Helen Mok

U-shaped relation between plasma oxytocin levels and behavior in the trust game.

Trust underpins much of social and economic exchanges across human societies. In experimental economics, the Trust Game has served as the workhorse for the study of trust in a controlled incentivized setting. Recent evidence using intranasal drug administration, aka ‘sniffing’, suggests that oxytocin (OT) can function as a social hormone facilitating trust and other affiliative behaviors. Here we hypothesized that baseline plasma OT is a biomarker that partially predicts the degree of trust and trustworthiness observed in the trust game. Using a large sample of 1,158 participants, we observed a significant U-shaped relationship between plasma OT with the level of trust, and marginally with the level of trustworthiness, especially among males. Specifically, subjects with more extreme levels of plasma OT were more likely to be trusting as well as trustworthy than those with moderate levels of plasma OT. Our results contribute to a deeper understanding of the biological basis of human trust and underscore the usefulness of peripheral plasma OT measures in characterizing human social behavior.

Improved sperm concentration, motility, and fertilization rates following Ficoll treatment of sperm in a human in vitro fertilization program

Duplicate sperm samples from the spouses of 54 patients admitted to an in vitro fertilization program were prepared by the swim-up and a simplified procedure using Ficoll. Cellsoft (CRYO Resources, New York, NY) sperm curvilinear velocities (microns/sec) and mean amplitude of lateral head displacement values (microns) equivalent to grade 1 and 2 visual sperm motility were significantly higher for Ficoll as compared with swim-up samples (P less than 0.01). Fertilization rates were significantly higher in the Ficoll as compared with the swim-up group for poor semen samples (grade less than 2: 58% versus 24%; P less than 0.01) and normal semen samples (grade greater than or equal to 2: 85% versus 78%; P less than 0.05). Ficoll sperm separation appears to be an excellent method of yielding increased fertilization rates in in vitro fertilization programs.

Chromosome analysis of two-cell mouse embryos frozen by slow and ultrarapid methods using two different cryoprotectants

Three freezing methods (slow-1,2 propanediol; ultrarapid-dimethyl sulphoxide; ultrarapid-1,2 propanediol) were used to assess the effects of low temperature storage on morphologic features and chromosome make-up of 2-cell mouse embryos. Weekly batches (15 weeks) of 2-cell mouse embryos were frozen for a period of 7 days using these three freezing methods, then thawed and subjected to chromosome analysis. After thawing, all three freezing regimens yielded 70.2% to 75.8% of healthy intact 2-cell embryos, and 5.5% to 8.1% of embryos with one healthy blastomere intact, respectively, out of 817 embryos examined. Chromosome analysis was possible in all 1- and 2-cell embryos. The incidence of aneuploidy and polyploidy in frozen-thawed embryos of all three methods (2.8% to 3.4%; 4.0% to 6.5%) was not significantly different from that of control unfrozen embryos (3.0%; 6.0%) (P greater than 0.01). Mitotic crossing over was observed in 3.5% of embryos frozen-thawed by the ultrarapid-dimethyl sulphoxide method only. It is not clear how the mitotic crossing over was induced by ultrarapid freezing in the presence of dimethyl sulphoxide.

Association between an intronic apolipoprotein E polymorphism and bone mineral density in Singaporean Chinese females.

INTRODUCTION Apolipoprotein E (ApoE) is implicated in the pathogenesis of osteoporosis. OBJECTIVE To investigate possible association of the non-classical APOE gene +113C/G (rs440446) intron 1 enhancer polymorphism with bone mineral density (BMD) in a homogeneous Chinese population in Singapore. METHODS A total of 655 volunteers, males and females, aged between 31 and 72 years, from the public participated. BMD was measured using dual-energy X-ray absorptiometry and APOE +113C/G (rs440446) genotypes were determined by Sequenom MassARRAY system. To adjust for potential confounders, anthropometric, demographic, and lifestyle determinants were obtained, and serum lipids and E(2) were measured. RESULTS The +113C/G (rs440446) polymorphism within the APOE gene was associated with BMD in Chinese Singaporean females only. Females with the heterozygous CG genotype were significantly associated with reduced total, lumbar spine, and femoral neck of hip BMD, after multilevel adjustment of confounders. The association was stronger in the spine than in the hip. When females were stratified according to WHO classification for osteoporosis, those with CG and GG genotypes had increased risk (OR 3.50 and 2.22, respectively) of developing osteopenia/osteoporosis in the lumbar spine. Serum lipids did not explain the influence of APOE +113 C/G (rs440446) on BMD. CONCLUSION This study demonstrated an association between APOE +113C/G (rs440446) polymorphism with measures of BMD in Singaporean Chinese females.

PLASMA LEVELS OF OESTRIOL-17β OESTRIOL AND HUMAN PLACENTAL LACTOGEN DURING BED REST

Plasma unconjugated oestradiol‐17/2, total oestriol and human placental lactogen levels were measured in twelve healthy volunteers admitted for bed rest in the last trimester of pregnancy. No significant alteration in levels was observed.

Evaluation of Chang's culture medium for mouse in vitro fertilization and embryonic development

Changs medium [with and without human serum (HS)] was compared with T6 medium [with and without bovine serum albumin (BSA)] for in vitro fertilization (IVF) and development of two-cell mouse embryos to the blastocyst stage. Changs medium without any supplementation gave significantly better fertilization rates (83.3%) than Changs with 10% HS (76.4%) or T6 and BSA (76.6%) (P <0.01). In a separate experiment 87.7% of the two-cell mouse embryos developed to the blastocyst stage in Changs medium supplemented with 10% HS, 76.6% of the embryos developed to the blastocyst stage and 17.2% stopped development after the morula stage. After 72 hr in vitro hatched trophoblast and inner-cell-mass cells from 26.5 and 30.8% of the embryos grown in Changs medium (with and without HS) attached to the plastic culture dishes and grew to form a mixed monolayer of epithelioid and fibroblastic cells. Changs medium can thus be successfully used for IVF and growth of mammalian embryos. Further, inner cell mass and trophoblast cell lines could be established for various reproductive studies using this medium.

The use of amniotic fluid and serum with propanediol in freezing of murine 2-cell embryos**Supported by the National University of Singapore with core-support from the World Health Organization.††Presented in part at the 5th World Congress on In Vitro Fertilization and Embryo Transfer, April 5 to 10, 1987, Norfolk, Virginia.

Human and mouse embryos have been cultured in amniotic fluid (AF). Human AF and human serum (HS) are used in the freeze-thaw of 2-cell mouse embryos. Two hundred seventy-five 2-cell embryos were collected into phosphate-buffered saline with 20% HS and 20% AF and into 100% HS and AF. The embryos were cooled with propanediol as cryoprotectant at a controlled rate. After thaw, they were cultured in T6 with 3 mg/ml bovine serum albumin. Blastocyst formation post-thaw was 56/79, 44/70, 51/61, and 56/79 of intact embryos from 20% HS, 20% AF, pure HS, and pure AF (NS). But blastocyst hatching was better from embryos frozen in pure HS (22/61, compared with 16/79 for 20% HS; P less than 0.05). Hence there is no advantage in using AF in freeze-thaw, but pure HS may be of use.