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L Buscail

Publications and source records attributed to L Buscail.

At least 19 recordsLinked to original sources
PubMed1992

Stimulation of a membrane tyrosine phosphatase activity by somatostatin analogues in rat pancreatic acinar cells.

A phosphoryl protein tyrosine phosphatase (PTPase) activity has been characterized in rat pancreatic acinar membranes using 32P-labeled poly(Glu,Tyr) as substrate. Acinar membranes exhibited a high affinity for the substrate, with an apparent Km of 0.46 microM and an apparent Vmax of 0.9 nmol.mg protein-1.min-1. Acinar membrane PTPase activity displayed specific characteristics of other PTPases; it was inhibited by the inhibitors Zn2+, orthovanadate and by the divalent cations Mn2+ and Mg2+, and was stimulated by the reducing-agent dithiothreitol. It was also inhibited by soybean trypsin inhibitor and stimulated by trypsin. Gel permeation of pancreatic acinar membranes gave a single peak of enzyme activity with an apparent molecular mass of 70 000 Da. Further purification by HPLC on DEAE revealed two peaks of PTPase activity at 120 mM and 180 mM NaCl. These two peaks reacted in a Western-blot procedure with anti-(peptide) serum directed towards conserved domain of PTPase as a common 67-kDa form associated with lower-molecular-mass proteolytic fragments (31-56 kDa). Incubation of pancreatic acini with somatostatin analogues, SMS 201-995 or BIM 23014, resulted in a stimulation of membrane PTPase activity. The stimulation was rapid and transient, with a maximal level reached within 15 min of addition. The two analogs stimulated PTPase activity in a dose-dependent manner with half-maximal activation occurring at 7 pM and 37 pM and maximal activation at 0.1 nM and 0.1-1 nM for SMS 201-995 and BIM 23014, respectively. The stimulated-membrane PTPase activity also eluted at an apparent molecular mass of 70 kDa in gel-permeation chromatography. The two analogs inhibited the binding of [125I-Tyr3]SMS 201-995 to pancreatic acinar membranes with similar relative potencies to that observed on stimulation of PTPase activity. We conclude that pancreatic acinar membranes possess a low-molecular-mass PTPase which is stimulated by somatostatin analogs at concentrations involving activation of membrane somatostatin receptors.

Amino Acid Sequence↗
PubMed1992

Microscopic examination of bile directly collected during endoscopic cannulation of the papilla. Utility in patients with suspected microlithiasis.

The usefulness of microscopic examination of pure bile directly collected from the biliary tract during endoscopic retrograde cholangiography and without hormonal simulation was prospectively evaluated in 72 patients. According to clinical, biochemical, ultrasonographic, and radiographic data, the patients were separated into two groups: group 1, patients with proven stones (N = 50), and group 2, patients with suspected microlithiasis presenting symptoms suggestive of cholelithiasis but without evidence of macroscopic stones at echography or cholangiography (N = 22). Cholesterol crystals and/or bilirubinate granules were observed (eg, positive examination) in the bile of 41 of the 50 patients of group 1 (82%). Among patients of group 2, seven (32%) had a positive bile examination: cholecystectomy (N = 2) or endoscopic sphincterotomy (N = 5) disclosed minute stones in all cases. In the 15 patients of group 2 with a negative bile examination, cholecystectomy (N = 3), sphincterotomy (N = 2), and clinical (and/or echographic) 20-month follow-up (N = 9) revealed biliary lithiasis in only one patient, in whom recurrent cholangitis led to disclosure of one bile duct stone. According to these results, microscopic examination of bile samples collected during endoscopic retrograde cholangiography exhibited a sensitivity and a specificity for cholelithiasis recognition of 82.7% and 100%, respectively, with a positive predictive value of 88%. We conclude that the accuracy of this method makes it useful to investigate and manage patients with suspected microlithiasis.

Aged↗
PubMed1992

Stimulation of rat pancreatic tumoral AR4-2J cell proliferation by pituitary adenylate cyclase-activating peptide.

In the present work the effects of the novel neuropeptide Pituitary Adenylate Cyclase Activating Peptide (PACAP) on both AR4-2J cell growth and the modulation of ornithine decarboxylase activity were investigated. Both PACAP38 and the amidated form PACAP27 caused a concentration-dependent stimulation of AR4-2J cell growth; the maximal increase was seen at 1 nmol/L (30% above control, P less than 0.01) with a half-maximal effect at 0.01 nmol/L. Ornithine decarboxylase activity was also increased by PACAP in a dose-dependent manner, reaching half-maximal stimulation at 0.5 nmol/L. The addition of 1 nmol/L of somatostatin analog SMS 201-995 totally suppressed PACAP-stimulated AR4-2J cell growth. Vasoactive intestinal polypeptide (3 mumol/L) and 8-bromo-cyclic adenosine monophosphate (1 mmol/L) had no effect on cell proliferation. Treatment of cells by pertussis toxin (25 ng.mL-1.day-1) suppressed PACAP-stimulated AR4-2J cell growth but enhanced PACAP-induced stimulation of adenylate cyclase activity. It was concluded that PACAP stimulates AR4-2J cell proliferation by a mechanism that seems independent of cyclic adenosine monophosphate production. The mitogenic effect of PACAP depends on a pertussis toxin-sensitive G protein and is associated with an increase of ornithine decarboxylase activity.

Adenylate Cyclase Toxin↗
PubMed1992

Characterization of a membrane tyrosine phosphatase in AR42J cells: regulation by somatostatin.

A phosphotyrosyl protein phosphatase (PTPase) activity has been characterized in the plasma membranes of confluent AR42J pancreatic tumor cells using 32P-labeled poly(Glu, Tyr) as substrate. Membrane PTPase activity exhibited an apparent Michaelis constant of 3 microM and an apparent maximal velocity of 0.9 nmol.min-1.mg-1. It was inhibited by orthovanadate, zinc, poly(Glu,Tyr) and was stimulated by EDTA and dithiothreitol. Gel filtration of solubilized plasma membranes gave a peak of enzyme activity at a relative molecular weight of 70,000. Plasma membrane PTPase activity was changed during AR42J cell growth. At the beginning of culture, the control PTPase activity was minimal. Over the 5 days of culture, PTPase activity increased to reach a maximum (3.5-fold over control activity) preceding confluency by 2 days. Then the high level of PTPase activity was sustained until confluency. Incubation of the cells with the stable somatostatin analogue SMS 201-995 (SMS) resulted in a rapid and transient activation of crude membrane PTPase activity. Activation reached a maximum level within 5 min of addition and return to control levels within 20 min. The effect of SMS was dose dependent with half-maximal and maximal activation occurring at 6 pM and 0.1 nM SMS respectively.

Animals↗
PubMed1991

The two forms of the pituitary adenylate cyclase activating polypeptide (PACAP (1-27) and PACAP (1-38)) interact with distinct receptors on rat pancreatic AR 4-2J cell membranes.

The existence of specific receptors for the two PACAPs (Pituitary Adenylate Cyclase Activating Peptides of 27 and 38 amino acids) was previously demonstrated on membranes from the pancreatic acinar cell line AR 4-2J (Buscail et al., FEBS Lett. 202, 77-81, 1990) by [125I]PACAP-27 binding. Here we demonstrate, by comparing Scatchard analysis of saturation curves and competition binding curves obtained with [125I]PACAP-27 and [125I]PACAP-38 as radioligands, the coexistence of two classes of receptors: 1/PACAP-A receptors that recognize PACAP-27 and PACAP-38 with the same high affinity (Kd 0.3 nM) and 2/PACAP-B receptors that recognize PACAP-38 with a high affinity (Kd 0.3 nM) and PACAP-27 with a lower affinity (Kd 30 nM). These two receptors are coupled to adenylate cyclase but can be clearly distinguished by the ability of PACAP(6-27) to specifically inhibit PACAP-27 adenylate cyclase activation.

Animals↗
PubMed1991

PACAP and VIP receptors in rat liver membranes.

Pituitary adenylate cyclase activating peptide (PACAP) tested as PACAP-(1-38)NH2 and PACAP-(1-27)NH2 and vasoactive intestinal polypeptide (VIP) were compared for their capacity to discriminate between high- and low-affinity VIP-preferring receptors that coexist in rat liver plasma membranes. This capacity was evaluated by the ability to 1) inhibit 125I-labeled-PACAP-(1-27)NH2, 125I-labeled-VIP, and 125I-labeled-helodermin binding and 2) to activate adenylate cyclase. PACAP-(1-27)NH2 bound specifically and reversibly to three classes of binding sites, as revealed by analysis of binding curves. On high-affinity VIP receptors (tested specifically by [125I]-helodermin binding), PACAP-(1-38)NH2 showed lower affinity than PACAP-(1-27)NH2 and VIP itself. On low-affinity VIP receptors, PACAP-(1-27)NH2 and -(1-38)NH2 showed similar modest affinity that was slightly higher however than that of VIP. For a third specific class of PACAP receptors (20% of PACAP receptors not recognized by VIP), PACAP-(1-38)NH2 showed higher affinity than PACAP-(1-27)NH2. Both PACAPs stimulated rat liver adenylate cyclase with the same low efficacy as VIP but with an affinity even greater [half-maximal effective concentration (EC50) 0.02 nM] than that of VIP (EC50 0.05 nM).

Amino Acid Sequence↗
PubMed1990

Purification and amino acid sequence of vasoactive intestinal peptide, peptide histidine isoleucinamide (1-27) and secretin from the small intestine of guinea pig.

The neuropeptides vasoactive intestinal peptide (VIP) and peptide histidine isoleucinamide (1-27) (PHI) and the hormone secretin were purified from the small intestine of guinea pig, being detected by radioimmunoassay and radioreceptor assay throughout six to seven chromatographic steps. After elution on a reverse-phase C18 column, the three peptides were separated on a Fractogel column. After cation-exchange chromatography of each peptide on Mono S, the final steps were performed using a reverse-phase RP8-e column. Guinea pig PHI differed from porcine PHI in having Tyr and Arg residues instead of Phe and Lys in, respectively, position 10 and 20. We confirmed the original sequence of guinea pig VIP previously documented (with Leu5, Thr9, Met19 and Val26). We also established the similarity of the primary structure of guinea pig secretin with that of porcine and bovine.

Amino Acid Sequence↗
PubMed1990

Presence of highly selective receptors for PACAP (pituitary adenylate cyclase activating peptide) in membranes from the rat pancreatic acinar cell line AR 4-2J.

We characterized highly selective receptors for PACAP, the pituitary adenylate cyclase activating peptide, in the tumoral acinar cell line AR 4-2J derived from the rat pancreas. PACAP, a novel hypothalamic peptide related to vasoactive intestinal peptide (VIP), was tested as the full natural 38-residue peptide (PACAP-38) and as an N-terminal amidated 27-residue derivative (PACAP-27). The binding sites showed considerable affinity for [125I]PACAP-27 (Kd = 0.4 nM) and PACAP-38, while their affinity for VIP and the parent peptide helodermin was 1000-fold lower. These receptors were coupled to adenylate cyclase, the potency of PACAP-38 and PACAP-27 (Kact = 0.2 nM) being much higher than that of VIP (Kact = 100 nM) and helodermin (Kact = 30 nM). Chemical cross-linking of [125I]PACAP-27 followed by SDS-PAGE and autoradiography revealed a specifically cross-linked peptide with an Mr of 68,000 (including 3000 for one PACAP-27 molecule).

Adenylyl Cyclases↗
PubMed1990

Gastric lipase in alcoholic pancreatitis. Comparison of secretive profiles following pentagastrin stimulation in normal adults and patients with pancreatic insufficiency.

The aims of this study were to evaluate the amount of gastric lipase secreted by the stomach in normal adults and to elucidate a possible adaptative secretion of this enzyme in response to pancreatic insufficiency secondary to alcoholic chronic pancreatitis. Forty-one subjects underwent a gastric intubation. Pentagastrin (6 micrograms.kg-1.h-1 IV) significantly increased gastric lipase concentration and output. Stimulated gastric lipase output in seven normal subjects was 12,598 +/- 2036 U/h (by using tributyrin as substrate). Outputs where higher (P less than 0.02) in 17 patients with pancreatic insufficiency who were not drinking alcohol, but were not significantly different in nine patients who continued to drink (20,413 +/- 1778 U/h and 21,953 +/- 4973 U/h, respectively). On the other hand, high gastric lipase outputs were found in eight patients with duodenal ulcers and no evidence of pancreatic dysfunction (23,180 +/- 262 U/h). The time required to reach maximal lipase output (peak output) following pentagastrin stimulation was the same in all groups (approximately 38 minutes) except for the group of patients with pancreatic insufficiency who did not drink alcohol, in whom it was significantly reduced (approximately 26.5 minutes). Secretory patterns of gastric lipase and pepsin were closely comparable. Gastric lipase secretion could be increased in several clinical conditions and particularly in patients with pancreatic insufficiency caused by alcoholic chronic pancreatitis who have been abstinent for a long time.

Adult↗
PubMed1990

Divergent regulation of beta 2-adrenoceptors and adenylate cyclase in the Cyc- mouse T lymphoma cell line TL2-9.

The radiation leukemia virus-induced murine Cyc- T lymphoma cell line TL2-9 expressed one homogeneous population of beta 2-adrenoceptors based on competition curves of [125I]cyanopindolol with the specific antagonist ICI 118.551 and three beta-adrenergic agonists. These receptors were uncoupled from adenylate cyclase due to the absence of Gs. The catalytical unit was directly stimulated by MnCl2, forskolin, and even more markedly in the simultaneous presence of both reagents. In contrast, the enzyme was inhibited in the presence of Gpp[NH]p, probably through interaction with Gi. Indeed, this inhibitory effect was constrained by preincubating cells in the presence of pertussis toxin and a 41 kDa protein was specifically ADP-ribosylated in the presence of the toxin. This cell line was therefore analogous to the Cyc- cell line derived from the murine S49 lymphoma cell line. When added to the culture medium, butyrate (2 mM) induced beta 2-adrenoceptors, the expression of these uncoupled receptors depending on protein synthesis, as judged by inhibitory effects of cycloheximide. In contrast, dBcAMP (1 mM) and TPA (tumor-promoting agent phorbol ester) increased the rate of disappearance of beta 2-adrenoceptors. Butyrate, dBcAMP and TPA systematically decreased adenylate cyclase activity. Besides, TPA (but neither butyrate nor dBcAMP) reduced the efficacy of Gpp[NH]p in inhibiting adenylate cyclase, suggesting a proportionately higher alteration of Gi. We conclude that beta 2-adrenoceptors, uncoupled from adenylate cyclase, are regulated independently from the catalytical unit and Gi, in this Cyc- T lymphoma cell line.

Adenylyl Cyclases↗
PubMed1990

Protective effect of misoprostol, a synthetic prostaglandin E1 analog, on cerulein-induced acute pancreatitis in rats.

This study was performed to assess the effects of misoprostol, a synthetic prostaglandin E1 analog, on cerulein-induced pancreatitis. Per group of 10 each, male Wistar rats received either cerulein (2.5 micrograms/kg/h subcutaneously), cerulein and misoprostol (500 micrograms/kg intraperitoneally at 0 and 4 h), or saline. Rats were killed 6 h after the first injection. Misoprostol treatment significantly reduced interstitial edema and acinar cell lesions induced by hyperstimulation. Pancreatic amylase and chymotrypsin contents were increased by cerulein and returned towards control levels in the misoprostol-treated group. The lysosomal volume density and the pancreatic beta-D-glucuronidase activity were significantly increased after hyperstimulation. The two parameters were significantly reduced by misoprostol. A protective effect of misoprostol against lesions induced by cerulein hyperstimulation would be a consequence of a lysosomal stabilizating effect.

Acid Phosphatase↗
PubMed1990

VIP receptors in human SUP-T1 lymphoblasts.

We characterized a new type of vasoactive intestinal peptide (VIP) receptors in the CD4+ Stanford University Pediatric (SUP)-T1 lymphoma cell line, by comparing receptor occupancy [in the presence of (125I)helodermin and (125I)(acetyl-His1)VIP] and adenylate cyclase activation (in the presence of GTP). The order of potency of peptides on both parameters was: helodermin greater than (acetyl-His1)VIP greater than (Phe1)VIP = VIP greater than PHI while secretin was ineffective. In membranes, when Gs was permanently activated by Gpp(NH)p or by ADP-ribosylation (after pretreating intact lymphoblasts for 2 h with cholera toxin), there resulted a variably increased affinity of receptors for VIP-like peptides, suggesting reduced receptor selectivity. Preexposing intact lymphoblasts to the same peptides induced, within 5 min, homologous desensitization (i.e. reduced binding capacity and even more so impaired capability to activate adenylate cyclase), whose extent correlated with the Kd of each peptide at time 0. After prolonged (16 h) exposure to 30 nM VIP that resulted in marked (75%) downregulation, 60% of the adenylate cyclase responsiveness could recover within 30-120 min even in the presence of cycloheximide, but further resensitization was cycloheximide-sensitive. To conclude, VIP receptors coupled to adenylate cyclase showed distinct specificity in human SUP-T1 lymphoblasts. Their specificity decreased when Gs was permanently activated. In intact cells exposed to VIP-like peptides, the receptors were rapidly desensitized, then down-regulated, the resensitization mechanism being not immediately inhibited by cycloheximide.

Adenylyl Cyclases↗
PubMed1989

The phorbol ester TPA stimulates the expression of functional beta-adrenoceptors in human T lymphoblasts Molt 3.

In crude membranes from human T lymphoblasts Molt 3 cultured under standard conditions, the adenylate cyclase system was stimulated by GTP, its beta gamma-imido analogue (p[NH]ppG,) NaF and forskolin, but not by isoprenaline, prostaglandin E1 and vasoactive intestinal peptide. TPA (tumour-promoting agent phorbol ester) added at low concentration (3.2 nM) to the culture medium induced a marked increase in functional beta 2-adrenoceptors. Competition curves of [125I]cyanopindolol with the antagonist ICI 118.551 and four beta-adrenergic agonists indicated that the emergence of functional beta 2-adrenoceptors corresponded to one class of binding sites, shifting from a high-affinity state for agonists to a low-affinity state in the presence of p[NH]ppG. This expression of beta 2-adrenoceptors after a 4 h lag period depended on newly formed mRNA and protein synthesis as judged by the inhibitory effects of actinomycin D and cycloheximide. Further effects of TPA included alterations of the stimulatory G-protein Gs and/or the catalytic unit of adenylate cyclase.

Adenylyl Cyclases↗
PubMed1989

Protective effect of misoprostol, a synthetic prostaglandin E1 analog, on experimental pancreatitis induced by pancreatic duct ligation in rat.

This study was performed to assess the effects of misoprostol (M), a synthetic prostaglandin E1 analog, on experimental pancreatitis in rat. Pancreatitis was induced by ligation of the main pancreatic duct of 3-month-old male Wistar rats. Pancreatic lesions were observed at 6, 12, 24, 48, and 96 h after pancreatic duct ligation (PDL). A time of 48 h was chosen to evaluate M treatment. M was injected intraperitoneally (500 micrograms/kg every 4 h) between time 0 and 48 h after PDL. Stereological analysis was performed on light and electron microscopy. Total pancreatic amylase and chymotrypsin concentrations were determined. Four groups of five rats were studied: sham operated (SO), M without PDL (PG), duct ligation without M (DL), and duct ligation with M (DLPG). Edema, dedifferentiation of pancreatic acinar cells, and heterogeneous distribution of zymogen granule diameters observed after PDL were significantly decreased by M in the DLPG group. Enzyme concentrations were also decreased by M in the DLPG group. Enzyme concentrations were also decreased by M both in normal (PG) and duct ligated rats (DL). M has protective effects against pancreatic lesions induced by PDL. In this model, the protective effect of M may be due to a blockade of the autodigestive secretions of the pancreatic acinar cells.

Alprostadil↗
PubMed1989

[Interobserver and intercenter agreement of gastro-esophageal endoscopic signs in cirrhosis. Results of a prospective multicenter study].

Because of the diagnostic and prognostic value of gastroesophageal endoscopic signs in cirrhosis, we studied their interobserver and intercenter agreement. Fifty cirrhotic patients without previous digestive bleeding were included in this study. The gastroesophageal endoscopic examinations of these patients, recorded on video tape, were independently viewed by 12 observers belonging to different hospitals. Agreement was evaluated by the kappa index (k), the values of which were given with p less than 0.001. Agreement was good for the presence (k = 0.40) or the size (k = 0.51) of esophageal varices as well as for red signs on the mucosa overlying esophageal varices, but it was poor for the color (k = 0.10) or the extent (k = 0.20) of esophageal varices. Agreement was poor for all gastric signs: fundic varices (k = 0.35), red spots (k = 0.28), associated lesions (k = 0.27), mosaic pattern (k = 0.27), gastropathy (k = 0.11). The mean diameter of esophageal varices, evaluated without any scale, varied from 3.5 +/- 1.4 to 7.5 +/- 4.0 mm between the 12 observers (p less than 0.001). Agreement was maximum for the more developed grade of a sign and minimum for the intermediate grade. The value of kappa indexes in this intercenter study was compared to that obtained in a previous study from one institution: interobserver agreement was significantly better within one center than between different centers. In conclusion, intercenter agreement is good for the size of esophageal varices and the presence of red signs, and poor for all the other signs. The millemetric measurement of esophageal varices diameter, without any scale, appears to be unreliable.(ABSTRACT TRUNCATED AT 250 WORDS)

Esophageal and Gastric Varices↗
PubMedDate not supplied

Amino acid sequence of VIP, PHI and secretin from the rabbit small intestine.

VIP, PHI and secretin were purified from rabbit small intestine throughout a maximum of 6 chromatographic steps. After elution on a reverse phase C18 column, the 3 peptides were separated on a Fractogel column using specific radioimmunoassays for detection. After cation exchange chromatography on Mono S, the final steps were performed using a reverse phase RP8-e column. For these steps, radioreceptor assays were utilized to detect VIP and PHI. We confirmed that the VIP sequence of rabbit was identical to that of porcine VIP. The PHI sequence was also found identical to that of porcine PHI. By contrast, rabbit secretin was highly original, differing from porcine secretin in having Leu, Arg and Leu-NH2 residues instead of Phe, Ser and Val-NH2 in, respectively, position 6, 16 and 27.

Amino Acid Sequence↗