Biomedical subjects

Zhi-Xin Lin

Publications and source records attributed to Zhi-Xin Lin.

9 recordsLinked to original sources

PubMed2006

Human acyl-CoA:cholesterol acyltransferase 2 gene expression in intestinal Caco-2 cells and in hepatocellular carcinoma.

Humans express two ACAT (acyl-CoA:cholesterol acyltransferase) genes, ACAT1 and ACAT2. ACAT1 is ubiquitously expressed, whereas ACAT2 is primarily expressed in intestinal mucosa and plays an important role in intestinal cholesterol absorption. To investigate the molecular mechanism(s) responsible for the tissue-specific expression of ACAT2, we identified five cis-elements within the human ACAT2 promoter, four for the intestinal-specific transcription factor CDX2 (caudal type homeobox transcription factor 2), and one for the transcription factor HNF1alpha (hepatocyte nuclear factor 1alpha). Results of luciferase reporter and electrophoretic mobility shift assays show that CDX2 and HNF1alpha exert a synergistic effect, enhancing the ACAT2 promoter activity through binding to these cis-elements. In undifferentiated Caco-2 cells, the ACAT2 expression is increased when exogenous CDX2 and/or HNF1alpha are expressed by co-transfection. In differentiated Caco-2 cells, the ACAT2 expression significantly decreases when the endogenous CDX2 or HNF1alpha expression is suppressed by using RNAi (RNA interference) technology. The expression levels of CDX2, HNF1alpha, and ACAT2 are all greatly increased when the Caco-2 cells differentiate to become intestinal-like cells. These results provide a molecular mechanism for the tissue-specific expression of ACAT2 in intestine. In normal adult human liver, CDX2 expression is not detectable and the ACAT2 expression is very low. In the hepatoma cell line HepG2 the CDX2 expression is elevated, accounting for its elevated ACAT2 expression. A high percentage (seven of fourteen) of liver samples from patients affected with hepatocellular carcinoma exhibited elevated ACAT2 expression. Thus, the elevated ACAT2 expression may serve as a new biomarker for certain form(s) of hepatocellular carcinoma.

Adult↗

PubMed2006

EMMA: an efficient massive mapping algorithm using improved approximate mapping filtering.

Efficient massive mapping algorithm (EMMA), an algorithm on efficiently mapping massive cDNAs onto genomic sequences, has recently been developed. The process of mapping massive cDNAs onto genomic sequences has been improved using more approximate mapping filtering based on an enhanced suffix array coupled with a pruned fast hash table, algorithms of block alignment extensions, and k-longest paths. When compared with the classical BLAT software in this field, the computing of EMMA ranges from two to forty-one times faster under similar prediction precisions.

Algorithms↗

PubMed2005

Comparison of cytocompatibility of zein film with other biomaterials and its degradability in vitro.

UNLABELLED: Cytocompatibility of particle zein (Pzein) and film zein (Fzein) was evaluated and compared with polyhydroxybutyrate (PHB), its copolymer poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV), polylactic acid (PLA), and collagen, using HL-7702 cells, in terms of cell attachment rate within 3 h, and cell viabilities at 3 and 6 days determined by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) method. The zein degradation test was carried out using collagenase and trypsin, and the degradation product was added to the culture medium at different concentrations in order to examine the concentration-dependent cytotoxic effect. RESULT: The adhesion rate of the HL-7702 cells on both Pzein and Fzein was higher than that on collagen film. Cell viabilities were higher on both Pzein and Fzein than on films of PLA, PHB, PHBV, and collagen from fish skin. Zein can be degraded by both trypsin and collagenase, and the degradation product can enhance cell viability within a certain range of concentrations.

Animals↗

PubMed2005

Heparin-loaded zein microsphere film and hemocompatibility.

Zein was studied as a drug-eluting coating film composed of zein microspheres for cardiovascular devices (e.g. stent). In vitro 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) analysis showed that both zein film and its degraded product had better biocompatibility compared with Corning culture plate on the growth of human umbilical veins endothelial cells (HUVECs, p<0.05, n=6), and the effect of zein degraded product on HUVECs was dose-dependent. The best result was obtained at 0.3 mg/ml of the addition. The encapsulation efficiency of heparin and heparin loading varied with the amount of both zein and heparin, and the highest encapsulation efficiency (heparin 1.33 mg/ml and zein 16 mg/ml) was 22.77+/-1.33% (n=3). Scanning electron microscope (SEM) observation indicated that the zein film was made of microspheres in diameter from nano- to micrometer, which could be controlled. Sizes of heparin-loaded zein microspheres changed before and after release of heparin because of conglutination among zein microspheres. Release rate of heparin from microsphere film reached to 33.5+/-1.2% within 12 h, and began to get into subsequent "slow release" phase; about 55% of the entrapped heparin was released after 20 days. Both zein film and heparin-loaded zein microsphere film were effective in suppressing platelet adhesion, and the heparin-loaded film showed a better anticoagulation as determined with thrombin time (TT) assay. These results suggest that zein film could be used directly as a new type of coating material for its better biocompatibility with HUVECs. Moreover, the heparin-loaded zein microsphere film can significantly improve the hemocompatibility.

Anticoagulants↗

PubMed2005

Two human ACAT2 mRNA variants produced by alternative splicing and coding for novel isoenzymes.

Acyl coenzyme A:cholesterol acyltransferase 2 (ACAT2) plays an important role in cholesterol absorption. Human ACAT2 is highly expressed in small intestine and fetal liver, but its expression is greatly diminished in adult liver. The full-length human ACAT2 mRNA encodes a protein, designated ACAT2a, with 522 amino acids. We have previously reported the organization of the human ACAT2 gene and the differentiation-dependent promoter activity in intestinal Caco-2 cells. In the current work, two human ACAT2 mRNA variants produced by alternative splicing are cloned and predicted to encode two novel ACAT2 isoforms, named ACAT2b and ACAT2c, with 502 and 379 amino acids, respectively. These mRNA variants differ from ACAT2a mRNA by lack of the exon 4 (ACAT2b mRNA) and exons 4-5 plus 8-9-10 (ACAT2c mRNA). Significantly, comparable amounts of the alternatively spliced ACAT2 mRNA variants were detected by RT-PCR, and Western blot analysis confirmed the presence of their corresponding proteins in human liver and intestinecells. Furthermore, phosphorylation and enzymatic activity analyses demonstrated that the novel isoenzymes ACAT2b and ACAT2c lacked the phosphorylatable site SLLD, and their enzymatic activities reduced to 25%-35% of that of ACAT2a. These evidences indicate that alternative splicing produces two human ACAT2 mRNA variants that encode the novel ACAT2 isoenzymes. Our findings might help to understand the regulation of the ACAT2 gene expression under certain physiological and pathological conditions.

Alternative Splicing↗

PubMed2004

Identification and characterization of a rat novel gene RSEP4 expressed specifically in central nervous system.

The low-abundantly expressed genes composed the majorities of the mRNAs expressed in the central nervous system (CNS), and were thought to be important for the normal brain functions. Through differential screening a low-abundance cDNA sublibrary with mRNA from neuropathic pain of chronic constriction injury (CCI) model, we have identified a novel rat gene, rat spinal-cord expression protein 4 gene (RSEP4). The total length of RSEP4 cDNA is 2006 bp, with a 501 nucleotide open reading frame (ORF) that encodes a 167 amino acid polypeptide. Northern blot revealed that RSEP4 was expressed specifically in the CNS. In situ hybridization showed that the mRNA of RSEP4 was strongly expressed in the CA1, CA2, CA3 and DG regions of hippocampus, the Purkinje cells of cerebellum, and the small sensory neurons of dorsal horn and large motor neurons of ventral horn of spinal cord. Over-expression of RSEP4-EGFP fusion protein in the human embryonic kidney 293T cells showed that RSEP4 protein was mainly localized in the cell cytoplasm. These results suggest that RSEP4 may play some roles in the CNS.

Amino Acid Sequence↗

PubMed2003

Preparation of an anti-Cdx-2 antibody for analysis of different species Cdx-2 binding to acat2 promoter.

The homeodomain protein, Cdx-2, as transcription factor has been implicated in the transcriptional regulation of genes expressed in small intestine and the process of tumorgenesis. In current work, a conserved mouse Cdx-2 domain (mCdx-2D) coded by its cDNA fragment, which was amplified and cloned into the expression vector pGEX-4T1, was expressed as a fusion protein with GST (GST-mCd x-2D) and purified by one step of affinity chromatography. A polyclonal antibody against Cdx-2 was raised by using the recombinant fusion protein GST-mCdx-2D as antigen and was fractionated from the rabbit anti-serum. Western blot and EMSA (electrophoretic mobility shift assay) demonstrate that the natural and denatured Cdx-2s from different species (mouse and human) can be detected by the prepared anti-Cdx-2 antibody. Most notably, we found that the Cdx-2 in human intestine cell line Caco-2 is expressed in a differentiation-dependent manner and can efficiently bind to the mouse and human acat2 (acyl-coenzyme A: cholesterol acyltransferase 2) promoter regions, suggesting that the transcriptional factor Cdx-2 may play a role in regulating the acat2 expression in the intestinal cells.

Amino Acid Sequence↗

PubMed2003

[Preparation and application of gel chip].

A new method for manufacturing three-dimensional gel film-coated chips was described in this paper and its advantages were evaluated by its application. A patch of polyacrylamide gel (15mm x 15mm x 20 microm) was fixed on the glass surface with Bind-Silane treatment, then activated by glutaraldehyde. The aldehyde groups in gel provided reactive sites that allowed covalent immobilization of molecules containing amino groups. Oligonucleotides were mechanically spotted by GMS 417 Arrayer. After hybridization with Cy-3 labeled probes, fluorescence signals of perfect binding can be discriminated from mismatched ones. Compared with two-dimensional glass chip, the capacity of oligonucleotides immobilized on gel film-coated chip is over 100 times. And the gel film-coated chip have lower background and shorter hybridization time. Monoclonal antibodys of cytokine IL-4, IL-5, IL-6, IL-7, ANG, I-309 and VEGF were also immobilized on the gel film-coated chips to make protein microarrays. After incubation with serum of breast cancer patients or normal persons, the microarray reacted with biotin-labeled second antibodys of cytokines and Cy-3-labeled streptavidin sequentially. Results show IL-4, IL-5, I-309 and VEGF of patients have higher expression level than normal persons. This kind of protein microarrays can be potentially helpful to clinical diagnosis. Furthermore different oligonucleotides or proteins can be performed in parallel in a single reaction with minimal amount of binding reagents. Such gel film-coated chips can be used widely in the fabrication of oligonucleotides and proteins microarrays.

Acrylic Resins↗

PubMed2002

A cDNA clone for beta-caryophyllene synthase from Artemisia annua.

An homology-based cloning strategy yielded a full-length cDNA from Artemisia annua that encoded a protein of 60.3 kDa which resembled a sesquiterpene synthase in sequence. Heterologous expression of the gene in Escherichia coli provided a soluble recombinant enzyme capable of catalyzing the divalent metal ion-dependent conversion of farnesyl diphosphate to beta-caryophyllene, a sesquiterpene olefin found in the essential oil of A. annua. In reaction parameters and kinetic properties, beta-caryophyllene synthase resembles other sesquiterpene synthases of angiosperms. The beta-caryophyllene synthase gene is expressed in most plant tissues during early development, and is induced in mature tissue in response to fungal elicitor thus suggesting a role for beta-caryophyllene in plant defense.

Artemisia annua↗