Bands in a miRNA gel - (Feb/21/2010 )

Hi,
I have got a miRNA candidate that I have validated by northern (please find attached the northern picture here). But I get 2 close bands at the top(sharp and above U6 band) and Mostly 1 prominent but a thicker band above 25nt. I have a few questions here -
1. Are the top two band pre-miRNA bands. If so why two bands.
2.What is the size of U6 RNA(plants).
3.What marker apart from NEB miRNA marker I can use for size determination of all these bands in a 15% denaturing gel.
Thanks,
lihkin
(PS: I am just a new member and did not know how to post so wrote in here,when I saw something relevant to my question).

Hi friends,
after figuring out how to upload the image and receive replies I am again trying it . Please help me with suggestions....the last three lanes are the miRNA that I have found to be up-regulated while others are different treatments that do no up-regulate the same.
Thanks in advance to all the suggestions.
lihkin