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Biomedical subjects

Xiang Liu

Publications and source records attributed to Xiang Liu.

65 records · Page 4Linked to original sources
PubMed2003

Influence of nonionic surfactant on the solubilization and biodegradation of phenanthrene.

Phenanthrene was solubilized in two different nonionic surfactants, Tween80 and Triton X-100. The bioavailability of phenanthrene to the bacteria isolated from the petroleum contaminated soils was studied based on the rotary flasks experiments. The results showed that the concentration of nonionic surfactants above the critical micelle concentration (CMC) can increase the solubility of phenanthrene in water and were innoxious to the phenanthrene-degrading bacteria; phenanthrene solubilized in the micelles of Tween80 was bioavailable and biodegradable. The research demonstrated the potential of surfactant-enhanced bioremediation of soils contaminated by hydrophobic organic compounds (HOCs).

Bacteria↗
PubMed2003

[Characterization of polycyclic aromatic hydrocarbons dissolved in nonionic surfactants].

Using three typical nonionic surfactants (Tween80, Tween20 and Triton X-100), the solubilization of four kinds of polycyclic aromatic hydrocarbons (PAHs) e.g. naphthalene, phenanthrene, fluorene and pyrene, were characterized. It was found that not only nonionic surfactants could enhance the solubilization of PAHs greatly in the range of concentration above critical micellar concentration (CMC), but also the solubility had the linear relationship with the concentration of nonionic surfactants. The effect of solubilization enhancement at three surfactants was Triton X-100 > Tween80 > Tween20. In the three nonionic surfactants solution the micelle-aqueous phase partitioning coefficient (K(m)) had very good linear proportional to the octanol-water partitioning coefficient (Kow) for the four tested PAHs.

Octoxynol↗
PubMed2003

[Relativity betweeen expression level of potato virus X coat protein and the codon usage of wobble codon].

The relationship between the quantities of rare codons and the expression levels of foreign genes is very important in gene engineering. But up to now, there is few experiment on it in multi-cellular eukaryotes, especially in plants. To study the effect of rare codons on the expression level of potato virus X (PVX) coat protein (CP) in transgenic tobacco, some preferred codons in PVX coat protein gene were substituted with synonymous rare codons without changing the encoded amino acid sequence using site-specific mutation. The modified coat protein gene (cpm) and non-modified coat protein gene (cpw) were inserted into binary vector under the control of CaMV35S promoter, and these two plant expression constructs were transferred into tobacco (Nicotiana tabacum cv. Xanthi) genomes via Agrobacterium mediated method and transgenic plants were generated. Western blot and ELISA of these transgenic tobaccos showed that the expression level of modified CP is about one third to one sixth of that of non-modified CP. Northern blot analysis of RNAs from some transformants indicated that the transcriptional levels of cpm are the same as that of cpw, which implicated that the quantity of rare codons in foreign gene was a possible limited factor in foreign gene expression process. Changing the quantity of rare codons maybe an effective method for organism to control gene expression.

Amino Acid Sequence↗
PubMed2002

Truncation of amino-terminal tail stimulates activity of human endonuclease III (hNTH1).

The human base excision repair enzyme hNTH1, a homologue of Escherichia coli endonuclease III (Nth), is a 36kDa DNA glycosylase with associated abasic (AP) lyase activity. It has significant sequence homology with Nth in its DNA-binding motifs and catalytic residues but possesses a unique amino (N)-terminal tail (residues 1-95). We investigated the structure and function of this tail. Controlled proteolysis cleaved hNTH1 into discrete fragments to generate a 25kDA core domain lacking the N-terminal 98 residues. Surprisingly, recombinant hNTH1 lacking 55, 72 or 80 residues from the N terminus had four- to fivefold higher activities than the full-length enzyme. Kinetic analysis at transition states revealed that release of the final product, an AP site with a 3'-nick, is the rate-limiting step in the multi-step reaction mediated by hNTH1. The N-terminal tail regulates its overall catalytic turnover by reducing this product release rate by five- to sevenfold without affecting either the glycosylase or AP lyase activities, or the steady-state equilibrium concentration of Schiff base intermediate, the covalent complex of hNTH1 and AP-site DNA formed after the base is excised. The inhibitory role of the N-terminal tail in catalytic turnover explains the low activity of hNTH1 compared to that of its E.coli homologue.

Amino Acid Sequence↗
PubMed2002

Endogenous interferon-alpha production by differentiating human monocytes regulates expression and function of the IL-2/IL-4 receptor gamma chain.

In vitro monocyte-derived macrophages (MDMac) and synovial fluid macrophages from inflamed joints differ from monocytes in their responses to interleukin 4 (IL-4). While IL-4 can suppress LPS-induced interleukin beta (IL-beta) and tumour necrosis factor alpha (TNF-alpha) production by monocytes, IL-4 can suppress LPS-induced IL-1 beta, but not TNFalpha production by the more differentiated cells. Recently we reported a correlation between the ability of IL-4 to regulate TNFalpha production by monocytes and the expression of the IL-4 receptor gamma chain or gamma common (gamma c chain). Like MDMac, interferon alpha (IFNalpha)-treated monocytes expressed less IL-4 receptor gamma c chain, reduced levels of IL-4-activated STAT6 and IL-4 could not suppress LPS-induced TNFalpha production. In addition, like monocytes and MDMac, IFNalpha-treated monocytes expressed normal levels of the IL-4 receptor alpha chain and IL-4 significantly suppressed LPS-induced IL-1 beta production. With addition of IFNalpha-neutralizing antibodies, the ability of IL-4 to suppress LPS-induced TNFalpha production with prolonged monocyte culture was restored. Detection of IFNalpha in synovial fluids from inflamed joints further implicates IFNalpha in the inability of IL-4 to suppress TNFalpha production by synovial fluid macrophages. This study identifies a mechanism for the differential expression of gamma c and varied responses to IL-4 by human monocytes compared with MDMac.

Cell Differentiation↗
PubMed2002

Enhanced antitumor effect of EGF R-targeted p21WAF-1 and GM-CSF gene transfer in the established murine hepatoma by peritumoral injection.

One of the major obstacles in current cancer gene therapy is the lack of a gene delivery system with high efficiency and targetability. In this paper, a nonviral gene delivery system GE7, which was designed to target EGF receptor (EGF R) overexpressed on the surface of cancer cel Is through an EGF R-binding oligopeptide (GE7), was used for in vivo gene therapy in a murine subcutaneous hepatoma model. It was demonstrated that the GE7 system could target the reporter gene beta-gal to EGF R-expressing hepatoma cells with high efficiency after in vitro transfection and in vivo peritumoral injection. To improve the therapeutic effect elicited by single gene transfer, human cyclin-dependent kinase inhibitor gene p21WAF-1 and murine cytokine gene GM-CSFwere used simultaneously in peritumoral injection of the GE7/DNA polyplex. The results showed that combined gene transfer of p21WAF-1 and GM-CSF could inhibit the growth of pre-established tumor more effectively and prolong the survival time of hepatoma-bearing mice more significantly than the transfer of a single gene. Apoptosis in the tumor tissues were found when injected with the p21WAF1-DNA polyplex. Prominent inflammatory infiltration was observed in the tumor tissue transfected with the GM-CSF DNA polyplex. Our data demonstrate that the GE7 system-mediated, EGF R-targeted cotransfer of p21WAF-1 and GM-CSF genes exhibit more potent antitumor effect by inducing tumor cell apoptosis and inflammatory responses.

Animals↗
PubMed2002

[Anther culture generated stem borer-resistance DH lines of Minghui 81(Oryza sativa L. subsp. indica) expressing modified cry1Ac gene].

2600 Anthers from T0 modified cry1 Ac-transgenic rice lines of Minghui 81, an elite restoring line of commercial CMS indica hybrid rice, were cultured on SK3 media. 83 green plantlets were recovered, 43 double haploid (DH) and 40 haploid among them. Results of PCR analyzes indicated that 55 plants of 83 were harbored the cry1Ac gene, and the ratio of cry1Ac-positive against cry1Ac-negative was 2:1 (55/28). 36 putative transgenic DH plants were further confirmed by Southern blot. ELISA detection showed that Cry1Ac level in different transgenic rice plants of the same cry1Ac-DH clone was almost equal and the highest one amount to 0.25% of the total soluble protein. Pest insect-resistant bioassay at field trials demonstrated that some of the homozygous cry1Ac-transgenic rice plants not only showed high-level resistance against striped stem borer (Chilo suppressalis) but also retained elite agronomy characters. These results demonstrated that rice anther culture has a great value in rice molecular breeding.

Animals↗
PubMed2002

[The characters of various commodity of chrysanthemums].

OBJECTIVE: To provide basis for making the quality standard of medicinal chrysanthemums [Dendranthema morifolium (Ramat.) Tzvel.]. METHOD: The character of pharmacognosy. RESULT: The characters of many of chrysanthemums as well as the differences between them have been clarified.

Chrysanthemum↗
PubMed2002

[Advances in the studies of plant basic leucine zipper (bZIP) proteins (B)--DNA-binding property, gene expression, function and application].

Plant basic leucine zipper (bZIP) proteins play an important role in the expression and regulation of higher plant genes. The DNA-binding properties of plant bZIP protein are introduced first in this article. Then their expression and function are discussed. Finally, their application to the studies of molecular biology and genetic engineering is reviewed.

English Abstract↗
PubMed1986

Relationship between electroacupuncture analgesia and descending pain inhibitory mechanism of nucleus raphe magnus.

Raphe-spinal (R-S) neurons were identified in the nucleus raphe magnus (NRM). The conduction velocity of their axons was calculated to be about 15-60 m/sec. The great majority of R-S neurons did not respond clearly to non-noxious stimuli, such as brushing hair or lightly pressing the skin, but they did respond to noxious stimuli (pricking or clamping), with increases or decreases in their firing rates. The receptive fields of the R-S neurons responding to noxious stimuli were very wide covering almost all of the body. The responses of R-S neurons to noxious stimulation were excitatory (increasing firing rates), inhibitory (decreasing) and unresponsive in type, and we unexpectedly found 3 reversibly excitatory-inhibitory type R-S neurons, the firing rate of inhibitory R-S neurons being higher than that of excitatory R-S neurons. The responses of the excitatory-inhibitory reversible neurons to noxious stimulation were also related to the background firing rates. The effects of electroacupuncture (EA) on the excitatory R-S neurons were mainly to increase their firing rates, and to inhibit their nociceptive responses. After the transection of DLF, the R-S neurons could still be activated by EA, but the post-inhibitory effects of EA on their nociceptive responses were obviously reduced. It is suggested that the EA can activate NRM, a supraspinal area mediating a negative feedback circuit modulating pain, thus inducing analgesia via descending inhibition.

Acupuncture Therapy↗