If you have any tubes that have JPEG speckling, then you can clean them up nicely before you use the tube in your project.
Before Clean-up
After Clean-up 
To clean up your tube, go to
Adjust > Add/Remove Noise > Edge Preserving Smooth. If you're using a version other than PSP8, then the path may be different.
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Usually an amount between 1-3 will work nicely (adjust the amount for the image that you are working with).
Then you may want to sharpen the image. I use Unsharp Mask to sharpen my images.
Adjust > Sharpness > Unsharp Mask:
Radius=1,
Strength=25-50 (or whatever looks best for your tube),
Clipping=0