猪血清酶和氟烷敏感性与肌肉品质关系的研究

 本文用54头ES系和30头斯格猪对血清肌酸激酶[CK，EC#-（2，7，3，2）]、乳酸脱氢酶[LDH，EC#-（1，1，1，2）]和氟烷敏感性与肌肉品质的关系进行了研究。结果表明：常规和药物应激后采血时血清CK活性与宰后45分钟肉质指标存在显著性相关（P＜0.01），血清LDH#-5同工酶和肉质指标高度相关（P＜0.001）。并且血清1ogCK值和LDH#-5同工酶在轻度PSE和正常肌肉猪之间存在极显著差异（P＜0.01）；氟烷阳性猪宰后表现典型PSE肌肉（斯格猪n=3），氟烷阴性宰后虽然未发生典型PSE肌肉，但存在轻度PSE肌肉胴体。     

Regulation of protein degradation pathways by amino acids and insulin in skeletal muscle of neonatal pigs

Background

The rapid gain in lean mass in neonates requires greater rates of protein synthesis than degradation. We previously delineated the molecular mechanisms by which insulin and amino acids, especially leucine, modulate skeletal muscle protein synthesis and how this changes with development. In the current study, we identified mechanisms involved in protein degradation regulation. In experiment 1, 6- and 26-d-old pigs were studied during 1) euinsulinemic-euglycemic-euaminoacidemic, 2) euinsulinemic-euglycemic-hyperaminoacidemic, and 3) hyperinsulinemic-euglycemic-euaminoacidemic clamps for 2 h. In experiment 2, 5-d-old pigs were studied during 1) euinsulinemic-euglycemic-euaminoacidemic-euleucinemic, 2) euinsulinemic-euglycemic-hypoaminoacidemic-hyperleucinemic, and 3) euinsulinemic-euglycemic-euaminoacidemic-hyperleucinemic clamps for 24 h. We determined in muscle indices of ubiquitin-proteasome, i.e., atrogin-1 (MAFbx) and muscle RING-finger protein-1 (MuRF1) and autophagy-lysosome systems, i.e., unc51-like kinase 1 (UKL1), microtubule-associated protein light chain 3 (LC3), and lysosomal-associated membrane protein 2 (Lamp-2). For comparison, we measured ribosomal protein S6 (rpS6) and eukaryotic initiation factor 4E (eIF4E) activation, components of translation initiation.

Results

Abundance of atrogin-1, but not MuRF1, was greater in 26- than 6-d-old pigs and was not affected by insulin, amino acids, or leucine. Abundance of ULK1 and LC3 was higher in younger pigs and not affected by treatment. The LC3-II/LC3-I ratio was reduced and ULK1 phosphorylation increased by insulin, amino acids, and leucine. These responses were more profound in younger pigs. Abundance of Lamp-2 was not affected by treatment or development. Abundance of eIF4E, but not rpS6, was higher in 6- than 26-d-old-pigs but unaffected by treatment. Phosphorylation of eIF4E was not affected by treatment, however, insulin, amino acids, and leucine stimulated rpS6 phosphorylation, and the responses decreased with development.

Conclusions

The rapid growth of neonatal muscle is in part due to the positive balance between the activation of protein synthesis and degradation signaling. Insulin, amino acids, and, particularly, leucine, act as signals to modulate muscle protein synthesis and degradation in neonates.     

Effects of dietary vitamin and fatty acid content in E on muscle vitamin E Aohan fine-wool sheep

Background： Increasing the polyunsaturated fatty acid （PUFA） content and decreasing the saturated fatty acid （SFA） content of mutton can help to improve its nutritional value for consumers. Several laboratories have evaluated the effects of vitamin E on the fatty acid （FA） composition of muscle in sheep. However, little information is available on wool sheep, even though wool sheep breeds are an important source of mutton, especially in northern China where sheep are extensively farmed. The present study was designed to address the effects of vitamin E on muscle FA composition in male Aohan fine-wool sheep. Methods： Forty-two male Aohan fine-wool lambs （5 mo old） with similar initial body weight were randomly divided into seven groups and fed diets supplemented with 0 （control group）, 20, 100, 200, 1,000, 2,000, or 2,400 IU/sheep/d vitamin E for 12 mo. Three lambs from each group were slaughtered to measure vitamin E and FA content in the Iongissimus lumborum （LL） and gluteus medius （GM） muscles. Results： Vitamin E concentrations in the LL and GM increased significantly after 12 mo of vitamin E supplementation （P 〈 0.05）. However, this increase did not occur in a dose-dependent manner because the muscle vitamin E concentration was highest in the 200 IU/sheep/d group. Dietary vitamin E supplementation also caused a significant reduction in SFA content and an increase in monounsaturated FA （MUFA） content in the LL and GM （P 〈 0.05）. All six doses of vitamin E significantly increased cis9 tronsl -conjugated linoleic acid （cgtl -CLA） content in the LL compared with the control group （P 〈 0.05）. Conclusions： Dietary supplementation with vitamin E increased muscle vitamin E content and improved the nutritional value of mutton by decreasing SFA content and increasing MUFA and c9tl 1-CLA contents in Aohan fine-wool sheep. These effects were greatest in sheep fed a diet containing 200 IU/sheep/d vitamin E.     

重金属镉在文蛤体内的富集和消除研究

[目的]研究重金属Cd在文蛤体内的富集和消除规律及其食用安全性.[方法]将文蛤在Cd2＋浓度为0、0.01、0.10、1.00、2.00mg/L试验海水中染毒.[结果]文蛤对Cd具有较强的富集能力.随着染毒时间的延长和Cd2＋浓度的增加,Cd在文蛤体内的富集量也相应增加.[结论]文蛤内脏团中Cd的富集和代谢能力均大于闭壳肌,说明食用闭壳肌是安全的.     

不同营养水平对虹鳟肌肉组织学的影响

[目的]探究不同营养水平对虹鳟肌肉组织学的影响。[方法]设计4种不同蛋白质水平(4种蛋白质水平分别为40.15%、38.92%、37.69%和36.45%)的基础日粮,通过显微镜对组织切片的观察,研究不同营养水平对虹鳟肌肉组织学的影响。[结果]随着基础日粮中蛋白质水平的增加,虹鳟肌肉肌纤维密度减小、肌纤维直径增大。其中,高蛋白质水平组(粗蛋白含量40.15%)肌纤维密度最小,4周时为(426.59±6.41)n/mm2,8周时为(395.43±13.26)n/mm2,肌纤维直径最大,4周时达到(50.92±3.17)μm,8周时达到(54.82±6.22)μm;低蛋白质水平组(粗蛋白含量36.45%)肌纤维密度最大,而肌纤维直径最小,4周时分别为(617.76±7.02)n/mm2、(44.67±0.86)μm;8周时分别为(543.67±2.65)n/mm2、(48.31±3.41)μm。[结论]为虹鳟的理论研究和生产实践提供了依据。     

Niacin supplementation induces type II to type I muscle fiber transition in skeletal muscle of sheep

Background

It was recently shown that niacin supplementation counteracts the obesity-induced muscle fiber transition from oxidative type I to glycolytic type II and increases the number of type I fibers in skeletal muscle of obese Zucker rats. These effects were likely mediated by the induction of key regulators of fiber transition, PPARδ (encoded by PPARD), PGC-1α (encoded by PPARGC1A) and PGC-1β (encoded by PPARGC1B), leading to type II to type I fiber transition and upregulation of genes involved in oxidative metabolism. The aim of the present study was to investigate whether niacin administration also influences fiber distribution and the metabolic phenotype of different muscles [M. longissimus dorsi (LD), M. semimembranosus (SM), M. semitendinosus (ST)] in sheep as a model for ruminants. For this purpose, 16 male, 11 wk old Rhoen sheep were randomly allocated to two groups of 8 sheep each administered either no (control group) or 1 g niacin per day (niacin group) for 4 wk.

Results

After 4 wk, the percentage number of type I fibers in LD, SM and ST muscles was greater in the niacin group, whereas the percentage number of type II fibers was less in niacin group than in the control group (P < 0.05). The mRNA levels of PPARGC1A, PPARGC1B, and PPARD and the relative mRNA levels of genes involved in mitochondrial fatty acid uptake (CPT1B, SLC25A20), tricarboxylic acid cycle (SDHA), mitochondrial respiratory chain (COX5A, COX6A1), and angiogenesis (VEGFA) in LD, SM and ST muscles were greater (P < 0.05) or tended to be greater (P < 0.15) in the niacin group than in the control group.

Conclusions

The study shows that niacin supplementation induces muscle fiber transition from type II to type I, and thereby an oxidative metabolic phenotype of skeletal muscle in sheep as a model for ruminants. The enhanced capacity of skeletal muscle to utilize fatty acids in ruminants might be particularly useful during metabolic states in which fatty acids are excessively mobilized from adipose tissue, such as during the early lactating period in high producing cows.     

红茶提取物对猪肉品质及生化指标的影响

[目的]研究红茶提取物对猪肉品质及生化指标的影响。[方法]选60头50 kg左右的杜长大肥育猪,随机分为对照组和试验组,分别饲喂基础日粮和基础日粮＋2 g/kg红茶提取物。至猪体重达100 kg左右时,测猪肉的各项指标。[结果]试验组猪的屠宰性能提高,屠宰率显著提高（P〈0.05）;猪肉品质得到显著改善,肉色显著改善（P〈0.05）,肌肉丰度极显著提高（P〈0.01）;生化指标得到改善,肌苷酸显著提高（P〈0.05）,胆固醇显著下降（P〈0.05）,铁、锌含量显著提高（P〈0.05）。[结论]饲料中添加2 g/kg红茶提取物可改善猪肉品质。     

家蚕副肌球蛋白／小副肌球蛋白基因的克隆及进化分析

1材料与方法 1．1材料家蚕为该实验室保存的“大造”品系,25℃桑叶育,羽化后2h内收集家蚕蛾于-70℃保存备用。 1．2家蚕副肌球蛋白（PM）和小副肌球蛋白（mPM）cDNA的克隆     

藏猪肌肉纤维生长发育规律研究

[目的]探讨藏猪肌肉纤维性状的生长发育规律。[方法]对藏猪公猪23头、母猪20头进行肌纤维性状测定。[结果]试验结果表明：2～6月龄藏公猪、藏母猪均出现肌纤维面积逐渐增大,其中藏公猪肌纤维增长幅度小于藏母猪。通过相关分析可知藏猪肌纤维面积与单位面积根数呈极显著负相关（P〈0．01）。[结论]该试验可为藏猪种质特性的深入研究提供参考。     

不同鸭品种肌纤维的发育规律研究

[目的]研究不同品种鸭在不同发育时期肌纤维的发育规律。[方法]采用电子显微镜观察相同条件下饲养10周的樱桃谷鸭、金定鸭、白羽番鸭、苏牧麻鸭（樱桃谷♂×金定♀）的胸肌肌纤维的超微结构,并测定肌原纤维的直径和肌节长度。[结果]随着日龄的增加,肌原纤维直径越来越粗,8周龄时达到高峰,然后保持稳定或有所下降;6周龄时,苏麻鸭的肌原纤维直径与其余3个品种差异显著（P〈0．05）;10周龄时苏麻鸭和白羽番鸭的肌节长度显著高于其他2个品种。各鸭品种肌纤维超微结构基本特征一致。[结论]该结果对鸭的选种及选育有着重要意义。