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31.
Detailed zooplankton records from a 26-cm sediment core with a time resolution of approximately 3–10 years were obtained from Lake Biwa, Japan, to examine the historical variations in the zooplankton community during the 20th century. In the sediments, selected zooplankton remains have fluctuated over the years. Daphnia – large zooplankton herbivores – did not occur from 1900 to 1920, and formed a very minor component of the zooplankton community in the following 30 years, while Bosmina – small zooplankton herbivores – were common during this period. In the mid-1960s, however, when eutrophication was noticeable in this lake, Daphnia numbers increased dramatically and became the dominant zooplankton thereafter. In contrast, Difflugia brevicolla and D. biwae, two amoeboid protozoans that live in connection with the lake bottom environment, occurred abundantly until the late 1950s, but gradually decreased after the mid-1960s. In particular, D. biwae, a species peculiar to this lake, was not found in sediment dated after 1980, suggesting its extinction. These results indicate that the zooplankton community structure changed greatly in the 1960s, and suggest that the eutrophication occurring at this time altered the relative strength of top-down and bottom-up forces on the zooplankton community in Lake Biwa. 相似文献
32.
Observed localization of the long-term cultured rat adherent natural killer cells in mammary tumor tissues 总被引:2,自引:0,他引:2
Adherent natural killer (A-NK) cells were isolated from splenic lymphocytes and treated with long-term culture in the presence
of recombinant interleukin-2 (rIL-2). Immunocytochemical and flow-cytometric analysis revealed that most of the A-NK cells
strongly expressed lymphocyte-function-associated antigen 1 (LFA-1α, and LFA-1β) throughout the incubation. All A-NK cells
from 8- to 150-day cultures, particularly those cultured for 8 days, showed significant cytolytic activity against all targets.
Analysis of the tissue distribution of the injected [3H] uridine-labeled A-NK cells demonstrated that, in the first 3 h, most (over 60%) cells localized in the lungs, and that
most cells remained temporally within the cavities of blood capillaries of the lungs and moved gradually into lymphoid and
other tissues. Peritumoral injection of various kinds of adjuvant, particularly Freund's complete adjuvant (FCA) plus bacillus
Calmetee-Guérin (BCG), resulted in a marked accumulation of [3H]A-NK cells in mammary tumor tissues 24 h after injection, and simultaneously in the formation of vessels resembling high-endothelium
venules (HEV), infiltration of LFA-1+ lymphocytes and expression of the ICAM-1 molecule on the tumor cells in the sites of tumor tissues. When 30 × 106 A-NK cells were intravenously administered, significant retardation of tumor growth and prolongation of survival of tumor-bearing
rats were observed in the groups that received the prior injection of adjuvants, especially FCA + BCG and Freund's incomplete
adjuvant (FIA) + BCG. The suppressive effect of combination therapy on tumor growth was blocked effectively by the injection
of anti-ICAM-1 mAb. These results indicate that the prior injection of proper adjuvant into the peritumoral region is effective
for the selective accumulation or infiltration of A-NK cells into the sites of tumor tissues, and results in the marked retardation
of tumor growth.
Received: 18 May 1999 / Accepted: 4 October 1999 相似文献
33.
34.
Daily and seasonal CO2 exchange in Scots pine grown under elevated O3 and CO2: experiment and simulation 总被引:3,自引:0,他引:3
Starting in early spring of 1994, naturally regenerated, 30-year-old Scots pine (Pinus sylvestris L.) trees were grown in open-top chambers and exposed in situ to doubled ambient O3,doubled ambient CO2 and a combination of O3 and CO2 from 15 April to 15 September. To investigate daily and seasonal responses of CO2 exchange to elevated O3 and CO2, the CO2 exchange of shoots was measured continuously by an automatic system for measuring gas exchange during the course of one year (from 1 Januray to 31 December 1996). A process-based model of shoot photosynthesis was constructed to quantify modifications in the intrinsic capacity of photosynthesis and stomatal conductance by simulating the daily CO2 exchange data from the field. Results showed that on most days of the year the model simulated well the daily course of shoot photosynthesis. Elevated O3 significantly decreased photosynthetic capacity and stomatal conductance during the whole photosynthetic period. Elevated O3 also led to a delay in onset of photosynthetic recovery in early spring and an increase in the sensitivity of photosynthesis to environmental stress conditions. The combination of elevated O3 and CO2 had an effect on photosynthesis and stomatal conductance similar to that of elevated O3 alone, but significantly reduced the O3-induced depression of photosynthesis. Elevated CO2 significantly increased the photosynthetic capacity of Scots pine during the main growing season but slightly decreased it in early spring and late autumn. The model calculation showed that, compared to the control treatment, elevated O3 alone and the combination of elevated O3 and CO2 decreased the annual total of net photosynthesis per unit leaf area by 55% and 38%, respectively. Elevated CO2 increased the annual total of net photosynthesis by 13%. 相似文献
35.
C. Helmschrodt S. BeckerJ. Thiery U. Ceglarek 《Biochemical and biophysical research communications》2014
The analysis of the oxysterols 7-keto-, 7-α/β-hydroxy-, 5α,6α-epoxy-, 5β,6β-epoxycholesterol and cholestane-3β,5α,6β-triol derived from reactive oxygen species (ROS) is of interest as biomarkers in the field of atherosclerosis. Preanalytical validation is a crucial point to minimize the susceptibility of oxysterols to in vitro autoxidation. The aim of this study was to standardize a preanalytical protocol for ROS-derived oxysterol analysis by liquid chromatography–tandem mass spectrometry in human plasma. 相似文献
36.
基于灰色关联度分析的辽西地区典型种植模式评价 总被引:6,自引:0,他引:6
不同种植模式评价是当今种植制度研究中的热点之一,针对辽西地区自然特点和种植模式混杂多样的现状,在多年试验研究和专家问卷调查的基础上,采用灰色关联度分析方法对辽西地区6种典型种植模式进行了评价。结果表明:无论是在等权关联度下还是在侧重生态环境指标或经济指标的变权重下,南果梨+南瓜种植模式与参考模式的关联度均为最大,分别为0.867、0.920和0.841,南果梨+花生种植模式次之,说明南果梨+南瓜‖花生的林粮间作模式的生态和经济效益最好,是辽西地区发展种植业的最佳模式,玉米/大豆间作模式的关联度最小,分别为0.848、0.901和0.821,这种模式的生态和经济效益最差。该研究结果对保护辽西地区生态环境,发展多熟立体农业,推动该区域的社会经济与环境的协调发展提供了理论依据。 相似文献
37.
围产期食物限制导致子代大鼠学习和记忆能力等的神经生物学变化,但其机制并不清楚。将成年Wistar雌性大鼠与雄性大鼠同笼,受孕后随机分为对照组 (n=9) 和食物限制组 (n=8) 。对照组母鼠在妊娠期和哺乳期自由进食和饮水,食物限制组母鼠从妊娠的第7天到子代大鼠出生后21天进行食物限制,食物限制量为对照组大鼠的50%。子代雄性大鼠成年后,通过Morris 水迷宫测试空间学习和记忆能力。之后,在海马CA1区在体记录场兴奋性突触后电位 (field excitatory postsynaptic potential,fEPSP),并采用免疫组织化学方法观察海马CA1区神经元型一氧化氮合酶 (nNOS) 阳性细胞密度的变化。结果表明,围产期食物限制降低了子代大鼠出生后第1、7、10、14和21天的体重,并减弱了成年子代大鼠的学习和记忆能力,海马CA1区fEPSP的斜率和nNOS阳性细胞的密度也明显降低。结果提示,围产期食物限制可能通过抑制NO的产生降低了海马突触可塑性,从而影响了子代大鼠的学习和记忆能力。 相似文献
38.
Davis Gruberts Ivars Druvietis Elga Parele Jana Paidere Arkadijs Poppels Janis Prieditis Arturs Skute 《Hydrobiologia》2007,584(1):223-237
During July 2004, various limnological characteristics of 24 floodplain lakes and reservoirs have been explored along the
Middle Daugava for the first time in order to reveal possible impact of the long-term mean annual flooding frequency on their
phytoplankton, zooplankton, macrozoobenthos and macrophyta communities. Obtained data series were analysed by Spearman’s rank
correlation method, Principal Component Analysis (PCA) method and Renkonen’s similarity test. UPMGA method was used for single
linkage clustering of the lakes based on the abundance of phyto- and zooplankton taxa. Low similarity between the obtained
cluster trees and hydrological grouping was stated indicating minor impact of the flooding hydrology on summer plankton communities
of these lakes. Significant correlation between the flooding frequency and several physicochemical and biological parameters
was found. Six main factors, which explain observed variations, were extracted by PCA. Significant negative impact of hydrological
connectivity on zooplankton species diversity as well as positive impact on Oligochaeta density was stated, whereas other
biotic parameters were affected by local factors, such as lake morphology, internal loading of nutrients from sediments, throphic
interactions as well as local source of dissolved organic matter. 相似文献
39.
The aim of the study was to evaluate the long-term development of a hard bottom benthic assemblage over a period of 20 years
in an area off the mouth of a large river. The artificial reef of Fregene was selected because benthic assemblage data were
available for the period 1981–1992. This artificial reef is located in the mid Tyrrhenian Sea, 5 nautical miles north of the
two mouths of the Tevere River (Latium, Italy) and 1.5 nautical miles offshore from Fregene (Rome, Italy). The artificial
reef was deployed in March 1981 for fisheries enhancement in 10–14 m of water on a sandy-silty seabed. The Tevere River carries
suspended materials and a heavy load of organics since it transports Rome’s effluent, resulting in the eutrophic state of
area waters. Benthic sampling was conducted in 2001 by SCUBA diving; two standard surfaces of 400 cm2 were scraped from the vertical walls of the same uppermost block in four different periods. All organisms were identified
and counted. The methodology used is the same as that adopted in the previous periods, so that the 2001 data could be compared
with past collected data. The benthic assemblage was analysed by cluster analysis using the Bray-Curtis index and clustered
using the group average clustering algorithm. The SIMPER procedure was used to identify those taxa that characterize each
station group identified by cluster analysis. Changes in benthic assemblages and hydrological trends of the Tevere River were
investigated using the cumulative sum series method. The 20-year development of the benthic community, starting from the new
substratum, is composed of different phases characterised by different benthic assemblages. In particular five different phases
were distinguished: 1. Pioneer species recruitment (May 1981–June 1981); 2. Mytilus galloprovincialis (mussel) dominance (August 1981–November 1983); 3. M. galloprovincialis regression (July 1984–October 1985); 4. M. galloprovincialis absence (91–92); 5. Bryozoans bioconstruction dominance (2001). The dynamic succession of the observed benthic assemblages
exhibited a good relation with the Tevere River flow. The Tevere River flow, and the subsequent sedimentation process, seems
to have strongly influenced the benthic assemblage succession of the Fregene artificial reef.
Guest editors: G. Relini & J. Ryland
Biodiversity in Enclosed Seas and Artificial Marine Habitats 相似文献
40.
Defining the coast and sentinel ecosystems for coastal observations of global change 总被引:1,自引:0,他引:1
The detection, attribution and prediction of global and large scale regional change are goals for the Global Observing Systems
of the United Nations. Coastal areas are particularly sensitive to global change, but there is a variety of limitations to
universal coverage of observations. The coastal module of the Global Terrestrial Observing System (C-GTOS) considers sentinel
ecosystems to address these goals for the terrestrial, wetland and freshwater ecosystems of the coast. Sentinel ecosystems
for observing systems are a limited number of well understood systems that have substantial datasets and are observed in a
sustained fashion, forming an early warning and core system for broader regional and global change. A necessary step in the
development of C-GTOS is the examination of current definitions of coastal areas by anticipated users and information providers,
and identification of potential coastal networks and sites. We applied the sentinel system framework to the selection of C-GTOS
observation sites from several international programs using various global delineations of coastal areas. Delineations were
based on the most common definitions of the coast adopted by potential C-GTOS users and information providers, and included
mapped areas of various distance from the coastline, coastal areas of low elevation, and a seaward boundary matching the Economic
Exclusive Zone (EEZ). Decreases in the number of sites within each international program occurred with each definition marking
area closer to the coastline. The Ramsar Convention on Wetlands demonstrates the greatest percentage of coastal sites by any
definition. The process of choosing specific sentinel sites for C-GTOS continues from this initial screening, and is the next
step towards the development of an in situ site network supporting the observation of global and large scale change.
An erratum to this article is available at . 相似文献