Biomedical subjects

X Zhao

Publications and source records attributed to X Zhao.

At least 19 recordsLinked to original sources

PubMed2006

Humoral and cellular immunity induced by tumor cell vaccine based on the chicken xenogeneic homologous matrix metalloproteinase-2.

Matrix metalloproteinase-2 (MMP-2) has been used as a target for cancer immunotherapy. The activation of immunization by breaking immune tolerance to self-MMP-2 may be one of the promising approaches for the treatment of MMP-2-positive tumors. In this study, we constructed the xenogeneic tumor cell vaccine c-MMP-2 by transfecting CT26 and LLC cells with chicken MMP-2 cDNA constructs. MMP-2-specific autoantibodies in sera and tumor cells were found in mice immunized with c-MMP-2. Protection against tumor growth was evaluated in respect of the relative contributions of autoantibodies, CD4+, and CD8+ T cells. Treatment with this vaccine (c-MMP-2) also prolonged the survival time of mice bearing cancer. The specific cytotoxic T-cell responses suggested that the treatment increased CD8+ T-cell activity. The antitumor activity of c-MMP-2 was abrogated by in vivo depletion of CD4+ and CD8+ T-lymphocytes and improved by adoptive transfer of CD4+ and CD8+ T-lymphocytes from the mice treated with c-MMP-2. An alternative DNA vaccination strategy for cancer therapy was identified in this study by eliciting humoral and cellular immunoresponse with a crossreacting transfectant.

Animals↗

PubMed2006

cDNA microarray analysis of gene expression in Brassica napus treated with oligochitosan elicitor.

An oilseed rape (Brassica napus H) cDNA microarray containing 8095 expressed sequence tags (ESTs) was used to analyze the B. napus gene expression changes elicited by oligochitosan. Transcript levels for 393 genes were altered twofold or more in oligochitosan-treated seedlings compared to control seedlings. Of the 393 genes, 257 were repressed and 136 were induced. Semi quantification RT-PCR of eight of these 393 genes confirmed the microarray results. These 393 genes were involved in different processes and had different functions including defense, primary metabolism, transcription, and signal transduction etc. Some of these genes were elicited by various pathogen-related or stress stimuli, and others were regulated by plant growth regulators like auxin and gibberellin. These manifested complicated interactions of oligochitosan and phytohormones. An important jasmonic acid (JA) synthase (2-oxophytodienoate-10,11-reductase) gene, a JA-mediated defense required kinase ATMPK4-homolog gene, an ethylene receptor gene, and two ethylene responsive element binding protein (EREBP) genes were induced by oligochitosan, suggesting that oligochitosan activated the plant self-defense through JA/ET signaling pathway.

Brassica napus↗

PubMed2006

Isolation of a novel Ser/Thr protein kinase gene from oligochitosan-induced tobacco and its role in resistance against tobacco mosaic virus.

Oligochitosan induces defense responses to pathogenic microbes in a wide variety of plants by acting as an elicitor. In the present study, mRNA differential display was used to investigate oligochitosan-induced transcriptional activation of defense-related genes. Accordingly, a novel Ser/Thr protein kinase gene was isolated and designated as oligochitosan-induced protein kinase (oipk). Molecular cloning showed that oipk contains six introns interrupted by seven exons. The open reading frame (ORF) of the gene is 1848 bp, which encodes a putative protein of 615 amino acids with the predicted molecular mass of 70.96 kDa and a pI of 6.32. A plant oipk antisense expression vector was constructed and transformed into tobacco by Agrobacterium tumefaciens. Decreased phenylalanine ammonia-lyase (PAL, EC 4.3.1.5) activity and decreased resistance to tobacco mosaic virus (TMV) were observed in transgenic tobacco. RT-PCR analysis revealed that oipk was expressed at high levels after oligochitosan induction in wild-type tobacco, but not in transgenic tobacco. These results indicated that oipk is involved in the signal pathway of oligochitosan-induced resistance in tobacco.

Amino Acid Sequence↗

PubMed2006

Zeolite (clinoptilolite) as feed additive to reduce manure mineral content.

Clinoptilolite (a species of zeolite) as grower hog feed additive can potentially improve nutrient ingestion and lower manure nutrient levels. A first objective was to establish the optimal particle size of the zeolite powder, as a fine size increases the adsorption surface while a coarse size can facilitate handling. The second objective tested the effect of feeding zeolite on manure nutrient levels. For the first objective, three zeolite powders (250-500 microm; 50-250 microm, and 50-500 microm) were exposed to an NH(4)(+) solution under a pH of either 7.0 or 2.0. The resulting solutions were tested for cation exchange. A commercial zeolite was also tested for the pH of 2.0 to evaluate zeolite stability. At 0%, 5% and 10% humidity, the same three particle size powders were subjected to shear tests to determine the zeolite's angle of friction. For the second objective using metabolic cages, female hogs were subjected to one of four rations (a control and three with zeolite) while collecting and analyzing their manures. For the first objective, the coarse particle zeolite performed best, adsorbing 158 and 123 Cmol(+)/kg of NH(4)(+) under neutral and acid pH, respectively, and releasing an equivalent amount of minerals only under neutral pH. The commercial zeolite with less clinoptilolite released more Al, Fe, Cu and Pb, showing less stability. The high internal angle of friction of zeolite did not vary with particle size and moisture, indicating funnel flow under gravity. For the second objective, hogs fed a zeolite diet produced manure with 15% and 22% less N and P, respectively, and demonstrated a better feed conversion, although not statistically significant (P>0.05). These results show that there is some potential in using high quality clinoptilolite in the ration of grower hogs.

Ammonia↗

PubMed2006

No association between the genetic polymorphisms in the RTN4R gene and schizophrenia in the Chinese population.

The RTN4R gene is located in the 22q11 region and it encodes a subunit of the receptor complex (RTN4R-p75NTR) which results in neuronal growth inhibitory signals in response to Nogo-66, MAG or OMG signaling. Previous studies have suggested that RTN4R might act as a potential candidate for schizophrenia susceptibility loci. We genotyped four SNPs within the gene and conducted a case-control study and TDT analysis, involving 707 schizophrenic patients, 689 controls and 372 unrelated small nuclear families with schizophrenic offspring in the Chinese population. We examined allele and genotype frequencies and haplotype distributions in both family- and nonfamily-based samples. Our results suggest that there is no significant association between the genetic polymorphisms and schizophrenia in the Han Chinese population.

Case-Control Studies↗

PubMed2006

Influence of diltiazem on the behavior of zolpidem-treated mice in the elevated-plus maze test.

The present study was undertaken to investigate the effect of diltiazem, a L-type calcium channel blocker (CCB), on the behavior of zolpidem-treated mice in the elevated plus-maze (EPM). Atypical benzodiazepine zolpidem significantly increased the percentage of open arm entries without influencing the total entries and total distance and average speed at the dose of 5 mg/kg (p.o.). Co-administration of zolpidem (2 mg/kg, p.o.) and diltiazem (5, 10 and 20 mg/kg, p.o.) significantly increased both the time spent and arm entries in the open arms without influencing the total entries and spontaneous activity notwithstanding that zolpidem at dose up to 2 mg/kg (p.o.) and diltiazem at dose up to 20 mg/kg (p.o.) did not show any effects on mice behavior in EPM. Zolpidem also attenuated the anxiogenic effect of 1-(3-Chlorophenyl)piperazine (mCPP, 0.7 mg/kg, i.p.) and 5-hydroxytryptophan (5-HTP, 30 mg/kg, i.p.). Even though the zolpidem at 1 mg/kg and diltiazem at 5 mg/kg were ineffective on mCPP-induced anxiety, respectively, the co-administration of zolpidem (1 mg/kg, i.p.) and diltiazem (5 mg/kg, p.o.) showed inhibitory effect on mCPP-induced anxiety in mice. These results suggested that diltiazem, a L-type CCB may augment the anxiolytic-like effect of zolpidem and also indicated that calcium channel modulation maybe involved in the anxiolytic-like properties of zolpidem.

5-Hydroxytryptophan↗

PubMed2006

Enhancement of transdermal delivery of theophylline using microemulsion vehicle.

A microemulsion vehicle had been studied as a possible matrix for transdermal delivery of theophylline. The existence of microemulsion regions were investigated in pseudo-ternary phase diagrams, and various microemulsion formulations were prepared using oleic acid, Cremophor RH40/Labrasol (1:2) and water. The optimal formulation of the microemulsion was evaluated in vitro using Franz diffusion cells. The droplet size of microemulsion was characterized by photo correlation spectroscopy. Pharmacokinetic study in vivo was conducted using rabbits, and the results indicated that AUC(0-->infinity) of transdermal administration was 1.65-fold higher than that of oral solution administration. These studies showed that microemulsion system of theophylline might be promising vehicles for the transdermal delivery of theophylline.

Administration, Cutaneous↗

PubMed2006

Systemic inhibition of tumor growth by soluble Flk-1 gene therapy combined with cisplatin.

Soluble Flk-1, a soluble vascular endothelial growth factor (VEGF) receptor, is a potent inhibitor of angiogenesis, which could restrain growth and metastasis of some experimental tumors. However, antiangiogenic agents alone cannot eradicate tumor completely, and should be combined with other therapy to enhance their effects. In this study, we evaluated the antitumor activity of the combination therapy in the immunocompetent BALB/c mice bearing H22 hepatoma and Meth A fibrosarcoma, respectively. Mice were treated with either msFlk-1 i.m. at 100 microg/mouse once every 3 days for four times from day 3 after the tumor cell injection, cisplatin cycled twice (2 mg/kg i.p. on days 4 and 11 after the tumor cell inoculation), or both agents together. Tumor growth and survival time were continually observed. Antiangiogenesis in vivo was determined by CD31 immunohistochemistry. Assessment of apoptotic cells and histological analysis was also conducted in tumor tissues. Our results showed that the combination therapy could evidently improve antitumor efficacy, including tumor growth suppression, mice survival prolongation, tumor cell apoptosis augmentation as well as neovascularization inhibition as compared with controls, without serious adverse effects. Our data suggest that the combination of DDP with msFlk-1 is more effective to suppress tumor growth in mice than either agent alone, and this combination regimen showed its potential for future clinical application.

Animals↗

PubMed2006

A proteomic analysis reveals the loss of expression of the cell death regulatory gene GRIM-19 in human renal cell carcinomas.

Gene associated with retinoid interferon-induced mortality (GRIM)-19, an inhibitor of transcription factor STAT3, was originally identified as a critical regulatory protein in a genetic screen that was designed to identify the gene products necessary for Interferon (IFN)-beta- and retinoic acid-induced cell death. Over expression of GRIM-19 activates cell death. Conversely, inactivation of its expression promotes cell growth. STAT3 is a transcription factor that regulates gene expression in response to multiple extra cellular growth factors. In contrast to its normal feedback inhibition, a constitutive activation of STAT3 has been documented in several tumors. Although many STAT3-inhibitors are described, their relevance to human cancer is unclear. In an attempt to define the molecular alterations associated with human renal cell carcinoma (RCC) using mass spectrometry, we have discovered that expression of GRIM-19 is lost or severely depressed in a number of primary RCC and in some urinogenital tumors. Using an RCC cell line, we show that down regulation of GRIM-19 promotes tumor growth via an augmentation of STAT3-dependent gene expression. These studies for the first time show a tumor-suppressor like activity of GRIM-19.

Apoptosis Regulatory Proteins↗

PubMed2006

Thermal desorption of hydrogen from carbon nanosheets.

Carbon nanosheets are a unique nanostructure that, at their thinnest configuration, approach a single freestanding graphene sheet. Temperature desorption spectroscopy (TDS) has shown that the hydrogen adsorption and incorporation during growth of the nanosheets by radio frequency plasma-enhanced chemical vapor deposition are significant. A numerical peak fitting to the desorption spectra (300-1273 K) via the Polanyi-Wigner equation showed that desorption followed a second order process, presumably by the Langmuir-Hinshelwood mechanism. Six peaks provide the best fit to the TDS spectra. Surface desorption activation energies were determined to be 0.59, 0.63, and 0.65 eV for the external graphite surface layers and 0.85, 1.15, and 1.73 eV for desorption and diffusion from the bulk. In contrast to TDS data from previously studied a-C:H films [Schenk et al. J. Appl. Phys. 77, 2462 (1995)], a greater amount of hydrogen bound as sp(2) hybridized carbon was observed. A previous x-ray diffraction study of these films has shown a significant graphitic character with a crystallite dimension of L(a)=10.7 nm. This result is consistent with experimental results by Raman spectroscopy that show as-grown carbon nanosheets to be crystalline as commercial graphite with a crystallite size of L(a)=11 nm. Following TDS, Raman data indicate that the average crystallite increased in size to L(a)=15 nm.

Journal Article↗

PubMed2006

Combination of MIG (CXCL9) chemokine gene therapy with low-dose cisplatin improves therapeutic efficacy against murine carcinoma.

MIG (monokine induced by interferon-gamma) is a CXC chemokine ligand (CXCL9) that can potently inhibit angiogenesis, and displays thymus-dependent antitumor effects. The effectiveness of a treatment combining gene therapy with plasmid-borne MIG (pORF-MIG) and low-dose cisplatin chemotherapy was determined using colon carcinoma (CT26) and Lewis lung carcinoma (LL/2c) murine models. The program was carried out via intramuscular delivery of pORF-MIG at 100 mug/mouse twice a week for 4 weeks, and/or intraperitoneal delivery of cisplatin at 0.6 mg/kg/mouse every 3 days for 48 days. Tumor volume and survival time were evaluated after treatment. CD31 immunohistochemical staining in tumor tissues and alginate capsule models in vivo was used to evaluate angiogenesis. Induction of apoptosis and cytotoxic T-lymphocyte (CTL) activity were also assessed. The combination of pORF-MIG and low-dose cisplatin produced significant antitumor activity, with complete tumor regression in 4/10 of CT26 colon carcinomas and 3/10 of LL/2c lung carcinomas, low vascularity, in alginate capsules, apparently degraded tumor microvessel density, and increased induction of apoptotic and CTL activities compared with either treatment alone. This study suggests that the combination of pORF-MIG plus cisplatin augments the inhibition of angiogenesis and the induction of apoptosis or CTL activity, all of which enhance antitumor activity. These findings may prove useful in further explorations of the application of combinatorial approaches to the treatment of solid tumors.

Animals↗

PubMed2006

Family-based association studies of the TCP1 gene and schizophrenia in the Chinese Han population.

A previous case-control study by Yang et al. indicated that the TCP1 gene in 6q25 was associated with schizophrenia in the Han population. To replicate this result, we selected eight SNPs (rs2273828, rs3818298, rs1547094, rs1547093, rs2295898, rs2295899, rs4832, rs15982) spanning the whole gene and performed a family-based study using 325 trios samples. Our transmission disequilibrium test showed neither allele nor haplotype association with schizophrenia, and suggests that the TCP1 locus is not associated with schizophrenia in the Chinese population. Since 6q25 has consistently been found to be a susceptible region for schizophrenia, we suggest that other genes within this region should be the focus of attention.

Adult↗

PubMed2006

Potentiating effects of L-type Ca(2+) channel blockers on pentobarbital-induced hypnosis are influenced by serotonergic system.

In order to elucidate the mechanism(s) behind the interactions between barbiturates and Ca(2+) antagonists, the effects of three structurally diverse types of Ca(2+) antagonists combined or not with 5-HT on pentobarbital-induced hypnosis in mice were investigated. The results showed that dihydropyridine derivative nifedipine (10.0 and 20.0 mg/kg, p.o.) and other types of Ca(2+) antagonist, verapamil (5.0 and 10.0 mg/kg, p.o.) and diltiazem (2.5, 5.0 and 10.0 mg/kg, p.o.) increased both the sleeping time in hypnotic dosage of pentobarbital (45 mg/kg, i.p.) treated mice and the rate of sleep onset in the sub-hypnotic dosage of pentobarbital (28 mg/kg, i.p.) treated mice in a dose-dependent manner, respectively, and these effects were significantly augmented by 5-hydroxytryptophan (5-HTP), the immediate precursor of 5-hydroxytryptamine (5-HT). Pretreatment with p-chlorophenylalanine (PCPA, 300 mg/kg, s.c.), an inhibitor of tryptophan hydroxylase, significantly decreased pentobarbital-induced sleeping time and nifedipine (10.0 mg/kg, p.o.), verapamil (5.0 mg/kg, p.o.) and diltiazem (2.5 mg/kg, p.o.) abolished this effect. From these results, it should be presumed that the augmentative effect of L-type Ca(2+) channel blockers on pentobarbital-induced sleep may be influenced by serotonergic system.

5-Hydroxytryptophan↗

PubMed2006

Altered PPARgamma expression and activation after transient focal ischemia in rats.

Stroke is a devastating disease with limited treatment options. Recently, we found that the peroxisome proliferator-activated receptor-gamma (PPARgamma) agonists troglitazone and pioglitazone reduce injury and inflammation in a rat model of transient cerebral ischemia. The mechanism of this protection is unclear, as these agents can act through PPAR-gamma activation or through PPAR-gamma-independent mechanisms. Therefore, we examined PPAR-gamma expression, DNA binding and transcriptional activity following stroke. In addition, we used a PPAR-gamma antagonist, T0070907, to determine the role of PPAR-gamma during ischemia. Using immunohistochemical techniques and real-time PCR, we found low levels of PPAR-gamma mRNA and PPAR-gamma immunoreactivity in nonischemic brain; however, PPAR-gamma expression dramatically increased in ischemic neurons, peaking 24 h following middle cerebral artery occlusion. Interestingly, we found that in both vehicle- and agonist-treated brains, DNA binding was reduced in the ischemic hemisphere relative to the contralateral hemisphere. Expression of a PPAR-gamma target gene, lipoprotein lipase, was also reduced in ischemic relative to nonischemic brain. Both DNA binding and lipoprotein lipase expression were increased by the addition of the PPAR-gamma agonist rosiglitazone. Finally, we found that rosiglitazone-mediated protection after stroke was reversed by the PPAR-gamma antagonist T0070907. Interestingly, infarction size was also increased by T0070907 in the absence of PPAR-gamma agonist, suggesting that endogenous PPAR-gamma ligands may mitigate the effects of cerebral ischemia.

Animals↗

PubMed2006

Characterization of a novel DRB114 allele (DRB11449) in the Han-Chinese population.

We report here a novel human leukocyte antigen (HLA) allele, DRB1*1449, in the Han-Chinese population. The nature of the new allele was confirmed by the sequencing-based typing (SBT) method. Genomic DNA and six subclones containing DNA fragment of DRB1 exon 2 were sequenced in both forward and reverse directions. The exon 2 nucleotide sequence of DRB1*1449 is closely related to DRB1*1432 allele based on sequence homology. It has four nucleotide (nt) substitutions at positions 71, 196, 244 and 245 in exon 2, which lead to changes of amino acid sequences. The serological assignment of DRB1*1449 is DR14 based on the serological HLA typing result. This novel allele might be a result of recombination between DRB1*1402 and DRB1*140101 like alleles, which are very common among Chinese population.

Alleles↗

PubMed2006

Synthesis and characterization of a novel hyaluronic acid hydrogel.

Hyaluronic acid (hyaluronan, HA) has many medical applications as a biomaterial. To enhance its biostability, a novel hydrogel of cross-linked hyaluronic acid was prepared using a double cross-linking process, which involves building cross-linkages between hydroxyl group pairs and carboxyl group pairs. The present study explored a number of cross-linking processes in order to obtain different degrees of cross-linking, which were evaluated by the measurement of water absorption capacity as an index of the gel network density. To gain a better understanding of the stability of the gel, the chemical structure and particularly the rheological behaviour of the cross-linked HA, which included the influences of factors, such as degree of cross-linking, HA concentration and gel particle size, were investigated. The in vitro biostability against hyaluronidase and free radical degradation was tested to show that the cross-linked hydrogel had improved resistance to in vitro hyaluronidase and free radical degradation.

Biocompatible Materials↗

PubMed2006

Formation of SWCnts in arc plasma: effect of graphitization of Fe-doped anode and optical emission studies.

Fe-doped (ca. 1 at%) homogeneous graphite electrodes (with different graphite microcrystallites, degree of graphitization and, thereby, electrical conductivities) were used to produce single-walled carbon nanotubes (SWCNTs) in Ar/Kr/Xe-H2 arc plasma under pressure equal to 26 kPa. The use of electrode with the smaller primary particle size (about 5 nm) comparing to the well-graphitized electrode (25 nm) drastically increased the yield of SWCNTs in Ar-H2 arc plasma, while plasma parameters (temperature, C2 content, and namely carbon vapor pressure) remained on similar levels. However, the use of electrodes with larger grain size (25 nm) can lead to SWCNTs growth when they are arc ablated under the presence of Kr (or Xe)-H2 gas mixture. Thus, the mechanism of CNT formation seems to be more complex that the one involving only simple carbon species (e.g., C2).

Crystallization↗

PubMed2006

Deferoxamine reduces tissue damage during endotoxin-induced mastitis in dairy cows.

The protective effects of 3 antioxidants on polymorphonuclear neutrophil-induced damage to mammary cells were evaluated in vivo using an endotoxin-induced mastitis model. Fifteen healthy, midlactation cows with no history of clinical Escherichia coli mastitis were randomly assigned to 1 of the 3 treatment groups corresponding to each modulator to be evaluated, that is, deferoxamine, catechin, and glutathione ethyl ester. Each cow had 1 quarter infused with saline and 1 quarter infused with the selected modulator; a third quarter was infused with lipopolysaccharides (LPS), whereas the fourth quarter received a combination of LPS and the modulator. Infusion of LPS caused acute mastitis as determined by visual observations and by large increases in milk somatic cell count, BSA, and proteolytic activity. These parameters were not affected by antioxidant administration. The extent of cell damage was evaluated by measuring milk levels of lactate dehydrogenase and N-acetyl-beta-D-glucosaminidase activity. Levels of these parameters were several times higher after LPS administration. Intramammary infusions of catechin or glutathione ethyl ester did not exert any protective effect, whereas infusion of deferoxamine, a chelator of iron, decreased milk lactate dehydrogenase and NA-Gase activity, suggesting a protective effect against neutrophil-induced damage. The protective effect of deferoxamine was also evidenced by a lower milk level of haptoglobin. The proteolytic activity of mastitic milk was not influenced by the presence of deferoxamine. Overall, our results suggest that local infusion of deferoxamine may be an effective tool to protect mammary tissue against neutrophil-induced oxidative stress during bovine mastitis.

Animals↗