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W R Rice

Publications and source records attributed to W R Rice.

48 records · Page 3Linked to original sources
PubMed1987

P2Y-purinoceptor regulation of surfactant secretion from rat isolated alveolar type II cells is associated with mobilization of intracellular calcium.

1 The effect of methylene, thio, and imido substituted analogues of adenosine 5'-triphosphate (ATP) on surfactant phospholipid secretion and calcium mobilization in rat isolated alveolar Type II cells was studied. 2 ATP was the most potent secretagogue of adenine nucleotides studied. The rank order of agonist potency for [3H]-phosphatidylcholine secretion was ATP greater than adenosine 5'-O-(3-thiotriphosphate) (gamma S-ATP) greater than beta, gamma-imido adenosine 5'-triphosphate (AMPPNP) greater than beta, gamma-methylene adenosine 5'-triphosphate (beta, gamma-CH2-ATP) greater than alpha, beta-methylene adenosine 5'-triphosphate (alpha, beta-CH2-ATP). The respective EC50S were 10(-6) M, 2 X 10(-6) M, 2 X 10(-5) M, and greater than 2.5 X 10(-4) M. 3 Exogenous ATP also induced a rapid mobilization of intracellular calcium monitored by changes in Fura 2 fluorescence. The rank order of agonist potency for calcium mobilization was similar to the rank order of agonist potency for surfactant secretion: ATP = gamma S-ATP greater than AMPPNP greater than alpha, beta-CH2-ATP. 4 There was no effect of EGTA on ATP-induced calcium mobilization, consistent with the hypothesis that exogenous ATP induces release of calcium from intracellular stores. 5 These data are consistent with a P2Y-purinoceptor regulating surfactant secretion from isolated Type II cells via mobilization of intracellular calcium, since: (a) non-hydrolyzed analogues of ATP are potent secretagogues, (b) beta, gamma-CH2-ATP was a more potent secretagogue than alpha, beta-CH2-ATP and (c) the rank orders of agonist potency for calcium mobilization and phospholipid secretion were the same.

Adenosine Triphosphate↗
PubMed1987

Surfactant-associated protein inhibits phospholipid secretion from type II cells.

Secretion of [3H]phosphatidylcholine ([3H]PC) from isolated rat pulmonary type II epithelial cells was inhibited by the surfactant-associated protein of Mr = 35,000 (SAP-35) purified from canine lung surfactant. SAP-35 inhibited [3H]PC secretion in a dose-dependent manner and significantly inhibited basal, phorbol ester, beta-adrenergic, and P2-purinergic agonist-induced [3H]PC secretion. SAP-35 significantly inhibited [3H]PC secretion from 1 to 3 h after treatment. The IC50 for inhibition of [3H]PC secretion by canine SAP-35 was 1-5 X 10(-6) g/ml and was similar for inhibition of both basal and secretagogue-stimulated release. Heat denaturation of SAP-35, addition of monoclonal anti-SAP-35 antibody, reduction and alkylation of SAP-35, or association of SAP-35 with phospholipid vesicles reversed the inhibitory effect on secretagogue-induced secretion. Inhibitory effects of SAP-35 were observed 3 h after cells were washed with buffer that did not contain SAP-35. Although SAP-35 enhanced reassociation of surfactant phospholipid with isolated type II cells, its inhibitory effect on secretion of [3H]PC did not result from stimulation of reuptake of secreted [3H]PC by type II cells. The inhibition of phospholipid secretion by SAP-35 was also not due to inhibition of PC or disaturated PC synthesis by SAP-35. SAP-35, the major phospholipid-associated protein in pulmonary surfactant, is a potent inhibitor of surfactant secretion from type II cells in vitro and may play an important role in homeostasis of surfactant in the alveolar space.

Adenosine Triphosphate↗
PubMed1986

Regulation of surfactant secretion from isolated Type II pneumocytes by substance P.

Substance P, an eleven amino acid neuropeptide, significantly inhibited release of [3H]phosphatidylcholine from pulmonary Type II epithelial cells in vitro. Basal release and release in response to the beta-adrenergic agonist, terbutaline and 12-O-tetradecanoylphorbol 13-acetate (TPA) were significantly decreased in the presence of substance P. Inhibitory effects of substance P were noted following a 1 h exposure of primary cultures of Type II cells in vitro and persisted up to 3 h in the presence of the secretagogues, TPA and terbutaline. The IC50 values for substance P inhibition of [3H]PC release were 10 microM for basal release, 40 microM for TPA-induced release and 50 microM for terbutaline-induced release. The related neuropeptide, physalaemin and the stable active analog of substance P, [pGlu5, MePhe8, MeGly9]substance P [5-11], had no significant inhibitory effects on surfactant release whether in the presence or absence of TPA or terbutaline. These data support the hypothesis that NH2-terminal basic groups of substance P are necessary for inhibition of surfactant secretion from isolated Type II cells and support the concept that an inhibitory system contributes to mediation of surfactant secretion from Type II epithelial cells.

Animals↗
PubMed1986

P2-purinoceptors regulate surfactant secretion from rat isolated alveolar type II cells.

Rat isolated alveolar Type II cells were utilized to examine the effect of purine and pyrimidine analogues on secretion of pulmonary surfactant. ATP potently stimulated [3H]-phosphatidylcholine ([3H]-PC) secretion in a time- and dose-dependent manner. The effect of ATP was noted by one hour of exposure and persisted for three hours. The EC50 (concentration producing 1/2 the maximal response) for ATP-induced [3H]-PC secretion was 100 nM. ADP was also a potent secretagogue for surfactant secretion, but AMP and adenosine had no significant effect on surfactant secretion at concentrations less than or equal to 250 microM. The EC50 for ADP-induced [3H]-PC secretion was 250 nM. Other purine and pyrimidine nucleotides (ITP, GTP, CTP, TTP) were examined for their effect on [3H]-PC secretion. All purine and pyrimidine triphosphates examined significantly augmented [3H]-PC secretion, but were much less potent than ATP. The EC50s were ITP = 10 microM; GTP = 100 microM; CTP = 250 microM; TTP = 100 microM. Neither 8-phenyltheophylline (10 microM, a P1-purinoceptor antagonist), propranolol (100 microM, a beta-adrenoceptor antagonist), nor indomethacin (10 microM, a prostaglandin synthetase inhibitor) inhibited ATP-induced [3H]-PC secretion from isolated Type II cells. These data provide evidence for regulation of surfactant secretion from alveolar Type II cells by a P2-purinoceptor.

Animals↗
PubMed1985

Activation of cAMP dependent protein kinase during surfactant release from type II pneumocytes.

Release of surfactant from pulmonary type II epithelial cells was stimulated by the beta-adrenergic agonist terbutaline and the diterpene forskolin. Cytosolic cyclic adenosine monophosphate (cAMP) concentrations increased significantly following exposure to terbutaline or forskolin and reached maximal levels within 5 min after treatment. Terbutaline and forskolin had a synergistic effect on cytosolic cAMP levels when added simultaneously. cAMP-dependent protein kinase activity was identified in cytosolic preparations of type II pneumocytes by phosphorylation of the peptide substrate Kemptide (Leu-Arg-Arg-Ala-Ser-Leu-Gly) and binding of 3H-cAMP to the regulatory components of cAMP-dependent protein kinase. Type I and type II regulatory subunits of the cANP-dependent kinase were present in approximately equal concentrations in type II cell cytosol. Activation ratio of cAMP-dependent protein kinase in cultured type II cells increased significantly in the presence of terbutaline, forskolin, or terbutaline plus forskolin. Activation ratios increased from 0.45 +/- 0.03 for control cells to 0.96 +/- 0.06 for cells exposed to terbutaline (10 microM) plus forskolin (5 microM) for 20 min. Release of 3H-phosphatidylcholine was also stimulated by terbutaline and forskolin. Effects of terbutaline and forskolin on surfactant release were approximately additive. Our results demonstrated increased cytosolic cAMP levels, increased cAMP-dependent protein kinase activation ratios, and subsequent augmented surfactant release from isolated type II pneumocytes in response to terbutaline and forskolin. These data support a role for activation of cAMP-dependent protein kinase as a mediator of surfactant release and document the utility of forskolin for study of cAMP-mediated effects in isolated type II cells.

Animals↗
PubMed1984

Inhibition of surfactant release from isolated Type II cells by compound 48/80.

Release of [3H]phosphatidylcholine from pulmonary Type II epithelial cells was stimulated by terbutaline, forskolin and cytochalasin D. Compound 48/80 inhibited both basal and agonist-stimulated release of [3H]PC. The IC50 for inhibition by compound 48/80 was 1-2 micrograms/ml, and was similar for inhibition of both basal and stimulated release of [3H]phosphatidylcholine. Inhibitory effects of 48/80 were noted following a 1 h exposure to compound 48/80 and persisted up to 3 h. The inhibitory effect of compound 48/80 was entirely reversed by removing compound 48/80 from the external milieu. Compound 48/80 had no effect on cytosolic cyclic AMP levels or lactate dehydrogenase release. Inhibition of surfactant release produced by compound 48/80 was unaffected by changes in extracellular calcium concentrations. Compound 48/80 is a non-toxic inhibitor of phosphatidylcholine release from Type II epithelial cells.

Animals↗
PubMed1984

Effect of cytochalasins on surfactant release from alveolar type II cells.

Cytochalasins enhanced surfactant secretion from primary cultures of [3H]choline-labeled type II epithelial cells from the rat. Cytochalasins A, B, C, D and dihydrocytochalasin B enhanced secretion of phosphatidyl-[3H]choline [(3H]PC) in a dose-dependent manner with EC50 values of 1, 2, 0.5, 0.1 and 1 microM for cytochalasins A, B, C, D and dihydrocytochalasin B, respectively. Only cytochalasin A caused significant cytotoxicity as determined by release of the intracellular enzyme lactate dehydrogenase (EC 1.1.1.17). Dose responses of surfactant release induced by cytochalasins B, C and D were biphasic; maximal release was observed between 0.1-1.0 microM for cytochalasins C and D between 1 and 10 microM for cytochalasin B. Secretion decreased toward control levels at concentrations of cytochalasin above these maximal concentrations. Increased rates of [3H]PC release were noted between 1 and 3 h after exposure to cytochalasin D. Increased rates of surfactant release induced by cytochalasin D were additive to release induced by the beta-adrenergic agonist, terbutaline, or forskolin, although cytochalasin D had no direct effect on cytosolic cyclic AMP levels. Changes in cell shape and microfilament organization were observed by phase-contrast microscopy and fluorescence microscopy using rhodamine-conjugated phalloidin after exposure of the isolated type II cells to cytochalasin D. Disruption of microfilaments associated with lamellar bodies of the purified type II cells occurred after treatment with cytochalasin D. Cytochalasin D augmented surfactant release from purified type II cells and disrupted the microfilament structure of those cells, supporting the hypothesis that alterations in microfilaments are associated with surfactant release.

Animals↗
PubMed1976

Pyruvate flux into resealed ghosts from human erythrocytes.

The kinetics of pyruvate transport across the isolated red blood cell membrane were studied by a simple and precise spectrophotometric method: following the oxidation of NADH via lactate dehydrogenase trapped within resealed ghosts. The initial rate of pyruvate entry was linear. Influx was limited by saturation at high pyruvate concentration. Pyruvate influx was greatly stimulated by increasing ionic strength in the outer but not the inner aqueous compartment. The Km ranged from 15.0 mM at mu = 0.05 to 3.7 mM at mu = 0.01, while the V went from 0.611 - 10(15) to 0.137 - 10(-15) mol - min-1 - ghost-1. Ionic strength was shown to affect the translocation step and not pyruvate binding. The energy of activation of pyruvate flux into resealed ghosts was 25 kcal/mol, similar to that found in intact red blood cells. Inhibitors of pyruvate influx included such anions as thiocyanate, chloride, bicarbonate, alpha-cyanocinnamate, salicylate and ketomalonate (but not acetate); noncompetitive inhibitors were phloretin, 1-fluoro-2,4-dinitrobenzene, 4-acetamido-4'-isothiocyanate-stilbene-2,2'-disulfonic acid and o-phenanthroline/CuSO4 mixtures. The last reagent, known to induce disulfide links in certain membrane proteins, blocked the ionic strength stimulation of pyruvate influx in this study.

Acetates↗
PubMedDate not supplied

Motivation: the most basic process in TQM/CQI.

Quality management professionals confront the challenge of motivating others to participate in the improvement of patient care. Producing this motivation frequently proves problematic. This article addresses the issue of motivation by presenting it as a process. Abraham Maslow's hierarchy of needs functions as the foundation of the process. A process model is used to demonstrate that satisfaction of the higher-level needs of esteem and self-actualization is required to produce true motivation. By understanding the process of motivation, we may become more effective in improving patient care.

Humans↗