Biomedical subjects

C Delporte

Publications and source records attributed to C Delporte.

45 records · Page 3Linked to original sources

PubMed1992

A new metallo- endopeptidase from human neuroblastoma NB-OK-1 cells which inactivates atrial natriuretic peptide by selective cleavage at the Ser123-Phe124 bond.

A novel metallo-endopeptidase from human neuroblastoma NB-OK-1 cells was partially purified and characterized. This enzyme activity was detected in the culture medium and could be detached from intact cells by gentle washing, suggesting a peripheral localization of the enzyme. This endopeptidase inactivated Atrial Natriuretic Peptide (ANP) by a unique and selective cleavage of the Ser123-Phe124 bond. It also produced hydrolysis at the Xaa-Phe, Xaa-Leu, or Xaa-Ile bonds of other peptide hormones such as bradykinin, somatostatin 14, litorin, substance P, neuromedin C and angiotensin II. The substrate selectivity and inhibition profile of the enzyme showed obvious similarities with the peptide hormone inactivating endopeptidase (PHIE) recently purified from Xenopus laevis skin secretions and indicated a thermolysin-like activity distinct from neutral endopeptidase (EC 3.4.24.11) and from angiotensin converting enzyme (EC 3.4.15.1).

Amino Acid Sequence↗

PubMed1991

Functional cholecystokinin receptors are distinguished kinetically by biotinyl-Tyr-Gly-(Thr28,Nle31)CCK(25-33) in rat pancreatic acini.

Biotinyl-tyrosine-glycine(Thr28,Nle31)CCK(25-33) (BTG-TN-CCK-9) promoted amylase secretion and phosphatidylinositol (PI) metabolism with the same potency and efficacy as TN-CCK-9 in dispersed rat pancreatic acini. A 1 min preincubation of the ligand with a 20-fold excess of streptavidin completely suppressed this biological activity. On the other hand, amylase secretion and PI metabolism prestimulated with BTG-TN-CCK-9 were blocked within 1-5 min after streptavidin addition. [125I]BTG-TN-CCK-9 bound to high (Kd 0.17 nM) and low (Kd 13 nM) affinity receptors. Its dissociation, in the presence of either streptavidin or TN-CCK-9, showed a rapid component and a slow component. The proportion of tracer dissociating slowly increased with increasing preincubation time as did the proportion of tracer that could not be washed away quickly by acidic treatment, in parallel experiments. This phenomenon occurred less readily at 4 degrees C or in the presence of 1 mM CCCP. In acini preincubated for 30 min with 0.3 nM [125I]BTG-TN-CCK-9 and various concentrations of unlabelled BTG-TN-CCK-9, then washed at neutral pH (in order to eliminate rapidly dissociating ligand preferentially), the tracer displacement curve was shifted leftward, suggesting that rapidly dissociating receptors corresponded to low affinity receptors. When acini were preincubated for 1 min with BTG-TN-CCK-9, then washed at neutral pH with buffer only, we observed residual stimulated secretion over the next 30 min period, that correlated with the BTG-TN-CCK-9 concentration offered during the short preincubation period. This phenomenon was inhibited by streptavidin suggesting that intracellularly accumulated intact BTG-TN-CCK-9 (as shown, by radio-HPLC) promoted residual secretion when free to bind again to cell surface receptors in the absence of streptavidin. Taken collectively, these data suggest the coexistence of at least 2 types (or states) of CCK receptors.

Amylases↗

PubMed1991

Characterization and regulation of atrial natriuretic peptide (ANP)-R1 receptors in the human neuroblastoma cell line NB-OK-1.

We characterized in membranes from the human neuroblastoma cell line NB-OK-1, an ANP-R1 receptor (Mr 130 kDa) for the atrial natriuretic peptide (ANP). This receptor recognized biologically active forms of ANP with high affinity but showed no affinity for truncated ANP forms. It was functional in that binding correlated with guanylate cyclase activation (a 2-fold increase in Vmax) with the following rank order of potency: rat ANP-(99-126) greater than human ANP-(99-126) greater than human ANP-(102-126) greater than porcine BNP (brain natriuretic peptide). The enzyme required free Mn2+ in addition to the Mn-GTP substrate (Km of about 0.3 mM for both basal and ANP-stimulated activity). In the presence of dithiothreitol, the dose-response curve of guanylate cyclase activation was shifted rightward by a factor of 30. ANP-R1 receptors were upregulated through protein synthesis in cells exposed to 1 mM carbamylcholine or 1 mM dibutyryl cyclic AMP for 8-24 h (ANP was ineffective).

Animals↗

PubMed1991

Response of rat parotid acini to barium.

The effect of barium on isolated acini was tested. Barium in the 0.1-10 mM concentration range non-competitively inhibited the efflux of 86Rb+ stimulated by carbamylcholine or substance P. This inhibition was independent of the presence of calcium in the extracellular medium. In the same preparation, barium did not affect the efflux of 45Ca2+ but, at a 10 mM concentration, it increased amylase release by 70%. Removal of extracellular calcium decreased basal amylase release and the response to carbamylcholine. Adding back calcium or barium to the incubation medium increased basal and carbamylcholine-stimulated amylase secretion, but calcium was more effective than barium. These results suggest that barium has two opposite effects on calcium-regulated processes in rat parotid gland: (1) it is an inhibitor of calcium-activated potassium channels; (2) it is a partial agonist of calcium-activated amylase secretion.

Amylases↗

PubMed1991

The metabolic effects of guanyl nucleotides on rat pancreatic acini permeabilized with streptolysin O suggest a widespread use of G proteins.

In streptolysin O permeabilized acini that were normally responsive to carbamylcholine and cholecystokinin octapeptide, amylase secretion was stimulated: a) by the stable guanyl nucleotides with a potency decreasing as follows: guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S) greater than guanylyl-imidodiphosphate (GMP-PNP) = guanylyl-(beta, gamma-methylene)-diphosphonate (GMP-PCP), in the presence of 0.5 mM calcium and b) by calcium alone (EC50 3 microM). The maximal secretory effect of calcium alone (a 2-fold increase) was less effective than that of GTP gamma S and calcium offered in combination (an 8-fold increase). In the virtual absence of Ca2+, GTP gamma S still stimulated amylase release (a 3-fold increase) while 12-O-tetradecanoylphorbol 13-acetate (TPA) did not. The relative potencies of guanyl nucleotides were GTP gamma S greater than GMP-PNP = GMP-PCP = GTP on phosphatidylinositol 4,5-bisphosphate (PIP2) breakdown, GTP gamma S greater than GMP-PNP greater than GMP-PCP = GTP on 45Ca2+ efflux, and GTP GMP-PNP = GMP-PCP = GTP gamma S on [1-14C]arachidonate efflux. Based on these data, the contribution of G proteins to stimulus-secretion coupling beyond the transduction of receptor signal is considered.

Amylases↗

PubMed1990

Spin-lattice relaxation times and nuclear Overhauser enhancement effect for 31P metabolites in model solutions at two frequencies: implications for in vivo spectroscopy.

The relaxation time T1 values and nuclear Overhauser enhancement factor for 31P signal were determined in model solutions of metabolites ATP, PCr and Pi, and AMP at two frequencies and in H2O and 2H2O solutions. The data were analyzed to resolve the contribution of different relaxation mechanisms. A knowledge of NOE is important in the light of recent applications of double resonance methods to enhance the sensitivity of in vivo 31P spectroscopy. The results show that chemical shift anisotropy is the dominant mechanism for 31P in ATP at the high field, whereas the dipolar interaction mechanism is the main feature for the 31P relaxation of PCr and Pi. The dipolar mechanism responsible for NOE originates from interactions of solvent water with 31P moiety. Implications for in vivo spectroscopy are indicated.

Adenosine Triphosphate↗

PubMedDate not supplied

Contrasting effects of PACAP and carbachol on [Ca2+]i and inositol phosphates in human neuroblastoma NB-OK-1 cells.

The effects of PACAPs on [Ca2+]i were compared to those of carbachol in human neuroblastoma NB-OK-1 cells. PACAP(1-27) and PACAP(1-38) increased [Ca2+]i in a biphasic manner: a transient rise and a secondary plateau. The transient phase reflected the mobilization of [Ca2+]i pool(s) via the inositol phosphate pathway. The modest sustained plateau required extracellular Ca2+. Carbachol also increased [Ca2+]i in a biphasic manner, but it mobilized intracellular Ca2+ pool(s) with a higher efficacy than PACAPs, then greatly increased Ca2+ entry, this being accompanied by a more marked and prolonged elevation of IP3 and IP4 than with PACAPs. It is likely that cAMP-mediated phosphorylations due to PACAPs facilitated desensitization at the PACAP receptor-phospholipase C level, so that there was less Ca2+ handling through PACAP receptors than with muscarinic M1 receptors.

Calcium↗

PubMedDate not supplied

Safety and efficacy of adenovirus-mediated transfer of the human aquaporin-1 cDNA to irradiated parotid glands of non-human primates.

This study evaluated the safety and efficacy of a single administration of a recombinant adenovirus encoding human aquaporin-1 (AdhAQP1) to the parotid glands of adult rhesus monkeys. In anticipation of possible clinical use of this virus to correct irradiation damage to salivary glands, AdhAQP1 was administered (at either 2 x 10(9) or 1 x 10(8) plaque-forming units/gland) intraductally to irradiated glands and to their contralateral nonirradiated glands. Radiation (single dose, 10 Gy) significantly reduced salivary flow in exposed glands. Virus administration resulted in gene transfer to irradiated and nonirradiated glands and was without untoward local (salivary) or systemic (sera chemistry, complete blood count) effects in all animals. However, the effect of AdhAQP1 administration varied and did not result in a consistent positive effect on salivary flow rates for all animals under these experimental conditions. We conclude that a single adenoviral-mediated gene transfer to primate salivary glands is well-tolerated, although its functional utility in enhancing fluid secretion from irradiated parotid glands is inconsistent.

Adenoviridae↗

PubMedDate not supplied

A new cucurbitacin glycoside from Kageneckia oblonga (Rosaceae).

A novel cucurbitacin glycoside has been isolated from aerial parts of Kageneckia oblonga R. et P. and shown to be 3beta-(beta-D-glucosyloxy)-16alpha,23alpha-epoxycuc urbita-5,24-dien-11-one. The structure was established by usual spectroscopic and two-dimensional (2D) NMR techniques. This compound has found to be nontoxic when tested in-vivo cell culture assays. In previous investigations we reported 23,24-dihydrocucurbitacin F and prunasine. This was the first report on cucurbitacins from the genus Kageneckia (Rosaceae).

Animals↗