Informace o publikaci
EFFECTS OF PHYSICAL AND NUTRITIONAL COUNTERMEASURES BEFORE AND DURING DECONDITIONING ON SINGLE MUSCLE FIBER PROPERTIES
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| Rok publikování | 2025 |
| Druh | Konferenční abstrakty |
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| Popis | The main purpose of this study was to evaluate the combined effects of a physical and nutritional countermeasure before and after a long term exposure to partial gravity in view of future lunar space missions. 70 female wistar rats were divided into different groups. They were submitted either to CONT conditions or 3 weeks of preconditionning conditions (PREC group) exercices en résistance et endurance, normal gravity), followed by a 7-day period of simulated microgravity (HU7 group ; harness unloaing) followed by a 15d-period of partial simulated weightbearing (Dr Marie Mortreux, Harvard Medical School, NASA validation), comprising resistance and endurance exercises. A nutritional countermeasure (HMB, Ergothioneine, Nacre powder) was administrated to all groups all along the entire protocol. Quadriceps intermedius was taken off and single muscle fibers were isolated from all the groups (20 fibers per group i.e. a total of fibers). After contractile experiments (pCa-tension relationships) and diameter measurements, SDS-PAGE electrophoresis was realized in order to determine their myosin heavy chain isoform profile i.e. slow, fast or hybrid types. After 7 days of HU as well as after PWB15 conditions (without preconditionning), there was a significant atrophy of ~15% in fiber diameter from both slow and fast fiber types. When preconditioning conditions were applied, the atrophy observed after HU7 was less important that the one observed in cont conditions. This was not the case for the PREC PWB15 where the atrophy was maintained. The fiber type distribution after HU7 or PWB15 conditions was modified since a large pool of hybrid fibers appeared, coexpressing a large pannel of slow and fast MHC isoforms. Thus, preconditionning conditions permitted to reduce muscle atrophy related to microgravity. For lunar gravity, our results could be due to the duration of the experiment, to the double exposure to HU and PWB conditions, or simply to the fact that the gravity of 0.2g induces a smaller effect than 0G. |