PubMed Health⌕ Search

Biomedical subjects

T R Henderson

Publications and source records attributed to T R Henderson.

At least 55 records · Page 3Linked to original sources
PubMed1981

Increased cytotoxicity and mutagenicity of diesel fuel after reaction with NO2.

Gas chromatography/mass spectrometry (GC/MS) of diesel fuel aromatics detected polynuclear aromatic hydrocarbons from naphthalenes to phenanthrenes, but no four- or five-ring aromatics. This aromatic fraction treated with NO2 was found to contain nitro-aromatics, but only the naphthalene and biphenyl nitro-aromatics were detectable by direct GC/MS. By reduction of the nitro groups to amines, diazotization and reduction to yield aryl-iodides, it was possible to demonstrate that nitro-derivatives of most of the starting aromatics were present after NO2-treatment. Diesel fuel was separated into aliphatic and aromatic fractions by extraction with diethyl sulfoxide. These fractions were devoid of mutagenic activity in the Ames bioassay and exhibited low cytotoxicity to CHO cells in culture. However, after reaction with NO2, the products contained frameshift mutagens which did not require activation by S-9 microsomal enzymes. The biological activity of the NO2-treated aromatic fraction from fuel was more than 40 times greater in Salmonella TA100 than fuel aliphatics treated with NO2. The LC50 to CHO cells in culture increased more than fivefold for aromatics and more than tenfold for aliphatics. Similar to the diesel exhaust particulate extract, the cytotoxicity of the nitrated fractions was decreased by serum and glutathione. Reaction of fuel aromatics with NO2 may be one mechanism which contributes to the formation of cytotoxic and mutagenic activities in diesel exhaust.

Animals↗
PubMed1981

A method for determining glass in rat lung after exposure to a glass fiber aerosol.

Inhalation toxicology studies of glass fibers require a knowledge of the dose deposited in the lungs of exposed animals. A method is described which uses the quantity of acid-insoluble sodium present in rat lungs to determine the lung burdens of glass by mass after exposure to glass fiber aerosol. The glass fibers used contained 7.3% sodium. This sodium was measured in lung homogenates after acid washing and fusion in Li2CO3. The lower limit of detection was estimated as 40 microgram of this glass in rat lung. Results of an in vitro dissolution study indicated that a portion of the sodium present in the glass fibers was dissolved at a faster rate than the glass itself. This preferential dissolution may result in a small (5-25%) underestimation of glass in lung. This method was used to determine lung burdens of glass in rats after 1, 2, 4 or 5 exposures to a glass fiber aerosol (count median diameter: 0.11 micrometer, count median length: 8.3 micrometer). Five 6-hour exposures at an average concentration of 47 mg/m3 resulted in a lung burden of 176 microgram of glass. It was estimated that 41-48% of the lung burden was cleared between daily exposures.

Aerosols↗
PubMed1975

Effects of dimethyl sulfoxide on subunit proteins.

The effects of DMSO are thought to result from the formation of hydrogen bonds with proton-donor groups on biopolymers, which are stronger than those formed with water. Since DMSO contains methyl groups, however, effects on hydrophobic bonding in proteins could be expected at higher DMSO levels. Our studies of the effects of DMSO on model subunit proteins can be interpreted in the above terms. At a concentration of 20% or less, DMSO changed glutamate dehydrogenase into the inactive monomer and the effects were fully reversible with the activator (ADP). Higher DMSO levels resulted in irreversible inactivation. The predominant effect noted on beta-glucuronidase was irreversible inactivation by 20% or more DMSO at 37 degrees C. Purified beta-glucuronidase exhibited an activation in 20% DMSO at high substrate levels; this resulted from an apparent substrate inhibition in the absence of DMSO. DMSO inhibited the clotting of fibrinogen by purified thrombin, but the major effect appeared to be due to competition between thrombin and DMSO for binding sites on fibrinogen. These effects appear to be largely due to interactions between DMSO and hydrophobic bonding in fibrinogen, although DMSO also appears to interfere with the aggregation of fibrin monomers through its effects on hydrophilic groups. These results suggest that reversible alterations in protein structure are the major effect of exposure of subunit proteins to low DMSO levels at low temperatues, while irreversible denaturation of subunit proteins may be an appreciable effect a higher temperatures and higher DMSO concentrations.

Adenosine Diphosphate↗
PubMed1966

DNA rplication.

Explore the source record for details and available documents.

Chemical Phenomena↗