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Cellular Responses of Human Postural Muscle to Dry Immersion.
Boris S Shenkman1, Inessa B Kozlovskaya2
1Myology Laboratory, State Scientific Center of Russian Federation - Institute of Biomedical Problems, Moscow, Russia.
Frontiers in Physiology
|March 28, 2019
Summary
Support withdrawal, simulated by dry immersion, inactivates slow muscle units, causing atrophy. This impacts muscle fiber function, reducing tension and protective mechanisms, crucial for understanding gravitational effects on the human locomotor system.
Area of Science:
- Physiology
- Gravitational Biology
- Cellular Biology
Background:
- Support withdrawal is a key factor in human locomotor system regulation.
- Support afferentation mechanisms and their role in postural control have been identified.
- The "dry immersion" model simulates mechanical support withdrawal, mimicking gravitational unloading.
Purpose of the Study:
- To review the utility of the "dry" immersion model for studying cellular responses in human postural muscles.
- To evaluate the impact of gravitational unloading on muscle structure and function.
- To understand the mechanisms behind muscle atrophy and functional decline during simulated weightlessness.
Main Methods:
- Utilizing the "dry immersion" model to simulate support withdrawal and gravitational unloading.
- Analyzing cellular responses in human postural muscles, particularly the soleus muscle.
- Examining the inactivation of slow motor unit pools and subsequent muscle fiber changes.
- Assessing muscle fiber properties, including cytoskeletal integrity, calcium sensitivity, and maximal tension.
Main Results:
- Removal of support afferentation inactivates the slow motor unit pool.
- Selective inactivation, atony, and atrophy of slow myosin heavy chain isoform expressing muscle fibers occur.
- Muscle fibers exhibit reduced cytoskeletal molecules, impairing actomyosin motor mobilization.
- Lowered calcium sensitivity and maximal tension in permeabilized fibers are observed.
- Decreased efficiency of protective mechanisms (nitric oxide synthase) and AMP-activated protein kinase activity are noted.
Conclusions:
- The "dry immersion" model is valuable for studying cellular responses to gravitational unloading.
- Support withdrawal leads to significant functional and structural degradation of postural muscles.
- These findings contribute to understanding gravitational physiology and its effects on skeletal muscle, with implications for spaceflight and rehabilitation.
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