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Biomedical subjects

T Zhang

Publications and source records attributed to T Zhang.

At least 55 records · Page 3Linked to original sources
PubMed2002

Microbial diversity of a mesophilic hydrogen-producing sludge.

A hydrogen-producing sludge degraded 99% of glucose at 36 degrees C and pH 5.5, producing a methane-free biogas (comprising 64% hydrogen) and an effluent comprising mostly butyrate, acetate, and ethanol. The yield was 0.26 l H2 g(-1) glucose and the production rate per gram of volatile suspended solids was 4.6 1 H2 day(-1). A 16S rDNA library was constructed from the sludge for microbial species determination. A total of 96 clones were selected for plasmids recovery, screened by denaturing gradient gel electrophoresis, and sequenced for rDNA. Based on the phylogenetic analysis of the rDNA sequences, 64.6% of all the clones were affiliated with three Clostridium species (Clostridiaceae), 18.8% with Enterobacteriaceae, and 3.1% with Streptococcus bovis (Streptococcaceae). The remaining 13.5% belonged to eight operational taxonomic units, the affiliations of which were not identified.

Bacteria↗
PubMed2002

AU-rich element-mediated translational control: complexity and multiple activities of trans-activating factors.

Tumour necrosis factor (TNF)-alpha mRNA contains an AU-rich element (ARE) in its 3' untranslated region (3'UTR), which determines its half-life and translational efficiency. In unstimulated macrophages, TNF-alpha mRNA is repressed translationally, and becomes efficiently translated upon cell activation. Gel retardation experiments and screening of a macrophage cDNA expression library with the TNF-alpha ARE allowed the identification of TIA-1-related protein (TIAR), T-cell intracellular antigen-1 (TIA-1) and tristetraprolin (TTP) as TNF-alpha ARE-binding proteins. Whereas TIAR and TIA-1 bind the TNF-alpha ARE independently of the activation state of macrophages, the TTP-ARE complex is detectable upon stimulation with lipopolysaccharide (LPS). Moreover, treatment of LPS-induced macrophage extracts with phosphatase significantly abrogates TTP binding to the TNF-alpha ARE, indicating that TTP phosphorylation is required for ARE binding. Carballo, Lai and Blackshear [(1998) Science 281, 1001-1005] showed that TTP was a TNF-alpha mRNA destabilizer. In contrast, TIA-1, and most probably TIAR, acts as a TNF-alpha mRNA translational silencer. A two-hybrid screening with TIAR and TIA-1 revealed the capacity of these proteins to interact with other RNA-binding proteins. Interestingly, TIAR and TIA-1 are not engaged in the same interaction, indicating for the first time that TIAR and TIA-1 can be functionally distinct. These findings also suggest that ARE-binding proteins interact with RNA as multimeric complexes, which might define their function and their sequence specificity.

3' Untranslated Regions↗
PubMed2002

Factors relating to the cardiac sequelae of Kawasaki disease one month after initial onset.

UNLABELLED: This study aimed to determine the risk factors related to the presence of cardiac sequelae 1 mo after initial onset and to examine the preventive effect of the early administration of high-dose gamma-globulin (GG) on cardiac sequelae in patients with Kawasaki disease. Patients treated with high-dose GG of 2000 +/- 100 mg kg(-1) were selected as subjects from the 15th nation-wide survey in Japan. Univariate and logistic multiple variable analyses were used to test the effects of background variables such as age and gender, variables relating to laboratory findings such as the percentage of neutrophil leucocytes, and variables relating to the GG treatment on the presence of cardiac sequelae. The odds ratios were significantly higher for males (1.48), those younger than 1 y of age (1.71), recurrent cases (2.42), and those with a low haematocrit (<32.5%) (1.45) and high percentage of neutrophil leucocytes (>68%) (1.63). The odds ratio was low for those who started GG administration in less than 6 d from onset between the patients with and without cardiac sequelae. The odds ratio for the duration of GG treatment was not significantly different between those with and without cardiac sequelae. CONCLUSION: Patients who received early administration of GG, less than 6 d from onset of the disease, had a lower risk than those received GG more than 6 d from the onset. The percentage of neutrophil leucocytes and the haematocrit level are useful indicators in predicting the development of cardiac sequelae.

Age Factors↗
PubMed2002

Expression of basic fibroblast growth factor and its receptor-1 in cardiac myxoma.

BACKGROUND: To clarify the significance of basic fibroblast growth factor (bFGF) in angiogenesis or proliferative activity in cardiac myxoma, the expression of bFGF and its receptor (FGFR-1) were immunohistochemically examined. METHODS: Formalin-embedded tissues of cardiac myxomas were obtained by surgical resection from 15 patients and analyzed by immunostaining of bFGF and FGFR-1. The microvessel density was measured in the 15 myxomas using platelet derived endothelial cell adhesion molecule-1. For evaluation of proliferative activity of the cardiac myxomas, proliferating cell nuclear antigen (PCNA) immunostaining was performed, and the PCNA labeling index was measured in each section. RESULTS: bFGF and FGFR-1 were observed in 73.3% and 67.7% of the myxomas, respectively. There was a close correlation between the expression of bFGF and FGFR-1. This co-expression was frequently observed in the myxoma cells around the microvessels appearing as a ring structure. Regarding possible relationships between the expression of bFGF or FGFR-1 and the clinicopathologic features, there were no parameters excluding the macroscopic type of myxoma. The microvessel density in the myxomas with bFGF or FGFR-1 expression was higher than that in myxomas without it. The PCNA labeling index in myxomas with bFGF expression was higher than that in myxomas without it, and the PCNA labeling index tended to be higher in myxomas with FGFR-1 expression than that in myxomas without it. CONCLUSIONS: bFGF and/or FGFR-1 was expressed in some of cardiac myxoma, and may be an important role for tumor angiogenesis and proliferative activity.

Aged↗
PubMed2001

PACAP mediates the neural proliferative pathway of Mastomys enterochromaffin-like cell transformation.

BACKGROUND AND AIM: Pituitary adenylate-cyclase activating peptide (PACAP) is a more potent proliferative agent than gastrin for rat enterochromaffin-like (ECL) cell proliferation in vitro. The role of this neurotransmitter during gastrin-mediated ECL cell tumor formation and gastrin-autonomous ECL cell neoplasia is unknown. METHODS AND RESULTS: ECL cell transformation was induced in the Mastomys using 16 wk H2 receptor blockade of acid inhibition. Examination of the epithelial fundic mucosa demonstrated that PACAP-immunoreactivity significantly increased in the tumor mucosa compared to the naïve stomach, and was associated with ECL cells. Naïve and tumor ECL cells were then purified (approximately 95%) from Mastomys and the presence of all three PACAP/VPAC receptor subtypes was demonstrated by polymerase chain-reaction amplification. Thereafter, cells were maintained in short-term (48 h) primary cultures. PACAP significantly (p<0.05) increased 24 h bromo-deoxyuridine uptake (approximately 4-fold) in both cell types with estimated EC(50) values of approximately 4x10(-16) M and approximately 2x10(-16) M, respectively. Specific receptor antagonists (PAC1/VPAC1) of PACAP competitively inhibited these proliferative effects in naïve cells. Oligonucleotide antisense directed against PAC1 significantly inhibited PACAP-stimulated DNA synthesis by approximately 85% (p<0.05) in tumor cells. CONCLUSION: PACAP is a potent and effective modulator of ECL cell proliferation. The expression of this neuropeptide and its receptors, particularly PAC1, suggest the existence of a neural regulatory pathway of ECL cell proliferation and transformation.

Animals↗
PubMed2001

Evidence that APC regulates survivin expression: a possible mechanism contributing to the stem cell origin of colon cancer.

Because colorectal cancers (CRCs) frequently display APC mutation, inhibition of apoptosis, and increased expression of the antiapoptotic protein survivin, we hypothesized that APC mutation inhibits apoptosis by allowing constitutive survivin expression. Using HT-29 CRC cell lines having inducible wild-type APC (wt-APC) or transfected dominant-negative TCF-4, we show that wt-APC down-regulates survivin expression via APC/beta-catenin/TCF-4 signaling. Using normal colonic epithelium, we found survivin by immunostaining/reverse transcription-PCR to be preferentially expressed in the lower crypt (which inversely correlates with wt-APC's expression pattern). Thus, wt-APC, by progressively decreasing survivin and increasing apoptosis from crypt bottom to top, may limit the population size of stem cells and other proliferative cells in the lower crypt; mutant APC may allow expansion of these populations, thereby initiating tumorigenesis.

Adenomatous Polyposis Coli Protein↗
PubMed2001

Time-dependent plasticity of synaptic transmission produced by long-term potentiation of C-fiber evoked field potentials in rat spinal dorsal horn.

Our previous work has shown that repetitive stimulation of Adelta-fibers depresses long-term potentiation (LTP) of C-fiber evoked field potentials in spinal dorsal horn. Here, we tested the effects of the Adelta stimulation on the spinal LTP at different time points following LTP induction. Fifteen minutes after LTP induction Adelta stimulation depressed LTP by 44.1+/-4.2% (mean+/-SEM, n=7) for 69.3+/-18.5 min and 1 h after LTP the same Adelta stimulation depressed spinal LTP by only 16.9+/-3.1% for 21.9+/-2.0 min (n=7). Three hours after LTP, however, the Adelta stimulation produced a further potentiation (31.9+/-6.3%, n=7) lasting for all the recording periods (1-3 h). These data indicate that the effects of repetitive stimulation of Adelta-fibers on established spinal LTP of C-fiber evoked field potentials is time-dependent.

Animals↗
PubMed2001

Conformational dynamics of the transcriptional regulator CooA protein studied by subpicosecond mid-infrared vibrational spectroscopy.

CooA, which is a transcriptional regulator heme protein allosterically triggered by CO, is studied by femtosecond visible-pump mid-IR-probe spectroscopy. Transient bleaching upon excitation of the heme in the Soret band is detected at approximately 1979 cm(-1), which is the absorption region of the CO bound to the heme. The bleach signal shows a nonexponential decay with time constants of 56 and 290 ps, caused by the rebinding of the CO to the heme. About 98% of dissociated CO recombines geminately. The geminate recombination rate in CooA is significantly faster than those in myoglobin and hemoglobin. The angle of the bound CO with respect to the porphyrin plane is calculated to be about 78 degrees on the basis of the anisotropy measurements. A shift of the bleached mid-IR spectrum of the bound CO is detected and has a characteristic time of 160 ps. It is suggested that the spectral shift is caused by a difference in the frequency of the bound CO in different protein conformations, particularly in an active conformation and in an intermediate one, which is on the way toward an inactive conformation. Thus, the biologically relevant conformation change in CooA was traced. Possible assignment of the observed conformation change is discussed.

Bacterial Proteins↗
PubMed2001

An early growth response protein (Egr) 1 cis-element is required for gonadotropin-releasing hormone-induced mitogen-activated protein kinase phosphatase 2 gene expression.

In pituitary gonadotropes, gonadotropin-releasing hormone (GnRH) activates all three major mitogen-activated protein kinase (MAPK) cascades. The MAPKs play key roles in transcriptional activation of GnRH-responsive genes. MAPK phosphatases (MKPs) are dual specificity protein phosphatases involved in feedback regulation of MAPK activity. Previous studies indicate that GnRH activates MKP-2 expression in gonadotropes, dependent upon activation of multiple MAPKs and discrete Ca(2+) signals. To further understand the transcriptional mechanism(s) of MKP-2 induction by GnRH, we studied the activity of a 198-nucleotide MKP-2 proximal promoter region that supports GnRH responsiveness in reporter gene assays. Functional analysis of the MKP-2 promoter confirmed a requirement for the protein kinase C-extracellular signal-regulated kinase (ERK) pathway and VGCC-derived Ca(2+) signals in transcriptional activation of the MKP-2 gene. However, the inhibitory effect of thapsigargin on MKP-2 protein expression previously identified was not mediated at the level of promoter activation, suggesting a distinct mechanism for the action of thapsigargin-sensitive Ca(2+) signals. MGRE (MKP-2 GnRH response element) within the MKP-2 promoter mediated promoter activation through the protein kinase C-ERK pathway. The zinc finger transcription factor Egr-1 was identified in the MGRE-binding complex. Egr-1/MGRE binding was induced by GnRH in an ERK-dependent manner. Transcriptional activity of Egr-1 protein was enhanced by GnRH treatment. In addition, overexpression of the Egr-interacting protein, NAB1, resulted in increased GnRH-stimulated MKP-2 gene transcription. Consistent with the putative role of Egr-1 in MKP-2 promoter regulation, Egr-1 protein expression closely correlated with the expression of MKP-2 protein in alpha T3-1 cells. Together, these data suggest that Egr-1 may be a key factor in mediating GnRH-dependent transcriptional activation of the MKP-2 gene.

Animals↗
PubMed2001

Application of analytical and preparative high-speed counter-current chromatography for separation of lycopene from crude extract of tomato paste.

Lycopene was isolated from 100 mg of crude extract of tomato paste containing about 9% of lycopene. Analytical high-speed counter-current chromatography (HSCCC) was first used for the systematic selection of the two-phase solvent system. Then preparative HSCCC separation was performed with a nonaqueous solvent system composed of n-hexane-dichloromethane-acetonitrile at an optimum volume ratio of 10:3.5:6.5. This yielded 8.6 mg of lycopene at over 98.5% purity as determined by HPLC analysis.

Carotenoids↗
PubMed2001

Increased expression and activity of RhoA are associated with increased DNA synthesis and reduced p27(Kip1) expression in the vasculature of hypertensive rats.

We have previously shown that the function of the small G protein Rho is required for vascular smooth muscle cell proliferation and migration. We hypothesized that changes in Rho or Rho signaling might contribute to enhanced vascular proliferative responses associated with hypertension. Western blot analysis revealed that total RhoA expression was approximately 2-fold higher in aortas, tail arteries, and aortic smooth muscle cells (ASMCs) obtained from adult male spontaneously hypertensive rats (SHR) compared with those from Wistar Kyoto rats (WKY). An increase in active GTP-bound RhoA was detected in aortic homogenates by affinity precipitation with the RhoA effector rhotekin and by examining RhoA-[(35)S]GTPgammaS binding. RhoA protein and activity were also increased in vessels from rats treated with N-nitro-L-arginine methyl ester to increase blood pressure. Thrombin-stimulated RhoA activation was also significantly greater in ASMCs from SHR. As a functional correlate of these changes in Rho signaling, thrombin-stimulated DNA synthesis was enhanced in tail arteries and ASMCs from SHR. Expression of the cyclin-dependent kinase inhibitor p27(Kip1) was decreased by two thirds in SHR, and this decrease was mimicked in ASMCs by expression of a constitutively active (GTPase-deficient) mutant of RhoA. Wortmannin (10 nmol/L) fully inhibited the decrease in p27(Kip1) induced by RhoA, and a membrane-targeted catalytic subunit of phosphatidylinositol-3 kinase (PI3K [p110(CAAX)]) decreased p27(Kip1) expression, suggesting that RhoA signals through PI3K. These data provide evidence that RhoA brings about changes in DNA synthesis through reduced expression of p27(Kip1), mediated in part via PI3K, and suggest that increases in RhoA expression and activity contribute to the enhanced vascular responsiveness observed in hypertension.

Androstadienes↗
PubMed2001

Hoxb2 and hoxb4 act together to specify ventral body wall formation.

Three different alleles of the Hoxb4 locus were generated by gene targeting in mice. Two alleles contain insertions of a selectable marker in the first exon in either orientation, and, in the third, the selectable marker was removed, resulting in premature termination of the protein. Presence and orientation of the selectable marker correlated with the severity of the phenotype, indicating that the selectable marker induces cis effects on neighboring genes that influence the phenotype. Homozygous mutants of all alleles had cervical skeletal defects similar to those previously reported for Hoxb4 mutant mice. In the most severe allele, Hoxb4(PolII), homozygous mutants died either in utero at approximately E15.5 or immediately after birth, with a severe defect in ventral body wall formation. Analysis of embryos showed thinning of the primary ventral body wall in mutants relative to control animals at E11.5, before secondary body wall formation. Prior to this defect, both Alx3 and Alx4 were specifically down regulated in the most ventral part of the primary body wall in Hoxb4(PolII) mutants. Hoxb4(loxp) mutants in which the neo gene has been removed did not have body wall or sternum defects. In contrast, both the Hoxb4(PolII) and the previously described Hoxb2(PolII) alleles that have body wall defects have been shown to disrupt the expression of both Hoxb2 and Hoxb4 in cell types that contribute to body wall formation. Our results are consistent with a model in which defects in ventral body wall formation require the simultaneous loss of at least Hoxb2 and Hoxb4, and may involve Alx3 and Alx4.

Alleles↗
PubMed2001

Differential scanning calorimetry studies of intraembryonic freezing and cryoprotectant penetration in zebrafish (Danio rerio) embryos.

Nucleation temperatures of intraembryonic water and cryoprotectant penetration in zebrafish embryos were studied using differential scanning calorimetry. The effects of embryo developmental stage, dechorionation, partial removal of yolk, cooling rate, and cryoprotectant treatment on the temperatures of intraembryonic freezing were investigated. Embryo stages were found to have a significant effect on the nucleation temperatures of intact embryos. Freeze onset temperatures of -11.9 +/- 1.5, -15.6 +/- 0.3, and -20.5 +/- 0.1 degrees C were obtained for intact embryos at 6-somite, prim-6, and high-pec stages, respectively. After dechorionation, the freeze onset temperatures of intraembryonic water shifted to significantly lower temperatures, being -23.5 +/- 0.8, -18.7 +/- 0.7, -24.9 +/- 0.8 degrees C for 6-somite, prim-6, and high-pec stages, respectively. Yolk-reduced high-pec stage embryos showed significantly lower nucleation temperatures with an average onset at -27.9 +/- 0.4 degrees C. The effect of cryoprotectant treatment on the nucleation temperatures of intraembryonic water varies among different embryo stages and different cryoprotectants. Thirty-minute treatment with 2 M methanol significantly decreased the nucleation temperatures of dechorionated 6-somite embryos whilst no temperature decrease was observed for prim-6 or yolk-reduced high-pec embryos. Thirty-minute exposure to 1 M propylene glycol did not significantly affect the nucleation temperatures of dechorionated 6-somite, prim-6, or yolk-reduced high-pec embryos. In order to increase the permeability of embryos to cryoprotectants, the yolk sacs of dechorionated embryos at 6-somite or prim-6 embryos were punctured with a sharp micro-needle before exposure to cryoprotectants. The punctured prim-6 embryos showed significantly lower temperatures of intraembryonic freezing after 30 min of exposure to 2 M methanol following the multi-punctures. The nucleation temperatures of punctured 6-somite or prim-6 embryos were also decreased significantly after exposure to 1 M propylene glycol for 30 min. These results suggested that in intact embryos, intraembryonic freezing appeared to be seeded by the external ice in the perivitelline fluid and that in dechorionated embryos (in the absence of external water) intraembryonic freezing was more likely a consequence of heterogeneous nucleation. Methanol was demonstrated to show a limited degree of penetration into prim-6 stage embryos, but it did not penetrate later-stage embryos such as prim-6 and yolk-reduced high-pec. No propylene glycol permeation was observed for embryos at all stages. However, multi-punctures of yolk resulted in the permeation of both cryoprotectants into prim-6 embryos and propylene glycol permeation into 6-somite embryos. These findings may have important implications in overcoming the problem associated with the low membrane permeability of zebrafish embryos to cryoprotectants.

Adaptation, Physiological↗
PubMed2001

Structural organization of the rat mitogen-activated protein kinase phosphatase 2 gene.

Mitogen-activated protein kinase (MAPK) phosphatases (MKPs) are dual specificity protein phosphatases that specifically inactivate MAPKs. Regulated expression of MKPs plays a key role in determining their physiological function. However, little is known about the molecular mechanism of the activation of MKP genes. In this study, we cloned the rat MKP-2 gene and characterized its structure. The MKP-2 gene has four exons and three introns. The organization of exons of the MKP-2 gene is very similar to that of the MKP-1 gene, suggesting that MKP-1 and MKP-2 are derived from the same ancestral gene. We identified multiple transcription start sites (TSSs) for the MKP-2 gene. There is no functional TATA motif in the 5' proximal region of the TSSs. Instead, this region is highly GC-rich and has two putative Sp1 sites. A 1.8 kb 5' flanking region of the MKP-2 gene is sufficient to mediate transcriptional activation of the luciferase reporter gene by phorbol ester in GH3 cells. These results provide essential information about structural organization and regulatory sequences of the MKP-2 gene for further investigation of the molecular mechanisms of MKP-2 induction by extracellular stimuli.

Amino Acid Sequence↗
PubMed2001

Screening for inborn errors of metabolism using gas chromatography-mass spectrometry.

Screening of newborns for inborn errors of metabolism (IEM) in China is both a challenging and undeveloped area for gynecologists and pediatricians. Since 1999, the Capital Institute of Pediatrics has been studied as regards screening for IEM using advanced gas chromatography-mass spectrometry (GC-MS) method in collaboration with the Matsumoto Institute of Life Science (MILS), Japan, and has successfully diagnosed 51 cases of IEM in a total of 393 patients. Galactosemia, phenylketonuria and methylmalonic acidemia were the most frequent disorders among 51 cases of IEM. Treatment by suitable drugs and/or diet therapy was very effective in the most cases.

Gas Chromatography-Mass Spectrometry↗
PubMed2001

Large-scale separation of resveratrol, anthraglycoside A and anthraglycoside B from Polygonum cuspidatum Sieb. et Zucc by high-speed counter-current chromatography.

High-speed counter-current chromatography was successfully applied to the large-scale separation of resveratrol, anthraglycoside A and anthraglycoside B from the crude extract of Polygonum cuspidatum Sieb. et Zucc using a two-phase solvent system composed of chloroform, methanol and water. Resveratrol, anthraglycoside A and anthraglycoside B were separated from multigram quantities (5 g) of crude extract of P. cuspidatum. The separation yielded 200 mg to 1 g of these three compounds each at over 98% purity as determined by HPLC. The chemical structures of these components were identified by nuclear magnetic resonance (NMR) and MS.

Anthracenes↗
PubMed2001

Cyclin a-CDK phosphorylation regulates MDM2 protein interactions.

The product of the MDM2 gene interacts with and regulates a number of proteins, in particular the tumor suppressor p53. The MDM2 protein is likely to be extensively modified in vivo, and such modification may regulate its functions in cells. We identified a potential cyclin-dependent kinase (CDK) site in murine MDM2, and found the protein to be efficiently phosphorylated in vitro by cyclin A-containing complexes (cyclin A-CDK2 and cyclin A-CDK1), but MDM2 was either weakly or not phosphorylated by other cyclin-containing complexes. Moreover, a peptide containing a putative MDM2 cyclin recognition motif specifically inhibited phosphorylation by cyclin A-CDK2. The site of cyclin A-CDK2 phosphorylation was identified as Thr-216 by two-dimensional phosphopeptide mapping and mutational analysis. Phosphorylation of MDM2 at Thr-216 both weakens its interaction with p53 and modestly augments its binding to p19(ARF). Interestingly, an MDM2-specific monoclonal antibody, SMP14, cannot recognize MDM2 phosphorylated at Thr-216. Changes in SMP14 reactivity of MDM2 in staged cell extracts indicate that phosphorylation of MDM2 at Thr-216 in vivo is most prevalent at the onset of S phase when cyclin A first becomes detectable.

3T3 Cells↗