Foliar persistence and residual activity of four insecticides of different mode of action on the predator Engytatus varians (Hemiptera: Miridae).

A greenhouse study was conducted to investigate the degradation kinetics of spinosad, flufenoxuron, dimethoate and imidacloprid in tomato (Solanum lycopersicum L.) foliage and their residual toxicity on Engytatus varians (Distant) (Hemiptera: Miridae), a predator of the tomato psyllid Bactericera cockerelli (Sulcer) (Hemiptera: Triozidae). Insecticides were sprayed at 100% and 50% of their maximum field-registered concentrations (MFRC). Starting 6 h after spraying, leaf samples were taken every 10 d for 40 d and analyzed while E. varians adults were exposed to treated leaves to evaluate residual toxicity. Immediately after application at 100% MFRC, the residue concentrations were 73.34 µg g-1 spinosyn A and 59.2 µg g-1 spinosyn D, 9.21 µg g-1 flufenoxuron, 71.49 µg g-1 dimethoate and 31.74 µg g-1 imidacloprid. At 50% MFRC, initial residue concentrations were between 75% and 90% those at 100% MFRC. The estimated half-life (DT50) of spinosyns A and D, flufenoxuron, and dimethoate was between 34 and 40 d, while that of imidacloprid was 112 d. Flufenoxuron caused no mortality, while mortality due to spinosad was less than 10%, and only during the first 10 d. Mortality caused by either imidacloprid or dimethoate was around 100% up to 10 d after application, then decreased to around 30% after 40 d. Dimethoate toxicity was approximately proportional to residue concentration, while for imidacloprid there was an apparent threshold around 15 µg g-1. These results can be used to establish periods harmless for release of E. varians in the control of B. cockerelli on tomato crops under greenhouse conditions.

Lethal and Sublethal Effects on Tamarixia triozae (Hymenoptera: Eulophidae), an Ectoparasitoid of Bactericera cockerelli (Hemiptera: Triozidae), of Three Insecticides Used on Solanaceous Crops.

Lethal and sublethal effects of refined soybean oil, imidacloprid, and abamectin on Tamarixia triozae (Burks; Hymenoptera: Eulophidae) were assessed after exposure of the eggs, larvae, and pupae of this parasitoid to three concentrations of these active substances: the LC50 for fourth-instar Bactericera cockerelli (Sulc.; Hemiptera: Triozidae) and 50% and 100% of the minimum field-registered concentration (MiFRC). Soybean oil caused 26-61% mortality in T. triozae eggs and 6-19% in larvae; mortality in both eggs and larvae was ≤19% for imidacloprid and 4-100% for abamectin. All three compounds caused <18% mortality of T. triozae pupae, with the exception of the abamectin 50% (47%) and 100% (72%) MiFRC. The mortality of larvae and pupae derived from treated eggs was ≤39% for all three insecticides, and that of pupae derived from treated larvae was ≤10%. In general, emergence of adults developed from treated eggs, larvae, and pupae was affected more by abamectin than by the other treatments. The proportion of females derived from all three development stages was not affected by treatment with the compounds, except when the parasitoid was treated as larvae with the soybean oil 100 and 50% MiFRC (66 and 68%, respectively) or when treated as pupae with the imidacloprid LC50 and 100% MiFRC (~60%). Female longevity was generally higher than that of males. The use of imidacloprid, soybean oil, and abamectin in combination with T. triozae for pest control may be effective when the parasitoid is in the pupal stage because this stage is less susceptible than other immature stages.

Long-Chain Omega-3 Fatty Acids Supplementation Accelerates Nerve Regeneration and Prevents Neuropathic Pain Behavior in Mice.

Fish oil (FO) is the main source of long chain omega-3 polyunsaturated fatty acids (ω-3 PUFAs), which display relevant analgesic and anti-inflammatory properties. Peripheral nerve injury is driven by degeneration, neuroinflammation, and neuronal plasticity which results in neuropathic pain (NP) symptoms such as allodynia and hyperalgesia. We tested the preventive effect of an EPA/DHA-concentrate fish oil (CFO) on NP development and regenerative features. Swiss mice received daily oral treatment with CFO 4.6 or 2.3 g/kg for 10 days after NP was induced by partial sciatic nerve ligation. Mechanical allodynia and thermal hypernociception were assessed 5 days after injury. CFO 2.3 g/kg significantly prevented mechanical and thermal sensitization, reduced TNF levels in the spinal cord, sciatic MPO activity, and ATF-3 expression on DRG cells. CFO improved Sciatic Functional Index (SFI) as well as electrophysiological recordings, corroborating the increased GAP43 expression and total number of myelinated fibers observed in sciatic nerve. No locomotor activity impairment was observed in CFO treated groups. These results point to the regenerative and possibly protective properties of a combined EPA and DHA oral administration after peripheral nerve injury, as well as its anti-neuroinflammatory activity, evidencing ω-3 PUFAs promising therapeutic outcomes for NP treatment.

Monitoring of beet armyworm resistance to spinosad and methoxyfenozide in Mexico.

BACKGROUND: Resistance to spinosad and methoxyfenozide has been studied in several insect pests, but there is a lack of information on Spodoptera exigua (Hübner) in Mexico. Therefore, evidence for the development of resistance in this pest to both compounds was examined. The effects of methoxyfenozide on reproductive parameters of S. exigua adults were also determined. RESULTS: Third instars from a field population were exposed for 24 h to the LC(50) of spinosad or methoxyfenozide for over six generations (G(2)-G(7)). No significant reduction in susceptibility to either compound was detected for up to five generations. In G(7), LC(50) values for insects exposed to spinosad and methoxyfenozide were respectively 2.75-fold and 1.25-fold greater than for G(1) larvae. Oral treatment with methoxyfenozide reduced the fecundity and fertility of G(7) adults, confirming sublethal effects on reproduction. Finally, five populations (Se-La Floriza, Se-Lazareto, Se-Bachigualato, Se-Los Agustinos and Se-Villa de Arista) of S. exigua were collected from fields in three states of Mexico for resistance monitoring to spinosad and methoxyfenozide. With the exception of Se-Villa de Arista, the other populations showed significant resistance to spinosad, with resistance ratios between 16- and 37-fold, compared with a susceptible laboratory colony. In contrast, only one population (Se-Lazareto) showed significant resistance to methoxyfenozide (13-fold). CONCLUSION: Resistance management programmes should be established, particularly in areas where S. exigua has developed resistance to spinosad.

High- and low-frequency transcutaneous electrical nerve stimulation delay sciatic nerve regeneration after crush lesion in the mouse.

The stimulation of peripheral nerve regeneration has been studied in different ways, including the use of electrical fields. The capacity of this modality to enhance nerve regeneration is influenced by the parameters used, including current type, frequency, intensity, and means of administration. Transcutaneous electrical nerve stimulation (TENS) is a frequently used form of administering electrical current to the body, but its effects on peripheral nerve regeneration are not known. This study assessed the influence of TENS on sciatic nerve regeneration, using a model of crush lesion in the mouse. Mice were stimulated 30 min a day, 5 days a week, for 5 weeks with both high- (100 Hz) and low- (4 Hz) frequency TENS. Control animals had the sciatic nerve crushed but were not stimulated. Assessment was performed weekly by functional analysis using the Static Sciatic Index for the mouse and at the end of the experiment by light and electron microscopy. The results showed that although there were no differences between the groups regarding the Static Sciatic Index values, TENS led to nerves with morphological signs of impaired regeneration. At light microscopy level, TENS nerves presented more axons with dark axoplasm, signs of edema, and a less organized cytoarchitecture. Electronmicrographs showed fewer and thinner thick myelinated fibers and increased number of Schwann cell nuclei. Myelinated axon diameters and density and diameter of nonmyelinated fibers were not affected by TENS, leading to the conclusion that this regimen of electrical stimulation leads to a delayed regeneration after a crush lesion of the sciatic nerve in the mouse. All these effects were more pronounced on high-frequency TENS nerves.

Amyloidogenicity and cytotoxicity of recombinant mature human islet amyloid polypeptide (rhIAPP).

Pancreatic amyloid plaques formed by the pancreatic islet amyloid polypeptide (IAPP) are present in more than 95% of type II diabetes mellitus patients, and their abundance correlates with the severity of the disease. IAPP is currently considered the most amyloidogenic peptide known, but the molecular bases of its aggregation are still incompletely understood. Detailed characterization of the mechanisms of amyloid formation requires large quantities of pure material. Thus, availability of recombinant IAPP in sufficient amounts for such studies constitutes an important step toward elucidation of the mechanisms of amyloidogenicity. Here, we report, for the first time, the successful expression, purification and characterization of the amyloidogenicity and cytotoxicity of recombinant human mature IAPP. This approach is likely to be useful for the production of other amyloidogenic peptides or proteins that are difficult to obtain by chemical synthesis.