Silicon and calcium controls on iron and aluminum mobility in Arctic soils.

Arctic permafrost soils store large amounts of organic carbon and nutrients. With deepening of the perennial thawing upper active layer due to rising temperatures in the Arctic, not only the mobility of organic matter (OM), but also those of elements like silicon (Si) or calcium (Ca) may increase. It is known that major elements like Si and Ca can affect mineralization rates of OM, consequently influencing the carbon cycle. But only little is known about the interactions of Si and Ca with inorganic nutrients like iron (Fe) or potentially toxic elements like aluminum (Al) in Artic soils. In this study, we analyzed the effect of Si and Ca fertilization in laboratory incubation experiments with soil samples from several Arctic regions. Our results show a significant increase in Fe and Al mobility (Mehlich-3 extractable) after increasing Si. Using high resolution X-ray microscopy (STXM/NEXAFS), we show that Si promotes Fe(II) phases and by this increases Fe mobility. Al mobility was increased for acidic and neutral pH soils but decreased for alkaline soils after increasing Si. Furthermore, we show a decreased Al mobility after increasing Ca, independent on the original pH values and the OM content of the soils. These results demonstrate the importance of interactions between Si and Ca on one hand and Fe and Al mobility on the other hand for Arctic soils.

Arctic soil respiration and microbial community structure driven by silicon and calcium.

Global warming is most pronounced in the Arctic region. Greenhouse gas (GHG) release from Arctic soils increase due to global warming. By this, the Arctic may change from currently being a carbon sink to a future source. To improve accurate predictions of future GHG release from Arctic soils, it is important to unravel factors controlling both the microbial community structure and activity. Soil microbial activity is important for Arctic greenhouse gas production, but depends on soil conditions such as salinity being increased by calcium (Ca) and decreased by amorphous silica (Si) potentially enhancing water availability. In the Arctic, climate changes may alter salinity by changing Si and Ca concentrations upon permafrost thaw as a result of global warming with Si potentially decreasing and Ca potentially increasing salinity. Here, we show that higher Si concentration increased and higher Ca concentrations decreased the microbial CO2 production for both a salt-poor and a salt-rich soil from Greenland. In the salt-rich soil, Si amendment increased CO2 production and the abundance of gram-negative bacteria. However, the bacterial community became dominated by spore-forming gram-positive Firmicutes and Actinobacteria. The CO2 release from soils was directly affected by the abundance of bacteria and fungi, and their community structure. Our results highlight the importance of the soil Si and Ca concentration on organic carbon turnover by strongly changing microbial abundance and community structure, with consequences for CO2 release in the Arctic. Consequently, Ca and Si and their relation to Arctic soil microbial community structure has to be considered when estimating pan-Arctic carbon budgets.

Fragmented Elastic Fibers in Focal Dermal Hypoplasia (Goltz-Gorlin Syndrome) Without Focal Dermal Hypoplasia: Report of a Male Case and Review of the Literature.

Goltz-Gorlin syndrome (GGS) (focal dermal hypoplasia) is a very rare developmental disorder affecting ectodermal and mesodermal structures. The syndrome is inherited in an X-linked manner, with the majority of affected individuals being female. We report the case of a 51-year-old man presenting with congenital skin lesions, syndactyly, facial and thoracic asymmetry, inguinal and laryngeal papillomas, cryptorchidism, polythelia, and dental anomalies. Molecular genetic analysis confirmed the clinically suspected diagnosis of GGS by detecting a known pathogenic mutation in the PORCN gene, c.502G>A [p.(Gly168Arg)] in the mosaic state. Histopathological examinations of skin biopsies of affected individuals typically show focal dermal hypoplasia and fat herniation; despite numerous skin biopsies, these characteristics were not found in the patient involved. Instead, we observed a notable reduction and fragmentation of the elastic fibers in the upper dermis. A systematic literature review regarding the histopathological presence or absence of dermal hypoplasia and/or information on elastic fibers revealed 240 histopathological descriptions of 173 individuals. Absence of dermal hypoplasia was found in 21 biopsies (8.8%). Information on elastic fibers was given in 47 cases (19.6%), showing decrease/absence in 31 cases and fragmentation of elastic fibers in 11 cases. Therefore, the histopathological absence of dermal hypoplasia does not exclude the diagnosis of the GGS. Decrease and fragmentation of elastic fibers may represent new histopathological clues to the diagnosis of this rare syndrome. At the same time, GGS should be included in the histopathological differential diagnoses of elastolytic disorders.

Tumor volume as a prognostic factor in resectable malignant melanoma.

BACKGROUND: Vertical tumor thickness according to Breslow and histological ulceration are still the most powerful predictors for the clinical outcome of resectable cutaneous malignant melanoma (MM) without lymph node infiltration. It has been proposed that tumor volume in MM may also be of prognostic relevance. METHODS: We retrospectively analyzed the prognostic impact of tumor volume and other established risk factors in 122 MM patients with a median follow-up period of 39.7 months. RESULTS: We found the logarithmic tumor volume to be a better prognostic factor compared to Breslow tumor thickness in multivariate analysis. MM with a tumor volume below a threshold of 140 mm(3) had a significantly higher relapse-free survival after 5 years of 98% compared to 47% in larger MMs (p < 0.0001). CONCLUSION: In some melanomas with a low tumor thickness, a higher tumor volume appeared to be linked to a higher risk of disease recurrence. Inclusion of tumor volume into the risk assessment of resectable MM may be of benefit in the future.

Heavy metals and arsenic fixation into freshwater organic matter under Gammarus pulex L. influence.

Organic sediments are a main sink for metal pollutants in aquatic systems. However, factors that make sediments a sink of metals and metalloids are still not clear. Consequently, we investigate the role of invertebrate shredders (Gammarus pulex L.) on quality of metal and arsenic fixation into organic partitions of sediment in the course of litter decay with laboratory microcosm experiments. During the decomposition of leaf litter, G. pulex significantly facilitated the development of small particles of organic matter. The capacity of metal fixation was significantly higher in smaller particles than leaf litter and litter residuals. Thus, G. pulex enhanced metal fixation into the organic partition of sediments by virtue of increasing the amount smaller particles in the aquatic system. Furthermore, invertebrates have a significant effect on formation of dissolved organic matter and remobilization of cobalt, molybdenum and cesium, but no significant effect on remobilization of all other measured elements.