Antagonism of catecholamine inhibition of insulin secretion by methysergide

Zusammenfassung Isoliertes Maus-, Hamster- und Kaninchenpankreas wurde in einer physiologischen Pufferlösung mit 3,0 mg/ml Glukose inkubiert. Dopamin ruft eine erhebliche Verringerung der radioimmunologisch reagierenden Insulinsekretion hervor. Die durch Dopamin ausgelöste Hemmung lässt sich teilweise oder vollständig durch den Serotoninantagonisten 1-Methyl-d-lysergsäure butanolamid (Deseril) aufheben.

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Supported by grants from the National Institute of Arthritis and Metabolic Diseases of the National Institutes of Health No. AM 01324, No. 5 T1 AM 5074 and No. K3 AM 17,954 and a Clinical Investigatorship from the Veterans Administration (JMF).     

Uptake of catecholamines into serotonergic nerve cells as demonstrated by fluorescence histochemistry

Zusammenfassung Die histochemische Fluoreszenzmethode wird zum Studium der Nervenzellen des Gehirnstammes der Ratte angewandt. Die erhebliche Zunahme des Dopamins, hervorgerufen durch die Injektion eines peripher wirkenden Dekarboxylase-Hemmstoffes zusammen mitl-DOPA, wird im Gehirn verfolgt und gefunden, dass serotonergische Neuronen imstande sind, Catecholamine aufzunehmen.

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This work has been supported by the Clinical Research Center for Parkinson's and Allied Diseases, grant No. NS05184.     

Solubilization of prolactin receptor by a Zwitterionic detergent

Summary About 60% of the prolactin receptors were solubilized from rabbit mammary gland membranes by Zwittergent 3–12. The use of Zwittergent 3–12 resulted in increased sensitivity of the receptor assay and permitted use of ovine prolactin instead of human growth hormone in the receptor assay.Acknowledgments. This work was supported by grant AM 17476 from the National Institutes of Health.     

A novel antagonist of serotonergic receptors,hymenidin, isolated from the Okinawan marine spongeHymeniacidon sp.

Summary A novel bromine-containing pyrrole compound, hymenidin, has been isolated from the Okinawan marine spongeHymeniacidon sp. as a potent antagonist of serotonergic receptors and its structure elucidated using spectral data.     

A novel antagonist of serotonergic receptors, hymenidin, isolated from the Okinawan marine sponge Hymeniacidon sp

A novel bromine-containing pyrrole compound, hymenidin, has been isolated from the Okinawan marine sponge Hymeniacidon sp. as a potent antagonist of serotonergic receptors and its structure elucidated using spectral data.     

Thrombosis of sympathectomized rats after strong excitation provoked by sound stimuli

Summary The data obtained are evidence of the decreased resistance of sympathectomized animals to excitement caused by afferent stimuli.     

A concept of intracellular transmission of excitation by means of the endoplasmic reticulum

Zusammenfassung Die morphologische Beobachtung von getrennten cytoplasmatischen Phasen in geschlossenen Membranen führt zur Annahme von Membranpotentialen innerhalb der Zelle. Schreibt man den Membranen des endoplasmatischen Reticulums die Eigenschaften der Plasmamembran zu, so leiten sie die Erregung ins Zellinnere und dienen als Potentialspeicher.     

Regulation of receptor function by cholesterol

Cholesterol influences many of the biophysical properties of membranes and is nonrandomly distributed between cellular organelles, subdomains of membranes, and leaflets of the membrane bilayer. In combination with the high dynamics of cholesterol distribution, this offers many possibilities for regulation of membrane-embedded receptors. Depending on the receptor, cholesterol can have a strong influence on the affinity state, on the binding capacity, and on signal transduction. Most important, cholesterol may stabilize receptors in defined conformations related to their biological functions. This may occur by direct molecular interaction between cholesterol and receptors. In this review, we discuss the functional dependence of the nicotinic acetylcholine receptor as well as different G protein-coupled receptors on the presence of cholesterol.     

K252a: A new blocker of the cell-cycle at G1 phase in a human hepatoma cell line

The administration of 200 nM K252a to HuH7 suppressed the proliferation of the cells almost completely. The uptake of [³H]thymidine was inhibited, and flow cytometry revealed only one peak at 2C on day 3 after treatment with 100 nM K252a. The expression of proto-oncogene c-myc was not reduced. Despite the blockage at G1, both the size of the cells and the amount of cell protein had increased by 4 times by day 3 after treatment with K252a, while the cells secreted albumin and -fetoprotein into the medium as usual. These results show that K252a can increase the cell size of HuH7 without losing its function by blocking the cell cycle at G1 phase.     

Inhibition and sex specific induction of spawning by serotonergic ligands in the zebra musselDreissena polymorpha (Pallas)

Serotonin (5-hydroxytryptamine, 5-HT) stimulates spawning in the zebra mussel (Dressena polymorpha), a macrofouling European bivalve that has recently invaded North America. To develop methods of controlling zebra mussel spawning, two vertebrate serotonin antagonists, methiothepin and metergoline, known to bind with high affinity to snail 5-HT receptors, were tested for their ability to block 5-HT-induced spawning in zebra mussels. Methiothepin inhibited 5-HT-induced spawning at concentrations as low as 10^–6 M. Metergoline (10^–4 M) inhibited 5-HT-induced spawning; however, at lower concentrations (10^–8 to 10^–5 M), metergoline by itself significantly induced spawning in male, but not female zebra mussels. Metergoline (10^–5 M)-induced male spawning was inhibited by 10^–5 M methiothepin. Thus, methiothepin is the most effective inhibitor and metergoline the most powerful inducer of spawning yet tested in zebra mussels.     

The excitation by suxamethonium of non-proprioceptive afferents from the caudal muscles in the rat

Résumé Des afférences myéliniques non-proprioceptives, à vitesse de conduction lente, en provenance des muscles de la queue du rat, sont excitées par le suxaméthonium d'une concentration de 1,0×10⁴. On considère les mécanismes possibles de cette excitation, dont la signification est discutée.     

Methyllycaconitine,a naturally occurring insecticide with a high affinity for the insect cholinergic receptor

Summary Studies of extracts ofDelphinium seeds, long known to be insecticidal, revealed that a principal insecticidal toxin was methyllycaconitine, which is shown to be a potent inhibitor of -bungarotoxin binding to housefly heads (K_inh=2.5×10^–10±0.5×10^–10M).Calgary for gifts of MLA, citrate and lycoctonine, and Dr W. Bowers of the University of Arizona for the original extract ofDelphinium seeds. We would also like to acknowledge the able technical support of Ms C. Dushin, Mr E.L. Bowman, Dr C. C. Gagne, Mr R. F. Borysewicz and Dr P. Mowery for his assistance in obtaining and interpreting the carbon-13 NMR spectra.     

Induced recovery of defective membrane expression of a CC chemokine receptor 5 mutant by phytohemagglutinin

CC chemokine receptor 5 (CCR5) is a member of the G-protein-coupled receptor superfamily. It plays an important role in macrophage tropic human immunodeficiency virus-1 entry and in some inflammatory reactions. CCR5-893(–) is a single-nucleotide deletion that results in complete truncation of the C tail of the gene product. We detected CCR5-893(–) in a sample of patients infected with non-tuberculosis mycobacteria and found that it was maintained heterozygously with a frequency of 2%. There is no association between this mutation and any immunodeficiency. Membrane expression of CCR5-893(–) was substantially reduced compared to the wild type, but this defective surface presentation recovered greatly recovered in the presence of 2 mg l-1 phytohemagglutinin (PHA). However, PHA inducement did not affect the total intracellular expression of CCR5-893(–) or wild-type CCR5. Thus we suggest there exist some PHA-induced factor(s) that could mediate the presentation of truncated CCR5.Received 23 July 2003; accepted 18 August 2003