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Biomedical subjects

Yongjun Li

Publications and source records attributed to Yongjun Li.

At least 19 recordsLinked to original sources

Synthesis, characterization, and self-assembly of nitrogen-containing heterocoronenetetracarboxylic acid diimide analogues: photocyclization of N-heterocycle-substituted perylene bisimides.

Novel dibenzocoronenetetracarboxylic acid diimide analogues and naphthoperylenetetracarboxylic acid diimide analogues containing imidazole, 1,2,4-triazole, and pyrazole rings embedded as functional constituents within the parent hydrocarbon backbone have been synthesized. The pi-rich and pi-poor heterocycles have different influences on the physical properties of the parent benzocoronenetetracarboxylic acid diimide and naphthoperylenetetracarboxylic acid diimide systems. The pi-rich 3 was able to self-assemble into one-dimensional nanostructures through strong pi-pi stacking, whereas the pi-poor 8 lacked the one-dimensional self-assembly capability, thus offering the potential to control the self-assembly capability of the pi-conjugated perylene core by decoration with N-heterocycles.

Journal Article↗

Gene-environment interactions in complex diseases: genetic models and methods for QTL mapping in multiple half-sib populations.

An interval quantitative trait locus (QTL) mapping method for complex polygenic diseases (as binary traits) showing QTL by environment interactions (QEI) was developed for outbred populations on a within-family basis. The main objectives, within the above context, were to investigate selection of genetic models and to compare liability or generalized interval mapping (GIM) and linear regression interval mapping (RIM) methods. Two different genetic models were used: one with main QTL and QEI effects (QEI model) and the other with only a main QTL effect (QTL model). Over 30 types of binary disease data as well as six types of continuous data were simulated and analysed by RIM and GIM. Using table values for significance testing, results show that RIM had an increased false detection rate (FDR) for testing interactions which was attributable to scale effects on the binary scale. GIM did not suffer from a high FDR for testing interactions. The use of empirical thresholds, which effectively means higher thresholds for RIM for testing interactions, could repair this increased FDR for RIM, but such empirical thresholds would have to be derived for each case because the amount of FDR depends on the incidence on the binary scale. RIM still suffered from higher biases (15-100% over- or under-estimation of true values) and high standard errors in QTL variance and location estimates than GIM for QEI models. Hence GIM is recommended for disease QTL mapping with QEI. In the presence of QEI, the model including QEI has more power (20-80% increase) to detect the QTL when the average QTL effect is small (in a situation where the model with a main QTL only is not too powerful). Top-down model selection is proposed in which a full test for QEI is conducted first and then the model is subsequently simplified. Methods and results will be applicable to human, plant and animal QTL mapping experiments.

Animals↗

An engineered vascular endothelial growth factor-activating transcription factor induces therapeutic angiogenesis in ApoE knockout mice with hindlimb ischemia.

OBJECTIVE: Angiogenesis is the growth and proliferation of blood vessels from existing vascular structures, and therapeutic angiogenesis seeks to promote blood vessel growth to improve tissue perfusion. Vascular endothelial growth factor (VEGF) is a prototypic angiogenic agent that exists in vivo in multiple isoforms, and studies with VEGF to date had used single isoform therapy with disappointing results. We tested plasmid and adenoviral vectors encoding a zinc-finger DNA-binding transcription factor (ZFP-32E) that was designed to increase the expression of all major VEGF isoforms in a preclinical model of peripheral arterial obstructive disease (PAOD) in hypercholesterolemic (ApoE knock-out) mice. METHODS: Unilateral femoral artery ligation/excision was performed in 117 mice. At 7 days postoperatively, the ischemic tibialis anterior (TA) and gastrocnemius (GAS) muscles received either ZFP-32E treatment (125 microg of plasmid, 2.5 x 10(11) viral particle units [vpu] of adenovirus; some mice received a second plasmid injection 3 days later) or no-ZFP treatment (125 microg of beta-galactosidase [beta-gal], a plasmid-lacking insert, or an equal dose of adenoviral encoding beta-gal; some mice received a second plasmid injection 3 days later). Group 1 mice (n = 31) were euthanized 3 days later, and VEGF messenger RNA (mRNA) and protein levels were measured. Group 2 mice (n = 38) were euthanized 7 days later, and measures of capillary density, cell proliferation, and apoptosis were quantified. Group 3 mice (n = 48) were euthanized 28 days later, and changes in lower limb blood flow perfusion were measured. RESULTS: In group 1, VEGF mRNA and protein levels were significantly higher in those with ZFP-32E treatment vs beta-gal. In group 2, capillary density and proliferating cells were significantly greater and apoptosis was significantly lower in those with ZFP-32E treatment vs beta-gal. Finally, in group 3, changes in the perfusion ratio (ischemic/nonischemic limb) at 21 days after injection were significantly greater in those with ZFP-32E treatment vs no-ZFP treatment. CONCLUSION: The ability of this engineered zinc-finger VEGF-activating transcription factor to induce therapeutic angiogenesis in hypercholesterolemic mice suggests this approach warrants investigation as a novel approach to treat PAOD.

Adenoviridae↗

Optimization of a crossing system using mate selection.

A simple model based on one single identified quantitative trait locus (QTL) in a two-way crossing system was used to demonstrate the power of mate selection algorithms as a natural means of opportunistic line development for optimization of crossbreeding programs over multiple generations. Mate selection automatically invokes divergent selection in two parental lines for an over-dominant QTL and increased frequency of the favorable allele toward fixation in the sire-line for a fully-dominant QTL. It was concluded that an optimal strategy of line development could be found by mate selection algorithms for a given set of parameters such as genetic model of QTL, breeding objective and initial frequency of the favorable allele in the base populations, etc. The same framework could be used in other scenarios, such as programs involving crossing to exploit breed effects and heterosis. In contrast to classical index selection, this approach to mate selection can optimize long-term responses.

Alleles↗

Synthesis and characterization of 3,5-bis(2-hydroxyphenyl)-1,2,4-triazole functionalized tetraaryloxy perylene bisimide and metal-directed self-assembly.

[structure: see text] New perylene bisimide dyes bearing 3,5-bis(2-hydroxyphenyl)-1,2,4-triazole receptor units with different spacers have been synthesized and characterized. The fluorescence and electronic properties of these compounds have been studied. MALDI-TOF, UV-vis, and fluorescence titration experiments proved that monotopic perylene bisimide ligands could be assembled into dimmers by Fe(III) coordination. The coordination properties of the ditopic perylene bisimide ligands have also been studied preliminarily. Furthermore, the SEM images indicated that well-defined nanoscale structures could be fabricated by self-assembly due to metal ion coordination and pi-pi stacking interactions of perylene rings with the help of a proper spacer.

Journal Article↗

Energy transfer switching in a bistable molecular machine.

[reaction: see text] A novel [2]rotaxane, containing pyrene and perylene bisimide as both stoppers and photoactive units, has been prepared. The shuttling of the protonated macrocycle switched the energy transfer (EN) from a pyrene moiety to a perylene moiety, which resulted in changes of fluorescence of the perylene moiety.

Journal Article↗

Fabrication of polydiacetylene nanowires by associated self-polymerization and self-assembly processes for efficient field emission properties.

The paper described here concerns a challenge of general interest for producing a novel structure of a polymer aggregate, the achievement of nanowires with controlled diameters. We provide a strategy for fabricating a supramolecular polymer, in which ordered polydiacetylene nanowires can be obtained by associated self-polymerization and self-assembly processes. The polymer nanowire film shows excellent field emission properties with the turn-on field of 8.2 V/mum at 10 muA/cm2 and the maximum current density of 5 mA/cm2 at an applied field of 15 V/mum.

Acetylene↗

Overexpression, purification and characterization of a new salicylate hydroxylase from naphthalene-degrading Pseudomonas sp. strain ND6.

A new salicylate hydroxylase from naphthalene-degrading Pseudomonas sp. strain ND6, NahU, has been identified. The nahU is an isofunctional gene of the classic salicylate hydroxylase gene, nahG, and situated outside the transcriptional unit forming the naphthalene degradation lower pathway. Both genes, nahU and nahG of Pseudomonas sp. ND6, have been cloned and overexpressed in Escherichia coli BL21 (DE3). NahU contains 429 amino acid residues and NahG contains 434 amino acid residues. SDS-PAGE analysis showed that both NahG and NahU are about 47 kDa. Both enzymes exhibit broad substrate specificities and metabolize salicylate, sulfosalicylate, aspirin, methylsalicylate, chlorosalicylate and 3,5-dinitrosalicylate. The comparison of the Km and Vmax values for NahG and NahU demonstrated that NahU possesses a higher binding ability to salicylate and cofactors and catalytic efficiency.

Bacterial Proteins↗

A Mycobacterium avium PPE gene is associated with the ability of the bacterium to grow in macrophages and virulence in mice.

PPE and PE gene families, which encode numerous proteins of unknown function, account for 10% of Mycobacterium tuberculosis genome. Mycobacterium avium genome has similar PPE and PE gene families. Using a temperature-sensitive phage phAE94 transposon mutagenesis system, a M. avium transposon library was created in the strain MAC109. Screening of individual mutants in human U937 macrophages for the ability to replicate intracellularly, we identified several attenuated clones. One of them, the 2D6 mutant, has a transposon interrupting a PPE gene (52% homologous to Rv 1787 in M. tuberculosis) was identified. The mutant and the wild-type strain had comparable ability to enter macrophages. Challenge of mice with the 2D6 mutant resulted in approximately 1 log and 2 log fewer bacteria in the spleen, at 1 and 3 weeks after infection, compared with the wild-type bacterium. The 2D6 mutant grows like the wild-type bacterium in vitro. Vacuoles containing the 2D6 mutant acidified to pH 4.8; whereas, vacuoles containing wild-type bacterium were only slightly acidic. It was also observed that, in contrast to the wild-type bacterium, the 2D6 mutant did not prevent phagosome-lysosome fusion, and it is only expressed within macrophage but not in 7H9 broth. These results revealed a role for this PPE gene in the growth of M. avium in macrophages and in virulence in mice.

Animals↗

[Polymeric nanoparticles with therapeutic gene for gene therapy: I. Preparation and in vivo gene transfer study].

VEGF nanoparticle (VEGF-NP) was prepared by a multi-emulsification technique using a biodegradable poly-dl-lactic-co-glycolic (PLGA) as matrix material. The nanoparticles were characterized for size, VEGF loading capacity, and in vitro release. VEGF-NP and naked VEGF plasmid were intramuscularly injected into the ischemia site of the rabbit chronic hindlimb ischemia model and the efficiency of VEGF-NP as gene delivery carrier for gene therapy in animal model was evaluated. Gene therapuetic effect was assessed evaluated by RT-PCR, immunohistochemistry and angiography assay. The average size of VEGF-NP was around 300 nm. The encapsulation efficiency of VEGF was above 96%. Loading amount of VEGF in the nanoparticles was about 4%. In vitro, nanoparticles maintained sustained-release of VEGF for two weeks. Two weeks post gene injection the capillary density in VEGF-NP group (81.22 per mm2) was significantly higher than that in control group (29.54 mm2). RT-PCR results showed greatly higher VEGF expression in VEGF-NP group (31.79au * mm) than that in naked VEGF group (9.15 au * mm). As a carrier system for gene therapy in animal model, VEGF-NP is much better than naked DNA plasmid. The results demonstrate great possibility of using NP carrier in human gene therapy.

Animals↗

Assembly and characterization of novel hydrogen-bond-induced nanoscale rods.

A class of bis-urea compounds with perylene bisimide was synthesized and characterized successfully. (1)H NMR and fluorescence spectra confirmed that strong hydrogen-bonding interactions between neighboring urea groups were formed. Interestingly, the photocurrent measurement showed that the self-assembled films of bis-urea compounds could produce steady and rapid anodic photocurrent responses. The TEM images indicated that well-defined nanoscale rods with uniform diameter distribution could be fabricated by self-assembly of hydrogen-bonding interactions and pi-pi stacking interactions of perylene rings.

Journal Article↗

The relation between His bundle and the first septal perforating artery: implications for percutaneous transluminal septal myocardial ablation.

The present study shows that in about 12.4% of subjects the first septal artery (FSA) is very near from the His bundle. Routine measurement of His-FSA distance during percutaneous transluminal septal myocardial ablation (PTSMA) procedure might be helpful to stratify which patient would be at higher risk of developing complete AV block.

Bundle of His↗

[Nanoparticle as a new gene transferring vector in specific expression gene].

OBJECTIVE: To evaluate the possibility and efficiency of nanoparticle as a new vector in specific gene transference. METHODS: Nanoparticle-DNA complex was prepared with PLGA bearing antisense monocyte chemotactic protein-1 (A-MCP-1), a specific expression gene, and the package efficiency, release progress in vitro, and size of the complex were determined. The nanoparticl-DNA was trasnsfected into the cultured smooth muscle cells. PCR was used to evaluate the transfection of A-MCP-1. Cationic lipid (lipofectamine) was used to transfect A-MCP-1 as control. Forty-eight hours later, DNA in the SMCs was extracted and examined by PCR. Twenty New Zealand White rabbits underwent jugular vein-to-artery bypass grafting procedure, of which 6 received grafts transfected with nanopaticle-A-MCP-1 (200 microgram), 6 received grafts with cationic liposome (DOTAP)-A-MCP-1 (200 microgram), 4 received grafts with LNCX plasmid, and 4 received grafts without transfection as control. Fourteen days after surgery grafts were harvested. The expression of A-MCP-1 and its effect on MCP-1 in vein grafts were detected by dot blotting. The morphology of the grafts was investigated. RESULTS: The package efficiency, release progress in vitro, and size of the nanoparticle-DNA complex thus prepared were 0.9%, 2 week, and 150 nm approximately 300 nm respectively. Genomic DNA PCR showed that A-MCP-1 gene could be successfully transfected into smooth muscle cells by nanoparticle. Two weeks later, antisense MCP-1 was expressed in the vascular walls of the groups with transfection methods by nanaoparticle or by cationic lipid to an almost same degree. The degree of vascular hyperplasia in gene transfection groups was lower than that in control group. There was no significant difference in inhibition of intimal hyperplasia between the two groups of transfection by different vectors. CONCLUSION: Nanoparticle acts as a vector to transfect specific gene in vitro and in vivo.

Animals↗

Fractionated-clamping for thoracoabdominal aortic aneurysm repair: a modified Crawford technique.

OBJECTIVE: To apply fractionated-clamping for repair of thoracoabdominal aortic aneurysm (TAA), and evaluate its effects in decreasing surgical mortality and severe complications, such as renal failure and paraplegia, a modified crawford procedure were prospectively evaluated. METHODS: Using modified shunting and cross-clamping techniques, modified Crawford repair in 13 thoracoabdominal aorta patients were performed in the Vascular Division at Peking Union Medical College Hospital. TAA Crawford classification: 1 type I, 2 type II, 2 type III and 3 type IV TAA. Debakey classification: 1 type I, 4 type III (including 2 ruptured aneurysms), and 1 aortic coarctation. RESULTS: Thirteen procedures were performed successfully. One died of ventricular fibrillation just before completing the operation. Surgical mortality rate was 7.7% (1/13). Postoperative complications included 1 acute necrotic pancreatitis, 1 ARDS, 1 paraplegia, 1 acute renal failure, and 2 thoracic cavity bleeding. Total complication rate was 53.8% (7/13). CONCLUSIONS: Fractionated-clamping in thoracoabdominal aortic aneurysm repair is our modified Crawford procedure and aortic bypass. Clinical results demonstrate that our procedure decreased surgical mortality and major complication rate, and also alleviated viscera ischemic injury. Fractionated-clamping in aorta replacement is a practical procedure for TAA repair under general anesthesia at normal temperature.

Adult↗

Ehlers-Danlos syndrome: case and pedigree report and review.

OBJECTIVE: To report a case and a firstly described pedigree with Ehlers-Danlos syndrome in China. METHODS: Clinical materials of a case of Ehlers-Danlos syndrome type IV and a pedigree of 6 members with 4 generations were analyzed. Dilated internal jugular vein in the proband was removed operatively. The diagnosis, surgical treatment, and postoperative complications were retrospectively summarized. Etiology, clinical characteristics and classification of Ehlers-Danlos syndrome were also analysed. RESULTS: Vessels of the proband in the pedigree were crisp and easily lacinated during the precedure for removal of his internal jugular vein. Repeat postoperative hemotomas were found though complete stanching was made during operation. The patient successfully recovered after prompt debridement in operative theatre and needle sucking. The other 5 members of the pedigrees all had the triads of Ehlers-Danlos syndrome, but no combined vascular diseases were found in them. CONCLUSIONS: Though the morbidity rate was extremely low, green attention should be paid to the high mortality rate and complication of Ehlers-Danlos syndrome during surgical management of in patients with Ehlers-Danlos syndrome type IV. Surgeons should be aware of the ponderance of its complications and combined diseases to avoid fatal intraoprative vascular lacination and incontrollable hamorrhage.

China↗

Expression of antisense thrombin receptor gene inhibits intimal hyperplasia of rat carotid artery after balloon injury.

OBJECTIVE: To study the mechanism of restenosis after angioplasty and to clarify the effect of thrombin and its receptor on restenosis development. METHODS: Balloon catheter-induced injury was adopted to induce intimal hyperplasia of the carotid arteries in rats. Antisense thrombin receptor (ATR) cDNA was transfected by perfusing recombinant LXSN ATR plasmid/nanoparticle complex into the segment of the injured carotid artery. RESULTS: PCR result showed integration of the recombined gene. Dot blot showed the expression of antisense TR mediated by recombinant LXSN ATR plasmid/nanoparticle complex in the wall of common carotid arteries of the experimental group rats, which enabled to inhibit TR gene expression and intimal hyperplasia of the injured arteries. CONCLUSIONS: Thrombin and its receptor play an important role in the formation of neointima after the injury, which provides a potential clue in developing a new approach for prevention and treatment of restenosis after angioplasty.

Animals↗

[Microarray in screening for differentially expressed genes of cellular cycle and apoptosis in abdominal aortic aneurysms].

OBJECTIVE: To analyze the functions of differentially expressed genes between abdominal aortic aneurysm and normal aortic tissue by cDNA microarray. METHODS: Total RNAs were respectively isolated from the normal aorta and aortic aneurysm, purified into mRNAs by oligotex. Subsequently they were reverse-transcribed into cDNAs incorporated with fluorescent dUTP to make hybridization probes, which were hybridized as the cDNA microarray for scanning of fluorescent signals and differentially expressed genes between the normal aortic and aortic aneurysm by using GenePix Pro 3.0 software. RESULTS: A total of 18 differentially expressed genes were detected, accounting for 0.44% of total genes. Among these genes, 11 were related to cell cycle and the remaining 7 to cell apoptosis. The number of upregulated genes in the aortic aneurysm was 9 (mean ratio: 3.860) and that of the downregulated 9 (mean Ratio: 0.294). Bio-informative analysis showed that these 18 genes might influence the growth and apoptosis of smooth muscle cells in abdominal aortic aneurysms. CONCLUSIONS: During the development of abdominal aortic aneurysms, modulations of multi-gene expression would undergo various changes. Cell cycle and apoptosis-related genes were related to the growth and apoptosis of smooth muscle cells in abdominal aortic aneurysms. Further research into these genes will clarify the mechanisms of abdominal aortic aneurysms.

Aortic Aneurysm, Abdominal↗