Effect of the Route of Administration on the Induction of Cytogenetic Damage and DNA Adducts in Peripheral Blood Lymphocytes of Rats and Mice by Polycyclic Aromatic Hydrocarbons

Experiments were designed to investigate how the route of exposure to polycyclic aromatic hydrocarbons (PAHs) in mice and rats affects the induction of cytogenetic end points and DNA adduction. Both mice and rats were exposed to 100 mg/kg of benz[ a ]anthracene (B[ a ]A), benzo[ b ]fluoranthene (B[ b ]F), benzo[ a ]pyrene (B[ a ]P), or chrysene (Chr) by gavage or by intraperitoneal injection (i.p.). Peripheral blood was removed by cardiac puncture 7 days after PAH administration. Blood samples were analyzed in parallel for sister chromatid exchange (SCE) frequency, the frequency of micronuclei in cytochalasin B-induced binucleate cells (MN bn ), and DNA adduction using 32P-postlabeling. The i.p. route of exposure produced both the highest levels of cytogenetic damage and DNA adducts for each PAH. The mouse was more sensitive than the rat to PAH exposure as measured by SCE induction and the total amount of DNA adducts/ w g DNA.     

Effects of diets high in saturated fat and cholesterol on the lipid composition of canine platelets

The phospholipid composition of platelets from dogs on various experimental diets was determined. Thyroidectomized foxhounds were fed a control diet or the control diet supplemented with (1) beef tallow, (2) beef tallow and cholesterol, or (3) beef tallow, cholesterol, and safflower oil for 23 weeks prior to isolation of platelets. Platelets from animals fed the control diet contained 36.7% phosphatidylcholine (PC), 22.8% phosphatidylethanolamine (PE), 18.4% sphingomyelin (Sph), 11.8% phosphatidylserine (PS), 6.3% phosphatidylinositol (PI), and 2.2% lysophosphatidylcholine. The PE was 77.6% in the plasmalogen form. No highly significant changes in the phospholipid class composition resulted from the experimental diets. Cholesterol supplementation of the diets, however, caused consistent alterations in the fatty acid compositions of the platelet phospholipids including increases in the percentages of 18∶1ω9 (oleic acid), 18∶2ω6 (linoleic acid), and 20∶3ω6 (homo-gamma linolenic acid) and a decrease in the percentage of 20∶4ω6 (arachidonic acid). Addition of safflower oil to the tallow-cholesterol diet partially reversed these effects. These cholesterol-induced alterations in fatty acid composition could be due to exchange with plasma lipids, de novo synthesis, or altered platelet metabolism. The mechanism remains to be determined. Der. Nelson’s current affiliation is the Lipid Metabolism Branch, Division of Heart and Vascular Diseases, National Heart, Lung, and Blood Institute.     

Synthesis of nitrogen-doped onion-like carbon and its use in carbon-based CoFe binary non-precious-metal catalysts for oxygen-reduction

Nitrogen-doped onion-like carbon-rich materials were synthesized by heat treatment of a “hybrid” containing hexamethylene diamine complex in the presence of Co and Fe species while preparing non-precious metal electrocatalyst for oxygen-reduction. As demonstrated by electrochemical rotating disk electrode and fuel cell tests, the binary CoFe-based catalyst containing graphitized onion-like carbon nanostructures provides for improved performance relative to the single Fe-based catalyst in which no such carbon structure was observed. In the binary catalysts, variation of the ratios of Co to Fe and the total metal loading during the synthesis leads to a markedly different activity and four-electron selectivity for oxygen reduction. The optimized binary catalyst was studied in fuel cell lifetime tests using both constant current and voltage models, showing a good combination of activity and durability. Possible reasons for the improved performance of the CoFe-based binary catalyst are discussed. The graphitized onion-like carbon structure exclusively derived from Co in this work may be providing a robust matrix to host non-precious metal active sites, which would prevent water flooding of them, and increase the resistance to oxidative attack in the oxygen cathode, thereby leading to an improvement in performance durability.     

Linear Fresnel lens concentrators

The use of the linear Fresnel lens as a seasonally adjusted or one-axis tracked solar concentrator is investigated. Ray tracing techniques are used to show that this type of concentrator is very good in the period of time within 1 hr of solar noon. However, increased refraction due to increased incident angles of the solar rays causes a sharp drop-off in energy delivered to the absorber at other hours of the day. Daily collection efficiencies are typically 50 per cent at concentration ratios of near 5. Effects of absorber width, distance from the lens to the absorber and alignment accuracy are considered in detail. Energy collected over a year's time is calculated assuming cloudless skies. Qualitative experimental results are presented that confirm the analytical results.     

Continuous analysis of dissolved gaseous mercury (DGM) and mercury flux in two freshwater lakes in Kejimkujik Park,Nova Scotia: evaluating mercury flux models with quantitative data

Diurnal patterns for dissolved gaseous mercury (DGM) concentration, mercury flux, several water variables (pH, oxidation reduction potential (ORP), water temperature), and meteorological variables (wind speed, air temperature, % relative humidity, solar radiation) were measured in two lakes with contrasting dissolved organic carbon (DOC) concentrations in Kejimkujik Park, Nova Scotia. A continuous analysis system made it possible to measure quick changes in DGM over time. Consistently higher DGM concentrations were found in the high DOC lake as compared to the low DOC lake. An examination of current mercury flux models using this quantitative data indicated some good correlations between the date and predicted flux (r ranging from 0.27 to 0.83) but generally poor fit (standard deviation of residuals ranging from 0.97 to 3.39). Cross-correlation analysis indicated that DGM dynamics changed in response to solar radiation with lag-times of 65 and 90 min. This relationship with solar radiation was used to develop new predictive models of DGM and mercury flux dynamics for each lake. We suggest that a generalized approach using time-shifted solar radiation date to predict DGM can be incorporated into existing mercury flux models. It is clear from the work presented that DOC and wind speed may also play important roles in DGM and mercury flux dynamics, and these roles have not been adequately accounted for in current predictive models.