High-throughput evaluation of pulmonary surfactant adsorption and surface film formation

The assessment of new therapeutic strategies to cure surfactant-associated lung disorders would greatly benefit from assay systems allowing routine evaluations of surfactant functions. We present a method to measure surfactant adsorption kinetics into interfacial air-liquid interfaces based on fluorescence microplate readers. The principle of measurement is simple, robust, and reproducible: Wells of a microtiter plate contain an aqueous solution of a light-absorbing agent. Fluorescence is excited and collected from the top of the wells so that fluorescently labeled surfactant injected into the bulk can be detected only once adsorbed into the air-liquid interface. Mass transfer from the bulk to the interface is achieved by orbital shaking implemented in the plate reader instrument. The method has been tested and validated by using phospholipids or surfactants of different origins, by using albumin as surfactant inhibitor, and by comparison of results with Wilhelmy balance measurements. The method is suited for implementation in high-throughput screening routines for conditions affecting, or improving, surfactant film formation. In contrast to surface tension measurements, our method gives a direct readout of the amount of surfactant adsorbing into the interface, including the functionally important amount of material firmly associating with the interfacial film.     

Gene expression in Eucalyptus branch wood with marked variation in cellulose microfibril orientation and lacking G-layers

In response to gravitational stresses, angiosperm trees form tension wood in the upper sides of branches and leaning stems in which cellulose content is higher, microfibrils are typically aligned closely with the fibre axis and the fibres often have a thick inner gelatinous cell wall layer (G-layer). Gene expression was studied in Eucalyptus nitens branches oriented at 45 degrees using microarrays containing 4900 xylem cDNAs, and wood fibre characteristics revealed by X-ray diffraction, chemical and histochemical methods. Xylem fibres in tension wood (upper branch) had a low microfibril angle, contained few fibres with G-layers and had higher cellulose and decreased Klason lignin compared with lower branch wood. Expression of two closely related fasciclin-like arabinogalactan proteins and a beta-tubulin was inversely correlated with microfibril angle in upper and lower xylem from branches. Structural and chemical modifications throughout the secondary cell walls of fibres sufficient to resist tension forces in branches can occur in the absence of G-layer enriched fibres and some important genes involved in responses to gravitational stress in eucalypt xylem are identified.     

生境破坏的空间结构对集合种群续存的影响

生境破坏及其影响是生态学亟待解决的问题之一,目前的研究主要集中在破坏数量,即遭破坏生境的比例,对物种续存的影响方面;其中最主要的结论是Levins原理和适合生境斑块最小数量(MASH),而关于生境破坏的空间结构的研究却比较稀少,在本文中,我们首先将偶对近似引入到集合种群的研究当中,并替代原有的均匀场假设.然后我们对生境破坏导致的集合种群大小、空间结构以及分布等做了全面讨论.结果显示:随破坏比例的增加,集合种群大小将下降并且其分布将远离破坏生境.进一步聚集式分布结构将瓦解.随着破坏规则化的下降,集合种群将萎缩并使其聚集结构崩溃,在破坏生境周围集合种群起初将增加然后迅速消失.根据这些结果,我们可以对边界效应进行分析:不能用破坏比例描述生境破坏的程度和影响,而只能用破坏区域边界的长短来描述.根据边界效应,我们可以得出在一连通生境上物种保护的条件是生境破坏后剩余的适合生境比例应该大于破坏前原始生境的一半.居住在斑块环境中的物种比连续生境中生存的物种可以更好地抵抗生境破坏带来的影响.     

Isolation of thermotolerant,halotolerant, facultative biosurfactant-producing bacteria

Several facultative bacterial strains tolerant to high temperature and salinity were isolated from the oil reservoir brines of an Iranian oil field (Masjed-I Soleyman). Some of these isolates were able to grow up to 60°C and at high concentration of NaCl (15% w/v). One of the isolates grew at 40°C, while it was able to grow at 15% w/v NaCl. Tolerances to NaCl levels decreased as the growth temperatures were increased. Surfactant production ability was detected in some of these isolates. The use of biosurfactant is considered as an effective mechanism in microbial-enhanced oil recovery processes detected in some of these isolates. The surfactant producers were able to grow at high temperatures and salinities to about 55°C and 10% w/v, respectively. These isolates exhibited morphological and physiological characteristics of the Bacillus genus. The partial sequencing of the 16S ribosomal deoxyribonucleic acid gene of the selected isolates was assigned them to Bacillus subtilis group. The biosurfactant produced by these isolates caused a substantial decrease in the surface tension of the culture media to 26.7 mN/m. By the use of thin-layer chromatography technique, the presence of the three compounds was detected in the tested biosurfactant. Infrared spectroscopy and ¹H nuclear magnetic resonance analysis were used, and the partial structural characterization of the biosurfactant mixture of the three compounds was found to be lipopeptidic in nature. The possibility of use of the selected bacterial strains reported, in the present study, in different sectors of the petroleum industry has been addressed.     

Property control of sophorolipids: influence of fatty acid substrate and blending

Sophorolipids (SLs) were synthesized by fed-batch fermentation of Candida bombicola on glucose and either palmitic acid (SL-p), stearic acid (SL-s), oleic acid (SL-o) or linoleic acid (SL-l) and the structural distribution accurately determined by atmospheric pressure chemical ionization-mass spectrometry (APCI-MS). The surfactant properties, including critical micelle concentration (CMC), minimum surface tension (min.ST) and oil-water interfacial tension (IFT) were measured by tensiometry. Minimum STs of 35–36 mN/m were obtained regardless of the substrate while IFTs ranged from 3–5 mN/m with the exception of SL-l, which had an IFT of 7 mN/m. The largest disparity occurred in the CMC values, which ranged from 35 ppm for SL-s to 250 ppm for SL-l. By manually mixing these four SLs in different ratios, it was possible to better control the CMC values without affecting the min.ST or IFT, which will prove beneficial as new applications for SLs are established. Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the U.S. Department of Agriculture.     

Dynamics of Nitric Oxide and Peroxynitrite During Global Brain Ischemia/Reperfusion in Rat Hippocampus: NO-sensor Measurement and Modeling Study

The dynamics of nitric oxide (NO) and peroxynitrite concentration changes during brain ischemia/reperfusion are poorly understood. In this paper, a NO-selective sensor was used to measure NO concentration changes in the rat brain hippocampus during global brain ischemia/reperfusion. Four-vessel occlusion model of transient global brain ischemia was used. Global cerebral ischemia was induced by occluding both common carotid arteries with artery nips (for 20 min) and reperfusion was induced by loosening the artery nips. Results showed that the changes of NO concentration during global brain ischemia/reperfusion could be divided into different stages. Together with the effects of O₂ tension changes and NO synthase (NOS) on nitric oxide levels, we determined five stages in the NO concentration profile: (1) acute O₂-limited decrease stage; (2) O₂-limited steady stage; (3) neuronal NOS activation stage; (4) acute O₂-recovery elevation stage; and (5) O₂-recovery steady stage. In addition, a chemical reaction network model was constructed to simulate the dynamics of peroxynitrite during the reperfusion stage, and the effects of a change in the NO formation rate on the dynamics of peroxynitrite were investigated specifically. Results show the rate of NO formation has a great influence on peroxynitrite dynamics.     

Border and ecotone detection by vegetation composition along forest‐savanna transects in Ivory Coast

Abstract. Question: How do properties of different vegetation components vary along ecotones of semi‐deciduous forest islands, and can the depth of edge influence (DEI) of the components be detected using a novel combination of analyses? Location: Comoé National Park (CNP), NE Ivory Coast. Methods: Along eight transects at semi‐deciduous forest islands tree individuals > 20 cm DBH were mapped. At one transect, tree and shrub individuals down to 1 cm DBH were measured and cover of species was estimated. Split moving window dissimilarity analysis (SMWDA) and moving window regression analysis (MWRA) were combined to detect statistical significance of borders in multivariate vegetation data along continuous transects, to determine the width of associated ecotones, and, thus, the DEI towards the forest interior. Results: For trees > 20 cm DBH, a distinct boundary formation was detected, dominated by the semi‐fire resistant tree species Anogeissus leiocarpus. The median of DEI towards the forest interior was 55 m. Ecotone detection with all species present revealed an interlocked sequence of ecotones for grasses, herbs, woody climbers, shrubs and trees, with each of these ecotones being narrower than the overall ecotone. DEI ranged from 10 m for grasses up to 120 m for trees and shrubs. Conclusions: The coherent set of analyses applied proved to be an objective method for detecting borders and the width of associated ecotones. The patterns found may be explained by successional processes at the forest‐savanna border. The DEI measured for the forest islands in the nearly undisturbed semi‐natural system of the CNP is of relevance to concepts of core‐area analysis and the protection of forest interior species in semi‐deciduous forests in tropical West Africa.     

Effects of forest fragmentation on small mammals in an Atlantic Forest landscape

Recent studies on the effects of tropical forest fragmentation indicate that fragmented landscapes are complex and heterogeneous systems influenced by factors other than the size or degree of isolation of forest remnants: of particular importance are the quality of the matrix and the edge-induced habitat changes. In order to investigate the influence of these factors, small mammals were surveyed in 36 sites in the landscape of Una, a region that encompasses some of the last and largest Atlantic Forest remnants in northeastern Brazil. Six sites were distributed on each of six landscape components – the interiors and edges of small remnants, the interiors and edges of large remnants, and the most common forested habitats found in the matrix. The survey comprised 46,656 trap-nights and yielded 1725 individuals of 20 species of rodents and marsupials. Results revealed: an increase in beta-diversity caused by fragmentation; the contrasting effects of the altered forested habitats of the matrix, which harbor both forest and disturbance-adapted species; a greater importance of edge effect than of patch size to the observed changes in small mammal community in remnants; an association among terrestrial forest species and among arboreal forest species in terms of the distribution and abundance in the Una mosaic; and a distinctive vulnerability of these two groups of species to fragmentation. Results emphasize the biological importance and conservation value of both fragmented landscapes and small remnants in the Atlantic Forest, as well as the importance of management techniques to control and attenuate edge effects.     

贻贝棘尾虫(原生动物,纤毛门)镜像骈体自身各部移接的实验

棘尾虫是细胞表面具有特殊纤毛结构排列方式的复杂下毛类纤毛虫。其镜像骈体的两列纤毛结构几乎完全是左右对称排列 ,一个是正常方式排列的 ,另一个是相反方式排列。本文包括两项移接实验 :1)将棘尾虫口对镜像骈体一侧细胞的后半部分倒转 180°与另一侧细胞的前半部分对接 ;2 )将此种骈体一侧后半部分调转90°与另一侧细胞的前半部分对接。接后定时分期固定接块 ,以蛋白银染色法 ,观察其发育过程及结果。实验 1的发育结果为有的仍形成口对镜像骈体 ;有的成为末端对末端的镜像骈体。实验 2的发育结果为全部成为口对镜像骈体。两项实验结果均可用位置值假说解释 ,实验 1属于位置值插入的结果 ;实验 2为位置值添加的结果。为何实验Ⅰ有的发育成口对镜像骈体有的发育成末端对末端的镜像骈体 ,而实验 2却全部发育成口对镜像骈体呢 ?这是接块发育中是否发生对折的结果。Shietal.(1991)认为与预存的缘棘毛和是否具有完整表膜的面积大小有关系。接块在发育中是否发生对折与接块的伤口一侧面积大小和具完整表膜有关系。接块具完整表膜和缘棘毛的一侧由于新缘棘毛和口围带的发育生长 ,造成该侧的伸张 ,产生前后两接块向伤口一侧对折的压力 ,从而接块发生对折形成口对镜像骈体。我们认为还应有其它因素 :(1)与细胞     

Sensitivity of Nematode Life-History Groups to Ions and Osmotic Tensions of Nitrogenous Solutions

Guild designation of nematodes of similar trophic function and life-history strategy provides a basis for using nematode faunal analyses in an integrative assessment of soil food web condition. Omnivorous and predaceous nematodes, categorized at the upper end of a colonizer-persister (c-p) continuum of nematode functional guilds are generally not abundant in cropped soil. These nematodes are more sensitive to heavy metal concentrations than those in other c-p groups, but whether sensitivity to agrochemicals contributes to the observed low abundance of high c-p groups in cropped soils is less well understood. An exposure assay in solution was used to compare the sensitivity of nematodes representing various guilds obtained from field soils and from laboratory culture to several nitrogen sources. Nematodes in c-p groups 4 and 5 were more sensitive to nitrogen solutions than nematodes representing lower c-p groups. There were both osmotic and specific ion effects—the latter most evident in exposure of nematodes to NaNO₂ and (NH₄)₂SO₄. The RC₅₀ (concentration resulting in nematode recovery of one half of that of distilled water) for (NH₄)₂SO₄ was < 0.052 M-N for c-p groups 4 and 5 compared to much greater values (0.34 to 0.81 M-N) for c-p groups 1 to 3. In non-ionic polyethylene glycol (PEG) solutions, osmotic tensions of 0.40 to 0.43 MPa reduced the recovery of exposed nematodes by half (RT₅₀; water potential of solution resulting in nematode recovery of one half of that of distilled water) for c-p groups 4 and 5 compared to > 1.93 MPa for c-p groups 1 to 3. RT₅₀ values for urea solutions, also non-ionic, were greater than for PEG. Caenorhabditis elegans N2 (c-p 1) and Meloidogyne javanica (c-p 3) reared on solid medium and in hydroponic culture, respectively, were slightly more sensitive to specific ion and osmotic effects than nematodes of similar c-p groups obtained from soil. The greater sensitivity of c-p 4 and 5 nematodes to nitrogen solutions suggests that fertilizers may contribute to the low abundance of these nematodes in annual cropping systems. This study supports the use of nematode faunal analyses as indicators of chemical stress in soil.