Søren Munch Kristiansen

Silver against Pseudomonas aeruginosa biofilms.

Silver has been recognized for its antimicrobial properties for centuries. Most studies on the antibacterial efficacy of silver, with particular emphasis on wound healing, have been performed on planktonic bacteria. Our recent studies, however, strongly suggest that colonization of wounds involves bacteria in both the planktonic and biofilm modes of growth. The action of silver on mature in vitro biofilms of Pseudomonas aeruginosa, a primary pathogen of chronic infected wounds, was investigated. The results show that silver is very effective against mature biofilms of P. aeruginosa, but that the silver concentration is important. A concentration of 5–10 μg/mL silver sulfadiazine eradicated the biofilm whereas a lower concentration (1 μg/mL) had no effect. The bactericidal concentration of silver required to eradicate the bacterial biofilm was 10–100 times higher than that used to eradicate planktonic bacteria. These observations strongly indicate that the concentration of silver in currently available wound dressings is much too low for treatment of chronic biofilm wounds. It is suggested that clinicians and manufacturers of the said wound dressings consider whether they are treating wounds primarily colonized either by biofilm‐forming or planktonic bacteria.

Ocean lead at the termination of the Younger Dryas cold spell

The Younger Dryas (YD) cold interval is one of the most abrupt climate events of Earth’s recent history. The origin of this rapid, severe cooling episode is still widely debated, but it was probably triggered by a large freshwater influx to the North Atlantic resulting in disruption of the Atlantic Meridional Overturning Circulation. The YD termination, despite having been even more abrupt than the onset has, however, received significantly less attention. Here using multi-proxy data from a high-resolution marine sediment record, we present evidence for a gradual decrease of the Labrador Current influence, northward migration of the Gulf Stream oceanic front and a rapid decline of sea-ice cover at the YD termination. Our data indicate a stepwise sequence of events with changes in ocean circulation clearly preceding those in atmospheric conditions, in contrast to the hitherto commonly assumed single-event rapid climatic shift at the YD–Holocene transition.

Association of Lithium in Drinking Water With the Incidence of Dementia

Importance Results from animal and human studies suggest that lithium in therapeutic doses may improve learning and memory and modify the risk of developing dementia. Additional preliminary studies suggest that subtherapeutic levels, including microlevels of lithium, may influence human cognition. Objective To investigate whether the incidence of dementia in the general population covaries with long-term exposure to microlevels of lithium in drinking water. Design, Setting, and Participants This Danish nationwide, population-based, nested case-control study examined longitudinal, individual geographic data on municipality of residence and data from drinking water measurements combined with time-specific data from all patients aged 50 to 90 years with a hospital contact with a diagnosis of dementia from January 1, 1970, through December 31, 2013, and 10 age- and sex-matched control individuals from the Danish population. The mean lithium exposure in drinking water since 1986 was estimated for all study individuals. Data analysis was performed from January 1, 1995, through December 31, 2013. Main Outcomes and Measures A diagnosis of dementia in a hospital inpatient or outpatient contact. Diagnoses of Alzheimer disease and vascular dementia were secondary outcome measures. In primary analyses, distribution of lithium exposure was compared between patients with dementia and controls. Results A total of 73 731 patients with dementia and 733 653 controls (median age, 80.3 years; interquartile range, 74.9-84.6 years; 44 760 female [60.7%] and 28 971 male [39.3%]) were included in the study. Lithium exposure was statistically significantly different between patients with a diagnosis of dementia (median, 11.5 µg/L; interquartile range, 6.5-14.9 µg/L) and controls (median, 12.2 µg/L; interquartile range, 7.3-16.0 µg/L; P < .001). A nonlinear association was observed. Compared with individuals exposed to 2.0 to 5.0 µg/L, the incidence rate ratio (IRR) of dementia was decreased in those exposed to more than 15.0 µg/L (IRR, 0.83; 95% CI, 0.81-0.85; P < .001) and 10.1 to 15.0 µg/L (IRR, 0.98; 95% CI, 0.96-1.01; P = .17) and increased with 5.1 to 10.0 µg/L (IRR, 1.22; 95% CI, 1.19-1.25; P < .001). Similar patterns were found with Alzheimer disease and vascular dementia as outcomes. Conclusions and Relevance Long-term increased lithium exposure in drinking water may be associated with a lower incidence of dementia in a nonlinear way; however, confounding from other factors associated with municipality of residence cannot be excluded.

Present-day soil distribution explained by prehistoric land-use: Podzol–Arenosol variation in an ancient woodland in Denmark

Abstract Archaeological evidence has rarely been used by soil scientists to explain the distribution of present-day soils, yet recent human influence is known to be important for all soils. Sites with abandoned prehistoric fields are commonly found throughout western Europe but the impact on present-day soils is not fully known. The studied site, Alstrup Krat, is an intact Bronze and Iron Age site with a well-preserved system of fields (infields) and common areas (common). It was abandoned around 2000 BP and has been beech wood since. This paper concerns the connection between the present-day soil distribution and this former land-use. The methods used in the field were soil survey, intensive ditching, and profile descriptions, and these were combined with soil physical and chemical laboratory analyses (texture, OC, N, P, Fe, Al, optical density on oxalate extracts [ODOE], and base ions). This revealed two distinct soil types whose borders coincided with the prehistoric common/infield border on the dominant parent material—sandy and gravelly tills. Hyperdystric Arenosols are found in the infields and Haplic Podzols in the common area. Entic Podzols or Spodic Arenosols are developed in the common/infield transition zone and in infields that were furthest from the dwellings during cultivation. Podzols had been expected in the infields, as Iron Age agriculture is believed to have exhausted the soil and caused podzolization. Chemical and physical differences between infields and the common area did not explain the observed soil distribution. The only difference between the two adjacent areas was prehistoric land-use until 2000 years ago. The main factor is probably agriculture during the Iron Age, which physically rejuvenated the soil in the infields. Archaeological information thus provided a powerful tool for explaining soil spatial distribution where standard soil science variables and methods would have failed.

Ultrastructural localization and chemical binding of silver ions in human organotypic skin cultures

Organotypic cultures of human breast skin incubated with silver bandage or treated with silver sulfadiazine accumulated silver in epithelial cells and in macrophages, fibroblasts and collagen fibrils and fibres of underlying connective tissue. Ultrastructurally, the accumulated silver was found in lysosome-like vesicles of the different cells and evenly spread along collagen structures. Apoptotic nuclei were present but few. Autometallographic amplification of 2D-PAGE gels revealed that glutathione S-transferase and glutathion detoxify silver ions in the epidermal cell by binding them in silver–sulphur nanocrystals. Thus, the cytotoxic effect of silver ions seems to be muted by silver ions by being: (1) taken up by undamaged cells, neutralised by glutathione (GSH) and accumulated in lysosomal vesicles, (2) bound extracellularly to SH-groups of the collagen fibres.

Phosphorus forms as affected by abandoned anthills (Formica polyctena Förster) in forest soils : sequential extraction and liquid-state 31P-NMR spectroscopy

Ants are known to concentrate phosphorus (P) inside their nests via collection of food and litter. To elucidate the possible effects on long-term availability of soil P, five anthills abandoned by Red wood ant (Formica polyctena Forster) > 5—20 years ago were characterized for soil P forms in a temperate Danish deciduous forest. Sequentially extracted P fractions and liquid-state 31P nuclear magnetic resonance (NMR) spectra were obtained on surface samples (0—10 cm) from abandoned anthills and adjacent topsoil; in addition one representative soil profile in an abandoned anthill was investigated. The results show that different inorganic and all organic P fractions were enriched by a factor of 2.0—3.3 inside anthills relative to the surrounding soil. The soil underneath the abandoned anthill had higher P contents until 50-cm depth. Phosphorus composition was less affected by former anthill construction. Only the younger anthills revealed a preferential accumulation of labile organic P forms such as Na-HCO3 extractable P or diester P. The accumulation of the stable and moderate labile P forms, however, persisted for ≥ 20 years after abandonment. We concluded that former ant activity enhanced long-term P availability of soil due to high local P inputs, whereas changes of the P form distribution lasted 5—10 years after nest abandonment. Auswirkungen von verlassenen Ameisenhugeln auf Phosphorformen in Waldboden: sequenzielle Extraktion und 31P-NMR-Spektroskopie Ameisen konnen in ihren Nestern Phosphor (P) mit gesammelter Nahrung und Streu akkumulieren. Um mogliche Auswirkungen auf die langfristige P-Versorgung des Bodens untersuchen zu konnen, wurden funf verlassene Bauten der roten Waldameise (Formica polyctena Forster) bezuglich ihrer P-Gehalte und -Verbindungen charakterisiert. Die Ameisenbauten befinden sich in einem danischen Mischwald und sind seit > 5—20 Jahren unbewohnt. Beprobt wurden die oberen 10 cm der Bauten und der umgebenden Boden, sowie jeweils ein reprasentatives Bodenprofil eines Ameisenbaus. Die Analysen umfassten die Bestimmung organischer und anorganischer P-Spezies nach sequenzieller Extraktion sowie nach 31P-Kernresonanz (NMR)-Spektroskopie. Die Ergebnisse zeigen, dass verschiedene anorganische und alle organischen P-Formen in den Ameisenbauten um den Faktor 2.0—3.3 angereichert sind. Der Boden unterhalb des Ameisennestes zeigte eine erhohte P-Akkumulation bis in 50 cm Tiefe. Die strukturelle P-Zusammensetzung wurde dagegen weniger durch den fruheren Bau der Ameisenhugel beeinflusst. Nur die jungeren Bauten zeigten eine bevorzugte Anreicherung labiler organischer P-Formen wie Na-HCO3-extrahierbarer P oder Diester-P. Die Akkumulation der stabilen und masig labilen P-Formen hingegen bleibt fur mehr als 20 Jahre nach Verlassen der Bauten erhalten. Wir folgern, dass Ameisen uber hohe lokale P-Eintrage die unmittelbare P-Versorgung am Standort langfristig verbessern. Dagegen wird die Zusammensetzung der P-Formen am Standort nur 5—10 Jahre lang, nach Verlassen der Bauten, beeinflusst.

Cu-nanoparticles ecotoxicity--explored and explained?

The nano-form of copper (Cu-NPs) is already extensively used. In this paper the toxic effect of Cu in the worm Enchytraeus crypticus (Oligochaeta: Enchytraeidae) was assessed following exposure to (1) Cu-salt: freshly spiked soil with copper-nitrate, (2) Cu-NPs: freshly spiked soil with Cu nanoparticles (80nm), and (3) Cu-field: historically Cu contaminated soil (80years ago). Our main aims were to compare the three different exposure regimes and respective toxicity, and to determine how the oxidation state of the Cu and dissolution state of the particles differed. Characterization of in situ-exposure included identification of oxidation states with synchrotron generated X-ray absorption near-edge spectroscopy (XANES) analysis, activity of free Cu(2+) in soil-solution (Ion Selective Electrode), and the relative distribution of the labile Cu-fractions (Sequential Extraction). Freshly spiked Cu-salt was the most toxic for reproductive output of the worms, followed by Cu-NPs and then Cu-field. XANES indicated only one oxidation state (II) in Cu-salt and Cu-field soil, whereas in Cu-NPs soil it was present in all oxidation states (0, I and II). The partial oxidation of the Cu-NPs (in soil) was evident and with limited dissolution.

Assessment of spatial variation in drinking water iodine and its implications for dietary intake: a new conceptual model for Denmark.

Iodine is essential for human health. Many countries have therefore introduced universal salt iodising (USI) programmes to ensure adequate intake for the populations. However, little attention has been paid to subnational differences in iodine intake from drinking water caused by naturally occurring spatial variations. To address this issue, we here present the results of a Danish nationwide study of spatial trends of iodine in drinking water and the relevance of these trends for human dietary iodine intake. The data consist of treated drinking water samples from 144 waterworks, representing approx. 45% of the groundwater abstraction for drinking water supply in Denmark. The samples were analysed for iodide, iodate, total iodine (TI) and other major and trace elements. The spatial patterns were investigated with Local Morans I. TI ranges from <0.2 to 126 μg L(-1) (mean 14.4 μg L(-1), median 11.9 μg L(-1)). Six speciation combinations were found. Half of the samples (n = 71) contain organic iodine; all species were detected in approx. 27% of all samples. The complex spatial variation is attributed both to the geology and the groundwater treatment. TI >40 μg L(-1) originates from postglacial marine and glacial meltwater sand and from Campanian-Maastrichtian chalk aquifers. The estimated drinking water contribution to human intake varies from 0% to >100% of the WHO recommended daily iodine intake for adults and from 0% to approx. 50% for adolescents. The paper presents a new conceptual model based on the observed clustering of high or low drinking-water iodine concentrations, delimiting zones with potentially deficient, excessive or optimal iodine status. Our findings suggest that the present coarse-scale nationwide programme for monitoring the populations iodine status may not offer a sufficiently accurate picture. Local variations in drinking-water iodine should be mapped and incorporated into future adjustment of the monitoring and/or the USI programmes.

Lithium in Drinking Water and Incidence of Suicide: A Nationwide Individual-Level Cohort Study with 22 Years of Follow-Up

Suicide is a major public health concern. High-dose lithium is used to stabilize mood and prevent suicide in patients with affective disorders. Lithium occurs naturally in drinking water worldwide in much lower doses, but with large geographical variation. Several studies conducted at an aggregate level have suggested an association between lithium in drinking water and a reduced risk of suicide; however, a causal relation is uncertain. Individual-level register-based data on the entire Danish adult population (3.7 million individuals) from 1991 to 2012 were linked with a moving five-year time-weighted average (TWA) lithium exposure level from drinking water hypothesizing an inverse relationship. The mean lithium level was 11.6 μg/L ranging from 0.6 to 30.7 μg/L. The suicide rate decreased from 29.7 per 100,000 person-years at risk in 1991 to 18.4 per 100,000 person-years in 2012. We found no significant indication of an association between increasing five-year TWA lithium exposure level and decreasing suicide rate. The comprehensiveness of using individual-level data and spatial analyses with 22 years of follow-up makes a pronounced contribution to previous findings. Our findings demonstrate that there does not seem to be a protective effect of exposure to lithium on the incidence of suicide with levels below 31 μg/L in drinking water.

Geochemistry of groundwater in front of a warm-based glacier in Southeast Greenland

Abstract Groundwater in front of warm‐based glaciers is likely to become a more integrated part of the future proglacial hydrological system at high latitudes due to global warming. Here, we present the first monitoring results of shallow groundwater chemistry and geochemical fingerprinting of glacier meltwater in front of a warm‐based glacier in outheast reenland (ittivakkat letscher, 65° 41′ , 37° 48′ ). The groundwater temperature, electrical conductivity and pressure head were monitored from ugust 2009 to ugust 2011, and water samples were collected in 2009 and analyzed for major ions and water isotopes (δD, δ18O). The 2-yrs of monitoring revealed that major outbursts of glacier water during the ablation season flushed the proglacial aquifer and determined the groundwater quality for the next 2–8 weeks until stable chemical conditions were reached again. Water isotope composition shows that isotopic fractionation occurs in both groundwater and glacier meltwater, but fractionation due to evaporation from near‐surface soil moisture prior to infiltration has the most significant effect. This study shows that groundwater in ow rctic reenland is likely to possess a combined geochemical and isotopic composition, which is distinguishable from other water sources in the proglacial environment. However, the shallow groundwater composition at a given time is highly dependent on major outbursts of glacier water in the previous months.