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Jun Guo

Publications and source records attributed to Jun Guo.

At least 19 recordsLinked to original sources
PubMed2026

Hypervirulence-associated pseudo-compound transposons as fundamental mobile units driving cross-species virulence dissemination in Enterobacteriaceae.

BACKGROUND: The rapid global spread of hypervirulence in Enterobacteriaceae, particularly in carbapenem-resistant Klebsiella pneumoniae, poses a significant public health threat. However, the key genetic vehicles and mechanisms driving horizontal transfer of hypervirulence-associated genes (iucA, iroB, rmpA, rmpA2, and peg-344) remain poorly defined, limiting effective surveillance. METHODS: We performed a large-scale genomic survey of 2,869 virulence-associated plasmid sequences and 2,337 complete Enterobacteriaceae chromosomes. Using comparative genomics and evolutionary analyses, we systematically identified and characterized Hypervirulence-associated Pseudo-Compound Transposons (Hva-PCTs), defined as structured mobile elements in which hypervirulence-associated genes are flanked by insertion sequences. RESULTS: Our results demonstrate that hypervirulence-associated genes are transmitted primarily as discrete IS-bounded units, which we term Hva-PCTs. We identified 29 distinct plasmid-borne Hva-PCTs (pHva-PCTs) and 30 chromosomal Hva-PCTs (cHva-PCTs). These modules show clear species-specific patterns: iucA/iroB-associated Hva-PCTs mainly originate in Escherichia coli and spread through IncFIB-containing multi-replicon plasmids (commonly combined with IncFIC(FII) and/or IncFII, while rmpA/rmpA2/peg-344-containing modules originate in K. pneumoniae and are disseminated via IncHI1B/repB plasmids. Three Hva-PCTs were detected on both plasmids and chromosomes (xHva-PCTs). In one clinical K. pneumoniae isolate (LS356), the identical composite module was present on both replicons. Simpler sub-modules, such as ISKqu3-rmpA2-iucA_1-IS102 and IS102-rmpA-peg-344-iroB_1-IS1A, frequently co-occur on the same plasmid; when positioned in tandem, they reconstitute the full composite structure. This assembly pattern is further supported by a partial duplication event in plasmid pP901. CD-HIT clustering (80% nucleotide identity and 90% coverage) showed that 13 of 22 major clusters contained both plasmid and chromosomal copies, with intra-cluster identities >80% across multiple sequence types and host species. CONCLUSION: Hypervirulence-associated genes in Enterobacteriaceae are disseminated mainly as IS-flanked Hva-PCTs rather than solely through intact virulence plasmids. These modules exhibit strong but not absolute host specificity. The presence of identical Hva-PCTs on plasmids and chromosomes suggests inter-replicon mobility, while their stepwise assembly from simpler sub-modules highlights modular accretion as a key evolutionary process. Tracking Hva-PCTs as distinct mobile units may complement existing plasmid- and gene-centric surveillance approaches for hypervirulent and convergent strains. Experimental validation of their transposition activity and phenotypic effects is still required.

Virulence↗
PubMed2006

Isothiazolopyrimidines and isoxazolopyrimidines as novel multi-targeted inhibitors of receptor tyrosine kinases.

A series of isothiazolopyrimidines and isoxazolopyrimidines were synthesized and identified as potent KDR inhibitors. SAR studies led to isothiazolopyrimidine urea analogs that potently inhibit VEGFR tyrosine kinases (KDR enzymatic and cellular IC(50) values below 10 nM) as well as cKIT and TIE2. The selected compounds 8 and 13 display 56% and 48% oral bioavailability in mice, respectively.

Administration, Oral↗
PubMed2006

Decolorization of triphenylmethane, azo, and anthraquinone dyes by a newly isolated Aeromonas hydrophila strain.

A broad-spectrum dye-decolorizing bacterium, strain DN322, was isolated from activated sludge of a textile printing wastewater treatment plant. The strain was characterized and identified as a member of Aeromonas hydrophila based on Gram staining, morphology characters, biochemical tests, and nearly complete sequence analysis of 16S rRNA gene and the gyrase subunit beta gene (gyrB). Strain DN322 decolorized a variety of synthetic dyes, including triphenylmethane, azo, and anthraquinone dyes. For color removal, the most suitable pH and temperature were pH 5.0-10.0 and 25-37 degrees C, respectively. Triphenylmethane dye, e.g., Crystal Violet, Basic Fuchsin, Brilliant Green, and Malachite Green (50 mg l(-1)) were decolorized more than 90% within 10 h under aerobic culture condition and Crystal Violet could be used as sole carbon source and energy source for cell growth. The color removal of triphenylmethane dyes was due to a soluble cytosolic enzyme, and the enzyme was an NADH/NADPH-dependent oxygenase; For azo and anthraquinone dyes, e.g., Acid Amaranth, Great Red GR, Reactive Red KE-3B, and Reactive Brilliant Blue K-GR (50 mg l(-1)) could be decolorized more than 85% within 36 h under anoxic condition. This strain may be useful for bioremediation applications.

Aeromonas hydrophila↗
PubMed2006

Scanning electrochemical microscopy combined with surface plasmon resonance: studies of localized film thickness variations and molecular conformation changes.

The combination of scanning electrochemical microscopy (SECM) with surface plasmon resonance (SPR) is described. By oxidizing ferrocenylalkanethiol self-assembled monolayer (SAM) with SECM-generated Ce4+, the coupled technique, SECM-SPR, is shown to be viable for determining local variations in thin film thickness. Factors (tip/substrate distance, tip potential scan rate, and solution composition change) affecting the SECM-SPR response and operation are also discussed. The approach was further extended to the determination of conformational changes of cytochrome c molecules attached electrostatically onto a negatively charged SAM during its reduction by the tip-generated methyl viologen monocation. The high sensitivity of the SPR equipped with a bicell detector facilitates the measurement of infinitesimal film thickness changes accompanying redox reactions, while the SECM provides a means to obviate the necessity of applying a potential to the SPR substrate, which tends to cause unwanted interferences and complications. The approach also affords an avenue for determining film thickness variations that are not subject to certain effects, such as the surface charge, the heterogeneity of the substrate, and the distance between the redox center of the immobilized molecule and the underlying substrate electrode.

Cytochromes c↗
PubMed2006

PTH/PTHrP receptor delays chondrocyte hypertrophy via both Runx2-dependent and -independent pathways.

The transcription factor, Runx2, promotes chondrocyte hypertrophy, whereas parathyroid hormone-related protein (PTHrP) delays this process. To examine whether PTHrP suppresses chondrocyte hypertrophy via Runx2-dependent or -independent pathways, Runx2 expression and chondrocyte differentiation were analyzed using bones from embryonic limbs of wild type and Runx2(-/-) mice. Treatment of cultured rudiments with PTH dramatically suppresses Runx2 mRNA levels in hypertrophic chondrocytes. PTH-induced delay of chondrocyte hypertrophy was observed in cultured tibiae from both Runx2(-/-) and wild-type embryos. This delay was also seen after PTH administration to limbs from wild type and Runx2(-/-) mice expressing Runx2 in chondrocytes via a collagen 2 promoter-driven transgene. To further explore Runx2-dependent and -independent effects of PTHrP, we examined embryonic tibiae and femurs from littermates null for PTHrP, Runx2, or both genes. Runx2(-/-) femurs exhibited no vascular invasion or chondrocytes expressing collagen type X or osteopontin mRNA. In contrast, Runx2(-/-)/PTHrP(-/-) mice exhibited limited vascular invasion and some chondrocytes expressing collagen X or osteopontin mRNA. In both tibia and femur, Runx2(-/-)/PTHrP(-/-) mice exhibited expanded regions of proliferating chondrocytes when compared to the same regions in PTHrP(-/-) mice. These data indicate that the delayed hypertrophy induced by PTHrP is mediated by both Runx2-dependent and -independent mechanisms.

Animals↗
PubMed2006

A cDNA-AFLP based strategy to identify transcripts associated with avirulence in Phytophthora infestans.

Expression profiling using cDNA-AFLP is commonly used to display the transcriptome of a specific tissue or developmental stage. Here, cDNA-AFLP was used to identify transcripts in a segregating F1 population of Phytophthora infestans, the oomycete pathogen that causes late blight. To find transcripts derived from putative avirulence (Avr) genes germinated cyst cDNA from F1 progeny with defined avirulence phenotypes was pooled and used in a bulked segregant analysis (BSA). Over 30,000 transcript derived fragments (TDFs) were screened resulting in 99 Avr-associated TDFs as well as TDFs with opposite pattern. With 142 TDF sequences homology searches and database mining was carried out. cDNA-AFLP analysis on individual F1 progeny revealed 100% co-segregation of four TDFs with particular AVR phenotypes and this was confirmed by RT-PCR. Two match the same P. infestans EST with unknown sequence and this is a likely candidate for Avr4. The other two are associated with the Avr3b-Avr10-Avr11 locus. This combined cDNA-AFLP/BSA strategy is an efficient approach to identify Avr-associated transcriptome markers that can complement positional cloning.

Chromosome Mapping↗
PubMed2006

Hemorheological abnormalities in lipoprotein lipase deficient mice with severe hypertriglyceridemia.

Severe hypertriglyceridemia (HTG) is a metabolic disturbance often seen in clinical practice. It is known to induce life-threatening acute pancreatitis, but its role in atherogenesis remains elusive. Hemorheological abnormality was thought to play an important role in pathogenesis of both pancreatitis and atherosclerosis. However, hemorheology in severe HTG was not well investigated. Recently, we established a severe HTG mouse model deficient in lipoprotein lipase (LPL) in which severe HTG was observed to cause a significant increase in plasma viscosity. Disturbances of erythrocytes were also documented, including decreased deformability, electrophoresis rate, and membrane fluidity, and increased osmotic fragility. Scanning electron microscopy demonstrated that most erythrocytes of LPL deficient mice deformed with protrusions, irregular appearances or indistinct concaves. Analysis of erythrocyte membrane lipids showed decreased cholesterol (Ch) and phospholipid (PL) contents but unaltered Ch/PL ratio. The changes of membrane lipids may be partially responsible for the hemorheological and morphologic abnormalities of erythrocytes. This study indicated that severe HTG could lead to significant impairment of hemorheology and this model may be useful in delineating the role of severe HTG in the pathogenesis of hyperlipidemic pancreatitis and atherosclerosis.

Animals↗
PubMed2006

Molecular determinants of cocaine block of human ether-á-go-go-related gene potassium channels.

The use of cocaine causes cardiac arrhythmias and sudden death. Blockade of the cardiac potassium channel human ether-á-go-go-related gene (hERG) has been implicated as a mechanism for the proarrhythmic action of cocaine. hERG encodes the pore-forming subunits of the rapidly activating delayed rectifier K(+) channel (I(Kr)), which is important for cardiac repolarization. Blockade of I(Kr)/hERG represents a common mechanism for drug-induced long QT syndrome. The mechanisms for many common drugs to block the hERG channel are not well understood. We investigated the molecular determinants of hERG channels in cocaine-hERG interactions using site-targeted mutations and patch-clamp method. Wild-type and mutant hERG channels were heterologously expressed in human embryonic kidney 293 cells. We found that there was no correlation between inactivation gating and cocaine block of hERG channels. We also found that consistent with Thr-623, Tyr-652, and Phe-656 being critical for drug binding to hERG channels, mutations in these residues significantly reduced cocaine-induced block, and the hydrophobicity of the residues at position 656 dictated the cocaine sensitivity of the channel. Although the S620T mutation, which removed hERG inactivation, reduced cocaine block by 21-fold, the S620C mutation, which also completely removed hERG inactivation, did not affect the blocking potency of cocaine. Thus, Ser-620 is another pore helix residue whose mutation can interfere with cocaine binding independently of its effect on inactivation.

Binding, Competitive↗
PubMed2006

Epidermal growth factor receptor-mediated proliferation of enterocytes requires p21waf1/cip1 expression.

BACKGROUND & AIMS: Epidermal growth factor receptor (EGFR)-mediated increase in enterocyte proliferation following massive resection is a major mechanism by which the small intestine adapts to the loss of its mucosal surface area. In addition, expression of the cyclin-dependent kinase inhibitor p21(waf1/cip1) is required for resection-induced enterocyte proliferation. This study sought to establish a mechanistic link between EGFR-mediated intestinal epithelial cell proliferation and p21(waf1/cip1) expression. METHODS: EGF was used to stimulate IEC-6 and HCA-7 cells. P21(waf1/cip1) messenger RNA (mRNA) and protein expression were measured by real-time polymerase chain reaction and Western blot, respectively. P21(waf1/cip1) promoter studies were performed using p21(waf1/cip1) promoter-driven luciferase assay. Pharmacologic inhibitors of PI3-kinase and mitogen activated protein kinase (MAPK) were used to block these pathways downstream of the activated EGFR. Constitutively active Ras, Raf, or MEK-1 constructs were transfected into cells for overexpression studies. Cell proliferation was measured by bromodeoxyuridine incorporation following p21(waf1/cip1) silencing with RNAi. Finally, Cyclin D(1)/Cdk interaction was evaluated by immunoprecipitation. RESULTS: EGFR activation in intestinal epithelial cells induced the expression of p21(waf1/cip1) mRNA and protein This event was transcriptionally regulated via a 50-bp segment of the p21(waf1/cip1) promoter as a result of MAPK activation. Exogenous EGF failed to induce proliferation in p21(waf1/cip1)-silenced cells and adaptive proliferation after intestinal resection in p21(waf1/cip1)-null mice. Functionally, p21(waf1/cip1) up-regulation was required for stabilizing Cyclin D/Cdk 4 complexes and intestinal cell proliferation. CONCLUSIONS: EGFR-mediated induction of enterocyte proliferation requires MAPK-dependent increase in p21(waf1/cip1) expression in intestinal epithelial cells. These studies elucidate an important mechanism for resection-induced enterocyte proliferation during intestinal adaptation.

Animals↗
PubMed2006

Inhibition of phosphorylation of the colony-stimulating factor-1 receptor (c-Fms) tyrosine kinase in transfected cells by ABT-869 and other tyrosine kinase inhibitors.

The properties of several multitargeted receptor tyrosine kinase inhibitors have been studied for their inhibition of colony-stimulating factor-1 receptor (CSF-1R) signaling. A structurally novel, multitargeted tyrosine kinase inhibitor (ABT-869), imatinib (STI571), and four compounds currently in clinical development (AG013736, BAY 43-9006, CHIR258, and SU11248) were tested for inhibition of CSF-1R signaling in both the enzymatic and cellular assays. ABT-869 showed potent CSF-1R inhibition in both the enzyme and cell-based assays (IC50s < 20 nmol/L). In contrast to a previous report, we have found that imatinib has activity against human CSF-1R in both assays at submicromolar concentrations. In enzyme assays, we have found that the inhibition of CSF-1R by both ABT-869 and imatinib are competitive with ATP, with Ki values of 3 and 120 nmol/L, respectively. SU11248 is a potent inhibitor of CSF-1R in the enzyme assay (IC50 = 7 nmol/L) and inhibits receptor phosphorylation in the cellular assay (IC50 = 61 nmol/L). AG013736 was also a potent inhibitor of CSF-1R in both assays (enzyme, IC50 = 16 nmol/L; cellular, IC50 = 21 nmol/L), whereas BAY 43-9006 is less potent in the enzyme assay (IC50 = 107 nmol/L) than in the cellular system (IC50 = 20 nmol/L). In contrast, we found that CHIR258 had less activity in the cellular assay (IC50 = 535 nmol/L) relative to its enzymatic potency (IC50 = 26 nmol/L). These results show the use of a cell-based assay to confirm the inhibitory activity of lead compounds and drug candidates, such as ABT-869, against the CSF-1R protein in situ.

3T3 Cells↗
PubMed2006

Preclinical activity of ABT-869, a multitargeted receptor tyrosine kinase inhibitor.

ABT-869 is a structurally novel, receptor tyrosine kinase (RTK) inhibitor that is a potent inhibitor of members of the vascular endothelial growth factor (VEGF) and platelet-derived growth factor (PDGF) receptor families (e.g., KDR IC50 = 4 nmol/L) but has much less activity (IC50s > 1 micromol/L) against unrelated RTKs, soluble tyrosine kinases, or serine/threonine kinases. The inhibition profile of ABT-869 is evident in cellular assays of RTK phosphorylation (IC50 = 2, 4, and 7 nmol/L for PDGFR-beta, KDR, and CSF-1R, respectively) and VEGF-stimulated proliferation (IC50 = 0.2 nmol/L for human endothelial cells). ABT-869 is not a general antiproliferative agent because, in most cancer cells, >1,000-fold higher concentrations of ABT-869 are required for inhibition of proliferation. However, ABT-869 exhibits potent antiproliferative and apoptotic effects on cancer cells whose proliferation is dependent on mutant kinases, such as FLT3. In vivo ABT-869 is effective orally in the mechanism-based murine models of VEGF-induced uterine edema (ED50 = 0.5 mg/kg) and corneal angiogenesis (>50% inhibition, 15 mg/kg). In tumor growth studies, ABT-869 exhibits efficacy in human fibrosarcoma and breast, colon, and small cell lung carcinoma xenograft models (ED50 = 1.5-5 mg/kg, twice daily) and is also effective (>50% inhibition) in orthotopic breast and glioma models. Reduction in tumor size and tumor regression was observed in epidermoid carcinoma and leukemia xenograft models, respectively. In combination, ABT-869 produced at least additive effects when given with cytotoxic therapies. Based on pharmacokinetic analysis from tumor growth studies, efficacy correlated more strongly with time over a threshold value (cellular KDR IC50 corrected for plasma protein binding = 0.08 microg/mL, >or=7 hours) than with plasma area under the curve or Cmax. These results support clinical assessment of ABT-869 as a therapeutic agent for cancer.

3T3 Cells↗
PubMed2006

Biophysical studies on the differentiation of human CD14+ monocytes into dendritic cells.

Dendritic cells (DCs), which are the most efficient antigen-presenting cells (APCs) currently known, can be derived from CD14+ monocytes (DC predecessor cells) in vitro. Immature DCs actively take up antigens and pathogens, generate major histocompatability complex-peptide complexes, and migrate from the sites of antigen acquisition to secondary lymphoid organs to become mature dendritic cells that interact with and stimulate T-lymphocytes. During this process, the cells must undergo deformation to translocate through several barriers, including the basement membrane and interstitial connective tissue in the blood vessel wall. To further understand the mechanisms of the activation of immunological responses and the migration from peripheral tissue to secondary lymphoid organs, we have applied biophysical and microrheological methods to study the development processes of DCs in vitro. The results showed that membrane fluidity, osmotic fragility, membrane viscoelastic properties, infrared spectroscopy, and cytoskeleton organization of DCs exhibit significant differences in different developmental stages.

Biophysical Phenomena↗
PubMed2006

Effect of Panax notoginseng saponins on lipopolysaccharide-induced adhesion of leukocytes in rat mesenteric venules.

Panax notoginseng is the root of the Chinese traditional herb, Panax notoginseng (Burk) F.H. Chen. This study was aimed to investigate the inhibitory effect of Panax notoginseng saponins (PNS) on the leukocyte adhesion and the expression of adhesion molecules in rat mesentery venules. Male Sprague-Dawley rats were anesthetized with urethane. These were divided into control, LPS (perfused with lipopolysaccharide), and PNS group (perfused with PNS). The mesenteric microcirculation was observed under a videomicroscope. The number of adherent leukocytes, which attached to the vascular wall during more than 10 seconds, was counted along single venules (30-50 microm in diameter, 200 microm in length). The expression of adhesion molecules was examined using flow-cytometry in blood which was taken from the abdominal aorta and incubated with FITC-labeled CD11b (or CD18) antibodies. The results showed that different changes in the leukocyte adhesion and the expression of adhesion molecules among three groups. In LPS group, the leukocyte adhesion increased significantly after 20 minutes during the observation time, while it was reduced markedly in PNS group. The expression of CD11b and CD18 on the neutrophils was induced in LPS group, while it was reduced significantly in PNS group. It was suggested that PNS could reduce leukocyte adhesion in venules under the inhibitory effect on the expression of adhesion molecules (CD11b and CD18) on neutrophils.

Animals↗
PubMed2006

Inhibition effect of cardiotonic pills on venous thrombosis induced in rat mesentery by photochemical reaction.

This paper was aimed to explore the inhibition effect of cardiotonic pills (CP) on venous thrombosis induced in rat mesentery by photochemical stimulation (PS). Male Sprague-Dawley rats were anesthetized with urethane. Thrombosis was induced in the mesenteric venule by PS with photosensitizer hematoporphyrin and an ultraviolet beam. The rats were divided into three groups: control (n = 6), PS (n = 6) and PS + CP group (n = 6) where CP solution (0.4 g/kg.b) was administrated orally 60 min before PS. Microcirculatory disturbances in the mesentery were observed under an inverted microscope with a color video-camera. Based on the recorded images, the development of thrombosis was evaluated in term of time of thrombosis appearance (T(a)) and area ratio of thrombus/vessel (AR). The expression of adhesion molecule (CD31) of platelet was examined in blood taken from the abdominal aorta, using flow cytometry. The T(a) was approximately 10 seconds after PS in PS group, but it was approximately 20 seconds in PS + CP group. The AR in PS + CP group was significantly reduced, compared to that in PS group, during the period of the observation. The CD31 expression was not changed in both groups, while positive cells were significantly increased in the number. It is suggested that CP might suppress thrombus development under the interaction of platelet with endothelium.

Animals↗
PubMed2006

Comparison of ileal digested production of parental rice and rice genetically modified with cowpeas trypsin inhibitor.

OBJECTIVE: To compare the ileal digestibility of protein and amino acids in parental rice and rice genetically modified with sck gene. METHODS: Six experimental swines were surgically fixed with a simple T-cannula at the terminal ileum and fed with parental rice and rice genetically modified with sck gene alternately. The ileum digesta were collected and analyzed for determination of apparent and true digestibility of protein and amino acids. RESULTS: The apparent and true digestibility of protein was similar in these two types of rice. Except for the apparent digestibility of lysine, there was no difference in the apparent and true digestibility of the other 17 amino acids. CONCLUSION: The digestibility of protein and amino acids is not changed by the insertion of foreign gene, so it can meet the request of "substantial equivalence" in digestibility of protein and amino acids.

Amino Acids↗
PubMed2006

[Properties of a triphenylmethane dyes decolorization enzyme TpmD from Aeromonas hydrophila strain DN322].

A novel bacterial decolorization enzyme for triphenylmethane dyes from Aeromonas hydrophila strain DN322 was purified, named TpmD. The purified enzyme catalyzes the decolorization of several triphenylmethane dyes, i.e., crystal violet, basic fuchsin, brilliant green and malachite green. The enzyme was identified by the clear transparent band development of zymogram stained with crystal violet, basic fuchsin, brilliant green and malachite green after polyacrylamide gel electrophoresis (PAGE) respectively. The decolorization enzyme was enzymologically characterized. The results showed that the molecular weight of TpmD is 29.4kDa and its isoelectric point (pI) is 5.6. The maximal activity of TpmD for above four triphenylmethane dyes was observed at 50 degrees C - 55 degrees C and pH 7.4 - 8.0. The temperature for losing half of the activity (t1/2) within 4h is 62 degrees C. The activities of decolorization enzyme are relatively stable at pH range of 5.5 - 9.0. The K(m) and V(max) of TpmD for decolorizing crystal violet, basic fuchsin, brilliant green and malachite green are 24.3, 40.6, 54.2, 68.5 micromol/L respectively, V(max) are 19.6, 74.1, 82.8, 115.6 micromol x L(-1) x s(-1) respectively. Both NADH/NADPH and molecular oxygen are necessary for the enzyme to decolorize triphenylmethane dyes, indicate the enzyme is an NADH/NADPH-dependent oxygenase.

Aeromonas hydrophila↗