Recent advances in biomechanical studies of abdominal aortic aneurysms / 医用生物力学

An abdominal aortic aneurysm (AAA) is a vascular pathology associated with localized and balloon-like dilatations of abdominal aorta. An untreated AAA may lead to an eventual rupture with a high mortality rate. In recent studies, the biomechanics of AAA has been widely used to assess the rupture risk in clinic. In this review paper, biomechanical testing methods on intraluminal thrombi and AAA are discussed, so as to fully understand biomechanical properties of intraluminal thrombi and aneurysmal tissues, as well as the influence of mechanical property changes on the AAA growth and remodeling under pathological environment. Then representative research findings on prediction of rupture risk by a series of experimental and computational biomechanical methods are reviewed, including finite element analysis on stress distributions on AAA wall, assessment of rupture risk index and judgment of rupture locations. The relevant microstructural changes caused by thrombus aging are described in detail, and the current situation of biomechanical studies on AAA and future challenges are briefly summarized.

Effect of substrate stiffness on biological behavior of fibroblasts / 中华烧伤杂志

<p><b>OBJECTIVE</b>To study the effect of substrate stiffness on proliferation, migration of fibroblast and integrin β(1) expression in fibroblast.</p><p><b>METHODS</b>Fibroblasts were inoculated on silicon substrate with stiffness of (16.2 ± 0.5), (19.8 ± 1.1), and (200.1 ± 2.6) kPa. After being cultured for 5 days or 6 days, cells were counted and cell proliferative activities (recorded as absorbance value) were assessed with methyl thiazolyl blue (MTT). After being cultured for 3 days, cell cycle was detected and proliferation index (PI) was calculated. The cell scratch test was used for determination of cell migration rate on post scratch day (PSD) 0 (the day of scratch), 1, 2, and 3. After being cultured for 2 days, the expression of integrin β(1) was determined by flow cytometry with fluorescence. Data were processed with one-way analysis of variance.</p><p><b>RESULTS</b>(1) The proliferative speed and proliferative activity of fibroblasts were all increased along with the increase in substrate stiffness. PI of fibroblasts inoculated on silicon substrate with stiffness of (16.2 ± 0.5), (19.8 ± 1.1), and (200.1 ± 2.6) kPa was respectively 24.8%, 27.4%, 32.4%. On PSD 2, migration rate of fibroblasts inoculated on silicon substrate with stiffness of (19.8 ± 1.1) and (200.1 ± 2.6) kPa was respectively (91.4 ± 5.1)%, (100.0 ± 1.3)%, which were higher than that of fibroblasts inoculated on silicon substrate with stiffness of (16.2 ± 0.5) kPa [(55.8 ± 6.8)%, with F value respectively 3.5, 4.0, P values all below 0.01]. (3) The expression rate of integrin β(1) in fibroblasts inoculated on silicon substrate with stiffness of (16.2 ± 0.5) kPa was the lowest (43.22%), and that in fibroblast inoculated on silicon substrate with stiffness of (200.1 ± 2.6) kPa was the highest (81.26%).</p><p><b>CONCLUSIONS</b>Substrate stiffness may have a great effect on proliferation and migration of fibroblast during the process of wound healing and scar formation, which can be related to regulation of integrin β(1) expression.</p>

Concentration polarization of low density lipoprotein at the distal end of carotid stenosis promotes atherogenesis / 生理学报

To test the hypothesis that concentration polarization of atherogenic lipids may occur in the arterial system and play an important role in localization of atherosclerosis, we simulated and measured in vitro the luminal surface concentration of low density lipoprotein (LDL) in local stenosis at the distal end of carotid artery by number simulation and laser scanning confocal microscopy, then we designed carotid stenosis model to test the role of LDL concentration polarization in atherogenesis. The in vitro experiment showed that the luminal surface LDL concentration was higher than the bulk concentration as predicted by the concentration polarization theory. The relative luminal surface LDL concentration changed with the flow velocity and ratio of stenosis. The wall concentration of LDL was highest in the round tube with 40% stenosis at the same velocity, while the wall concentration of LDL was higher when Re was 250 than Re was 500 at the same extent of narrowness. The animal experiment also revealed that general atherogenic plaques obviously occurred at the distal end of local stenosis where concentration polarized. The results strongly support our hypothesis that concentration polarization of lipoproteins occurs in local stenosis at the distal end of carotid artery, and this in turn promotes the localization of atherosclerosis which develops in the arterial system.

Development of drug coating on drug eluting stents / 中国医疗器械杂志

Researches on drug-eluting stents are now focusing on three main aspects: the stent materials, the coating matrix material and the selection, adhesion and controlled release of the biological agents. The current development progresses of the coating materials, their characteristics, and the coating method for metallic stents are reviewed in this paper.

In vitro study of platelet glycoprotein monoclonal antibody eluting stents / 中国医疗器械杂志

In order to prove the feasibility of preparation of the drug-incorporated stent by immersing stent wires in the monoclonal antibody (mAb) solution, fluorescence stain and image analysis were used to evaluate the L-PLA-coated stent. Absorption was measured using a radioisotope technique after preparing the mAb-incorporated stent, and the absorption curve was determined from the absorption data. In an in vitro perfusion circuit, the antibody was eluted from the stent matrices, and the related influence factors were evaluated based on the release data.

Study on surface modification and biocompatibility of NiTi alloy intravascular stents / 中国医疗器械杂志

This paper introduces the surface modification of NiTi alloy intravascular stents for roughness by chemical erosion and plasma deposition technology. The stent which had been granulated with chemical erosion was treated with TiO2 film prepared with Gel-sol. The study on the biocompatibility of the modified stent by the above two ways shows that the modified stent is rougher, and its anticoagulation and hydrophilicity are improved. However, the capability of erosion resistance is not enhanced significantly.

Research advances of small-diameter vascular grafts / 中国医疗器械杂志

This review is a summary of some useful methods and advances about improving clinical applications to small-diameter vascular grafts in recent years, and it points out the developing orientation of small-diameter vascular grafts in the future.

Analysis of Microbial Flora in Full Autotrophic Ammonium Removal System / 微生物学通报

The microbial flora of fungi,bacterial and actinomycetes in full autotrophic ammonium removal reactor and activated sludge was analyzed,and the amount of nitrite-oxidizing bacteria and ammonia-oxidizing bacteria was also compared.The result showed that the population,species,species number and dominates of microorganisms in full autotrophic ammonium removal reactor were different from that in activated sludge.In full autotrophic ammonium removal reactor,the amount of ammonia-oxidizing bacteria was increased remarkably which indicated that the accumulation of ammonia-oxidizing bacteria was a remarkable feature of full autotrophic ammonium removal system.

Gene Cloning of the Crucial Degumming Enzyme and Its Integration and Expression in Aspergillus niger / 微生物学通报

The xylanase gene of Bacillus subtilis B10 which had an excellent capacity for degumming ramie fibres was cloned by PCR amplification. The xylanase gene was cloned into vector pBluescript II KS+ and the CaMV 35S promoter was inserted in front of the gene, and the expression vector pKS-35SXYHyg was constructed successfully after the Hyg~(r) gene was inserted into the multi-cloning sites of pBluescript II KS+. The expression vector was linearized and transformed protoplasts of Aspergillus niger strain An1. Hygromycin-resistant transformants were generated and the integration of xylanase gene was confirmed by genomic Southern blotting analysis. Compared with An1, the xylanase activity of the transformant AT1 was increased more than trebled, and the residual gum content was decreased by 55.18% after the ramie was treated by culture supernatants from AT1.

The Research Advancement of the Enzymatic Degumming of Ramie (Boehmeria nivea) / 微生物学通报

The enzymatic degumming of ramie bast fibers is a kind of method with high performance, superior quality, free from pollution that directly makes use of the extra cellular enzyme or zymin produced in the fermentation process of microorganisms to degrade the gum. So far, many investigations regarding this aspect have been conducted at home and abroad, and screened various strains including aerobic bacteria and anaerobic bacteria. Comparison with the chemical degumming, the enzymatic degumming shows the advantage of improving the quality of refined dried-ramie, significantly lowering the pollution of the environment, and isone of the main development directions in the future. At the same time, if the degumming technology is extensively applied into industrialization production, the dosage of enzymes will prodigiously increase, which will promote the development of the industry on enzymes.