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We have examined the function of beta1 integrin receptors and N-cadherin in the development of the Xenopus retinotectal projection. In vivo perturbation experiments were performed by injecting antibodies directed against beta1 integrin receptors and N-cadherin into the embryonic optic pathway. The antibodies were present during the initial development of the retinal projection, when the axons of the ganglion cells are migrating through the optic tract and terminating within the optic tectum. When injected individually, the antibodies were insufficient to cause obvious pathfinding errors. However, when injected together, the antibodies caused specific abnormalities in the development of the retinotectal projection. Pathfinding errors most commonly observed included ectopically projecting axons within the optic tract region, meandering and splaying of axons in the optic tectum, and the induction of prominent ipsilateral projections. IgGs and Fab' fragments of the antibodies produced pathfinding errors; these defects were not observed in animals injected with control antibodies. These in vivo results show that beta1 integrin receptors and N-cadherin have important roles during the development of the visual projection and provide evidence that a balance between cell-cell and cell-matrix adhesion may be critical for the normal development of the vertebrate visual system.

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Ken Stone conducted the first study of WalMart stores’ economic impact in Iowa in 1988. Since then, research on WalMart’s impacts has exploded. Recent studies employ sophisticated statistical techniques to more accurately measure the size and direction of effects. Many reach conclusions similar to Stone’s original work. This article updates the original Stone study with additional years of data. It draws on recent methodological advances to help account for the effects of WalMart’s strategic location decisions on estimated retail sales in Iowa. As is consistent with previous studies, we find that WalMart’s entry into smaller trade centers in Iowa had a big initial impact on host-town retail sales, with some categories experiencing significant increases while others saw declines in sales per capita. WalMart’s presence helped stabilize or even expand the local retail sector of most rural Iowa host communities. To conclude, we discuss policy implications for local economic development officials.