Biomedical subjects

Jun Liu

Publications and source records attributed to Jun Liu.

At least 91 records · Page 5Linked to original sources

PubMed2006

Oct-3/4 dose dependently regulates specification of embryonic stem cells toward a cardiac lineage and early heart development.

The transcriptional mechanisms underlying lineage specification and differentiation of embryonic stem (ES) cells remain elusive. Oct-3/4 (POU5f1) is one of the earliest transcription factors expressed in the embryo. Both the pluripotency and the fate of ES cells depend upon a tight control of Oct-3/4 expression. We report that transgene- or TGFbeta-induced increase in Oct-3/4 mRNA and protein levels in undifferentiated ES cells and at early stages of differentiation triggers expression of mesodermal and cardiac specific genes through Smad2/4. cDNA antisense- and siRNA-mediated inhibition of upregulation of Oct-3/4 in ES cells prevent their specification toward the mesoderm and their differentiation into cardiomyocytes. Similarly, Oct-3/4 siRNA injected in the inner cell mass of blastocysts impairs cardiogenesis in early embryos. Thus, quantitative Oct-3/4 expression is regulated by a morphogen, pointing to a pivotal and physiological function of the POU factor in mesodermal and cardiac commitments of ES cells and of the epiblast.

Animals↗

PubMed2006

BMI modifies associations of IL-6 genotypes with insulin resistance: the Framingham Study.

OBJECTIVE: The -174 interleukin (IL)-6 gene polymorphism has been proposed as a risk factor for type 2 diabetes, but data are conflicting. Because white fat is a major source of IL-6 in resting individuals, we tested the hypothesis that BMI modifies the association among the IL-6 genotype, insulin resistance (IR) (measured using the homeostasis model), and risk of diabetes. RESEARCH METHODS AND PROCEDURES: Outcomes were assessed in a community-based cohort study of 1525 adults (mean age, 55.6 years; 753 men), who participated in the Framingham Offspring Study during the 1991 to 1995 examinations. RESULTS: We found a significant interaction between IL-6 genotype and BMI on levels of IR in men (p < 0.0001), with obese homozygotes for the minor C allele being most resistant. The IL-6-BMI interaction was not significant (p = 0.46) in women. Among men with the CC genotype, increasing BMI was associated with increased prevalence of diabetes [odds ratio (OR) per unit increase in BMI, 1.30; 95% confidence interval (CI), 1.11 to 1.50] but not among those with the GG (OR, 1.10; 95% CI, 0.98 to 1.22) or GC genotype (OR, 1.05; 95% CI, 0.97 to 1.14). DISCUSSION: The -174 IL-6 promoter polymorphism modifies the association of obesity with IR and diabetes risk in men. Weight loss regimens targeted at reducing the risk of diabetes may be of particular benefit for men with a -174 IL-6 CC genotype.

Blood Glucose↗

PubMed2006

Cloning, characterization and tissue-specific expression of a cDNA encoding a novel EMBRYONIC FLOWER 2 gene (OsEMF2) in Oryza sativa.

EMBRYONIC FLOWER 2 (EMF2) gene plays a major role in maintain vegetative development and repress flower development. Here, we present the cloning, characterization and tissue-specific expression of a putative EMF2 (OsEMF2) gene in Oryza sativa. The full-length cDNA of OsEMF2 was 1899 bp and contained an 1872 bp open reading frame (ORF) encoding a 624 amino acid protein. Homologous analysis showed that OsEMF2 contain a single conserved C2H2-type zinc finger motif. Sequence alignment shows that there is a homology between the deduced amino acid sequence of OsEMF2 and EMF2 in Zea mays (55%). Moreover, pI of OsEMF2 are predicted. The tissue-specific expression pattern of OsEMF2 reveals that it is abundant in shoot apical meristem and inflorescence meristem, while its expression level is much lower in leaf, root, immature seed and callus.

Amino Acid Sequence↗

PubMed2006

Expression of tobacco ethylene receptor NTHK1 alters plant responses to salt stress.

Ethylene has been regarded as a stress hormone involved in many stress responses. However, ethylene receptors have not been studied for the roles they played under salt stress condition. Previously, we characterized an ethylene receptor gene NTHK1 from tobacco, and found that NTHK1 is salt-inducible. Here, we report a further investigation towards the function of NTHK1 in response to salt stress by using a transgenic approach. We found that NTHK1 promotes leaf growth in the transgenic tobacco seedlings but affects salt sensitivity in these transgenic seedlings under salt stress condition. Differential Na+/K+ ratio was observed in the control Xanthi and NTHK1-transgenic plants after salt stress treatment. We further found that the NTHK1 transgene is also salt-inducible in the transgenic plants, and the higher NTHK1 expression results in early inductions of the ACC (1-aminocyclopropane-1-carboxylic acid) oxidase gene NtACO3 and ethylene responsive factor (ERF) genes NtERF1 and NtERF4 under salt stress. However, NTHK1 suppresses the salt-inducible expression of the ACC synthase gene NtACS1. These results indicate that NTHK1 regulates salt stress responses by affecting ion accumulation and related gene expressions, and hence have significance in elucidation of ethylene receptor functions during stress signal transduction.

Ethylenes↗

PubMed2006

Compatibility of porcine and human interleukin 2: implications for xenotransplantation.

BACKGROUND: Xenotransplantation provides a possible solution to the severe shortage of allogeneic organ donors. The pig, which shares many physiological similarities with humans, makes it an optimal species for preclinical experimentation and clinical applications. Interleukin 2 (IL2) is a potent growth factor secreted primarily by T helper lymphocytes and it is vital to the cellular expansion required for a productive immune response and the development and peripheral expansion of CD4+CD25+ regulatory T cells. Therefore, it is essential to understand of the compatibility of IL2 between pigs and humans. METHODS: We first compared the cDNA and protein sequences and the crystal structures of human and porcine IL2 and IL2 receptors, respectively. The effect of IL2 to induce T cell proliferation was determined by 3H-thymidine incorporation and cell cycle detection. RESULTS: Porcine IL2 induced very limited proliferation of human lymphocytes while it functioned well on porcine lymphocytes. Human IL2 had remarkably reduced effects on porcine lymphocytes whereas it worked well on human lymphocytes. CONCLUSION: Our present study showed that the interaction of IL2 and IL2R across species might have defects. Together with the wide physiological functions of IL2, our data indicated that physiological disorders could be caused by the poor function of xenogeneic donor IL2 on host cells in full hematopoietic chimera. Our data suggested an additional potential advantage for the mixed xenogeneic chimeras.

Amino Acid Sequence↗

PubMed2006

The ESAT-6/CFP-10 secretion system of Mycobacterium marinum modulates phagosome maturation.

Virulence of Mycobacterium tuberculosis and related pathogenic mycobacteria requires the secretion of early secretory antigenic 6 kDa (ESAT-6) and culture filtrate protein 10 (CFP-10), two small proteins that lack traditional signal sequences and are exported through an alternative secretion pathway encoded primarily by the RD1 genetic locus. Mutations affecting the synthesis or secretion of ESAT-6 or CFP-10 attenuate the virulence of M. tuberculosis in murine models of infection. However, the specific functions of these proteins and of their secretion system are currently unclear. In this study, we isolated a mutant of Mycobacterium marinum defective in the secretion of ESAT-6 and CFP-10. The mutation was localized within MM5446, which is orthologous to Rv3871 of M. tuberculosis H37Rv and encodes an ATPase that is a component of the ESAT-6/CFP-10 secretion system. The mutant bacteria were unable to replicate within J774 macrophages although their growth in 7H9 medium was equivalent to the parental strain. Phagosome maturation and acidification were analysed in infected macrophages by confocal and electron microscopy using the late endosome/lysosome marker LAMP-1, along with various fluid-phase markers such as rhodamine-dextran and ferritin and the acidotropic dye LysoTracker Red. These studies demonstrated that while the wild-type parental strain of M. marinum primarily resides in a poorly acidified, non-lysosomal compartment, a significantly higher percentage of the MM5446 mutant organisms are in acidified compartments. These results suggest that the ESAT-6/CFP-10 secretion system plays a role in preventing phagolysosomal fusion, a novel function that accounts for the ability of bacteria to survive inside host cells. This finding provides a mechanism by which the ESAT-6/CFP-10 secretion system potentiates the virulence of pathogenic mycobacteria.

Amines↗

PubMed2006

Ubiquinone (coenzyme Q) biosynthesis in Chlamydophila pneumoniae AR39: identification of the ubiD gene.

Ubiquinone is an essential electron carrier in prokaryotes. Ubiquinone biosynthesis involves at least nine reactions in Escherichia coli. 3-octaprenyl-4-hydroxybenzoate decarboxylase (UbiD) is an important enzyme on the pathway and deletion of the ubiD gene in E. coli gives rise to ubiquinone deficiency in vivo. A protein from Chlamydophila pneumoniae AR39 had significant similarity compared with protein ubiD from E. coli. Based on this information, the protein-encoding gene was used to swap its counterpart in E. coli, and gene expression in resultant strain DYC was confirmed by RT-PCR. Strain DYC grew using succinate as carbon source and rescued ubiquinone content in vivo, while ubiD deletion strain DYD did not. Results suggest that the chlamydial protein exerts the function of UbiD.

Amino Acid Sequence↗

PubMed2006

Antimalarial effects of human immunodeficiency virus type 1 protease inhibitors differ from those of the aspartic protease inhibitor pepstatin.

Human immunodeficiency virus type 1 protease inhibitors (HIVPIs) and pepstatin are aspartic protease inhibitors with antimalarial activity. In contrast to pepstatin, HIVPIs were not synergistic with a cysteine protease inhibitor or more active against parasites with the cysteine protease falcipain-2 knocked out than against wild-type parasites. As with pepstatin, HIVPIs were equally active against wild-type parasites and against parasites with the food vacuole plasmepsin aspartic proteases knocked out. The antimalarial mechanism of HIVPIs differs from that of pepstatin.

Animals↗

PubMed2006

AsnB is involved in natural resistance of Mycobacterium smegmatis to multiple drugs.

Mycobacteria are naturally resistant to most common antibiotics and chemotherapeutic agents. The underlying molecular mechanisms are not fully understood. In this paper, we describe a hypersensitive mutant of Mycobacterium smegmatis, MS 2-39, which was isolated by screening for transposon insertion mutants of M. smegmatis mc2155 that exhibit increased sensitivity to rifampin, erythromycin, or novobiocin. The mutant MS 2-39 exhibited increased sensitivity to all three of the above mentioned antibiotics as well as fusidic acid, but its sensitivity to other antibiotics, including isoniazid, ethambutol, streptomycin, chloramphenicol, norfloxacin, tetracycline, and beta-lactams, remained unchanged. Uptake experiment with hydrophobic agents and cell wall lipid analysis suggest that the mutant cell wall is normal. The transposon insertion was localized within the asnB gene, which is predicted to encode a glutamine-dependent asparagine synthetase. Transformation of the mutant with wild-type asnB of mc2155 or asnB of Mycobacterium tuberculosis complemented the drug sensitivity phenotype. These results suggest that AsnB plays a role in the natural resistance of mycobacteria.

Anti-Bacterial Agents↗

PubMed2006

Roles of Lsr2 in colony morphology and biofilm formation of Mycobacterium smegmatis.

The lipid-rich cell wall is a defining feature of Mycobacterium species. Individual cell wall components affect diverse mycobacterial phenotypes including colony morphology, biofilm formation, antibiotic resistance, and virulence. In this study, we describe a transposon insertion mutant of Mycobacterium smegmatis mc2 155 that exhibits altered colony morphology and defects in biofilm formation. The mutation was localized to the lsr2 gene. First identified as an immunodominant T-cell antigen of Mycobacterium leprae, lsr2 orthologs have been identified in all sequenced mycobacterial genomes, and homologs are found in many actinomycetes. Although its precise function remains unknown, localization experiments indicate that Lsr2 is a cytosolic protein, and cross-linking experiments demonstrate that it exists as a dimer. Characterization of cell wall lipid components reveals that the M. smegmatis lsr2 mutant lacks two previously unidentified apolar lipids. Characterization by mass spectrometry and thin-layer chromatography indicate that these two apolar lipids are novel mycolate-containing compounds, called mycolyl-diacylglycerols (MDAGs), in which a mycolic acid (alpha- or alpha'-mycolate) molecule is esterified to a glycerol. Upon complementation with an intact lsr2 gene, the mutant reverts to the parental phenotypes and MDAG production is restored. This study demonstrates that due to its impact on the biosynthesis of the hydrophobic MDAGs, Lsr2 plays an important role in the colony morphology and biofilm formation of M. smegmatis.

Amino Acid Sequence↗

PubMed2006

Magnetic resonance imaging and magnetic resonance spectroscopy study of deficits in hippocampal structure in fire victims with recent-onset posttraumatic stress disorder.

OBJECTIVE: To explore hippocampal structural abnormalities in fire victims with recent-onset posttraumatic stress disorder (PTSD). METHOD: We compared 12 patients with recent-onset PTSD diagnosed according to DSM-IV criteria 6 to 8 months after a major fire with 12 individuals without PTSD who were victims of the same fire accident. Voxel-based morphometry (VBM) and magnetic resonance spectroscopy (MRS) were combined to examine hippocampal structural abnormalities in patients with recent-onset PTSD. RESULTS: Results of VBM showed that the grey matter density of the left hippocampus was lower in the group with PTSD than it was in the group without PTSD. Results of MRS showed that the ratio of N-acetyl asparate and creatine in the left hippocampus was significantly lower in patients with PTSD than in control subjects. CONCLUSION: Patients with recent-onset PTSD had hippocampal structural abnormalities.

Adult↗

PubMed2006

Establishment and application of a high throughput model for Rho kinase inhibitors screening based on fluorescence polarization.

Rho kinase (ROCK) inhibitors are effective candidates for neural or cardiovascular disorders. High throughput model for screening ROCK inhibitors is a basic foundation to pick up ROCK inhibitors from thousands of compounds for drug developing. The high throughput model was established based on purified recombinant rat ROCK catalytic domain (rROCK-CD) from Escherichia coli (E. coli). There are two steps of reaction in the model: incubation of 5.0 microl recombinant rROCK-CD (2.0 microg/ml), 5.0 microl different compounds, 5.0 microl fluorescent S6-peptide (200 nM), and 5.0 microl ATP (10 microM) at 37 degrees C for 60 min was made the first reaction, and the second reaction was made by incubating them with additional 60 microl binding reagent at ambient temperature for 30 min. The phosphorylated S6 peptide can bind to a binding reagent, and the fluorescence varies from low polarization to high according to the amount of the phosphorylated peptide. IC50 was calculated based on polarization variation. Compound, which IC50 was less than 10 microM, was recognized as a lead compound which taken bioactivity evaluation in PC12 by observing neurite outgrowth. The Z'-factor of the model is 0.81 (above 0.5). The model screened five lead compounds from 3294, which promoted neurite outgrowth to different extent. The results suggested that the model is suitable for high throughput screening (HTS), and the five lead compounds are worth of further investigation.

Animals↗

PubMed2006

Harvest active recombinant Rho kinase from Escherichia coli.

Rho kinase (ROCK) inhibitors are effective candidates for treating nerve or myocardial injury, erectile dysfunction, and other cardiovascular diseases. Purified ROCK is a foundation for ROCK inhibitors screening and for its function research in vitro. This article established an easy way to harvest active recombinant ROCK catalytic domain (ROCK-CD) of rat in Escherichia coli (E. coli). The cDNA of ROCK-CD was amplified by RT-PCR, and subcloned to pET28a(+) vector to express the protein in E. coli BL(21) as inclusion bodies. The protein was purified by HiTrap chelating column, and its refolding was achieved by gradient dilution from guanidine hydrochloride solution, and desalinated by ultrafiltration. The result of DNA sequencing and protein sequence analysis indicate there were three amino acid residua of mutation, but the activity was not significantly affected. The activity of the recombinant protein was confirmed by ROCK II activity fluorescence polarization kit. Therefore, this is an easy and rapid procedure to harvest a large quantity of activity recombinant ROCK-CD at low cost.

Amino Acid Sequence↗

PubMed2006

[Genetic analysis and SSR marker of tolerance to submergence in rice].

Submergence stress has severe harm to rice (Oryza sativa L.) production. It is important to identify molecular markers associated with tolerance to submergence for marker-assisted selection (MAS). F1 and F2 populations ware obtained from reciprocal crosses between submergence tolerant parent FR13A and submergence sensitive parent IR39595-503-2-1-2. No difference in reciprocal crosses in F1 population was detected for tolerance to submergence. This indicates that the submergence character is controlled by nucleic factor(s). Tolerance to submergence derived from FR13A appeared to be a quantitative-qualitative trait as revealed by the segregation of F2 population in two submergent experiments. Under light submergence stress, multiple minor genes might work and the trait inherited quantitatively it appeared a quantity trait, While under severe submergence stress, it exhibited a qualitative inheritance controlled by a major gene. Among the 187 pairs of SSR primers, 73 (39%) were polymorphic between the two parents and were used to tag submergence in the F2 population. Primer RM219 was detected to be linked to submergence tolerant trait loci. This result confirmed that tolerance to submergence is controlled by the major gene sub1, which will be helpful in improvement of the trait in rice.

DNA Primers↗

PubMed2006

Why can't the immune system control HIV-1? Defining HIV-1-specific CD4+ T cell immunity in order to develop strategies to enhance viral immunity.

Globally, at least 60 million people have been infected with the human immunodeficiency virus type 1 (HIV-1), the majority of whom will develop the acquired immunodeficiency syndrome (AIDS) leading to tremendous morbidity and the mortality. Understanding the immunopathogenesis of AIDS and the immune correlates of viral protection are necessary to develop effective vaccines and immunotherapies. A major focus of our laboratory has been to understand the CD4+ T cell immune response directed against HIV- 1, and to determine mechanisms of T cell dysfunction that lead to viral escape. In addition, we are interested in evaluating the TNF-TNFR family members as potential molecular adjuvants that could be incorporated into vaccines which could be used to further boost T cell immunogenicity in healthy or HIV-1-infected individuals, as many of these molecules have been shown to replace the functions of CD4+ T cell help.

AIDS Vaccines↗

PubMed2006

A new species of haploporid (Digenea) from the South China Sea.

Megasolena dongzhaiensis n. sp. was collected from the intestine of Scatophagus argus (Linnaeus) (Perciformes: Scatophagidae) from the Dongzhai Bay (110 degrees 32'-37'E, 19 degrees 51'-20 degrees 1'N), Hainan Province, China. It resembles Megasolena acanthuri Machida and Uchida, 1991 in having larger body size, but it differs from the latter species in having an oral sucker that is larger, instead of smaller, than the acetabulum (sucker length ratio 1:0.456-0.494, and width ratio 1:0.61-0.65 in M. dongzhaiensis n. sp., as opposed to 1:1.3-1.7 in M. acanthuri). Moreover, the cuticle is spinose rather than aspinose; there is a band of circular muscle in the pharynx, and its eggs are smaller instead of larger (0.062-0.068 x 0.036-0.039 in M. dongzhaiensis n. sp., compared with 0.087-0.103 x 0.058-0.072 in M. acanthuri). Finally, the intestinal bifurcation is anterior, instead of dorsal, to the acetabulum. It resembles other species of Megasolena Linton, 1910 in having oral sucker larger than the acetabulum, and in having a circular muscle band in the oral sucker and pharynx, but it differs in having a larger body and smaller eggs. This is the first record of a Megasolena species from ray-finned fishes as well as in China.

Animals↗

PubMed2006

Arsenic in drinking water and peripheral nerve conduction velocity among residents of a chronically arsenic-affected area in Inner Mongolia.

BACKGROUND: It remains unclear whether chronic ingestion of arsenic in drinking water affects the peripheral nervous system. We examined the effects of arsenic exposure on nerve conduction velocity using electromyography. METHODS: A cross-sectional study was conducted of a population living in an arsenic-affected village in Hetao Plain, Inner Mongolia, China. A total of 134 (93.7%) of 143 inhabitants took part in the study, and 36 (76.6%) of 47 inhabitants in a low-arsenic exposed village were recruited as a control group. Of the participants, 109 inhabitants in the arsenic-affected village and 32 in the low-arsenic exposed village aged > or =18 years were used for the analyses. An expert physician performed skin examinations, and median nerve conduction velocity was examined by electromyography. Arsenic levels in tube-well water and urine were measured. A mean level of arsenic in tube-well water in the arsenic-affected village was 158.3 microg/L, while that in the low-arsenic exposed village was 5.3 microg/L. RESULTS: No significant differences in the means of the motor nerve conduction velocity (MCV) and sensory nerve conduction velocity (SCV) were observed in relation to arsenic levels in tube wells, urine, and the duration of tube-well use. Further, no differences in mean MCV or SCV were found between the subjects with and without arsenic dermatosis, with mean SCV of 52.8 m/s (SD 6.3) in those without and 54.6 m/s (5.2) in subjects with arsenic dermatosis (p=0.206). CONCLUSION: These findings suggest that chronic arsenic poisoning from drinking water is unlikely to affect nerve conduction velocity, at least within the range of arsenic in drinking water examined in the present study.

Adolescent↗

PubMed2006

The celiac ganglia: anatomic study using MRI in cadavers.

OBJECTIVE: Our objective was to facilitate the in vivo identification of the celiac ganglia on MRI by using MRI to identify the celiac ganglia in cadavers. CONCLUSION: MRI can show the celiac ganglia accurately in cadavers when the ganglia are large and labeled with gadolinium. The findings in cadavers can be a reference for identifying the celiac ganglia in vivo.

Cadaver↗