PubMed Health⌕ Search

Biomedical subjects

S Wei

Publications and source records attributed to S Wei.

At least 19 recordsLinked to original sources
PubMed2006

Novel role of Stat1 in the development of docetaxel resistance in prostate tumor cells.

A major obstacle for clinicians in the treatment of advanced prostate cancer is the inevitable progression to chemoresistance, especially to docetaxel. It is essential to understand the molecular events that lead to docetaxel resistance in order to identify means to prevent or interfere with chemoresistance. In initial attempts to detect these events, we analysed genomic differences between non-resistant and docetaxel-resistant prostate tumor cells and, of the genes modulated by docetaxel treatment, we observed Stat1 and clusterin gene expression heightened in the resistant phenotype. In this study, we provide biochemical and biological evidence that these two gene products are related. Stat1 and clusterin protein expression was induced upon docetaxel treatment of DU145 cells and highly overexpressed in the docetaxel-resistant DU145 cells (DU145-DR). The increase in total Stat1 corresponded to an increase in phosphorylated Stat1. Interestingly, there was no detectable difference between DU145 and DU145-DR cells expression of total Stat3 and phosphorylated Stat3. Treatment of DU145-DR cells with small interfering RNA targeted for Stat1 not only resulted in the knockdown of Stat1 expression, but it also caused the inhibition of clusterin expression. Thus, Stat1 appears to play a key role in the regulation of clusterin. Remarkably, inhibition of Stat1 or clusterin expression resulted in the re-sensitization of DU145-DR cells to docetaxel. These results offer the first evidence that Stat1, and its subsequent regulation of clusterin, are essential for docetaxel resistance in prostate cancer. Targeting this pathway could be a potential therapeutic means for intervention of docetaxel resistance.

Antineoplastic Agents, Phytogenic↗
PubMed2006

Trace organic contamination in biota collected from the Pearl River Estuary, China: a preliminary risk assessment.

The marine ecosystem of the Pearl River Delta, located on the southern coast of China, has been heavily exploited following the rapid economic growth that has occurred since the 1980s. This investigation aimed to elucidate trace organic contamination in marine biota inhabiting the Pearl River Delta area. Biota samples, including green-lipped mussels (Perna viridis), oysters (Crassostrea rivularis) and shrimp (Penaeus orientalis) were sampled from 16 stations fringing the Estuary. Elevated concentrations (on a dry weight basis) of polycyclic aromatic hydrocarbons (27.8-1041.0 ng/g), petroleum hydrocarbons (1.7-2345.4 microg/g), polychlorinated biphenyls (2.1-108.8 ng/g), DDTs (1.9-79.0 ng/g), and hexachlorocyclohexanes (n.d.-38.4 ng/g) were recorded. A human health risk assessment was conducted to estimate the risk to local residents associated with the consumption of biota collected from the Pearl River Estuary. The results indicated that PCBs were at levels that may cause deleterious health effects in populations that consume large amounts of seafood. However, it would be instructive to establish health criteria for trace organic contaminants that are specific to the local populations, in order to derive a more accurate and relevant health risk assessment.

Animals↗
PubMed2006

Identification of genetic differences between two clinical isolates of Streptococcus mutans by suppression subtractive hybridization.

Streptococcus mutans is generally considered to be the principal aetiological agent for dental caries. Phenotypic variation in strains is often associated with differences in gene content, so the isolation of DNA fragments from these genes or associated regions is illuminating. The S. mutans strains 9-1 and 9-2, which both colonized the same oral cavity, were selected after screening for the possession of suspected virulence traits. Genomic DNA of strain 9-1 was used as the tester, and that of 9-2 was used as the driver. Suppression subtractive hybridization (SSH) was applied between the tester and the driver DNAs. The subtractive products were cloned into a pCR2.1 vector. Clone libraries representing sequence differences were obtained. The subtractive fragments that were found specifically in strain 9-1 but not in strain 9-2 were identified by dot blotting and then sequenced. BLASTn and BLASTx sequence homology analyses were subsequently performed. Twenty-seven sequences were found in the genome of strain 9-1 that were not in 9-2. Among them, three revealed no homology to published nucleotide sequences while the remaining sequences showed 81-100% homology to known genes of S. mutans strain UA159. These sequences are involved in competence development, signal transduction and transcriptional regulation, repairing stress damage, transport, carbohydrate catabolism, biochemical synthesis, or unknown functions. Differences exist in the genomes of different S. mutans isolates. SSH is effective in screening for S. mutans strain specific DNA sequences.

Adult↗
PubMed2004

Dermal fibroblast-associated gene induction by asiaticoside shown in vitro by DNA microarray analysis.

BACKGROUND: Asiaticoside, isolated from Centella asiatica, promotes fibroblast proliferation and extracellular matrix (ECM) synthesis in wound healing. The precise mechanism, however, in molecular and gene expression levels is still unclear. OBJECTIVE: Using cDNA microarray technology, the alteration of gene expression profiles was determined for human dermal fibroblasts in vitro in the presence of asiaticoside (30 microg mL(-1)). Fifty-four genes, with known functions for cell proliferation, cell cycle progression and synthesis of ECM, were significantly upregulated in our 'genome-nest' expression profile at various time points. Furthermore, the mRNA levels and protein production of certain genes responsible for ECM synthesis (e.g. encoding type I and type III collagen proteins) were evaluated by Northern blot and radioimmunoassay, respectively. RESULTS: We found that there is a close correlation between the gene profile, mRNA and protein production in the response of the cells to asiaticoside stimulation. CONCLUSIONS: This information could be used for exploring the response of the target genes to asiaticoside in fibroblasts.

Blotting, Northern↗
PubMed2004

Actin cytoskeletal reorganizations and coreceptor-mediated activation of rac during human immunodeficiency virus-induced cell fusion.

The membrane fusion events which initiate human immunodeficiency virus type 1 (HIV-1) infection and promote cytopathic syncytium formation in infected cells commence with the binding of the HIV envelope glycoprotein (Env) to CD4 and an appropriate coreceptor. Here, we show that HIV Env-coreceptor interactions activate Rac-1 GTPase and stimulate the actin filament network reorganizations that are requisite components of the cell fusion process. Disrupting actin filament dynamics with jasplakinolide or latrunculin A arrested fusion at a late step in the formation of Env-CD4-coreceptor complexes. Time-lapse confocal microscopy of living cells revealed vigorous activity of actin-based, target cell membrane extensions at the target cell-Env-expressing cell interface. The expression of dominant-negative forms of actin-regulating Rho-family GTPases established that HIV Env-mediated syncytium formation relies on Rac-1 but not on Cdc42 or Rho activation in target cells. Similar dependencies were found when cell fusion was induced by Env expressed on viral or cellular membranes. Additionally, Rac activity was specifically upregulated in a coreceptor-dependent manner in fusion reaction cell lysates. These results define a role for HIV Env-coreceptor interactions in activating the cellular factors essential for virus-cell and cell-cell fusion and provide evidence for the participation of pertussis toxin-insensitive signaling pathways in HIV-induced membrane fusion.

Actins↗
PubMed2003

Mutations in the gamma-actin gene (ACTG1) are associated with dominant progressive deafness (DFNA20/26).

Age-related hearing loss (presbycusis) is a significant problem in the population. The genetic contribution to age-related hearing loss is estimated to be 40%-50%. Gene mutations that cause nonsyndromic progressive hearing loss with early onset may provide insight into the etiology of presbycusis. We have identified four families segregating an autosomal dominant, progressive, sensorineural hearing loss phenotype that has been linked to chromosome 17q25.3. The critical interval containing the causative gene was narrowed to approximately 2 million bp between markers D17S914 and D17S668. Cochlear-expressed genes were sequenced in affected family members. Sequence analysis of the gamma-actin gene (ACTG1) revealed missense mutations in highly conserved actin domains in all four families. These mutations change amino acids that are conserved in all actins, from protozoa to mammals, and were not found in >100 chromosomes from normal hearing individuals. Much of the specialized ultrastructural organization of the cells in the cochlea is based on the actin cytoskeleton. Many of the mutations known to cause either syndromic or nonsyndromic deafness occur in genes that interact with actin (e.g., the myosins, espin, and harmonin). The mutations we have identified are in various binding domains of actin and are predicted to mildly interfere with bundling, gelation, polymerization, or myosin movement and may cause hearing loss by hindering the repair or stability of cochlear cell structures damaged by noise or aging. This is the first description of a mutation in cytoskeletal, or nonmuscle, actin.

Actins↗
PubMed2003

Group IIA secretory phospholipase A2 stimulates exocytosis and neurotransmitter release in pheochromocytoma-12 cells and cultured rat hippocampal neurons.

Recent evidence shows that secretory phospholipase A2 (sPLA2) may play a role in membrane fusion and fission, and may thus affect neurotransmission. The present study therefore aimed to elucidate the effects of sPLA2 on vesicle exocytosis. External application of group IIA sPLA2 (purified crotoxin subunit B or purified human synovial sPLA2) caused an immediate increase in exocytosis and neurotransmitter release in pheochromocytoma-12 (PC12) cells, detected by carbon fiber electrodes placed near the cells, or by changes in membrane capacitance of the cells. EGTA and a specific inhibitor of sPLA2 activity, 12-epi-scalaradial, abolished the increase in neurotransmitter release, indicating that the effect of sPLA2 was dependent on calcium and sPLA2 enzymatic activity. A similar increase in neurotransmitter release was also observed in hippocampal neurons after external application of sPLA2, as detected by changes in membrane capacitance of the neurons. In contrast to external application, internal application of sPLA2 to PC12 cells and neurons produced blockade of neurotransmitter release. Our recent studies showed high levels of sPLA2 activity in the normal rat hippocampus, medulla oblongata and cerebral neocortex. The sPLA2 activity in the hippocampus was significantly increased, after kainate-induced neuronal injury. The observed effects of sPLA2 on neurotransmitter release in this study may therefore have a physiological, as well as a pathological role.

Animals↗
PubMed2003

Extracellular MUC3 mucin secretion follows adherence of Lactobacillus strains to intestinal epithelial cells in vitro.

BACKGROUND: Mucins are large complex glycoproteins that protect intestinal mucosal surfaces by limiting access of environmental matter to their epithelial cells. Several mucin genes have been described, including MUC3 that is a membrane associated mucin of the small intestine. Increased MUC3 mRNA transcription is induced by incubation of intestinal epithelial cells with a Lactobacillus strain known to be adherent to them. AIMS: To determine whether increased epithelial cell MUC3 mucin expression in response to Lactobacillus strains results in increased extracellular secretion of MUC3 mucins and the importance of epithelial cell adherence in modulation of MUC3 mucin expression. METHODS: HT29 cells grown to enhance expression of MUC3 mucins were incubated with selected Lactobacillus strains. Spent cell culture medium was collected for detection of secreted MUC3 mucins using dot blot immunoassay with a generated MUC3 antibody. Post-incubation HT29 cell RNA was collected for analysis of MUC3 expression by northern blot analysis using a MUC3 cDNA probe. In vitro binding studies using Lactobacillus strains incubated alone or coincubated with enteropathogenic Escherichia coli strain E2348/69 were used for adherence and inhibition of adherence studies, respectively. RESULTS: Lactobacillus strains with minimal ability to adhere to HT29 cells failed to induce upregulation of mucin gene expression. There was a direct correlation between upregulation of MUC3 mucin mRNA expression and extracellular secretion of MUC3 mucin. The same Lactobacillus strains that increased extracellular secretion of MUC3 mucin led to reduced adherence of enteropathogen E coli E2348/69 during coincubation experiments. CONCLUSION: Probiotic microbes induce MUC3 mucin transcription and translation with extracellular secretion of the MUC3 mucins. Epithelial cell adherence enhances the effects of probiotics on eukaryotic mucin expression.

Bacterial Adhesion↗
PubMed2002

Incidence of p53 and ras gene mutations in DMBA-induced rat leukemias.

Leukemia, a form of haematological malignancy, is a multi-stage disease and a wide range of diverse genes has been speculated to correlate with its initiation and development. Ras has been speculated to be an initiating gene for haematological malignancy, but more investigation will be needed to determine the genes associated with the progression of the disease. 7,12-dimethylbenz(a)anthracene (DMBA)-induced rat leukemia provides a good tool for research into various stages of the disease. The entire coding regions of p53 and ras genes were examined for mutations in the present study. In this experiment, we used fluorescence-labeled polymerase chain reaction single-stranded conformation polymorphism analysis (PCR-SSCP) and direct sequencing to detect mutations of both genes on rat erythroleukemia. Fifteen out of 18 (83.3%) rat leukemias were found to have N-ras codon 61 mutation, consistent with previous results. The result of direct sequencing showed a single base substitution (CAA to CTA), resulting in an amino-acid change from Gln to Leu. No mutations were found in H-ras, K-ras or codon 12 of N-ras. The incidence of p53 gene mutation was 16.6% (3/18) in rat leukemia at late-stage. In the present study, mutation of the p53 gene was detected in three DMBA-induced leukemias as follows: a single-base substitution (CAT to CGT) at codon 177 (exon 5), resulting in an amino-acid change from Arg to Leu, a CGG to CTG/CGG changed at codon 211 (exon 6) resulting in an amino-acid change from His to Arg/His, and a GGG to TGG at codon 242 (exon 6) resulting in an amino-acid change from Gly to Trp, respectively. Thus, mutations of p53 gene do not seem to respond to the carcinogenesis of the DMBA-induced leukemia, in contrast to mutation of the N-ras oncogene, and may possibly be involved in the progress of multi-stage leukemogenesis.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed2001

Cloning and characterization of a p53-related protein kinase expressed in interleukin-2-activated cytotoxic T-cells, epithelial tumor cell lines, and the testes.

A human protein kinase, p53-related protein kinase (PRPK), was cloned from an interleukin-2-activated cytotoxic T-cell subtraction library. PRPK appears to be a homologue of a growth-related yeast serine/threonine protein kinase, YGR262c. However, a complementation assay using YGR262c-disrupted yeast indicated that PRPK is not functionally identical to the yeast enzyme. PRPK expression was observed in interleukin-2-activated cytotoxic T-cells, some human epithelial tumor cell lines, and the testes. The intrinsic transcriptional activity of p53 was up-regulated by a transient transfection of PRPK to COS-7 cells. PRPK was shown to bind to p53 and to phosphorylate p53 at Ser-15. These results indicate that PRPK may play an important role in the cell cycle and cell apoptosis through phosphorylation of p53.

Amino Acid Sequence↗
PubMed2001

A membrane protein enriched in endoplasmic reticulum exit sites interacts with COPII.

Although all mammalian COPII components have now been cloned, little is known of their interactions with other regulatory proteins involved in exit from the endoplasmic reticulum (ER). We report here that a mammalian protein (Yip1A) that is about 31% identical to S. cerevisiae and which interacts with and modulates COPII-mediated ER-Golgi transport. Yip1A transcripts are ubiquitously expressed. Transcripts of a related mammalian homologue, Yip1B, are found specifically in the heart. Indirect immunofluorescence microscopy revealed that Yip1A is localized to vesicular structures that are concentrated at the perinuclear region. The structures marked by Yip1A co-localized with Sec31A and Sec13, components of the COPII coat protein complex. Immunoelectron microscopy also showed that Yip1A co-localizes with Sec13 at ER exit sites. Overexpression of the hydrophilic N terminus of Yip1A arrests ER-Golgi transport of the vesicular stomatitis G protein and causes fragmentation and dispersion of the Golgi apparatus. A glutathione S-transferase fusion protein with the hydrophilic N terminus of Yip1A (GST-Yip1A) is able to bind to and deplete vital components from rat liver cytosol that is essential for in vitro vesicular stomatitis G transport. Peptide sequence analysis of cytosolic proteins that are specifically bound to GST-Yip1A revealed, among other proteins, mammalian COPII components Sec23 and Sec24. A highly conserved domain at the N terminus of Yip1A is required for Sec23/Sec24 interaction. Our results suggest that Yip1A is involved in the regulation of ER-Golgi traffic at the level of ER exit sites.

Amino Acid Sequence↗
PubMed2001

Cooperative regulation of Mcl-1 by Janus kinase/stat and phosphatidylinositol 3-kinase contribute to granulocyte-macrophage colony-stimulating factor-delayed apoptosis in human neutrophils.

Polymorphonuclear neutrophils (PMN) are phagocytic cells constitutively programmed for apoptotic cell death. Exposure to GM-CSF delays apoptosis as measured by annexin-V staining and cell morphological change. We found that STAT5B, STAT1, and STAT3 DNA-binding activity was induced by GM-CSF. We also detected activation of the phosphatidylinositol 3-kinase (PI 3-kinase) pathway after GM-CSF treatment which was inhibited by treatment with the PI 3-kinase inhibitors, wortmannin and LY294002. We investigated whether STAT or PI 3-kinase activity was necessary for the pro-survival response of GM-CSF in PMN. Exposure of PMN to GM-CSF in the presence of either AG-490, antisense STAT3 oligonucleotides, or wortmannin resulted in a partial inhibition of GM-CSF-mediated pro-survival activity. GM-CSF induced a time-dependent increase in the mRNA and protein expression of the anti-apoptotic Bcl-2-family protein, Mcl-1. We examined the hypothesis that Janus kinase/STAT and PI 3-kinase regulation of Mcl-1 contributed to GM-CSF-delayed apoptosis. Using either AG-490 or wortmannin alone, we observed a dose-dependent inhibition of GM-CSF-induced Mcl-1 expression. Using suboptimal doses of AG-490 and wortmannin, we found that both drugs together had an additive effect on delayed apoptosis and Mcl-1 expression. These data suggest that cooperative regulation of Mcl-1 by the Janus kinase/STAT and PI 3-kinase pathways contribute to GM-CSF-delayed apoptosis.

Apoptosis↗
PubMed2001

Immune-type receptor genes in zebrafish share genetic and functional properties with genes encoded by the mammalian leukocyte receptor cluster.

An extensive, highly diversified multigene family of novel immune-type receptor (nitr) genes has been defined in Danio rerio (zebrafish). The genes are predicted to encode type I transmembrane glycoproteins consisting of extracellular variable (V) and V-like C2 (V/C2) domains, a transmembrane region and a cytoplasmic tail. All of the genes examined encode immunoreceptor tyrosine-based inhibition motifs in the cytoplasmic tail. Radiation hybrid panel mapping and analysis of a deletion mutant line (b240) indicate that a minimum of approximately 40 nitr genes are contiguous in the genome and span approximately 0.6 Mb near the top of zebrafish linkage group 7. One flanking region of the nitr gene complex shares conserved synteny with a region of mouse chromosome 7, which shares conserved synteny with human 19q13.3-q13.4 that encodes the leukocyte receptor cluster. Antibody-induced crosslinking of Nitrs that have been introduced into a human natural killer cell line inhibits the phosphorylation of mitogen-activated protein kinase that is triggered by natural killer-sensitive tumor target cells. Nitrs likely represent intermediates in the evolution of the leukocyte receptor cluster.

Amino Acid Sequence↗
PubMed2001

Local structure evolution of FexNi77-xCu(1-)Nb2P14B6 soft magnetic materials by mechanical alloying.

Mechanically alloyed Fe(x)Ni77-xCu1Nb2P14B6 soft magnetic materials have been prepared with different atomic compositions. The alloy structures are investigated by X-ray absorption fine structure (XAFS). The results show that mechanical alloying (MA) can drive the Fe(x)Ni77-xCu1Nb2P14B6 powder mixture to produce amorphous alloy while the atomic concentration of Fe element is about and over 40%. On the contrary, the MA Fe(x)Ni77 xCu1Nb2P14B6 is a solid solution with a fcc-like structure in the region of lower Fe atomic concentration (<22%), preserving a medium-range order around Ni and Fe atoms. Moreover, we have found that the local structure geometry of Fe atom is similar to that of Ni atom for all the MA Fe(x)Ni77-xCu1NbP14B6 samples. It indicates that the local structures of Fe and Ni atoms in a Fe(x)Ni77-xCu1Nb2P14B6 sample only depend on the x value of element Ni after ball milling.

Journal Article↗
PubMed2001

U7C beamline and XAFS station of national synchrotron radiation laboratory.

The XAFS station on beamline U7C of National Synchrotron Radiation Laboratory (NSRL) was completely constructed in December 1998. The source for XAFS station is from a 3-pole superconducting wiggler with magnetic field of 6 T inserted in the straight section of the storage ring. Using a Si(111) double crystal monochromator with a fixed slit, the X-ray intensity at the sample position is about 3x10(9) photons/second at the energy of 8980 eV of Cu K-edge. The Keithley 65 17 electrometers are used to record the electron charges that are produced in the ionization chambers. A high ratio of signal to noise has been obtained for the XAFS spectra of Cu, Ni and Fe foils. Furthermore, the XAFS spectrum of Cu foil in NSRL is in good agreement with that obtained in BSRF and KEK.

Journal Article↗
PubMed2001

Annealed crystallization of ultrafine amorphous NiB alloy studied by XAFS.

XAFS has been used to investigate the local structure evolutions of ultrafine amorphous NiB alloy during the annealed crystallization process. A nanocrystalline Ni phase with the local structure of crystalline Ni-like and a crystalline Ni3B, have been produced for ultrafine amorphous NiB alloy under the annealed temperature of 573 K. The results rule out Rojo et al.'s devitrification mechanism of Ni80B20 amorphous alloy in which they considered that an amorphous pure Ni phase is formed in the first exothermic process. However, our results are almost identical with Riveiro et al.'s conclusion in which the intermediate state is interpreted as two metastable crystalline phases of Ni3B and Ni-rich NiB alloy. With the annealed temperature going onto 773 K, the ultrafine NiB sample is further decomposed and crystallized into crystalline Ni with long-range order.

Journal Article↗
PubMed2001

Local structures of mechanically alloyed Fe100-xCux solid solutions studied by X-ray absorption fine structure.

The local structures of the immiscible Fe(100-x)Cu(x) alloys (x= 0, 10, 20, 40, 60, 80 and 100) produced by mechanical alloying have been investigated by XAFS. For the Fe(100-x)Cu(x) (x > or = 40) solid solutions, the local structures around Fe atoms change from bcc structure to fcc one and the Cu atoms maintain the original coordination geometry after milling for 160 hours. On the contrary, the local structures around Cu atoms in both of Fe80Cu20 and Fe90Cu10 alloys appear a transition from fcc to bcc structure. We found that the Debye-waller factor sigma of fcc Fe-Cu phase is larger than that of bcc Fe-Cu phase, and the sigma (0.099 A) around Fe atoms is larger than that (0.089 A) of Cu in the Fe(100-x)Cu(x) (x > or = 40) solid solutions. This suggests that the mechanically alloyed Fe(100-x)Cu(x) supersaturated solid solution is not a homogeneous alloy, and consists of Fe-rich and Cu-rich regions for various compositions. A possible mechanism for bcc-to-fcc and fcc-to-bcc changes in Fe(100-x)Cu(x) solid solutions is discussed in relation to the interdiffusion and transition induced by the ball milling.

Journal Article↗