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To evaluate the relationship between the occurrence of split-hull paddies and incidence of pecky rice damage caused by two mirid pests, Stenotus rubrovittatus（Matsumura）（Heteroptera: Miridae）and Trigonotylus caelestialium（Kirkaldy）（Heteroptera: Miridae）, among eight rice varieties, we conducted release experiments in a greenhouse. For each variety, we released a male and female pair of adult mirids onto a rice panicle for 3 days with three replications. By examining the correlation between the percentage of split-hull paddies and the pest species to the incidence of pecky rice damage, only the percentage of split rice hulls was significant. There was no pest species effect, indicating adults of the two species examined have a similar potential to cause pecky rice damage. Thus, the number of split-hull paddies and the level of pecky rice damage caused by adults of the two mirid pests were related regardless of the rice variety. Further studies are needed to predict pecky rice damage caused by the two mirids in the field, because the abundance of both adults and nymphs of T. caelestialium are known to be related to the level of pecky rice damage. [ABSTRACT FROM AUTHOR]

The first-pass hydrolysis of oral ester-type prodrugs in the liver and intestine is mediated mainly by hCE1 and hCE2 of the respective predominant carboxylesterase (CES) isozymes. In order to provide high blood concentrations of the parent drugs, it is preferable that prodrugs are absorbed as an intact ester in the intestine, then rapidly converted to active parent drugs by hCE1 in the liver. In the present study, we designed a prodrug of fexofenadine (FXD) as a model parent drug that is resistant to hCE2 but hydrolyzed by hCE1, utilizing the differences in catalytic characteristics of hCE1 and hCE2. In order to precisely predict the intestinal absorption of an FXD prodrug candidate, we developed a novel high-throughput system by modifying Caco-2 cells. Further, we evaluated species differences and aging effects in the intestinal and hepatic hydrolysis of prodrugs to improve the estimation of in vivo first-pass hydrolysis of ester-type prodrugs. Consequently, it was possible to design a hepatotropic prodrug utilizing the differences in tissue distribution and substrate specificity of CESs. In addition, we successfully established three useful in vitro systems for predicting the intestinal absorption of hCE1 substrate using Caco-2 cells. However, some factors involved in estimating the bioavailability of prodrugs in human, such as changes in recognition of drug transporters by esterification, and species differences of the first-pass hydrolysis, should be comprehensively considered in prodrug development.