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Results for “Halogenation”

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At least 1,351 records · Page 75Linked to original sources
PubMed1975

Short-term inhalation toxicity of halogenated hydrocarbons: effects on fasting rats.

Male rats, fasted overnight (18 hours), and exposed to various materials in inhalation were more sensitive to the hepatotoxic effects of carbon tetrachloride, 2-chlorobutadiene, 1,1-dibromoethylene, and 1,1-dichloroethylene (DCE). Vinyl chloride monomer and 1,1-difluoroethylene were not acutely hepatotoxic in fed or fasted rats at any concentration tested. Vinyl chloride monomer when administered simultaneously with DCE prevented the injury associated with DCE inhalation in fasted rats. This prevention of injury may be a result of a competitive interaction since the effect was concentration dependent.

Aerosols↗
PubMed2006

Hydroxyquinol pathway for microbial degradation of halogenated aromatic compounds.

Several peripheral metabolic pathways can be used by microorganisms to degrade toxic aromatic compounds that are known to pollute the environment. Hydroxyquinol (1,2,4-trihydroxybenzene) is one of the central intermediates in the degradative pathway of a large variety of aromatic compounds. The present review describes the microorganisms involved in the degradative pathway, the key enzymes involved in the formation and splitting of the aromatic ring of (chloro)hydroxyquinol as well as the central intermediates formed. An attempt was also made to provide some estimation for genetic basis of the hydroxyquinol pathway.

Bacteria↗
PubMed2001

MTD-PLS: a PLS-based variant of the MTD method. A 3D-QSAR analysis of receptor affinities for a series of halogenated dibenzoxin and biphenyl derivatives.

MTD-PLS, the Partial Least Squares (PLS) variant of the Minimum Topological Difference (MTD) method is described. In MTD-PLS, molecules are characterised not only by the occupancy or nonoccupancy of the hypermolecular vertices (as in classical MTD), but also by additional descriptors for each vertex: fragmental van der Waals volumes, fragmental hydrophobicities, partial atomic charges, etc. This method was applied to a series of 73 polyhalogenated derivatives of dibenzo-p-dioxine, dibenzofuran and biphenyl (induction of aryl hydrocarbon hydrolase and affinities to rat cytosolic receptor), previously studied by MTD. The separation of steric, hydrophobic, and electrostatic effects was achieved retranslating from the latent variable space into a linear combination of the initial structural variables. The MTD-PLS method yields more detailed results compared to classical MTD, indicating the importance of electrostatic effects at some substituent positions.

Binding Sites↗
PubMedDate not supplied

Nucleosides and nucleotides. 192. Toward the total synthesis of cyclic ADP-carbocyclic-ribose. Formation of the intramolecular pyrophosphate linkage by a conformation-restriction strategy in a syn-form using a halogen substitution at the 8-position of the adenine ring.

The synthesis of cyclic ADP-carbocyclic-ribose (2), as a stable mimic for cyclic ADP-ribose, was investigated. Construction of the 18-membered backbone structure was successfully achieved by condensation of the two phosphate groups of 19, possibly due to restriction of the conformation of the substrate in a syn-form using an 8-chloro substituent at the adenine moiety. SN2 reactions between an optically active carbocyclic unit 8, which was constructed by a previously developed method, and 8-bromo-N6-trichloroacetyl-2',3'-O-isopropylideneadenosine 9c gave N-1-carbocyclic derivative, which was deprotected to give 5'-5"-diol derivatives 18. When 18 was treated with POCl3 in PO(OEt)3, the bromo group at the 8-position was replaced to give N-1-carbocyclic-8-chloroadenosine 5',5"-diphosphate derivative 19 in 43% yield. Treatment of 19 with 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride gave the desired intramolecular condensation product 20 in 10% yield. This is the first chemical construction of the 18-membered backbone structure containing an intramolecular pyrophosphate linkage of a cADPR-related compound with an adenine base.

Adenine↗
PubMed1993

Human glutathione S-transferase-expressing Salmonella typhimurium tester strains to study the activation/detoxification of mutagenic compounds: studies with halogenated compounds, aromatic amines and aflatoxin B1.

We have developed Salmonella typhimurium strains expressing human glutathione S-transferases (GSTs) to establish the role of these enzymes in chemical activation and deactivation. Alpha and pi class GSTs, GSTA1-1 and GSTP1-1, were expressed in Salmonella TA100 using a regulatable tac promoter expression system. The ability of these GST to modulate the mutagenicity of a range of mutagens including ethylene dibromide, ethylene dichloride and methylene dichloride was then investigated. Ethylene dibromide, ethylene dichloride and methylene dichloride were directly mutagenic in the control TA100 strain. The mutagenicity of ethylene dibromide and ethylene dichloride was increased in cells expressing GSTA1-1, but not in cells expressing GSTP1-1. In contrast, methylene dichloride mutagenicity was unaffected by the presence of either GST. The mutagenicity of 2-aminofluorene, was not altered by the presence of either GST isozyme, while that of N-hydroxy-2-acetylaminofluorene was slightly reduced with both isozymes. The mutagenicity of aflatoxin B1 (AFB1) was marginally decreased in strains expressing GSTP1-1. When GSTA1-1 expression was maximally induced, however, a more pronounced reduction was observed suggesting a role for GSTA1-1 in AFB1 deactivation. The tester strains described here should be valuable in establishing the specificity of human GST isozymes towards chemical toxins and carcinogens, especially for compounds whose reactive intermediates are short lived.

Aflatoxin B1↗
PubMed1981

Induction of endogenous viral gene expression by halogenated hydrocarbons.

Endogenous avian RNA tumor virus gene expression was induced in chick embryo cells by the 1,1,1-trichloro-2-, 2-bis(p-chlorophenyl ethane) metabolites bis(chlorophenyl)acetic acid and dichlorodiphenyl dichloroethylene and the antibacterial agent hexachlorophene. Line 100 x 7, C/ABE, chick cell cultures were incubated with each of these chemicals or the known endogenous virus inducer bromodeoxyuridine. At subtoxic levels, all four chemicals induced the production of virus particles as determined by assay for the viral-specific reverse transcriptase and infectivity. Since the endogenous virus produced is of subgroup E and consequently unable to infect surrounding cells of the type C/ABE, amplification of the induced virions was accomplished by infecting the subgroup E susceptible cell line 15B C/C with supernatants from the chemically treated cultures. Fluorescent antibody treatment of line 100 x 7 C/ABE cultures showed approximately 35% to 40% of the cells stained in the chemically treated cell cultures, suggesting that only a portion of the cells were responding to the chemical induction.

Animals↗
PubMed1984

Application of a rapid scanning plasma emission detector and gas chromatography for multi-element quantification of halogenated hydrocarbons.

A microwave induced plasma emission detector is used as an element-selective detector for gas chromatography. The spectrometer, which is fitted with a rapid scanning galvanometer mirror, is used to scan a pre-selected spectral window to provide information in the multi-element mode. This information is used to determine the per mole response of some elements as a function of molecular structure. Despite the low microwave powers employed, the response per mole appears to be independent of the molecular structure. Detection limits and linear dynamic ranges are determined by narrowing the spectral coverage to increase the sensitivity. Calibration curves are linear over several orders of magnitude and detection limits are at the pg/sec levels.

Chromatography, Gas↗