Toxicity and Sublethal Effects of Phthalides Analogs to Rhyzopertha dominica

Phthalides and their precursors have demonstrated a large variety of biological activities. Eighteen phthalides were synthesized and tested on the stored grain pest Rhyzopertha dominica. In the screening bioassay, compounds rac‐(2R,2aS,4R,4aS,6aR,6bS,7R)‐7‐bromohexahydro‐2,4‐methano‐1,6‐dioxacyclopenta[cd]pentalen‐5(2H)‐one ( 15 ) and rac‐(3R,3aR,4R,7S,7aS)‐3‐(propan‐2‐yloxy)hexahydro‐4,7‐methano‐2‐benzofuran‐1(3H)‐one ( 17 ) showed mortality similar to the commercial insecticide, Bifenthrin® (≥90 %). The time (LT₅₀) and dose (LD₅₀) necessary to kill 50 % of the R. dominica population were determined for the most efficacious phthalides 15 and 17 . Compound 15 presented the lowest LD₅₀ (1.97 μg g^?1), being four times more toxic than Bifenthrin® (LD₅₀=9.11 μg g^?1). Both compounds presented an LT₅₀ value equal to 24 h. When applied at a sublethal dose, both phthalides (especially compound 15 ), reduced the emergence of the first progeny of R. dominica. These findings highlight the potential of phthalides 15 and 17 as precursors for the development of insecticides for R. dominica control.     

Comparison of polyacrylamide gel electrophoresis (PAGE), immuno-electron microscopy (IEM) and enzyme immunoassay (EIA) for the rapid diagnosis of rotavirus infection in children

Detection of rotavirus RNA by polyacrylamide gel electrophoresis (PAGE) proved to be a highly sensitive and rapid diagnostic test. A comparison of this assay with immuno-electron microscopy (IEM) and enzyme immunoassay (EIA) in 245 faeces from children with gastroenteritis revealed complete agreement between the three assays in 238 (97.14%) samples. Among 75 samples positive in at least one of the three assays, negative results were observed in 5 (6.48%) by PAGE, in 6 (6.76%) by EIA and in none by IEM. Silver staining greatly increased the sensitivity of the PAGE assay. We conclude that although IEM remains the most sensitive and rapid rotavirus diagnostic assay, the PAGE technique has many advantages in its favour, including the non-requirement of expensive equipment, the use of only chemically defined reagents and the capacity to distinguish virus subgroup and variants and to detect non-crossreactive rotaviruses which are missed in serological assays.     

Characterization of polymicrobial biofilms obtained from saliva or carious lesions in dentin

Abstract

This study aimed to compare the formation of polymicrobial biofilms using carious dentin or saliva as inoculum for application in in vitro microbiological studies on caries research. For biofilm growth, combined samples of infected dentin or saliva from three donors were used. The biofilms were grown on glass coverslips, under a regimen of intermittent exposure (6?h day^?1) to 1% sucrose for 4?days. Total bacterial loads, as well as specific aciduric bacteria and mutans streptococci loads were quantified and correlated with biofilm acidogenicity and susceptibility to chlorhexidine. The data were evaluated using the Student’s-t, Mann Whitney and Kruskal-Wallis tests. The two biofilms showed similar microbial loads (total bacteria, aciduric bacteria and mutans streptococci) on day 4, and high acidogenicity after 48?h and were susceptible to chlorhexidine at different time intervals. In conclusion, both dentin and saliva can be used as an inoculum in in vitro studies of processes related to biofilm formation.     

Contributions of climate and Brassica oleracea cultivar to gastropod abundance and assemblage in southeastern Brazil

1. Terrestrial gastropods (slugs and snails, Mollusca: Eupulmonata) are destructive pests of brassica crops. These organisms defoliate plants and contaminate the harvest, leading to reduced crop yield and marketability. Losses caused by molluscs have escalated in recent years in Brazil.
2. We aimed to determine the seasonal activity of gastropods in brassica fields and unravel the environmental variables associated with these dynamics. Gastropod abundance, assemblage and within-plant distribution were also compared among Brassica oleracea cultivars (broccoli, cabbage and cauliflower).
3. Mild temperatures and rainy periods were found to coincide with gastropod peaks. Regression analyses confirmed a positive association of rainfall and humidity with gastropod abundance, whereas gastropod abundance increased with decreasing temperature. Deroceras laeve (Müller) (Agriolimacidae) and Bradybaena similaris (Férussac) (Bradybaenidae) were the most constant species. Mollusc abundance and assemblage differed amid B. oleracea cultivar; cabbage had the highest abundance and its species composition differed from broccoli and cauliflower. Slugs and snails were more concentrated on lower plant portions, regardless of the cultivar.
4. Management efforts should be reinforced in mild-temperature and rainy periods to reduce damage by gastropods, and cabbage should be monitored more closely than other cultivars.

     

Tyrosine 9 is the key amino acid in microcin J25 superoxide overproduction

Escherichia coli microcin J25 (MccJ25) is a lasso-peptide antibiotic comprising 21 l -amino acid residues (G¹-G-A-G-H⁵-V-P-E-Y-F¹⁰-V-G-I-G-T¹⁵-P-I-S-F-Y²⁰-G). MccJ25 has two independent substrates: RNA-polymerase (RNAP) and the membrane respiratory chain. The latter is mediated by oxygen consumption inhibition together with an increase of superoxide production. In the present paper, the antibiotic MccJ25 was engineered by substituting Tyr⁹ or Tyr²⁰ with phenylalanine. Both mutants were well transported into the cells and remained active on RNAP. Only the Y9F mutant lost the ability to overproduce superoxide and inhibit oxygen consumption. The last results confirm that the Tyr⁹, and not Tyr²⁰, is involved in the MccJ25 action on the respiratory chain target.     

Assessing the relative contribution of functional divergence and guild aggregation to overall functional structure of species assemblages

The study of functional structure in species assemblages emphasizes the detection of significant guild aggregation patterns. Thus, protocols based on intensive resampling of empirical data have been proposed to assess guild structure. Such protocols obtain the frequency distribution of a given functional similarity metric, and identify a threshold value (often the 95th percentile) beyond which clusters in a functional dendrogram are considered as significant guilds (using one-tailed tests). An alternative approach sequentially searches for significant differences between clusters at decreasing levels of similarity in a dendrogram until one is detected, then assumes that all subsequent nodes should also be significant. Nevertheless, these protocols do not test both the significance and sign of deviations from random at all levels of functional similarity within a dendrogram. Here, we propose a new bootstrapping approach that: (1) overcomes such pitfalls by performing two-tailed tests for each node in a dendrogram of functional similarity after separately determining their respective sample distributions, and (2) enables the quantification of the relative contribution of guild aggregation and functional divergence to the overall functional structure of the entire assemblage. We exemplify this approach by using long-term data on guild dynamics in a vertebrate predator assemblage of central Chile. Finally, we illustrate how the interpretation of functional structure is improved by applying this new approach to the data set available.     

Parasitoid associated with Liriomyza huidobrensis (Diptera: Agromyzidae) outbreaks in tomato fields in Brazil

1. The knowledge of natural factors that affect pest populations is essential in predicting the occurrence of pest outbreaks and in developing integrated pest management programmes. Natural enemies, climatic elements and host plants are among the most important factors affecting pest dynamics.
2. Tomato (Solanum lycopersicum) is the second most consumed vegetable worldwide. The pea leaf miner Liriomyza huidobrensis (Diptera: Agromyzidae) is a major pest to the tomato in Brazil.
3. This study aimed to determine the main natural factors that regulate L. huidobrensis populations in tomato fields in Brazil.
4. Liriomyza huidobrensis densities were evaluated by directly counting the number of active mines on the basal leaf of the middle section of the plant canopy, and predators and parasitoids were assessed using the leaf‐beating‐against‐a‐tray technique. Eight commercial tomato fields were assessed over two years. The phenological growth stages of the tomato plants (vegetative and reproductive) were noted during the assessments.
5. Liriomyza huidobrensis populations peaked between the middle and end of the planting season.
6. Opius sp. (Hymenoptera: Braconidae) was the main natural enemy of L. huidobrensis.
7. Our results suggest that phenological growth stage and Opius sp. are associated with population dynamics of L. huidobrensis in tomato fields.
8. Therefore, integrated pest management programmes should aim to preserve populations of the parasitoid Opius sp.