青霉素和NAA与6—BA配合在离体草莓器官建成中的作用

本实验研究了青霉素和ＮＡＡ与６－ＢＡ配合对离体草莓器官建成以及体内过氧化物同工酶的影响。结果表明：青霉素促进不定根的分化,但抑制不定根的伸长和不定芽的分化,并且不同程度地影响器官建成过程中过氧化和抽工酶的谱带和活性。青霉素与植物激素一样,参与了植物体内的生理代谢而引起植物器官建成。     

中国无患子科的地理分布

无患子科是一个乏热带分布科,全世界有１４４属,１６８０种,本文着重阐述：１．无患子科的分类系统及演化;２．世界无患子科的地理分布;３．中国无患子科的地理分布;４．无患子科的早期化地点及散布途径。结果表明无患子科现代分布变异中心在亚洲（印度－马西亚）－非洲－南美洲。中国无患子科有２５属,５４种,特有成分外,均与印度一马来西亚共有,大多数位于分布区的边缘。根据化石记录及现代及分布推断,无患子科可能在白     

植食性同翅目昆虫寻找和接受植物韧皮部过程中的细胞与化学探试(英文)

植食性同翅目昆虫在最终接受其宿主植物的过程中,将感受从叶表层直到韧皮部筛管途中存在的多种化学物质,并导致不同的刺探和取食行为。本文就植物叶表层存在的糖类和生物碱类物质,叶肉层的多糖类、酸碱度和酚类物质以及韧皮部内的氨基酸、蛋白质、碳水化合物和植物次生物质等对昆虫寻找及取食韧皮部行为的影响作一综述,并且还探讨了植物叶肉层的细胞结构对昆虫刺探及取食行为的可能影响。此外,结合刺探电位(electrical penetration graphs,EPGs)的研究结果,还讨论了昆虫感受植物叶组织内部的各种化学和细胞结构信息的可能机制。     

无花果蛋白酶在阴离子交换树脂上的固定化

无花果蛋白酶通过８％戊二醛活化载体,共价结合到聚苯乙烯阴离子交换树脂ＧＭ２０１上,固定化作用在ｐＨ７．７,酶浓度０．８ｍｇ／ｇ树脂,４℃下进行６ｈ。得到的固定化酶表观Ｋ_ｍ值（酪蛋白,１．１１×１０~（－４）ｍｏｌ／Ｌ）小于溶液酶Ｋ_ｍ值（１．９６×１０~（－４）ｍｏｌ／Ｌ）;固定化酶活性在ｐＨ６～８保持稳定,溶液酶最适ｐＨ为７．２;固定化酶最适温度由溶液酶的５０～６０℃移至３７℃;固定化酶２５℃保持７ｄ,重复水解酪蛋白７次后,保留８３．３％活性。固定化酶对酪蛋白水解度达４７．５％,对大豆球蛋白达１１．６％。     

家鸡和原鸡的线粒体DNA多态性比较

本文运用１１种限制性内切酶分析了家鸡（茶花鸡、尼西鸡、大理漾濞黄鸡）和原鸡共１０只个体的线粒体ＤＮＡ限制性片段长度多态性（ＲＦＬＰ）,平均每个个检测到的片段为４０条左右。但仅发现３种变异的限制性片制性格局,即ＳｔｕＩ－Ｂ,Ｅｃａ－Ｉ－ｂ和ＲＩ－Ｂ．其中ＳｔｕＩ－Ｂ和ＳｃａＩ－Ｂ为首次报道,而且均为原鸡所物有,ＥｃｏＲＩ－Ｂ则为大理漾濞黄鸡所特有。茶花鸡和尼西鸡拥有完全相同的限制性格局。经过计算,原     

L-异亮氨酸和甘氨酸对大肠杆菌表达与分泌邻苯二酚2,3-双加氧酶的作用

证实了甘氨酸与L-异亮氨酸对大肠杆菌表达邻苯二酚2,3-双加氧酶(CatO_2ase)的促进作用和甘氨酸促使该酶分泌至胞外培养基中的作用.产酶量高低和分泌量多少与培养基种类、甘氨酸和L-异亮氨酸的浓度以及培养时间等因素有关.在甘氨酸存在的情况下,胞壁对溶菌酶的敏感性有所增加,超微形态似有变化,还存在其他物质的伴随分泌,故甘氨酸可能是引起细胞壁结构的改变而导致邻苯二酚2,3-双加氧酶等胞内容物被动分泌至胞外.     

Evidence for natural horizontal transfer of tetQ between bacteria that normally colonize humans and bacteria that normally colonize livestock.

Though numerous studies have shown that gene transfer occurs between distantly related bacterial genera under laboratory conditions, the frequency and breadth of horizontal transfer events in nature remain unknown. Previous evidence for natural intergeneric transfers came from studies of genes in human pathogens, bacteria that colonize the same host. We present evidence that natural transfer of a tetracycline resistance gene, tetQ, has occurred between bacterial genera that normally colonize different hosts. A DNA sequence comparative approach was taken to examine the extent of horizontal tetQ dissemination between species of Bacteroides, the predominant genus of the human colonic microflora, and between species of Bacteroides and of the distantly related genus Prevotella, a predominant genus of the microflora of the rumens and intestinal tracts of farm animals. Virtually identical tetQ sequences were found in a number of isolate pairs differing in taxonomy and geographic origin, indicating that extensive natural gene transmission has occurred. Among the exchange events indicated by the evidence was the very recent transfer of an allele of tetQ usually found in Prevotella spp. to a Bacteroides fragilis strain.     

Multiple genotypes of mitochondrial DNA within a horse population from a small region in Yunnan province of China

mtDNA genotypes of six domestic horses (three adult short horses whose heights are under 1 m and three common domestic horses) from a small region of 15 km² in Malipo county of Yunnan province of China were investigated by the technique of restriction fragment length polymorphism (RFLP) with 16 restriction endonucleases which recognize 6-bp sequences. An average of 56 fragments for an individual was obtained. Unlike other domestic animals, this population of horses exhibits high mtDNA genetic diversity. Each of the six horses has a specific mtDNA genotype showing a pattern of multiple maternal origins, as suggested by fossil and literature records. We think the population of horses is an amazing seed-resource pool of horses and hence deserves to be paid more attention from the view of conservation genetics. However, it is also remarkable that we did not find any typical mtDNA genetic markers which would discriminate between short horses and common domestic horses.     

Flow-induced detachment of red blood cells adhering to surfaces by specific antigen-antibody bonds.

Fixed spherical swollen human red blood cells of blood type B adhering on a glass surface through antigen-antibody bonds to monoclonal mouse antihuman IgM, adsorbed or covalently linked on the surface, were detached by known hydrodynamic forces created in an impinging jet. The dynamic process of detachment of the specifically bound cells was recorded and analyzed. The fraction of adherent cells remaining on the surface decreased with increasing hydrodynamic force. For an IgM coverage of 0.26%, a tangential force on the order of 100 pN was able to detach almost all of the cells from the surface within 20 min. After a given time of exposure to hydrodynamic force, the fraction of adherent cells remaining increased with time, reflecting an increase in adhesion strength. The characteristic time for effective aging was approximately 4 h. Results from experiments in which the adsorbed antibody molecules were immobilized through covalent coupling and from evanescent wave light scattering of adherent cells, imply that deformation of red cells at the contact area was the principal cause for aging, rather than local clustering of the antibody through surface diffusion. Experiments with latex beads specifically bound to red blood cells suggest that, instead of breaking the antigen-antibody bonds, antigen molecules were extracted from the cell membrane during detachment.