Current Risk Assessment Approaches to Address Petroleum Hydrocarbon Mixtures in Soils

Products that exist as complex chemical mixtures, such as petroleum products, are used widely in commerce, and accidental releases of these products into the environment have led to thousands of contaminated sites nationwide. Developing sound estimates of potential health risks posed by these sites is challenging because of the composition of these products, their behavior in the environment, and the paucity of toxicological information available for many of the component compounds. In developing risk based cleanup goals for petroleum products and other complex commercial mixtures, the simplest approach is to assume that the entire mixture is comprised of the most toxic constituent, particularly when standards are unavailable for each of the components of the mixture. This approach often results in excessively conservative regulatory goals; thus, methods are needed which more accurately reflect the actual composition and aggregate toxicity of the mixture. Three approaches for the development of risk based soil cleanup goals for petroleum hydrocarbon mixtures are identified and illustrated using mineral spirits as an example. For the examples presented, estimates of the proportions of components in mineral spirits were based on virgin, unused product; however, detailed component analysis of weathered samples may permit the calculation of more precise, site specific cleanup goals.     

Optimizing the location of watercraft inspection stations to slow the spread of aquatic invasive species

The accidental spread of aquatic invasive species (AIS) by recreational boaters is a major concern of state and county environmental planners in the USA. While programs for watercraft inspection to educate boaters and slow AIS spread are common practice, large numbers of boats and waterbodies, together with limited budgets, make program design difficult. To facilitate program design, we developed an integer programming model for allocation of scarce inspection resources among lakes. Our model uses species-specific infestation status of lakes and estimates of boat movement between lakes. The objective is to select lakes for inspection stations to maximize the number of risky boats inspected, where risky boats are ones that move from infested to uninfested lakes. We apply our model in Stearns County in central Minnesota, USA, to prioritize lakes for inspection stations and evaluate alternative management objectives. With an objective of protecting uninfested lakes within and outside Stearns County, the optimal policy is to locate stations at infested lakes having the most boats departing for uninfested lakes inside and outside the county. With an objective of protecting only Stearns County lakes, the optimal policy is to locate stations at both infested and uninfested lakes having the riskiest boats arriving from within and outside the county and departing to in-county lakes. The tradeoff between these objectives is significant.

     

An Amino-Terminal Polo Kinase Interaction Motif Acts in the Regulation of Centrosome Formation and Reveals a Novel Function for centrosomin (cnn) in Drosophila

The formation of the pericentriolar matrix (PCM) and a fully functional centrosome in syncytial Drosophila melanogaster embryos requires the rapid transport of Cnn during initiation of the centrosome replication cycle. We show a Cnn and Polo kinase interaction is apparently required during embryogenesis and involves the exon 1A-initiating coding exon, suggesting a subset of Cnn splice variants is regulated by Polo kinase. During PCM formation exon 1A Cnn-Long Form proteins likely bind Polo kinase before phosphorylation by Polo for Cnn transport to the centrosome. Loss of either of these interactions in a portion of the total Cnn protein pool is sufficient to remove native Cnn from the pool, thereby altering the normal localization dynamics of Cnn to the PCM. Additionally, Cnn-Short Form proteins are required for polar body formation, a process known to require Polo kinase after the completion of meiosis. Exon 1A Cnn-LF and Cnn-SF proteins, in conjunction with Polo kinase, are required at the completion of meiosis and for the formation of functional centrosomes during early embryogenesis.     

Membrane phase state and the rearrangement of hematopoietic cell surface receptors.

Transformed murine hematopoietic cells of several lineages bound the fluorescent membrane probe merocyanine 540, whereas their normal counterparts did not. Similar selective binding was reproduced in artificial liposomes which bound this probe above their phase transition temperature, but not below it. The regions of the membrane to which merocyanine 540 binds along with the receptors for the lectin concanavalin A, but not the receptors for the lectin wheat germ agglutinin, were rearranged during the course of induced differentiation of erythroleukemia cells. Based on these findings, we propose a model of hematopoietic cell surface differentiation in which proteins such as concanavalin A receptors, which are destined for removal from the plasma membrane, are specifically associated with disordered, liquid-like lipid domains which can be visualized with merocyanine 540. For the specific case of erythroid differentiation, these domains and their associated proteins are collected at the region of the membrane where nuclear extrusion occurs and are eliminated from the reticulocyte plasma membrane by the enucleation event.