How to extract DNA for PFGE - (Nov/10/2008 )

I already used lysozyme, proteinase k and lyticase with various conditions to break my cell for PFGE but it seems not working as it is a cyst stage of a protozoal organism. Anybody can advise on the cell lysis part? maybe any mild mechanical lysis for PFGE? Freeze thaw will be helpful without shearing the DNA? Thanks. My attached PFGE photo shows the S. cerevisiae- the commercial marker and lysed in house- got the bands but the sample have no bands (the middle lanes).
Thank you

check the protocol at http://memorias.ioc.fiocruz.br/926/3428mm.html

Thanks Microlight