Biomedical subjects

Tong Zhang

Publications and source records attributed to Tong Zhang.

At least 91 records · Page 5Linked to original sources

PubMed2004

[Flocculating mechanism of microbial flocculant MBFTRJ21].

The bioflocculant MBFTRJ21 for nature soda was exploited in our lab, and its flocculating mechanism was studied. The bioflocculant produced by Lactobacillus, has some advantages, such as less dosage, better flocculating effects, and etc. MBFTRJ21 is mainly composed of polysaccharide, which is determined by Anthrone reaction, Coomassie blue reaction and Elson-Morgan method. The acting force between bioflocculant and nature soda is hydrogen bond, which is determined by xi electric potential, hydrogen bond and electrovalent bond determination. The bioflocculant is treated by heat and KIO4, which indicate the active ingredient of bioflocculant is protein and osamine. Bridge occur during flocculation process, which is determined by particle size distribution. The results showed that the flocculating mechanism of MBFTRJ21 resulted from the combination of nature soda with MBFTRJ21 by hydrogen bond at the active position of glycosaminoglycan.

Flocculation↗

PubMed2004

[Differentially expressed genes in prostate cancer and benign prostatic hyperplasia].

OBJECTIVE: To detect and analyze the differentially expressed genes in prostate cancer (PCa) and benign prostatic hyperplasia (BPH). METHODS: Oligonucleotide microarray containing 465 genes was used to investigate the differentially expressed genes in PCa and BPH. RESULTS: There were 35 differentially expressed genes between PCa and BPH, of which 17 were up-regulated and 18 down-regulated in PCa. CONCLUSION: The study of the differentially expressed genes in PCa and BPH should help to understand the molecular mechanism of PCa and identify the markers for diagnostic and therapeutic use.

Down-Regulation↗

PubMed2003

Grb2 regulates Stat3 activation negatively in epidermal growth factor signalling.

EGF (epidermal growth factor) binding to its receptor (EGFR) induces dimerization and autophosphorylation of the receptor at multiple tyrosine residues, which serve as docking sites for recruitment of proteins with SH2 (Src homology 2) domains that activate multiple downstream signalling pathways. The adaptor protein Grb2 (growth factor receptor-binding protein 2) binds to EGFR, which leads to activation of Ras-MAPK (mitogen-activated protein kinase) cascade. The latent transcription factors, STAT (signal transduction and activator of transcription), can also be activated by EGF in certain cell types. Since Ras-MAPK and STAT pathways are simultaneously stimulated by EGF, and Tyr-1086 and Tyr-1068 of EGFR are reported to be the binding sites for both Grb2 and Stat3, we investigated the possible regulatory role of Grb2 in STAT activation. In the present study, we report that transient expression of Grb2 specifically down-regulates EGF-stimulated tyrosine phosphorylation of Stat3, which leads to a repression of Stat3 transcriptional activity. In contrast, depletion of Grb2 by RNA interference substantially increases Stat3 tyrosine phosphorylation induced by EGF. The inhibition is neither mediated by a direct interaction between Grb2 and Stat3 nor via activation of tyrosine phosphatases. However, the repression was abolished by a mutation in the SH2 domain, but not the SH3 domains of Grb2, suggesting that inhibition involves binding of the receptor. Indeed, Grb2 inhibits the interaction between Stat3 and EGFR by competitive binding to the EGFR. On the other hand, Grb2 does not interact with the same sites as Stat3 on the interleukin-6 receptor and, therefore, has no effect on interleukin-6-induced tyrosine phosphorylation of Stat3. Taken together, our results demonstrate that, in EGF signalling, Grb2 regulates Stat3 activation negatively at the receptor level.

Adaptor Proteins, Signal Transducing↗

PubMed2003

Insulin resistance of gluconeogenic pathways in neonatal rats after prenatal ethanol exposure.

Alcohol exposure during pregnancy is associated with fetal growth restriction and programs the offspring to insulin resistance later in life. The underlying mechanisms are still uncertain, but a dysregulation of gluconeogenesis and adipose hormones may be contributory. Newborn rats from dams that had been given ethanol (EtOH) or water (controls) during pregnancy were studied. Adiponectin mRNA was determined in subcutaneous fat by RT-PCR, and serum adiponectin was measured by RIA. Subsets of rats were killed before and after intraperitoneal administration of insulin, to determine, by RT-PCR, the hepatic expression of gluconeogenic enzymes and that of the transcription factor peroxisome proliferator-activated receptor-coactivator (PGC)-1, which promotes gluconeogenesis. EtOH offspring had delayed hypoglycemic response to insulin but normal adiponectin mRNA and serum levels compared with controls. The inhibitory response of the gluconeogenic enzyme phosphoenol- pyruvate carboxykinase (PEPCK) and PGC-1 mRNAs to insulin was blunted in EtOH offspring compared with controls. The data suggest that intrauterine EtOH exposure causes insulin resistance of genes for PGC-1 and PEPCK early in life.

Adiponectin↗

PubMed2003

Roles of CaMKII, PKA, and PKC in the induction and maintenance of LTP of C-fiber-evoked field potentials in rat spinal dorsal horn.

Long-term potentiation (LTP) of C-fiber-evoked field potentials in spinal dorsal horn may be relevant to hyperalgesia, an increased response to noxious stimulation. The mechanism underlying this form of synaptic plasticity is, however, still unclear. Considerable evidence has shown that calcium/calmodulin-dependent protein kinase II (CaMKII), protein kinase A (PKA), and protein kinase C (PKC) are important for LTP in hippocampus. In this study, the roles of these three protein kinases in the induction and maintenance of LTP of C-fiber-evoked field potentials were evaluated by application of specific inhibitors of CaMKII (KN-93 and AIP), PKA (Rp-CPT-cAMPS), and PKC (chelerythrine and Gö 6983) at the recording segments before and after LTP induction in urethane-anesthetized Sprague-Dawley rats. We found both KN-93 and AIP, when applied at 30 min prior to tetanic stimulation, completely blocked LTP induction. At 30 min after LTP induction, KN-93 and AIP reversed LTP completely, and at 60 min after LTP induction, they depressed spinal LTP in most rats tested. Three hours after LTP induction, however, KN-93 or AIP did not affect the spinal LTP. Rp-CPT-cAMPS, chelerythrine, and Gö 6983 blocked the spinal LTP when applied at 30 min before tetanic stimulation and reversed LTP completely at 15 min after LTP induction. In contrast, at 30 min after LTP induction, the drugs never affected the spinal LTP. These results suggest that activation of CaMKII, PKA, and PKC may be crucial for the induction and the early-phase but not for the late-phase maintenance of the spinal LTP.

Animals↗

PubMed2003

Expression of NPM-RARalpha fusion gene in hematopoietic cells confers sensitivity to troglitazone-induced apoptosis.

We have investigated the effects of acute promyelocytic leukemia (APL) fusion gene NPM-RARalpha on the function of PPARgamma using the monoblastic cell line U937. U937 cells were transduced using a retrovirus carrying NPM-RARalpha. While treatment with the synthetic PPARgamma ligand troglitazone (TG) had no effect on the viability of U937 cells, TG treatment of U937/NPM-RARalpha cells resulted in a dramatic decrease in cell viability, dependent upon both the concentration of TG and the level of expression of NPM-RARalpha. Analysis of the cell cycle profile and flow cytometry with annexin V confirmed that these effects of TG were due to induction of apoptosis. Induction of apoptosis was accompanied by caspase-8 and caspase-9 activation, and could be blocked by treatment with the caspase inhibitor Z-VAD-FMK. Cotreatment of U937/NPM-RARalpha cells with all-trans retinoic acid (atRA) abrogated the induction of apoptosis by TG. Induction of apoptosis was seen also in the PML-RARalpha-expressing APL cell line NB4, and in several other atRA-sensitive leukemia cell lines, demonstrating that this effect is limited neither to the monocyte lineage nor to the rare NPM-RARalpha fusion variant. RXRalpha/NPM-RARalpha heterodimers were found to interact directly with a PPARgamma-responsive element in vitro. We conclude that in the presence of X-RARalpha, TG induces cell death due to apoptosis via the caspase pathway. These observations suggest the investigation of PPARgamma ligands as therapeutic agents in acute leukemia.

Antineoplastic Agents↗

PubMed2003

Akt-mediated cardiomyocyte survival pathways are compromised by G alpha q-induced phosphoinositide 4,5-bisphosphate depletion.

Expression of the wild type alpha subunit of Gq (GqWT) in cardiomyocytes induces hypertrophy, whereas a constitutively active G alpha q subunit (GqQ209L) induces apoptosis. Akt phosphorylation increases with GqWT expression but is markedly attenuated in cardiomyocytes expressing GqQ209L or in those expressing GqWT and treated with agonist. A membrane-targeted Akt rescues GqQ209L-expressing cardiomyocytes from apoptotic cell death. In contrast, leukemia inhibitory factor fails to activate Akt or promote cell survival in these cells. Association of Akt and PDK-1 with the membrane is also diminished in GqQ209L-expressing cardiomyocytes. Phosphatidylinositol 3,4,5-trisphosphate (PIP3), the primary regulator of Akt, increases significantly in GqWT-expressing cells but not in cardiomyocytes expressing GqQ209L. Levels of phosphatidylinositol 4,5-bisphosphate (PIP2), the immediate precursor of PIP3, are also markedly lower in GqQ209L-expressing compared to control cells. Expression of a GqQ209L mutant that has diminished capacity to activate phospholipase C does not decrease PIP2 or Akt or induce apoptosis. In transgenic mice with cardiac G alpha q overexpression, heart failure and increased cardiomyocyte apoptosis develop during the peripartal period. Akt phosphorylation and PIP2 levels decrease concomitantly. Our findings suggest that an Akt-mediated cell survival pathway is compromised by the diminished availability of PIP2 elicited by pathological levels of Gq activity.

Animals↗

PubMed2003

A novel sequence in the coiled-coil domain of Stat3 essential for its nuclear translocation.

Stat3 is activated by cytokines and growth factors via specific tyrosine phosphorylation, dimerization, and nuclear translocation. However, the mechanism involved in its nuclear translocation is unclear. In this study, by systematic deletion and site-directed mutagenesis we identified Arg-214/215 in the alpha-helix 2 region of the coiled-coil domain of Stat3 as a novel sequence element essential for its nuclear translocation, stimulated by epidermal growth factor as well as by interleukin-6. Furthermore, we identified Arg-414/417 in the DNA binding domain as also required for the nuclear localization of Stat3. This sequence element corresponds to Lys-410/413 of Stat1, a reported sequence for Stat1 nuclear translocation. On the other hand, Leu-411 of Stat3, corresponding to Leu-407 of Stat1, a necessary residue for Stat1 nuclear transport, is not essential for Stat3 nuclear import. The mutant of Arg-214/215 or Arg-414/417 was shown to be tyrosyl-phosphorylated normally but failed to enter the nucleus in response to epidermal growth factor or interleukin-6. The defect, however, can be rescued by the wild-type Stat3 but cannot be compensated by these two mutants. Mutations on Arg-414/417, but not Arg-214/215, destroy the DNA binding activity of Stat3. Our data for the first time identified a sequence element located in the coiled-coil domain that is involved in the ligand-induced nuclear translocation of Stat3. This novel sequence together with a conserved sequence element in the DNA binding domain coordinates to mediate the nuclear translocation of Stat3.

Amino Acid Sequence↗

PubMed2003

Transgenic CaMKIIdeltaC overexpression uniquely alters cardiac myocyte Ca2+ handling: reduced SR Ca2+ load and activated SR Ca2+ release.

Ca2+/calmodulin-dependent protein kinase II (CaMKII) delta is the predominant cardiac isoform, and the deltaC splice variant is cytoplasmic. We overexpressed CaMKIIdeltaC in mouse heart and observed dilated heart failure and altered myocyte Ca2+ regulation in 3-month-old CaMKIIdeltaC transgenic mice (TG) versus wild-type littermates (WT). Heart/body weight ratio and cardiomyocyte size were increased about 2-fold in TG versus WT. At 1 Hz, twitch shortening, [Ca2+]i transient amplitude, and diastolic [Ca2+]i were all reduced by approximately 50% in TG versus WT. This is explained by >50% reduction in SR Ca2+ content in TG versus WT. Peak Ca2+ current (ICa) was slightly increased, and action potential duration was prolonged in TG versus WT. Despite lower SR Ca2+ load and diastolic [Ca2+]i, fractional SR Ca2+ release was increased and resting spontaneous SR Ca2+ release events (Ca2+ sparks) were doubled in frequency in TG versus WT (with prolonged width and duration, but lower amplitude). Enhanced Ca2+ spark frequency was also seen in TG at 4 weeks (before heart failure onset). Acute CaMKII inhibition normalized Ca2+ spark frequency and ICa, consistent with direct CaMKII activation of ryanodine receptors (and ICa) in TG. The rate of [Ca2+]i decline during caffeine exposure was faster in TG, indicating enhanced Na+-Ca2+ exchange function (consistent with protein expression measurements). Enhanced diastolic SR Ca2+ leak (via sparks), reduced SR Ca2+-ATPase expression, and increased Na+-Ca2+ exchanger explain the reduced diastolic [Ca2+]i and SR Ca2+ content in TG. We conclude that CaMKIIdeltaC overexpression causes acute modulation of excitation-contraction coupling, which contributes to heart failure.

Animals↗

PubMed2003

The deltaC isoform of CaMKII is activated in cardiac hypertrophy and induces dilated cardiomyopathy and heart failure.

Recent studies have demonstrated that transgenic (TG) expression of either Ca2+/calmodulin-dependent protein kinase IV (CaMKIV) or CaMKIIdeltaB, both of which localize to the nucleus, induces cardiac hypertrophy. However, CaMKIV is not present in heart, and cardiomyocytes express not only the nuclear CaMKIIdeltaB but also a cytoplasmic isoform, CaMKIIdeltaC. In the present study, we demonstrate that expression of the deltaC isoform of CaMKII is selectively increased and its phosphorylation elevated as early as 2 days and continuously for up to 7 days after pressure overload. To determine whether enhanced activity of this cytoplasmic deltaC isoform of CaMKII can lead to phosphorylation of Ca2+ regulatory proteins and induce hypertrophy, we generated TG mice that expressed the deltaC isoform of CaMKII. Immunocytochemical staining demonstrated that the expressed transgene is confined to the cytoplasm of cardiomyocytes isolated from these mice. These mice develop a dilated cardiomyopathy with up to a 65% decrease in fractional shortening and die prematurely. Isolated myocytes are enlarged and exhibit reduced contractility and altered Ca2+ handling. Phosphorylation of the ryanodine receptor (RyR) at a CaMKII site is increased even before development of heart failure, and CaMKII is found associated with the RyR in immunoprecipitates from the CaMKII TG mice. Phosphorylation of phospholamban is also increased specifically at the CaMKII but not at the PKA phosphorylation site. These findings are the first to demonstrate that CaMKIIdeltaC can mediate phosphorylation of Ca2+ regulatory proteins in vivo and provide evidence for the involvement of CaMKIIdeltaC activation in the pathogenesis of dilated cardiomyopathy and heart failure.

Animals↗

PubMed2003

GRIM-19, a death-regulatory gene product, suppresses Stat3 activity via functional interaction.

Signal transducer and activator of transcription 3 (Stat3) is a latent cytoplasmic transcription factor that can be activated by cytokines and growth factors. Stat3 plays important roles in cell growth, anti-apoptosis and cell transformation, and is constitutively active in various cancers. We examined its potential regulators by yeast two-hybrid screening. GRIM-19, a gene product related to interferon-beta- and retinoic acid-induced cancer cell death, was identified and demonstrated to interact with Stat3 in various cell types. The interaction is specific for Stat3, but not for Stat1 and Stat5a. The interaction regions in both proteins were mapped, and the cellular localization of the interaction was examined. GRIM-19 itself co-localizes with mitochondrial markers, and forms aggregates at the perinulear region with co-expressed Stat3, which inhibits Stat3 nuclear translocation stimulated by epidermal growth factor (EGF). GRIM-19 represses Stat3 transcriptional activity and its target gene expression, and also suppresses cell growth in Src-transformed cells and a Stat3-expressing cell line. Our data suggest that GRIM-19 is a novel negative regulator of Stat3.

3T3 Cells↗

PubMed2003

Upregulation of GLUT1 expression is necessary for hypertrophy and survival of neonatal rat cardiomyocytes.

During hypertrophy the heart increases its utilization of glucose and decreases that of fatty acids, resuming a fetal pattern of substrate metabolism. As demonstrated here, GLUT1 protein expression is increased in association with in vivo pressure-overload-induced hypertrophy. The relationship of changes in GLUT1 to enhanced glucose uptake and to cardiomyocyte hypertrophy and survival is not known. To explore this question we first examined the effect of prostaglandin F2alpha (PGF2alpha), an established hypertrophic agonist, on GLUT1 expression and glucose uptake in neonatal rat ventricular myocytes (NRVMs). PGF2alpha treatment for 24 h led to a fivefold increase in GLUT1 expression and a sixfold increase in glucose uptake. However, NRVMs cultured in the absence of glucose or with 3-O-methyl glucose, a competitive inhibitor of glucose uptake, still exhibited PGF2alpha-induced hypertrophic growth. In addition, we determined that overexpression of GLUT1 using adenovirus was insufficient to cause an increase in cell size, myofibrillar organization, or atrial natriuretic factor (ANF) expression. On the other hand, adenoviral overexpression of antisense GLUT1 (which blocked PGF2alpha-induced increases in GLUT1 protein) prevented PGF2alpha-stimulated cell enlargement and increases in ANF transcription. Overexpression of GLUT1 or addition of PGF2alpha also protected cells against serum deprivation-induced apoptosis; this effect was blocked by antisense GLUT1 but, surprisingly, was not dependent on glucose. Together, these data suggest that upregulation of GLUT1 serves a role in agonist-induced hypertrophy and survival which can be dissociated from its role in glucose transport.

Adenoviridae↗

PubMed2003

Biohydrogen production from starch in wastewater under thermophilic condition.

Batch experiments were conducted to convert starch in wastewater into hydrogen at 55 degrees C at various wastewater pH (4.0-9.0) and starch concentrations (9.2-36.6 g/l). The maximum hydrogen yield of 92 ml/g of starch added (17% of the theoretical value) was found at wastewater pH 6.0, and the maximum specific hydrogen production rate of 365 ml/(g-VSS.d) was at wastewater pH 7.0. The methane-free biogas contained up to 60% of hydrogen. The mixed liquor was composed mostly of acetate (40.2-53.4%) and butyrate (26.0-40.9%). Phylogenetic analysis based on 16S rDNA sequences of the 72 clones developed from the sludge at pH 6.0 shows that 85.7% of the clones were closely affiliated with genus Thermoanaerobacterium in family Thermoanaerobacteriaceae; the remaining 14.3% were with an uncultured Saccharococcus sp. clone ETV-T2.

Bacteria↗

PubMed2003

Thermophilic H2 production from a cellulose-containing wastewater.

Cellulose in wastewater was converted into H2 by a mixed culture in batch experiments at 55 degrees C with various wastewaters pH (5.5-8.5) and cellulose concentrations (10-40 g l(-1)). At the optimal pH of 6.5, the maximum H2 yield was 102 ml g(-1) cellulose and the maximum production rate was 287 ml d(-1) for each gram of volatile suspended solids (VSS). Analysis of 16S rDNA sequences showed that the cellulose-degrading mixed culture was composed of microbes closely affiliated to genus Thermoanaerobacterium.

Bioreactors↗

PubMed2003

Enhanced tumor immunogenicity through coupling cytokine expression with antigen presentation.

The density of tumor antigen in conjunction with major histocompatibility complex (MHC) class I molecules on the cell surface affects cytotoxic T cell (CTL) function in an active antitumor immune response. Thus, methods to enhance antigen expression/presentation could augment the effect of cancer immune therapy. In the present study, we investigated the feasibility of modifying a cytokine signal peptide with a tumor antigenic epitope. We inserted the genes encoding the MHC class I-restricted antigenic epitope of chicken ovalbumin and tyrosinase-related protein 2 into the signal sequence of the interleukin-2 gene, replacing part of the signal sequence at different positions. Our results showed that these modified signal peptides still functioned, as indicated by cytokine secretion. The antigenic epitope within the modified signal peptide could be processed properly and presented on tumor cell surface. Tumor cells demonstrated enhanced immunogenicity as indicated by increased susceptibility to CTL lysis in vitro and decreased tumor grow in vivo after gene modification. These data provide potential perspectives in designing therapeutic or vaccine strategies in immuno-gene therapy of cancer.

Amino Acid Sequence↗

PubMed2003

Efficient transduction of murine primary T cells requires a combination of high viral titer, preferred tropism, and proper timing of transduction.

Retroviral vectors have been used exclusively for genetic modification of primary T cells. Most T cell infection protocols have been developed for human T cells, whereas systematic investigations of the optimal conditions for transduction of murine primary T cells are limited. In this study, ecotropic and 10A1-pseudotyped retroviral vectors were compared for their efficiency in infecting murine primary T cell cells, as well as T cell lines. Various factors that affect transduction efficiency were also explored, including virus titer, times of exposure, timing of infection, low-speed centrifugation, and use of fibronectin fragment. Our results showed that up to 80% of murine primary T cells could be infected after a single exposure. Successful infection required a combination of high virus titer (>10(7) CFU/ml), proper timing of infection (within 24 h after mitogen stimulation), and preferred tropism (ecotropic vectors). These optimization results may help to establish a standard protocol for infection of murine primary T cells and provide some insight into the obstacles to retroviral infection of T cells.

Animals↗

PubMed2003

Protein synthesis inhibition blocks the late-phase LTP of C-fiber evoked field potentials in rat spinal dorsal horn.

Previous studies have demonstrated that in the hippocampus the maintenance of long-term potentiation (LTP) requires de novo protein synthesis. To investigate the role of protein synthesis in the maintenance of LTP of C-fiber evoked field potentials in spinal dorsal horn, which may be relevant to hyperalgesia, protein synthesis inhibitor (either cycloheximide or anisomycin) was applied locally to the recording segments of spinal cord in anesthetized rats, 30 min prior to tetanic stimulation to the sciatic nerve. We found that both cycloheximide and anisomycin selectively inhibited late-phase maintenance of the spinal LTP but affected neither LTP induction nor baseline responses of C-fiber evoked field potentials. In the presence of cycloheximide, LTP of C-fiber evoked field potentials was 281.5 +/- 16.5% (n = 6) of baseline 1 h after tetanic stimulation and the potentiation significantly decreased to 235.5 +/- 18.5% at 145 min after tetanic stimulation (P < 0.05). Afterward, LTP of C-fiber evoked field potentials decreased continuously and at 270 min after tetanic stimulation reached 130.8 +/- 18.0%, which was no longer different from baseline (P > 0.05). Spinal application of anisomycin at 30 min before tetanic stimulation yielded similar results (n = 6). These results suggest that protein synthesis may be crucial for the late-phase maintenance of LTP of C-fiber evoked field potentials in spinal dorsal horn.

Animals↗

PubMed2003

Linkage of beta1-adrenergic stimulation to apoptotic heart cell death through protein kinase A-independent activation of Ca2+/calmodulin kinase II.

beta(1)-adrenergic receptor (beta(1)AR) stimulation activates the classic cAMP/protein kinase A (PKA) pathway to regulate vital cellular processes from the change of gene expression to the control of metabolism, muscle contraction, and cell apoptosis. Here we show that sustained beta(1)AR stimulation promotes cardiac myocyte apoptosis by activation of Ca(2+)/calmodulin kinase II (CaMKII), independently of PKA signaling. beta(1)AR-induced apoptosis is resistant to inhibition of PKA by a specific peptide inhibitor, PKI14-22, or an inactive cAMP analogue, Rp-8-CPT-cAMPS. In contrast, the beta(1)AR proapoptotic effect is associated with non-PKA-dependent increases in intracellular Ca(2+) and CaMKII activity. Blocking the L-type Ca(2+) channel, buffering intracellular Ca(2+), or inhibiting CaMKII activity fully protects cardiac myocytes against beta(1)AR-induced apoptosis, and overexpressing a cardiac CaMKII isoform, CaMKII-deltaC, markedly exaggerates the beta(1)AR apoptotic effect. These findings indicate that CaMKII constitutes a novel PKA-independent linkage of beta(1)AR stimulation to cardiomyocyte apoptosis that has been implicated in the overall process of chronic heart failure.

Animals↗