非均匀电场对气/液界面脂单层膜畴结构的诱导

荧光显微膜天平技术研究了非均匀电场对气/液界面脂单层膜的作用.在脂膜的液晶/凝胶两相共存区,观测了电场诱导下畴结构的聚集与排开,并根据自由能极小原理导出一理论公式用以计算畴结构聚集的大小.用该公式对磷脂两相偶极短密度差大小的估算和对一些现象的解释均得到满意结果.此外,还比较了不同膜压下畴结构聚集的大小,并探讨了非均匀电场引起的脂膜表面膜压变化.     

Spread of the autonomous transposable element hobo in the genome of Drosophila melanogaster

The transposable element hobo has been introduced into the previously empty Drosophila melanogaster strain Hikone so that its dynamics can be followed and it can be compared with the P element. Five transformed lines were followed over 58 generations. The results were highly dependent on the culture temperature, the spread of hobo element being more efficient at 25 degrees C. The multiplication of hobo sequences resulted in a change in the features of these lines in the hobo system of hybrid dysgenesis. The number of hobo elements remained low (two to seven copies) and the insertions always corresponded to complete sequences. Our findings suggest that, despite their genetic similarities, P and hobo elements differ in many aspects, such as mobility and regulation mechanisms.      

Current voltage curves of biomolecular lipid membranes.

The first part of this paper describes the current voltage curves of bimolecular membranes of oxidized cholesterol formed between two aqueous solutions of tetrabutylammonium chloride. These membranes are selectively permeable for cations and the membrane interfaces are electrically uncharged. The dependence of the membrane conductivity on the membrane potential can be described as the product of the conductivity at zero current ("zero conductivity") and a function called "overlinearity". The zero conductivity increases linearly with the concentration of tetrabutylammonium chloride. The overlinearity is independent of the concentration of tetrabutylammonium chloride. In the second part the Nernst-Planck and Poisson equations are integrated numerically for a three-phase system consisting of an aqueous electrolyte solution, a membrane and an aqueous electrolyte solution. Each phase is characterized by material constants. Appropriate boundary conditions cause the electric current to build up electrical double layers on both sides of the membrane. The opposing double layers with opposite electrical signs inject the soluble ions into the membrane. This ion injection accounts for the overlinearity of the current voltage curves, thus explaining the measured characteristics.     

蝾螈神经胚时期各种中胚层构造的决定和分化以及它们的发育机制

甲、绪论通过原肠建成的运动,中胚层由原肠期的表面的位置移进胚胎的内部,到神经胚时期移进的部分和外胚层与内胚层分开,介于它们之间,在这里进行进一步的分化,将来分化为肌节、前肾、侧板、血细胞、肢体、心脏等构造,在这些器官里,某些器官的分化和发育,甚至它们轴的决定,都已经被详细研究过,但是相反的它们的决定情况,它们发生决定的原因,什么因素使得中胚层沿着背腹轴的不同高度水平分化为各种不同的器官,它们之间相互的关系如何,在一段比较长的期间内却没有受到应有的注意。被忽略的     

四川短尾唾液腺的组织学观察

利用生物显微技术观察和研究了四川短尾鼩(Anourosorex squamipes)唾液腺的组织结构。结果表明,腮腺属纯浆液腺,有闰管和分泌管,无颗粒曲管;颌下腺属混合腺,以混合性腺泡为主,有少量浆液性腺泡和黏液性腺泡,有闰管、颗粒曲管和分泌管;舌下腺属纯黏液腺,有闰管和分泌管,无颗粒曲管,但在分泌管上存在有颗粒曲管细胞。     

Involvement of JIM13- and JIM8-Responsive Carbohydrate Epitopes in Early Stages of Cell Wall Formation

Beta vulgaris L.). The spatial and temporal expression of both antigens was studied in suspension cells used as the source-tissue for protoplast isolation, in suspension- and mesophyll-derived protoplasts, and in cells which developed from both types of protoplast. Immunofluorescence and immunocytochemical-electron microscopic methods revealed that labeling was present in the cell walls of most suspension cells and also in the incipients of cell walls synthesized around the protoplasts. This signal became much more intense as rebuilding of the cell wall progressed during culture. Relatively weaker labeling was observed in the cytoplasm, where it was frequently associated with the vacuolar compartment. Signal intensity varied between individual cells of the same population and in successive stages of development, but was always stronger with JIM13 than with JIM8. The role of JIM13-responsive epitope in the development of suspension-derived protoplasts was further studied by its ability to bind antibody added to cultures of different ages. Both JIM8- and JIM13-responsive epitopes were widespread in sugar beet cells of different origin and stage of cell wall synthesis. These epitopes may play an important role in cell wall formation and growth under in vitro conditions. Received 17 August 1998/ Accepted in revised form 13 January 1999     

Function and energy metabolism of isolated hearts obtained from hyperthyroid spontaneously hypertensive rats (SHR)

It was the aim of this study to evaluate the effects of hyperthyroidism on heart function and cardiac energy metabolism of spontaneously hypertensive (SHR) rats. Hyperthyroidism was induced by daily injections of T₃ (0.2 mg/kg s.c.) for 14 days. The hearts were then isolated and perfused in the Langendorff mode. ATP, phosphocreatine (PCr), and inorganic phosphate (Pi) were measured continuously by means of³¹P-nuclear magnetic resonance (NMR) spectroscopy. Work load was altered by varying stepwise the Ca⁺⁺ concentration in the perfusion fluid from 0.5 to 1.0, 1.5, and 2.0 mM, respectively. At every elevation of the Ca⁺⁺ concentration, the increase in left ventricular developed pressure (LVDP) was higher in the hyperthyroid SHR than in the untreated SHR hearts. The ATP and PCr concentrations were lower in the hyperthyroid SHR compared to the untreated SHR hearts throughout the perfusion period. PCr decreased at every Ca⁺⁺ elevation in both the untreated and hyperthyroid SHR hearts. The PCr/ATP ratio was not altered at any Ca⁺⁺ concentration neither in the untreated SHR nor in the hyperthyroid SHR hearts. The Ca⁺⁺-induced stepwise elevation in LVDP was higher at any given PCr/Pi ratio in the hyperthyroid SHR than in the untreated SHR hearts. Thus, the Ca⁺⁺-inducible contractile reserve was greater in the hyperthyroid SHR heart.     

泰和鸡肾小球旁器的观察

本文用光镜和透射电镜对泰和鸡(乌骨鸡)的肾小球旁器进行了观察。结果表明,泰和鸡的肾小球旁器由球旁细胞、过渡型致密斑、球外间膜细胞和极周细胞所组成。极周细胞在鸟类还属首次报道,它位于肾小囊脏层与壁层上皮移行处,环绕着肾小体的血管极,其结构与哺乳动物的相似。本文还就泰和鸡肾小球旁器的结构与功能的关系作了讨论。     

Role of ants in structuring the aphid community on apple

1. The aphids Dysaphis plantaginea Passerini, Aphis spp. (Aphis pomi De Geer and Aphis spiraecola Patch), and Eriosoma lanigerum Hausmann are commonly found together in apple orchards. Ants establish a mutualistic relationship with the myrmecophilous aphids D. plantaginea and Aphis spp. but not with E. lanigerum. 2. Field surveys and one experiment manipulating the presence of ants and the aphid species were conducted to test the hypothesis that ants play a role in structuring the community of these aphids on apple. 3. Ants tended D. plantaginea and Aphis spp. but not E. lanigerum colonies. In the field, D. plantaginea performed better in the presence of ants while no effect was observed in Aphis spp. Contrarily, populations of Aphis spp. in the manipulative experiment performed better in the presence of ants while no differences were observed for D. plantaginea. Such differences between field and manipulative conditions could be related to thermal tolerance, phenology, and life cycles. In contrast, populations of E. lanigerum were reduced in the presence of ants. 4. Ants also had a significant negative effect on the abundance of natural enemies, which could partially explain the benefits to the tended aphids. However, while ants did not provide a benefit to Aphis spp. when it was reared alone, in the presence of other species ant attendance increased Aphis abundance by 256% and simultaneously reduced E. lanigerum abundance by 63%. Therefore, ants benefited Aphis by reducing competition with other aphid species, which involves a different mechanism, explaining the benefit of ant attendance. Considering all the aphid species together, ants had a net positive effect on aphid abundance, which was consequently considered harmful for the plant. 5. Our results highlighted the role that ants play in structuring apple aphid communities and give support to the observed pattern that ants can benefit tended aphids while simultaneously reducing the abundance of untended herbivores.     

Complex phylogeographic patterns in the freshwater alga Synura provide new insights into ubiquity vs. endemism in microbial eukaryotes

The global distribution, abundance, and diversity of microscopic freshwater algae demonstrate an ability to overcome significant barriers such as dry land and oceans by exploiting a range of biotic and abiotic colonization vectors. If these vectors are considered unlimited and colonization occurs in proportion to population size, then globally ubiquitous distributions are predicted to arise. This model contrasts with observations that many freshwater microalgal taxa possess true biogeographies. Here, using a concatenated multigene data set, we study the phylogeography of the freshwater heterokont alga Synura petersenii sensu lato. Our results suggest that this Synura morphotaxon contains both cosmopolitan and regionally endemic cryptic species, co‐occurring in some cases, and masked by a common ultrastructural morphology. Phylogenies based on both proteins (seven protein‐coding plastid and mitochondrial genes) and DNA (nine genes including ITS and 18S rDNA) reveal pronounced biogeographic delineations within phylotypes of this cryptic species complex while retaining one clade that is globally distributed. Relaxed molecular clock calculations, constrained by fossil records, suggest that the genus Synura is considerably older than currently proposed. The availability of tectonically relevant geological time (10⁷–10⁸ years) has enabled the development of the observed, complex biogeographic patterns. Our comprehensive analysis of freshwater algal biogeography suggests that neither ubiquity nor endemism wholly explains global patterns of microbial eukaryote distribution and that processes of dispersal remain poorly understood.