Biomedical subjects

Lei Wang

Publications and source records attributed to Lei Wang.

At least 127 records · Page 7Linked to original sources

PubMed2006

Value of mink vomit model in study of anti-emetic drugs.

AIM: To establish a new, reliable vomit model of minks. METHODS: Adult male minks were randomly divided into 8 groups (n=6): cisplatin (7.5 mg/kg) intraperitoneal injection (i.p.) group, copper sulfate (40 mg/kg) intragastric injection (i.g.) group, apomorphine (1.6 mg/kg) subcutaneous injection (s.c.) group, and 18 Gy whole-body X-irradiation group, ondansetron injection group (2 mg/kg i.p.) 30 min later followed by cisplatin (7.5 mg/kg) i.p., normal saline (NS) i.p. injection control group, metoclopramide injection group (4 mg/kg i.p.) 30 min later followed by apomorphine (1.6 mg/kg) s.c., NS i.g. control group. The frequency of retching and vomiting was calculated. After behavioral experiment, distribution of 5-HT in the ileum was detected by immunohistologic method. RESULTS: Cisplatin, apomorphine, copper sulfate and X-irradiation administered to minks evoked a profound emetic response in the animals. However, retching and vomiting were significantly inhibited by pretreatment with ondansetron and metoclopramide in cisplatin and copper sulfate groups (P=0.018). Immunohistologic result showed that 5-HT released from enterochromaffin cells (EC cells) was involved in vomiting mechanism. CONCLUSION: Mink vomit model has a great value in studying the vomiting mechanism and screening new antiemetic drugs.

Animals↗

PubMed2006

Histone deacetylase-associating Atrophin proteins are nuclear receptor corepressors.

Drosophila Tailless (Tll) is an orphan nuclear receptor involved in embryonic segmentation and neurogenesis. Although Tll exerts potent transcriptional repressive effects, the underlying molecular mechanisms have not been determined. Using the established regulation of knirps by tll as a paradigm, we report that repression of knirps by Tll involves Atrophin, which is related to vertebrate Atrophin-1 and Atrophin-2. Atrophin interacts with Tll physically and genetically, and both proteins localize to the same knirps promoter region. Because Atrophin proteins interact with additional nuclear receptors and Atrophin-2 selectively binds histone deacetylase 1/2 (HDAC1/2) through its ELM2 (EGL-27 and MTA1 homology 2)/SANT (SWI3/ADA2/N-CoR/TFIII-B) domains, our study establishes that Atrophin proteins represent a novel class of nuclear receptor corepressors.

Alanine↗

PubMed2006

A thaumatin-like protein from larvae of the beetle Dendroides canadensis enhances the activity of antifreeze proteins.

The levels of thermal hysteresis (antifreeze activity) produced by purified antifreeze proteins (DAFPs) from the larvae of the beetle Dendroides canadensis at endogenous concentrations are lower than what are present in the hemolymph of overwintering larvae. Thermal hysteresis activity of DAFPs is dependent not only on AFP concentration but also on the presence of enhancers that may be either proteins (including other hemolymph DAFPs) or low-molecular mass enhancers such as glycerol. The purpose of this study was to identify endogenous protein enhancers using yeast two-hybrid, co-immunoprecipitation, and finally the enhancement of antifreeze activity. Here we show that a thaumatin-like protein from D. canadensis, until recently known only from plants, significantly enhances the thermal hysteresis of DAFP-1 and -2. Glycerol can further this enhancement, presumably by promoting the interaction of the DAFPs and thaumatin-like protein.

Amino Acid Sequence↗

PubMed2006

Establishment and applications of epstein-barr virus-based episomal vectors in human embryonic stem cells.

Human embryonic stem (hES) cells are capable of unlimited cell proliferation yet maintain the potential to differentiate into many cell types. Here we reported an Epstein-Barr virus (EBV)-based vector system used to improve transfection efficiency in hES cells. Plasmids containing oriP, the latent replication origin of EBV, can be propagated stably as episomal DNA in human cells that express the EBV nuclear antigen 1 (EBNA1), which binds to oriP and functions as the trans-acting replication initiator. It was reported that the EBV replicon could harbor a DNA fragment of up to 330 kilobase pairs. Plasmids containing an enhanced green fluorescent protein (EGFP)/puromycin resistance gene cassette along with or without oriP were used to transfect hES cells that stably express EBNA1. The presence of oriP moderately increased the transient transfection efficiency and more importantly it elevated the stable transfection efficiency by approximately 1,000-fold as compared with oriP-minus plasmids. The oriP plasmid as episomal DNA and green fluorescent protein expression in hES cells was maintained for months in the presence of drug selection and gradually lost (2%-4% per cell doubling) in the absence of selection. The presence of EBNA1 did not interfere with the hES cell properties or differentiation we tested and could maintain stable EGFP expression during differentiation. In addition to transgene expression, the EBV vector system could effectively enhance the RNA interference efficiency in hES cells. Thus, the EBV vector system that allows a large DNA insert and sustained expression of transgene or small hairpin RNA will enhance basic and translational research using hES cells.

Bone Morphogenetic Protein 4↗

PubMed2006

A novel post-transcriptional mechanism of regulation of luteinizing hormone receptor expression by an RNA binding protein from the ovary.

Luteinizing hormone/human chorionic gonadotropin (LH/hCG) receptor, a member of the rhodopsin/beta(2) adrenergic receptor subfamily of G-protein coupled receptors, is expressed primarily in the gonads and essential for the regulation of reproductive function. In the ovary, the expression of the receptor is post-transcriptionally regulated under physiological conditions. Studies from our laboratory showed that the ligand-induced down-regulation of the receptor occurs by accelerated degradation of the mRNA rather than by decreased transcription. We have identified a cytoplasmic LHR mRNA binding protein (LRBP) as a trans-acting factor in regulating LHR mRNA levels. LRBP binds to the coding region of LHR mRNA and causes accelerated degradation of mRNA. The RNA binding activity of LRBP was found to be inversely correlated to LH/hCG receptor mRNA levels. LRBP was purified to homogeneity and its identity was established as mevalonate kinase by N-terminal microsequencing and MALDI analysis. Mevalonate kinase, an enzyme involved in de novo synthesis of cholesterol, belongs to the GHMP family of kinases having a potential RNA binding fold. The expression of MVK mRNA and MVK protein levels were induced in response to hCG treatment prior to the down-regulation of LH/hCG receptor mRNA expression. A model for the post-transcriptional regulation of LH/hCG receptor in the ovary by mevalonate kinase is proposed.

Amino Acid Sequence↗

PubMed2006

Sonocatalytic degradation of methyl parathion in the presence of nanometer and ordinary anatase titanium dioxide catalysts and comparison of their sonocatalytic abilities.

The degradation of methyl parathion (O,O-dimethyl-O-(4-nitrophenyl)-phosphorothioate) using anatase titanium dioxide (TiO(2)) powder as heterogeneous sonocatalysts is reported. The influences of reaction parameters such as the species of TiO(2) sonocatalysts, methyl parathion concentrations, TiO(2) adding amount, pH, ultrasonic intensity, ultrasonic frequency and temperature have been investigated and the optimal conditions for eliminating methyl parathion have been identified. The efficiencies of sonocatalytic degradation in both nanometer and ordinary anatase systems are compared and the results indicate that the sonocatalytic activity of nanometer anatase TiO(2) powder is better than that of ordinary anatase TiO(2) powder. The primary degradation and the total mineralization of methyl parathion have been monitored by high performance liquid chromatography (HPLC) and UV-vis spectra, respectively. Methyl parathion got destroyed to some extent in both nanometer and ordinary anatase systems under ultrasonic irradiation. The kinetics for the degradation process of methyl parathion follows the first-order reaction. The degradation ratio of methyl parathion surpassed 90% within 50min in the optimal experiment conditions.

Catalysis↗

PubMed2006

Locally applied nerve growth factor enhances bone consolidation in a rabbit model of mandibular distraction osteogenesis.

Distraction osteogenesis is widely used in treating deformities, defects, and fractures of both long bones and craniofacial bones. Demands for acceleration of bone consolidation are increased in distraction osteogenesis. Nerve growth factor (NGF) can enhance innervation and bone regeneration in a fracture model and stimulate differentiation of osteoblastic cells. In this study, we tested the ability of locally applied NGF to enhance bone regeneration in a rabbit model of mandibular distraction osteogenesis. Twenty rabbits underwent bilateral distraction osteogenesis with a rate of 0.5 mm per 12 h. Two times 0.04 mg human NGFbeta (hNGFbeta) in buffer was injected into the callus after distraction. The contralateral side received placebo injections. Rabbits were euthanized at consolidation times of 14 and 28 days. Specimens were subjected to radiography, callus dimensions measurement, mechanical testing, and bone histological and histomorphometric analysis. The maximum load, bone volume/total volume, mineral apposition rate of the 1st to 11th day, and mineralized bone percentage were significantly higher in the hNGFbeta side at 14 and 28 days (p<0.05). The data indicate that locally applied hNGFbeta can accelerate callus maturation and may be an option to shorten the consolidation period in distraction osteogenesis.

Administration, Topical↗

PubMed2006

Identification of breast cancer metastasis-associated proteins in an isogenic tumor metastasis model using two-dimensional gel electrophoresis and liquid chromatography-ion trap-mass spectrometry.

To better understand the molecular mechanisms underlying breast cancer metastasis and search for potential markers for metastatic progression, we have developed a highly metastatic variant of human MDA-MB-435 breast cancer cell line through in vivo stepwise selection of pulmonary metastatic cells caused by parental MDA-MB-435 cells in the athymic mice. Comparative proteomic analysis using 2-DE and LC-IT-MS revealed that 102 protein spots were reproducibly altered more than three-fold between the selected variant and its parental counterpart. Eleven differentially expressed protein spots were identified with high confidence using SEQUEST with uninterpreted tandem mass raw data. Cathepsin D precursor, peroxiredoxin 6 (PDX6), heat shock protein 27 (HSP27), HSP60, tropomyosin 1 (TPM1), TPM2, TPM3, TPM4, 14-3-3 protein epsilon, and tumor protein D54 were up-regulated in the highly metastatic variant, whereas alpha B-crystalline (CRAB) was only detected in its parental counterpart. Differential expression was confirmed for four proteins including PDX6, CRAB, TPM4, and HSP60 by real-time quantitative PCR and Western blotting analysis in our model. Immunohistochemical analysis in 80 breast cancer donors demonstrated a significant association of TPM4 (p = 0.002), HSP60 (p = 0.001), PDX6 (p = 0.002) but not CRAB (p = 0.113) staining with the presence of lymph node metastasis. In addition, TPM4 staining was also associated with clinical stage (p = 0.000), but no significant association was found between TPM4, PDX6, CRAB, and HSP60 expression and tumor size, hormone receptor, and HER-2 status (p > 0.05). The functional implication of these identified proteins was also discussed. These proteomic data are valuable and informative for understanding breast cancer metastasis and searching for potential markers for metastatic progression.

Animals↗

PubMed2006

An auxin-inducible F-box protein CEGENDUO negatively regulates auxin-mediated lateral root formation in Arabidopsis.

Previously, we characterized 92 Arabidopsis genes (AtSFLs) similar to the S-locus F-box genes involved in S-RNase-based self-incompatibility and found that they likely play diverse roles in Arabidopsis. In this study, we investigated the role of one of these genes, CEGENDUO (CEG, AtSFL61), in the lateral root formation. A T-DNA insertion in CEG led to an increased lateral root production, which was complemented by transformation of the wild-type gene. Its downregulation by RNAi also produced more lateral roots in transformed Arabidopsis plants whereas its overexpression generated less lateral roots compared to wild-type, indicating that CEG acts as a negative regulator for the lateral root formation. It was found that CEG was expressed abundantly in vascular tissues of the primary root, but not in newly formed lateral root primordia and the root meristem, and induced by exogenous auxin NAA (alpha-naphthalene acetic acid). In addition, the ceg mutant was hyposensitive to NAA, IAA (indole-3-acetic acid) and 2,4-D (2,4-dichlorophenoxyacetic acid), as well as the auxin transport inhibitor TIBA (3,3,5-triiodobenzoic acid), showing that CEG is an auxin-inducible gene. Taken together, our results show that CEG is a novel F-box protein negatively regulating the auxin-mediated lateral root formation in Arabidopsis.

Arabidopsis↗

PubMed2006

Nerve growth factor and tyrosine kinase A in human salivary adenoid cystic carcinoma: expression patterns and effects on in vitro invasive behavior.

PURPOSE: Perineural invasion is a frequent occurrence in salivary adenoid cystic carcinoma (ACC) and may prevent complete surgical resection. Studies have indicated that nerve growth factor (NGF) and its high-affinity receptor tyrosine kinase A (TrkA) may play a role in perineural invasion in several malignancies in which perineural invasion is observed. The present study was conducted to investigate the expression of NGF and TrkA in salivary ACC and to examine the effects of NGF on adhesion, migration and invasion capacities of a salivary ACC cell line (SACC-83) in vitro. PATIENTS AND METHODS: Expression of NGF and TrkA was explored using immunohistochemistry in paraffin-embedded tissues of 32 cases of salivary ACC. The effects of NGF on in vitro adhesion, migration, and invasion capacities of the SACC-83 cell line were examined using an MTT assay and a modified Boyden chamber assay respectively. RESULTS: In ACC specimens, 31 (96.9%) and 32 (100%) tumors showed immunoreactivity for NGF and TrkA respectively. Significant correlations were found between NGF/TrkA expression levels and perineural invasion (P < .05). In cell adhesion assay, the percent adherences of SACC-83 cells co-cultured with 25 ng/ml NGF at 1.5 hours and 5, 25 ng/ml NGF at 6 hours were significantly higher than that co-cultured with 0 ng/ml NGF (P < .05). However, high concentration of NGF (500 ng/ml) resulted in a significant inhibition of invasion (P < .05). CONCLUSION: Overexpression of NGF and TrkA in human salivary ACC tissues may constitute a reason for perineural invasion in salivary ACC.

3T3 Cells↗

PubMed2006

Sonocatalytic damage of bovine serum albumin (BSA) in the presence of nanometer anatase titanium dioxide (TiO2).

The nanometer anatase titanium dioxide (TiO2) (a kind of crystal type of TiO2) powder was adopted as the sonocatalyst for the damage of bovine serum albumin (BSA) used as a model protein by low-power ultrasound (US) (80 kHz, 80 W). The effects of several factors on the damage of BSA molecule were reviewed by means of ultraviolet destruction and circular dichroism spectra. It was found that the BSA molecule underwent destruction of the secondary structure and loss of the alpha-helical configuration to a certain extent under ultrasonic irradiation in the presence of nanometer anatase TiO2 powder and that the damage caused by US integrated with TiO2 was more serious than those by only US or only TiO2. Furthermore, the damage degree was aggravated with the increase of TiO2, added to saturation, and then it was slowly weakened with the excessive TiO2. When a suitable amount of acid or base was added into the BSA solution, the sonocatalytic damage was also aggravated. Because the functions of proteins are decided by their space configurations, the changes of the configurations might cause the forfeiture of their function, even the apoptosis or necrosis of cells. Perhaps, an effective method of killing cancer cells by sonocatalytic damage of protein molecules in the presence of nanometer anatase TiO2 could be obtained from these experimental results.

Animals↗

PubMed2006

Proteomic analysis of effect of hyperthermia on spermatogenesis in adult male mice.

We characterized cellular and molecular mechanisms involved in spermatogenesis following short-term heat exposure of murine testis. For these studies, we utilized a proteomic approach with two-dimensional gel electrophoresis (2DE) analyses and mass spectroscopic identification of proteins with altered expression in mouse testes at different times after heat shock. We established a proteome reference map from 7-wk-old mouse testis linked to a federated proteome database. We used these tools to analyze quantitative variations in the tissue over a time course of 0.5, 2, 6, and 12 h following heat exposure. We separated 108 protein spots expressed differentially between the heat shock tissues and the control mouse testes. Of these spots, we identified 36 by comparing with the control reference map. We then focused on the heterogeneous nuclear ribonucleoproteins (hnRNPs) and the chaperonins containing t-complex polypeptide-1 (CCT). Further analysis in this heat-shocked model suggests numerous potential mechanisms for heat shock-induced spermatogenic disorder.

Animals↗

PubMed2006

The in vivo synaptic plasticity mechanism of EGb 761-induced enhancement of spatial learning and memory in aged rats.

It has not been uniform to date that the Ginkgo biloba extracts enhance cognitive function in aged animals, and the mechanisms of action remain difficult to elucidate. In this study, the Morris water maze task and electrophysiological methods were used to study the effects of repeated daily administration of EGb 761, a standardized extract from G. biloba leaves, on hippocampal-dependent spatial learning and memory and synaptic plasticity of aged rats. The adult subjects perform the Morris water maze task better than aged rats, as a cellular mechanism, the hippocampal long-term potentiation (LTP) elicited from adult animals is robust (139.29+/-2.7%). In addition, the spatial learning and memory of aged rats that had been fed on an EGb 761-supplemented diet (60 mg kg(-1)) for 30 days were significantly better than those of control aged rats. The magnitude of LTP (116.63+/-3.6%) recorded in vivo from the hippocampus CA1 area of aged rats was significantly enhanced by EGb 761 (60 mg kg(-1)). In conclusion, the spatial learning and memory of aged rats is worse than that of young subjects, and EGb 761, acting as a 'cognitive enhancer', has benefit on synaptic plasticity and cognition in aged rats. The present data further confirmed that enhancement of synaptic plasticity of the hippocampus might ameliorate the deficit in spatial learning and memory in aged rats.

Aging↗

PubMed2006

The brassinosteroid signal transduction pathway.

Steroids function as signaling molecules in both animals and plants. While animal steroid hormones are perceived by nuclear receptor family of transcription factors, brassinosteroids (BR) in plants are perceived by a cell surface receptor kinase, BRI1. Recent studies have demonstrated that BR binding to the extracellular domain of BRI1 induces kinase activation and dimerization with another receptor kinase, BAK1. Activated BRI1 or BAK1 then regulate, possibly indirectly, the activities of BIN2 kinase and/or BSU1 phosphatase, which directly regulate the phosphorylation status and nuclear accumulation of two homologous transcription factors, BZR1 and BES1. BZR1 and BES1 directly bind to promoters of BR responsive genes to regulate their expression. The BR signaling pathway has become a paradigm for both receptor kinase signaling in plants and steroid signaling by cell surface receptors in general.

Brassinosteroids↗

PubMed2006

Heterotrimeric G protein alpha subunit is involved in rice brassinosteroid response.

Heterotrimeric G proteins are known to function as messengers in numerous signal transduction pathways. The null mutation of RGA (rice heterotrimeric G protein alpha subunit), which encodes the alpha subunit of heterotrimeric G protein in rice, causes severe dwarfism and reduced responsiveness to gibberellic acid in rice. However, less is known about heterotrimeric G protein in brassinosteroid (BR) signaling, one of the well-understood phytohormone pathways. In the present study, we used root elongation inhibition assay, lamina inclination assay and coleoptile elongation analysis to demonstrated reduced sensitivity of d1 mutant plants (caused by the null mutation of RGA) to 24-epibrassinolide (24-epiBL), which belongs to brassinosteroids and plays a wide variety of roles in plant growth and development. Moreover, RGA transcript level was decreased in 24-epiBL-treated seedlings in a dose-dependent manner. Our results show that RGA is involved in rice brassinosteroid response, which may be beneficial to elucidate the molecular mechanisms of G protein signaling and provide a novel perspective to understand BR signaling in higher plants.

Arabidopsis Proteins↗

PubMed2006

Stromal cell-derived factor 1alpha mediates neural progenitor cell motility after focal cerebral ischemia.

In the adult rodent, stroke induces an increase in endogenous neural progenitor cell (NPC) proliferation in the subventricular zone (SVZ) and neuroblasts migrate towards the ischemic boundary. We investigated the role of stromal cell-derived factor 1alpha (SDF-1alpha) in mediating NPC migration after stroke. We found that cultured NPCs harvested from the normal adult SVZ, when they were overlaid onto stroke brain slices, exhibited significantly (P<0.01) increased migration (67.2+/-25.2 microm) compared with the migration on normal brain slices (29.5+/-29.5 microm). Immunohistochemistry showed that CXCR 4, a receptor of SDF-1alpha, is expressed in the NPCs and migrating neuroblasts in stroke brain. Blocking SDF-1alpha by a neutralizing antibody against CXCR 4 significantly attenuated stroke-enhanced NPC migration. ELISA analysis revealed that SDF-1alpha levels significantly increased (P<0.01) in the stroke hemisphere (43.6+/-6.5 pg/mg) when compared with the normal brain (25.2+/-1.9 pg/mg). Blind-well chamber assays showed that SDF-1alpha enhanced NPC migration in a dose-dependent manner with maximum migration at a dose of 500 ng/mL. In addition, SDF-1alpha induced directionally selective migration. These findings show that SDF-1alpha generated in the stroke hemisphere may guide NPC migration towards the ischemic boundary via binding to its receptor CXCR 4 in the NPC. Thus, our data indicate that SDF-1alpha/CXCR 4 is important for mediating specific migration of NPCs to the site of ischemic damaged neurons.

Animals↗

PubMed2006

Neurogenin 1 mediates erythropoietin enhanced differentiation of adult neural progenitor cells.

Proneuronal basic helix-loop-helix (bHLH) transcription factor, neurogenin 1 (Ngn1), regulates neuronal differentiation during development of the cerebral cortex. Akt mediates proneuronal bHLH protein function to promote neuronal differentiation. Here, we show that recombinant human erythropoietin (rhEPO) significantly increased Akt activity and Ngn1 mRNA levels in neural progenitor cells derived from the subventricular zone (SVZ) of adult rat, which was coincident with increases of neural progenitor cell proliferation, differentiation, and neurite outgrowth. Inhibition of Akt activity by the phosphatidylinositol 3-kinase/Akt (PI3K/Akt) inhibitor, LY294002, abolished rhEPO-increased Ngn1 mRNA levels and the effects of rhEPO on neural progenitor cells. In addition, reducing expression of endogenous Ngn1 by means of short-interfering RNA (siRNA) blocked rhEPO-enhanced neuronal differentiation and neurite outgrowth but not rhEPO-increased proliferation. Furthermore, treatment of stroke rat with rhEPO significantly increased Ngn1 mRNA levels in SVZ cells. These data suggest that rhEPO acts as an extracellular molecule that activates the PI3K/Akt pathway, which enhances adult neural progenitor cell proliferation, differentiation, and neurite outgrowth, and Ngn1 is required for Akt-mediated neuronal differentiation and neurite outgrowth.

Animals↗

PubMed2006

Quantitation of hydroxyl radicals from photolysis of Fe(III)-citrate complexes in aerobic water.

BACKGROUND: For their high photoreactivity, Fe(III)-carboxylate complexes are important sources of H2O2 for some atmospheric and surface waters. Citrate is one kind of carboxylate, which can form complexes with Fe(III). In our previous study, we have applied Fe(III)-citrate complexes to degrade and decolorize dyes in aqueous solutions both under UV light and sunlight. Results have shown that carboxylic acids can promote the photodegradation efficiency. It is indicated that the photolysis of Fe(III)-citrate complexes may cause the formation of some reactive species (e. g. H2O2 and *OH). This work is attempted to quantify hydroxyl radicals generated in the aqueous solution containing Fe(III)-citrate complexes and to interpret the photoreactivity of Fe(III)-citrate complexes for degrading organic compounds. METHODS: By using benzene as the scavenger to produce phenol, the photogeneration of *OH in the aqueous solution containing Fe (III)-citrate complexes was determined by HPLC. RESULTS AND DISCUSSION: In the aqueous solution containing 60.0/ 30.0 microM Fe(III)/citrate and 7.0 mM benzene at pH 3.0, 96.66 microM *OH was produced after irradiation by a 250 W metal halid light (lambda > or = 313 nm) for 160 minutes. Effects of initial pH value and concentrations of Fe(III) and citrate on *OH radical generation were all examined. The results show that the greatest from 3.0 to 7.0) was at pH 3.0. The photoproduction of *OH increased with increasing Fe(III) or citrate concentrations. CONCLUSION: In the aqueous solutions containing Fe(III)-citrate complexes, *OH radicals were produced after irradiation by a 250 W metal halide light. It can be concluded that Fe(III)-citrate complexes are important sources of *OH radicals for some atmospheric and surface waters. RECOMMENDATIONS AND OUTLOOK: It is believed that the photolysis of Fe(III)-citrate complexes in the presence of oxygen play an important role in producing *OH both in atmospheric waters and surface water where high concentrations of ferric ions and citrate ions exist. The photoproduction of *OH has a high oxidizing potential for the degradation of a wide variety of natural and anthropogenic organic and inorganic substances. We can use this method for toxic organic pollutants such as organic dyes and pesticides.

Benzene↗