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Biomedical subjects

Z Xiao

Publications and source records attributed to Z Xiao.

At least 19 recordsLinked to original sources
PubMed2004

Automatic localization of epileptic zones using magnetoencephalography.

Conventional visual identification of epileptic spike is a challenging problem in the clinical application of magnetoencephalography (MEG). More importantly, the conventional method has problems of detecting other abnormalities such as high frequency oscillation in the human epileptic brain. The objective of this study was to develop a new approach using magnetic spectral analysis and spatial filtering. Twelve patients with seizure have been studied with a whole cortex MEG system. Fifteen epochs were recorded for each patient; each epoch was 120 seconds. Neuromagnetic spectrum was analyzed using a new method called accumulated spectrogram. Focal increases of spectral power were localized using synthetic aperture magnetometry (SAM). The MEG results were then compared with clinical findings. Focal increases of spectral power have been identified in all patients (12/12, 100%). The locations of the focal increases of spectral power were in agreement with dipole locations of spikes in 9 patients (9/12, 75%). A comparison between MEG results and clinical findings indicated that SAM revealed focal epileptic activities in two patients when dipole fitting failed. The results suggest that epileptic regions could be quantitatively identified and accurately localized using accumulated spectrogram and SAM. In comparison to visual identification of spike, the new approach is objective and sensitive, and provides the possibility of analyzing much wider frequency bands.

Adolescent↗
PubMed2002

A three-step strategy for targeting drug carriers to human ovarian carcinoma cells in vitro.

To improve tumor-to-tissue ratios of anticancer agents in radioimmunotherapy, a three-step targeting approach was used to deliver biotinylated liposomes to human ovarian cancer cells (NIH:OVCAR-3, SK-OV-3) in vitro. Targeting was based upon the use of two antibodies specific for the CA-125 antigen that is highly expressed on NIH:OVCAR-3 cells but not expressed on SK-OV-3 cells. Briefly, the approach consists of prelabeling target cells with biotinylated anti-CA-125 antibody and FITC-labeled streptavidin (SAv) prior to administration of biotinylated liposomes containing a marker dye for visualization by confocal laser scanning microscopy (CLSM). In addition, the two anti-CA-125 antibodies (B27.1 and B43.13) were labeled with FITC and incubated with ovarian cancer cells at 37 degrees C from 30 min to 24 h to study binding and uptake kinetics. Shedding kinetics of bound antibody from tumor cells was performed using radiolabeled B27.1. Results demonstrated that both B27.1 and B43.13 specifically bound to the cell surface of OVCAR-3 cells but not to SK-OV-3 cells. Biotinylation, FITC-labeling and radiolabeling of the antibodies did not compromise immunoreactivity. Less than 6% of the bound B27.1 was shed from tumor cells by 4 h following incubation, and the antibody-antigen complex resided predominantly on the cell surface by 4 h at 37 degrees C with slow internalization by 12-24 h. Biotinylated, conventional liposomes were specifically and effectively delivered to OVCAR-3 cells prelabeled with biotinylated B27.1 and SAv. The slow internalization and shedding properties of these antibodies are useful for multistep pretargeting methods. Thus, a modified targeting strategy, utilizing a bispecific antibody and liposomes, may be feasible for radioimmunoliposomal therapy of ovarian cancer.

Antibodies, Monoclonal↗
PubMed2001

Design and synthesis of Pfmrk inhibitors as potential antimalarial agents.

The synthesis and inhibitory activities of 10 potential inhibitors of Pfmrk, a Plasmodium falciparum cyclin-dependent protein kinase, are described. The most potent inhibitor is a 3-phenyl-quinolinone compound with an IC(50) value of 18 microM. It is the first compound reported to inhibit Pfmrk at the micro molar range.

Animals↗
PubMed2001

A comparison between microsatellite analysis and cytology of urine for the detection of bladder cancer.

We have studied, in a blinded fashion, cytology and microsatellite analysis on urine sediments of 143 Chinese with or without bladder lesions. Microsatellite analysis succeeded in all 143 individuals, while cytology could not be performed on 42 subjects due to insufficient urine samples. Both microsatellite analysis and routine urine cytology succeeded in 81 bladder cancer patients. Seventy-three patients (90%) were identified by microsatellite analysis, while only 41 patients (51%) were identified by cytology. However, four patients were identified by routine cytology but not by microsatellite analysis. Our results proved that microsatellite analysis is more sensitive than routine cytology but the two methods are complementary to each other.

Adult↗
PubMed2001

Nucleocytoplasmic shuttling of Smad1 conferred by its nuclear localization and nuclear export signals.

Smad1 mediates signaling by bone morphogenetic proteins (BMPs). In the resting state, Smad1 is found in both the nucleus and cytosol. BMP addition triggers Smad1 serine phosphorylation, binding of Smad4, and its accumulation in the nucleus. Mutations in the Smad1 N-terminal basic nuclear localization signal (NLS)-like motif, conserved among all Smad proteins, eliminated its ligand-induced nuclear translocation without affecting its other functions, including DNA binding and complex formation with Smad4. Addition of leptomycin B, an inhibitor of nuclear export, induced rapid nuclear accumulation of Smad1, whereas overexpression of CRM1, the receptor for nuclear export, resulted in Smad1 re-localization to the cytoplasm and inhibition of BMP-induced nuclear accumulation. Thus, in addition to the NLS, Smad1 also contains a functional nuclear export signal (NES). We identified a leucine-rich NES motif in the C terminus of Smad1; its disruption led to constitutive Smad1 nuclear distribution. Reporter gene activation assays demonstrated that both the NLS and NES are required for optimal transcriptional activation by Smad1. Despite its constitutive nuclear accumulation, a Smad1 NES mutant did not display higher basal reporter gene activity. We conclude that Smad1 is under constant nucleocytoplasmic shuttling conferred by its NLS and NES; nuclear accumulation after ligand-induced phosphorylation represents a change in the balance of the activities of these opposing signals and is essential for transcriptional activation.

Active Transport, Cell Nucleus↗
PubMed2001

Quantitation of serum prostate-specific membrane antigen by a novel protein biochip immunoassay discriminates benign from malignant prostate disease.

The lack of a sensitive immunoassay for quantitating serum prostate-specific membrane antigen (PSMA) hinders its clinical utility as a diagnostic/prognostic biomarker. An innovative protein biochip immunoassay was used to quantitate and compare serum PSMA levels in healthy men and patients with either benign or malignant prostate disease. PSMA was captured from serum by anti-PSMA antibody bound to ProteinChip arrays, the captured PSMA detected by surface-enhanced laser desorption/ionization mass spectrometry, and quantitated by comparing the mass signal integrals to a standard curve established using purified recombinant PSMA. The average serum PSMA value for prostate cancer (623.1 ng/ml) was significantly different (P < 0.001) from that for benign prostate hyperplasia (117.1 ng/ml) and the normal groups (age <50, 272.9 ng/ml; age >50, 359.4 ng/ml). These initial results suggest that serum PSMA may be a more effective biomarker than prostate-specific antigen for differentiating benign from malignant prostate disease and warrants additional evaluation of the surface-enhanced laser desorption/ionization PSMA immunoassay to determine its diagnostic utility.

Adult↗
PubMed2001

Functional cloning of the proto-oncogene brain factor-1 (BF-1) as a Smad-binding antagonist of transforming growth factor-beta signaling.

Using the plasminogen activator inhibitor (PAI) promoter to drive the expression of a reporter gene (mouse CD2), we devised a system to clone negative regulators of the transforming growth factor-beta (TGF-beta) signaling pathway. We infected a TGF-beta-responsive cell line (MvLu1) with a retroviral cDNA library, selecting by fluorescence-activated cell sorter single cells displaying low PAI promoter activity in response to TGF-beta. Using this strategy we cloned the proto-oncogene brain factor-1 (BF-1). BF-1 represses the PAI promoter in part by associating with both unphosphorylated Smad3 (in the cytoplasm) and phosphorylated Smad3 (in the nucleus), thus preventing its binding to DNA. BF-1 also associates with Smad1, -2, and -4; the Smad MH2 domain binds to BF-1, and the C-terminal segment of BF-1 is uniquely and solely required for binding to Smads. Further, BF-1 represses another TGF-beta-induced promoter (p15), it up-regulates a TGF-beta-repressed promoter (Cyclin A), and it reverses the growth arrest caused by TGF-beta. Our results suggest that BF-1 is a general inhibitor of TGF-beta signaling and as such may play a key role during brain development.

3T3 Cells↗
PubMed2001

Detecting bladder cancer in the Chinese by microsatellite analysis: ethnic and etiologic considerations.

BACKGROUND: Microsatellite analysis of urine sediments has shown promise as a highly sensitive and specific technique for the detection of bladder cancer. However, most studies have been conducted in Western countries with Caucasian subjects. We explored the potential of microsatellite analysis for detecting bladder cancer in Chinese people. METHODS: We performed microsatellite analysis of surgical specimens and urine sediment cells collected from Chinese patients with bladder tumors. Those microsatellite markers giving clearly readable patterns and showing susceptibility to alterations were used as a panel to detect primary tumors. A blinded study of additional patients with bladder cancer was performed to investigate the practical value of this panel for detecting bladder cancer. All statistical tests were two-sided. RESULTS: Thirty-eight bladder tumors and corresponding urine sediment specimens were initially screened for 60 microsatellite markers from 18 chromosomes. Nine markers, most of which were different from those that had been used for Western patients, with frequent alterations in the initial patients were selected for further analysis. In the subsequent blinded experiment, microsatellite alterations were observed in urine sediments from 22 (96%) of 23 patients with bladder cancer and from all three patients with inverted papilloma. None of the urine sediments from the one patient with bladder lipoma, from the one patient with neurofibroma, or from the 12 individuals without evidence of bladder tumor showed any microsatellite alterations. CONCLUSIONS: Microsatellite analysis of urine sediments could be a practical method for detecting bladder cancer in the Chinese. Our identification of different microsatellite markers highlights possible ethnic and etiologic disparities between the Chinese and Western bladder cancer patients.

Adult↗
PubMed2001

Redox thermodynamics of mutant forms of the rubredoxin from Clostridiumpasteurianum: identification of a stable Fe(III)(S-Cys)3(OH) centre in the C6S mutant.

Redox thermodynamic data provide a detailed insight into control of the reduction potential E degrees' of the [Fe(S-Cys)4] site in rubredoxin. Mutant forms were studied in which specific structural changes were made in both the primary and secondary coordination spheres. Those changes have been probed by resonance Raman spectroscopy. The decrease of approximately 200 mV in E degrees' observed for the [Fe(S-Cys)3(O-Ser)]-/2- couples in the surface ligand mutants C9S and C42S is essentially enthalpic in origin and associated with the substitution of ligand thiolate by ligand olate. However, the pH dependence of the potentials below characteristic pKa(red) approximately equals 7 is an entropic contribution, plausibly associated with increased conformational flexibility induced by a longer Fe(II)-O(H)-Ser bond in the reduced form. The presence of a second surface Ser ligand in the new double mutant protein C9S/C42S affects the enthalpic term primarily for pH>pKa(red) > or = 9.3, but for pH pKa approximately 9: [Fe(III)(S-Cys)3(OH)]- + e- --> [Fe(II)(S-Cys)3(OH)]2-. pH [Fe(II)(S-Cys)3(OH2)]-.

Clostridium↗
PubMed2001

Chemiluminescence flow sensor for berberine with immobilized reagents.

A sensitive chemiluminescence (CL) sensor for berberine combined with flow-injection (FI) technology is described. The analytical reagents involved in the CL reaction, including luminol and potassium ferricyanide, were both immobilized on an anion-exchange resin column. While a volume of sodium phosphate was passed through the column, the two CL reagents were eluted from the resin and then mixed with a berberine stream under alkaline conditions. By means of the fast oxidation reaction between berberine and potassium ferricyanide, potassium ferrocyanide was generated, which then inhibited the CL reaction of luminol and potassium ferricyanide. The decreased CL intensity was correlated with the berberine concentration in the range from 0.05 to 300 ng mL(-1 )with a relative standard deviation of less than 4.3%, and the limit of detection was 0.02 ng mL(-1) at a flow rate of 2.0 mL min(-1). It was shown that the flow sensor could greatly improve the selectivity and sensitivity for determination of berberine. The determination of analyte could be performed in 2 min, including sampling and washing and be stable for over 300 analyses. Some interference and additives in preparations were tested. Two herbal medicines commonly found in compound prescriptions, rutin and baicalin, were studied preliminarily. The method has been applied for the determination of berberine in pharmaceutical preparations successfully.

Berberine↗
PubMed2001

Molecular characterization of genomic AML1-ETO fusions in childhood leukemia.

T(8;21) AML1(CBFA2)-ETO(MTG8) is the most common chromosomal translocation in acute myeloid leukemia (AML) in both children and adults. We sought to understand the structure and gain insight into the fusion process between AML1 and ETO by sequencing genomic fusions in 17 primary childhood AMLs and two cell lines with t(8;21). Reciprocal translocations were sequenced for seven of the 19 samples. We assumed a null hypothesis that the translocation breakpoints would be evenly distributed along the intronic breakpoint cluster regions. Testing for multimodality via smoothed bootstrap statistical methods suggested, however, the presence of two separate cluster regions within both the AML1 and ETO breakpoint cluster regions. ETObreakpoints were predominantly located in intron 1B in a defined cluster 5' of exon 1A (scan statistic P value = 0.00001). All patients with available RNA expressed an AML1-ETO mRNA fusion between exon 5 of AML1 and exon 2 of ETO. Since the structural restraints for the fusion protein of AML1-ETO exclude exon 1A, we reason that ETO intron 1B harbors a structural feature with propensity for breakage and/or recombination. Chromosomal breakpoints displayed evidence of fusion by a non-homologous end joining process, with microhomologies and nontemplate nucleotides at some fusion junctions. Breakpoints in general displayed similar complexity of duplications, deletions, and insertions to other common pediatric leukemia translocations (TEL-AML1, MLL-AF4, PML-RARA, CBFB-MYH11) that we and others have analyzed.

Acute Disease↗
PubMed2001

Effects of matrix proteins on the expression of matrix metalloproteinase-2, -9, and -14 and tissue inhibitors of metalloproteinases in human cytotrophoblast cells during the first trimester.

The activity of matrix metalloproteinases (MMPs) specifies the ability of the trophoblast cell to degrade extracellular matrix (ECM) substrates. Usually the process of normal human placentation involves a coordinated interaction between the fetal-derived trophoblast cells and their microenvironment in the uterus. In this study, the effects of ECM proteins on the expression of MMP-2, -9, and -14 (membrane-type MMP-1); and the production of tissue inhibitors of metalloproteinase (TIMP) types -1, -2, and -3 have been investigated. Cytotrophoblast cells at 9 or 10 wk of gestation were cultured on various ECM coated dishes under serum-free conditions. Gelatin zymography analysis showed that cells grown on fibronectin (FN), laminin (LN), and vitronectin (VN) secreted more MMP-9 (about 1.5- to 3-fold more) than cells cultured on collagen I (Col I), whereas the secretion of MMP-9 by cells cultured on collagen IV (Col IV) was only half that by the cells on Col I. Northern Blot analysis gave the same results as zymography, indicating that expression of the MMP-9 gene in cytotrophoblast cells can be affected by matrix proteins. There was no significant difference in the expression of MMP-2 either at protein or mRNA levels among the cells cultured on the different matrix substrates. The expression of MMP-14 was regulated in a manner similar to that of MMP-2. Using ELISA, we detected higher levels of TIMP-1 in the culture medium of cells grown on VN, LN, and FN compared with that grown on Col I. But the expression of TIMP-3 mRNA was remarkably inhibited by VN, and ECM proteins had no effect on TIMP-1 and TIMP-2 mRNA expression. It was also observed that cultured cytotrophoblast cells expressed the corresponding receptors for the tested matrix proteins, such as integrins alpha(1), alpha(5), alpha(6), beta(1), and beta(4). Furthermore, the adhesiveness of cytotrophoblast cells on Col I, Col IV, FN, and LN was increased by 62%, 45%, 21%, and 22%, respectively, when compared with adhesiveness on VN. Isolated cytotrophoblast cells remained stationary when cultured on dishes coated with Col I and Col IV, but they assumed a more motile morphology and aggregated into a network when cultured on LN and VN. These data indicate that human trophoblast cells interact with their microenvironment to control their behavior and function.

Adult↗
PubMed2001

Modern trends in radioimmunotherapy of cancer: pretargeting strategies for the treatment of ovarian cancer.

A review of published data on some of the problems associated in treating cancer using radioimmunotherapy is presented. Potential improvements for this type of therapy using pretargeting strategies are discussed and preliminary results on a novel multistep regimen to treat human ovarian cancer are presented. A pretargeting strategy using a biotinylated, anti-CA125 monoclonal antibody (MAb) to attract biotinylated long-circulating liposomes to the surface of CA125-expressing ovarian cancer cells, was employed. Confocal laser scanning microscopy and fluorescent labels were used to establish the biodistribution patterns in NIH:OVCAR-3 (CA-125 positive) and SK-OV-3 (CA-125 negative) human ovarian cancer cells. Shedding kinetics of the pretargeted stage were measured using 125I labeled MAbs. No significant internalization of the MAb used in the pretargeting step was observed by 4 hrs. The antibody was gradually internalized starting at 6 hrs, and most of the labelled MAb was detected in cytoplasm by 24 hrs. Shedding and exocytosis of the antigen-MAb complex was not significant for up to 6-hours following administration of the iodinated MAb. Biotinylated liposomes were shown to specifically target the biotinylated MAb/streptavidin complex on the cell surface. We have demonstrated that by a three-step pretargeting approach, biotinylated liposomes can be specifically delivered to cells pretargeted with biotinylated MAb/SAv complex. The slow internalization and shedding properties of the two MAbs are ideal for multistep pretargeting methods. A successful multistep linkage was established with the biotinylated MAb B27.1, streptavidin and biotinylated liposomes to OVCAR-3 cells, but not to SK-OV-3 cells.

Antibodies, Monoclonal↗
PubMed2001

AlphaIIbbeta3 and its antagonism at the new millennium.

Because of its major role in regulating platelet functions and its prominence on the cell surface, integrin alphaIIbbeta3 has been the subject of intensive investigations. Such studies have provided substantial insights into its structure-function relationships and have led to the development of anti-thrombotic drugs that target the receptor. Nevertheless, recent findings have indicated that our understanding of the structure and function of alphaIIbbeta3 remains inadequate. This article addresses two aspects of still evolving alphaIIbbeta3 function: 1) the interface between alphaIIbbeta3 and the blood coagulation system, resulting from interaction of prothrombin with the receptor; and 2) the molecular basis for recognition of the RGD and the fibrinogen gamma-chain peptide ligands by alphaIIbbeta3. As illustrated by these two examples, there is still much to be learned about alphaIIbbeta3 if we are to fully appreciate its functions and its potential as a therapeutic target.

Animals↗
PubMed2001

[Effect of 3'-UTR of EG I from Trichoderma reesei on its gene expression in Saccharomyces cerevisiae].

Several industrial yeast are developed as ideal expression hosts for the production of the commercially useful proteins. The expression levels in yeast cells of the heterologous proteins are affected by the regulation factors of the genes themselves. The full-length cDNA coding for EG I from Trichoderma reesei, the cellulose-degrading filamentous fungus, was expressed in Saccharomyces cerevisiae H158. EG I produced by the recombinant S. cerevisiae exhibits maximal activity at 50 degrees C-60 degrees C, pH 5.0. It was observed that removal of the 3'-untranslated region (3'-UTR) from EG I cDNA resulted in no active EG I produced by recombinant yeast. RT-PCR analysis indicated that unlike the yeast cells harboring full-length EG I cDNA, there was no detectable EG I mRNA in the yeast cells harboring EG I cDNA without 3'-UTR. The data suggested that 3'-UTR is important for the expression of EG I in Saccharomyces cerevisiae.

3' Untranslated Regions↗
PubMed2001

[Cloning and expression of Trichoderma reesei endoglucanase III (EG III) gene in Saccharomyces cerevasiae].

Using Congo red-staining method, one positive clone with CMCase activity was isolated from the Trichoderma ressei cDNA gene bank constructed in Saccharomyces cerevasiae. Sequencing result showed that the 1.5 kb-length DNA fragment inserted in the recombinant plasmid encoded EG III gene from T. reesei. Enzymatic characterization of the EG III produced by recombinant S. cerevasiae was analyzed. The experimental results indicated that the optimum pH and temperature for EG III are 5.0 and 60 degrees C, respectively. The effects of secretory system components SSO 2 and SEB1 of S. cerevisiae on EG III secretion were examined. The results indicated that the amount of EG III secreted by the strain with SSO 2-overexpression was highest among the different recombinant S. cerevisiae strains, showed that SSO 2 is a rate-limiting component of the secretory machinery in the process of EG III secretion. Furthermore, the EG III expression level was increased 5.3 times by deletion. Furthermore, the EG III expression level was increased 5.3 times by deletion of the 98 bp in 5' untranslated region of eg3 mRNA sequence. This result suggested that the regulation region could exist in the 5' untranslated region of EG III mRNA, which is recognized by the gene expression related factors of S. cerevasiae.

Cellulase↗
PubMed2000

Importin beta mediates nuclear translocation of Smad 3.

Smad proteins are intracellular mediators of transforming growth factor-beta (TGF-beta) and related cytokines. Although ligand-induced nuclear translocation of Smad proteins is clearly established, the pathway mediating this import is yet to be determined. We previously identified a nuclear localization signal (NLS) in the N-terminal region of Smad 3, the major Smad protein involved in TGF-beta signal transduction. This basic motif (Lys(40-)Lys-Leu-Lys-Lys(44)), conserved among all the pathway-specific Smad proteins, is required for Smad 3 nuclear import in response to ligand. Here we studied the nuclear import pathway of Smad 3 mediated by this NLS. We demonstrate that the isolated Smad 3 MH1 domain displays significant specific binding to importin beta, which is diminished or eliminated by mutations in the NLS. Full-size Smad 3 exhibits weak but specific binding to importin beta, which is enhanced after phosphorylation by the type I TGF-beta receptor. In contrast, no interaction was observed between importin alpha and Smad 3 or its MH1 domain, indicating that nuclear translocation of Smad proteins may occur through direct binding to importin beta. We propose that activation of all of the pathway-specific Smad proteins (Smads 1, 2, 3, 5, 8, and 9) exposes the conserved NLS motif, which then binds directly to importin beta and triggers nuclear translocation.

Activin Receptors, Type I↗