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W B Stallcup

Publications and source records attributed to W B Stallcup.

At least 73 records · Page 4Linked to original sources
PubMed1981

Two types of potassium channels in the PC12 cell line.

Activation of K+ channels in the PC12 cell line was studied by comparing 86Rb+ efflux under depolarizing and non-depolarizing conditions. Evidence for both Ca2+-dependent and voltage-dependent K+ channels was obtained by studying depolarization-induced 86Rb+ efflux in solutions of varying Ca2+ concentration and in the presence of K+ and Ca2+ channel blocking agents.

Adrenal Gland Neoplasms↗
PubMed1980

Binding properties of a neurotoxin from the venom of the green mamba, Dendroaspis viridis.

A toxin, alpha-mambatoxin, was purified from the venom of the green mamba Dendroaspis viridis using the procedures of Shipolini et al. (Shipolini, R. A., Bailey, G. S., Edwardson, J. A., and Banks, E. C. (1973) Eur. J. Biochem. 40, 337-344). The purified toxin blocks agonist-induced activation of acetylcholine receptors on muscle cells but, like alpha-bungarotoxin, it does not affect agonist-induced activation of receptors on a clonal sympathetic nerve cell line (PC12), an endothelial cell line, cultured chick ciliary ganglion neurons, or frog cardiac ganglion neurons. The toxin does block binding of alpha-bungarotoxin to cultures of muscle and nerve, and iodinated alpha-mambatoxin binds to cultures of muscle and nerve. The alpha-mambatoxin binding component on muscle was identified as acetylcholine receptor on the basis of sedimentation, immunoprecipitation, and rate of degradation. The alpha-mambatoxin binding component on PC12 cells, like the alpha-bungarotoxin binding component on these cells, is not recognized by anti-acetylcholine receptor antisera which do recognize acetylcholine receptor on these cells. The number of alpha-mambatoxin binding sites on both nerve and muscle when assayed in situ is twice that of alpha-bungarotoxin binding sites. However, when muscle cells are solubilized in nonionic detergents and then labeled with toxins, the number of alpha-mambatoxin binding sites is reduced and the two toxins bind in equal molar amounts. Finally, unlike alpha-bungarotoxin, which dissociates from complexes formed with nerve, alpha-mambatoxin forms complexes with nerve which dissociate only very slowly if at all.

Animals↗
PubMed1980

Substance P enhances cholinergic receptor desensitization in a clonal nerve cell line.

Substance P inhibits carbamylcholine-induced 22Na+ uptake in the clonal cell line PC12. This inhibition is noncompetitive with agonist but competitive with Na+. Octahydrohistrionicotoxin (H8-HTX) also exhibits this same pattern of inhibition. Moreover, both substance P and H8-HTX are very effective in enhancing agonist-induced receptor desensitization. Local anesthetics, such as QX222, also cause inhibition that is competitive with Na+, but they have only marginal effects on desensitization. Because substance P and H8-HTX cannot by themselves cause desensitization, their action is dependent on and synergistic with the action of agonist. Furthermore, substance P and H8-HTX do not appear to compete for the same site as QX222, which is thought to bind to the ion channel. Finally, substance P can stabilize the desensitized state of the receptor even when added subsequent to the actual desensitization and removal of agonist. Thus, substance P does not require open ion channels for binding and may modulate the activity of the receptor-ionophore complex by binding to a distinct regulatory site.

Amphibian Venoms↗
PubMed1979

Sodium and calcium fluxes in a clonal nerve cell line.

1. 22Na+ and 45Ca2+ fluxes were studied in the clonal nerve cell line PC12. Three distinct types of ion channels were found: (a) voltage-dependent Na+ channels, (b) voltage-dependent Ca2+ channels, and (c) acetylcholine-activated channels permeable to both ions. 2. 22Na+ uptake through voltage-dependent Na+ channels is induced by veratridine and scorpion venom, and is inhibited 50% by 5 X 10(-7) M-tetrodotoxin and greater than 98% by 5 X 10(-6) M-tetrodotoxin. 3. 45Ca2+ uptake through voltage-dependent Ca2+ channels is induced by depolarizing the cells in 50 mM-KCl. This flux is not dependent on the presence of Na+ in the medium and is insensitive to 5 X 10(-6) M-tetrodotoxin. However, 1 mM-Mn2+ causes a 95% inhibition of K+-induced 45Ca2+ uptake. 4. Veratridine and scorpion venom also induce voltage-dependent 45Ca2+ uptake which can be blocked by 1mM-Mn2+. In contrast to KCl-induced 45Ca2+ uptake, this flux is completely blocked by 5 X 10(-6) M-tetrodotoxin and is abolished by removal of Na+ from the medium. Thus the depolarizing stimulus for Ca2+ uptake in this case is Na+ from the medium. Thus the depolarizing stimulus for Ca2+ uptake in this case is Na+ influx through voltage-dependent Na+ channels. 5. Carbamylcholine induces both 22Na+ and 45Ca2+ fluxes which are blocked by nicotinic cholinergic antagonists with the exception of alpha-bungarotoxin. The 22Na+ flux occurs exclusively via acetylcholine receptor channels, as evidenced by the lack of effect of 5 X 10(-6) M-tetrodotoxin. In the presence of Na+, almost all of the 45Ca2+ uptake can be blocked by 1 mM-Mn2+ and thus occurs via voltage-dependent Ca2+ channels which are activated by the depolarizing Na+ influx. 6--8% of the total 45Ca2+ flux, however, is insensitive to 1 mM-Mn2+, suggesting that this portion of the uptake occurs via the acetylcholine receptor channels. In Na+-free medium, the Mn2+-resistant 45Ca2+ component increases to 40% of the total uptake, apparently due to lack of competition from Na+ for the acetylcholine receptor channels. This receptor-linked flux still causes sufficient depolarization to induce the additional 60% of the Ca2+ flux through voltage-dependent, Mn2+ sensitive Ca2+ channels. 6. Mn2+ inhibits Ca2+ flux through voltage-dependent Ca2+ channels by competing for entry through these channels. 50 mM-KCl induces 54Mn2+ fluxes in PC12 cells that are comparable in magnitude to 45Ca2+ fluxes. 7. In normal saline 45Ca2+ efflux from PC12 cells is several times more rapid than in Na+-free medium, indicating the presence of a Ca2+-Na+ exchange mechanism.

Animals↗
PubMed1977

The derivation and characterization of neuronal cell lines from rat and mouse brain.

This study shows that permanent cell lines can be established from rat and mouse brain by direct tissue culture methodology without the aid of exogenous chemical or viral transforming agents. These cells were derived from specific areas of the brain, such as the cerebellum and hippocampus, at chosen times during fetal and neonatal development. Success in establishing neuronal cell lines was dependent upon the use of selection pressures designed to keep the background of glial cells and fibroblasts at a minimum. These manipulations included care in the choice and processing of the original tissue, utilization of cytotoxic anti-glial sera, and continuous manual isolation of cells with neuronal morphology. Slow-growing nerve cells were thus allowed to adapt spontaneously to culture with a minimum of competition from faster-adapting cell types. Many of these cell lines are judged to be neuronal on the basis of their electrical excitability and their characteristic surface antigens. The cells respond positively in a sodium flux assay which has been shown to correlate well with the ability to generate an action potential, and also express one or more of three antigens previously found to be specific for nerve cells.

Animals↗
PubMed1977

Specificity of adhesion between cloned neural cell lines.

We have investigated the phenomenon of intercellular adhesion using cloned cell lines derived from the rat central nervous system. Adhesion is assayed by measuring the rate at which a suspension of labeled (probe) cells of one type adheres to monolayers of other cell types. In general a given probe cell such as the nerve line B50 will adhere rapidly to most other cell lines, providing little information about the specificity of the interactions. However, we discovered several methods of pretreating the B50 cells which specifically alter their rate of adhesion to various types of monolayers. Treating the B50 cells with trypsin, coating them with an antinerve antiserum, or simply lowering the assay temperature from 20 degrees C to 0 degrees C were 3 separate procedures which resulted in slower rates of adhesion of the B50 probe cells to 3 distinct subclasses of monolayers. These data suggest that different mechanisms are involved in the adhesion of B50 cells to the various other cell lines. To account for the differences, we postulate the existence of pairs of interlocking or complementary surface components on the cell lines, a concept that has also been valuable in understanding interactions in other systems. We discuss the characterization of these proposed components and outline their usefulness in categorizing the cell lines.

Animals↗
PubMed1977

Immunological distinction between acetylcholine receptor and the alpha-bungarotoxin-binding component on sympathetic neurons.

Clone PC12 of a rat sympathetic neuron cell line binds alpha-bungarotoxin and exhibits carbamoylcholine-stimulated uptake of sodium ions. Concentrations of alpha-bungarotoxin that saturate the alpha-bungarotoxin-binding site have no effect on agonist-stimulated sodium uptake. Conversely, antibodies against eel acetylcholine receptor block the agonist-induced sodium flux but fail to recognize the alpha-bungarotoxin-binding component. Detergent extracts of the PC12 clone inhibit the ability of antibody to eel acetylcholine receptor to recognize 125I-alpha-bungarotoxin-acetylcholine receptor complexes derived from muscle. These results distinguish between a ganglionic nicotinic acetylcholine receptor and an alpha-bungarotoxin-binding component on these cells, and provide evidence for antigenic similarities between muscle acetylcholine receptor and ganglionic acetylcholine receptor.

Acetylcholine↗