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Biomedical subjects

Z G Chen

Publications and source records attributed to Z G Chen.

At least 37 records · Page 2Linked to original sources
PubMed1992

Identification of a Fab interaction footprint site on an icosahedral virus by cryoelectron microscopy and X-ray crystallography.

Biological processes frequently require the formation of multi-protein or nucleoprotein complexes. Some of these complexes have been produced in homogeneous form, crystallized, and analysed at high resolution by X-ray crystallography (for example, see refs 1-3). Most, however, are too large or too unstable to crystallize. Individual components of such complexes can often be purified and analysed by crystallography. Here we report how the coordinated application of cryoelectron microscopy, three-dimensional image reconstruction, and X-ray crystallography provides a powerful approach to study large, unstable macromolecular complexes. Three-dimensional reconstructions of native cowpea mosaic virus (CMPV) and a complex of CPMV saturated with a Fab fragment of a monoclonal antibody against the virus have been determined at 23 A resolution from low-irradiation images of unstained, frozen-hydrated samples. Despite the nominal resolution of the complex, the physical footprint of the Fab on the capsid surface and the orientation and position of the Fab have been determined to within a few ångstroms by fitting atomic models of CPMV4 and Fab (Kol)5 to reconstructed density maps.

Antibodies, Monoclonal↗
PubMed1992

Emodin O-methyltransferase from Aspergillus terreus.

Emodin O-methyltransferase, an enzyme catalyzing methylation of the 8-hydroxy group of emodin, was identified in the mould Aspergillus terreus IMI 16043, a (+)-geodin producing strain. The enzyme catalyzed the formation of questin from emodin and S-adenosyl-L-methionine. By chromatography on DEAE-cellulose, Phenyl Sepharose, Q-Sepharose, Hydroxyapatite, and CM-cellulose, emodin O-methyltransferase was purified to apparent homogeneity. The purified protein had a molecular weight of 322 kDa as estimated by gel filtration and 53.6 kDa as estimated by gel electrophoresis under denaturing conditions, suggesting that the active enzyme was a homohexamer. The enzyme showed pI 4.4 and optimum pH 7-8. Magnesium ion or manganese ion was not an absolute requirement, nor increased the enzyme activity. The enzyme had strict substrate specificity and very low Km values for both emodin (3.4 x 10(-7) M) and S-adenosyl-L-methionine (4.1 x 10(-6) M).

Aspergillus↗
PubMed1992

[Endoscopic balloon dilatation for achalasia: an effect observation in 38 cases].

From February 1988 to November 1990, thirty eight patients with achalasia were treated endoscopically with micro-vasive regiflex dilator (MRBD). Immediate success rate was 100% and the long-term effect 89.4%. No serious complications such as perforation of bleeding occurred. MRBD is superior to conventional dilators in treating this disease and probably the method of first choice.

Adolescent↗
PubMed1992

[Epidemiological trend in late stage of control in Malayan filariasis endemic areas with Anopheles anthropophagus as main vector].

During 1982-1990, a longitudinal observation on prevalence trend of malayan filariasis has been made in endemic areas with An. anthropophagus as the main vector. A total of 22,795 person-times of blood examination were made, and 30,439 An. anthropophagus and 10,061 An. sinensis were dissected respectively. The microfilaraemia rate dropped from 1.0% to 0.14%, and the infection rate of An. anthropophagus decreased from 0.74% to 0.09% in 3 endemic villages, while no positive case or infected vector occurred in 5 villages where microfilaraemia cases were absent since the beginning of the study. In a cross-sectional survey, 855 villages of 17 counties has been monitored for 10 years. Out of 213,934 person-times of blood examination, only 56 were positive, the average microfilaraemia rate being 0.0262%, and 94.64% of the positive had already been detected before 1986. Based on these data, it has been suggested that in endemic areas with An. anthropophagus as main vector, when the microfilaraemia rate dropped to less than 1% after control, there was no indication that the rate would upgrade during the survey period. A decline trend of the transmission of malayan filariasis, therefore, has been exhibited.

Animals↗
PubMed1991

Identification of emodinanthrone oxygenase in fungus Aspergillus terreus.

Emodinanthrone oxygenase, which catalyzes the oxidation of emodinanthrone to emodin, has been identified in fungus, Aspergillus terreus. The fixation of an oxygen atom at the C-10 position of emodinanthrone from molecular oxygen catalyzed by the enzyme was proved by the 18O2 incubation experiment and analyses of the product emodin by mass spectrometry and nuclear magnetic resonance. The fact that the reaction did not require any foreign electron donor suggested the involvement of internal monooxygenase. Emodinanthrone oxygenase activities were found in other microbes which produce anthraquinone related metabolites.

Aspergillus↗
PubMed1990

Structural studies of bean pod mottle virus, capsid, and RNA in crystal and solution states by laser Raman spectroscopy.

Structures of protein and RNA components of bean pod mottle virus (BPMV) have been investigated by use of laser Raman spectroscopy. Raman spectra were collected from both aqueous solutions and single crystals of BPMV capsids (top component) and virions (middle and bottom components, which package, respectively, small and large RNA molecules). Analysis of the data permits the assignment of conformation-sensitive Raman bands to viral protein and RNA constituents and observation of structural similarities and differences between solution and crystalline states of BPMV components. The Raman results show that the protein subunits of the empty capsid contain between 45% and 55% beta-strand and beta-turn secondary structure, in agreement with the recently determined X-ray crystal structure, and that this total beta-strand content undergoes a small increase (approximately 5%) with packaging of RNA. The subunits are relatively deficient in alpha-helix secondary structure, estimated at less than 25%, and therefore must contain extensive amounts (greater than 20%) of loops and irregular chain conformations. The Raman spectra also show the following: (1) The molecular environments of as many as four tryptophan residues per subunit are altered upon packaging RNA, resulting in stronger 1N-H hydrogen bonding for two Trp residues and more hydrophobic environments for two indole rings. (2) Hydrogen-bonding states of the seven Tyr residues per subunit do not change detectably when RNA is packaged. At least five tyrosine OH groups are involved exclusively as strong hydrogen bond donors to protein acceptor groups, which suggests restricted access of solvent H2O molecules to these parahydroxyls.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗
PubMed1990

Investigation of the amount of dissolved iron in food cooked in Chinese iron pots and estimation of daily iron intake.

The amount of dissolved iron in food cooked in Chinese iron pots and that in food cooked in aluminum, stainless steel, and clay pots were determined. It was found that the amount of dissolved iron in food cooked in Chinese iron pots was two to five times higher than that in food cooked in the other types of pots. According to the test results, the estimated increase in daily iron intake was about 14.5 mg for adults and 7.4 mg for children when Chinese iron pots were used.

Aluminum↗
PubMed1989

IL-1 and IL-6 release by tumor-associated macrophages from human ovarian carcinoma.

Our study was designed to investigate the production of interleukin-1 (IL-1) and IL-6 in tumor-associated macrophages (TAM) isolated from ascites (18 cases) or solid (7 cases) human ovarian carcinoma. These are pleiotropic monokines which, in addition to affecting proliferation and differentiation of lymphocytes, act on various targets, including vascular cells and liver, and may therefore be involved in the pathogenesis of certain manifestations of malignancy. IL-1 was measured by the thymocyte co-stimulator assay, under conditions in which IL-6 was inactive, and, in 8 cases, by radioimmunoassay (RIA). IL-6 was measured as hybridoma growth factor (HGF) on the 7TD1 cell line. TAM did not release appreciable levels of IL-1 spontaneously and, upon LPS stimulation, were poor producers of this monokine compared to blood monocytes. In contrast, TAM supernatants contained a high level of HGF in the absence of deliberate stimulation, and exposure to LPS either did not affect or further augmented production of this monokine. HGF activity of TAM supernatants was completely blocked by anti-IL-6 antibodies. Ascites fluid from 8 ovarian-carcinoma patients contained high levels of HGF activity, blocked by anti-IL-6 antibodies. Thus, TAM exhibit a dissociation in their capacity to release the functionally related monokines IL-1 and IL-6. IL-6 produced by TAM may account for the elevation of liver-derived acute-phase proteins associated with malignancy.

Carcinoma↗
PubMed1989

Protein-RNA interactions in an icosahedral virus at 3.0 A resolution.

Nearly 20 percent of the packaged RNA in bean-pod mottle virus (BPMV) binds to the capsid interior in a symmetric fashion and is clearly visible in the electron density map. The RNA displaying icosahedral symmetry is single-stranded with well-defined polarity and stereochemical properties. Interactions with protein are dominated by nonbonding forces with few specific contacts. The tertiary and quaternary structures of the BPMV capsid proteins are similar to those observed in animal picornaviruses, supporting the close relation between plant comoviruses and animal picornaviruses established by previous biological studies.

Amino Acid Sequence↗
PubMed1989

Production of a retroviral P15E-related chemotaxis inhibitor by IL-1-treated endothelial cells. A possible negative feedback in the regulation of the vascular response to monokines.

The effects of IL-1 on vascular endothelium result in a complex set of alterations which are potentially disruptive of vessel wall and underlying tissue integrity. The present study was aimed at investigating possible regulation of such potentially destructive responses elicited by IL-1 on endothelial cells. Culture supernatants of IL-1-treated human umbilical vein endothelial cells (HEC) were depleted of retroviral p15E-related Ag with immobilized anti-p15E mAb. The monocyte chemotactic and polarizing activity of supernatants of IL-1-treated HEC (presumably related to colony-stimulating factors being released by HEC) was markedly augmented by absorption on immobilized anti-p15E antibodies. Irrelevant IgG had no effect and anti-p15E antibodies did not affect the chemotactic activity of supernatants from unstimulated HEC. The material eluted from Sepharose-bound anti-p15E antibodies was devoid of chemotactic and polarizing activity and suppressed the polarization and migration of monocytes in response to chemoattractants. The alpha and beta molecular species of IL-1 were equally effective in inducing the production of p15E-related inhibitor. The production of a p15E-related inhibitor of chemotaxis induced by IL-1 in HEC may represent a negative signal in the regulation of the potentially destructive responses to pro-inflammatory cytokines.

Aminopeptidases↗
PubMed1989

Recombinant human interleukin 5 is a selective eosinophil chemoattractant.

Human recombinant interleukin (IL) induced migration across polycarbonate filters of human peripheral blood eosinophils. The contribution of chemotaxis vs. chemokinesis was investigated using a checkerboard design with both polycarbonate and nitrocellulose filters. When different cytokine concentrations were seeded above and below the filter, maximal induction of migration required a positive concentration gradient between the lower and upper compartments of the chamber, though some gradient-independent augmentation of migration occurred. These results indicate that induction of eosinophil migration across filter involves actual chemotaxis. The effect of IL5 was selective for eosinophils with no effect on neutrophils and monocytes. Conversely, granulocyte-macrophage colony-stimulating factor elicited migration of both eosinophils and neutrophils. Thus, human IL5 is a potent and selective chemoattractant for human eosinophils. Eosinophils are selectively localized in tissues under a variety of physiological and pathological conditions. Locally produced IL5 may play a role in the selective recruitment of eosinophils from the blood compartment.

Chemotaxis, Leukocyte↗
PubMed1989

Interleukin-1 and tumor necrosis factor production in acute non-lymphoid leukemia.

We have investigated interleukin-1 (IL-1) and tumor necrosis factor (TNF) release in 20 patients with acute non-lymphoid leukemia (ANLL) after culture with bacterial lipopolysaccharide (LPS) or in the absence of deliberate stimulation. IL-1 and TNF were identified by appropriate bioassays inhibitable by specific antibodies. The capacity to produce IL-1 was expressed by most ANLL cases investigated irrespective of the FAB (French, American, British) subtype. However, the M4 and M5 cases tended to be better producers of IL-1 than M1-M3 cases. In contrast, TNF release was only restricted to M5 leukemias (3 out of 4 cases examined). Cytokine production may therefore provide additional criteria for a functional classification of ANLL. A considerable proportion of ANLL cases (7/18 bone marrow samples and 12/20 blood samples) released appreciable quantities of IL-1 in culture in the absence of deliberate stimulation. "Spontaneous" TNF production was also detected in 1 out of 3 M5 cases. Cells were cultured under LPS-negative conditions and polymixin B did not affect spontaneous cytokine release. Moreover, Northern blot analysis showed that freshly isolated, non-cultured ANLL cells expressed IL-1 beta transcripts. Inasmuch as IL-1 is responsible for hemopoietin-1 activity and IL-1 induces colony stimulating factor production in various cell types, the observation of IL-1 production in ANLL suggests that this mediator may be involved in regulatory amplifying circuits of leukemic cell proliferation.

Biomarkers, Tumor↗
PubMed1989

[Endoscopic bipolar circumactive electrocoagulation in acute upper gastrointestinal bleeding].

Bipolar circum-active probe (BICAP) is a new endoscopically deliverable bipolar electrocoagulator. 57 patients with acute upper gastrointestinal bleeding have been treated by the endoscopic BICAP and the value of the technique in the control of acute bleeding has been assessed. 57 patients underwent 47 qg probe applications with a mean value of 8.3 for each case. Immediate hemostasis was achieved in out of 57 cases (93%). Rebleeding after hemostasis by BICAP was noted in 4 out of 53 cases (7.5%). There were no complications related to the procedure. It is an important technique for the control of acute upper gastrointestinal bleeding.

Adolescent↗
PubMed1988

Induction of monocyte migration by recombinant macrophage colony-stimulating factor.

Human recombinant macrophage-CSF (M-CSF) induced migration across polycarbonate or nitrocellulose filters of human peripheral blood monocytes. Checkerboard analysis of M-CSF-induced migration, performed by seeding different cytokine concentrations above and below the filter, revealed that the locomotory response involved chemotaxis, though some gradient-independent augmentation of migration occurred. Polymixin B did not affect M-CSF chemotaxis and M-CSF was active on monocytes from the LPS-unresponsive mouse strain C3H/HeJ. These findings rule out a contribution of minute endotoxin contamination, below the sensitivity of the Limulus assay, in M-CSF chemotaxis. Rabbit anti-M-CSF antibodies inhibited the chemotactic activity of recombinant M-CSF, thus further indicating that the M-CSF molecule was indeed responsible for chemotaxis. M-CSF preparations encoded by 224 or 522 amino acid cDNA clones were equally effective in inducing monocyte migration. Recombinant M-CSF did not elicit a migratory response in large granular lymphocytes and in endothelial cells under conditions in which appropriate reference attractants were active. A modest stimulation of migration of polymorphonuclear leukocytes, inhibitable by antibodies, was observed at high cytokine concentrations (10 to 100 times higher than those required for monocyte locomotion). The maximal polymorphonuclear leukocytes response evoked by M-CSF was small compared to that evoked by reference chemoattractants or to that evoked by the same cytokine in monocytes. Hence, M-CSF is a potent chemoattractant for mononuclear phagocytes and exerts its action preferentially on cells of the monocyte-macrophage lineage. M-CSF, produced locally by activated macrophages, may play a role in the selective recruitment from the blood compartment of mononuclear phagocytes to amplify resistance against certain noxious agents.

Chemotactic Factors↗
PubMed1988

Chemotactic activity of recombinant human granulocyte colony-stimulating factor.

Recombinant human granulocyte colony-stimulating factor (rhG-CSF) induced migration across polycarbonate filters of human polymorphonuclear leukocytes (PMN). rhG-CSF was active in inducing PMN migration at concentrations greater than or equal to 10 to 100 U/mL (7 to 70 ng/mL). rhG-CSF did not contain appreciable levels of endotoxin contamination as assessed by Limulus amebocyte assay, and Polymixin B did not affect the chemotactic activity of rhG-CSF. A monoclonal anti-G-CSF antibody blocked the induction of migration by G-CSF, thus establishing that the cytokine was responsible for the activity of the recombinant preparation. Checkerboard analysis was performed by seeding different concentrations of G-CSF above and/or below the filter and revealed that the migratory response to this cytokine was best observed in the presence of a positive concentration gradient between the lower and upper compartments of the chamber, thus indicating an actual chemotactic effect. When different migrating cells were examined, rhG-CSF was inactive on large granular lymphocytes and endothelial cells under conditions in which appropriate reference attractants were active. In contrast, rhG-CSF elicited a chemotactic response in monocytes inhibited by specific antibody. Thus, G-CSF is a chemotactic signal for phagocytes. This cytokine, when produced at inflammatory sites, may contribute to the recruitment of phagocytes from the blood compartment to amplify resistance against certain noxious agents.

Antibodies, Monoclonal↗