Biomedical subjects

Dong Chen

Publications and source records attributed to Dong Chen.

At least 19 recordsLinked to original sources

PubMed2006

Prevention of renal ischemic injury by silencing the expression of renal caspase 3 and caspase 8.

BACKGROUND: Apoptotic pathways mediated by caspases play a critical role in renal ischemia-reperfusion injury (IRI). Downregulation of the caspase cascade, using small interfering RNA (siRNA) to silence the expression of caspase 3 and caspase 8, may have substantial therapeutic potential for limiting renal injury. METHODS: IRI was induced in mice by clamping of the renal vein and artery for 25 or 35 min at 37 degrees C. Caspase 3 and caspase 8 (caspase 3/8) siRNA was administrated by hydrodynamic injection. Quantitative polymerase chain reaction (PCR) and immunohistochemistry were used to analyze the gene silencing efficacy, and the therapeutic effects of siRNA were evaluated by renal function analysis, histological examination, and overall survival of mice suffering from IRI. RESULTS: In this study, we have shown, using quantitative PCR, that IRI is associated with increased levels of renal caspase 3/8 mRNA. Mice treated with caspase 3/8 siRNA showed a significant down-regulation in kidney expression of caspase 3/8 at both, transcriptional and protein levels. Kidney function in IRI was protected by siRNA therapy, as levels of blood urea nitrogen and creatinine were significantly reduced in mice treated with siRNA. Histological examination demonstrated that tissue injury caused by IRI was significantly reduced as a result of caspase 3/8 siRNA treatment. Furthermore, survival data showed that more than 70% of mice in siRNA-treated groups survived until the end of the eight-day observation period. CONCLUSION: Herein, we have demonstrated the therapeutic potential of using siRNA to knock down the expression of caspases and prevent acute renal injury.

Animals↗

PubMed2006

Protection of renal ischemia injury using combination gene silencing of complement 3 and caspase 3 genes.

BACKGROUND: Ischemia/reperfusion (I/R) injury occurs in clinical kidney transplantation, which results in graft dysfunction and rejection. It has been documented that I/R injury is associated with complement activation and renal cell apoptosis. The purpose of this study was to develop a strategy to prevent I/R injury using small interfering RNA (siRNA) that target complement 3 (C3) and caspase 3 genes. METHODS: siRNA-expression vectors were constructed to target C3 and caspase 3 genes. Gene silencing efficacy was assessed using real-time polymerase chain reaction. In vivo gene silencing was performed by hydrodynamic injection with C3 and caspase 3 siRNA. Renal I/R injury was induced through clamping the renal vein and artery for 25 min. I/R injury was evaluated using kidney histopathology, blood urea nitrogen (BUN), serum levels of creatinine, and survival. RESULTS: Effective gene silencing was first confirmed in vitro. Notably upregulated expression of C3 and caspase 3 genes was observed from 2 to 48 hr after I/R injury, which were effectively and specifically inhibited by C3 and caspase 3 siRNA. In comparison with control mice, serum levels of creatinine and BUN were also significantly decreased in C3 and caspase 3 siRNA-treated mice. Furthermore, the therapeutic effect of siRNA was assessed in a severe, lethal I/R injury experiment, in which siRNA treatment significantly reduced mortality. Tissue histopathology showed an overall reduction in injury area in siRNA-treated mice. CONCLUSIONS: This is the first demonstration that renal I/R injury can be prevented through silencing the complement gene and apoptosis gene, highlighting the potential for siRNA-based clinical therapy.

Animals↗

PubMed2006

Study of biochemical pathways and enzymes involved in pyrene degradation by Mycobacterium sp. strain KMS.

Pyrene degradation is known in bacteria. In this study, Mycobacterium sp. strain KMS was used to study the metabolites produced during, and enzymes involved in, pyrene degradation. Several key metabolites, including pyrene-4,5-dione, cis-4,5-pyrene-dihydrodiol, phenanthrene-4,5-dicarboxylic acid, and 4-phenanthroic acid, were identified during pyrene degradation. Pyrene-4,5-dione, which accumulates as an end product in some gram-negative bacterial cultures, was further utilized and degraded by Mycobacterium sp. strain KMS. Enzymes involved in pyrene degradation by Mycobacterium sp. strain KMS were studied, using 2-D gel electrophoresis. The first protein in the catabolic pathway, aromatic-ring-hydroxylating dioxygenase, which oxidizes pyrene to cis-4,5-pyrene-dihydrodiol, was induced with the addition of pyrene and pyrene-4,5-dione to the cultures. The subcomponents of dioxygenase, including the alpha and beta subunits, 4Fe-4S ferredoxin, and the Rieske (2Fe-2S) region, were all induced. Other proteins responsible for further pyrene degradation, such as dihydrodiol dehydrogenase, oxidoreductase, and epoxide hydrolase, were also found to be significantly induced by the presence of pyrene and pyrene-4,5-dione. Several nonpathway-related proteins, including sterol-binding protein and cytochrome P450, were induced. A pyrene degradation pathway for Mycobacterium sp. strain KMS was proposed and confirmed by proteomic study by identifying almost all the enzymes required during the initial steps of pyrene degradation.

Bacterial Proteins↗

PubMed2006

A simple solution route to single-crystalline Sb2O3 nanowires with rectangular cross sections.

We report a simple solution route to large-scale synthesis of uniform, single-crystalline, and well-faceted orthorhombic antimony trioxide (Sb(2)O(3)) nanowires with rectangular cross sections by direct air oxidation of bulk metal antimony (Sb) in a mixed solution made of ethylenediamine (EDA) and deionized water (DIW). The as-synthesized products were analyzed by range of methods, such as XRD, SEM, EDX, TEM, SAED, HRTEM, FTIR, Raman, UV-vis absorption, and photoluminescence (PL) spectra. The as-synthesized Sb(2)O(3) nanowires with rectangular cross sections are usually hundreds of micrometers in length, typically 80-100 nm in width, and 60-80 nm in thickness. The novel room temperature photoluminescence properties of Sb(2)O(3) nanowires with rectangular cross sections displayed a significant UV luminescence with a strong emission band at 374 nm, which was reported for the first time, indicating the as-synthesized products with an optical band gap E(g) = 3.3 eV. It is expected that as-synthesized Sb(2)O(3) nanowires would be a new member of functional materials and used in the manufacture of advanced nanodevices.

Antimony↗

PubMed2006

BRCA1 negatively regulates the cancer-associated aromatase promoters I.3 and II in breast adipose fibroblasts and malignant epithelial cells.

CONTEXT: Heterozygous mutations of the breast cancer susceptibility gene 1 (BRCA1) gene that lead to haploinsufficiency increase the risk of breast cancer. The underlying mechanism is unknown. OBJECTIVE: Because excessive estrogen production increases the risk of breast cancer, we determined whether BRCA1 suppresses aromatase expression and thus local estrogen production in breast adipose fibroblasts (BAFs) and breast malignant epithelial cells by interacting with the cancer-associated promoter I.3/II region of the aromatase gene. RESULTS: Treatment of BAFs with prostaglandin E2 or a surrogate hormonal cocktail of dibutyryl (Bt2) cAMP plus phorbol 12, 13-diacetate (PDA) significantly reduced BRCA1 levels and induced aromatase mRNA levels. Reduction of BRCA1 in BAFs and in MCF7 and SKBR3 malignant breast epithelial cells using small interfering RNA (siRNA) or small hairpin RNA significantly increased aromatase mRNA levels and enzyme activity. This effect of BRCA1 was mediated via selective inhibition of aromatase promoters I.3 and II that are up-regulated by prostaglandin E2 or Bt2cAMP + PDA treatment. Chromatin immunoprecipitation assays revealed that BRCA1 binds directly to the aromatase promoter I.3/II region and that BRCA1 binding is abolished by treatment with Bt2cAMP + PDA. CONCLUSIONS: Selective inhibition of aromatase expression by BRCA1 binding to the I.3/II tumorigenic promoter region may be an important protective mechanism against breast cancer development.

Adipose Tissue↗

PubMed2006

Preparation of titania-coated polystyrene particles in mixed solvents by ammonia catalysis.

A mixed-solvent method was developed to coat polystyrene (PS) spheres with smooth, homogeneous shells of amorphous titania by ammonia catalysis. The TEM images showed that, in the presence of ammonia, the thickness of titania shells could be controlled in the range of 8-65 nm by varying the concentration of titanium tetrabutoxide (TBOT) in the ethanol/acetonitrile mixed solvents with an appropriate volume ratio. The diffusion-controlled mechanism of the mixed solvents and the catalysis mechanism of ammonia were investigated. After the calcination of core-shell particles for 2 h at 500 degrees C, spherical hollow titania shells could be obtained, and the surfaces of the particles remained quite smooth and homogeneous. The XRD analysis indicated that calcination promoted the transformation of amorphous titania into an anatase phase.

Journal Article↗

PubMed2006

The role of Thr5 in human neuron growth inhibitory factor.

GIF, a member of the metallothionein (MT) family (assigned as MT3), is a neuron growth inhibitory factor that inhibits neuron outgrowth in Alzheimer's disease. The conserved Thr5 is one of the main differences between GIF and other members in the MT family. However, natural sheep GIF has an unusual Ala5, casting doubt on the role of common Thr5. We constructed a series of human GIF mutants at site 5, and characterized their biochemical properties by UV spectroscopy, circular dichroism spectroscopy, EDTA reaction, 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB) reaction, and pH titration. Their inhibitory activity toward neuron survival and neurite extension was also examined. Interestingly, the T5A mutant exhibited distinct metal thiolate activity in the EDTA and DTNB reactions, and also lost its bioactivity. Meanwhile, the T5S mutant had similar biochemical properties and biological activity as wild-type human GIF, indicating the hydroxyl group on the Thr5 was critical to the bioactivity of human GIF. We suggest the hydroxyl group in human GIF may help stabilize the biologically active conformation. On the other hand, lack of the hydroxyl group in sheep GIF may be partially compensated by its abnormal structure.

Animals↗

PubMed2006

Increase in extracellular cross-linking by tissue transglutaminase and reduction in expression of MMP-9 contribute differentially to focal segmental glomerulosclerosis in rats.

Tissue transglutaminase (tTG) is a Ca(2+)-dependent enzyme which stabilizes the extracellular matrix (ECM) through post-translational modification, and may play an important role in the pathogenesis of focal and segmental glomerulosclerosis (FSGS). Here, we have investigated whether tTG contributes to the glomerular ECM expansion in the puromycin aminonucleoside (PAN)-injection-induced experimental rat model of FSGS. The localization and expression of tTG, MMP-9 gelatinase, and the ECM component fibronectin (FN) in kidneys was determined by immunohistochemistry and measured by semi-quantitative analysis. Protein levels of tTG and MMP-9 were also analyzed by Western blotting.In situtransglutaminase activity was assayed by measurement of incorporated substrate and the immunofluorescence staining for the cross-linking product, epsilon-(gamma-glutamyl) lysine. Prominent proteinuria, a typical pathological feature of FSGS, was observed in PAN injection group rats. tTG immunoreactivity was located markedly in glomeruli and the levels of this protein in whole-kidney homogenates of PAN injection group rats were significantly increased (361+/- 106% control, P< 0.05). Similarly, transglutaminase activity and epsilon-(gamma-glutamyl) lysine were also predominately located within glomeruli and were much more intense in the PAN-injected group than that in control animals. MMP-9 was also located primarily within glomeruli. In PAN-injected kidneys, protein levels of active MMP-9 were significantly reduced (59+/- 27% control, P< 0.01), while pro-MMP-9 levels increased (148+/- 42% control, P< 0.05). Remarkable expression of glomerular fibronectin (FN) was found in PAN injection group rats. Semi-quantitative analysis demonstrated this increased intensity of FN staining in the PAN-injected rats was 149+/- 23% of the control values (P< 0.05). Enhanced cross-linking of ECM by tissue transglutaminase and decreased degradation due to reduced active MMP-9 expression may be at least partially responsible for the deposition of FN within injured glomeruli in experimental FSGS.

Animals↗

PubMed2006

H-Ras, R-Ras, and TC21 differentially regulate ureteric bud cell branching morphogenesis.

The collecting system of the kidney, derived from the ureteric bud (UB), undergoes repetitive bifid branching events during early development followed by a phase of tubular growth and elongation. Although members of the Ras GTPase family control cell growth, differentiation, proliferation, and migration, their role in development of the collecting system of the kidney is unexplored. In this study, we demonstrate that members of the R-Ras family of proteins, R-Ras and TC21, are expressed in the murine collecting system at E13.5, whereas H-Ras is only detected at day E17.5. Using murine UB cells expressing activated H-Ras, R-Ras, and TC21, we demonstrate that R-Ras-expressing cells show increased branching morphogenesis and cell growth, TC21-expressing cells branch excessively but lose their ability to migrate, whereas H-Ras-expressing cells migrated the most and formed long unbranched tubules. These differences in branching morphogenesis are mediated by differential regulation/activation of the Rho family of GTPases and mitogen-activated protein kinases. Because most branching of the UB occurs early in development, it is conceivable that R-Ras and TC-21 play a role in facilitating branching and growth in early UB development, whereas H-Ras might favor cell migration and elongation of tubules, events that occur later in development.

Animals↗

PubMed2006

Ultrasonic control of ceramic membrane fouling: Effect of particle characteristics.

In this study, the effect of particle characteristics on the ultrasonic control of membrane fouling was investigated. Ultrasound at 20 kHz was applied to a cross-flow filtration system with gamma-alumina membranes in the presence of colloidal silica particles. Experimental results indicated that particle concentration affected the ability of ultrasound to control membrane fouling, with less effective control of fouling at higher particle concentrations. Measurements of sound wave intensity and images of the cavitation region indicated that particles induced additional cavitation bubbles near the ultrasonic source, which resulted in less turbulence reaching the membrane surface and subsequently less effective control of fouling. When silica particles were modified to be hydrophobic, greater inducement of cavitation bubbles near the ultrasonic source occurred for a fixed concentration, also resulting in less effective control of fouling. Particle size influenced the cleaning ability of ultrasound, with better permeate recovery observed with larger particles. Particle size did not affect sound wave intensity, suggesting that the more effective control of fouling by large particles was due to greater lift and cross-flow drag forces on larger particles compared to smaller particles.

Equipment Failure↗

PubMed2006

New technique for lacrimal system intubation.

PURPOSE: To propose a new technique for silicone intubation in disorders of the lacrimal system in children and adults. DESIGN: Retrospective, noncomparative case series. METHODS: The surgery was performed in 513 eyes of 426 patients from March 2003 to July 2005 in our hospital. With the help of a so-called soft probe and intranasal endoscope, silicone tubes were inserted through both puncta into nasolacrimal duct and left in place for three to six months. RESULTS: The surgery was performed successfully in all cases. No intraoperative complications were found in the procedure. Tubes were removed between 2.1 and 5.3 months (mean 3.4 months) after surgery. Mean follow-up time after tube removal was 15.1 months (range 3.3 to 27.5 months). Tube displacement occurred in 11 cases (2.14%); no other complications associated with silicone tubes, such as granuloma formation or corneal erosion, occurred. All the tubes were removed successfully. No ophthalmic injuries occurred during tube removal. CONCLUSIONS: The technique proved to be effective in both children and adults. This technique, which is atraumatic, easy to perform, time-saving, and better tolerated, may be considered as an alternative method for lacrimal system intubation.

Adolescent↗

PubMed2006

In vitro and in vivo characterization of huperzine a loaded microspheres made from end-group uncapped poly(d,l-lactide acid) and poly(d,l-lactide-co-glycolide acid).

The purpose of this work was to develop biodegradable microspheres for long term delivery of a potent acetyl cholinesterase inhibitor, huperzine A (Hup-A), which is of interest in the palliative treatment of Alzheimer's disease. Microspheres were successfully prepared with specifically end-group uncapped poly(d,l-lactide acid) and poly(d,l-lactide-co-glycolide acid) using a simple o/w solvent evaporation method. The morphology, particle size and size distribution, drug loading capacity, drug entrapment efficiency (EE) and in vitro drug release were studied in detail. It was found that the terminal group and the inherent viscosity (IV) of the polymers played key role in the drug encapsulation: higher EE was achieved with end-group uncapped and low IV polymers. In vitro drug release from microspheres made from the selected three kinds of polymers revealed sustained release of Hup-A without significant burst release. Preliminary pharmacokinetic study following subcutaneous injection of Hup-A loaded microspheres illustrated the sustained release of the drug over 6-8 weeks at clinically relevant doses in vivo. The studies demonstrated the feasibility of long term delivery of Hup-A using biodegradable microspheres.

Alkaloids↗

PubMed2006

Alveolar Echinococcus species from Vulpes corsac in Hulunbeier, Inner Mongolia, China, and differential development of the metacestodes in experimental rodents.

Adults of alveolar Echinococcus species with different uterine structures were collected from Vulpes corsac in the Hulunbeier Pasture of Northeastern China in 2001. They were Echinococcus multilocularis Leuckart, 1863 (type No. 3, similar to E. m. multilocularis), with vaselike uterus; Echinococcus cf. sibiricensis Rausch et Schiller, 1954 (type No. 1), with pyriform uterus; and Echinococcus sp. (type No. 2) with spherical uterus at segment top. The metacestode development in rodents also differed among those 3 parasites. In the case of E. multilocularis (type No. 3), many germinal cells grew on the inner surface of early cysts, most of which metastasized into host tissue to form brood vesicles or from the germinal cell layer on the inner surface of the vesicle wall. Cells also had an appearance of proliferating by means of alveolar buds from alveolar tissue that developed outward to form new alveolar foci. In Echinococcus cf. sibiricensis (type No. 1), the formation of alveolar vesicles was due to the metastasizing of germinal tissue into host tissue; protoscoleces grew in the center of alveolar vesicles. In type No. 2 (Echinococcus sp.), the formation of the alveolar vesicle was by multiplication of germinal cell layers on the inner surface of alveolar cysts; protoscoleces grew from the germinal cell layer and mesh in the vesicles. On the basis of uterine structure and on differences in development of metacestodes in experimental rodents, we propose that the 3 types of Echinococcus represent 3 independent species: E. multilocularis, Echinococcus sibiricensis, and Echinococcus sp. (type No. 2-as yet under study).

Animals↗

PubMed2006

[Experimental study on the effect of tiangui gengnian capsule on the aged female rats ostepoprosis].

OBJECTIVE: To study the therapeutic action of Seabuckthorn Fatty Acid on the aged female rats osteoporosis, and explore the corresponding mechanism related in hormone and cytokine. METHODS: The change of bone density (BMD), biomechanics and bone morphology were measured and E2, TGF-beta1, IGF-1 level in plasma were determined respectively for the young female rats, aged female rats (Seabuckthorn Fatty Acid 0.72, 1.8, 4.5 g/kg, E2 0.02 g/kg) after they were administrated corresponding drugs for 45 days. RESULTS: The bone density (BMD), bone biomechanics, bone morphology for female rats aged 22-months all decreased. The BMD, bone biomechanics, the number of bone trabeculas and cortical thickness in Seabuckthorn Fatty Acid treated groups (1.8 g/kg, 4.5 g/kg) were upgraded (P < 0.05). The TGF-beta1, IGF-1 level in plasma were increased, too (P < 0.05). CONCLUSION: Seabuckthorn Fatty Acid can meliorate bone metabolism in post-menopause and heighten the bone density. The adjustment mechanism may be based on the function of estrogen and cell cytokine.

Animals↗

PubMed2005

Production and characterization of mouse ureteric bud cell-specific rat hybridoma antibodies utilizing subtractive immunization and high-throughput screening.

The highly branched collecting system of the kidney arises developmentally from the ureteric bud (UB) by a process of branching morphogenesis. This process is critical for the normal development of the collecting ducts and pelvis of the kidney, and is tightly controlled by the spatial and temporal expression of numerous proteins. To identify cell proteins that are differentially expressed by the UB relative to those expressed by the highly differentiated collecting ducts of the adult kidney, two mouse cell populations derived from either the early UB or the adult inner medullary collecting duct (IMCD) were used. A subtractive immunization strategy was performed in rats to generate monoclonal antibodies that preferentially reacted with antigens on UB, but not IMCD cells. In addition, the technique of antibody printing, a novel high-throughput antibody screening method for determining the specificities of a large number of monoclonal antibodies, is described. The methodologies outlined in this manuscript have broad applicability as they demonstrate that subtractive immunization can be performed in rats with cells derived from mice. Additionally, the high-throughput screening methods should facilitate the use of subtractive immunization for identifying antibodies that can distinguish differences in proteins expressed in closely related cell types.

Animals↗

PubMed2005

Ultrasonic control of ceramic membrane fouling by particles: effect of ultrasonic factors.

Ultrasound at 20 kHz was applied to a cross-flow ultrafiltration system with gamma-alumina membranes in the presence of colloidal silica particles to systematically investigate how ultrasonic factors affect membrane cleaning. Based on imaging of the ultrasonic cavitation region, optimal cleaning occurred when the membrane was outside but close to the cavitation region. Increasing the filtration pressure increased the compressive forces driving cavitation collapse and resulted in fewer cavitation bubbles absorbing and scattering sound waves and increasing sound wave penetration. However, an increased filtration pressure also resulted in greater permeation drag, and subsequently less improvement in permeate flux compared to low filtration pressure. Finally, pulsed ultrasound with short pulse intervals resulted in permeate flux improvement close to that of continuous sonication.

Ceramics↗

PubMed2005

Shape-controlled synthesis of copper colloids with a simple chemical route.

The new electrical and optical properties of nanomaterials depend sensitively on both size and shape, which are of both fundamental and technological interest. This paper introduces a simple chemical method to produce copper particles, which has the ability to shape the particle without using any capping agent or template. In our synthetic procedure, the reactant concentration and temperature exerted a strong influence on the shape of the copper particles. At low reactant concentrations, the particles were cubic; at high reactant concentrations, obtained particles were spherical. The number of hollow particles greatly increased when the synthesis was performed at low temperature. We also synthesized a copper cubic ring at lower temperature, and it has been rarely reported. The absorption spectrum of hollow particles showed obvious red shifts, which suggests the possible assembly of novel optical materials.

Journal Article↗

PubMed2005

Inhibition of Pkhd1 impairs tubulomorphogenesis of cultured IMCD cells.

Fibrocystin/polyductin (FPC), the gene product of PKHD1, is responsible for autosomal recessive polycystic kidney disease (ARPKD). This disease is characterized by symmetrically large kidneys with ectasia of collecting ducts. In the kidney, FPC predominantly localizes to the apical domain of tubule cells, where it associates with the basal bodies/primary cilia; however, the functional role of this protein is still unknown. In this study, we established stable IMCD (mouse inner medullary collecting duct) cell lines, in which FPC was silenced by short hairpin RNA inhibition (shRNA). We showed that inhibition of FPC disrupted tubulomorphogenesis of IMCD cells grown in three-dimensional cultures. Pkhd1-silenced cells developed abnormalities in cell-cell contact, actin cytoskeleton organization, cell-ECM interactions, cell proliferation, and apoptosis, which may be mediated by dysregulation of extracellular-regulated kinase (ERK) and focal adhesion kinase (FAK) signaling. These alterations in cell function in vitro may explain the characteristics of ARPKD phenotypes in vivo.

Animals↗