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W R Rice

Publications and source records attributed to W R Rice.

At least 37 records · Page 2Linked to original sources
PubMed1995

Cloning and expression of the alveolar type II cell P2u-purinergic receptor.

Adenosine triphosphate (ATP) regulates surfactant phospholipid secretion from alveolar type II cells by interacting with P2-purinoceptors on the alveolar type II cell surface. To further characterize regulation of surfactant secretion, we have cloned the type II cell P2u-purinoceptor and expressed a functional receptor in an unrelated cell line. The coding sequence of the P2u clone isolated from a type II cell cDNA library was 1.1 kb, encoding a putative protein of 374 amino acids. The putative protein demonstrated > 97% homology with the P2u-purinoceptor previously identified in the hybrid neuroblastoma x glioma cell line, NG 108-15, 87% homology to the recently cloned human P2u-purinoceptor, and 34% homology to the P2u-purinoceptor cloned from chicken brain. The putative type II cell P2u protein contains seven membrane-spanning domains, characteristic of G-protein-coupled receptors. The type II cell P2u-purinoceptor nucleotide sequence also demonstrated > 95% homology to the nucleotide sequence of the NG 108-15 clone. However, the type II cell cDNA also demonstrated presence of an additional 208 bp insert in the 5' untranslated region, which was not present in the NG 108-15 clone. Using reverse transcriptase polymerase chain reaction, we examined expression of the two different sizes of mRNA in various rat tissues. Only the larger type II cell mRNA was expressed in rat heart, kidney, lung, spleen, and testis, with no expression of P2u-purinoceptor mRNA noted in brain or liver. The smaller species of mRNA was only detected in mouse N18-TG2 cells, and these cells expressed a larger species as well, found in the rat tissues noted.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1994

Degeneration of a nonrecombining chromosome.

Comparative studies suggest that sex chromosomes begin as ordinary autosomes that happen to carry a major sex determining locus. Over evolutionary time the Y chromosome is selected to stop recombining with the X chromosome, perhaps in response to accumulation of alleles beneficial to the heterogametic but harmful to the homogametic sex. Population genetic theory predicts that a nonrecombining Y chromosome should degenerate. Here this prediction is tested by application of specific selection pressures to Drosophila melanogaster populations. Results demonstrate the decay of a nonrecombining, nascent Y chromosome and the capacity for recombination to ameliorate such decay.

Animals↗
PubMed1994

Extending nondirectional heterogeneity tests to evaluate simply ordered alternative hypotheses.

Biologists frequently use nondirectional heterogeneity tests when comparing three or more populations because a suitable directional test is unavailable or is not practical to implement. Here we describe a test, the ordered heterogeneity test, that permits testing against simply ordered alternative hypotheses in the context of almost any nondirectional test. The test has a wide range of parametric and nonparametric applications. Graphs are developed for calculating exact P values.

Genetics, Population↗
PubMed1993

Production of immortalized distal respiratory epithelial cell lines from surfactant protein C/simian virus 40 large tumor antigen transgenic mice.

Murine lung epithelial (MLE) cell lines representing the distal bronchiolar and alveolar epithelium were produced from lung tumors generated in transgenic mice harboring the viral oncogene simian virus 40 (SV40) large tumor antigen under transcriptional control of a promoter region from the human surfactant protein C (SP-C) gene. The cell lines exhibited rapid growth, lack of contact inhibition, and an epithelial cell morphology for 30-40 passages in culture. Microvilli, cytoplasmic multivesicular bodies, and multilamellar inclusion bodies (morphologic characteristics of alveolar type II cells) were detected in some of the MLE cell lines by electron microscopic analysis. The MLE cells also maintained functional characteristics of distal respiratory epithelial cells including the expression of surfactant proteins and mRNAs and the ability to secrete phospholipids. Expression of the exogenous SV40 large tumor antigen gene was detected in all of the generated cell lines. The SP-C/SV40 large tumor antigen transgenic mice and the MLE cell lines will be useful for the study of pulmonary surfactant production and regulation as well as lung development and tumorigenesis.

Animals↗
PubMed1993

Regulation of surfactant phosphatidylcholine secretion from alveolar type II cells during Pneumocystis carinii pneumonia in the rat.

We used an immunosuppressed rat model to test the hypothesis that normal mechanisms regulating surfactant phosphatidylcholine synthesis and secretion in alveolar type II cells are aberrant in Pneumocystis carinii pneumonia. Animal groups included: group 1, healthy controls; group 2, immunosuppressed, without pneumocystosis; group 3, immunosuppressed with pneumocystosis; group 4, immunosuppressed with well-established pneumocystosis treated with trimethoprim-sulfamethoxazole (TMP-SMX). Type II cells were isolated from rats in each group and compared for [3H]choline incorporation into phospholipid and response of the type II cells to secretagogues. Incorporation of [3H]choline into phospholipid subclasses exhibited significant differences. Incorporation into phosphatidylcholine fell from 89.3 +/- 2.2% of total incorporation in group 1 control rats to 79.6 +/- 3.1% in group 3 rats with P. carinii pneumonia, while incorporation into sphingomyelin rose from 5.6 +/- 1.2% in group 1 animals to 15.2 +/- 2.7% in group 3 rats. Incorporation of [3H]choline into phospholipid subclasses in cells from group 2 and group 4 animals was not different from incorporation for group 1 animals. Type II cells from group 1 and group 2 (immunosuppressed control) rats responded appropriately to the secretagogues ATP, TPA, and terbutaline with a marked increase in surfactant phosphatidylcholine secretion; the effect of ATP was also blocked by the lectin, concanavalin A. In contrast, type II cells from group 3 rats failed to respond to the secretagogues with a significant increase in phospholipid secretion. Although treatment of group 4 rats with TMP-SMX markedly reduced the P. carinii organism burden, type II cells from these animals also responded poorly to the secretagogues. The depressed type II cell function described here provides a mechanism for the observed decrease in surfactant phospholipids from bronchoalveolar lavage fluid of experimental animals and patients with P. carinii pneumonia. The data also suggest this defect may become irreversible with advanced disease.

Animals↗
PubMed1992

Sexually antagonistic genes: experimental evidence.

When selection differs between the sexes, a mutation beneficial to one sex may be harmful to the other (sexually antagonistic). Because the sexes share a common gene pool, selection in one sex can interfere with the other's adaptive evolution. Theory predicts that sexually antagonistic mutations should accumulate in tight linkage with a new sex-determining gene, even when the harm to benefit ratio is high. Genetic markers and artificial selection were used to make a pair of autosomal genes segregate like a new pair of sex-determining genes in a Drosophila melanogaster model system. A 29-generation study provides experimental evidence that sexually antagonistic genes may be common in nature and will accumulate in response to a new sex-determining gene.

Animals↗
PubMed1991

Distinguishing mechanisms for the evolution of co-operation.

The existence of co-operation between species has been cast as a problem to the selfish-gene view of evolution: why does co-operation persist, when it would seem that individual selection should favor the unco-operative individual who exploits the co-operative tendencies of its partner and gives nothing in return? The recent literature has emphasized one type of model as underlying the evolution and stability of interspecific co-operation, which we term the "partner-fidelity" model, and which is typified by the game theory model known as the iterated Prisoner's Dilemma game. Under this mechanism, individuals are associated with the same partner(s) during an indefinite sequence of interactions. Individuals who at any time fail to co-operate with their partner can be penalized by those same partners in subsequent trials, hence the co-operation can be evolutionarily stable. Many examples of biological co-operation that have been offered appear to conform to this model. However, a few examples appear instead to fit a different and unrecognized mechanism, termed "partner-choice". Under partner-choice, individuals are associated for just one interaction, but an asymmetry enables one member to differentially reward co-operative vs. unco-operative partners in advance of any possible exploitation. Possible examples of co-operation maintained through partner-choice mechanisms are provided by the yucca/yucca moth system and the fig/fig wasp system.

Animals↗
PubMed1990

P2-purinoceptor regulation of surfactant phosphatidylcholine secretion. Relative roles of calcium and protein kinase C.

Ca2+ and protein kinase C have both been proposed as intracellular signals for subsequent phosphatidylcholine secretion by alveolar Type II cells. We have determined the relative roles of Ca2+ and protein kinase C in regulating surfactant phosphatidylcholine secretion by utilizing exogenous ATP and the phorbol ester TPA (12-O-tetradecanoylphorbol 13-acetate) as secretagogues, along with MAPTAM to chelate intracellular Ca2+ and sphingosine to inhibit endogenous protein kinase C. Exposure of Type II cells to the P2-purinoceptor agonist, ATP, results in a dose-dependent increase in surfactant phosphatidylcholine secretion from isolated alveolar Type II cells with an EC50 (concn. producing 50% of maximal response) of 2 microM. Administration of exogenous ATP to Type II cells also results in a dose-dependent increase in inositol trisphosphate production, Ca2+ mobilization and [3H]phorbol 12,13-dibutyrate ([3H]PDBu) binding as a measure of protein kinase C translocation. The EC50 in each case is 1-5 microM, indicating association of these events with surfactant phosphatidylcholine secretion. Loading Type II cells with non-hydrolysable GTP analogue (GTP[S]) inhibited ATP-induced Ca2+ mobilization, supporting the hypothesis that Type II cell P2-purinoceptors are coupled to phospholipase C via a GTP-binding protein. The ATP-induced elevation of cytosolic Ca2+ was also inhibited by MAPTAM (a cell-permeant EGTA analogue) by 90%, but MAPTAM was without effect on surfactant phosphatidylcholine secretion induced by ATP. Sphingosine inhibited both ATP- and TPA-induced surfactant phosphatidylcholine secretion as well as [3H]PDBu binding with a similar IC50 (concn. producing 50% of maximal inhibition) (10 microM). Sphingosine did not affect surfactant phosphatidylcholine secretion induced by terbutaline and did not have a significant effect on Ca2+ mobilization induced by exogenous ATP. These results are consistent with a prominent role for protein kinase C in regulation of P2-purinoceptor-induced surfactant phosphatidylcholine secretion, and indicate that Ca2+ mobilization is not a necessary step for ATP-induced surfactant phosphatidylcholine secretion.

Adenosine Triphosphate↗
PubMed1990

Effects of extracellular ATP on surfactant secretion.

Extracellular ATP is the most potent endogenous stimulus for surfactant phospholipid secretion from alveolar type II cells identified to date. This effect of ATP appears mediated via a P2-purinoceptor because the rank order of agonist potency is ATP greater than ADP greater than AMP = adenosine. Examination of other ATP analogues demonstrates a rank order of agonist potency of ATP = gamma S-ATP greater than AMPPNP greater than AMPPCP greater than AMPCPP for surfactant secretion, consistent with a P2y-purinoceptor mediating this effect. This hypothesis is further supported by experiments with reactive blue 2, which selectively inhibits ATP-stimulated surfactant phospholipid secretion and has been purported as a specific inhibitor at P2y-purinoceptors. Several second messenger systems are activated in the type II cell following agonist binding: intracellular Ca2+ is mobilized, prostaglandin levels increase, and protein kinase C is activated. Of these three second messengers, protein kinase C appears to be the most important for surfactant secretion because inhibition of protein kinase C activation blocks ATP-induced surfactant secretion whereas inhibition of Ca2+ mobilization and prostaglandin production does not affect ATP-induced surfactant secretion.

Adenosine Diphosphate↗
PubMed1989

Surfactant peptides stimulate uptake of phosphatidylcholine by isolated cells.

To determine whether small hydrophobic surfactant peptides (SP-B and SP-C) participate in recycling of pulmonary surfactant phospholipid, we determined the effect of these peptides on transfer of 3H- or 14C-labelled phosphatidylcholine from liposomes to isolated rat alveolar Type II cells and Chinese hamster lung fibroblasts. Both natural and synthetic SP-B and SP-C markedly stimulated phosphatidylcholine transfer to alveolar Type II cells and Chinese hamster lung fibroblasts in a dose- and time-dependent fashion. Effects of the peptides on phospholipid uptake were dose-dependent, but not saturable and occurred at both 4 and 37 degrees C. Uptake of labelled phospholipid into a lamellar body fraction prepared from Type II cells was augmented in the presence of SP-B. Neither SP-B nor SP-C augmented exchange of labelled plasma membrane phosphatidylcholine from isolated Type II cells or enhanced the release of surfactant phospholipid when compared to liposomes without SP-B or SP-C. Addition of native bovine SP-B and SP-C to the phospholipid vesicles perturbed the size and structure of the vesicles as determined by electron microscopy. To determine the structural elements responsible for the effect of the peptides on phospholipid uptake, fragments of SP-B were synthesized by solid-phase protein synthesis and their effects on phospholipid uptake assessed in Type II epithelial cells. SP-B (1-60) stimulated phospholipid uptake 7-fold. A smaller fragment of SP-B (15-60) was less active and the SP-B peptide (40-60) failed to augment phospholipid uptake significantly. Like SP-B and SP-C, surfactant-associated protein (SP-A) enhanced phospholipid uptake by Type II cells. However, SP-A failed to significantly stimulate phosphatidylcholine uptake by Chinese hamster lung fibroblasts. These studies demonstrate the independent activity of surfactant proteins SP-B and SP-C on the uptake of phospholipid by Type II epithelial cells and Chinese hamster lung fibroblasts in vitro.

Animals↗
PubMed1989

One-way analysis of variance with unequal variances.

We have designed a statistical test that eliminates the assumption of equal group variances from one-way analysis of variance. This test is preferable to the standard technique of trial-and-error transformation and can be shown to be an extension of the Behrens-Fisher T test to the case of three or more means. We suggest that this procedure be used in most applications where the one-way analysis of variance has traditionally been applied to biological data.

Analysis of Variance↗
PubMed1989

Reactive blue 2 selectively inhibits P2y-purinoceptor-stimulated surfactant phospholipid secretion from rat isolated alveolar type II cells.

1. The effect of reactive blue 2 on adenosine 5'-triphosphate (ATP), 12-O-tetradecanoylphorbol 13-acetate (TPA) and terbutaline-induced surfactant phospholipid secretion from rat isolated alveolar Type II cells was studied. 2. Reactive blue 2 significantly inhibited ATP-induced surfactant phospholipid secretion, but was without effect on C-kinase agonist (TPA) or beta-adrenoceptor agonist (terbutaline)-stimulated surfactant phospholipid secretion. The IC50 for inhibition of ATP-induced surfactant secretion was 1.5 x 10(-4)M. 3. These data are consistent with a P2y-purinoceptor regulating surfactant phospholipid secretion from isolated Type II cells and support previous work suggesting reactive blue 2 is a specific inhibitor at P2y-purinoceptors.

Adenosine Triphosphate↗
PubMed1989

Calcium mobilization and response recovery following P2-purinoceptor stimulation of rat isolated alveolar type II cells.

1. The effect of adenosine 5'-triphosphate (ATP) on surfactant phospholipid secretion, calcium mobilization, and the time course for recovery of the response system was studied in isolated alveolar Type II cells of the rat. 2. ATP (10 microM) stimulated a biphasic intracellular Ca2+ transient monitored by changes in Fura-2 fluorescence, from a basal level of 126 +/- 9 nM, to a rapid peak of 391 +/- 1 nM, followed by a prolonged plateau 26 +/- 4 nM above baseline (mean +/- s.e.mean, n = 26). 3. ATP-stimulated surfactant phospholipid secretion and peak Ca2+ levels had similar EC50s (1 x 10(-6) M), and were unaffected by chelation of extracellular Ca2+. However, the prolonged plateau phase was abolished by chelation of extracellular Ca2+. 4. There was a 15 min refractory period before full recovery of the Ca2+-response to ATP. Recovery was dependent on extracellular Ca2+, was accelerated by removing extracellular agonist and was prolonged following stimulation with the poorly hydrolyzed ATP analogue, ATP-gamma-S. 5. While the Type II cell was capable of multiple ATP-induced Ca2+ transients following recovery, no additional surfactant phospholipid was released with sequential stimulation. 6. These findings suggest initial exposure of Type II cells to ATP mobilizes intracellular Ca2+, stimulates phospholipid secretion and rapidly desensitizes the cell to further stimulation by ATP. Recovery of the ATP-induced Ca2+-response depends on presence of extracellular Ca2+ and removal of agonist.

Adenosine Triphosphate↗
PubMed1989

Binding and uptake of pulmonary surfactant protein (SP-A) by pulmonary type II epithelial cells.

A glycoprotein of Mr 26-36,000 (SP-A) is an abundant phospholipid-associated protein in pulmonary surfactant. SP-A enhances phospholipid reuptake and inhibits secretion by Type II epithelial cells in vitro. We have used two electron microscopic cytochemical methods to demonstrate selective binding and uptake of SP-A by rat pulmonary Type II epithelial cells. Using an immunogold bridging technique, we showed that SP-A binding was selective for Type II cell surfaces. Binding was dose dependent and saturable, reaching maximal binding at approximately 10 ng/ml. On warming to 23 degrees C, SP-A binding sites were clustered in coated pits on the cell surface. To characterize the internalization and intracellular routing of SP-A, we used the biotinyl ligand-avidin-gold technique. Biotinyl SP-A was bound by rat Type II epithelial cells as described above. On warming, biotinyl SP-A was seen in association with coated vesicles and was subsequently located in endosomes and multivesicular bodies. Biotinyl SP-A-gold complexes were seen in close approximation to lamellar bodies 10-60 min after warming. Binding of biotinyl SP-A was inhibited by competition with unlabeled SP-A. These results support the concept that Type II epithelial cells bind and internalize SP-A by receptor-mediated endocytosis. This newly described uptake system may play a role in the recycling of surfactant components or mediate the actions of SP-A on surfactant phospholipid secretion.

Animals↗
PubMed1989

Effect of oxygen exposure on ATP content of rat bronchoalveolar lavage.

Exogenous ATP stimulates surfactant phospholipid secretion in vitro through binding to P2-purinoceptors on the surface of the alveolar type II cell. To determine whether ATP is present in the bronchoalveolar space at concentrations sufficient to stimulate phospholipid secretion, we determined bronchoalveolar lavage ATP content in rats exposed to different inspired oxygen concentrations. Bronchoalveolar lavage ATP content of control animals exposed to room air was 155 +/- 12 nmol ATP/lavage (n = 17) and fell in a dose-dependent fashion to 34 +/- 5 nmol ATP/lavage in animals exposed to 85% oxygen for 72 h (n = 17). Airway content of ATP metabolites fell in a similar fashion in response to oxygen exposure. The decrease in airway ATP content after oxygen exposure was also time-dependent. ATP content in young adult male rats exposed to 85% oxygen decreased from a mean of 236 nmol ATP/lavage on d 1 of exposure to 18 nmol ATP/lavage after 4 d. There was no further decrease in bronchoalveolar lavage ATP content after 4-7 d of oxygen exposure. Despite the fall in airway levels of ATP, disaturated phosphatidylcholine levels increased. Rat bronchoalveolar lavage contained measurable concentrations of ATP, indicating the presence of ATP in the airway at levels which modulate surfactant phospholipid secretion from isolated alveolar type II cells in vitro. Bronchoalveolar lavage ATP content decreased significantly with exposure to oxygen, whereas disaturated phosphatidylcholine content increased.

Adenosine Triphosphate↗
PubMed1988

Regulation of surfactant phospholipid secretion from isolated rat alveolar type II cells by lectins.

The major surfactant-associated protein is a potent inhibitor of surfactant phospholipid secretion from isolated type II cells. Since the major surfactant-associated protein contains a carboxy terminal polypeptide domain which is homologous to the lectin-like liver mannose-binding protein, we tested whether lectins inhibit surfactant phospholipid secretion from rat alveolar type II cells. Concanavalin A, wheat germ agglutinin and Maclura pomifera agglutinin were potent inhibitors of surfactant phospholipid secretion. When adenosine 5'-triphosphate (ATP) was utilized as a secretagogue, the IC50 values for inhibition of surfactant phospholipid secretion were 5.10(-7) (wheat germ agglutinin), 1.10(-6) (concanavalin A) and 2.5.10(-5) M (M. pomifera agglutinin). Similar results were obtained when 12-O-tetradecanoylphorbol 13-acetate was utilized as a secretagogue: IC50 values of 1.10(-6) M for concanavalin A and wheat germ agglutinin and 2.5.10(-5) M for M. pomifera agglutinin. Hapten sugars were utilized to antagonize the inhibitory effect of the lectins. N-Acetyl-D-glucosamine significantly reversed inhibition of phospholipid secretion by wheat germ agglutinin in a dose-dependent fashion and methyl alpha-D-mannoside significantly reversed inhibition of phospholipid secretion by concanavalin A. N-Acetyl-D-galactosamine had no significant effect on inhibition of secretion produced by any of the lectins. The inhibitory effect of the lectins did not appear to be due to cytotoxicity since lactate dehydrogenase was not released above control levels and the inhibition of the surfactant phospholipid secretion by wheat germ agglutinin could be reversed after treatment of cells with wheat germ agglutinin by washing the lectin from the cells followed by treatment of the cells with ATP. These studies demonstrate a direct inhibitory effect of plant lectins on phospholipid secretion from type II cells in vitro.

Acetylglucosamine↗
PubMed1987

Genetic hitchhiking and the evolution of reduced genetic activity of the Y sex chromosome.

A new model for the evolution of reduced genetic activity of the Y sex chromosome is described. The model is based on the process of genetic hitchhiking. It is shown that the Y chromosome can gradually lose its genetic activity due to the fixation of deleterious mutations that are linked with other beneficial genes. Fixation of deleterious Y-linked mutations generates locus-specific selection for dosage tolerance and/or compensation. The hitchhiking effect is most pronounced when operating in combination with an alternative model, Muller's ratchet. It is shown, however, that the genetic hitchhiking mechanism can operate under conditions where Muller's ratchet is ineffective.

Alleles↗