几种豆科树木结瘤固氮的初步研究

 作者通过野外调查和盆栽试验,探讨了几种豆科树种的结瘤固氮特征,土壤条件的影响和植株生长。木豆、山毛豆、刺槐在南亚热带褐红土种植,山合欢、刺槐在中亚热带紫色土种植,对绿化荒山荒地、改良土壤和促进生态平衡具有重要意义。     

芦毒蛾越冬场所及越冬习性的研究

芦毒蛾是洞庭湖区重要的芦苇害虫,1年发生3代,以1龄幼虫在芦苇或杂草的枯叶中越冬。对于幼虫在其寄主植物之间的转移行为亦进行了观察。     

铁红圆酵母属两个类群的培养特征初步研究

通过超滤膜过滤法,在大连市黑石礁海域２５００米以内,分离到白色与铁红圆酵母两类海洋酵母。铁红圆酵母分属于Ｔｏｒｕｌｏｐｓｉｓｐｕｌｃｅｒｒｉｍａ类群和Ｔｏｒｕｌｏｐｓｉｓｃａｎｄｉｄａ类群。葡萄糖——蛋白胨——酵母膏液体培养基静止培养条件下,Ｔ．ｐｕｌｃｅｒｒｉｍａ类群培养五天半,活酵母数量达到第一次高峰,为１．２×１０￣８／ｍｌ,大约在八天半之后,达到最高数量,为２．０×１０８／ｍｌ。Ｔ．ｃａｎｄｉｄａ类群,培养大约二天半后,酵母数量达到第一次高峰,为１．８×１０￣７／ｍｌ,培养大约十天半,活细胞数达到最高峰,为１．２×１０￣（－８）／ｍｌ。由于铁红园酵母具有易培性,耐不良环境能力强的优点,作为未来水产养殖业幼体饵料微生物具有广泛地应用前景。     

假丝酵母一新种——北京假丝酵母

本文研究了一株从水果表皮分离到的假丝酵母,它与至今已发表的所有已知假丝酵母均不相同,定名为北京假丝酵母(Candida beijingensis)。     

The endosperm development and the variations of structures of embryo sacs: unravelling the low fecundity of Zephyranthes candida (Amaryllidaceae)

To unravel a low fecundity in Zephyranthes candida (Lindl.) Herb., the development of the endosperm was studied using conventional paraplast section technique. The results show that the endosperm develops normally and comprises four major stages viz. syncytial, cellularization, differentiation and maturation. Both proliferation of antipodal cells and their close contact with the primary endosperm nucleus were observed, which should favor transportation of nutrients and accelerate development of embryo and endosperm. In Z. candida, at least four events of nuclear migration occurred during the course of embryogenesis and endosperm development. The 12.7% structurally and functionally abnormal ovules, along with the 22.3% collapsed and aborted ovules observed accounts for the low fecundity to some extent.     

雪白睡莲花酚类成分研究

采用大孔树脂、硅胶、ODS RP-18和Sephadex LH-20柱从雪白睡莲的干燥花蕾中分离得到7个酚类成分,通过理化性质和波谱学方法鉴定化合物的结构,分别为:isostrictiniin(1)、老鹤草素(2)、鞣花酸(3)、短叶苏木酚(4)、Annulatin 3’-O-β-D-xyloside(5)、短叶苏木酚酸甲酯(6),1,2,3,4,6-五没食子酰基葡萄糖(7)。这些化合物均为首次从该植物中分离得到,化合物1,2,5和6首次从该属植物中分得。     

南极假丝酵母脂肪酶B在离子液体/超临界流体体系中的稳定性模拟

脂肪酶在离子液体/超临界流体体系中的结构稳定性是影响其活性的重要因素。本文采用分子动力学方法分别研究了南极假丝酵母脂肪酶B(CALB)在离子液体CYPHOS IL-201/极性超临界流体CHF_3两相体系和离子液体CYPHOS IL-201/非极性超临界流体CO_2两相体系中的结构稳定性,揭示影响CALB结构稳定性的因素。研究结果表明,在超临界CHF_3中,CHF_3破坏蛋白维持α螺旋结构的氢键是蛋白结构不稳定的主要原因;在超临界CO_2中,CALB蛋白的结构紧密性降低,有序二级结构发生了变化,导致稳定性下降。离子液体和两种超临界流体均形成了两相体系,蛋白处于离子液体相中,离子液体不溶于超临界流体,但超临界流体部分进入离子液体相,降低了离子液体相的黏度。其中,相比于CYPHOS IL-201/CO_2体系,CYPHOS IL-201/CHF_3体系的黏度降低多。在离子液体CYPHOS IL-201与超临界流体(CHF_3、CO_2)形成的两相体系中,离子液体CYPHOS IL-201具有保护蛋白结构的作用,使CALB蛋白结构更加稳定。     

A novel mechanism of fluconazole resistance associated with fluconazole sequestration in Candida albicans isolates from a myelofibrosis patient

A series of 10 strains of Candida albicans, from TIMM 3309 to TIMM 3318, were repeatedly isolated in one myelofibrosis-complicated patient with recurrent candidemia. The latter five isolates, from TIMM 3314 to TIMM 3318, became suddenly resistant to fluconazole during the 10 to 16 weeks after antimycotic therapy. We investigated the resistant mechanism of fluconazole using one susceptible isolate and two of the five resistant isolates in the series. The ergosterol synthesis by cell-free extracts from the two resistant isolates was less susceptible to fluconazole partly as a result of a decreased affinity of cytochrome P-450. Unexpectedly, these two resistant isolates showed higher levels of an intracellular accumulation of [H]fluconazole than the susceptible isolate and the control strain of C. albicans ATCC 10231. In the resistant isolate, TIMM 3318, most intracellular incorporated fluconazole was distributed in the 12,000 X g pellet (P-120) fraction by centrifugation unlike the two susceptible strains. An observation of the ultrastructure of TIMM 3318 showed the most notable alteration to be the characteristic appearance of numerous vesicular vacuoles (diameter, 150 to 400 nm); these vacuoles were not observed, however, in either of the susceptible strains. A direct observation of the subcellular fraction prepared from TIMM 3318 by the electron microscopy negative-staining method suggests that most of the vesicular vacuoles were recovered in the P-120 fraction. These results suggest that fluconazole sequestration caused by vesicular vacuoles of the resistant isolate might act as a novel mechanism of fluconazole resistance besides the decreased affinity of cytochrome P-450.     

Collembola respond to aphid herbivory but not to honeydew addition

Abstract. 1. Euedaphic collembola alter their soil distribution in response to above‐ground aphid herbivory of Poa annua L. Graminae, a host grass. 2. Two mechanisms potentially underpin this effect. Carbon‐rich aphid honeydew falling onto the soil surface may affect mycophagous collembola; alternatively aphid‐induced changes in root biomass may be necessary to produce changes in collembola abundance. 3. When compared to a plant‐only control, aphid herbivory increased the number of collembola in the top 5 cm of soil, reduced both foliar and root biomass, and increased shoot/root ratio. Honeydew addition had no effect on collembola numbers or any recorded host‐plant parameter. 4. Honeydew deposition is not responsible for the increased numbers of collembola found in the upper soil after aphid herbivory; aphid‐induced reductions in root biomass may be the most important factor explaining knock‐on effects of aphid herbivory on soil fauna.     

Direct comparison of the pharmacodynamics of four antifungal drugs in a mouse model of disseminated candidiasis using microbiological assays of serum drug concentrations

The aim of this study was to compare the pharmacodynamics of the azole antifungal drugs fluconazole, itraconazole and ketoconazole, and the polyene antifungal amphotericin B, in a mouse model of disseminated Candida albicans infection. In order to directly compare effective serum concentrations of these antifungals, drug concentrations were assayed microbiologically by measuring inhibition of C. albicans mycelial growth (mMIC) in a mouse serum-based assay (serum antifungal titer). Efficacy in the mouse infection model was determined using an organ-based (kidney burden) endpoint. For all four drugs, the serum antifungal titers, 8 hr after administration of single doses of drugs at a range of drug concentrations, correlated closely with C. albicans kidney fungal burden in the mouse model. The results showed that determining serum antifungal titer may be used to accurately represent kidney fungal burden in a mouse model of disseminated candidiasis and allowed direct comparison of the pharmacodynamics of differing classes of antifungal drugs.