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Biomedical subjects

Xin Li

Publications and source records attributed to Xin Li.

At least 253 records · Page 14Linked to original sources
PubMed2004

[mRNA expression of activin a and follistatin in rabbit mandibular distraction osteogenesis].

OBJECTIVE: To examine the mRNA expression of activin A(ACT A) and follistatin(FS) during mandibular lengthening and to elucidate the regulating pattern of during mandibular distraction osteogenesis. METHODS: Skeletally mature white New Zealand rabbits were established right mandibular distraction osteogenesis models and the mandibles were lengthened 7 days after osteomy. At the end of latency period and the end of distraction period, 10, 20, 30, 40 and 60 days after fixation, the regenerating tissue of animals' lengthened mandibles and that of the other side normal mandibles were harvested to extract RNA and to analyse ACT A, FS mRNA by RT-PCR. RESULTS: The expression of ACT A mRNA was not detectable in normal bone tissue and ACT A mRNA began to express at the end of latency period. The expression of ACT A mRNA increased gradually along with the beginning of distraction and reached the peak on the 10th and 20th days of distraction which was 5.04 and 4.98 times as much as that of the end of latency period, respectively. The trend of expression of FS mRNA during mandibular distraction osteogenesis was the same as expression of ACT A mRNA. CONCLUSION: ACT A/FS play an important role during rabbit mandibular distraction osteogenesis. To examine the mRNA expression of activin A(ACT A) and follistatin(FS) during mandibular lengthening and to elucidate the regulating pattern of during mandibular distraction osteogenesis.

Activins↗
PubMed2004

[Establishment and evaluation of the method for removing albumin and IgG in serum proteomics].

OBJECTIVE: To establish and evaluate the method for removing albumin and IgG in serum proteomics. METHODS: Elimination of serum albumin and IgG was achieved by filtering with Micro Bio-Spin column and the efficiency of purification evaluated by two-dimensional polyacrylamide gel electrophoresis (2-DE). RESULTS: The method for removing serum albumin and IgG was established, which enabled visualization of low-abundance proteins better in 2-DE map. CONCLUSION: The established method for purifying serum proteins can be effectively applied in serum proteomic study of diseases.

Blood Protein Electrophoresis↗
PubMed2004

cDNA cloning, gene organization and expression analysis of human peptidylarginine deiminase type VI.

Peptidylarginine deiminase (PAD) catalyzes the post-translational modification of protein through the conversion of arginine to citrulline in the presence of calcium ions. Human, similar to rodents, has four isoforms of PAD (type I, II, III and IV/V), each of which is distinct in substrate specificity and tissue specific expression. In our large-scale sequencing project, we identified a new human PAD cDNA from a human fetal brain cDNA library. The putative protein encoded by this cDNA is designated hPADVI. Expression analysis of hPADVI showed that it is mainly expressed in adult human ovary and peripheral blood leukocytes. We conclude that hPADVI may be orthologous to mouse ePAD, basing on sequence comparison, chromosome localization and exon-intron structure analysis. PAD-mediated deimination of epithelial cell keratin resulting in cytoskeletal remodeling suggests a possible role for hPADVI in cytoskeletal reorganization in the egg and in early embryo development. This study describes a new important member of the human PAD family.

Amino Acid Sequence↗
PubMed2004

[Genetic analysis of cultivated ginseng population with the assistance of RAPD technology].

OBJECTIVE: To provide reference for breeding of cultivated ginseng by researching the genetic diversities among different strains. METHOD: To make up the systematic diagram of genetic relationship by calculating the proximity coefficient with SPSS 10.0 software and clustered by between-groups linkage method. RESULT: The selected 18 random primers used in PCR amplification to produce 145 bands in 17 samples, among which 53 bands (36.5%) are polymorphic. The results of cluster analysis show that the genetic relationship between different strains of Da-maya is closer than that of Er-maya, which proves that it is feasible to differentiate the cultivated groups in molecular level on outside character. CONCLUSION: RAPD is a favorable molecular marker to assist ginseng breeding.

Cluster Analysis↗
PubMed2004

[The experimental study of the effect of tanshinone on artery restenosis in mouse].

OBJECTIVE: To observe the preventive and therapeutic effect of tanshinone (TA) on artery restenosis in mice and primarily explore the mechanism. METHOD: Female KM mice were randomly divided into model control, low dose and high dose TA groups. Each group had 12 mice. The low and high dose drug groups were respectively given TA 3 and 6 g x kg(-1) x d(-1) by ig; the model control group was given the same volume solvent. The controlateral carotid of ligated artery of model control group was regarded as normal control. 2 days later, the mice' s left common carotid artery was dissected and ligated near the carotid bifurcation, leading to intima hyperplasia and then establishing restenosis model. 4 weeks later, the artery was harvested and stained by hematoxylin-elsin (HE) and immunohistochemistry of PCNA. The morphological changes were checked under microscope; the area of the intimal and medial layer of the vessels, and their ratios were analyzed with image analysis software. The expression level of PCNA was expressed as the positive index. RESULT: Compared with those of normal artery, the intimal area, media area and intima-to-media ratio of ligated artery increased obviously (P < 0.01). But TA could significantly decrease all of these parameters (P < 0.01), and also decrease the positive index of PCNA (P < 0.01). CONCLUSION: TA effectively inhibits intima hyperplasia, which is mainly characterized with the proliferation and migration of smooth muscle cell induced by abnormal hemodynamic changes. This result suggestes that TA may play a positive role in the prevention of restenosis after PTCA.

Abietanes↗
PubMed2004

[Synthetical evaluation of promoting effect of some kinds of transdermal enhancers with grey relational cluster method].

OBJECTIVE: Synthetical evaluation of promoting effect of some kinds of transdermal enhancers was carried through. METHOD: Diclofenac sodium was used as model, and azone and l-menthol and synthetic borneol and olieic acid and essential oil from Cnidium monnieri were used as transdermal enhancers. Transdermal absorption experimentation of diclofenac sodium on the device of penetrating skins in vitro was done. Cumulation of permeation amount and penetrating rates and steady fluxes and lag times were observed, and grey relational cluster method was used to evaluate the promoting effect of some kinds of transdermal enhancers. RESULT: As for promoting effect on diclofenac sodium, azone and l-menthol were the best, and synthetic borneol and olieic acid ranked behind. CONCLUSION: Grey relational cluster method can evaluate promoting effect objectively and fairly.

Administration, Cutaneous↗
PubMed2004

[Cross-linked beta-cyclodextrin polymer used for bilirubin removal].

A new material for adsorption of bilirubin was synthesized with cross-linking reaction of beta-cyclodextrin. The kinetic adsorption behaviors of bilirubin such as the effects of temperature, pH, the initial bilirubin concentration as well as bovine seum albumin on the removal of bilirubin have been investigated. It is demonstrated that bilirubin could be adsorbed well on the prepared sorbent quickly and higher temperature favored the adsorpion of bilirubin. The percentage of removal of bilirubin reached 92.6% with initial bilirubin concentration of 40 mg/L in phosphate buffer at pH 7.8. With the increase of initial bilirubin concentration, the percentage of removal of bilirubin decreased; however, the adsorption capacity increased.

Adsorption↗
PubMed2003

Changes in susceptibility to posaconazole in clinical isolates of Candida albicans.

OBJECTIVES: To characterize the molecular mechanisms responsible for reduced susceptibility to azoles in Candida albicans clinical isolates. MATERIALS AND METHODS: Seven sequential C. albicans isolates were cultured from an AIDS patient treated with posaconazole for refractory oropharyngeal candidiasis. Expression levels of the CDR1, CDR2 and MDR1 genes, encoding efflux pumps previously implicated in azole resistance, and ERG11, encoding the azole target site, were monitored using northern blot and real-time PCR. The ERG11 genes from all seven isolates were sequenced. RESULTS: The seven closely related isolates exhibited significant decreases in susceptibility to fluconazole (MIC >or= 32 mg/L) and voriconazole (MIC >or= 2 mg/L) and progressive decreases in susceptibility to both posaconazole (isolates 1-4 MIC 0.25 mg/L, isolates 5-7 MIC 2 mg/L) and itraconazole (isolates 1-4 MIC 1 mg/L, isolates 5-7 MIC > 8 mg/L). None of the isolates exhibited any significant changes in the expression levels of ERG11 or the efflux pump genes. All seven isolates had multiple mutations in ERG11; isolates one through four each had five missense mutations; four of the resultant amino acid changes were previously associated with azole resistance. The fifth isolate had an additional novel mutation in one copy of ERG11, resulting in a Pro-230 to Leu substitution. This mutation was present in both ERG11 genes in the last two isolates. Select ERG11 genes were expressed in Saccharomyces cerevisiae, the ERG11 allele with all six mutations conferred the highest level of posaconazole resistance. CONCLUSIONS: Multiple mutations in ERG11 are required to confer decreased susceptibility to posaconazole.

AIDS-Related Opportunistic Infections↗
PubMed2003

Knockout analysis of Arabidopsis transcription factors TGA2, TGA5, and TGA6 reveals their redundant and essential roles in systemic acquired resistance.

Arabidopsis nonexpresser of pathogenesis-related (PR) genes (NPR1) is the sole positive regulator that has been shown to be essential for the induction of systemic acquired resistance. In npr1 mutant plants, salicylic acid (SA)-mediated PR gene expression and pathogen resistance are abolished completely. NPR1 has been shown to interact with three closely related TGA transcription factors-TGA2, TGA5, and TGA6-in yeast two-hybrid assays. To elucidate the biological functions of these three TGA transcription factors, we analyzed single and combined deletion knockout mutants of TGA2, TGA5, and TGA6 for SA-induced PR gene expression and pathogen resistance. Induction of PR gene expression and pathogen resistance by the SA analog 2,6-dichloroisonicotinic acid (INA) was blocked in tga6-1 tga2-1 tga5-1 but not in tga6-1 or tga2-1 tga5-1 plants. Loss of INA-induced resistance to Peronospora parasitica Noco2 cosegregated with the tga6-1 mutation in progeny of multiple lines that were heterozygous for tga6-1 and homozygous for tga2-1 tga5-1 and could be complemented by genomic clones of wild-type TGA2 or TGA5, indicating that TGA2, TGA5, and TGA6 encode redundant and essential functions in the positive regulation of systemic acquired resistance. In addition, tga6-1 tga2-1 tga5-1 plants had reduced tolerance to high levels of SA and accumulated higher basal levels of PR-1 under noninducing conditions, suggesting that these TGA factors also are important for SA tolerance and the negative regulation of the basal expression of PR-1.

Arabidopsis↗
PubMed2003

A gain-of-function mutation in a plant disease resistance gene leads to constitutive activation of downstream signal transduction pathways in suppressor of npr1-1, constitutive 1.

Plants have evolved sophisticated defense mechanisms against pathogen infections, during which resistance (R) genes play central roles in recognizing pathogens and initiating defense cascades. Most of the cloned R genes share two common domains: the central domain, which encodes a nucleotide binding adaptor shared by APAF-1, certain R proteins, and CED-4 (NB-ARC), plus a C-terminal region that encodes Leu-rich repeats (LRR). In Arabidopsis, a dominant mutant, suppressor of npr1-1, constitutive 1 (snc1), was identified previously that constitutively expresses pathogenesis-related (PR) genes and resistance against both Pseudomonas syringae pv maculicola ES4326 and Peronospora parasitica Noco2. The snc1 mutation was mapped to the RPP4 cluster. In snc1, one of the TIR-NB-LRR-type R genes contains a point mutation that results in a single amino acid change from Glu to Lys in the region between NB-ARC and LRR. Deletions of this R gene in snc1 reverted the plants to wild-type morphology and completely abolished constitutive PR gene expression and disease resistance. The constitutive activation of the defense responses was not the result of the overexpression of the R gene, because its expression level was not altered in snc1. Our data suggest that the point mutation in snc1 renders the R gene constitutively active without interaction with pathogens. To analyze signal transduction pathways downstream of snc1, epistasis analyses between snc1 and pad4-1 or eds5-3 were performed. Although the resistance signaling in snc1 was fully dependent on PAD4, it was only partially affected by blocking salicylic acid (SA) synthesis, suggesting that snc1 activates both SA-dependent and SA-independent resistance pathways.

Amino Acid Sequence↗
PubMed2003

[The significance of activation-induced cell death (AICD) in pathogenesis of hepatitis B].

OBJECTIVE: To explore the significance of activation-induced cell death (AICD) in pathogenesis of hepatitis B. METHODS: Peripheral blood mononuclear cells (PBMCs) were isolated from 10 healthy blood donors. PBMCs from one person were divided into two samples. One sample was incubated with the HBV-DNA positive serum. The other was incubated with the serum of healthy person (HBV-DNA negative serum). After 72 hours incubation, the apoptosis of the PBMCs was assayed by the method of propidium iodide (PI) staining with flow cytometry. PBMCs were isolated from 14 patients with chronic hepatitis B, 6 patients with chronic severe hepatitis B and 10 healthy blood donors. The PBMCs were incubated with PHA-P. After 72 hours incubation, the apoptosis of the PBMCs was assayed by the method of PI staining with flow cytometry. RESULTS: The apoptotic rate of PBMCs incubated with HBV-positive serum was significantly higher than that with the serum of normal persons [(39.56 +/- 7.03)% vs (27.57 +/- 7.78)%, P < 0.02]. The apoptotic rate of PBMCs of patients with chronic hepatitis B (30.57 +/- 13.43%) was significantly higher than that of healthy blood donors [(11.45 +/- 5.27)%, P < 0.01] and higher than that of the patients with chronic severe hepatitis B [(13.59 +/- 6.44)%, P < 0.01]. CONCLUSION: HBV infection induces apoptosis of PBMC. AICD may be one of the important mechanisms of peripheral immune tolerance in HBV chronic infection.

Adult↗
PubMed2003

A novel anthracenyl tagged protecting group for "phase-switching" applications in parallel synthesis.

A new "phase-switching" protecting group 1 that facilitates the parallel synthesis of carboxylic acids, esters, and carboxamides is described. Its use permits chemistries to be performed in solution, which may be conveniently monitored with conventional analytical techniques, followed by subsequent immobilization onto a solid-phase support to aid compound purification. Carboxylic acids, esters, and carboxamides are then cleaved from the solid support following activation of the "safety-catch" and treatment with the desired nucleophile.

Journal Article↗
PubMed2003

Immunofluorescence assay and flow-cytometry selection of bead-bound aptamers.

An immunofluorescence assay was developed to identify proteins specifically binding to oligonucleoside phosphorodithioate (ODN) aptamers from a bead-bound ODN library. Accordingly, NF-kappaB p50 protein was incubated with either bead-bound NF-kappaB consensus sequence or a bead-bound ODN combinatorial library and adsorption was then assessed using a specific primary antibody and a secondary antibody conjugated with Alexa 488 fluorescent dye. This assay avoids any problems related to fluorescently labeling target proteins. The method is straightforward and readily applicable to other transcription factors and proteins, and the feasibility of its application for high-throughput screening of large aptamer bead-based libraries by flow cytometry is demonstrated.

Binding, Competitive↗
PubMed2003

Gene expression profiles and transcription factors involved in parathyroid hormone signaling in osteoblasts revealed by microarray and bioinformatics.

Parathyroid hormone (PTH) binds to its receptor PTH1R (parathyroid hormone 1 receptor) in osteoblastic cells to regulate bone remodeling and calcium homeostasis. While prolonged exposure to PTH causes increased bone resorption, intermittent injections of PTH have an anabolic effect on bone. The molecular mechanisms regulating these processes are still largely unknown. Here, we present our results on gene expression profile changes in the PTH-treated osteoblastic cell line, UMR 106-01, using DNA microarray analysis. A total of 125 known genes and 30 unknown expressed sequence tags (ESTs) were found to have at least 2-fold expression changes after PTH treatment at 4, 12, and 24 h. 14 genes were previously known to be PTH-regulated but many were unknown to be regulated by PTH prior to our experiments. Real-time reverse transcriptase-PCR confirmed that 90 and 50% of the genes are regulated more than 2-fold by PTH in UMR 106-01 and rat primary osteoblastic cells, respectively. Most genes belong to the following protein families: hormones, growth factors, and receptors; signal transduction pathway proteins; transcription factors; proteases; metabolic enzymes; structural and matrix proteins; transporters; etc. These results provide a comprehensive and deeper knowledge about PTH regulation of osteoblastic gene expression. Next, we designed a computational method to extract information about transcription factors likely involved in regulating these genes. These factors include those previously known to be involved in PTH signaling (AP-1 and the cAMP response element-binding protein), those that were identified by microarray data (C/EBP), and some novel transcription factors (AP-2, AP-4, SP1, FoxD3, etc.). Our results suggest that a reliable bioinformatics approach can be easily applied for other systems.

Animals↗