If you saved the file from the "Follow TCP Stream" dialog, you saved only the stream data (read this page:
http://www.wireshark.org/docs/wsug_html_chunked/ChAdvFollowTCPSection.html)
If you want to save only the packets of a particular stream, do a "Follow TCP stream", then close the "Follow TCP Stream" dialog... you will find that a display filter has been applied to show you only frames matching that TCP stream. Then select File > Save As and select "Displayed" and "All Packets" in the "Packet Range" options. That will result in a tcpdump capture file containing only the stream of your interest which you can subsequently open in Wireshark.
HTH
Abhik
