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Quantitative freeze-fracture electron microscopic study of muscle plasma membrane of experimental anoxic myopathy
Abstract:
The numerical change of intramembranous particles (IMP) and square arrays (SA) was investigated in the muscle plasma membrane after anoxia. The proximal portion of the hind limb of Wistar rats weighing 250-350 g was strongly tied with steel wire. The contralateral hind limb was served as control. After 3 and 6 h, the extensor digitorum longus (EDL) muscles of both control and anoxic groups were studied by freeze-fracture electron microscopy. The findings of anoxic EDL plasma membrane included the presence of band-like or patchy form particle free areas with the tendency to increase from 3 to 6 h and the preservation of SA even after 6 h of anoxia. However, the IMP and caveolae densities between control and anoxic groups were not statistically different. The group median densities of SA/micron2 of control P face were 4.9 with midrange of 2.2-9.7 and 7.1 with mid-range of 2.7-10.9 after 3 and 6 h; whereas those of anoxic P face were 6.0 with mid-range of 1.8-8.2 (P greater than 0.1) and 6.9 with mid-range of 3.3-13.5 (P greater than 0.1), respectively. These changes are quite different from those of muscle plasma membrane in Duchenne muscular dystrophy.
Insights
Anoxia in rat muscle plasma membranes caused particle-free areas but preserved square arrays (SA). Intramembranous particle (IMP) and caveolae densities remained unchanged, differing from Duchenne muscular dystrophy.
Area of Science:
- Cell Biology
- Muscle Physiology
- Biophysics
Background:
- Muscle plasma membrane integrity is crucial for function.
- Anoxia, or oxygen deprivation, can significantly impact cellular structures.
- Intramembranous particles (IMP) and square arrays (SA) are key membrane components.
Purpose of the Study:
- To investigate the effects of anoxia on IMP and SA in rat skeletal muscle plasma membranes.
- To quantify changes in particle-free areas and SA density under anoxic conditions.
- To compare these anoxic effects with known changes in Duchenne muscular dystrophy.
Main Methods:
- Induction of anoxia in rat hind limb extensor digitorum longus (EDL) muscles by arterial tie.
- Comparison with contralateral control limbs.
- Analysis of muscle plasma membrane ultrastructure using freeze-fracture electron microscopy after 3 and 6 hours of anoxia.
Main Results:
- Anoxic EDL plasma membranes showed increasing band-like or patchy particle-free areas from 3 to 6 hours.
- Square arrays (SA) were preserved even after 6 hours of anoxia.
- No statistically significant differences were observed in IMP and caveolae densities between control and anoxic groups.
Conclusions:
- Anoxia induces specific structural alterations in the muscle plasma membrane, including particle-free zones.
- The preservation of SA suggests a degree of resilience in these specific membrane structures.
- Observed changes differ markedly from those seen in Duchenne muscular dystrophy, highlighting distinct pathological mechanisms.