Figure 1 Frozen-thawed guineapig embryos at magnification x80. Cryoprotectant used was 1.5 mmol/L dimethyl sulphoxide. Embryos have been collected on day 2.5 of pregnancy after superovulation. (a) Normal light illumination, (b) Same embryos as in Figure 1a after fluorescien diacetate A staining. An ultraviolet filter for green fluorescence at 546 nm was used. Viable blastomers show green fluorescence