饥饿对异育银鲫主要器官组织游离氨基酸含量和生化组成的影响

异育银鲫在饥饿60d的过程中,设置11个时间点取样,采用茚三酮方法测定异育银鲫主要器官组织游离氨基酸总量,同时测定粗脂肪、粗蛋白、水分含量,探讨在饥饿过程中各器官组织生化组成和游离氨基酸库中游离氨基酸含量的变化规律。结果发现:①饥饿过程中,鲫鱼各器官组织粗脂肪和水分含量都有所降低,不同器官组织下降的趋势不一致;而全鱼、肌肉和肝胰脏粗蛋白含量基本保持不变。②饥饿0～60d,各器官组织游离氨基酸含量变化不一致。以饥饿60d和0d值比较,降低比例依次为肠道71.09%、肝胰脏70.95%、肌肉58.14%、肾脏50.02%、心脏38.87%,降低比例较大;而脾脏、大脑、性腺含量则变化不大。③整个饥饿过程,各器官组织游离氨基酸含量并不是一直下降的,部分器官组织出现上升的过程。游离氨基酸含量呈上升趋势的时间:肌肉和肠道出现在饥饿5～10d;全鱼、肾脏出现在5～20d;而肝脏、心脏在1～3d。     

冷却肉的营养与卫生

随着人们生活水平的不断提高，我国肉类消费发生了明显变化，呈现了从食用冷冻肉到温鲜肉、近年来又逐步发展到食用冷却肉的过程。１　冷却肉的特点刚屠宰完毕的猪胴体由于血液和氧气供应停止，正常代谢中断，肉中糖原在无氧条件下酵解产生乳酸，肉的ｐＨ值逐渐下降，导致肌肉蛋白凝固，肌纤维硬化、肌肉僵直，这一过程称为肉的僵直。在正常情况下，宰后２４ｈ猪肉ｐＨ值可降至５．８，在２～４℃条件下约经１～２天，肉在酸性介质中又逐渐软化，肉的营养价值提高、风味改善、嫩度增高，这个过程称为肉的成熟。本世纪初，随着制冷技术的发展…     

人参皂苷Rb1对微血管自律性舒缩活动及大鼠心肌微血管内皮细胞内钙瞬时变化的影响

探讨人参皂苷Rb1(GSRb1)对人合谷穴区皮内微血管自律性舒缩活动振幅及大鼠心肌微血管内皮细胞(RMMECs)内游离钙离子瞬时变化的影响。利用激光多普勒血流测定仪结合离子导入仪检测微血管自律性舒缩活动的振幅。利用激光共聚焦显微镜、钙离子荧光探针Fluo-3AM检测ATP引起的RMMECs细胞内钙离子的变化及Rb1对其的影响。结果表明:试验确定了能够引起RMMECs细胞内游离钙离子释放的ATP的最低量为0.5μg·mL-1,瞬时升高差异显著的剂量是0.7μg·mL-1,能够影响RMMECs细胞内钙离子变化的GSRb1的最低量为8μg·mL-1。RMMECs经8μg·mL-1 GSRb1孵育后,能够刺激细胞内游离钙离子释放的ATP的最低量升高为1.5μg·mL-1。本研究说明,提高微血管自律运动振幅的中药成分GSRb1能够通过对RMMECs胞内钙离子的影响,提高RMMECs对ATP的耐受能力(ATP的刺激量由0.5μg·mL-1升高到1.5μg·mL-1)。     

DNA甲基化与去甲基化调控肌肉发育研究进展

肌肉发育是一个复杂的生物学过程,其调控机制尚不完善。但近年来表观遗传修饰对肌肉发育的调控作用逐渐成为热点领域,研究发现DNA甲基化与去甲基化修饰对肌肉发生与发育起到重要的调控作用。肌肉干细胞特异位点通过DNA甲基化修饰,影响肌肉发育过程关键基因的表达,进而调控早期发育的生肌过程。本文主要围绕肌肉发育过程中DNA甲基化及去甲基化修饰的变化、重要的甲基转移酶和去甲基化酶以及营养物质通过DNA甲基化修饰影响肌肉发生的作用进行论述。     

北京鸭在不同发育时期血钙的变化

众所周知,血钙具有生理活性,能影响许多重要的生理过程,如骨的形成、神经传导、肌肉收缩、心脏活动、血液凝固、细胞膜和毛细血管的通透性、肾小管功能、某些酶的激活以及内分泌腺的激素分泌等多种器官或组织的机能活动。血清中的钙,统称“血清总钙”(血钙),可分为结合钙、络合钙和游离钙,它们各有不同的作用,游离的钙离子具有生理活性,而结合钙主要起“钙贮备”的作用。     

黄芪多糖对小鼠免疫细胞信号转导相关分子的影响

为探讨黄芪多糖(APS)免疫调节的作用机理，观察了黄芪多糖对小鼠腹腔巨噬细胞一氧化氮(NO)生成、对体外培养的小鼠脾脏淋巴细胞内游离钙离子水平和蛋白激酶C(PKC)活性的影响。结果显示黄芪多糖能明显促进小白鼠腹腔巨噬细胞NO生成，显著升高小鼠脾淋巴细胞内游离钙离子的水平，引起细胞PKC活性明显升高。提示黄芪多糖通过NO介导信号传递通路，调节脾淋巴细胞内游离钙离子的浓度，升高细胞蛋白激酶活性而影响机体免疫细胞的信号转导，发挥其免疫调节作用。     

钙蛋白酶在肉嫩化过程中的作用

钙蛋白酶在宰后肉类成熟过程中通过降解肌肉蛋白质而提高肉嫩度.作者阐述了与肉嫩化有关钙蛋白酶的结构,在肉宰后成熟过程中的嫩化作用,宰后活性变化及影响钙蛋白酶活性的理化因素等.     

草地藏系绵羊羊肉品质特性研究

对草地藏系绵羊羊肉的常规营养成分、总能、总糖、胆固醇、游离氨基酸、矿物质及羊肉嫩度进行了测定,并用分析了羊肉的可溶性蛋白含量及组分.研究结果表明草地藏系绵羊羊肉蛋白质含量高,脂肪含量适中,胆固醇含量低;游离氨基酸、矿物质含量丰富,肌肉细嫩;肌肉可溶性蛋白组分主要集中在分子量16.8 ku和96.8 ku之间.草地藏系绵羊肉质较好,具有较高的开发价值.     

莱芜猪肌肉组织学特性与肉质关系的研究

本研究采用二因子多水平有重复的试验方法,对１４头育肥莱芜猪不同屠宰体重及不同解剖部位肌肉的组织结构和肌纤维的组织学特性及肉质性状进行研究。结果表明：随屠宰体重的提高,肌肉纤维直径（ＤＭＦ）,密度（ＭＦＤ）和宰后僵直肌工降度（ＳＬ）没有发生显著变化（Ｐ〉０．０５）,组织学显示的肌肉３种构成分在不同体重组间差异也不显著,但除ｐＨ外,其他各测定性状在不同部位肌肉都存在极显著的差异（Ｐ〈０．０１）,研究下     

孕酮处理对蛋鸡蛋壳钙化过程中CaBP-d28k基因表达的影响

实验旨在研究孕酮对蛋鸡CaBP-d28k基因表达的影响。对产蛋高峰期蛋鸡进行孕酮和孕酮受体拮抗剂(RU-486)处理,利用实时荧光定量PCR技术(QRT-PCR),测定在蛋壳形成过程中输卵管子宫部钙结合蛋白(CaBP-d28k)、孕酮受体(PGR)的表达量;同时对血液中钙离子和孕酮浓度变化进行测定。结果表明:孕酮处理后,血液中钙离子浓度显著降低(P<0.05),输卵管子宫部CaBP-d28k表达量也显著降低(P<0.05);孕酮受体拮抗剂处理后,血液中钙离子浓度显著升高(P<0.05),输卵管子宫部CaBP-d28k表达量极显著升高(P<0.01)。结果提示,在蛋壳钙化过程中,孕酮对CaBP-d28k表达和钙离子转运起负调控作用。     

Production of dark firm dry meat in slaughtered pigs with so-called liver degeneration characterized by yellowish discoloration and high lipid contents

The livers which are discolored yellowish and have a large amount of lipids (liver degeneration) are frequently observed in slaughtered pigs. Dark firm dry (DFD) meat and liver degeneration have a common etiological agent of exhaustion in pigs before slaughter. The correlation between them was examined. In 65 cases of 77 slaughtered pigs with the degenerative liver, which contained more than 6.6% total lipids of liver wet weight, the carcasses showed early rigor mortis and the higher final pH above 6.0. R values of the muscles, which indicated the decrease of ATP, were higher. The meat had a DFD appearance and the muscle fibers had no tendency to shrink. These data showed that the pigs with liver degeneration produced DFD meat at a high rate. In 4 cases of 5 pigs exhausted experimentally by 53 hr fasting and hard exercise before slaughter, both liver degeneration and DFD meat were produced simultaneously. The livers of them were discolored and contained about 8.0% or more total lipids. The carcasses of them showed early rigor mortis and the higher final pH above 6.0. From these data, it was suggested that the exhaustion in pigs before slaughter caused both liver degeneration and DFD meat.     

Measurements of the degree of development of rigor mortis as an indicator of stress in slaughtered pigs

The degree of development of rigor mortis in the carcases of slaughter pigs was assessed subjectively on a three-point scale 35 minutes after they were exsanguinated, and related to the levels of cortisol, lactate and creatine kinase in blood collected at exsanguination. Earlier rigor development was associated with higher concentrations of these stress indicators in the blood. This relationship suggests that the mean rigor score, and the frequency distribution of carcases that had or had not entered rigor, could be used as an index of the degree of stress to which the pigs had been subjected.     

Comparison of postmortal changes in the ultrastructure of the masseter muscle and the longissimus dorsi muscle in pigs with PSE-meat]

Samples of the two muscles were taken from 8 Landrace fattened pigs, affected with pale, soft exudative meat, during stunning and 15, 30, 45 and 60 minutes after death; also 2, 3, 6, 12, 24 and 48 hours after slaughter, with storage at 20 degrees C for the first six hours and 2-5 degrees C subsequently. Considerable changes were found during the first hour after death, or even in samples taken during stunning, in longissimus dorsi samples. These consisted of destruction of mitochondria and sarcoplasmic reticulum, breakdown of cell membranes, liberation of clumps of fibre protein, disappearance of glycogen, rigor and destruction of capillaries. Such changes would account for the features of pale, soft exudative meat such as water loss, brief rigor, pale colour, deficiency of energy-rich phosphates. By contrast, in the masseter muscles of the same animal these changes did not occur until later, or were in port absent. In both muscle the breakdown of fibres took place by destruction of the "I" bands and the "Z" strips, and this process also commenced in longissimus dorsi before masseter.     

Changes in the muscle proteome after compensatory growth in pigs

Sixteen female pigs (Duroc x Landrace x Large White) were divided into 2 groups, which had either free access to the diet (control group) or were feed-restricted from d 28 to 80 and then had free access to the diet (compensatory growth group). The sensory analysis showed that the pigs exhibiting compensatory growth produced meat with increased tenderness compared with control pigs (P < 0.05). To gain further knowledge of the influence of compensatory growth on meat tenderness, the sarcoplasmic protein fraction of muscle tissue was studied at the time of slaughter and 48 h postmortem using proteome analysis. At slaughter, 7 different proteins were found to be affected by compensatory growth: HSC70, HSP27, enolase 3, glycerol-3-phosphate dehydrogenase, aldehyde dehydrogenase E2, aldehyde dehydrogenase E3, and biphosphoglycerate mutase. The HSC70 and HSP27 both belong to the heat shock family and are known to play a role during muscle development. Hence, they may be affected by compensatory growth and increased protein turnover. Forty-eight hours after slaughter, 8 different proteins were found to be affected by compensatory growth: myosin light chain (MLC) II, MLC III, sulfite oxidase, chloride intracellular channel 1, 14-3-3 protein gamma, elongin B, and phosphohistidine phosphatase 14. The changes observed on MLC II and MLC III could be a consequence of enzymatic cleavage in the neck region of the globular myosin head domain that causes the release of MLC II and MLC III from the actomyosin complex. It has previously been hypothesized that compensatory growth results in an increased postmortem proteolysis; thus it was presumed that the intensity of some protein fragments would be affected by compensatory growth. However, the peptides that were found to be affected at 48 h postmortem were all full-length proteins. The 14-3-3 protein gamma has been proposed to play a role in the contraction of muscle during rigor and may thereby have an effect on meat tenderness. This study reveals some very interesting changes in the muscle proteome affected by compensatory growth, which may be useful in understanding the relationship among compensatory growth, protein turnover, and meat tenderness.     

Effect of Chilling Method and Deboning Time on Broiler Breast Fillet Quality

A study was conducted to determine the effects of chilling method and postmortem aging time on broiler breast fillet quality. One hundred fifty eviscerated broiler carcasses were removed from a commercial processing line before chilling and transported to the laboratory. Half of the carcasses were chilled by dry air, whereas the other half were chilled by water immersion. Immersion-chilled (IC) carcasses were divided into 3 groups (0, 1.67, and 24 h) based on postchill fillet aging time on the carcass. Air-chilled (AC) carcasses were divided into 2 groups based on fillet aging time (0 and 24 h postchill). Because AC requires more time to reach the same temperature, fillets removed immediately after chilling (0 h) were the same postmortem age as the 1.67 h IC fillets. Average pH values of IC and AC fillets were similar when fillets were aged for the same length of time postmortem. Method of chilling had no effect on raw breast fillet color; however, postmortem aging time had a slight but significant effect on fillet lightness. Shear values of IC fillets removed 0 and 1.67 h after chilling were similar and corresponded to sensory panel categories of slightly tough to tough (>8 kg/g). Shear values of AC fillets deboned at 0 h (8.4 kg/g) were slightly lower but not significantly different than the shear values for IC fillets (10.3 kg/g) aged for the same length of time (1.67 h). After 24 h of aging, shear values for IC and AC fillets were <8 kg/g and corresponded to sensory panel categories of tender to very tender. Cook yield (%) of AC fillets was significantly higher than cook yield (%) of IC fillets for all deboning times. Results show that air chilling has an accelerating effect on rigor mortis onset, but postchill aging time is required to maximize the proportion of tender meat.     

不同饲养条件下海兰蛋鸡的肉心肝蛋中部分矿物质含量分析

研究不同饲养条件下海兰蛋鸡的肉、心、肝和蛋中矿物含量 ,以便采取合理的饲养方法 ,提高鸡肉、心、肝和蛋中的矿物质营养 ,为研制开发绿色营养食品提供科学依据。 60羽 7周龄海兰蛋鸡随机分成两大组 ,一组为对照组采用自由放养不供配合饲料 ;另一组则为试验组采取笼养并供给配合饲料。用火焰原子吸收分光光度法分别对鸡肉、鸡心、鸡肝和鸡蛋中 1 1种矿物质元素含量进行测定。结果表明试验组蛋清、蛋黄中的 Ca、P含量明显高于对照 ;而 6种微量元素在鸡肉、鸡心、鸡肝及鸡蛋中的含量 ,试验组也明显高于对照组。为人们合理膳食提供了科学依据     

Regulation of taste-active components of meat by dietary leucine

1. Regulation of meat taste is one effective method for improvement of meat quality. In this study, effects of dietary leucine (Leu) content on taste-active components, especially free glutamate (Glu), in meat were investigated. 2. Broiler chickens (28 d old) were fed on diets with graded dietary Leu content (100, 130 or 150% of Leu requirement in NRC, 1994) for 10 d before marketing. Taste-active components of meat (free amino acids and ATP metabolites) and sensory score of meat soup were estimated. 3. Free Glu content, the main taste-active component of meat, was significantly increased by dietary Leu. Compared with the Leu 130% group, free Glu was increased by 17% in the Leu 100% group. Free Glu of meat tended to decrease in the Leu 150% group. In contrast, inosine monophosphate content in meat did not change among all groups. 4. Sensory evaluation of meat soup from the Leu 100 and 150% groups showed that they had different meat tastes. Sensory scores of overall preference, umami taste and chicken-like taste were significantly higher in the Leu 100% group. 5. These results suggest that dietary Leu content is a regulating factor of free Glu in meat. Decreasing dietary Leu induces an increase in the free Glu content of meat and improves meat taste.     

Regulation of taste-active components of meat by dietary branched-chain amino acids; effects of branched-chain amino acid antagonism

1. The effects of dietary branched-chain amino acids (BCAAs) including leucine (Leu), isoleucine (Ile) and valine (Val) on taste-active components, especially free glutamate (Glu), in meat were investigated. 2. Broiler chickens (28 d old) were given varied dietary BCAA levels for 10 d before marketing. Dietary BCAA content ratios were either 100:100:100 (Low Leu group), 150:100:100 (Control group) or 150:150:150 (High Ile + Val group) for Leu:Ile:Val (% of each BCAA requirement according to NRC, 1994). Taste-related components of meat (free amino acids and ATP metabolites) and sensory scores of meat soup were estimated. 3. Free Glu content, the main taste-active component of meat, was significantly increased by dietary BCAA. Compared to the Control group, free Glu content increased by 30% in the High Ile + Val group. However, the inosine monophosphate (IMP) content in meat did not change among groups. 4. Sensory evaluation of meat soups showed that Control and High Ile + Val groups had different meat flavours. The sensory score of overall taste intensity was significantly higher in the High Ile + Val group. 5. These results suggest that dietary BCAA concentrations regulate free Glu in meat. Increasing dietary Ile + Val induces an increase in free Glu content of meat, improves meat taste and is more effective for increasing free Glu content in meat than decreasing dietary Leu level.     

Inosine‐5'‐monophosphate is a candidate agent to resolve rigor mortis of skeletal muscle

The object of the present study was to reveal the action of inosine‐5'‐monophosphate (IMP) toward myofibrils in postmortem muscles. IMP solubilized isolated actomyosin within a narrow range of KCl concentration, 0.19‐0.20 mol/L, because of the dissociation of actomyosin into actin and myosin, but it did not solubilize the proteins in myofibrils with 0.2 mol/L KCl. However, IMP could solubilize both proteins in myofibrils with 0.2 mol/L KCl in the presence of 1 m mol/L pyrophosphate or 1.0–3.3 m mol/L adenosine‐5'‐diphosphate (ADP). Thus, we presumed that pyrophosphate and ADP released thin filaments composed of actin, and thick filaments composed of myosin from restraints of myofibrils, and then both filaments were solubilized through the IMP‐induced dissociation of actomyosin. Thus, we concluded that IMP is a candidate agent to resolve rigor mortis because of its ability to break the association between thick and thin filaments.