PubMed Health⌕ Search

Biomedical subjects

M C Liu

Publications and source records attributed to M C Liu.

At least 199 records · Page 11Linked to original sources
PubMed1986

Human lung macrophage-derived histamine-releasing activity is due to IgE-dependent factors.

Human lung macrophages obtained from surgical specimens spontaneously secreted a factor(s) (which we term macrophage factor) during 24-hr culture that induced calcium-dependent histamine release from human basophils and lung mast cells. Macrophage factor induced noncytotoxic histamine release from purified (85%) basophils. The kinetics of release were relatively slow and similar to that of anti-IgE. We performed a series of experiments to test the IgE dependence of macrophage factor-induced release. Preincubation of basophils with anti-IgE in calcium-free medium resulted in complete desensitization to macrophage factor-induced histamine release (i.e., when calcium and macrophage factor were added to the basophils, no histamine release occurred), and preincubation with macrophage factor in calcium-free medium resulted in partial desensitization to anti-IgE-induced histamine release. Pretreatment of basophils with pH 3.9 lactic acid buffer, which dissociates basophil IgE from its receptors, markedly reduced the capacity of basophils to release histamine in response to macrophage factor. Basophils that were incubated with IgE myeloma (but not with IgG) after lactic acid treatment partially or completely regained their capacity to release histamine in response to macrophage factor. Fluid-phase IgE myeloma (15 micrograms/ml) (but not IgG) inhibited basophil histamine release induced by two macrophage-derived supernatants, whereas IgE myeloma (200 micrograms/ml) did not inhibit release due to other supernatants. IgE-affinity columns removed the histamine-releasing activity of five macrophage-derived supernatants, and IgG-affinity columns had similar effects. However, neither affinity column removed the histamine-releasing activity of three other macrophage-derived supernatants. On Sephadex G-75 chromatography, nearly all of the histamine-releasing activity migrated as single peak with an apparent m.w. of 18,000. These results suggest that, although macrophage factor are heterogeneous, they are related, as they are a IgE-dependent factors that induce histamine release by interacting with cell surface IgE. These macrophage factors may be responsible for stimulation of basophil/mast cell mediator release in chronic allergic reactions.

Basophils↗
PubMed1986

Profiling of prostaglandin biosynthesis in biopsy fragments of human lung carcinomas and normal human lung by capillary gas chromatography-negative ion chemical ionization mass spectrometry.

Methods for the profiling of prostaglandin F2 alpha (PGF2 alpha), prostaglandin D2 (PGD2), prostaglandin E2 (PGE2), thromboxane B2 (TXB2) and 6-keto-prostaglandin F1 alpha (6KPGF1 alpha) biosynthesis in tissue samples of clinical origin by capillary gas chromatography-negative ion chemical ionization mass spectrometry (CGC-NICIMS) are detailed. Aliquots (25 microliter 1) of incubates (1 ml volume) of human lung carcinoma and normal human lung tissue fragments (total protein content = 0.2 to 2.0 mg) were derivatized for vapor phase analysis in the presence of 0.75 to 1.60 ng of tetradeuterated analogs of PGE2, PGF2 alpha and 6KPGF1 alpha without prior extraction and/or chromatography. The derivatized analytes and internal standards were detected by simultaneous monitoring of ions at six different masses characteristic for each of the derivatized prostanoids. The inter-sample and intra-sample coefficients of variation for the assay method were typically less than 12%. The analysis of biological samples was completed with less than 2.5% of each derivatized sample per injection. The samples were of adequate purity for the identification and quantitation of each of the eicosanoids. The methods described in this report are highly selective and highly sensitive with detection limits of 0.1 to 0.2 picograms per injection. The analytical procedures provide the basis for comparisons of the qualitative and quantitative profiles of prostaglandin biosynthesis and should be adaptable for use in a variety of biological and clinical studies.

Biopsy↗
PubMed1986

Properties and electron transfer specificity of copper proteins from the denitrifier "Achromobacter cycloclastes".

A blue copper protein (Mr 12,000) was purified from cells of "Achromobacter cycloclastes" grown as a denitrifier. When reduced, the blue copper protein transferred electrons to the copper protein nitrite reductase purified from the same cells, whereas a variety of cytochromes from denitrifiers failed to do so. Inclusion of a protease inhibitor, phenylmethylsulfonyl fluoride, in the buffers employed during preparation yielded purified blue copper protein with 18 more amino acid residues and two times more specific enzyme activity than other researchers have found.

Alcaligenes↗
PubMed1985

Synthesis of 1-[[2-hydroxy-1-(hydroxymethyl)ethoxy] methyl]-5-benzyluracil and its amino analogue, new potent uridine phosphorylase inhibitors with high water solubility.

Acyclic nucleosides 1-[[2-hydroxy-1-(hydroxymethyl)ethoxy] methyl]-5-benzyluracil (DHPBU) (1) and 1-[[2-hydroxy-1-(aminomethyl)ethoxy]methyl]-5-benzyluracil (AHPBU) (2) have been synthesized by direct coupling of bis(trimethylsilyl)-5-benzyluracil with the corresponding chloromethyl ether, followed by removal of the blocking groups. Compounds 1 and 2 were found to be very potent inhibitors of uridine phosphorylase isolated from Sarcoma 180 cells, with a Ki value of 0.098 and 0.020 microM, respectively, and exhibited no apparent cytotoxicity against Sarcoma 180 host cells. Furthermore, 1 and 2 have shown excellent water solubility (270 and greater than 300 mg/mL at 25 degrees C, respectively), which is a factor critical for the formulation that often limits the usefulness of a particular compound as a chemotherapeutic agent.

Animals↗
PubMed1985

Isolation of tyrosine-O-sulfate by Pronase hydrolysis from fibronectin secreted by Fujinami sarcoma virus-infected rat fibroblasts.

In a recent paper, we reported the loss of large amounts of protein-bound tyrosine sulfate after infection of rat fibroblasts by avian sarcoma viruses. The analogy to the reported loss of surface fibronectin on malignant transformation, which contained sulfate of unknown location, called our attention to this compound. In a previous paper, we briefly reported on isolation from the supernatant fraction of rat fibroblasts infected by Fujinami sarcoma virus fibronectin that yielded tyrosine-O-sulfate on Pronase hydrolysis. In this paper, we confirm and enlarge on this observation. Highly purified fibronectin was obtained from the supernatant fraction secreted by Fujinami sarcoma virus infected rat fibroblasts that contained 1.52 residues of sulfated tyrosine per protein molecule after exhaustive Pronase hydrolysis. Assuming some loss during work up, this probably indicates 2 residues of the tyrosine sulfated per fibronectin molecule.

Animals↗
PubMed1985

Tyrosine sulfation of proteins from the human hepatoma cell line HepG2.

[35S]Sulfate labeling of the human hepatoma cell line HepG2 showed it to contain many sulfated proteins of diverse molecular weight range. The isolation of tyrosine O-sulfate indicated the supernatant fraction to contain a 5- to 7-fold higher level than the cellular fraction at the end of a 24-hr incubation. The proteins in the supernatant fraction were immunoprecipitated and examined for sulfation. Of 15 proteins tested, 7 were found to be sulfated as indicated by [35S]sulfate incorporation into proteins separated by NaDodSO4/PAGE and detected by autoradiography. The 35S-labeled bands were excised from the dried gel and subjected to extensive Pronase hydrolysis and the hydrolysates were analyzed for tyrosine [35S]sulfate by a two-dimensional procedure combining high-voltage electrophoresis and thin-layer chromatography [Liu, M. C. & Lipmann, F. (1984) Proc. Natl. Acad. Sci. USA 81, 3695-3698]. Of the sulfated proteins, three--fibrinogen, alpha-fetoprotein, and fibronectin--were found to contain tyrosine O-sulfate. The simultaneous presence of carbohydrate-bound sulfate, however, could not be exactly determined, but the other four [35S]sulfate-containing proteins--alpha 1-antitrypsin, alpha 1-antichymotrypsin, alpha 2-macroglobulin, and transferrin--did not reveal any tyrosine O-sulfate and might be sulfated on their carbohydrate moieties.

Carcinoma, Hepatocellular↗
PubMed1985

Human lung macrophages induce histamine release from basophils and mast cells.

Human lung macrophages isolated from surgical specimens, when cultured for 24 h, acquired the capacity to induce histamine release from human basophils. This releasing activity was entirely accounted for by soluble, nondialyzable factor(s) (molecular weight, more than 2,000 daltons) released from cultured macrophages. The basophil release reaction was dose-dependent, and also Ca++ (optimal concentration = 5 mM) and temperature (optimal = 37 degrees C) dependent. Supernatants derived from the equivalent of 3 X 10(6) macrophages/ml released 50% histamine from basophils of sensitive donors. The supernatants also induced histamine release from lung mast cells. These results are the first report of a human macrophage-derived product that activates basophils and mast cells to release histamine.

Basophils↗
PubMed1984

NMR studies of a dihaem cytochrome from Pseudomonas perfectomarinus (ATCC 14405).

Pseudomonas perfectomarinus (ATCC 14405) dihaem cytochrome c552 was studied by 300-MHz proton magnetic resonance. Some of the haem resonances were assigned in the fully reduced and fully oxidized states. No evidence was found for methionine haem axial coordination. The oxidation-reduction equilibrium was studied in detail. Due to the large difference in mid-point redox potential between the two haems (+174 mV, for haem II and -180 mV for haem I) an intermediate oxidation state could be obtained containing reduced haem I and oxidized haem II. In this way the total paramagnetic shift at different oxidation levels could be decomposed in the intrinsic and extrinsic contributions. It was found that the two haems interact. The rate of electron exchange is slow on the NMR time scale. The redox equilibria are discussed for four possible redox species in solution.

Chemical Phenomena↗
PubMed1984

NMR and electron-paramagnetic-resonance studies of a dihaem cytochrome from Pseudomonas stutzeri (ATCC 11607) (cytochrome c peroxidase).

A dihaem cytochrome (Mr 37 400) with cytochrome c peroxidase activity was purified from Pseudomonas stutzeri (ATCC 11 607). The haem redox potentials are far apart: one of the haems is completely ascorbate-reducible and the other is only reduced by dithionite. The coordination, spin states and redox properties of the covalently bound haems were probed by visible, NMR and electron paramagnetic resonance (EPR) spectroscopies in three oxidation states. In the oxidized state, the low-temperature EPR spectrum of the native enzyme is a complex superimposition of three components: (I) a low-spin haem indicating a histidinyl-methionyl coordination; (II) a low-spin haem indicating a histidinyl-histidinyl coordination; and (III) a minor high-spin haem component. At room temperature, NMR and optical studies indicate the presence of high-spin and low-spin haems, suggesting that for one of the haems a high-spin to low-spin transition is observed when temperature is decreased. In the half-reduced state, the component I (high redox potential) of the EPR spectrum disappears and induces a change in the g-values and linewidth of component II; the high-spin component II is no longer detected at low temperature. Visible and NMR studies reveal the presence of a high-spin ferric and a low-spin (methionyl-coordinated) ferrous state. The NMR data fully support the haem-haem interaction probed by EPR. In the reduced state, the NMR spectrum indicates that the low-potential haem is high-spin ferrous.

Chemical Phenomena↗