Problem: you made your figures in PowerPoint but the journal wants super high resolution files for publication. When you try to blow up normal output from PowerPoint the images, especially the line art, look fuzzy.
Solution: print to a ridiculously high resolution PDF file (you need Acrobat Professional for this), open in Photoshop and specify a righ resolution, and resave as TIF.
There are other ways to do this, but this is simple if you have access to PowerPoint, Acrobat Professional, and Photoshop. Follow the screen snaps below.
Here's an example original PowerPoint; all the line drawings and text including the orange cell in the lower right were made using PowerPoint.
From the Print menu:
and print to a PDF.
In Photoshop, open the PDF using a high pixels per inch:
Finally, save as TIF with LZW compression which is lossless. Most figures have a lot of white space so saving with compression will make the file much smaller than uncompressed TIF and the end result is identical.