EFFECTS OF NEEDLE TIP BEVEL AND ASPIRATION PROCEDURE ON THE MORPHOLOGY AND DEVELOPMENTAL CAPACITY OF BOVINE COMPACT CUMULUS OOCYTE COMPLEXES

Effects of the needle tip bevel and the aspiration procedure on the mo rphology of cumulus-oocyte-complexes (COCs) and the developmental capa city of the oocytes after IVF were studied in 2 in vitro oocyte pick-u p (OPU) simulations using a disposable ovum pick-up needle guidance sy stem. In Experiment 1, the influence of the length of the needle bevel was investigated using a short and a long bevelled 20-g disposable ne edle. After being aspirated from slaughterhouse ovaries, the retrieved COCs were divided into 3 categories: 1) oocytes surrounded by a compa ct cumulus, 2) oocytes with an expanded cumulus, 3) partially naked oo cytes. In Experiment 2, the influence of 5 different levels of aspirat ion vacuum for 3 different needle diameters (18-g, 19-g, 20-g) and 2 d ifferent needle bevels (long, short) was tested on the recovery and on the morphology of the cumulus investment of a fixed number of previou sly scored compact cumulus oocytes complexes (CCOCs), retrieved after slicing slaughterhouse ovaries. The re-retrieved COCs were allocated t o Categories 1 and 3. The results show that the length of the needle b evel has a significant effect on oocyte recovery, in favor of the long -bevelled needle. As soon as higher aspiration vacua are used, a decre ase of the number of CCOCs can be observed, which is less prominent fo r the short-bevelled needle compared to the long-bevelled one. The fin al number of blastocysts is similar for both needle types. In Experime nt 2, the disposable needle system proved to be highly effective since nearly 80% of the CCOCs were retrieved. At low aspiration vacuum, up to 90% of the CCOCs withstand the aspiration procedure undamaged. Incr easing the aspiration vacuum results in a decrease of the number of CC OCs, which is less pronounced using thinner needles. Averaged over all needle types, the prevalence of blastocysts expressed relative to the number of recovered oocytes decreases with higher aspiration vacuum. (C) 1997 by Elsevier Science Inc.