Ants as egg predators of Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) in Australian cotton crops

Abstract Helicoverpa armigera is a major pest of Australian cotton crops. To assess the impact of ant predation on H. armigera populations, the behaviour of four common ant taxa was observed in cotton crops in northern New South Wales over the 1999−2000 and 2001−02 seasons. Areas of cotton were artificially stocked with H. armigera eggs prior to observation. Pheidole spp. were the most frequently observed ants within the crop canopy in 1999−2000 and took the most H. armigera eggs. Iridomyrmex spp. were more frequently observed than Pheidole spp. in 2001−02 and also took some H. armigera eggs. Neither Paratrechina spp. nor Rhytidoponera metallica (Smith) took any H. armigera eggs, although both were seen in the crop canopy. Irrigation, cultivation and insecticide application disrupted foraging ants and limited their impact on H. armigera populations.     

Drosophila Cu,Zn superoxide dismutase gene confers resistance to paraquat in Escherichia coli

Superoxide dismutase (SOD) is known to protect organisms from reactive oxygen metabolites. We tested the hypothesis that the Drosophila Cu,Zn SOD is capable of protecting Escherichia coli from oxidative damage caused by the herbicide paraquat. The Cu,Zn Sod gene of Drosophila sechellia was subcloned into pET-20b(+) expression vector. Transformation of E. coli with the constructed vector resulted in an overexpression of this eukaryotic superoxide dismutase, as evidenced by dramatically increased levels of the Cu,Zn SOD polypeptide in bacterial cytosolic extracts. As well, the E. coli transformants showed resistance to paraquat-mediated inhibition of growth and survival. Paraquat is known to promote formation of the superoxide radical anion inside cells and thus the data have been interpreted as indicating that the cloned superoxide dismutase provides protection in E. coli against damage attributable to free radicals.     

Using pedigree reconstruction to estimate population size: genotypes are more than individually unique marks

Estimates of population size are critical for conservation and management, but accurate estimates are difficult to obtain for many species. Noninvasive genetic methods are increasingly used to estimate population size, particularly in elusive species such as large carnivores, which are difficult to count by most other methods. In most such studies, genotypes are treated simply as unique individual identifiers. Here, we develop a new estimator of population size based on pedigree reconstruction. The estimator accounts for individuals that were directly sampled, individuals that were not sampled but whose genotype could be inferred by pedigree reconstruction, and individuals that were not detected by either of these methods. Monte Carlo simulations show that the population estimate is unbiased and precise if sampling is of sufficient intensity and duration. Simulations also identified sampling conditions that can cause the method to overestimate or underestimate true population size; we present and discuss methods to correct these potential biases. The method detected 2–21% more individuals than were directly sampled across a broad range of simulated sampling schemes. Genotypes are more than unique identifiers, and the information about relationships in a set of genotypes can improve estimates of population size.     

A Neutron Scattering Study of the Ternary Complex EF-Tu•GTP-valy1-tRNAVal 1A

Abstract

The complex formation between elongation factor Tu (EF-Tu), GTP, and valyl-tRNA^Val _1A has been investigated in a hepes buffer of “pH” 7.4 and 0.2 M ionic strength using the small-angle neutron scattering method at concentrations of D₂O where EF-Tu (42% D₂O) and tRNA (71% D₂O) are successively matched by the solvents. The results indicate that EF-Tu undergoes a conformational change and contracts as a result of the complex formation, since the radius of gyration decreases by 15% from 2.82 to 2.39 nm. tRNA^Val _1A, on the other hand, seems to mainly retain its conformation within the complex, since the radii of gyration for the free (after correction for interparticular scattering) and complexed form are essentially the same. 2.38 and 2.47 nm, respectively.     

Comparing two estimations of the quadriceps force distribution for use during patellofemoral simulation

EMG analysis has indicated that the vastus lateralis and vastus medialis contribute less to the quadriceps moment during knee extension than the physiological cross-sectional areas (PCSA's) of the muscles indicate. Both PCSA- and EMG-based quadriceps force distributions were utilized while computationally simulating knee extension. For both distributions, a 10 degrees increase in the Q-angle and a 50% decrease in the force applied by the vastus medialis were simulated, and the influence of these changes on the resultant force and moment applied by the quadriceps muscles and the patella tendon was quantified. For both quadriceps force distributions, increasing the Q-angle increased the lateral force and the moment acting to rotate the distal patella laterally. Due to the relatively large forces initially attributed to the vastus medialis and vastus lateralis for the PCSA-based quadriceps force distribution, decreasing the vastus medialis force created a large force imbalance between these two muscles. For the PCSA-based quadriceps force distribution, decreasing the vastus medialis force increased the lateral rotation moment and the moment acting to tilt the patella laterally. For the EMG-based quadriceps force distribution, decreasing the vastus medialis force produced relatively little change in the tilt and rotation moments. For both quadriceps force distributions, increasing the Q-angle increased the maximum and mean cartilage pressure during flexion, but decreasing the vastus medialis force only increased the cartilage pressures for the PCSA-based quadriceps distribution. The choice of the initial quadriceps distribution can influence the outcome of patellofemoral simulation when manipulating quadriceps muscle forces.     

Strain diversity of Borrelia burgdorferi in ticks dispersed in North America by migratory birds

The role of migratory birds in the dispersal of Ixodes scapularis ticks in the northeastern U.S. is well established and is presumed to be a major factor in the expansion of the geographic risk for Lyme disease. Population genetic studies of B. burgdorferi sensu stricto, the agent of Lyme disease in this region, consistently reveal the local presence of as many as 15 distinct strain types as designated by major groups of the ospC surface lipoprotein. Recent evidence suggests such strain diversity is adaptive to the diverse vertebrate hosts that maintain enzootic infection. How this strain diversity is established in emergent areas is unknown. To determine whether similar strain diversity is present in ticks imported by birds, we examined B. burgdorferi strains in I. scapularis ticks removed from migrants at an isolated island site. Tick mid‐guts were cultured and isolates underwent DNA amplification with primers targeting ospC. Amplicons were separated by gel electrophoresis and sequenced. One hundred thirty‐seven nymphal ticks obtained from 68 birds resulted in 24 isolates of B. burgdorferi representing eight ospC major groups. Bird‐derived ticks contain diverse strain types of B. burgdorferi, including strain types associated with invasive Lyme disease. Birds and the ticks that feed on them may introduce a diversity of strains of the agent of Lyme disease to emergent areas.     

Environment and archeology in Beringia

The occupation of Beringia remains one of the most complex problems in human paleoecology. This is because of the wide array of variables that are likely to have affected the timing and character of settlement in the now partially submerged land that lies between the Lena and Mackenzie Rivers. At a minimum, these variables include changing sea levels and coastlines, advancing and retreating glaciers, changing fauna and flora (including trees), and evolving human adaptations to high‐latitude environments. Humans occupied Beringia during the interval between the end of the Last Glacial Maximum cold peak (ca. 20,000 cal BP) and the beginning of the Holocene (11,600 cal BP), when all of these variables were in an almost constant state of flux.     

Characterization of SNAREs determines the absence of a typical Golgi apparatus in the ancient eukaryote Giardia lamblia

Giardia is a eukaryotic protozoal parasite with unusual characteristics, such as the absence of a morphologically evident Golgi apparatus. Although both constitutive and regulated pathways for protein secretion are evident in Giardia, little is known about the mechanisms involved in vesicular docking and fusion. In higher eukaryotes, soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) of the vesicle-associated membrane protein and syntaxin families play essential roles in these processes. In this work we identified and characterized genes for 17 SNAREs in Giardia to define the minimal set of subcellular organelles present during growth and encystation, in particular the presence or not of a Golgi apparatus. Expression and localization of all Giardia SNAREs demonstrate their presence in distinct subcellular compartments, which may represent the extent of the endomembrane system in eukaryotes. Remarkably, Giardia SNAREs, homologous to Golgi SNAREs from other organisms, do not allow the detection of a typical Golgi apparatus in either proliferating or differentiating trophozoites. However, some features of the Golgi, such as the packaging and sorting function, seem to be performed by the endoplasmic reticulum and/or the nuclear envelope. Moreover, depletion of individual genes demonstrated that several SNAREs are essential for viability, whereas others are dispensable. Thus, Giardia requires a smaller number of SNAREs compared with other eukaryotes to accomplish all of the vesicle trafficking events that are critical for the growth and differentiation of this important human pathogen.     

Fibrin gel-immobilized VEGF and bFGF efficiently stimulate angiogenesis in the AV loop model

The modulation of angiogenic processes in matrices is of great interest in tissue engineering. We assessed the angiogenic effects of fibrin-immobilized VEGF and bFGF in an arteriovenous loop (AVL) model in 22 AVLs created between the femoral artery and vein in rats. The loops were placed in isolation chambers and were embedded in 500 microL fibrin gel (FG) (group A) or in 500 microL FG loaded with 0.1 ng/microL VEGF and 0.1 ng/microL bFGF (group B). After two and four weeks specimens were explanted and investigated using histological, morphometrical, and ultramorphological [scanning electron microscope (SEM) of vascular corrosion replicas] techniques. In both groups, the AVL induced formation of densely vascularized connective tissue with differentiated and functional vessels inside the fibrin matrix. VEGF and bFGF induced significantly higher absolute and relative vascular density and a faster resorption of the fibrin matrix. SEM analysis in both groups revealed characteristics of an immature vascular bed, with a higher vascular density in group B. VEGF and bFGF efficiently stimulated sprouting of blood vessels in the AVL model. The implantation of vascular carriers into given growth factor-loaded matrix volumes may eventually allow efficient generation of axially vascularized, tissue-engineered composites.