Analysis of metabolism revealed that vitrification had less impact on the metabolic rate of the embryo than freezing, which was reflected in higher survival rate and subsequent development in vitro. Excellent pregnancy outcomes followed the warming and transfer of vitrified cleavage-stage embryos. These data provide further evidence that vitrification imparts less trauma to cells and is, therefore, a more effective means of cryopreserving the human embryo than conventional slow freezing. Clinicaltrials.gov identifier: NCT00608010.

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The guanylate cyclase activity [GTP pyrophosphate-lyase (cyclizing), EC 4.6.1.2] in membrane preparations from 3T3 mouse fibroblasts is stimulated approximately 5-fold by lysolecithin at concentrations of 100 Mg/mi and above. The stimulation of the adenylate cyclase activity in these preparations by sodium fluoride is inhibited up to 95% by lysolecithin over a similar concentration range. The regulatory properties of Iysolecithin appear to result from the surfactant properties of the phospholipid, since (i) the activity cannot be attributed to any single substructure within the molecule, and (ii) lysolecithin affects the subcellular distribution of guanylate cyclase in rat heart homogenates in a manner similar to that reported for the non-ionic detergent Triton X-100. Stimulation of guanylate cyclase by lysolecithin was observed with membrane preparations from both 3T3 cells and simian virus 40 transformed 3T3 cells (SV3T3). These results suggest a possible role for lysolecithin in the coordinate regulation of the intracellular levels of both cyclic nucleotides, and in the control of the responsiveness of target tissues to hormone or mitogen stimulation.Studies on cultured mouse cells (3T3) have contributed a body of evidence indicating a role for cyclic nucleotides in the regulation of the proliferation of nontransformed cells (1, 2). Stimulation of 3T3 cell growth by insulin induces an approximately 75% drop in intracellular cyclic AMP concentration (3) at 5 min after treatment. In contrast, insulin induces a concentration-dependent increase in the intracellular concentration of cyclic GMP ranging from 10-to 40-fold (1, 2). These results and the results of several additional studies of the effects of various drugs and hormones on the levels of cyclic nucleotides in their target tissues have been interpreted by Goldberg and his associates (1,4)

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