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Search Results: 1 - 10 of 58294 matches for " Ji-Xin Cheng "
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Single-Cell Profiling Reveals the Origin of Phenotypic Variability in Adipogenesis
Thuc T. Le, Ji-Xin Cheng
PLOS ONE , 2009, DOI: 10.1371/journal.pone.0005189
Abstract: Phenotypic heterogeneity in a clonal cell population is a well-observed but poorly understood phenomenon. Here, a single-cell approach is employed to investigate non-mutative causes of phenotypic heterogeneity during the differentiation of 3T3-L1 cells into fat cells. Using coherent anti-Stokes Raman scattering microscopy and flow cytometry, adipogenic gene expression, insulin signaling, and glucose import are visualized simultaneously with lipid droplet accumulation in single cells. Expression of adipogenic genes PPARγ, C/EBPα, aP2, LP2 suggests a commitment to fat cell differentiation in all cells. However, the lack of lipid droplet in many differentiating cells suggests adipogenic gene expression is insufficient for lipid droplet formation. Instead, cell-to-cell variability in lipid droplet formation is dependent on the cascade responses of an insulin signaling pathway which includes insulin sensitivity, kinase activity, glucose import, expression of an insulin degradation enzyme, and insulin degradation rate. Increased and prolonged insulin stimulation promotes lipid droplet accumulation in all differentiating cells. Single-cell profiling reveals the kinetics of an insulin signaling cascade as the origin of phenotypic variability in drug-inducible adipogenesis.
Coherent anti-Stokes Raman scattering imaging of lipids in cancer metastasis
Thuc T Le, Terry B Huff, Ji-Xin Cheng
BMC Cancer , 2009, DOI: 10.1186/1471-2407-9-42
Abstract: Coherent anti-Stokes Raman scattering (CARS) microscopy is employed to study cancer cell behaviours in excess lipid environments in vivo and in vitro. The impacts of a high fat diet on cancer development are evaluated in a Balb/c mice cancer model. Intravital flow cytometry and histology are employed to enumerate cancer cell escape to the bloodstream and metastasis to lung tissues, respectively. Cancer cell motility and tissue invasion capability are also evaluated in excess lipid environments.CARS imaging reveals intracellular lipid accumulation is induced by excess free fatty acids (FFAs). Excess FFAs incorporation onto cancer cell membrane induces membrane phase separation, reduces cell-cell contact, increases surface adhesion, and promotes tissue invasion. Increased plasma FFAs level and visceral adiposity are associated with early rise in circulating tumour cells and increased lung metastasis. Furthermore, CARS imaging reveals FFAs-induced lipid accumulation in primary, circulating, and metastasized cancer cells.Lipid-rich tumours are linked to cancer metastasis through FFAs-induced physical perturbations on cancer cell membrane. Most importantly, the revelation of lipid-rich circulating tumour cells suggests possible development of CARS intravital flow cytometry for label-free detection of early-stage cancer metastasis.Excess lipid in the body has been shown to aggravate cancer. Animal studies showed that high fat diets and obesity enhanced cancer metastasis [1]. In human, a body mass index above 30 kg/m2 is strongly correlated with increased risk for various types of cancer [2]. It is generally accepted that diet and obesity are accountable for 30% of preventable causes of cancer [2]. Indeed, diet, nutrition, and physical activity are widely promoted as effective means for cancer prevention by the World Cancer Research Fund and the American Institute for Cancer Research [3]. Nonetheless, the relationship between diet and cancer incidence and mortality in huma
Glutamate Excitotoxicity Inflicts Paranodal Myelin Splitting and Retraction
Yan Fu, Wenjing Sun, Yunzhou Shi, Riyi Shi, Ji-Xin Cheng
PLOS ONE , 2009, DOI: 10.1371/journal.pone.0006705
Abstract: Paranodal myelin damage is observed in white matter injury. However the culprit for such damage remains unknown. By coherent anti-Stokes Raman scattering imaging of myelin sheath in fresh tissues with sub-micron resolution, we observed significant paranodal myelin splitting and retraction following glutamate application both ex vivo and in vivo. Multimodal multiphoton imaging further showed that glutamate application broke axo-glial junctions and exposed juxtaparanodal K+ channels, resulting in axonal conduction deficit that was demonstrated by compound action potential measurements. The use of 4-aminopyridine, a broad-spectrum K+ channel blocker, effectively recovered both the amplitude and width of compound action potentials. Using CARS imaging as a quantitative readout of nodal length to diameter ratio, the same kind of paranodal myelin retraction was observed with applications of Ca2+ ionophore A23187. Moreover, exclusion of Ca2+ from the medium or application of calpain inhibitor abolished paranodal myelin retraction during glutamate exposure. Examinations of glutamate receptor agonists and antagonists further showed that the paranodal myelin damage was mediated by NMDA and kainate receptors. These results suggest that an increased level of glutamate in diseased white matter could impair paranodal myelin through receptor-mediated Ca2+ overloading and subsequent calpain activation.
Real-Time CARS Imaging Reveals a Calpain-Dependent Pathway for Paranodal Myelin Retraction during High-Frequency Stimulation
Terry B. Huff,Yunzhou Shi,Wenjing Sun,Wei Wu,Riyi Shi,Ji-Xin Cheng
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0017176
Abstract: High-frequency electrical stimulation is becoming a promising therapy for neurological disorders, however the response of the central nervous system to stimulation remains poorly understood. The current work investigates the response of myelin to electrical stimulation by laser-scanning coherent anti-Stokes Raman scattering (CARS) imaging of myelin in live spinal tissues in real time. Paranodal myelin retraction at the nodes of Ranvier was observed during 200 Hz electrical stimulation. Retraction was seen to begin minutes after the onset of stimulation and continue for up to 10 min after stimulation was ceased, but was found to reverse after a 2 h recovery period. The myelin retraction resulted in exposure of Kv 1.2 potassium channels visualized by immunofluorescence. Accordingly, treating the stimulated tissue with a potassium channel blocker, 4-aminopyridine, led to the appearance of a shoulder peak in the compound action potential curve. Label-free CARS imaging of myelin coupled with multiphoton fluorescence imaging of immuno-labeled proteins at the nodes of Ranvier revealed that high-frequency stimulation induced paranodal myelin retraction via pathologic calcium influx into axons, calpain activation, and cytoskeleton degradation through spectrin break-down.
A Comparative Study of Fat Storage Quantitation in Nematode Caenorhabditis elegans Using Label and Label-Free Methods
Kelvin Yen,Thuc T. Le,Ankita Bansal,Sri Devi Narasimhan,Ji-Xin Cheng,Heidi A. Tissenbaum
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0012810
Abstract: The nematode Caenorhabditis elegans has been employed as a model organism to study human obesity due to the conservation of the pathways that regulate energy metabolism. To assay for fat storage in C. elegans, a number of fat-soluble dyes have been employed including BODIPY, Nile Red, Oil Red O, and Sudan Black. However, dye-labeled assays produce results that often do not correlate with fat stores in C. elegans. An alternative label-free approach to analyze fat storage in C. elegans has recently been described with coherent anti-Stokes Raman scattering (CARS) microscopy. Here, we compare the performance of CARS microscopy with standard dye-labeled techniques and biochemical quantification to analyze fat storage in wild type C. elegans and with genetic mutations in the insulin/IGF-1 signaling pathway including the genes daf-2 (insulin/IGF-1 receptor), rict-1 (rictor) and sgk-1 (serum glucocorticoid kinase). CARS imaging provides a direct measure of fat storage with unprecedented details including total fat stores as well as the size, number, and lipid-chain unsaturation of individual lipid droplets. In addition, CARS/TPEF imaging reveals a neutral lipid species that resides in both the hypodermis and the intestinal cells and an autofluorescent organelle that resides exclusively in the intestinal cells. Importantly, coherent addition of the CARS fields from the C-H abundant neutral lipid permits selective CARS imaging of the fat store, and further coupling of spontaneous Raman analysis provides unprecedented details including lipid-chain unsaturation of individual lipid droplets. We observe that although daf-2, rict-1, and sgk-1 mutants affect insulin/IGF-1 signaling, they exhibit vastly different phenotypes in terms of neutral lipid and autofluorescent species. We find that CARS imaging gives quantification similar to standard biochemical triglyceride quantification. Further, we independently confirm that feeding worms with vital dyes does not lead to the staining of fat stores, but rather the sequestration of dyes in lysosome-related organelles. In contrast, fixative staining methods provide reproducible data but are prone to errors due to the interference of autofluorescent species and the non-specific staining of cellular structures other than fat stores. Importantly, both growth conditions and developmental stage should be considered when comparing methods of C. elegans lipid storage. Taken together, we confirm that CARS microscopy provides a direct, non-invasive, and label-free means to quantitatively analyze fat storage in living C. elegans.
TDMA-based Distributed Dynamic Slot Algorithm for Ad hoc Networks
Ad hoc网络TDMA分布式动态时隙算法

CHENG Nan,LIU Zhi-min,WANG Ji-xin,

计算机应用研究 , 2005,
Abstract: With the development of the GPS technology and application,it's not a problem to synchronize the terminal in Ad hoc network. So the slot-based MAC scheme, such as TDMA, becomes more interesting for Ad hoc network. Introduces a new distributed slot dynamic assignment algorithm. It has low collision of data, and is fit for the dynamic networks. Every terminal has the same opportunity to transmit data. The paper analyzes the performance of the new algorithm, and compares the slot utilization of the new algorithm with the slot-aloha. It can be concluded that the slot utilization of the new algorithm is far higher than that of slot-aloha.


物理学报 , 1997,
Abstract: 用半经典方法建立了波包在强单色激光场中的激发和演化的一般模型.通过模拟计算表明,只要局域模振动的跃迁偶极矩远大于与之耦合的背景态的跃迁偶极矩,用强单色激光场可以长时间地选择激发分子的一个局域模振动


物理学报 , 1997,
Abstract: Trapping vibrational energy into one single bond is a key problem of bond-selective chemistry. We explored this possibility by means of restricting local mode wavepacket dephasing with multi-color laser field. The vibrational excitation and evolution of molecules in weak and strong multi-color laser fields are discussed by field-quantization method and semi-classical method. The results demonstrate that population can not be trapped in a local mode wave-packet using multi-color weak field, while it is possible to trap vibrational population between the ground state and local mode vibration by making use of power-broadening induced by strong laser field and the interference between two wave-packets excited by two strong laser of different frequencies.

CHEN Ji-Xin,HONG Wei,YIN Xiao-Xing,CHENG Feng,YAN Pin-Pin,

红外与毫米波学报 , 2006,
Abstract: 采用0.18um GaAs PHEMT工艺,设计和研制了毫米波压控振荡器.该压控振荡器采用反射式结构,并针对了我国本地多点分配业务(LMDS)频段进行了优化设计,芯片采用OMM IC ED02AH工艺实现,芯片的尺寸为1.2mm×0.8mm.实测性能指标为:在28.46GHz,该压控振荡器的输出功率为7.3dBm,偏移1MHz处的相位噪声为-101dBc/Hz,调谐范围为27.5~30.4GHz.

TANG Zhen-jie,LIAO Wen-jun,YU Bing,ZHONG Ji-xin,ZHU Hui-fen,YE Qing,CHENG Xin,LI Wen-han,SHEN Guan-xin,

生物物理学报 , 2005,
Abstract: 3D Graphic model of two single-chains Fv (scFv) , named A4 and A10, against liver cancer was constructed by computer aided molecular design software. The VH (heave variable region) and VL(light variable region) domains of scFv were modeled respectively and then the whole three-dimensional structure of scFv was constructed. Based on these, the whole three-dimensional structure was refined by the methods of molecular mechanics and dynamics. It was proved by Profile-3D program to the structure of scFv was reasonable reliable. Computer graphic modeling indicated that all places of the linker, variable region of the heave (VH) and light (VL) chains were suitable. The VH region, as well as the VL region, was involved in composing the "hydrophotic pocket". The linker was isolated from VH and VL regions. The complementary determinant regions (CDRs) of VH and VL regions surrounded the "hydrophobic pocket". This study provides a structural basis for analyzing the functions of scFv and developing bispecific antibody with high affinity and specificity.
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