Biomedical subjects

B Colas

Publications and source records attributed to B Colas.

At least 37 records · Page 2Linked to original sources

PubMed1994

Butyrylcholinesterase amphiphilic forms of the mucosal cells of rat intestine bind heparin.

Mucosal cells of rat intestine express amphiphilic monomer (G1) and dimer (G2) as well as hydrophilic tetramer (G4) of butyrylcholinesterase (BChE). After incubation with heparin (3 and 15 microM), amphiphilic G2 form showed decreased migrations in nondenaturing electrophoresis whereas in these conditions, the mobility of hydrophilic forms from rat and human serum BChEs was unchanged. Sucrose gradient sedimentation and chromatography performed on HPLC gel filtration and on heparin-Sepharose confirmed that amphiphilic G1 and G2 forms were able to bind heparin. Increasing concentrations of heparin resulted in higher sizes of heparin-BChE complex. These properties of intestinal BChE may be related to the possible occurrence of endogenous heparin in this tissue.

Animals↗

PubMed1992

Amphiphilic forms of butyrylcholinesterase in mucosal cells of rat intestine.

The properties of a cholinesterase from mucosal cells of rat intestine have been characterized. The enzyme was identified as butyrylcholinesterase because it was more sensitive to iso-OMPA (IC50 = 1.0 x 10(-6) M) than to BW284C51 (IC50 = 5.5 x 10(-5) M) and was not inhibited by substrate excess. It displayed a higher affinity for acetylthiocholine than for butyrylthiocholine. A major molecular form was observed sedimenting at 5.9 S. Two other minor molecular forms were identified as a hydrophilic tetramer (G4, sedimenting at 10.5 S) and a monomer (G1, sedimenting at 4.3 S). The 5.9 S component was referred to as "G" form (G for globular) and not "G2" as usual dimers for the following reasons: (i) the G form was unaffected by the reducing agents, beta-mercaptoethanol and dithiothreitol, which converted disulfide-linked dimers of acetylcholinesterase into monomers, (ii) the G form was shifted from 5.9 to 3.4 S when the sucrose gradient contained Triton X-100. This value of 3.4 S (in Triton X-100) appeared too low for a typical G2 form. The shift in the S value was partly reversible: the 3.4 S form resedimented at 5.2 S in the absence of detergent. The behavior of the G form in sucrose gradients indicated that it was amphiphilic. This was confirmed in nondenaturing electrophoreses and also by quantitative binding of the G form to octyl-Sepharose. The hydrophobic domain of the G form was not a glycolipid, as shown by its insensitivity to Bacillus thuringiensis phosphatidylinositol-specific phospholipase C and its nonaggregating properties in the absence of nondenaturing detergent.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

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

Basic fibroblast growth factor induces proliferation of a rat pancreatic cancer cell line. Inhibition by somatostatin.

AR4-2J, a rat pancreatic acinar-tumor cell line, was used to investigate long-term effects of basic fibroblast growth factor (bFGF) and somatostatin on pancreatic cancer cells. We observed that bFGF stimulated cell proliferation when cells were cultured in serum-free medium. The effect was dose-dependent with half-maximal and maximal effects at 25 pM and I nM bFGF, respectively. The somatostatin analog SMS 201-995 (SMS) decreased the growth-promoting effect of bFGF. The maximal effect was observed at I nM SMS and the half-maximal effect at 20 pM SMS. Characterization of bFGF receptor-binding properties with [125I]bFGF revealed that AR4-2J cells exhibited 2 classes of bFGF binding site with respective KD values of 47 pM and 3 nM and binding capacities of 14 fmol and 0.9 pmol/10(6) cells. High-affinity receptors correlated with bFGF stimulation of AR4-2J cell growth, suggesting that the effects of bFGF are receptor-mediated.

Animals↗

PubMed1992

Behaviour of butyrylcholinesterase in the intestinal epithelial cells of starved and refed rats.

1. The activity and the molecular characteristics of butyrylcholinesterase were studied in the epithelial cells of the following intestinal segments: duodenum, jejunum, ileum, caecum and colon of starved and refed rats. 2. After starvation, the specific activity of the enzyme is found to increase in the jejunum. The same level of activity was maintained after refeeding. No notable changes were observed in the other intestinal segments after either starvation or refeeding. 3. The behaviour of aminopeptidase, a well-characterized intestinal enzyme, is comparable to that of butyrylcholinesterase, except in the duodenum where the aminopeptidase activity is increased after refeeding. 4. In this cell type, BuChE is found only in its globular forms (G1, G2 and G4). Starvation resulted in a higher value of the sedimentation coefficient of the ileal G2 form, suggesting the existence of a complex between the enzyme and non-cholinesterase components. 5. After refeeding, the sedimentation profile was similar to that of control.

Aminopeptidases↗

PubMed1991

Human intestine epithelial cell acetyl- and butyrylcholinesterase.

The epithelial cells of the human intestine exhibit a cholinesterase activity which is restricted to the apex of the villi. This activity displays a maximum in the colon and a minimum in the jejunum. Contrary to most of the studied vertebrates, the human cells present both acetylcholinesterase and butyrylcholinesterase activities, acetylcholinesterase being predominant in all the intestinal segments: duodenum, jejunum, ileum and colon. Like in the other vertebrates, only globular forms are identified by sucrose gradient centrifugation. However, the simultaneous presence, on the one hand of three globular forms (G1, G2 and G4) and, on the other hand of soluble as well as detergent-soluble molecular species seems to be a particular feature of the human cells.

Acetylcholinesterase↗

PubMed1991

Sex-related differences in the expression of chick enterocyte butyrylcholinesterase during embryonic and post-hatching development.

The butyrylcholinesterase activity of chick enterocytes was studied from day 15 in ovo up to day 90 after hatching. The activities detected in both sexes at the level of jejuno-ileum change in a parallel manner, but the activity is always higher in the female than in the male during embryonic development. After hatching, the differences are less apparent although the study of the enzyme distribution along the intestine showed sex-related variations, mainly at the level of the anterior and middle parts of jejuno-ileum in the young adult. Analysis of butyrylcholinesterase by sucrose gradient centrifugation allowed to identify two globular soluble species (G1 and G4 forms). The G4/(G1 + G4) ratio decreases during the development but this variation in the female does not parallel that observed in the male. Besides, the molecular form distribution along the intestine, studied after hatching, differs according to the sex. Taken together our results lead to hypothesize that the ontogeny and the regulation of the chick enterocyte butyrylcholinesterase depend on hormones.

Aging↗

PubMed1991

Influence of water on the mobility of small molecules dispersed in a polymeric system.

The rotational mobility of paramagnetic solutes dispersed in partially hydrated macromolecules (proteins, polysaccharides, synthetic polymers) was measured using Electron Spin Resonance. A critical minimum amount of water was observed to be necessary for these molecules to reach a level of mobility of the same order as in dilute solutions. This amount of water depended on the size of the diffusing solute and on the microporosity of the macromolecule. Above this critical moisture range, a progressive increase of the proportion of mobile solute occurred over a hydration range determined by the size of the diffusing solute. At the same time, the rotational diffusivity of the mobile solute increased linearly with water content. The mobilization pattern of spin-labelled side chains of caseinates was observed to be similar to that of the solute. Results are discussed with reference to free volume theory.

Caseins↗

PubMed1990

Embryonic and post-natal changes in activity and molecular forms of mucosal cell butyrylcholinesterase in chicken intestine.

The mucosal cells of the chicken intestine contain a cholinesterase activity essentially due to butyrylcholinesterase. The enzyme is present during embryonic and post-hatching development. The activity reaches a maximum value at day 19 in ovo and decreases prior to and after hatching up to day 4 ex ovo. Then the activity again rises reaching a second maximum at 2-3 weeks. Beyond this stage, the activity slowly decreases leveling off to the value determined in adult chicken. The enzyme exists as two globular forms (G1 and G4) soluble at low-ionic strengths. The G4 form is predominant in ovo up to day 19. From this stage and after hatching the G1 form is the main one. This change in the form proportion differentiates the mucosal cell butyrylcholinesterase from butyrylcholinesterase of other origins such as the chicken plasma enzyme which always shows a predominant G4 form.

Animals↗

PubMed1990

Effects of acute nicotine and mecamylamine administration on somatostatin concentration and binding in the rat brain.

Since nicotine and somatostatin have regulatory effects on locomotor activity it was of interest to determine whether the receptors for somatostatin are modulated by the cholinergic nicotine-like effects. An i.v. dose of 0.3 mg/kg nicotine induced an increase in the concentrations of somatostatin-like immunoreactivity at 4 min in the parietal cortex and at 15 min in the hippocampus. These changes were associated with a significant increase in the total number of specific somatostatin receptors in the parietal cortex at 15 min and in the hippocampus at 30 min following injection. To determine if the above mentioned changes are related to the nicotine activation of central nicotine-like acetylcholine receptors, a cholinergic nicotinic blocking agent, mecamylamine, was administered before the nicotine injection. Pretreatment with mecamylamine (5.0 mg/kg i.v.) prevented the nicotine-induced changes in somatostatin level and binding in both brain areas. Mecamylamine alone had no observable effect on the somatostatinergic system. These results suggest that the somatostatinergic system can be regulated by nicotine-like acetylcholine receptors and may be involved in some of the behavioral central effects of nicotine.

Animals↗

PubMed1990

Solubilization and characterization of active somatostatin receptors from rat pancreas.

Somatostatin receptors were solubilized from rat pancreatic membranes with the zwitterionic detergent 3-[(3-cholamidopropyl)dimethylammonio]-1-propane-sulfonic acid (CHAPS). The binding of an iodinated somatostatin analog [125I-Tyr3]SMS to the soluble fraction was time-dependent, saturable, and reversible. Scatchard analysis of equilibrium binding data indicated that the soluble extract contained a single class of somatostatin binding sites with a Kd of 0.3 nM and a Bmax of 210 fmol/mg. As observed with membrane-bound receptors, soluble binding receptors were sensitive to the GTP analog GTP gamma S indicating that they are functionally linked to a G protein. A molecular weight of about 400,000 was determined for soluble receptors under native conditions by gel filtration. In denaturing gel electrophoresis, photoaffinity labeling of soluble receptors identified a major protein of Mr = 100,000 and two minor proteins of Mr = 56,000 and 21,000. Isoelectric focusing of soluble receptors revealed that the somatostatin receptor is an acidic protein with pI 4.8. The soluble somatostatin receptor is a glycoprotein which can be specifically bound to the wheat germ agglutinin lectin and eluted by triacetyl-chitotriose.

Animals↗

PubMed1990

Somatostatin inhibition of VIP- and isoproterenol-stimulated cyclic AMP accumulation in dissociated cells from rat cerebral cortex.

Freshly dissociated cerebral cortex cells from adult rats have been used in the present study to determine if dual regulation of cyclic AMP levels by inhibitory and stimulatory agents can be expressed in the mature brain. Somatostatin, an inhibitory agent, barely affected the basal cyclic AMP metabolism while vasoactive intestinal peptide (VIP) and isoproterenol, two stimulatory agents enhanced cyclic AMP production. However, this increase was depressed by somatostatin, which decreased the efficiency, but not the potency, of the effects of the two stimulatory agents on cyclic AMP accumulation.

Animals↗

PubMed1990

Effects of electrical stimulation on molecular forms of butyrylcholinesterase in denervated fast and slow latissimus dorsi muscles of newly hatched chicken.

The effects of denervation and direct electrical stimulation upon the activity and the molecular form distribution of butyrylcholinesterase (BuChE) were studied in fast-twitch posterior latissimus dorsi (PLD) and in slow-tonic anterior latissimus dorsi (ALD) muscles of newly hatched chicken. In PLD muscle, denervation performed at day 2 substantially reduced the rate of rapid decrease of BuChE specific activity which takes place during normal development, whereas in the case of ALD muscle little change was observed. Moreover, the asymmetric forms which were dramatically reduced in denervated PLD muscle were virtually absent in denervated ALD muscle at day 14. Denervated PLD and ALD muscles were stimulated from day 4 to day 14 of age. Two patterns of stimulation were applied, either 5-Hz frequency (slow rhythm) or 40-Hz frequency (fast rhythm). Both patterns of stimulation provided the same number of impulses per day (about 61,000). In PLD muscle, electrical stimulation almost totally prevented the postdenervation loss in asymmetric forms and led to a decrease in BuChE specific activity. In ALD muscle, electrical stimulation partially prevented the asymmetric form loss which occurs after denervation. This study emphasizes the role of evoked muscle activity in the regulation of BuChE asymmetric forms in the fast PLD muscle and the differential response of denervated slow and fast muscles to electrical stimulation.

Animals↗

PubMed1989

Effects of insulin-induced hypoglycemia on somatostatin level and binding in rat cerebral cortex and hippocampus.

The effects of severe insulin-induced hypoglycemia on somatostatin level and specific binding in the cerebral cortex and hippocampus were examined using 125I-Tyr11-somatostatin as a ligand. Severe insulin-induced hypoglycemia did not affect the level of somatostatin-like immunoreactivity in the brain areas studied. However, the number (but not the affinity) of specific somatostatin receptors was significantly decreased in membrane preparation from the hippocampus but not in the cerebral cortex at the onset of hypoglycemic coma (5-10 min). Administration of glucose at the onset of hypoglycemic coma brought about extensive recovery of hippocampal somatostatin receptor number. These results suggest that glucose modulates the somatostatin receptor in the rat hippocampus. The physiological significance of these findings remains to be clarified.

Animals↗

PubMed1989

Characterization of cholinesterase molecular forms in the mucosal cells along the intestine of the chicken.

The presence of a butyrylcholinesterase (BuChE, EC 3.1.1.8) in the musocal cells of the chicken intestine was demonstrated by histochemical and biochemical methods. The study of its distribution, along the intestine from duodenum to rectum, showed that the jejuno-ileum possesses the highest activity. Sucrose gradient centrifugation revealed, in all intestinal areas, two globular forms with sedimentation coefficients of 4.3 S (G1 form) and 10.8 S (G4 form). The presence of Triton X-100 in the preparations did not modify the sedimentation profiles of these two forms which can be considered as soluble BuChE. The ratio of G1/G4-forms progressively decreases along the intestine from duodenum to rectum indicating a predominance of the G4 form in the areas where the activity is low. Our results are discussed in relation to other studies of globular forms of chicken BuChE.

Acetylcholinesterase↗

PubMed1989

Long-term haloperidol treatment decreases somatostatin binding in rat brain.

The effects of short and long-term haloperidol treatment on somatostatin concentration and specific binding in rat cerebral cortex and hippocampus were examined using the binding ligand 125I-Tyr1-somatostatin. Haloperidol treatment did not affect the concentration of somatostatin-like immunoreactivity in the two brain areas. Nevertheless, long-term, and not short-term, haloperidol treatment decreased the number of somatostatin receptors in the cerebral cortex and hippocampus. No significant differences in the apparent binding affinity values were seen after haloperidol treatment. When added at the time of the binding assay haloperidol 34.2 microM produced a 42% and 27% decrease in cerebrocortical and hippocampal membrane somatostatin receptors respectively.

Animals↗

PubMed1988

Acetylcholinesterase and butyrylcholinesterase in the gut mucosal cells of various mammal species: distribution along the intestine and molecular forms.

1. A cholinesterase activity was shown to be present in the homogenates of the gut mucosal cells from seven mammal species examined. 2. The distribution of the cholinesterase activity in the mucosal cells along the intestine differs from one species to another. This distribution is not correlated with that of the aminopeptidase which is a specific marker of the enterocyte plasma membranes. 3. Except rabbit, all the other species contain a (G4) globular tetrameric form and either a (G1) monomeric form (pig, ox) or a (G2) dimeric form (mouse, rat, sheep). Both (G1) and (G2) forms are found with the (G4) form in the mucosal cells of kitten and cat. The solubility characteristics of these various forms were studied by sucrose gradient centrifugations in the presence and the absence of 1% Triton X-100. 4. The mucosal cells from the studied species essentially possess either acetylcholinesterase (rabbit, kitten, cat) or butyrylcholinesterase (ox, pig, sheep, rat, mouse). These findings indicate that both enzymes probably present identical physiological functions in this cell type.

Acetylcholinesterase↗

PubMed1988

Partial enterectomy decreases somatostatin-binding sites in residual intestine of rabbits.

1. Three weeks after partial enterectomy in the rabbit there was an increased somatostatin concentration and a decreased number of somatostatin-binding sites (without changes in the corresponding affinity values) in the cytosol of the residual intestinal tissue, except in the terminal ileum and the colon. 2. Five weeks after surgery both the somatostatin concentration and the number of somatostatin-binding sites returned towards control values. 3. These results suggest that an increase in bowel somatostatin content could lead to down-regulation of somatostatin-binding sites in the intestinal mucosa.

Animals↗