Microtubule behavior during guidance of pioneer neuron growth cones in situ.

The growth of an axon toward its target results from the reorganization of the cytoskeleton in response to environmental guidance cues. Recently developed imaging technology makes it possible to address the effect of such cues on the neural cytoskeleton directly. Although high resolution studies can be carried out on neurons in vitro, these circumstances do not recreate the complexity of the natural environment.

Pre-axonogenesis migration of afferent pioneer cells in the grasshopper embryo.

In insects, afferent neurons arise primarily from the ectodermal epithelium in the periphery and differentiate at the site of their precursor mitosis. Here we describe ectodermally derived cells that migrate away from their site of origin and initiate axonogenesis at a distant location. In embryonic grasshopper limb buds, the first two pairs of afferents to differentiate are the pair of Ti1 pioneers at the limb tip and the pair of Cx1 cells found at the base of the limb.

Disoriented pathfinding by pioneer neurone growth cones deprived of filopodia by cytochalasin treatment.

A major question in developmental neurobiology is how developing nerve cells accurately extend processes to establish connections with their target cells. This problem involves both the nature of cues for growth cone guidance and also the question of how growth cones survey their environment for cues and respond by altering their direction of migration. The filopodia which normally extend from neuronal growth cones have been shown to affect growth cone steering in vitro and it has been proposed that they function in vivo in the detection of and response to guidance cues.

Embryonic and postembryonic morphogenesis of a grasshopper interneuron.

The object of this study was to describe the embryonic and postembryonic morphogenesis of a grasshopper interneuron in order to determine how, and when, this cell comes to assume its mature form. DCMD is an intensively investigated interneuron whose morphology, input and output physiology, and role in behavior are relatively well-known in the adult. We examined the morphology of DCMD in the brain at each stage of its development with silver-intensified cobalt-fills.

Quantitative staging of embryonic development of the grasshopper, Schistocerca nitens.

During development of the grasshopper embryo, it is feasible to examine the structure, pharmacology, and physiology of uniquely identified cells. These experiments require a fast, accurate staging system suitable for live embryos. We present a system comprising (1) subdivision of embryogenesis into equal periods, (2) expression of stage in percent of complete embryogenesis time, (3) characterization of stages by light micrographs (and descriptive test), and (4) illustration of stages at the egg, embryo, and limb levels of resolution.