Factors affecting population trends of plant-parasitic nematodes on rangeland grasses.

The effects of environmental conditions on population trends of plant-parasitic nematodes were studied in experimental plots of five wheatgrasses in the western Utah desert. In a 3-year (1984-86) field study, soil water and temperature affected the population trends of the ectoparasites, Tylenchorhynchus acutoides and Xiphinema americanum, and the migratory endoparasite, Pratylenchus neglectus, on Fairway crested wheatgrass, Agropyron cristatum; 'Hycrest' crested wheatgrass, A. cristatum X A. desertorura; 'Rosana' western wheatgrass, Pascopyrum smithii; 'Oahe' intermediate wheatgrass, Thinopyrum intermedium; and RS-1 hybrid (Elytrigia repens X Pseudoroegneria spicata). The largest soil populations of these nematode species were collected in 1984 under good plant-growth conditions. A reduction in nematode populations occurred in 1985 and 1986, possibly because of low soil-water conditions. There was a positive relationship between high soil water and maximum population densities of T. acutoides in the spring and fall of 1984, and between low soil water and minimum population densities of the nematode in 1985 and 1986. Pratylenchus neglectus populations were affected by soil water, although to a lesser degree than the ectoparasitic nematodes. Population densities of the three nematode species were significantly lower in the drier years of 1985 and 1986 than in 1984. Nematode populations were greater at the lower soil depths in the fall than in the spring or summer.

The choice of methods for immunoglobulin IgG purification: yield and purity of antibody activity.

Six methods for the purification of immunoglobulin G (IgG) from serum were compared, using rabbit antiserum to Bacillus anthracis spores as a model. Antibody activity was monitored by a solid-phase immunoradiometric assay (IRMA). Salt precipitation/ion exchange chromatography and ethanol precipitation both resulted in IgG of high purity but there was considerable inactivation of antibody. Salt precipitation/affinity chromatography gave poor yields of antibody. PEG precipitation and gel filtration of Sephacryl S-300 gave moderate yields and purity of IgG, with little evidence of antibody inactivation. Salt precipitation was marginally more destructive than the last 2 methods, but is recommended for routine use on grounds of its simplicity. Should IgG prepared by salt precipitation prove inadequate for particular applications, gel filtration is recommended since it allows the balance of yield and purity to be altered at will.