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H Liang

Publications and source records attributed to H Liang.

At least 55 records · Page 3Linked to original sources
PubMed2001

[Study on the interaction between Pd(II) and Rhus vernicifera laccase].

The influence of the mixing time of Pd(II) and Rhus vernicifera laccase on the oxidation of 5,6-dibromo-2,3-dicyanohydroquinone (DDBQH2) catalyzed by laccase has been studied through spectrophotometer at pH 4.5 and (30 +/- 0.1 degree C). The activation of Pd(II) on the laccase activity is gradually converted into inhibition and ultimately inactivation with the extension of the mixing time of Pd(II) and laccase, and the rate of such conversion goes up with the increase of Pd(II) concentration. The influence of Pd(II) on the absorption spectrum of laccase suggests that it is the type I site in laccase with which Pd(II) interacts and Pd(II) may gradually and at last substitute Cu(II) from the site. The substitution may be the cause of decrease and disappearance of laccase activity.

Binding Sites↗
PubMed2000

Protection of Aotus monkeys by Plasmodium falciparum EBA-175 region II DNA prime-protein boost immunization regimen.

Aotus monkeys received 4 doses of Plasmodium falciparum EBA-175 region II vaccine as plasmid DNA (Dv-Dv) or recombinant protein in adjuvant (Pv-Pv) or as 3 doses of DNA and 1 dose of protein (Dv-Pv). After 3 doses, antibody titers were approximately 10(4) in DNA-immunized monkeys and 10(6) in protein-immunized monkeys. A fourth dose did not significantly boost antibody responses in the Dv-Dv only or Pv-Pv only groups, but titers were boosted to approximately 10(6) in monkeys in the Dv-Pv group. Four weeks after the last immunization, the animals were challenged with 10(4) P. falciparum-parasitized erythrocytes. Peak levels of parasitemia were lower in the 16 monkeys that received region II-containing plasmids or proteins than in the 16 controls (geometric mean: 194,178 and 410,110 parasites/microL, respectively; P=.013, Student's t test). Three of 4 monkeys in the Dv-Pv group did not require treatment. These data demonstrate that immunization with EBA-175 region II induces a significant antiparasite effect in vivo.

Adjuvants, Immunologic↗
PubMed2000

Signal peptidase and oligosaccharyltransferase interact in a sequential and dependent manner within the endoplasmic reticulum.

We demonstrate that the signal peptides of prepro-alpha-factor and preinvertase must be cleaved before Asn-X-Ser/Thr acceptor tripeptides located near the signal peptides of these precursors can be efficiently glycosylated within the endoplasmic reticulum of the yeast Saccharomyces cerevisiae. The data support a model whereby the interaction of a signal peptide with the membrane prevents an acceptor tripeptide juxtaposed to the signal peptide from accessing the oligosaccharyltransferase active site until the signal peptide is cleaved.

Amino Acid Sequence↗
PubMed2000

Bradykinin activates the Janus-activated kinase/signal transducers and activators of transcription (JAK/STAT) pathway in vascular endothelial cells: localization of JAK/STAT signalling proteins in plasmalemmal caveolae.

Bradykinin (BK) is an important physiological regulator of endothelial cell function. In the present study, we have examined the role of the Janus-activated kinase (JAK)/signal transducers and activators of transcription (STAT) pathway in endothelial signal transduction through the BK B2 receptor (B2R). In cultured bovine aortic endothelial cells (BAECs), BK activates Tyk2 of the JAK family of tyrosine kinases. Activation results in the tyrosine phosphorylation and subsequent nuclear translocation of STAT3. BK also activates the mitogen-activated p44 and p42 protein kinases, resulting in STAT3 serine phosphorylation. Furthermore, Tyk2 and STAT3 form a complex with the B2R in response to BK stimulation. Under basal conditions, Tyk2, STAT3 and the B2R are localized either partially or entirely in endothelial plasmalemmal caveolae. Following BK stimulation of BAECs, however, the B2R and STAT3 are translocated out of caveolae. Taken together, these data suggest that BK activates the JAK/STAT pathway in endothelial cells and that JAK/STAT signalling proteins are localized in endothelial caveolae. Moreover, caveolar localization of the B2R and STAT3 appears to be regulated in an agonist-dependent manner.

Active Transport, Cell Nucleus↗
PubMed2000

Causal influences in primate cerebral cortex during visual pattern discrimination.

Anatomical studies of the visual cortex demonstrate the existence of feedforward, feedback and lateral pathways among multiple cortical areas. Yet relatively little evidence has previously been available to show the causal influences of these areas on one another during visual information processing. We simultaneously recorded event-related local field potentials (LFPs) from surface-to-depth bipolar electrodes at six sites in the ventral region of the right hemisphere visual cortex in a highly trained macaque monkey during performance of a visual pattern discrimination task. Applying a new statistical measure, the short-time directed transfer function (STDTF), to the LFP data set, we charted the changing strength and direction of causal influence between these cortical sites on a fraction-of-a-second time scale. We present results showing, for the first time, the dynamics of distinct feedforward, feedback and lateral influences in the ventral portion of the primate visual cortex during visual pattern processing.

Action Potentials↗
PubMed2000

The role of cell surface receptors in the activation of human B cells by phosphorothioate oligonucleotides.

Phosphorothioate oligodeoxynucleotides (sODN) containing the CpG motif or TCG repeats induce T cell-independent polyclonal activation of human B cells. To elucidate the mechanism of this response, the role of cell surface receptors was investigated. Sepharose beads coated with stimulatory but not nonstimulatory sODNs induced B cell proliferation comparably with soluble sODNs. The B cell stimulatory activity of Sepharose-bound sODN did not result from free sODN released from the beads since media incubated with coated beads were inactive. Using FITC-labeled sODNs as probes, binding to human B cells could be detected by flow cytometry. Binding was rapid, saturable, initially temperature independent, but with a rapid off-rate. Competition studies indicated that both stimulatory sODNs and minimally stimulatory sODNs bound to the same receptor. By contrast, phosphodiester oligonucleotides with the same nucleotide sequence as sODNs and bacterial DNA inhibited the binding of sODNs to B cells minimally. Charge appeared to contribute to the binding of sODNs to B cells since binding of sODNs was competitively inhibited by negatively charged molecules, including fucoidan, poly I, and polyvinyl sulfate. These data indicate that human B cells bind sODNs by a receptor-mediated mechanism that is necessary but not sufficient for polyclonal activation.

Adult↗
PubMed2000

Differential expression of a novel C-terminally truncated splice form of SMAD5 in hematopoietic stem cells and leukemia.

SMADs are evolutionarily conserved transducers of the differentiation and growth arrest signals from the transforming growth factor/BMP (TGF/BMP) family of ligands. Upon receptor activation, the ligand-restricted SMADs(1-35) are phosphorylated in the C-terminal MH2 domain and recruit the common subunit SMAD4/DPC-4 gene to the nucleus to mediate target gene expression. Frequent inactivating mutations of SMAD4, or less common somatic mutations of SMAD2 seen in solid tumors, suggest that these genes have a suppressor function. However, there have been no identified mutations of SMAD5, although the gene localizes to the critical region of loss in chromosome 5q31.1 (chromosome 5, long arm, region 3, band 1, subband 1) in myelodysplasia (MDS) and acute myelogenous leukemia (AML). A ubiquitously expressed novel isoform, SMAD5beta, encodes a 351 amino acid protein with a truncated MH2 domain and a unique C-terminal tail of 18 amino acids, which may be the functional equivalent of inactivating mutations. The levels of SMAD5beta transcripts are higher in the undifferentiated CD34(+) hematopoietic stem cells than in the terminally differentiated peripheral blood leukocytes, thereby implicating the beta form in stem cell homeostasis. Yeast 2-hybrid interaction assays reveal the lack of physical interactions between SMAD5beta and SMAD5 or SMAD4. The expression of SMAD5beta may represent a novel mechanism to protect pluripotent stem cells and malignant cells from the growth inhibitory and differentiation signals of BMPs. (Blood. 2000;95:3945-3950)

Alternative Splicing↗
PubMed2000

Chromosomal mapping and genomic organization of an evolutionarily conserved zinc finger gene ZNF277.

A novel C2H2 zinc finger gene, ZNF277, has been localized to human chromosome 7q31.1. The gene is encoded by 12 exons in a genomic fragment of >100 kb between the microsatellite markers D7S523 and D7S471, deleted in a number of malignancies. The predicted open reading frame (ORF) of 438 amino acids shows an overall homology of 50% to the putative ORF F46B6.7 of Caenorhabditis elegans. The presence of a 30-amino-acid coiled-coil domain in both the C. elegans ORF F46B6.7 and ZNF277 is suggestive of functional similarities. ESTs for the murine orthologue ZFP277 are found in early embryonic stem cells, 16-cell stage embryo, and blastocysts. The evolutionary conservation and the expression profile suggest ZNF277 to be a critical regulator of development and differentiation.

Amino Acid Sequence↗
PubMed2000

NMR and mutagenesis evidence for an I domain allosteric site that regulates lymphocyte function-associated antigen 1 ligand binding.

The leukocyte integrin, lymphocyte function-associated antigen 1 (LFA-1) (CD11a/CD18), mediates cell adhesion and signaling in inflammatory and immune responses. To support these functions, LFA-1 must convert from a resting to an activated state that avidly binds its ligands such as intercellular adhesion molecule 1 (ICAM-1). Biochemical and x-ray studies of the Mac-1 (CD11b/CD18) I domain suggest that integrin activation could involve a conformational change of the C-terminal alpha-helix. We report the use of NMR spectroscopy to identify CD11a I domain residues whose resonances are affected by binding to ICAM-1. We observed two distinct sites in the CD11a I domain that were affected. As expected from previous mutagenesis studies, a cluster of residues localized around the metal ion-dependent adhesion site (MIDAS) was severely perturbed on ICAM-1 binding. A second cluster of residues distal to the MIDAS that included the C-terminal alpha-helix of the CD11a I domain was also affected. Substitution of residues in the core of this second I domain site resulted in constitutively active LFA-1 binding to ICAM-1. Binding data indicates that none of the 20 substitution mutants we tested at this second site form an essential ICAM-1 binding interface. We also demonstrate that residues in the I domain linker sequences can regulate LFA-1 binding. These results indicate that LFA-1 binding to ICAM-1 is regulated by an I domain allosteric site (IDAS) and that this site is structurally linked to the MIDAS.

Allosteric Site↗
PubMed2000

Simplified quantitation of myeloid dendritic cells in peripheral blood using flow cytometry.

BACKGROUND: Recognition of the importance of dendritic cells (DC) in the initiation of T-cell-dependent immune responses has led to increasing interest in methods for the identification of DC within the circulation. We sought to develop a flow cytometric method that would allow the reliable enumeration of absolute myeloid DC counts in minimally manipulated blood samples. METHODS: Myeloid DC were identified by three-color staining of whole blood leukocytes as a discrete population of mononuclear cells expressing high levels of HLA-DR and CD33, yet having little or no expression of CD14 and CD16. This method was analyzed for reproducibility and variation in blood DC number during typical clinical day hours and after exercise. The new method was compared to an established commercial kit method. RESULTS: FACS sorting of the CD33(+) DC showed that they morphologically resembled immature DC, and developed cytoplasmic projections typical of mature DC following overnight culture in granulocyte macrophage-colony stimulating factor (GM-CSF). Within peripheral blood, these DC were found at a mean concentration of 17. 4 +/- 5.4 x 10(6) per liter, corresponding to 0.93 +/- 0.27% of mononuclear cells. Comparison of duplicate samples stained and analyzed in parallel showed that the intrasample variability was very low, with an intraclass correlation coefficient of 0.95. The frequency of CD33(+) myeloid DC and their light scatter characteristics were similar to that of CD11c(+) myeloid cells. Four-color FACS analysis revealed complete identity of CD11c(hi), HLA-DR(+) DC with CD33(+), HLA-DR(+) DC. Only rare CD33(+) DC coexpressed CD123 and HLA-DR. Numbers of blood myeloid DC, identified by CD33 staining, showed no significant variation during standard laboratory hours. However, their numbers rose significantly during vigorous exercise, in parallel to other blood cells. CONCLUSIONS: The method described herein is rapid, reproducible, requires only small volumes of blood, can be readily used by a clinical immunology laboratory, and requires fewer antibodies than a currently available commercial method.

Antibodies, Monoclonal↗
PubMed2000

Transgenic expression of granulocyte-macrophage colony-stimulating factor induces the differentiation and activation of a novel dendritic cell population in the lung.

The role of granulocyte-macrophage colony-stimulating factor (GM-CSF) in the differentiation of dendritic cells (DCs) during pulmonary viral infection was investigated by using a mouse model of GM-CSF transgene expression established with an adenoviral vector (AdGM-CSF). GM-CSF gene transfer resulted in increased levels of GM-CSF in the lung, which peaked at day 4 and remained increased up to day 19. A striking cellular response composed predominantly of macrophage-like cells was observed in the lung receiving AdGM-CSF but not control vector. By FACS analysis, the majority of these cells were identified at an early time point as macrophages and later as mature/activated myeloid DCs characterized by CD11b(bright), CD11c(bright), MHC class II(bright), and B7.1(bright). In contrast, GM-CSF had a weak effect on a small DC population that was found present in normal lung and was characterized by CD11c(bright) and CD11b(low). By immunohistochemistry staining for MHC II, the majority of activated antigen-presenting cells were localized to the airway epithelium and peribronchial/perivascular areas in the lung. A concurrently enhanced Th1 immune response was observed under these conditions. The number of CD4 and CD8 T cells was markedly increased in the lung expressing GM-CSF, accompanied by increased release of interferon (IFN)gamma in the lung. Furthermore, lymphocytes isolated from either lung parenchyma or local draining lymph nodes of these mice but not the control mice released large amounts of IFNgamma on adenoviral antigen stimulation in vitro. These findings reveal that GM-CSF promotes the differentiation and activation of a myeloid DC population primarily by acting on macrophages during pulmonary immune responses.

Adenoviridae↗
PubMed2000

Responses of human B cells to DNA and phosphorothioate oligodeoxynucleotides.

Emerging information has documented that certain DNA and sODNs can be both immunogenic and immunostimulatory. sODNs, but not DNA, induce T-cell-independent polyclonal activation of human B cells by engaging cell-surface receptors. Manifestations of sODN-induced human B-cell activation include expression of activation markers, proliferation, Ig production and anti-DNA antibody production. IL-2 and intact T cells enhanced B-cell responses to sODNs but were not required. Monocytes also provided a modest enhancement of human B-cell responses induced by sODNs. The chemical nature of sODNs capable of stimulating human B cells and the specific cell-surface receptors involved have not been completely delineated. Further studies will be necessary to elucidate the potential role of stimulatory sODNs in disease pathogenesis and to develop a means to employ ODNs as therapeutic agents in humans.

Animals↗
PubMed2000

Artifact reduction in electrogastrogram based on empirical mode decomposition method.

Severe contamination of the gastric signal in electrogastrogram (EGG) analysis by respiratory, motion, cardiac artifacts, and possible myoelectrical activity from other organs, poses a major challenge to EGG interpretation and analysis. A generally applicable method for removing a variety of artifacts from EGG recordings is proposed based on the empirical mode decomposition (EMD) method. This decomposition technique is adaptive, and appears to be uniquely suitable for nonlinear, non-stationary data analysis. The results show that this method, combined with instantaneous frequency analysis, effectively separate, identify and remove contamination from a wide variety of artifactual sources in EGG recordings.

Artifacts↗
PubMed2000

Study of the binding characteristics and transportation properties of a 4-aminopyridine imprinted polymer membrane.

Molecularly imprinted polymer membranes containing artificial recognition sites for 4-aminopyridine have been prepared by photopolymerization using 4-aminopyridine as template. Reference membranes were prepared with the same monomer mixture but in the absence of the template. The binding characteristics of the imprinted polymer membrane were investigated by a batch method and the transport properties of the membranes were investigated using diffusion chambers. The results showed that the binding amount of 4-aminopyridine is higher than that of 2-aminopyridine whereas the latter can transport the 4-aminopyridine imprinted polymer membrane faster than 4-aminopyridine.

Acrylic Resins↗
PubMed2000

Short-window spectral analysis of cortical event-related potentials by adaptive multivariate autoregressive modeling: data preprocessing, model validation, and variability assessment.

In this article we consider the application of parametric spectral analysis to multichannel event-related potentials (ERPs) during cognitive experiments. We show that with proper data preprocessing, Adaptive MultiVariate AutoRegressive (AMVAR) modeling is an effective technique for dealing with nonstationary ERP time series. We propose a bootstrap procedure to assess the variability in the estimated spectral quantities. Finally, we apply AMVAR spectral analysis to a visuomotor integration task, revealing rapidly changing cortical dynamics during different stages of task processing.

Animals↗
PubMed2000

Chromosomes are target sites for photodynamic therapy as demonstrated by subcellular laser microirradiation.

The present investigation has been undertaken to examine the possibility that the cell nucleus, and specifically the genetic material, is a target site for photodynamic therapy. PTK2 and Hep-2 cells are pretreated with a medium containing 15 microg/ml (0.09 mM) 5-aminolevulinic acid (ALA). Individual fluorescence images are recorded for each selected cell using a cooled charge-coupled device (CCD). A laser microbeam system generating 630 nm is used for subcellular-region irradiation of specific targets: chromosomes, the mitotic spindle, the perispindle region and the peripheral cytoplasm. Nuclei of interphase cells are also irradiated. Data comparing the sensitivities of the different subcellular microirradiation sites in ALA-treated mitotic cells demonstrate that under the irradiation conditions used, the chromosome is the most sensitive subcellular target followed by the perispindle region, the peripheral cytoplasm and spindle, and, lastly, the interphase nucleus.

Aminolevulinic Acid↗