生物教学中的录像直观与实验直观的比较研究初探

吸收作用是被子植物生理的一个重要方面,但吸收作用的原理非常抽象。为了更好地完成教学任务,加强直观教学就显得尤为重要。为此,笔者在“吸收作用”的教学中使用了挂图、投影、录像和演示实验,就“根对无机盐离子的交换吸附”问题,分别用实验录像和实验操作在９７级１班、２班作了对比演示,课后对两个班学生作了问卷调查,对调查结果作了统计分析,从而对生物教学中的录像直观与实验直观问题作了初步的研究,得出了初步的结论。１　调查与统计１．１　试验组看录像。１９９８年３月１７日,在９７级１班进行“吸收作用”教学时,播放…     

高等植物体内的谷胱甘肽

谷胱甘肽(GSH)在植物对生物与非生物胁迫中起着重要的作用,其作用机制仍是国内外研究的热点之一。从GSH在植物体内的结构、代谢、功能及其分子生物学领域的研究作了综述,并对该领域存在的问题及前景作了展望。     

森林生态系统中土壤微生物的作用与应用

土壤微生物作为森林生态系统的重要组成部分,在林业可持续发展中扮演重要角色．本文就土壤微生物在森林生态系统中的作用作了综述．内容包括：土壤微生物区系及生物量在林业可持续发展中的作用、菌根在林业可持续发展中的作用、植物病原微生物对林业可持续发展的影响、PGPR在林业可持续发展中的作用．并对其今后的发展趋势及应用前景等问题作了探讨,提出了今后应进一步开展的研究方向．     

ERβ--一种新型的雌激素受体

介绍了一种新型的雌激素受体ＥＲβ,对其基因及蛋白结构、分布、作用机制方面的研究进展作了综述,并将其与的雌激素受体ＥＲα作了比较。     

影响微生物互作的重要基因研究进展：以大肠杆菌为例

微生物在自然界中广泛存在,微生物间的相互作用对群落结构和功能有重要影响。目前已经对微生物相互作用的机制给予了很大的关注,通过高通量测序技术和统计学分析方法的结合可以定位获得影响菌株互作的重要基因。为了深入研究微生物相互作用的遗传机制,本文以大肠杆菌(Escherichia coli)为例,综述了与大肠杆菌运动性、耐药性、营养物质吸收和代谢调节相关的基因在互作条件下发挥的作用,并从这几个方面分别阐述了大肠杆菌互作遗传机制。总之,这些基因在大肠杆菌与其他微生物互作中发挥重要作用,同时增强了对细菌互作机制的理解,为今后研究更复杂的微生物群落互作遗传机制奠定了理论基础。     

miRNA介导植物-微生物互作中的调控作用及其研究进展北大核心CSCD

微生物与植物之间存在错综复杂的双向交流和串扰,植物与病原微生物互作直接影响寄主植物的生存状况,而植物和益生微生物互作则有利于宿主的生长和健康,共生微生物也会从中受益。不管是病原微生物还是有益微生物进入植物体内,植物miRNA都会迅速做出响应,同时微生物也可以产生miRNA样RNA(miRNA-likeRNA,milRNA)影响植物健康,可见miRNA(或milRNA)是植物与微生物互作过程中迅速响应的重要媒介分子,其内在机制研究近年来取得了许多进展。文中概述了植物-病原微生物、植物-益生微生物互作中miRNA的调控作用,重点阐述了植物miRNA在植物-病原微生物互作过程中对寄主植物抗病性的调控作用和植物-益生微生物互作过程中对宿主植物生长发育及代谢的调控,以及真菌milRNA对寄主植物的跨界调控作用。     

环境大气臭氧污染对植物的影响（三）

(六)O_3与环境因素的互作环境中诸多的生物因素和非生物因素(表3) 都可与 O_3发生互作(相互作用),产生相加作用(=单独作用之和)、协同作用(>单独作用之和)和拮抗作用(<单独作用)。在互作的双方中,O_3起主要的作用。但互作可影响植物对 O_3的反应方式和程度。此外,已经证明,与植物 O_3     

生化他感作用的种群生态学意义

对生化他感作用的种群生态学意义,包括种群动态、种群关系、种群进化的影响,作了概述。     

钙与果实采后生理

本文简介钙在果实中的积累、分布、存在形式和生理功能,同时对其在果实采后的生理作用、作用机制以及提高钙含量的可行措施作了归纳。     

花生油对酒精所致胃粘膜损伤的保护作用

着重研究了花生油对无水酒精所引起的大白鼠胃粘膜损伤的保护作用,并对花生油作用的有效部位和机制作了初步探讨。     

Interaction between ellagic acid and calf thymus DNA studied with flow linear dichroism UV-VIS spectroscopy

The interaction between ellagic acid and DNA has been characterized with respect to the geometry of the ellagic acid-DNA complex, and the active form of ellagic acid has been identified. Optical spectroscopic methods have been employed to examine the interaction between double-stranded calf thymus DNA and ellagic acid in low-ionic-strength aqueous solutions at pH values of 5.5, 7.0, and 8. 8. Based on normal absorption titration and flow linear dichroism experiments, it is confirmed that the neutral form of ellagic acid present at pH 5.5 binds to double-stranded DNA. It is found that the plane of the ellagic acid chromophore is positioned at an angle relative to the DNA helix axis, which is in accordance with intercalation of ellagic acid in DNA. It is concluded that at higher values of pH no or a very limited amount of ellagic acid binds to DNA. These results prove that the direct interaction between ellagic acid and DNA must be taken into account when evaluating the mechanism underlying the observed biological effects of this plant phenol.     

Effects of cultivar, fruit number and reflected photosynthetically active radiation on Fragaria x ananassa productivity and fruit ellagic acid and ascorbic acid concentrations

BACKGROUND AND AIMS: A number of strawberry varieties were surveyed for their total ellagic acid concentration, and attempts were made to determine if ellagic acid and ascorbic acid concentrations of two strawberry cultivars could be increased by polythene reflective mulches. METHODS: After adjusting crop yields and cultivation using polythene mulches with two different PAR reflective capacities, field- and polytunnel-grown strawberries were analysed for ellagic acid and ascorbic acid concentrations by HPLC. Comparative measurements of yield and fruit quality were determined along with plant developmental changes. KEY RESULTS: Ellagic acid concentration varied widely with strawberry cultivar (60-341 microg g(-1) frozen weight), as did the ratio of conjugated ellagic acid : free ellagic acid. Also, there was significant year-to-year variation in total ellagic acid concentration with some cultivars. Mulches with different reflective capacities impacted on strawberry production; highly reflective mulches significantly increased growth and yield, the latter due to increases in fruit size and number. CONCLUSIONS: Highly reflective mulches significantly increased total concentrations of ellagic acid and ascorbic acid relative to control in fruit of different cultivars. The potential of agronomic practices to enhance the concentration and amounts of these important dietary bioactive compounds is discussed.     

Utilization of acorn fringe for ellagic acid production by Aspergillus oryzae and Endomyces fibuliger

Conversion of acorn fringe extract into ellagic acid production by Aspergillus oryzae and Endomyces fibuliger were investigated. The results showed that ellagic acid production was maximized when co-fermentation of the two fungi was performed at 30 degrees C and pH 5.0 with 5.7 g/l of initial substrate concentration, which were close to the optimal values for both fungi to yield an appropriate consortium of hydrolytic enzymes. Meanwhile, it was found that the co-fermentation could compensate the deficiencies in the level of polyphenol oxidase activity from pure A. oryzae and the levels of ellagitannin acyl hydrolase and beta-glucosidase activities from pure E. fibuliger, resulting in. 0.91 g/l of biomass concentration containing 1.84 g/l of ellagic acid. The research not only demonstrates that the co-fermentation is an effective approach to utilize forest byproduct for ellagic acid production, but also provides more evidences for understanding evolution of ellagic acid production with enzymes actions, which is important for process control of ellagic acid production in industrial application.     

DNA damaging activity of ellagic acid derivatives

A strain of yeast rendered repair deficient by the conditional expression of the RAD52 locus was used to search for natural products capable of damaging DNA. Four ellagic acid derivatives, namely 3,3'-dimethyl-4'-O-beta-D-glucopyranosyl ellagic acid (1), 3,3',4-trimethyl-4'-O-beta-D-glucopyranosyl ellagic acid (2), 3'-methyl-3,4-O,O-methylidene ellagic acid (3) and 3'-methyl-3,4-O,O-methylidene-4'-O-beta-D-glucopyranosyl ellagic acid (4), were identified by this assay as DNA damaging natural principles from several plants, including Alangium javanicum, Anisophyllea apetala, Crypteronia paniculata, Mouririi sp. and Scholtzia parviflora. Although none of the isolated principles mediated frank strand scission of DNA in vitro, all of them potently inhibited the growth of yeast in the absence of expression of RAD52.     

Ellagic acid from acorn fringe by enzymatic hydrolysis and combined effects of operational variables and enzymes on yield of the production

The individual effects of three different enzyme types -- one single enzyme (ellagitannin acyl hydrolase) and two combinations of enzymes (ellagitannin acyl hydrolase-beta-glucosidase-polyphenol oxidase and ellagitannin acyl hydrolase-cellulase-xylanase) -- on ellagic acid yield, combined with other process parameters -- enzyme concentration, hydrolysis time, particle size and solid-to-liquid ratio -- were evaluated by response surface methodology. The selection of the enzymes for the study was based on preliminary experiments that showed higher increments in ellagic acid yield. The quantitative parameters studied were enzyme concentration (0.1, 0.45, 2 w/w or %), solid-to-liquid ratio (0.05, 0.15, 0.2), particle size (220, 445, 900 microm) and hydrolysis time (60, 89, 132 min). Experimental data for ellagic acid yield obtained with a single enzyme and two combination enzymes correlated very well with process parameters (P<0.0001), resulting in models with high coefficient of determination for ellagic acid yield (r(2)=0.9636). The combinations of enzymes appeared more effective for ellagic acid production than the single enzyme did. The yield of ellagic acid from non-heat-treated acorn fringe by the use of enzymes in general increased, compared with that from heat-treated material. The research opens a technological-efficient way and develop easily-available renewable raw material for ellagic acid production.     

Pharmacokinetic study of ellagic acid in rat after oral administration of pomegranate leaf extract

Quantification of ellagic acid, the principal bioactive component of pomegranate leaf extract, in rats plasma following oral administration of pomegranate leaf extract was achieved by using a high-performance liquid chromatographic method. The calibration curve for ellagic acid was linear (r2=0.9998) ver the concentration range 0.026-1.3 microg/ml. The intra- and inter-day assays of ellagic acid from rat plasma were less than 6.52% at concentration range from 26 to 1300 ng/ml and good overall recoveries (94.5-102.4%) were found on same concentrations. The concentration-time profile was fitted with an open two-compartment system with lag time and its max concentration of ellagic acid in plasma was 213 ng/ml only 0.55 h after oral administration extract 0.8 g/kg. The pharmacokinetic profile indicates that ellagic acid has poor absorption and rapid elimination after oral administration pomegranate leaf extract, and part of it was absorbed from stomach.     

Growth inhibition of selected food-borne bacteria by tannic acid, propyl gallate and related compounds

Tannic acid, propyl gallate, gallic acid and ellagic acid were tested for their inhibitory effects on selected food-borne bacteria by the well assay technique. Tannic acid and propyl gallate were inhibitory whereas gallic acid and ellagic acid were not.     

Optimization of ellagic acid production from ellagitannins by co-culture and correlation between its yield and activities of relevant enzymes

Aspergillus oryzae was co-cultured with Trichoderma reesei using acorn cups extract containing up to 62% ellagitannins as substrate to produce ellagic acid with relatively high levels of ellagitannin acyl hydrolase, cellulase and xylanase. Ellagitannins concentration, initial pH, T. reesei and A. oryzae during the fermentation were identified as important process parameters effecting ellagic acid accumulation and the enzymes syntheses. These parameters were optimized by uniformity design to determine the optimum condition for ellagic acid production. Under optimum operational condition, ellagic acid yield could be arrived at 24%, when the fermentation run lasted 96h with an initial pH of 4.5, an ellagitannins concentration of 4gl(-1), T. reesei of 3ml and A. oryzae of 3ml. Meanwhile, it was found that the three enzymes activities correlated very well with ellagic acid yield, resulting in model with high coefficient of determination (R(2)=0.98). The results indicate that the mixed culture of T. reesei and A. oryzae is an effective approach to produce an enzyme system of degrading ellagitannins for ellagic acid production.     

Ellagic acid mitigates rotenone-induced damage via modulating mitochondria function in Drosophila melanogaster

Constant, systematic exposure to rotenone has been utilized in animal models to induce Parkinsonism. Ellagic acid is a polyphenol with anti-inflammatory and antioxidative properties which is found in numerous natural fruits. Here, we investigated the therapeutic effects of ellagic acid in rotenone-induced toxicity in Drosophila melanogaster evaluating their antioxidant and mitoprotective properties. Adult flies were treated with rotenone and ellagic acid through their diet for 7 days, thereafter markers of neurotoxicity (acetylcholinesterase, monoamine oxidase, tyrosine hydroxylase), antioxidant and oxidative stress markers (hydrogen peroxide, nitric oxide, lipid peroxidation, protein carbonyl contents, catalase, total thiol, and nonprotein thiol) was measured. Mitochondrial respiration was also evaluated in the flies. Survival assay was carried out with both genders of the flies, and we observed a significant increase in the survival rate of flies exposed to both rotenone and ellagic acid when compared with the increased mortality rate in the groups exposed to rotenone alone. The impaired locomotion, altered redox status, and enzymes of neurotoxicity induced by rotenone were significantly ameliorated by ellagic acid to levels comparable to the control. In addition, rotenone-induced complex 1 inhibition and altered bioenergetic state were restored upon ellagic acid supplementation. These findings show the beneficial properties of ellagic acid against pesticides induced toxicity.