Biomedical subjects

Jianguo Chen

Publications and source records attributed to Jianguo Chen.

At least 19 recordsLinked to original sources

PubMed2006

14-3-3gamma affects dynamics and integrity of glial filaments by binding to phosphorylated GFAP.

Recent findings indicated a protective role of GFAP in ischemic brain, injured spinal cord, and in neurodegenerative disease. We previously demonstrated that 14-3-3gamma, once thought to be neuronal specific, was up-regulated by ischemia in astrocytes and may play a specific protective role in astrocytes. Here we report that 14-3-3gamma associates with both soluble and filamentous GFAP in a phosphorylation- and cell-cycle-dependent manner in primary cultured astrocytes. The amount of association increases during G2/M phase due to more phosphorylated GFAP. Moreover, this interaction is independent of vimentin, another type III intermediate filament protein in astrocytes which forms glial filaments with GFAP. A series of domain deletion mutants and substitution mutations at phosphorylation sites (from serine to alanine) on GFAP demonstrated that serine 8 in the head domain is essential for the direct association of GFAP to 14-3-3gamma. Overexpression of 14-3-3gamma destroyed the integrity and affected the movement of GFAP intermediate filaments. This data demonstrates that 14-3-3gamma contributes to the regulation of dynamics of GFAP filaments, which may contribute to the stability of the cytoskeleton and the mechanisms of central nervous system neurodegenerative disease.

14-3-3 Proteins↗

PubMed2006

Preparation of silver nanoparticles in water-in-oil AOT reverse micelles.

Colloidal silver nanoparticles were synthesized in AOT microemulsions. The effects of the precursors' concentration and the molar ratios of water to AOT on the particle size and size distribution were investigated. UV-vis spectra showed that the Ag+4 intermediates formed at low N2H4 concentration. TEM micrographs confirmed that the silver nanoparticles are all spherical with mean diameters in the range 2-5 nm and have a narrow size distribution. Not only the particle size but also the size distribution was increasing with the W value. The silver colloid has favorable stability and can be preserved for a long time without precipitation.

Colloids↗

PubMed2006

Modulation of Ca2+ signals by phosphatidylinositol-linked novel D1 dopamine receptor in hippocampal neurons.

Recent evidence indicates the existence of a putative novel phosphatidylinositol-linked D1 dopamine receptor in brain that mediates phosphatidylinositol hydrolysis via activation of phospholipase Cbeta. The present work was designed to characterize the Ca(2+) signals regulated by this phosphatidylinositol-linked D(1) dopamine receptor in primary cultures of hippocampal neurons. The results indicated that stimulation of phosphatidylinositol-linked D1 dopamine receptor by its newly identified selective agonist SKF83959 induced a long-lasting increase in basal [Ca(2+)](i) in a time- and dose-dependent manner. Stimulation was observable at 0.1 microm and reached the maximal effect at 30 microm. The [Ca(2+)](i) increase induced by 1 microm SKF83959 reached a plateau in 5 +/- 2.13 min, an average 96 +/- 5.6% increase over control. The sustained elevation of [Ca(2+)](i) was due to both intracellular calcium release and calcium influx. The initial component of Ca(2+) increase through release from intracellular stores was necessary for triggering the late component of Ca(2+) rise through influx. We further demonstrated that activation of phospholipase Cbeta/inositol triphosphate was responsible for SKF83959-induced Ca(2+) release from intracellular stores. Moreover, inhibition of voltage-operated calcium channel or NMDA receptor-gated calcium channel strongly attenuated SKF83959-induced Ca(2+) influx, indicating that both voltage-operated calcium channel and NMDA receptor contribute to phosphatidylinositol-linked D(1) receptor regulation of [Ca(2+)](i).

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗

PubMed2006

Novel changes in discoidal high density lipoprotein morphology: a molecular dynamics study.

ApoA-I is a uniquely flexible lipid-scavenging protein capable of incorporating phospholipids into stable particles. Here we report molecular dynamics simulations on a series of progressively smaller discoidal high density lipoprotein particles produced by incremental removal of palmitoyloleoylphosphatidylcholine via four different pathways. The starting model contained 160 palmitoyloleoylphosphatidylcholines and a belt of two antiparallel amphipathic helical lipid-associating domains of apolipoprotein (apo) A-I. The results are particularly compelling. After a few nanoseconds of molecular dynamics simulation, independent of the starting particle and method of size reduction, all simulated double belts of the four lipidated apoA-I particles have helical domains that impressively approximate the x-ray crystal structure of lipid-free apoA-I, particularly between residues 88 and 186. These results provide atomic resolution models for two of the particles produced by in vitro reconstitution of nascent high density lipoprotein particles. These particles, measuring 95 angstroms and 78 angstroms by nondenaturing gradient gel electrophoresis, correspond in composition and in size/shape (by negative stain electron microscopy) to the simulated particles with molar ratios of 100:2 and 50:2, respectively. The lipids of the 100:2 particle family form minimal surfaces at their monolayer-monolayer interface, whereas the 50:2 particle family displays a lipid pocket capable of binding a dynamic range of phospholipid molecules.

Apolipoprotein A-I↗

PubMed2006

Detection of Newcastle disease virus using nucleic acid sequence-based amplification.

Newcastle disease (ND) is a contagious and widespread avian disease affecting most species of birds. ND virus (NDV) is the only member of the avian paramyxovirus serotype 1 (APMV1) causing ND outbreak in bird flocks. The technique of nucleic acid sequence-based amplification (NASBA) is a potential method to rapidly and reliably detect NDV isolates. Here, we describe an effective and unprecedented method for detecting NDV strains of all pathotypes. A conserved region of the fusion protein gene was used for designing oligonucleotides specific to all NDV pathotypes. The dynamic range of this NDV NASBA detection method is comparable to virus culture and therefore the NDV NASBA method is a potential alternative for NDV screening and surveillance.

Animals↗

PubMed2006

Stevioside counteracts the glyburide-induced desensitization of the pancreatic beta-cell function in mice: studies in vitro.

The sulfonylurea glyburide (GB) is one of the most frequently used drugs in diabetes treatment. Long-term pretreatment with GB causes elevated basal insulin secretion (BIS) and decreased glucose-stimulated insulin secretion (GSIS). These characteristics may play an important role for the development of hypoglycemia and secondary failure. Stevioside (SVS), a substance extracted from leaves of Stevia rebaudiana Bertoni, enhances GSIS but not BIS. The aim of the present study was to clarify whether 24-hour exposure of isolated mouse islets to GB causes dose-dependent decrease in the GSIS and whether it is possible to counteract this desensitization by SVS. We also tested the impact of the incretin glucagon-like peptide-1 (GLP-1) on the GB-induced desensitization. After 24-hour preincubation with GB in combination with SVS or GLP-1, we measured the basal and glucose-stimulated insulin responses and the total islet insulin content. We also determined the fold change in gene expression of pancreatic and duodenal homeobox 1 and glucose transporter isoform 2. After 24-hour preincubation in 11.1 mmol/L glucose, GB (10(-11)-10(-3) mol/L) caused a dose-dependent decrease in GSIS (16.7 mmol/L glucose) (P < .001). GB (10(-7) mol/L) pretreatment elevated BIS, but neither SVS (10(-7) mol/L) nor GLP-1 (10(-7) mol/L) could reverse this. Interestingly, the GB-induced desensitization of GSIS was counteracted by both SVS (P < .05) and GLP-1 (P < .05). SVS reversed the decrease in insulin content caused by GB pretreatment (P < .05). GB pretreatment did not change gene expression of pancreatic and duodenal homeobox 1 nor glucose transporter isoform 2, whereas SVS significantly up-regulated the expression of both genes by more than 2-fold (P < .05). Our results showed that SVS in combination with GB did not reverse GB-induced increase in BIS, whereas both SVS and GLP-1 counteracted GB-induced desensitization of GSIS. SVS is able to counteract the desensitizing effects of GB and may be a putative new drug candidate for the treatment of type 2 diabetes mellitus.

Animals↗

PubMed2006

Baculovirus surface display of SARS coronavirus (SARS-CoV) spike protein and immunogenicity of the displayed protein in mice models.

The baculovirus surface display technique has provided an ideal tool to display foreign proteins with natural conformation, functions, and immunogenicity. In this work, we explored the application of this technique on SARS-associated coronavirus (SARS-CoV) spike (S) protein, and further analyzed the immunogenicity of displayed S protein. The entire ectodomain of S protein was fused between the gp64 signal peptide and the VSV-G membrane anchor and successfully displayed on the baculovirus surface. Subcutaneous injection with purified S-displayed baculoviruses without adjuvant elicited highly effective production of specific and neutralizing antibodies against S protein in mice. These results confirmed a successful surface display of S protein on baculoviruse, and suggested a potential role of S-displayed baculoviruses as a novel live virus-based vaccine candidate for SARS-CoV.

Animals↗

PubMed2006

Inhibition of cardiac PGC-1alpha expression abolishes ERbeta agonist-mediated cardioprotection following trauma-hemorrhage.

PGC-1alpha (peroxisome proliferator-activated receptor [PPARgamma] coactivator-1alpha) activates PPARalpha and mitochondrial transcription factor A (Tfam), which regulate proteins, fatty acid and ATP metabolism (i.e., FAT/CD36, MCAD, and COX I). Recently we found that the salutary effects of estradiol (E2) on cardiac function following trauma-hemorrhage (T-H) are mediated via estrogen receptor (ER)beta. In this study we tested the hypothesis that ERbeta-mediated cardioprotection is induced via up-regulation of PGC-1alpha through PPARalpha or Tfam-dependent pathway. Male rats underwent T-H and received ERalpha agonist propylpyrazole-triol (PPT), ERbeta agonist diarylpropionitrile (DPN), E2, or vehicle. Another group was treated with antisense PGC-1alpha oligonucleotides prior to administration of DPN. E2 and DPN treatments attenuated the decrease in cardiac mitochondrial ATP, abrogated the T-H-induced lipid accumulation, and normalized PGC-1alpha, PPARalpha, FAT/CD36, MCAD, Tfam, and COX I after T-H. In contrast, PPT administration did not abrogate lipid accumulation. Moreover, in PPT-treated animals mitochondrial ATP remained significantly lower than those observed in DPN- or E2-treated animals. Prior administration of antisense PGC-1alpha prevented DPN-mediated cardioprotection and increase in ATP levels and Tfam but not in PPARalpha following T-H. These findings suggest that the salutary effects of E2 on cardiac function following T-H are mediated via ERbeta up-regulation of PGC-1alpha through Tfam-dependent pathway.

Acyl-CoA Dehydrogenase↗

PubMed2006

Protective effects of breviscapine on ischemic vascular dementia in rats.

Breviscapine, a traditional Chinese medicine, is extensively used in clinic to treat cardiovascular diseases and cerebrovascular injury. In this study, we demonstrated the effects of breviscapine on vascular dementia (VD) rats, which were mimicked by permanent occlusion of bilateral common carotid arteries. Breviscapine (2 mg/kg for 14 d) improved the performance of learning and memory of VD rats in Morris water maze, decreased the level of lipid peroxidation and free radicals, and attenuated the pathological alterations, such as nuclear shrink, cellular edema and irregular arrangement of pyramidal layer in the hippocampal CA(1) area. In vitro experiment, breviscapine (50 microg/l) protected cortical neuron from injury and decreased intracellular calcium overloading induced by H2O2 (10 mM). The results suggest that breviscapine has therapeutic effect on cerebral ischemia and vascular dementia.

Animals↗

PubMed2006

[Experimental studies on the porous calcium phosphate cement combined with recombinant human bone morphogenetic protein 2 for bone defects repair].

OBJECTIVE: To study in vitro sustained release behaviour of the recombinant human bone morphogenetic protein 2 (rhBMP-2) from the sample which porous calcium phosphate cement (PCPC) was combined with rhBMP-2, and to evaluate the effect of PCPC/rhBMP-2 composite on repairing bone defect in the animal study. METHODS: rhBMP-2 was absorbed into PCPC by vacuum-adsorption and freeze-dried at -40 degrees C, the PCPC/rhBMP-2 enwrapped with chitosan as the experimental group, the pure PCPC/rhBMP-2 as the control group, then the sustained release of rhBMP-2 from PCPC was determined in simulated body fluid (SBF) by UV-VIS spectrophotometer. At same time, the PCPC/rhBMP-2 composites with chitosan were implanted into the (4.2 mm x 5.0 mm femora defects of rabbits, which were considered as the experimental group, whereas in the control group only PCPC was implanted. The effect of repairing bone defect was evaluated in the 4th and 8th week postoperatively by radiograph and histomorphology. RESULTS: The PCPC have a high absorption efficiency to rhBMP-2, and the release of rhBMP-2 was sustained release system. The release of rhBMP-2 from PCPC in the experimental group (99% after 350 hours) was slower than that in the control group (100% after 150 hours). In the experimental group, the radiological and histomorphological evaluations showed that the interfaces between the materials and host bones became blurred both at 4th and 8th week. The implanted materials were partially absorbed, and the implanted areas exhibited the formation of new bone. In the control group, a little amount of new bones was observed. CONCLUSION: The PCPC shows great clinical potential as a carrier for rhBMP-2. The PCPC/rhBMP-2 composite possesses much potentialities of osteoinductivity and the ability of repairing bone defect, so it can be used as a novel bone substitute clinically.

Animals↗

PubMed2005

Stevioside does not cause increased basal insulin secretion or beta-cell desensitization as does the sulphonylurea, glibenclamide: studies in vitro.

We have shown that stevioside (SVS) enhances insulin secretion and thus may have a potential role as antihyperglycemic agent in the treatment of type 2 diabetes mellitus. However, whether SVS stimulates basal insulin secretion (BIS) and/or cause desensitization of beta cells like sulphonylureas (SU), e.g. glibenclamide (GB), is not known. To explore and compare the effects of SVS pretreatment with those of GB and glucagon-like peptide-1 (GLP-1), we exposed isolated mouse islets to low or high glucose for 1 h after short-term (2 h) or long-term (24 h) pretreatment with SVS, GB or GLP-1, respectively. BIS at 3.3 or 5.5 mM glucose were not changed after short-term pretreatment with SVS (10(-7) M), while it increased about three folds after pretreatment with GB (10(-7) M). Glucose stimulated insulin secretion (GSIS) (16.7 mM) increased dose-dependently after long-term pretreatment with SVS at concentrations from 10(-7) to 10(-5) M. Pretreatment for 24 h with GB (10(-7) M) increased the subsequent BIS (3.3 mM glucose) (p < 0.001), but decreased GSIS (16.7 mM glucose) (p < 0.001). In contrast SVS (10(-7) M) and GLP-1 (10(-7) M) did not stimulate BIS but both enhanced the subsequent GSIS (16.7 mM glucose) (p < 0.05 and p < 0.05, respectively). While SVS pretreatment increased the intracellular insulin content, GB pretreatment decreased the insulin content. Our study suggests that SVS pretreatment does not cause a stimulation of BIS and does not desensitize beta-cells, i.e. SVS seems to have advantageous characteristics to GB as a potential treatment of type 2 diabetes.

Animals↗

PubMed2005

The short-term effect of fatty acids on glucagon secretion is influenced by their chain length, spatial configuration, and degree of unsaturation: studies in vitro.

The influence of fatty acids on beta cell function has been well established whereas little is known about the role of fatty acids on alpha cell function. The aim of our study was to investigate the short-term effects of chain length, spatial configuration, and degree of unsaturation of fatty acids on glucagon secretion from isolated mouse islets and alpha tumor cell 1 clone 6 cells (alpha TC1-6 cells). Glucagon release was measured with different saturated and unsaturated fatty acids as well as cis and trans isomers of fatty acids at low and high glucose. Palmitate (0.1-0.5 mmol/L) immediately stimulated glucagon release in a dose-dependent manner from both isolated islets and alpha TC 1-6 cells. The longer chain length of saturated fatty acids, the higher glucagon responses were obtained. The average fold increase in glucagon to saturated fatty acids (0.3 mmol/L) compared to control was octanoate 1.5, laurate 2.0, myristate 2.9, palmitate 5.4, and stearate 6.2, respectively. Saturated fatty acids were more effective than unsaturated fatty acids in stimulating glucagon secretion. At an equimolar concentration, trans-fatty acids were more potent than their cis isomers. Fatty acids immediately stimulate glucagon secretion from isolated mouse islets pancreatic alpha cells. The chain length, spatial configuration, and degree of unsaturation of fatty acids influence the glucagonotropic effect.

Animals↗

PubMed2005

Lipoprotein-like particles and cholesteryl esters in human Bruch's membrane: initial characterization.

PURPOSE: To isolate and characterize cholesteryl ester-containing, lipoprotein-like particles (LLPs) from normal aged human Bruch's membrane (BrM)/choroid (Ch). METHODS: From BrM/Ch of 20 eyes of 10 donors aged >60 years, LLPs were released by high-salt buffer, fractionated by density gradient ultracentrifugation, and characterized by determining cholesterol, triglyceride, and phospholipid concentration (by enzymatic colorimetry and fluorometry); cholesteryl ester composition (by electrospray ionization mass spectrometry, ESI/MS); and particle morphology (by negative stain electron microscopy). Apolipoprotein (apo) gene expression was determined with RT-PCR, Western blot analysis, and immunofluorescence of retinal-choroidal cryosections. In paraformaldehyde-preserved eyes (20 eyes of 20 donors), cholesteryl ester composition of BrM/Ch, cornea, and sclera was determined by ESI/MS. RESULTS: A pooled fraction of LLP released from BrM/Ch (concentrated total LLP, density [d] < 1.24 g/mL fraction) was fractionated into two peaks. A large Peak 1 (with plasma LDL-HDL density range), containing predominantly phospholipid and unesterified cholesterol, was morphologically heterogeneous. A small Peak 2 (with plasma VLDL density range), enriched with esterified cholesterol, contained approximately 100 nm diameter round electron-lucent particles. Both peaks contained apoB and apoA-I, RPE and retina contained apoA-I mRNA transcripts, and BrM and drusen contained apoA-I immunoreactivity. Peaks 1 and 2, native RPE, and fresh BrM/Ch were cholesteryl linoleate enriched and contained little cholesteryl docosahexaenoate. Preserved BrM/Ch was cholesteryl oleate-enriched, unlike sclera and cornea. CONCLUSIONS: BrM/Ch LLP do not resemble plasma lipoproteins in density profile, cholesterol distribution, or morphology. Peak 2 contains EC-rich LLP resembling BrM particles in situ. BrM/Ch cholesteryl esters respond to long-term storage differently than esters of plasma lipoprotein origin accumulated in other ocular tissues. Evidence of intraocular apoB and apoA-I expression supports an emerging hypothesis that the RPE assembles and secretes a large, possibly novel, lipoprotein particle.

Apolipoprotein A-I↗

PubMed2005

[Pharmacokinetics of the methylprednisolone, dexamethasone and hydrocortisone in the inner ear after administered via round window].

OBJECTIVE: To compare the pharmacokinetics of Methylprednisolone, Dexamethasone and Hydrocortisone in the inner era of guinea pig after administered via round window. METHOD: Guinea pig was divided into groups chronologically. After a drop of 100 g/L corticosteroid applied into the round window niche, the tympanic perilymph was sampled chronologically. Concentration of the three corticosteroid in perilymph were measured via HPLC and analyzed by 3P97 software. RESULT: The highest concentration of the three drug appeared at 30 min, 60 min and 30 min. Then the concentration declined rapidly. CONCLUSION: All three corticosteroid permeate the round window membrane easily, but the concentration declined rapidly after the peak appearing.

Administration, Topical↗

PubMed2004

Double belt structure of discoidal high density lipoproteins: molecular basis for size heterogeneity.

We recently proposed an all-atom model for apolipoprotein (apo) A-I in discoidal high-density lipoprotein in which two monomers form stacked antiparallel helical rings rotationally aligned by interhelical salt-bridges. The model can be derived a priori from the geometry of a planar bilayer disc that constrains the hydrophobic face of a continuous amphipathic alpha helix in lipid-associated apoA-I to a plane inside of an alpha-helical torus. This constrains each apoA-I monomer to a novel conformation, that of a slightly unwound, curved, planar amphipathic alpha 11/3 helix (three turns per 11 residues). Using non-denaturing gradient gel electrophoresis, we show that dimyristoylphosphocholine discs containing two apoA-I form five distinct particles with maximal Stokes diameters of 98 A (R2-1), 106 A (R2-2), 110 A (R2-3), 114 A (R2-4) and 120 A (R2-5). Further, we show that the Stokes diameters of R2-1 and R2-2 are independent of the N-terminal 43 residues (the flexible domain) of apoA-I, while the flexible domain is necessary and sufficient for the formation of the three larger complexes. On the basis of these results, the conformation of apoA-I on the R2-2 disc can be modeled accurately as an amphipathic helical double belt extending the full length of the lipid-associating domain with N and C-terminal ends in direct contact. The smallest of the discs, R2-1, models as the R2-2 conformation with an antiparallel 15-18 residue pairwise segment of helixes hinged off the disc edge. The conformations of full-length apoA-I on the flexible domain-dependent discs (R2-3, R2-4 and R2-5) model as the R2-2 conformation extended on the disc edge by one, two or three of the 11-residue tandem amphipathic helical repeats (termed G1, G2 and G3), respectively, contained within the flexible domain. Although we consider these results to favor the double belt model, the topographically very similar hairpin-belt model cannot be ruled out entirely.

Apolipoprotein A-I↗

PubMed2004

Genome comparison of a novel foot-and-mouth disease virus with other FMDV strains.

The genome of a novel foot-and-mouth disease virus, HKN/2002, was 8104 nucleotides (nt) in length (excluding the poly(C) tract and poly(A) tail) and was composed of a 1042-nt 5'-untranslated region (UTR), a 6966-nt open reading frame, and a 93-nt 3'-UTR. Genome sequences of HKN/2002 and other known FMDV strains were compared. The VP1, VP2, and VP3-based neighbor-joining (NJ) trees were divided into distinct clusters according to different serotypes, while other region-based NJ trees exhibited some degree of intercross among serotypes. Mutations in HKN/2002 were revealed, including frequent deletions and insertions in the G-H loop of VP1, and deletion involving 10 amino acid residues in the 3A protein. An evolutionary relationship of HKN/2002 with an Asian FMDV lineage isolated from a Hong Kong swine host in 1970 was postulated. A 43-nt deletion identified in the 5'-UTR of HKN/2002 possibly contributed to the loss of one pseudo-knot domain.

3' Untranslated Regions↗

PubMed2004

Highly infectious SARS-CoV pseudotyped virus reveals the cell tropism and its correlation with receptor expression.

Studies of SARS coronavirus (SARS-CoV)-the causative agent of severe acute respiratory syndrome (SARS)-have been hampered by its high transmission rate and the pathogenicity of this virus. To permit analysis of the host range and entry mechanism of SARS-CoV, we incorporated the humanized SARS-CoV spike (S) glycoprotein into HIV particles to generate a highly infectious SARS-CoV pseudotyped virus. The infection on Vero E6-a permissive cell line to SARS-CoV-could be neutralized by sera from convalescent SARS patients, and the entry was a pH-dependent process. With these highly infectious SARS-CoV pseudotypes, several cell lines derived from various tissues were revealed as susceptible to SARS-CoV, which were highly corresponding to the expression pattern of virus's receptor angiotensin-converting enzyme 2 (ACE2). In addition, we also demonstrated angiotensin 1 converting enzyme (ACE)-the homologue of ACE2 could not function as a receptor for SARS-CoV.

Angiotensin-Converting Enzyme 2↗

PubMed2004

The physicochemical properties of the solidification of calcium phosphate cement.

In this article, the physicochemical properties of the solidification of calcium phosphate cement (CPC) were investigated, and the components of the solidified body and the characteristics involved in the application were measured. The setting process of CPC was moderate and slightly exothermic, the heat liberation rate was slow, and the temperature increased little. At the initial stage of the hydration, the compressive strength rose linearly with time, and reached the maximum value after 4 hours. The volume was slightly shrunken by 1% during the setting process, and the total heavy metal content was below 2 ppm. The porosity of the solidified body was about 30%, which was mainly the gel pore with size below 0.1 microm. The final product of hydration was low crystalline hydroxyapatite (HAP). Its real density was 2.859 g/cm(3), which was lower than the theoretical value. This may be due to the existence of lattice defects, which will lead to a slight rise in solubility when leached in physiological saline.

Adhesives↗