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排序方式: 共有523条查询结果,搜索用时 46 毫秒
91.
B Gammelgaard K Jensen B Steffansen 《Journal of trace elements in medicine and biology》1999,13(1-2):82-88
The purpose of these studies was to compare the in vitro absorption of two inorganic chromium(III) compounds: chromium chloride and chromium nitrate, with organic chromium(III)-picolinate; and to investigate if any in vitro metabolism of chromium(VI) takes place. The in vitro metabolism studies showed that chromium (VI) was reduced by artificial gastric juice. The reduction followed first order kinetics with a half-life of 23 min. The studies also showed that the chromium picolinate complex was stable in artificial gastric juice for 4 hours. By the rat everted gut sac technique, chromium chloride, chromium nitrate and chromium picolinate penetrated the rat jejunum with 165 +/- 59, 160 +/- 26 and 127 +/- 36 ng chromium per g rat jejunum, respectively, whereas the permeability coefficients (Papp) were 0.7 +/- 0.3, 1.0 +/- 0.4, and 9.6 +/- 2.2 microns/min, respectively. Absorption studies on pig intestine in Ussing chambers showed a nearly total adsorption of chromium(III) by the chambers, resulting in unreliable data. 相似文献
92.
Bente B. Klitgaard 《Plant Systematics and Evolution》1999,219(1-2):1-25
Floral organogenesis and development of the tropical legume treesDalbergia brasiliensis, Machaerium villosum, Platymiscium floribundum, andPterocarpus rotundifolius were studied using scanning electron microscopy. The aims were to compare ontogenies and to elucidate if floral ontogenetic data will provide new character states diagnostic of the tribe Dalbergieae, which is considered a basal papilionoid tribe and primarily defined on fruit characters. Organ inception is principally acropetal in all taxa studied. Carpel inception is, however, consistently precocious. InD. brasiliensis sepals are initiated in an order not previously reported in Papilionoideae. It may be considered modified helical. InP. rotundifolius the inner whorl of stamens initiate in an unusual way, this is lateral two stamens first, then the two abaxial ones, and last the adaxial one, opposed to the unidirectional order usually seen in Papilionoideae. Generally the differences in flower development among the studied genera appear at initiation and late stage in ontogenesis, rather than at mid-stage. 相似文献
93.
Thomas Vanneste Ottar Michelsen Bente Jessen Graae Magni Olsen Kyrkjeeide Håkon Holien Kristian Hassel Sigrid Lindmo Rozália Erzsebet Kapás Pieter De Frenne 《Ecological Research》2017,32(4):579-593
Climate change is affecting the composition and functioning of ecosystems across the globe. Mountain ecosystems are particularly sensitive to climate warming since their biota is generally limited by low temperatures. Cryptogams such as lichens and bryophytes are important for the biodiversity and functioning of these ecosystems, but have not often been incorporated in vegetation resurvey studies. Hence, we lack a good understanding of how vascular plants, lichens and bryophytes respond interactively to climate warming in alpine communities. Here we quantified long-term changes in species richness, cover, composition and thermophilization (i.e. the increasing dominance of warm-adapted species) of vascular plants, lichens and bryophytes on four summits at Dovrefjell, Norway. These summits are situated along an elevational gradient from the low alpine to high alpine zone and were surveyed for all species in 2001, 2008 and 2015. During the 15-year period, a decline in lichen richness and increase in bryophyte richness was detected, whereas no change in vascular plant richness was found. Dwarf-shrub abundance progressively increased at the expense of lichens, and thermophilization was most pronounced for vascular plants, but occurred only on the lowest summits and northern aspects. Lichens showed less thermophilization and, for the bryophytes, no significant thermophilization was found. Although recent climate change may have primarily caused the observed changes in vegetation, combined effects with non-climatic factors (e.g. grazing and trampling) are likely important as well. At a larger scale, alpine vegetation shifts could have a profound impact on biosphere functioning with feedbacks to the global climate. 相似文献
94.
The antennal lobe is the primary processing center for olfactory information in insects. To understand further the neural
circuitry of this brain area, we have investigated the distribution of γ-aminobutyric acid (GABA) and its colocalization with
neuropeptides in the antennal lobe of the noctuid moth Heliothis virescens. Immunocytochemical experiments with an antiserum against GABA showed a large number of labeled somata in the antennal lobe;
these somata were located exclusively in the lateral cell cluster. Stained neurites innervating all antennal-lobe glomeruli,
including the male-specific macroglomerular complex, suggested a prominent role of GABA in processing olfactory information,
including signals from pheromones, interspecifically acting odors, and plant odors. Fibers in two antennocerebral tracts (the
middle and dorsal antennocerebral tract) exhibited prominent GABA immunoreactivity. Double-labeling experiments revealed that
immunostaining for three neuropeptides, viz., A-type allatostatin, Manduca sexta allatotropin, and FMRFamide-related peptides, was largely colocalized with GABA in cell bodies of the lateral cell cluster.
The general absence of peptide immunostaining in the antennocerebral tracts strongly indicated that these peptides were colocalized
with GABA in local interneurons of the antennal lobe. In contrast, tachykinin-related peptides occurred in a distinct population
of local antennal-lobe neurons that did not exhibit GABA immunostaining. Thus, local interneurons that were not GABAergic
were present in the moth antennal lobe.
This work was supported by the Norwegian University of Science and Technology (project no. 80902101). 相似文献
95.
Jon Amund Kyte Sissel Trachsel Bente Risberg Per thor Straten Kari Lislerud Gustav Gaudernack 《Cancer immunology, immunotherapy : CII》2009,58(10):1609-1626
Cancer vaccine trials frequently report on immunological responses, without any clinical benefit. This paradox may reflect
the challenge of discriminating between effective and pointless immune responses and sparse knowledge on their long-term development.
Here, we have analyzed T cell responses in long-term survivors after peptide vaccination. There were three main study aims:
(1) to characterize the immune response in patients with a possible clinical benefit. (2) To analyze the long-term development
of responses and effects of booster vaccination. (3) To investigate whether the Th1/Th2-delineation applies to cancer vaccine
responses. T cell clones were generated from all nine patients studied. We find that surviving patients harbor durable tumor-specific
responses against vaccine antigens from telomerase, RAS or TGFβ receptor II. Analyses of consecutive samples suggest that
booster vaccination is required to induce robust T cell memory. The responses exhibit several features of possible clinical
advantage, including combined T-helper and cytotoxic functionality, recognition of naturally processed antigens and diverse
HLA-restriction and fine-specificity. CD4−CD8− T cell clones display unconventional cytotoxicity and specifically kill tumor cells expressing mutated TGFβ receptor II.
Cytokine profiling on the long-term survivors demonstrates high IFNγ/IL10-ratios, favoring immunity over tolerance, and secretion
of multiple chemokines likely to mobilize the innate and adaptive immune system. Interestingly, these pro-inflammatory cytokine
profiles do not follow a Th1/Th2-delineation. Most IFNγhigh/IL4low/IL10low cultures include high concentrations of hallmark Th2-cytokines IL-5 and IL-13. This does not reflect a mixture of Th1- and
Th2-clones, but applies to 19/20 T cell clones confirmed to be monoclonal through TCR clonotype mapping. The present study
identifies several factors that may promote clinical efficacy and suggests that cytokine profiling should not rely on the
Th1/Th2-paradigm, but assess the overall inflammatory milieu and the balance between key cytokines.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
96.
Verrucophora farcimen is renamed Pseudochattonella farcimen , and V. farcimen should be regarded as a synonym of P. farcimen for reasons of priority. 相似文献
97.
Daphna D.J. Habets Will A. Coumans Mohammed El Hasnaoui Elham Zarrinpashneh Luc Bertrand Benoit Viollet Bente Kiens Thomas E. Jensen Erik A. Richter Arend Bonen Jan F.C. Glatz Joost J.F.P. Luiken 《Biochimica et Biophysica Acta (BBA)/Molecular and Cell Biology of Lipids》2009,1791(3):212-219
Enhanced contractile activity increases cardiac long-chain fatty acid (LCFA) uptake via translocation of CD36 to the sarcolemma, similarly to increase in glucose uptake via GLUT4 translocation. AMP-activated protein kinase (AMPK) is assumed to mediate contraction-induced LCFA utilization. However, which catalytic isoform (AMPKα1 versus AMPKα2) is involved, is unknown. Furthermore, no studies have been performed on the role of LKB1, a kinase with AMPKK activity, on the regulation of cardiac LCFA utilization. Using different mouse models (AMPKα2-kinase-dead, AMPKα2-knockout and LKB1-knockout mice), we tested whether LKB1 and/or AMPK are required for stimulation of LCFA and glucose utilization upon treatment of cardiomyocytes with compounds (oligomycin/AICAR/dipyridamole) which induce CD36 translocation similar to that seen upon contraction. In AMPKα2- kinase-dead cardiomyocytes, the stimulating effects of oligomycin and AICAR on palmitate and deoxyglucose uptake and palmitate oxidation were almost completely lost. Moreover, in AMPKα2- and LKB1-knockout cardiomyocytes, oligomycin-induced LCFA and deoxyglucose uptake were completely abolished. However, the stimulatory effect of dipyridamole on palmitate uptake and oxidation was preserved in AMPKα2-kinase-dead cardiomyocytes. In conclusion, in the heart there is a signaling axis consisting of LKB1 and AMPKα2 which activation results in enhanced LCFA utilization, similarly to enhanced glucose uptake. In addition, an unknown dipyridamole-activated pathway can stimulate cardiac LCFA utilization by activating signaling components downstream of AMPK. 相似文献
98.
Lekve K Bagøien E Dahl E Edvardsen B Skogen M Stenseth NC 《Proceedings. Biological sciences / The Royal Society》2006,273(1605):3047-3055
In this paper, we demonstrate that the seasonal dynamics in the abiotic factors, without including seasonal changes in the biological relationships, can appropriately account for the seasonal dynamics of Chrysochromulina spp. This is through the analysis of data on the population dynamics of Chrysochromulina spp. off southern Norway that is evaluated in relation to environmental factors and season by the analyses of 12 year monthly time-series. Chrysochromulina spp. abundance, nutrient concentrations, hydrographical properties, as well as current and wind data were analysed on a monthly scale by means of autoregressive moving average models, principal component analyses (PCA), and linear and nonlinear regression models. Seasonal development of the Chrysochromulina assemblage was well predicted from regression models forced with two PCA components representing seasonal variation in nutrient and chlorophyll a levels and ratios, inflow of North Seawater to the Skagerrak and northeasterly wind along the Norwegian coast. Assuming these to be general results, we might hypothesis that marine algal communities are governed by seasonally varying abiotic factors to a large extent. 相似文献
99.
Pocanschi CL Apell HJ Puntervoll P Høgh B Jensen HB Welte W Kleinschmidt JH 《Journal of molecular biology》2006,355(3):548-561
Membrane protein insertion and folding was studied for the major outer membrane protein of Fusobacterium nucleatum (FomA), which is a voltage-dependent general diffusion porin. The transmembrane domain of FomA forms a beta-barrel that is predicted to consist of 14 beta-strands. Here, unfolded FomA is shown to insert and fold spontaneously and quantitatively into phospholipid bilayers upon dilution of the denaturant urea, which was shown previously only for outer membrane protein A (OmpA) of Escherichia coli. Folding of FomA is demonstrated by circular dichroism and fluorescence spectroscopy, by SDS-polyacrylamide gel electrophoresis, and by single-channel recordings. Refolded FomA had a single-channel conductance of 1.1 nS at 1 M KCl, in agreement with the conductance of FomA isolated from membranes in native form. In contrast to OmpA, which forms a smaller eight-stranded beta-barrel domain, folding kinetics of the larger FomA were slower and provided evidence for parallel folding pathways of FomA into lipid bilayers. Two pathways were observed independent of membrane thickness with two different lipid bilayers, which were either composed of dicapryl phosphatidylcholine or dioleoyl phosphatidylcholine. This is the first observation of parallel membrane insertion and folding pathways of a beta-barrel membrane protein from an unfolded state in urea into lipid bilayers. The kinetics of both folding pathways depended on the chain length of the lipid and on temperature with estimated activation energies of 19 kJ/mol (dicapryl phosphatidylcholine) and 70 kJ/mol (dioleoyl phosphatidylcholine) for the faster pathways. 相似文献
100.