| 1. |
- Blomstrand, Peter, et al.
(författare)
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Pulsed tissue Doppler imaging for the detection of myocardial ischaemia, a comparison with myocardial perfusion SPECT
- 2004
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Ingår i: Clinical Physiology and Functional Imaging. - : John Wiley & Sons. - 1475-0961 .- 1475-097X. ; 24:5, s. 289-295
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Tidskriftsartikel (refereegranskat)abstract
- In order to compare the diagnostic ability of pulsed tissue Doppler and myocardial perfusion Single Photon Emission Computed Tomography (SPECT) in patients with a history of unstable coronary artery disease, CAD, 26 patients, 22 men and four women, age 47-76 years, were investigated in a prospective study, 5-10 day after an episode of unstable angina. Tissue Doppler and two-dimensional echocardiography were performed during dobutamine stress testing and myocardial scintigraphy after bicycle exercise and at rest. Patients with a normal SPECT had higher peak systolic velocity during dobutamine infusion, 18.9 ± 4.1 cm s-1, than patients with ischaemia, 12.2 ± 3.8 cm s-1 (P<0.001) or scar, 8.8 ± 3.0 cm s-1 (P<0.01). In a territorial analysis the difference in peak systolic velocity between areas with a normal and abnormal SPECT was less apparent. Failure to achieve ≥13 cm s-1 in mean-peak systolic velocity was the most accurate criterion for detection of significant CAD on SPECT. We conclude that pulsed tissue Doppler can be used for objective quantification of left ventricular wall motion during dobutamine stress testing and for identification of patients with CAD on SPECT but not for identification of regional ischaemia.
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| 2. |
- Rundqvist, Håkan Claes, et al.
(författare)
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Influence of nutrient ingestion on amino acid transporters and protein synthesis in human skeletal muscle after sprint exercise
- 2017
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Ingår i: Journal of applied physiology. - : American Physiological Society. - 8750-7587 .- 1522-1601. ; 123:6, s. 1501-1515
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Tidskriftsartikel (refereegranskat)abstract
- Nutrient ingestion is known to increase the exercise-induced stimulation of muscle protein synthesis following resistance exercise. Less is known about the effect of nutrients on muscle protein synthesis following sprint exercise. At two occasions separated by one month, twelve healthy subjects performed three 30-s sprints with 20-min rest between bouts. In randomized order, they consumed a drink with essential amino acids and maltodextrin (nutrient) or flavored water (placebo). Muscle biopsies were obtained 80 and 200 min after the last sprint and blood samples were taken repeatedly during the experiment. Fractional synthetic rate (FSR) was measured by continuous infusion of L-[(2)H5]-phenylalanine up to 200 min postexercise. The mRNA and protein expression of SNAT2 were both 1.4-fold higher (P < 0.05) after nutrient intake compared to placebo at 200 min postexercise. Phosphorylated Akt, mTOR and p70S6k was 1.7- to 3.6-fold higher (P<0.01) 80 min after the last sprint with nutrient ingestion as compared to placebo. In addition, FSR was higher (P<0.05) with nutrients when plasma phenylalanine (FSRplasma) was used as a precursor, but not when intracellular phenylalanine (FSRmuscle) was used. Significant correlations were also found between FSRplasma on the one hand and plasma leucine and serum insulin on the other hand in the nutrient condition. The results show that nutrient ingestion induces the expression of the amino acid transporter SNAT2, stimulates Akt/mTOR signaling and most likely the rate of muscle protein synthesis following sprint exercise.
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| 3. |
- Andersson, Ulrika, et al.
(författare)
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Inactivation of aconitase and oxoglutarate dehydrogenase in skeletal muscle in vitro by superoxide anions and/or nitric oxide.
- 1998
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Ingår i: Biochemical and Biophysical Research Communications - BBRC. - : Elsevier BV. - 0006-291X .- 1090-2104. ; 249:2, s. 512-6
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Tidskriftsartikel (refereegranskat)abstract
- Strips of rat soleus muscle were incubated in media containing a superoxide generating system and/or the nitric oxide donor sodium nitroprusside (SNP) before the maximal catalytic activities of aconitase, citrate synthase, and oxoglutarate dehydrogenase were measured. The maximal activities of aconitase and oxoglutarate dehydrogenase were both decreased by 25-30% by superoxide anions; however, only the maximal activity of aconitase was decreased, by approximately 50%, by incubation of muscles with SNP. Furthermore, when both superoxide and NO were present in the medium, aconitase activity was decreased by 70%. The maximal activity of citrate synthase was not affected by any of the treatments. This is the first time that superoxide anions or NO has been shown to inactivate aconitase and oxoglutarate dehydrogenase in skeletal muscle. It is suggested that these effects may be responsible for some alterations in skeletal muscle metabolism, and these possibilities are discussed.
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| 4. |
- Apró, William, et al.
(författare)
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Amino Acid-induced S6K1 Activity In Human Skeletal Muscle Is Mediated By Increased mTor/Rheb Interaction : 128 June 1, 11: 15 AM - 11: 30 AM.
- 2016
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Ingår i: Medicine And Science In Sports And Exercise 2016 May; Vol. 48 (5S Suppl 1), pp. 17.. - : Ovid Technologies (Wolters Kluwer Health). ; 48:5 Suppl 1, s. 17-
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Konferensbidrag (refereegranskat)abstract
- Cell culture studies have shown that amino acids activate mTORC1 signaling by increasing the interaction between mTOR and its essential activator Rheb. However, the existence of this mechanism in human skeletal muscle remains to be determined.PURPOSE: To determine if increased mTORC1 signaling in response to amino acids in human skeletal muscle is due to an increased interaction between mTOR and Rheb.METHODS: Eight well trained men performed resistance exercise on two separate occasions. In connection with the exercise, subjects were supplemented with flavored water (Pla) and essential amino acids (EAA) in a double-blind, randomized cross-over design. Muscle biopsies were taken in the vastus lateralis muscle before, immediately after and 90 and 180 min post exercise. Activity of the mTORC1 pathway was assessed by a radiolabeled in-vitro kinase assay for its immediate downstream target S6K1. Protein-protein interactions were determined by western blot following co-immunoprecipitation of mTOR with Rheb. Co-immunoprecipitation was performed on pooled muscle samples from three of the eight subjects.RESULTS: Activity of S6K1 remained unchanged immediately after exercise in both trials. However, at 90 min post exercise, S6K1 activity increased by approximately 2- and 8-fold (p<0.05) from baseline the Pla and EAA trials, respectively. At the 180 min time point, S6K1 activity remained elevated in both trials being approx. 3-fold higher in the Pla trial and 5-fold higher (p<0.05) in the EAA trial. The fold-change in mTOR and Rheb interaction largely resembled the activity pattern of S6K1 in both trials; in the Pla trial the fold-change was 0.9, 1.3 and 1.4 while in the EAA trial the fold-change was 1.6, 2.9 and 1.9 immediately after, 90 min after and 180 min after exercise, respectively.CONCLUSIONS: The large increase in S6K1 activity following EAA intake appears to be mediated by an increased interaction between mTOR and its proximal activator Rheb. This is the first time this mechanism has been demonstrated in human skeletal muscle.
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| 5. |
- Apró, William, 1980-, et al.
(författare)
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Endurance Exercise Does Not Impair mTOR Signalling After Resistance Exercise : D-58 Thematic Poster - Skeletal Muscle Cell Signaling: JUNE 2, 2011 3:15 PM - 5:15 PM: ROOM: 304
- 2011
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Ingår i: Medicine & Science in Sports & Exercise. - 0195-9131 .- 1530-0315. ; 43:5, s. 52-
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Resistance exercise is known to stimulate muscle hypertrophy and this effect is mainly mediated by the mammalian target of rapamycin (mTOR) pathway. In contrast, endurance exercise results in a divergent phenotypic response which to a large extent is mediated by adenosine monophosphate-activated protein kinase (AMPK). Research indicates that molecular interference may exist, possibly through an inhibitory effect on mTOR signalling by AMPK, when these two modes of exercise are combined. PURPOSE: To investigate the impact of subsequent endurance exercise on resistance exercise induced mTOR signalling. METHODS: In a randomized and cross-over fashion, ten male subjects performed either heavy resistance exercise (R) or heavy resistance exercise followed by endurance exercise (RE) on two separate occasions. The R protocol consisted of thirteen sets of leg press exercise with 3 minutes of recovery allowed between each set. In the RE session, resistance exercise was followed by 15 minutes recovery after which 30 min of cycling was initiated at an intensity equal to 70 % of the subjects' maximal oxygen consumption. Muscle biopsies were collected before, 1 and 3 hours after resistance exercise in both trials. Samples were analyzed for several signalling proteins in the mTOR pathway using western blot technique. RESULTS: Phosphorylation of mTOR increased approx. twofold at 1 h post resistance exercise and remained elevated at the 3 h time point (p< 0.01) with no difference between the two trials. Phosphorylation of p70S6k, a downstream target of mTOR, was increased about 6-and18-fold at 1 h and 3 h post resistance exercise (p< 0.01). There was no difference in p70S6k phosphorylation at any time point between the two trials. Phosphorylation of the eukaryotic elongation factor eEF2 was decreased 3- to 4-fold at both time points post resistance exercise (p< 0.01) with no difference between trials. Phosphorylation of AMPK was unchanged at the 1 h time point but decreased approximately 30 % from pre-exercise values in both trials at 3 h post resistance exercise (p< 0.01). CONCLUSIONS: The signalling response following heavy resistance exercise is not blunted by subsequent endurance exercise. Supported by the Swedish National Centre for Research in Sports.
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| 6. |
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| 7. |
- Apró, William, et al.
(författare)
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Influence of supplementation with branched-chain amino acids in combination with resistance exercise on p70S6 kinase phosphorylation in resting and exercising human skeletal muscle.
- 2010
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Ingår i: Acta Physiologica. - : Wiley. - 1748-1708 .- 1748-1716. ; 200:3, s. 237-48
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Tidskriftsartikel (refereegranskat)abstract
- AIM: Skeletal muscle growth is thought to be regulated by the mammalian target of rapamycin (mTOR) pathway, which can be activated by resistance exercise and branched-chain amino acids (BCAA). The major aim of the present study was to distinguish between the influence of resistance exercise and BCAA on key enzymes considered to be involved in the regulation of protein synthesis, including p70(S6) kinase (p70(S6k)). METHODS: Nine healthy subjects (four men and five women) performed unilateral resistance exercise on two occasions separated by 1 month. Subjects were randomly supplied either a mixture of BCAA or flavoured water. Muscle biopsies were taken from both resting and exercising muscle before, after and 1 h after exercise. RESULTS: Phosphorylation of Akt was unaltered by either resistance exercise and/or BCAA supplementation whereas mTOR phosphorylation was enhanced (P<0.05) to a similar extent in both exercising and resting muscle following exercise in the absence (70-90%) and presence of BCAA supplementation (80-130%). Phosphorylation of p70(S6k) was unaffected by resistance exercise alone; however, BCAA intake increased (P<0.05) this phosphorylation in both legs following exercise. In resting muscle, a 5- and 16-fold increase in p70(S6k) was observed immediately after and 1 h after exercise, respectively, as compared to 11- and 30-fold increases in the exercising muscle. Phosphorylation of eukaryotic elongation factor 2 was attenuated 1 h after exercise (P<0.05) in both resting (10-40%) and exercising muscle (30-50%) under both conditions. CONCLUSION: The present findings indicate that resistance exercise and BCAA exert both separate and combined effects on the p70(S6k) phosphorylation in an Akt-independent manner.
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| 8. |
- Apró, William, et al.
(författare)
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Is leucine induced p70S6 kinase phosphorylation following resistance exercise dependent on elevated phenylalanine levels in human skeletal muscle?
- 2010
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Ingår i: The FASEB Journal. - 0892-6638 .- 1530-6860. ; 24, s. lb273-
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of this study was to investigate the specific role ofleucine in the stimulation of the mammalian target of rapamycinsignalling pathway. Six male subjects performed four heavyresistance exercise sessions, each separated by approximately oneweek. Subjects were randomly supplemented with one of fourdrinks: placebo (flavored water), leucine or essential amino acids(EAA) with and without leucine. Immediately following eachexercise session, four subjects were infused with a flooding dose ofL-[2H5] phenylalanine (Inf) while two subjects served as controls(Ctrl). Muscle biopsies were taken before and one hour afterexercise. In the Ctrl group, resistance exercise resulted in asubstantial increase (45-fold) in p70 kinase phosphorylationwhen all EAA were ingested, whereas ingestion of leucine alonehad no greater effect than that of placebo. In the Inf group,however, ingestion of leucine alone and EAA increased p70phosphorylation to a similar extent (35-fold). The divergentsignalling response in the two groups suggests that leucine alone isinsufficient to increase p70phosphorylation. Indeed, in the Infgroup, there was a strong correlation (r=0.91) betweenp70 phosphorylation and the product of muscle leucine andphenylalanine levels. These results suggest that the stimulatoryeffect of leucine on p70 phosphorylation is dependent onelevated muscle phenylalanine levels. Supported by the SwedishNational Centre for Research in Sports
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| 9. |
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| 10. |
- Apró, William, et al.
(författare)
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Leucine does not affect mechanistic target of rapamycin complex 1 assembly but is required for maximal ribosomal protein s6 kinase 1 activity in human skeletal muscle following resistance exercise
- 2015
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Ingår i: The FASEB Journal. - : Wiley. - 0892-6638 .- 1530-6860. ; 29:10, s. 4358-4373
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Tidskriftsartikel (refereegranskat)abstract
- We examined how the stimulatory effect of leucine on the mechanistic target of rapamycin complex 1 (mTORC1) pathway is affected by the presence of the remaining essential amino acids (EAAs). Nine male subjects performed resistance exercise on 4 occasions and were randomly supplied EAAs with leucine, EAAs without leucine (EAA-Leu), leucine alone, or flavored water (placebo; control). Muscle biopsies were taken from the vastus lateralis before and 60 and 90 min after exercise. Biopsies were analyzed for protein phosphorylation, kinase activity, protein-protein interactions, amino acid concentrations, and tracer incorporation. Leucine alone stimulated ribosomal protein s6 kinase 1 (S6K1) phosphorylation similar to 280% more than placebo and EAA-Leu after exercise. Moreover, this response was enhanced by 60-75% after intake of EAAs compared with that of leucine alone (P < 0.05). Kinase activity of S6K1 reflected that of S6K1 phosphorylation; 60 min after exercise, the activity was elevated 3.3- and 4.2-fold with intake of leucine alone and with EAAs, respectively (P < 0.05). The interaction between mammalian target of rapamycin and regulatory-associated protein of mammalian target of rapamycin was unaltered in response to both resistance exercise and amino acid provision. Leucine alone stimulates mTORC1 signaling, although this response is enhanced by other EAAs and does not appear to be caused by alterations inmTORC1 assembly.
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