Influence of preceding crop on wireworm (Coleoptera: Elateridae) abundance in the coastal plain of North Carolina

Three studies were conducted to determine the effect of preceding crop on wireworm (Coleoptera: Elateridae) abundance in the coastal plain of North Carolina. In all three studies, samples of wireworm populations were taken from the soil by using oat, Avena sativa L., baits. Treatments were defined by the previous year's crop and were chosen to reflect common crop rotations in the region. Across all three studies, eight wireworm species were recovered from the baits: Conoderus amplicollis (Gyllenhal), Conoderus bellus (Say), Conoderus falli (Lane), Conoderus lividus (Degeer), Conoderus scissus (Schaeffer), Conoderus vespertinus (F.), Glyphonyx bimarginatus (Schaeffer), and Melanotus communis (Gyllenhal). The effect of corn, Zea mays L.; cotton, Gossypium hirsutum L.; fallow; soybean, Clycine max (L.) Merr.; sweet potato, Ipomoea batatas (L.) Lam.; and tobacco (Nicotiana spp.) was evaluated in a small-plot replicated study. M. communis was the most frequently collected species in the small-plot study and was found in significantly higher numbers following soybean and corn. The mean total number of wireworms per bait (all species) was highest following soybean. A second study conducted in late fall and early spring assessed the abundance of overwintering wireworm populations in commercial fields planted to corn, cotton, peanut (Arachis hypogaea L.), soybean, sweet potato, and tobacco in the most recent previous growing season. C. lividus was the most abundant species, and the mean total number of wireworms was highest following corn and soybean. A survey was conducted in commercial sweet potato in late spring and early summer in fields that had been planted to corn, cotton, cucurbit (Cucurbita pepo L.), peanut, soybean, sweet potato, or tobacco in the most recent previous growing season. C. vespertinus was the most abundant species, and the mean total number of wireworms per bait was highest following corn.     

Lateral interactions among membrane proteins. Valid estimates based on freeze-fracture electron microscopy.

We consider the lateral distribution of intrinsic membrane proteins from the viewpoint of the statistical-mechanical theory of liquids. We connect the information in freeze-fracture electron micrographs--positions of proteins but not lipids or aqueous species--to a well developed theory of liquid mixtures. An algorithm, based on the Born-Green-Yvon integral equation, is presented for deducing forces between proteins from correlations among protein positions that are observed in micrographs. The algorithm is tested on simulated micrographs, obtained by Monte-Carlo methods, where forces between proteins are known analytically. We conclude that valid estimates of such forces, both attractions and repulsions, can be obtained from the positions of a few thousand proteins.     

Purification of recombinant antigenic epitopes of the human 68-kDa (U1) ribonucleoprotein antigen using the expression system pH6EX3 followed by metal chelating affinity chromatography.

A novel plasmid expression vector (pH6EX3) that directs the synthesis of a fusion protein with a histidine hexapeptide at its N-terminus and a foreign protein at its C-terminus was constructed. The fusion gene is controlled by a strong tac promoter, leading to high-level expression of recombinant protein in several bacterial strains; the protein is deposited mainly as an insoluble mass in inclusion bodies. The fusion protein can be purified from the insoluble cell fraction by one-step affinity chromatography based on the selective interaction between the histidine hexapeptide and a metal chelating matrix charged with Ni2+ ions. The principle of this new system was tested by expressing and purifying antigenic epitopes of the human 68-kDa (U1) ribonucleoprotein autoantigen. With the use of column chromatography and pH gradient elution, about 25 micrograms recombinant protein/ml of bacterial culture was obtained.     

Broad and narrow heritabilities of quantitative traits in a founder population

Estimation of the components of variance for a quantitative trait allows one to evaluate both the degree to which genetics influences the trait and the trait's underlying genetic architecture. For particular traits, the estimates also may have implications for discriminating between potential models of selection and for choosing an appropriate model for linkage analysis. Using a recently developed method, we estimate the additive and dominance components of variance--or, equivalently, the narrow and broad sense heritabilities--of several traits in the Hutterites, a founder population with extensive genealogical records. As a result of inbreeding and because Hutterite individuals are typically related through multiple lines of descent, we expect that power to detect dominance variance will be increased relative to that in outbred studies. Furthermore, the communal lifestyle of the Hutterites allows us to evaluate the genetic influences in a relatively homogeneous environment. Four phenotypes had a significant dominance variance, resulting in a relatively high broad heritability. We estimated the narrow and broad heritabilities as being, respectively,.36 and.96 for LDL,.51 and 1.0 for serotonin levels, and.45 and.76 for fat free mass (FFM). There was no significant additive component for systolic blood pressure (SBP), resulting in a narrow heritability of 0 and a broad heritability of.45. There were several traits for which we found no significant dominance component, resulting in equal broad and narrow heritability estimates. These traits and their heritabilities are as follows: HDL,.63; triglycerides,.37; diastolic blood pressure,.21; immunoglobulin E,.63; lipoprotein(a),.77; and body-mass index,.54. The large difference between broad and narrow heritabilities for LDL, serotonin, FFM, and SBP are indicative of strong dominance effects in these phenotypes. To our knowledge, this is the first study to report an estimate of heritability for serotonin and to detect a dominance variance for LDL, FFM, and SBP.     

Tracing the development of oligodendrocytes from precursor cells using monoclonal antibodies, fluorescence-activated cell sorting, and cell culture

We have used antibody and complement-mediated cell killing, fluorescence-activated cell sorting and tissue culture to study the development of rat oligodendrocytes. We show that (1) three ligands that bind to the majority of CNS neurons (the monoclonal antibodies A4 and A2B5 and tetanus toxin) also bind to immature oligodendrocytes and to precursor cells in 14-day embryonic rat brain that develop into oligodendrocytes in vitro; and (2) precursor cells in 17- to 18-day embryonic rat optic nerve can develop into oligodendrocytes in vitro in the absence of living neurons.     

Influence of soil temperature, rainfall, and planting and harvest dates on Chaetocnema confinis (Coleoptera: Chrysomelidae) damage to sweetpotato roots

A study was carried out in 10 counties of North Carolina from 2004 to 2006 to determine the effect of planting and harvest times on flea beetle, Chaetocnema confinis Crotch (Coleoptera: Chrysomelidae), damage to sweetpotato, Ipomoea batatas (L.), storage roots. Planting and harvesting of sweetpotatoes later in the season resulted in less damage than early planting and harvesting. Regression analysis was done to study the relationship of weather parameters with the flea beetle damage. Weather parameters included air temperature (Celsius), soil temperature at 5- and 10-cm depth (Celsius), rainfall (millimeters), and soil moisture (volume:volume) at 0-10-, 10-40-, and 40-100-cm depth. The best regression model included mean soil temperature at 10-cm depth, total rainfall, and number of adults caught on yellow sticky traps as independent variables (all between 1 August and harvest date of each field). Soil temperature and adult catches on yellow sticky traps of C. confinis were positively related to damage, whereas rainfall was negatively correlated. The model explained 45% of the total variation in the flea beetle damage. Soil temperature alone accounted for 32% of the total variation in flea beetle damage followed by rainfall (9%) and adult catches (4%). When the time interval was limited to 30 d before harvest, soil temperature was still the best explanatory variable accounting for 23% of the total variation in flea beetle damage followed by rainfall (7%) and adult catches (4%). Understanding the effects of planting/harvesting and weather factors on flea beetle damage will be useful in predicting the time when the sweetpotato crop is at greater risk from high levels of damage by C. confinis.     

Calculation of resonance energy transfer in crowded biological membranes.

Analytical and numerical models were developed to describe fluorescence resonance energy transfer (RET) in crowded biological membranes. It was assumed that fluorescent donors were linked to membrane proteins and that acceptors were linked to membrane lipids. No restrictions were placed on the location of the donor within the protein or the partitioning of acceptors between the two leaflets of the bilayer; however, acceptors were excluded from the area occupied by proteins. Analytical equations were derived that give the average quantum yield of a donor at low protein concentrations. Monte Carlo simulations were used to generate protein and lipid distributions that were linked numerically with RET equations to determine the average quantum yield and the distribution of donor fluorescence lifetimes at high protein concentrations, up to 50% area fraction. The Monte Carlo results show such crowding always reduces the quantum yield, probably because crowding increases acceptor concentrations near donor-bearing proteins; the magnitude of the reduction increases monotonically with protein concentration. The Monte Carlo results also show that the distribution of fluorescence lifetimes can differ markedly, even for systems possessing the same average lifetime. The dependence of energy transfer on acceptor concentration, protein radius, donor position within the protein, and the fraction of acceptors in each leaflet was also examined. The model and results are directly applicable to the analysis of RET data obtained from biological membranes; their application should result in a more complete and accurate determination of the structures of membrane components.