Showing papers by "Sichuan University published in 2001"

Bone formation induced by calcium phosphate ceramics in soft tissue of dogs: a comparative study between porous alpha-TCP and beta-TCP.

Abstract: Two kinds of tri-calcium phosphate ceramics (Ca/P = 1.50), alpha-TCP and beta-TCP, which has the same macrostructure and microstructure, but different phase composition, were implanted in dorsal muscles of dogs. The samples were retrieved at 30, 45 and 150 days, respectively, after implantation, and were analyzed histologically. There were critically different tissue responses between alpha-TCP ceramic and beta-TCP ceramic. Higher cell populations were observed inside the pores of beta-TCP than those of alpha-TCP, bone tissue was found in beta-TCP at 45 and 150 days, but no bone formation could be detected in any alpha-TCP implants in this study. On the other hand, the bone tissue in beta-TCP seemed to degenerate at 150 days. The results indicate that porous beta-TCP can induce bone formation in soft tissues of dogs; while the rapid dissolution of the ceramic and the higher local Ca2+, PO(4)3- concentration due to the rapid dissolution of alpha-TCP may resist bone formation in alpha-TCP and the less rapid dissolution of beta-TCP may be detrimental to already formed bone in beta-TCP.

Bone induction by porous glass ceramic made from Bioglass (45S5).

Abstract: Porous glass ceramic, which was prepared from Bioglass® powder (45S5, U.S. Biomaterials) by foaming with diluted H2O2 solution and sintering at 1000 °C for 2 h, was implanted as cylinders (5 mm in diameter and 6 mm in length) in thigh muscles of dogs for 3 months. Histological observation was made on thin un-decalcified sections. Bone formation was histologically found in pores of all implants (X16) retrieved from 16 dogs. The bone tissue was also identified with backscattered scanning electron microscopy observation (BSE) and energy dispersive X-ray microanalysis (EDX). This is the first report of bone induction in soft tissues of animals by glass ceramic that has long been recognized as a bioactive (osteoconductive) biomaterial. The present results justify the impetus to investigate the osteoinductivity of calcium phosphate-based biomaterials, to study the mechanism of bone induction (osteoinduction) by calcium phosphate-based biomaterials, to develop osteoinductive calcium phosphate-based biomaterials, and to examine the relation between osteoinduction and osteoconduction. © 2001 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 58: 270–276, 2001

Preparation of polymer/inorganic nanoparticles composites through ultrasonic irradiation

Abstract: In this paper, ultrasonic induced encapsulating emulsion polymerization was first used to prepare the novel polymer/inorganic nanoparticles composites. The behaviors of several inorganic nanoparticles (SiO2, Al2O3, TiO2) under ultrasonic irradiation, such as dispersion, crushing, and activation, were studied. The dispersion stability, morphology, and structure of the ultrasonic irradiated nanoparticles were characterized by means of transmission electron microscopy (TEM), Fourier transform infrared (FTIR), and spectrophotometry, respectively. The results show that the inorganic nanoparticles in the aqueous solution can redisperse more effectively by ultrasonic irradiation than by conventional stirring. This is the basis for preparation of polymer/inorganic nanoparticles composites. By this technique, the long-term stable latex, which mainly consists of polymer/inorganic nanoparticles composite latex particles, were successfully prepared. TEM, FTIR, thermogravimetric analysis, X-ray photoelectron spectroscopy, spectrophotometry, and element analysis confirmed that well-dispersed nanoparticles were encapsulated by the formed polymer, and the thickness of encapsulating polymer layer was in the range of 5–65 nm. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1478–1488, 2001

Immunogene therapy of tumors with vaccine based on xenopus homologous vascular endothelial growth factor as a model antigen

Abstract: Overcoming immune tolerance of the growth factors associated with tumor growth should be a useful approach to cancer therapy by active immunity. We used vascular endothelial growth factor (VEGF) as a model antigen to explore the feasibility of the immunogene tumor therapy with a vaccine based on a single xenogeneic homologous gene, targeting the growth factors associated with angiogenesis. To test this concept, we constructed a plasmid DNA encoding Xenopus homologous VEGF (XVEGF-p) and control vectors. We found that immunogene tumor therapy with a vaccine based on XVEGF was effective at both protective and therapeutic antitumor immunity in several tumor models in mice. VEGF-specific autoantibodies in sera of mice immunized with XVEGF-p could be found in Western blotting analysis and ELISA assay. The purified immunoglobulins were effective at the inhibition of VEGF-mediated endothelial cell proliferation in vitro, and at antitumor activity and the inhibition of angiogenesis by adoptive transfer in vivo. The elevation of VEGF in the sera of the tumor-bearing mice could be abrogated with XVEGF-p immunization. The antitumor activity and production of VEGF-specific autoantibodies, significantly elevated IgG1 and IgG2b, could be abrogated by the depletion of CD4+ T lymphocytes. The observations may provide a vaccine strategy for cancer therapy through the induction of autoimmunity against the growth factors associated with tumor growth in a cross reaction with single xenogeneic homologous gene and may be of importance in the further exploration of the applications of other xenogeneic homologous genes identified in human and other animal genome sequence projects in cancer therapy.

Global dynamics of Hopfield neural networks involving variable delays

Abstract: In this article, a model describing dynamics of Hopfield neural networks involving variable delays is considered. Existence and uniqueness of the equilibrium point under fairly general and easily verifiable conditions are also established. Further, we derive sufficient criteria of global asymptotic stability (GAS) of the equilibrium point.

Synthesis and Characterization of Conductive Polyaniline Nanoparticles Through Ultrasonic Assisted Inverse Microemulsion Polymerization

Abstract: Polyaniline (PANI) nanoparticles were prepared through ultrasonic assisted inverse microemulsion polymerization method. Polymerization of aniline was confined to a nanoreactor named ‘water pool’ surrounded by surfactant molecules in the apolar continuous phase. The size of the PANI nanoparticles decreases with the decrease of the ω value. The spherical nanoparticles (10–50 nm) can further form the uniform submicrometer aggregates with a size of 200 ∼ 400 nm induced by ethanol, and the size of the aggregate decreases with the decrease of the ω value. The morphology of aggregates as well as aggregation behavior of PANI nanoparticles were characterized by TEM. The polymerization rate, UV–vis absorption spectra, FTIR spectra, XRD, as well as the conductivity were examined at different [water]/[surfactant] molar ratio, i.e. ω value. Ultrasound enhances the polymerization rate of aniline that is usually very slow under conventional stirring in inverse microemulsion and contributes to produce spherical nanoparticles. Also, ultrasound irradiation promotes the diffusion of HCl molecules and improves the degree of doping. Polymerization of aniline occurred in the confined nanoreactor in microemulsion and strengthens the hydrogen-bonding of amine and imine of PANI molecular chains, which improves the degree of crystallinity. The conductivity of obtained PANI is in the magnitude of 10-1 S cm-1, and is changed with ω value.

Hardy type and Rellich type inequalities on the Heisenberg group

Abstract: This paper contains some interesting Hardy type inequalities and Rellich type inequalities for the left invariant vector fields on the Heisenberg group.

Study on ultrasonic induced encapsulating emulsion polymerization in the presence of nanoparticles

Abstract: In this paper, the ultrasonic induced encapsulating emulsion polymerization technique was used to prepare polymer/inorganic nanoparticle composites. The main affecting factors in ultrasonic induced encapsulating emulsion polymerization were studied systematically. The experimental results suggested that the pH value, the type of monomers, the type, content, and surface properties of nanoparticles, the type and concentration of surfactant have great influence on the ultrasonic induced encapsulating emulsion polymerization and the obtained latex stability. If selecting cationic emulsifier (such as cetyl trimethylammonium bromide), low water soluble monomer (such as n-butyl acrylate and styrene), and hydrophobic nano silica, the inorganic nanoparticles could be encapsulated by polymers through ultrasonic irradiation successfully under alkalescent condition, forming a novel polymer/inorganic nanoparticles composite. The mechanism of ultrasonic induced encapsulating emulsion polymerization and the composite latex stabilization are proposed. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1130–1139, 2001

Area modulation grating for sinusoidal structure illumination on phase-measuring profilometry.

Abstract: Sinusoidal structured illumination is used widely in three-dimensional (3-D) sensing and machine vision. Phase algorithms, for example, in phase-measuring profilometry, are inherently free of errors only with perfect sinusoidal fringe projection. But it is difficult to produce a perfect sinusoidal grating. We propose a new concept, area modulation, to improve the sinusoidality of structured illumination. A binary-coded picture is made up of many micrometer units. An aperture is open in every micrometer unit, and its area is determined by the value of the sinusoidal function. When such a grating is projected onto an object surface, the image of the grating becomes sinusoidal because of the convolution function of an optical system. We have designed and manufactured an area modulation grating for sinusoidal structure illumination using a large-scale integration technique. The area modulation grating has been used in the high-precision phase-measuring profilometry system, and the phase errors caused by the area modulation grating are reduced to 0.1%. The grating guaranteed the entire measuring accuracy to a 1% equivalent wavelength. The experimental results proved that area modulation grating would be of significant help in improving the phase-measurement accuracy of the 3-D sensing system.

Effect of endotoxin on P-glycoprotein-mediated biliary and renal excretion of rhodamine-123 in rats.

Abstract: The effects of Klebsiella pneumoniae endotoxin on the biliary excretion and renal handling of rhodamine-123 were investigated in rats at different times after intraperitoneal injection (1 mg/kg of body weight). The typical substrates for P glycoprotein, i.e., cyclosporine, colchicine, and erythromycin, inhibited the biliary clearance of rhodamine-123, whereas a substrate for organic cation transporter, cimetidine, did not inhibit clearance, suggesting that rhodamine-123 is transported mainly by P glycoprotein. The biliary, renal, and tubular secretory clearances of rhodamine-123 and the glomerular filtration rate significantly decreased 6 h after injection of endotoxin but returned to control levels by 24 h. These results suggest that endotoxin-induced decreases in P-glycoprotein-mediated biliary excretion and renal handling of rhodamine-123 were probably due to impairment of P-glycoprotein-mediated transport ability. Pretreatment with pentoxifylline (50 mg/kg) significantly inhibited endotoxin-induced increases in tumor necrosis factor alpha (TNF-) levels in plasma, which ameliorated the endotoxin-induced reduction of the biliary excretion of rhodamine-123. It is likely that endotoxin-induced impairment of the transport of rhodamine-123 is caused, in part, by overproduction of TNF-. The effect of endotoxin on the expression of P-glycoprotein mRNA in liver and kidneys of rats was investigated by using a reverse transcriptase PCR. The expression of Mdr1a mRNA in both liver and kidney decreased 6 h after endotoxin injection and returned to control levels after 24 h, whereas the expression of Mdr1b mRNA in liver increased at both times and that in kidney decreased at 24 h. These findings suggest that K. pneumoniae endotoxin dramatically decreases P-glycoprotein-mediated biliary and renal excretion of rhodamine-123 probably by decreasing the expression of Mdr1a, which is likely due to increased plasma TNFlevels.

Möbius isotropic submanifolds in {$S\sp n$}

Abstract: Let $x:\M^m\to \hs^n$ be a submanifold in the $n$-dimensional sphere $\hs^n$ without umbilics. Two basic invariants of $x$ under the Mobius transformation group in $\hs^n$ are a 1-form $\F$ called the Mobius form and a symmetric $(0,2)$ tensor $\bf A$ called the Blaschke tensor. $x$ is said to be Mobius isotropic in $\hs^n$ if $\F\equiv 0$ and ${\bf A}=\l dx\cdot dx$ for some smooth function $\l$. An interesting property for a Mobius isotropic submanifold is that its conformal Gauss map is harmonic. The main result in this paper is the classification of Mobius isotropic submanifolds in $\hs^n$. We show that (i) if $\l >0$, then $x$ is Mobius equivalent to a minimal submanifold with constant scalar curvature in $\hs^n$; (ii) if $\l=0$, then $x$ is Mobius equivalent to the pre-image of a stereographic projection of a minimal submanifold with constant scalar curvature in the $n$-dimensional Euclidean space $\R^n$; (iii) if $\l <0$, then $x$ is Mobius equivalent to the image of the standard conformal map $\t: \text{\bi H}^n\to \hs^n_+$ of a minimal submanifold with constant scalar curvature in the $n$-dimensional hyperbolic space $\text{\bi H}^n$. This result shows that one can use Mobius differential geometry to unify the three different classes of minimal submanifolds with constant scalar curvature in $\hs^n$, $\R^n$ and $\text{\bi H}^n$.

Use of an osteoinductive biomaterial as a bone morphogenetic protein carrier.

Abstract: A porous calcium phosphate ceramic, which induced bone formation in soft tissues of dogs, was termed as osteoinductive biomaterial and studied as a carrier of bone morphogenetic protein (rhBMP-2). Cylinder implants (o 4×5 mm) impregnated with 0, 1, 10 and 40 μg rhBMP-2 were implanted in dorsal muscles of rabbits for five weeks. Histological observation and histomorphometric analysis were performed on thin un-decalcified sections. No bone formation was detected in the implants without rhBMP-2, while mature lamellar bone was found inside the implants with 1 μg rhBMP-2, both on the outer surface and inside the implants with 10 μg and 40 μg rhBMP-2. Little difference in formed bone was found between 1 μg and 10 μg rhBMP-2, but no difference was found between 10 μg and 40 μg rhBMP-2. A significant difference in bone marrow formation was found among 1, 10 and 40 μg rhBMP-2. The more rhBMP-2, the more bone marrow formed. The present results indicate that osteoinductive biomaterial is a good carrier of BMP and high dose of BMP is not necessary for bone formation in clinic. © 2001 Kluwer Academic Publishers

In situ production of Fe-VC and Fe-TiC surface composites by cast-sintering

Abstract: Using a new cast-sintering technique, iron-base surface composites reinforced by VC and TiC particles which were produced in situ and consisting of self-lubricant graphite and chromium-carbide, were sintered on the surface of cast steel during casting. The structure and composition of the surface composites were studied with the help of a SEM, an electron probe and XRD. From the outside in of the iron-based surface composites, the concentration of V and Ti was relatively stable and consistently retained a high level, while the concentration of Cr and Ni took on a gradient distribution and decreased gradually. The fine particles of VC and TiC measuring between 1 and 3 μm in diameter were uniformly dispersed in their matrices, and there was a perfect metallurgy-bond between the surface composite layer and the master-alloy. Under the condition of dry slipping with a heavy load, the Fe–VC and Fe–TiC surface composites offer virtually unique wear-resistance.

An evaluation of a polyethersulfone hollow fiber plasma separator by animal experiment.

Abstract: Membrane plasma separators are being used routinely for therapy in various diseases. In this study, a newly developed plasma separator made of polyethersulfone (PES) hollow fibers was evaluated for its plasma filtration efficiency and blood compatibility by animal experiment. Hemolysis did not occur under the usual conditions of plasma separation. The sieving coefficients of total protein and albumin were over 95%, and the total cholesterol was over 90% throughout the perfusions. Decreases in white blood cells, platelets, fibrinogen, and coagulation factors were observed during the early stage of plasma separation, but appear to be within acceptable ranges for clinical use.

In vitro flowering of bitter melon.

Abstract: Flowers were formed from shoot tips of bitter melon (Momordica charantia L.) cultured on Murashige and Skoog medium supplemented with 90 mM sucrose, 0.05 mM Fe2+ and 4 µM N6-benzyladenine (BA). The addition of 0.05 mM Fe2+ to the medium prevented chlorosis of the explant and promoted normal flowering. Increasing the ratio of carbon to nitrogen promoted male flower formation but intensively inhibited vegetative growth. The influence of cytokinin on the morphogenesis of the explant was highly notable. Flowers could be formed after a 15- to 20-day exposure to kinetin (Kin) or BA. Kin and BA had opposite effects with regard to the development of the explant. Kin promoted flower formation, especially female, but inhibited branch bud formation. Conversely, BA promoted branch bud formation and also promoted male flower formation when present at a concentration of 1–2 µM, but completely inhibited flower formation at 4–8 µM. Fluorescein diacetate staining and in vitro germination showed that in vitro pollen were of a fairly high viability.

Evaluation of Interpolation Accuracy of Neural Kriging with Application to Temperature-Distribution Analysis

Abstract: An interpolation method based on a multilayer neural network (MNN), has been examined and tested for the data of irregular sample locations The main advantage of MNN is in that it can deal with geoscience data with nonlinear behavior and extract characteristics from complex and noisy images The training of MNN is used to modify connection weights between nodes located in different layers by a simulated annealing algorithm (one of the optimization algorithms of the network) In this process, three types of errors are considered: differences in values, semivariograms, and gradients between sample data and outputs from the trained network The training is continued until the summation of these errors converges to an acceptably small value Because the MNN trained by this learning criterion can estimate a value at an arbitrary location, this method is a form of kriging and termed Neural Kriging (NK) In order to evaluate the effectiveness of NK, a problem on restoration ability of a defined reference surface from randomly chosen discrete data was prepared Two types of surfaces, whose semivariograms are expressed by isotropic spherical and geometric anisotropic gaussian models, were examined in this problem Though the interpolation accuracy depended on the arrangement pattern of the sample locations for the same number of data, the interpolation errors of NK were shown to be smaller than both those of ordinary MNN and ordinal kriging NK can also produce a contour map in consideration of gradient constraints Furthermore, NK was applied to distribution analysis of subsurface temperatures using geothermal investigation loggings of the Hohi area in southwest Japan In spite of the restricted quantity of sample data, the interpolation results revealed high temperature zones and convection patterns of hydrothermal fluids NK is regarded as an interpolation method with high accuracy that can be used for regionalized variables with any structure of spatial correlation