Polycyclic aromatic hydrocarbons in surface sediments held in experimental mesocosms

Sediment was collected from three locations along a pollution gradient in Narragansett Bay and transplanted to controlled mesocosms. Total hydrocarbons and eleven individual polycyclic aromatic hydrocarbons (PAHs) were measured in these sediments over a period of 394 days. Total hydrocarbon concentrations increased in the “relatively uncontaminated”; (Rhode Island Sound) sediment that was held in the mesocosms, but did not change in the two other sediments. The concentrations of four PAHs: naphthalene, 2‐methyl naphthalene, 1‐methyl naphthalene and biphenyl, decreased in the “contaminated”; (Providence River) sediment during the experiment and the calculated half‐lives for these compounds were 287, 353, 321 and 333 days, respectively.     

Bioavailability and tissue distribution of Dechloranes in wild frogs (Rana limnocharis) from an e-waste recycling area in Southeast China

Dechlorane Plus(DP), a flame retardant used as an alternative to decabromodiphenylether, has been frequently detected in organisms, indicating its bioaccumulation and biomagnification potential in aquatic and terrestrial species. However, little data is available on the bioaccumulation of DP in amphibians. Dechlorane Plus and its analogs(DPs) were detected in the liver, muscle and brain tissues of wild frogs(Rana limnocharis), which were collected from an e-waste recycling site, Southeast China. DP, Mirex, Dec 602 and a dechlorinated compound of DP(anti-Cl11-DP) varied in the range of 2.01–291, 0.650–179, 0.260–12.4, and not detected(nd)–8.67 ng/g lipid weight, respectively. No difference of tissue distribution was found for syn-DP, Mirex and Dec 602 between the liver and muscle tissue(liver/muscle concentration ratio close to 1, p 0.05). However, higher retention was observed for anti-DP and anti-Cl11-DP in the frog muscle relative to the liver tissue(liver/muscle concentration ratio 1, p 0.05). Additionally, the blood-brain barrier was found to work efficiently to suppress these compounds entering brain tissues in this species(liver/brain concentration ratio 1, p 0.05), and the molecular weight was a key factor impacting the extent of the blood-brain barrier. Compared to levels in the muscle and brain tissue, a preferential enrichment of syn-DP was observed in the liver tissue, suggesting the occurrence of stereo-selective bioaccumulation in the wild frog.     

Mass spectral studies of 6‐n‐propyl‐2‐thiouracil,its oxygen,selenium and fluorinated congeners∗

The electron ionization mass spectra of the clinically used antithyroid agent 6‐n‐propyl‐2‐thiouracil (la), its minor metabolite, 6‐n‐propyluracil (lb) and their synthetic selenium and fluorinated analogs (1c and d) have been examined. The fragmentation pattern of these thiouracil and selenouracil studied bear strong similarities with those previously derived from a study of uracil analogs. Thus, the first step in the fragmentation is a retro Diel‐Alder decomposition with the loss of HCNX (X=O, S or Se) and the production of an ion radical which undergoes further fragmentation pathways which are discussed. 6‐n‐Propyl‐2‐selenouracil (1c) did show more complicated spectra due to the six natural isotopic abundance exhibited by the selenium atom. While the fluorinated analogs (1d) did substantiate the fact that the fragmentation pattern of these derivatives proceed through fragmentation between C₂ and N₃ bond since this produces the more resonance stabilized ion.     

Connecting today's climates to future climate analogs to facilitate movement of species under climate change

Increasing connectivity is an important strategy for facilitating species range shifts and maintaining biodiversity in the face of climate change. To date, however, few researchers have included future climate projections in efforts to prioritize areas for increasing connectivity. We identified key areas likely to facilitate climate‐induced species’ movement across western North America. Using historical climate data sets and future climate projections, we mapped potential species’ movement routes that link current climate conditions to analogous climate conditions in the future (i.e., future climate analogs) with a novel moving‐window analysis based on electrical circuit theory. In addition to tracing shifting climates, the approach accounted for landscape permeability and empirically derived species’ dispersal capabilities. We compared connectivity maps generated with our climate‐change‐informed approach with maps of connectivity based solely on the degree of human modification of the landscape. Including future climate projections in connectivity models substantially shifted and constrained priority areas for movement to a smaller proportion of the landscape than when climate projections were not considered. Potential movement, measured as current flow, decreased in all ecoregions when climate projections were included, particularly when dispersal was limited, which made climate analogs inaccessible. Many areas emerged as important for connectivity only when climate change was modeled in 2 time steps rather than in a single time step. Our results illustrate that movement routes needed to track changing climatic conditions may differ from those that connect present‐day landscapes. Incorporating future climate projections into connectivity modeling is an important step toward facilitating successful species movement and population persistence in a changing climate.     

Synthesis and pharmacological properties of certain analogs of pilocarpine

The synthesis of 4‐(4'‐pyrimidinylmethyl)oxacyclohexan‐2‐one (2a) and 4‐(4'‐pyrimidinylmethyl)oxacycloheptan‐2‐one (3a) were achieved through the Michael addition of the anion derived from 4‐methylpyrimidine with oxacyclyo‐3‐hexen‐2‐one and oxacyclo‐3‐hepten‐2‐one respectively. These compounds 2a and 3a and their quaternary methiodide salts lack cholinomimetic activity.