Influence of natural weathering on colour stability of materials used for facial prosthesis

Colour stability of resin and silicone is an important factor for longevity of facial prostheses. The aim of this study was to evaluate the colour stability of resins and silicone for facial prostheses. Three brands of acrylic resin and one of facial silicone were evaluated considering pigment incorporation for the colourless materials. Ten samples of each material were fabricated and submitted to measurements of chromatic alteration initially and after 90 and 180 days of weathering natural through visual analysis and spectrophotometry. Data were evaluated by ANOVA and Tukey test (p < 0.05). Statistically significant colour alteration was observed among some materials regardless of the period. The materials did not present a statistical difference between 90 and 180 days except for the pigmented heat-polymerized resin. The colour difference between pigmented Silastic MDX4-4210 and colourless Silastic was statistically significant (p < 0.01) in both periods as well as between pigmented and colourless heat-polymerized resin, and between the resins Rapidaflex and Lentaflex. The visual method demonstrated colour alteration in all materials evaluated during the first 90 days of ageing. All materials exhibited colour alteration due to exposure to environment.     

The effect of image colour distortion on evaluation of donor liver suitability for transplantation

Some medical applications rely on the use of colour in the diagnostic process, even when poor colour reproduction can affect diagnosis. In this paper, we investigate the effect colour distortion can have on assessment of livers for possible transplantation. We compare the diagnostic effects for the likely colour shifts when illuminant and camera remain uncalibrated or when a monitor is incorrectly calibrated. We describe methods that can result in accurate reproduction of image colour on visual displays and determine whether accurate colour reproduction is necessary for effective liver assessment.     

The effect of different humeral prosthesis fin designs on shoulder stability: A computational model

Humeral prostheses commonly use a fin structure as an attachment point for the supraspinatus muscle in total shoulder arthroplasty (TSA), but these fins may cause injury to the muscle during implantation, inadvertently influencing stability. In order to prevent supraspinatus injury, the effect of different humeral prostheses on shoulder joint stability needs to be investigated. A commercially available prosthesis and two modified humeral prostheses that substituted the fin structure for 2 (2H) or 3 holes (3H) were evaluated using computational models. Glenohumeral abduction was simulated and the superioinferior/anterioposterior stability of the shoulder joint after TSA was calculated. The results revealed that the 2H design had better superioinferior stability than the other prostheses, but was still less stable than the intact shoulder. There were no obvious differences in anterioposterior stability, but the motion patterns were clearly distinguishable from the intact shoulder model. In conclusion, the 2H design showed better superioinferior stability than the 3H design and the commercial product during glenohumeral joint abduction; the three prostheses show similar results in anterioposterior stability. However, the stability of each tested prosthesis was not comparable to the intact shoulder. Therefore, as a compromise, the 2H design should be considered for TSA because of its superior stability.     

面动脉穿支蒂颊黏膜瓣重建泪道的解剖学基础

目的为面动脉穿支蒂颊黏膜瓣重建泪道提供解剖基础。方法在10个20侧动脉内灌注红色乳胶的成人头标本上解剖观测:①面动脉穿支的起源、分支与分布;②颊动脉的起源、分支与分布;③面动脉与颊动脉的吻合。另在1侧新鲜标本上进行摹拟手术设计。结果颊黏膜的血供为多源性,主要由面动脉、颊动脉和上牙槽后动脉发出的穿支供养。①面动脉自颈外动脉发出,行至咬肌前缘越过下颌骨底达面部后,再斜向内上至内眦处与鼻背动脉吻合,沿途除发出分支营养颈、面部相应区域外,在口角外侧(1.10±0.31)cm处分出1～3支颊支,支配颊肌与颊黏膜前中部,并与颊动脉颊支、上牙槽后动脉颊支形成吻合;②颊动脉发自上颌动脉的翼肌段,行于颞肌下部深面前下方向,沿途发支分布于颊黏膜后中部,并与面动脉穿支相互吻合。当上颌动脉分出颊支细短时,则由粗大的上牙槽后动脉颊支(占5%)代偿。结论颊黏膜瓣血供丰富,可形成以面动脉穿支为蒂颊黏膜瓣转位重建泪道。     

生理信号时问序列周期性和平稳性对近似熵和样本熵算法的影响分析

目的提高近似熵和样本熵算法在评价生理信号时间序列非线性复杂度应用中的精度。方法首先生成生理信号时间序列数据库,通过对周期序列和叠加有周期成分的非线性序列的分析,研究序列周期性对熵测度算法的影响,并通过对心率变异性（hear trat evariability,HRV）序列在去除非平稳趋势前后的对比分析,研究序列平稳性对熵测度算法的影响。结果在序列长度范围内,不同重复频率的周期序列熵测度不同,不同比重的周期成分叠加到非线性序列中引起序列熵测度的变化也不同。生理信号时间序列中大都存在非平稳成分,而非平稳成分会降低序列的复杂度,因此进行熵测度计算前首先要去除非平稳成分。结论周期性和非平稳成分显著影响生理信号时间序列的熵测度算法。     

Influence of glycosylphosphatidylinositol-linked H-2Dd molecules on target cell protection and natural killer cell specificity in transgenic mice

The expression of certain major histocompatibility complex (MHC) class I ligands on target cells is one important determinate of their susceptibility to lysis by natural killer (NK) cells. NK cells express receptor molecules that bind to MHC class I. Upon binding to their MHC class I ligand, the NK cell is presumed to receive a signal through its receptor that inhibits lysis. It is unclear what role the MHC class I molecules of the effector and target cells play in signaling to the NK cell. We have investigated the role of the cytoplasmic and transmembrane domains of MHC class I molecules by producing a glycosylphosphatidylinositol (GPI)-linked H-2D^d molecule. The GPI-linked H-2D^d molecule is recognized by H-2D^d-specific antibodies and cytotoxic T lymphocytes. Expression of the GPI-linked H-2D^d molecule on H-2^b tumor cells resulted in protection of the tumor cells after transplantation into D8 mice (H-2^b, H-2D^d) from rejection by NK cells. In addition, NK cells from mice expressing the GPI-linked H-2D^d molecule as a transgene were able to kill nontransgenic H-2^b lymphoblast target cells. The GPI-linked MHC class I molecule was able to alter NK cell specificity at the target and effector cell levels. Thus, the expression of the cytoplasmic and transmembrane domains of MHC class I molecules are not necessary for protection and alteration of NK cell specificity.     

Influence of implant length and bone defect situation on primary stability after distal femoral replacement in vitro

Background

Aseptic loosening is the major reason for failure of distal femoral replacement using current modular megaprostheses. Although the same stems are used for proximal and distal replacement, survival rates in clinical studies with distal reconstruction were lower within the same system compared to proximal reconstruction. We analyzed whether primary stability as presupposition for long-term fixation can be achieved with a current tapered stem design. Additionally, we hypothesized that stem length affects primary stability depending on bone defect situations.

Transferrin receptors on tumor and bone marrow cells: Lack of involvement as target structure for natural killer cells

Summary Two different experimental approaches based on the specificity of monoclonal antibodies (mAbs) have been taken to verify the hypothesis that the transferrin receptor (TfR) on proliferating cells serves as a common target structure for natural killer (NK) cells. Thus, by the lysostrip technique the TfR was removed from the surface of K562 and Molt4 tumor cells by incubation with two different anti-TfR mAbs. The effect of removal of the TfR was controlled by uptake of radiolabeled transferrin, and by binding of non-cross-reacting monoclonal anti-TfR receptor antibodies. Though the modulation of TfR on the membrane of viable cells was nearly complete, the cells remained fully susceptible to NK lysis. The second approach consisted in removal of TfR-bearing cells from bone marrow cell suspensions by an indirect rosetting technique. Using mAbs bound to ox erythrocytes the rosetted TfR-bearing cells could be removed from bone marrow cell suspension by density centrifugation with an efficiency of >99%. It could be shown that both fractions, TfR⁺ and TfR^– cells, could be lysed to the same degree by NK cells. Thus, the evidence obtained speaks against a role of TfR as a recognition structure for NK cells.Abbreviations BM Bone marrow - mAb Monoclonal antibody - NK cell Natural killer cell - PBL Peripheral blood mononuclear cell - TfR Transferrin receptor This work is dedicated to Professor Hans Dierk Waller on the occasion of his 60th birthdayThis work was supported in part by the Deutsche Forschungsgemeinschaft, Bonn, SFB 217     

Stable expression of EBV-gp350 on the surface of NC37 cells confers natural killer (NK)-cell susceptibility or resistance, depending on the assay used to assess NK-mediated function

NC37 cells containing the Epstein-Barr virus (EBV) genome do not express the viral glycoprotein-350 (gp350) on the cell surface. Despite being a cancer cell line, NC37 cells show resistance to natural killer (NK) cell cytotoxicity by the standard chromium (⁵¹Cr) release assay (CRA). EBV-gp350 has been identified as a ligand for antibody dependent cell-mediated cytotoxicity (ADCC). The stable expression of gp350 on the NC37 cell surface membrane could make this cell line a suitable target for measuring ADCC antibody. The pcDNA3.1-gp350 was transfected into the stably expressing enhanced green fluorescent protein (EGFP)-NC37 cell line. The transfected cells were then selected for expression of gp350 on the cell surface using immunomagnetic bead-based sorting. The gp350-EGFP-NC37 cell line was then re-examined for resistance to NK cytotoxicity, and compared with the standard K562 and EGFP-K562 cell lines using the CRA and a flow cytometric method, respectively. Surprisingly, the gp350-EGFP-NC37 cells, like the parental NC37 cell line, showed comparable resistance to NK cell-mediated cytotoxic activity by the CRA, while demonstrating susceptibility to NK cell cytotoxicity comparable to EGFP expressing K562 cells by the flow cytometric method. The susceptibility of gp350-EGFP-NC37 cells to NK cell cytotoxic activity is dependent on the type of assay.     

DNA from buccal swabs recruited by mail: evaluation of storage effects on long-term stability and suitability for multiplex polymerase chain reaction genotyping

We provide details of an inexpensive and rapid method for extraction of DNA from buccal swabs (including samples received through the mail) and from a range of other tissue samples. The procedure we have developed provides amounts of DNA adequate for several thousand polymerase chain reactions (PCRs), and we have validated its potential for long-term storage. Samples stored for >4 years are of comparable concentration and provide as robust PCR templates as those tested immediately after extraction. The availability of this technology is of considerable significance in planning DNA banks from population collections and cohorts.     

Glycopolymer Polyelectrolyte Multilayers Composed of Heparin and Maltose‐Modified Poly(ethylene imine) as a Strong/Weak Polyelectrolyte System for Future Drug Delivery Coatings: Influence of pH and Sugar Architecture on Growth of Multilayers and Multilayer Swelling and Stability

Establishing highly sophisticated polymer films for delivery systems in a biological environment and bioanalytical tasks, the formation, thickness, swelling behavior, and (physiological) stability of highly biocompatible polyelectrolyte multilayers (PEMs) are described. These PEMs are composed of the very weak polycation maltose‐modified hyperbranched poly(ethylene imine) (PEI‐Mal) and the strong polyanion heparin sodium salt (HE^?Na⁺) deposited on Si wafer substrates . Two different glyco architectures for PEI‐Mal are used, characterized by two different degrees of maltose decoration on a PEI scaffold. Using two pH‐dependent deposition approaches for optimizing the (physiological) PEM stability and swelling, PEMs are characterized by (in situ) ellipsometry, atomic force microscopy (AFM), and (in situ) attenuated total reflection‐Fourier‐transform infrared (ATR‐FTIR). Thus, PEMs reveal significantly different thicknesses, growth mechanisms (linear versus exponential), and swelling behavior in dependence of both the polycation architectures and the deposition protocol. These PEMs will allow the study of their complexation and release properties as preswollen PEMs against anionic drug molecules, especially under physiological conditions in the future.