Like I wrote in the beginning, there is bound to be some overlap between the 2 words,
gasp and
pant. I think there are
some cases DE>EN where japsen=gasp do not work well.
I'd translate the sentence from the first Duden example(thread starter) as:
I climbed up the stairs so quickly that I was panting when I reached the top.
For me it is preferable to "gasp" in this particular example. "Gasp" could sound like the person was near death, or was about to fall over unconscious.
Isn't it fairly common in German
der Hund japste, etc? Dogs don't usually gasp, but they pant all the time.
aus Dackel, Spitz und Handfeger. Die zwei waren zum Schießen, der Hund raste
japsend die Böschung rauf, warf sich auf den Rücken, schoß wieder runter wie ein zotteliger...
Auf einmal blieb der Hund stehen, immer noch
japsend, Hinterbeine breit und...
http://books.google.de/books?id=-J9bAAAAIAAJ...Here, too, pant or panting sound more idiomatic to my ears. Gasping doesn't sound right, or if it was used, it would sound like something was wrong with the dog and I don't think that's the case here. Panting can also be very heavy. It depends on the context.
Another example, this time EN>DE:
Gasp, especially alone, can have a negative emotional connotation that is not present in japsen, as I understand it.
"You mean, he's dead?" she gasped.
Would
japsen work here to express the shock or horror of the speaker? Then again, I don't know if
schnaufen or
keuchen, LEO's current suggestions for "gasp", are any better in this context.
That's all from me. Others feel free to comment :-)