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Biomedical subjects

J Liu

Publications and source records attributed to J Liu.

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

Association of preconceptional health care utilization and early initiation of prenatal care.

OBJECTIVE: To assess whether women having preconceptional health care utilization were more likely to have early initiation of prenatal care than were women not having preconceptional health care utilization. STUDY DESIGN: In this cohort study, data were collected prospectively from a population-based Perinatal Health Care Surveillance System in China. The analysis included 195 796 women who delivered single live births in 13 cities/counties during 1997 to 2000. Mantel-Haenszel test was employed to calculate risk ratios and 95% confidence intervals (CI). Multivariate logistic regression was conducted to assess the association between preconceptional health care utilization and early initiation of prenatal care after controlling for maternal residence, age at delivery, educational attainment, occupation, parity, preconceptional medical disorders, and high-risk medical experiences during the first trimester. SPSS 11.5 (SPSS Inc.) was employed for data analysis. RESULTS: Women having preconceptional health care utilization were 2.6 times (95%CI: 2.5 to 2.6) more likely to have early initiation of prenatal care compared with women not having preconceptional health care utilization. When stratified by maternal residence, age at delivery, educational attainment, occupation, parity, preconceptional medical disorder, high-risk medical experiences during the first trimester, and preconceptional medical disorders, this association still existed. After controlling for stratification factors mentioned above and the interaction of maternal age, educational attainment, and parity, women having preconceptional health care utilization were 2.7 times (95%CI: 2.6 to 2.8) more likely to have early initiation of prenatal care than were women not having preconceptional health care utilization. CONCLUSION: Women who had preconceptional health care utilization were more likely to have early prenatal care than were women not having preconceptional health care utilization.

Adult↗
PubMed2006

Phi c31 integrase induces chromosomal aberrations in primary human fibroblasts.

Phi c31 integrase is investigated as a novel tool for nonviral gene therapy as the enzyme can direct site-specific integration into a host chromosome. In order to investigate effects of phi c31 integrase expression in normal human cells, we have generated stably transfected primary human fibroblasts expressing the enzyme. All control cells were cytogenetically normal, but in cells expressing phi c31 integrase, numerous chromosomal abnormalities including various translocations were found, suggesting that the enzyme itself acts as a mutagen.

Attachment Sites, Microbiological↗
PubMed2006

Dysregulated expression of mitotic regulators is associated with B-cell lymphomagenesis in HOX11-transgenic mice.

Dysregulated expression of the homeobox gene, HOX11 is a frequent etiologic event in T-cell acute lymphoblastic leukemias. HOX11-transgenic mice (IgHmu-HOX11Tg)-expressing HOX11 in the B-cell compartment develop B-cell lymphomas with extended latency. The latency suggests that additional genetic events are required prior to the onset of malignant lymphoma. We report the identification of 17 HOX11 collaborating genes, revealed through their propensity to be targeted in a proviral insertional mutagenesis screen. Seven integrations disrupted genes in mitotic spindle checkpoint control, suggesting that cells with elevated HOX11 expression are especially sensitive to dysregulation of chromosome segregation during mitosis. IgHmu-HOX11Tg primary B-lymphocyte cultures exposed to the aneugenic agents, colchicine and colcemid, exhibited increased incidences of chromosome missegregation as assessed by cytokinesis-block micronucleus assays. Additionally, IgHmu-HOX11Tg cultures were shown to exhibit aberrant bypass of spindle checkpoint arrest, as assessed by the increased presence of cycling cells determined by assessment of DNA content and by BrdU immunolabelling. Western immunoblotting revealed elevated expression of the mitotic effector molecules, cyclin A, cyclin B1 and cdc20 in IgHmu-HOX11Tg cultures. Moreover, spontaneously arising lymphoid neoplasms in IgHmu-HOX11Tg mice frequently exhibit aberrant expression of mitotic regulators, concomitant with increased development of micronuclei, abnormal mitotic checkpoint control and increased incidences of abnormal karyotypes when expanded in culture. Collectively, these findings indicate that abnormal regulation of spindle checkpoint control as a result of HOX11 overexpression leads to a heightened predisposition for development of aneuploidy, contributing to oncogenesis.

Animals↗
PubMed2006

Observation of a near-threshold enhancement in the omega(phi) mass spectrum from the doubly OZI-suppressed decay J/psi-->gamma(omega)phi.

An enhancement near threshold is observed in the omega(phi) invariant mass spectrum from the doubly Okubo-Zweig-Iizuka-suppressed decays of J/psi-->gamma(omega)phi, based on a sample of 5.8 x 10(7) J/psi events collected with the BESII detector. A partial wave analysis shows that this enhancement favors JP=0+, and its mass and width are M=1812(+19)(-26)(stat)+/-18(syst) MeV/c2 and Gamma=105+/-20(stat)+/-28(syst) MeV/c2. The product branching fraction is determined to be B(J/psi-->gammaX)B(X-->omega(phi))=[2.61+/-0.27(stat)+/-0.65(syst)]x10(-4).

Journal Article↗
PubMed2006

Cardiovascular risk factors and anthropometric measurements of adolescent body composition: a cross-sectional analysis of the Third National Health and Nutrition Examination Survey.

OBJECTIVE: To assess the association between certain cardiovascular risk factors that are commonly clustered among individuals with insulin resistance syndrome (IRS) and adolescents' body composition measurements. METHODS: We examined a total of 1068 adolescents aged 12-16 years from the Third National Health and Nutrition Examination Survey. The sex-specific third tertiles of glucose, triglycerides, systolic blood pressure and first tertile of high-density-lipoprotein (HDL) cholesterol were used to classify the presence of each IRS component. We compared adolescents with none, one, two and three/four IRS components across a series of body composition measurements and lipid profile. RESULTS: About 18% of the adolescents had three or four IRS components. Overall, IRS among adolescents is more likely to be associated with body weight and measurements related to body girths and less likely to be associated with the measurements related to body lengths. Multivariate analysis results showed that the odds of being at increased risk of obesity (body mass index z-score> 0.85) were significantly greater among those with two (odds ratio (OR)=4.5; 95% CI 2.5-8.2) and three/four (OR=8.9, 95% CI 4.5-17.5) IRS components compared to those without any IRS components. Across sex, the level of non-HDL cholesterol was significantly higher among adolescents with more IRS components (P for trends <0.05). CONCLUSIONS: The clustered cardiovascular risk factors are strongly associated with an increased risk of obesity and higher levels of non-HDL cholesterol among adolescents.

Adolescent↗
PubMed2006

Biodiesel production using a membrane reactor.

The immiscibility of canola oil in methanol provides a mass-transfer challenge in the early stages of the transesterification of canola oil in the production of fatty acid methyl esters (FAME or biodiesel). To overcome or rather, exploit this situation, a two-phase membrane reactor was developed to produce FAME from canola oil and methanol. The transesterification of canola oil was performed via both acid- or base-catalysis. Runs were performed in the membrane reactor in semi-batch mode at 60, 65 and 70 degrees C and at different catalyst concentrations and feed flow rates. Increases in temperature, catalyst concentration and feedstock (methanol/oil) flow rate significantly increased the conversion of oil to biodiesel. The novel reactor enabled the separation of reaction products (FAME/glycerol in methanol) from the original canola oil feed. The two-phase membrane reactor was particularly useful in removing unreacted canola oil from the FAME product yielding high purity biodiesel and shifting the reaction equilibrium to the product side.

Bioreactors↗
PubMed2006

Evaluation and analysis of colonoscopy in the diagnosis of 186 cases of ulcerative colitis patients.

The objective of this study was to evaluate the diagnostic value of colonoscopy plus biopsy in patients with ulcerative colitis (UC). Retrospective analysis was performed on clinical data in 186 cases. Erosions, or ulcers, together with mucosal hyperemia and oedema were the most common manifestations of colonoscopy in 87% of patients. In about 56.4% of 186 cases, such manifestations occurred in the rectum and the sigmoid colon. Nearly 65.6% of the patients had a chronic intermittent clinical course. One case developed colon cancer, and another case had toxic megacolon; each case represents 0.05% of the total 186 patients. Therefore, prevalence of both malignancy and complication is low. Colonoscopy plus biopsy is considered to be the major means of the diagnosis of UC, demonstrating its value in differential diagnosis.

Adolescent↗
PubMed2006

Microrheology probes length scale dependent rheology.

We exploit the power of microrheology to measure the viscoelasticity of entangled F-actin solutions at different length scales from 1 to 100 microm over a wide frequency range. We compare the behavior of single probe-particle motion to that of the correlated motion of two particles. By varying the average length of the filaments, we identify fluctuations that dissipate diffusively over the filament length. These provide an important relaxation mechanism of the elasticity between 0.1 and 30 rad/sec.

Actins↗
PubMed2006

Sodium selenite induces apoptosis in cultured cortical neurons with special concomitant changes in expression of the apoptosis-related genes.

Sodium selenite was used to examine whether selenium compound is able to trigger apoptotic degeneration in cultured cortical neurons in vitro and to explore the detailed changes in expression of the related genes during the apoptotic processes using molecular biological and flow cytometric examinations. The results indicated that: (1) cortical neurons treated with sodium selenite with different dosages (0.0008, 0.004, 0.0200, 0.1000, and 0.5000 microM) and different exposure times (2, 4, 24, and 48 h) exhibited dose- and time-dependent apoptotic processes as revealed by typical DNA ladder formation detected by agarose gel electrophoresis; (2) the internucleosomal DNA fragmentation detected by flow cytometric examination showed a prominent peak of hypodiploid DNA contents as early as 4h after exposure of 0.1 microM sodium selenite; (3) the DNA fragmentation induced by sodium selenite as revealed by the above two examinations could be blocked by aurintricarboxylic acid; (4) the transcriptions of mRNAs related to bcl-2, bax, c-fos, p53, and acetylcholinesterase (AChE) genes, as detected by RT-PCR assays, showed down-regulation for bcl-2 and up-regulation for bax, c-fos, p53, and AChE genes after exposure of sodium selenite. This study suggests that the sodium selenite is effective for inducing apoptosis in cultured cortical neurons and that relevant changes in expression of several apoptosis-related genes might further our understanding of the mechanism(s) that initiates and maintains the apoptotic processes.

Acetylcholinesterase↗
PubMed2006

A role for the immunomodulatory molecules CD200 and CD200R in regulating bone formation.

Altered osteoprotogerin (OPG) and OPG ligand (RANKL) ratios are known to regulate bone metabolism. We investigated whether CD200:CD200R interaction would alter OPG:RANKL ratios, and thus modulate bone differentiation in cultures derived from neonatal calvariae, a source of osteoblast precursors (OBp), or bone marrow-derived myeloid cells as a source of osteoclast precursors (OCp). We characterized cells in cultures using real-time PCR to measure expression of a number of mRNAs characteristic of cells differentiating towards the osteoblast or osteoclast lineage, and enumerated bone nodule formation and osteoclasts directly. CD200Fc or anti-CD200 mAbs were included as modulating agents. In addition, calvariae from transgenic mice overexpressing CD200 under control of a doxycycline-inducible promoter were used as a source of OBp endogenously overexpressing CD200. Our data show that increased endogenous expression of CD200 on OBp, or addition of CD200Fc into cultures, led to increased OPG:RANKL ratios and increased bone nodule growth, while anti-CD200 abolished this effect.

Animals↗
PubMed2006

Downregulation of E-cadherin by hepatitis B virus X antigen in hepatocellullar carcinoma.

Hepatitis B virus (HBV)-encoded X antigen (HBxAg) contributes to the development of hepatocellular carcinoma (HCC). A frequent characteristic of HCC is reduced or absent expression of the cell adhesion protein, E-cadherin, although it is not known whether HBxAg plays a role. To address this, the levels of E-cadherin were determined in HBxAg-positive and -negative HepG2 cells in culture, and in tumor and surrounding nontumor liver from a panel of HBV carriers. The results showed an inverse relationship between HBxAg and E-cadherin expression both in tissue culture and in vivo. In HBxAg-positive cells, E-cadherin was suppressed at both the mRNA and protein levels. This was associated with hypermethylation of the E-cadherin promoter. Depressed E-cadherin correlated with HBxAg trans-activation function, as did the migration of HepG2 cells in vitro. Decreased expression of E-cadherin was also associated with the accumulation of beta-catenin in the cytoplasm and/or nuclei in tissues and cell lines, which is characteristic of activated beta-catenin. Additional work showed that HBxAg-activated beta-catenin. Together, these results suggest that the HBxAg is associated with decreased expression of E-cadherin, accumulation of beta-catenin in the cytoplasm and nucleus, and increased cell migration, which may contribute importantly to hepatocarcinogenesis.

Cadherins↗
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

Synthesis of a potentially bioactive, hydroxyapatite-nucleating molecule.

A human phosphophoryn (PP) cDNA was previously cloned from immature root apex total RNA in our laboratory. This cDNA comprises 2,364 bp, encoding 788 amino acids. More than 80% of the sequences are arranged as (DSS)(n) (n = 1-16), DS, and NSS motifs. We hypothesize that the capability of PP to bind Ca(2+) and nucleate hydroxyapatite may depend on these repeated sequences. Two polypeptides were synthesized based on the human PP cDNA sequence to test the hypothesis. One polypeptide has the amino acid sequence DDPNSSDESNGNDD (synthetic polypeptide 1, SP1), which is from the N-terminal end of PP; the other polypeptide, DSKSDSSKSESDSS (synthetic polypeptide 2, SP2), is the PP repeated sequence motif. Phosphorylation of the polypeptides was accomplished by reacting them with adenosine triphosphate and casein kinases I and II. The ability of these molecules to cause mineralization was tested in a steady-state agarose gel system. The results show that phosphorylated SP2 (P-SP2) precipitated approximately 60% of the total Ca + PO(4) precipitated by PP. P-SP1 precipitated about 23% of that precipitated by PP and was similar to the amount precipitated in the control gel, that is, without added peptides. Transmission electron microscopy and X-ray diffraction analysis showed that the precipitate formed in the P-SP2-containing gel was hydroxyapatite. The capability of P-SP2 to nucleate Ca + PO(4) and precipitate hydroxyapatite is a result of the repeated sequence motif, which contains a high percentage of phosphorylated serine. This molecule could be used in the repair and regeneration of dental tissue.

Adenosine Triphosphate↗
PubMed2006

FGF ligand family mRNA expression profile for mouse preimplantation embryos, early gestation human placenta, and mouse trophoblast stem cells.

Signaling by fibroblast growth factor (FGF) is essential is for trophoblast stem (TS) cells and preimplantation embryos. FGF4 provides essential signaling, but the expression of the complete set of 23 FGF family members has not been analyzed. Here, semi-quantitative RT-PCR and microarray analyses were used to define expression of all FGF ligand mRNA. RT-PCR was done for developmentally important FGF subfamilies, FGF10/FGF22 and FGF8/FGF17/FGF18 as well as FGF11. FGF4 and FGF18 are detected at highest levels by RT-PCR and microarrays. FGF10 was detected at low levels in both assays. FGF11 was detected at moderate levels by microarray, but not by RT-PCR. FGF17 was detected at low levels by array and moderate levels by RT-PCR. FGF8 and FGF22 were detected by RT-PCR, but not by microarrays during late cleavage divisions. FGF8, FGF5, and FGF9 were detected in the oocyte by microarray. FGF2, FGF3, and FGF7 were not detected by RT-PCR or microarrays and FGF13, FGF14, and FGF23 were not detected by microarray. Since a major role of FGF is to maintain TS cells, we tested human and mouse placental cell lines and early gestation human placenta for expression of FGF ligands. Expression in mouse TS cells was compared with preimplantation embryos, and human placental cell line expression was compared with human placenta, to infer which ligands are expressed in placental lineage vs. other cell lineages. The data suggest that human and mouse placenta share FGF18 and its high expression suggests preimplantation and early placental function.

Animals↗
PubMed2006

Culturing in vitro produced blastocysts in sequential media promotes ES cell derivation.

Embryonic stem (ES) cell lines are routinely derived from in vivo produced blastocysts. We investigated the efficiency of ES cells derivation from in vitro produced blastocysts either in monoculture or sequential culture. Zygotes from hybrid F1 B6D2 mice were cultured in vitro to the blastocyst stage in Potassium (K(+)) simplex optimised medium (KSOM) throughout or in KSOM and switched to COOK blastocyst medium on day 3 (KSOM-CBM). Blastocysts were explanted on a feeder layer of mitomycin C-inactivated murine embryonic fibroblasts (MEF) in TX-WES medium for ES cell derivation. Sequential KSOM-CBM resulted in improved blastocyst formation compared to KSOM monoculture. ES cells were obtained from 32.1% of explanted blastocsyts cultured in KSOM-CBM versus 18.4% in KSOM alone. ES cell lines were characterized by morphology, expression of SSEA-1, Oct-4 and alkaline phosphatase activity, and normal karyotype. These results indicate that in vitro culture systems to produce blastocysts can influence the efficiency of ES cell line derivation.

Animals↗
PubMed2006

Making myc.

Myc regulates to some degree every major process in the cell. Proliferation, growth, differentiation, apoptosis, and metabolism are all under myc control. In turn, these processes feed back to adjust the level of c-myc expression. Although Myc is regulated at every level from RNA synthesis to protein degradation, c-myc transcription is particularly responsive to multiple diverse physiological and pathological signals. These signals are delivered to the c-myc promoter by a wide variety of transcription factors and chromatin remodeling complexes. How these diverse and sometimes disparate signals are processed to manage the output of the c-myc promoter involves chromatin, recruitment of the transcription machinery, post-initiation transcriptional regulation, and mechanisms to provide dynamic feedback. Understanding these mechanisms promises to add new dimensions to models of transcriptional control and to reveal new strategies to manipulate Myc levels.

Animals↗
PubMed2006

Screening and expression analysis of Phytophthora infestans induced genes in potato leaves with horizontal resistance.

Horizontal resistance to late blight with quantitative and durable characteristics is a major objective for potato breeding programs. With the aim of investigating the molecular aspects of horizontal resistance, a cDNA microarray was used to identify Phytophthora infestans-induced genes from 100 expressed sequence tags (ESTs) selected from a subtractive cDNA library. Of the 100 cDNA clones represented on the array, 76 were differentially expressed in infected plants as compared with mock-inoculated control plants. Four groups of genes could be identified according to their expression patterns at three time points, 24, 48 and 72 h postinoculation (hpi). Group A appeared to be strongly induced (>10-fold) at 72 hpi. Group B demonstrated up-regulated expression patterns at all the three time points. The transcripts of group C peaked at 48 hpi, while genes of group D were up-regulated at 24 hpi and decreased slightly thereafter. Blast algorithm searches revealed that the largest set of up-regulated genes (about 35%) was assigned to the primary/secondary metabolism. Other genes with known or putative functions included disease defense or cell rescue (about 18%), transcription, signal transduction, cellular transporter/transport facilitation, development, protein synthesis/destination, as well as those playing roles in cellular organization. Furthermore, 15 genes encoding unknown function proteins were also identified. The results indicated that multiple defense mechanisms are involved in horizontal potato resistance to late blight and alteration in metabolic pathways is one of the most important defense responses.

Blotting, Northern↗