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J M Oliver

Publications and source records attributed to J M Oliver.

At least 19 recordsLinked to original sources
PubMed1992

Fc epsilon RI-mediated tyrosine phosphorylation and activation of the 72-kDa protein-tyrosine kinase, PTK72, in RBL-2H3 rat tumor mast cells.

In RBL-2H3 rat tumor mast cells, cross-linking the high-affinity IgE receptor Fc epsilon RI causes tyrosine phosphorylation of multiple proteins. These phosphoproteins include phospholipase C gamma 1, the beta and gamma subunits of the Fc epsilon RI, the Src family protein-tyrosine kinase Lyn, and a 72-kDa protein that coimmunoprecipitates from lysates of antigen-stimulated cells with antibody to the receptor beta subunit. We now present evidence that the 72-kDa Fc epsilon RI-associated protein is the protein-tyrosine kinase PTK72 that forms part of the antigen receptor complex in B lymphocytes. The identification is based on immunoreactivity with anti-PTK72 antiserum, chromatographic profiles on the affinity resin heparin/agarose, and one-dimensional phosphopeptide mapping studies. Enzymatic activity of the kinase is increased in anti-PTK72 immune complexes prepared from lysates of antigen-activated RBL-2H3 cells. The 72-kDa protein-tyrosine kinase is the principal substrate for in vitro tyrosine phosphorylation in anti-phosphotyrosine immunoprecipitates of RBL-2H3 cells. The discovery that RBL-2H3 mast cells share a receptor-activated protein-tyrosine kinase, PTK72, with B lymphocytes provides additional support for the existence of common signaling pathways initiated by multichain immune recognition receptors.

Animals↗
PubMed1992

Frosted branch angiitis associated with cytomegalovirus retinitis.

We examined three patients with acquired immunodeficiency syndrome who had frosted branch angiitis associated with small patches of cytomegalovirus retinitis. Each patient had a low CD4-helper T-lymphocyte count and a T-lymphocyte helper-suppressor ratio of less than 0.1. Treatment with intravenous anticytomegalovirus antibiotics caused the vascular sheathing to resolve within two weeks in all three patients, but each patient continued to have a smoldering retinitis. Retinal biopsy in one of the patients demonstrated virions whose morphologic characteristics were consistent with cytomegalovirus on electron microscopy and the identity of which was confirmed by immunohistochemistry. Although frosted branch angiitis in otherwise healthy patients responds to corticosteroids, similar treatment with corticosteroids for frosted branch angiitis associated with cytomegalovirus retinitis in patients with AIDS does not seem to be indicated. Before corticosteroid treatment is started for a patient with the clinical signs and symptoms of frosted branch angiitis, careful medical examination of the patient is necessary.

Acquired Immunodeficiency Syndrome↗
PubMed1992

Tyrosine phosphorylation of vav proto-oncogene product containing SH2 domain and transcription factor motifs.

Activation of receptor-linked and cytoplasmic protein tyrosine kinases is crucial in the control of normal and abnormal cell growth and differentiation. Some substrates of protein tyrosine kinases such as phospholipase C gamma and ras GTPase-activating protein (GAP) contain sequences homologous to the src protein domains SH2 and SH3 (refs 3-9). The proto-oncogene vav is expressed in haematopoietic cells and its product Vav contains sequence motifs commonly found in transcription factors, such as helix-loop-helix, leucine-zipper and zinc-finger motifs and nuclear localization signals, as well as a single SH2 and two SH3 domains. Here we show that stimulation of T-cell antigen receptor on normal human peripheral blood lymphocytes or on human leukaemic T cells, and the crosslinking of IgE receptors on rat basophilic leukaemia cells, both promote the phosphorylation of tyrosine residues in Vav. Moreover, activation of the receptor for epidermal growth factor leads to marked tyrosine phosphorylation of Vav in cells transiently expressing vav, and Vav associates with the receptor through its SH2 domain. We propose that vav encodes a new class of substrates whose tyrosine phosphorylation may provide a mechanism for direct signal transduction linking receptors at the cell surface to transcriptional control.

3T3 Cells↗
PubMed1992

Importance of bicarbonate ion for intracellular pH regulation in antigen- and ionomycin-stimulated RBL-2H3 mast cells.

In RBL-2H3 rat basophilic leukemia cells, Ca2+ influx and secretion are activated by antigens that crosslink IgE-receptor complexes and by the Ca2+ ionophore, ionomycin. Here we report that antigen-stimulated Ca2+ influx and secretion are impaired and ionomycin-induced responses are strongly inhibited following the removal of HCO3- from the medium. These results raised the possibility that HCO3(-)-dependent pH regulation mechanisms play a role in the cascade of events leading to mast cell activation. To test this hypothesis, intracellular pH (pHi) was measured by ratio imaging microscopy in individual RBL-2H3 cells labeled with 2',7'-bis-(2-carboxyethyl)-5-(6) carboxyfluorescein (BCECF). In unstimulated cells, it was found that basal pHi in the presence of HCO3- is 7.26, significantly greater than pHi in its absence, 7.09 (P less than 10(-6]. These results, as well as evidence that pHi increases rapidly when HCO3- is added to cells initially incubated in HCO3(-)-free medium, indicate that unstimulated cells use a HCO3(-)-dependent mechanism to maintain cytoplasmic pH. Further analyses comparing unstimulated with stimulated cells showed that antigen causes a small transient acidification in medium containing HCO3- and a larger sustained acidification in HCO3(-)-depleted medium. Ionomycin is a more potent acidifying agent, stimulating a sustained acidification in complete medium and causing further acidification in HCO3(-)-free medium. These results support the hypothesis that the inhibition of antigen- and ionomycin-induced 45Ca2+ influx and secretion in cells incubated in HCO3(-)-free medium is at least partially due to the inactivation of HCO3(-)-dependent mechanisms required to maintain pH in unstimulated cells and to permit pH recovery from stimulus-induced acidification.

Animals↗
PubMed1992

Improving responses in hepatomas with circadian-patterned hepatic artery infusions of recombinant interleukin-2.

Previous studies on continuous hepatic artery infusions of recombinant interleukin-2 (IL-2) have shown that in a nontumor-bearing animal a continuous infusion given in a circadian "day cycled" pattern was much less toxic and could be given with 10 times higher doses of IL-2 than if the constant pattern of infusion was used. In the present study, circadian-patterned continuous hepatic artery infusions of IL-2 were used in hepatoma-bearing rats. Doses of 10 mg/m2/day could be tolerated when IL-2 was given in a "day cycle" rhythm. Control animals were given 1 mg/m2/day of constant infusion IL-2, which was the highest hepatic artery infusion dose tolerated at a constant rate without mortality in nontumor-bearing animals. Animals treated with the constant infusions of IL-2 had a 37.5% mortality rate and a 25% objective response rate in measurable tumor size. Animals receiving the "day cycle" had no mortality and a 100% objective response rate. The conclusion was that "day cycled" circadian-patterned continuous hepatic artery infusions of IL-2 could be given with much lower toxicity and much improved tumor response rates than constant continuous infusions.

Animals↗
PubMed1992

Fc epsilon R1-mediated tyrosine phosphorylation of multiple proteins, including phospholipase C gamma 1 and the receptor beta gamma 2 complex, in RBL-2H3 rat basophilic leukemia cells.

In basophils, mast cells, and the RBL-2H3 tumor mast cell line, cross-linking the high-affinity immunoglobulin E receptor (Fc epsilon R1) stimulates a series of responses, particularly the activation of phospholipase C (PLC), that lead to allergic and other immediate hypersensitivity reactions. The mechanism of activation of PLC, however, is not clear. Here, we show that cross-linking Fc epsilon R1 on RBL-2H3 cells causes the tyrosine phosphorylation of at least 12 cellular proteins, including PLC gamma 1 (PLC gamma 1) and the receptor beta and gamma subunits. 32P-labeled PLC gamma 1 can be detected by anti-phosphotyrosine antibody as early as 10 s after the addition of antigen. The tyrosine-phosphorylated 33-kDa beta subunit and 9- to 11-kDa gamma subunit of the Fc epsilon R1 are additionally phosphorylated on serine and theonine residues, respectively, and are found as complexes with other phosphotyrosine-containing proteins in antigen-stimulated cells. Our results indicate a means by which the Fc epsilon R1 may control PLC activity in RBL-2H3 cells and raise the possibility that other receptor-mediated signalling events in mast cells may also be controlled through protein tyrosine phosphorylation.

Animals↗
PubMed1992

The effects on toxicity of circadian patterning of continuous hepatic artery infusion.

Long term continuous hepatic artery infusion of FUDR was carried out in 34 rats. In the animals who received a constant infusion schedule of 15 mg/kg/day all died of toxicity with a mean survival of 9.3 days. If the pattern of the continuous infusion was changed so that over 60% of the infusion was given during the hours of 3pm to 9pm than all of the animals survived the 14 day infusion. If the maximum dose of infusion was changed so that 60% of the infusion was given at night from 3am to 9am the infusion became more toxic and all the animals died in a mean of 5.5 days. Pathologic sectioning of all the livers reflected the above outcomes with the greatest amount of hepatic necrosis in the animals on the night cycles. This study underscores the recent advances in chronobiology demonstrating that for continuous hepatic arterial infusions the timing of delivery is crucial in determining the toxicity.

Animals↗
PubMed1992

[Post-antibiotic diarrheas: role of Klebsiella oxytoca].

From May 1989 to January 1991, 20 patients were investigated for antibiotic-associated acute diarrhea. Colonoscopy or rectosigmoidoscopy was performed in each patient. Cultures of colonic mucosal biopsies were carried out using conventional culture grounds (cystine-lactose-electrolyte-deficient). The aim of this study was to investigate the role of a gram negative bacillus: Klebsiella oxytoca. Among the 20 patients with antibiotic-associated acute diarrhea, 11 had bloody and mucus diarrhea and colitis ranging from a right-sided hemorrhagic to diffuse acute ulcerative or erosive colitis, 7 had a grossly normal colonic appearance, while 2 had mucus diarrhea and pseudomembranous colitis. Of colonic biopsies cultures obtained from 36 control patients, 15 had a normal colonic appearance, 15 had ulcerative or crohn's colitis, 6 had well-tolerated amoxicillin therapy. Klebsiella oxytoca was never found in the 36 control patients; Klebsiella oxytoca was noted among 8/11 patients with mucus-discharging and bloody diarrhea. These results suggest that antibiotic-associated, non pseudomembranous colitis is frequently associated with Klebsiella oxytoca infection, which may be the cause of this type of colitis.

Adult↗
PubMed1992

[Left atrial thrombus. Its evolution with oral anticoagulation].

UNLABELLED: Left ventricular thrombi were found in 25 patients by two-dimensional echocardiography. All patients were in atrial fibrillation, 16 had mitral or mitroaortic valve diseases and nine mitral or mitroaortic bioprosthetic valves. Nine patients (36%) had history of arterial embolism. At diagnostic time, oral anticoagulation with coumadin was instaured in all the patients. Periodic clinic and echocardiography follow-up was performed. Left atrial thrombi either disappeared (18 patients [72%]) or reduced their size (one patient). Six patients with mitral stenosis were considered as candidates to percutaneous mitral valvuloplasty, which was performed in 4 patients whose thrombi disappeared with anticoagulation therapy in 6 months. During the follow-up one patient had cerebral embolism without sequelae. CONCLUSIONS: 1st. Patients with left atrial thrombi have high risk for arterial embolism. 2nd. Left atrial thrombi disappear in a high proportion after prescribing oral anticoagulation, which has some important therapeutic implications.

Administration, Oral↗
PubMed1991

Tyrosine kinase-dependent phosphatidylinostiol turnover and functional responses in the Fc epsilon R1 signalling pathway.

In RBL-2H3 rat basophilic leukemia cells, Fc epsilon R1 crosslinking by multivalent antigen stimulates phosphatidylinositol (PI) turnover and Ca2+ influx and causes functional responses that include secretion, membrane ruffling and actin polymerization. Here, we show that the tyrosine kinase inhibitor, genistein, inhibits antigen-induced PI turnover, determined from assays of 1,4,5-inositol trisphosphate production, and impairs receptor-mediated secretion, ruffling and actin polymerization. Genistein has little effect on several functional responses to stimuli that bypass PI hydrolysis (ionomycin-induced secretion, phorbol ester-induced ruffling) but it inhibits phorbol ester-induced actin polymerization. These data implicate a common tyrosine kinase-dependent event, most likely the activation of phospholipase C gamma, in the Fc epsilon R1-mediated stimulation of PI turnover, secretion and ruffling. There may be additional tyrosine kinase-mediated events in the actin assembly pathway.

Actins↗
PubMed1991

Role of isoprenoid metabolism in IgE receptor-mediated signal transduction.

In the 2H3 subline of rat basophilic leukemia cells (RBL-2H3), IgE receptor cross-linking stimulates a signal transduction pathway that leads to the secretion of histamine, serotonin, and other inflammatory mediators; the assembly of F-actin; and the transformation of the cell surface from a microvillous to a lamellar or ruffled architecture. We report here that 20 h incubation of RBL-2H3 cells with 10 microM lovastatin, an inhibitor of 3-hydroxy-3-methyl-glutaryl coenzyme A reductase (HMG CoA reductase), inhibits both the secretory and morphologic responses to IgE receptor cross-linking. Ag-induced Ca2+ mobilization, determined from the influx and efflux of 45Ca2+, and Ag-induced 1,4,5-inositol trisphosphate production are also inhibited in lovastatin-treated RBL-2H3 cells. Under the same conditions, lovastatin does not alter cell proliferation or IgE receptor expression, and it causes only a small impairment of responses initiated by drugs that bypass the earliest steps in the receptor-activated transduction pathway (ionomycin-induced secretion and PMA-induced membrane ruffling). Receptor-mediated Ca2+ mobilization, secretion, and ruffling are all restored by 0.5- to 4-h incubation of lovastatin-treated cells with mevalonic acid, the product of HMG CoA reductase and the first committed intermediate of the isoprenoid biosynthetic pathway. In contrast, dolichol and cholesterol, which are synthesized from products of the isoprenoid pathway, do not restore receptor-activated responses. These data implicate an isoprenoid pathway intermediate in an early step in the IgE receptor-activated signal-transduction sequence. We postulate that this intermediate is required for a newly described post-translational modification of proteins, their post-synthetic isoprenylation. The substrates for this modification include the ras family of GTP-binding proteins and the gamma subunits of the heterotrimeric guanine nucleotide-binding protein.

Animals↗
PubMed1991

Regulation of IgE receptor-mediated secretion from RBL-2H3 mast cells by GTP binding-proteins and calcium.

In RBL-2H3 rat basophilic leukemia cells, cholera toxin does not per se stimulate secretion but it enhances secretion stimulated by antigens that crosslink IgE receptors, by the Ca2+ ionophore, ionomycin, and by thapsigargin, a tumor promoter that releases cytoplasmic Ca2+ stores. Calmodulin inhibitors reduce both the basal and cholera toxin-enhanced secretory responses to antigen and Ca2(+)-mobilizing agents. These synergistic effects suggest that the activation of a Gs-like GTP-binding protein, together with a (probably calmodulin-dependent) event activated by an increase in cytoplasmic Ca2+ levels, may jointly provide a sufficient signal for secretion. Antigen-stimulated secretion is inhibited by depleting cells of GTP with mycophenolic acid but is maximal in cells treated with mycophenolic acid plus cholera toxin. The simplest explanation is that cholera toxin selectively reactivates the Gs-coupled pathway leading to secretion in GTP-depleted cells without restoring the activity of a separate GTP-binding protein(s) that constrains antigen-stimulated secretion.

Animals↗
PubMed1991

Relationship of IgE receptor topography to secretion in RBL-2H3 mast cells.

In RBL-2H3 rat leukemic mast cells, cross-linking IgE-receptor complexes with anti-IgE antibody leads to degranulation. Receptor cross-linking also stimulates the redistribution of receptors on the cell surface, a process observed here by labeling the anti-IgE with 15 nm protein A-gold particles that are visible by back-scattered electron imaging in the scanning electron microscope. We report that anti-IgE binding stimulates the redistribution of IgE-receptor complexes at 37 degrees C from a dispersed topography to distributions dominated sequentially by short chains, small clusters, and large aggregates of cross-linked receptors. Cells incubated with 1 microgram/ml anti-IgE, a concentration that stimulates maximum net secretion, redistribute receptors into chains and small clusters during a 15 min incubation period. At 3 and 10 micrograms/ml anti-IgE, net secretion is reduced and the majority of receptors redistribute rapidly into clusters and large aggregates. The addition of Fab fragments with the high anti-IgE concentrations, to reduce cross-linking, delays receptor aggregation and enhances secretion. The progression of receptors from small clusters to large aggregates is prevented in cells treated with dihydrocytochalasin B to prevent F-actin assembly. These results establish that characteristic patterns of receptor topography are correlated with receptor activity. In particular, they link the formation of large receptor aggregates to reduced signalling activity. Cytoskeleton-membrane interaction is implicated in the formation or stabilization of the large receptor clusters.

Actins↗
PubMed1991

Impaired secretion and increased insolubilization of IgE-receptor complexes in mycophenolic acid-treated (guanine nucleotide-depleted) RBL-2H3 mast cells.

In RBL-2H3 rat leukemic mast cells, cross-linking anti-DNP IgE-receptor complexes with multivalent antigen (DNP-BSA) activates a signal transduction pathway leading to Ca2+ influx and secretion. Cross-linking IgE-receptor complexes also stimulates a pathway that inactivates (desensitizes) receptors; this pathway becomes important at high concentrations of cross-linking antigen. Recent evidence that antigen-induced secretion is impaired by mycophenolic acid (MPA), an inhibitor of guanine nucleotide synthesis de novo, has implicated a GTP-binding protein (G protein) in the signaling pathway. Other recent studies have indicated that the conversion of cross-linked receptors to a detergent-insoluble (cytoskeleton-associated) form at high antigen concentrations is correlated with the loss of signaling activity. Here we show that secretion elicited by an optimal concentration of antigen (0.05 micrograms/ml DNP-BSA) is only inhibited by about 25% in guanine nucleotide-depleted cells, whereas secretion elicited by 5 micrograms/ml DNP-BSA, a concentration in the range that causes the high-dose inhibition of secretion, is inhibited by more than 60%. We also show that IgE-receptor complexes are insolubilized in response to 5 but not 0.05 micrograms/ml DNP-BSA in both control and guanine nucleotide-depleted cells. Importantly, the extent of insolubilization elicited by 5 micrograms/ml DNP-BSA is increased by more than 60% in the guanine nucleotide-depleted samples. These results raise the possibility that guanine nucleotide depletion reduces the secretory response to high antigen concentrations in two ways: by inhibiting the G protein-coupled signaling pathway and by increasing the availability of receptors to the pathway leading to receptor insolubilization and inactivation.

Animals↗
PubMed1991

Isoprenoid pathway activity is required for IgE receptor-mediated, tyrosine kinase-coupled transmembrane signaling in permeabilized RBL-2H3 rat basophilic leukemia cells.

Previously, we reported that the isoprenoid pathway inhibitor, lovastatin, blocks the activation by IgE receptor cross-linking of 45Ca2+ influx, 1,4,5-inositol trisphosphate production, secretion, and membrane changes (ruffling, spreading) in intact RBL-2H3 rat basophilic leukemia cells. These results indicated that an isoprenoid pathway intermediate, very likely an isoprenylated protein, is importantly involved in the control of IgE receptor-mediated signal transduction. Here, we show that 20 h of pretreatment with lovastatin also inhibits antigen-induced secretion and membrane responses in streptolysin O-(SLO)-permeabilized cells. However, lovastatin does not inhibit secretion stimulated by the nonhydrolyzable GTP analog, GTP gamma S. Furthermore, the membrane responses to GTP gamma S persist, although in an attenuated form, in lovastatin-treated permeabilized cells. The relative insensitivity of GTP gamma S-induced responses to lovastatin was one of several indications that antigen and GTP gamma S may activate separate pathways leading to transmembrane responses in permeabilized cells. Further experiments showed that the beta-thio derivative of GDP, GDPBAS, inhibits the secretory and membrane responses to GTP gamma S, as expected for a GTP-binding protein-dependent signaling pathway, while having little effect on antigen-induced responses. Conversely, genistein blocks the secretory and membrane responses to antigen, as expected for a tyrosine kinase-dependent pathway, without altering the GTP gamma S-induced responses. From these results, and from additional data from cells treated with tyrphostins and sodium orthovanadate, we propose that IgE receptor-mediated secretion from permeabilized RBL-2H3 cells occurs by a tyrosine kinase-dependent pathway that requires isoprenoid pathway activity for function. We propose further that RBL-2H3 cells contain a separate GTP-binding protein-mediated signaling pathway whose direct activation by GTP gamma S is either independent of isoprenoid pathway activity or depends on the activity of an isoprenylated protein that is not significantly depleted after 20 h of lovastatin treatment.

Animals↗
PubMed1990

Antigen-dependent transition of IgE to a detergent-insoluble form is associated with reduced IgE receptor-dependent secretion from RBL-2H3 mast cells.

In mast cells, basophils, and the RBL-2H3 tumor mast cell model, crosslinking cell surface IgE-receptor complexes by multivalent ligands activates a signal transduction pathway that leads to the secretion of histamine, serotonin, and other inflammatory mediators. Receptor crosslinking in RBL-2H3 cells also changes cell surface morphology and increases F-actin assembly. Previously, Robertson et al. demonstrated that crosslinked IgE-receptor complexes become associated with the Triton X-100-insoluble fraction (the "cytoskeleton") of RBL-2H3 cells and raised the possibility that receptor-cytoskeletal association may be a required step in the stimulation of secretion. The studies reported here confirm by flow cytometry that crosslinking cell surface IgE by antigen induces the association of the crosslinked complexes with the detergent-insoluble fraction. Dose-response studies, also reported here, indicate that the detergent insolubility of the complexes does not correlate with secretion. Thus, secretion increases with antigen concentration to a maximum beyond which more antigen causes less, not more, secretion. There is little residual detergent-insoluble IgE at the concentrations of antigen that promote optimal secretion, whereas the association of IgE with the detergent-insoluble fraction is maximal at the high antigen concentrations that result in reduced secretion. The addition of monovalent hapten to reduce the amount of crosslinking caused by high concentrations of antigen increases secretion and simultaneously reduces the association of IgE with the detergent-insoluble fraction. Dihydrocytochalasin B, an inhibitor of antigen-stimulated actin polymerization, also increases the rate and extent of secretion and simultaneously delays the association of crosslinked IgE-receptor complexes with the detergent-insoluble fraction. From these data, we propose that the association of crosslinked IgE receptors with the detergent-insoluble fraction of RBL-2H3 cells increases with increased receptor crosslinking, is enhanced by antigen-induced actin polymerization, and is more likely related to the termination than the stimulation of secretion. The ligand-induced conversion of receptors to a detergent-insoluble form is not restricted to mast cells but occurs in a variety of cell types. Its general function may be to limit the generation or transmission of transmembrane signals.

Animals↗