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991.
Marinella Pompei Cristina Mazziotti Franca Guerrini Monica Cangini Silvia Pigozzi Margherita Benzi Simona Palamidesi Laurita Boni Rossella Pistocchi 《Harmful algae》2003,2(4):301-316
The formation of massive amounts of suspended mucilaginous organic matter which periodically affects the Adriatic Sea, has been regarded as a complex physico-chemical phenomenon resulting from the production of extracellular material by phytoplankton. Although the exact cause has remained obscure, the mechanism of its formation has usually been considered to be a long-term process, starting after the late winter-early spring blooms, and involving the participation of various algal species, mainly within the diatom group. In this paper we report on the results of a phytoplankton monitoring programme in northern Adriatic seawaters off the Emilia-Romagna coast of Italy which revealed the constant concomitant presence of the dinoflagellate Gonyaulax fragilis (Schütt) Kofoid and mucilaginous formations. In the early stages of the phenomenon the dinoflagellate was clearly observable by microscopic examination in the mucilage, but as the mucilage aged this alga almost completely decomposed and diatom cells increased in number and became predominant. Although characterized by a slow growth rate in culture, in natural seawater G. fragilis was observed to reach cell densities of up to 7.0×106 cells l−1. The results of this study lead us to propose the hypothesis that the appearance of mucilage in the water column of the Adriatic Sea is the consequence of a seasonal growth of this dinoflagellate favoured by specific environmental circumstances. 相似文献
992.
One of the most endangered assemblages of species in Europe is insectsassociated with old trees. For that reason there is a need of developing methodsto survey this fauna. This study aims at comparing three methods – windowtrapping, pitfall trapping and wood mould sampling – to assess speciesrichness and composition of the saproxylic beetle fauna in living, hollow oaks.We have used these methods at the same site, and to a large extent in the sametrees. Useful information was obtained from all methods, but they partiallytarget different assemblages of species. Window trapping collected the highestnumber of species. Pitfall trapping collected beetles associated with treehollows which rarely are collected by window traps and therefore it isprofitable to combine these two methods. As wood mould sampling is the cheapestmethod to use, indicator species should preferably be chosen among specieswhich are efficiently collected with this method. 相似文献
993.
994.
Akon Higuchi Yasunari Takanashi Takeshi Ohno Tetsuo Asakura Chong-Su Cho Toshihiro Akaike Mariko Hara 《Cytotechnology》2002,39(3):131-137
The fibroblast cells from normal human skin were cultured on Langmuir-Blodgett (LB) and cast membranes prepared using extracellular
matrix proteins (e.g., collagen, fibronectin, laminin and vitronectin). The cell density of the fibroblast cells cultured
on the cast membranes was found to be higher than that on the cast membranes made of fibronectin, vitronectin and collagen-blended
membranes. This indicates that not only the primary structure of proteins but the preparation methods of the membranes, i.e.,
casting and LB methods, are a strong factor affecting cell growth. The concentration and production of interferon-β per unit
cell were found to be higher on the LB membranes than on the cast membranes made of the same proteins except in the case of
collagen. However, the cell density on the cast membranes was higher than that on the LB membranes. These results appear to
result from the suppressed growth of NB1-RGB cells on the LB membranes leading to the enhanced production of interferon-β
on the LB membranes. The highest production of interferon-β per unit cell was observed for the NB1-RGB cells on the collagen-blended
membranes with fibronectin and vitronectin. The collagen-blended membranes appear to offer a more natural and appropriate
environment for NB1-RGB cells to produce interferon-β.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
995.
Radial basis function (RBF) artificial neural network (ANN) and response surface methodology (RSM) were used to build a predictive model of the combined effects of independent variables (pH, temperature, inoculum volume) for extracellular protease production from a newly isolated Pseudomonas sp. The optimum operating conditions obtained from the quadratic form of the RSM and ANN models were pH 7.6, temperature 38 °C, and inoculum volume of 1.5 with 58.5 U/ml of predicted protease activity within 24 h of incubation. The normalized percentage mean squared error obtained from ANN and RSM models were 0.05 and 0.1%, respectively. The results demonstrated an higher prediction accuracy of ANN compared to RSM. This superiority of ANN over other multi factorial approaches could make this estimation technique a very helpful tool for fermentation monitoring and control. 相似文献
996.
997.
Plasma extracellular superoxide dismutase activity in healthy pregnant women is not influenced by zinc supplementation 总被引:1,自引:0,他引:1
Tsunenobu Tamura Katherine L. Olin Robert L. Goldenberg Kelley E. Johnston Mary B. DuBard Carl L. Keen 《Biological trace element research》2001,80(2):107-113
We hypothesized that plasma extracellular superoxide dismutase (EC-SOD) activity reflects the zinc nutriture of healthy pregnant
women. Sixty-three women were selected from 580 African-American women who participated in a clinical trial to evaluate the
effect of prenatal zinc supplementation on pregnancy outcome. Half of the women received zinc (25 mg/d) and the other half
was given a placebo from about 19 wk gestation to delivery. In the trial, a positive effect of zinc supplementation on birthweight
was observed, indicating that the population as a whole had suboptimal zinc nutriture. Using plasma samples obtained during
the trial, EC-SOD activities were measured and the values were compared with plasma zinc concentrations and plasma alkaline
phosphatase activities. Plasma EC-SOD activities in our subjects were lower than previously published values for healthy adults
in Korea. Although plasma EC-SOD activity may reflect severe zinc deficiency, it is not a sensitive marker for marginal deficiency
status. Plasma EC-SOD activities did not prove to be a better indicator of zinc nutriture of pregnant women than either plasma
zinc or plasma alkaline phosphatase activities. 相似文献
998.
Joachim Schütze Alexander Skorokhod Isabel M. Müller Werner E.G. Müller 《Journal of molecular evolution》2001,53(4-5):402-415
One crucial event during evolution to multicellularity was the development of either direct cell–cell contact or indirect
interaction via extracellular matrix (ECM) molecules. The identification of those polypeptides provides conclusive data on
the phylogenetic relationship of metazoan phyla and helps us to understand the position of the Metazoa among the other kingdoms.
Recently it became evident that the ECM of sponges is amazingly complex; it is composed of fibrous molecules, e.g., collagen,
and their corresponding receptors, which are highly similar to those existing in other metazoan phyla. While these data already
support the view of monophyly of Metazoa, additional studies are required to understand whether these molecules, which are
similar in their primary sequence, also have the same function throughout the metazoan kingdom. In the present study we identified
the ligand for one of the autopomorphic characters of Metazoa, the single-transmembrane receptor protein with the receptor
tyrosine kinase (RTK) from G. cydonium, as an example: the putative mucus-like protein from G. cydonium. This protein was upregulated during autograft fusion in the homologous system with kinetics similar to those of the RTK.
Additionally, a cDNA was isolated from S. domuncula whose deduced polypeptide displays a high sequence similarity to dermatopontin, an ECM molecule found exclusively in Metazoa.
Furthermore, it is documented that expression of the fibrous ECM molecule collagen is regulated by the characteristic metazoan
morphogens myotrophin and endothelial monocyte-activating polypeptide. These data indicate that the ECM of sponges is not
an unstructured ground substance but provides the basis for integrated cell communication.
Received: 26 October 2000 / Accepted: 1 February 2001 相似文献
999.
Field studies were conducted in order to compare the effectiveness of unbaited probe traps and grain trier samples in the detection of several beetle species. On June 15, 1997, fourteen probe traps were placed in three steel bins containing wheat in Central Greece. Two of them were inserted in the central zone of the bulk, five in the half of the bin radius (median zone) and seven near the bin wall (distal zone). From June 30 up to and including January 1998, the traps were checked for adult beetles every fifteen days (15 sampling dates in total). On each date, samples were also taken from spots adjacent to trap locations, using a grain trier. The mean temperatures recorded near the bulk surface decreased by an average of 1.16 °C per sampling date. Twenty-four species, belonging to 14 families of Coleoptera were found. The most abundant species in the traps were Cryptolestes ferrugineus and Tribolium castaneum, while Sitophilus oryzae was the most abundant in the samples. Significantly greater numbers of adults were found in traps than in samples, during the whole sampling period; traps also detected adults in most locations while in the corresponding samples no adults were found. Significantly higher numbers of adults were found in the central sampling zone, using both devices. Taylor's power law parameters showed that in both sampling methods the most abundant species showed aggregated spatial patterns. Although the correlation coefficient values between trap catches and number of adults per trier sample differ significantly from zero (P < 0.01) in a high number of sampling dates, it can be concluded that traps are poor indicators of population density. The accuracy provided as a percentage of the mean, decreases exponentially with the increase of the mean value. Based on traps, the desired accuracy level (35%) is not achievable even in higher mean values or even with high numbers of traps. On the contrary, with trier samples it is possible to estimate population density with a relatively low number of sampling units. Significant differences in the required number of sampling units (sample size) were noted among species. 相似文献
1000.
目的:探讨采用软骨细胞外基质材料制备的定向结构软骨支架复合软骨细胞,在体外静态培养条件下生成组织工程软骨的可能性。方法:制备牛关节软骨细胞外基质材料,利用温度梯度热诱导相分离技术构建具备垂直定向孔道结构的软骨支架,同时采用传统冷冻干燥方法制备非定向支架,检测两组支架的力学性能;提取兔关节软骨细胞,分别接种两组支架,体外静态培养2周及4周后取材,对构建的组织工程软骨进行组织切片染色、生物化学分析及生物力学检测。结果:定向软骨支架的压缩弹性模量数值明显高于非定向软骨支架,体外培养时定向支架上种子细胞在3-9d内增殖高于非定向支架,差异有统计学意义(P〈0.05);体外静态培养4周后形成的两组新生组织工程软骨进行软骨特异性染色均呈阳性,在定向组新生软骨切片中在垂直方向上可见大量呈规则平行排列的粗大胶原纤维,两组新生软骨的生物化学检测包括总DNA、总GAG及总胶原含量差异无统计学意义(P〉0.05)。定向组织工程软骨压缩弹性模量在2周及4周时均高于非定向组织工程软骨,差异有统计学意义(P〈0.05)。但两组组织工程软骨上述指标均显著低于正常关节软骨(P〈0.05)。结论:软骨细胞外基质材料制备的定向结构软骨支架复合软骨细胞,在体外静态培养条件下能够成功生成具有定向纤维结构的组织工程软骨,并可以有效促进新生软骨组织力学性能的提升,在软骨组织工程中具有良好的应用前景。 相似文献