Atrial natriuretic peptide receptors in sheep cotyledons

Effects dependent on atrial natriuretic peptide are mediated through specific atrial natriuretic peptide plasma membrane receptors. We previously demonstrated the presence of specific atrial natriuretic peptide receptors in human placental membranes. We asked whether atrial natriuretic peptide specific receptors are present in sheep cotyledons. Sheep cotyledons were obtained from pregnant ewes at 125 to 142 days' gestation. Each cotyledon was separated into two components, the outer layer (maternal capsule) and the spongy inner layer (fetal component). A microsomal plasma membrane fraction was prepared from each layer. Atrial natriuretic peptide receptors were detected by in vitro radioligand techniques with 125I-alpha-human atrial natriuretic peptide. In sheep cotyledons there are two sets of atrial natriuretic peptide receptors that show either high-affinity/low-capacity or low-affinity/high-capacity binding characteristics. Moreover, membranes from the inner layer (fetal component) appear to have a lower concentration of high-affinity atrial natriuretic peptide binding sites than those from the maternal capsule.     

Diesel particulate matter exposure to railroad train crews

Exposure assessments were conducted aboard diesel locomotives. Results were evaluated to determine variables that affect exposure to DPM (diesel particulate matter) and to assess use of EC (elemental carbon) and OC (organic carbon) as surrogates for DPM. National Institute for Occupational Safety and Health Method 5040 was used for collection and analysis of samples in locomotives and in nonrailroad settings. The level of EC, but not OC, in locomotives was found to be significantly affected by position of exhaust stacks and windows. EC ranged from < 1 to 45 micrograms/m3 with a geometric mean (GM) of 3.7 micrograms/m3 and OC ranged from 4 to 4570 micrograms/m3 with a GM of 36.3 micrograms/m3. Background measurements of EC ranged from < 1 to 8 micrograms/m3 and OC levels were 4 to 84 micrograms/m3. This study confirms that train crew exposure to DPM is much lower than exposures for miners, is comparable to background urban exposures, and is lower than but comparable to exposures for truck drivers. It also indicates that EC levels are highly predictive of diesel exhaust exposure whereas OC levels are not, and that open windows and exhaust stack(s) in front of the locomotive cab have a significant effect on EC.     

Risks to the public from historical releases of radionuclides and chemicals at the Rocky Flats Environmental Technology Site

This paper summarizes the methods and results of estimating risks of cancer incidence resulting from plutonium, carbon tetrachloride, and beryllium releases from operations at the Rocky Flats Environmental Technology Site, near Denver, Colorado, from 1953 through 1989. The key findings show that people who lived near the facility were exposed to plutonium mainly through inhalation during routine operations, from a major fire in 1957, and from plutonium resuspended from contaminated soil from an outdoor drum storage area, called the 903 Area. Results were presented for five exposure scenarios that were location-independent. Individuals described by the laborer scenario received the highest risk of all scenarios considered. Upper bound (95th percentile) incremental lifetime cancer incidence risks for the laborer scenario were in about the 10(-4) range (1 chance in 10,000) for developing cancer from Rocky Flats plutonium releases during a lifetime. At the 5th percentile level, the maximum cancer risk was about 10(-7) (1 chance in 10 million) for developing cancer during a lifetime. Estimated cancer risks at the 95th percentile level are within the range of for acceptable risks established by the US Environmental Protection Agency of 10(-6) to 10(-4). Carbon tetrachloride was found to be the chemical that presented the highest risk to the public. The 5th and 95th percentile risk values for exposure to carbon tetrachloride were 9.2x10(-7) and 2.5x10(-5), respectively.