Transillumination increases oocyte recovery from ovaries collected at slaughter. A new technique report

An inexpensive and convenient method of collecting large number of oocytes for in vitro procedures is by aspiration of follicles visible on the surfac e of isolated ovary. This method yielded only moderate numbers of oocytes p er ovary, and it was found that the yield could be improved by slicing the tissue to reach deep, cortical follicles. However, slicing was time consumi ng and increased chances for sepsis. We developed a new technique that allo ws direct viewing of cortical follicles for aspiration of oocytes by transi llumination of the ovarian medulla and cortex with a Plexiglas rod inserted through a small incision at the hilus. The technique, called "Transillumin ation-Aspiration Ovary" (TAO), increased the oocyte yield by 50% per ovary. The oocytes are probably recovered from deeper follicles which are difficu lt to identify during regular oocyte aspiration. The oocytes had a normal g rading and exhibited normal in vitro development efficiency. Using the "TAO" technique we recovered 777 oocytes from 2160 follicles in 1 06 ovaries, a recovery rate of 36% from follicles and a mean of 7.3 oocytes /ovary. When we aspirated only surface follicles, we obtained 523 oocytes i n 1384 visible follicles in 107 ovaries, for a recovery rates of 37% but a mean yield of 4.9 oocytes per ovary. Mean number of follicles were 20.5% wi th TAO and 12.8% without, thus recovery rates of oocytes per follicle were similar with both methods, but yield of oocytes per ovary was higher with T AO, thus showing that the difference between the two methods lies in higher numbers of visible follicles with TAO. Moreover, with the TAO technique 71 % of the total oocytes we recovered (n=551) were grade I or II oocytes, in which 52% cleaved to the 2 to 4-cell stage and 26% h ad reached the blastoc yst stage. We conclude that the method is effective for accurately locating cortical a nd peripheral follicles that contain oocytes suitable for IVF and in vitro embryo production (IVP). (C) 2001 by Elsevier Science Inc.