Ion leaching from a sugar maple forest in response to acidic deposition and nitrification

Year-to-year variation in acidic deposition within a mature sugar maple-dominated forest and in leaching of ions from the associated podzolic soil were examined at the Turkey Lakes Watershed between 1981 and 1986. Below-canopy inputs to the soil of SO₄ ^2? and NO₃ ^? in throughfall averaged 640 and 295 eq. ha^?1 yr^?1; the corresponding ranges were 493–917 and 261–443 eq. ha^?1 yr^?1. The contribution of atmospheric deposition to SO₄ ^2? NO₃ ^? and Ca²⁺ leaching decreased over the six years. During the study period, the mean annual volume-weighted NO₃ ^? concentration decreased in throughfall and forest-floor percolate and increased in the mineral-soil solution collected below the effective rooting zone. A substantial shift in the balance between SO₄ ^2? and NO₃ ^?leaching from the mineral soil was observed; leaching of SO₄ ^2?decreased and NO₃ ^? leaching increased with time. Leaching of Ca²⁺ and Mg²⁺ from the soil was increased as a result of excess NO₃ ^? production in the soil. The calculated output of NO₃ ^? from the soil, which averaged 1505 eq. ha^?1 yr^?1, considerably exceeded the atmospheric deposition of NO₃ ^?, whereas SO₄ ^2? outputs were only moderately greater than inputs.     

Investigations on N-nitrosopyrrolidine in dry-cured bacon

Dry-cured or "country-style" bacon is a low volume specialty product typically made by small producers whose production practices vary widely. These practices include the direct application of dry-cure formulations containing varying concentrations of salt, sugar, flavoring agents, sodium nitrite, and sometimes sodium nitrate, and the use of lengthy curing and processing times. Because of the possibility of generating higher levels of N-nitrosopyrrolidine (NPYR) after frying in this product type compared with pump-cured bacon, an investigation was carried out on dry-cured bacon obtained from cooperating state or federally inspected establishments. Three different samples from each of the 16 plants were analyzed. Only one sample from each of 2 different producers exceeded the Food Safety and Inspection Service (FSIS) action level of 17 ppb NPYR, indicating that the majority of samples tested were in compliance. A significant correlation (P less than 0.01) was found between residual NaNO2 prior to frying and NPYR after frying. The elimination of added nitrate in the dry-cure formulations is recommended.     

Incorporating LASSO effects into a mixed model for quantitative trait loci detection

The identification of quantitative trait loci (QTL) can be viewed as a subset selection problem. In a simulation study the least absolute selection and shrinkage operator (LASSO) is shown to be a useful and powerful tool for QTL identification. LASSO effects are embedded into a mixed model allowing simultaneous modeling of genetic and experimental effects. This provides the flexibility to model the experiment in conjunction with the power of LASSO QTL identification. Estimation is performed using an approximation to the restricted likelihood and modified Gaussian elimination. The extended mixed model is used to analyze a cattle gene mapping dataset.     

Optimization of chick embryotoxicity bioassay for testing toxicity potential of fungal metabolites

The optimization of a simple, sensitive procedure using a chick embryotoxicity screening test (CHEST) bioassay for detection of toxic compounds is presented. Dosing protocols of eggs, using several mycotoxins (aflatoxin B1, deoxynivalenol, T-2 toxin) and appropriate controls, were evaluated for embryonic sensitivity, overall practicality of the procedure, and consistency of results. It was found that both type of carrier solvent and volume injected could significantly affect overall embryonic mortality. The chick embryo was most sensitive to the effects of toxins and solvents after 1 or 2 days of incubation; a rapid decrease in response was observed as the age of the embryo at dosing increased. Following administration of the toxins just below the shell membrane by way of a small hole (less than 0.5 mm diameter) punched in the shell, a good dose-response (% mortality) could be obtained regardless of the site of injection (except directly into the yolk), although dosing via the air sac position resulted in a slightly better statistical outcome. Although some variations in calculated LD50 values were found among repeated assays, statistical analyses showed that the differences were not due to dosing protocol but to the variations in embryo sensitivities among batches of eggs. Thus, if standard reference toxins for comparison are run concurrently, the CHEST assay can prove to be a very satisfactory model, as well as having considerable flexibility to be adapted to the needs and resources of many laboratories.     

Effects of two adenoviruses (type 1 and type 8) on functional properties of bovine alveolar macrophages in vitro.

Cultures of bovine alveolar macrophages were inoculated with type-1 and type-8 adenoviruses, initially isolated from calves with respiratory tract disease, and functional properties of the cells were observed over a period of 10 to 11 days. Both viruses replicated in macrophages; viral titers were low (less than 3.75 log10 TCID50/0.1 ml), and intranuclear inclusions were detected by indirect immunofluorescence in 5 to 10% of the cells from 3 days after inoculation. Highest titers were induced by type-1 adenovirus, which also induced the greatest functional changes. Expression of Fc and complement receptors was reduced by both viruses, although the greatest effects were seen with type 1. Phagocytosis of Candida krusei cells was reduced following type 1 infection, whereas phagocytosis in type-8-infected cells was not different from that of noninfected macrophages. Ability to kill ingested Candida cells also was reduced following type-1 infection, whereas type-8-infected macrophages had lower killing ability only at 2 to 4 days after inoculation. Neither virus had substantial effects on the production of neutrophil chemotactic factors by the macrophages.     

Blood bactericidal assay (Pasteurella haemolytica) comparison of morbidity in marketed feeder calves

An in vitro bactericidal assay that used bovine heparinized blood was investigated for its usefulness in detecting differences in the bactericidal immunity of calves against Pasteurella haemolytica serotype 1 (Ph1). Greater than 90% of killing occurred within 30 minutes. The substitution of fetal calf serum for autologous calf plasma caused loss of bactericidal activity of the blood. Decomplemented calf serum also was low in bactericidal activity. The blood bactericidal assay appears to be opsonin antibody-dependent and complement-dependent. The coefficient of variation (CV) that can be expected with this assay was established by use of a group of 8 calves; within-day CV maximum was 0.9, and between-day CV maximum was 2.1. The blood bactericidal assay was used to evaluate 30 calves under typical market stress from 4 farms in eastern Tennessee. All calves had decreased bactericidal activity, as they moved into a feedyard in Texas. The bactericidal activity was reduced among sick calves, based on the severity of clinical signs. Morbidity was highest during the first 14 days in the feedlot. During this period, healthy calves had a decreased bactericidal index (BI) of 4 points, and calves with clinical signs of bovine respiratory tract disease for 3 days had a decreased BI of 8 points. The average reduction in the BI of calves with clinical signs of bovine respiratory tract disease for 6 or more days was 14 points.     

Comparison of direct and indirect blood pressure measurements in anesthetized dogs.

The precision and accuracy of an indirect oscillometric blood pressure measurement technique (Dinamap 8100) was assessed in 11 anesthetized Beagle dogs weighing 8 to 11.5 kg. Direct blood pressure measurements were made by catheterization of the lingual artery, and simultaneous indirect measurements were determined by placing a cuff over the median artery (midradial area). Blood pressure measurements at 2 different planes of anesthesia (light and deep) were recorded in triplicate. At a light plane of anesthesia, the Dinamap 8100 underestimated diastolic and mean arterial pressure, and at a deep anesthetic plane overestimated systolic pressure. The indirect technique had good repeatability of systolic pressures. Regression analysis for the 2 techniques showed excellent correlation (r = 0.93). The results indicate that the indirect oscillometric blood pressure measurement technique provides a good estimate of systolic, diastolic, and mean arterial pressure in dogs weighing 8-11.5 kg.     

Efficacy of an in-feed ivermectin formulation against gastrointestinal helminths, lungworms, and sarcoptic mites in swine

The efficacy of ivermectin as an in-feed formulation was evaluated against naturally acquired gastrointestinal helminths, lungworms, and sarcoptic mites (experiment 1; n = 24) and against induced infection with intestinal nematodes (experiment 2; n = 24) in pigs. Treatments consisted of ivermectin administered in feed at concentrations calculated to provide 100 or 200 micrograms/kg of body weight/d for 7 days or of nonmedicated feed (controls) for 7 days. At concentration of 100 micrograms of ivermectin/kg/d, efficacy against naturally acquired infections was 97.7% for Ascaris suum, 97.8% for Metastrongylus spp, greater than 99% for Oesophagostomum spp, 100% for Macracanthorhynchus hirudinaceus, and 89.7% for Ascarops strongylina. Against induced infections (fourth-stage larvae), efficacy was 100% for A suum and 96.9% for Oesophagostomum spp. At concentration of 200 micrograms of ivermectin/kg/d, efficacy against naturally acquired infections was 100% for A suum, Hyostrongylus rubidus, Metastrongylus spp, and Ascarops strongylina; greater than 99% for Oesophagostomum spp; and 85.9% for Macracanthorhynchus hirudinaceus. Against induced infections (fourth-stage larvae), efficacy was 100% for A suum and 95% for Oesophagostomum spp. At concentrations of 100 and 200 micrograms of ivermectin/kg/d, efficacy against Sarcoptes scabiei var suis was evidenced by elimination of the mite by posttreatment day 14.