Zur Verbreitung von Buchenkrebs in Naturverjüngungen in Baden-Württemberg     

B. Metzler  Rudolf Frhr. v. Erffa 《European Journal of Forest Research》2000,119(1-6):297-309

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Radiocarbon dating of a very large African baobab     

Patrut A  von Reden KF  Lowy DA  Alberts AH  Pohlman JW  Wittmann R  Gerlach D  Xu L  Mitchell CS 《Tree physiology》2007,27(11):1569-1574

In late 2004, Grootboom, probably the largest known African baobab (Adansonia digitata L.), collapsed unexpectedly in northeastern Namibia. Ten wood samples collected from different areas of the trunk were processed and investigated by accelerator mass spectrometry radiocarbon dating. The radiocarbon dates of three samples were greater than 1000 years BP (radiocarbon years before present, i.e., before AD 1950). The corresponding calibrated calendar age of the oldest sample was 1275 +/- 50 years, making Grootboom the oldest known angiosperm tree with reliable dating results. Variations in radiocarbon dates among the wood samples indicated that, morphologically, Grootboom was a quintuple tree, whereas genetically, it was a single individual. Ages of extreme lateral samples revealed that, over the past 500-600 years, Grootbooom had almost ceased growing, providing information about climate changes in central southern Africa. The sudden demise of Grootboom coincided with the spread of the poorly studied baobab disease, which has become epidemic in Namibia.  相似文献   

Treatment of sickle cell anemia mouse model with iPS cells generated from autologous skin   总被引：2，自引：0，他引：2  

Hanna J  Wernig M  Markoulaki S  Sun CW  Meissner A  Cassady JP  Beard C  Brambrink T  Wu LC  Townes TM  Jaenisch R 《Science (New York, N.Y.)》2007,318(5858):1920-1923

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Bose-Einstein condensation of cesium     

Weber T  Herbig J  Mark M  Nägerl HC  Grimm R 《Science (New York, N.Y.)》2003,299(5604):232-235

Bose-Einstein condensation of cesium atoms is achieved by evaporative cooling using optical trapping techniques. The ability to tune the interactions between the ultracold atoms by an external magnetic field is crucial to obtain the condensate and offers intriguing features for potential applications. We explore various regimes of condensate self-interaction (attractive, repulsive, and null interaction strength) and demonstrate properties of imploding, exploding, and non-interacting quantum matter.  相似文献   

Adipose triglyceride lipase contributes to cancer-associated cachexia     

Das SK  Eder S  Schauer S  Diwoky C  Temmel H  Guertl B  Gorkiewicz G  Tamilarasan KP  Kumari P  Trauner M  Zimmermann R  Vesely P  Haemmerle G  Zechner R  Hoefler G 《Science (New York, N.Y.)》2011,333(6039):233-238

Cachexia is a multifactorial wasting syndrome most common in patients with cancer that is characterized by the uncontrolled loss of adipose and muscle mass. We show that the inhibition of lipolysis through genetic ablation of adipose triglyceride lipase (Atgl) or hormone-sensitive lipase (Hsl) ameliorates certain features of cancer-associated cachexia (CAC). In wild-type C57BL/6 mice, the injection of Lewis lung carcinoma or B16 melanoma cells causes tumor growth, loss of white adipose tissue (WAT), and a marked reduction of gastrocnemius muscle. In contrast, Atgl-deficient mice with tumors resisted increased WAT lipolysis, myocyte apoptosis, and proteasomal muscle degradation and maintained normal adipose and gastrocnemius muscle mass. Hsl-deficient mice with tumors were also protected although to a lesser degree. Thus, functional lipolysis is essential in the pathogenesis of CAC. Pharmacological inhibition of metabolic lipases may help prevent cachexia.  相似文献   

Stem cells. Setting standards for human embryonic stem cells     

Brivanlou AH  Gage FH  Jaenisch R  Jessell T  Melton D  Rossant J 《Science (New York, N.Y.)》2003,300(5621):913-916

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Microbial reefs in the Black Sea fueled by anaerobic oxidation of methane     

Michaelis W  Seifert R  Nauhaus K  Treude T  Thiel V  Blumenberg M  Knittel K  Gieseke A  Peterknecht K  Pape T  Boetius A  Amann R  Jørgensen BB  Widdel F  Peckmann J  Pimenov NV  Gulin MB 《Science (New York, N.Y.)》2002,297(5583):1013-1015

Massive microbial mats covering up to 4-meter-high carbonate buildups prosper at methane seeps in anoxic waters of the northwestern Black Sea shelf. Strong 13C depletions indicate an incorporation of methane carbon into carbonates, bulk biomass, and specific lipids. The mats mainly consist of densely aggregated archaea (phylogenetic ANME-1 cluster) and sulfate-reducing bacteria (Desulfosarcina/Desulfococcus group). If incubated in vitro, these mats perform anaerobic oxidation of methane coupled to sulfate reduction. Obviously, anaerobic microbial consortia can generate both carbonate precipitation and substantial biomass accumulation, which has implications for our understanding of carbon cycling during earlier periods of Earth's history.  相似文献   

Vergleich von Nitrat- und Amino-N-Schnelltest zur Charakterisierung des Stickstoff-Versorgungsgrades von Winterweizen     

Rudolf Schulz  Horst Marschner 《植物养料与土壤学杂志》1987,150(5):348-353

Comparison of the rapid tests for nitrate and amino-N for evaluating the N-status of winter wheat Nitrogen fertilizer trials with winter wheat were conducted in 1985 and 1986 to compare the efficacy of the rapid test for nitrate (in the stem base) and a newly developed rapid test for amino-N (in fully expanded green leaves) for evaluating the N-status of plants. In addition, the influence of weather conditions on the results given by both tests when using ammonium nitrate (NH₄NO₃ + CaCO₃) (AN) and urea-ammonium nitrate solution (UAN), was evaluated to determine wether the rapid test for amino-N gives more accurate information on the N-status of winter wheat than the rapid test for nitrate. The results show that the rapid test for nitrate is suitable to characterize the N-status of winter wheat when nitrogen is predominantly taken up by roots as nitrate. This is normaly the case when plants are fertilized with the salt form of nitrogen, als well as with liquid fertilizer, such as UAN applied through tubes in the soil, as for fertilization of winter wheat at later growing stages. However, during dry weather (1986 field trial) UAN application on leaves at shooting and ear emergence can result in high nitrogen uptake by leaves, causing an underestimation of plant N-status by the rapid test for nitrate, and thus, subsequent excess N-fertilizer application may be recommended (order of magnitude: 20 kg N/ha). Under these conditions the rapid test for amino-N in leaves (pressed sap) is a more accurate test for estimation of plant N-status because it determines glutamine and amino acids, the most important storage forms of reduced nitrogen in plants. When UAN fertilizer on leaves is washed off by rain (1985 field trial), crop N-fertilizer requirements predicted by both tests are comparable. If storage of nitrate in the stem base occurs, due, for example to low radiation intensity during spring (lower nitrate reduction), with the rapid test for amino-N an underestimation of plant N-status can be obtained.  相似文献   

Der Einsatz von Kationenaustauscherharzen zur Charakterisierung verfügbarer Kationen aus natürlich gelagerten Bodenproben     

Martina K. Zuleger  Rudolf Schierl 《植物养料与土壤学杂志》1990,153(4):277-278

Investigation of cation release of undisturbed soil columns via cation exchange resins Undisturbed soil columns were investigated with cation exchange resins. Similar to roots there is an exchange of H⁺ and cations. The ability for release of cations by molecular diffusion is decreasing with time, so that an asymptotic approximation to a final value occurs. A part of the protons is buffered, for example by aluminium-hydroxides. Samples rich in organic carbon show different graphs for iron and manganese which is probably due to microbial reduction processes.  相似文献   

Masked mycotoxins: determination of a deoxynivalenol glucoside in artificially and naturally contaminated wheat by liquid chromatography-tandem mass spectrometry     

Berthiller F  Dall'Asta C  Schuhmacher R  Lemmens M  Adam G  Krska R 《Journal of agricultural and food chemistry》2005,53(9):3421-3425

Conjugated mycotoxins, in which the toxin is usually bound to a more polar substance like glucose, are referred to as masked mycotoxins, as these substances escape routine detection methods but can release their toxic precursors after hydrolysis. This is the first report on the natural occurrence of a glucoside of deoxynivalenol (DON) in Fusarium-infected wheat and maize. To obtain appropriate standards, we chemically synthesized deoxynivalenol-3-beta-D-glucopyranoside (DON-3-glucoside) and deoxynivalenol-15-beta-D-glucopyranoside (DON-15-glucoside). The synthesis products were characterized by liquid chromatography-tandem mass spectrometry. The DON-glucosides showed different collision-induced dissociation (CID) fragmentation behaviors and could therefore be distinguished. Wheat plants were either treated with DON (n = 52) or with Fusarium spp. (n = 4) at anthesis, and after harvest, wheat ears were analyzed for DON and DON-glucosides. All 56 treated wheat samples contained DON and a DON-glucoside with the same retention time, molecular mass, and CID fragmentation behavior as the synthetic DON-3-glucoside. Moreover, the DON-glucoside was also found in two out of three analyzed naturally DON-contaminated maize and in five out of five naturally contaminated wheat samples, in a range from 4 to 12% of the DON concentration. To further confirm the identity of the DON-glucoside, the compound was isolated from wheat extracts and characterized as DON-3-glucoside with NMR. The results of this study indicate the importance to consider both DON and DON-3-glucoside with regard to food and feed safety.  相似文献