Fuel metabolism during exercise in euglycaemia and hyperglycaemia in patients with type 1 diabetes mellitus—a prospective single-blinded randomised crossover trial

Aims/hypothesis: We assessed systemic and local muscle fuel metabolism during aerobic exercise in patients with type 1 diabetes at euglycaemia and hyperglycaemia with identical insulin levels. Methods: This was a single-blinded randomised crossover study at a university diabetes unit in Switzerland. We studied seven physically active men with type 1 diabetes (mean ± SEM age 33.5 ± 2.4years, diabetes duration 20.1 ± 3.6years, HbA1c 6.7 ± 0.2% and peak oxygen uptake [ $$\mathop {\text{V}}\limits^{\text{.}} {\text{O}}_{2{\text{peak}}}$$ ] 50.3 ± 4.5ml min−1 kg−1). Men were studied twice while cycling for 120min at 55 to 60% of $$\mathop {\text{V}}\limits^{\text{.}} {\text{O}}_{{\text{2peak}}}$$ , with a blood glucose level randomly set either at 5 or 11mmol/l and identical insulinaemia. The participants were blinded to the glycaemic level; allocation concealment was by opaque, sealed envelopes. Magnetic resonance spectroscopy was used to quantify intramyocellular glycogen and lipids before and after exercise. Indirect calorimetry and measurement of stable isotopes and counter-regulatory hormones complemented the assessment of local and systemic fuel metabolism. Results: The contribution of lipid oxidation to overall energy metabolism was higher in euglycaemia than in hyperglycaemia (49.4 ± 4.8 vs 30.6 ± 4.2%; p < 0.05). Carbohydrate oxidation accounted for 48.2 ± 4.7 and 66.6 ± 4.2% of total energy expenditure in euglycaemia and hyperglycaemia, respectively (p < 0.05). The level of intramyocellular glycogen before exercise was higher in hyperglycaemia than in euglycaemia (3.4 ± 0.3 vs 2.7 ± 0.2 arbitrary units [AU]; p < 0.05). Absolute glycogen consumption tended to be higher in hyperglycaemia than in euglycaemia (1.3 ± 0.3 vs 0.9 ± 0.1 AU). Cortisol and growth hormone increased more strongly in euglycaemia than in hyperglycaemia (levels at the end of exercise 634 ± 52 vs 501 ± 32nmol/l and 15.5 ± 4.5 vs 7.4 ± 2.0ng/ml, respectively; p < 0.05). Conclusions/interpretation: Substrate oxidation in type 1 diabetic patients performing aerobic exercise in euglycaemia is similar to that in healthy individuals revealing a shift towards lipid oxidation during exercise. In hyperglycaemia fuel metabolism in these patients is dominated by carbohydrate oxidation. Intramyocellular glycogen was not spared in hyperglycaemia. Trial registration: ClinicalTrials.Gov NCT00325559 Funding: This study was supported by unrestricted grants from the Oetliker-Stiftung für Physiologie, from the Swiss Diabetes Foundation, from NovoNordisk, Switzerland, and from the Swiss National Science Foundatio

The Ionic Charge of Solar Energetic Particles with Energies of 0.3-70 MeV per Nucleon

With the three particle sensors Low Energy Ion Composition Analyzer (LICA), Heavy Ion Large Area Proportional Counter Telescope (HILT), and Mass Spectrometer Telescope (MAST) on board the polar orbiting Solar, Anomalous, and Magnetospheric Particle Explorer (SAMPEX) satellite, the ionic charge of solar energetic particles (SEP) was measured over a wide energy range from 0.3 to 70 MeV per nucleon. For each sensor, the evaluation was performed separately. The results obtained with LICA (0.3-10 MeV per nucleon) and MAST (15-70 MeV per nucleon) were published earlier by Mason et al. and Leske et al., respectively. In this work we present the results of the HILT sensor (7-50 MeV per nucleon) and discuss the combined results of the three instruments. With HILT, the mean ionic charge of SEP was measured for carbon, nitrogen, oxygen, neon, magnesium, silicon, sulfur, argon, calcium, and iron in the energy range 7È50 MeV per nucleon during two consecutive large SEP events in 1992 OctoberÈNovember. The mean ionic charge was inferred from the rigidity-dependent geomagnetic flux cutoff. The coronal temperatures deduced from the mean ionic charges are well in accordance with the value of ~2x10^6 K except for neon and magnesium, as previously reported. The data measured with the three sensors, LICA, HILT, and MAST, agree well and are in accordance with data previously measured at energies below 3 MeV per nucleon (Luhn et al.), except for iron, where we observed a significant energy dependence of the mean charge over the energy range 0.3-70 MeV per nucleon

Charge States of Solar Cosmic Rays and Constraints on Acceleration Times and Coronal Transport

We examine effects on the charge states of energetic ions associated with gradual solar flares due to shock heating and stripping at high ion velocities. Recent measurements of the mean charges of various elements after the flares of 1992 Oct 30 and 1992 Nov 2 allow one to place limits on the product of the electron density times the acceleration or coronal residence time. In particular, any residence in coronal loops must be for < 0.03 s, which rules out models of coronal transport in loops, such as the bird cage model. The results do not contradict models of shock acceleration of energetic ions from coronal plasma at various solar longitudes.Comment: 7 pages LaTeX + 2 tables in separate LaTeX file, necessary AAS macros are included, accepted by Astrophys. J. Let

Deconvolution of Interplanetary Transport of Solar Energetic Particles

We address the problem of deconvolving the effects of interplanetary transport on observed intensity and anisotropy profiles of solar energetic particles with the goal of determining the time profile and spectrum of particle injection near the Sun as well as the interplanetary scattering mean free path. Semi-automated techniques have been developed to quantitatively determine the best fit injection profile, assuming (1) a general piecewise linear profile or (2) a Reid profile of the form [C/(t-t_0)]exp[-A/(t-t_0)-(t-t_0)/B]. The two assumptions for the form of the injection profile yielded similar results when we tested the techniques using ISEE 3 proton data from the solar flare events of July 20, 1981 (gradual flare), and January 2, 1982 (impulsive flare). For the former event, the duration of injection was much shorter for protons of higher energy (75-147 MeV), which may be interpreted as indicating that the coronal mass ejection-driven shock lost the ability to accelerate protons to $\sim$100 MeV after traveling beyond a certain distance from the Sun.Comment: 14 pages + 5 figures, LaTeX style files included, to appear in J. Geophys. Re

Evaluation eines Praktikumsversuches zum Mach-Dvorak- und Pulfrich-Phänomen an einer grossen Probandenzahl

Am Physiologischen Institut der Universitaet Bern wurde ein Praktikum fuer Medizinstudenten entwickelt, welches die Verarbeitung raeumlicher Informationen untersucht. Die beiden Beziehungen ("Tiefe gegen Transmission" im Pulfrich-Phaenomen ud "Tiefe gegen Zeitdifferenz" im Mach- Dvorak- Phaenomen) wurden graphisch verglichen. Es wurde untersucht, ob die graphische Ermittlung auch gilt, wenn die Untersuchungen von unerfahrenen Probanden durchgefuehrt werden. Die Phaenomene wurden fuer je drei Phasnverschiebungen respektive Filterstaerken vor dem linken und rechten Auge mit je drei Wiederholungen untersucht. Alle Probanden hatten den Drehsinn der beiden Phaenomene richtig erkannt und die Einzelmessungen lagen im Bereich von ±3% bis ±20% ihres Mittelwertes. Die Abweichungen der Nullpunktbestimmungen betrugen fuer das Pulfrich- Phaenomen - 0.6 mm ±3.00 mm (Mean ±SD) und fuer das Mach-Dvorak-Phaenomen + 2.3 mm ±4.45 mm. Fuer das Mach- Dvorak-Phaenomen wichen die Nullpunktbestimmungen signifikant von Null ab (p<.0005). Fuer den untersuchten Bereich von bis zu 25 msec Zeitunterschied zwischen linkem und rechtem Auge im Mach-Dvorak-Phaenomen stieg in der Probandenpopulation die beobachtete Tiefe linear mit der Zeitverzoegerung an (r = 0.9989). Die Probanden beobachteen jedoch nur 50% - 90% der erwarteten Tiefe. Die Ursache dieser Diskrepanz liegt vermutlich in der tiefen Bildpraesentationsrate von 13.3 Hz. Schon bei 20 Hz liegt die beobachtete Tiefe deutlich unter dem Erwartungswert (Morgan, 1979). The Physiological Institute of the University of Bern developed a practical student course for medical students to illustrate aspects of binocular vision and mechanisms of primary visual transduction. Both determinations (depth against transmission and depth against time) were compared graphically. This study investigated if the graphical determination is valid too when the experiments are done by inexperienced subjects. Both phenomenons were studied with three different phase differences and filter densties in front of the left and the right eye. All subjects correctly recognised the sense of rotation in both phenomena in every trial and individual measurements were in the range of ±3% to ±20% of the subjects mean. Deviations for the zero-setting were -.6 mm ±3 mm (mean ± SD) for the Pulfrich phenomenon and +2.3 mm ±4.45 mm for the Mach-Dvorak phenomenon. In the Mach- Dvorak phenomenon the deviation from zero was significant (p<0.0005). In the range investigated of up to 25 msec delay between left and rght eye in the Mach-Dvorak phenomenon the observed depth rose linearly with the induced delay (r = 0.9989). But the subjects observed only 50% - 90% of the expected depth in the Mach-Dvorak phenomenon. None of the subjects observed greater depth illusionsthan expected. The reason for this discrepancy lies presumably in the low rate of image presentation (13.3 Hz). Already at 20 Hz the observed depth values are clearly below the expected values (Morgan, 1979)