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J C Rousselle

Publications and source records attributed to J C Rousselle.

30 records · Page 2Linked to original sources
PubMed1983

5-Hydroxytryptamine receptors in neurones and glia.

Crude membranal fractions isolated from mammalian brain tissue contain two classes of recognition sites capable of binding [3H]5-HT with high affinity constants. These classes of sits are characteristics of the postsynaptosomal membrane fraction for the higher affinity and of a glial cell membrane fraction for the lowest. They are observed with similar properties in cultured neuronal and glial cell respectively. Two 5-HT stimulated adenylate cyclases are present in crude membrane fraction; they are also separable as neuronal and glial components. These observations correspond likely to the existence of two classes of receptors for 5-HT. Their mechanisms of regulation involve presumably structural conformation changes of the recognition site coupled to various states of the activity of the receptor.

Adenylyl Cyclases↗
PubMed1981

[Increase in binding affinity of the 5-HT receptor and decrease in 5-HT sensitive adenylate cyclase activity following prolonged exposure to 5-HT (author's transl)].

Previously, a 5-hydroxytryptamine receptor has been described in neuronal membrane preparations. This receptor corresponds to a recognition site for 5-HT, and is seemingly related to an effector which consists of an adenylate cyclase activated by 5-HT and having a high apparent affinity constant (KD close to 1 nM). Moreover, this neuronal receptor is distinct of the glial serotoninergic receptor (Fillion et al., 1980). The method used to measure the binding of 3H-5-HT has been previously reported (FILLION et al., 1978). Adenylate cyclase activity was determined by measurement of cAMP using a radioimmunoassay (FILLION et al., 1979 a, b). Membranes were pretreated as follows: (1) membranes were preexposed to 5-HT (i.e.: incubated in the presence of 5-HT, generally 10 nM) at 37 degrees C, washed by centrifugation and resuspended in a medium free of 5-HT (or diluted in the same medium) or (2) membranes were incubated with a single concentration of 5-HT for a prolonged duration. Results were as follows: 1. The binding of 3H-5-HT, incubated for 10 min at 37 degrees C, corresponds to a KD close to 20 nM whereas a prolongation of the incubation duration to 15-25 induces the binding of 5-HT with a KD close to 2 nM. 2. Preexposure of the membranes to 5-HT leads to the same increase in affinity with, apparently, a reduced number of sites. 3. N-ethylmaleimide pretreatment of the membranes prior to their preexposure to 5-HT inhibits the change in affinity. 4. GTP, but not GDP, reverses the affinity change. 5. The adenylate cyclase activated by 5-HT is desensitized by preexposure of the membranes to 5-HT. 6. GTP reverses the process of desensitization. These results support the hypothesis of the existence of a regulatory mechanism for the 5-HT neuronal receptor. The regulatory mechanism would involve structural conformation changes of the recognition site corresponding to different affinities of the adenylate cyclase. A nucleotide binding protein is presumably involved in the coupling of these two subunits of the receptor.

Adenylyl Cyclases↗
PubMed1980

[3H]5-HT binding sites and 5-HT-sensitive adenylate cyclase in glial cell membrane fraction.

Glial cell membrane fractions were prepared using glial cells preparations isolated from horse brain striatum. [3H]5-HT binding was measured by the filtration technique and the adenylate cyclase activity determined by measuring the cAMP production using a radioimmunoassay. Serotonin binds to glial membrane fractions with an affinity corresponding to a dissociation constant Kd = nM. The corresponding site is serotoninergic specific: [3H]5-HT binding is inhibited by 5-HT agonists (5 OH NM-DMT, 5-MeOHT, 5-MeOH-DMT, NN-DMT) or antagonists (cinanserine, cyproheptadine, methysergide, LSD) and not (or poorly) inhibited by non-serotoninergic related drugs. The population of sites binding 5-HT, present in neuronal membrane preparations and determined in parallel assays is distinct from that observed in glial preparations. The glial membrane fractions contains an adenylate cyclase activated by 5-HT with an apparent affinity constant close to 1 microM. It is serotonin-specific and clearly distinct from the DA-stimulated adenylate cyclase present in the same preparation. The sites binding 5-HT and activating the adenylate cyclase with low affinities might be directly related. This system, clearly distinct from the postsynaptosomal serotoninergic receptor, represents presumably a glial serotoninergic receptor; however, it cannot be totally excluded that these sites may refer to presynaptic membranes.

Adenylyl Cyclases↗
PubMed1980

[Connection between 3H 5-HT and adenyl cyclase activation induced by 5-HT in preparations of cerebral glial membranes].

Purified glial membrane preparations have been isolated from horse brain striatum. Tritiated 5-HT bound to these membranes with a high affinity (KD = 10 nM); the corresponding binding is reversible and appears specific of the serotoninergic structure. In parallel, 5-HT activates an adenylate cyclase with a low affinity (KD = 1 microM). The sites involved in this binding and in this adenylate cyclase activation appear different from the serotoninergic sites reported in the neuronal membrane preparations.

Adenylyl Cyclases↗
PubMed1977

[5-hydroxytryptamine-sensitive adenylate cyclase activity in brain synaptosomal membrane preparations].

A serotonine-sensitive adenylate cyclase system has been observed in horse brain membrane preparations. In crude mitochondrial fraction two types of activation sites were characterized, the Ka being = 2 nM and 1 micrometer. In purified synaptosomal membranes, a single adenylate cyclase activation was observed corresponding to the highest apparent affinity (KD = 2nM). This activation site might be related to the high affinity binding site (KD = 2NM) were previously described in the same membrane preparations.

Adenylyl Cyclases↗
PubMed1977

[High affinity binding of 5-hydroxytryptamine to some membrane preparations from cattle brain. Relationship to lysergic acid diethylamide (LSD)].

5 hydroxytryptamine binds to crude brain membrane preparations with two different affinities (KD = 1 to 2 X 10(-9) M for the highest, 1 to 2 X 10(-8) M for the lowest). LSD also binds with two affinities (KD = 3 to 4 X 10(-9) M and KD = 2 to 3 X 10(-8) M). Subcellular distribution of these sites shows that binding involves the two binding affinities in microsomal membranes but solely the high affinity binding sites are present in purified synaptosomal membranes. High affinity sites for 5 HT and for LSD are different as no direct competitive inhibition is observed in that case. On microsomal membranes, direct relationship occurs between low affinity binding for 5 HT and high affinity binding for LSD.

Animals↗
PubMedDate not supplied

Nonspecific B and T cell-stimulatory activity mediated by mast cells is associated with exosomes.

Bone marrow-derived mouse mast cells (BMMC) and mast cell lines P815 and MC9 have recently been shown to induce antigen-independent B and T lymphocyte activation. It has been demonstrated that a physical contact between mast cells and B and T lymphocytes is not necessary since mast cell supernatants contain full activity. Electron microscopy studies revealed the presence in mast cell supernatants of small vesicles called exosomes with a heterogeneous size from 60 to 100 nm of diameter. When cocultured with spleen cells, purified exosomes induce B and T cell blast formation, proliferation as well as IL-2 and IFN-gamma production. In contrast to P815 and MC9 mast cell lines, a pretreatment with IL-4 is required for BMMC to produce active exosomes. Structurally, these exosomes were found to harbor immunologically relevant molecules such as MHC class II, CD86, LFA-1 and ICAM-1. Here we provide for the first time the evidence that mast cells use exosomes as sophisticated messengers to communicate with cells of the immune system.

Animals↗
PubMedDate not supplied

Solubilization and characterization of [3H] 5HT high affinity binding sites (5HT1 and 5HT3).

The solubilization of the serotonergic 5HT1 and 5HT3 sites was performed with digitonin and sodium cholate at 1% (final concentration). Two binding sites for [3H]5HT were observed on rat or horse brain synaptosomal membranes solubilized with these detergents. The corresponding dissociation constants (KD) were 1-3 nM and 13-30 nM respectively. These values were closely similar to those corresponding to 5HT1 and 5HT3 sites located in intact membranes. The solubilized sites specifically bound 5HT. The effect of GTP decreasing the binding to 5HT1 sites was lost on solubilized 5HT1 sites; it was recovered, however, by addition of phospholipids (asolectin 0,2%). The apparent molecular weights of these sites were determined using the gel filtration method (438 and 235 K daltons). The photoactivation of [3H]5HT by U.V. light was used to label 5HT1 and 5HT3 sites irreversively in membranes. The binding of [3H]5HT following U.V. irradiation was not dissociated after dilution; it was saturable and prevented by serotonergic drugs and not by adrenergic or dopaminergic antagonists. Moreover, GTP added prior to the irradiation reduced it markedly thus showing that 5HT1 sites were labelled. Electrophoretic and fluorographic analyses of the labelled material evidenced a 60 K dalton-band specifically labelled with [3H]5HT (5 or 20 nM). These results tend to indicate that the 60 K dalton-proteic band might represent a proteic subunit constituting part of 5HT1 and 5HT3 sites.

Animals↗