S-adenosyl-l-methionine: (S) -7,8,13, 14-tetrahydroberberine--n-methyltransferase, a branch point enzyme in the biosynthesis of benzophenanthridine and protopine alkaloids.

The enzyme which transfers the CH3-group of S-adenosylmethionine to the nitrogen atom of (S)-tetrahydroberberine and (S)-stylopine is found to occur in a number of plant cell cultures originating from species containing alkaloids; it is located at an important branch point in isoquinoline alkaloid biosynthesis

Cost-Effective Strategies for Reducing Nitrogen Deposition in Europe

This paper explores the potential cost savings which would result from a combined control of emissions of nitrogen oxides and ammonia for the cost-effective achievement of nitrogen deposition targets in Europe. Using the Regional Acidification INformation and Simulation (RAINS) model a framework has been constructed for a simultaneous optimization of NOx and NH3 emission reductions using nitrogen depositions from both pollutants as side constraints. The paper first demonstrates that the same nitrogen deposition resulting from the currently committed reductions of NOx emissions (without measures for NH3 emissions) can be achieved at only 55 percent of the costs if measures for ammonia reduction would also be applied. The analysis shows that no large scale substitutions of NO, reductions by ammonia measures occur. The cost savings mainly result from replacing the most expensive (and ineffective) NOx abatement at a few places in Europe with inexpensive ammonia control measures. Consequently, the total level of NOx emissions is hardly higher than in the reference case, but substantial NH3 reductions are implemented lowering total cost. The second case explores the potential contribution ammonia control can make for attaining the same nitrogen deposition levels resulting from the maximum application of NOx abatement technologies solely. In this case reductions of ammonia emissions can lower total abatement costs by 23 percent, basically by modified manure handling, stable adaptations for poultry and the control of industrial ammonia emissions

Trading of Emission Reduction Commitments for Sulfur Dioxide in Europe

This paper analyzes the potential role of emission trading systems for non-uniformly dispersed air pollutants, for which the geographical location of emissions has a significant impact on the location and extent of environmental damage. The paper derives the necessary conditions for trading schemes to be cost-effective and introduces the concept of offset rates. Offset rates describe the amount of emissions one source has to decrease if another source increases its emissions by one unit. To explore the potential performance of alternative trading schemes a simulation framework based on' the IIASA-RAINS model has been developed. Simulation runs to achieve regionally specified maximum levels of sulfur deposition (target loads) in Europe show that trading may result in cost savings. The extent to which such cost savings are possible and whether the originally specified target deposition levels are exceeded, depends crucially on the pre-trade level of emissions, the availability of information on costs, and the behavior of the trading partners. Further analysis is necessary before drawing final conclusions

Effect of acute severe hypoxia on peripheral fatigue and endurance capacity in healthy humans

Effect of acute severe hypoxia on peripheral fatigue and endurance capacity in healthy humans. Am J Physiol Regul Integr Comp Physiol 292: R598–R606, 2007. First published September 7, 2006; doi:10.1152/ajpregu.00269.2006.—We hypothesized that severe hypoxia limits exercise performance via decreased contractility of limb locomotor muscles. Nine male subjects [mean SE maximum O2 uptake (V˙ O2 max) 56.5 2.7 ml kg 1 min 1] cycled at 90% V˙ O2 max to exhaustion in normoxia [NORM-EXH; inspired O2 fraction (FIO2) 0.21, arterial O2 saturation (SpO2) 93 1%] and hypoxia (HYPOX-EXH; FIO2 0.13, SpO2 76 1%). The subjects also exercised in normoxia for a time equal to that achieved in hypoxia (NORM-CTRL; SpO2 96 1%). Quadriceps twitch force, in response to supramaximal single (nonpotentiated and potentiated 1 Hz) and paired magnetic stimuli of the femoral nerve (10–100 Hz), was assessed pre- and at 2.5, 35, and 70 min postexercise. Hypoxia exacerbated exercise-induced peripheral fatigue, as evidenced by a greater decrease in potentiated twitch force in HYPOX-EXH vs. NORM-CTRL ( 39 4 vs. 24 3%, P 0.01). Time to exhaustion was reduced by more than two-thirds in HYPOX-EXH vs. NORM-EXH (4.2 0.5 vs. 13.4 0.8 min, P 0.01); however, peripheral fatigue was not different in HYPOX-EXH vs. NORM-EXH ( 34 4 vs. 39 4%, P 0.05). Blood lactate concentration and perceptions of limb discomfort were higher throughout HYPOX-EXH vs. NORM-CTRL but were not different at end-exercise in HYPOX-EXH vs. NORM-EXH. We conclude that severe hypoxia exacerbates peripheral fatigue of limb locomotor muscles and that this effect may contribute, in part, to the early termination of exercise

Effects of arterial oxygen content on peripheral locomotor muscle fatigue

The effect of arterial O2 content (Ca(O2)) on quadriceps fatigue was assessed in healthy, trained male athletes. On separate days, eight participants completed three constant-workload trials on a bicycle ergometer at fixed workloads (314 +/- 13 W). The first trial was performed while the subjects breathed a hypoxic gas mixture [inspired O2 fraction (Fi(O2)) = 0.15, Hb saturation = 81.6%, Ca(O2) = 18.2 ml O2/dl blood; Hypo] until exhaustion (4.5 +/- 0.4 min). The remaining two trials were randomized and time matched with Hypo. The second and third trials were performed while the subjects breathed a normoxic (Fi(O2) = 0.21, Hb saturation = 95.0%, Ca(O2) = 21.3 ml O2/dl blood; Norm) and a hyperoxic (Fi(O2) = 1.0, Hb saturation = 100%, Ca(O2) = 23.8 ml O2/dl blood; Hyper) gas mixture, respectively. Quadriceps muscle fatigue was assessed via magnetic femoral nerve stimulation (1-100 Hz) before and 2.5 min after exercise. Myoelectrical activity of the vastus lateralis was obtained from surface electrodes throughout exercise. Immediately after exercise, the mean force response across 1-100 Hz decreased from preexercise values (P < 0.01) by -26 +/- 2, -17 +/- 2, and -13 +/- 2% for Hypo, Norm, and Hyper, respectively; each of the decrements differed significantly (P < 0.05). Integrated electromyogram increased significantly throughout exercise (P < 0.01) by 23 +/- 3, 10 +/- 1, and 6 +/- 1% for Hypo, Norm, and Hyper, respectively; each of the increments differed significantly (P < 0.05). Mean power frequency fell more (P < 0.05) during Hypo (-15 +/- 2%); the difference between Norm (-7 +/- 1%) and Hyper (-6 +/- 1%) was not significant (P = 0.32). We conclude that deltaCa(O2) during strenuous systemic exercise at equal workloads and durations affects the rate of locomotor muscle fatigue development