牛宰后肌肉生物电阻抗值变化及其影响因素的研究

本试验用四电极法在多频(5-200KHz)条件下对宰后牛骨骼肌肉的电阻抗特性进行了初步的研究。发现牛骨骼肌生物电阻抗与肌肉纤维方向,电流信号频率和宰后肌肉所经历的阶段有关。横向电阻(沿垂直于骨骼肌纤维方向)大于纵向电阻(沿骨骼肌纤维方向),而且受电流信号频率的影响较明显,尤其是在5KHz～100KHz范围内。牛宰后生物电阻抗的变化与pH值的变化有一定的相关性。     

Effect of Hibiscus anthocyanins-rich extract induces apoptosis of proliferating smooth muscle cell via activation of P38 MAPK and p53 pathway

Hibiscus sabdariffa L. (Malvaceae), an attractive plant believed to be native to Africa, is cultivated in Sudan and in eastern Taiwan. It has been reported to contain a number of protocatechuic acid and anthocyanins. In vitro experimental studies have shown that anthocyanins administration of the extract produces anti-inflammation and chemoprevention effects. In spite of the wide use of Hibiscus sabdariffa L. in folk medicine for treating various diseases, our previous study indicated a potency of Hibiscus sabdariffa extract (HSE) in anti-atherosclerosis. The mechanisms of anthocyanins administration of the extract produce from Hibiscus sabdariffa L. to attenuate atherosclerosis were not clarified. In this study, we found that Hibiscus anthocyanins (HAs) could inhibit the serum-stimulated proliferation of smooth muscle cell (SMC) and result in cell apoptosis. The HAs inducing cell apoptosis was dose dependent. We further used SB203580 (p38 inhibitor) to block cellular apoptosis and evaluate its effect on the HAs-inducing SMC death via some apoptosis criteria including DNA fragmentation and flow cytometry. We suggested that the mechanisms of the inhibitory effect of HAs on atherosclerosis could be via inhibiting the proliferation of SMC. HAs induces apoptosis via (i) activating p38 MAP kinase that subsequently phosphorylates target protein c-Jun and transduces the signal to further activate the apoptotic protein cascades that contain Fas-mediated signaling (Fas/caspase-8 signaling module) and (ii) activating p53 and inducing bax expression. As an outcome of the events, cytochrome c releases from the mitochondria, leading to cell apoptosis. In these experiments, HAs showed strong potential to induce SMC cell apoptosis via p38 and p53 pathway. In consequence, the rate of atherosclerotic formation is slowed down, and the progress is suppressed.     

Aging and Processing Affect Color, Metmyoglobin Reductase and Oxygen Consumption of Beef Muscles

Color stability and various biochemical properties were determined in bovine longissimus dorsi and psoas major at different times postmortem (8 hr to 21 days) and during retail display. Surface metmyoglobin accumulation, metmyoglobin reductase activity and oxygen consumption rate were affected by muscle type, postmortem aging, and fabrication method (p < 0.01). Psoas steaks had greater metmyoglobin accumulation, lower metmyoglobin reductase activity, and greater oxygen consumption than longissimus steaks. However, color stability of muscles was similar after grinding, which increased oxygen consumption. Color was most stable in steaks fabricated at 4 or 7 days postmortem. The order of color stability was knife-cut steaks > saw-cut steaks > ground muscle.     

黄伞菌丝体多糖提取及其抗疲劳活性的研究

目的：探讨黄伞菌丝体多糖最佳提取条件及其对改善疲劳状态下肌力的减退作用.方法：采用不同料液比、不同浸提温度和浸提时间,研究黄伞菌丝体多糖的最佳提取条件;采用脉冲式电流刺激离体腓肠肌作为疲劳模型,研究黄伞多糖对离体肌肉疲劳的影响.结果：料液比1：30、在100℃下和4h的浸提时间时的菌丝体多糖得率最高;中浓度组（0.2mg/mL）多糖和低浓度组（0.02mg/mL）多糖能明显延缓离体骨骼肌疲劳的发生.结论：黄伞菌丝体多糖最佳提取条件为料液比1：30、浸提温度100℃和4h的浸提时间;此多糖具有抗疲劳作用.     

Relationship Between Thermal Denaturation of Porcine Muscle Proteins and Water-holding Capacity

ABSTRACT: Differential scanning calorimetry was used to investigate denaturation characteristics of pork muscle proteins from carriers and noncarriers of the RN-gene. Pork from RN-carriers deviated from noncarriers in maximum denaturation temperatures and denaturation enthalpy, with proteins of RN-carriers being the most heat-labile. Correlation studies on the results showed that water-holding capacity was significantly correlated to changes in enthalpy of the population mainly representing myosin tails and sarcoplasmic proteins (p < 0.001). Finally, the influence of ultimate pH and preheating on thermal characteristics of porcine muscle proteins was studied. Myosin tails and sarcoplasmic proteins were most sensitive to pH changes, while myosin heads were most sensitive to preheating simulating stress-induced temperature increases.     

Production of dialysable iron by in vitro digestion of chicken muscle protein fractions: the size of the dialysable iron

Muscle foods enhance the absorption of non‐haem iron. We studied the size of the dialysable iron species produced following in vitro digestion of soluble and insoluble chicken muscle proteins and compared the results with those for egg white and whey protein. Digestion of chicken muscle proteins caused a four‐ to fivefold increase in dialysable iron, whereas egg white showed only a slight increase and whey protein caused a reduction, as compared with the control. All the dialysable iron species produced by egg white and whey were smaller than 1 kDa. In contrast, chicken muscle proteins produced dialysable iron species of all sizes up to 10 kDa, but the majority were in the range 2–3.5 kDa for both soluble and insoluble muscle proteins. Copyright © 2005 Society of Chemical Industry     

Protein extractability and thermal gel formability of myofibrils isolated from skeletal and cardiac muscles at different post-mortem periods

The effects of the post-mortem ageing period on the extractability of myofibrillar proteins from pork cardiac and rabbit skeletal muscles under various conditions of pH and ionic strength were studied with particular reference to the changes in the solubility of individual myofibrillar proteins and their denaturation characteristics. The ultimate influence of these changes on the heat-induced gel forming ability of myofibrils isolated from cardiac and skeletal muscles at different post-mortem stages was also investigated. Results showed that pork cardiac myofibrils always exhibited lower solubility than those from rabbit skeletal muscles under identical conditions of pH, ionic strength and temperature. SDS-PAGE profiles indicated several quantitative differences in the relative proportion of individual protein species present in cardiac and skeletal myofibrils. The solubility of various proteins present in myofibrils was also affected differently on heating in 0-1 and 0-6 _M NaCl solution at various pH values. Thermal denaturation of cardiac myofibrils occurred at about 10°C higher than that of skeletal myofibrils as revealed by differential scanning calorimetry. Cardiac myofibrils formed much weaker heat-induced gels than those produced by skeletal myofibrils under identical conditions of temperature, pH, ionic strength and protein content.     

兔骨骼肌肌球蛋白的纯化及溶液浊度和溶解度研究

从雄兔的腰大肌(Pasoas majjor,简称PM)和半膜肌(Semimembranosus proprius，简称SMp)中提取纯化了肌球蛋白，并用双缩脲法测定其浓度，采用Laemli的不连续SDS-PAGE系统检验其纯度。结果表明，提取纯化的肌球蛋白浓度为20～30mg／ml，提取率为1％左右，在SDS-PAGE图谱上出现四条带，一条为肌球蛋白重链，其分子量为205kDa和三条轻链，分子量分别为25．9、17．8和13．8kDa。研究了肌球蛋白质量浓度、pH值、离子强度、温度对PM和SMp肌球蛋白溶液的浊度和溶解度的影响。结果表明，肌球蛋白浓度与浊度呈正线性相关(R^2=0．97)。PM和SMp肌球蛋白在离子强度为0．6的．KCI溶液中pH值为5．5时浊度最大，溶解度在pH值大于5．0时显著上升。离子强度下降，肌球蛋白溶液的浊度会上升，而溶解度下降。相同浓度下温度升高肌球蛋白溶液浊度上升，PM肌球蛋白在55℃，SMp肌球蛋白在60℃其浊度达到最大值。而温度升高溶解度下降。     

萝卜硫素通过抑制PINK1/Parkin信号通路介导的线粒体自噬减轻力竭运动诱导的骨骼肌损伤和疲劳

目的 评价萝卜硫素（SFN）对力竭运动所致小鼠骨骼肌损伤和疲劳的影响。方法 将60只雄性昆明小鼠随机分成对照组（Control）、力竭运动组（EE）、SFN低剂量组（SFN-L,20 mg/kg/d）、SFN中剂量组（SFN-M,40 mg/kg/d）和SFN高剂量组（SFN-H,60 mg/kg/d）,每组12只。共给药4周,然后进行力竭运动。测定各组小鼠肌酸激酶（CK）、乳酸（LA）、乳酸脱氢酶（LDH）、丙二醛（MDA）、超氧化物歧化酶（SOD）和过氧化氢酶（CAT）水平。苏木精-伊红染色观察组织病理学改变。透射电镜观察线粒体超微结构。通过测定柠檬酸合成酶（CS）、琥珀酸脱氢酶（SDH）及肝脏和股四头肌糖原含量来评估能量水平。用RT-qPCR和Western blot检测骨骼肌中与线粒体自噬相关的mRNA和蛋白表达水平。结果 与EE组相比,SFN-L组、SFN-M组和SFN-H组的CK、LA、LDH和MDA水平显著降低,而SOD和CAT活性显著升高（P<0.05）。SFN明显减轻了EE小鼠的骨骼肌损伤并改善了线粒体形态。与EE组相比,SFN-L组、SFN-M组和SFN-H组的肝糖原和肌糖原含量、CS表达和SDH活性显著升高（P<0.05）。与EE组相比,SFN-L组、SFN-M组和SFN-H组小鼠股四头肌组织中PINK1、Parkin、Lc3-Ⅱ、p62和ubiquitin的蛋白表达水平显著降低（P<0.05）。与EE组相比,SFN-L组、SFN-M组和SFN-H组小鼠股四头肌组织中PINK1和Parkin的mRNA表达水平显著降低（P<0.05）。结论 SFN通过抑制PINK1/Parkin信号通路介导的线粒体自噬来发挥抗疲劳作用。