Using 20-gauge percutaneous peripheral catheters to reliably collect serial 4-mL blood samples from conscious dogs

Objective To determine the reliability of collecting serial 4-mL blood samples over 13 h using a 20-gauge, cephalic catheter in conscious dogs. Design Prospective, observational study. Animals Twelve (6 males, 6 females) healthy, neutered, lean dogs. Procedure Percutaneous placement of a 20-gauge, 1.1 × 30 mm intravenous over-the-needle catheter into the cephalic vein was performed in each dog on three occasions. Catheter patency was maintained by intermittent flushing with 0.9% saline and 1 IU/mL heparinised saline solutions. Blood samples (4 mL) were obtained at 10 time-points over 13 h, with close monitoring of the dogs and the indwelling catheters. Blood volume, resistance on aspirating blood sample (minimal or marked resistance) and the methods used to improve blood flow were recorded. Results A high proportion (93%) of blood sample collections achieved the required 4-mL volume, and the remaining samples were greater than 1.5 mL. Of the 358 collections via the cephalic catheter, 311 (87%) were obtained with ‘minimal resistance’. The remaining collections had ‘marked resistance’ (n=47) and were associated with a loose catheter in 11% (5/47) and of unknown cause in 89% (42/47). After ‘marked resistance’ had been encountered and the catheter was flushed with saline and heparin solutions, subsequent sampling with ‘minimal resistance’ was frequently possible from the same catheter. Conclusion Use of a percutaneous, 20-gauge intravenous cephalic catheter allowed reliable serial collection of 4-mL blood samples over 13 h in conscious dogs.     

The Effect of Wildfire on Soil Mercury Concentrations in Southern California Watersheds

Mercury (Hg) stored in vegetation and soils is known to be released to the atmosphere during wildfires, increasing atmospheric stores and altering terrestrial budgets. Increased erosion and transport of sediments is well-documented in burned watersheds, both immediately post-fire and as the watershed recovers; however, understanding post-fire mobilization of soil Hg within burned watersheds remains elusive. The goal of the current study is to better understand the impact of wildfire on soil-bound Hg during the immediate post-fire period as well as during recovery, in order to assess the potential for sediment-driven transport to and within surface waters in burned watersheds. Soils were collected from three southern California watersheds of similar vegetation and soil characteristics that experienced wildfire. Sampling in one of these watersheds was extended for several seasons (1.5 years) in order to investigate temporal changes in soil Hg concentrations. Laboratory analysis included bulk soil total Hg concentrations and total organic carbon of burned and unburned samples. Soils were also fractionated into a subset of grain sizes with analysis of Hg on each fraction. Low Hg concentrations were observed in surface soils immediately post-fire. Accumulation of Hg coincident with moderate vegetative recovery was observed in the burned surface soils 1 year following the fire, and mobilization was also noted during the second winter (rainy) season. Hg concentrations were highest in the fine-grained fraction of unburned soils; however, in the burned soils, the distribution of soil-bound Hg was less influenced by grain size. The accelerated accumulation of Hg observed in the burned soils, along with the elevated risk of erosion, could result in increased delivery of organic- or particulate-bound Hg to surface waters in post-fire systems.     

Evidence for upwelling of corrosive "acidified" water onto the continental shelf

The absorption of atmospheric carbon dioxide (CO2) into the ocean lowers the pH of the waters. This so-called ocean acidification could have important consequences for marine ecosystems. To better understand the extent of this ocean acidification in coastal waters, we conducted hydrographic surveys along the continental shelf of western North America from central Canada to northern Mexico. We observed seawater that is undersaturated with respect to aragonite upwelling onto large portions of the continental shelf, reaching depths of approximately 40 to 120 meters along most transect lines and all the way to the surface on one transect off northern California. Although seasonal upwelling of the undersaturated waters onto the shelf is a natural phenomenon in this region, the ocean uptake of anthropogenic CO2 has increased the areal extent of the affected area.     

The potential for respiratory droplet-transmissible A/H5N1 influenza virus to evolve in a mammalian host

Avian A/H5N1 influenza viruses pose a pandemic threat. As few as five amino acid substitutions, or four with reassortment, might be sufficient for mammal-to-mammal transmission through respiratory droplets. From surveillance data, we found that two of these substitutions are common in A/H5N1 viruses, and thus, some viruses might require only three additional substitutions to become transmissible via respiratory droplets between mammals. We used a mathematical model of within-host virus evolution to study factors that could increase and decrease the probability of the remaining substitutions evolving after the virus has infected a mammalian host. These factors, combined with the presence of some of these substitutions in circulating strains, make a virus evolving in nature a potentially serious threat. These results highlight critical areas in which more data are needed for assessing, and potentially averting, this threat.     

Determination of temperature and time thresholds for BIOTIC irrigation of peanut on the Southern High Plains of Texas

The timely application of irrigation water to a crop is essential for optimizing yield and production efficiency. The Biologically Identified Optimal Temperature Interactive Console (BIOTIC) is an irrigation protocol that provides irrigation scheduling based upon measurements of canopy temperatures and the temperature optimum of the crop species of interest. One of the goals of this paper is to document the gradual development of the method and its implementation. Two threshold values are required to implement BIOTIC irrigation of a crop in a given region, a species-specific temperature threshold and a species/environment-specific time threshold. The temperature threshold, an indication of the thermal optimum for the plant, is derived from the thermal dependence of its metabolism. The time threshold, which represents the average amount of time each day that the canopy temperature of the well-watered crop will exceed the temperature threshold, is calculated from weather data. Interest in the use of BIOTIC for irrigation scheduling for peanut ( Arachis hypogaea L.) resulted in this study in which the temperature and time thresholds for peanut were determined on the Texas Southern High Plains. A temperature threshold value of 27°C was determined from the thermal dependence of the reappearance of photosystem II variable fluorescence (PSII Fv) following illumination. A time threshold of 405 min was calculated from an analysis of weather data collected over the course of the 1999 growing season. The determination of these threshold values for peanut provides the basis for the application of the BIOTIC protocol to irrigation scheduling of peanut on the Southern High Plains of Texas.Names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by the USDA implies no approval of the product to the exclusion of others that may also be suitable.     

Determination of fluoroacetate in biological matrixes as the dodecyl ester

A new method for the quantitative determination of fluoroacetate in biological samples was applied to a number of avian samples. Fluoroacetate is isolated as its potassium salt by ion-exchange chromatography and directly converted to its dodecyl ester, using a novel derivatization procedure. The ester is quantified by capillary gas chromatography with a flame ionization detector for the range 1.0-10.0 micrograms/g and by selected ion monitoring GC/mass spectrometry for the range 0.01-1.00 microgram/g. Recoveries from 1 g chicken muscle were about 80%. The method was applied to the determination of fluoroacetate in the crop, stomach, liver, heart, intestine, and breast muscle of 5 Zebra finches (Peophila guttata) that had been fed millet containing 9 micrograms/g of sodium fluoroacetate. Despite a wide variation in dose, the levels in organs and tissues were approximately 1 microgram/g except for heart tissue which was about 2 micrograms/g. The presence of interfering peaks at low levels necessitated the use of selected ion monitoring GC/MS when sample weights were less than 1 g or when levels were less than 1 microgram/g. Samples can be analyzed within hours of receipt; therefore, the method is suitable for routine use in a diagnostic laboratory.     

Wet deposition of mercury and ambient mercury concentrations at a site in the Lake Champlain basin

The “Great Waters” program, established in the 1990 Clean Air Act Amendments, mandated that atmospheric deposition of hazardous air pollutants to Lake Champlain (including Hg) be assessed. An assessment of the magnitude and seasonal variation of atmospheric Hg deposition in the Lake Champlain basin was initiated in December 1992 with one year of event precipitation collection, as well as collection of vapor and particle phase Hg in ambient air. Samples were collected at the Vermont Monitoring Cooperative air monitoring site at the Proctor Maple Research Center in Underhill Center, VT. The average volume-weighted concentration for Hg in precipitation was 8.3 ng/L for the sampling year and the average amount of Hg deposited with each precipitation event was 0.069 μg/m². The total amount of Hg deposited through precipitation during 1993 was 9.26 μg/m²/yr. A seasonal pattern for Hg in precipitation was evident, with increased concentrations and deposition during spring and summer months. Meteorological analysis indicated the highest levels of Hg in precipitation were associated with regional transport from the south regardless of season, and with transport from the west, southwest and northwest during spring and summer months. Concentrations of ambient vapor phase Hg were typical of rural locations and consistent across seasons. Ambient particulate Hg concentrations averaged 11 pg/m³ with highest concentrations during the winter months.     

Chemical contaminants in foods: some analytical considerations

Data on the incidence and levels of chemical contaminants in foods are needed for continuous assessment of the safety of the food supply and to inform the public about the safety of food. A larger share of the total analytical resource--federal and state government, private sector, and academia--could profitably be directed to collection and publication of data on the occurrence of chemical contaminants in foods. The quest for more data must be accompanied by measures to ensure data reliability and comparability and to estimate the uncertainty of measurements. Research to improve the efficiency of analysis may be the top priority for future methods improvement studies. Analytical chemistry will continue to be an essential factor in assuring a safe food supply and in communicating to the public accurate information and conclusions about food safety.