动物的的变态

变态是动物学中一个较重要的专用名词,有关内容在中学课本也多处涉及到。现择要介绍一点动物变态的知识,供动物学教学参考。何谓动物的变态动物由于外在和内在的原因,个体形态发生变化,这叫变态。但动物学所讲的变态,是狭义地从发生学角度理解,即胚胎不直接转变为成体,而是在后期发育过程中,先形成形态、生理、生态方面特殊的幼体,行独立生活和生长,以后在某阶段发生急剧变化,转变为成体。青     

活的不可培养的细菌的研究进展

活的不可培养微生物(VBNC)即一些微生物明显地丧失了可培养的特性,但是保留了自身原有的代谢活力,并且在一定条件下,又可以回复到可培养的状态。从VBNC细菌的诱导条件、生物学特性和检测方法3个方面对VBNC细菌研究进展做一综述。     

高频率的波动对于种子的萌发和植物的发育的影响

本文主要是以理论和试验来说明音波对植物的生长发育和种子萌发所起的影响。在农业实践上音波所起的作用,据现在所知:有缩短植物成熟期,加速萌芽和增强植物的生长发育等。这一些非但具有理论和实践上的意义,同时在今後把物理科学应用到农业科学中开辟了极广阔的前程。     

真核细胞的基因的组织

一、真核细胞基因的基本结构 1.转录单位: 从已知的数十种基因的顺序,可得出一个具有功能的基因的共同规律,在基因5’端-25至-75区,有CCAAT和TATAAA区(后者又称ATA box或Hogness box),相当于促进子区(Promotor),为体外转录所必需。     

由吸附的缩氨酸诱导的细胞膜的形变

研究了由一系列相互平行的吸附在细胞膜上的缩氨酸引起的膜的弹性形变,以及膜对缩氨酸的包裹行为,得到膜的平衡方程,用它可以来处理大尺度的形变,弯曲能量、吸附能量和弹性形变的相互竞争导致膜对缩氨酸发生从不吸附到部分吸附乃至完全包裹的结构转变．在膜的形变很小的时候,可以得到系统能量的解析解。     

远古的人们是怎样认识自己的起源的

人是从那里来的? 回答这个问题,你也许会说这有什么困难——人是从古猿变来的;甚至你还会进一步说,在这个从猿到人的转变过程中,劳动起着决定性的作用。然而这个现在看来比较明了的道理,恰是经历了多么漫长的认识过程才达到的呵!现在让我们首先来谈谈,远古的人们是怎样认识自己的起源的。最初的原始人可能还想不到自己的起源在人类诞生的最早时期,“最初的、从动物界分离出来的人,在一切本质方面是和动物本身一样不自由的”(恩格斯:《反杜林论》),这些最初的原始人为艰苦     

敲除pckA基因的结核杆菌引起的免疫反应的研究

研究结核杆菌pckA基因编码的磷酸烯醇型丙酮酸羧激酶(PEPCK)诱导机体产生的保护性免疫反应。用敲除pckA基因的牛结核杆菌BCG和野生型BCG分别感染小鼠,取肝、肺、脾进行病理分析,并进行脾细胞培养,检测CD4 、CD4 /CD8 、细胞因子IFNI-γI、L-12和TNF等。用敲除pckA基因的BCG感染的小鼠比野生型BCG感染的小鼠体内产生的结核结节少且不典型,炎性程度低。野生型BCG感染的小鼠脾脏内的CD4 T细胞和CD4 /CD8 、细胞因子IFN-γ、IL-12、TNF均明显高于敲除pckA基因BCG感染的小鼠。pckA基因为结核杆菌生长所必需,其编码产物PEPCK能够刺激机体产生免疫反应,是一种很好的疫苗候选分子。     

分离的蚕豆细胞核的RNA聚合酶活力的研究

利用Triton X-100对叶绿体膜的作用,可快速地从蚕豆幼叶制备较纯净的细胞核,它具有较高的RNA聚合酶活力。比较了两种分离核的方法,证明利用匀浆法制备的核具有较高的活力。核活力与发育时期有关系,茎端和第1对幼叶的核活力显著高于第2和第3对叶片的核活力。此外,核活力明显地受反应液内锰离子的抑制。     

正红菇的化学成分的研究

采用ＧＣ、ＨＰＬＣ、ＧＣ／ＭＳ．凝胶过滤层析等方法对正红菇（Ｒｕｓｓｕｌａ ｖｉｎｏｓａ）的某些成分的分析结果表明：正红菇其色素由红紫色素和黄色素两个组分的组成,其中红紫色素对酸稳定,对碱及高温不稳定,而黄色素对它们则表现一定的稳定性。其多糖含量２．７４％,含有五种多糖组分。在脂肪酸组成上,主要是油酸和亚油酸,并有可能 存在ＥＰＡ和ＤＨＡ。全氨基酸分析表明含有十六种氨基酸,必需氨基酸占总氨基酸的５     

Immobilization of Alcaligenes eutrophus using PVA crosslinked with sodium nitrate

A new cell immobilization technique using polyvinyl alcohol crosslinked with sodium nitrate was developed. This new technique can simultaneously eliminate the agglomeration of PVA beads and the toxicity of boric acid caused by the PVA-boric acid and PVA-orthophosphate methods. Alcaligenes eutrophus was immobilized using four different PVA entrapment processes. The stability, swelling, relative mechanical strength and denitrification activity of the PVA beads were compared in this study. © Rapid Science Ltd. 1998     

Immobilization of Oenococcus oeni in lentikats® to develop malolactic fermentation in wines

Entrapment of Oenococcus oeni into a polymeric matrix based on polyvinyl alcohol (PVA) (Lentikats®) was successfully used to get a better development of malolactic fermentation (MLF) in wine. The incubation of immobilized cells in a nutrient medium before starting the MLF, did not improve the degradation of malic acid. In only one day, 100% of conversion of malic acid was achieved using a high concentration of immobilized cells (0.35 g gel/ml of wine with a cell‐loading of 0.25 mg cells/mg of gel). While a low concentration of 0.21 g gel/ml of wine (cell‐loading of 0.25 mg cells/mg of gel) needed 3 days to get a reduction of 40%. The entrapped cells could be reused through six cycles (runs of 3 days), retaining 75% of efficacy for the conversion of malic acid into lactic acid. The immobilized cells in PVA hydrogels gave better performance than free cells because of the increase of the alcohol toleration. Consequently, the inhibitory effect of ethanol for developing MLF could be reduced using immobilized cells into PVA hydrogels. © 2012 American Institute of Chemical Engineers Biotechnol. Prog., 2013     

聚乙烯醇固定化酵母细胞制备CTP研究

以聚乙烯醇为固定化载体,固定化冷冻处理过的啤酒酵母细胞从CMP制备CTP;分别从胶的型号、浓度和固定化方法的优化等方面摸索了最适的固定化条件,固定化细胞在试验条件下连续发酵8次,转化率维持在85%～95%。同时,还对固定化细胞的稳定性进行试验研究,并用HPLC对产品进行了分离鉴定。     

Immobilization of Acidithiobacillus ferrooxidans by a PVA–boric acid method for ferrous sulphate oxidation

Acidithiobacillus ferrooxidans was immobilized in poly(vinyl alcohol) (PVA) by a PVA–boric acid method, and spherical beads of uniform size were produced. Biooxidation of ferrous iron by immobilized cells was investigated in repeated batch culture and continuous operation in a laboratory scale packed-bed bioreactor. During repeated batch culture, the cell-immobilized gels were stable and showed high constant iron-oxidizing activity. In continuous operation in a packed-bed bioreactor, biooxidation of ferrous iron fits a plug-flow reaction model well. A maximum Fe²⁺ oxidation rate of 1.89 g l⁻¹ h⁻¹ was achieved at the dilution rate of 0.38 h⁻¹ or higher, while no obvious precipitate was detected in the bioreactor.     

Enzymatic synthesis of 3,4-dihydroxyphenyl-L-alanine by free and immobilized Citrobacter freundii cells

The Citrobacter freundii 62 cells immobilized in PAAG and possessing the tyrosine-phenol-lyase (TPL) activity catalyse the synthesis of 3,4-dihydroxyphenyl-L-alanine (DOPA) from pyrocatechol and ammonium pyruvate. The synthesis of DOPA was studied using both free and immobilized bacterial cells. When the concentration of pyrocatechol is over 0.1 M the TPL activity of the cells is inhibited. The concentration of pyrocatechol can be increased up to 0.3 M by using an equimolar mixture of pyrocatechol and boric acid. The addition of ascorbic acid as an antioxidant results in a lower TPL activity of both free and immobilized bacterial cells.     

Immobilization of hydrocarbon-oxidizing bacteria in poly(vinyl alcohol) cryogels hydrophobized using a biosurfactant

A simple biosurfactant-based hydrophobization procedure for poly(vinyl alcohol) (PVA) cryogels was developed allowing effective immobilization of hydrocarbon-oxidizing bacteria. The resulting partially hydrophobized PVA cryogel granules (granule volume 5 microl) contained sufficient number (6.5 x 10(3)) of viable bacterial cells per granule, possessed high mechanical strength and spontaneously located at the interface in water-hydrocarbon system. Such interfacial location of PVA granules allowed high contact of immobilized biocatalyst with hydrophobic substrate and water phase, thus providing bacterial cells with mineral and organic nutrients. As a result, n-hexadecane oxidation efficiency of 51% after 10-day incubation was achieved using immobilized biocatalyst. PVA cryogels with increased hydrophobicity can be used for immobilization of bacterial cultures performing oxidative transformations of water-immiscible organic compounds. Immobilization of in situ biosurfactant producing Rhodococcus bacteria into PVA cryogel is discussed. PVA cryogel granules with entrapped alkanotrophic rhodococcal cells were stable after 10-month storage at room temperature.     

Removal of flatulence-inducing sugars by using free and polyvinyl alcohol immobilized α-Galactosidase from Aspergillus oryzae

Consumption of soymilk and soybean derived foods has been hampered due to the presence of RFOs (raffinose family oligosaccharides). Soy-based foods free from RFOs have positive impact on their acceptance as protein rich food. α-Galactosidase was entrapped in PVA (polyvinyl alcohol) cross linked with boric acid. Immobilized enzyme showed shift in optimum pH of 0.4 units and the activity yield of the immobilized α-galactosidase was found to be 76%. Immobilized enzyme was used to reduce RFOs in soymilk. In batch reaction after 12 h incubation soluble and immobilized enzyme showed 92 and 83% reduction of RFOs in soymilk, respectively. In repeated batch experiments immobilized enzyme showed 64% of its hydrolyzing activity after 6th cycle. PVA-immobilized α-galactosidase in fluidized bed reactor showed highest reduction (92%) of RFOs at a flow rate of 30 mL/h. The results of this study are interesting for their use in food processing industry.     

PVA-卡拉胶混合载体固定化大肠杆菌-酵母菌混合体系生产谷胱甘肽

提出了ＰＶＡ－卡拉胶混合载体固定化微生物细胞的技术,确定了较好的制备工艺,并用该载体对大肠杆菌－酵母菌混合体系进行了固定化研究。结果表明：在ＰＶＡ浓度１０％,卡拉胶浓度０．５％,成型剂的ｐＨ值６．４,菌体量０．５ｇ／ｇ固定化细胞,固化时间３６ｈ的条件下,固定化细胞具有较好的机械强度和较高的酶活力。     

Biodesulfurization using Pseudomonas delafieldii in magnetic polyvinyl alcohol beads

AIMS: To immobilize Pseudomonas delafieldii R-8 cells in magnetic polyvinyl alcohol (PVA) beads for biodesulfurization. METHODS AND RESULTS: Magnetic PVA beads were prepared by a freezing-thawing technique under liquid nitrogen. The beads have distinct super-paramagnetic properties and their saturation magnetization is 8.02 emu g(-1). The desulfurization rate of the immobilized cells could reach 40.2 mmol kg(-1) h(-1). Desulfurization patterns of dibenzothiophene in model oil with the immobilized and free cells were represented by the Michaelis-Menten equation. The Michaelis constant for both immobilized and free cells was 1.3 mmol l(-1). CONCLUSIONS: The cells immobilized in magnetic PVA beads could be stably stored and be repeatedly used over 12 times for biodesulfurization. The immobilized cells could be easily separated by magnetic field. SIGNIFICANCE AND IMPACT OF THE STUDY: Magnetic PVA beads are easy to prepare. The immobilization process in the paper is to increase the efficiency of cells and to decrease the cost of operations.