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Hui Chen

Publications and source records attributed to Hui Chen.

At least 55 records · Page 3Linked to original sources
PubMed2006

Gammadelta T cells recognize tumor cells via CDR3delta region.

The principles governing gammadelta T cell specificity and diversity remain unclear due to lack of detailed structural analysis. To elucidate key structural basis of the specificity of gammadelta TCR for tumors, we analyzed the binding activities of synthesized TCR Vdelta2 CDR3 peptides derived from tumor infiltrating lymphocyte (TIL) s in ovarian epithelial carcinoma (OEC) via biospecific interaction analysis approach, enzyme immunoassay and immunofluorescence assays. Besides, we used human CDR3delta grafted-Ig to repeat major tests. We found that synthesized OEC-derived CDR3delta peptides could bind specifically to tumor cell lines and tissues. CDR3delta-graft Ig showed a similar binding specificity with CDR3delta peptides, suggesting the determinant role of CDR3delta in antigen binding. Moreover, CDR3delta peptide-mediated binding specificity was blocked by pre-incubation with same peptide, which decreased the cytotoxicity of gammadelta T cells to OEC cells in vitro. Our finding indicates that CDR3delta peptide could mimic antigen-binding specificity of gammadelta TCR. Our strategy provides a novel, simple and convenient approach to investigate the binding activity and function of gammadelta TCR.

Antigen Presentation↗
PubMed2006

FOXO1 represses peroxisome proliferator-activated receptor-gamma1 and -gamma2 gene promoters in primary adipocytes. A novel paradigm to increase insulin sensitivity.

FOXO1 and peroxisome proliferator-activated receptor-gamma (PPARgamma) are crucial transcription factors that regulate glucose metabolism and insulin responsiveness in insulin target tissues. We have shown that, in primary rat adipocytes, both factors regulate transcription of the insulin-responsive GLUT4 gene and that PPARgamma2 detachment from the GLUT4 promoter upon thiazolidinedione binding up-regulates GLUT4 gene expression, thus increasing insulin sensitivity (Armoni, M., Kritz, N., Harel, C., Bar-Yoseph, F., Chen, H., Quon, M. J., and Karnieli, E. (2003) J. Biol. Chem. 278, 30614-30623). However, the mechanisms regulating PPARgamma gene transcription are largely unknown. We studied the effects of FOXO1 on human PPARgamma gene expression in primary rat adipocytes and found that both genes are endogenously expressed. FOXO1 coexpression dose-dependently repressed transcription from either the PPARgamma 1 or PPARgamma2 promoter reporter by 65%, whereas insulin (100 nm, 20-24 h) either partially or completely reversed this effect. Phosphorylation-defective FOXO1 mutants T24A, S256A, S319A, and T24A/S256A/S319A still repressed the PPARgamma1 promoter and partially lost their effects on the PPARgamma2 promoter in either basal or insulin-stimulated cells. Use of DNA binding-defective FOXO1 (H215R) indicated that this domain is crucial for FOXO1 repression of the PPARgamma2 (but not PPARgamma1) promoter. Progressive 5'-deletion and gel retardation analyses revealed that this repression involves direct and specific binding of FOXO1 to the PPARgamma2 promoter; chromatin immunoprecipitation analysis confirmed that this binding occurs in cellulo. We suggest a novel paradigm to increase insulin sensitivity in adipocytes in which FOXO1 repression of PPARgamma, the latter being a repressor of the GLUT4 promoter, consequently leads to GLUT4 derepression/up-regulation, thus enhancing cellular insulin sensitivity. The newly identified FOXO1-binding site on the PPARgamma2 promoter may serve as a therapeutic target for type 2 diabetes.

Adipocytes↗
PubMed2006

Ab initio study on deactivation pathways of excited 9H-guanine.

The complete active space with second-order perturbation theory/complete active space self-consistent-field method was used to explore the nonradiative decay mechanism for excited 9H-guanine. On the 1pipi* (1L(a)) surface we determined a conical intersection (CI), labeled (S0pipi*)(CI), between the 1pipi* (1L(a)) excited state and the ground state, and a minimum, labeled (pipi*)min. For the 1pipi* (1L(a)) state, its probable deactivation path is to undergo a spontaneous relaxation to (pipi*)min first and then decay to the ground state through (S0pipi*)(CI), during which a small activation energy is required. On the 1n(N)pi* surface a CI between the 1n(N)pi* and 1pipi* (1L(a)) states was located, which suggests that the 1n(N)pi* excited state could transform to the 1pipi* (1L(a)) excited state first and then follow the deactivation path of the 1pipi* (1L(a)) state. This CI was also possibly involved in the nonradiative decay path of the second lowest 1pipi* (1L(b)) state. On the 1n(O)pi* surface a minimum was determined. The deactivation of the 1n(O)pi* state to the ground state was estimated to be energetically unfavorable. On the 1pisigma* surface, the dissociation of the N-H bond of the six-membered ring is difficult to occur due to a significant barrier.

Guanine↗
PubMed2006

Preparation of inorganic molecularly imprinted polymers with higher adsorption and selectivity by sol-gel method.

Preparation of inorganic molecularly imprinted polymers (IMIPs) with higher adsorption and selectivity has been developed on caffeine as model compound by sol-gel processes. In our study, by introducing pore-forming agent, lactic acid, into sol-gel process, the porosity of IMIPs was enhanced and the performance of IMIPs was thus improved. And, by introducing base catalyst in the sol-gel process, large pore volume was obtainable, and the caffeine adsorption of IMIPs was increased. Competition adsorption experiments between caffeine (CAF) and structure analogous molecule, theophylline (TH), were determined by HPLC analysis. It was found that adding pore-forming agent method produced better caffeine adsorption (ca. 20 micromol/g) than by adding base catalyst. But adding base catalyst method was found to yield better selectivity (ca. 4) (Selectivity (alpha) is the ratio of CAF bound to TH bound.) In addition, caffeine adsorption of IMIPs with template removed by calcination is two times that by extraction without sacrificing the selectivity of IMIPs.

Adsorption↗
PubMed2006

A conformational switch in vinculin drives formation and dynamics of a talin-vinculin complex at focal adhesions.

Dynamic interactions between the cytoskeleton and integrins control cell adhesion, but regulatory mechanisms remain largely undefined. Here, we tested the extent to which the autoinhibitory head-tail interaction (HTI) in vinculin regulates formation and lifetime of the talin-vinculin complex, a proposed mediator of integrin-cytoskeleton bonds. In an ectopic recruitment assay, mutational reduction of HTI drove assembly of talin-vinculin complexes, whereas ectopic complexes did not form between talin and wild-type vinculin. Moreover, reduction of HTI altered the dynamic assembly of vinculin and talin in focal adhesions. Using fluorescence recovery after photobleaching, we show that the focal adhesion residency time of vinculin was enhanced up to 3-fold by HTI mutations. The slow dynamics of vinculin correlated with exposure of its cryptic talin-binding site, and a talin-binding site mutation rescued the dynamics of activated vinculin. Significantly, HTI-deficient vinculin inhibited the focal adhesion dynamics of talin, but not paxillin or alpha-actinin. These data show that talin conformation in cells permits vinculin binding, whereas the autoinhibited conformation of vinculin constitutes the barrier to complex formation. Down-regulation of HTI in vinculin to Kd approximately 10(-7) is sufficient to induce talin binding, and HTI is essential to the dynamics of vinculin and talin at focal adhesions. We therefore conclude that vinculin conformation, as modulated by the strength of HTI, directly regulates the formation and lifetime of talin-vinculin complexes in cells.

Fluorescence↗
PubMed2006

Differential densities of muscarinic acetylcholine receptor and I(K,ACh) in canine supraventricular tissues and the effect of amiodarone on cholinergic atrial fibrillation and I(K,ACh).

BACKGROUND: Vagal nerve plays an important role in the induction and maintenance of atrial fibrillation (AF). This study investigated the differential densities of M2 receptor and acetylcholine-induced inward rectifier K+ current (I(K,ACh)) in atrial appendage, atrium, pulmonary vein (PV) and super vena cava (SVC) to discuss the role of atrial appendage and PV in cholinergic AF. METHODS AND RESULTS: In 10 dogs, action potential duration was determined at 24 sites during bilateral cervical vagal stimulation and amiodarone administration. AF could be induced at first in right atrial appendage (RAA) and right atrium (RA) without left atrial appendage (LAA) and left atrium (LA). Amiodarone decreased the initiation of AF in vivo. Western blot and patch clamp were used to determine M2 receptor and I(K,ACh) in RAA, LAA, RA, LA, PV and SVC. The densities of M2 receptor and I(K,ACh) in LAA, RAA and LA were higher than that in RA, PV and SVC (21.34 +/- 0.92 vs. 8.24 +/- 0.45 pA/pF, p < 0.05). Furthermore, the densities of the M2 receptor and I(K,ACh) in LAA and RAA were higher than that in LA (21.34 +/- 0.92 vs. 14.17 +/- 0.65 pA/pF, p < 0.05). After amiodarone administration, densities of I(K,ACh) in LA and RA were not different, but densities of I(K,ACh )were also less in atrium than in atrial appendage. CONCLUSIONS: Densities of the M2 receptor and I(K,ACh) are higher in atrial appendage than other sites. Atrial appendage perhaps plays an important role in initiation of cholinergic AF. However, PV and SVC less often play an important role in vagotonic paroxysmal AF. Reduced dispersion of I(K,ACh) is the mechanism for amiodarone to therapy AF.

Action Potentials↗
PubMed2006

Constitutive activation of the jasmonate signaling pathway enhances the production of secondary metabolites in tomato.

The phytohormone jasmonic acid (JA) regulates the synthesis of secondary metabolites in a wide range of plant species. Here, we show that exogenous methyl-JA (MeJA) elicits massive accumulation of caffeoylputrescine (CP) in tomato leaves. A mutant (jai1) that is defective in jasmonate perception failed to accumulate CP in flowers and MeJA-treated leaves. Conversely, a transgenic tomato line (called 35S::PS) that exhibits constitutive JA signaling accumulated high levels of leaf CP in the absence of jasmonate treatment. RNA blot analysis showed that genes encoding enzymes in the phenylpropanoid and polyamine pathways for CP biosynthesis are upregulated in MeJA-treated wild-type plants and in untreated 35S::PS plants. These results indicate that CP accumulation in tomato is tightly controlled by the jasmonate signaling pathway, and provide proof-of-concept that the production of some plant secondary metabolites can be enhanced by transgenic manipulation of endogenous JA levels.

Chromatography, High Pressure Liquid↗
PubMed2006

Prospective study of 174 de novo acute myelogenous leukemias according to the WHO classification: subtypes, cytogenetic features and FLT3 mutations.

We report a prospective study of 174 unselected adult de novo acute myeloid leukemia (AML) cases diagnosed using the WHO classification. Of those, 57 (33%) were AML with recurrent cytogenetic abnormalities, 41 were (24%) AML with multilineage dysplasia, 74 (42%) were AML not otherwise categorized, and two were acute leukemias of ambiguous lineage. Clonal cytogenetic abnormalities were detected in 64% of the WHO AML cases with t(15;17) (15%), t(8;21) (12%), +8 (11%), -7/del7q (8%) and del9q (5%) being the most common ones. The FLT3/ITD mutations (FMS-like tyrosine kinase 3/internal tandem duplication) were observed in 12% of the WHO AML cases, which is much lower than ones in the literature, while the 6% incidence of the FLT3-activating loop mutations (either FLT3/D835 or FLT3/I836) was comparable with others. Both mutations were associated with leukocytosis. Our study also suggests that the FLT3 mutations are biomarkers independent of cytogenetic characteristics.

Adolescent↗
PubMed2006

Improvement of proline chiral stationary phases by varying peptide length and linker.

Seven new stationary phases with different number of proline units and/or different linkage to silica gel were prepared and evaluated in order to improve the performance of proline chiral stationary phases. The average separation factor achieved with the 53 analytes increases with the number of proline units in the stationary phases. When the proline peptides are directly attached to the 3-methylaminopropyl silica gel without using the 6-methylaminohexanoic acid linker, the stationary phases perform better overall. For decaproline chiral stationary phase 8, the separation also depends on the mobile phase system used. For this stationary phase, the CH2Cl2/hexanes/2-propanol system significantly outperforms the 2-propanol/hexanes system. For the 53 analytes tested, the separation factors achieved with this stationary phase compare well with those for three commercial columns.

Chromatography↗
PubMed2006

Zebrafish G protein gamma2 is required for VEGF signaling during angiogenesis.

Vascular endothelial growth factor (VEGF) is a major mediator of pathologic angiogenesis, a process necessary for the formation of new blood vessels to support tumor growth. Historically, VEGF has been thought to signal via receptor tyrosine kinases, which are not typically considered to be G protein dependent. Here, we show that targeted knockdown of the G protein gng2 gene (Ggamma2) blocks the normal angiogenic process in developing zebrafish embryos. Moreover, loss of gng2 function inhibits the ability of VEGF to promote the angiogenic sprouting of blood vessels by attenuating VEGF induced phosphorylation of phospholipase C-gamma1 (PLCgamma1) and serine/threonine kinase (AKT). Collectively, these results demonstrate a novel interaction between Ggamma2- and VEGF-dependent pathways to regulate the angiogenic process in a whole-animal model. Blocking VEGF function using a humanized anti-VEGF antibody has emerged as a promising treatment for colorectal, non-small lung cell, and breast cancers. However, this treatment may cause considerable side effects. Our findings provide a new opportunity for cotargeting G protein- and VEGF-dependent pathways to synergistically block pathologic angiogenesis, which may lead to a safer and more efficacious therapeutic regimen to fight cancer.

Animals↗
PubMed2006

Cigarette smoke exposure reprograms the hypothalamic neuropeptide Y axis to promote weight loss.

RATIONALE: Despite irrefutable epidemiologic evidence, cigarette smoking remains the major preventable cause of lung disease morbidity worldwide. The appetite-suppressing effect of tobacco is a major behavioral determinant of smoking, but the underlying molecular and neuronal mechanisms are not understood. Neuropeptide Y (NPY) is an orexigenic neuropeptide, whose activity in the hypothalamic paraventricular nucleus governs appetite. OBJECTIVES: To compare the effects of smoke exposure and equivalent food restriction on body weight, organ mass, cytokines, and brain NPY in Balb/c mice. METHODS: A pair-feeding study design compared smoke exposure (4 wk; 1 cigarette, 3 x /d, 5 d/wk) to equivalent food restriction (pair-fed) and sham-exposed control mice. RESULTS: Smoke exposure rapidly induced mild anorexia. After 4 wk, smoke-exposed and pair-fed groups were lighter than control mice (22.0 +/- 0.2, 23.2 +/- 0.5, 24.9 +/- 0.4 g, respectively; p < 0.05). Brown and white fat masses were only reduced by smoke exposure, relative to control mice. NPY concentration in the paraventricular nucleus was significantly and paradoxically reduced by smoke exposure, despite lower plasma leptin concentrations; this was not observed in the pair-fed group experiencing 19% food restriction. Adipose mRNA expression of uncoupling proteins, inflammatory cytokines interleukin 6 and tumor necrosis factor alpha, and adipose triglyceride lipase was decreased by smoke exposure, and even lower in pair-fed mice. CONCLUSIONS: In contrast to food restriction, smoke exposure caused a reduction in hypothalamic NPY and fat mass, and regulated adipose cytokines. These findings may contribute to understanding weight loss in smoking-related lung disease and in the design of more effective smoking cessation strategies.

Adipose Tissue↗
PubMed2006

APOBEC3A is a potent inhibitor of adeno-associated virus and retrotransposons.

APOBEC3 proteins constitute a family of cytidine deaminases that provide intracellular resistance to retrovirus replication and transposition of endogenous retroelements. One family member, APOBEC3A (hA3A), is an orphan, without any known antiviral activity. We show that hA3A is catalytically active and that it, but none of the other family members, potently inhibits replication of the parvovirus adeno-associated virus (AAV). hA3A was also a potent inhibitor of the endogenous LTR retroelements, MusD, IAP, and the non-LTR retroelement, LINE-1. Its function was dependent on the conserved amino acids of the hA3A active site, consistent with a role for cytidine deamination, although mutations in retroelement sequences were not found. These findings demonstrate the potent activity of hA3A, an APOBEC3 family member with no previously identified function. They also highlight the functional differences between APOBEC3 proteins. The APOBEC3 family members have distinct functions and may have evolved to resist various classes of genetic elements.

Cell Line, Tumor↗
PubMed2006

Improvement of proline enantioselective stationary phases by replacing the 9-fluorenylmethoxycarbonyl group.

The role of 9-fluorenylmethoxycarbonyl (Fmoc) in previously reported proline enantioselective stationary phases was investigated. Seven stationary phases in which the Fmoc group was replaced by other groups were prepared and evaluated in normal phase mode. The Fmoc group proved nonessential for the broad enantioselectivity observed, as the stationary phase with a trimethylacetyl (Tma) group proved much more effective than the one with the Fmoc group. For the 53 analytes studied, the stationary phase with the Tma group resolved 39, while the one with the Fmoc group resolved 19. Separation factors achieved for the stationary phase with the Tma group are also significantly higher than those for the stationary phase with the Fmoc group. The stationary phase with the (-)-2-(2,4,5,7-tetranitro-9-fluorenylideneaminooxy)propionyl (Tapa) group provides very different selectivity profile when compared to the one with the Tma group. In most of the proline stationary phases studied, pi-pi interaction is not the dominant interaction for the enantioselective recognition.

Fluorenes↗
PubMed2006

Reduced stem cell factor links smooth myopathy and loss of interstitial cells of cajal in murine diabetic gastroparesis.

BACKGROUND & AIMS: Diabetic gastroparesis involves neuropathy, myopathy, and depletion of interstitial cells of Cajal (ICC), which may cause dysrhythmias and impaired neural control. Most murine gastric ICC depend on stem cell factor (SCF) signaling but can also be maintained with insulin or insulin-like growth factor-I (IGF-I). We investigated whether SCF could mediate the actions of insulin and IGF-I. METHODS: Expression of insulin receptor, IGF-I receptor, and SCF was studied in gastric muscles and purified ICC by immunohistochemistry and reverse transcription-polymerase chain reaction (RT-PCR). The effects of insulin/IGF-I deficiency on SCF, ICC, smooth muscle, and neurons were investigated in nonobese diabetic mice and organotypic cultures by immunohistochemistry, microarrays, and/or quantitative RT-PCR. ICC in organotypic cultures were also studied after immunoneutralization of endogenous SCF. RESULTS: Insulin and IGF-I receptors were detected in smooth-muscle cells and myenteric neurons but not in ICC. Cell-surface expression of SCF was only found in smooth-muscle cells. ICC depletion in diabetes was accompanied by smooth-muscle atrophy and reduced SCF, whereas neuron-specific gene expression remained unchanged. In organotypic cultures, prevention of ICC loss by insulin or IGF-I was paralleled by rescue of smooth-muscle cells and SCF expression but not of myenteric neurons. Immunoneutralization of endogenous SCF caused ICC depletion closely resembling that elicited by insulin/IGF-I deficiency. CONCLUSIONS: Reduced insulin/IGF-I signaling in diabetes may lead to ICC depletion and its consequences by causing smooth-muscle atrophy and reduced SCF production. Thus, myopathy may play a more central role in diabetic gastroenteropathies than previously recognized.

Animals↗
PubMed2006

Effects of intravitreal dispase on vitreoretinal interface in rabbits.

OBJECTIVE: To explore the efficacy and safety of dispase on the production of posterior vitreous detachment (PVD) following intravitreal injection at various concentrations for different exposure times in the rabbit eyes. METHODS: Sixty-four pigmented rabbits were assigned to two groups according to different combinations of concentrations of dispase and exposure times, namely group 1 (10, 5, or 1 U/ml for 30 min) and group 2 (0.25, 0.1, or 0.05 U/ml for one week). The control was established in both groups. One eye of each experimental rabbit was injected with dispase, and one eye of each control rabbit was injected with phosphate buffered saline. The presence of PVD and intraocular toxicity were observed by biomicroscope, macroexamination, and histology. RESULTS: None of the control eyes showed PVD. In group 1, PVD was present in 6 of 7 eyes in each sub-group. In group 2, all 7 eyes of 0.25 U/ml or 0.1 U/ml and 6 of 7 eyes of 0.05 U/ml showed PVD. Intraocular toxicity including inflammation in anterior chamber, vitreous haze, epiretinal membrane, and retinal damage were found in the experimental eyes with relatively higher concentrations of dispase. CONCLUSIONS: Although dispase has a definite effect on the induction of PVD in rabbits, its toxicity to retina also alerts us to the application in clinic. The intravitreal injection of dispase of 1 U/ml for 30 min may be acceptable.

Animals↗
PubMed2006

Energy transfer among chlorophylls in trimeric light-harvesting complex II of Bryopsis corticulans.

A study on energy transfer among chlorophylls (Chls) in the trimeric unit of the major light-harvesting complex II (LHC II) from Bryopsis corriculan, was carried out using time-correlated single photon counting. In the chlorophyll Q region of LHC II, six molecules characterized as Chlb628, Chlb646, Chlb652(654,657), Chla664(666), Chla674(677,680) and Chla682(683) were discriminated according to their absorption spectrum and fluorescence emission spectrum. Then, excited by pulsed light of 628 nm, fluorescence kinetics spectra in the chlorophyll Q region were measured. In accordance with the principles of fluorescence kinetics, these kinetics data were analyzed with a multi-exponential model. Time constants on energy transfer were obtained. An overwhelming percentage of energy transfer among chlorophylls undergoes a process longer than 97 picoseconds (ps), which shows that, before transferring energy to another Chl, the excited Chl might convert energy to vibrations of a lower state with different multiplicity (intersystem crossing). Energy transfer at the level of approximately 10 ps was also obtained, which was interpreted as the excited Chls may go through internal conversion before transferring energy to another Chl. Although with a higher standard deviation, time constants at the femtosecond level can not be entirely excluded, which can be attributed to the ultrafast process of direct energy transfer. Owing to the arrangement and direction of the dipole moment of Chls in LHC II, the probability of these processes is different. The fluorescence lifetimes of Chlb652(654,657), Chla664(666), Chla674(677,680) and Chla682(683) were determined to be 1.44 ns, 1.43 ns, 636 ps and 713 ps, respectively. The percentages of energy dissipation in the pathway of fluorescence emission were no more than 40% in the trimeric unit of LHC II. These results are important for a better understanding of the relationship between the structure and function of LHC II.

Chlorophyll↗
PubMed2006

Determination of ceftriaxone sodium in pharmaceutical formulations by flow injection analysis with acid potassium permanganate chemiluminescence detection.

Based on the chemiluminescence (CL) emission generated from the oxidation of ceftriaxone sodium alkali hydrolysate by potassium permanganate in polyphosphoric acid (PPA), a novel determination method for ceftriaxone sodium was developed by using a flow-injection technique. The calibration curve appears to be linear in the range between 0.05 and 100 microg mL(-1) with a detection limit (3sigma) of 25 ng mL(-1), and a relative standard deviation (RSD) of 0.6% for eleven replicate determinations of 5.0 microg mL(-1) ceftriaxone sodium. The proposed method has been successfully utilized for the determination of ceftriaxone sodium in pharmaceutical formulations, while the chemiluminescence reaction mechanisms were investigated.

Calibration↗