An in vitro biomechanical comparison of the breaking strength and stiffness of polydioxanone (sizes 2, 7) and polyglactin 910 (sizes 3, 6) in the equine linea alba

OBJECTIVE: To determine failure strength, stiffness, and failure mode of 4 suture materials in equine linea alba. STUDY DESIGN: Randomized complete block design. SAMPLE POPULATION: Linea albas collected from 12 adult horses (mean weight, 475 kg; mean age, 10 years). METHODS: The ventral abdominal fascia, including the linea alba, was collected and bisected along the linea alba into right and left halves. Each half was divided into four, 5-cm sections extending from the umbilicus cranially, and randomly assigned to 1 of 4 suture materials: 2 polydioxanone (2 PD), 3 polyglactin 910 (3 PG), 6 polyglactin 910 (6 PG), and 7 polydioxanone (7 PD). A single cycle to failure test was performed on each specimen at a distraction rate of 100 mm/min. Differences in failure strength and stiffness for the materials were evaluated using a mixed linear model with significance set at P<.05. RESULTS: In 94 of 96 test sections, constructs failed by suture failure. There were significant differences in failure strength (P<.0001) and stiffness (P<.001) among the suture/tissue constructs. 7 PD had the highest breaking strength (316.8 N) followed by 6 PG (281.3 N), 3 PG (229.9 N), and 2 PD (193.0 N). Six PG had the largest stiffness (14 N/mm) followed by 3 PG (12.7 N/mm), 7 PD (10.1 N/mm), and 2 PD (7.2 N/mm). Suture breaking strength and stiffness were not affected by linea or fascia thickness, individual horse, half of the linea alba, or abdominal wall position. Eighty-five (90.4%) suture loops failed adjacent the knot. CONCLUSIONS: When tested in single cycle to failure, suture material was more likely to fail than the linea alba. Larger suture materials had higher breaking strengths than smaller suture materials and stiffness was also affected by suture material and size. CLINICAL RELEVANCE: Given its high initial breaking strength and its relatively longer in vivo strength retention, 7 PD seems an appropriate choice of suture material for closure of the equine linea alba when maximal short-term failure strength is desired.     

Physicochemical properties of the thermal gel of water-washed meat in the presence of the more soluble fraction of porcine sarcoplasmic protein

We investigated the physicochemical properties of the thermal gel of water‐washed pork meat (WWM) in the presence of the soluble fraction of porcine sarcoplasmic protein (SP) obtained with ammonium sulfate at 75 percent saturation. Two precipitated fractions of SP were obtained at 0–50 percent and 50–75 percent saturation, named SP‐f1 and SP‐f2, respectively, and the soluble fraction obtained at 75 percent saturation, SP‐f3, was used. Sodium dodecyl sulfate‐polyacrylamide gel electrophoresis showed that SP‐f3 contained mainly glyceraldehyde‐3‐phosphate dehydrogenase (GAPDH), while SP‐f1 and SP‐f2 had other SPs such as phosphorylase b, enolase, actin and phosphoglycerate mutase. The gel strength of WWM was greater when SP‐f3 rather than one of various animal proteins such as bovine plasma (BP), egg white, or whey protein isolates (WPI), was added and SP‐f3 had a gel‐enhancing effect as good as that of polyphosphate (PP). The gel strength of WWM with added SP‐f3 increased significantly with NaCl at 0.15 mol/L or more, but not in the absence of NaCl (0 mol/L). The effect of SP‐f3 was evident at neutral pH and maximum gel strength was obtained at a pH above 6.0. Differential scanning calorimetric (DSC) analysis showed that an endothermic peak corresponding to myosin heads in WWM shifted to a lower temperature with the addition of SP‐f3, as in the case of PP, though there was no such shift in the presence of other animal proteins (BP, egg white and WPI), suggesting that SP‐f3 increases the gel strength of WWM through the dissociation of actomyosin similar to PP. Scanning electron microscopy (SEM) revealed wall‐like structures among the protein strands in the WWM gel matrix in the presence of SP‐f3. The results of DSC and SEM indicated that the formation of a gel network in meat products is reinforced with GAPDH in SP after the interaction between GAPDH and myofibrillar protein.     

6株羊源乳酸杆菌电转化条件的优化

选取质粒pLEM415-egfp电转化源于陕北白绒山羊瘤胃的乳酸杆菌,研究不同生长时期及电场强度对6株羊源乳酸杆菌电转化效率的影响,并优化其转化条件。在37 ℃培养条件下,培养6株羊源乳酸杆菌,当D_{600 nm} 达到0.4、0.6、0.8、1.0和1.2时,离心收集菌体,制备感受态细胞;在电阻200 Ω、电容25 uF条件下,分别采用1.5、2.0和2.5 kV 3种电场强度电击转化感受态细胞。结果表明,羊源植物乳酸杆菌(Lactobacillus plantarum)、干酪乳酸杆菌(Lactobacillus casei)、罗伊乳酸杆菌(Lactobacillus reuteri)、短乳杆菌(Lactobacillus brevis)、棒状乳酸杆菌(Lactobacillus coryniformis)和弯曲乳酸杆菌(Lactobacillus curvatus)获得最高转化效率的D_{600 nm}和电场强度分别为0.8、1.2、1.0、0.6、0.8、0.4和1.5、1.5、1.5、1.5、1.5、2.0 kV。羊源乳酸杆菌最佳转化条件的确立,为后续乳酸杆菌转基因工程菌的构建及其应用奠定了基础。     

退化高寒草甸斑块根—土复合体特征研究

高寒草甸斑块的根-土复合体对局部水土流失过程具有调控作用,为研究其特征及抗侵蚀效应,本研究选取三江源区达日县境内典型中度退化草甸的植被斑块为研究对象,调查草甸斑块中心与边缘植物群落特征,测定斑块边缘0～10 cm土层和斑块中心0～20 cm土层的容重、含水率、毛管孔隙度等土壤物理性质,并开展单根拉伸和根-土复合体直剪试验。结果表明：受优势种矮嵩草的分布影响,地上生物量主要分布在斑块中心,根系主要分布在0～10 cm土层;斑块中心区域土壤抗剪强度、内摩擦角和粘聚力均随土层深度的增加而减小;斑块边缘区域土壤粘聚力,抗剪强度明显高于斑块中心区域,草甸斑块植物根系是土壤抗剪强度的主要影响因素。草甸斑块根-土复合体能明显增加退化草甸土壤的抗侵蚀能力,研究结果可为深入研究高寒草甸根系固土功能及水土流失调控提供科学依据。     

养殖业兽医社会化服务模式分析

我国养殖业的兽医服务方式多样,其中兽医社会化服务能力不足的问题由来已久,亟需发展壮大。在有关政策法规的指导下,多地结合自身条件,因地制宜探索推行了兽医社会化服务模式。本文介绍了兽医服务公司承接、"企业+农户"、"购买产品+服务"、合作社承接、科研院所服务、信息化平台服务等6种养殖业兽医社会化服务模式,并对不同模式的服务组织、服务内容、服务机制、服务特点等进行了分析,其中"兽医服务公司承接模式"和"合作社承接模式"的社会化程度较高,也是目前基层最为推广的模式。这提示当前的兽医社会化服务组织需进一步扩大服务范围、拓展服务对象、提升技术能力,推动整体升级转型。     

灰铸铁生产技术的一些新进展

对灰铸铁的研究现状和生产中的一些新技术做了评述。重点介绍了高强度薄壁灰铸铁的生产现状以及先进的制造工艺和先进的制造手段在灰铸铁生产中应用所取得的技术成果。     

基于正交试验分析影响透水混凝土性能的主要因素

透水混凝土作为一种环保型材料,在水利工程和道路工程等方面得到越来越广泛的应用。影响其性能的主要因素有：水灰比、骨灰比和骨料粒径。采用正交试验方法[L9（3^4）],以28d抗压强度和透水系数为性能指标,分析研究了3个因素及其不同的水平对透水混凝土性能的影响,并通过回归分析和极差方差分析确定抗压强度和透水系数影响因素的显著性大小,得出了骨料粒径和骨灰比对透水混凝土性能的影响较为显著,水灰比影响较小的结论。