Effects of Dietary Resistant Starch on the Wnt Signaling Pathway and Preneoplastic Cells in the Colons of Azoxymethane-Treated Rats.

Dietary resistant starch (RS) has been suggested to reduce colonic neoplasia. To determine the effects of digestion-resistant cornstarch on colonic carcinogenesis and Wnt signaling in azoxymethane (AOM)-treated F344 rats, diets containing naturally occurring RS from corn lines derived partially from Guat209 (GUAT), AR16035 (AR), or a hybrid (ARxGUAT), containing 34.5 ± 2.0, 0.2 ± 0.1, and 1.9 ± 0.1% RS, respectively, were fed at 55% of the diet. GUAT-fed rats had increased cecal content and tissue weight and decreased cecal pH compared with AR- or ARxGUAT-fed rats. Numbers of aberrant crypt foci (ACF) were not different among diet groups. Increased numbers of crypts/focus were observed in AOM-injected rats fed GUAT compared with rats fed other diets. ß-catenin mRNA expression of the crypts was significantly increased in GUAT-fed rats injected with AOM relative to those injected with saline. These findings suggest that selected dietary RSs may at some level further enhance colonocyte proliferation and differentiation in an AOM-treated colon.

Effect of environment on resistance to the European corn borer (Lepidoptera: Crambidae) in maize.

The European corn borer, Ostrinia nubilalis (Hübner) (Lepidoptera: Crambidae), is a major pest of maize, Zea mays L., in many temperate parts of the world. Genotype-by-environment interaction effects can make relative performance unpredictable and may hamper selection for resistance to European corn borer. The objective of this study was to determine the effect of environment on genotypic reaction to European corn borer resistance in maize. A set of 12 maize inbred lines was chosen to represent a range of European corn borer responses. Eleven testing environments ranged from Delaware, Ohio, Illinois, Iowa, Nebraska, Missouri, to Mississippi. For length of stalk tunneling, environmental and genotypic main effects (estimated by restricted maximum likelihood) were >20- and 10-fold larger than their interaction effect, respectively. Length of tunneling means for genotypes (across environments) ranged from 10.1 to 35.4 cm. Several putatively resistant genotypes grouped with the susceptible checks, B73 and Mol7. By breaking factors and the interaction into single degree of freedom components, we observed that GEMS-0001 had significant crossover interactions toward less susceptibility in both Mississippi and the Nebraska environments. Environments displaying several crossover interactions indicated that European corn borer screening at these sites would not necessarily apply to other locations, whether due to small differences in experimental conduct and/or environmental effects. The five most resistant genotypes were fairly consistent across environments. Because all environments except Illinois used larvae from the same insectary, and these environments differed in damage intensity and rankings, it is unlikely that insect biotype was a factor contributing to genotype-by-environment effects.