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At least 343 records · Page 19Linked to original sources
PubMed1996

Antioxidant behaviors of vitamin E analogues in unilamellar vesicles.

The antioxidant behaviors of vitamin E and its analogues, 2,2,5,7,8-pentamethyl-6-hydroxychroman and 1,2-diacyl-sn-glycero3-phospho-2'-(hydroxyethyl)-2'- 5',7',8'-tetramethyl-6'-hydroxychroman, were studied in unilamellar vesicles. The two analogues scavenged aqueous radicals generated from azo compounds more efficiently than vitamin E. On the other hand, vitamin E scavenged the lipid peroxyl radicals preferentially. It is concluded that the superior antioxidant activity of vitamin E is attributed to its location suitable for breaking the chain propagation reaction.

Antioxidants↗
PubMed1996

Simple detection of xylosidase activity in single colonies, using 1-naphthyl-beta-D-xylopyranoside.

Since the xylosidase of Bacillus pumilus hydrolyzed 1-naphthyl-beta-D-xylopyranoside (naphthyl-X) to produce xylose and 1-naphthol and a chromogenic azo compound is produced by coupling 1-naphthol and Fast Blue Salt B, a simple method for detection of xylosidase activity in single colonies was studied. Escherichia coli JM109 carrying the xylosidase gene of B. pumilus was cultivated at 37 degrees C for 18 h on a LB plate containing 0.5 mg/ml naphthyl-X, and then the plate was overlaid with 3 ml of a top layer containing 24 mg of agar and 6 mg of Fast Blue Salt B. After incubation of the plate at 37 degrees C for 1 h, each colony became reddish-brown. Even a small colony with xylosidase on the plate was easily distinguished from colonies without the enzyme.

Bacillus↗
PubMed2006

Photopolarimeter based on two gratings recorded in thin organic films.

A photopolarimeter based on two different kinds of diffraction gratings (a two-grating photopolarimeter) has been developed for real-time measurements of the four elements of the Stokes vector. The main elements of the device are a pure polarization grating and an ordinary transmission grating, both recorded by means of holographic techniques in thin films of organic materials. The first one consists of a diffraction grating recorded by two interfering opposite circularly polarized beams in a Langmuir-Blodgett film of an azo-compound material. The second component is a grating recorded by two interfering parallel circularly polarized beams in a thin film of a photosensitive polymer. Both gratings offer long time stability and good diffraction efficiency. Four photodiodes collect the first-order diffracted beams from these gratings, the output signals of which are read through an analog-to-digital converter by a PC. The optical alignment of the device is easy and the calibration is realized in a one-step procedure.

Journal Article↗
PubMed1983

Influence of bilirubin on the determination of acid phosphatase in serum.

Bilirubin interferes greatly in the continuous measurement of acid phosphatase, using alpha-naphthyl phosphate as substrate and diazotized 2-amino-5-chlorotoluene (Fast Red TR) as the colorimetric reagent. Fast Red TR and the so-called "direct" (but not "indirect") bilirubin form a coloured azo-compound which absorbs light above 480 nm. Negative absorbance changes are observed at 405 nm, which is used in the determination of acid phosphatase. This leads to apparently negative activities.

Acid Phosphatase↗
PubMedDate not supplied

Suppression of radical-induced lipid peroxidation in a model system by alkyl esters of cinnamate quaternary ammonium salts.

Three new groups of phenolic antioxidants, quaternary ammonium salts with a phenol ring and alkyl chains of different length (pyrrolidine ethyl esters of 3,5-di-t-butyl-4-hydroxydihydrocinnamic acid n-alkoxymethylchlorides (PYE-n) or n-alkylbromides (PYA-n) and 2-dimethylaminoethyl ester n-alkylbromides (PPA-n), were synthesized. Some of them were previously found to efficiently protect yeast cells against oxidants and to inhibit the production of thiobarbituric acid-reactive substances in whole yeast cells and in isolated membrane lipids. The new antioxidants (at 1-100 microM) abolished or diminished peroxidation of olive oil emulsions caused by the OH*-producing Fe2+ and RO* and ROO*-producing tert-butylhydroperoxide (TBHP) and the azo compounds 2,2'-azobis-(amidinopropane)dihydronitrile (AAPH) and 1,1'-azobis-(1-cyclohexanecarbonitrile) (ACHN): all present at 10 mM. The efficiency of individual both antioxidants was examined in relation to the type of lipid peroxidation inducer, the site of antioxidant incorporation into the emulsion lipid phase, the length of the alkyl chain, and the maximum concentration of effective antioxidant monomers given by its critical micelle concentration. PYA-n class compounds were highly efficient against all peroxidation inducers and their efficiency did not depend on the position of their molecules in the lipid phase and/or on the aliphatic chain length. In contrast, the efficiency of PYE-n and PPA-n class compounds depended both on the type of oxidant and on the length of their aliphatic chain. Their potency against Fe2+ and ACHN increased with increasing alkyl chain length whereas with AAPH it dropped with increasing alkyl chain length. A similar pattern was found with the action of PYE-n against TBHP whereas in the PPA-n group an extending alkyl chain reduced the anti-TBHP efficiency. These relationships may not be entirely straightforward and other factors (chemical nature of each compound, its possible interaction with fluorescent probes used for diagnostics, etc.) may play a considerable and not yet quite clear role. PPA-n class antioxidants have the lowest critical micelle concentration, which may limit their efficiency. Nevertheless, these phenolic antioxidants can be conveniently employed as highly efficient inhibitors of lipid peroxidation.

Antioxidants↗
PubMed1995

A differential staining method for adenohypophyseal cells.

A modification of azan staining (Heidenhain, 1915) for a better differential demonstration than previously of adenohypophyseal cells is reported. Human hypophyses were fixed in Bouin's solution, washed in 70% alcohol, dehydrated and then embedded in paraffin. Sections of about 5 microns thickness were cut and mounted on albumin-coated glass slides. These sections were gently oxidized with a mixture of potassium permanganate and sulphuric acid, and then stained according to the original azan technique; thereafter a procedure of staining with aniline blue was added. With this improvement, human adenohypophyseal cells were clearly classified into six groups on the basis of the color and intensity of staining of the cytoplasm. The alpha-acidophilic cells were stained clear red with azocarmine and the epsilon-acidophilic cells, orange-red with orange G, respectively. With aniline blue, beta-basophilic cells stained a deep blue, while delta-basophilic cells were more weakly stained. The gamma-chromophobic cells were faintly stained red, and the ACTH-cells very faintly blue. Collagenous fibers developed a blue color, while erythrocytes were orange-red to red. This modified method produces much better results in differential staining of the adenohypophyseal cells than either the original azan or Masson-Goldner staining methods.

Adult↗
PubMed2003

Reestimation of Cypridina luciferin analogs (MCLA) as a chemiluminescence probe to detect active oxygen species--cautionary note for use of MCLA.

Cypridina luciferin analogs have been widely used as a specific chemiluminescence probe for the detection of superoxide anion (O2-) and singlet oxygen (1O2). However, light emission during the reaction of Cypridina luciferin analogs and other active oxygen species (AOS) has not been reported in detail. Therefore, we re-evaluated 2-methyl-6-(p-methoxyphenyl)-3,7-dihydroimidazo[1,2-a]pyrazine-3-one (MCLA), one of the Cypridina luciferin analogs, as a chemiluminescence probe to detect various AOS. MCLA-dependent chemiluminescence was observed when MCLA was incubated with the following systems; 1) hypoxanthine plus xanthine oxidase (O2-), 2) thermolysis of endoperoxide (1O2), 3) hydrogen peroxide plus ferrous ion (hydroxyl radical), 4) ferrous ion, 5) thermolysis of azo compound (alkyl peroxyl radical) and 6) hydrogen peroxide. Superoxide dismutase inhibited MCLA-dependent chemiluminescence observed during ferrous ion-induced decomposition of hydrogen peroxide. Alkyl peroxyl radical reacted with MCLA, but light was not emitted when the concentration of MCLA was high. These results suggest that radicals, except O2-, appeared not to be direct inducers of MCLA-dependent light emission. In summary, MCLA-dependent chemiluminescence was induced by various AOS in addition to O2- and 1O2, but active species must be O2- and 1O2 in many cases. These points should be appreciated when Cypridina luciferin analogs, such as MCLA, are used for the detection of AOS.

Free Radicals↗
PubMed1989

Newer 5-aminosalicylic acid based drugs in chronic inflammatory bowel disease.

Since the discovery that 5-aminosalicylic acid (5-ASA) is the active moiety of sulphasalazine in the treatment of chronic inflammatory bowel disease, several new 5-ASA based drugs have been developed. These consist either of slow- or delayed-release formulations of plain 5-ASA or sulpha-free azo compounds of 5-ASA. The different formulations and compounds have varying bioavailabilities, which makes it possible to use them alternatively in different clinical situations. A review of the literature is given, together with suggestions as to how the new drugs might be used in different clinical situations.

Administration, Oral↗
PubMed1989

Disposition of 5-aminosalicylic acid from 5-aminosalicylic acid-delivering drugs during accelerated intestinal transit in healthy volunteers.

In eight healthy volunteers accelerated intestinal transit time was induced with bisacodyl, and urinary and faecal excretion of sulphasalazine, olsalazine, 5-aminosalicylic acid (5-ASA), and acetyl-5-ASA was studied after a single oral dose of 3.3 mmol sulphasalazine, olsalazine, Pentasa, and Salofalk and 2.6 mmol of Asacol. The faecal and urinary excretion of acetyl-5-ASA was lowest after intake of sulphasalazine and olsalazine and highest after intake of Pentasa and Salofalk. The figures for Asacol were intermediate. This indicates insufficient release of 5-ASA from sulphasalazine and olsalazine. When the results of this study are compared with those of a previous study without accelerated transit time, the disposition of 5-ASA from all the 5-ASA-delivering drugs is influenced unfavourably by an accelerated gut transit but most pronounced in the case of sulphasalazine, olsalazine, and Asacol. The impaired release from the azo compounds sulphasalazine and olsalazine is a result of far less complete splitting of the diazo bond.

Adult↗
PubMedDate not supplied

Hyperthermic sensitization by the radical initiator 2,2'-azobis (2-amidinopropane) dihydrochloride (AAPH). I. In vitro studies.

AAPH (2,2'-azobis-(2-amidinopropane dihydrochloride)) is a water-soluble, heat-labile azo compound which undergoes thermal decomposition to produce carbon-centred free radicals. These carbon-centred radicals might be directly cytotoxic or may react with oxygen to produce potentially cytotoxic alkoxyl and peroxyl radicals. The rate of free radical production as a result of AAPH thermal decomposition increases with increasing temperature. We have evaluated the efficacy of AAPH as a heat sensitizer for Chinese hamster V79 cells by the clonogenic assay. AAPH (50 mM) was not cytotoxic to V79 cells at 37 degrees C for exposures up to 3 h. In contrast, AAPH (50 mM) was found to markedly sensitize cells exposed to 42, 43 and 45 degrees C. For a 75 min exposure to 42 degrees C alone, cell survival was reduced to 9 x 10(-1); however, a 75 min exposure at 42 degrees C+AAPH resulted in survival of 5.5 x 10(-4). For 43 and 45.5 degrees C heating, cell survival was potentiated by AAPH at the 1% survival level by 4.1 and 1.4-fold, respectively. AAPH was also found to sensitize both hypoxic cells and thermotolerant cells. These findings would encourage in vivo evaluation of AAPH (or analogues) as a temperature-dependent heat sensitizer. AAPH represents a new class of heat sensitizers which may have use in unravelling the mechanism(s) of heat killing and may have utility in local hyperthermia treatment.

Amidines↗
PubMed1991

Vitamin E and the peroxidizability of erythrocyte membranes in neonates.

We showed the increased susceptibility of neonatal biomembranes to oxidation by a kinetic analysis using an azo compound as a free-radical initiator and red blood cell (RBC) ghosts as a model membrane. When the RBC ghosts were oxidized, oxygen consumption was suppressed during the induction period in which membrane tocopherol was consumed at a constant rate, while increased oxygen uptake was observed after the tocopherol was exhausted. The total tocopherol content was similar in cord, maternal, and adult RBC ghosts, and there were no differences in the induction period (tinh) among the three types of ghosts. While the oxygen uptake rate during the induction period (Rinh) was similar in cord and adult ghosts, the rate in the subsequent phase (Rp) was considerably faster in the cord ghosts. Fatty acid analysis in the membrane lipids showed that the active bisallylic hydrogen (active H) content was greater in cord ghosts than in adult ghosts. The active H content closely correlated with the Rp, but did not with the Rinh. The kinetic chain length (KCL), i.e., the ratio of the rate of propagation to that of initiation, was calculated from Rp and tocopherol consumption rate and KCL values were higher in cord ghosts than in adult ghosts. The faster Rp and the higher KCL of the cord ghosts were attributable to a greater active H content rather than to the tocopherol content.

Adult↗
PubMed2000

Peroxidation of proteins before lipids in U937 cells exposed to peroxyl radicals.

This study provides the first report of the formation of protein hydroperoxides in cells attacked by reactive oxygen species. U937 cells exposed to peroxyl radicals generated by the thermal decomposition of a water-soluble azo compound gradually accumulated hydroperoxide (-OOH) groups. In an incubation for 22 h, 1.2 mM peroxyl radicals was generated and each cell acquired 1.5x10(8) -OOH groups. These groups were located on the cell proteins; no lipid peroxidation was detected. The extent of protein peroxidation was proportional to the rate of generation of the peroxyl radicals. There was no lag period before the onset of peroxidation, indicating that cell antioxidants could not protect the proteins. The half-life of protein hydroperoxides in cell suspensions was approx. 4 h at 37 degrees C. Our results suggest that protein hydroperoxides might have a significant role as intermediates in the development of biological damage initiated by reactive oxygen species.

Humans↗
PubMed1999

[Determination of nitrite in serum and tissue by oscillopolarography].

A method for determining nitrite in serum and placenta tissue by oscillopolaropgraphy is reported in this paper. Nitrite in 0.10 ml of serum or placenta homogenate reacts with sulfanilmide and N-1 (1-Naphthyl)-ethylendiamindihydrochloride in diluted hydrochloric acid medium to form an azo compound which can produce a sensitive reductive polarographic wave in ammonium alkaline medium. The wave height is directly proportional to the nitrite content, the method has a detection limit of 0.56 microgram/L (corresponding to the nitrite content of 0.61 mumol/L in serum or 0.22 microgram/g), RSD, of 6.1%-7.8% and recoveries of 92.0%-108.0% (mean value 100.6%). The method is sensitive, simple and can determine the nitrite directly without removal of the proteins in the samples.

Humans↗