Spatial distribution of Aphis glycines (Hemiptera: Aphididae): a summary of the suction trap network.

The soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), is an economically important pest of soybean, Glycine max (L.) Merrill, in the United States. Phenological information of A. glycines is limited; specifically, little is known about factors guiding migrating aphids and potential impacts of long distance flights on local population dynamics. Increasing our understanding of A. glycines population dynamics may improve predictions of A. glycines outbreaks and improve management efforts. In 2005 a suction trap network was established in seven Midwest states to monitor the occurrence of alates. By 2006, this network expanded to 10 states and consisted of 42 traps. The goal of the STN was to monitor movement of A. glycines from their overwintering host Rhamnus spp. to soybean in spring, movement among soybean fields during summer, and emigration from soybean to Rhamnus in fall. The objective of this study was to infer movement patterns of A. glycines on a regional scale based on trap captures, and determine the suitability of certain statistical methods for future analyses. Overall, alates were not commonly collected in suction traps until June. The most alates were collected during a 3-wk period in the summer (late July to mid-August), followed by the fall, with a peak capture period during the last 2 wk of September. Alate captures were positively correlated with latitude, a pattern consistent with the distribution of Rhamnus in the United States, suggesting that more southern regions are infested by immigrants from the north.

Potential of suction traps as a monitoring tool for Aphis glycines (Hemiptera: Aphididae) in soybean fields.

The current study evaluated the potential of using counts of winged adults captured in suction traps to forecast the local abundance of soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), in soybean, Glycine max (L.) Merr., fields. The abundance of aphids was evaluated weekly by sampling plants in four to 11 soybean fields and recording the number of aphids in suction traps between 2006 and 2008 in four counties in Indiana and Illinois. Fields in each county were located within 10 km of their respective suction trap, which allowed us to evaluate the relation between aphid abundance on soybean plants and in suction traps at the county level. Migrant soybean aphids caught in suction traps exhibited distinct seasonal trends each year: in 2006, trapped migrants consisted predominantly of individuals dispersing from soybean to buckthorn (Rhamnus sp.); in 2007, in contrast, the majority of trapped migrants were apparently individuals dispersing among soybean fields. The cumulative number of aphids captured in suction traps was positively related to aphid densities on soybean plants. However, the utility of suction traps as a monitoring tool may be limited by the variation in temporal patterns observed in suction traps and on soybean plants each year, and the spatial variation in aphid abundance among soybean fields within a county.

A regional initiative to improve cleaning of high-touch surfaces in long-term care facilities.

A total of 38 long-term care facilities within a region participated in a 3-month quality improvement initiative focused on environmental cleaning and disinfection. Significant improvements in daily and discharge cleaning were observed during the project period. Further study of the sustainability and clinical impact of this type of initiative is warranted.

Counties not countries: Variation in host specificity among populations of an aphid parasitoid.

Parasitic wasps are among the most species-rich groups on Earth. A major cause of this diversity may be local adaptation to host species. However, little is known about variation in host specificity among populations within parasitoid species. Not only is such knowledge important for understanding host-driven speciation, but because parasitoids often control pest insects and narrow host ranges are critical for the safety of biological control introductions, understanding variation in specificity and how it arises are crucial applications in evolutionary biology. Here, we report experiments on variation in host specificity among 16 populations of an aphid parasitoid, Aphelinus certus. We addressed several questions about local adaptation: Do parasitoid populations differ in host ranges or in levels of parasitism of aphid species within their host range? Are differences in parasitism among parasitoid populations related to geographical distance, suggesting clinal variation in abundances of aphid species? Or do nearby parasitoid populations differ in host use, as would be expected if differences in aphid abundances, and thus selection, were mosaic? Are differences in parasitism among parasitoid populations related to genetic distances among them? To answer these questions, we measured parasitism of a taxonomically diverse group of aphid species in laboratory experiments. Host range was the same for all the parasitoid populations, but levels of parasitism varied among aphid species, suggesting adaptation to locally abundant aphids. Differences in host specificity did not correlate with geographical distances among parasitoid populations, suggesting that local adaption is mosaic rather than clinal, with a spatial scale of less than 50 kilometers. We sequenced and assembled the genome of A. certus, made reduced-representation libraries for each population, analyzed for single nucleotide polymorphisms, and used these polymorphisms to estimate genetic differentiation among populations. Differences in host specificity correlated with genetic distances among the parasitoid populations.

Voracity and prey preference of insidious flower bug (hemiptera: anthocoridae) for immature stages of soybean aphid (hemiptera: aphididae) and soybean thrips (thysanoptera: thripidae).

The generalist predator, Orius insidiosus (Say), is an important natural enemy of the soybean aphid, Aphis glycines Matsumura. Soybean thrips, Neohydatothrips variabilis (Beach), serve as an important prey resource for O. insidiosus in soybeans, sustaining the predator's population before the arrival of the soybean aphid. Although generalist predators can forage on a broad range of prey, they may show distinct preferences for particular prey, attacking prey at levels disproportionate to their relative numbers. To assess the preference of O. insidiosus for soybean aphid and soybean thrips, attack rates of nymphal and adult O. insidiosus were measured in the laboratory. For both adults and nymphs, the number of prey attacked increased as more prey were provided. For nymphs, the total number of prey attacked increased as the predator matured. In general, the number of prey attacked by adult predators was relatively constant as the predator aged. Both O. insidiosus nymphs and adults displayed a preference for soybean thrips, by disproportionately attacking soybean thrips over soybean aphid regardless of the relative densities of the two prey. We discuss implications of this preference on O. insidiosus life history characteristics and the potential impact on O. insidiosus-prey dynamics in the field.

"Engage" therapy: Prediction of change of late-life major depression.

OBJECTIVE: Engage grew out of the need for streamlined psychotherapies that can be accurately used by community therapists in late-life depression. Engage was based on the view that dysfunction of reward networks is the principal mechanism mediating depressive symptoms. Accordingly, Engage uses "reward exposure" (exposure to meaningful activities) and assumes that repeated activation of reward networks will normalize these systems. This study examined whether change in a behavioral activation scale, an index of reward system function, predicts change in depressive symptomatology. METHODS: The participants (N = 48) were older adults with major depression treated with 9 weekly sessions of Engage and assessed 27 weeks after treatment. Depression was assessed with the 24-item Hamilton Depression Rating Scale (HAM-D) and behavioral activation with the four subscales of Behavioral Activation for Depression Scale (activation, avoidance/rumination, work impairment, social impairment) at baseline, 6 weeks (mid-treatment), 9 weeks (end of treatment), and 36 weeks. RESULTS: Change only in the Activation subscale during successive periods of assessment predicted depression severity (HAM-D) at the end of each period (F1, 47 = 21.05, p<0.0001). An increase of one standard deviation in the Activation score resulted in a 2.04 (95% CI: 1.17-2.92) point decrease in HAM-D. For every one point increase in the Activation score, HAM-D was decreased by 0.22 points (95% CI: 0.12-0.31). LIMITATIONS: No comparison group. Partial overlap of Activation Subscale with HAM-D, lack of detailed neurocognitive assessment and social support. CONCLUSION: Change in behavioral activation predicts improvement of depressive symptoms and signs in depressed older adults treated with Engage.

Soybean plant stage and population growth of soybean aphid.

The soybean aphid, Aphis glycines Matsumura, is a newly invasive species of aphid in North America. Previous studies disagree as to whether soybean, Glycine max (L.) Merr., plant stage has an impact on aphid intrinsic rate of increase. Therefore, the growth rate of soybean aphids on soybean plants of different stages was examined at two different scales in the field. A planting date experiment was used to measure the population growth of soybean aphids on plants of different stages. Clip-cages were used to measure life history characteristics of individual aphids on plants of different stages. No differences were found in the population growth or dynamics of soybean aphids in the planting date experiment. The life history characteristics of individual aphids also showed no significant difference when feeding on different growth stages of soybean plants. The impact of these findings on soybean aphid management is discussed and the possible reasons why the results differ from previous estimates of the aphid growth-plant stage relationship are considered.

Impact of developmental maturity of soybean on the seasonal abundance of soybean aphid (Hemiptera: Aphididae).

The soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), alternates between a primary overwintering host (buckthorn, Rhamnus sp.) and a secondary summer host (soybean, Glycine max). Selection of soybean cultivars with different maturity groups may provide growers with a management tool for A. glycines, either directly through its effect on summer populations that cause economic damage or indirectly through its effect on the production of migrants that disperse to the primary host in fall. This study investigated the abundance and seasonality of A. glycines on soybean cultivars with different maturity rates in central Indiana. The abscission of soybean foliage occurred earlier for early maturing than late maturing cultivars, but no other consistent difference in development or yield was detected among the cultivars tested in this study. The abundance of aphids did not vary consistently among cultivars when soybean was most susceptible to economic damage. A laboratory assay evaluating the larviposition preference of A. glycines alate females, combined with a 7-yr survey documenting the colonization of buckthorn by winged aphids, indicated that the production of gynoparae on soybean began in mid-September and continued until leaf abscission. The abundance of aphids during this period was higher on late maturing cultivars than on early maturing cultivars in both 2006 and 2008, whereas no significant effect was detected in 2007. Altogether, these results suggest that planting early maturing soybean cultivars has little effect on damage by aphids on the current season crop but may reduce the number of fall migrants to the primary host.

Tracking the role of alternative prey in soybean aphid predation by Orius insidiosus: a molecular approach.

The soybean aphid, Aphis glycines (Hemiptera: Aphididae), is a pest of soybeans in Asia, and in recent years has caused extensive damage to soybeans in North America. Within these agroecosystems, generalist predators form an important component of the assemblage of natural enemies, and can exert significant pressure on prey populations. These food webs are complex and molecular gut-content analyses offer nondisruptive approaches for examining trophic linkages in the field. We describe the development of a molecular detection system to examine the feeding behaviour of Orius insidiosus (Hemiptera: Anthocoridae) upon soybean aphids, an alternative prey item, Neohydatothrips variabilis (Thysanoptera: Thripidae), and an intraguild prey species, Harmonia axyridis (Coleoptera: Coccinellidae). Specific primer pairs were designed to target prey and were used to examine key trophic connections within this soybean food web. In total, 32% of O. insidiosus were found to have preyed upon A. glycines, but disproportionately high consumption occurred early in the season, when aphid densities were low. The intensity of early season predation indicates that O. insidiosus are important biological control agents of A. glycines, although data suggest that N. variabilis constitute a significant proportion of the diet of these generalist predators. No Orius were found to contain DNA of H. axyridis, suggesting intraguild predation upon these important late-season predators during 2005 was low. In their entirety, these results implicate O. insidiosus as a valuable natural enemy of A. glycines in this soybean agroecosystem.

The structure of Cryptococcus neoformans thymidylate synthase suggests strategies for using target dynamics for species-specific inhibition.

The ternary complex crystal structures of Cryptococcus neoformans and Escherichia coli thymidylate synthase (TS) suggest mechanisms of species-specific inhibition of a highly conserved protein. The 2.1 Angstrom structure of C. neoformans TS cocrystallized with substrate and the cofactor analog CB3717 shows that the binding sites for substrate and cofactor are highly conserved with respect to human TS, but that the structure of the cofactor-binding site of C. neoformans TS is less constrained by surrounding residues. This feature might allow C. neoformans TS to form TS-dUMP-inhibitor complexes with a greater range of antifolates than human TS. 3',3''-Dibromophenol-4-chloro-1,8-naphthalein (GA9) selectively inhibits both E. coli TS and C. neoformans TS (K(i) = 4 microM) over human TS (K(i) >> 245 microM). The E. coli TS-dUMP-GA9 complex is in an open conformation, similar to that of the apoenzyme crystal structure. The GA9-binding site overlaps the binding site of the pABA-glutamyl moiety of the cofactor. The fact that human apoTS can adopt an unusual fold in which the GA9-binding site is disordered may explain the poor affinity of GA9 for the human enzyme. These observations highlight the critical need to incorporate multiple target conformations in any computational attempt to facilitate drug discovery.

Some fundamental issues with non-inferiority testing in active controlled trials.

In an active controlled non-inferiority trial without a placebo arm, it is often not entirely clear what the primary objective is. In many cases the considered goal is to demonstrate that the experimental treatment preserves at least some fraction of the effect of the active control. The active control effect is a parameter, the value of which is unknown. To test the hypothesis of effect preservation, the classical confidence interval approach requires specification of a non-inferiority margin which is a function of the unknown active control effect. When the margin is estimated, it is also not clear what is the relevant type I error of making a false assertion about preservation of the active control effect. The statistical uncertainty of the estimated margin arguably needs to be incorporated in evaluation of the type I error. In this paper we discuss these fundamental issues. We show that the classical confidence interval approach cannot attain the target type I error exactly since this error varies as the sample size or as the values of the nuisance parameters in the active controlled trial change. In contrast, the preservation tests, as proposed in literature, can attain the target type I error rate exactly, regardless of the sample size and the values of the nuisance parameters, but can do so only at the price of several strong assumptions holding that may not be directly verifiable. One assumption is the constancy condition holding whereby the effect of the active control in the historical trial populations is assumed to carry to the population of the active control trial. When this condition is violated, both the confidence interval approach and the preservation test method may be problematic.

Phylogenetic classification of protozoa based on the structure of the linker domain in the bifunctional enzyme, dihydrofolate reductase-thymidylate synthase.

We have determined the crystal structure of dihydrofolate reductase-thymidylate synthase (DHFR-TS) from Cryptosporidium hominis, revealing a unique linker domain containing an 11-residue alpha-helix that has extensive interactions with the opposite DHFR-TS monomer of the homodimeric enzyme. Analysis of the structure of DHFR-TS from C. hominis and of previously solved structures of DHFR-TS from Plasmodium falciparum and Leishmania major reveals that the linker domain primarily controls the relative orientation of the DHFR and TS domains. Using the tertiary structure of the linker domains, we have been able to place a number of protozoa in two distinct and dissimilar structural families corresponding to two evolutionary families and provide the first structural evidence validating the use of DHFR-TS as a tool of phylogenetic classification. Furthermore, the structure of C. hominis DHFR-TS calls into question surface electrostatic channeling as the universal means of dihydrofolate transport between TS and DHFR in the bifunctional enzyme.