Exercise 9.2 - Actin & Myosin-Microscopic Observation of Muscle

LEVEL I

Figure 9.2 TEM of striated muscle

Materials

• Glycerinated rabbit muscle fibers
  
• 5 mM ATP in 0.01 M Tris-HCl buffer, pH 7.6 plus 0.05 M KCl
  
• 0.001 M CaCl
  
• Prepared slides of striated muscles (longitudinal sections)
  
• Phase contrast microscope, slides, coverslips

Procedure

1. Obtain a prepared slide of striated muscle cells. Draw the structure of an individual cell, paying particular attention to the striations. Measure the distance between successive bands of the muscle and indicate these on the drawing.

2. Compare the image seen in the light microscopic to that in Figure 9.2.

3. Tease a small fiber from the glycerinated rabbit muscle and place in on a microscope slide. Place a coverslip gently over the muscle fiber and examine with a phase contrast microscope.

4. Measure the distance between the bands and compare to the distance found in the prepared slide.

5. Gently lift off the coverslip (or use a second fiber) and add a drop of ATP and a drop of CaCl. Return the coverslip and immediately monitor the cells through the microscope. Once again measure the distance between the bands.

Optional

To observe the contraction of the muscle, carefully add the ATP and Ca to the edge of the coverslip and allow it to diffuse under the coverslip. You may also time the contraction process with a stopwatch. Finally, variations in the ion concentration as well as alternative ions can be added to other muscle fibers to test the effects of ions on muscle contraction.

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