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1.  Ideotype Population Exploration: Growth, Photosynthesis, and Yield Components at Different Planting Densities in Winter Oilseed Rape (Brassica napus L.) 
PLoS ONE  2014;9(12):e114232.
Rapeseed is one of the most important edible oil crops in the world and the seed yield has lagged behind the increasing demand driven by population growth. Winter oilseed rape (Brassica napus L.) is widely cultivated with relatively low yield in China, so it is necessary to find the strategies to improve the expression of yield potential. Planting density has great effects on seed yield of crops. Hence, field experiments were conducted in Wuhan in the Yangtze River basin with one conventional variety (Zhongshuang 11, ZS11) and one hybrid variety (Huayouza 9, HYZ9) at five planting densities (27.0×104, 37.5×104, 48.0×104, 58.5×104, 69.0×104 plants ha–1) during 2010–2012 to investigate the yield components. The physiological traits for high-yield and normal-yield populations were measured during 2011–2013. Our results indicated that planting densities of 58.5×104 plants ha–1 in ZS11 and 48.0×104 plants ha–1 in HYZ9 have significantly higher yield compared with the density of 27.0×104 plants ha–1for both varieties. The ideal silique numbers for ZS11 and HYZ9 were ∼0.9×104 (n m–2) and ∼1×104 (n m-2), respectively, and ideal primary branches for ZS11 and HYZ9 were ∼250 (n m–2) and ∼300 (n m–2), respectively. The highest leaf area index (LAI) and silique wall area index (SAI) was ∼5.0 and 7.0, respectively. Moreover, higher leaf net photosynthetic rate (Pn) and water use efficiency (WUE) were observed in the high-yield populations. A significantly higher level of silique wall photosynthesis and rapid dry matter accumulation were supposed to result in the maximum seed yield. Our results suggest that increasing the planting density within certain range is a feasible approach for higher seed yield in winter rapeseed in China.
doi:10.1371/journal.pone.0114232
PMCID: PMC4269386  PMID: 25517990
2.  Plasmon resonance enhanced multicolour photodetection by graphene 
Nature communications  2011;2:579.
Graphene has the potential for high-speed, wide-band photodetection, but only with very low external quantum efficiency and no spectral selectivity. Here we report a dramatic enhancement of the overall quantum efficiency and spectral selectivity that enables multicolour photodetection, by coupling graphene with plasmonic nanostructures. We show that metallic plasmonic nanostructures can be integrated with graphene photodetectors to greatly enhance the photocurrent and external quantum efficiency by up to 1,500%. Plasmonic nanostructures of variable resonance frequencies selectively amplify the photoresponse of graphene to light of different wavelengths, enabling highly specific detection of multicolours. Being atomically thin, graphene photodetectors effectively exploit the local plasmonic enhancement effect to achieve a significant enhancement factor not normally possible with traditional planar semiconductor materials.
doi:10.1038/ncomms1589
PMCID: PMC4235953  PMID: 22146398
3.  A systematic study of atmospheric pressure chemical vapor deposition growth of large-area monolayer graphene† 
Journal of materials chemistry  2012;22(4):1498-1503.
Graphene has attracted considerable interest as a potential material for future electronics. Although mechanical peel is known to produce high quality graphene flakes, practical applications require continuous graphene layers over a large area. The catalyst-assisted chemical vapor deposition (CVD) is a promising synthetic method to deliver wafer-sized graphene. Here we present a systematic study on the nucleation and growth of crystallized graphene domains in an atmospheric pressure chemical vapor deposition (APCVD) process. Parametric studies show that the mean size of the graphene domains increases with increasing growth temperature and CH4 partial pressure, while the density of domains decreases with increasing growth temperature and is independent of the CH4 partial pressure. Our studies show that nucleation of graphene domains on copper substrate is highly dependent on the initial annealing temperature. A two-step synthetic process with higher initial annealing temperature but lower growth temperature is developed to reduce domain density and achieve high quality full-surface coverage of monolayer graphene films. Electrical transport measurements demonstrate that the resulting graphene exhibits a high carrier mobility of up to 3000 cm2 V−1 s−1 at room temperature.
doi:10.1039/C1JM14272K
PMCID: PMC4235958  PMID: 25414547
4.  Increasing Burn Severity in Mice is Associated with Delayed Mobilization of Circulating Angiogenic Cells 
Angiogenesis is an important component of wound healing. Mobilization of circulating angiogenic cells (CACs) has been observed in patients with cutaneous burn wounds, but a systematic exploration of the phenomenon in an animal model has not been carried out. Using a murine model, in which burn depth can be varied precisely, and a validated culture method for quantifying circulating CACs, we found that increasing burn depth resulted in a progressive delay in the time to mobilization of circulating CACs. This delay in CAC mobilization was associated with a delay in perfusion and vascularization of the burn wound tissue. Analysis of CACs in the peripheral blood of human burn patients, using the same culture assay, confirmed results previously obtained by flow cytometry, that CAC levels peak early after the burn wound, and point to the clinical relevance of findings from the murine model.
doi:10.1001/archsurg.2009.285
PMCID: PMC4209728  PMID: 20231626
5.  Impaired Angiogenesis and Mobilization of Circulating Angiogenic Cells in HIF-1α Heterozygous-Null Mice after Burn Wounding 
Hypoxia-inducible factor 1 (HIF-1) is a transcription factor that controls vascular responses to hypoxia and ischemia. In this study, mice that were heterozygous for a null allele at the locus encoding the HIF-1α subunit (HET mice) and their wild type (WT) littermates were subjected to thermal injury involving 10% of body surface area. HIF-1α protein levels were increased in burn wounds of WT but not of HET mice on day 2. Serum levels of stromal-derived factor 1α, which binds to CXCR4, were increased on day 2 in WT but not in HET mice. Circulating angiogenic cells were also increased on day 2 in WT but not in HET mice and included CXCR4+Sca1+ cells. Laser Doppler perfusion imaging demonstrated increased blood flow in burn wounds of WT but not HET mice on day 7. Immunohistochemistry on day 7 revealed a reduced number of CD31+ vessels at the healing margin of burn wounds in HET as compared to WT mice. Vessel maturation was also impaired in wounds of HET mice as determined by the number of α-smooth muscle actin-positive vessels on day 21. The remaining wound area on day 14 was significantly increased in HET mice compared to WT littermates. The percentage of healed wounds on day 14 was significantly decreased in HET mice. These data delineate a signaling pathway by which HIF-1 promotes angiogenesis during burn wound healing.
doi:10.1111/j.1524-475X.2010.00570.x
PMCID: PMC4206187  PMID: 20163569
6.  Endothelial Na+/H+ exchanger NHE1 participates in redox-sensitive leukocyte recruitment triggered by methylglyoxal 
Cardiovascular Diabetology  2014;13(1):134.
Background
Excessive levels of methylglyoxal (MG) encountered in diabetes foster enhanced leukocyte-endothelial cell interactions, mechanisms of which are incompletely understood. MG genomically upregulates endothelial serum- and glucocorticoid-inducible kinase 1 (SGK1) which orchestrates leukocyte recruitment by regulating the activation and expression of transcription factors and adhesion molecules. SGK1 regulates a myriad of ion channels and carriers including the Na+/H+ exchanger NHE1. Here, we explored the effect of MG on SGK1-dependent NHE1 activation and the putative role of NHE1 activation in MG-induced leukocyte recruitment and microvascular hyperpermeability.
Methods
Using RT-PCR and immunoblotting, we analyzed NHE1 mRNA and protein levels in murine microvascular SVEC4-10EE2 endothelial cells (EE2 ECs). NHE1 phosphorylation was detected using a specific antibody against the 14-3-3 binding motif at phospho-Ser703. SGK in EE2 ECs was silenced using targeted siRNA. ROS production was determined using DCF-dependent fluorescence. Leukocyte recruitment and microvascular permeability in murine cremasteric microvasculature were measured using intravital microscopy. The expression of endothelial adhesion molecules was determined by immunoblotting and confocal imaging analysis.
Results
MG treatment significantly upregulated NHE1 mRNA and dose-dependently increased total- and phospho-NHE1. Treatment with SGK1 inhibitor GSK650394, antioxidant Tempol and silencing SGK all blunted MG-triggered phospho-NHE1 upregulation in EE2 ECs. NHE1 inhibitor cariporide attenuated MG-triggered ROS production, leukocyte adhesion and emigration and microvascular hyperpermeability, without affecting leukocyte rolling. Cariporide treatment did not alter MG-triggered upregulation of P- and E-selectins, but reduced endothelial ICAM-1 expression.
Conclusion
MG elicits SGK1-dependent activation of endothelial Na+/H+ exchanger NHE1 which participates in MG-induced ROS production, upregulation of endothelial ICAM-1, leukocyte recruitment and microvascular hyperpermeability. Pharmacological inhibition of NHE1 attenuates the proinflammatory effects of excessive MG and may, thus, be beneficial in diabetes-associated inflammation.
doi:10.1186/s12933-014-0134-7
PMCID: PMC4193979  PMID: 25270604
Methylglyoxal; NHE1; Oxidative stress; SGK1; Leukocyte recruitment
7.  Strengthening the Skin with Topical Delivery of Keratinocyte Growth Factor-1 Using a Novel DNA Plasmid 
Molecular Therapy  2014;22(4):752-761.
Fragile skin, susceptible to decubitus ulcers and incidental trauma, is a problem particularly for the elderly and for those with spinal cord injury. Here, we present a simple approach to strengthen the skin by the topical delivery of keratinocyte growth factor-1 (KGF-1) DNA. In initial feasibility studies with the novel minimalized, antibiotic-free DNA expression vector, NTC8385-VA1, the reporter genes luciferase and enhanced green fluorescent protein were delivered. Transfection was documented when luciferase expression significantly increased after transfection. Microscopic imaging of enhanced green fluorescent protein–transfected skin showed green fluorescence in hair follicles, hair shafts, and dermal and superficial epithelial cells. With KGF-1 transfection, KGF-1 mRNA level and protein production were documented with quantitative reverse transcriptase–polymerase chain reaction and immunohistochemistry, respectively. Epithelial thickness of the transfected skin in the KGF group was significantly increased compared with the control vector group (26 ± 2 versus 16 ± 4 µm) at 48 hours (P = 0.045). Dermal thickness tended to be increased in the KGF group (255 ± 36 versus 162 ± 16 µm) at 120 hours (P = 0.057). Biomechanical assessment showed that the KGF-1–treated skin was significantly stronger than control vector–transfected skin. These findings indicate that topically delivered KGF-1 DNA plasmid can increase epithelial thickness and strength, demonstrating the potential of this approach to restore compromised skin.
doi:10.1038/mt.2014.2
PMCID: PMC3982499  PMID: 24434934
8.  Electroacupuncture decreases cognitive impairment and promotes neurogenesis in the APP/PS1 transgenic mice 
Background
Alzheimer’s disease (AD) is a severe neurodegenerative disease for which there is currently no effective treatment. The purpose of this study was to investigate whether repeated electroacupuncture (EA) stimulation would improve cognitive function and the pathological features of AD in amyloid precursor protein (APP)/presenilin 1 (PS1) double transgenic mice.
Methods
Cognitive function of APP/PS1 double transgenic mice was assessed using the Morris water maze test before and after EA treatment. Levels of amyloid β-peptide (Aβ) deposits in the hippocampus and cortex were evaluated by immunofluorescence, western blot and enzyme-linked immunosorbent assay. Expression of brain-derived neurotrophic factor (BDNF) was also examined by immunofluorescence and western blot. The neurogenesis was labeled by the DNA marker bromodeoxyuridine.
Results
EA stimulation significantly ameliorated the learning and memory deficits of AD mice by shortening escape latency and increasing the time spent in the target zone during the probe test. Additionally, decreased Aβ deposits and increased BDNF expression and neurogenesis in the hippocampus and cortex of EA-treated AD mice were detected. The same change was detected in wild-type mice after EA treatment compared with wild-type mice without EA treatment.
Conclusions
Repeated EA stimulation may improve cognitive function, attenuate Aβ deposits, up-regulate the expression of BDNF and promote neurogenesis in the APP/PS1 double transgenic mice. This suggests that EA may be a promising treatment for AD.
doi:10.1186/1472-6882-14-37
PMCID: PMC3907495  PMID: 24447795
Alzheimer’s disease; Electroacupuncture; Neurogenesis; BDNF; Aβ deposits
9.  RECENT PROGRESS IN MULTIFOCAL MULTIPHOTON MICROSCOPY 
Journal of innovative optical health sciences  2012;5(3):10.1142/S1793545812500186.
Multifocal multiphoton microscopy (MMM) has recently become an important tool in biomedicine for performing three-dimensional fast fluorescence imaging. Using various beamsplitting techniques, MMM splits the near-infrared laser beam into multiple beamlets and produces a multifocal array on the sample for parallel multiphoton excitation and then records fluorescence signal from all foci simultaneously with an area array detector, which significantly improves the imaging speed of multiphoton microscopy and allows for high efficiency in use of the excitation light. In this paper, we discuss the features of several MMM setups using different beamsplitting devices, including a Nipkow spinning disk, a microlens array, a set of beamsplitting mirrors, or a diffractive optical element (DOE). In particular, we present our recent work on the development of an MMM using a spatial light modulator (SLM).
doi:10.1142/S1793545812500186
PMCID: PMC3868482  PMID: 24363782
Multifocal multiphoton microscopy (MMM); microlens array; beamsplitter; diffractive optical element (DOE); spatial light modulator (SLM)
10.  High Yield Chemical Vapor Deposition Growth of High Quality Large-Area AB Stacked Bilayer Graphene 
ACS nano  2012;6(9):8241-8249.
Bernal stacked (AB stacked) bilayer graphene is of significant interest for functional electronic and photonic devices due to the feasibility to continuously tune its band gap with a vertical electrical field. Mechanical exfoliation can be used to produce AB stacked bilayer graphene flakes but typically with the sizes limited to a few micrometers. Chemical vapor deposition (CVD) has been recently explored for the synthesis of bilayer graphene but usually with limited coverage and a mixture of AB and randomly stacked structures. Herein we report a rational approach to produce large-area high quality AB stacked bilayer graphene. We show that the self-limiting effect of graphene growth on Cu foil can be broken by using a high H2/CH4 ratio in a low pressure CVD process to enable the continued growth of bilayer graphene. A high temperature and low pressure nucleation step is found to be critical for the formation of bilayer graphene nuclei with high AB stacking ratio. A rational design of a two-step CVD process is developed for the growth of bilayer graphene with high AB stacking ratio (up to 90 %) and high coverage (up to 99 %). The electrical transport studies demonstrated that devices made of the as-grown bilayer graphene exhibit typical characteristics of AB stacked bilayer graphene with the highest carrier mobility exceeding 4,000 cm2/V·s at room temperature, comparable to that of the exfoliated bilayer graphene.
doi:10.1021/nn302918x
PMCID: PMC3493488  PMID: 22906199
bilayer graphene; band gap; AB stacking; chemical vapor deposition; copper foil
11.  Methylglyoxal modulates endothelial nitric oxide synthase-associated functions in EA.hy926 endothelial cells 
Background
Increased levels of the sugar metabolite methylglyoxal (MG) in vivo were shown to participate in the pathophysiology of vascular complications in diabetes. Alterations of endothelial nitric oxide synthase (eNOS) activity by hypophosphorylation of the enzyme and enhanced monomerization are found in the diabetic milieu, and the regulation of this still remains undefined. Using various pharmacological approaches, we elucidate putative mechanisms by which MG modulates eNOS-associated functions of MG-stimulated superoxide O2•- production, phosphorylation status and eNOS uncoupling in EA.hy926 human endothelial cells.
Methods
In cultured EA.hy926 endothelial cells, the effects of MG treatment, tetrahydrobiopterin (BH4; 100 μM) and sepiapterin (20 μM) supplementation, NOS inhibition by NG-nitro-L-arginine methyl ester (L-NAME; 50 μM), and inhibition of peroxynitrite (ONOO-) formation (300 μM Tempol plus 50 μM L-NAME) on eNOS dimer/monomer ratios, Ser-1177 eNOS phosphorylation and 3-nitrotyrosine (3NT) abundance were quantified using immunoblotting. O2•-–dependent fluorescence was determined using a commercially available kit and tissue biopterin levels were measured by fluorometric HPLC analysis.
Results
In EA.hy926 cells, MG treatment significantly enhanced O2•- generation and 3NT expression and reduced Ser-1177 eNOS phosphorylation, eNOS dimer/monomer ratio and cellular biopterin levels indicative of eNOS uncoupling. These effects were significantly mitigated by administration of BH4, sepiapterin and suppression of ONOO- formation. L-NAME treatment significantly blunted eNOS-derived O2•- generation but did not modify eNOS phosphorylation or monomerization.
Conclusion
MG triggers eNOS uncoupling and hypophosphorylation in EA.hy926 endothelial cells associated with O2•- generation and biopterin depletion. The observed effects of the glycolysis metabolite MG presumably account, at least in part, for endothelial dysfunction in diabetes.
doi:10.1186/1475-2840-12-134
PMCID: PMC4015749  PMID: 24050620
Methylglyoxal; eNOS uncoupling; Superoxide; Tyrosine nitration; Biopterins; eNOS phosphorylation
12.  Scalable fabrication of self-aligned graphene transistors and circuits on glass 
Nano Letters  2011;12(6):2653-2657.
High frequency graphene transistors with the intrinsic cut-off frequency up to 300 gigahertz (GHz) have been demonstrated for radio frequency (RF) applications. However, functional graphene RF circuits such as frequency doublers and mixers operating in the gigahertz range is yet to demonstrated. Here we report a scalable approach to fabricate self-aligned graphene transistors and circuits that can operate in gigahertz regime. The devices are fabricated through a self-aligned aligned process on glass substrate using chemical vapor deposition (CVD) grown graphene and a dielectrophoretic assembled nanowire gate array. The self-aligned process allows to achieving unprecedented performance in CVD graphene transistors with a highest transconductance of 0.36 mS/μm. With the minimization of parasitic capacitance on insulating substrate, the resulting graphene transistors exhibit a record high extrinsic cut-off frequency (> 50 GHz) achieved in graphene transistors to date. The excellent extrinsic cut-off frequency readily allows configuring the graphene transistors into frequency doubling or mixing circuits functioning in the 1–10 GHz regime, a significant advancement over previous report (~20 MHz). The studies open a pathway to scalable fabrication of high speed graphene transistors and functional circuits, and represent a significant step forward to graphene based radio frequency devices.
doi:10.1021/nl201922c
PMCID: PMC3269556  PMID: 21648419
graphene transistors; self-aligned gate; cut-off frequency; RF mixers
13.  Domain Wall Motion in Synthetic Co2Si Nanowires 
Nano letters  2012;12(4):1972-1976.
We report the synthesis of single crystalline Co2Si nanowires, and electrical transport studies of single Co2Si nanowire devices at low temperature. The butterfly-shaped magnetoresistance shows interesting ferromagnetic features including negative magnetoresistance, hysteretic switch fields and step-wise drops in magnetoresistance. The non-smooth step-wise magnetoresistance response is attributed to magnetic domain wall pinning and de-pinning motion in the Co2Si nanowires probably at crystal defects or morphology defects. The temperature dependence of the domain wall de-pinning field is observed and is described by a model based on thermally assisted domain wall de-pinning over a single energy barrier.
doi:10.1021/nl204510p
PMCID: PMC3493485  PMID: 22469009
nanowires; magnetoresistance; domain wall; de-pinning field
14.  The protective effect and underlying mechanism of metformin on neointima formation in fructose-induced insulin resistant rats 
Background
Insulin resistance is strongly associated with the development of type 2 diabetes and cardiovascular disease. However, the underlying mechanisms linking insulin resistance and the development of atherosclerosis have not been fully elucidated. Moreover, the protective effect of antihyperglycemic agent, metformin, is not fully understood. This study investigated the protective effects and underlying mechanisms of metformin in balloon-injury induced stenosis in insulin resistant rats.
Methods
After 4 weeks high fructose diet, rats received balloon catheter injury on carotid arteries and were sacrificed at 1 and 4 weeks post injury. Biochemical, histological, and molecular changes were investigated.
Results
Plasma levels of glucose, insulin, total cholesterol, triglyceride, free fatty acids, and methylglyoxal were highly increased in fructose-induced insulin resistant rats and treatment with metformin significantly improved this metabolic profile. The neointimal formation of the carotid arteries was enhanced, and treatment with metformin markedly attenuated neointimal hyperplasia. A significant reduction in BrdU-positive cells in the neointima was observed in the metformin-treated group (P < 0.01). Insulin signaling pathways were inhibited in insulin resistant rats while treatment with metformin enhanced the expression of insulin signaling pathways. Increased expression of JNK and NFKB was suppressed following metformin treatment. Vasoreactivity was impaired while treatment with metformin attenuated phenylephrine-induced vasoconstriction and enhanced methacholine-induced vasorelaxation of the balloon injured carotid arteries in insulin resistant rats.
Conclusion
The balloon-injury induced neointimal formation of the carotid arteries is enhanced by insulin resistance. Treatment with metformin significantly attenuates neointimal hyperplasia through inhibition of smooth muscle cell proliferation, migration, and inflammation as well as by improvement of the insulin signaling pathway.
doi:10.1186/1475-2840-12-58
PMCID: PMC3642024  PMID: 23561047
Neointimal hyperplasia; Insulin resistance; Methylglyoxal; Metformin; Rat
15.  Pharmacological Inhibition of p38 Mitogen-Activated Protein Kinases Affects KC/CXCL1-Induced Intraluminal Crawling, Transendothelial Migration, and Chemotaxis of Neutrophils In Vivo 
Mediators of Inflammation  2013;2013:290565.
p38 mitogen-activated protein kinase (MAPK) signalling is critical in the pathophysiology of a variety of inflammatory processes. Leukocyte recruitment to the site of inflammation is a multistep process governed by specific signalling cascades. After adhesion in the lumen, many leukocytes crawl to optimal sites at endothelial junctions and transmigrate to extravascular tissue in a Mac-1-dependent manner. The signalling mechanisms that regulate postadhesion steps of intraluminal crawling, transmigration, and chemotaxis in tissue remain incompletely understood. The present study explored the effect of p38 MAPK inhibitor SB203580 on various parameters of neutrophil recruitment triggered by chemokine KC (CXCL1) gradient. Neutrophil-endothelial interactions in microvasculature of murine cremaster muscle were determined using intravital microscopy and time-lapsed video analysis. SB203580 (100 nM) did not change leukocyte rolling but significantly attenuated neutrophil adhesion, emigration, and transmigration and impaired the initiation of neutrophil crawling and transmigration. In response to KC chemotactic gradient, SB203580 significantly reduced the velocity of migration and chemotaxis index of neutrophils in tissue. The upregulation of Mac-1 expression in neutrophils stimulated by KC was significantly blunted by SB203580 in vitro. Collectively, our findings demonstrate that pharmacological suppression of p38 MAPK significantly impairs multiple steps of neutrophil recruitment in vivo.
doi:10.1155/2013/290565
PMCID: PMC3603207  PMID: 23533303
16.  Tie2-dependent knockout of HIF-1 impairs burn wound vascularization and homing of bone marrow-derived angiogenic cells 
Cardiovascular Research  2011;93(1):162-169.
Aims
Hypoxia-inducible factor 1 (HIF-1) is a heterodimer composed of HIF-1α and HIF-1β subunits. HIF-1 is known to promote tissue vascularization by activating the transcription of genes encoding angiogenic factors, which bind to receptors on endothelial cells (ECs) and bone marrow-derived angiogenic cells (BMDACs). In this study, we analysed whether HIF-1 activity in the responding ECs and BMDACs is also required for cutaneous vascularization during burn wound healing.
Methods and results
We generated mice with floxed alleles at the Hif1a or Arnt locus encoding HIF-1α and HIF-1β, respectively. Expression of Cre recombinase was driven by the Tie2 gene promoter, which is expressed in ECs and bone marrow cells. Tie2Cre+ and Tie2Cre− mice were subjected to burn wounds of reproducible diameter and depth. Deficiency of HIF-1α or HIF-1β in Tie2-lineage cells resulted in delayed wound closure, reduced vascularization, decreased cutaneous blood flow, impaired BMDAC mobilization, and decreased BMDAC homing to burn wounds.
Conclusion
HIF-1 activity in Tie2-lineage cells is required for the mobilization and homing of BMDACs to cutaneous burn wounds and for the vascularization of burn wound tissue.
doi:10.1093/cvr/cvr282
PMCID: PMC3243042  PMID: 22028336
Hypoxia; Wound healing; Conditional knockout; Angiogenesis
17.  Inhibition of nitric oxide synthesis enhances leukocyte rolling and adhesion in human microvasculature 
Background
Nitric oxide (NO) is a multifunctional signaling molecule that regulates important cellular events in inflammation including leukocyte recruitment. Previous studies have shown that pharmacological inhibition of NO synthesis induces leukocyte recruitment in various in vitro and animal models. However, it is not known whether NO modulation has similar effects on leukocyte-endothelial cell interactions within the human microvasculature. The present study explored the effect of systemic L-NAME treatment on leukocyte recruitment in the SCID-hu mouse model.
Methods
Human skin xenografts were transplanted in SCID mice to study human leukocyte dynamics in human vasculature. Early events of human leukocyte recruitment in human vasculature were studied using intravital microscopy. NO synthesis was pharmacologically inhibited using NG-nitro-L-arginine methyl ester (L-NAME). Immunohistochemical analysis was performed to elucidate E-selectin expression in human xenograft skin. Human neutrophil-endothelial cell interactions were also studied in an in vitro flow chamber assay system. P- and E-selectin expression on cultured human umbilical vein endothelial cells (HUVECs) was measured using ELISA. Platelet-activating factor (PAF) synthesis was detected using a TLC-based assay.
Results
L-NAME treatment significantly enhanced the rolling and adhesion of human leukocytes to the human vasculature. Functional blocking of P- and E-selectins significantly inhibited rolling but not adhesion induced by inhibition of NO synthesis. Systemic L-NAME treatment enhanced E-selectin expression in human xenograft skin. L-NAME treatment significantly enhanced P- and E-selectin expression on HUVECs. L-NAME treatment did not significantly modify neutrophil rolling or adhesion to HUVECs indicating that L-NAME−induced subtle P- and E-selectin expression was insufficient to elicit dynamic neutrophil-HUVEC interactions in vitro. Moreover, synthesis of endothelial-derived PAF was not significantly modified by L-NAME treatment. These results point to the accelerated leukocyte recruitment in human vasculature following suppression of NO synthesis, effects that are mediated by P- and E-selectins. The findings are, however, not supported by the in vitro data.
Conclusion
Inhibition of endogenous NO triggers early events of human leukocyte recruitment in human vasculature, involving complex cellular or molecular mechanisms in addition to P- and E-selectin-mediated leukocyte rolling.
doi:10.1186/1476-9255-9-28
PMCID: PMC3414823  PMID: 22812684
Leukocyte recruitment; nitric oxide; P-selectin; E-selectin; L-NAME; SCID-Hu
18.  Top-gated CVD Graphene Transistors with Current Saturation 
Nano letters  2011;11(6):2555-2559.
Graphene transistors are of considerable interest for radio frequency (RF) applications. In general, transistors with large transconductance and drain current saturation is desirable for RF performance, which is however nontrivial to achieve in graphene transistors. Here we report high performance top-gated graphene transistors based on chemical vapor deposition (CVD) grown graphene with large transconductance and drain current saturation. The graphene transistors were fabricated with evaporated high dielectric constant material (HfO2) as the top-gate dielectrics. Length scaling studies of the transistors with channel length from 5.6 µm to 100 nm shows that complete current saturation can be achieved in 5.6 µm devices and the saturation characteristics degrade as the channel length shrinks down to 100–300 nm regime. The drain current saturation was primarily attributed to drain bias induced shift of the Dirac points. With the selective deposition of HfO2 gate dielectrics, we have further demonstrated a simple scheme to realize a 300 nm channel length graphene transistors with self-aligned source-drain electrodes to achieve the highest transconductance of 250 µS/µm reported in CVD graphene to date.
doi:10.1021/nl201331x
PMCID: PMC3236244  PMID: 21548551
Graphene; transistors; dielectrics; current saturation; self-alignment
19.  Hypoxia and Hypoxia-Inducible Factor in the Burn Wound 
The importance of hypoxia-inducible factor (HIF) in promoting angiogenesis and vasculogenesis during wound healing has been demonstrated. It is widely accepted that HIF activity can be promoted by many factors, including hypoxia in the wound or cytokines from inflammatory cells infiltrating the wound. However, there has not been a systematic exploration of the relationship between HIF activity and hypoxia in the burn wound. The location of the hypoxic tissue has not been clearly delineated. The time course of the appearance of hypoxia and the increased activity of HIF and appearance of HIF’s downstream transcription products has not been described. The aim of this study was to utilize pimonidazole, a specific tissue hypoxia marker, to characterize the spatial and temporal course of hypoxia in a murine burn model and correlate this with the appearance of HIF-1α and its important angiogenic and vasculogenic transcription products VEGF and SDF-1. Hypoxia was found in the healing margin of burn wounds beginning at 48 hours after burn and peaking at day 3 after burn. On sequential sections of the same tissue block, positive staining of HIF-1α, SDF-1, and VEGF all occurred at the leading margin of the healing area and peaked at day 3, as did hypoxia. Immunohistochemical analysis was used to explore the characteristics of the hypoxic region of the wound. The localization of hypoxia was found to be related to cell growth and migration, but not to proliferation or inflammatory infiltration.
doi:10.1111/j.1524-475X.2010.00656.x
PMCID: PMC3075089  PMID: 21362088
ypoxia; Hypoxia-inducible factor -10α; Burn; Wound Healing; Ki67 Cell Proliferation; Keratin17
20.  Synthesis and White-Light Emission of ZnO/HfO2: Eu Nanocables 
Nanoscale Research Letters  2010;5(9):1418-1423.
ZnO/HfO2:Eu nanocables were prepared by radio frequency sputtering with electrospun ZnO nanofibers as cores. The well-crystallized ZnO/HfO2:Eu nanocables showed a uniform intact core–shell structure, which consisted of a hexagonal ZnO core and a monoclinic HfO2 shell. The photoluminescence properties of the samples were characterized. A white-light band emission consisted of blue, green, and red emissions was observed in the nanocables. The blue and green emissions can be attributed to the zinc vacancy and oxygen vacancy defects in ZnO/HfO2:Eu nanocables, and the yellow–red emissions are derived from the inner 4f-shell transitions of corresponding Eu3+ ions in HfO2:Eu shells. Enhanced white-light emission was observed in the nanocables. The enhancement of the emission is ascribed to the structural changes after coaxial synthesis.
doi:10.1007/s11671-010-9655-5
PMCID: PMC2920422  PMID: 20730130
ZnO; HfO2:Eu; Nanocables; White-light emission; Electrospinning
21.  Synthesis and White-Light Emission of ZnO/HfO2: Eu Nanocables 
Nanoscale Research Letters  2010;5(9):1418-1423.
ZnO/HfO2:Eu nanocables were prepared by radio frequency sputtering with electrospun ZnO nanofibers as cores. The well-crystallized ZnO/HfO2:Eu nanocables showed a uniform intact core–shell structure, which consisted of a hexagonal ZnO core and a monoclinic HfO2 shell. The photoluminescence properties of the samples were characterized. A white-light band emission consisted of blue, green, and red emissions was observed in the nanocables. The blue and green emissions can be attributed to the zinc vacancy and oxygen vacancy defects in ZnO/HfO2:Eu nanocables, and the yellow–red emissions are derived from the inner 4f-shell transitions of corresponding Eu3+ ions in HfO2:Eu shells. Enhanced white-light emission was observed in the nanocables. The enhancement of the emission is ascribed to the structural changes after coaxial synthesis.
doi:10.1007/s11671-010-9655-5
PMCID: PMC2920422  PMID: 20730130
ZnO; HfO2:Eu; Nanocables; White-light emission; Electrospinning
22.  Age-dependent Impairment of HIF-1α̣Expression in Diabetic Mice: Correction with Electroporation-facilitated Gene Therapy Increases Wound Healing, Angiogenesis, and Circulating Angiogenic Cells 
Journal of cellular physiology  2008;217(2):319-327.
Wound healing is impaired in elderly patients with diabetes mellitus. We hypothesized that age-dependent impairment of cutaneous wound healing in db/db diabetic mice: (a) would correlate with reduced expression of the transcription factor hypoxia-inducible factor 1α (HIF-1α) as well as its downstream target genes; and (b) could be overcome by HIF-1α replacement therapy. Wound closure, angiogenesis, and mRNA expression in excisional skin wounds were analyzed and circulating angiogenic cells were quantified in db/db mice that were untreated or received electroporation-facilitated HIF-1α gene therapy. HIF-1α mRNA levels in wound tissue were significantly reduced in older (4–6 months) as compared to younger (1.5–2 months) db/db mice. Expression of mRNAs encoding the angiogenic cytokines vascular endothelial growth factor (VEGF), angiopoietin 1 (ANGPT1), ANGPT2, platelet derived growth factor B (PDGF-B), and placental growth factor (PLGF) was also impaired in wounds of older db/db mice. Intradermal injection of plasmid gWIZ-CA5, which encodes a constitutively active form of HIF-1α, followed by electroporation, induced increased levels of HIF-1α mRNA at the injection site on day 3 and increased levels of VEGF, PLGF, PDGF-B, and ANGPT2 mRNA on day 7. Circulating angiogenic cells in peripheral blood increased 10-fold in mice treated with gWIZ-CA5. Wound closure was significantly accelerated in db/db mice treated with gWIZ-CA5 as compared to mice treated with empty vector. Thus, HIF-1α gene therapy corrects the age-dependent impairment of HIF-1α expression, angiogenic cytokine expression, and circulating angiogenic cells that contribute to the age-dependent impairment of wound healing in db/db mice.
doi:10.1002/jcp.21503
PMCID: PMC2716010  PMID: 18506785
Aging; Angiogenesis; Diabetes; Wound Healing
23.  Intraluminal crawling of neutrophils to emigration sites: a molecularly distinct process from adhesion in the recruitment cascade 
The Journal of Experimental Medicine  2006;203(12):2569-2575.
The prevailing view is that the β2-integrins Mac-1 (αMβ2, CD11b/CD18) and LFA-1 (αLβ2, CD11a/CD18) serve similar biological functions, namely adhesion, in the leukocyte recruitment cascade. Using real-time and time-lapse intravital video-microscopy and confocal microscopy within inflamed microvessels, we systematically evaluated the function of Mac-1 and LFA-1 in the recruitment paradigm. The chemokine macrophage inflammatory protein-2 induced equivalent amounts of adhesion in wild-type and Mac-1−/− mice but very little adhesion in LFA-1−/− mice. Time-lapse video-microscopy within the postcapillary venules revealed that immediately upon adhesion, there is significant intraluminal crawling of all neutrophils to distant emigration sites in wild-type mice. In dramatic contrast, very few Mac-1−/− neutrophils crawled with a 10-fold decrease in displacement and a 95% reduction in velocity. Therefore, Mac-1−/− neutrophils initiated transmigration closer to the initial site of adhesion, which in turn led to delayed transmigration due to movement through nonoptimal emigration sites. Interestingly, the few LFA-1−/− cells that did adhere crawled similarly to wild-type neutrophils. Intercellular adhesion molecule-1 but not intercellular adhesion molecule-2 mediated the Mac-1–dependent crawling. These in vivo results clearly delineate two fundamentally different molecular mechanisms for LFA-1 and Mac-1 in vivo, i.e., LFA-1–dependent adhesion followed by Mac-1–dependent crawling, and both steps ultimately contribute to efficient emigration out of the vasculature.
doi:10.1084/jem.20060925
PMCID: PMC2118150  PMID: 17116736
24.  LSP1 is an endothelial gatekeeper of leukocyte transendothelial migration 
Leukocyte-specific protein 1 (LSP1), an F-actin binding protein and a major downstream substrate of p38 mitogen-activated protein kinase as well as protein kinase C, has been reported to be important in leukocyte chemotaxis. Although its distribution has been thought to be restricted to leukocytes, herein we report that LSP1 is expressed in endothelium and is essential to permit neutrophil emigration. Using intravital microscopy to directly visualize leukocyte rolling, adhesion, and emigration in postcapillary venules in LSP1-deficient (Lsp1−/−) mice, we found that LSP1 deficiency inhibits neutrophil extravasation in response to various cytokines (tumor necrosis factor-α and interleukin-1β) and to neutrophil chemokine keratinocyte-derived chemokine in vivo. LSP1 deficiency did not affect leukocyte rolling or adhesion. Generation of Lsp1−/− chimeric mice using bone marrow transplantation revealed that in mice with Lsp1−/− endothelial cells and wild-type leukocytes, neutrophil transendothelial migration out of postcapillary venules is markedly restricted. In contrast, Lsp1−/− neutrophils in wild-type mice were able to extravasate normally. Consistent with altered endothelial function was a reduction in vascular permeability to histamine in Lsp1−/− animals. Western blot analysis and immunofluorescence microscopy examination confirmed the presence of LSP1 in wild-type but not in Lsp1−/− mouse microvascular endothelial cells. Cultured human endothelial cells also stained positive for LSP1. Our results suggest that LSP1 expressed in endothelium regulates neutrophil transendothelial migration.
doi:10.1084/jem.20040830
PMCID: PMC2213033  PMID: 15684321
25.  A vascular bed–specific pathway regulates cardiac expression of endothelial nitric oxide synthase  
Journal of Clinical Investigation  1999;103(6):799-805.
The endothelial nitric oxide synthase (eNOS) gene is induced by a variety of extracellular signals under both in vitro and in vivo conditions. To gain insight into the mechanisms underlying environmental regulation of eNos expression, transgenic mice were generated with the 1,600-bp 5′ flanking region of the human eNos promoter coupled to the coding region of the LacZ gene. In multiple independent lines of mice, transgene expression was detected within the endothelium of the brain, heart, skeletal muscle, and aorta. β-galactosidase activity was consistently absent in the vascular beds of the liver, kidney, and spleen. In stable transfection assays of murine endothelial progenitor cells, the 1,600-bp promoter region was selectively induced by conditioned media from cardiac myocytes, skeletal myocytes, and brain astrocytes. Cardiac myocyte–mediated induction was partly abrogated by neutralizing anti–platelet-derived growth factor (PDGF) antibodies. In addition, promoter activity was upregulated by PDGF-AB. Analysis of promoter deletions revealed that a PDGF response element lies between –744 and –1,600 relative to the start site of transcription, whereas a PDGF-independent cardiac myocyte response element is present within the first 166 bp of the 5′ flanking region. Taken together, these results suggest that the eNos gene is regulated in the cardiac endothelium by both a PDGF-dependent and PDGF-independent microvascular bed–specific signaling pathway.
PMCID: PMC408151  PMID: 10079100

Results 1-25 (25)