Nitrate leaching from three afforestation chronosequences on former arable land in Denmark

In regions dominated by agricultural activities, nitrogen (N) is recognized as a major pollutant in aquatic environments. In north‐western Europe, afforestation of agricultural land is part of a strategy to improve water quality. In Denmark, former arable land has been afforested during the past 40–50 years. This study evaluated the effect of afforestation of former arable land on nitrate leaching, based on three afforestation chronosequences. Precipitation, canopy throughfall and soil water were collected and soil moisture was monitored at two Danish locations, Vestskoven (nutrient‐rich, medium deposition) and Gejlvang (nutrient‐poor, high deposition). Afforestation was performed using Norway spruce [Picea abies (Karst.) L.] and common oak (Quercus robur L.) at Vestskoven and Norway spruce at Gejlvang. The results suggest that afforestation of former arable land initially leads to lower nitrate leaching than that occurring under the former agricultural land use, and largely below the standard of 50 mg NO⁻₃ L⁻¹ for groundwater to be utilized as drinking water. Nitrate concentrations became almost negligible in forest stands of 5–20 years of age. However, after canopy closure (>20 years) nitrate concentrations below the root zone and nitrate leaching tended to increase. This was attributed to increased N deposition with increasing canopy development and decreased N demand once the most N‐rich biomass compartments had been built up. Nitrate leaching started to increase at a throughfall deposition level of about 10 kg N ha⁻¹ yr⁻¹. Compared with nutrient‐poor sandy soils, nutrient‐rich clayey soils appeared more vulnerable to disturbance of the N cycle and to increased N deposition, leading to N saturation and enhanced nitrate leaching. In approximately the first 35 years after afforestation, nitrate leaching below the root zone was generally higher below oak than below Norway spruce.     

Microbial diversity and community structure in Fynbos soil

The Fynbos biome in South Africa is renowned for its high plant diversity and the conservation of this area is particularly important for the region. This is especially true in the case of endangered vegetation types on the lowlands such as Sand Fynbos, of which only small fragments remain. The question is thus whether the diversity of the above‐ground flora is mirrored in the below‐ground microbial communities. In order to determine the relationship of the above‐ and below‐ground communities, the soil community composition of both fungal and bacterial groups in Sand Fynbos was characterized over space and time. A molecular approach was used based on the isolation of total soil genomic DNA and automated ribosomal intergenic spacer analysis of bacterial and fungal communities. Soil from four different sites was compared to resolve the microbial diversity of eubacterial and fungal groups on a local (alpha diversity) scale as well as a landscape scale (beta diversity). The community structures from different sites were compared and found to exhibit strong spatial patterns which remained stable over time. The plant community data were compared with the fungal and the bacterial communities. We concluded that the microbial communities in the Sand Fynbos are highly diverse and closely linked to the above‐ground floral communities.     

Molecular Comparison of the Mitochondrial and Cytoplasmic hsp 70 of Trypanosoma cruzi, Trypanosoma brucei and Leishmania major

ABSTRACT. We compared the expression and localization of the mitochondrial and cytoplasmic hsp70 of the protozoans Trypanosoma cruzi, Trypanosoma brucei and Leishmania major. The mitochondrial protein is encoded by multiple mRNA in all species, while the cytoplasmic protein is encoded by a single mRNA. In all three species, the mitochondrial hsp70 is concentrated in the kinetoplast, a submitochondrial structure that houses the unusual DNA (kDNA) that characterizes this group of organisms, while the cytoplasmic protein is distributed throughout the cell. These results suggest that, in all kinetoplastid species, mt-hsp70 has a specific function in kDNA biology, possibly in the processes of kDNA replication, RNA editing or kinetoplast structure.     

Sequence Diversity and Linkage Disequilibrium within the Merozoite Surface Protein-1 (Msp-1) Locus of Plasmodium falciparum: A Longitudinal Study in Brazil

ABSTRACT. The merozoite surface protein‐1 (MSP‐1) is a major vaccine candidate for the asexual blood stage of malaria. We examined both the extent of sequence diversity in block 17, the 3′end of Msp‐1 gene coding for a 19‐kDa polypeptide (MSP‐1₁₉) putatively involved in red blood cell binding, and the patterns of linkage disequilibrium between polymorphic sites throughout the Msp‐1 locus. The parasite population sample consisted of Plasmodium falciparum isolates collected between 1985 and 1998 in Rondônia. an area of hypoendemic malaria transmission in the southwestern Brazilian Amazon. Results were summarized as follows. (I) Seven block‐17 sequence variants or haplotypes were found among 130 isolates, including two new haplotypes (novel combinations of previously reported amino acid replacements), here named Brazil‐1 (E‐TSR‐F) and Brazil‐2 (Q‐TSR‐F). (2) As previously shown for other Msp‐1 polymorphisms, frequencies of block‐17 haplotypes displayed significant temporal variation. (3) Extensive linkage disequilibrium was demonstrated between neighboring dimorphic sites within block 17, as well as between polymorphisms at the 5′and 3′ends of Msp‐1 (map distance range: 3.83–4.99 kb). (4) The overall patterns of linkage disequilibrium within Msp‐1 remained stable over a period of nearly one decade, and examples of possible ‘epidemic’ expansion of parasites carrying particular Msp‐1 alleles were found in the 1980s and 1990s. These results are discussed in relation to the population biology of P. falciparum and the development of malaria vaccines based on MSP‐1.     

Increased Blood Levels of Human S100 in Melanoma Chick Embryo Xenografts’ Circulation

The chorioallantoic membrane (CAM) of the fertilized egg allows grafting of human melanomas for short‐term investigations and offers the opportunity to investigate the behavior of metastasizing cells and the release of S100β into peripheral blood. Tissue from one primary melanoma as well as cutaneous and subcutaneous metastases of 10 melanoma patients with elevated levels of S100 in the peripheral blood before surgery were transplanted onto the CAM of chick embryos at day 5/6 of development. Grafts were nourished by the host blood supply 2 days after transplantation. Histologically, 3 days after grafting, metastasizing melanoma cells could be found near the vessels of the host membrane, penetrating the endothelial layer and entering the blood system. Growth conditions remained stable for 6 days after transplantation. Blood samples were taken from a larger CAM vessel before collecting the xenografts 5 days after grafting. Measurement of human S100 in peripheral blood was performed in a blinded manner. No negative control showed elevated levels of human S100 protein. Samples deriving from melanoma xenografts contained highly elevated levels of S100 protein in 80% of cases. The data strongly support the concept of graft–host interaction concerning adherence of tumors and extravasation of human melanoma cells.     

Two-Dimensional Solid-State NMR Applied to a Chimeric Potassium Channel

Solid-state NMR (ssNMR) represents a spectroscopic method to study membrane protein structure and dynamics in lipid bilayers. We present two-dimensional correlation experiments conducted on a fully [¹³C,¹⁵N] labeled version of a chimeric potassium (KcsA-Kv1.3) channel. Data obtained by using two different ion concentrations suggest a structural conservation of the selectivity filter region. SsNMR experiments conducted at two different temperatures point to differential molecular dynamics of the channel.