Summary. Intra-vaginal and intra-uterine pressure changes during human coitus were monitored by the use of a pressure-sensitive radiopill.Pressure was found to be negative in the vagina during intromission and male orgasm but became positive during female orgasm. In the uterus, the pressure changes were minimal during male orgasm but increased markedly during female orgasm to a positive pressure of 40 cm H2O2 followed by a sharp fall after orgasm to a negative pressure of 26 cm H2O.The reliability of these results is discussed in relation to their possible significance in the pattern of sperm transport, and it is suggested that the final negative pressure following female orgasm may effect aǹ insuck' of the cervical mucus with its entrapped spermatozoa.

STUDY QUESTIONCan time-lapse analysis of cell division timings [morphokinetics (MK)] in mouse embryos detect toxins at concentrations that do not affect blastocyst formation?SUMMARY ANSWERAn MK algorithm enhances assay sensitivity while providing results 24–48 h sooner than the traditional mouse embryo assay (MEA).WHAT IS KNOWN ALREADYCurrent quality control testing methodology is sensitive but further improvements are needed to assure optimal culture conditions. MKs of embryo development may detect small variations in culture conditions.STUDY DESIGNCross sectional—control versus treatment. Mouse embryo development kinetics of 466 embryos were analyzed according to exposure to various concentrations of toxins and toxic mineral oil.MATERIALS, SETTING, METHODSCryopreserved 1-cell embryos from F1 hybrid mice were cultured with cumene hydroperoxide (CH) (0, 2, 4, 6 and 8 µM) and Triton X-100 (TX-100; 0, 0.0008, 0.0012, 0.0016 and 0.002%). Using the Embryoscope, time-lapse images were obtained every 20 min for 120 h in seven focal planes. End-points were timing and pattern of cell division and embryo development. The blastocyst rate (BR) was defined as the percentage of embryos that developed to the expanded blastocyst stage within 96 h.MAIN RESULTS AND THE ROLE OF CHANCEBR was not affected for embryos cultured in the three lowest concentrations of CH and the four lowest concentrations of TX-100. In contrast, a unique MK model detected all concentrations tested (P < 0.05). The MK model identified toxicity in two lots of toxic mineral oil that did not affect BR (P < 0.05).LIMITATIONS, REASONS FOR CAUTIONA limited number of toxins were used so that the results may not apply to all potential embryo toxins. A larger sample size may also demonstrate other statistically significant developmental kinetic parameters.WIDER IMPLICATIONS OF THE FINDINGSMKs in mouse embryos are a sensitive and efficient method for quality control testing of in vitro culture conditions. BR, the end-point of traditional quality control assays, did not detect sublethal concentrations of toxins in the culture milieu in our study. This study demonstrates that temporal variation at key developmental stages reflects the quality of the culture environment. An MEA that incorporates MK will provide enhanced sensitivity and faster turn-around times.STUDY FUNDING/COMPETING INTEREST(S)The study was supported by Mayo Clinic Department of Obstetrics and Gynecology Small Grant Program. The authors have no competing interests to declare.

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what is known already: Current quality control testing methodology is sensitive but further improvements are needed to assure optimal culture conditions. MKs of embryo development may detect small variations in culture conditions. study design: Cross sectional-control versus treatment. Mouse embryo development kinetics of 466 embryos were analyzed according to exposure to various concentrations of toxins and toxic mineral oil. materials, setting, methods: Cryopreserved 1-cell embryos from F1 hybrid mice were cultured with cumene hydroperoxide (CH) (0, 2, 4, 6 and 8 mM) and Triton X-100 (TX-100; 0, 0.0008, 0.0012, 0.0016 and 0.002%). Using the Embryoscope, time-lapse images were obtained every 20 min for 120 h in seven focal planes. End-points were timing and pattern of cell division and embryo development. The blastocyst rate (BR) was defined as the percentage of embryos that developed to the expanded blastocyst stage within 96 h. main results and the role of chance: BR was not affected for embryos cultured in the three lowest concentrations of CH and the four lowest concentrations of TX-100. In contrast, a unique MK model detected all concentrations tested (P , 0.05). The MK model identified toxicity in two lots of toxic mineral oil that did not affect BR (P , 0.05).limitations, reasons for caution: A limited number of toxins were used so that the results may not apply to all potential embryo toxins. A larger sample size may also demonstrate other statistically significant developmental kinetic parameters.wider implications of the findings: MKs in mouse embryos are a sensitive and efficient method for quality control testing of in vitro culture conditions. BR, the end-point of traditional quality control assays, did not detect sublethal concentrations of toxins in the culture milieu in our study. This study demonstrates that temporal variation at key developmental stages reflects the quality of the culture environment. An MEA that incorporates MK will provide enhanced sensitivity and faster turn-around times.

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