This subproject focuses on a major problem in the health of American women specifically addressing the question of age related oocyte dysfunction and infertility. Our goal is to develop instrumentation capable of determining the viability of oocytes and preimplantation embryos. With this instrument, a new derivative of the self-referencing technology, we are using indicators of metabolic activity or cell physiology, to assay viability. Our work to date has focussed on the mouse oocyte or embryo but we will soon move to consider the hamster oocyte, which shows an age-related dysfunction similar of the human. Our initial studies in this area used the Seris calcium electrode to measure transmembrane ion flux and successfully demonstrated differences between embryos that went on to divide in culture and those that did not. Most recently, however, we have begun to apply the newly developed Serp-oxygen electrodes. The results are very encouraging. Not only can changes in oxygen consump-tion be discriminated after fertilization but also an increase is recorded as the embryo develops to a blastocyst. Most surprisingly we have been able to record oxygen consumption from the oocyte, a feat commonly held to be impossible. The use of this technology has required considerable changes in the normal operating procedure, including the regulation of temperature and careful handling. Most recently the two P.I.s on this project have acquired funding to develop a tailor made system to be housed in the Laboratory for Reproductive Medicine and operated by a full time associate. We expect to see rapid progress in this field over the next year.