A novel method for cryopreservation of individual human spermatozoa.

The purpose of this study is to develop a novel method for the cryopreservation and efficient post-thaw recovery of individual or small numbers of human spermatozoa. Spermatozoa equilibrated in cryoprotectant buffer were injected with an intracytoplasmic sperm injection (ICSI) needle into a droplet of cryoprotectant on a homemade cryoleaf. The droplet was of cryoprotectant and seminal plasma at a ratio of 1:1. The sperm-loaded cryoleaf was slowly lowered over and stored in liquid nitrogen. Spermatozoa were thawed in a 37°C oil bath without dilution and centrifugation. To test the fertilizing ability of these spermatozoa, the recovered spermatozoa were injected by ICSI into 1-d-old or in vitro-matured human oocytes. Fresh spermatozoa from the same semen samples served as controls. The trials were performed in two separate experiments. In the first set of experiments, 92 spermatozoa were thawed and carefully investigated. The spermatozoa from percutaneous epididymal sperm aspiration had a motility recovery of 92.9% (13/14); ejaculated spermatozoa had a motility recovery of 61.5% (48/78), and only 1.3% (1/78) was lost. Together in the first and second set of experiments, the fertilization rates for the fresh and frozen-thawed spermatozoa were 67.6% (25/37) and 60.6% (40/66), respectively (P = 0.052). The mean embryo cleavage rates in the fresh and frozen-thawed groups were 88% (22/25) and 85% (34/40), respectively (P = 0.990). This cryopreservation method for individual or small numbers of human spermatozoa was efficient and simple. These findings make this method a promising technique for the clinical application of ejaculated sperm from oligozoospermic patients.

Definitions of human fertilization and preimplantation growth revisited.

Assisted reproductive techniques and the science of embryology have advanced rapidly over the last decades. The fact that social and moral objectives vary from country to country has resulted in differences not only in legislation, but also in the definition of embryological terms. Among the latest additions to the field has been nuclear transfer technology, which has led to concerns about the possibilities of human cloning. These facts call for a review of gametogenesis and early embryogenesis. The aim of the present paper is to initiate a discussion on terminology with a view to reaching a consensus. As a starting point definitions are proposed for the most important terms.