Population dynamics of a Western corn rootworm (Coleoptera: Chrysomelidae) variant in east central Illinois commercial maize and soybean fields.

Three on-farm sites in Iroquois County, IL, each containing an adjacent 16.2-ha commercial production maize, Zea mays L., and soybean, Glycine max (L.) Merr., field, were monitored for western corn rootworm, Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae), adults from June through September 1999-2001. Mean captures of D. v. virgifera adults as measured with Pherocon AM yellow sticky traps were significantly greater in maize than in soybean. Overall mean numbers of D. v. virgifera adults captured with vial traps were significantly greater in soybean than in maize. Emergence cage data revealed that after 50% emergence of D. v. virgifera adults occurred, peak captures of D. v. virgifera adults occurred in maize as measured with vial and Pherocon AM traps. After maize reached the R2 (blister stage, 10-14 d after silking) stage of development and 90% emergence of D. v. virgifera adults had occurred, peak captures of D. v. virgifera adults were observed in soybean by using vial and Pherocon AM traps. Also, after maize reached the R2 stage of development, numbers of females significantly increased in soybean and decreased in maize. Captures of female D. v. virgifera adults frequently exceeded published economic thresholds in soybean, regardless of trap type used. Estimated survival of variant D. v. virgifera (egg to adult) in these commercial rotated maize fields was 10.7 and 9.4% from 1999 to 2000 and from 2000 to 2001, respectively. This compares with nonvariant D. v. virgifera survival estimates in continuous maize production systems in Iowa of 6.7 and 11% from 1983 to 1984 and from 1984 to 1985, respectively.

Analysis of the dynamics of adaptation to transgenic corn and crop rotation by western corn rootworm (Coleoptera: Chrysomelidae) using a daily time-step model.

Western corn rootworm, Diabrotica virgifera virgifera LeConte, has overcome crop rotation in several areas of the north central United States. The effectiveness of crop rotation for management of corn rootworm has begun to fail in many areas of the midwestern United States, thus new management strategies need to be developed to control rotation-resistant populations. Transgenic corn, Zea mays L., effective against western corn rootworm, may be the most effective new technology for control of this pest in areas with or without populations adapted to crop rotation. We expanded a simulation model of the population dynamics and genetics of the western corn rootworm for a landscape of corn; soybean, Glycine max (L.); and other crops to study the simultaneous development of resistance to both crop rotation and transgenic corn. Results indicate that planting transgenic corn to first-year cornfields is a robust strategy to prevent resistance to both crop rotation and transgenic corn in areas where rotation-resistant populations are currently a problem or may be a problem in the future. In these areas, planting transgenic corn only in continuous cornfields is not an effective strategy to prevent resistance to either trait. In areas without rotation-resistant populations, gene expression of the allele for resistance to transgenic corn, R, is the most important factor affecting the evolution of resistance. If R is recessive, resistance can be delayed longer than 15 yr. If R is dominant, resistance may be difficult to prevent. In a sensitivity analysis, results indicate that density dependence, rotational level in the landscape, and initial allele frequency are the three most important factors affecting the results.

The effect of molluscan glue proteins on gel mechanics.

Several molluscs have been shown to alternate between a non-adhesive trail mucus and a similar gel that forms a strong glue. The major structural difference between the two secretions is the presence of specific proteins in the adhesive mucus. The present study identifies similar proteins from the glue of the slug Arion subfuscus and the land snail Helix aspersa. To investigate the role played by these proteins in adhesion, the proteins were isolated from the adhesive mucus of different molluscs and added to commercial polymer solutions. The effect was observed qualitatively, and quantified using a dynamic rheometer. The isolated proteins triggered gelling or visible stiffening of agar, pectin and polygalacturonic acid. The effect was stronger on more negatively charged polymers. The effect of the proteins was concentration dependent with an optimal concentration of 1-1.5 mg ml(-1), and was weakened when their structure changed. Other proteins and carbohydrates found in the adhesive mucus had no clear mechanical effect on gels. These findings show that the addition of these proteins to large, anionic polymers plays a central role in the formation of a glue from a mucus-like secretion. Such a mechanism may be common among invertebrates, and it may guide biomimetic approaches in the development of glues and gels.

Interactions between Nosema pyrausta (Microsporidia: Nosematidae) and Bacillus thuringiensis subsp. kurstaki in the European corn borer (Lepidoptera: Pyralidae).

Larval susceptibility to Bacillus thuringiensis was determined for Nosema pyrausta-infected and uninfected European corn borers, Ostrinia nubilalis (Hübner), in bioassays using a commercial formulation of B. thuringiensis subsp. kurstaki, Dipel ES, incorporated into diet. LC50 values for N. pyrausta-infected larvae were significantly lower (P<0.0001) than for uninfected larvae and declined with increasing levels of infection. LC50 values for a 15-d bioassay using field-colony first instars were 0.006 and 0.027 mg of Dipel ES/kg of diet for larvae moderately infected by N. pyrausta and uninfected larvae, respectively. Nosema pyrausta-infected larvae reared on Dipel ES-amended diets produced 70-fold fewer spores (P<0.0001) than larvae reared on standard diet. For example, 15 d after placement as first instars on standard diet, infected field-colony larvae produced 7.6-8.7 million N. pyrausta spores per larva; similar larvae placed on diet containing 0.09 mg of Dipel ES/kg of diet produced 85-103 thousand spores per larva. Infected larvae also weighed less and failed to mature on Dipel ES-amended diets. Increased susceptibility of N. pyrausta-infected larvae to Dipel ES and reduced N. pyrausta spore production in larvae feeding on diet containing Dipel ES suggest that Bt corn will have a direct adverse effect on the survival and continual impact of N, pyrausta as a regulating factor on European corn borer populations.

Heparin-bonded central venous lines reduce thrombotic and infective complications in critically ill children.

OBJECTIVE: To determine whether heparin bonding reduces the incidence of catheter-related thrombosis and infection in critically ill children. DESIGN: A prospective double-blind randomized controlled study. SETTING: A tertiary paediatric intensive care unit. PATIENTS: Two hundred and nine patients, 123 males and 86 females, aged 0-16 years, admitted to the intensive care unit and needing a central venous line (CVL), were randomized to receive either a heparin-bonded (HB, n = 102) or a non-heparin-bonded line (NHB, n = 107). Nine patients were excluded owing to incomplete data. INTERVENTION: HB or NHB CVL. MEASUREMENTS: Blood cultures were carried out on insertion of the line and every 3 days thereafter. Ultrasound was performed within the first 3 days and every 3 days thereafter. On removal the line was sent for culture. RESULTS: The two groups were comparable for age, sex, severity of illness and length of time that the catheter was in situ. Proportional hazards modelling showed that heparin bonding was associated with a significant reduction in infections (hazard ratio 0.11, P < 0.00005). The incidence of infection was 4% and 33% in HB and NHB CVLs, respectively (4/97 vs. 34/103, P < 0.0005). The incidence of thrombosis was 0% and 8% in HB and NHB CVLs, respectively (0/97 vs. 8/103, P = 0.006). The number of HB CVLs which would need to be used to avoid one episode of infection or thrombosis was 3 and 13, respectively. CONCLUSION: Our study shows a significant reduction in the incidence of infection and thrombosis associated with the use of HB CVLs.

Prenatal origins of human intrapulmonary arteries: formation and smooth muscle maturation.

Recent studies on the morphogenesis of the pulmonary arteries have focused on nonhuman species such as the chick and the mouse. Using immunohistochemical techniques, we have studied 16 lungs from human embryos and fetuses from 28 d of gestation to newborn, using serial sections stained with a panel of antibodies specific for endothelium, smooth muscle, and extracellular matrix proteins. Cell replication was also assessed. Serial reconstruction showed a continuity of circulation between the heart and the capillary plexus from at least 38 d of gestation. The intrapulmonary arteries appeared to be derived from a continuous expansion of the primary capillary plexus that is from within the mesenchyme, by vasculogenesis. The arteries formed by continuous coalescence of endothelial tubes alongside the newly formed airway. Findings were consistent with the pulmonary arterial smooth muscle cells being derived from three sites in a temporally distinct sequence: the earliest from the bronchial smooth muscle, later from the mesenchyme surrounding the arteries, and last from the endothelial cells. Despite their different origins, all smooth muscle cells followed the same sequence of expression of smooth muscle-specific cytoskeletal proteins with increasing age. The order of appearance of these maturing proteins was from the subendothelial cells outward across the vessel wall and from hilum to periphery. The airways would seem to act as a template for pulmonary artery development. This study provides a framework for studying the signaling mechanisms controlling the various aspects of lung development.

Growth of the vascular tree.

Major changes occur in the pulmonary circulation at birth. Failure of normal adaptation leads to pulmonary hypertension of the newborn. The basis for this may be abnormal growth of the lung in utero or a failure of the mechanisms which lead to vasodilatation in the newborn period. This article describes normal development of the pulmonary arteries and veins, their branching pattern and structure and discusses the factors which may control this growth. Endothelial function and dysfunction are crucial in adaptation, and new experimental studies are aiding our understanding of the control and action of factors produced by the endothelium, e.g. nitric oxide, prostacyclin and endothelin. The study of infants with pulmonary hypertension, together with the experimental studies, will aid in producing effective methods of controlling increased pulmonary artery pressure in the newborn period.

Phylogenetic analysis of the S10 gene of field and laboratory strains of bluetongue virus from the United States.

The sequence of the S10 gene segment of the United States prototype strains of BTV serotypes 10, 11, 13, and 17 obtained from the American Type Culture Collection (ATCC), the commercial modified live virus vaccine strains of BTV serotypes 10, 11, and 17, and 20 field isolates of BTV serotypes 10, 11, 13, and 17 was determined to better define the molecular epidemiology of BTV infection in the US. All S10 gene segments were 822 nucleotides in length with two in-frame initiation codons (nucleotides 20 to 22 and 59 to 61) and a single termination codon (nucleotides 707 to 709), thus all S10 genes were predicted to encode two proteins (NS3, NS3A). Nucleotide differences between the S10 genes from field isolates of BTV ranged from zero (100% identity) to 142 (81.8% identity). The sequences of the S10 gene segments from the US prototype ATCC strains of BTV 10 and 11 were very different from the previously published sequences of putative US prototype viruses of the same serotypes (Lee and Roy, 1986; Hwang et al., 1992). Comparison of the predicted NS3/NS3A proteins encoded by the S10 gene showed little variation between the various viruses (from 93 to 100% identity). This apparent conservation of NS3/NS3A amongst different strains and serotypes of BTV likely is a reflection of functional constraints on the protein that tolerate little variation. The various US isolates of BTV segregate into two distinct monophyletic groups based on their S10 gene sequences and clustering of viruses was independent of serotype, year of isolation, geographical origin, and of host species of isolation. The S10 sequence data also show that viruses that segregated within each of these two monophyletic groups co-circulated in the western US between 1953 and 1990, and that reassortment of the S10 gene segment likely occurs in nature. Comparison of dendograms derived from sequence analysis of the S3 (de Mattos et al., 1996)and the S10 gene segments from the same viruses also indicates that the S10 gene segment evolves and reassorts independently of the S3 gene segment.

Homotypic and heterotypic neutralization determinants of bluetongue virus serotype 17.

Homotypic and heterotypic neutralization determinants of bluetongue virus serotype 17 (BTV-17) were investigated with a panel of five neutralizing monoclonal antibodies (MAbs). One MAb (MAb 034) was originally raised to BTV serotype 10 (BTV-10) but also neutralizes BTV-17 (P. V. Rossitto, and N. J. MacLachlan, 1992, J. Gen. Virol. 73, 1947-1952). Competitive binding studies indicate that the MAbs recognize at least two epitopes on the neutralizing outer capsid protein VP2 of BTV-17. The MAbs were used to select neutralization-resistant variant [escape mutant (EM)] viruses and to determine the phenotypic characteristics of these EM viruses by immunoprecipitation and neutralization assays. Sequencing of the L2 gene, which encodes VP2, identified mutations responsible for the altered phenotypic properties exhibited by each EM virus. Four amino acids in three regions of VP2 are critical to the expression of the epitopes recognized by the panel of neutralizing MAbs. Amino acid 199 affects the binding of MAbs 17.82, 17.83, and 17.813; amino acid 213 affects the binding of MAb 17.85; and amino acids 327 and 582 synergistically affect the binding of MAb 034. Similarly, amino acids 327 and 402 synergistically affect the binding of MAb 034 to BTV-10 (C. D. DeMaula, H. W. Heidner, P. V. Rossitto, C. M. Pierce, and N. J. MacLachlan, 1993, Virology 195, 292-296), suggesting that the neutralizing epitope common to BTV-10 and BTV-17 has a similar location in VP2 of these two antigenically distinct viruses.

Neutralization determinants of United States bluetongue virus serotype ten.

A panel of five neutralization-resistant escape mutant (EM) viruses was used to investigate the neutralization determinants of the U.S. prototype strain of bluetongue virus serotype 10 (BTV-10). The phenotypic properties of each EM virus were characterized by neutralization and immuneprecipitation assays with a panel of four monoclonal antibodies (MAbs). These MAbs were used to select the various EM viruses and together the MAbs define four distinct neutralizing epitopes on the prototype strain of BTV-10 (Heidner, H.W., Rositto, P.V., and MacLachlan, N.J., Virology 176, 658-661 (1990)). Sequencing of the L2 gene identified mutations responsible for the altered phenotypic properties exhibited by each EM virus. The L2 gene encodes BTV outer capsid protein VP2 which is responsible for virus neutralization. Four amino acids in three distinct regions of VP2 are critical to expression of the epitopes recognized by the MAb panel. Both amino acid 208 and 211 can affect the binding of MAb 039 and MAb 045, amino acid 327 affects binding of MAb 041, and amino acids 327 and 402 cooperatively interact to affect binding by MAb 034. The location of two of these critical regions on VP2 of BTV-10 is identical to two of those which affect neutralization of Australian BTV-1, despite the fact that these two viruses are antigenically distinct and have divergent L2 gene sequences (Gould, A.R., and Eaton, B.T., Virus Res. 17, 161-172 (1990)). The four individual neutralizing epitopes on VP2 of BTV-10 are interactive (Heidner, H.W., Rositto, P.V., and MacLachlan, N.J., Virology 176, 658-661 (1990)) and at least two are conformationally dependent.

A modified Regressive Coping Checklist: some Australian data.

The Regressive Coping Checklist has been used to measure the extent to which individuals cope with stress by denying, minimizing, or avoiding stressful situations. In this study, the checklist was modified to include the frequency of use of regressive coping strategies and was shown to be a moderately reliable instrument (alpha = .57) when used with a sample of 750 Australian postprimary teachers.

Some developmental trends in children's information-processing strategies.

The problem-solving strategies of 120 children from two age levels were compared by means of exploratory factor analyses. Essentially, these results replicated the factor structures of earlier studies based on the Das-Luria model. Disparities in factor loadings on some tasks were interpreted as suggestive of developmental differences in children's coding strategies which are compatible with Bruner's description of the course of cognitive growth.

Psychological and biographical differences between secondary school teachers experiencing high and low levels of burnout.

A total of 750 teachers from 16 government and non-government schools from areas of contrasted socio-economic status (SES) responded to a questionnaire designed to investigate associations between selected aspects of burnout among teachers working in secondary schools in Victoria, Australia. By comparing high and low burnout groups on biographic, psychological and work pattern variables, differences between teachers experiencing high and low levels of burnout were identified. Multiple regression analyses assessed the relative importance of these variables in accounting for the variance in each of the three burnout subscales. School type was related to perceptions of stress and burnout. Higher levels of burnout were associated with poorer physical health, higher rates of absenteeism, lower self-confidence and more frequent use of regressive coping strategies. Teachers classified as experiencing high levels of burnout attributed most of the stress in their lives to teaching and reported low levels of career commitment and satisfaction. Further, teachers who recorded high levels of burnout were characterised by lower levels of the personality disposition of hardiness, lower levels of social support, higher levels of role stress and more custodial pupil control ideologies than their low-burnout counterparts. Psychological variables were found to be more significant predictors of burnout than biographical variables.