lecture 8

Ablation is a medical procedure that removes or destroys tissue

• Removing the synergists forces the remaining muscle (in this case, the soleus) to take on more load, simulating increased activity or overload.

2 groups of rats

• Non-irradiated group (normal satellite cell function)

• Gamma-irradiated group (satellite cells disabled)

✅ Non-Irradiated Group (Satellite Cells Intact)

• 40% increase in soleus weight = significant hypertrophy

• 12% of fibers were small (new or regenerating fibers)

• 11% of fibers expressed embryonic myosin heavy chain (MHC):

  • A marker of developing or regenerating muscle

  • Suggests active satellite cell fusion and new muscle fiber formation

🧠 Interpretation: Satellite cells are activated by overload → proliferate → fuse with existing fibers or form new ones → muscle grows

🚫 Gamma-Irradiated Group (Satellite Cells Inactivated)

• No hypertrophy observed — muscle did not grow despite overload

• No small fibers seen

• No embryonic MHC expression

🧠 Interpretation: Without functional satellite cells, the muscle cannot hypertrophy, even when overloaded.

• IGF-1, testosterone, GH are all anabolic (muscle-building) hormones

• IL-6 - inflammatory cytoline → catabolism → muscle breakdown