Biology help?

[Siva]

So I'm working on a lab where we stained muscle fibers. There are three types of fibers, slow oxidative, fast oxidative, and glycolytic (anaerobic). The cells have three different types of appearance, light and big, medium color and intermediate size, and dark and small. I'm wondering which type of cell is which.

My assumption is
light = slow oxidative
medium = fast oxidative
dark = glycolytic

But I could be wrong. Anywhere, here's a picture

http://www.shadow-imaging.net/Images/siva/display.php?id=713&name=Frog1small.jpg

You can clearly see the three different types of cells, I'm just not sure how to determine which is which and why.

 

[Anonemous]

ask a histology tech/pathologist?

 

[DingDingDao]

You've got it backwards.

Slow oxidative fibers are characterized by increased vascularization, a high amount of myoglobin, and a higher amount of mitochondria, all of which make it darker in appearance.
Fast glycolytic fibers are exactly the opposite: low vascularization, low myoglobin, low mitochondrial levels, high glycogen stores, hence the lighter appearance.

EDIT: Cliffs:

Slow/Ox : dark
Fast/Gly : light

EDIT 2:

Just looked at the image. That looks like it could be a PAS (periodic acid schiff) stain. In that case, the reaction product occurs in the presence of glycogen, in which case you'd be right. However, Type IIA and IIB fibers (Fast/Ox and Fast/Gly) tend to be larger in diameter, which would support my initial assessment.

 

[chr6]

nm, out of it this morning

 

[DingDingDao]

Originally posted by: chr6
wouldn't anaerobic cells be larger from hypertrophy

Why would anaerobic cells exhibit hypertrophy...?

 

[Gibsons]

one point to remember is that mitochondria are very dark. The darkness of the fibers is largely determined by how dense the mitochondria are in the fiber.

edit: darkness might also vary with staining as DingDingDao pointed out.

 

[DingDingDao]

Originally posted by: Gibsons
one point to remember is that mitochondria are very dark. The darkness of the fibers is largely determined by how dense the mitochondria are in the fiber.

Yup. Although the high amount of oxygen-bound myoglobin found in Slow/Ox fibers also contributes to the dark appearance, as well.

OP, do you know what kind of stain was used on the myofibers in that pic? It would really help to solve the problem. Also, what type of muscle is this? Leg? Trunk?