奶牛瘤胃中一株纤维分解菌的筛选与鉴定

试验从奶牛瘤胃中分离得到1株纤维分解菌,研究其生化性质和种属分类.将富集的纤维分解菌群,通过厌氧平板分离培养得到纤维分解菌.利用全自动微生物分析系统的革兰氏阴性菌鉴定卡鉴定纤维分解菌的生化图谱,并对菌株16SrDNA进行PCR扩增并测序,与GenBank数据库中序列进行同源性比对,确定其种属分类地位.结果表明:通过体外培养,分离得到纤维分解菌CB11,纤维分解平均消失率达82%,革兰氏染色为阴性,绝对厌氧,能够产生β-半乳糖苷酶、β-葡萄糖苷酶、β-木糖苷酶等.通过建立系统发育树,CB11的16SrDNA序列与解肝素拟杆菌的相似度达99%.     

3种生理调节剂对山羊瘤胃液中脂肪酸组成的影响

研究3种生理调节剂对山羊瘤胃液中共轭亚油酸(CLA)前体反式油酸的积累与CLA含量的影响,选用8只装有永久性瘤胃瘘管的山羊,采用4×4拉丁方设计,试验设对照、葵花油、海南霉素和丙酮酸钙4个处理,每只山羊每天添喂剂量分别为0、0.3、0.05、0.05 g/kg体重。每两周采集瘤胃液样品,采用毛细管气相色谱法分析瘤胃液中反式油酸、CLA含量及其他脂肪酸组成,并对CLA与反式油酸含量进行了相关性分析。结果表明,3种生理调节剂都能在不同程度上提高C18∶1 trans-11(TVA)和CLA含量,其作用效果依次为葵花油>海南霉素>丙酮酸钙。瘤胃中TVA和CLA含量呈极显著正相关(P<0.01)。     

不同水分TMR对绵羊瘤胃纤维分解酶活力与微生物生态的影响

为探讨不同水分的全混合日粮(TMR)对绵羊瘤胃纤维分解酶活力和微生物生态的影响,以延边半细毛羊为为试材,手术安装瘤胃瘘管以接取瘤胃液进行试验,喂不另加水分的TMR日粮(A组)、加35%水分的TMR日粮(B组)、加50%水分的TMR日粮(C组)共3组,检测瘤胃pH值、瘤胃内纤毛虫数、瘤胃内酶活力。结果表明,瘤胃pH值A组略低于B、C组但各组之间差异不显著,瘤胃纤毛虫数和瘤胃内酶活力的变化与pH值的变化呈一致性,即不同水分的TMR直接影响瘤胃内pH值的变化,利于维持瘤胃内pH的平衡;间接影响瘤胃内纤毛虫数和酶活力,这有助于维持瘤胃内微生物生态环境的稳定。     

Impacts of the unsaturation degree of long-chain fatty acids on the volatile fatty acid profiles of rumen microbial fermentation in goats in vitro

This study investigated the impacts of the degree of unsaturation(unsaturity) of long-chain fatty acids on volatile fatty acid(VFA) profiles of rumen fermentation in vitro. Six types of long-chain fatty acids, including stearic acid(C18:0, control group), oleic acid(C18:1, n-9), linoleic acid(C18:2, n-6), α-linolenic acid(C18:3, n-3), arachidonic acid(C20:4, n-6) and eicosapentaenoic acid(C20:5, n-3), were tested. Rumen fluid from three goats fitted with ruminal fistulae was used as inoculum and the inclusion rate of long-chain fatty acid was at 3%(w/w) of substrate. Samples were taken for VFA analysis at 0, 3, 6, 9, 12, 18 and 24 h of incubation, respectively. The analysis showed that there were significant differences in the total VFA among treatments, sampling time points, and treatment×time point interactions(P0.01). α-Linolenic acid had the highest total VFA(P0.01) among different long-chain fatty acids tested. The molar proportion of acetate in total VFA significantly differed among treatments(P0.01) and sampling time points(P0.01), but not treatment×time point interactions(P0.05). In contrast, the molar proportion of propionate did not differ among treatments during the whole incubation(P0.05). However, for butyrate molar proportions, significant differences were found not only among sampling time points but also among treatments and treatment×time point interactions(P0.01), with eicosapentaenoic acid having the highest value(P0.01). Additionally, no statistically significant differences were found in the acetate to propionate ratios among treatments groups(P0.05), even the treatments stearic acid and α-linolenic acid were numerically higher than the others. The inclusion of 3% long-chain unsaturated fatty acids differing in the degree of unsaturation brought out a significant quadratic regression relation between the total VFA concentration and the double bond number of fatty acid. In conclusion, the α-linolenic acid with 3 double bonds appeared better for improving rumen microbial fermentation and the total VFA concentration.     

In vitro investigation of the effect of dairy propionibacteria on rumen pH,lactic acid and volatile fatty acids

Ruminal acidosis is a prevalent disorder in ruminants such as dairy cows and feedlot beef cattle, caused primarily by the inclusion of a high percentage of readily fermentable concentrates in the diet. The disorder presents as an accumulation of lactic acid, a decrease of p H in the rumen and a subsequent imbalance of the rumen fermentation process with detrimental impacts on the animal's health and productivity. Dairy propionibacteria, a group of bacteria characterised by utilization of lactic acid as the favoured carbon source, with propionic acid produced as a by-product, were evaluated in this study as potential direct-fed microbials for use in controlling ruminal acidosis. Acidosis was simulated by introduction of high concentrations of lactic acid into rumen fluid samples and a multi-strain in vitro analysis was conducted, whereby changes in p H and lactic acid metabolism were compared in identical acidified rumen samples, following inoculation with various propionibacteria. This was followed by a study to evaluate the effect of bacterial inoculation dosage on acid metabolism. The results indicated that lactic acid levels in the rumen fluid were significantly reduced, and propionic acid and acetic acid concentrations both significantly increased, following addition of propionibacteria. Significant ‘between strains' differences were observed, with Propionibacterium acidopropionici 341, Propionibacterium freudenreichii CSCC 2207, Propionibacterium jensenii NCFB 572 and P. jensenii 702 each producing more rapid reduction of lactic acid concentration than P. freudenreichii CSCC 2206, P. acidopropionici ATCC 25562 and Propionibacterium thoenii ATCC 4874. Furthermore, the efficacy of this application was dosage related, with the rates of reduction in lactic acid levels and production of propionic acid, both significantly greater for the higher(1010 cfu mL~(-1)) compared with lower(105 cfu mL~(-1)) dosage inoculation. The results confirmed that the introduction of propionibacteria could promote more rapid reduction of lactic acid levels than would occur without their addition, demonstrating their potential in controlling ruminal acidosis.     

脂肪酸值测定方法的研究

采用两种方法进行小麦粉脂肪酸值测定的对比实验，证明GB／T 15684－1995法与GB5510－85法存在差异性。分析了实验操作步骤对测定结果的影响，并对测定方法提出了建议。     

苏子油对瘤胃体外发酵模式、脂肪酸组成及甲烷生成的影响

为探讨苏子油对瘤胃体外发酵的影响,采用人工瘤胃技术分析不同添加水平的苏子油对瘤胃发酵模式、发酵参数和瘤胃脂肪酸代谢的影响.结果表明:添加不同剂量苏子油对发酵液pH值和氨氮(NH3-N)含量无显著影响(P0.05);与对照相比较,随着苏子油添加量的增加干物质降解率、中性洗涤纤维降解率、酸性洗涤纤维降解率、发酵底物单位产气量显著降低(P0.05),甲烷产量呈下降趋势(P0.05);对TVFA无显著影响(P0.05),丙酸含量显著增加(P0.05),乙酸含量和乙酸丙酸比例显著降低(P0.05);C18:1、c9,t11-CLA和总的长链脂肪酸浓度均明显升高(P0.01).表明在粮中添加一定量的苏子油,可改变瘤胃发酵类型、降低甲烷产量、调节瘤胃液脂肪酸组成.     

Nucleotide sequence of a bovine clone encoding the angiogenic protein, basic fibroblast growth factor

Basic and acidic fibroblast growth factors (FGF's) are potent mitogens for capillary endothelial cells in vitro, stimulate angiogenesis in vivo, and may participate in tissue repair. An oligonucleotide probe for bovine basic FGF was designed from the nucleotide sequence of the amino-terminal exon of bovine acidic FGF, taking into account the 55 percent amino acid sequence homology between the two factors. With this oligonucleotide probe, a full length complementary DNA for basic FGF was isolated from bovine pituitary. Basic FGF in bovine hypothalamus was shown to be encoded by a single 5.0-kilobase messenger RNA; in a human hepatoma cell line, both 4.6- and 2.2-kilobase basic FGF messenger RNA's were present. Both growth factors seem to be synthesized with short amino-terminal extensions that are not found on the isolated forms for which the amino acid sequences have been determined. Neither basic nor acidic FGF has a classic signal peptide.     

Enzyme specificity as a factor in regulation of fatty acid chain length in Escherichia coli

Various acyl-acyl carrier protein intermediates in saturated and unsaturated fatty acid biosynthesis were tested as substrates for beta-ketoacyl-acyl carrier protein synthetase. With both classes of substrates the condensing enzyme in fatty biosynthesis demonstrates specificities which indicate that it might be an important factor in determining fatty acid chain length in Escherichia coli.     

The effects of step-wise improvement of forage combination in total mixed rations on fatty acid profile in the rumen and milk of Holstein cows

Five lactating Holstein cows in a 5×5 Latin square experiment were fed five high-concentrate total mixed rations(TMRs) to investigate the effects of step-wise improvement of forage combination on ruminal and milk fatty acid profiles. The ratio of concentrate to forage was fixed as 61:39, and the step-wise improvement of forage combination was applied as: TMR1, a ration containing corn stover; TMR2, a ration containing corn stover and ensiled corn stover; TMR3, a ration containing ensiled corn stover and Chinese wild ryegrass hay(Leymus chinensis); TMR4, a ration containing the ryegrass hay and whole corn silage; TMR5, a ration containing the ryegrass hay, whole corn silage and alfalfa hay. The TMRs were offered to the cows twice daily at 0700 and 1900 h. The entire experiment was completed in five periods, and each period lasted for 18 days. Diurnal samples of rumen fluids were collected at 0100, 0700, 1300 and 1900 h(day 16); 0300, 0900, 1500 and 2100 h(day 17); and 0500, 1100, 1700 and 2300 h(day 18). The step-wise improvement of forage combination increased energy and crude protein contents and decreased fibre content. As a result, the step-wise improvement of forage combination increased dry matter intake and milk yield(P0.05). The step-wise improvement increased dietary content of linolenic acid(C18:3 n-3), but did not alter dietary proportions of palmitic acid(C16:0), stearic acid(C18:0), oleic acid(C18:1 cis-9), linoleic acid(C18:2 n-6) and arachidic acid(C20:0). In response to the forage combination, ruminal concentration of C16:0, C18:2 n-6 and C18:3 n-3 linearly increased against their dietary intakes(P0.10). The step-wise improvement increased milk contents of C10:0, C12:0, C14:0, C16:0, C18:2 n-6 and C18:3 n-3(P0.10) and decreased milk contents of C18:0 and C18:1 cis-9(P0.05). Milk yields of C16:0, C18:1 cis-9, C18:2 n-6 and C18:3 n-3 were linearly increased by the increase of these fatty acids in the rumen(R2≥0.79, P0.05), and milk yields of C18:2 n-6 and C18:3 n-3 were also positively correlated with dietary intake of these fatty acids(R2≥0.85, P0.05). The step-wise improvement increased the transfer efficiencies from feed to milk for C18:2 n-6 from 11.8 to 14.2% and for C18:3 n-3 from 19.1 to 22.3%. In a brief, along with the step-wise improvement of forage combination, more dietary linoleic and linolenic acids might escape microbial hydrogenation in the rumen and consequently accumulated in milk fat though these fatty acids were present in low concentrations in ruminal fluids. The step-wise improvement of forage combinations could be recommended as a dietary strategy to increase the transfer efficiency of linoleic and linolenic acids from feed to milk.     

芫菁体内脂肪酸组分的气相色谱分析

芫菁虫又名斑蝥,隶属于鞘翅目芫菁科昆虫。现代医学研究证明,斑蝥的药用成分主要是斑蝥素（Cantharidin;C10H12O4）,是一种倍半萜类物质。在长期的研究过程中,许多工作都是围绕着斑蝥素来开展的,而对于斑蝥体内其他物质的研究却很少,从而限制对这一宝贵资源的全面认识、客观评价及对其作为中药的深入了解。鉴于此,本研究对芫菁体内的脂肪酸组成进行测定分析。现将结果报告如下：     

Human platelet-derived growth factor (PDGF): amino-terminal amino acid sequence

Human platelet-derived growth factor (PDGF) obtained from outdated human platelets was subjected to amino-terminal amino acid sequence analysis by automated Edman degradation. Despite the apparent presence of limited proteolytic degradation of the protein derived from this method, the sequence analysis reveals two primary peptide sequences and suggests that active PDGF is composed of two, possibly homologous, peptides linked by a disulfide bond or bonds.     

Gibberellic acid: a growth factor in the unicellular alga Gymnodinium breve

Gibberellic acid stimulates growth in the unicellular alga Gymnodinium breve (dinoflagellate). The maximum effect was obtained with 10(-7) molar gibberellic acid, whereas concentrations greater than 5 x 10(-7) mole per liter were inhibitory. The effect of the compound is observed as a marked shortening of the lag period, which is normally 6 to 8 days after innoculation.     

Brain-derived acidic fibroblast growth factor: complete amino acid sequence and homologies

Bovine brain-derived acidic fibroblast growth factor (aFGF) is a protein mitogen originally identified in partially purified preparations of whole brain. The protein was purified to homogeneity and shown to be a potent vascular endothelial cell mitogen in culture and angiogenic substance in vivo. The homology of aFGF to human interleukin-1 beta was inferred from partial sequence data. The complete amino acid sequence of aFGF has now been determined and observed to be similar to both basic FGF and interleukin-1's. A neuropeptide-like sequence, flanked by basic dipeptides, was observed within the aFGF sequence.     

Mitogenic activity of sterculic acid, a cyclopropenoid fatty acid

Hepatocytes in rainbow trout and rat are stimulated to augmented DNA synthesis and cell division by low concentrations of cyclopropenoid fatty acids in the diet. Sterculic acid isolated as the methyl ester from Sterculia foetida oil has been identified as one of the mitogenic principles.     

Change in the fatty acid composition and physicochemical properties of pig back fat depending on growth rate

It is established that the content of saturated fatty acids increases and that of monounsaturated decreases with increase of growth rate at the finishing stage. The content of polyunsaturated fatty acids is related to growth rate to a lesser degree. The content of water in fat and refractive index decrease with its increase in the first fattening stage. An insignificant increase in high meltability of fat with increase of growth rate in the finishing stage is noted.     

牛瘤胃未培养细菌中一个β-葡萄糖苷酶基因umbgl3A的克隆及鉴定

通过构建牛瘤胃未培养细菌的宏基因组文库,共获得12 000个克隆,文库外源DNA总容量为4.2×108 bp,筛选得到九个表达β-葡萄糖苷酶活性的克隆,并对其中的一个表达β-葡萄糖苷酶活性的克隆pGXN1009进行亚克隆,将β-葡萄糖苷酶基因定位在4.3 kb的片段上.测序结果表明在4.3kb的片段上有一个全长为1956 bp的ORF,编码一个可能的β-葡萄糖苷酶基因umbgl3A,其编码产物与一个来源于小鼠大肠未培养细菌的β-葡萄糖苷酶(GenBank Acession NOAAX16378.1)一致性为63%、相似性为79%;与哈氏噬纤维菌(Cytophaga hutchinsonii)的β-葡萄糖苷酶(GenBank Acession NOZP-00308419)的一致性为50%、相似性为67%.利用SMART软件对Umbgl3A结构组件预测表明,Umbgl3A包含一个家族3糖基水解酶(glycosyl hydrolase)功能域和一个家族3C糖基水解酶功能域.遗传进化分析表明umbgl3A基因可能是来自牛瘤胃微生物噬纤维菌属未培养的一个种.     

Structure of fungal fatty acid synthase and implications for iterative substrate shuttling

We report crystal structures of the 2.6-megadalton alpha6beta6 heterododecameric fatty acid synthase from Thermomyces lanuginosus at 3.1 angstrom resolution. The alpha and beta polypeptide chains form the six catalytic domains required for fatty acid synthesis and numerous expansion segments responsible for extensive intersubunit connections. Detailed views of all active sites provide insights into substrate specificities and catalytic mechanisms and reveal their unique characteristics, which are due to the integration into the multienzyme. The mode of acyl carrier protein attachment in the reaction chamber, together with the spatial distribution of active sites, suggests that iterative substrate shuttling is achieved by a relatively restricted circular motion of the carrier domain in the multifunctional enzyme.