Challenges in tissue engineering.

Almost 30 years have passed since a term 'tissue engineering' was created to represent a new concept that focuses on regeneration of neotissues from cells with the support of biomaterials and growth factors. This interdisciplinary engineering has attracted much attention as a new therapeutic means that may overcome the drawbacks involved in the current artificial organs and organ transplantation that have been also aiming at replacing lost or severely damaged tissues or organs. However, the tissues regenerated by this tissue engineering and widely applied to patients are still very limited, including skin, bone, cartilage, capillary and periodontal tissues. What are the reasons for such slow advances in clinical applications of tissue engineering? This article gives the brief overview on the current tissue engineering, covering the fundamentals and applications. The fundamentals of tissue engineering involve the cell sources, scaffolds for cell expansion and differentiation and carriers for growth factors. Animal and human trials are the major part of the applications. Based on these results, some critical problems to be resolved for the advances of tissue engineering are addressed from the engineering point of view, emphasizing the close collaboration between medical doctors and biomaterials scientists.     

Promotion of fibrovascular tissue ingrowth into porous sponges by basic fibroblast growth factor

Fibrovascular tissue ingrowth into poly(vinyl alcohol) (PVA) sponges of different pore sizes was investigated by incorporating basic fibroblast growth factor (bFGF) into the sponges. The average pore size of PVA sponges used in this study was 30, 60, 110, 250, 350, and 700 m and gelatin microspheres were employed as release carrier of bFGF. The sponges were subcutaneously implanted into the back of mice after incorporating free bFGF or gelatin microspheres containing bFGF into the sponges. Fibrovascular tissue infiltrated with time into the sponge pores and the extent of fibrous tissue ingrowth showed a maximum at a pore size around 250 m 1 and 6 weeks after implantation. Significant promotion of the growth of fibrous tissue by bFGF was observed only at 3 weeks post-implantation (p < 0.05). New capillaries were formed in the tissue at any time, as long as bFGF was given to the sponges. Both empty gelatin microspheres and phosphate buffered solution neither promoted tissue ingrowth nor induced capillary formation in the sponges. It was concluded that bFGF was essential to induce the fibrovascular tissue ingrowth into the pores of PVA sponges. ©2000 Kluwer Academic Publishers     

世界设计史研究回顾及对我国设计史研究的展望

从英国的威廉·莫里斯到德国的彼得·贝伦斯,从德国工业同盟到荷兰风格派,现代设计的历史在颠覆与创新中不断前进.对于设计史的研究是整个设计学界的重要课题,也是更好地推动现代设计发展的必然途径.文章在梳理欧洲设计史研究与日本设计史研究的基础上,分析我国设计史研究现状,展望我国设计史研究发展的未来.     

Knowledge Acquisition for Bridge Design Expert Systems

Abstract: Knowledge acquisition for developing design knowledge bases is difficult and time consuming. In this paper, a new approach for acquiring design knowledge is presented. The object-oriented approach is applied to model the design objects and the design process. It is discussed that in the case of routine bridge design, synthesis of the bridge structure can be achieved through recursive top-down refinement using selection among predefined types, and decomposition of the structure into predefined components. Having this design model, a methodology for using analogy to augment the knowledge base is proposed. Analogy can be used to retrieve and modib an available design object in order to create a similar object interactively. A prototype system that implements this methodology is presented.     

Effect of a pulsed Nd:YAG laser irradiation on multi-walled carbon nanotubes film

Multi-walled carbon nanotubes (MWCNTs) film have been analyzed by Raman spectroscopy to clarify the effect of a pulsed Nd:YAG laser heating. The MWCNTs film surface was flashed with the fundamental harmonic (λ = 1064 nm) or the second harmonic (λ = 532 nm) of a single pulse of Nd:YAG laser in the air. The dynamics of pulsed nanosecond laser heating process was simulated by the solution of the one-dimensional heat conduction equation. At the laser fluence of 500 mJ/cm² with Nd:YAG laser (λ = 1064 nm), the surface reached the maximum temperature 1395 °C at 12 ns. Moreover, the Raman spectroscopy of MWCNTs films before and after irradiation were measured. The intensity of the two characteristic Raman shifts I_D (defect-mode) and I_G (graphite-mode) was measured by the Raman spectroscopy. The maximum surface temperature was calculated and compared with the I_G/I_D ratio of MWCNTs film. The graphitization occurred on the sample after irradiation.     

A Connecting Link between Hyaluronan Synthase 3-Mediated Hyaluronan Production and Epidermal Function

Hyaluronan (HA), an essential component of the extracellular matrix of the skin, is synthesized by HA synthases (HAS1-3). To date, epidermal HA has been considered a major player in regulating cell proliferation and differentiation. However, a previous study reported that depletion of epidermal HA by Streptomyces hyaluronidase (St-HAase) has no influence on epidermal structure and function. In the present study, to further explore roles of epidermal HA, we examined effects of siRNA-mediated knockdown of HAS3, as well as conventional HA-depletion methods using St-HAase and 4-methylumbelliferone (4MU), on epidermal turnover and architecture in reconstructed skin or epidermal equivalents. Consistent with previous findings, HA depletion by St-HAase did not have a substantial influence on the epidermal architecture and turnover in skin equivalents. 4MU treatment resulted in reduced keratinocyte proliferation and epidermal thinning but did not seem to substantially decrease the abundance of extracellular HA. In contrast, siRNA-mediated knockdown of HAS3 in epidermal equivalents resulted in a significant reduction in epidermal HA content and thickness, accompanied by decreased keratinocyte proliferation and differentiation. These results suggest that HAS3-mediated HA production, rather than extracellularly deposited HA, may play a role in keratinocyte proliferation and differentiation, at least in the developing epidermis in reconstructed epidermal equivalents.     

Hankel Singular Values and Vectors of a Class of Infinite-Dimensional Systems: Exact Hamiltonian Formulas for Control and Approximation Problems

This paper derives exact formulas for singular values and vectors of Hankel operators whose symbol is a product of a single-input single-output inner function and a multi-input multi-output rational function. This class of Hankel operators arises from the sensitivity minimization H ^∞ control problem with a rational weight function and the approximation problem of transfer functions having rational outer parts. It is shown that there is a Hamiltonian transcendental equation characterizing singular values which leads to a matrix function formula for singular vectors. Date received: May 12, 1998. Date revised: May 14, 1999.     

Honokiol Acts as a Potent Anti-Fibrotic Agent in the Liver through Inhibition of TGF-β1/SMAD Signaling and Autophagy in Hepatic Stellate Cells

Chronic liver injury may result in hepatic fibrosis, which can progress to cirrhosis and eventually liver failure. There are no drugs that are specifically approved for treating hepatic fibrosis. The natural product honokiol (HNK), a bioactive compound extracted from Magnolia grandiflora, represents a potential tool in the management of hepatic fibrosis. Though HNK has been reported to exhibit suppressive effects in a rat fibrosis model, the mechanisms accounting for this suppression remain unclear. In the present study, the anti-fibrotic effects of HNK on the liver were evaluated in vivo and in vitro. In vivo studies utilized a murine liver fibrosis model, in which fibrosis is induced by treatment with carbon tetrachloride (CCl₄). For in vitro studies, LX-2 human hepatic stellate cells (HSCs) were treated with HNK, and expression of markers of fibrosis, cell viability, the transforming growth factor-β (TGF-β1)/SMAD signaling pathway, and autophagy were analyzed. HNK was well tolerated and significantly attenuated CCl₄-induced liver fibrosis in vivo. Moreover, HNK decreased HSC activation and collagen expression by downregulating the TGF-β1/SMAD signaling pathway and autophagy. These results suggest that HNK is a new potential candidate for the treatment of hepatic fibrosis through suppressing both TGF-β1/SMAD signaling and autophagy in HSCs.     

天然橡胶隔震支座的内部老化特性及预测方法

各种环境因素会使橡胶材料老化,使其更硬更脆,导致橡胶隔震支座无法有效发挥其变形吸能的功能,最终影响隔震结构的安全.由于已经老化的橡胶会阻止氧化进一步向内部深入,因此橡胶隔震支座内部的老化并不均一.本文对常用的天然橡胶(nature rubber,NR)块体进行一系列不同温度下的加速环境老化试验,并对老化后的NR块体进行切片,定量分析了橡胶支座内部不同位置处NR老化的发展情况.结果表明,在支座表面老化最快,而一定深度以内则不会发生老化,在此基础上总结出天然橡胶块体内部的老化规律,建立了老化模型以预测天然橡胶隔震支座的内部老化特性.     

The significance of cross-racial/ethnic friendships: Associations with peer victimization, peer support, sociometric status, and classroom diversity.

This short-term longitudinal study examined the associations between cross-racial/ethnic friendships and relative changes in forms of peer victimization or peer support and the roles of classroom diversity and sociometric status (i.e., social preference) in these associations. A total of 444 children (age range: 9–10 years) from racially/ethnically diverse elementary schools participated in this study. Results demonstrated that cross-racial/ethnic friendships (but not same-racial/ethnic friendships) uniquely predicted relative decreases in relational victimization. Further, classroom diversity moderated the relations of cross-racial/ethnic friendships with relative decreases in physical victimization and relative increases in peer support, such that these relations were stronger for children in highly diverse classrooms. Finally, social preference mediated the association between cross-racial/ethnic friendships and relative decreases in relational victimization. The associations among cross-racial/ethnic friendships, same-racial/ethnic friendships, social experiences with peers, and classroom diversity are discussed. (PsycINFO Database Record (c) 2011 APA, all rights reserved)