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Biomedical subjects

M C Liu

Publications and source records attributed to M C Liu.

At least 145 records · Page 8Linked to original sources
PubMed1993

Isolation and characterization of a novel microsomal membrane-bound phenol sulfotransferase from bovine liver.

A novel phenol sulfotransferase (PST) was detected in bovine liver microsomal membrane fraction. The enzyme was found to be capable of catalyzing the sulfation of simple phenolic compounds, with 3'-phosphoadenosine-5'-phosphosulfate as the sulfate donor. Detergent extracted PST showed a pH optimum of 5.7 and, among the simple phenols tested, the PST exhibited highest activity toward alpha-naphthol. No activities were detected when tyrosine and its derivatives were used as substrates. Both 2,6-dichloro-4-nitrophenol and chlorpromazine were capable of inhibiting the activity of the PST toward p-nitrophenol with inhibition Coefficient50 values of 100 nM and 4 mM, respectively.

Animals↗
PubMed1992

Synthesis and antitumor activity of 3- and 5-hydroxy-4-methylpyridine-2-carboxaldehyde thiosemicarbazones.

To develop an alpha-(N)-heterocyclic carboxaldehyde thiosemicarbazone with clinical utility as an anticancer agent, two analogues, 3-hydroxy-4-methylpyridine-2-carboxaldehyde thiosemicarbazone (3-HMP) and 5-hydroxy-4-methylpyridine-2-carboxaldehyde thiosemicarbazone (5-HMP), of 5-hydroxypyridine-2-carboxaldehyde thiosemicarbazone (5-HP) have been designed and synthesized by two different methods. 3-HMP and 5-HMP both showed better antitumor activity than their respective parent compounds, 3-hydroxypyridine-2-carboxaldehyde thiosemicarbazone and 5-HP, in mice bearing the L1210 leukemia.

Animals↗
PubMed1992

Synthesis and antitumor activity of amino derivatives of pyridine-2-carboxaldehyde thiosemicarbazone.

Various substituted pyridine-2-carboxaldehyde thiosemicarbazones (12 compounds) have been synthesized and evaluated for antineoplastic activity in mice bearing the L1210 leukemia. Oxidation of 3-nitro-2-picoline,5-nitro-2-picoline,3-nitro-2,4-lutidine, and 5-nitro-2,4-lutidine with selenium dioxide was employed to generate the corresponding pyridine-2-carboxaldehydes, which were then converted to cyclic ethylene acetals and subsequently reduced to amino and hydroxyamino derivatives by catalytic hydrogenation. Condensation of nitro aldehydes and acetals with thiosemicarbazide afforded the respective thiosemicarbazones. Acetylation of the amino acetals and alkylsulfonation of the 5-amino acetal, followed by condensation with thiosemicarbazide was employed to yield amide thiosemicarbazones. The most active compounds synthesized were 3-aminopyridine-2-carboxaldehyde thiosemicarbazone and 3-amino-4-methylpyridine-2-carboxaldehyde thiosemicarbazone which produced against the L1210 leukemia, % T/C values of 246 and 255, and 40% 60-day long-term survivors at two daily doses of 40 mg/kg and 10 mg/kg, respectively, for six consecutive days.

Animals↗
PubMed1992

Cytogenetic study of acute lymphoblastic leukemia and its correlation with immunophenotype and genotype.

Among 72 Chinese patients with acute lymphoblastic leukemia (ALL), 50 had clonal chromosomal abnormalities. Structural abnormalities were detected in 42 patients: these included t(9;22) in 9, t(1;19) in 6, t(4;11) in 5, del(11)(q23) in 4, and del(6q) in 4. Adults had a higher incidence of t(9;22) and t(1;19) but a lower incidence of t(4;11) and hyperdiploid greater than 50 karyotype than children. A significant difference was also noted in white blood cell (WBC) count among various karyotypic groups. Patients with chromosomal abnormalities t(9;22), t(1;19), t(4;11) and del(11) (q23) had a shorter complete remission duration as compared with patients free of these abnormalities. Immunophenotyping was performed on 69 patients. All patients with t(9;22), t(1;19), and t(4;11) had B-lineage ALL restricted to certain stages of maturation: groups III and IV, groups IV and V, and group II, respectively (according to the classification of Foon and Tood). Among patients with t(9;22), t(4;11), and del(11)(q23), which have been considered to be associated with acute mixed-lineage leukemia, one each, respectively, showed myeloid antigen expression on the leukemic blasts (My+ ALL). No cross-lineage rearrangements of immunoglobulin (Ig) or T-cell receptor (TCR) genes were detected in these karyotypic subgroups of patients who underwent gene analysis.

Adolescent↗
PubMed1992

Platelet activation in the lung after antigen challenge in a model of allergic asthma.

The purpose of this study was to investigate whether platelets are activated and release their products in the human lung after antigen challenge. Using subsegmental antigen challenge as a model of asthma, bronchoalveolar lavage fluids from ragweed-allergic asthmatic subjects were assayed for the alpha granule products, platelet factor 4 (PF4) and beta-thromboglobulin (beta-TG), prior to challenge (baseline) and at 5 min and 19 h after challenge with ragweed antigen. Airway segments challenged with normal saline were used as controls. Five minutes after antigen challenge, levels of platelet products in BAL fluid were not elevated from baseline or normal saline control levels. However, 19 h after antigen challenge, a 10-fold increase in platelet products in BAL fluids was found. The mean PF4 levels increased from baseline and saline control values of less than 1.0 to 7.2 ng/ml (p less than 0.05) 19 h after antigen challenge. beta-TG increased from baseline and control levels of less than 1.0 to 6.6 ng/ml (p less than 0.05). Elevations in PF4 and beta-TG were highly correlated with each other (r = 0.98, p less than 0.0001). Levels of platelet products during the 19-h response correlated with albumin, with kinins, with the prostaglandins 6-keto-PGF1 alpha, PGE2, and PGF2 alpha, and with the eosinophil-derived proteins, eosinophil-derived neurotoxin and eosinophil peroxidase. We conclude that platelet activation in the lung is a feature of the late inflammatory response to antigen challenge and that platelets may play an important role in allergic inflammation and asthma.

Adult↗
PubMed1992

Peripheral airways resistance in smokers.

To determine peripheral airways resistance (Rp) in asymptomatic smokers, we used a wedged bronchoscope technique to study 19 volunteers (18 to 44 yr of age) who actively smoked for 2 to 28 pack-years. A fiberoptic bronchoscope was wedged in a subsegmental bronchus of the right upper lobe. Using a double lumen catheter inserted through the working channel of the bronchoscope, we infused 5% CO2 in air through one lumen and measured pressure through the second lumen. Rp was determined as the average of the peripheral resistance measured at three or more flow rates. This resistance ranged from 0.003 to 0.075 cm H2O/ml/min in the 19 subjects. We have previously shown normal subjects to have an average Rp of 0.009 +/- 0.002 cm H2O/ml/min (mean +/- SE) and asthmatic subjects an average of 0.069 +/- 0.017 cm H2O/ml/min. Thus, despite normal pulmonary function as assessed by spirometry, these asymptomatic smokers demonstrated a wide range of Rp values from normal to that observed in asthmatic subjects. These findings are consistent with a mechanism that considers the high resistance to result from inflammatory changes in the small airways.

Adolescent↗
PubMed1992

Altered adhesion molecule expression and endothelial cell activation accompany the recruitment of human granulocytes to the lung after segmental antigen challenge.

Mounting evidence suggests that inflammatory cells recruited to the lung can contribute to the pathogenesis of asthma. The factors governing the activation and recruitment of circulating cells to the lung remain unknown, but an early step in this process is the interaction of adhesion molecules on circulating cells with those on endothelial cells. We used a segmental antigen challenge model followed 18 h later by bronchoalveolar lavage (BAL) to study granulocyte recruitment to the lung in 14 allergic subjects. Using immunofluorescence and flow cytometry, we determined the expression of the adhesion molecules CD11b, L-selectin (LECAM-1), and VLA-4 on BAL and peripheral blood granulocytes. Total cell count and percentages of recovered eosinophils and basophils were significantly increased in BAL fluids from antigen-challenged segments. Compared with their peripheral blood counterparts, CD11b expression was increased 2- to 3-fold on BAL eosinophils, basophils, and neutrophils (n = 9, P less than 0.05). In contrast, L-selectin expression was significantly decreased on BAL cells (n = 3 to 4, P less than 0.05). Similar phenotypic changes were observed on all three cell types, and on neutrophils recovered from saline-challenged control lung segments. In two subjects, VLA-4 alpha (CD49d) expression on BAL eosinophils was 78 +/- 5% of that seen on peripheral blood eosinophils. Because ELAM-1 (endothelial leukocyte adhesion molecule-1, E-selectin) expression occurs during allergic inflammation and is shed after endothelial activation, we used a sensitive enzyme-linked immunosorbent assay to analyze BAL supernatants for a soluble form of this molecule (sELAM-1).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Plasma ammonia in patients with acute leukemia.

Plasma ammonia level (PAL) was studied in 43 cases of acute leukemia (AL). PAL was 39.21 +/- 26.2 mumol/L in normal controls and 38.8 +/- 16.6 mumol/L in leukemic patients before chemotherapy. High PAL was found in 40 cases after chemotherapy. Six cases showed clinical manifestations due to severe hyperammonemia, including dizziness, lethargy, confusion, coma and mental changes of various degree, and there was also respiratory alkalosis. After ammonia-trapping therapy, 4 of the 5 patients recovered. The authors believe that high PAL is not uncommon after chemotherapy in leukemic patients. Respiratory alkalosis and unexplained mental and neurologic changes following intensive chemotherapy are useful clues for the diagnosis of hyperammonemia syndrome. Early diagnosis and treatment with ammonia-trapping may improve the rates of remission and survival.

Adolescent↗
PubMed1992

Post-translational modification of protein by tyrosine sulfation: active sulfate PAPS is the essential substrate for this modification.

In vitro tyrosine sulfation of recombinant proteins would be a valuable tool in converting those proteins expressed in prokaryotic vectors to their natural form. For this purpose tyrosylprotein sulfotransferase (TPST), the enzyme responsible for tyrosine sulfation of proteins, was characterized from a bovine liver Golgi preparation. TPST was active in a acidic environment with a pH optimum of 6.25, and displayed a stimulation by the Mn2+, with the optimum activity in the presence of 5mM MnCl2. TPST was able to sulfate recombinant hirudin variant 1 (rHV-1) expressed in Escherichia coli and the C-terminal hirudin fragment 54-65 but not the N-terminal hirudin fragment 1-15 by using 3'-phosphoadenosine 5'-phosphosulfate (PAPS), indicating its specificity for the naturally sulfated tyrosine 63. Comparison of the reaction kinetics on synthetic peptides showed that the bovine liver TPST has a higher affinity and reaction rates for those peptides with a aspartyl residue on the N-terminal side of the tyrosine when compared with a glutamyl residue.

Amino Acid Sequence↗
PubMed1992

Characterization of Philadelphia-chromosome-positive acute leukemia by clinical, immunocytochemical, and gene analysis.

Philadelphia chromosome (Ph') was detected at presentation in 10 out of 110 patients with acute lymphoblastic leukemia (ALL) and five of 168 patients with acute myelogenous leukemia (AML). Two other ALL patients who had studies at relapse were also included in the analyses. One of the 12 Ph'-positive (Ph+) ALL patients had simultaneous expression of myeloid-associated antigen on the leukemic blasts, while all the five AML patients coexpressed markers of lymphoid cells. Double labeling of the cells with myeloperoxidase and CD10 on three Ph+ AML cases showed that most leukemic blasts expressed either myeloperoxidase activity or CD10 but not both. Cross-lineage gene rearrangements of T-cell receptor (TCR) beta-chain gene were detected in three of the eight Ph+ ALL patients tested. All the four Ph+ AML cases studied showed immunoglobulin heavy chain gene rearrangements, and three of them also had simultaneous rearrangements of TCR beta-chain gene. The results revealed that Ph+ acute leukemia in this study belonged either to ALL or mixed lineage leukemia, and none was pure AML. This finding is contrary to that of acute blast crisis of chronic myelogenous leukemia in which the majority of patients had myeloid transformation. Rearrangements of bcr were detected in four of the 10 Ph+ ALL and three of the four Ph+ AML patients tested. No significant difference was noted in the clinical or hematologic manifestations among Ph+ leukemia with or without bcr rearrangements.

Adult↗
PubMed1992

Enzymatic synthesis of PAPS with an ATP-regeneration system.

Sulfate activating enzymes, ATP sulfurylase and APS kinase, were newly isolated from a thermophile, Bacillus stearothermophilus. Adenosine 3'-phosphate 5'-phosphosulfate (PAPS) was synthesized by these enzymes. The reaction proceeded more efficiently when an ATP-regeneration system, using acetate kinase, was coupled to the reaction system.

Acetate Kinase↗
PubMed1992

[A study on pathogenesis and therapy of hemorrhagic fever with renal syndrome].

581 early cases of typical hemorrhagic fever with renal syndrome (HFRS) were dynamically studied on the clinical manifestations and laboratory findings from 1986 to 1989. All the patients were treated with various methods. The results showed: (1) The manifestations of microvascular damage, proteinuria and thrombocytopenia can be found at the first day of the onset in 80.0%, 72.2% and 33.3% respectively. In a word, the characteristic features of HFRS appear at the onset of the disease. (2) In 446 early cases the initial severity of the disease corresponded with the final severity at a rate of 89.2%; it indicated that the damage of HFRS may result from the first attack. (3) The time of the onset, peak and persistence of all the characteristic features were similar; it is suggested that the course of HFRS may be self-limited. (4) Based on the clinical understanding and the effective results in the 446 early cases treated with fluid therapy alone, we consider that the effective treatment of HFRS is early and reasonable fluid therapy.

Adolescent↗
PubMed1992

Production of granulocyte/macrophage colony-stimulating factor in human airways during allergen-induced late-phase reactions in atopic subjects.

Granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-3 (IL-3) are hematopoietic growth factors that have been shown to induce proliferation and activation of inflammatory cells, and may play a role in allergic reactions. Since little is known about the involvement of cytokines in allergic inflammation in the lung, the levels of GM-CSF and IL-3 were measured in bronchoalveolar lavage (BAL) fluids obtained in the late phase after segmental lung antigen (Ag) challenge in 14 allergic rhinitis subjects with or without bronchial asthma. BAL fluids either after Ag (ragweed, dust mite, or timothy) or saline control challenge were recovered 19 h later. In 6 of the 14 patients, BAL fluids were concentration-dialyzed (20x) and assayed for cytokine activity. Cytokine assays were performed using the human megakaryocytic leukemic cell line M-07e, which is responsive to either GM-CSF or IL-3. The level of GM-CSF-equivalents was approximately 25 times higher in Ag-challenged sites (49.9 +/- 12.7 pg/ml; mean +/- SEM), compared to saline challenge sites (2.2 +/- 1.0, p < 0.01, n = 9). Neutralization experiments using a polyclonal specific antibody (Ab) against GM-CSF and IL-3 revealed that the bulk of the activity was GM-CSF. BAL fluids from Ag- and saline-challenged sites in one nonatopic subject contained no significant GM-CSF activity. Furthermore, the level of GM-CSF in Ag-challenged BAL fluid and the percentage of eosinophils in BAL from each subject correlated significantly (r = 0.73, p < 0.005, n = 14).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Evaluation of an enzyme-linked immunosorbent assay for detection of Eperythrozoon suis antibodies in swine.

An ELISA was developed and tested to detect antibodies to Eperythrozoon suis in swine. Results were compared with those of the indirect hemagglutination (IHA) test. Antigen isolated from swine heavily infected with E suis was used for both tests. Comparison of the ELISA with the IHA test revealed a significant (P less than 0.001) correlation between results. Of 114 samples obtained from 9 swine infected with E suis, 87.7% were seropositive (titer greater than or equal to 200) via the ELISA, and 80.7% were seropositive (titer greater than or equal to 20) via the IHA test. The sensitivity of the ELISA was greater than that of the IHA test. All blood samples obtained from specific-pathogen-free swine tested negative for E suis antibody. Cross-reactions were not observed between E suis antigen and antisera against various swine and cattle disease agents using ELISA. We concluded that the ELISA may be used for rapid and effective diagnosis of infection with E suis in swine.

Animals↗
PubMed1991

Polarized secretion of tyrosine-sulphated proteins and free tyrosine O-sulphate by filter-grown Madin-Darby canine kidney (MDCK) cells.

Filter-grown Madin-Darby canine kidney (MDCK) cells labelled for 24 h with [35S]sulphate were found to secrete macromolecules [35S]sulphated on their carbohydrate moieties predominantly into the basolateral medium, whereas the tyrosine-[35S]sulphated proteins synthesized were predominantly secreted into the apical medium. In contrast with the predominant apical secretin of tyrosine-[35S]sulphated proteins, the free tyrosine O-[35S]sulphate (Tyr[35S]) was released mostly into the basolateral medium. A time-lapse study using prelabelled MDCK cells incubated in fresh medium revealed that, during the 48 h time course monitored, the release of tyrosine-[35S]sulphated proteins into the apical medium was faster and quantitatively greater than that into the basolateral medium. During the same time there was a concomitant release, predominantly into the basolateral medium, of the free Tyr[35S] derived from the degradation of tyrosine-[35S]sulphated proteins. An endocytotic degradation experiment was performed to demonstrate the endocytosis of tyrosine-sulphated proteins and their degradation to generate free TyrS. It was found that free Tyr[35S] was generated and released when an apically secreted (or basolaterally secreted) tyrosine-[35S]sulphated protein preparation was added to the apical medium (or the basolateral medium) of unlabelled filter-grown MDCK cells. In both cases, the free Tyr[35S] generated was predominantly released into the basolateral medium similar to the results obtained in the time-lapse study.

Animals↗
PubMed1991

Post-translational modifications and binding properties of the apically secreted 80-kDa glycoprotein from Madin-Darby canine kidney cells: similarities to the C-terminal portion of the basolaterally secreted fibronectin.

Apically secreted 80-kDa glycoprotein (gp 80) from Madin-Darby canine kidney cells was found to be immunoprecipitated by the polyclonal antiserum against fibronectin or a monoclonal antibody specific for the fibronectin C-terminal fibrin binding domain. Upon sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), gp 80 migrated as a doublet band under nonreducing conditions. Under reducing conditions, gp 80 was resolved into three distinct bands, respectively of 45-, 40-, and 35-kDa molecular mass. Analysis by two-dimensional SDS-PAGE revealed that gp 80 exists in two molecular forms: one consisting of a 45-kDa subunit and a 40-kDa subunit, and one consisting of a 45-kDa subunit and a 35-kDa subunit. V-8 protease mapping indicated the 40 and 35-kDa subunits as being of the same homologous group and also as bearing partial homology to the 45-kDa subunit. Radioactive labeling revealed that labeled gp 80 was subjected to covalent modifications by sulfation and phosphorylation. Sulfate analysis showed that [35S]sulfate-labeled gp 80 contained ca. 2.45 +/- 0.07% tyrosine-bound [35S]sulfate with the rest being presumably carbohydrate-bound. [32P]-Phosphate-labeled gp 80, on the other hand, was found to contain serine-O-phosphate as the predominant phosphorylated amino acid residue. Employing the affinity gel fractionation technique, it was shown that gp 80 exhibited binding affinities toward heparin and fibrin. Binding of gp 80 to heparin-agarose or fibrin-Sepharose, however, was inhibited in the presence of added fibronectin or the monoclonal antibody. Tryptic peptide mapping revealed common peptide spots between fibronectin and the three subunits of gp 80. Furthermore, Western blot analysis showed that fibronectin could be recognized and bound by anti-gp 80 antibodies. These results indicate that gp 80 bears both structural and functional similarities to the C-terminal portion of the fibronectin molecule.

Animals↗