Induction of tumors in mice by genomic hypomethylation

Genome-wide DNA hypomethylation occurs in many human cancers, but whether this epigenetic change is a cause or consequence of tumorigenesis has been unclear. To explore this phenomenon, we generated mice carrying a hypomorphic DNA methyltransferase 1 (Dnmt1) allele, which reduces Dnmt1 expression to 10% of wild-type levels and results in substantial genome-wide hypomethylation in all tissues. The mutant mice were runted at birth, and at 4 to 8 months of age they developed aggressive T cell lymphomas that displayed a high frequency of chromosome 15 trisomy. These results indicate that DNA hypomethylation plays a causal role in tumor formation, possibly by promoting chromosomal instability.     

Transport of energy in muscle: the phosphorylcreatine shuttle

In order to explain the insulin-like effect of exercise, it was proposed in 1951 that contracting muscle fibers liberate creatine, which acts to produce an acceptor effect--later called respiratory control--on the muscle mitochondria. The development of this notion paralleled the controversy between biochemists and physiologists over the delivery of energy for muscle contraction. With the demonstration of functional compartmentation of creatine kinase on the mitochondrion, it became clear that the actual form of energy transport in the muscle fiber is phosphorylcreatine. The finding of an isoenzyme of creatine phosphokinase attached to the M-line region of the myofibril revealed the peripheral receptor for the mitochondrially generated phosphorylcreatine. This established a molecular basis for a phosphorylcreatine-creatine shuttle for energy transport in heart and skeletal muscle and provided an explanation for the inability to demonstrate experimentally a direct relation between muscle activity and the concentrations of adenosine triphosphate and adenosine diphosphate.     

Quantitative und qualitative Veränderungen im A-Horizont von Sandböden nach Umwandlung von Dauergrünland in Ackerland

Quantitative and qualitative changes in soil properties of A- horizons of sandy soils caused by conversion of grassland to arable land Changes in physical soil properties and in soil organic matter of the A-horizons due to the conversion of permanent grassland to arable land are quantified and described as a function of time for sandy soils. The study was carried out in an area northeast of Hannover. A decrease of about 100 t/ha C_org (- 57%), 5 – 6 t/ha N_org (- 58%) and 1 t/ha S_t (- 58%) was measured for a period of 2 – 4 years after grassland conversion. Thereby the quality of the soil organic matter remains unchanged (no changes of the C/N ratio and of the distribution of N_org in 5 N-fractions). However, an increase of soil bulk density from 1.0 to 1.3 g/cm³ and a decrease of total pore volume from 0.59 to 0.47 were observed. The fast mineralization of soil organic matter in the A-horizon following the conversion of grassland soils results in a temporary heavily increased nitrate input into the groundwater. Furthermore mineralization and leaching of nitrate and sulfate induces an acidification push in the soil by a proton release in the order of 350 keq/ha during a 2 – 4 years period. However, this proton production is compensated quantitatively by several applications of lime or marl by farmers and by the buffering of bases cations released from mineralized soil organic matter.     

Natürlicher gehalt und anthropogene anreicherung von Schwermetallen in den Sedimenten von Elbe, Eider, Trave und Schwentine

The sediments of four rivers in Northern Germany were analysed for heavy metals. 371 sediment samples were taken from 24 investigation sites of the rivers Elbe, Eider, Trave and Schwentine and from North Sea tidal flat areas. Within each investigation site strong positive relationships exist between the heavy metal contents and the contents of the fine size fractions < 2 μm and < 20 μm of the sediments. To compare the metal contents in the sediments from different areas, differences in grain size were eliminated by computing the metal contents for a clay content of 25% by means of regression equations.The fluvial sediments at a few inland investigation sites, as well as the tidal flat sediments are not detectably polluted with heavy metals. Their metal contents could be used as background values for computing enrichment factors of polluted fluvial deposits.Sediments from the river Elbe in and upstream of the port of Hamburg, and from some parts of the rivers Eider and Trave near industrial and densely populated districts, are highly enriched with heavy metals. The highest enrichment factors are for Hg 85, Cd 56, Pb 37, Cu 34, Zn 29, As 19, Cr 6, Ni 4 and Co 3 times the background values.The ecological importance of the heavy metal contents in the sediments is discussed.     

Simplified N fertilization strategies for winter wheat. Part 1: plants: compensation capacity of modern wheat varieties

ABSTRACT

Winter wheat in northwestern Europe is often fertilized with several doses of calcium-ammonium-nitrate (CAN). For economy, farmers fertilize using a combination of N-doses. Here, we examined the necessity of N splitting (1–3) and application timing in experiments conducted in 2010 using a one-factorial fully randomized block design, and in 2011–2012 using a two-factorial split-plot design (four replicates). The study site, in southwestern Germany, had silty loam soil, and modern cultivars (2010: one cultivar, 2011–2012: three cultivars) with different genetic abilities to develop the yield components of interest were tested. A late first or single N application at stage BBCH 29/31 did not lead to differences in grain yields or protein contents compared to three N applications. However, a single N application at stage BBCH 25/27 resulted in a reduced protein content. Yield component development did not significantly differ among the cultivars. Early N application increased plant density but not yield. In two years, low plant densities were compensated by higher numbers of kernels per spike. Hence, under the tested conditions, the number of N applications could be reduced, as the high compensation ability of modern cultivars allows N fertilization consisting of two or even one application.     

Importance of reservoirs for the conservation of freshwater molluscs in a tropical urban landscape

Freshwater species and ecosystems are gravely imperiled, particularly within urban landscapes of tropical Asia. In one of the region’s most urbanized landscapes (i.e., Singapore), we determined: (1) the importance of six different habitats (i.e., catchment reservoirs, estuarine reservoirs, forest streams, rural streams, ponds and monsoon canals) for conserving the diversity of freshwater molluscs; (2) key environmental factors (e.g., pH) affecting molluscan distribution; (3) important biogeographical determinants (e.g., area) of molluscan richness within each habitat; and (4) the habitat affinities of introduced species. High sampling saturation was achieved at most study habitats with minimal sampling effort, suggesting that the utilization of molluscs as bioindicators can expedite freshwater conservation initiatives. Estuarine reservoirs (6.0 ± 2.0) had the highest molluscan richness, vis-à-vis catchment reservoirs, forest streams, rural streams, ponds and monsoon canals (3.0 ± 1.5; 0; 3.3 ± 2.0; 1.8 ± 0.5 and 3.5 ± 0.5 respectively). Both reservoir types possessed species compositions distinct from other habitats and contained majority (76%) of the sampled species. Reservoirs therefore serve to conserve the bulk of local freshwater malacofauna, especially if they are maintained at near-neutral pH levels (i.e., ∼7.3) and contain large substrates (i.e., rocks). Area was the best predictor of molluscan richness across all habitats, implying that larger freshwater habitats require higher conservation priorities than smaller ones. Introduced (non-native) species (e.g., Pomacea canaliculata) had high affinities for reservoirs, which are in need of monitoring to curb population expansions. The interminable growth of human settlements urgently requires a reconciliatory approach, which includes the ecologically-sound design and management of modified habitats to complement reserves in sustaining native freshwater species.     

Rind puncture resistance in maize: inheritance and relationship with resistance to pink stem borer attack

The main pest of maize in north‐western Spain is the pink stem borer, Sesamia nonagrioides, and stem lodging is one of the consequences of attack. Since rind puncture resistance is related to stem lodging resistance, the objectives of this work were to estimate the genetic effects involved in the inheritance of rind puncture resistance and to determine the phenotypic correlation coefficients between rind puncture resistance and pink stem borer damage. Six generations from the crosses ‘CM109’בEP31’ and ‘CM109’בEP42’ and a 10‐inbred line diallel were evaluated in Pontevedra, Spain, in 1995 and 1996. The inheritance of rind puncture resistance had two significant components, one additive and one dominant. Non‐allelic and genotype × environment interactions were not significant. Improvement for internode rind puncture resistance to increase stem strength and stalk lodging resistance could have some positive influence on resistance to pink stem borer. However, its use as an estimator of pink stem borer resistance cannot be generalized and so must be restricted to programmes that involve materials exhibiting physical resistance to pink stem borer attack.     

H?henlage und Sp?tfrostgef?hrdung

Ohne Zusammenfassung