排序方式: 共有208条查询结果,搜索用时 15 毫秒
41.
White DJ Puranen S Johnson MS Heino J 《The international journal of biochemistry & cell biology》2004,36(8):1405-1410
The four collagen receptor integrins, alpha1beta1, alpha2beta1, alpha10beta1 and alpha11beta1, form a structurally and functionally distinct subgroup when compared to other members of the integrin family. In this review, we discuss the structures of these receptors and their differences in collagen binding and signalling function. 相似文献
42.
Helena Keski-Hynnil Knut Raanaa Jyrki Taskinen Risto Kostiainen 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》2000,749(2):56
Direct, quantitative capillary electrophoresis–electrospray ionisation mass spectrometric (CE–ESI-MS) and tandem mass spectrometric (CE–ESI-MS–MS) methods are described for the quantitation of 3-O-glucuronides of E- and Z-entacapone isomers (EEG and EZG) and tolcapone (TG) in urine. 3-O-Glucuronide of nitecapone was used as internal standard. Good separation of glucuronides was achieved with 20 mM ammonium acetate as separation solution at pH 6.84. Stacking was used to increase the sensitivity of the method by introducing samples in 5 mM ammonium acetate. CE–ESI-MS and CE–ESI-MS–MS methods are linear with correlation coefficients better than 0.9983 and 0.9982, and repeatable with relative standard deviations below 9 and 14%, respectively. The limit of detection (LOD) in CE–ESI-MS at signal-to-noise ratio 3 is 100 ng/ml for EEG and EZG and 250 ng/ml for TG. The CE–ESI-MS–MS method was the more sensitive; LOD was 7 ng/ml for all compounds, without any concentration of the sample. 相似文献
43.
Marja Maljanen Narasinha Shurpali Jyrki Hyt?nen P?ivi M?kiranta Lasse Aro Hannamaria Potila Jukka Laine Changsheng Li Pertti J. Martikainen 《Biogeochemistry》2012,108(1-3):199-218
Pristine peatlands have generally low nitrous oxide (N2O) emissions but drainage and management practices enhance the microbial processes and associated N2O emissions. It is assumed that leaving peat soils from intensive management, such as agriculture, will decrease their N2O emissions. In this paper we report how the annual N2O emission rates will change when agricultural peat soil is either left abandoned or afforested and also N2O emissions from afforested peat extraction sites. In addition, we evaluated a biogeochemical model (DNDC) with a view to explaining GHG emissions from peat soils under different land uses. The abandoned agricultural peat soils had lower mean annual N2O emissions (5.5?±?5.4?kg?N?ha?1) than the peat soils in active agricultural use in Finland. Surprisingly, N2O emissions from afforested organic agricultural soils (12.8?±?9.4?kg?N?ha?1) were similar to those from organic agricultural soils in active use. These emissions were much higher than those from the forests on nutrient rich peat soils. Abandoned and afforested peat extraction sites emitted more N2O, (2.4?±?2.1?kg?N?ha?1), than the areas under active peat extraction (0.7?±?0.5?kg?N?ha?1). Emissions outside the growing season contributed significantly, 40% on an average, to the annual emissions. The DNDC model overestimated N2O emission rates during the growing season and indicated no emissions during winter. The differences in the N2O emission rates were not associated with the age of the land use change, vegetation characteristics, peat depth or peat bulk density. The highest N2O emissions occurred when the soil C:N ratio was below 20 with a significant variability within the measured C:N range (13–27). Low soil pH, high nitrate availability and water table depth (50–70?cm) were also associated with high N2O emissions. Mineral soil has been added to most of the soils studied here to improve the fertility and this may have an impact on the N2O emissions. We infer from the multi-site dataset presented in this paper that afforestation is not necessarily an efficient way to reduce N2O emissions from drained boreal organic fields. 相似文献
44.
Satu Turtola Matti Rousi† Jyrki Pusenius Keiko Yamaji‡ Susanne Heiska Veijo Tirkkonen§ Beat Meier¶ Riitta Julkunen-Tiitto 《Global Change Biology》2005,11(10):1655-1663
The effects of enhanced UVB radiation and drought stress on willow secondary phenolics were studied using the leaves of 8‐week‐old micropropagated plantlets from interspecific hybrids (Salix myrsinites L. ×S. myrsinifolia Salisb.) and pure species (S. myrsinifolia). The plantlets were subjected for 4 weeks to two levels of UVB radiation (ambient, enhanced) and two levels of watering (well‐watered, drought‐stressed) according to a 2 × 2 factorial design. Enhanced UVB radiation increased the total concentration of flavonoids and phenolic acids in all plantlets, while the total concentration of salicylates remained unaffected. Drought stress reduced the total concentration of salicylates and phenolic acids in S. myrsinifolia plantlets, while in hybrids only phenolic acids were affected. The response of phenolic acids to enhanced UVB in drought‐stressed plantlets was different from that in well‐watered ones, indicating that drought stress limited the accumulation of phenolic acids under enhanced UVB radiation. Flavonoids increased in response to enhanced UVB radiation in drought‐stressed plantlets, although drought caused serious physiological stress on growth. There were significant differences between hybrid and S. myrsinifolia plantlets with respect to the composition of phenolics and between families and clones with respect to their concentration. In addition, the response of salicylates, flavonoids and phenolic acids to enhanced UVB and drought stress was clone‐specific, which may indicate that climatic changes will alter the genetic composition of northern forests. 相似文献
45.
Sarita Keski-Saari Jyrki Pusenius Riitta Julkunen-Tiitto 《Global Change Biology》2005,11(7):1180-1194
We studied the ability of tree seedlings to respond to two environmental factors, elevated ultraviolet B (UVB) radiation and availability of nitrogen (N), at the beginning of their development. Seeds of two birch species, Betula pubescens Ehrh. (common white birch) and B. pendula Roth (silver birch), were germinated and the seedlings grown in an experimental field in eastern Finland. The experimental design consisted of a constant 50% increase in UVB radiation (including a slight increase in UVA), a UVA control (a slight increase in UVA) and a control. The seedlings were fertilized with three levels of N. The experiment lasted for 2 months; aboveground biomass was measured and the most mature leaf of each seedling was taken for the analyses of phenolics. Growth of the seedlings was not significantly affected by enhanced UVB, but was increased by increasing N. Elevated UVB induced significant changes in phenolic compounds. Quercetin glycosides were accumulated in the leaves of both species in response to UVB; this is considered to be a protective response. However, the direction of the responses of individual phenolics to different N regimens differed. In addition, concentration of soluble condensed tannins was lower at moderate N than that at lower levels of N in both species; on the contrary, in B. pubescens the concentration of insoluble condensed tannins was highest at moderate N. No significant interaction between UV and N was detected, and the responses of the two species were highly similar to UVB, while the responses to N regimens varied slightly more between species. 相似文献
46.
Jyrki Rasku Martti Juhola Esko Toppila Ilmari Pyykk 《Biomedical signal processing and control》2007,2(1):1-8
The objective of the present research was to investigate whether hidden Markov models can be used to recognise and classify balance signals extracted from two subject groups, the healthy and patients suffering from otoneurological vertiginous diseases. Two different testing protocols were applied: arising from a chair and standing on the force platform. Signals recorded according to these protocols were trained for models with different numbers of states to find the best choices as model structures. We found that these models with 7–15 states were able to recognise the healthy subjects from the patients with the accuracy between 70 and 90% although their balance measurements were visually very similar and difficult to separate between two groups. 相似文献
47.
Claudio Colosio Silvia Fustinoni Emanuela Corsini Cristina Bosetti Sarah Birindelli Daisy Boers Laura Campo Carlo La Vecchia Jyrki Liesivuori Sirpa Pennanen Tatjana Vergieva Ludovic G. P. M. Van Amelsvoort Peter Steerenberg Gerard M. H. Swaen Christo Zaikov Henk Van Lveren 《Biomarkers》2007,12(6):574-588
The aim of this study was to investigate the health effects induced by exposure to the fungicide mancozeb in Italian vineyard workers. Ninety-three Italian subjects entered the study - 48 vine-growers intermittently exposed to mancozeb and 45 healthy controls. The subjects were investigated three times: before the seasonal application of pesticides (T0), 30 days after the beginning of the application period (T30), and 45 days after T0 (T45). At T0 the comparison between agricultural workers and controls showed a higher prevalence of cold or flu symptoms, a statistically significant lower percentage of monocytes, higher absolute count of T lymphocytes, CD4 and natural killer cells, and lower plasma levels of IgA and IgM in workers. Such differences were not confirmed at T30 and T45. In fact at T30 in exposed workers, besides a significant increase of urinary ethylenethiourea, confirming mancozeb exposure, T lymphocytes, CD4 and natural killer cells, IgA and IgM returned to values comparable to those observed in controls. Moreover, no other differences in clinical signs, haematological, and immune parameters, such as the immune functional capability evaluated as a response to hepatitis B vaccination, was observed. Altogether the differences between exposed and controls were not consistently correlated to any clinical impairment and suggest that the seasonal application of mancozeb does not pose a significant health risk to exposed subjects. 相似文献
48.
49.
Sini Savilaakso Jenny Koivisto Timo O. Veteli Jyrki Pusenius Heikki Roininen 《Biodiversity and Conservation》2009,18(14):3931-3948
Many of the protected forest areas in Uganda have been subject to logging in the past. It is known that logging changes communities,
but how long these changes last is unclear. Most of the studies on butterflies and moths have looked at the effects of logging
relatively shortly (<15 years) after the logging took place. In this study we investigated community of herbivorous lepidopteran
larvae and its temporal dynamics in a natural forest and three differently managed forest compartments after 40 years of regeneration.
We collected samples of larvae from the leaves of Neoboutonia macrocalyx Pax. between April 2006 and March 2008 in Kibale National Park, Western Uganda. Herbivory, density of larvae, and species
richness were significantly lower in logged compartments than in natural forest. Furthermore, the community composition differed
significantly between the logged compartments and the natural forest. There was seasonal variation in larval density, species
richness and diversity. In species richness and diversity the variation was synchronous in all the study areas, but larval
density did not vary synchronously across the compartments, probably due to the impact of logging on the environment. We also
observed changes in the community composition during different seasons in all the study areas. We attribute the long term
impact of logging to the hindered regeneration of logged compartments and recommend restoration activities to help to return
the logged areas closer to the natural state. 相似文献
50.
Arachidonic acid (AA) release is a central message in cell signaling. Fatty acid release is generally assessed by manual sampling of radioactivity release from cells prelabeled with a radiolabeled fatty acid. The assay is laborious, time-consuming, and susceptible to high noise. Here we present a fast and reproducible method for 96-well filter plates and cells in suspension, a method that is best suited for agonist concentration-response studies and, thus, for ligand screening. The method offers tremendous time and effort savings and enables execution of large experimental series previously unattainable for AA release studies. 相似文献