Discrete Neurons Research Articles

Distribution and co-localization of calbindin D 28k with VIP and neuropeptide Y but not somatostatin, galanin and substance P in the enteric nervous system of the rat

Calbindin D 28k, previously demonstrated in the mammalian central nervous system, has been localized to discrete neurons in the enteric nervous system of the rat. Calbindin D 28k is present in cell bodies in both the myenteric and submucous plexi and in interganglionic nerve fibers in all regions of the gastrointestinal tract. Immunoreactive nerve fibers were also detected in the mucosal region, although none were observed in the pyloric sphincter, circular or longitudinal muscle layers. The highest concentration of immunoreactivity was present in the submucosal plexus and mucosa of the colon. Western blot analysis of the protein detected by the antiserum confirmed that it comigrated with purified calbindin D 28k and the single immunoreactive band seen in extracts from rat brain. The colocalization of calbindin D 28k with components of the peptidergic innervation was also investigated. Of the peptides studied the neurons containing both vasoactive intestinal polypeptide and neuropeptide Y in the submucous plexus were seen to exhibit calbindin D 28k immunoreactivity. The neurons containing somatostatin, galanin and substance P did not demonstrate co-localization. In the stomach, calbindin D 28k was detected within a small number of epithelial cells which were found to correspond to a sub-population of the somatostatin-immunoreactive endocrine cells.

Regulation of the Drosophila dopa decarboxylase gene in neuronal and glial cells.

A cis-regulatory element selectively required for the Drosophila melanogaster dopa decarboxylase gene (Ddc) in the central nervous system has been identified previously (Scholnick et al. 1986). Here, we show that at least one additional regulatory element is required for normal neuronal expression of Ddc. We find that Ddc is normally expressed in about 125 discrete neurons and in a diffused network comprising a subset of glial cells. The expression of in vitro-altered Ddc genes was studied by immunohistochemistry following germ line reintegration with P-element vectors. Normal neuron-specific Ddc gene expression requires both the initially identified element (element I) which is 60 bp upstream from the RNA start site, and an additional regulatory element located 800-2200 bp upstream. This latter element is required for neuronal expression but is not necessary for glial expression of Ddc. We provide a model to explain how interactions between multiple regulatory elements may serve to specify cell-specific gene expression.

On periodic responses generated by a degenerate analog neuron model with periodic inputs.

Periodic responses to periodically varying stimulating pulse sequences are mathematically described for a degenerate analog neuron model. The model used was derived by Yoshizawa et al. (1982) in their investigation of the state transition of an electronic model using a tunnel diode in a degenerate case. Periodic responses to constant pulse sequences for the model were described by them. In this paper, it is shown that periodic responses to periodically varying pulse sequences for the model are identical with those which the author previously described for a discrete neuron model.

Afferent C-fibres: physiological and biochemical correlations

Immunocytochemistry has uncovered many populations of biochemically discrete neurons throughout the central and peripheral nervous systems. It seemed reasonable to assume that particular biochemical types of neuron would also share morphological and physiological properties, yet the evidence for this is still far from compelling. In the case of primary afferent fibres there are at least four major subgroups of unmyelinated sensory fibres, defined by their cytoplasmic content of various enzymes or peptides, and as many if not more types of receptive field profile. However, to date no direct correlation between physiological and biochemical subtypes has been made. Here we review the evidence for heterogeneity in the biochemical and physiological make-up of C-fibres and attempt to make some correlations.

Neurons of the rat hypothalamus reactive with antisera against endorphins, ACTH, MSH and ?-LPH

In rat brains intraventricularly injected with colchicine, the same discrete neurons of the arcuate and ventromedial nuclei can be stained with antisera against alpha- and beta-endorphins, (1-24)ACTH, (17-39)ACTH, alpha- and beta-MSH, and beta-LPH, as demonstrated by comparative studies in consecutive serial sections. These neurons are strongly reactive with anti-(17-39)ACTH, anti-beta-endorphin, anti-alpha-MSH and anti-beta-MSH, and more faintly stained with anti-alpha-endorphin, anti-beta-LPH and anti-(1-24)ACTH. Exceptionally, neurons reactive with anti-(17-39)ACTH and anti-beta-endorphin are poorly stained or completely negative with anti-alpha-MSH and anti-beta-MSH. Immunoreactive fibers end in the lateral median eminence and in the arcuate nucleus proper, or form ascending pathways along the third ventricle. Comparative studies with other antisera or with the Falck and Hillarp technique show that these neurons differ from the elements producing LH-RH, somatostatin, neurophysin, oxytocin, vasopressin and dopamine. These results suggest that the same neurons of the rat hypothalamus synthesize several neuropeptides identical with or immunologically related to endorphins, ACTH, alpha-MSH and beta-LPH, probably arising from a common precursor molecule similar to that found in the corticotropic cells of the pituitary. These neuropeptides of a common cellular and molecular origin might be involved in basic processes of the central nervous system as neurotramsmitters or neuromodulators.

Infundibular neurons of the human hypothalamus simultaneously reactive with antisera against endorphins, ACTH, MSH and ?-LPH

In man, discrete neurons of the infundibular (arcuate) nucleus contain compounds that can be stained with anti-endorphin (alpha and beta), anti-ACTH, anti-MSH (alpha and beta) and anti-beta-LPH immune sera (I.S.). In the fetus, certain neurons stain with anti-beta-endorphin or anti((17--39)ACTH starting from the 11th week of fetal life. At the ultrastructural level, these neurons contain elementary granules that are immunoreactive with anti-beta-endorphin. In the adult, neurons immunoreactive with anti-beta-endorphin are found in the infundibular nucleus. Their axonal fibers terminate around blood vessels in the neurovascular zone and in the pituitary stalk, or establish contacts with non-immunoreactive perikarya of the infundibular nucleus. These neurons can be stained with anti(17--39)ACTH and anti-beta-endorphin I.S. The most reactive are also stained moderately with anti-alpha-MSH, anti-beta-MSH, anti-beta-LPH, anti-alpha-endorphin, or anti(1--24)ACTH I.S. These results indicate that, in man, compound(s) identical with or immunologically related to endorphins, beta-LPH, ACTH and MSH are secreted by certain hypothalamic neurons. These agents probably originate from a common precursor molecula similar to the so-called pro-opiocortin.

The structure of the terminal ganglionic mass of the locust, Schistocera gregaria (Forskäl).

AbstractSections of the terminal ganglionic mass reveal a neuropile comprising four fused units corresponding to the eighth, ninth, tenth, and eleventh abdominal ganglia. Segmentally arranged groups of interneurons further illustrated the segmental nature of this ganglionic mass. Condensation of the component ganglia has resulted in a reduction in the number of commissures, the eighth ganglion retaining five of the original eight found in a simple ganglion, and each subsequent ganglion retaining four. There is a reduction in the number of discrete neuron groups and in the number of lateral interneurons coincident with the degree of condensation. Associated with the degree of condensation is a relocation of the motor neurons from the lateral ventral regions of the ganglion to the dorsal surface. One‐hundred‐five neurons have been traced within the terminal ganglionic mass.