Organic matter transport in an Appalachian Mountain river in Virginia,U.S.A.

Organic material transport in the New River, Virginia, was investigated over a 12 month period. Collections were made using drift nets and grab water samples from bridges at two sites about 210 km apart. About midway between the two sampling sites is a 1920 ha impoundment used for flood control and power generation. Dissolved organic matter (DOM) ranged 1–50 mg l^–1 at Site 1, upstream from the impoundment, and 11–19 mg l^–1 at Site 2 and was the most abundant form of organic matter at both sites during most periods of the year. Fine particulate organic matter (FPOM) ranged 1–45 mg l^–1 at Site 1 and 1–9 mg l^–1 at Site 2. Concentration of coarse particulate organic matter (CPOM) ranged 0.1–0.7 mg l^–1 at Site 1 and 0.1–0.2 mg l^–1 at Site 2. On an annual basis, the organic matter loads at Site 1 and Site 2 were computed to be 67 000 and 76 800 T y^–1, respectively, suggesting that the impoundment trapped and processed POM, and that municipal and industrial treatment facilities between the study sites supplemented DOM in the river.     

Seasonal Variability of Particulate Organic Matter in a Mountain Stream in Central Spain

The aim of this paper was to study the influence of environmental characteristics of the Mediterranean climate on seasonal variability of particulate organic matter abundance in a mountain stream. Coarse and fine fractions of both suspended and benthic particulate organic matter were determined on 14 occasions between February 1998 and November 1999 in a second‐order Mediterranean stream in Central Spain (Arroyo Mediano). Temporal variability of suspended organic matter followed a seasonal pattern, attributed to litter‐fall inputs, instream processing, and the hydrological regime. Suspended organic matter (SOM) and its seasonal variability fall well within the range reported for streams in temperate non‐Mediterranean deciduous forest. However, we found no seasonal trend in benthic organic matter (BOM) storage, and it seems that the amount of BOM remained fairly constant throughout the year. Reach retention (evaluated as the ratio between BOM and SOM per m²) was higher in summer during reduced stream flow, mainly due to coarse particulate organic matter storage. These observations do not differ from those reported for other headwater streams in temperate forested biomes, from which we conclude that there was no evidence of a Mediterranean influence on particulate organic matter dynamics in the Mediano stream, nor probably in other headwater Mediterranean streams. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

吸入~(133)Xe测定猕猴大脑血流量的研究

本文报告了用~(133)Xe吸入法测定10只猕猴大脑血流量的研究。在平均血压110毫米汞柱时,灰质平均血流量为84.5毫升/100克/分,白质为24.5毫升/100克/分,而大脑灰质血流量与血压有直接关系。结果表明本方法较敏感、可靠、无损伤性和容易操作。     

颗粒有机质的来源、测定及其影响因素

土壤活性有机质及其组分作为土壤质量的重要指标在土壤化学、物理和生物性质方面起着重要作用。颗粒有机质能够有效地反映有机质的特性,与微生物生长、营养供给及C、N的生物学调节密切相关。作为活性有机质的一个量度指标,颗粒有机质越来越受到人们的重视。本文综述了土壤颗粒有机质的来源及其在土壤有机质转化过程中的作用,对其测定方法作了系统的描述,阐明了土壤理化性质、农业措施(施肥与耕作)及土地利用类型对土壤颗粒有机质在土壤形成及维持其稳定性方面的影响。     

Effect of postweaning protein deficiency on the content and lipid composition of gray and white matter in neonatally undernourished rat brain

The effects of neonatal undernutrition and postweaning protein deficiency on the content and lipid composition of gray and white matter of 63 days old rat brain have been studied. The concentrations of different lipids remain the same, but the relative proportion of gray and white matter changes thus reflecting the differences in the concentration of whole brain lipids.     

The Effect of Mineral Particulate Matter on the Productive Characteristics of Bacterioplankton and the Degradation of Labile Organic Material

The effect of mineral particulate matter on the population of bacterioplankton, its aggregation, and productive characteristics was studied in model experiments with different concentrations of particulate kaolin and the same concentration of organic substance (sodium humate). It was found that the presence of mineral particulate matter stimulated the aggregation of bacterioplankton, improved bacterial production, and extended the productive period of bacterioplankton. The integral specific production of aggregated bacterioplankton was higher than that of free-swimming bacterioplankton. The energy metabolic coefficient K ₂ of bacterioplankton in the presence of mineral particulate matter was higher than in its absence.     

土地利用方式对土壤有机质的影响

通过对地带性常绿阔叶林、杉木人工林、农田、竹林等不同土地利用方式下土壤有机质总量、活性有机质及其组分的研究,发现土地利用方式对土壤有机质和活性有机质各组分的影响差异显著,其中阔叶林含量最高,杉木人工林低于阔叶林,竹林和农田最低。这些差别主要是由于凋落物的数量、质量以及各种管理措施不同所致。     

A meta-analysis on pyrogenic organic matter induced priming effect

Pyrogenic organic matter (PyOM) is considered an important soil carbon (C) sink. However, there are evidences that its addition to soil may induce a priming effect (PE) thus influencing its C abatement potential. The direction, the size and the mechanisms responsible for PyOM induced PE are far from being understood. We collected approximately 650 data points from 18 studies to analyse the characteristics of the PE induced by PyOM. The database was divided between the PE induced on the native soil organic matter and on fresh organic matter. Most of the studies were short-term incubation therefore the projections of findings on the long term may be critical. Our findings indicate that over 1 year PyOM induces an average positive PE of 0.3 mg C g⁻¹ soil on native soil organic matter and a PE of approximately the same size but opposite direction on fresh organic matter. We studied the correlation of PE with several properties of soil, of the added PyOM, and time after PyOM addition. We found that PyOM primes positively the native soil organic matter in the first 20 days while negative PE appears in a later stage. Negative PE was correlated with the soil C content. PyOM characterized by a low C content induced a higher positive PE on native soil organic carbon. No correlation was found between the factors record in our database and the PE induced on the fresh organic matter. We reviewed the mechanisms proposed in literature to explain PE and discussed them based on findings from our meta-analysis. We believe that the presence of a labile fraction in PyOM may trigger the activity of soil microorganisms on the short term and therefore induce a positive PE, while on the long term PyOM may induce a negative PE by promoting physical protection mechanisms.     

Anoxia Effects on CNS Function and Survival: Regional Differences

The effects of anoxia on function and survival of different central nervous system (CNS) areas were tested. As expected, synaptic function in a typical gray matter area of the brain, hippocampus, failed rapidly during 30 min of anoxia and did not recover. Mouse optic nerve and corpus callosum, two white matter (WM) areas of the brain, showed persistent function during total anoxia for periods as long as two hours. Moreover, even after two hours of anoxia followed by a recovery period, nearly half of the axons that were excitable at the outset remained functional. The corpus callosum contains a high percentage of unmyelinated axons while optic nerve axons are completely myelinated. These studies indicate that CNS structures vary greatly in their ability to function and survive anoxia. Mammalian WM, independent of myelination, is remarkably tolerant of anoxia implying that CNS axons generate enough ATP by anaerobic energy metabolism to sustain function.Special issue dedicated to Lawrence F. Eng.     

DECOMPOSITION IN ESTUARINE ECOSYSTEMS

SUMMARY

The varied sources of estuarine plant detritus and the processes and organisms involved in its decomposition are discussed in this review. In the case of emergent and peripheral vegetation, microbial decomposition commences in the phylloplane, with fairly rapid leaching of DOM occurring soon after immersion. Residual POM, largely cellulose, is decomposed more slowly by cellulolytic micro-organisms. Phytoplankton start contributing to the DOM pool before senescence by excreting soluble substances during normal metabolism and interesting regulatory mechanisms are Involved in the bacterial utilization of this material. Bacteria play a more important role than fungi in decomposition and the latter appear to be prominent only in the breakdown of mangrove litter. Predaceous microflagellates and other protists occur in association with the bacteria and feed on them, enhancing decomposition by maintaining optimal bacterial growth rates. They appear to play a more important role in mineralization than do the bacteria, which are more effective in the conservation of nutrients upon which their efficiency of detritus incorporation Is dependent. Aerobic decomposition tends to terminate in complete mineralization, whereas under anaerobic conditions incomplete oxidation yields organic end products such as volatile fatty acids. A comparison of this process with the functioning of the herbivore rumen leads to the conclusion that the latter is more cost-effective in energy terms. Contrary to earlier published statements that estuaries are major exporters of energy in the form of detritus, many export very little of this material, or are net importers. Finally, the methods for studying decomposition in estuaries must be carefully chosen because of the environmental diversity of these systems. This is particularly true of radio-labelled substrates used for uptake and turnover studies; there appears to be no universal substrate or approach.     

利用激光显微切割与microarray 技术对恒河猴脑中白质与 灰质基因表达的差异性的研究

目的:利用激光显微切割技术和microarray技术比较恒河猴脑组织中前额叶皮质(prefontal cortex,PFC)与小脑皮质(cere-bellar cortex,CBC)的灰质与白质基因表达的差异。方法:利用激光显微切割技术(laser capture dissection,LCM)与microarray技术的有效结合,提取恒河猴PFC与CBC的白质与灰质,分别提取RNA,合成cDNA文库。最后利用GeneChip 1.0 ST芯片技术,分析得出大脑与小脑中灰质与白质的表达差异性。结果:无论是灰质还是白质,在PFC中的高表达基因都要远远多于在CBC中的高表达基因。结论:使用LCM可以提取单一的细胞群,从而用于要求更为精确的实验当中。     

Transport of seston in the karstic hydrosystem of the Plitvice Lakes (Croatia)

Research into spatial and temporal variation in seston transport was carried out during the year 2000 on three reaches on the longitudinal profile of the karstic cascading system of the Plitvice Lakes in Croatia. The three investigated reaches were (i) a channel over a barrier with low gradient; (ii) flow through a deep lake; and (iii) a channel with cascades and a steep gradient. The aim of the study was to establish the influence of physiographical and hydrological differences of these reaches on the quality and quantity of seston transport and food resources in the seston. To calculate the seston transport, we measured: total suspended matter (TSM), particulate inorganic matter (PIM), particulate organic matter (POM), chlorophyll-a (chl-a), heterotrophic bacteria and discharge. The PIM contribution from TSM ranged between 60 and 90%, while the percentage of POM in TSM was the highest in summer and ranged from 33 to 46%. POM and discharge were significantly negatively correlated (r = −0.43, P < 0.05). For the transport of TSM, PIM, POM and chlorophyll-a statistically significant differences between the three reaches were established. In a principal component analysis, 86% of the variance was explained by the first two factors. The first factor corresponded well with net transport of TSM, PIM, POM and chl-a and distinguished investigated reaches in two groups: the 1^st group with increasing (reaches with low gradient and with high gradient), and the 2nd group with decreasing net seston transport (reach with flow through a deep lake). The second factor corresponded strongly with discharge and distinguished investigated reaches according to their temporal variability. Electronic Supplementary Material Supplementary material is available in the online version of this article at and is accessible for authorized users Handling editor: J. Padisak     

外源亚精胺和精胺对NaHCO3胁迫下南蛇藤抗氧化系统的影响

研究了叶面喷施亚精胺和精胺对NaHCO₃胁迫下南蛇藤叶片抗氧化系统的影响.结果表明：外源亚精胺和精胺处理使NaHCO₃胁迫下南蛇藤叶片O₂^-·产生速率、H₂O₂、丙二醛(MDA)含量和电解质外渗率显著降低(P<0.05).亚精胺处理明显提高了盐胁迫下超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、过氧化物酶(POD)和抗坏血酸过氧化物酶(APX)等抗氧化酶的活性,以及还原型谷胱甘肽(GSH)、类胡萝卜素(CAR)和脯氨酸(Pro)等抗氧化剂的含量,但对还原型抗坏血酸(AsA)含量没有作用;精胺处理明显提高NaHCO₃胁迫下POD和APX的活性以及GSH、CAR和Pro的含量,但对SOD和AsA含量影响不显著,甚至引起CAT活性明显降低.亚精胺和精胺处理明显改善了NaHCO₃胁迫下南蛇藤的生长.外源亚精胺和精胺可以改善NaHCO₃胁迫下南蛇藤叶片的膜保护功能,减少叶片中活性氧的积累,从而提高南蛇藤对NaHCO₃胁迫的抗性.     

Does extensification of rich grasslands alter the C and N cycles, directly or via species composition?

Extensification modify the C and N cycles in grassland ecosystems, but it is not clear whether reduced exploitation increases or decreases soil nitrogen availability, and whether these changes result from a direct effect of the treatment or from an indirect treatment effect through a change in plant species composition. A formerly intensively exploited grassland was submitted to the following treatments: (i) control with one mowing and four grazing periods per year (4G+M), (ii) cessation of mowing (4G), (iii) cessation of mowing and suppression of three grazing periods (1G). During the 13th year of the experiment, the species composition and key indicators of the C and N cycles were measured, using 20 samples per treatment. Lolium perenne and Trifolium repens disappeared in favor of tall caespitose grasses in 4G, and of rhizomatous species in 1G. The species composition and the nitrate concentration of the soil solution suggested an increase in nutrient availability under reduced exploitation, whereas the nitrification and denitrification potentials decreased. More particulate organic matter accumulated in proportion to the below-ground phytomass, whereas the C:N ratio remained constant. Testing treatment effect at similar species composition and plant community effect within the same treatment showed that: (1) the increase in POM residence time was mainly due to the changes in species composition, (2) the decrease in nitrification activity resulted mainly from a direct effect of the treatment, and (3) a compensation between a direct positive and an indirect negative effect of the treatment resulted in no change in extractable N. All results suggested that soil N availability was not decreased, although litter degradability decreased.

Zusammenfassung

Ein Unterlassen der Heuernte und eine Reduktion der Beweidungsintensität ändern die C- und N-Kreisläufe in Grünland-Ökosystemen. Bislang ist unklar, ob eine extensive Nutzung die Nährstoffverfügbarkeit erhöht oder senkt, und ob diese Änderung der Nährstoffverfügbarkeit in direkter Verbindung mit der verringerten Nutzung steht, oder indirekt ein Resultat der sich ändernden botanischen Zusammensetzung ist. In der vorliegenden Untersuchung wurden die botanische Zusammensetzung sowie die C- und N-Kreisläufe im Boden eines naturnahen, ehemals intensiv beweideten Grünlands nach 12 Jahren unterschiedlicher Nutzungsintensitäten – eine Heuernte und vier Beweidungen jährlich (4G+M), viermalige (4G) und einmalige (1G) jährliche Beweidung – verglichen. Pro Weide wurden je 20 Punkte beprobt. Bei verringerter Nutzung waren die Nitrifikation/Denitrifikation geringer als bei intensiver Nutzung. Die botanische Zusammensetzung sowie die Nitrat-Konzentration im Bodenwasser wurden mehr eutroph. So wurden Lolium perenne und Trifolium repens durch horstbildende Grässer (4G) bzw. rhizombildende Arten (1G) abgelöst. Bei extensiver Nutzung war das Verhältnis von organischer Bodenmasse (particle organic matter, POM) zu unterirdischen pflanzlicher Biomasse höher, hatte jedoch keinen Einfluss auf das C/N-Verhältnis. Ein Vergleich von Weiden gleicher botanischer Zusammensetzung (Nutzungs-Effekt) und von Weiden gleicher Nutzung aber unterschiedlicher botanischer Zusetzung (plant-community-Effekt) zeigte: (i) eine Zunahme der POM-Verweildauer in Folge einer veränderten botanischen Zusammensetzung, (ii) eine Abnahme der Nitrifikation in Folge der verringerten Nutzung und (iii) Kompensation der verringerten Nutzung durch eine Änderung der botanischen Zusammensetzung, womit der leicht verfügbare N unverändert blieb. Eine abnehmende Streu-Qualität scheint keinen Einfluss auf das N-Nachlieferungsvermögen zu haben. Eine hohe N-Verfügbarkeit in Verbindung mit geringer Streu Zersetzung scheinen verantwortlich für eine funktionelle Änderung des Ökosystems und seiner Biodiversität.     

Sexual dimorphism in the adolescent brain: Role of testosterone and androgen receptor in global and local volumes of grey and white matter

Here we examined sex differences in the volumes of grey and white matter, and in grey-matter “density,” in a group of typically developing adolescents participating in the Saguenay Youth Study (n = 419; 12-18 years). In male adolescents, we also investigated the role of a functional polymorphism in androgen-receptor gene (AR) in moderating the effect of testosterone on volumes of grey and white matter and grey-matter density. Overall, both absolute and relative volumes of white matter were larger in male vs. females adolescents. The relative grey-matter volumes were slightly larger in female than male adolescents and so was the grey-matter density in a large number of cortical regions. In male adolescents, functional polymorphism of AR moderated the effect of testosterone on relative white- and grey-matter volumes. Following a discussion of several methodological and interpretational issues, we outline future directions in investigating brain-behavior relationships vis-à-vis psychopathology.     

草地土壤有机质不同组分氮库对长期氮添加的响应

土壤氮库对生态系统的养分循环至关重要。目前多数研究主要关注氮沉降对土壤总氮的影响, 而对土壤不同有机质组分的氮库对氮沉降响应的研究较为缺乏。该研究基于内蒙古典型草地的长期多水平施氮(0、8、32、64 g·m^-2·a^-1)实验平台, 利用土壤密度分级方法, 探究氮添加处理13年后典型草地中两种土壤有机质组分(颗粒态有机质(POM), 矿质结合态有机质(MAOM))氮含量的变化及调控机制。结果显示: 土壤总碳含量、POM和MAOM的碳含量在施氮处理间均没有显著差异。土壤总氮含量则随着施氮水平增加呈显著增加的趋势, 同时施氮处理下POM的氮含量显著上升, 而MAOM的氮含量没有变化。进一步分析发现, 施氮促进植物地上生物量积累, 增加了凋落物量及其氮含量, 从而导致POM的氮含量增加。由于MAOM主要通过黏土矿物等吸附土壤中小分子有机质形成, 其氮含量受土壤中黏粒与粉粒含量影响, 而与氮添加水平无显著相关关系。该研究结果表明长期氮添加促进土壤氮库积累, 但增加的氮主要分布在稳定性较低的POM中, 受干扰后容易从生态系统中流失。为了更准确地评估和预测氮沉降对陆地生态系统的氮循环过程的影响, 应考虑土壤中不同有机质组分的差异响应。     

Role of Ribonuclease and Ribonuclease Inhibitor Activities in Alzheimer''s Disease

It has been suggested that defects in the relationship between ribonuclease and its proteinaceous inhibitor could be a contributory factor in Alzheimer's disease. We have investigated this possibility further by analysing free and bound enzyme activities and the activity of the inhibitor in nine regions of diseased and normal brain. These were chosen to include areas known to be affected by the disease, regions not histologically affected but thought to be involved in the disease process, and areas not thought to be involved in the disease. Neither the enzyme nor its inhibitor is defective in its activities in the chosen areas of Alzheimer's disease brain when compared with those of carefully age-matched controls.     

重金属污染对土壤有机质积累的影响

采用田间采样分析与室内培养试验相结合的方法,研究了不同重金属污染土壤中有机质积累的差异及重金属污染强度对土壤有机质矿化动态变化的影响.结果表明：污染土壤中重金属的大量积累可减弱有机物质的矿化速率,增加土壤有机质的积累.土壤中颗粒态有机质及其占总有机碳的比例随重金属积累的增加而增加;而微生物生物量碳占总碳的比例却随土壤重金属污染水平的提高而下降.污染土壤中颗粒态有机质对重金属有显著的富集,这可能是影响土壤有机物质进一步矿化的原因之一.重金属污染可改变土壤有机质的矿化速率,影响土壤有机质的积累与分配.