According to the certification page, the 1Z0-144 is still valid, but the 1Z0-051 does not appear as a valid pre-requisite for the OCA certification, since it has been retired.
But in another thread I got confirmation that a retired certification (10g SQL Expert OCE) is still valid as a pre-requisite for current certification paths (even if it does not appear in the page), so probably the exam is till valid, I would wait for a confirmation from someone from Oracle.
The 051 exam results are still valid in the certification path. Be sure that you register for the 144 exam using the same Oracle Testing ID.
Oracle Certification Program