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PubMed1997

The protective effects of dihydrolipoamide and glutathione against photodynamic damage by Al-phtalocyanine tetrasulfonate.

In spite of well-known ability of lipoamide/dihydrolipoamide (LipS2NH2/Lip(SH)2NH2) and oxidized/reduced glutathione (GSSG/GSH) couples to scavenge singlet oxygen (1O2), the possible protective effects of these compounds against photodynamical damage by Alphtalocyanine tetrasulfonate (Al-PcS4) were examined. Using erythrocyte glutathione reductase, pig heart lipoamide dehydrogenase and hamster kidney fibroblast culture as model systems, we have found that protective effects of Lip(SH)2NH2 and LipS2NH2 were close to that of azide, far exceeding the effects of GSH and GSSG, and paralleling the rates of Al-PcS4-sensitized photooxidation of these compounds. We have failed to observe a previously described (Devasagayam, T.P.A., et al. (1991) Biochim Biophys. Acta 1088, 409-412) enhancement of damaging action of 1O2 by GSH. These findings point out to the possibility of LipS2NH2/Lip(SH)2NH2 to neutralize the side-effects of photodynamic therapy, and to a minor but definitely protective role of GSH.

Animals↗
PubMed1979

Mutagenicity of halogenated and oxygenated three-carbon compounds.

Four structurally related three-carbon compounds, known for their antifertility activity in the male, and the brominated derivatives of two of these compounds were tested for mutagenic activity by the Salmonella typhimurium test of Ames et al. In the presence of strain TA-100, a base-pair substituion detector strain, 1,2-dibromo-3-chloropropane (DBCP), was the most active compound tested but required enzymatic conversion by 59 microsomal preparation to an active mutagen. Three of these compounds containing an epoxide group-epichlorohydrin, epibromohydrin, and glycidol-were highly active direct mutagens, not requiring 59 for activation, alpha-Chlorohydrin was the least active compound tested; alpha-bromohydrin was 40 times more active than its chlorinated analog. Epibromohydrin was only slightly more active than epichlorohydrin, but both were highly active. With both of the halogenated epoxides, 59 preparation caused a substantial decrease in mutagenic activity at every concentration tested. All six compounds showed dose-related responsiveness for the base-pair substitution detector strains used. However, they were relatively inactive against the frameshift detector strain of S. typhimurium, TA-98. Glycerol, propylene glycol, and n-propanol, which are also three-carbon compounds containing one or more hydroxy groups, were inactive when trested at high concentrations with strain TA-100.

Alcohols↗
PubMed1990

Complex mixtures of urban air pollutants: identification and comparative assessment of mutagenic and tumorigenic chemicals and emission sources.

Current research on the cancer risks of complex mixtures of urban air pollutants addresses the identification and comparative assessment of mutagenic and carcinogenic chemicals and emission sources. To identify genotoxic compounds in urban air, micromutagenesis methods are coupled to analytical fractionation and new chemical characterization methods. Among polar mutagenic compounds, many appeared to be nitrated and or oxygenated aromatic compounds. Source apportionment of the mutagenic activity observed in urban air shows that vehicles and residential heating are major contributors to the ambient mutagenicity of the aerosol fraction. Comparative tumorigenesis and DNA adduct dosimetry studies are also being conducted with these same combustion emission sources and urban aerosols. The potential hazard and sources of the gaseous emissions have not been determined, but appear to be significantly increased by atmospheric transformation by ozone and nitrogen oxides.

Air Pollutants↗
PubMed1982

Oxygen uptake in the radiolysis of aqueous solutions of nucleic acids and their constituents.

The 60Co-gamma-irradiation of organic compounds in oxygenated aqueous solution leads to consumption of oxygen. G (O2 uptake) have been measured for 27 compounds in N2O/O2 (4:1)- saturated solutions using an oxygen sensitive electrode. G (O2 uptake) (in brackets, measured at 20 degrees C and a dose rate of 0.4 Gy s-1) for isopropanol (3.0), sodium formate (3.0), D-glucose (3.2), 2-deoxy-D-ribose (3.0), t-butanol (4.2) and diethyl ether (4.5) were found to be in agreement with th expectation based on product yields and/or known mechanisms. High O2 uptake was observed with polyethyleneoxide (10.2), which increases with decreasing dose rate and/or increasing temperature (G(O2 uptake) = 40 at 0.04 Gy s-1 and 50 degrees C). These results are explained by assuming a chain reaction. The nucleotides 5'-thymidylic acid (4.4), 5'-deoxy-cytidylic acid (4.8), 5'-deoxyadenylic acid (1.9) and 5'-deoxyguanylic acid (1.6) show that the pyrimidine derivatives consume considerably more oxygen than the purine derivatives. Analogous results are obtained with the nucleobases and nucleosides. The pyrimidine-purine difference is even more pronounced in the corresponding polymer, poly U (21) and poly A (3.5). The large value of poly U shows that a significant contribution of a chain reaction is present. G(O2 uptake) for DNA are dose-rate, temperature and concentration-dependent. The O2 uptake for single-stranded DNA (6.8) and double-stranded DNA (4.6) is higher than for an equivalent mixture of nucleotides (3.2). These results indicate that in DNA also a short chain reaction takes place.

Cobalt Radioisotopes↗
PubMed2002

Synthesis of a novel, highly symmetric bis-oxa-bridged compound.

A highly oxygenated, novel pentacyclic bis-oxa-bridged compound 8 was synthesized with remarkable efficiency starting from readily available tetrachloro-5,5-dimethoxyclopentadiene and 1,4-cyclohexadiene in three steps. The ruthenium-catalyzed oxidation of 2:1 bis-adduct 1 followed by a one-pot transformation of the resulting bis-alpha-diketone 3 furnished (after esterification) the title compound in an overall yield of 29.1%. The versatility of this simple method was further demonstrated with other norbornyl alpha-diketones to obtain the corresponding strained oxa-bridged derivatives.

Journal Article↗
PubMedDate not supplied

Evaluation of the influence of the aqueous phase bioconstituent environment on the F-19 T1 of perfluorocarbon blood substitute emulsions.

Oxygen-sensitive F-19 magnetic resonance imaging of perfluorocarbon compounds requires that fluorocarbon T1 changes correlate with the local PO2 and not with the composition of the surrounding aqueous phase. The influence of various bioconstituents and paramagnetic ions within the aqueous phase on the F-19 fluorocarbon phase T1 for PFC emulsions was evaluated at 0.14 and 0.66 T. T1 was measured for FC-43, perflubron, and a fluorinated surfactant. Controlled variables introduced in the aqueous phase included annex solution constituents, blood, pH changes, and Gd-DTPA. For a constant PO2, the F-19 T1s were independent of the emulsion constituents, blood concentration, and pH. For FC-43 and perflubron, F-19 T1 was independent of the Gd-DTPA concentration, while the aqueous phase T1 decreased by more than an order of magnitude. XMO-10 (smallest emulsion particle size) showed a slight decrease in F-19 T1 with increasing Gd-DTPA concentration at 0.66 T.

Animals↗
PubMed2006

Lethality of essential oil constituents towards the human louse, Pediculus humanus, and its eggs.

Essential oils have been widely used in traditional medicine for the eradication of lice, including head lice, but due to the variability of their constitution the effects may not be reproducible. In an attempt to assess the contribution of their component monoterpenoids, a range of common individual compounds were tested in in vitro toxicity model against both human lice (Pediculus humanus, an accepted model of head lice lethality) and their eggs, at different concentrations. No detailed study into the relative potencies of their constituent terpenoids has so far been published. Adult lice were observed for lack of response to stimuli over 3 h and the LT(50) calculated, and the percentage of eggs failing to hatch was used to generate ovicidal activity data. A ranking was compiled for adult lice and partially for eggs, enabling structure-activity relationships to be assessed for lethality to both, and showed that, for activity in both life-cycle stages, different structural criteria were required. (+)-Terpinen-4-ol was the most effective compound against adult lice, followed by other mono-oxygenated monocyclic compounds, whereas nerolidol was particularly lethal to eggs, but ineffective against adult lice.

Animals↗
PubMed1992

Reactivity of orthoquinones involved in tyrosinase-dependent cytotoxicity: differences between alkylthio- and alkoxy-substituents.

It may be possible to use the melanogenic pathway as a therapeutic targeting strategy for melanoma, and encouraging clinical pilot studies of 4-hydroxyanisole have led to the search for more active analogue substrates of tyrosinase. A recent study of a range of alkoxy- and alkylthio-phenol analogues of tyrosine has shown that sulphur-containing compounds exhibit different behaviour to that of similar oxygen-containing compounds, indicating modified reactivities of their corresponding tyrosinase-induced o-quinones towards crucial cellular targets, in particular, thiols. We have therefore examined by pulse radiolysis the reactivities of a group of unstable alkylthio- and alkoxy-substituted o-quinones towards the biologically relevant thiols, cysteine and glutathione. The o-quinones were generated by rapid (microsecond) one-electron oxidation of the corresponding stable synthesized catechols, forming semiquinones which disproportionated over milliseconds to o-quinones. The latter reacted with the thiols in a pH-dependent manner, indicative of increased nucleophilicity of the thiolate anions as compared with their protonated forms, with rate constants in the region of 10(5)-10(6) M-1s-1. At pH 7.2, within the physiological range, the alkylthio-substituted o-quinones reacted with the thiols approximately 5-10 times faster than the alkoxy-substituted o-quinones. The corresponding alkylthio-substituted phenols might, therefore, in principle, be expected to be more effective targeted anti-melanoma drugs than their alkoxy-substituted counterparts. NMR studies of the reactions of several of the quinones with cysteine indicate that, where addition occurs, the product is exclusively the 6-S-cysteinyl-4-substituted-catechol.

Cell Survival↗
PubMed1998

Application of Natural Bond Orbital Analysis and Natural Resonance Theory to Delocalization and Aromaticity in Five-Membered Heteroaromatic Compounds.

The various measures of delocalization in all of the five-membered nitrogen and oxygen heteroaromatic compounds (azoles and oxoles) were obtained from MO calculations at the HF/6-31G level and the application of natural bond orbital analysis and natural resonance theory. The hydrogen transfer and aromatic energies of these compounds were also calculated. These were compared to the relative ranking of aromaticity reported by Katritzky from a principal component analysis of other measures of aromaticity. It was concluded that the extent of the transfer of electron density from the p(z)() orbital of the heteroatom to the rest of the pi system is the best measure of delocalization and "aromaticity" of these compounds. This indicated that all of the oxoles are less delocalized than any of the azoles because the electronegativity of the oxygen atom prevents the interaction of its lone pair of electrons with the pi system. For this reason the range of delocalization in the oxoles is also much narrower. The degree of delocalization in the pi system is the result of the geometry imposed by the sigma structure, which in turn is defined by the identity and arrangement of the atoms of the ring.

Journal Article↗
PubMed1984

Effects of oxygen and sulphydryl-containing compounds on irradiated transforming DNA. III. Reaction rates.

The absolute rate for the repair reaction of radiation-induced, oxygen-dependent lesions in bacterial transforming DNA with the sulphydryl (SH)-containing compound dithiothreitol (DTT) has been determined using a fast response method, the gas explosion technique, to be 1.6 X 10(6) mol-1 s-1. Glutathione reacts ten times slower than DTT with the irradiated transforming DNA. It can also be calculated that transforming DNA radicals react with O2 in a damage-fixing reaction with a rate of about 3 X 10(8) dm3 mol-1 s-1. These rates are compared with values in the literature for reaction rates of SH, compounds and O2 with irradiated DNA constituents and with bacterial cells.

Bacillus subtilis↗