The pectic disaccharides lepidimoic acid and β-d-xylopyranosyl-(1→3)-d-galacturonic acid occur in cress-seed exudate but lack allelochemical activity

Background and aims Cress-seed (Lepidium sativum) exudate exerts an allelochemical effect, promoting excessive hypocotyl elongation and inhibiting root growth in neighbouring Amaranthus caudatus seedlings. We investigated acidic disaccharides present in cress-seed exudate, testing the proposal that the allelochemical is an oligosaccharin—lepidimoic acid (LMA; 4-deoxy-β-l-threo-hex-4-enopyranuronosyl-(1→2)-l-rhamnose).Methods Cress-seed exudate was variously treated [heating, ethanolic precipitation, solvent partitioning, high-voltage paper electrophoresis and gel-permeation chromatography (GPC)], and the products were bioassayed for effects on dark-grown Amaranthus seedlings. Two acidic disaccharides, including LMA, were isolated and characterized by electrophoresis, thin-layer chromatography (TLC) and nuclear magnetic resonance (NMR) spectroscopy, and then bioassayed.Key Results Cress-seed exudate contained low-M_r, hydrophilic, heat-stable material that strongly promoted Amaranthus hypocotyl elongation and inhibited root growth, but that separated from LMA on electrophoresis and GPC. Cress-seed exudate contained ∼250 µm LMA, whose TLC and electrophoretic mobilities, susceptibility to mild acid hydrolysis and NMR spectra are reported. A second acidic disaccharide, present at ∼120 µm, was similarly characterized, and shown to be β-d-xylopyranosyl-(1→3)-d-galacturonic acid (Xyl→GalA), a repeat unit of xylogalacturonan. Purified LMA and Xyl→GalA when applied at 360 and 740 µm, respectively, only slightly promoted Amaranthus hypocotyl growth, but equally promoted root growth and thus had no effect on the hypocotyl:root ratio, unlike total cress-seed exudate.Conclusions LMA is present in cress seeds, probably formed by rhamnogalacturonan lyase action on rhamnogalacturonan-I during seed development. Our results contradict the hypothesis that LMA is a cress allelochemical that appreciably perturbs the growth of potentially competing seedlings. Since LMA and Xyl→GalA slightly promoted both hypocotyl and root elongation, their effect could be nutritional. We conclude that rhamnogalacturonan-I and xylogalacturonan (pectin domains) are not sources of oligosaccharins with allelochemical activity, and the biological roles (if any) of the disaccharides derived from them are unknown. The main allelochemical principle in cress-seed exudate remains to be identified.     

Monomeric A beta and metals reduce their cytotoxicities to each other

The present study has examined the effect of metals, such as iron and copper on the cytotoxicity of amyloid beta protein 1-40 (Abeta40). First, we showed that monomeric Abeta40 has stronger cytotoxicity than various type of aggregated Abeta40. Next we showed the addition of metals into the monomeric Abeta40 reduced the cytotoxicity of either monomeric Abeta40 or metals (iron and copper) although the addition of metals into monomeric Abeta40 resulted in a marked increase of aggregated form of Abeta40, which composed of beta-sheeted Abeta40 and Abeta40 aggregation not characterized by beta-sheet fibrils (coagrated Abeta40). Taken together, the metals and monomeric Abeta40 affect on each other and cause the reduction of their cell toxicity.     

哈尔滨郊区人为鼠疫疫源地鼠类种群动态分析

根据黑龙江省哈尔滨市郊区人为鼠疫疫源地1952～1996 年达乌尔黄鼠密度监测资料,建立了黄鼠密度的自回归模型D_t=0.1374+1.130 2D_t-1-0.4754D_t-2+0.8033D_t-3-0.4680D_t-4 , 对1997～2000 年的密度进行了预测。1952～1980 年, 人工捕黄鼠率极为显著地影响黄鼠密度(P<0.001)。在该地区, 1982～1996年共捕啮齿动物6种, 其中黄鼠和大仓鼠为野外优势种, 褐家鼠为室内优势种, 其余为常见种。大仓鼠、黑线仓鼠、黑线姬鼠均与夜行鼠总捕获率正相关(P<0.01),逐步回归模型为总捕获率=0.5219+1.1733 大仓鼠+10312 黑线仓鼠+ 1.1273小家鼠+ 0.9242 褐家鼠(P<0.0001)。黄鼠密度与捕获率不相关(P>0.10)。     

生态效率视角下旅游业生态福利及驱动因素——以常州市为例

经济效益最大化与环境影响最小化是绿色旅游与可持续发展的内在诉求。本文立足于生态效率模型,创新性地提出旅游业生态福利指数,据此分析1995—2017年常州市旅游业生态福利变化趋势及驱动效应,旨在为评价旅游产业绿色可持续发展能力提供新视角。研究发现:(1)1995年来常州市生态足迹呈现先增长后下降趋势,但旅游业各部门生态足迹均不断增长,游客人均资源消耗约为本地居民人均资源消耗的2.81—9.37倍,面临艰巨的节能减排压力。(2)1995年来常州市本底生态效率与旅游生态效率逐年提升,分别增加了37033元/hm²和44226元/hm²;同等资源消耗下,旅游业平均每单位产出高14409元/hm²,但游客年均消耗的自然资源却为本地居民的5.78倍。(3)1995—2007年间常州市旅游生态福利升降波动频繁,2007年来呈以直线式地骤降,受规模效益影响,旅游业的绿色生态福利和高效性不断弱化,为全市的资源节约量下降了10.7倍。(4)迪氏对数指标分解法(Logarithmic Mean Disivia Index, LMDI)揭示规模...     

Biochemical characterization of a lichenase from Penicillium occitanis Pol6 and its potential application in the brewing industry

The purification and characterization of an extracellular lichenase from the fungus Penicillium occitanis Pol6 were studied. The strain produced the maximum level of extracellular lichenase (45 ± 5 U ml⁻¹) when grown in a medium containing oat flour (2%, w/v) at 30 °C for 7 days. The purified enzyme EG_L showed as a single protein band on SDS–PAGE with a molecular mass of 20 kDa. Its N-terminal sequence of 10 amino acid residues was determined as LDNGAPLLNV. The purified enzyme showed an optimum activity at pH 3.0 and 50–60 °C. The half-lives of EG_L at 60 °C and 70 °C were 80 min and 21 min, respectively. Substrate specificity studies revealed that the enzyme is a true β-1,3-1,4-d-glucanase. The enzyme hydrolyzed lichenan to yield trisaccharide, and tetrasaccharide as the main products. Under simulated mashing conditions, addition of EG_L (20 U/ml) or a commercial β-glucanase (20 U/ml) reduced the filtration time (25% and 21.3%, respectively) and viscosity (10% and 8.18%, respectively). These characteristics indicate that EG_L is a good candidate in the malting and brewing industry.     

Biomineralization of 2,3,4,6-Tetrachlorophenol by Bacillus sp. and Staphylococcus sp. Isolated from Secondary Sludge of Pulp and Paper Mill

Three 2,3,4,6-tetrachlorophenol (2,3,4,6-TeCP)-mineralizing bacteria were isolated from the secondary sludge of a pulp and paper industry. The isolates used 2,3,4,6-TeCP as a source of carbon and energy and were capable of degrading this compound, as indicated by stoichiometric release of chloride and biomass formation. Based on 16S rRNA gene sequence analysis, the bacteria were identified as Bacillus megaterium (CL3), Staphylococcus suciri (CL10), and Bacillus thuringensis (CL11). High-performance liquid chromatography (HPLC) analysis revealed that these isolates were able to degrade 2,3,4,6-TeCP at higher concentrations (600 mg/L or 2.5 mM). A consortia of the isolates completely removed 2,3,4,6-TeCP from the sludge obtained from a pulp and paper mill within 2 weeks when supplemented at a rate of 100 mg/L or 0.43 mM. A bacterial consortium also significantly reduced absorbable organic halogen (AOX) and extractable organic halogen (EOX) by 63% and 68%, respectively, from the sludge. These isolates have a high potential to remove 2,3,4,6-TeCP and may be used for remediation of pulp paper mill waste containing 2,3,4,6-TeCP.     

大气污染对珠江三角洲村边林植被的影响

在群落结构与组成分析的基础上,阐明了陶瓷工业污染对自然条件下生长的植被伤害状况、程度和原因,为类似地理气候区重度污染背景下退化生态系统的植被恢复提供参考。野外调查样地位于广东省佛山市南海区一村边半自然次生林内。结果表明,该森林以隆缘桉和尾叶桉占优势,其次是乡土树种鸭脚木、泥竹,重要值依次为26.75、17.08、16.27和11.50,其它伴生种的重要值不足30。根据冠层叶可见症状、失绿和脱叶对植物受害进行综合评价,分死亡(受害程度100%,全部叶死亡脱落)、重度(60%-100%)、中度(25%-60%)、轻度(10%-25%)和健康(<10%)5个级别。隆缘桉和马尾松冠层叶完全脱落属于死亡类,泥竹、南岭黄檀属重度受害种类。尽管其它伴生树种有较低的重要值,但其中多数种类显示出较强耐受能力,这些种类包括鸭脚木、珊瑚树、酒饼叶、光叶山矾、白背叶、银柴、竹节树、山黄麻、构树、粗叶榕、潺槁树等。和乔木层比较,林下灌木和草本植物受污染的伤害大大降低。桉树类树种因其速生、快速郁闭的特点被认为是华南荒山、退化丘陵地区植被恢复的重要种类,在重度污染地区已经受到严重威胁,应该引起重视。另一方面,某些乡土树种在重度污染地区环境修复中显示出潜力和前景。     

我国宠物业现状、机遇与挑战

我国宠物业是一个朝阳产业,发展速度快,问题多,整体水平不高,以市场化为主。宠物业的发展应当是全面的,逐步走向成熟。我们在宠物饲养观念、宠物在社会生活中的作用研究、宠物疾病防治、宠物与人共患疾病的关注度、宠物医疗、宠物药品、宠物食品、宠物医学教育等全方位面临机会和挑战。今后,中国大陆的宠物业在宠物疫苗研制、新宠物药品研发、新中兽药研制和推广、高质量宠物食品和处方食品生产、高水平的宠物医疗机构的扩展、和宠物与人类比较医学上必将得到很大的发展机会。     

一个新兴的朝阳产业——宠物行业的前景

随着人民生活水平提高,物质生活富裕,传统家庭结构发生了变化和工作压力的增大,人际关系逐渐趋于淡化,使越来越多的人将感情投注于宠物身上,宠物与人类的关系已经发生了变化,人们越来越注重休闲生活情趣的培养,不再以追求温饱为主要目标,人与宠物间的依赖关系,随着时间的流逝而日益浓厚。饲养的犬猫不再扮演看门和捉老鼠的角色,而是人类休闲时的玩伴。在社会提倡人与人之间关爱的同时,也提升了人们对动物福利的理念,对社会的关爱和爱心,但他们迫切需要兽医医疗、疫病防控和饲养管理的指导。怎样将兽医知识教育公众并增加公众对饲养宠物的理解、对人兽共患病的认识,对所有影响动物福利问题的意识是我们的责任。伴随着宠物数量的增长,围绕宠物经济和宠物行业的发展催生了一些新兴的产业,这些产业带来的不仅是相关产品的诞生,我们看到了这些产业上升的空间和它的发展前途,成就了人们的就业和再就业,同时也给宠物行业带来了不可估量的经济效益,并对社会产生了巨大的社会价值和难以估计的经济产值。目前国内宠物市场已进入一个高速发展的时期,全球发达国家都将目光投向了中国日益增长的消费水平,这也标志着中国宠物市场发展的时机已经成熟。宠物市场涌现出的商机不可小觑,也正是我们看到的中国巨大的商机。以宠物为主题的产业日新月异,中国的宠物行业将迈上一个新的台阶。