Albert Zijlstra, Department of Physics, UMIST, P.O. Box 88, Manchester, M60 1QD, UK
Planetary nebulae originate from a phase of enhanced mass loss on the AGB, when the envelope abundances are still close to the stellar progenitor abundances. However, a few PNe are known to show regions with very low hydrogen abundances, and some PNe have [WC] stars where a hydrogen-poor wind impacts an otherwise normal PN. I will discuss the characteristics of these nebulae and their relation to Sakurai's Object.