitro by Fusobacterium sp. 2, a human intestinal anaerobe, to a product which is mutagenic when metabolically activated by liver S9 preparations in the Salmonella/mammalian-microsome mutagenicity test. This mutagenic metabolite has been identified as 2,4,5-trimethylaniline.

Aniline Compounds↗
PubMed1997

Higher frequency of atopic dermatitis and decrease in viral warts among children exposed to chemicals liberated in a chemical accident in Frankfurt, Germany.

BACKGROUND: In february 1993, a major accident occurred in a chemical plant in Frankfurt, Germany, resulting in the emission of a cloud containing 10 m3 of chlorinated and azo compounds such as o-nitroanisole. An inner zone of the suburb Schwanheim was severely polluted. OBJECTIVE AND METHODS: To assess possible long-lasting effects of this environmental accident on the incidence of skin diseases, we examined a total of 511 children from the inner and outer zones of Schwanheim 18 months later and compared the findings to those obtained from a control group of 143 children from the Frankfurt area and South Hessen. For 402 children of the exposed group, information about the exposure status was available, clearly defining presence of absence in the inner zone at the time of the accident. RESULTS: We observed an overall increase in atopic dermatitis among children present during the accident with an odds ratio of 2.44 (95% CI: 1.25-4.76, p value = 0.009). The prevalence of atopic dermatitis was most marked among exposed children in the age group of 6-12 years with a peak of 22.1% compared to 9.2% in the control group and 11.7% among non-exposed children from the outer zone. All cases of atopic dermatitis were mild, however, and did not require hospital treatment. A history of atopic dermatitis was obtained in 20.3% of all children. In the inner zone, 34.2% of the present cases with atopic dermatitis had a previous history of this disease compared to 31% in the outer zone and only 16.2% in the control group. Other skin diseases, such as birthmarks, congenital skin tumours, psoriasis or acne, did not differ, except for viral warts (verrucae vulgares), which were much more frequent in the control group. CONCLUSIONS: The data suggest that acute exposure to a major chemical burden is a risk factor that contributes even after the considerable time period of 1.5 years to the exacerbation of latent and also the development of 'new' atopic dermatitis.

Accidents, Occupational↗
PubMed2004

Surfactant lipid peroxidation damages surfactant protein A and inhibits interactions with phospholipid vesicles.

The goal of these studies was to examine the effect of lipid peroxidation (LPO) on the function of surfactant protein A (SP-A). First, the optimal dialysis conditions for quantitative removal of EDTA and redoxactive metals from reagents were established. Surfactant phospholipids were incubated with free radical generators in the absence or presence of the SP-A or with BSA as a control. We found that SP-A inhibited copper-initiated LPO to an extent similar to BSA (P < 0.05). Exposure of SP-A to LPO was associated with an increase in the level of SP-A-associated carbonyl moieties and a marked reduction in SP-A-mediated aggregation of liposomes. LPO initiated by an azo-compound also resulted in enhanced protein oxidation and markedly inhibited SP-A-mediated liposome aggregation. The kinetics of aggregation of auto-oxidized and nonoxidized liposomes by nonoxidized SP-A was similar, suggesting that SP-A has similar affinities for oxidized and nonoxidized lipids. Oxidative inactivation of SP-A did not occur upon direct incubation of the protein with malondialdehyde alone. We conclude that exposure of SP-A to LPO results in oxidative modification and functional inactivation of SP-A by phospholipid radicals.

Edetic Acid↗
PubMed1991

Susceptibility of neonatal lipoproteins to oxidative stress.

We compared peroxidizability of neonatal and adult lipoproteins exposed to oxidative stress initiated by an azo-compound. Oxygen uptake showed a two-phase pattern, with slow oxygen uptake in the first phase and faster uptake in the second phase. During the first phase, tocopherol was consumed progressively, inhibiting lipid peroxidation by scavenging peroxy radicals. After the tocopherol concentration fell below a critical level, extensive propagation of chain oxidative reactions produced the rapid oxygen uptake in the second phase. In the first phase of neonatal lipoprotein oxidation, a faster oxygen uptake was observed and the length of this phase was shorter than in adults. The oxygen uptake rate in the second phase was smaller in the neonatal lipoproteins. In other words, neonatal lipoproteins were more susceptible to oxidative stress than were adult ones when tocopherol remained in lipoproteins, but after tocopherol depletion the reverse was true. These results were consistent with the finding that in neonatal lipoproteins the tocopherol/lipid ratio was significantly lower (length of the inhibitory phase was closely correlated to the lipoprotein tocopherol content). In addition, the average number of active bisallylic hydrogen atoms, which are considered to determine the relative susceptibility of polyunsaturated fatty acids to oxidation, was significantly smaller (oxygen uptake rate in the second phase was closely correlated to the active bisallylic hydrogen number) in neonatal lipoproteins, and the ratio of active bisallylic hydrogen to tocopherol content (which closely correlated to oxygen uptake rate in the first phase) was also significantly lower compared with the adult ratio. Under physiologic conditions, an intensive oxidation of lipoproteins sufficient to cause lipoprotein tocopherol to fall below critical levels is unlikely to occur.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

The protective effect of taurine on the biomembrane against damage produced by oxygen radicals.

The effect of taurine in protecting biomembrane against oxygen radicals was investigated using canine erythrocytes. 2,2'-Azobis(2-amidinopropane) dihydrochloride (AAPH), a water-soluble azo-compound, was used as the oxygen-radical generator. Taurine suppressed erythrocyte hemolysis more effectively than alpha-alanine, used for comparison. To clarify the relationship to the lipid peroxidation, the amount of lipid peroxide was measured using liposomes prepared with egg yolk lecithin. However, the peroxidation was not suppressed by taurine. When intact erythrocytes were subjected to hemolysis by hyposmotic solutions, taurine suppressed the osmotic hemolysis more effectively than alpha-alanine. These results suggest that taurine does not have an antioxidative effect like vitamin E, but interacts with the biomembrane, and helps to protect it against damage caused by AAPH.

Amidines↗
PubMed2005

Inhibitory effect of coumarins from Weigela subsessilis on low density lipoprotein oxidation.

Oxidation of low density lipoprotein (LDL) is thought to be a major factor in the pathophysiology of atherosclerosis. In the present study, we found that coumarins isolated from Weigela subsessilis (Caprifoliaceae) inhibited LDL oxidation mediated by either catalytic copper ions (Cu2+) or free radicals generated with the azo compound 2,2'-azobis-(2-amidinopropane)dihydrochloride (AAPH). Of the coumarins tested, scopoletin (1) and cleomiscosin A (2) increased the lag time of conjugated diene formation and inhibited the generation of thiobarbituric acid reactive substances (TBARS) in a dose-dependent manner. In addition, it was found that compounds 1 and 2 had the capacity to protect the fragmentation of apolipoprotein B-100 (apoB-100). These results suggest that W. subsessilis and its active coumarins, 1 and 2, may have a role to play in preventing the LDL oxidation involved in atherogenesis.

Caprifoliaceae↗