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Biomedical subjects

M Mogensen

Publications and source records attributed to M Mogensen.

7 recordsLinked to original sources
PubMed2006

The potential for mitochondrial fat oxidation in human skeletal muscle influences whole body fat oxidation during low-intensity exercise.

The purpose of this study was to investigate fatty acid (FA) oxidation in isolated mitochondrial vesicles (mit) and its relation to training status, fiber type composition, and whole body FA oxidation. Trained (Vo(2 peak) 60.7 +/- 1.6, n = 8) and untrained subjects (39.5 +/- 2.0 ml.min(-1).kg(-1), n = 5) cycled at 40, 80, and 120 W, and whole body relative FA oxidation was assessed from respiratory exchange ratio (RER). Mit were isolated from muscle biopsies, and maximal ADP stimulated respiration was measured with carbohydrate-derived substrate [pyruvate + malate (Pyr)] and FA-derived substrate [palmitoyl-l-carnitine + malate (PC)]. Fiber type composition was determined from analysis of myosin heavy-chain (MHC) composition. The rate of mit oxidation was lower with PC than with Pyr, and the ratio between PC and Pyr oxidation (MFO) varied greatly between subjects (49-93%). MFO was significantly correlated to muscle fiber type distribution, i.e., %MHC I (r = 0.62, P = 0.03), but was not different between trained (62 +/- 5%) and untrained subjects (72 +/- 2%). MFO was correlated to RER during submaximal exercise at 80 (r = -0.62, P = 0.02) and 120 W (r = -0.71, P = 0.007) and interpolated 35% Vo(2 peak) (r = -0.74, P = 0.004). ADP sensitivity of mit respiration was significantly higher with PC than with Pyr. It is concluded that MFO is influenced by fiber type composition but not by training status. The inverse correlation between RER and MFO implies that intrinsic mit characteristics are of importance for whole body FA oxidation during low-intensity exercise. The higher ADP sensitivity with PC than that with Pyr may influence fuel utilization at low rate of respiration.

Adult↗
PubMed2006

Cycling efficiency in humans is related to low UCP3 content and to type I fibres but not to mitochondrial efficiency.

The purpose of this study was to investigate the hypothesis that cycling efficiency in vivo is related to mitochondrial efficiency measured in vitro and to investigate the effect of training status on these parameters. Nine endurance trained and nine untrained male subjects (V(O2peak) = 60.4 +/- 1.4 and 37.0 +/- 2.0 ml kg(-1) min(-1), respectively) completed an incremental submaximal efficiency test for determination of cycling efficiency (gross efficiency, work efficiency (WE) and delta efficiency). Muscle biopsies were taken from m. vastus lateralis and analysed for mitochondrial respiration, mitochondrial efficiency (MEff; i.e. P/O ratio), UCP3 protein content and fibre type composition (% MHC I). MEff was determined in isolated mitochondria during maximal (state 3) and submaximal (constant rate of ADP infusion) rates of respiration with pyruvate. The rates of mitochondrial respiration and oxidative phosphorylation per muscle mass were about 40% higher in trained subjects but were not different when expressed per unit citrate synthase (CS) activity (a marker of mitochondrial density). Training status had no influence on WE (trained 28.0 +/- 0.5, untrained 27.7 +/- 0.8%, N.S.). Muscle UCP3 was 52% higher in untrained subjects, when expressed per muscle mass (P < 0.05 versus trained). WE was inversely correlated to UCP3 (r = -0.57, P < 0.05) and positively correlated to percentage MHC I (r = 0.58, P < 0.05). MEff was lower (P < 0.05) at submaximal respiration rates (2.39 +/- 0.01 at 50% V(O2max)) than at state 3 (2.48 +/- 0.01) but was neither influenced by training status nor correlated to cycling efficiency. In conclusion cycling efficiency was not influenced by training status and not correlated to MEff, but was related to type I fibres and inversely related to UCP3. The inverse correlation between WE and UCP3 indicates that extrinsic factors may influence UCP3 activity and thus MEff in vivo.

Adult↗
PubMed2005

Mitochondrial efficiency in rat skeletal muscle: influence of respiration rate, substrate and muscle type.

AIM: To investigate the hypothesis that mitochondrial efficiency (i.e. P/O ratio) is higher in type I than in type II fibres during submaximal rates of respiration. METHODS: Mitochondria were isolated from rat soleus and extensor digitorum longus (EDL) muscles, representing type I and type II fibres, respectively. Mitochondrial efficiency (P/O ratio) was determined with pyruvate (Pyr) or palmitoyl-l-carnitine (PC) during submaximal (constant rate of adenosine diphosphate infusion) and maximal (V(max), state 3) rates of respiration and fitted to monoexponential functions. RESULTS: There was no difference in V(max) between PC and Pyr in soleus but in EDL V(max) with PC was only 58% of that with Pyr. The activity of 3-hydroxyacyl-CoA dehydrogenase was threefold higher in soleus than in EDL. P/O ratio at V(max) was 8-9% lower with PC [2.33 +/- 0.02 (soleus) and 2.30 +/- 0.02 (EDL)] than with Pyr [2.52 +/- 0.03 (soleus) and 2.54 +/- 0.03 (EDL)] but not different between the two muscles (P > 0.05). P/O ratio was low at low rates of respiration and increased exponentially when the rate of respiration increased. The asymptotes of the curves were similar to P/O ratio at V(max). P/O ratio at submaximal respirations was not different between soleus and EDL neither with Pyr nor with PC. CONCLUSION: Mitochondrial efficiency, as determined in vitro, was not significantly different in the two fibre types neither at V(max) nor at submaximal rates of respiration. The low V(max) for PC oxidation in EDL may relate to low activity of beta-oxidation.

Adenosine Diphosphate↗
PubMed2004

Advanced anodes for high-temperature fuel cells.

Fuel cells will undoubtedly find widespread use in this new millennium in the conversion of chemical to electrical energy, as they offer very high efficiencies and have unique scalability in electricity-generation applications. The solid-oxide fuel cell (SOFC) is one of the most exciting of these energy technologies; it is an all-ceramic device that operates at temperatures in the range 500-1,000 degrees C. The SOFC offers certain advantages over lower temperature fuel cells, notably its ability to use carbon monoxide as a fuel rather than being poisoned by it, and the availability of high-grade exhaust heat for combined heat and power, or combined cycle gas-turbine applications. Although cost is clearly the most important barrier to widespread SOFC implementation, perhaps the most important technical barriers currently being addressed relate to the electrodes, particularly the fuel electrode or anode. In terms of mitigating global warming, the ability of the SOFC to use commonly available fuels at high efficiency, promises an effective and early reduction in carbon dioxide emissions, and hence is one of the lead new technologies for improving the environment. Here, we discuss recent developments of SOFC fuel electrodes that will enable the better use of readily available fuels.

Ceramics↗
PubMed1999

[Lymphedema in patients treated for breast cancer. A cross-sectional study in the county of Ribe. The need of manual lymph drainage; risk factors].

Over a period of three months circumferences of the upper and lower arm were measured in 334 patients previously treated for breast cancer. Lymphoedema was found in 25 (7.5%) of these patients. The total number of patients with breast cancer who had lymphoedema in one year in Ribe Amt was calculated to 40. As more than one half of the patients only had modest or no subjective symptoms, it is expected that about 20 patients pr. year need manual lymph drainage, and about 20 patients need prophylactic physiotherapy. It was found that the risk for increased circumference of the upper arm was correlated to axillary radiotherapy and the total number of lymph nodes removed from the axilla. The risk of increased circumference of the lower arm was correlated to chemotherapy.

Adult↗
PubMedDate not supplied

Experimental microgyri disrupt the barrel field pattern in rat somatosensory cortex.

Transcranial freeze lesions in neonatal rat pups produce microgyri and adjacent epileptogenic regions of neocortex that can be used to model human polymicrogyria. The hypothesis that the presence of microgyri is associated with abnormal cortical organization occurring within as well as adjacent to the microgyri was tested by creating microgyri within the face representation of somatosensory cortex. Microgyri were associated with a widespread disruption of the stereotypic whisker barrel field pattern delineated with cytochrome oxidase (CO) staining. CO-stained patches resembling barrel hollows were absent within the microgyrus, and were abnormally shaped and distributed outside of the microgyrus. Adjacent Nissl- or acetylcholinesterase-stained sections demonstrated that both cell clusters and thalamocortical afferents contributed to the abnormally organized paramicrogyral zone identified in CO-stained sections. Field potential recordings showed that this region of heavy CO staining corresponded to the epileptogenic zone adjacent to the microgyrus. Results support our hypothesis that the epileptogenic paramicrogyral zone develops an abnormal organization of cell clusters and thalamocortical projections that could contribute to epileptogenesis in the paramicrogyral zone.

Age Factors↗