Changes in traffic-related air pollution exposures and associations with adverse birth outcomes over 20 years in Texas.

Background: Billions of dollars have been spent implementing regulations to reduce traffic-related air pollution (TRAP) from exhaust pipe emissions. However, few health studies have evaluated the change in TRAP emissions and associations with infant health outcomes. We hypothesize that the magnitude of association between vehicle exposure measures and adverse birth outcomes has decreased over time, parallelling regulatory improvements in exhaust pipe emissions.

The effect of chemical mutagens on purine and pyrimidine nucleotide biosynthesis.

Nucleotide biosynthesis in Novikoff hepatoma cells is markedly altered by a variety of chemical mutagens, whether the mechanism of mutagenesis is by base substitution, covalent binding (adduct formation), intercalation, or cross-linking of DNA. The compounds investigated (N-methyl-N'-nitro-N-nitrosoguanidine, 4-nitroquinoline 1-oxide, 9-aminoacridine, and mitomycin C), at concentrations that cause some inhibition of RNA and DNA synthesis, bring about a large increase in the pool levels of all four nucleoside triphosphates. At the same time, reactions leading to the synthesis of CTP from exogenous uridine and GTP and ATP from exogenous hypoxanthine are severely inhibited.

Use of radioisotopes in quantitative studies of lung metabolism.

Quantitatively accurate studies of macromolecule and lipid synthesis in lung and other tissues by using radioactive substrates require detailed knowledge of the specific radioactivity of the appropriate pool of precursor molecules serving the synthetic pathway. A brief summary is provided of how considerations of precursor availability, metabolism, and compartmentation, as well as product remodeling, may affect the accuracy with which rates of protein, DNA, RNA, and lipid synthesis can be measured. Where possible, the application of this material to studies of lung metabolism is discussed, along with approaches that may minimize experimental uncertainties.