DNA-binding studies with diesel exhaust particle extract

This study examines whether chemical components from diesel exhaust particulates react with DNA to form covalently bound adducts. Experiments in this report describe the in vitro reaction of purified DNA with a dichloromethane extract of diesel exhaust particulates in the absence or presence of enzyme activation by rat liver microsomes. The reactivity of the particle extract was compared to that of benzo[a]pyrene metabolites using low temperature fluorescence techniques which detect small quantities of polycyclic aromatic compounds bound to DNA. Incubation of DNA with the particle extract in the presence of microsomal enzymes produced no detectable fluorescent adducts in contrast to model experiments using benzo[a]pyrene. However, addition of the particle extract to incubation mixtures containing benzo[a]pyrene markedly decreased formation of benzo[a]pyrene-DNA adducts because the particle extract inhibits microsomal enzymes which activate benzo[a]pyrene and other polycyclic aromatic hydrocarbons. In the absence of microsomal enzymes, fluorescent material was detected in DNA exposed to high concentrations of the particle extract, but probably not as a result of covalent binding because the mutagenic activity of the particle extract remained unchanged during prolonged incubation with DNA. This stability is in contrast to the rapid decrease in mutagenic activity of benzo[a]pyrene-4,5-oxide during incubation with DNA. Thus, direct mutation of bacteria by the particle extract may require activation by bacterial enzymes as is known to occur with nitroaromatic compounds.     

Trace Element Contaminants in Sediments From the Noaa National Status and Trends Programme Compared to Data From Throughout the World

The National Oceanic and Atmospheric Administration's (NOAA) National Status and Trends (NS&T) Programme has analyzed samples of surface sediment collected at almost 300 coastal and estuarine sites throughout the United States since 1984. the overall distributions for concentrations of each element are approximately lognormal allowing a definition of geometric means and of “high” concentrations as those exceeding the mean plus one standard deviation of the lognormal distribution. Those mean and “high” concentrations should be useful for comparing the NS&T data set and with other reports on sediment contamination. A world-wide data set, constructed from data in the literature, was summarized in an identical manner. It was found, after excluding locally extreme values, that the NS&T and world-wide data sets yielded very similar mean and “high” concentrations for Cu, Ni, Pb and Zn. Chromium was the sole element showing higher summary statistics in the NS&T data set, a result attributed to NS&T sampling in areas of naturally (not contaminated) elevated Cr content. It remains undetermined, however, why the world-wide data set, even with exclusion of “hot spots”, yielded higher means and “highs” for Cd, Hg, As, and Ag.     

Carbon dioxide and climate: an astrophysical perspective

In this survey the earth is viewed from the astrophysical perspective, i.e. using global mean values of environmental parameters. The role of carbon dioxide is described in the processes of energy transfer from the earth's surface to space, which determine “global climate” as measured by the mean surface temperature. Analogies and differences between the problems of the terrestrial atmosphere and those of the solar and stellar atmospheres are examines, both in the computation of model atmosphere and in remote sensing of atmospheric temperature and composition. Subsequently, the temporal astrophysical perspective, with a review of the evolution of CO₂ abundance and climate on astrophysical or geological time scales, on earth as on Venus (the runaway greenhouse) and on Mars is introduced. Variation of CO₂ may have been critical to the maintenance of an environment in which life could originate and evolve, and may itself have been affected by life. On human time scales, the recent and continuing increase in atmospheric CO₂ raises new problems, which are briefly surveyed. It is argued, that the differential greenhouse effect of increased CO₂ in the earth's atmosphere is essentially identical to the “blanketing effect” of spectral lines on the temperature structure of stellar atmospheres. The methods used by astrophysicists in such studies are reviewed and compared with those used to evaluate the differential greenhouse effect of CO₂ in radiative-convective models of the earth's atmosphere. The latter methods remain relatively crude, but recent results by different authors are in reasonably good agreement; however, the astrophysical perspective, i.e. the use of one-dimensional global mean models, remains a gross simplification of the real complexity of the earth's climate system, which is also true in stellar atmospheres.     

The Role of Organic Matter in Natural Aquatic Systems: Analytical Constraints

The dissolved organic matter in aquatic systems consists of a heterogeneous mixture of compounds with wide ranging chemical properties and diverse origins. the presence of organic matter (OM) in surface and ground waters has important implications with regard to the mobility and therefore fate of many potential organic and inorganic pollutants. the majority of the analytical approaches in current use require exhaustive pre-treatment steps which may lead to the formation of artefacts within the sample. an analytical technique based upon gel permeation chromatography is proposed as a more reliable procedure for the characterisation of naturally occurring dissolved organic matter.     

Eggs of cabbage root fly stimulate conspecific oviposition: Evaluation of the activity and determination of an egg-associated compound

Summary. Previous studies indicated the presence of antennally-active compounds in extracts of eggs laid by female cabbage root flies, Delia radicum, that stimulated oviposition by conspecific females. We confirmed that previously laid D. radicum eggs stimulated oviposition by other D. radicum females, in a dose-dependent manner. Methanol extracts of conspecific eggs stimulated oviposition by females D. radicum, whereas egg extracts of D. antiqua and Psila rosae had no effect. Electrophysiological recordings from the tarsal sensilla of D. radicum females indicated that neurones of the C₅ sensillum responded to the egg extracts from both D. radicum and D. antiqua, but not P. rosae. Chemical analysis revealed that the extract of eggs from D. radicum contained the thia-triaza-fluorene compound, 1,2-dihydro-3-thia-4,10,10b-triaza-cyclopenta[.a.]fluorene-1-carboxylic acid (CIF-1), an oviposition stimulant found previously only in cruciferous plants. Another potentially active component has yet to be identified.     

Endogenous technical change and environmental regulation

A model of environmental regulation under uncertainty is developed to compare the effect of price versus quantity rules upon technical change. Quantity rules tend to encourage more efficient levels of technical change.     

The ultraviolet photolysis of tetrachlorodibenzofurans

Several tetrachlorodibenzofuran isomers were photolyzed by ultraviolet irradiation and the relative amounts of the various trichlorodibenzofurans produced were determined. A simple set of guidelines for predicting the relative amounts of these photolysis products has been formulated.