猪HUMMLC2B基因第一内含子单核苷酸多态与胴体、肉质性状的相关分析

快肌肌浆球蛋白轻链2(fast skeletal myosin light chain2,HUMMLC2B或MYLPF)是一种钙结合蛋白,参与多种生命活动.实验获得克隆猪HUMMLC2B基因(GenBank登录号:DQ533994),并采用PCR-RFLP技术,分析了HUMMLC2B基因第1内含子中的Msp Ⅰ酶切多态(T613C)在7个品种猪中的多态性分布;分析了多态性与36头长白猪、5个群体104头猪以及长白和5个群体之和的140头猪胴体性状和肉质性状间的相关,结果表明,在检测的猪群中除长白猪中A等位基因与B等位基因频率的比例为1:2外,其余的均为B等位基因占绝对优势,且A等位基因纯合个体只在长白猪中检测到.在不同组合的相关性分析中,基因型效应与瘦肉率、眼肌高度、眼肌面积肌内脂肪和肌内水分等差异极显著(P<0.01)或显著(P<0.05).HUMMLC2B基因在12个猪器官或组织中均表达,在心脏和骨骼肌中表达量最高.     

应用酵母双杂交系统筛选与CASTOR相互作用的蛋白

CASTOR编码百脉根中的离子通道蛋白，它是共生途径上的功能基因，作用于结瘤因子诱导产生的钙离子激增（calcium spiking）信号转导途径的上游，突变后不能形成根瘤。为了进一步揭示CASTOR调控共生信号途径的分子机制，本文通过酵母双杂交系统在百脉根的cDNA文库中筛选可能与CASTOR相互作用的蛋白，以酵母配合的方法初筛获得111个阳性克隆，经β- Gal检测进一步确认有99个蓝色克隆子，测序以及NCBI BLAST比对分析鉴定出JAB1、CLPA、钙调素结合的翻译延伸因子等7种可能与CASTOR相互作用的蛋白，利用RT-PCR方法检测了这些基因在接种以及不接种根瘤菌的百脉根中的表达水平，分析推测CASTOR可能与上述蛋白形成复合物参与共生信号的转导。     

利用单根肌纤维法分离和培养猪骨骼肌卫星细胞及其成肌诱导分化

建立单根肌纤维法体外培养猪骨骼肌卫星细胞的体系,了解其增殖和成肌特性。通过Ⅰ型胶原酶消化,从猪骨骼肌中分离完整的单根肌纤维并培养,用细胞免疫荧光鉴定肌纤维上的卫星细胞,随后对从单根肌纤维上游离出来的卫星细胞进行细胞免疫荧光染色,传代培养,成肌诱导分化和Western blot分析骨骼肌卫星细胞成肌特异性蛋白的表达。结果显示:分离并培养的单根肌纤维上附着有卵圆形的细胞,并随时间的推移,细胞缓慢向外迁移并增殖,卫星细胞特异性标志基因对盒转录因子(Paired protein box,Pax7)和成肌分化抗原(Myogenic Differentiation Antigen,MyoD)免疫荧光染色呈阳性,且阳性率达到90%以上。成肌诱导分化后,细胞开始汇合,并呈方向性生长,最终形成多核肌管,且成肌特异性标志基因Myogenin和myosin heavy chain(MyHC)表达呈阳性。MyoD蛋白高表达于增殖期,而Myogenin和MyHC在进入分化期才表达。该实验成功建立了猪骨骼肌单根肌纤维的体外培养方法并获得了高纯度的卫星细胞,为骨骼肌卫星细胞进行活体移植治疗相关疾病研究提供了实验材料。     

纳米铜对大鼠肝毒性相关蛋白磷脂酰乙醇胺结合蛋白1(PEBP1)的分离鉴定及生物信息学分析

为筛选纳米铜对大鼠(Rattus norvegicus)肝脏毒性的差异蛋白,探讨其毒性作用机制,本研究应用双向电泳(two dimensional gel electro-phoresis,2-DE)和质谱等蛋白质组学方法,分离和鉴定肝毒性相关差异蛋白,并利用荧光定量PCR验证和生物信息学分析。结果共筛选到显著差异表达的蛋白斑点共43个,其中下调的一个差异蛋白点1006被鉴定为磷脂酰乙醇胺结合蛋白1(phosphatidy lethanolamine-binding protein 1,PEBP1);荧光定量PCR验证与双向电泳结果一致。PEBP1蛋白的生物信息学分析表明其性质稳定,不存在信号肽,定位于细胞质,可能属于非分泌性蛋白,含磷脂酰乙醇胺结合蛋白家族信号位点64YTLVLTDPDAPSRKDPKFREWHH86;主要二级结构元件为无规则卷曲和延伸链。同源性分析表明,大鼠PEBP1蛋白与其他9个物种有较高同源性,并构建了PEBP1蛋白的系统进化树。中毒组大鼠肝脏PEBP1蛋白表达下调,导致肝细胞线粒体功能障碍,可能是纳米铜发挥毒性作用的途径之一。     

猪UMMLC2B基因第一内含子单核苷酸多态与胴体、肉质性状的相关分析

快肌肌浆球蛋白轻链2（fast skeletal myosin light chain 2,HUMMLC2B 或 MYLPF）是一种钙结合蛋白,参与多种生命活动。实验获得克隆猪HUMMLC2B基因（GenBank登录号：DQ533994）,并采用PCR．RFLP技术,分析了HUMMLC2B基因第1内含子中的MspⅠ酶切多态（T613C）在7个品种猪中的多态性分布;分析了多态性与36头长白猪、5个群体104头猪以及长自和5个群体之和的140头猪胴体性状和肉质性状间的相关,结果表明,在检测的猪群中除长白猪中A等位基因与B等位基因频率的比例为1：2外,其余的均为B等位基因占绝对优势,且A等位基因纯合个体只在长白猪中检测到。在不同组合的相关性分析中,基因型效应与瘦肉率、眼肌高度、眼肌面积肌内脂肪和肌内水分等差异极显著（P〈0．01）或显著（P〈0．05）。HUMMLC2B基因在12个猪器官或组织中均表达,在心脏和骨骼肌中表达量最高。     

鸡肉在成熟过程中肌原纤维蛋白的降解机制研究

为了探讨肉在成熟过程中肌原纤维蛋白的降解机制,五只肉鸡分别宰杀后,迅速取出胸肉约3 g为0 d样品,其余肉样剪碎后随机分成六组,一组作为对照,另5组分别用30 mmol/L EGTA、20 mmol/L CaCl2、酶复合抑制剂、100μmol/L细胞凋亡酶3抑制剂（DEVD-CHO）、20 mmol/L CaCl2和酶复合抑制剂处理,在4℃成熟1、3、7 d后取样。通过SDS-PAGE和蛋白质印迹分析测定了骨骼肌中和肉嫩度高度相关的拌肌球蛋白（titin）、伴肌动蛋白（nebulin）、肌间线蛋白（desmin）、肌钙蛋白T（troponin-T）的降解变化。结果显示蛋白水解酶复合抑制剂和DEVD-CHO抑制了蛋白的降解,单独的钙离子加速蛋白降解。这表明肉的成熟是内源酶的作用,钙离子很可能通过激活钙激活酶发挥作用,另外细胞凋亡酶3也很可能参与了肉的成熟。     

JAK2/STAT3信号通路对小鼠骨骼肌发育和能量代谢相关基因mRNA表达的影响

利用AG490特异性抑制剂阻断Janus蛋白酪氨酸激酶2(JAK2)/信号转导和转录激活子3(STAT3)信号通路,研究该通路对骨骼肌发育和能量代谢相关基因mRNA表达水平的影响.雄性健康昆明小白鼠(Mus musculus),用JAK2特异性抑制剂AG490连续腹腔注射15 d,定期测体重和体温,小鼠处死后取腿肌提取总RNA,利用RT-PCR检测JAK2/STAT3信号通路关键因子JAK2和STAT3、骨骼肌发育相关基因成肌分化因子(MyoD)和生肌决定因子(Myf5)及能量代谢相关基因肝X受体(LXRα)和解偶联蛋白3(UCP3)mRNA表达.结果显示,与对照组相比,处理组小鼠体重下降,差异显著(P<0.05);小鼠体温维持在正常浮动范围内;JAK2和STAT3mRNA表达量下降,差异显著(P<0.05);骨骼肌发育相关基因MyoD和Myf5mRNA表达量下降,差异极显著(P<0.01);能量代谢相关基因LXRα和UCP3 mRNA表达量下降,差异极显著(P<0.01).结果提示JAK2/STAT3信号通路可通过降低骨骼肌发育和能量代谢相关基因的mRNA表达而调节骨骼肌发育和能量代谢.     

氨基酸转运蛋白介导植物免疫研究进展

植物生长发育需要大量的氮素养分,氨基酸作为大多数植物体内主要的氮素运输形式,影响植物整个生命活动。氨基酸转运蛋白负责氨基酸在组织和细胞间的跨膜运输,其通过调节植物体内氨基酸稳态,影响着植物的生长发育和抗逆能力。近年来,氨基酸和氨基酸转运蛋白在植物免疫和抗病中的功能及其调控机制取得了一些突破性的研究进展。我们详细阐述了氨基酸运输、代谢在植物防御中的作用,总结了参与植物免疫的氨基酸透性酶家族(AAPs)、赖氨酸组氨酸转运蛋白家族(LHTs)、阳离子氨基酸转运蛋白家族(CATs)以及多种酸进出转运蛋白家族(UMAMITs)基因在病原菌侵染植物过程中的调节机制。转运蛋白LHT1不仅介导植物根系氨基酸的吸收和地上部氨基酸的转运,还参与了植物生长和免疫调节。本文以LHT1为例,对比了拟南芥和水稻lht1突变体植物在感染病原菌后自身的免疫过程,突出其在参与植物感染活体营养型和死体营养型病原菌过程中功能的差异性,构建了氨基酸转运蛋白调控植物免疫过程的基本分子模型。未来研究需要重点解析：1)哪些氨基酸是植物防御机制的关键营养或信号物质;2)病原菌侵染植物后,植物体内氨基酸信号的传导过程;3)植物氨基酸转...     

鸭PPARs启动子扩增、序列比较及其转录因子表达模式的聚类分析

过氧化物酶体增殖物激活受体(peroxisome proliferators-activated receptors,PPARs)是核激素受体超家族的一员,分α、β/δ、γ3个亚型,是调节细胞生长和分化的重要因子.为了解PPARs各成员在鸭(Anas platyrhynchos)骨骼肌发育中的不同作用,本研究克隆了鸭PPARα、PPARβ和PPARγ基因启动子区,预测其共同转录因子结合位点,用qRT-PCR检测PPARs及共同转录因子在鸭胚及出生后骨骼肌发育过程中的表达,比较表达模式并进行聚类分析.结果表明,扩增出鸭PPARα、PPAEβ和PPARγ启动子序列分别为2 526、1 631和2 942 bp,GenBank登录号分别为KX845431、KX845432和KX845433.鸭PPARs启动子区存在典型的CAAT-box、TATA-box顺式作用元件,预测存在共同的特异性蛋白1(specificity protein 1,Sp1)、核因子κB(nuclear factor kappa B,NF-κB)和CCAAT增强子结合蛋白(CCAAT/enhancer binding protein alpha,C/EBP-α)转录因子结合位点.PPARs成员在鸭胸肌、腿肌组织中均有表达.在胸肌中,转录因子NF-κB与PPARβ基因的表达模式一致;在腿肌中,Sp1、NF-κB、PPARβ和PPARγ的表达模式一致.PPARs各成员均参与了骨骼肌的发育调控,PPARβ作用可能更大;PPAPβ、PPARγ在鸭骨骼肌发育过程中的功能可能相似;此外,NF-κB可能调控PPARβ在骨骼肌中的表达.研究结果为PPARs基因的表达和功能鉴定提供理论依据.     

梅山猪氨肽酶基因N(pAPN)cDNA克隆、序列分析及重要变异位点的筛选

氨肽酶N(aminopeptidase N,APN)蛋白是猪(Sus scrofa)传染性胃肠炎病毒(Transmissible gastroenteritis virus,TGEV)和猪的流行性腹泻病毒(Porcine epidemic diarrhea virus,PEDV)等一系列冠状病毒的受体蛋白。为探讨梅山猪APN基因的分子结构特征以及重要的变异位点,本研究通过PCR扩增和测序技术,结合生物信息学分析梅山猪APN基因功能区域和重要变异位点,对其蛋白质结构进行预测和分析。结果表明,梅山猪APN基因cDNA全长2 886 bp(GenBank登录号:KF280271),含有20个外显子,编码961个氨基酸。与GenBank数据库公布的标准序列(登录号:NM_214277.1)相比,梅山猪APN基因编码区变异共引起10处氨基酸突变与2处氨基酸缺失,其中Phe82Asn、Leu107Phe、Leu108 Ile、Ser330Pro、Trp399Arg和Glu465 Gly等6处突变位于APN酶催化活性区域,Gln747His突变、748Tyr和749Ser缺失突变位于APN病毒结合区域。蛋白结构和编码产物功能分析发现,pAPN为不稳定的亲水性蛋白,无信号肽,具有1个跨膜螺旋(跨膜区位于12~34氨基酸,二级结构元件以α螺旋和β折叠为主,编码产物主要参与细胞被膜(cell envelope)、中央中间代谢(central intermediary metabolism)、辅酶因子生物合成(biosynthesis of cofactors)等功能。Gln747His、748Tyr和749Ser缺失突变可能与氨肽酶N结合病毒能力有关。本研究对梅山猪pAPN基因功能的分析及变异位点的筛选,为今后筛选猪抗病毒性腹泻的有效遗传标记提供理论基础。     

AGE-induced interference of glucose uptake and transport as a possible cause of insulin resistance in adipocytes

The purpose of this study was to investigate the distinct roles of advanced glycation end products (AGEs) on insulin-mediated glucose disposal in 3T3-L1 adipocytes and C2C12 skeletal muscle cells. AGE-modified proteins, namely, GO-AGEs, were prepared by incubating bovine serum albumin (BSA) with glyoxal (GO) for 7 days. Glucose utilization rates and the expression of insulin signaling-associated proteins, including Akt, insulin receptor substrate-1, and glucose transporter 4, were determined. GO-AGEs caused insulin resistance (IR) by suppressing insulin-stimulated glucose uptake both in 3T3-L1 adipocytes and C2C12 muscle cells. Interestingly, an unexpected finding was that insulin-stimulated glucose transport in adipocytes was affected by GO-AGEs in a biphasic manner, with an initial steep increase (168%) during the first 8 h of incubation followed by a significantly impaired uptake after extended culture times (24-48 h, p < 0.05). Treatment with GO-AGEs for 24 h markedly accelerated lipid droplet formation compared to the BSA control; however, it was blocked by incubation with an anti-RAGE antibody. Our study suggests that GO-AGEs induce an early dramatic elevation of glucose transport in adipocytes that may be related to the activation of insulin signaling; however, subsequent IR may result from increased oxidative stress and proinflammatory TNF-α production.     

Double phosphorylation of the myosin regulatory light chain during rigor mortis of bovine Longissimus muscle

To investigate changes in myosin light chains (MyLCs) during postmortem aging of the bovine longissimus muscle, we performed two-dimensional gel electrophoresis followed by identification with matrix-assisted laser desorption ionization time-of-flight mass spectrometry. The results of fluorescent differential gel electrophoresis showed that two spots of the myosin regulatory light chain (MyLC2) at pI values of 4.6 and 4.7 shifted toward those at pI values of 4.5 and 4.6, respectively, by 24 h postmortem when rigor mortis was completed. Meanwhile, the MyLC1 and MyLC3 spots did not change during the 14 days postmortem. Phosphoprotein-specific staining of the gels demonstrated that the MyLC2 proteins at pI values of 4.5 and 4.6 were phosphorylated. Furthermore, possible N-terminal region peptides containing one and two phosphoserine residues were detected in each mass spectrum of the MyLC2 spots at pI values of 4.5 and 4.6, respectively. These results demonstrated that MyLC2 became doubly phosphorylated during rigor formation of the bovine longissimus, suggesting involvement of the MyLC2 phosphorylation in the progress of beef rigor mortis. Keywords: Bovine; myosin regulatory light chain (RLC, MyLC2); phosphorylation; rigor mortis; skeletal muscle.     

Suppression of free fatty acid-induced insulin resistance by phytopolyphenols in C2C12 mouse skeletal muscle cells

It was reported that increased plasma levels of free fatty acids (FFAs) are associated with profound insulin resistance in skeletal muscle and may also play a critical role in the insulin resistance of obesity and type 2 diabetes mellitus. Skeletal muscle is the major site for insulin-stimulated glucose uptake and is involved in energy regulation and homeostasis. In this study, we used 12-O-tetradecanoylphorbol 13-acetate (TPA), a protein kinase C (PKC) activator, and palmitate to induce insulin resistance in C2C12 mouse skeletal muscle cells. Our data show that epigallocatechin gallate (EGCG) and curcumin treatment reduce insulin receptor substrate-1 (IRS-1) Ser307 phosphorylation, and curcumin is more potent to increase Akt phosphorylation in TPA induction. Moreover, we found that after 5 h of palmitate incubation, epicatechin gallate (ECG) can suppress IRS-1 Ser307 phosphorylation and significantly promote Akt, ERK1/2, p38 MAPK, and AMP-activated protein kinase activation. With a longer incubation with palmitate, IRS-1 exhibited a dramatic depletion, and treatment with EGCG, ECG, and curcumin could reverse IRS-1 expression, Akt phosphorylation, and MAPK signaling cascade activation and improve glucose uptake in C2C12 skeletal muscle cells, especially ECG and curcumin. In addition, treatment with these polyphenols can suppress acetyl-CoA carboxylase activation, but only EGCG could inhibit lipid accumulation in the intracellular site. These findings may suggest that curcumin shows the best capacity to improve FFA-induced insulin resistance than the other two, and ECG was more effective than EGCG in attenuating insulin resistance.     

Effects of dietary supplementation with cysteamine on growth hormone receptor and insulin-like growth factor system in finishing pigs

The present study was conducted to test the hypothesis that chronic cysteamine (CS) supplementation may affect serum insulin-like growth factor (IGF)-I concentrations and growth hormone (GH) receptor (GHR), IGF-I, IGF-I receptor (IGF-IR), IGF binding protein (IGFBP)-3, and insulin receptor (IR) mRNA levels in different tissues of finishing pigs. A total of 24 finishing pigs (60.05 +/- 1.24 kg; 12 gilts and 12 barrows) were assigned randomly to one of the three dietary groups, with four pens/group (per pen: one gilt, one barrow). The pigs were fed a basal diet containing 0 (control), 70, or 140 mg/kg cysteamine feed additive (containing 28% cysteamine hydrochloride) for 47 days. The results indicated that CS supplementation (70 mg/kg) increased the average daily gain (ADG) and serum IGF-I level, upregulated mRNA levels of GHR and IGF-I (liver, stomach, muscle), IGF-IR (stomach, duodenum, muscle), and IGFBP-3 (liver) but downregulated IGFBP-3 (stomach, duodenum, muscle). CS supplementation (70 mg/kg) did not affect mRNA levels of GHR and IGF-I (duodenum), IGF-IR (liver), and IR (liver, stomach, duodenum, muscle). CS supplementation (140 mg/kg) downregulated GHR (duodenum), IGF-I, and IGF-IR mRNA (liver, stomach, duodenum, muscle) but upregulated IGFBP-3 and IR mRNA (liver, stomach, duodenum, muscle) and did not affect ADG and serum IGF-I concentration. Collectively, the results suggest that dietary CS supplementation modulates the growth rate, serum IGF-I concentrations, and the gene expression of GHR, IGF-I, IGF-IR, IGFBP-3, and IR in a dose-dependent manner. CS supplementation has tissue-specific regulation of GHR, IGF-I, IGF-IR, and IGFBP-3 mRNA levels. Moreover, the results also imply the possible physiologic role of the GH-IGF axis in mediating the dietary CS supplementation-supported growth of finishing pigs.     

In vitro proteolysis of myofibrillar proteins from beef skeletal muscle by caspase-3 and caspase-6

The objective of the study was to investigate in vitro degradation of myofibrils by caspase-3 or -6. Myofibrillar proteins prepared from beef skeletal muscle were incubated with caspase-3 or -6 at 30 °C for 2 or 12 h, and subsequently, protein degradation was detected. Results showed that caspase-3 and -6 reproduced the degradation patterns of titin and nebulin observed during normal postmortem (PM) aging; however, they only reproduced the 28 kDa fragment derived from troponin-T. Caspase-3 induced only minor degradation of desmin. However, caspase-6 caused increasing degradation of desmin with extended incubation time and produced three degradation fragments (45, 29, and 27 kDa) of which only the 45 kDa fragment has been reported in aged beef. Therefore, caspase-3 or -6 could only reproduce a part of myofibrillar protein degradation or degradation fragments observed in naturally aged meat and may be involved in PM proteolysis of muscle proteins together with other endogenous proteases.     

Ability of carnosine and other skeletal muscle components to quench unsaturated aldehydic lipid oxidation products

Breakdown of lipid peroxides results in the formation of aldehydic compounds which are toxic to biological systems and deleterious to food quality. To determine the potential of skeletal muscle compounds to protect biomolecules from lipid oxidation products, the ability of carnosine and various other related compounds to quench monounsaturated and polyunsaturated aldehydes was investigated. Carnosine, the most abundant dipeptide in skeletal muscle, is capable of quenching alpha,beta-monounsaturated aldehydes and 4-hydroxy-2-trans-nonenal (HNE) more effectively than its constituent amino acid. Carnosine (5 mM) reduced 44% of headspace trans-2-hexenal (0.5 mM) after 1 h incubation at 40 degrees C and pH 7.4. Other histidine-containing dipeptides and the amine compounds, spermine and spermidine, had similar or slightly lower quenching activity than carnosine. Glutathione and thioctic acid had superior quenching ability than carnosine, but their overall contribution to aldehyde quenching compared to carnosine is limited due to their lower concentration in skeletal muscle. The results suggest that carnosine could be important for decreasing the toxicity of lipid oxidation products in biological systems and for minimizing rancidity in muscle foods.     

Peroxynitrite-induced oxidation of lipids: implications for muscle foods.

Peroxynitrite (ONOO(-)), formed from the nearly diffusion limited reaction between nitric oxide and superoxide, could be an important prooxidant in muscle foods. The objective of this study was to determine whether peroxynitrite caused oxidation of pyrogallol red, liposomes, muscle microsomes, and skeletal muscle homogenate. Oxidation of pyrogallol red, liposomes, and microsomes initiated by peroxynitrite continuously produced by 3-morpholinosydnonimine (SIN-1, 2 mM) was time-dependent and enhanced by CO(2) (1 mM). Reagent peroxynitrite (2 mM) caused concentration-dependent oxidation of pyrogallol red, liposomes, and muscle microsomes that was very rapid with no change after 5 min. Peroxynitrite-induced oxidation was suppressed by CO(2) and low pH. Skeletal muscle homogenate oxidized by reagent peroxynitrite (0.5 mM) exhibited gradual oxidation with time and was suppressed by CO(2), low pH, and metal chelators. These data suggest that peroxynitrite could be an important prooxidant in muscle foods.     

连续施用无害化污泥对沙质潮土土壤肥力和微生物学性质的影响

以小麦-玉米轮作体系下的沙质潮土为研究对象,选用经无害化处理后的城市污泥产物,通过2013~2015年田间定位试验,研究了不同城市污泥施用量对土壤肥力的影响,以期为城市污泥资源化利用提供理论基础和技术依据。设置单施化肥(CK)、CK+污泥15 t·hm~(-2)(CS1)、CK+污泥30 t·hm~(-2)(CS2)和CK+污泥45 t·hm~(-2)(CS3)共4个处理。主要研究结果如下:(1)连续定位试验结果表明,同一施用量污泥处理的土壤p H值随施用时间的增加呈下降趋势;土壤有机质(SOM)和养分含量如全氮(TN)、有效磷(AP)和速效钾(AK)随施用时间的增长呈上升趋势;(2)与CK比较,在2015年玉米季施用污泥各处理的土壤p H值显著降低了0.34~0.83个单位(P0.05),且与污泥施用量呈反比,以高施量污泥45 t·hm~(-2)下降最多;土壤SOM、TN、AP和AK分别显著提高了52.1%~166.9%、77.3%~177.8%、215.7%~486.3%和167.2%~379.0%(P0.05),且与污泥施用量呈正比,以高施量污泥45 t·hm~(-2)效果最显著;(3)试验所用污泥施用量范围内不会造成土壤和植物籽粒重金属污染,能够保持土壤环境健康;(4)与CK比较,施用污泥各处理土壤微生物量碳(MBC)、氮(MBN)含量均显著提高(P0.05),且与污泥施用量呈正比,并且季节不同也显著影响土壤MBC、MBN含量(P0.05);施用污泥能够显著提高土壤MBC/MBN(P0.05),说明施用污泥能够改变土壤微生物群落组成;(5)施用污泥,尤其是高施量污泥45 t·hm~(-2),在保证土壤和植物籽粒质量安全下,其土壤培肥效果最优。     

Areas with high concentrations of selenium in the soil and forage produce beef with enhanced concentrations of selenium

Beef provides a significant portion of human dietary selenium (Se), and it is possible that modest portions of beef produced in areas with high-Se soil and forage could provide the entire Recommended Dietary Allowance (RDA) for Se. The present study has addressed the environmental conditions that resulted in the production of high-Se beef. One hundred and thirty-eight cull cows were obtained from 21 ranches in five distinct geographic regions that, on the basis of soil parent material, reports of Se deficiency, and previous soil and forage Se surveys, were likely to have high or low Se concentrations in the soil. Grass and soil samples were taken from ranch sites, and hair, whole blood, skeletal muscle, diaphragm muscle, and liver samples were obtained from the animals. Hair and whole blood samples were taken 1 day prior to shipping. Selenium concentrations of all samples were determined by hydride generation atomic absorption spectroscopy. Geographic origin affected Se content of all samples (p < 0.05). Selenium concentrations in soil (r = 0.53; p < 0.01) and grass (r = 0.63; p < 0.01) were correlated to Se content of skeletal muscle. Selenium concentrations in whole blood, diaphragm, hair, and liver also were significantly correlated to Se content of skeletal muscle (p < 0.01). Cows that received Se in mineral supplements did not have significantly higher concentrations of Se in sampled tissues (p > 0.05). Results of this study suggest that the greatest source of variation in Se content of bovine skeletal muscle was the geographic region from which the beef originated and not production or management practices. Results also demonstrated that a 100 g serving of high-Se beef could provide 100% of the RDA for Se.