Physical properties of a porcine internal thoracic artery fixed with an epoxy compound

This study aimed to investigate the physical properties of a porcine internal thoracic artery fixed with an epoxy compound. Fresh and glutaraldehyde-fixed porcine arteries were used as controls. Both the epoxy-fixed and glutaraldehyde-fixed porcine arteries showed significant increases in fixation index and denaturation temperature as compared to the fresh one. Additionally, the resistance of porcine arteries against bacterial collagenase In vitro degradation increased significantly after cross-linking with the epoxy compound or glutaraldehyde. The reduction of the tensile strength of the epoxy-fixed artery after bacterial collagenase degradation was more severe than in its glutaraldehyde-fixed counterpart. Generally, with increasing pH, temperature or fixative concentration, the fixation indices and denaturation temperatures of the epoxy-fixed porcine arteries increased. The results obtained in this study may be used to optimize the fixation process for developing a small-diameter biological vascular graft fixed by an epoxy compound.     

Biocompatibility study of biological tissues fixed by a natural compound (reuterin) produced by Lactobacillus reuteri

Glutaraldehyde-fixed biological tissues have been used extensively to fabricate various bioprostheses. However, the tendency for glutaraldehyde to markedly alter tissue stiffness and promote tissue calcification is a well-recognized drawback of this crosslinking agent. To overcome the aforementioned deficiency with the glutaraldehyde-fixed bioprostheses, a fixation technique using a natural compound (reuterin) produced by Lactobacillus reuteri to crosslink biological tissues was developed by our group. It was reported that reuterin inhibits the growth of gram-positive and gram-negative bacteria as well as yeasts, fungi, and protozoa. The study was conducted to evaluate the biocompatibility of the reuterin-fixed tissues with or without ethanol sterilization implanted subcutaneously in a growing rat model. Fresh and the glutaraldehyde-fixed counterparts were used as controls. The results showed that both glutaraldehyde and reuterin are effective antimicrobial agents in the sterilization of biological tissues. The degrees in inflammatory reaction for the reuterin-fixed tissues with or without ethanol sterilization were significantly less than their glutaraldehyde-fixed counterparts throughout the entire course of the study. Additionally, the reuterin-fixed tissues have comparable tensile strengths and resistance against degradation as the glutaraldehyde-fixed tissues. The results obtained at 12-month postoperatively showed that the glutaraldehyde-fixed tissue without ethanol sterilization became significantly stiff and calcified. However, it was found that ethanol sterilization of the glutaraldehyde-fixed tissue may inhibit calcification. Additionally, reuterin fixation may inhibit tissue calcification as compared to glutaraldehyde fixation. These observations implied that the biocompatibility of the reuterin-fixed tissue is superior to the glutaraldehyde-fixed tissue.     

Study of the degradation mechanisms of oxidized Cellulose-Derivative hemostatic agent by using model compound

Degradable hemostatic agents are the essential materials for controlling the hemorrhage. Hemostatic oxidized cellulose carboxylate sodium fiber (OCCSF) has been synthesized via a simple neutralization reaction between water-insoluble oxidized cellulose fiber (OCF) and NaOH. Importantly, the degradation mechanisms of OCCSF have been investigated in vitro assay. Chemical structure of the material is tested by using FT-IR and NMR, and no obvious change was detected before and after degradation. Degree of polymerization (DP) of OCCSF declines with prolonging the degradation period, accompanying with the decrease in carboxyl content (CC), so that it could be concluded that OCCSF may undergo decarboxylation degradation process. Besides, combined the change of fiber color with UV, another elimination degradation mechanism of OCCSF could be deduced, and this has been demonstrated using 1,2-cyclohexanedione as the model compound.     

矿化蚕丝基骨材料的生物相容性及体内降解的观察

目的探讨仿生制备的矿化蚕丝基骨材料在大鼠体内的生物相容性及体内降解性。方法成年雄性SD大鼠16只,体重230-300克。在背部肌肉内和腹腔内植入矿化蚕丝基骨材料,观察时间阶段为2周,4周,6周,8周。结果分别在术后2周,4周,6周,8周,行大体观察,细胞毒性研究,组织学切片观察材料的情况,植入2周后出现炎症反应明显,材料框架基本存在,术后8周大鼠体内植入的矿化蚕丝基骨材料没有明显的排异反应,而且大部分被吸收。结论矿化蚕丝基骨材料具有良好的生物相容性和适宜的生物降解性能,是比较理想的骨缺损的替代材料。     

Measurement of thermal and ultrasonic properties of some biological tissues

The measurement of thermal and ultrasonic properties of biological tissues is essential for the assessment of the temperature rise induced in vivo by diagnostic ultrasound. In this paper, we present measurements of thermal conductivity, thermal diffusivity, speed of sound and ultrasonic attenuation of fresh ex vivo porcine tissue, namely ‘muscle’ (from abdomen and leg), ‘skin with subcutaneous fat’ (from abdomen and leg), ‘abdominal fat’ and ‘bone’. The measurements of the thermal properties of biological tissue samples are based on a transient method. Thermal property measurements show that subcutaneous fat has the lowest thermal conductivity (0.23 W m^?1 K^?1), while muscle gives the highest values (0.46 W m^?1 K^?1). Thermal diffusivity of muscle tissue recorded the highest value among the studied tissues (0.16 mm² s^?1) while that of skin with subcutaneous fat gave the lowest value (0.11 mm² s^?1). A scanning acoustic macroscope was used to measure attenuation coefficient and speed of sound for the tissue samples. The results for the speed of sound are broadly similar to those reported in the literature. The power law dependence of the attenuation coefficient of the form η = a f ^b as a function of frequency was found to be more appropriate than the linear fit in this study.     

Dual-phase lag effects on thermal damage to biological tissues caused by laser irradiation

A dual-phase lag (DPL) bioheat conduction model, together with the broad beam irradiation method and the rate process equation, is proposed to investigate thermal damage in laser-irradiated biological tissues. It is shown that the DPL bioheat conduction model could predict significantly different temperature and thermal damage in tissues from the hyperbolic thermal wave and Fourier's heat conduction models. It is also found that the DPL bioheat conduction equations can be reduced to the Fourier heat conduction equations only if both phase lag times of the temperature gradient (τ_T) and the heat flux (τ_q) are zero. This is different from the DPL model for pure conduction materials, for which it can be reduced to the Fourier's heat conduction model provided that τ_q=τ_T. Effects of laser parameters and blood perfusion on the thermal damage simulated in tissues are also studied. The result shows that the overall effects of the blood flow on the thermal response and damage are similar to those of the time delay τ_T.     

In vitro studies of degradation of birch and timothy pollen allergen preparations by human duodenal juice

The hydrolysis of birch and timothy pollen allergen preparations by duodenal juice from an adult volunteer was studied in vitro with the aid of rocket immunoelectrophoresis, radiorocket immunoelectrophoresis and RAST-inhibition. The results achieved with all methods were similar. The duodenal juice had the capacity to hydrolyse both the grass and tree pollen proteins, and after 30 min preincubation only 10% of the original birch and timothy allergenic activity remained. Heat treatment of the duodenal juice completely destroyed the proteolytic activity (i.e. no hydrolysis occurred) while protease inhibitors only marginally prevented the hydrolysis.     

生物硬组织材料力学研究方法进展

研究生物硬组织材料的力学性质对于预防和治疗骨科和口腔疾病具有重要意义。同时,经过长期的进化,生物材料具有独特的力学性质,研究这些材料的结构与力学性质可以为工程材料的设计提供解决方案。与工程材料不同,生物材料的力学研究需要采用特殊的方法来准确描述其力学性质。本文针对生物硬组织材料力学性质的研究方法进行综述,包括生物硬组织材料的常规力学实验方法、断裂力学和压痕测试技术,以及微观和宏观力学数值模拟技术。     

体外动物组织热变过程中的光学特性变化

目的 研究热变过程中生物组织的光学特性变化。方法 采用犬肝、犬肾、犬肌肉和鼠肌肉4种动物组织作为样本,使用积分球系统测量650 nm波长激光照射下的样本在热风枪从30℃升温到100℃过程中的准直透射光、漫透射光和漫反射光光强随温度变化的数据,根据Kubelka-Munk模型计算得出吸收系数、散射系数和散射各向异性因子变化曲线。结果 温度变化使组织光学特性改变,热变过程中样本透射减弱,吸收系数和散射系数增大,散射各向异性因子减小,不同组织的变化有一定差别。结论 热变性使组织透射减弱,吸收和散射增强。     

In vitro assessment of three-dimensionally plotted nagelschmidtite bioceramic scaffolds with varied macropore morphologies

It is known that porous scaffolds play an important role in bone/periodontal tissue engineering. A new nagelschmidtite (NAGEL, Ca₇Si₂P₂O₁₆) ceramic has recently been prepared which shows excellent apatite mineralization ability and osteo-/cementostimulation properties in vitro. However, up to now porous NAGEL scaffolds have not been developed yet. There has been no systematic study of the effect of macropore morphology of bioceramic scaffolds on their physico-chemical and biological properties. The aim of this study was to prepare NAGEL scaffolds for bone tissue engineering applications. We applied a modified three-dimensional (3-D) plotting method to prepare highly controllable NAGEL scaffolds and investigated the effect of macropore morphology on the physico-chemical and biological properties. The results showed that the macropore size and morphology of 3-D plotted NAGEL scaffolds could be effectively controlled. Compared with β-tricalcium phosphate (β-TCP) scaffolds NAGEL scaffolds possess a significantly enhanced compressive strength, a higher modulus and better degradability. Nagel scaffolds with a square pore morphology presented a higher compressive strength, a higher modulus and greater weight loss rate than those with triangular and parallelogram pore morphologies. In addition, all of the NAGEL scaffolds with the three macropore morphologies supported the attachment and proliferation of MC3T3 cells. The proliferation of MC3T3 cells on NAGEL scaffolds with triangular and parallelogram structures was higher than that on β-TCP scaffolds with the same pore structure. Cells on all three groups of NAGEL scaffolds revealed higher alkaline phosphatase (ALP) activity compared with cells on β-TCP scaffolds, and among the three NAGEL scaffolds groups those with a parallelogram pore structure showed the highest ALP activity. Furthermore, the angiogenic cell experiments showed that the ionic products from NAGEL scaffolds promoted tube formation, expression of pro-angiogenic factors and their receptors on human umbilical vein endothelial (HUVECs) compared with β-TCP scaffolds, indicating that NAGEL scaffolds possessed improved angiogenesis capacity. Our results suggest that 3-D plotted NAGEL scaffolds are a promising bioactive material for bone tissue engineering by virtue of their highly controllable macropore structure, excellent mechanical strength, degradability and in vitro biological response to osteogenic/angiogenic cells.     

聚乳酸三维细胞支架降解行为研究

研究孔隙全连通的聚乳酸三维细胞支架，在磷酸盐缓冲溶液中的降解行为。支架采用致孔剂粘结——溶液浇铸／颗粒沥析技术制备，其孔隙率为88．88％，孔径分别为220μm～355μm和450μm，600μm。在37℃，pH7．4缓冲溶液中降解时，支架的重量逐渐降低，分子量呈线性关系下降；吸水率逐渐增大，第8周后趋于稳定，其中大孔径支架吸水率更高；降解过程中，支架外观尺寸和孔隙率基本维持不变。结果表明：孔隙间全连通的三维细胞支架。其自催化降解行为被明显抑制，支架的外观尺寸和孔隙率稳定，有利于获得外观尺寸稳定的工程化组织。     

超抗原诱导T细胞凋亡或增殖的体外研究

研究抗原递呈细胞在超抗原诱导人外周血特异性Ｔ细胞反应中的作用。方法金黄色葡萄球菌Ａ肠毒素刺激短期人外周血ＳＥＡ反应Ｔ细胞系的作用中,通过去除或加入Ａｐｃ观察细胞形态,ＦＣＭ检测细胞亚ＧＯ／Ｇ１峰大小及１．８％ＤＮＡ琼脂糖凝胶电泳观察凋亡特征条带。     

In vitro heterogeneous degradation of alginate and its validation of different molecular weight on blood bio-compatibility

In the present work, sodium alginate (ALG) was degraded by heterogeneous phase acid degradation. The molecular weight distribution of ALG after degradation was close to homogenization. Then the blood bio-compatibility of ALG with different molecular weights (ALG-0h 50,075, ALG-0.5h 20,680, ALG-2h 13,170 and ALG-96h 1170 kDa) was evaluated in vitro and vivo. The human umbilical vein endothelial cells were used to assess the cytotoxicity of ALGs, ALG-0.5h and ALG-2h exhibited greater increment in percentage of cell viability comparing with ALG-0h and ALG-96h. With increasing of molecular weight of ALG, the blood clotting time was shortened and the hemolysis rate was slightly decreased. The different degree aggregation of red blood cells (RBCs) was observed in the ALG with different molecular groups and ALG-0h caused a severe aggregation of RBCs. Hematology analysis in vivo behavior after intraperitoneal (i.p.) injection indicated ALG-0h could cause blood solidification. Above results provided a reference for molecular weight selection in different applications.     

Self-reinforced composites of bioabsorbable polymer and bioactive glass with different bioactive glass contents. Part II: In vitro degradation

The in vitro degradation behavior of self-reinforced bioactive glass-containing composites was investigated comparatively with plain self-reinforced matrix polymer. The materials used were spherical bioactive glass 13-93 particles, with a particle size distribution of 50-125 microm, as a filler material and bioabsorbable poly-L,DL-lactide 70/30 as a matrix material. The composites containing 0, 20, 30, 40 and 50 wt.% of bioactive glass were manufactured using twin-screw extruder followed by self-reinforcing. The samples studied were characterized determining the changes in mechanical properties, thermal properties, molecular weight, mass loss and water absorption in phosphate-buffered saline at 37 degrees C for up to 104 weeks. The results showed that the bioactive glass addition modified the degradation kinetics and material morphology of the matrix material. It was concluded that the optimal bioactive glass content depends on the applications of the composites. The results of this study could be used as a guideline when estimating the best filler content of other self-reinforced osteoconductive filler containing composites which are manufactured in a similar way.     

Assessing the residual antibacterial activity of clinical materials disinfected with glutaraldehyde, o-phthalaldehyde, hydrogen peroxide or 2-bromo-2-nitro-1,3-propanediol by means of a bacterial toxicity assay

This study investigated the use of a rapid bacterial toxicity test for detecting disinfectant residues released by disinfected materials. The test substances included an environmental disinfectant used in hospitals in high-risk areas, such as critical care units or emergency services, and three disinfectants used on clinical devices when a high level of disinfection is required. The test materials were polyurethane, polypropylene, glass, latex and cotton from different instruments and utensils used in hospitals. Of the four test disinfectants, o-phthalaldehyde (OPA) and 2-bromo-2-nitro-1,3-propanediol (BNP) showed the greatest inhibitory activity (as much as 300-fold greater than hydrogen peroxide in the case of OPA) according to the toxicity text. However, with the exception of hydrogen peroxide on latex, it was the most porous test materials, namely latex and cotton, that accumulated the least residue. BNP was the disinfectant that left the least residue on the five test materials, while the greatest residual concentration was left by hydrogen peroxide on latex (as much as 5 microg/cm2). The biotest used in this study permitted the detection of disinfectant residues released by different types of previously disinfected clinical materials, and can be adapted to simulate elution conditions similar to those existing in routine hospital practice.     

In vitro reactivation of latent herpes simplex virus by the demethylating compound hexamethylene-bis-acetamide

We have characterized previously a model of herpes simplex virus (HSV) infection of rat dorsal root ganglia (DRG) following cutaneous infection. During acute infection HSV can be isolated from co-cultivated rat ganglia in (mean ± S.E.M) 4.8 ± 0.33 days (d) and from latently infected ganglia in 7.8 ± 0.53 (d) (P 0.0001). We treated co-cultivated rat ganglia from acute and latent infected rats with the demethylating compound hexamethylene-bis-acetamide (HEX) to see what effect, if any, it would have on HSV infection. HEX-treated ganglia from rats with acute infection did not differ significantly from controls in the proportion of rats, skin or ganglia positive for HSV. The mean time to detect virus was not different between treated (3.6 ± 0.38 d) and control (3.1 ± 0.46 d) (P> 0.05) groups. In latent infected rats there was no difference between treated and controlled groups in the proportions of rats, skin and ganglia positive for HSV. There was a significant difference in the mean time to CPE between the HEX and control groups respectively (4.5 ± 0.72 d vs 8.92 ± 1.42 d, P < 0.01). We conclude that HEX converted latent HSV infection to a productive one.     

Rescue of cognitive-aging by administration of a neurogenic and/or neurotrophic compound

Aging is characterized by a progressive decline of cognitive performance, which has been partially attributed to structural and functional alterations of hippocampus. Importantly, aging is the major risk factor for the development of neurodegenerative diseases, especially Alzheimer's disease. An important therapeutic approach to counteract the age-associated memory dysfunctions is to maintain an appropriate microenvironment for successful neurogenesis and synaptic plasticity. In this study, we show that chronic oral administration of peptide 021 (P021), a small peptidergic neurotrophic compound derived from the ciliary neurotrophic factor, significantly reduced the age-dependent decline in learning and memory in 22 to 24-month-old Fisher rats. Treatment with P021 inhibited the deficit in neurogenesis in the aged rats and increased the expression of brain derived neurotrophic factor. Furthermore, P021 restored synaptic deficits both in the cortex and the hippocampus. In vivo magnetic resonance spectroscopy revealed age-dependent alterations in hippocampal content of several metabolites. Remarkably, P021 was effective in significantly reducing myoinositol (INS) concentration, which was increased in aged compared with young rats. These findings suggest that stimulating endogenous neuroprotective mechanisms is a potential therapeutic approach to cognitive aging, Alzheimer's disease, and associated neurodegenerative disorders and P021 is a promising compound for this purpose.     

In vitro uptake of 5-hydroxytryptamine and dopamine by rat mast cells after exocytosis induced by antigen or compound 48/80.

Mast cells from the peritoneal and pleural cavities of actively sensitized rats were isolated and incubated with biogenic amines (5-hydroxytryptamine and dopamine) with or without pretreatment with specific antigen. An anaphylactic reaction resulting in the release of 20-25% of the histamine in the cells led to a slightly reduced amine uptake. At concentrations which induced histamine release comparable to that during the anaphylactic reaction compound 48/80 had a similar effect on the uptake of the two amines. Histamine release induced by higher concentrations of compound 48/80 led to a more pronounced reduction in the uptake of the amines, the reduction being roughly proportional to the extent of the histamine release. It is concluded that the reduction in the in vitro amine uptake after anaphylactic and compound 48/80-induced histamine release is due to the fact that there are a fewer intact granules capable of storing histamine and not primarily due to a damage to the mechanisms by which mast cells take up biogenic amines in vitro. The observations further strengthen the view that anaphylactic and compound 48/80-induced histamine release are non-cytolytic processes.     

体外模拟和体内植入实验分析磷酸钙骨水泥的降解活性

目的 研究CPC及CPC／BMP复合人工骨降解性能，寻找加快CPC降解的有效途径，方法将CPC作为BMP的载体制成CPC／BMP复合物，在体外模拟生理环境进行CPC和CPC／BMP复合物的溶解试验。通过植入小鼠肌袋和犬桡骨植入试验，观察材料在体内的降解情况和降解规律。结果BMP促进了CPC的体外溶解。肌肉内植入CPC／BMP可以异位诱导新骨形成。植入骨缺损后CPC／BMP可以诱导新骨形成，有效地修复骨缺损。新骨形成的同时，材料出现了较快的降解。CPC不能异位诱导新骨形成，骨缺损修复能力较弱，降解缓慢。结论CPC／BMF，生物活性人工骨具有理想的降解性能和成骨能力，可望成为新型的骨缺损修复材料。