Duncan K Stuart

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Central nervous system (CNS) in leech comprises segmentally iterated progeny derived from five embryonic lineages (M, N, O, P and Q). Segmentation of the leech CNS is characterized by the formation of a series of transverse fissures that subdivide initially continuous columns of segmental founder cells in the N lineage into distinct ganglionic primordia. We(More)
1. The activity of units in the auditory system of alert, freely moving rats was studies during the acquisition and extinction of a tone-signaled, appetitive classically conditioned response. Responses of neurons in inferior colliculus (N = 28), medial geniculate (N = 32), posterior nucleus of thalamus (N = 28), pretectal region (N = 19), and cortex (N =(More)
We have investigated the development of neurotransmitter metabolism in embryos of the glossiphoniid leech Haementeria ghilianii. The neurotransmitter content of dissected embryonic tissues was measured by means of radioenzymatic assays, while the presence of neurotransmitters in individual identified neurons was detected by means of immunocytochemical and(More)
In the metameric CNS of leeches, identified neurons occupy highly stereotyped positions in each segmental ganglion. Although many of the neural precursor cells arise near their definitive positions, some arise outside the prospective domain of the segmental ganglia and thus must migrate into the CNS. Here, we report the results of an analysis of the role of(More)
The nervous system of the glossiphoniid leech includes segmentally iterated neurons that contain serotonin (5-HT) and dopamine. These have been investigated in Helobdella triserialis, Theromyzon rude, and Haementeria ghilianii. Five types of 5-HT neurons are identified by immunocytochemistry in the abdominal ganglia of the ventral nerve cord: the(More)
1. Radiolabeled peptides released from an isolated cluster of bag cell neurons, during an after discharge, were compared with the polypeptide egg-laying hormone (ELH), 4,500 daltons, pI 9.0-9.3, as purified from homogenates of bag cell clusters. A peptide, labeled with methionine, leucine, and arginine, which is selectively released from after discharging(More)
The responses of 35 inferior colliculus multiple units (MUs) to tone onset were measured in 10 freely moving rats before and after differential behavioral conditioning. MU response changes were found in the 16.8 msec after tone onset (includes 2 msec air travel time) after learning. Responses to CS+ onset increased in 12 of the 35 individual MUs, and in the(More)
1. Egg-laying hormone (ELH) is a polypeptide of about 4,500 mol wt synthesized in the bag cell neurons of the abdominal ganglion of Aplysia. We studied the effects of ELH on the neuronal activity of the attached head ganglia (buccal, cerebral, pleural, and pedal), on the isolated buccal ganglia, as well as on feeding in intact Aplysia. 2. Starved animals (n(More)
The leech nervous system comprises a relatively simple network of longitudinal (connective) and transverse (segmental) nerves. We have followed the normal pattern of axon development in the glossiphoniid leech Theromyzon rude by immunostaining embryonic preparations with antibody to acetylated alpha-tubulin. The dependence of the normal pattern of axon(More)
In embryos of leeches (phylum Annelida), metameric structures arise sequentially from a germinal plate comprising the descendants of five pairs of embryonic stem cells called teloblasts. It has been shown that transverse stripes of cells expressing ht-en (a homolog of engrailed, a Drosophila segment polarity gene), arise in the germinal plate prior to the(More)