Identification and biosynthesis of an aggregation pheromone of the storage mite Chortoglyphus arcuatus.

In an effort to identify new pheromones from mites, the headspace of undisturbed colonies of the storage mite Chortoglyphus arcuatus was analyzed by GC-MS by use of a closed-loop stripping apparatus (CLSA) or solid-phase microextraction (SPME). The major compound emitted from the mites is (4R,6R,8R)-4,6,8-trimethyldecan-2-one (4R,6R,8R-8). The structure was elucidated by analysis of the mass spectrum, synthesis of authentic samples, and gas chromatography on a chiral phase.

Stimulation of insulin and somatostatin release by two meglitinide analogs.

Several meglitinide analogs are currently under investigation as potential insulinotropic tools for the treatment of noninsulin-dependent diabetes. The present study aimed to further insight into the effect of these agents on the secretion of insulin, glucagon, and somatostatin by the isolated perfused pancreas. Both repaglinide (0.

Stimulation of insulin release by repaglinide and glibenclamide involves both common and distinct processes.

The action of repaglinide, a novel insulin secretagogue, was compared with the sulfonylurea glibenclamide with regard to the hypoglycemic action in vivo, binding to betaTC-3 cells, insulin secretion from perifused mouse islets, and capacity to stimulate exocytosis by direct interaction with the secretory machinery in single voltage-clamped mouse beta-cells. Two binding sites were identified: a high-affinity repaglinide (KD = 3.6 nmol/l) site having lower affinity for glibenclamide (14.

Repaglinide, glibenclamide and glimepiride administration to normal and hereditarily diabetic rats.

Repaglinide (1 microg/g body wt), glibenclamide (10 microg/g) or glimepiride (10 microg/g) were administered orally to either fed or overnight fasted normal rats and hereditarily diabetic animals (GK rats). In both fed and starved normal rats, repaglinide provoked a greater and more rapid increase in plasma insulin concentration and an earlier fall in glycemia than those observed after administration of the hypoglycemic sulfonylureas. Likewise, in fed GK rats, the plasma insulin concentration was already increased by 30.

Effect of antidiabetic agents on the increase in glycemia and insulinemia caused by refeeding in hereditarily diabetic rats.

The hypoglycemic agents, glibenclamide and repaglinide, when administered intragastrically to overnight fasted hereditarily diabetic animals, were found to oppose the rise in the plasma insulin/glucose ratio otherwise evoked by refeeding of the GK rats. Such was not the case after oral administration of glimepiride, despite the fact that this sulfonylurea minimized the rise in glycemia associated with refeeding. The altered restoration of a high insulin/glucose ratio in GK rats that received glibenclamide or repaglinide before refeeding suggests that these long-acting hypoglycemic agents may delay the refeeding-induced relief of the B-cell from the fasting-associated refractoriness to glucose.

Localization of Y1 receptors for NPY and PYY on vascular smooth muscle cells in rat pancreas.

To localize binding sites for peptide YY (PYY) in the pancreas we utilized a slide-mount autoradiographic technique on frozen sections of rat pancreas incubated with 125I-Tyr36-PPY. Saturable autoradiographic labeling was located over pancreatic blood vessels, whereas islets, acinar cells, ducts, and neural elements did not appear to be specifically labeled. Isolated vascular fragments were prepared by collagenase digestion of rat pancreas.

[Pro34]neuropeptide Y selectively identifies postjunctional-mediated actions of neuropeptide Y in vivo in rats and dogs.

Anaesthetised rats and dogs were used to study the pre- and postjunctional actions of neuropeptide Y (NPY) and [Pro34]NPY simultaneously. Increases in arterial blood pressure indicated postjunctional actions and both NPY and [Pro34]NPY elicited these. Change in pulse interval evoked by stimulation of the cut peripheral end of the right vagus nerve, indicated prejunctional action of the peptides: NPY caused prolonged attenuation of vagal action in rats and dogs but [Pro34]NPY did not attenuate vagal action in rats or dogs.

Structure-function studies on neuropeptide Y and pancreatic polypeptide--evidence for two PP-fold receptors in vas deferens.

The biological effects of neuropeptide Y (NPY), rat pancreatic polypeptide (rPP), hybrid analogs of NPY and PP, and C-terminal fragments of NPY were studied in the field-stimulated rat vas deferens model. The results were correlated with peptide binding experiments in Y1 and PP receptor assays on rat PC-12 cells and Y2 receptors on porcine hippocampal membranes. NPY and rPP inhibited the electrically induced contractions in the vas deferens with an IC50 of 25 and 22 nM respectively.

The antiparallel pancreatic polypeptide fold in the binding of neuropeptide Y to Y1 and Y2 receptors.

Neuropeptide Y (NPY) belongs to the pancreatic polypeptide fold (PP-fold) family of regulatory peptides. Analysis of circular dicroic spectra of NPY showed that it has a high degree of secondary structure in aqueous solution which is in agreement with the globular, folded crystal structure of PP. Using three different approaches with synthetic peptides, we have probed the importance of the PP-fold structure in the interaction of NPY with two types of binding sites, Y1 and Y2 receptors.

Y1 receptors for neuropeptide Y are coupled to mobilization of intracellular calcium and inhibition of adenylate cyclase.

Two types of binding sites have previously been described for neuropeptide Y (NPY), called Y1 and Y2 receptors. The intracellular events following Y1 receptor activation was studied in the human neuroblastoma cell line SK-N-MC. Both NPY and the specific Y1 receptor ligand, [Leu31,Pro34]-NPY, caused a rapid and transient increase in the concentration of free calcium in the cytoplasm as measured by the fluorescent probe, Fura-2.

[Leu31, Pro34]neuropeptide Y: a specific Y1 receptor agonist.

Two types of binding sites have previously been described for 36-amino acid neuropeptide Y (NPY), called Y1 and Y2 receptors. Y2 receptors can bind long C-terminal fragments of NPY-e.g.

Primary structure of tetranectin, a plasminogen kringle 4 binding plasma protein: homology with asialoglycoprotein receptors and cartilage proteoglycan core protein.

Tetranectin binds to plasminogen and to isolated kringle 4 [Clemmensen, I., Petersen, L. C.