Biomedical subjects

Hong Zhang

Publications and source records attributed to Hong Zhang.

At least 55 records · Page 3Linked to original sources

PubMed2006

Ubiquitin hydrolase Uch-L1 rescues beta-amyloid-induced decreases in synaptic function and contextual memory.

The neuronal ubiquitin/proteasomal pathway has been implicated in the pathogenesis of Alzheimer's disease (AD). We now show that a component of the pathway, ubiquitin C-terminal hydrolase L1 (Uch-L1), is required for normal synaptic and cognitive function. Transduction of Uch-L1 protein fused to the transduction domain of HIV-transactivator protein (TAT) restores normal enzymatic activity and synaptic function both in hippocampal slices treated with oligomeric Abeta and in the APP/PS1 mouse model of AD. Moreover, intraperitoneal injections with the fusion protein improve the retention of contextual learning in APP/PS1 mice over time. The beneficial effect of the Uch-L1 fusion protein is associated with restoration of normal levels of the PKA-regulatory subunit IIalpha, PKA activity, and CREB phosphorylation.

Alzheimer Disease↗

PubMed2006

Cloning and characterization of porcine Fc gamma receptor II (FcgammaRII).

Receptors for the Fc region (FcgammaRs) of IgG play a crucial role in the immune system and host protection against infection. In the present study, we describe the cloning, sequencing and characterization of porcine FcgammaRII. By screening a translated EST database with the protein sequence of the human FcgammaRII (CD32) we identified a putative porcine homologue. Using rapid amplification of cDNA ends (RACE), we isolated the full-length cDNA encoding porcine FcgammaRII from peripheral blood leucocyte RNA. The porcine FcgammaRII cDNA was 1488bp long, encoding a 297 amino acid trans-membrane glycoprotein composed of two immunoglobulin-like extracelluar domains, a trans-membrane region and a cytoplasmic tail with an immunoreceptor tyrosine-based inhibitory motif (ITIM). The predicted amino acid sequence was found to be 67% and 52% identitical with human and mouse FcgammaRIIB. RT-PCR indicated porcine FcgammaRII transcripts expressed in liver, alveolar, mesenteric lymph node and PBLs. COS-7 cells transfected with the pig FcgammaRII cDNA were able to bind chicken erythrocytes sensitized with porcine IgG. Identification of porcine FcgammaRII will aid in the understanding IgG-FcgammaR interactions, and may help in developing new immunization protocols.

Amino Acid Motifs↗

PubMed2006

Impaired integrin-dependent function in Wiskott-Aldrich syndrome protein-deficient murine and human neutrophils.

Wiskott-Aldrich syndrome (WAS) is a primary immunodeficiency that manifests as increased susceptibility to many pathogens. Although the spectrum of infections suffered by WAS patients is consistent with defects in neutrophil (PMN) function, the consequences of WAS protein (WASp) deficiency on this innate immune cell have been unclear. We report that deficiency of WASp in both human and murine PMNs resulted in profound defects in clustering of beta2 integrins, leading to defective adhesion and transendothelial migration under conditions of physiologic shear flow. Wild-type PMNs redistributed clustered beta2 integrins to the uropod of the cell during active migration, whereas WASp-deficient cells remain unpolarized. The WASp-deficient PMNs also showed reduced integrin-dependent activation of degranulation and respiratory burst. PMNs from a WAS patient manifested similar defects in integrin clustering and signaling. These results suggest that impaired beta2 integrin function in WASp-deficient PMNs may contribute substantially to the clinical immunodeficiency suffered by WAS patients.

Animals↗

PubMed2006

Service utilization in community health centers in China: a comparison analysis with local hospitals.

BACKGROUND: Being an important part of China's Urban Health Care Reform System, Community Health Centers (CHCs) have been established throughout the entire country and are presently undergoing substantial reconstruction. However, the services being delivered by the CHCs are far from reaching their performance targets. In order to assess the role of the CHCs, we examined their performance in six cities located in regions of South-East China. The purpose of this investigation was to identify the utilization and the efficiency of community health resources that are able to provide basic medical and public health services. METHODS: The study was approved by Peking University Health Science Center Institutional Reviewing Board (NO: IRB00001052-T1). Data were collected from all the local health bureaux and processed using SPSS software. Methods of analysis mainly included: descriptive analysis, paired T-test and one-way ANOVA. RESULTS: The six main functions of the CHCs were not fully exploited and the surveys that were collected on their efficiency and utilization of resources indicate that they have a low level of performance and lack the trust of local communities. Furthermore, the CHCs seriously lack funding support and operate under difficult circumstances, and residents have less positive attitudes towards them. CONCLUSION: The community health service must be adjusted according to the requirements of urban medical and health reform, taking into account communities' health needs. More research is required on the living standards and health needs of residents living within the CHC's range, taking into consideration the users' needs in expanding the newly implemented service, and at the same time revising the old service system so as to make the development of CHCs realistic and capable of providing a better service to patients. Several suggestions are put forward for an attainable scheme for developing a community health service.

Adolescent↗

PubMed2006

A second p53 binding site in the central domain of Mdm2 is essential for p53 ubiquitination.

Mdm2 negatively regulates p53 by inhibiting its transcriptional activity and promoting its degradation by functioning as an E3 ubiquitin ligase. The primary p53 binding site on mdm2 is located in its N-terminal domain. Through binding to p53 at its N-terminal transactivation domain, mdm2 directly blocks the transcriptional activation function of p53. We discovered that truncated mdm2 protein constructs without the N-terminal p53 binding domain are at least as active as full-length mdm2 in catalyzing p53 ubiquitination. Furthermore, the deletion of the central acidic domain significantly reduces the E3 ligase activity of mdm2 toward p53. We have also performed GST pull-down experiments to probe the direct binding of various mdm2 domain constructs toward full length p53 and found that mdm2 constructs without the N-terminal p53 binding domain retain the ability to bind to p53. Our kinetic and binding data localize the second p53 binding site between amino acids 211 and 361, including the acidic domain and the zinc finger region. Our work, consistent with other reports, suggests that the p53 tetramer interacts with at least two sites on mdm2. Although the interaction between the N-termini of mdm2 and p53 blocks the transactivation activity of p53, the interaction between the central domain of mdm2 and the core domain of p53 is critical for the ubiquitination and degradation of p53. This second mdm2-p53 interaction site represents an alternative target for small molecule modulators of the mdm2-p53 pathway.

Animals↗

PubMed2006

Homocysteine-mediated activation and mitochondrial translocation of calpain regulates MMP-9 in MVEC.

Hyperhomocysteinemia (HHcy) is associated with atherosclerosis, stroke, and dementia. Hcy causes extracellular matrix remodeling by the activation of matrix metalloproteinase-9 (MMP-9), in part, by inducing redox signaling and modulating the intracellular calcium dynamics. Calpains are the calcium-dependent cysteine proteases that are implicated in mitochondrial damage via oxidative burst. Mitochondrial abnormalities have been identified in HHcy. The mechanism of Hcy-induced extracellular matrix remodeling by MMP-9 activation via mitochondrial pathway is largely unknown. We report a novel role of calpains in mitochondrial-mediated MMP-9 activation by Hcy in cultured rat heart microvascular endothelial cells. Our observations suggested that calpain regulates Hcy-induced MMP-9 expression and activity. We showed that Hcy activates calpain-1, but not calpain-2, in a calcium-dependent manner. Interestingly, the enhanced calpain activity was not mirrored by the decreased levels of its endogenous inhibitor calpastatin. We presented evidence that Hcy induces the translocation of active calpain from cytosol to mitochondria, leading to MMP-9 activation, in part, by causing intramitochondrial oxidative burst. Furthermore, studies with pharmacological inhibitors of calpain (calpeptin and calpain-1 inhibitor), ERK (PD-98059) and the mitochondrial uncoupler FCCP suggested that calpain and ERK-1/2 are the major events within the Hcy/MMP-9 signal axis and that intramitochondrial oxidative stress regulates MMP-9 via ERK-1/2 signal cascade. Taken together, these findings determine the novel role of mitochondrial translocation of calpain-1 in MMP-9 activation during HHcy, in part, by increasing mitochondrial oxidative stress.

Animals↗

PubMed2006

The Arabidopsis ascorbate peroxidase 3 is a peroxisomal membrane-bound antioxidant enzyme and is dispensable for Arabidopsis growth and development.

Ascorbate peroxidase (APX) exists as several isoforms that are found in various compartments in plant cells. The cytosolic and chloroplast APXs appear to play important roles in antioxidation metabolism in plant cells, yet the function of peroxisomal APX is not well studied. In this study, the localization of a putative peroxisomal membrane-bound ascorbate peroxidase, APX3 from Arabidopsis, was confirmed by studying the green fluorescent protein (GFP)-APX3 fusion protein in transgenic plants. GFP-APX3 was found to co-localize with a reporter protein that was targeted to peroxisomes by the peroxisomal targeting signal 1. The function of APX3 in Arabidopsis was investigated by analysing an APX3 knockout mutant under normal and several stress conditions. It was found that loss of function in APX3 does not affect Arabidopsis growth and development, suggesting that APX3 may not be an important antioxidant enzyme in Arabidopsis, at least under the conditions that were tested, or the function of APX3 could be compensated by other antioxidant enzymes in plant cells.

Amino Acid Sequence↗

PubMed2006

[Age-related change of bone biochemical markers and their relationships to mineral density in healthy Chinese men].

OBJECTIVE: To study the age-related changes of bone formation markers, i.e., serum bone alkaline phosphatase (sBAP) and serum osteocalcin (sOC), bone resorption marker, i.e., cross-linked N-telopeptides of type 1 collagen (sNTX), and bone mineral density (BMD) in healthy men. METHODS: Serum sBAP, sOC, and sNTX of 389 randomly selected males, aged 20 - 80, all of Han nationality, were measured by using enzyme-linked immunosorbent (ELISA). Dual energy X-ray densitometer was used to measure the BMD of the lumbar vertebrae, left femoral neck, Ward's triangle, and hip. The relationships of these markers to age were analyzed. RESULTS: (1) The sBAP, sOC, and sNTX were negatively correlated with age, the cubic regression model being better with age-related changes of bone biochemical markers as compared with the other regression models (R(2) = 0.013 - 0.029, P < 0.05); (2) When all subjects were stratified by 10-years, the bone biochemical marker values were the highest in the age group 20 - 29, with the sBAP of 30.9 U/L +/- 12.6 U/L, sOC of 12.6 microg/L +/- 6.2 microg/L, and sNTX of 18.2 micromol/L +/- 6.6 micromol/L; then decreased with aging and to a nadir level in the age group 50 - 59, with the sBAP of 26.9 U/L +/- 8.6 U/L, sOC of 9.2 microg/L +/- 5.3 microg/L, and sNTX of 15.6 micromol/L +/- 6.1 micromol/L. After the age of 60, sNTX increased slightly 16.0 micromol/L +/- 6.1 micromol/L, however, BAP and sOC remained stable; (3) After adjustment for age, height, weight, BMI and smoking, serum BAP was negatively correlated with BMD of multiple skeletal sites. sOC was inversely associated with BMD of multiple skeletal sites except lateral spine; and sNTX was negatively correlated with BMD of the lumbar spine and total hip. CONCLUSION: Negatively correlated with BMD, sBAP, sOC, and sNTX may be sensitive and relatively specific markers to evaluate age-related changes of bone turnover.

Adult↗

PubMed2006

Simple, sensitive and rapid LC-MS method for the quantitation of indapamide in human plasma--application to pharmacokinetic studies.

A sensitive and specific method using liquid chromatography with electrospray ionization mass spectrometry (LC-ESI-MS) has been developed and validated for the identification and quantification of indapamide in human plasma. A simple liquid-liquid extraction procedure was followed by injection of the extracts on to a C18 column with gradient elution and detection using a single quadrupole mass spectrometer in selected ion monitoring (SIM) mode. The method was tested using six different plasma batches. Linearity was established for the concentration range 0.5-100.0 ng/ml, with a coefficient of determination (r) of 0.9998 and good back-calculated accuracy and precision. The intra- and inter-day precision (RSD%) was lower than 10%, and accuracy ranged from 85 to 115%. The lower limit of quantification was reproducible at 0.2 ng/ml with 0.2 ml plasma. The proposed method enables the unambiguous identification and quantification of indapamide for pre-clinical and clinical studies.

Antihypertensive Agents↗

PubMed2006

Changes of inducible protein-10 and regulated upon activation, normal T cell expressed and secreted protein in acute rejection of pancreas transplantation in rats.

AIM: To investigate the role of IFN-gamma inducible protein -10 (IP-10) and regulated upon activation, normal T cell expressed and secreted (RANTES) protein in acute pancreatic allograft rejection in rats. METHODS: An experimental pancreas transplantation model was established using diabetic SD rats as the recipient, induced by applying streptozocin (STZ). Pancreas transplantation was performed with a physiologic method of portal venous and enteric drainage. Rats were divided into two groups, isograft group (group A, n = 24) and allograft group (group B, n = 24) in which either healthy SD rats or Wistar rats served as donors, respectively. Twelve diabetic or healthy SD rats were used as controls. At d 1, 4, 7, and 10 post transplantation, serum IP-10 and RANTES were assessed by ELISA and their expression in the allografts was determined by immunohistochemistry. RESULTS: In group B (allograft group), the development of acute rejection was significantly correlated with increased serum concentration and tissue expression of IP-10 and RANTES, with a peak level at d 7 post transplantation. In contrast, there was no obvious change before and after transplantation in group A (isograft group). CONCLUSION: Our study suggests a possible role of IP-10 and RANTES in acute rejection and early monitoring of chemokines may be helpful in predicting the outcome of pancreas transplantation.

Animals↗

PubMed2006

Effect of Tetrandrine on LPS-induced NF-kappaB activation in isolated pancreatic acinar cells of rat.

AIM: To investigate the effect of Tetrandrine (Tet) on LPS-induced NF-kappaB activation and cell injury in pancreatic acinar cells and to explore the mechanism of Tetrandrine preventing LPS-induced acinar cell injury. METHODS: Male rat pancreatic acinar cells were isolated by collagenase digestion, then exposed to LPS (10 mg/L), Tet (50 micromol/L, 100 micromol/L) or normal media. At different time point (30 min, 1 h, 4 h, 10 h) after treatment with the agents, cell viability was determined by MTT, the product and nuclear translocation of subunit p65 of NF-kappaB was visualized by immunofluorescence staining and nuclear protein was extracted to perform EMSA which was used to assay the NF-kappaB binding activity. RESULTS: LPS induced cell damage directly in a time dependent manner and Tet attenuated LPS-induced cell damage (50 micromol/L, P < 0.05; 100 micromol/L, P < 0.01). NF-kappaB p65 immunofluorescence staining in cytoplasm increased and began showing its nuclear translocation within 30 min and the peak was shown at 1 h of LPS 10 mg/L treatment. NF-kappaB DNA binding activity showed the same alteration pattern as p65 immunofluorescence staining. In Tet group, the immunofluorescence staining in cytoplasm and nuclear translocation of NF-kappaB were inhibited significantly. CONCLUSION: NF-kappaB activation is an important early event that may contribute to inflammatory responses and cell injury in pancreatic acinar cells. Tet possesses the protective effect on LPS-induced acinar cell injury by inhibiting NF-kappaB activation.

Acute Disease↗

PubMed2006

BDNF-mediated neurotransmission relies upon a myosin VI motor complex.

Brain-derived neurotrophic factor (BDNF) has been implicated in higher-order cognitive functions and in psychiatric disorders such as depression and schizophrenia. BDNF modulates synaptic transmission and plasticity primarily through the TrkB receptor, but the molecules involved in BDNF-mediated synaptic modulation are largely unknown. Myosin VI (Myo6) is a minus end-directed actin-based motor found in neurons that express Trk receptors. Here we report that Myo6 and a Myo6-binding protein, GIPC1, form a complex that can engage TrkB. Myo6 and GIPC1 were necessary for BDNF-TrkB-mediated facilitation of long-term potentiation in postnatal day 12-13 (P12-13) hippocampus. Moreover, BDNF-mediated enhancement of glutamate release from presynaptic terminals depended not only upon TrkB but also upon Myo6 and GIPC1. Similar defects in basal synaptic transmission as well as presynaptic properties were observed in Myo6 and GIPC1 mutant mice. Together, these results define an important role for the Myo6-GIPC1 motor complex in presynaptic function and in BDNF-TrkB-mediated synaptic plasticity.

Adaptor Proteins, Signal Transducing↗

PubMed2006

Mechanisms of the acute ischemia-induced arrhythmogenesis--a simulation study.

The underlying ionic mechanisms of ischemic-induced arrhythmia were studied by the computer simulation method. To approximate the real situation, ischemic cells were simulated by considering the three major component conditions of acute ischemia (elevated extracellular K(+) concentration, acidosis and anoxia) at the level of ionic currents and ionic concentrations, and a round ischemic zone was introduced into a homogeneous healthy sheet to avoid sharp angle of the ischemic tissue. The constructed models were solved using the operator splitting and adaptive time step methods, and the perturbation finite difference (PFD) scheme was first used to integrate the partial differential equations (PDEs) in the model. The numerical experiments showed that the action potential durations (APDs) of ischemic cells did not exhibited rate adaptation characteristic, resulting in flattening of the APD restitution curve. With reduction of sodium channel availability and long recovery of excitability, refractory period of the ischemic tissue was significantly prolonged, and could no longer be considered as same as APD. Slope of the conduction velocity (CV) restitution curve increased both in normal and ischemic region when pacing cycle length (PCL) was short, and refractory period dispersion increased with shortening of PCL as well. Therefore, dynamic changes of CV and dispersion of refractory period rather than APD were suggested to be the fundamental mechanisms of arrhythmia in regional ischemic myocardium.

Acidosis↗

PubMed2006

Improvement of expression level and bioactivity of soluble tumor necrosis factor-related apoptosis-inducing ligand (Apo2L/TRAIL) by a novel zinc ion feeding strategy.

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (Apo2L/TRAIL) is a new member of the TNF superfamily. In this work, the key role of Zn(2+) in high-level expression of soluble TRAIL was confirmed. The yield of soluble TRAIL reached 1.6 g l(-1) using a novel, two-stage Zn(2+) feeding strategy, and the accumulation of TRAIL inclusion bodies decreased. Furthermore, the purified TRAIL showed stronger cytotoxicity activity against human pancreatic 1990 tumor cells as the molar ratio of Zn(2+) to TRAIL monomer was 2 in purified TRAIL solution.

Apoptosis↗

PubMed2006

A new triterpene synthase from Arabidopsis thaliana produces a tricyclic triterpene with two hydroxyl groups.

[structure: see text] Thirteen oxidosqualene cyclase homologues exist in the genome of Arabidopsis thaliana. One of these genes, At4g15340, was amplified by PCR and expressed in yeast. The yeast transformant accumulated tricyclic triterpene, (3S,13R)-malabarica-17,21-dien-3,14-diol (arabidiol), whose structure was determined by NMR and MS analyses. Its epoxide analogue, (3S,13R,21S)-malabarica-17-en-20,21-epoxy-3,14-diol (arabidiol 20,21-epoxide), was also isolated from the transformed yeast. This is the first example of a triterpene synthase that yields a tricyclic triterpene with two hydroxyl groups.

Arabidopsis↗

PubMed2006

Suppression of Winfree turbulence under weak spatiotemporal perturbation.

Winfree turbulence is a chaotic wave pattern developing through negative-tension instability of scroll wave filaments in three-dimensional weak excitable media. Here, we investigate the response of Winfree turbulence to a spatiotemporal forcing in the form of a traveling-wave modulation of the medium excitability. It is shown that turbulent waves can be suppressed much more rapidly by this method, in comparison with the space-uniform modulation of the medium excitability. Since the occurrence of Winfree turbulence is currently regarded as one of the possible mechanisms underlying cardiac fibrillation, this method turns out to be suggestive of a possible low-amplitude defibrillation approach.

Journal Article↗

PubMed2006

Femtosecond studies of charge-transfer mediated proton transfer in 2-butylamino-6-methyl-4-nitropyridine N-oxide.

We have unraveled the effects of an amino substituent in the ortho position on the excited-state dynamics of 4-nitropyridine N-oxide by studying the picosecond fluorescence kinetics and femtosecond transient absorption of a newly synthesized compound, 2-butylamino-6-methyl-4-nitropyridine N-oxide, and by quantum chemical calculations. Similar to the parent compound, the S(1) state of the target molecule has significant charge-transfer character and shows a large (approximately 8000 cm(-1)) static Stokes shift in acetonitrile. Analysis of the experimental and the theoretical results leads, however, to a new scenario in which this intramolecular charge transfer triggers in polar, aprotic solvents an ultrafast (around 100 fs) intramolecular proton transfer between the amino and the N-O group. The electronically excited N-OH tautomer is subsequently subject to solvent relaxation and decays with a lifetime of approximately 150 ps to the ground state.

Computer Simulation↗

PubMed2006

Use of proteomic analysis of endometriosis to identify different protein expression in patients with endometriosis versus normal controls.

OBJECTIVE: To use proteomic techniques, including two-dimensional electrophoresis (2-DE), Western blot, and mass spectrometry, to screen and identify proteins that were expressed differently in patients with endometriosis versus normal controls. DESIGN: First, we aimed to find a difference in the way serum and eutopic endometrial proteins were expressed in women with and without endometriosis. Second, we were interested in searching for endometriotic proteins, which were specifically recognized by sera from patients with endometriosis. SETTING: Collaborative investigation in an academic research environment. PATIENT(S): Consenting women of reproductive age taking no medications and with laparoscopically proven endometriosis. INTERVENTION(S): Surgical excision of eutopic and ectopic endometrial biopsy and phlebotomization of patients with endometriosis and controls. MAIN OUTCOME MEASURE(S): Protein expression. RESULT(S): Thirteen protein spots from serum correlated with 11 known proteins and 11 protein spots from endometrium correlated with 11 known proteins were found differently expressed between women with and without endometriosis. Some proteins may be cytoskeletons, and some may be involved in the regulation of cell cycle, signal transduction, or immunological function. Three proteins, which were identified as vimentin, beta-actin, and ATP synthase beta subunit, hybridized significantly differently between endometriosis sera and normal sera. CONCLUSION(S): The data help to establish a human endometriosis proteome database and broaden our understanding of the pathogenesis of endometriosis. Further study of the proteins identified herein will assist in the eventual development of new diagnoses and treatments for endometriosis.

Actins↗