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991.
Radovan Murín Ghasem Mohammadi Dieter Leibfritz Bernd Hamprecht 《Neurochemical research》2009,34(7):1195-1203
The three essential amino acids, valine, leucine and isoleucine, constitute the group of branched-chain amino acids (BCAAs).
BCAAs are rapidly taken up into the brain parenchyma, where they serve several distinct functions including that as fuel material
in brain energy metabolism. As one function of astrocytes is considered the production of fuel molecules that support the
energy metabolism of adjacent neural cells in brain. Astroglia-rich primary cultures (APC) were shown to rapidly dispose of
the BCAAs, including valine, contained in the culture medium. While the metabolisms of leucine and isoleucine by APC have
already been studied in detail, some aspects of valine metabolism remained to be determined. Therefore, in the present study
an NMR analysis was performed to identify the 13C-labelled metabolites that are generated by APC during catabolism of [U-13C]valine and that are subsequently released into the incubation medium. The results presented show that APC (1) are potently
disposing of the valine contained in the incubation medium; (2) are capable of degrading valine to the tricarboxylic acid
(TCA) cycle member succinyl-CoA; and (3) release into the extracellular milieu valine catabolites and compounds generated
from them such as [U-13C]2-oxoisovalerate, [U-13C]3-hydroxyisobutyrate, [U-13C]2-methylmalonate, [U-13C]isobutyrate, and [U-13C]propionate as well as several TCA cycle-dependent metabolites including lactate.
This article is dedicated to Dr. George DeVries. 相似文献
992.
993.
The dispersal of gametes and larvae plays a key role in the population dynamics of sessile marine invertebrates. Species with
internal fertilisation are often associated with very localised larval dispersal, which may cause small-scale patterns of
neutral genetic variation. This study on the brooding coral Seriatopora hystrix from the Red Sea focused on the smallest possible scale: Two S. hystrix stands (~100 colonies each) near Dahab were completely sampled, mapped and analysed at five microsatellite markers. The sexual
mode of reproduction, the likely occurrence of selfing and the level of immigration were in agreement with previous studies
on this species. Contrary to previous findings, both stands were in Hardy–Weinberg proportions. Also, no evidence for spatially
restricted larval dispersal within the sampled areas was found. Differences between this and previous studies on S. hystrix could reflect variation in life history or varying environmental conditions, which opens intriguing questions for future
research. 相似文献
994.
Lutz Kunzmann Zlatko Kvaček Dieter Hans Mai Harald Walther 《Review of Palaeobotany and Palynology》2009,153(1-2):153-183
Fossil remains of Taxodium from upper Eocene to lower Miocene localities in Germany, the Czech Republic and Russia are investigated to reconsider taxonomic concepts. It is demonstrated that all material belongs to one species which is named Taxodium dubium (Sternberg) Heer emend. Using the whole-plant concept, T. dubium is considered as a synthetic species comprising foliage, seed cones, seeds, and male cones with pollen in situ. Shared identity of T. dubium and the wood morpho-taxon Taxodioxylon taxodii Gothan is assumed. Taxodium dubium underwent evolutionary changes through the Oligocene expressed mainly in changes of the cone scale ornamentation. To designate this intraspecific variation taxonomically two morpho-formae are distinguished: T. dubium forma heerii (Dorofeev) Kunzmann, Kva?ek, Mai et Walther stat. nov. et emend. and T. dubium forma dubium. Simultaneous intraspecific variations in leaf morphology and leaf epidermal anatomy are missing. Taxodium dubium occurs from the late Eocene to late Miocene in the (Atlantic-) Boreal province sensu Mai of Central Europe and from the late Oligocene to late Pliocene in the Transeuropean Paratethys province sensu Mai. 相似文献
995.
Igor E. Kasheverov Maxim N. Zhmak Alexander Fish† Prakash Rucktooa† Alexey Yu. Khruschov Alexey V. Osipov Rustam H. Ziganshin Dieter D'hoedt‡ Daniel Bertrand‡ Titia K. Sixma† August B. Smit§ Victor I. Tsetlin 《Journal of neurochemistry》2009,111(4):934-944
α-Conotoxins interact with nicotinic acetylcholine receptors (nAChRs) and acetylcholine-binding proteins (AChBPs) at the sites for agonists/competitive antagonists. α-Conotoxins blocking muscle-type or α7 nAChRs compete with α-bungarotoxin. However, α-conotoxin ImII, a close homolog of the α7 nAChR-targeting α-conotoxin ImI, blocked α7 and muscle nAChRs without displacing α-bungarotoxin ( Ellison et al. 2003, 2004 ), suggesting binding at a different site. We synthesized α-conotoxin ImII, its ribbon isomer (ImII iso ), 'mutant' ImII(W10Y) and found similar potencies in blocking human α7 and muscle nAChRs in Xenopus oocytes. Both isomers displaced [125 I]-α-bungarotoxin from human α7 nAChRs in the cell line GH4 C1 (IC50 17 and 23 μM, respectively) and from Lymnaea stagnalis and Aplysia californica AChBPs (IC50 2.0–9.0 μM). According to SPR measurements, both isomers bound to immobilized AChBPs and competed with AChBP for immobilized α-bungarotoxin ( K d and IC50 2.5–8.2 μM). On Torpedo nAChR, α-conotoxin [125 I]-ImII(W10Y) revealed specific binding ( K d 1.5–6.1 μM) and could be displaced by α-conotoxin ImII, ImII iso and ImII(W10Y) with IC50 2.7, 2.2 and 3.1 μM, respectively. As α-cobratoxin and α-conotoxin ImI displaced [125 I]-ImII(W10Y) only at higher concentrations (IC50 ≥ 90 μM), our results indicate that α-conotoxin ImII and its congeners have an additional binding site on Torpedo nAChR distinct from the site for agonists/competitive antagonists. 相似文献
996.
Angela B. Clement Martin Gamerdinger Irfan Y. Tamboli† Dieter Lütjohann‡ Jochen Walter† Isabell Greeve§ Gerald Gimpl¶ Christian Behl 《Journal of neurochemistry》2009,111(3):669-682
Chronic oxidative stress has been causally linked to several neurodegenerative disorders. As sensitivity for oxidative stress greatly differs between brain regions and neuronal cell types, specific cellular mechanisms of adaptation to chronic oxidative stress should exist. Our objective was to identify molecular mechanisms of adaptation of neuronal cells after applying chronic sublethal oxidative stress. We demonstrate that cells resistant to oxidative stress exhibit altered cholesterol and sphingomyelin metabolisms. Stress-resistant cells showed reduced levels of molecules involved in cholesterol trafficking and intracellular accumulation of cholesterol, cholesterol precursors, and metabolites. Moreover, stress-resistant cells exhibited reduced SMase activity. The altered lipid metabolism was associated with enhanced autophagy. Treatment of stress-resistant cells with neutral SMase reversed the stress-resistant phenotype, whereas it could be mimicked by treatment of neuronal cells with a specific inhibitor of neutral SMase. Analysis of hippocampal and cerebellar tissue of mouse brains revealed that the obtained cell culture data reflect the in vivo situation. Stress-resistant cells in vitro showed similar features as the less vulnerable cerebellum in mice, whereas stress-sensitive cells resembled the highly sensitive hippocampal area. These findings suggest an important role of the cell type-specific lipid profile for differential vulnerabilities of different brain areas toward chronic oxidative stress. 相似文献
997.
The yellowhammer Emberiza citrinella is a common European bird that sings in dialects that for decades have been distinguished by the existence of one single
element (called a “specific”). In this study we looked into other possibilities for dialect discrimination, measuring 24 different
variables. For the first time, multivariate statistics were used to discriminate dialect in yellowhammer song. Two similar
dialects (XlB and XsB) that are not clearly defined in the literature were studied. Statistics incorporated (1) all variables,
(2) no variables of “specific” elements, and (3) no variables under the influence of these “specific” variables. Multivariate
statistics support dialect discrimination by ear and confirmed that only one element in yellowhammer song characterises dialect.
In addition, we looked for local differences within two dialects and found that one local observation area showed a higher
separation than the other sites (Meck1). However, as yet there is insufficient evidence for the existence of a new subdialect.
The experiments comply with the current laws of the study area. 相似文献
998.
999.
1000.
Rafael Beine Alfred Rocas Valente Rebekka Biedendieck Dieter Jahn Jürgen Seibel 《Process Biochemistry》2009,44(10):1103-1114
Many biocatalysts exhibit strict stereospecificity and regioselectivity. However, their thermodynamically controlled equilibria often limit yields in industrial production processes. Herein, we describe the synthesis of fructooligosaccharides from sucrose by various fructansucrases. We previously demonstrated that transfructosylation to diverse acceptors yields d-glucose and the fructose-containing product along with diverse by-products. To streamline this reaction, we developed a procedure that allows the enhanced transfructosylation of diverse acceptors by different fructansucrases. By diverting the released glucose from the reaction via metabolism by living cells we limited the back reaction and forced the consumption of sucrose. The basic conditions for the resulting fermentation process were optimized by a genetic algorithm and integrated into a kinetic model. This strategy allows the prediction of optimal reaction parameters for the production of desired target compounds. 相似文献