Figure 1. Negative Regulation of Cell Shape, Motility, and Navigation.

Various experimental examples of negative cellular behaviors and the terms used to describe them (See also Box 1). (a) Regenerating axons (black) grow extensively on some substrates (ventral and dorsal roots) and not others (spinal cord, red). (Lugaro 1906). (b) Cultured cells retract upon contact and change direction. (Weiss 1958). (c) Neuronal fiber extension (black) is inhibited/repelled upon co-culturing in proximity to a tissue explant (red). (Ebendal 1982). (d) Axons (black) circuitously grow away (red) or towards (green) different tissues explants. (Peterson and Crain 1982). (e) Axons (black) avoid substrates (red), a phenomenon that is abolished upon high temperature treatment (heat); revealing that axons grow on certain substrates not because of “attraction”, but because of avoidance of other substrates. (Walter et al. 1987b). (f) A neuronal growth cone (black) collapses/retracts upon contact with an unlike neuronal fiber (red). (Kapfhammer and Raper 1987a).