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1.
Filtration rate capacities in 6 species of European freshwater bivalves 总被引:12,自引:0,他引:12
Summary Filtration rate capacities in undisturbed freshwater bivalves were determined by means of two different methods (indirect clearance and suction methods) in Anodonta anatina (L.), Unio tumidus Philipsson, Unio pictorum (L.), Unio crassus Philipsson, Dreissena polymorpha (Pallas) and Sphaerium corneum (L.). In A. anatina, D. polymorpha, and S. corneum the filtration rate (FR, 1 h-1) at 19–20°C as a function of dry tissue weight (DW, g) or ash-free dry weight (AFDW, g) could be expressed by the equations: 1.10 DW0.78, 6.82 DW0.88, and 2.14 AFDW0.92, respectively. In U. tumidus, U. pictorum, and U. crassus filtration rates were comparable with those of A. anatina. In D. polymorpha the b value of the corresponding regression of gill area on dry weight was 0.87. The rates of water transport in freshwater bivalves are 2–8 times lower than in marine bivalves of comparable size. A corresponding difference in the filtration rate per gill area unit is found. The measured filtration rates in undisturbed bivalves are substantially higher (at least 4 times) than previously reported. This indicates that the impact of bivalve water processing on freshwater ecosystems is greater than hitherto suggested. 相似文献
2.
A highly sensitive enzymatic assay for diadenosine 5′,5?-P1,P3-triphosphate (Ap3A) has been established on the basis of the coupled luminescence assay for diadenosine 5′,5?-P1,P3-tetraphosphate (A. Ogilvie (1981)Anal. Biochem.115, 302–307). Snake venom phosphodiesterase splits Ap3A into AMP plus ADP which can be measured in a luminescence reaction containing pyruvate kinase, phosphoenolpyruvate and luciferin-luciferase. The procedure is linear with Ap3A levels ranging from 0.1 to 2 pmol. The assay has been used to measure Ap3A in various eukaryotic cells after ion-exchange chromatography and high-performance liquid chromatography of acidic extracts of the cells. The level of diadenosine triphosphate was higher in all instances than the level of diadenosine tetraphosphate. When growing in the abdominal cavity of mice, Ehrlich ascites tumor cells contained high amounts of Ap3A (), allowing direct optical determination in the HPLC chromatography. The quantitative measurement of Ap3A with the luminescence assay gave identical results. Ap3A extracted from Ehrlich cells was also chromatographed with authentic nucleotide in two thin-layer systems providing additional proof for the existence of Ap3A in biological material. 相似文献
3.
The relationship between the source strength and the “manifest vector” in the Einthoven Triangle is derived for a line and
a point dipole source and confirmed experimentally. The result permits the interpretation of the standard ECG leads in absolute
terms and corrected for body size. The manifest vector is shown to be approximately
times what it would be in an otherwise similar circular slab which circumscribes the triangle. 相似文献
4.
5.
The relationship between physical and chemical conditions and low microbial diversity in the Blue Lagoon geothermal lake in Iceland 总被引:1,自引:0,他引:1
Abstract: The Blue Lagoon in Iceland is a shallow geothermal lake with average temperatures of 37°C, pH 7.5 and about 2.5% salinity. It was formed in 1976 from the effluents of the Svartsengi geothermal power plant and is saturated with silica which constantly precipitates in the lake. It has been colonized by a few types of specialized microorganisms which seem to proliferate in this unusual ecosystem. The average bacterial colony count in the lake was 1.3 × 105 ml−1 on plate count agar made with 50% Blue Lagoon fluid but 2.6 × 106 ml−1 when determined with the MPN method. A total of 99 isolates were purified and characterized by 54 phenotypic tests and then grouped using Numerical Taxonomy. At similarity values of 80%, one major cluster was formed containing 85% of the isolates. Four representative strains from this cluster were further characterized and all shown to be Gram-negative, obligately aerobic, non-motile rods. They were oxidase positive, catalase negative and grew optimally at 45°C and in 3.5% NaCl with doubling time of about 80 min. 相似文献
6.
Jaep de Boer Hillie Plijter-Groendijk Klaas R. Visser Gerrit A. Mook Jakob Korf 《European journal of applied physiology and occupational physiology》1994,69(4):281-286
We have evaluated the possibility of monitoring the plasma lactate concentration in human volunteers during cycle ergometer exercise using subcutaneous and transcutaneous microdialysis. In transcutaneous microdialysis, the relative increase in dialysate lactate concentration exceeded that of plasma lactate concentration by a factor of 6 during exercise due to exercise-induced lactate secretion in sweat. During exercise the subcutaneous microdialysis dialysate lactate concentration underestimated the plasma lactate concentration possibly due to diffusion limitation or adipose tissue lactate production. While it was demonstrated that microdialysis can be used for on-line lactate monitoring, neither subcutaneous nor transcutaneous dialysate lactate concentration were linearly related to the plasma lactate concentration during exercise, and it was found therefore that it was not possible to monitor directly plasma lactate concentration during exercise. 相似文献
7.
Hui Yang Seth M. Munson Chris Huntingford Nuno Carvalhais Alan K. Knapp Xiangyi Li Josep Peñuelas Jakob Zscheischler Anping Chen 《Global Change Biology》2023,29(8):2351-2362
Negative extreme anomalies in vegetation growth (NEGs) usually indicate severely impaired ecosystem services. These NEGs can result from diverse natural and anthropogenic causes, especially climate extremes (CEs). However, the relationship between NEGs and many types of CEs remains largely unknown at regional and global scales. Here, with satellite-derived vegetation index data and supporting tree-ring chronologies, we identify periods of NEGs from 1981 to 2015 across the global land surface. We find 70% of these NEGs are attributable to five types of CEs and their combinations, with compound CEs generally more detrimental than individual ones. More importantly, we find that dominant CEs for NEGs vary by biome and region. Specifically, cold and/or wet extremes dominate NEGs in temperate mountains and high latitudes, whereas soil drought and related compound extremes are primarily responsible for NEGs in wet tropical, arid and semi-arid regions. Key characteristics (e.g., the frequency, intensity and duration of CEs, and the vulnerability of vegetation) that determine the dominance of CEs are also region- and biome-dependent. For example, in the wet tropics, dominant individual CEs have both higher intensity and longer duration than non-dominant ones. However, in the dry tropics and some temperate regions, a longer CE duration is more important than higher intensity. Our work provides the first global accounting of the attribution of NEGs to diverse climatic extremes. Our analysis has important implications for developing climate-specific disaster prevention and mitigation plans among different regions of the globe in a changing climate. 相似文献
8.
Jakob Noske Josef Paul Kynast Dominik Lemm Steffen Schmidt Birte Höcker 《Protein science : a publication of the Protein Society》2023,32(1):e4516
The ability to design customized proteins to perform specific tasks is of great interest. We are particularly interested in the design of sensitive and specific small molecule ligand-binding proteins for biotechnological or biomedical applications. Computational methods can narrow down the immense combinatorial space to find the best solution and thus provide starting points for experimental procedures. However, success rates strongly depend on accurate modeling and energetic evaluation. Not only intra- but also intermolecular interactions have to be considered. To address this problem, we developed PocketOptimizer, a modular computational protein design pipeline, that predicts mutations in the binding pockets of proteins to increase affinity for a specific ligand. Its modularity enables users to compare different combinations of force fields, rotamer libraries, and scoring functions. Here, we present a much-improved version––PocketOptimizer 2.0. We implemented a cleaner user interface, an extended architecture with more supported tools, such as force fields and scoring functions, a backbone-dependent rotamer library, as well as different improvements in the underlying algorithms. Version 2.0 was tested against a benchmark of design cases and assessed in comparison to the first version. Our results show how newly implemented features such as the new rotamer library can lead to improved prediction accuracy. Therefore, we believe that PocketOptimizer 2.0, with its many new and improved functionalities, provides a robust and versatile environment for the design of small molecule-binding pockets in proteins. It is widely applicable and extendible due to its modular framework. PocketOptimizer 2.0 can be downloaded at https://github.com/Hoecker-Lab/pocketoptimizer . 相似文献
9.
Anti-predator defence behaviour of Holocnemus pluchei (Araneae, Pholcidae) was studied in the laboratory and the field. Bouncing, in which this web-building spider moves its body rapidly up and down while keeping its legs on the silk, was the most frequent response to disturbance. Less often, H. pluchei left the web when disturbed. Experiments were carried out to determine the types of stimuli that elicited bouncing and leaving the web: tactile stimulation (striking the spider with a brush) and air movement (blowing on the spider) elicited bouncing and leaving the web, but there was no evidence that chemical stimuli from potential predators were important. Tactile stimulation elicited stronger responses than air movement. There were no evident differences in how H. pluchei responded to tactile stimulation in the laboratory and the field. 相似文献
10.
Karri Silventoinen Sampo Sammalisto Markus Perola Dorret I Boomsma Belinda K Cornes Chayna Davis Leo Dunkel Marlies De Lange Jennifer R Harris Jacob V B Hjelmborg Michelle Luciano Nicholas G Martin Jakob Mortensen Lorenza Nisticò Nancy L Pedersen Axel Skytthe Tim D Spector Maria Antonietta Stazi Gonneke Willemsen Jaakko Kaprio 《Twin research》2003,6(5):399-408
A major component of variation in body height is due to genetic differences, but environmental factors have a substantial contributory effect. In this study we aimed to analyse whether the genetic architecture of body height varies between affluent western societies. We analysed twin data from eight countries comprising 30,111 complete twin pairs by using the univariate genetic model of the Mx statistical package. Body height and zygosity were self-reported in seven populations and measured directly in one population. We found that there was substantial variation in mean body height between countries; body height was least in Italy (177 cm in men and 163 cm in women) and greatest in the Netherlands (184 cm and 171 cm, respectively). In men there was no corresponding variation in heritability of body height, heritability estimates ranging from 0.87 to 0.93 in populations under an additive genes/unique environment (AE) model. Among women the heritability estimates were generally lower than among men with greater variation between countries, ranging from 0.68 to 0.84 when an additive genes/shared environment/unique environment (ACE) model was used. In four populations where an AE model fit equally well or better, heritability ranged from 0.89 to 0.93. This difference between the sexes was mainly due to the effect of the shared environmental component of variance, which appears to be more important among women than among men in our study populations. Our results indicate that, in general, there are only minor differences in the genetic architecture of height between affluent Caucasian populations, especially among men. 相似文献