Age- and time interval-specific gamma radiation-induced DNA damage in adult maize weevils, Sitophilus zeamais Motschulsky, assessed using comet assays.

The gamma radiation-induced DNA damage in adult maize weevils, Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae), was assessed using single-cell electrophoresis (comet assay). Analysis of DNA damage following 0.5 and 1.0 kGy of gamma radiation was performed using cells from 1- and 15-day-old adults. Gamma-irradiated adults from both age groups showed typical DNA fragmentation, whereas cells from non-irradiated adults showed more intact DNA than young S. zeamais. Investigations using the comet assay showed that tail length, % tail DNA and % DNA damage all increased in adults of both age groups when compared to the control insects. A maximum comet length of 227.33 µm was recorded for 15-day-old adults at 24h after irradiation with 1.0 kGy and a minimum of 50.12 µm for 1-day-old adults at 0 h after irradiation with 0.5 kGy. The percentage of DNA damage increased up to 57.31% and 68.15% for 1- and 15-day-old adults, respectively, at 24h after irradiation with 1.0 kGy, whereas only 8.58% and 12.22% DNA damage were observed in the control batches. The results also showed that percentage of DNA damage increased at 24h after irradiation compared to that at 0 h. However, further studies are needed to confirm these results.

Detection of gamma radiation-induced DNA damage in maize weevil, Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae) assessed using the comet assay.

PURPOSE: The Deoxyribonucleic Acid (DNA) Comet assay, being a quick, simple, sensitive, reliable and fairly inexpensive method for measuring DNA strand breaks, has been used to assess DNA damage caused by gamma radiation in developmental stages of maize weevil Sitophilus zeamais Motschulsky. MATERIALS AND METHODS: An analysis of DNA damage following gamma radiation ((60)Cobalt) treatments at a dose of 0.5 and 1.0 kGy (Kilo Gray) has been carried out with cells obtained from the larvae, pupae and adults of S. zeamais. RESULTS: Gamma radiation induced significant damage at DNA level in the experimental larvae, pupae and adults as manifested by increased strand breaks compared to intact cells from non-irradiated ones. Comet assay revealed that tail length and % tail DNA varied significantly for all developmental stages of S. zeamais. CONCLUSIONS: This study suggests that the comet assay would be a potentially useful tool for detecting DNA damage in insect pest control strategies due to its advantages in the requirement of small numbers of cells per sample and sensitivity in detecting low levels of DNA damage.

Infestation and development of Sitophilus spp. in pouch-packaged spaghetti in Japan.

Infestation of pouch-packaged spaghetti by Sitophilus oryzae (L.) (Coleoptera: Curculionidae) was observed in Japan in May 2006. It was suggested that 30% of all shipped pasta products sustain damage to the packages heat-sealed before reaching retail stores. Hence, we investigated the mechanisms by which S. oryzae and Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae) adults invade pasta packaged in polypropylene pouches. In the damaged packages, both species entered through the breaks in the seal and laid their eggs on the pasta. However, in the intact packages, the adults of both species bit around air vent holes in the film, but they did not make the holes big enough for entry into the pouch. We also compared each species' developmental periods from oviposition to emergence in pasta and brown rice (Oryza spp.). The average developmental period of both species at 25 degrees C was shorter in rice than in pasta. The number of individuals emerging from brown rice was significantly higher than that from pasta. Finally, we suggested a measure to prevent infestation by insect pests in pouch-packaged pasta products.

Soft-electron beam and gamma-radiation sensitivity and DNA damage in phosphine-resistant and -susceptible strains of Rhyzopertha dominica.

The soft-electron beam (low-energy electrons) and gamma-radiation sensitivities of phosphine-resistant (PHR) and -susceptible (PHS) strains of adults lesser grain borer Rhyzopertha dominica (F.) were studied, with particular reference to DNA damage assessed using single-cell electrophoresis (comet assay). Results showed that mortality in adult R. dominica varied significantly between both PHR and PHS strains. Adults of the PHR strain were found to be more tolerant toward soft-electron and gamma radiation than adults of the PHS strain. Studies on the longevity of strains showed that mean survival time and dose rate were highly correlated with both strains and treatments. Results also showed that adults of the PHR strain lived longer than adults of PHS strain for both treatments. Radiation sensitivity indices, however, decreased as radiation dose increased in both strains. Analysis of DNA damage, after 40- and 160-Gy gamma radiation, was carried out using cells obtained from both strains. Gamma-irradiated adults of both strains showed typical DNA fragmentation, compared with cells from nonirradiated adults, which showed more intact DNA. Investigations using the comet assay showed that tail length, moment, olive-tail moment, percentage of tail DNA, and percentage of DNA damage were all greater in the PHS strain compared with the PHR strain and the control insects. Results also showed that DNA damage remained at a constant level for up to 24 h after irradiation. The results have been discussed in relation to the observed strain differences in radiation sensitivity and resistance to phosphine.

Effect of risk information exposure on consumers' responses to foods with insect contamination.

This study explores the impact that scientific information about insect contamination of food has on consumer perceptions. Participants (n = 320, Japanese consumers) were randomly assigned to 1 of 8 information-type conditions: (1) information about insect type, (2) information about contamination processes, (3) information about the safety of contaminated food, (4, 5, 6) combinations of 2 of (1), (2), and (3) above, (7) all information, and (8) no-information, and asked to rate their valuation, behavioral intention, and attitude toward food with insect contamination. Results demonstrated that some combinations of scientific information that include the safety of the contaminated food are effective to reduce consumers' compulsive rejection of insect contamination in food, whereas the single presentation of information about insect type increases consumers' explicit rejection of both the contaminated product and the manufacturer. These findings have implications for the coordination of risk communication strategies.

Avidin expressed in transgenic rice confers resistance to the stored-product insect pests Tribolium confusum and Sitotroga cerealella.

Rice (Oryza sativa var. Nipponbare) was transformed with an artificial avidin gene. The features of this construct are as follows: (1) a signal peptide sequence derived from barley alpha amylase was added at the N-terminal region, (2) codon usage of the gene was optimized for rice, and (3) the gene was driven by rice glutelin GluB-1, an endosperm-specific promoter. Avidin was produced in the grain of the transgenic rice but not in the leaves. The concentration of avidin in the kernels was about 1,800 ppm. All larvae of the confused flour beetle (Tribolium confusum) and Angoumois grain moth (Sitotroga cerealella) died when fed transgenic avidin rice powder or kernels, respectively, whereas most of the test insects developed into adults when they were fed a nontransgenic rice control diet. Avidin extracted from the transgenic rice kernel lost most biotin-binding activity after 5 min heating at 95 degrees C.