FISH ASSEMBLAGE RESPONSES TO DIFFERENT SECONDARY CHANNEL DESIGNS IN THE LOWER MISSISSIPPI RIVER,U.S.A.:A TEMPLATE FOR RIVER RESTORATION

The lower Mississippi River(LMR) has been heavily modified for multiple human purposes such as navigation, flood control, and bank stabilization. However, the LMR simultaneously supports a diverse fish fauna that includes recreational and commercial fisheries. Due to river training and diversion structures constructed during the past 80 years, the historic characteristics of the LMR have been drastically altered and have likely influenced fishes and fisheries in the system. One common restoration measure used throughout the LMR has been to "notch" wing-dike structures that close secondary(side) river channels. Dike notching allows year-round flows through secondary channels, which enhances habitat diversity and promotes biological productivity at the ecosystem scale. Although notching is presumed good for LMR fishes and other biota, few studies have examined its effects on fish assemblages. In this study, fish assemblages were sampled at seven LMR secondary channels spanning from river kilometer(rkm) 628(Louisiana-Mississippi, U.S.A.) upstream to rkm 1504(Missouri-Kentucky, U.S.A.). Four secondary channels were termed "permanent"(i.e.,with notched dikes) while three secondary channels were termed "temporary"(i.e., without notched dikes).Fishes were sampled by boat-mounted electrofishing conducted during falling and low stages from1995—1997. Fish assemblages differed between permanent and temporary secondary channels, and varied somewhat between falling and low stages. Gizzard shad(Dorosoma cepedianum), threadfin shad(D. petenense), and white bass(Morone chrysops) demonstrated consistent preferences for low-current conditions associated with temporary secondary channels. Conversely, blue catfish(Ictalurus furcatus), flathead catfish(Pylodictis olivaris), and freshwater drum(Aplodinotus grunniens) were more associated with permanent secondary channels. Future restoration strategies in the LMR should consider dike notching and resultant maintenance of permanent secondary channels in selected river reaches. However, temporary secondary channels also contain unique fish species, and also appear to be important sites of riverine primary production. Restoration strategies should consider a balance of both secondary channel types, which should support the greatest biodiversity for the LMR ecosystem.     

Applications of stem cells and bioprinting for potential treatment of diabetes

Currently, there does not exist a strategy that can reduce diabetes and scientists are working towards a cure and innovative approaches by employing stem cellbased therapies. On the other hand, bioprinting technology is a novel therapeutic approach that aims to replace the diseased or lost β-cells, insulin-secreting cells in the pancreas, which can potentially regenerate damaged organs such as the pancreas. Stem cells have the ability to differentiate into various cell lines including insulinproducing cells. However, there are still barriers that hamper the successful differentiation of stem cells into β-cells. In this review, we focus on the potential applications of stem cell research and bioprinting that may be targeted towards replacing the β-cells in the pancreas and may offer approaches towards treatment of diabetes. This review emphasizes on the applicability of employing both stem cells and other cells in 3 D bioprinting to generate substitutes for diseased β-cells and recover lost pancreatic functions. The article then proceeds to discuss the overall research done in the field of stem cell-based bioprinting and provides future directions for improving the same for potential applications in diabetic research.     

Behavioral and neural auditory thresholds in a frog

Vocalizations play a critical role in mate recognition and mate choice in a number of taxa, especially, but not limited to, orthopterans, frogs, and birds. But receivers can only recognize and prefer sounds that they can hear. Thus a fundamental question linking neurobiology and sexual selection asks-what is the threshold for detecting acoustic sexual displays? In this study, we use 3 methods to assess such thresholds in tdngara frogs: behavioral responses, auditory brainstem responsesz and multi unit electrophysiological recordi ngs from the midbrain.We show that thresholds are lowest for multiunit recordings (ca. 45 dB SPL), and then for behavioral responses (ca. 61 dB SPL), with auditory brainstem responses exhibiting the highest thresholds (ca. 71 dB SPL). We discuss why these estimates differ and why, as with other studies, it is unlikely that they should be the same. Although all of these studies estimate thresholds they are not measuring the same thresholds;behavioral thresholds are based on signal salienee whereas the 2 neural assays estimate physiological thresholds. All 3 estimates, however, make it clear that to have an appreciation for detection and salienee of acoustic signals we must listen to those signals through the ears of the receivers.     

中国省级行政区生态环境可持续性评价

从自然条件、人类胁迫、生态环境效应和社会响应4个主题出发,构建了包含28个指标的中国省级行政区生态环境可持续性评价指标体系,并通过专家调查和层次分析法为各主题层中的指标赋权.分别用各主题层中的指标和对应的权重,采用加权平均法构建自然条件(NSI)、人类胁迫(HPI)、生态环境效应(EEI)和社会响应(SRI)4个分指数,然后用这4个分指数通过灰色关联法构建综合生态环境可持续性指数(CEI),对我国各省级行政区生态环境可持续性进行评价.同时论文通过主成分分析法和相关分析法分析造成各指数地域差异的主导因素和评价中指标赋权的合理性.最后以4个分指数作为变量,采用快速样本聚类法对我国31个省级行政区进行聚类分析.评价结果表明,2003年我国各生态环境指数存在显著的地域差异.自然条件从东南到西北呈明显的由优到劣的过渡趋势,降雨量、年均气温、森林覆盖率和水网密度4个指标是导致地域差异的主导因素;人类胁迫东部发达地区明显高于西部和中部地区,同一个地区经济发展水平存在显著的正相关;生态环境效应西北地区最为显著,同各地区自然条件存在显著的负相关,在人类活动干扰下,自然条件差的地区更容易发生生态损害与退化;社会响应无明显的地域分析规律,各地区经济发展水平对其有一定影响,但并非决定性因素.区域综合生态环境可持续性由区域NSI、HPI、EEI和SRI共同决定,综合评价得到2003年我国各省级行政区生态环境可持续性排序情况,其中生态环境可持续性最强的几个地区为海南、云南、广西、江西等地,最弱的几个地区为内蒙古、宁夏、上海、西藏、新疆等地.最后,聚类分析把我国31个省级行政区聚为生态环境特点各异的六大类,可以促进我国生态环境的分类管理.     

A lubricant boundary condition for a biological body lined by a thin heterogeneous biofilm

We study the asymptotic behavior of an incompressible viscous fluid flow in a biological body lined by a thin biological film with a cellular microstructure,varying thickness,and a heterogeneous viscosity regulated by a time random process.Let ting the thickness of the film tend to zero,we derive an effective biological slip boundary condition on the boundary of the body.This law relates the tangential fluxes to the tangential velocities via a proportional coefficient corresponding to the energy of some local problem.This law describes the ability of the biological film to function as a lubricant reducing friction at the wall of the body.The tangential velocities are functions of the random trajectories of a finely concentrated biological particle.     

微生物在水环境污染物降解中的应用

每年有大量来自工业、农业、养殖业和城市污水处理厂的废水被排入到水环境中,因此,地球上的水环境面临大量来自生活废水、工农业废水、非法排放的废水及其它废水的污染物质(如抗生素、杀虫剂,除草剂、烃等)的严重挑战,特别是近年来随着集约化养殖的发展,废水污染问题日益突出,并且随着分析手段的进步,能够检测到被排入水环境中的化学污染物质也越来越多,这些化学污染物对水环境中的生物产生有害影响.但是,微生物在污染控制上具有许多重要的作用.因此,本文对微生物在水环境污染物降解中的应用进行了评论.结果表明微生物主要是应用在水产养殖水中,而在其它的水体系(如河、湖、海)的应用较少.     

猛犸雪原

正我对东北的了解和向往,最早来自上世纪70年代初期读过的描写北大荒知青生活的小说《征途》。我最感兴趣的是书中描述的东北的自然风光和动物植物:"遮天蔽日的红松林,尽管被大雪覆盖,但远远望去,依然是郁郁苍苍。朔风吹过,发出万马奔腾的松涛声。那一望无际的桦树林,好像千百株银枝玉树,俊秀挺拔地屹立在冰天雪地中";"咱这疙瘩呀,是‘棒打獐子瓢舀鱼,雉鸡飞到饭锅里’。汽车在公路上撞死几个挡道的狍子,跟你们南方碾死一条蛇一样不稀     

我国近代发酵工业的先驱——金培松

金培松(又名金柏卿,英文名Pei-sung King)1906年10月30日生于浙江省东阳后岑山村.童年时他是在农村渡过,牛角挂书,放牛识字.1919年进入东阳县长山小学,1923年高小毕业,入东阳县城初级中学,3年后毕业,考入浙江省立第一中学高中部,1年后因家庭经济困难辍学,1927年9月以高中肄业学历被上海劳动大学农学院农艺化学系录取,1931年毕业.     

Monitoring of brown stink bug (Hemiptera: Pentatomidae) population dynamics in corn to predict its abundance using weather data

The brown stink bug (BSB), Euschistus servus (Say)(Hemiptera: Pentatomidae), is a serious economic pest of corn production in the southeastern United States. The BSB population dynamics was mon itored for 17 weeks from tasseling to preharvest of corn plants (i.e., late May to mid-September) using pheromone traps in three corn fields from 2005 to 2009. The trap data showed two peaks in early June and mid-August, respectively. The relationship between trap catch and pregrowing season weather data was examined using correlation and stepwise multiple factor regression analyses. Weather indices used for the analyses were accumulated growing degree day (AGDD), number of days with minimum temperature below 0℃(Subz), accumulated daily maximum (AMaxT) and minimum temperatures (AMinT) and rainfall (ARain). The weather indices were calculated with lower (10℃) and upper (35℃) as biological thresholds. The parameters used in regression analysis were seasonal abundance (or overall mean of BSB adult catch)(BSBm), number of BSB adults caught at a peak (PeakBSB), and peak week (Peakwk). The BSBm was negatively related to high temperature (AmaxT or AGDD) consistently, whereas IstPeakBSB was positively correlated to both ARain and Subz, irrespective of weather data durations (the first 4, 4.5, and 5 months). In contrast, the 7-month weather data (AGDD7) were negatively correlated to the BSBm only, but not correlated to the second PeakBSB. The 5-year monitoring study demonstrated that weather data can be used to predict the BSB abundance at its first peak in tasseling corn fields in the southeastern U.S. states.     

多种神经活性物质在幼年猫和鸡视网膜神经细胞中的共存(简报)

视网膜起源于前脑泡,结构简单层次分明,因此常被视为脑的简化模型。但近期工作证明,视网膜包含的神经活性物质(神经递质、调质和神经肽)种类之多、分布之复杂并不亚于脑。尤其是无长突细胞不仅包含多种递质和肽类,而且还有递质与肽类或肽类与肽类在一个细胞中的共存。对视网膜神经递质、调质和神经肽的研究将是探索脑奥秘的有效途径。     

注射装载孕酮的红细胞膜泡诱发蟾蜍卵成熟的研究

中华大蟾蜍长足的卵母细胞,经注入装载水相孕酮的红细胞膜泡,能被诱发成熟;直接注入水相孕酮的卵母细胞,无能恢复成熟分裂。将蛋白酶处理的红细胞制备成装载水相孕酮的膜泡,注入卵内,照样能诱发其成熟分裂;然而,分别用根皮素结合或磷脂酶A_2水解红细胞膜磷脂,制备的膜泡,虽亦包裹着水相孕酮,但注射的卵母细胞都未能被诱发成熟。这些结果表明,在通过红细胞膜转运孕酮诱发卵母细胞成熟过程中,红细胞膜上的某些膜蛋白可能不是必要的成份,而膜磷脂类却是关键成份,它不仅可能保证孕酮不被迅速代谢,且保证孕酮从卵母细胞内部诱发成熟分裂。     

低分子量神经丝蛋白(NF-L)的体外组装

利用超速离心和离子交换层析技术,从牛脊髓中分离纯化了神经丝蛋白三组分:NF-L,NF-M和NF-H。应用电镜负染色和金属投影方法研究神经丝的形态结构与NF-L的体外组装,结果表明:神经丝由10nm的核心纤维与外周的丝状突起组成;在近似生理条件下,NF-L可在60min内组装成10nm纤维,纤维由4根亚丝缠绕而成;在碱性缓冲液中,NaCl能促进NF-L装配成短纤维,这种10nm的短纤维无法连接成长纤维。     

Molecular structure for microbial polysaccharides: conformation of the Klebsiella serotype K9 capsular polysaccharide

Fibre type X-ray diffraction patterns have been obtained from oriented, semicrystalline films prepared from the sodium salt form of the bacterial capsular polysaccharide of Klebsiella serotype K9. The molecule has a pentasaccharide repeating sequence, with four neutral residues in the backbone and a glucoronic acid side chain. A novel feature of the molecule is the incorporation of α-l-rhamnose residues, one 1,2 linked and two 1,3 linked in the backbone. Analysis of the X-ray diffraction results indicate an extended three-fold helical conformation with an axially projected chemical repeat of 1.377 nm. Both left and right handed helices have been examined using linked atom least squares techniques to optimize the stereochemistry while simultaneously meeting the observed helical parameters.     

细胞骨架对凝血酶诱导人血小板分泌反应的调节(英文)

本文利用血小板表面外露的GMP-140为血小板分泌反应的特异性标志,通过放射免疫分析法定量测定血小板表面GMP-140分子数,研究了细胞骨架抑制剂对凝血酶诱导血小板分泌反应的影响。结果表明,凝血酶激活使血小板表面GMP-140的外露明显增加,反应迅速,并在一定范围内呈剂量和时间依赖性;而ADP刺激则几乎不引起GMP-140外露的增加。凝血酶激活前加入不同的细胞骨架抑制剂处理可产生不同的效应:细胞松驰素B(肌动蛋白微丝抑制剂)可明显上调凝血酶诱导的GMP-140外露;而秋水仙素(微管抑制剂)则下调GMP-140的外露;两者同时处理仍呈现明显的上调作用。提示凝血酶作为一种强激活剂,不仅可通过受体-G蛋白-第二信使的途径启动血小板分泌反应,而且可能经诱导肌动蛋白微丝的形成对分泌反应起反馈性负调节作用。微管的存在则可能对凝血酶诱导的分泌反应起促进作用。虽然两种细胞骨架的作用相反,但以微丝的作用为主,两者间无相互拮抗现象。     

盐胁迫诱导的植物细胞凋亡--植物抗盐的可能生理机制

近来的研究表明,一定条件的盐胁迫可导致植物细胞程序性死亡。本文利用DNALaddering、石蜡切片原位检测以及染色体涂片原位检测,从组织、细胞以及DNA等多个方面对盐胁迫下的玉米、水稻和烟草根尖细胞死亡作了研究,形态特别是生化方面的证据表明盐胁迫诱导的植物细胞凋亡可能在植物界具有一定的普遍性。但各个物种之间有一定差异。本实验结果对盐胁迫下的植物生理机制提供了新的研究思路。同时,我们还对基于染色体制片和石蜡切片的原位检测方法进行了比较和讨论。我们认为,基于染色体制片的原位标记技术适合于定性和定量检测单个细胞的凋亡,具有一些石蜡切片所不可及的优点。     

金鱼精子质膜和核膜的区域特异性

本文结合采用扫描和透射电子显微镜(包括冷冻断裂-蚀刻、超薄切片以及细胞化学染色法),研究了金鱼精子的超微结构特征,结果表明金鱼精子的质膜和核膜都具有区域特异性:1)精子质膜内大部分区域含有许多蛋白颗粒,但在特定区域内,蛋白颗粒呈有序排列,构成晶格状结构。2)精子头颈部和尾部均有液泡密集之处,凡是覆盖着液泡区的质膜内,几乎都不含有蛋白颗粒。3)液泡区能被细胞化学方法染成致密色,表明内含糖蛋白。4)核膜孔只集中存在于靠近颈部的核膜上,而其他部分则没有。本文对上述诸点进行了讨论。     

Chlorophyll isolation,structure and function: major landmarks of the early history of research in the Russian Empire and the Soviet Union

This paper covers major events of the early history of chlorophyll research in the Russian Empire and the Soviet Union from 1771 until 1952, when the modern period of studies on photosynthesis began in full swing. Short biographical sketches of key scientists, reviews of their major research contributions and some selected photographs are included. This revised version was published online in August 2006 with corrections to the Cover Date.     

环境温度影响蟾蜍卵母细胞成熟能力的机制之实验分析

长年饲养在高温(28—30℃)环境中雌性中华大蟾蜍,它们的卵母细胞可以长足,但经激素处理时,生发泡不破裂,仅显示成熟过程早期阶段的变化。值得注意的是,在孕酮刺激后的高温卵卵质中,出观了一种能诱发低温卵恢复减数分裂的物质,称作为“依赖冬眠因子的促成熟物质”(HF-MPS)。HF-MPS 与MPF 有不少相似之处,如孕酮处理后,它们在卵质中出现的时间相仿,它们的形成均不依赖于转录水平,而是依赖于翻译水平的蛋白质合成活动;但亦存在不同之处,如MPF 诱发低温卵GVBD 时程不受温度影响,而HF-MPS 在10℃环境中,诱发低温卵GVBD 的时间明显延缓;MPF 不仅能诱发低温卵GVBD,而且同样能诱发高温卵GVBD,然而,HF-MPS 只能诱发低温卵GVBD。由此表明,MPF 和HF-MPS 似乎是截然不同的两类活性蛋白质。高温卵缺少低温诱发产生的“冬眠因子”,所以不能恢复cdc 2基因的转录活动,不能实现MPF 自身催化扩增作用,不能保证孕酮处理后的卵母细胞完成正常成熟的全过程变化。足见,低温是中华大蟾蜍卵母细胞恢复减数分裂过程中的必要条件,是导致中华大蟾蜍现有区域分布的内在原因之一。