Die Bestimmung der effektiven Kationenaustauschkapazität von Gesteinen     

Gerd Deutschmann  Holger Rummenhohl  Jamal Tarrah 《植物养料与土壤学杂志》1997,160(2):151-155

The determination of the effective cation exchange capacity of rocks The extractable cations (1 N NH₄Cl) of broken, mortared, and ground rocks (Sandstone, Clay schist, Diabase, Alkali-Olivinbasalt) were determined using vibration extraction and percolation. These methods were evaluated by re-exchange experiments. In addition mineralogical components, specific surface and effective porosity of the rocks were determined. Al-silicates which are cation exchangers like Illite and Zeolite minerals were found in these rocks. Mortaring and grinding increased the specific surface and the exchange capacity of the rocks which have a low porosity (Clay schist and Basalt). For example, the CEC of broken Clay schist was 27 μmol_c g^?1 and increased to ≈ 40 μmol_c g^?1 after mortaring. The CEC of the rocks with a high porosity (Diabase and Sandstone) did not depend on the particle size. Therefore we assume, that inner parts of the broken rocks were reached by extraction. The CEC amounts to ≈ 50–80% of the sum of the cations, which could be extracted with NH₄Cl. This difference is probably due to the dissolution of salts. Mortaring and grinding increased the amount of cations derived from dissolving of salts. The results show, that rocks are of signficance not only for silicate weathering, but also for the cation exchange.  相似文献   

Speciation in the parthenogenetic oribatid mite genus Tectocepheus (Acari, Oribatida) as indicated by molecular phylogeny   总被引：2，自引：0，他引：2  

Michael Laumann  Roy A. Norton  Gerd Weigmann  Stefan Scheu  Mark Maraun  Michael Heethoff 《Pedobiologia》2007,51(2):111-122

Despite the lack of universal concepts for species and speciation, both sexual and asexual organisms are expected to diversify into discrete genotypic and morphological clusters. Species-rich clusters of parthenogenetic oribatid mites likely evolved in the absence of sexual reproduction. We used nucleotide sequences of the large and small rDNA genes (18S and 28S) and the coding genes for heat shock protein 82 (hsp82) and elongation factor-1 alpha (ef-1α) for phylogenetic analyses of three morphotypes of the parthenogenetic oribatid mite genus Tectocepheus. DNA sequence divergences of the different morphotypes were similar to those of sexual species in other organisms. Maximum likelihood analyses of single genes and combined data sets were largely congruent in reconstructing the phylogeny of the Tectocepheus species. The results suggest that the different morphotypes of Tectocepheus indeed evolved in the absence of sexual reproduction, and that Tectocepheus minor, Tectocepheus velatus and Tectocepheus sarekensis are best considered distinct species. Further, the results suggest that 18S rDNA, hsp82 and ef-1α are powerful markers for resolving phylogenetic relationships of oribatid mites. Saturation plots indicated that the D3-region of 28S is much more saturated than all other examined genes. This indicates that the D3-region is unsuitable for resolving ancient splits in oribatid mites.  相似文献   

Design and chemical synthesis of a homogeneous polymer-modified erythropoiesis protein     

Kochendoerfer GG  Chen SY  Mao F  Cressman S  Traviglia S  Shao H  Hunter CL  Low DW  Cagle EN  Carnevali M  Gueriguian V  Keogh PJ  Porter H  Stratton SM  Wiedeke MC  Wilken J  Tang J  Levy JJ  Miranda LP  Crnogorac MM  Kalbag S  Botti P  Schindler-Horvat J  Savatski L  Adamson JW  Kung A  Kent SB  Bradburne JA 《Science (New York, N.Y.)》2003,299(5608):884-887

We report the design and total chemical synthesis of "synthetic erythropoiesis protein" (SEP), a 51-kilodalton protein-polymer construct consisting of a 166-amino-acid polypeptide chain and two covalently attached, branched, and monodisperse polymer moieties that are negatively charged. The ability to control the chemistry allowed us to synthesize a macromolecule of precisely defined covalent structure. SEP was homogeneous as shown by high-resolution analytical techniques, with a mass of 50,825 +/-10 daltons by electrospray mass spectrometry, and with a pI of 5.0. In cell and animal assays for erythropoiesis, SEP displayed potent biological activity and had significantly prolonged duration of action in vivo. These chemical methods are a powerful tool in the rational design of protein constructs with potential therapeutic applications.  相似文献   

Neuroscience. Microglia: the enemy within?     

Kempermann G  Neumann H 《Science (New York, N.Y.)》2003,302(5651):1689-1690

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Bacterial community structure in lake sediments of microcosms contaminated with nonylphenol     

Miriam Jontofsohn  Gerd Pfister  Gabriele Severin  Karl-Werner Schramm  Anton Hartmann  Michael Schloter 《Journal of Soils and Sediments》2002,2(4):211-215

The impact of nonylphenol, an estrogenic degradation product of alkylphenol polyethoxylates, on the bacterial community structure in contaminated sediments of aquatic microcosms was investigated over a period of 20 weeks using a 16S rDNA-based molecular phylogenetic approach. All microcosms showeda strong seasonal fluctuation of the dominant as well as the active bacterial microflora independent of their degree of contamination with nonylphenol. These changes were correlated with the dynamic of the total organic carbon content (TOC), ranging from 4–39 g/kg sediment dry weight and the redox potential in the sediment. Even at the highest observed nonylphenol concentration (3.4 mg/kg sediment dry weight) the bacterial community structure was mostly unchanged.  相似文献   

The impact of environmental change on the intensity and spatial pattern of water erosion in a semi-arid mountainous Andean environment     

Veerle Vanacker  Gerard Govers  Jean Poesen  Jozef Deckers  Gerd Dercon  George Loaiza 《CATENA》2003,51(3-4):329-347

Aerial photographs taken in 1976 and 1989 and a field survey in 1999 showed that land use in a 900-ha catchment in the southern part of the Ecuadorian Andes is highly dynamic. Over 23 years, ca. 83 ha of arable land was abandoned and ca. 70 ha was taken into agricultural production. Changes in land use were not spatially homogeneous. Parcels on unstable geologic formations and close to village centres were preferably set-aside. Land taken into cultivation was preferably located on gently sloping areas close to newly built sites and arterial roads. The area with bush vegetation increased by regeneration of natural vegetation on fields set-aside in the late 1970s and early 1980s. There was a complex interaction between water erosion and environmental change in the study area. Land taken into production was levelled for furrow irrigation: this led to a net reduction in the area susceptible to water erosion. However, one quarter of the area affected only by sheet and rill erosion 23 years ago has since become incised by deep gullies. This increase in gully density was related to inadequate construction and management of irrigation infrastructure, rather than to change in vegetation cover and/or soil erodibility caused by agricultural practices. This factor is often overlooked in studies of the effects of environmental change on geomorphologic processes.  相似文献   

Wasserhaushalt und Dickenwachstum von Kiefern in Abhängigkeit des Grundwasserflurabstandes     

Gerd Wessolek  Winfried Riek  Angela Von Lührte  Michael Facklam 《植物养料与土壤学杂志》1995,158(1):15-22

Water budget and annual ring growth of pines for different groundwater depth conditions Relation between annual ring width and water supply was examined for different groundwater depth in an old pine stand on a sandy soil. The quotient Ereal/Epot is a suitable parameter to quantify water stress. Multiple regression analyses were used to describe the dependence between annual ring width and water stress. Mean growth of basal area can be expressed by Ereal/Epot of the actual and previous year. This site specific function was used to quantify growth reduction affected by ground-water lowering for various soil conditions.  相似文献   

Hemophilia B (factor IX deficiency) with concomitant factor XII degradation in a male crossbreed cat     

Lutze G  Kutschmann K  Fürst K  Schneppenheim R 《Berliner und Münchener tier?rztliche Wochenschrift》2005,118(5-6):255-260

A male cat suffered from a severe haemorrhagic disorder manifesting as deep, partly infected cutaneous haematomas, enhanced and prolonged bleeding after injuries and subsequent lameness at several occasions. Bleeding resulted in severe anaemia with haematocrit falling to as low as 0.10 L/L. Haemophilia B was diagnosed based on factor IX deficiency with a functional residual activity of 5% and factor IX antigen of 8%, respectively. Additionally, factor XII activity was reduced to 32% of normal. The mutation 31217G==>A in exon 8 of the factor IX gene, predicting the amino acid exchange G366R was identified as the cause of moderate factor IX deficiency. This is the first mutation identified in cats with haemophilia B. Treatment was limited to local therapy and palliation, insufficient to prevent lethal outcome due to severe anaemia.  相似文献   

Dietary anthocyanin-rich tart cherry extract inhibits intestinal tumorigenesis in APC(Min) mice fed suboptimal levels of sulindac     

Bobe G  Wang B  Seeram NP  Nair MG  Bourquin LD 《Journal of agricultural and food chemistry》2006,54(25):9322-9328

A promising approach for cancer chemoprevention might be a combination therapy utilizing dietary phytochemicals and anticarcinogenic pharmaceuticals at a suboptimal dosage to minimize any potential adverse side effects. To test this hypothesis, various dosages of anthocyanin-rich tart cherry extract were fed in combination with suboptimal levels of the nonsteroidal anti-inflammatory drug sulindac to APCMin mice for 19 weeks. By the end of the feeding period, fewer mice that were fed the anthocyanin-rich extract in combination with sulindac lost more than 10% of body weight than mice fed sulindac alone. Mice that were fed anthocyanin-rich extract (at any dose) in combination with sulindac had fewer tumors and a smaller total tumor burden (total tumor area per mouse) in the small intestine when compared to mice fed sulindac alone. These results suggest that a dietary combination of tart cherry anthocyanins and sulindac is more protective against colon cancer than sulindac alone.  相似文献   

IGF-I- and EGF-dependent DNA synthesis of porcine myoblasts is influenced by the dietary isoflavones genistein and daidzein     

Mau M  Kalbe C  Wollenhaupt K  Nürnberg G  Rehfeldt C 《Domestic animal endocrinology》2008,35(3):281-289

Soy-derived isoflavones have been reported to be specific inhibitors of protein tyrosine kinases like the type 1 insulin-like growth factor receptor (IGF-1R) and the epidermal growth factor receptor (EGFR). This study was conducted to investigate, whether IGF-I and EGF stimulate porcine myoblast growth and whether the responses are influenced by isoflavones. Satellite cell-born myoblasts derived from the semimembranosus muscle of newborn piglets were treated for 26h with IGF-I or EGF alone and in combination with genistein or daidzein. The DNA amount was measured and DNA synthesis was recorded as 6 h-[(3)H]thymidine incorporation during exponential growth in serum-free basal medium. IGF-I and EGF synergistically stimulated DNA synthesis of porcine myoblast with EGF causing a greater response. Genistein (100mumol/l) effectively reduced the growth factor-mediated DNA synthesis, which was associated with an inhibition of growth factor receptor protein expression. In response to daidzein no reduction in growth factor-mediated DNA synthesis was found. Daidzein (1; 10mumol/l) combined with IGF-I caused even a slight increase in DNA amount compared with the untreated control. The expression of the IGF-1R precursor protein was reduced with 10 and 100mumol/l daidzein, whereas the EGFR expression remained unchanged with daidzein. The results suggest that dietary isoflavones may interact with growth factor-induced stimulation of pig skeletal muscle growth.  相似文献