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991.
992.
Mühling J Engel J Halabi M Müller M Fuchs M Krüll M Harbach H Langefeld TW Wolff M Matejec R Welters ID Menges T Hempelmann G 《Amino acids》2006,31(1):11-26
Summary. We have examined the effects of Nω-nitro-L-arginine-methylester-hydrochloride [L-NAME; inhibitor of nitric oxide synthase], S-nitroso-N-acetyl-penicillamine
[SNAP; nitric oxide donor], α-difluoro-methyl-ornithine [DFMO; inhibitor of ornithine decarboxylase] arginine or ornithine
as well as the combination of arginine or ornithine with L-NAME, SNAP or DFMO on intracellular free amino- and α-keto acid
profiles and the immune function markers superoxide anion and hydrogen peroxide generation as well as released myeloperoxidase
activity in neutrophils (PMN). Although the underlying mechanisms still remain unclear, we believe from our results that nitric
oxide as well as polyamine-dependent pathways are involved in the signal transmission of free radical molecule, beneficial
nutritional therapy or maleficient pharmacological stress-induced alterations in PMN nutrient composition. Relevant changes
in intragranulocyte free amino- and α-keto acid homeostasis and metabolism, especially, may be one of the determinants in
PMN nutrition that positively or negatively influences and modulate neutrophil host defence capability and immunocompetence. 相似文献
993.
Na+/K+-ATPase plays a key role in the transport of Na+ throughout the nephron, but ageing appears to be accompanied by changes in the regulation and localization of the pump. In
the present study, we examined the effect of in vitro cell ageing on the transport of Na+ and K+ ions in opossum kidney (OK) cells in culture. Cells were aged by repeated passing, and Na+/K+-ATPase activity and K+ conductance were evaluated using electrophysiological methods. Na+K+-ATPase α1– and β1-subunit expression was quantified by Western blot techniques. Na+/H+ exchanger activity, changes in membrane potential, cell viability, hydrogen peroxide production and cellular proliferation
were determined using fluorimetric assays. In vitro cell ageing is accompanied by an increase in transepithelial Na+ transport, which results from an increase in the number of Na+/K+-ATPase α1- and β1-subunits, in the membrane. Increases in Na+/K+-ATPase activity were accompanied by increases in K+ conductance as a result of functional coupling between Na+/K+-ATPase and basolateral K+ channels. Cell depolarization induced by both KCl and ouabain was more pronounced in aged cells. No changes in Na+/H+ exchanger activity were observed. H2O2 production was increased in aged cells, but exposure for 5 days to 1 and 10 μM of H2O2 had no effect on Na+/K+-ATPase expression. Ouabain (100 nM) increased α1-subunit, but not β1-subunit, Na+/K+-ATPase expression in aged cells only. These cells constitute an interesting model for the study of renal epithelial cell
ageing. 相似文献
994.
The arrangement and composition of flowpath types within a given network are thought to govern its functioning. This concept
assumes that different flowpath types are functionally distinct. We investigated this assumption in a fluvial ecosystem by
comparing the riparian zone, parafluvial zone (in-channel gravel bars), and surface stream. We hypothesized that differences
in advection, uptake, and sorption would render material cycles more (a) open and (b) mutable in the surface stream, whereas
the converse would occur in the riparian zone, and an intermediate state would be seen in the intervening parafluvial zone.
To test our first hypothesis, we predicted that spatial heterogeneity in solute concentrations would be least in the surface
stream, greater in the parafluvial zone, and greatest in the riparian zone. Using a null model, we ascertained that this pattern
was shown by all solute species we examined (nitrate, ammonium, total dissolved inorganic nitrogen [DIN], dissolved organic
N, total dissolved N, soluble reactive phosphorus, dissolved organic carbon, and chloride). To test our second hypothesis,
we predicted that temporal change in spatial heterogeneity would be greatest in the surface stream, less in the parafluvial
zone, and least in the riparian zone. Nitrate, DIN, and chloride showed this pattern. In particular, surface stream inorganic
N was less spatially variable following months of high rainfall. According to an extant hypothesis, these results suggest
that inorganic N processing may be a stable function in this ecosystem. Other solute species did not support our second prediction,
perhaps because their retention and release dynamics are influenced principally by geochemistry. Generally, our findings indicate
that a geomorphic template can generate spatial patterns in ecosystem function, warranting an expansion of the spiraling framework
to a variety of flowpath types. 相似文献
995.
Forti G Agostiano A Barbato R Bassi R Brugnoli E Finazzi G Garlaschi FM Jennings RC Melandri BA Trotta M Venturoli G Zanetti G Zannoni D Zucchelli G 《Photosynthesis research》2006,88(3):211-240
This historical review was compiled and edited by Giorgio Forti, whereas the other authors of the different sections are listed alphabetically after his name, below the title of the paper; they are also listed in the individual sections. This review deals with the research on photosynthesis performed in several Italian laboratories during the last 50 years; it includes research done, in collaboration, at several international laboratories, particularly USA, UK, Switzerland, Hungary, Germany, France, Finland, Denmark, and Austria. Wherever pertinent, references are provided, especially to other historical papers in Govindjee et al. [Govindjee, Beatty JT, Gest H, Allen JF (eds) (2005) Discoveries in Photosynthesis. Springer, Dordrecht]. This paper covers the physical and chemical events starting with the absorption of a quantum of light by a pigment molecule to the conversion of the radiation energy into the stable chemical forms of the reducing power and of ATP. It describes the work done on the structure, function and regulation of the photosynthetic apparatus in higher plants, unicellular algae and␣in photosynthetic bacteria. Phenomena such as photoinhibition and the protection from it are also included. Research in biophysics of photosynthesis in Padova (Italy) is discussed by G.M. Giacometti and G.␣Giacometti (2006). 相似文献
996.
van der Heijden MG Bakker R Verwaal J Scheublin TR Rutten M van Logtestijn R Staehelin C 《FEMS microbiology ecology》2006,56(2):178-187
Symbiotic interactions are thought to play a key role in ecosystems. Empirical evidence for the impact of symbiotic bacteria on plant communities is, however, extremely scarce because of experimental constraints. Here, in three complementary experiments, we show that nitrogen-fixing rhizobia bacteria act as a determinant of plant community structure and diversity. Grassland microcosms inoculated with a mixture of rhizobia had a higher above-ground plant productivity (+35%), contained more nitrogen (+85%) and had significant higher community evenness (+34%) than control microcosms without rhizobia. Moreover, three of the four studied legume species required rhizobia to successfully coexist with other plant species. In contrast, the growth and survival of three grass and five forb species were not affected by the presence or absence of rhizobia. Finally, our results also showed that the legume species largely relied on symbiotically fixed nitrogen, both in the field and in the microcosms. This indicates that results in the microcosms are indicative for processes occurring in the field. It is concluded that symbiotic interactions between plants and prokaryotes can contribute to plant productivity, plant community structure and acquisition of limiting resources in legume-rich grassland communities. 相似文献
997.
Time-resolved fluorescence of 3-methylbenzimidazole (m3B) was used to study stacking interaction between base moieties in di-, tri- and tetra-phosphate analogues of 3-methylbenzimidazolyl(5′-5′)guanosine (m3Bp
n
G, n = 2, 3, 4), using 5′-triphosphate of 3-methylbenzimidazole riboside (m3BTP) as reference. Fluorescence intensity decays of all compounds cannot be satisfactory fitted with single-exponential function. Although an increase of a number of exponents led to better fits, interpretation of the individual exponential terms, i.e. pre-exponential amplitudes and fluorescence lifetimes, cannot be adequately characterized. We show that these fluorescence decays are best fitted by power-like function derived from physically justified distribution of the fluorescence lifetimes, and characterized by the mean value of the excited-state lifetime and relative variance of lifetime fluctuations around the mean value. The latter led to the parameter of heterogeneity and number of decay paths, which depend on the factors responsible for non-radiative decay of the excited state, including base–base stacking interaction. This was studied by means of changes of temperature and the number of phosphate groups in dinucleotides. It was shown that the strongest effect of stacking interactions, characterized by lowest values of both fluorescence mean decay time and relative variance, occurs in the case of m3Bp3G containing the same number of phosphates as natural mRNA cap. The possible importance of these results for interpretation of the mechanism of function of the mRNA cap structure is discussed. 相似文献
998.
PPAR基因与脂肪代谢调控 总被引:2,自引:0,他引:2
过氧化物酶体增值剂激活受体(PPARs)基因属于类固醇/甲状腺/维甲酸受体超家族,有3个亚型,即:PPAR-α、PPAR-β和PPAR-γ。PPARs具有多种生物学功能,如增强机体对胰岛素敏感性,调节体内糖平衡等,尤其在脂肪分化、生成等多方面起到重要作用,是目前的研究热点,文章从PPARs基因的结构,表达及功能等方面讨论了其与脂肪代谢调控的关系。 相似文献
999.
蛋白激酶Ca相互作用蛋白的结构与功能 总被引:1,自引:0,他引:1
蛋白激酶Cα相互作用蛋白(proteininteractingwithCαkinase,PICK1)是蛋白激酶Cα(proteinkinaseCα,PKCα)的靶蛋白之一,也是在PKCα和突触后膜受体蛋白间起重要作用的衔接蛋白。PICK1分别由PDZ结构域、BAR结构域以及卷曲螺旋区和酸性氨基酸区组成。PICK1中的PDZ结构域和受体蛋白、转运蛋白、衔接蛋白的相互作用报道较多,BAR结构域则与支架蛋白、质膜等相互作用。PICK1在突触可塑性、神经递质传递、外周神经感觉、细胞生长和黏连等方面发挥重要作用。本文对PICK1的结构和功能进行综述。 相似文献
1000.
We previously demonstrated that chronic treatment with the mixed endothelin A and B (ETA and ETB) receptor blocker bosentan improved isolated working heart function in streptozotocin (STZ) diabetic rats. Endothelin-1 (ET-1)
peptide levels, ET-1 mRNA and ETA and ETB receptor mRNA were all increased in diabetic hearts, but were unaffected by bosentan treatment, indicating that the beneficial
effects of bosentan on heart appear to be on downstream effectors of ET-1 and ET receptors rather than the ET-1 system itself.
Stimulation of ET-1 receptors leads to increased activation of protein kinase C (PKC), which is associated with PKC translocation
from the cytosol to the membrane. Persistent activation of specific PKC isoforms has been proposed to contribute to diabetic
cardiomyopathy. The purpose of this study was to determine whether chronic treatment with bosentan influences the activation
of PKC isoforms in hearts from diabetic rats. Male Wistar rats were divided into four groups: control, bosentan-treated control,
diabetic, and bosentan-treated diabetic. Diabetes was induced by the intravenous injection of 60 mg/kg streptozotocin. One
week later, treatment with bosentan (100 mg/kg/day) by oral gavage was begun and continued for 10 weeks. The heart was then
removed, homogenized, separated into soluble (cytosolic) and particulate (membrane) fractions and PKC isoform content in each
fraction was determined by Western blotting. PKC α, β2, δ, ε and ζ were all detected in hearts from both control and diabetic
rats. However, no change in the levels or distribution between the soluble and particulate fractions of any of these isoforms
could be detected in chronic diabetic hearts compared to control, whether untreated or treated with bosentan. These observations
indicate that bosentan does not improve cardiac performance in STZ diabetic rats by affecting the activation of PKC isoforms. 相似文献