| 1. |
- Calbet, J, et al.
(författare)
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Maximal vascular conductances during whole body upright exercise in humans
- 2004
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Ingår i: The Journal of Physiology. - : Wiley. - 0022-3751 .- 1469-7793. ; 558:1, s. 319-331
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Tidskriftsartikel (refereegranskat)abstract
- That muscular blood flow may reach 2.5 l kg�1 min�1 in the quadriceps muscle has led to the suggestion that muscular vascular conductance must be restrained during whole body exercise to avoid hypotension. The main aim of this study was to determine the maximal arm and leg muscle vascular conductances (VC) during leg and arm exercise, to find out if the maximal muscular vasodilatory response is restrained during maximal combined arm and leg exercise. If during maximal exercise arms and legs had been vasodilated to the observed maximal levels then mean arterial pressure would have dropped at least to 75�77 mmHg in our experimental conditions. It is concluded that skeletal muscle vascular conductance is restrained during whole body exercise in the upright position to avoid hypotension. AVKORTAT ABSTRACT
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| 2. |
- Calbet, J, et al.
(författare)
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Why do the arms extract less oxygen than the legs during exercise?
- 2005
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Ingår i: American Journal of Physiology. Regulatory Integrative and Comparative Physiology. - : American Physiological Society. - 0363-6119 .- 1522-1490. ; 289, s. 1448-1458
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Tidskriftsartikel (refereegranskat)abstract
- To determine whether conditions for O2 utilization and O2 off-loading from the hemoglobin are different in exercising arms and legs, six cross-country skiers participated in this study. Femoral and subclavian vein blood flow and gases were determined during skiing on a treadmill at 76% maximal O2 uptake (O2 max) and at O2 max with different techniques: diagonal stride (combined arm and leg exercise), double poling (predominantly arm exercise), and leg skiing (predominantly leg exercise). The percentage of O2 extraction was always higher for the legs than for the arms. At maximal exercise (diagonal stride), the corresponding mean values were 93 and 85% (n = 3; P < 0.05). During exercise, mean arm O2 extraction correlated with the PO2 value that causes hemoglobin to be 50% saturated (P50: r = 0.93, P < 0.05), but for a given value of P50, O2 extraction was always higher in the legs than in the arms. Mean capillary muscle O2 conductance of the arm during double poling was 14.5 (SD 2.6) ml·min–1·mmHg–1, and mean capillary PO2 was 47.7 (SD 2.6) mmHg. Corresponding values for the legs during maximal exercise were 48.3 (SD 13.0) ml·min–1·mmHg–1 and 33.8 (SD 2.6) mmHg, respectively. Because conditions for O2 off-loading from the hemoglobin are similar in leg and arm muscles, the observed differences in maximal arm and leg O2 extraction should be attributed to other factors, such as a higher heterogeneity in blood flow distribution, shorter mean transit time, smaller diffusing area, and larger diffusing distance, in arms than in legs. diffusing capacity; fatigue; oxygen extraction; performance; training
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| 3. |
- Holmberg, Hans-Christer, et al.
(författare)
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Lung function and oxygen uptake during double poling, running and diagonal skiing in elite cross-country skiers
- 2007
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Ingår i: Scandinavian Journal of Medicine and Science in Sports. - : Wiley. - 0905-7188 .- 1600-0838. ; 17:4, s. 437-444
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Tidskriftsartikel (refereegranskat)abstract
- Arterial desaturation during exercise is common in endurance-trained athletes, a phenomenon often more pronounced when the muscle mass engaged in the exercise is large. With this background, the present study monitored seven international-level cross country skiers performing on a treadmill while running (RUN), double poling (DP; upper body exercise) and diagonal skiing (DIA; arm and leg exercise). Static and dynamic lung function tests were performed and oxygen uptake was measured during submaximal and maximal exercise. Lung function variables (including the diffusion capacity) were only 5-20% higher than reported in sedentary men. Vital capacity was considerably lower than expected from the skiers' maximal oxygen uptake (VO(2max)), but the maximal ventilation followed a linear relationship with VO(2max). None or only a mild desaturation was observed in DP, RUN and DIA. Blood lactate concentration was slightly higher in DIA than in DP but not different from RUN. In DIA, VO(2max) was 6.23 +/- 0.47 L/min (mean +/- SD), which was 3.8% and 13.9% higher than in RUN and DP, respectively, with similar peak heart rates for the three exercise modes. No relationships were present either between the degree of desaturation and pulmonary functions tests, or with peak oxygen uptakes. The low blood lactate accumulation during the exhaustive efforts contributed to the arterial oxygen saturation being mild in spite of the very high oxygen uptake observed in these skiers.
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| 4. |
- Rosdahl, Hans, et al.
(författare)
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Effect of physiological hyperinsulinemia on blood flow and interstitial glucose concentration in human skeletal muscle and adipose tissue studied by microdialysis
- 1998
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Ingår i: Diabetes. - : American Diabetes Association. - 0012-1797 .- 1939-327X. ; 47:8, s. 1296-1301
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Tidskriftsartikel (refereegranskat)abstract
- The effect of an euglycemic-hyperinsulinemic glucose clamp (94 +/- 5 microU/ml) on blood flow and glucose extraction fraction in human skeletal muscle and adipose tissue was investigated. Limb blood flow was measured by venous occlusion pletysmography and tissue blood flow by the microdialysis ethanol technique. Insulin infusion resulted in an increased blood flow in the calf and forearm (64 and 36%, respectively; P < 0.01) but not in the studied muscles of these limbs (ethanol outflow-to-inflow ratio: m. gastrocnemius 0.144 +/- 0.009 to 0.140 +/- 0.011, NS; m. brachioradialis 0.159 +/- 0.025 to 0.168 +/- 0.027, NS). This was accompanied by an increased extraction fraction of glucose, as measured by an increased arteriovenous difference over the forearm (0.16 +/- 0.04 to 0.70 +/- 0.10 mmol/l; P < 0.001) and by an increase in the estimated arterial-interstitial glucose difference in the gastrocnemius (0.82-1.42 mmol/l) and brachioradialis muscle (0.82-1.97 mmol/l). The blood flow in adipose tissue was significantly increased during insulin infusion, as evidenced by a decreased ethanol outflow-to-inflow ratio (0.369 +/- 0.048 to 0.325 +/- 0.046; P < 0.01). This was accompanied by an unchanged concentration of glucose in the dialysate (-2.6%, NS). In summary, during physiological hyperinsulinemia 1) a blood flow increase was detected in the calf and forearm, but not in the studied muscles of these limbs; 2) the blood flow increased in the subcutaneous adipose tissue; and 3) the estimated arterial-interstitial glucose difference increased in both muscles studied and was larger in the forearm muscle than the arteriovenous glucose difference over the forearm. The present study shows that microdialysis is a useful tool to obtain tissue-specific information about the effect of insulin on blood flow and glucose extraction in human skeletal muscle and adipose tissue.
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| 5. |
- Van Hall, G, et al.
(författare)
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Leg and arm lactate and substrate kinetics during exercise
- 2003
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Ingår i: American Journal of Physiology. Endocrinology and Metabolism. - : American Physiological Society. - 0193-1849 .- 1522-1555. ; 284:1, s. E193-E205
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Tidskriftsartikel (refereegranskat)abstract
- To study the role of muscle mass and muscle activity on lactate and energy kinetics during exercise, whole body and limb lactate, glucose, and fatty acid fluxes were determined in six elite cross-country skiers during roller-skiing for 40 min with the diagonal stride (Continuous Arm + Leg) followed by 10 min of double poling and diagonal stride at 72-76% maximal O(2) uptake. A high lactate appearance rate (R(a), 184 +/- 17 micromol x kg(-1) x min(-1)) but a low arterial lactate concentration ( approximately 2.5 mmol/l) were observed during Continuous Arm + Leg despite a substantial net lactate release by the arm of approximately 2.1 mmol/min, which was balanced by a similar net lactate uptake by the leg. Whole body and limb lactate oxidation during Continuous Arm + Leg was approximately 45% at rest and approximately 95% of disappearance rate and limb lactate uptake, respectively. Limb lactate kinetics changed multiple times when exercise mode was changed. Whole body glucose and glycerol turnover was unchanged during the different skiing modes; however, limb net glucose uptake changed severalfold. In conclusion, the arterial lactate concentration can be maintained at a relatively low level despite high lactate R(a) during exercise with a large muscle mass because of the large capacity of active skeletal muscle to take up lactate, which is tightly correlated with lactate delivery. The limb lactate uptake during exercise is oxidized at rates far above resting oxygen consumption, implying that lactate uptake and subsequent oxidation are also dependent on an elevated metabolic rate. The relative contribution of whole body and limb lactate oxidation is between 20 and 30% of total carbohydrate oxidation at rest and during exercise under the various conditions. Skeletal muscle can change its limb net glucose uptake severalfold within minutes, causing a redistribution of the available glucose because whole body glucose turnover was unchanged.
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| 6. |
- Ainegren, Mats, 1963-, et al.
(författare)
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Breathing resistance in automated metabolic systems is high in comparison with the Douglas Bag method and previous recommendations
- 2018
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Ingår i: Proceedings of the Institution of Mechanical Engineers, Part P. - : SAGE Publications. - 1754-3371. ; 232:2, s. 122-130
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of this study was to investigate the resistance (RES) to breathing in metabolic systems used for the distribution and measurement of pulmonary gas exchange. A mechanical lung simulator was used to standardize selected air flow rates ( , L/s). The delta pressure (∆p, Pa) between ambient air and the air inside the equipment was measured in the breathing valve’s mouthpiece adapter for four metabolic systems and four types of breathing valves. RES for the inspiratory and expiratory sides was calculated as RES = ∆p / , Pa/L/s. The results for RES showed significant (p < 0.05) between-group variance among the tested metabolic systems, as well as the breathing valves and between most of the completed . The lowest RES among the metabolic systems was found for a Douglas Bag system, with approximately half of the RES compared to the automated metabolic systems. The automated systems were found to have higher RES already at low in comparison to previous recommendations. For the hardware components, the highest RES was found for the breathing valves while the lowest RES was found for the hoses. Conclusion: The results showed that RES in metabolic systems can be minimized through conscious choices of system design and hardware components.
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| 7. |
- Ainegren, Mats, 1963-, et al.
(författare)
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Breathing resistance in metabolic systems : Its effects on pulmonary ventilation and oxygen uptake in elite athletes with high aerobic power
- 2020
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Ingår i: Proceedings of the Institution of Mechanical Engineers, Part P. - : Sage Publications. - 1754-3371. ; 234:3, s. 217-226
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to investigate the effects on pulmonary ventilation and oxygen uptake ( (V) over dot athletes with a very high maximal oxygen uptake (V) over dotO(2)max) and corresponding high ventilation capacity when using a modern metabolic system with relatively high resistance to breathing (HIGH(RES)), compared to a traditional system with low resistance to breathing (LOWRES). Four rowers and three cross-country skiers (without asthma), competing at a high international level, performed in experimental conditions with LOWRE (S)and HIGH(RES) using a rowing ergometer and roller skis on a treadmill. The results showed that (V) over dotO(2), blood lactate, heart rate and respiratory exchange ratio were not different between the LOWRES and HIGH(RES) test conditions during both submaximal and maximal exercise. Also, the athlete's time to exhaustion (treadmill) and mean power (rowing ergometer) from maximal tests were no different between the two conditions. However, ventilation and expiratory O-2 and CO2 concentrations were different for both submaximal and maximal exercise. Thus, the authors have concluded that the differences in resistance to breathing of metabolic systems influence elite endurance athletes (V) over dot(E)at low to very high workloads, thus affecting the expired gas fractions, but not the submaximal (V) over dotO(2), (V) over dotO(2)maxand performance in a laboratory setting at sea level.
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| 8. |
- Andersson, Eva, 1946-, et al.
(författare)
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Differential effects of UV irradiation on nuclear retinoid receptor levels in cultured keratinocytes and melanocytes
- 2003
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Ingår i: Experimental dermatology. - : Wiley. - 0906-6705 .- 1600-0625. ; 12:5, s. 563-71
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Tidskriftsartikel (refereegranskat)abstract
- A major risk factor for skin cancer is UV irradiation, which not only damages DNA and other photosensitive compounds like vitamin A, but may also perturb cellular signaling, e.g. via the retinoid receptor system believed to be important for cancer protection. We used cultured normal human keratinocytes and melanocytes to examine the effects of UV irradiation on the expression of the predominant retinoid receptors in the human skin (RARalpha, RARgamma and RXRalpha) and the AP-1 protein c-Jun; mRNA levels were studied by real-time PCR and protein levels by Western blot. In keratinocytes, a single dose of UVB (50 mJ/cm2) caused a rapid drop in the expression of all three receptors (mRNA levels minus 35-50% after 4 h; protein levels minus 20-45% after 8 h), which was followed over the next 40 h by a variable response, leading to full normalization for RARalpha only. In contrast, the levels of c-Jun did not change significantly after UV exposure. In melanocytes, UVB caused a similar drop of the retinoid receptor levels as in keratinocytes but this was soon followed by an increased expression leading to a complete normalization of all receptor levels within 1-3 days. The c-Jun levels in melanocytes increased 1 day after UV exposure and remained high (plus 50%) thereafter. In both cell types, a approximately 3-fold increase in apoptosis (measured by DNA fragmentation) was observed 8-48 h after UVB irradiation. In conclusion, a depletion of vitamin A and retinoid receptors by UV irradiation, together with unchanged or even increased c-Jun levels, might seriously interfere with retinoid signaling and thus promote future tumor development, especially in keratinocytes.
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| 9. |
- Andersson, Eva, et al.
(författare)
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Differential effects of UV irradiation on the nuclear retinoid receptor levels of cultured keratinocytes and melanocytes
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Skin cancer is the most common malignancy in man. A major risk factor is UV irradiation, which not only damages DNA but may also perturb cellular signaling, e.g. via the retinoid receptor system believed to be important for cancer protection. We used cultured normal human keratinocytes and melanocytes to study the effects of UV radiation on the expression of the retinoid receptors RARα, RARβ, RARγ and RXRα. By real-time PCR and Western blot technique, the mRNA and protein levels were monitored, before and up to 4 days following 50 mJ/cm2 UVB. In keratinocytes, UVB caused a rapid drop in all four mRNA levels (minus 50-70% the first 8 h) and protein levels dropped by 30-40% followed by a gradual increase, but full normalization was ouly reached for RARα within the study period. ln melanocytes, UVB caused a quick drop both in the receptor mRNA and protein levels (minus 50-60% after 4 h), followed by normalization of the protein levels for all receptors within 2-3 days. The UV-induced depletion of vitamin A and retinoid receptors might abrogate the retinoid signaling, which subsequently might promote tumor development.
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| 10. |
- Andersson, Eva, 1946-, et al.
(författare)
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Ultraviolet irradiation depletes cellular retinol and alters the metabolism of retinoic acid in cultured human keratinocytes and melanocytes
- 1999
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Ingår i: Melanoma research. - 0960-8931 .- 1473-5636. ; 9:4, s. 339-346
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Tidskriftsartikel (refereegranskat)abstract
- Vitamin A is an intrinsic modulator of proliferation and differentiation in human epidermis, and may be destroyed by ultraviolet radiation (UVR) impinging on the skin. To identify the deleterious effects of a perturbed cellular vitamin A status, we investigated the endogenous retinoid concentrations and the metabolism of [3H]retinol and all-trans [3H]retinoic acid in cultured human keratinocytes and melanocytes exposed to UVR, using high performance liquid chromatography. Before UVR the retinoid content was similar in keratinocytes and melanocytes, but the uptake of [3H]retinol was three-fold higher and the uptake of [3H]retinoic acid was 10-fold higher in the melanocytes. In both cell types, UVR (UVA 360 mJ/cm2 plus UVB 140 mJ/cm2) instantaneously reduced the concentration of retinol by about 50% and that of 3,4-didehydroretinol by about 20%. The retinoid concentrations returned to normal within 1-2 days post-irradiation, despite there being no overt increase in the uptake of [3H]retinol or the biosynthesis of 3,4-didehydroretinol. However, in both types of irradiated cells, the accumulation of the biologically most active metabolite, all-trans [3H]retinoic acid, was about 60% higher than in control cells. Furthermore, the metabolism of authentically supplied [3H]retinoic acid was reduced, especially in irradiated keratinocytes, which probably contributed to the restoration of retinoid levels after UV exposure.
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