Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P01275 (glucagon)
 26,492 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Imidazole and isocytosine-furan derivatives inhibited H2 receptor activity in HGT-1 cells, in accordance with the following relative potencies (IC50 = 2.3 microM cimetidine as reference): SKF 93479 = cimetidine = 100 greater than metiamide = 62 greater than SKF 92408 = 2 greater than SKF 91581 = 0.07). The Schild plot for cimetidine was linear (slope = 0.97) with a pA2 value of 6.72 +/- 0.12 (Ki = 0.18 microM cimetidine), suggesting competitive inhibition. Preincubation of HGT-1 cells for 10 min with H2 antagonists at 2 microM concentration resulted in 90-100% inactivation (SKF 93479 and oxmetidine) and 65% inactivation (ranitidine) which persisted for 30 min, even after a washout period. Accordingly, the kinetics of 2 microM [3H] SKF 93479 binding to HGT-1 cells revealed a half-time for association of 10 min and a dissociation half-time of 120 min. There was a good correlation between the kinetics and relative potencies of cimetidine and SKF 93479 in inhibiting H2 receptor activity in purified plasma membranes (40 nM) as well as in intact HGT-1 cells preincubated for 2 hr with SKF 93479 before histamine addition (45 nM). Chronic treatment of HGT-1 cells for 6 days with 2 microM SKF 93479 specifically blocked H2 receptor activity since cyclic AMP generation induced by other hormones and agents such as VIP, glucagon, GIP and sodium fluoride was unaltered. In contrast, short term and chronic treatment by cimetidine was readily reversible. The isocytosine-furan derivative SKF 93479 differs from the imidazole analogue cimetidine by its apparent irreversible action, due to the slow onset of association from HGT-1 cells. The isocytosine ring in SKF 93479 and oxmetidine seems to play a preponderant role in their apparent long-lasting, irreversible actions.
 ...
PMID:Pharmacology of histamine H2 receptor antagonists in the human gastric cancer cell line HGT-1. Structure-activity relationship of isocytosine-furan and imidazole derivatives related to cimetidine. 287 95

Glucose is the main stimulator and physiological regulator of insulin secretion. The great sensitivity of the B cell to glucose variations between 1 g/l (5.5 mM) and 3 g/l (16.6 mM) and its rapid response ensure the constant adaptation of its secretion to plasma glucose level. The cellular mechanisms involved in insulin response can be schematically represented in three stages: The first stage is the recognition of the insulinotropic agent. In the case of glucose, this involves its metabolism. The second one is the coupling of the recognition process to activation of the effector system and implies a series of intracellular signals. Coupling factors include metabolites and cofactors, ions, cyclic AMP, polyphosphoinositides. The result of all these cellular events is the increase in cytosolic Ca2+ and the activation of protein-kinases: Ca2+-calmodulin-, cAMP- and Ca2+-phospholipid-dependent protein kinases. The last stage corresponds to a mechanical one, involving granule migration and extrusion. The polymerization of microtubules associated with contraction of microfilaments would cause granule movement. Ca2+-calmodulin-dependent protein kinases would play a major role. While glucose is the main stimulator of insulin secretion, numerous factors can influence it. The regulation of this secretion is essentially under the control of three classes of elements: nutrients, hormones and neurotransmitters. As to stimulation of insulin secretion by nutrients, it seems to be secondary to an increase in intracellular metabolism. However it must be underlined that the insulin secretory effect of most nutrients requires the presence of glucose which is consequently a permissive factor. A number of gastrointestinal and pancreatic hormones stimulate, in presence of glucose, insulin secretion and play an essential role during food intake, which results in a better fitting of insulin secretion to energy supply. The term "incretin" designates a hormonal transmitter between the gastrointestinal tract and the B cell; the "incretin" factors are included in what is termed enteroinsular axis. Of the gastrointestinal hormones, GIP (gastric inhibitory polypeptide) appears to play the most important physiological role in potentiating the insulin secretory effect of glucose. Pancreatic glucagon potentiates the effect of glucose too; it is difficult to distinguish between its endocrine and paracrine role. The pancreatic B cell is under neural regulation. The cholinergic system stimulates insulin secretion and the B cell is fitted with receptors of muscarinic type.(ABSTRACT TRUNCATED AT 400 WORDS)
 ...
PMID:[Current data on insulin secretion and its regulation]. 288 Oct 28

Elevated serum levels of gastrin, pancreatic polypeptide, and glucagon were found in 10 uraemic patients, whereas gastric inhibitory polypeptide and somatostatin levels were normal. After renal transplantation there was a significant reduction in serum gastrin (median, 5 pmol/l; p = 0.05, n = 9), pancreatic polypeptide (145 pmol/l; p less than 0.01, n = 9), GIP (9.5 pmol/l; p = 0.02, n = 7), and glucagon (92 pg/l; p less than 0.02, n = 9), whereas no alteration was seen in the somatostatin level. Meal stimulation produced consistent increases in serum levels of all hormones, and the response appeared to be unchanged after renal transplantation.
 ...
PMID:The immediate effect of human renal transplantation on basal and meal-stimulated levels of gastrointestinal hormones. 288 97

Dietary fibre has a beneficial influence on glucose homeostasis, varying for different fibre sources. Fruit, wheat, rye and beet fibre were studied in isoenergetic meals for NIDD patients and healthy volunteers. The effects of extrusion cooking and flaking were also evaluated. The metabolic response was followed by continuous glucose monitoring and by analyses of pancreatic and gastrointestinal hormones as well as plasma lipid concentrations, For NIDD patients the effects, reflected in the area and the shape of the glucose curve, were greater for the more soluble fibre types, but the insulin and C-peptide responses were largely unaffected by dietary fibre. Beet fibre gave increased somatostatin concentrations also in age-matched healthy controls. They showed, however, unchanged plasma glucose responses and markedly decreased insulin and C-peptide levels. These changes were associated with less pronounced postprandial glycerol reduction, but otherwise none of the fibre preparations affected the postprandial lipemia. Extruded bread, based on wholegrain wheat flour, with high availability of in vitro starch, elicited a greater glucose response than wholegrain wheat bread, associated with a modest increase of GIP and insulin and with a stimulated early glucagon secretion. Flaked rye seemed to contain both faster and slower carbohydrates than the corresponding rye bread of similar fibre content. Analyses of the glucose curves suggested that the effect of fibre might be mediated by an effect on glucose absorption and parallel experiments in rat indicated that a delayed rate of gastric emptying might contribute. Further, the liver glycogen content was higher in rats given a slowly absorbed gastric load. A realistic increase in fibre content, given in long-term treatment, improved the metabolic control in NIDD patients, by decreasing the fasting blood glucose and LDL-cholesterol levels, as well as the LDL/HDL ratio. Hypothetically, slower absorption achieved with dietary fibre increases the proportion of glycogen in the liver. This postprandial improvement may cause the long-term trend to normalization of the fasting blood glucose level.
 ...
PMID:Fibre and the diabetic diet. An evaluation of the metabolic response to standardized meals. 288 21

Functional and specific receptors for vasoactive intestinal peptide (VIP) (determined by their capacity to bind 125I-VIP and activate adenylate cyclase) and cyclic AMP-dependent phosphodiesterase activities were characterized in enterocytes of human fetal small intestine between 18 and 23 weeks of gestation. Half-maximal stimulation of the cyclase and inhibition of 125I-VIP binding in membrane preparations were respectively observed at 1.4 and 5 X 10(-10) M VIP. The peptides structurally related to VIP activated the cyclic AMP generating system at pharmacological doses (10(-7) M and above) in the following order of potency: VIP greater than PHI greater than GRF greater than secretin. Other peptides or test substances, including GIP, pancreatic glucagon, somatostatin-14, gastrin, CCK, neurotensin, pancreatic polypeptide, PYY, substance P, histamine and isoproterenol are inactive in this system, while the ubiquitous adenylate cyclase activators NaF, forskolin and prostaglandins were effective. These results, combined with the appearance of intestinal VIP in nerve fibers at 8 weeks and with the morphological and enzymatic maturation at 9-12 weeks of the intestinal mucosa, indicate that this neuropeptide may regulate either the differentiation or function of enterocytes during the early development of human intestinal mucosa.
 ...
PMID:Vasoactive intestinal peptide receptor activity in human fetal enterocytes. 298 18

Short and middle term effects of Acarbose were studied in volunteers on a standardized, low-fibre, mixed diet for the development of tolerance phenomena with gas exhalations and some peptide hormone levels as main parameters. Both hydrogen and methane were measured quantitatively as diurnal profiles. Acarbose caused an about 20-fold increase of H2 exhalation and had only moderate effects on methane production, indicating the presence of fermentable carbohydrates in the large bowel. Methanogenic individuals exhaled significantly less H2 than did non-methanogenic subjects. Changes in blood glucose, serum insulin, GIP, gastrin, and plasma glucagon, caused by Acarbose, reflected delayed glucose absorption and were plausible within the regulatory framework of carbohydrate assimilation. When the Acarbose regime was maintained for 5 weeks on a controlled diet, abdominal sensations like e.g. meteorism declined remarkably while carbohydrate fermentation remained high and lowered GIP was sustained. Thus functional responses of the gastro-intestinal tract to altered carbohydrate supplies, elicited by Acarbose, were found by 3 independent parameters: anaerobic gas production, peptide hormone levels, and subjective abdominal sensations. The objective parameters seem to remain constant in the longer run, while subjective parameters show long-term adaptation.
 ...
PMID:Effect of Acarbose on the production of hydrogen and methane and on hormonal parameters in young adults under standardized low-fibre mixed diets. 298 18

Three separate sets of receptors sensitive to VIP, GIP and pancreatic/entero-glucagons, have been characterized in HGT-1 cells. The order of relative potencies of VIP receptor agonists was VIP greater than rh GRF-43, rh GRF-29 greater than PHI greater than hp GRF-40, secretin. G-37 was about 4 times less potent than G-29 in HGT-1 cells (G-29 greater than G-37), whereas it was about 20 times more potent than G-29 in rat fundic glands (G-37 greater than G-29). Adenylate cyclase in HGT-1 cells was stimulated by VIP, G-29, G-37 and GIP, over a concentration from 3.16 X 10(-9) to 3.16 X 10(-7) M GIP. The experimental data: (1) support the enterogastrone activity of GIP, via adenylate cyclase activation and somatostatin release by gastric D cells; (2) demonstrate that HGT-1 cells originating from a human fundic tumor are sensitive to the glucagon-like peptides G-29 and -37, as rat fundic glands; (3) indicate that the pharmacological properties of the VIP receptor in this human gastric cell line are similar to those characterized in normal human gastric glands.
 ...
PMID:Functional receptors for VIP, GIP, glucagon-29 and -37 in the HGT-1 human gastric cancer cell line. 301 90

The structural requirements for VIP interaction with receptors on synaptosomes from rat cerebral cortex was investigated by the ability of VIP and VIP fragments, secretin analogues and fragments, peptides of the VIP/secretin family and several other regulatory peptides to inhibit specific 125I-VIP binding. Only large VIP fragments interacted with the VIP receptors with potencies relative to VIP ranging from 0.9-0.006%. The rank order of inhibition was: VIP 7-27 greater than VIP 11-28 greater than VIP 1-22-NH2 greater than VIP 16-28. Shorter fragments: VIP 18-28; VIP 18-28-NH2; VIP 19-28; VIP 21-28; VIP 22-28; VIP 1-18; VIP 1-18-NH2; VIP 1-10-NH2; VIP 1-6; VIP 16-20 and VIP 16-19 had no effect. Secretin fragments and analogues inhibited 125I-VIP binding with potencies of 2.2-0.01% relative to VIP in the order; secretin greater than (Ala4, Val5) secretin greater than (D-Ala4) secretin greater than (D-Phe6) secretin greater than secretin 5-27 greater than secretin 14-27. Other peptides of the VIP/secretin family inhibited 125I-VIP binding with potencies of 200-1%; avian VIP greater than porcine VIP greater than PHI = secretin greater than human GRF, whereas glucagon and GIP showed no inhibition. Among twenty-five other regulatory peptides only avian PP and somatostatin were inhibitors with relative potencies of 0.02% and 0.03%, respectively. In conclusion it may be emphasized that the intact VIP molecule is essential for VIP interaction with its receptors in the rat brain cortex.(ABSTRACT TRUNCATED AT 250 WORDS)
 ...
PMID:VIP binding sites on synaptosomes from rat cerebral cortex: structure-binding relationship. 301 96

A model is proposed for the receptors of the VIP family peptides including a ligand and a cellular domain. Specificities of the receptors are due to different ligand binding sites. Three subgroups of the family can be distinguished accordingly: glucagon and oxyntomodulin; GIP; VIP, secretin r and hGRF, PHI and PHM. In the same species, the expression of these different sites is cell-specific resulting in a stoichiometry of the ligand-receptor interaction which is compatible with physiological regulation of cell function. Specificities of the interaction as studied by native and synthetic analogs is supported both by restricted sequences of amino acids (such as that including the N-terminal histidine residue), and membrane-induced configuration of the ligand. Identity of the receptors is related to their interactions with subunits of the adenylate cyclase system. Arguments are put forward indicating that the alpha subunit of the guanyl regulatory protein is a reasonable candidate for directly transducing to the adenylyl cyclase the information contained in the activated ligand-binding site subunits. Evidence of functional and molecular heterogeneity of the recognizing site and of the alpha subunits leads to the supposition that some types of specific complementarity is retained at this level of interaction, further enhancing the possibility of species and cell differences. On the other hand, the identities found in other sequences of the alpha and ras oncogene products extend to the receptor of the VIP family peptides a pattern of organization which is similar to that recently described for the insulin family of receptors. The role of ligand specific receptor mediated regulation in homologous or heterologous desensitization is reviewed in brief for the peptides of the VIP family as well as the appearance of the specific receptor during the ontogenesis or the cell differentiation. The co-distribution of plasma membrane receptors from other families further adds to the cell specificity resulting for each differentiated cell in unique patterns of recognizing site. Some examples of receptor-receptor interaction are given, indicating that the integration of the different signals by cells might occur at an early step through the transmembranair domain of the receptor.
 ...
PMID:The receptors of the VIP family peptides (VIP, secretin, GRF, PHI, PHM, GIP, glucagon and oxyntomodulin). Specificities and identity. 301 7

Saccharomyces cerevisiae strains were transformed with plasmids coding for modified mating factor alpha 1 leader sequences followed by glucagon. Glucagon-containing peptides which were secreted into the fermentation broth were isolated and their amino acid sequences determined. The yeast strain transformed with the sequence coding for the complete mating factor alpha 1 leader sequence preceding the glucagon gene (MT556) secreted glucagon plus glucagon extended at its N-terminal by parts of the leader sequence. The yeast strain transformed with the sequence coding for a truncated mating factor alpha 1 leader sequence before the glucagon gene (MT615) secreted glucagon. These observations suggest that S. cerevisiae is a suitable vehicle for the efficient expression of plasmids coding for polypeptides similar to glucagon (e.g. VIP, secretin, GIP).
 ...
PMID:The secretion of glucagon by transformed yeast strains. 302 66


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>