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Lei Liu

Publications and source records attributed to Lei Liu.

At least 55 records · Page 3Linked to original sources
PubMed2006

Tunable single-walled carbon nanotube microstructure in the liquid and solid states using poly(acrylic acid).

Poly(acrylic acid) is shown to control the level of SWNT dispersion in aqueous mixtures and the state of dispersion in a solid composite. At low pH, PAA-stabilized suspensions containing 0.1 wt % SWNT have a waterlike viscosity, but this mixture thickens as the pH is raised. This behavior is reversed when pH is again lowered. Changing pH varies the SWNT microstructure between aggregated and well-exfoliated states, as evidenced by electron microscopy and electrical conductivity measurements.

Acrylic Resins↗
PubMed2006

Two-stage fuzzy-stochastic robust programming: a hybrid model for regional air quality management.

In this study, a hybrid two-stage fuzzy-stochastic robust programming (TFSRP) model is developed and applied to the planning of an air-quality management system. As an extension of existing fuzzy-robust programming and two-stage stochastic programming methods, the TFSRP can explicitly address complexities and uncertainties of the study system without unrealistic simplifications. Uncertain parameters can be expressed as probability density and/or fuzzy membership functions, such that robustness of the optimization efforts can be enhanced. Moreover, economic penalties as corrective measures against any infeasibilities arising from the uncertainties are taken into account. This method can, thus, provide a linkage to predefined policies determined by authorities that have to be respected when a modeling effort is undertaken. In its solution algorithm, the fuzzy decision space can be delimited through specification of the uncertainties using dimensional enlargement of the original fuzzy constraints. The developed model is applied to a case study of regional air quality management. The results indicate that reasonable solutions have been obtained. The solutions can be used for further generating pollution-mitigation alternatives with minimized system costs and for providing a more solid support for sound environmental decisions.

Air Pollutants, Occupational↗
PubMed2006

Proliferation and pluripotency potential of ectomesenchymal cells derived from first branchial arch.

Cranial neural crest-derived ectomesenchymal cells are multipotential progenitors that contribute to various tissue types during embryogenesis. Their potential to be expanded in culture as a monolayer and to be induced into different cell lineages in vitro has not been previously reported in detail. In this study, the ectomesenchymal cells in the first branchial arch were enzymatically isolated from the mandibular processes of BALB/c mice and were maintained in an intact state in a medium containing leukaemia inhibitory factor. Here, we first evaluated the proliferative activity of the cells after the third passage, using bromodeoxyuridine labelling and in situ hybridization of telomerase mRNA. Positive staining for expression of HNK-1, S-100 and vimentin confirmed that the population of stem cells originated from the ectomesenchyme, which did not express cytokeratin. Then we investigated the molecular and cellular characteristics of the ectomesenchymal cells during their differentiation towards neurogenic, endothelial, myogenic and odontogenic lineages. Expression of multiple lineage-specific genes and proteins was detected by utilizing a range of molecular and biochemical approaches when the cells were transferred to inductive medium. Histological and immunohistochemical analysis of the induced cells at various intervals indicated obvious phenotypic alteration and presence of specific proteins for the differentiated lineages, for example nestin, factor VIII, alpha-SMA and dentin sialophosphoprotein (DSPP), respectively. Correlatively, results of reverse transcription-PCR corroborated at mRNA level the expression of the characteristic molecules during differentiation. Therefore, it is suggested that the ectomesenchymal cells derived from the first branchial arch may represent a novel source of multipotential stem cells capable of undergoing expansion and variant differentiation in vitro.

Animals↗
PubMed2006

Comparisons of graph-structure clustering methods for gene expression data.

Although many numerical clustering algorithms have been applied to gene expression data analysis, the essential step is still biological interpretation by manual inspection. The correlation between genetic co-regulation and affiliation to a common biological process is what biologists expect. Here, we introduce some clustering algorithms that are based on graph structure constituted by biological knowledge. After applying a widely used dataset, we compared the result clusters of two of these algorithms in terms of the homogeneity of clusters and coherence of annotation and matching ratio. The results show that the clusters of knowledge-guided analysis are the kernel parts of the clusters of Gene Ontology (GO)-Cluster software, which contains the genes that are most expression correlative and most consistent with biological functions. Moreover, knowledge-guided analysis seems much more applicable than GO-Cluster in a larger dataset.

Algorithms↗
PubMed2006

Expression of basic fibroblast growth factor results in the decrease of myostatin mRNA in murine C2C12 myoblasts.

During the development and regeneration of skeletal muscle, many growth factors, such as basic fibroblast growth factor (bFGF, FGF-2) and myostatin, have been shown to play regulating roles. bFGF contributes to promote proliferation and to inhibit differentiation of skeletal muscle, whereas myostatin plays a series of contrasting roles. In order to elucidate whether the expression of bFGF has any relationship with the expression of myostatin in skeletal muscle cells, we constructed a eukaryotic expression vector for the expression of exogenous bFGF in murine C2C12 myoblasts. Quantitative RT-PCR assays indicated that with the increase of the expression of exogenous bFGF gene, the expression of endogenous myostatin gene was suppressed at mRNA level and protein level.

Animals↗
PubMed2006

Characterization of ectomesenchymal cells isolated from the first branchial arch during multilineage differentiation.

Ectomesenchymal cells isolated from the first branchial arch have the potential to differentiate into a variety of cell lineages both in vitro and in vivo. This study was aimed to confirm the plasticity of multilineage differentiation with molecular and cellular characterization. Monolayer cultures of ectomesenchymal cells harvested from the first branchial arch primordia in embryonic day 9.5 BALB/c mice were passaged 3 times before analysis. Staining with antibodies against S-100, p75 and vimentin suggested that the population of stem cells originated from ectomesenchyme, with few contaminating cells stained for cytokeratin. Then, cells were transferred to adipogenic, osteogenic, chondrogenic and odontogenic media. The initiation of controlled differentiation was determined with histological assays, and the expression of tissue-specific genes was detected using immunocytochemical staining and reverse transcription polymerase chain reaction. The adipogenic ectomesenchymal cells showed accumulation of lipid vacuoles and expression of lipoprotein lipase and peroxisome proliferator-activated receptor gamma(2). Following osteoinduction, the fibroblast-like cells became cuboidal and formed mineralized nodules. In addition, the expression of mRNA encoding osteocalcin and osteopontin proved osteogenesis at the molecular level. Chondrogenic lineage expressed collagen type II, aggrecan and Sox9 with a low level of collagen type I in monolayer culture. Odontogenesis was determined by dentin sialophosphoprotein, collagen type I and dentin matrix protein 1 expression. Therefore, we have demonstrated that ectomesenchymal cells from the first branchial arch are capable of extensive multilineage differentiation in vitro, controllable by the culture environment. This makes them a relevant and valuable source of stem cells for research of craniofacial development and tissue engineering of restoration.

Animals↗
PubMed2006

Corneal epitheliotrophic capacity of three different blood-derived preparations.

PURPOSE: Serum eye drops have been successfully used in the treatment of severe ocular surface disorders. Fresh frozen plasma (FFP) and platelet concentrates have not yet been tested for use as eye drops, although they are easily available as quality-controlled products from blood banks and are routinely used for transfusion. To test whether FFP or platelet-derived growth factor solutions could be used for ocular surface diseases, we compared the epitheliotrophic capacity of platelet releasate and FFP with that of serum in cell culture models. METHODS: The concentrations of EGF, TGF-beta1, PDGF-AB, fibronectin, vitamin A and vitamin E in serum, FFP, and platelet releasate were evaluated with ELISA and HPLC. Corneal epithelial cells were incubated with the various preparations and cell proliferation, migration, and differentiation were evaluated by means of a luminescence-based adenosine triphosphate (ATP) assay, a colony dispersion assay, and scanning electron microscopy. RESULTS: Growth factor concentrations were significantly higher in platelet releasate than in serum and were lowest in FFP. Fibronectin and vitamins were found in higher concentrations in serum than in FFP and were lowest in platelet releasate. Cell proliferation was best supported by platelet releasate followed by serum and FFP; however, cell migration and differentiation were better supported by serum than by platelet releasate and FFP. The reduced nutrient capacity of FFP was in part found to be due to an antiproliferative effect of citrate used as an anticoagulant in the production process. CONCLUSIONS: Platelet releasate but not FFP may offer additional potential for the treatment of severe ocular surface disease. Platelet releasate may be suitable as a novel treatment option for ocular surface disease with a superior effect on cell growth.

Animals↗
PubMed2006

Development and characterization of a normalized canine retinal cDNA library for genomic and expression studies.

PURPOSE: Identification of causative mutations for retinal blinding disorders is often limited by restricted understanding of gene expression and underlying molecular mechanisms that trigger degenerative processes. This study was conducted to develop a catalog of canine retina-expressed genes that would provide a unique tool to investigate normal and altered function in the adult retina. Because of the conserved syntenies between the dog and human, this approach would identify new potential disease candidate genes for both species. METHODS: A canine normalized retinal cDNA library was produced and analyzed by using a modified PhredPhrap algorithm. Computerized annotation provided gene homology and chromosomal location for individual clones and contigs in a Web-accessible database. RESULTS: From 6316 cDNA clones, 3980 retinal expressed sequence tags (ESTs) were derived. Homology to the canine genome draft sequence was found for more than 99% of all ESTs, but only for 32% when compared with annotated canine cDNAs. Functional analysis suggests an enrichment of this library for genes involved with eye function and development, chaperone, or ribosomal functions when compared with mouse and human National Center for Biotechnology Information (NCBI) RefSeq entries. CONCLUSIONS: A combination of annotation approaches with ongoing mapping and expression studies provide functional data covering at least 27% to 30% of the currently proposed canine catalog of genes expressed in the retina. This is an essential first step toward establishing an integrated network for gene identification and expression patterns suitable for functional genetics, comparative genomics and evolutionary analysis of genes and gene families with respect to the developmental and degenerative processes of the retina.

Animals↗
PubMed2006

[Identification of three novel mutations of IRF6 in Chinese families with Van der Woude syndrome].

OBJECTIVE: To identify mutations of interferon regulatory factor 6 (IRF6) gene in Van der Woude syndrome (VWS) patients in China. METHODS: Three Chinese VWS families were screened to IRF6 gene mutation via PCR and sequence techniques. After amplification of exons 1-8 and their flanking splice junctions and part of exon 9 of the IRF6 gene by polymerase chain reaction, mutations were detected by direct sequencing. RESULTS: Three novel mutations, one in each family, were identified in all the affected members in the three families. There were one missense mutation 1214 (T-->C) in exon 9, two nonsense mutations 981 (T-->A) in exon 7 and 1234 (C-->T) in exon 9. All affected members of the three families were heterozygous for their respective mutation. CONCLUSION: Mutations in IRF6 gene were found in all VWS patients. This observation supports the hypothesis that IRF6 is the gene responsible for VWS across different populations.

Asian People↗
PubMed2006

[Clinicopathologic studies of 11 cases of primary cardiac valve tumors].

OBJECTIVE: To study the clinicopathologic features of primary cardiac valve tumors. METHODS: Eleven cases of primary valve tumors collected from Fuwai Hospital during the period from 1983 to 2005 were enrolled into the study. The tumors were stained with hematoxylin and eosin and Weigert-Van Gieson stain. Immunohistochemistry was also carried out in selected examples. RESULTS: Primary cardiac valve tumors were uncommon and accounted for only 3% (11/426) of all primary cardiac tumors. Most of them (10/11) were benign and malignancy was rarely encountered (1/11). The tumor subtypes included papillary fibroelastoma (4/11), cavernous hemangioma (4/11), glomus tumor (1/11), angiosarcoma (1/11) and hamartoma (1/11). Of the 11 tumors studied, 4 involved the tricuspid valve, 4 involved the mitral valve, 2 involved the pulmonary valve and 1 involved the aortic valve. The diagnosis was established by preoperative echocardiography in 7 patients. The remaining 4 cases were either misdiagnosed or undiagnosed. CONCLUSIONS: Preoperative diagnosis of primary cardiac valve tumors can be difficult due to lack of detailed information related to this group of lesions. Although benign cardiac valve tumors carry a good prognosis, the clinical outcome may be disastrous as a result of hemodynamic disturbances. Intraoperative frozen section examination is advisable for guiding proper surgical management.

Adolescent↗
PubMed2006

Study of biological safety of scaffold material with heterologous deproteinized bone.

OBJECTIVE: To evaluate the biological safety of manufactured heterologous deproteinized bone and to provide an experimental basis for clinical applications. METHODS: Deproteinized bone (10 mm) and leaching liquor were made from pig ribs with a series of physical and chemical methods, then were evaluated through acute and subacute toxicity test, hemolysis test, pyrogen test, intracutaneous test, intramuscular implantation test and cytotoxity test. RESULTS: No obvious toxicity, hemolysis, pyrogenic characteristics, skin irritation, inflammatory reaction after intramuscular implantation and cytotoxity were observed. CONCLUSIONS: The heterologous deproteinized bone has good biological safety and meets all the demands of scaffold material for tissue engineering.

Animals↗
PubMed2006

[Management of nutritional support and stress hyperglycemia after orthotopic liver transplantation].

OBJECTIVE: To study the influence of different nutritional regimes on the stress hyperglycemia and the outcome after orthotopic liver transplantation, for the purpose of optimizing nutritional regime for early post-operative period. METHODS: One hundred and seventy-two patients who received liver transplantation for chronic hepatitis B virus (HBV) or hepatitis C virus (HCV) induced hepatic function failure or end-stage cirrhosis were enrolled, and the post-operative complications and length of stay in intensive care unit (ICU) were retrospectively analyzed, in regard to high caloric (HC) or low caloric (LC) nutritional regime with their blood glucose controlled to a optimal level. RESULTS: After the liver transplantation, those patients who were supplied with LC (83.7-104.6 kJ.kg(-1).d(-1)), energized stepwise with higher fat ratio (sugar:fat=50%:35%) with blood glucose being maintained <8 mmol/L, had less exogenous insulin requirement (P<0.01), lower infection-related mortality rate (P<0.05), and shortened weaning from mechanical ventilation time and length of stay in ICU (both P<0.05), compared with those who were supplied with HC nutrition (125.5-146.4 kJ.kg(-1).d(-1)) with routine sugar and fat ratio (55%:35%), and blood glucose maintained at the same level. However, there was no significant differences in serum bilirubin contents, incidences of poor healing of incision and anastomosis as well as hypoglycemia, and extrinsic albumin requirement between two groups. CONCLUSION: LC nutrition regime and controlling the blood glucose <8 mmol/L during the early post-operative period may reduce the incidence of post-operative complications without influencing the prognosis.

Adult↗
PubMed2006

[An experimental study on rat bone marrow mesenchymal stem cells transfected with dentin sialophosphoprotein gene in vitro].

OBJECTIVE: To evaluate the expression of dentin sialophosphoprotein (DSPP) in transfected rat bone marrow mesenchymal stem cells (BM-MSC) and the influence of the transfection. METHODS: Plasmid containing mice dentin DSPP was constructed by using the cytomegalovirus (CMV) promoter and then transfected the cultured BM-MSC by lipofectamine; The expression of Pax-9 and dentin matrix protein 1 (DMP1) gene of transfected BM-MSC were detected by RT-PCR. The expression of DSPP was examined by immunocytochemical staining, and the formation ratio of mineralized nodules of transfected BM-MSC was compared with untransfected ones after mineralized induction. RESULTS: The constructed pcDNA3.1(+)/mDSPP could produced 3.0 kb and 5.4 kb fragments, DSPP gene and Pax9 gene were expressed 24 h and 48 h respectively, after BM-MSC were transfected Pax-9 gene was exprssed, but DMP1 gene was not; Immunohistochemical staining showed that DSPP was positive in transfected BM-MSC; The formation ratio of mineralized nodules of transfected BM-MSC was higher than that of untransfected ones after mineralized induction. CONCLUSIONS: The expression of mice DSPP in BM-MSC by gene transfection can induce the expression of tooth development-associated gene Pax9 and enhance the formation of mineralized nodules, which suggests that DSPP gene might induce odontogenic differentiation of BM-MSC.

Animals↗
PubMed2006

[Anatomical and water physiological plasticity of Grewia biloba var. parviflora leaf and secondary xylem].

Based on the anatomical observations of leaf and secondary xylem as well as the measurements of leaf water physiological parameters, this paper studied the anatomical and water physiological plasticity of Grewia biloba var. parviflora growing in different succession stage communities. The results showed that G. biloba var. parviflora leaf was characterized by thin bifacial with thin cuticle and few stoma, indicating that it was mesophyte anatomically, while the secondary xylem had typical xeromorphic traits, such as short and thin vessel, high vessel frequency, low percentage single pores, and short fibers and rays. G. biloba var. parviflora had high plasticity in the anatomical structure and water physiological features of leaf and secondary xylem, and the plasticity index was in the order of secondary xylem anatomical structure (0. 24) > water physiological traits (0. 19) > leaf anatomical structure (0. 18). Compared with those growing in mixed forest and Platycladus orientalis forest, the individuals of G. biloba var. parviflora in shrub communities had the xeromorphic traits in the aspects of (1) their secondary xylem had shorter vessel elements, higher vessel frequency, less single porous percentage, lower rays, higher relative conductivity and lower vulnerability index, and (2) their leaf had lower water potential, lower water content and free water content, higher bound water content, high ratio of bound to free water content, and less specific leaf area. The phenotypic plasticity, both anatomical and physiological, made G. biloba var. parviflora tolerate to the drought at earlier succession stages and better adapt to the mesophytic condition at later stages, and consequently, become a widely distributed and dominant species in mixed forests.

Adaptation, Physiological↗
PubMed2006

[The clinicopathological endomyocardial biopsy analysis in cardiac transplant recipients due to end-stage heart failure].

OBJECTIVE: Endomyocardial biopsies from 42 (35 males and 7 females, aged 43.3 years) heart transplant recipients due to end-stage heart failure between June 2004 and January 2006 in our institute were obtained for pathological studies. METHODS: Sixteen patients underwent 1 endomyocardial biopsy (right ventricular septum) between 13 days to 5 months, 13 patients underwent second biopsy between 1.5 to 8 months and 10 patients underwent third biopsy between 3 to 8.5 months post transplantation. Specimen were stained by hematoxylin-eosin (HE) and Phosphotungstic Acid Hematoxylin (PTAH) and observed under light microscope and cardiac allograft rejection were evaluated according to the Revision of the 1990 working formulation for the standardization of nomenclature in the diagnosis of heart rejection in 2004. RESULTS: The rejection grades were as follows: Grade 0 R in 31 biopsies; Grade 1 R (mild rejection 1990 grade 1A, 1B and 2.) in 30 biopsies; Grade 2 R (moderate rejection, 1990 grade 3A) in 3 biopsies; Grade 1 R cellular rejection companies with humoral rejection in 1 biopsy. Cellular rejection with Quilty effect was found in 2 biopsies. Ischemic myocardial injury presented in 4 biopsies. Quilty effect was observed in 1 biopsy. Cytomegalovirus or toxoplasmic myocarditis was not observed. CONCLUSIONS: Endomyocardial biopsy (EMB) is a valuable diagnostic procedure for rejection surveillance in heart allograft recipients. The observed low rejection incidence and mild rejection from specimens of our heart recipients were comparable to the results of developed countries.

Adolescent↗
PubMed2005

Advances in glycoprotein synthesis.

The development of chemical and enzymatic methods for the synthesis of homogeneous glycoproteins is a fascinating challenge at the interface between chemistry and biology. Discussed here are the currently available methods for preparation of homogeneous glycoproteins. These methods include (1) glycopeptide ligation; (2) glycoprotein remodeling; and (3) in vivo suppressor tRNA technology.

Carbohydrate Conformation↗
PubMed2005

Rapid inhibitory effect of glucocorticoids on airway smooth muscle contractions in guinea pigs.

The common disease asthma is characterized by the obstruction, inflammation and increased sensitivity of the airways. Glucocorticoids (GCs) are one of the most potent anti-inflammatory agents available for treating allergic disease. In this study, we report that the GC budesonide (BUD) can rapidly inhibit the histamine-induced contractions of airway smooth muscle in a process mediated by non-genomic mechanisms. The tracheas of albino Hartley guinea pigs were used. We measured the effects of BUD on the increased isometric tension of trachea segment rings and the shrinking of single airway smooth muscle cells (ASMCs) induced by histamine. With the application of each reagent, the changes in the isometric tension of the segment rings upon maximum contraction and at four time points were recorded. We found that BUD significantly suppressed the increase in isometric tension induced by histamine in guinea pigs within 15 min. We also observed that BUD can reduce the histamine-induced shrinking of single ASMCs in an even shorter time. Mifepristone (RU486) and actidione did not depress the inhibitory effect of BUD. The results preclude action via genomic-mediated responses that usually take several hours to occur. We conclude therefore that GCs have a rapid non-genomic inhibitory effect on guinea pig airway smooth muscle contractions, and provide a new way to investigate this non-genomic mechanism. Further study can provide theoretical evidence for the clinical application of GCs in asthma and other allergic diseases.

Animals↗