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Biomedical subjects

B Rossignol

Publications and source records attributed to B Rossignol.

At least 73 records · Page 4Linked to original sources
PubMed1985

Comparative effects of cytochalasin D on the protein discharge induced by alpha- and beta-adrenergic or cholinergic agonists in rat exorbital lacrimal glands.

Cytochalasin D altered the kinetics of peroxidase and radiolabeled protein discharge from rat exorbital lacrimal glands in vitro, in response to various secretagogues. The changes were different with each inducer. The discharge due to isoproterenol was immediately inhibited by 95%; the discharge evoked by noradrenaline via alpha-adrenergic receptors was progressively reduced and was inhibited by 50% after 30 min, whereas that evoked by carbachol was not influenced during the initial discharge period and was diminished by only 30% after 30 min. When calcium was removed from the incubation medium, the secretory responses were lowered and the inhibitory effect of cytochalasin D was still observed. The rate of protein discharge inhibition was related to the dose and was maximal with 2 X 10(-6) M cytochalasin D when the discharge resulted from cholinergic, alpha- or beta-adrenergic or dibutyryl cAMP stimulation. Cytochalasin D did not impair cellular energetics nor other stimulations induced through muscarinic or adrenergic receptors. Cytochalasin D effects could be related to interaction with actin, leading to the inhibition of the release of proteins into the incubation medium following the activation of the adrenergic system.

Adrenergic alpha-Agonists↗
PubMed1985

Cytochalasin D suppresses beta-adrenergic induced protein discharge without inhibiting membrane fusion.

Biochemical studies have shown that low doses of Cytochalasin D (CD) inhibit protein discharge evoked by isoproterenol, a beta-adrenergic inducer, in isolated lobules of Rat parotid gland. Ultrastructural and radioautographic studies reported here indicate that, when lobules are treated by CD before isoproterenol stimulation, the connection of secretory granules with the acinar lumen is indeed prevented, but fusion of membrane granules evoked by isoproterenol still occurs. This fusion takes place with vacuoles induced by CD and possibly with other granules.

Animals↗
PubMed1985

ATP-dependent calcium transport in rat parotid microsomes. I. Localization, properties, Ca2+-ATPase activity and phosphoenzyme formation.

ATP-dependent Ca2+ transport was studied in rat parotid microsomes; the activity appears to be associated with rough endoplasmic reticulum vesicles, as indicated by marker distribution in subcellular fractions and by electron microscopic observations. Purified rough microsomes exhibit an ATP-dependent Ca2+ accumulation and a Ca2+-dependent ATPase activity; these activities are similarly stimulated by K+ and display an apparent Km for free calcium of 0.6-0.7 microM. A phosphoprotein, with a molecular weight of about 110,000, was detected after short incubation with [gamma 32P] ATP and CaCl2; it is suggested that this compound represents a phosphorylated intermediate form of the Ca2+-ATPase.

Animals↗
PubMed1985

[Efficacy of oral bepridil in ventricular arrhythmias in stable coronary insufficiency].

The electrophysiological properties of bepridil suggest a possible ventricular antiarrhythmic effect. This prospective multicentre trial was undertaken to study the antiarrhythmic efficacy of oral bepridil on ventricular arrhythmias in patients with stable coronary insufficiency and more than 1 000 ventricular extrasystoles per 24 hours or ventricular tachycardia. The patients were divided into 3 groups according to the arrhythmias observed and the dosage used. In group I, the dosage was 300 mg/day and 12 out of 44 patients (27%) responded favourably to two criteria of efficacy (decrease of 84% of the number of ventricular extrasystoles; suppression of complex ventricular extrasystoles). In group II, the dosage was 300 mg/day, and then increased to 500 mg in non responders. Using the same criteria of efficacy, 13 out of 19 positive results were observed (68.4%). Group III comprised all cases of ventricular tachycardia; bepridil was effective in 3 out of 6 cases, associated with amiodarone in 1 case. The results demonstrate an antiarrhythmic effect of bepridil which is modest at 300 mg/day but which becomes more marked at the dosage of 500 mg/day.

Administration, Oral↗
PubMed1984

Protein secretion induced by isoproterenol or pentoxifylline in lacrimal gland: Ca2+ effects.

In exorbital lacrimal glands, pentoxifylline (a methylxanthine) induces labeled protein secretion in a dose-related manner: the half-maximal and maximal stimulations are at 4 and 10 mM, respectively. In the presence of papaverine (10(-5) M), a phosphodiesterase inhibitor, labeled protein discharge is strongly stimulated by isoproterenol, via beta-adrenergic receptors: the maximal response is at 10(-6) M. l-Propranolol specifically inhibits the secretory stimulation to isoproterenol in a dose-related manner: for 5 X 10(-6) M isoproterenol in the presence of 10(-5) M papaverine, the half-maximal and maximal inhibitions are at 3 X 10(-7) and 10(-5) M, respectively. The beta-adrenergic response is mimicked by the adenosine 3',5'-cyclic monophosphate (cAMP) analogue dibutyryl cAMP (DBcAMP) at a 10(-3) M concentration. The time course of labeled protein secretion induced by pentoxifylline, DBcAMP, and isoproterenol shows a latency. In the presence or absence of extracellular calcium, pentoxifylline and isoproterenol immediately increase the cAMP intracellular level. Extracellular calcium omission increases the observed latency and also affects the maximal rate of protein secretion. As opposed to the cholinergic agonist, pentoxifylline has only a slight but sustained effect on 45Ca efflux, whereas isoproterenol has none. These data suggest that labeled protein secretion, such as that of peroxidase, can also be stimulated in rat exorbital lacrimal gland, through beta-adrenergic receptors; in the stimulation evoked by a beta-adrenergic agonist, DBcAMP, or methylxanthine, calcium could play a key role.

Animals↗
PubMed1983

Forskolin as a tool to study the beta-adrenergic receptor-elicited, labeled protein secretion in rat lacrimal gland.

In rat lacrimal glands, Forskolin induces a dose-dependent [3H]protein release. This effect can be potentiated by papaverine. As for the other inducers whose effects on protein secretion are assumed to be cAMP-mediated, Forskolin secretion time course shows a latency. Isoproterenol decreases the Forskolin EC50 at least 60-times. On the other hand, Forskolin enhances the efficacy of isoproterenol without affecting its potency. As a whole, the data collected show that isoproterenol-induced [3H]protein secretion in rat lacrimal glands involved adenylate cyclase activation by coupling with beta-adrenergic receptors.

Animals↗
PubMed1983

Comparative effect of atropine on the adrenergic and muscarinic stimulation of phospholipid 32P labelling in isolated parotid cells: atropine, a possible blocker of alpha-adrenergic receptors.

The inhibitory effect of atropine on phospholipid 32P labelling stimulated by muscarinic or alpha-adrenergic agonists was studied in isolated parotid cells. Atropine (10(-11) to 10(-4) M) had no effect on phospholipid 32P labelling in unstimulated cells. In contrast, 10(-8) to 10(-7) M atropine provoked a competitive inhibition of the cholinergic stimulation (i.e. this effect was completely wiped out at high agonist concentration). The atropine app. KD for the muscarinic receptor was 5 X 10(-9) M. Moreover, atropine inhibits the adrenergic stimulation of phospholipid 32P labelling by decreasing the efficacity and potency of the adrenergic agonists. The atropine app. KD for the alpha-adrenergic receptor can be estimated at 10(-5) M. This inhibition of alpha-adrenergic stimulation appears to be specific since atropine was without effect on the substance P or beta-adrenergic stimulation. At very low concentration (10(-10) - 10(-9) M) atropine seems to be a modulator (activator) of the muscarinic or adrenergic agonist-receptor complex. From the present data, it is suggested that atropine, besides its classical blocker effect at the muscarinic receptor, at high concentration is a specific alpha-adrenergic antagonist.

Animals↗
PubMed1982

Microtubules and protein secretion in rat lacrimal glands: localization of short-term effects of colchicine on the secretory process.

The pathway and kinetics of the secretory protein transport in rat lacrimal exorbital gland have been established by an in vitro time-course radioautographic study of pulse-labeled protein secretion. The colchicine-sensitive steps have been localized by using the drug at various times with respect to the pulse labeling of proteins. Colchicine (10 microM) does not block any step of the secretory protein transport, but when introduced before the pulse it decreases the transfer of labeled proteins from the rough endoplasmic reticulum to the Golgi area, suppressing their temporary accumulation in the Golgi area before any alteration of this organelle is detectable. Moreover, colchicine inhibits protein release only from the secretory granules formed in its presence because the peroxidase discharge is diminished 1 h after colchicine addition, and the secretion of newly synthesized proteins is strongly inhibited only when colchicine is introduced before secretory granule formation. Morphometric studies show that there is a great increase of secondary lysosomes, related to crinophagy, as early as 40-50 min after colchicine is added. However, changes in lysosomal enzymatic activities remained biochemically undetectable. We conclude that: (a) the labile microtubular system does not seem indispensable for protein transport in the rough endoplasmic reticulum-Golgi area but may facilitate this step, perhaps by maintaining the spatial organization of this area; and (b) in the lacrimal gland, colchicine inhibits protein release not by acting on the steps of secretion following the secretory granule formation, but by acting chiefly on the steps preceding secretory granule formation, perhaps by making the secretory granules formed in its presence incapable of discharging their content.

Animals↗
PubMed1981

A tentative explanation of the stimulatory effect of methylxanthines (pentoxifylline and isobutylmethylxanthine) on the secretory process in rat extraorbital lacrimal gland.

In the present paper we report the effect of two methylxanthines (pentoxifylline and isobutylmethylxanthine) on the protein secretion in a model of exocrine gland (rat lacrimal gland). Both compounds are able to increase the protein release. This effect is dependent on the calcium concentration gradient between the extra- and intracellular media. The larger the difference, the greater the pentoxifylline or isobutylmethylxanthine effect. Moreover, pentoxifylline and isobutylmethylxanthine can potentiate the norepinephrine or isoproterenol effect by inhibiting phosphodiesterases (even in the absence of calcium). All these data suggest pentoxifylline and isobutylmethylxanthine can act on the cell functions in two ways: (a) by a calcium-dependent mechanism, either by increasing the influx of calcium into the cell or by mobilizing the pool of intracellular calcium; (b) by a mechanism independent of calcium and dependent on a system involving cyclic nucleotides. The first possibility seems to be very attractive for further investigations of the mechanism of action of pentoxifylline and especially when this drug is used to affect the cell motility or deformability controlled by calcium.

1-Methyl-3-isobutylxanthine↗
PubMed1980

Effects of carbachol on extracellular Na-dependent AIB uptake in rat parotid gland.

In rat parotid glands the uptake of 2-[1-14C]aminoisobutyric acid (AIB), in vitro, depends on a Na concentration gradient between the intra- and extracellular medium. Ouabain (1 mM) which inhibits the Na+-K+-ATPase and a Na+ ionophore, monensin (which dissipates the Na+ gradient), both suppress this amino acid uptake. Carbachol (5 microM) (through muscarinic receptors) evokes a decrease in AIB uptake, and in the presence of 0.1 mM ouabain the cholinergic effect is enhanced. Ouabain alone (0.1 mM) very slightly depresses the [14C]AIB uptake. Neither 1 microM isoproterenol, nor 1 microM Ca2+ ionophore A23187, which affect the membrane potential in rat parotid acinar cells, modifies the AIB uptake. When the Ca is removed from the incubation medium, carbachol still evokes a small decreasing effect on AIB uptake. From these data we can suggest that the reduced AIB uptake (induced by the cholinergic agonist) appears to be related to a process dependent on variation of intracellular Na concentration that may be triggered by the cholinergic agonist.

Absorption↗
PubMed1979

The halophilic properties of pyruvate kinase from Vibrio costicola, a moderate halophile.

Pyruvate kinase from Vibrio costicola, a moderate halophile, appears to be adapted to functioning in the presence of salt. Its stability depends on the ionic strength of the medium. The amino acid composition resembles that of other halophilic enzymes. It is proposed that the halophilic pyruvate kinase utilizes preferentially the Mn++ cofactor which forms more stable complexes in the presence of physiological concentrations of salt.

Amino Acids↗
PubMed1979

Microtubules and protein secretion in rat lacrimal glands. Inhibitory effect of the tubulin . colchicine complex isolated from lacrimal glands upon brain tubulin polymerization. Identification of the complex by gel electrophoresis.

The specific inhibitory effect of colchicine upon protein secretion by lacrimal glands could be related to the formation of a complex between colchicine and tubulin from the soluble fraction of the gland. By gel electrophoresis under nondissociating conditions, it is shown that this complex is similar to the colchicine . tubulin complex from brain. The complex isolated from lacrimal glands is highly inhibitory upon brain tubulin assembly since as low as 0.07 microM complex impedes the polymerization of 8 microM tubulin by 50%, compared to 3 microM for free colchicine. Therefore, a small percentage of complexed tubulin (0.9%) is enough for polymerization to be blocked. In lacrimal glands the complex might prevent the polymerization of tubulin, and colchicine shift the tubulin in equilibrium microtubules equilibrium to microtubules disassembly. The disorganization of the labile microtubular system could lead to a modification of the transport of the secretory granules and to a perturbation of secretion.

Animals↗
PubMed1979

[Value of potassium canrenoate in the prevention of arrhythmia during the acute phase of myocardial infarction].

This study was based on a series of 486 patients with acute myocardial infarction. All were treated with heparin and nitrite derivatives. 320 patients received 600 mg/24 h Potassium Canrenoate for 5 days (long duration); 90 patients received 1000 mg of Potassium for the first 36 hours only. 76 patients did not receive the drug and served as controls. The biochemical changes due to Potassium Canrenoate are discussed with special emphasis on the serum and intraerythrocytic potassium levels. The antiarrhythmic action of the potassium was assessed directly (the number of ventricular extra systoles decreased significantly) and indirectly (the amount of antiarrhythmic therapy required in association was three times less in patients treated by Potassium Canrenoate). The mortality rate changed from 17 to 12%. The beneficial effect of Potassium Canrenoate is attributed to the maintenance or the restoration normal potassium levels of ischaemic myocardial tissue.

Acute Disease↗