No. But that only answers the question you asked.
If you have PowerPoint 2002 (I don't recall the method for prior versions),
you can re-apply font size changes to any text that uses the placeholders in
the master. This will make the font conform to whatever you set the Master
slide to be (Font/size/color/shading/shadowing).
Textboxes that are not placeholders are not affected by changes to the
master slides. For these you will need to select and edit them
individually, get an add-in that will allow standardizing all text, or sink
your hands into the murky world of VBA programming.
Alternately, you can do a slide at a time by selecting everything on the
slide (Ctl-A) and applying the changes you want to the text formatting.
Unfortunately, you can not do multiple slides in this fashion.
When you get the rest of your current project done, take a browse over to:
www.pptfaq.com There are some wonderful tips there on making your
presentations better and building them easier.
B