R David Heathcote

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The cellular mechanisms that underlie formation of an autonomic ganglion have been investigated by studying the formation of the cardiac ganglion of the frog. Analysis of the genesis of neurons with [3H]thymidine autoradiography revealed that neuronal precursors do not divide via a "stem cell lineage" but rather divide exponentially, such that both daughter(More)
The development of the parasympathetic cardiac ganglion of the frog Xenopus laevis was marked by the differentiation of a population of adrenergic small intensely fluorescent (SIF) cells. The neural crest contributes precursors for both SIF cells and the well-studied cholinergic cardiac ganglion neurons; this situation provided an opportunity to determine(More)
Dystroglycan is a member of the transmembrane dystrophin glycoprotein complex in muscle that binds to the synapse-organizing molecule agrin. Dystroglycan binding and AChR aggregation are mediated by two separate domains of agrin. To test whether dystroglycan plays a role in receptor aggregation at the neuromuscular junction, we overexpressed it by injecting(More)
Synapse formation involves a large number of macromolecules found in both presynaptic nerve terminals and postsynaptic cells. Many of the molecules involved in synaptogenesis of the neuromuscular junction have been discovered through morphological localization to the synapse and functional cell culture assays, but their role in embryonic development has(More)
During embryonic and larval development of the frog Xenopus laevis, a bilateral population of cerebrospinal fluid-contacting neurons matures in the ventral spinal cord. These cells are catecholaminergic and form a dispersed or nonrandom pattern of spacing within each of their spinal cord columns. In order to test the mechanisms underlying pattern formation(More)
In the frog Xenopus laevis, gamma-aminobutyric acid (GABA)-immunoreactive spinal cord neurons (Kolmer-Agduhr cells) formed a dispersed pattern within two columns on either side of the midline. The cellular pattern became established during embryonic and larval development. The GABA-immunoreactive cells are cerebrospinal fluid (CSF)-contacting neurons that(More)
The differentiation of an identified sensory neuron, the grasshopper wing hinge Stretch Receptor (SR), is examined throughout embryogenesis. The morphological features of the SR axon, as it finds its path from the peripheral cell body to the CNS, and the timing of this peripheral growth were determined by intracellular injection of Lucifer yellow. The(More)
1. During the differentiation of skeletal muscle, there is a synchronized expression of a number of muscle-specific proteins including the acetylcholine-gated ion channel (AChR). Another muscle-specific ion channel, responsible for chloride conductance, was shown to be expressed in an anticoordinate fashion to AChR. An organ culture system for rat lumbrical(More)
During development, spinal cord cells of the frog Xenopus laeuis undergo a reduction in size. This phenomenon occurs during neural tube formation and continues at least until the start of metamorphosis. The number and shape of spinal cord cells also changes, but not always in synchrony with the reduction in cell size. The concomitant change in size and(More)