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Y Landry

Publications and source records attributed to Y Landry.

At least 109 records · Page 6Linked to original sources
PubMed1981

Inhibition of antigen-induced histamine release from rat mast cells by a cyclic GMP-phosphodiesterase inhibitor and sodium nitrite.

Antianaphylactic properties have been attributed to cyclic nucleotide phosphodiesterase inhibitors through increase of cyclic AMP levels, according to the concept that increases in cyclic AMP reduce release and increases in cyclic GMP enhance release. However, Coulson et al. [3] showed that the inhibition of histamine release from human lung is correlated to the inhibition of cyclic GMP hydrolysis. We studied the effect of specific inhibitors of cyclic AMP and cyclic GMP hydrolysis on the antigen-induced mediator release from rat mass cells and human basophils and on airways relaxation [4]. The results suggested that the modulation of mediator release was different from one cell type to the other, enhancement of cyclic AMP levels leading to the inhibition of release from basophils, while cyclic GMP appears to be predominantly involved in mast cells. The present paper shows that high concentrations of sodium nitrite, a stimulating agent of guanylate cyclase, inhibit histamine release from rat mast cells in the presence or absence of M&B 22948, a selective cyclic GMP phosphodiesterase inhibitor.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed1981

Effects of cyclic AMP- and cyclic GMP- phosphodiesterase inhibitors on immunological release of histamine and on lung contraction.

1 Cyclic adenosine 3',5'-monophosphate (cyclic AMP)- and cyclic guanosine 3',5'-monophosphate (cyclic GMP)-phosphodiesterase activities from rat lung were selectively inhibited by ZK 62711 and M & B 22948, respectively. Theophylline and papaverine inhibited both activities. 2 Rat lung strips contracted by carbachol were relaxed by 4-(3-cyclopentyloxy-4-methoxyphenyl)-2-pyrrolidone (ZK 26711, EC25 = 7 x 10(-8)M) and 2-O-propoxyphenyl-8-azapurin-6-one (M & B 22948, EC25 = 5 x 10(-7)M) indicating relaxant properties of both cyclic AMP and cyclic GMP. 3 The antigen-induced histamine release from human basophils was inhibited by ZK 62711 (IC25 = 8 x 10(-7)M), whereas M & B 22948 had no effect. On the contrary, the release from rat mast cells was inhibited by M & B 22948 (IC25 = 10(-6)M), while ZK 62711 had no effect. 4 These data show an inhibitory effect of cyclic AMP on histamine release to be involved with basophils, whereas cyclic GMP is predominantly involved with mast cells. Is is suggested that the antianaphylactic properties of cyclic nucleotide phosphodiesterase inhibitors are mainly linked to the increase of cyclic GMP.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1977

[Not Available].

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Canada↗
PubMed1976

Transport of calcium ions by Ehrlich ascites-tumour cells.

Ehrlich ascites-tumour cells accumulate Ca2+ when incubated aerobically with succinate, phosphate and rotenone, as revealed by isotopic and atomic-absorption measurements. Ca2+ does not stimulate oxygen consumption by carefully prepared Ehrlich cells, but des so when the cells are placed in a hypo-osmotic medium. Neither glutamate nor malate support Ca2+ uptake in 'intact' Ehrlich cells, nor does the endogenous NAD-linked respiration. Ca2+ uptake is completely dependent on mitochondrial energy-coupling mechansims. It was an unexpected finding that maximal Ca2+ uptake supported by succinate requires rotenone, which blocks oxidation of enogenous NAD-linked substrates. Phosphate functions as co-anion for entry of Ca2+. Ca2+ uptake is also supported by extra-cellular ATP; no other nucleoside 5'-di- or tri-phosphate was active. The accumulation of Ca2+ apparently takes place in the mitochondria, since oligomycin and atractyloside inhibit ATP-supported Ca2+ uptake. Glycolysis does not support Ca2+ uptake. Neither free mitochondria released from disrupted cells nor permeability-damaged cells capable of absorbing Trypan Blue were responsible for any large fraction of the total observed energy-coupled Ca2+ uptake. The observations reported also indicate that electron flow through energy-conserving site 1 promotes Ca2+ release from Ehrlich cells and that extra-cellular ATP increase permeability of the cell membrane, allowing both ATP and Ca2+ to enter the cells more readily.

Adenosine Triphosphate↗
PubMed1975

Physiological and genetic modifications of the expression of the yeast mitochondrial adenosine triphosphatase inhibitor.

1. The oligomycin-sensitive ATPase activity of submitochondrial particles of the glycerol-grown "petite-negative" yeast: Schizosaccharomyces pombe is markedly stimulated by incubation at 40 degrees C and by trypsin activations are treatment. Both increased in Triton-X 100 extracts of the submitochondrial particles. 2. A trypsin-sensitive inhibitory factor of mitochondrial ATPase with properties similar to that of beef heart has been extracted and purified from glycerol-grown and glucose-grown S. pombe wild type, from the nuclear pleiotropic respiratory-deficient mutant S. pombe M126 and from Saccharomyces cerevisiae. 3. ATPase activation by heat is more pronounced in submitochondrial particles isolated from glycerol-grown than from glucose-grown S. pombe. An activation of lower extent is observed in rat liver mitochondrial particles but is barely detectable in the "petite-positive" yeast: S. cerevisiae. No activation but inhibition by heat is observed in the pleitotropic respiratory-deficient nuclear mutant S. pombe M126. 4. The inhibition of S. pombe ATPase activity by low concentrations of dicyclohexylcarbodiimide dissapears at inhibitor concentrations above 25 muM. In Triton-extract of submitochondrial particles net stimulation of ATPase activity is observed at 100 muM dicyclohexylcarbodiimide. The pattern of stimulation of ATPase activity by dicyclohexylcarbodiimide in different genetic and physiological conditions parallels that produced by heat and trypsin. A similar mode of action is therefore proposed for the three agents: dissociation or inactivation of an ATPase inhibitory factor. 5. We conclude that "petite-positive" and "petite-negative" yeasts contain an ATPase inhibitor factor with properties similar to those of the bovine mitochondrial ATPase inhibitor. The expression of the ATPase inhibitor, measured by ATPase activation by heat, trypsin or high concentrations of dicyclohexylcarbodiimide, is sensitive to alterations of the hydrophobic membrane environment and dependent on both physiological state and genetic conditions of the yeast cells.

Adenosine Triphosphatases↗
PubMed1975

[Active transport of calcium in thymocytes].

Calcium uptake was studied on thymocytes from rabbits with 45Ca loading followed by rapid filtration. Datta shown that the substrates of the mitochondrial electron transport chain did not allowed calcium uptake. Exogenous ATP was required to observe a large influx of calcium in thymocytes. Succinate, magnesium and phosphate ions increased this ATP induced influx of calcium, which was not completely inhibited with atractyloside or ruthenium red.

Adenosine Triphosphate↗
PubMedDate not supplied

Epithelial modulation of thromboxane A2 and PAF involvement in IgE- and IgG-mediated guinea pig anaphylaxis.

The role of prostanoids and platelet-activating factor (PAF) was studied in the in vitro response of guinea pig trachea to immunochallenge according to the presence or the absence of the epithelial layer and to the sensitization procedure leading to the preferential synthesis of immunoglobulin E (IgE) or immunoglobulin G (IgG) antibodies. Indomethacin, a cyclooxygenase inhibitor, potentiated the antigen-induced contractions both in IgE and IgG models, suggesting the involvement of relaxant prostaglandins (PGs), independently of the presence of the airway epithelium. UK-38485, a thromboxane synthetase inhibitor, did not modify the tracheal response to antigen in the IgE model. However, this compound enhanced the maximum contractile response to antigen of the intact tracheal strips of IgG-sensitized guinea pig, but reduced the contractile response of the epithelium-free tracheal strips. Two potent non-structurally related PAF antagonists, Ro 19-3704 and BN 52021, reduced antigen-induced contraction of the epithelium-free tracheal strips in the IgE model. In contrast, these compounds did not affect the contractile responses of the preparations in the IgG model. These results suggest the selective implication of thromboxane A2 and PAF, in IgG- and IgE-mediated guinea pig anaphylaxis respectively. Finally, these results indicate that thromboxane A2 (TXA2) and PAF are potent inducers of epithelium-derived mediators.

Anaphylaxis↗
PubMedDate not supplied

Peptidergic pathway in human skin and rat peritoneal mast cell activation.

The common pathway of heterogenous mast cell activation as mediated by antigens is through the cross-linking of IgE bound to Fc epsilon RI receptors. The peptidergic pathway of mast cell activation, achieved by cationic secretagogues, is restricted to "serosal" mast cells, the experimental models being rat peritoneal and human skin mast cells. Cationic secretagogues include positively charged peptides but also various amines such as compound 48/80 and natural polyamines. An early intracellular event of this pathway is the activation of pertussis toxin-sensitive G proteins. The correlation observed between the ability of basic compounds to trigger mast cell exocytosis and their potency to activate purified G proteins strongly suggests that cationic compounds activate mast cell G proteins via a receptor-independent but membrane-assisted process. In this paper, alternative mechanisms are discussed. The consequence of G protein stimulation is the activation of phospholipase C with an increase in inositol triphosphates. Natural polyamines are relatively poor triggers of mast cells (10(-4) to 10(-2) M). Neuropeptides such as substance P, neuropeptide Y or vasoactive intestinal peptide, peptidic hormones such as kinins, and venoms such as mastoparan and mast cell degranulating peptide, are all active in a concentration range from 10(-7) to 10(-4) M. The cationic anaphylatoxin C3a also stimulates mast cells at concentrations below precursor complement C3 blood levels. The component C3 of the complement system is one of only a few plasma proteins having activation fragments (i.e. C3a) that can be generated at micromolar levels. The effects of basic secretagogues defines a peptidergic pathway of mast cell activation, which represents a potentially toxic process considering the tissue effects caused by exogenous basic compounds such as venom peptides and certain amine containing drugs. Peptidergic activation of mast cells may also be a pathophysiological process having an important role in neurogenic inflammation and in diseases involving extensive activation of the blood complement cascade.

Amino Acid Sequence↗