Functional characterization of the promoter of pp63, a gene encoding a natural inhibitor of the insulin receptor tyrosine kinase.

PP63 is a liver specific phosphorylated glycoprotein encoded by a single copy gene, which has the property of inhibiting both autophosphorylation and tyrosine kinase activity of the insulin receptor. In this study, we have analyzed the structure activity relationship of the pp63 gene promoter. Five protein binding sites were found in the proximal 5' flanking region of the gene (-223 to +4).

Evidence for a direct stimulatory effect of cibenzoline on insulin secretion in rats.

The effect of cibenzoline succinate, a new antiarrhythmic agent, was studied on insulin secretion in rats. Experiments were performed both in vivo and in vitro using two preparations: the isolated perfused pancreas and isolated islets. In anaesthetized rats, cibenzoline was able to increase plasma insulin levels and to reduce glycaemia.

Trans-ACPD inhibits cAMP formation via a pertussis toxin-sensitive G-protein.

In primary cultured striatal neurons we found that (+-)-trans-1-amino-cyclopentyl-1,3-dicarboxylate (trans-ACPD) could inhibit forskolin-induced cAMP formation in a dose-dependent manner (EC50 156 +/- 38 microM, n = 5, maximal inhibition 37.8 +/- 1.2, n = 37).

Nitric oxide-induced blockade of NMDA receptors.

We studied the effects of nitric oxide (NO)-producing agents on N-methyl-D-aspartate (NMDA) receptor activation in cultured neurons. 3-Morpholino-sydnonimine (SIN-1) blocked both NMDA-induced currents and the associated increase in intracellular Ca2+. The actions of SIN-1 were reversible and suppressed by hemoglobin.

Pharmacological characterization of inositol 1,4,5-trisphosphate binding sites: relation to Ca2+ release.

Two subcellular fractions, one enriched in plasma membranes and the other in endoplasmic reticulum membranes, were obtained from WRK1 cells using a combination of differential centrifugations and Percoll gradient fractionation. Specific inositol 1,4,5-trisphosphate (Ins(1,4,5)P3) binding sites were detected in these two preparations. Endoplasmic reticulum membranes exhibited a binding capacity which was about 5-fold higher than that of plasma membranes.

Characterization of binding sites for oxyntomodulin on a somatostatin-secreting cell line (RIN T3).

Oxyntomodulin (OXM), a glucagon-containing peptide extended at its C-terminal end by an octapeptide, is a potent inhibitor of gastric acid secretion in rat and man. OXM appears to act on gastric mucosa at least partially through a stimulation of gastric somatostatin release. We have investigated the effects of OXM on a somatostatin-secreting cell line (RIN T3) derived from a radiation-induced rat insulinoma and characterized specific binding sites for this peptide.

Characterization of a novel 5-HT4 receptor antagonist of the azabicycloalkyl benzimidazolone class: DAU 6285.

Three chemical classes of serotonin 5-HT4 receptor agonists have been identified so far: 5-substituted indoles (e.g. 5-HT), benzamides (e.

A Nitric Oxide Synthase Activity Selectively Stimulated by NMDA Receptors Depends on Protein Kinase C Activation in Mouse Striatal Neurons.

In mouse striatal neurons in primary culture, the maximal increase in intracellular cyclic guanosine monophosphate level evoked by N-methyl-d-aspartic acid (NMDA) receptor activation was twice that induced by kainate, KCl and ionomycin. Quisqualate was almost inactive. All responses were mediated by nitric oxide (NO) production since they were blocked by haemoglobin (a NO scavenger) and by l-NG-monomethylarginine and l-NG-nitroarginine, the effects of both arginine analogues being reversed by an excess of l-arginine.

N-acetyl oxyntomodulin30-37: pharmacokinetics and activity on gastric acid secretion.

Oxyntomodulin, an intestinal hormone which inhibits gastric acid secretion, is composed of glucagon and a C-terminal octapeptide. This octapeptide mimics the biological activity of the hormone. We have studied the activity of the N-acetyl octapeptide, partially protected against enzymatic degradation, on pentagastrin-, histamine- and milk meal-stimulated secretion in conscious rats and compared it to that of oxyntomodulin and its derivatives.

Fluorescent peptide hormones: development of high affinity vasopressin analogues.

Highly potent and specific peptide hormone analogues with fluorescent reporter groups are current research goals. Until now, however, only moderately potent analogues have been described. We report here several types of vasopressin (VP) analogues with different fluorophores attached to the peptide.

Sodium nitroprusside blocks NMDA receptors via formation of ferrocyanide ions.

The effects of a nitric oxide (NO) donor, sodium nitroprusside (SNP), on N-methyl-D-aspartate (NMDA) receptors were assessed by optical measurements of intracellular calcium concentration ([Ca2+]i) and patch-clamp techniques in cultured central neurons. SNP selectively blocked NMDA-mediated currents and increases in [Ca2+]i. SNP inhibited the binding of [3H]-CGS 19755.

The metabotropic glutamate receptor (MGR): pharmacology and subcellular location.

A pharmacological characterization of the metabotropic glutamate receptor (MGR) was performed in striatal neurons. Among the excitatory amino acid receptor antagonists tested, only D, L-2-amino-3-phosphonopropionate (D, L-AP3) inhibited QA-induced inositol phosphate (InsP) formation in a competitive manner (mean pKi = 4.45 +/- 0.

Oxyntomodulin and related peptides control somatostatin secretion in RIN T3 cells.

We studied the effects of oxyntomodulin (OXM), of its C-terminal (19-37) fragment (OXM (19-37)) and of glucagon (GLU) on somatostatin release, cyclic AMP accumulation and inositol phosphate turnover in somatostatin-secreting RIN T3 cells in culture. Rapid changes in cellular free Ca2+ were also measured using fura-2. Carbachol was used as a control test agent for the parameters involving the inositol phosphate/Ca2+ cascade.

Coupling of receptors to G proteins, pharmacological implications.

There are four main classes of membrane-bound receptors: receptors which are also enzymes (tyrosine protein-kinase or guanylate cyclase), receptor channels, receptors coupled to G proteins (GTP binding proteins) and receptors with unknown transduction mechanisms. Receptors coupled to G proteins which have been cloned, constitute a superfamily of proteins containing seven hydrophobic transmembrane helices. The binding site of the ligand is within the hydrophobic core of the protein and the domain of interaction of the G proteins is constituted by the N- and C-terminal parts of the third intracellular loop, plus the C-terminal tail, adjacent to the transmembrane VII.

Oxyntomodulin and its (19-37) and (30-37) fragments inhibit histamine-stimulated gastric acid secretion in the conscious rat.

Oxyntomodulin, a hormone released from jejuno-ileum and composed of the glucagon sequence extended by a C-terminal octapeptide displays original tissue specificity for the gastric mucosa. The aim of this study was to compare the effect of oxyntomodulin on histamine (0.4 mg/kg per h)-stimulated gastric acid secretion in the conscious rat to that of three of its fragments: oxyntomodulin-(19-37) produced from oxyntomodulin by enzymatic cleavage, oxyntomodulin-(30-37) corresponding to the molecular difference between oxyntomodulin and glucagon and oxyntomodulin-(32-37) produced during proglucagon processing to glucagon.

beta-N-methylamino-L-alanine is a low-affinity agonist of metabotropic glutamate receptors.

beta-N-methylamino-L-alanine (L-BMAA) is an excitotoxin whose neurodegenerative effects are associated with its agonist properties at the N-methyl-D-aspartate (NMDA) receptor. We measured the effects of L-BMAA on inositol phosphate (InsP) formation in primary cultured striatal neurons. This culture is almost devoid of glial cells and the pharmacology of glutamate receptors is well-defined.

Angiotensin receptors from rat liver, brain and pituitary gland. Expression of two subtypes in Xenopus oocytes.

Xenopus laevis oocytes were used to express angiotensin receptors encoded by mRNAs extracted from rat liver, adenohypophysis and brain. Groups of ten mRNA-injected oocytes were loaded with 45Ca2+ and the responsiveness to angiotensin II (A II) and related molecules tested by monitoring 45Ca2+ outflux. A II and angiotensin III (A III) induced a marked and transient increase in 45Ca2+ outflux from mRNA, but not from control, water-injected, oocytes.

Pharmacological characterization of the quisqualate receptor coupled to phospholipase C (Qp) in striatal neurons.

A detailed pharmacological characterization of the quisqualate (QA) receptor coupled to phospholipase C (Qp) was performed in striatal neurons. The experiments were carried out in the presence of the ionotropic antagonists MK-801 (1 microM) and 6-cyano-7-nitroquinoxaline-2,3-dione (30 microM), concentrations that block N-methyl-D-aspartate (NMDA) or alpha-amino-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors in these cells. QA, ibotenate and trans-1-aminocyclopentyl-1,3-dicarboxylate (ACPD) evoked dose-dependent inositol phosphate formations with EC50 values of 0.

G proteins and G-protein-coupled receptors: structure, function and interactions.

The G protein family continues to grow and at least 15 heterotrimeric G proteins have now been identified. This review deals with the nature of the functional domains of the members of the G-protein-coupled receptor family as well as the associated G proteins.

Pharmacological characterization of type B cholecystokinin binding sites on the human JURKAT T lymphocyte cell line.

Recent studies have demonstrated the presence and the regulatory function of some neuropeptides in the immune system. In the present study, we have used labeled cholecystokinin (26-33) amide to characterize high affinity cholecystokinin (CCK) binding sites on a human JURKAT lymphoma cell line. Binding was temperature dependent, saturable, and specific.

A radioiodinated linear vasopressin antagonist: a ligand with high affinity and specificity for V1a receptors.

A linear vasopressin antagonist, Phaa-D-Tyr(Me)-Phe-Gln-Asn-Arg-Pro-Arg-Tyr-NH2 (Linear AVP Antag) (Phaa = Phenylacetyl), was monoiodinated at the phenyl moiety of the tyrosylamide residue at position 9. This antagonist appeared to be a highly potent anti-vasopressor peptide with a pA2 value in vivo of 8.94.

Azabicycloalkyl benzimidazolone derivatives as a novel class of potent agonists at the 5-HT4 receptor positively coupled to adenylate cyclase in brain.

Recent experimental evidence indicates that central 5-HT4 receptors which are positively coupled to adenylate cyclase, are stimulated by a family of 2-methoxy-4-amino-5-chloro substituted benzamide derivatives. These compounds are also potent stimulants of the gastro-intestinal motility. In this study the ability of three azabicycloalkyl benzimidazolone derivatives, BIMU 1, BIMU 8, and DAU 6215 (structural formulas are given in the text), to stimulate cAMP formation in colliculi neurons in primary culture have been tested.