Influences on the antimicrobial activity of surface-adsorbed nisin

The efficacy of the antimicrobial peptide nisin was examined after adsorption to silica surfaces. Three protocols were used to evaluate nisin's activity against adhered cells ofListeria monocytogenes: bioassay usingPediococcus pentosaceous FBB 61-2 as the sensitive indicator strain; visualization and enumeration of cells by microscopic image analysis; and viability of adhered cells as determined by lodonitrotetrazolium violet uptake and crystallization. The activity of adsorbed nisin was highly dependent upon conditions of adsorption. The highest antimicrobial activity of adsorbed nisin occurred with high concentrations of nisin (1.0 mg ml^–1) and brief contact times (1 h) on surfaces of low hydrophobicity. Sequential adsorption of a second protein (-lactoglobulin or bovine serum albumin) onto surfaces consistently resulted in decreased nisin activity. These data provide direction for the development of applications to limit microbial attachment on food contact surfaces through the use of adsorbed antimicrobial peptides.     

陆地表层系统动力学机制研究Ⅰ．──陆地表层系统和动力学方程

对陆地表层动力学的研究对象、研究内容及其基本理论方法作了阐述,以多学科综合的观点定义了陆地表层系统,包括时空尺度范围的约定、状态变量的选择、物质循环以及外界因子等的讨论;依据物质和能量守恒原理建立了陆地表层系统的非线性控制方程组,表述了各圈层之间物质循环和能量循环过程、反馈关系及其动力学联系;讨论了控制方程组的整体运作功能以及人类活动对陆地表层系统的影响．     

FIBONACCI级数与菊花结构规律的研究

本文论证了菲波纳斯（Fibonacci）级数与菊花花冠结构的关系,发现了花冠的通用数学模式：花冠（数目）＝（5×倍数）十F_n（F_(n－1)＋F_(n-2)）     

几种细胞分裂素诱导石竹外植体直接再分化成花芽的机理

用ＭＳ＋２,４－Ｄ０．１ｍｇ／Ｌ为基本培养基,分别附加不同浓度的ＺＴ、ＢＡ和ＫＴ,对石竹的叶片、茎和花等外植体直接再分化成花芽的试验表明：叶片的外植体在有ＢＡ时可再分化出只有红色花瓣的不正常花芽;在含ＺＴ的培养基中再分化出具有１～２片叶或无叶的花芽,其花有两性花,雌花和仅单个雌蕊的不正常花,两性花可发育成结籽的果实;ＫＴ未能诱导花芽分化。茎外植体,３种ＣＴＫ都不能诱导出花芽。花等外植体仅在ＫＴ３ｍｇ／Ｌ的培养中再分化出无叶的不正常花芽,ＺＴ和ＢＡ的处理均不能诱导出花芽。     

Structures of wild-type and mutant signal sequences of Escherichia coli ribose binding protein.

The structure of a chemically synthesized 25-residue-long functional signal peptide of Escherichia coli ribose binding protein was compared with that of a nonfunctional mutant-signal peptide using circular dichroism and two-dimensional 1H NMR in solvents mimicking the amphiphilic environments. The functional peptide forms an 18-residue-long alpha-helix starting from the NH2-terminal region and reaching to the hydrophobic stretch in a solvent consisting of 10% dimethylsulfoxide, 40% water, and 50% trifluoroethanol (v/v). The nonfunctional mutant peptide, which contains a Pro at position 9 instead of a Leu in the wild-type peptide, does not have any secondary structure in that solvent but forms a 12-residue-long alpha-helix within the hydrophobic stretch in water/trifluoroethanol (50:50, v/v) solvent. It seems that the Pro-9 residue in the nonfunctional peptide disturbs the helix propagation from the hydrophobic stretch to the NH2-terminal region. Because both of these peptides have stable helices within the hydrophobic stretch, it may be concluded that the additional 2 turns of the alpha-helix in the NH2-terminal region of the wild-type signal peptide is important for its function.     

Variations in Immune Response of Popillia japonica and Acheta domesticus to Heterorhabditis bacteriophora and Steinernema Species

The infectivities of Steinernema carpocapsae, S. glaseri, S. scapterisci, and Heterorhabditis bacteriophora to Japanese beetle larvae, Popillia japonica, and house cricket adults, Acheta domesticus, were compared using external exposure and hemocoelic injection. Only H. bacteriophora and S. glaseri caused high P. japonica mortality after external exposure. When nematodes were injected, P. japonica had a strong encapsulation and melanization response to all species except S. glaseri. Heterorhabditis bacteriophora and S. carpocapsae were able to overcome the immune response, but S. scapterisci was not. All species except S. scapterisci were able to kill and reproduce within the host. Only S. scapterisci and S. carpocapsae caused A. domesticus mortality after external exposure. When nematodes were injected, A. domesticus had a strong immune response to all species except S. scapterisci. Steinernema carpocapsae effectively overcame the strong immune response and caused high host mortality, but S. glaseri and H. bacteriophora did not. Steinernema scapterisci caused high host mortality and reproduced, S. glaseri and H. bacteriophora caused low host mortality but only S. glaseri reproduced, and S. carpocapsae was able to kill the host but reproduced poorly. Most (ca. 90%) of the S. carpocapsae in the hemocoel of P. japonica became encapsulated and melanized within 8 hours postinjection. The symbiotic bacterium, Xenorhabduf nematophilus, was often released before this encapsulation and melanization.     

Pine needle growth and fine structure after prolonged acid rain treatment in the subarctic

The growth and morphology of Scots pine needles were studied in a long-term acid rain experiment in the far north of Finnish Lapland. Pine trees 5 m tall of age 50–70 years were exposed, by spraying the foliage and soil from a height of 2 m, to either clean water (IC) or acidified water over the period 1985–1992, the acidification site being divided into sub-areas in which the precipitation contained two levels of either sulphuric (Sm, Sh) or nitric (Nm, Nh) acid, or both (SNm, SNh). The treatments with medium and high sulphate-S over eight consecutive years yielded a total sulphur deposition of 3·4 and 17·1 gm⁻², respectively, and those with medium and high nitrate-N a total nitrogen deposition of 1·1 and 5·9 g m⁻². Needles were collected for light and electron microscopy, growth measurements and morphometry. Growth in branch height had decreased by about 40% after 6 years of SNm or SNh treatment, and needle growth by 15% in the SNh trees as compared with the irrigated control trees (IC), although decreases were statistically significant only with respect to the non-irrigated control trees (DC). Growth of branches and needles was slightly better in the Nh treatment than in the IC group. The areas of the whole needle, the mesophyll and the phloem decreased in response to SNh treatment as compared with IC or DC, and a statistically significant decrease of about 30–40% was seen in the area of the xylem in comparison with DC. Cellular damage was observed following the acid treatments, especially with a high acid load. The damage was manifested in collapse of the cellular compartments, increases in lipid accumulations and swelling or disorganization of the protoplast. Increased vacuolization of the cytoplasm, plasmalemma irregularities and chilling-type damage to the mitochondria were also observed.     

河南叶县下寒武统辛集组单板类和腹足类化石的研究

本文描述和讨论了河南叶县杨寺庄下寒武统辛集组单板类１３种,腹足类２种,未定类１种。其中包括２新属６新种：Ｒｅｐｅｎｏｃｏｎｕｓ ｘｉｎｊｉｅｎｓｉｓ ｇｅｎ．ｎｏｖ．,Ｓｃｅｎｅｌｌａ ｐｙｃｎａ ｓｐ．ｎｏｖ．,Ｓｅｃｕｒｉｃｏｎｕｓ ｖｕｌｇａｒｉｓ ｓｐ．ｎｏｖ．,Ｏｂｔｕｓｏｃｎｕｓ ｇｒｏｓｓｉｃｏｓｔｕｓ ｓｐ．ｎｏｖ．,Ｉｇｏｒｅｌｌｉｎａ ｐｒｏｂｏｓｃｉｓ ｓｐ．ｎｏｖ．,Ｇａｌ     

鱼类寄生毛细科线虫－新属新种的研究

作者在武陵山地区的鱼类寄生线虫调查工作中,发现一种毛细线虫,经研究,为一新种,定名为岁新毛细线虫,新种（Ｎｅｏｃａｐｉｌｌａｒｉａｐｈｏｘｉｎｉｓｐ．ｎｏｖ．）。根据其特征,为此建立一新属──新毛细线虫属。     

武陵山地区鱼类寄生杆咽属线虫两新种

本文报道在武陵山地区的白甲鱼［（Ｖａｒｉｃｏｒｋｉｎｕｓ（Ｏｎｙｃｈｏｓｔｏｍａ）ｓｉｍｕｓ（ＳａｕｖａｇｅｅｔＤａｂｒｙ）］和沪溪直口峻（ＲｅｃｔｏｒｉｓｌｕｘｉｅｎｓｉｓＷｕｅｔＹａｏ）中发现的两种杆咽属（Ｒｈａｂｄｏｃｈｏｎａ）线虫新种,定名为白甲鱼杆咽线虫,新种（ＲｈａｂｄＯｃｈｏｎａｏｎｙｒｋｏｓｔｏｍｉｓｐ．ｎｏｖ．）和短咽杆咽线虫,新种（ＲｈａｂｄＯｃｈｏｎａｂｒｅｖｉｃｈｏｎａｓｐ．ｎｏｖ．）,并对两新种进行了测量和详细的描述。