瘤胃微生物不同区系的硝态氮还原、甲烷产生和发酵参数比较

【目的】以硝态氮为惟一氮源,评价体外培养瘤胃微生物不同区系还原硝酸盐的程度以及对甲烷产生和发酵参数的影响。【方法】采用Menke人工瘤胃产气法进行24h厌氧发酵,以硝酸钠、可溶性淀粉和微晶纤维素组成纯合日粮,用物理离心和化学抑制剂相结合的方法,将瘤胃液分成8种区系:全瘤胃液(WRF)、原虫(P)、细菌(B)、真菌(F)、原虫+细菌(P+B)、原虫+真菌(P+F)、细菌+真菌(B+F)和负对照(CTN),测定微生物硝酸盐降解率及发酵参数。【结果】P区系硝酸盐降解率显著高于B区系(P0.001),P+F及B+F区系硝酸盐降解率低;WRF产气量和硝酸盐降解率最高,P+B和P区系次之,这3个区系的甲烷(CH4)、总挥发酸(TVFA)含量和乙酸比例均高于其它区系(P0.001);硝酸盐的还原有利于微生物蛋白的合成,P+B区系的合成量最高。【结论】瘤胃原虫(P)和细菌(B)区系具有高还原硝酸盐(NO3-)和亚硝酸盐(NO2-)能力,原虫区系的硝态氮还原能力更强;真菌(F)区系培养于此发酵底物中,还原硝酸盐的能力很弱,几乎可以忽略。瘤胃原虫和细菌区系是硝态氮还原、产甲烷和微生物蛋白合成的主要区系。     

瘤胃微生物降解纤维素的研究进展

综述了不同的瘤胃微生物降解纤维素的相对贡献和发酵特征,说明纤维素在瘤胃内的降解是在细菌、原虫和真菌的协同作用下完成的.     

日粮添加烟酸对活体外瘤胃发酵和纤维降解的影响

采用体外产气量法,研究了在高水平玉米秸(70%)底物日粮中添加烟酸(0、3和9μg/mL)对瘤胃发酵和纤维降解的影响。结果显示:日粮添加烟酸显著提高了72 h产气量、48 h总挥发酸的浓度、发酵液的羧甲基纤维素酶和木聚糖酶的活性以及72 h干物质、中性洗涤纤维的降解率(P<0.05),而对发酵液的潜在产气量、产气速度、pH、氨态氮浓度、各挥发酸摩尔比、原虫和细菌的数量以及微晶纤维素酶活、酸性洗涤纤维的降解率无显著影响(P>0.05)。随烟酸添加水平的增加,原虫的数量(P=0.082)、潜在产气量(P=0.056)、微晶纤维素酶活(P=0.078)和酸性洗涤纤维的降解率(P=0.093)均呈上升的趋势。添加烟酸3和9μg/mL组的乙酸生成量分别提高5.33%、7.57%,丙酸生成量分别提高5.61%、7.74%,干物质降解率分别提高3.34%、3.37%,中性洗涤纤维降解率分别提高2.69%、2.76%,酸性洗涤纤维降解率分别提高了2.33%、2.41%。体外试验表明:在高水平玉米秸(70%)底物日粮中添加烟酸促进了纤维降解。     

棉酚对瘤胃真菌和细菌体外发酵稻草活力的影响

体外研究了不同质量浓度5、20、40 mg/L棉酚对瘤胃厌氧真菌和瘤胃细菌发酵稻草活力的影响。瘤胃真菌发酵试验中,各处理组的底物消失率均显著低于对照组(0)(P<0.05)。产气量结果表明,20、40 mg/L两试验组的发酵明显滞后于其它各组,且发酵24 h和48 h的累计产气量显著低于对照组及51、0 mg/L试验组(P<0.05),说明20 mg/L和40 mg/L的棉酚可显著抑制瘤胃真菌的发酵。在瘤胃细菌发酵试验中,51、0 mg/L棉酚处理组的底物消失率与对照组(0)无明显差异,而20和40 mg/L棉酚处理组的底物消失率显著低于对照组(P<0.05)。累计产气量结果表明,各浓度水平的棉酚对瘤胃细菌发酵无明显的滞后效应。因此,瘤胃真菌对棉酚较为敏感,而瘤胃细菌对棉酚有较强的耐受能力,但高浓度的棉酚对细菌发酵活力有一定的抑制作用。     

瘤胃微生物不同种群对小麦秸体外降解的研究

实验设置5个处理组,研究瘤胃微生物不同种群对小麦秸的降解作用。结果发现：瘤胃细菌在整体上对纤维素性物质的降解力强;瘤胃真菌也能降解部分粗纤维类物质,但作用较小;瘤胃细菌和真菌在降解中具有一定的互作关系。体外干物质降解率、总挥发性脂肪酸、总气体产量、总甲烷气体产量、羧甲基纤维素酶活力可以作为评定瘤胃微生物降解活力的指标。     

产气量法研究不同植物提取物对瘤胃体外发酵的影响

为研究植物蜕皮甾酮、大蒜提取物、苍术提取物、桑叶提取物和牛蒡子提取物对瘤胃体外发酵的影响,试验利用体外产气量法设对照组(未添加组)和5个试验组,每种植物提取物的添加水平为1.5%,测定了发酵24和48h的DM消化率以及发酵96h的发酵参数。结果显示:1)和对照组相比,各试验组24hDM消化率无显著性差异(P0.05),植物蜕皮甾酮和大蒜提取物组48h的DM消化率显著高于对照组(P0.05);2)各植物提取物对96h产气量、理论最大产气量以及产气速率均无显著性影响(P0.05);3)各组之间pH无显著性差异(P0.05);植物蜕皮甾酮、桑叶提取物和苍术提取物组的NH3-N浓度显著低于对照组(P0.05);植物蜕皮甾酮和桑叶提取物显著降低了总挥发酸浓度(P0.05),而牛蒡子提取物显著提高了总挥发酸浓度(P0.05);各提取物均降低乙酸摩尔比,升高了丙酸的摩尔比,但差异不显著(P0.05)。添加上述提取物能够降低体外发酵NH3-N浓度、提高48hDM消化率,可以一定程度的改善瘤胃发酵模式。     

瘤胃原虫对反刍动物的影响

反刍动物瘤胃内栖生着大量微生物，主要包括细菌、真菌和原虫，它们对于饲料在瘤胃内的降解起着十分重要的作用。本文主要论述了瘤胃内原虫对瘤胃营养物质代谢的影响。研究发现，去原虫后，瘤胃发酵类型发生改变，丙酸产量增加，甲烷产量减少。并且去原虫后，可以改变淀粉及蛋白质的消化，有利于改善家畜的生产性能。     

植物病原真菌细胞壁降解酶的研究进展

综述了植物病原真菌细胞壁降解酶的类型,阐明了细胞壁降解酶在植物病原真菌侵染中的作用,归纳了影响细胞壁降解酶产生的因素以及细胞壁降解酶之间的协同作用.     

3种挥发油对肉牛体外瘤胃发酵、甲烷生成和微生物种群的影响

为研究不同挥发油对肉牛体外瘤胃发酵及微生物种群的影响,试验首先分析了不同水平的大蒜油、肉桂油和牛至油对瘤胃产气量及甲烷生成的影响,并筛选可降低甲烷生成量、但产气量变化不显著的挥发油添加水平(即大蒜油50 mg/L、肉桂油100 mg/L和牛至油200 mg/L)。进一步分析不同挥发油处理对瘤胃液p H值、VFA、NH_3-N和MCP浓度等发酵参数以及微生物种群数量的影响。结果显示:除了200 mg/L牛至油使VFA显著下降外(P0.05),其余的p H值、挥发性脂肪酸、NH_3-N和微生物粗蛋白浓度等发酵参数变化不显著(P0.05);上述剂量的3种挥发油对真菌和原虫影响不显著(P0.05),对古菌抑制极显著(P0.01)。所以,大蒜油、肉桂油和牛至油可以有效的降低瘤胃的甲烷产量而不影响其发酵,具有开发反刍动物瘤胃降甲烷微生态制剂的潜在应用价值。     

两株侧耳属真菌对小麦秸秆化学组分及瘤胃消化率的影响

小麦秸秆木质素含量高,蛋白质等营养物质含量低,作为反刍家畜的粗饲料营养价值低,饲料化利用受到限制.通过室内小麦秸秆固态发酵试验,研究了两株侧耳属真菌Tf1(Pleurotus sajor-caju)和JG1(Pleurotus Cornucopiae Roll)对小麦秸秆细胞壁化学组分的降解、瘤胃消化率和粗蛋白含量的影响.结果表明,经菌株JG1、Tf1和两菌复合发酵21 d的小麦秸秆,木质素降解率分别为28.20%、30.78%和38.41%,纤维素降解率分别为19.26%、19.28%和26.65%;48 h干物质瘤胃消化率分别比未发酵秸秆提高了38.62%、44.81%和55.89%,中性洗涤纤维(NDF)消化率分别提高了38.91%、49.00%和63.08%;粗蛋白含量分别比未发酵秸秆提高了58.60%、69.53%和72.22%.表明菌株JG1和Tf1在选择性降解木质素,改善瘤胃消化率,提高粗蛋白含量方面的优势,而且两菌株复合发酵具有协同作用,与单菌发酵相比.木质素降解率、瘤胃消化率和粗蛋白含量都明显提高.     

Segregation of form, color, movement, and depth: anatomy, physiology, and perception

Anatomical and physiological observations in monkeys indicate that the primate visual system consists of several separate and independent subdivisions that analyze different aspects of the same retinal image: cells in cortical visual areas 1 and 2 and higher visual areas are segregated into three interdigitating subdivisions that differ in their selectivity for color, stereopsis, movement, and orientation. The pathways selective for form and color seem to be derived mainly from the parvocellular geniculate subdivisions, the depth- and movement-selective components from the magnocellular. At lower levels, in the retina and in the geniculate, cells in these two subdivisions differ in their color selectivity, contrast sensitivity, temporal properties, and spatial resolution. These major differences in the properties of cells at lower levels in each of the subdivisions led to the prediction that different visual functions, such as color, depth, movement, and form perception, should exhibit corresponding differences. Human perceptual experiments are remarkably consistent with these predictions. Moreover, perceptual experiments can be designed to ask which subdivisions of the system are responsible for particular visual abilities, such as figure/ground discrimination or perception of depth from perspective or relative movement--functions that might be difficult to deduce from single-cell response properties.     

Mineralogy, petrology, and surface features of lunar samples 10062,35, 10067,9, 10069,30, and 10085,16

The primary rocks are a sequence of titanium-rich basic volcanics, composed of clinopyroxene, plagioclase, and ilmenite with minor olivine, troilite, and native iron. The soil and microbreccias are respectively loose and compacted mixtures of fragments and aggregates of similar rocks, minerals, and glassy fragments and spheres. Impact events are reflected by the presence of shock metamorphosed rock fragments, breccias, and glasses and their resulting compaction to form complex breccias, glass-spattered surfaces, and numerous glass-lined craters. Chemistry of the glasses formed by the impact events is highly variable, and the high iron and nickel content of a few moundlike features suggests that at least some of the projectiles are iron and nickel-rich meteorites.     

Values,technologies, and epistemology

The aim of this paper is to make possible dialogue between those who claim that technologies are coded with social, political, or ethical values and those who argue that they are value-neutral. To demonstrate the relevance of this bridge-building project, the controversy regarding agrifood biotechnology will be used as a case study. Drawing on work by L. H. Nelson about the nature of human knowledge-building enterprises and E. F. Kittay’s account of the relationally-constituted self, the argument will be made that all technologies embody the values of the communities that created them. Zahra Meghani is an assistant professor in the Department of Philosophy at the University of Rhode Island. Her research interests are philosophy of technology, feminist theory (especially feminist epistemology and feminist philosophy of science), normative ethics, practical ethics (especially health care ethics), disability issues, and political theory.     

Research and development, productivity, and inflation

R & D, through its effects on the rate of productivity increase, can significantly restrain the rate of inflation in the medium and long run. High rates of inflation damage the workings of the price system and impair the efficiency of practically all economic activities, including R & D. Findings suggest that the percentage increase between 1969 and 1979, in total real R & D expenditures, has been exaggerated due to the inadequacy of the gross national product deflator as applied to R & D.     

Space, stars, c60, and soot

Although carbon has been subjected to far more study than all other elements put together, the buckminsterfullerene hollow-cage structure, recently proposed to account for the exceptional stability of the C(60) cluster, has shed a totally new and revealing light on several important aspects of carbon's chemical and physical properties that were quite unsuspected and others that were not previously well understood. Most significant is the discovery that C(60) appears to form spontaneously, and this has particularly important implications for particle formation in combustion and in space as well as for the chemistry of polyaromatic compounds. The intriguing revelation that 12 pentagonal "defects" convert a planar hexagonal array of any size into a quasi-icosahedral cage explains why some intrinsically planar materials form quasi-crystalline particles, as appears to occur in the case of soot. Although the novel structural proposal has still to be unequivocally confirmed, this article pays particular attention to the way in which it provides convincing explanations of puzzling observations in several fields, so lending credence to the structure proposed for C(60).     

Strategic command, control, communications, and intelligence

Command, control, communications, and intelligence (C(3)l) for nuclear forces are essential elements in the deterrence of nuclear war. The present C(3)l) system has vulnerabilities associated with its reliability, survivability, and endurance under attack, thereby weakening deterrence by increasing the ambiguity in our capabilities. Development of a reliable and enduring C(3)l) system would reduce this ambiguity. Its reliable, positive control of nuclear forces would give the national leadership more time to assess situations, ensure discriminate retaliation, and improve our ability to manage crises in general. These capabilities could help to stop a war rapidly should one start. A reliable and enduring C(3)1) system will be needed for a long time to come, even if a freeze on strategic nuclear forces is accomplished or other arms control successes achieved. Indeed, C(3)l) may be the best source today of confidence-building measures to reduce tensions and the threat of nuclear catastrophe.     

Beliefs,knowledge, and values held by inner-city youth about gardening,nutrition, and cooking

Changes in the US food system and an interest in changing dietary habits among youth have impelled numerous schools and communities to develop programs such as community gardens. Youth community gardens have the potential to positively influence dietary behaviors and enhance environmental awareness and appreciation. However, actual data supporting youth gardening and its influence are limited. The purpose of this study was to explore the effects of community gardens on youth dietary behaviors, values and beliefs, and cooking and gardening behaviors. Focus groups were conducted with inner-city youth living in Minneapolis/St. Paul, Minnesota and compared those involved in a youth garden program with those uninvolved in order to investigate whether the gardening program influenced their habits, beliefs, and values. Findings indicate that youth garden program participants were more willing to eat nutritious food and try ethnic and unfamiliar food than those not in the program. Additionally, it was apparent that garden participants had a stronger appreciation for other individuals and cultures and were more likely to cook and garden on their own than youth not involved in a garden program. The findings suggest that garden programs positively impact youth garden habits, food choice, social skills, nutrition knowledge, and cooking skills. Lauren Lautenschlager is currently a graduate student at the University of Minnesota and working toward obtaining her MS in nutrition and becoming a registered dietitian. She is interested in the education of youth on the food system. Chery Smith is an associate professor in the Department of Food Science and Nutrition at the University of Minnesota. Her research interests include the dietary behavior and nutritional status of low-income and homeless people, community and international nutrition, and food systems.