Søren Jessen

Hydrology and pore water chemistry in a permafrost wetland, Ilulissat, Greenland

Hydrological and geochemical processes controlling the pore water chemistry in a permafrost wetland, with loam overlain by sphagnum peat, were investigated. The vertical distributions of dissolved Cl, and of pore water δ18O, appeared unrelated to ion freeze-out and isotope ice-water fractionation processes, respectively, dismissing solute freeze-out as a main control on the water chemistry. However, concentrations of major ions, others than Cl, generally increased with depth into the active layer. A conceptual model for water and solute movement in the active layer was derived. The model indicates upward diffusive transport of elements, released in the loam layer by mineral weathering, to the peat layer, in which lateral advective transport dominates. Active layer pore water and water of melted core sections of permafrost were of Ca-Mg-HCO3 type (1:1:4 stoichiometry) and were subsaturated for calcite and dolomite. The results are consistent with an annual cycling of inorganic carbon species, Ca and Mg, via cryogenic carbonate precipitation during fall freeze-up and their redissolution following spring thaw. Similarly, elevated Fe2+ concentrations appear to be related to cryogenic siderite formation. Pore water in the active layer showed high partial pressures of CO2, indicating the feasibility of bubble ebullition as a greenhouse gas emission pathway from permafrost wetlands. Elevated concentrations of geogenic trace elements (Ni, Al, and As) were observed, and the controlling geochemical processes are discussed. The conceptual model for water and solute movement was applied to quantify the contribution of released trace elements to a downstream lake in the permafrost catchment.

Mechanisms underlying enhancements in muscle force and power output during maximal cycle ergometer exercise induced by chronic β2-adrenergic stimulation in men

The study was a randomized placebo-controlled trial investigating mechanisms by which chronic β2-adrenergic stimulation enhances muscle force and power output during maximal cycle ergometer exercise in young men. Eighteen trained men were assigned to an experimental group [oral terbutaline 5 mg/30 kg body weight (bw) twice daily (TER); n = 9] or a control group [placebo (PLA); n = 9] for a 4-wk intervention. No changes were observed with the intervention in PLA. Isometric muscle force of the quadriceps increased (P ≤ 0.01) by 97 ± 29 N (means ± SE) with the intervention in TER compared with PLA. Peak and mean power output during 30 s of maximal cycling increased (P ≤ 0.01) by 32 ± 8 and 25 ± 9 W, respectively, with the intervention in TER compared with PLA. Maximal oxygen consumption (V̇o2max) and time to fatigue during incremental cycling did not change with the intervention. Lean body mass increased by 1.95 ± 0.8 kg (P ≤ 0.05) with the intervention in TER compared with PLA. Change in single fiber cross-sectional area of myosin heavy chain (MHC) I (1,205 ± 558 μm(2); P ≤ 0.01) and MHC II fibers (1,277 ± 595 μm(2); P ≤ 0.05) of the vastus lateralis muscle was higher for TER than PLA with the intervention, whereas no changes were observed in MHC isoform distribution. Expression of muscle proteins involved in growth, ion handling, lactate production, and clearance increased (P ≤ 0.05) with the intervention in TER compared with PLA, with no change in oxidative enzymes. Our observations suggest that muscle hypertrophy is the primary mechanism underlying enhancements in muscle force and peak power during maximal cycling induced by chronic β2-adrenergic stimulation in humans.

Decadal variations in groundwater quality: A legacy from nitrate leaching and denitrification by pyrite in a sandy aquifer

Twenty-five years of groundwater quality monitoring in a sandy aquifer beneath agricultural fields showed large temporal and spatial variations in major ion groundwater chemistry, which were linked closely to the nitrate (NO3) content of agricultural recharge. Between 1988 and 2013, the NO3 content of water in the oxidized zone of the aquifer nearly halved, following implementation of action plans to reduce N leaching from agriculture. However, due to denitrification by pyrite oxidation in the aquifer, a plume of sulfate-rich water migrates through the aquifer as a legacy of the historical NO3 loading. Agriculture thus is an important determinant of major ion groundwater chemistry. Temporal and spatial variations in the groundwater quality were simulated using a 2D reactive transport model, which combined effects of the historical NO3 leaching and denitrification, with dispersive mixing into the pristine groundwater residing deeper in the aquifer. Reactant-to-product ratios across reaction fronts are altered by dispersive mixing and transience in reactant input functions. Modelling therefore allowed a direct comparison of observed and simulated ratios of concentrations of NO3 (reactant) in the oxidized zone to those of SO4 (product) in the reduced zone, which aided a stoichiometric assessment of the mechanisms of denitrification. Denitrification by pyrite in the Rabis Creek aquifer results in oxidation of S−1 and Fe2+ in pyrite to S6+ in dissolved SO4 and Fe3+ in Fe-oxide. Neither precipitation of elemental sulfur (S0), nor of jarosite, was supported by observations, and adsorption of sulfate was also dismissed.

Influence of exercise in normal and hot ambient conditions on the pharmacokinetics of inhaled terbutaline in trained men

This study investigated the pharmacokinetics of inhaled terbutaline at rest and after exercise in normal and hot ambient conditions with respect to doping analysis. Thirteen trained young men participated in the study. Urine and blood samples were collected after inhalation of 4 mg terbutaline during three trials: exercise in hot ambient conditions (30–35 °C) (EXH), exercise in normal ambient conditions (20–25 °C) (EX), and rest (20–25 °C) (R). Exercise consisted of 130 min at various intensities. Adjustment of urine concentrations of terbutaline to a specific gravity (USG) of 1.02 g/mL was compared with no adjustment. Area under the serum concentration–time curve within the first 6 h was higher for EX (27 ± 3 ng/mL/h) (P ≤ 0.01) and EXH (25 ± 4 ng/mL/h) (P ≤ 0.05) than for R (20 ± 3 ng/mL/h). When unadjusted for USG, urine concentrations of terbutaline after 4 h were different in the order EXH > EX > R (P ≤ 0.01). When unadjusted for USG, urine concentrations of terbutaline were 299 ± 151 ng/mL higher (P ≤ 0.001) after 4 h compared with adjusted concentrations in EXH. Excretion rate of terbutaline was higher (P ≤ 0.001) for EX than for EXH and R within the first 0–1½ h. In conclusion, EXHs results in higher urine concentrations of terbutaline. This should be considered when evaluating doping cases of terbutaline.

Spatiotemporal variation of stable isotopic composition in precipitation: post-condensational effects in a humid area

In the present study, a two year dataset on δ18O and δ2H in precipitation is used to investigate hydrometeorologic controls on the isotopic compositions in a temperate maritime climate. Data was collected in Denmark along a transect of six sampling stations across a landscape with a small topographic gradient and predominant westerly winds. Data showed the local meteoric water line for this region is expressed by the equation δ2H = 7.4δ18O + 5.36‰. A significant trend correlating enriched isotopic values to humidities around 70% during dry season and more depleted isotopic ratios to humidities around 90% during wet season was derived from the dataset. Temperature was found to only influence the isotopic composition in a secondary way, while no significant relationship is obtained for precipitation amount and evapotranspiration. It is suggested that sub-cloud post-condensation exchange strongly influence the isotopic composition at the study site. A simple model of evaporation on falling rain was applied with the aim to reproduce observational data and show the potential influence of changing humidity conditions on precipitation compositions. The rather simple model approach did not fully explain the observational data, but it highlights the drastic isotopic changes from a falling raindrop, that potentially can occur due to its release into a dryer atmosphere. This study shows that regional conditions and especially humidity can alter the isotopic composition in precipitation substantially even in regions without major topographic and hydrometeorologic gradients.

Groundwater flow and heterogeneous discharge into a seepage lake: Combined use of physical methods and hydrochemical tracers

Groundwater discharge into a seepage lake was investigated by combining flux measurements, hydrochemical tracers, geological information and a telescopic modelling approach using first two-dimensional (2D) regional then 2D local flow and flow path models. Discharge measurements and hydrochemical tracers supplement each other. Discharge measurements yield flux estimates, but rarely provide information about the origin and flow path of the water. Hydrochemical tracers may reveal the origin and flow path of the water, but rarely provide any information about the flux. While aquifer interacting with the lake remained under seemingly steady state conditions across seasons, a high spatial and temporal heterogeneity in the discharge to the lake was observed. The results showed that part of the groundwater flowing from the west passes beneath the lake and discharges at the eastern shore, where groundwater springs and high discharge zones (HDZs) are observed at the lake bottom and at seepage faces adjacent to the lake. In the 2D cross-section, surface runoff from the seepage faces delivers 64% of the total groundwater inputs to the lake, and a 2 m wide offshore HDZ delivers 13%. Presence of HDZs may control nutrient fluxes to the lake. This article is protected by copyright. All rights reserved.

Hypertrophic effect of inhaled beta2-agonist with and without concurrent exercise training: A randomized controlled trial

Due to a high prevalence of asthma and exercise‐induced bronchoconstriction in elite athletes, there is a high use of beta2‐adrenoceptor agonists (beta2‐agonists) in the athletic population. While anabolic in rodents, no study has been able to detect hypertrophy in humans after chronic beta2‐agonist inhalation. We investigated whether inhaled beta2‐agonist, terbutaline, alters body composition and metabolic rate with and without concurrent exercise training in healthy young men. Sixty‐seven participants completed a 4‐week intervention of daily terbutaline (8 × 0.5 mg) or placebo treatment without concurrent training (habitual; n = 23), with resistance (n = 23) or endurance (n = 21) training 3 times weekly. Before and after the interventions, participants body composition was determined by dual‐energy X‐ray absorptiometry and resting metabolic rate and substrate oxidation by indirect calorimetry. Terbutaline increased lean body mass by 1.03 kg (95% CI 0.29‐1.76; P < .05) and 1.04 kg (95% CI 0.16‐1.93; P < .05) compared to placebo in the habitual and resistance training group, respectively, but had no effect compared to placebo in the endurance training group [−0.56 kg (95% CI −1.74‐0.62; P > .05)]. Fat mass, bone mineral content, and resting metabolic rate did not change differently between treatments with the intervention. Daily inhalation of terbutaline in near‐therapeutic doses induces skeletal muscle growth. This observation should be a concern for antidoping authorities.

Beta2‐adrenoceptor agonist salbutamol increases protein turnover rates and alters signalling in skeletal muscle after resistance exercise in young men

Animal models have shown that beta2‐adrenoceptor stimulation increases protein synthesis and attenuates breakdown processes in skeletal muscle. Thus, the beta2‐adrenoceptor is a potential target in the treatment of disuse‐, disease‐ and age‐related muscle atrophy. In the present study, we show that a few days of oral treatment with the commonly prescribed beta2‐adrenoceptor agonist, salbutamol, increased skeletal muscle protein synthesis and breakdown during the first 5 h after resistance exercise in young men. Salbutamol also counteracted a negative net protein balance in skeletal muscle after resistance exercise. Changes in protein turnover rates induced by salbutamol were associated with protein kinase A‐signalling, activation of Akt2 and modulation of mRNA levels of growth‐regulating proteins in skeletal muscle. These findings indicate that protein turnover rates can be augmented by beta2‐adrenoceptor agonist treatment during recovery from resistance exercise in humans.