Is embryo-cryopreservation really neutral? A new long-term effect of embryo freezing in mice: protection of adults from induced cancer according to strain and sex.

BACKGROUND: Beneficial or harmful effects of embryo freezing have been described in man and animals, raising the question of the neutrality of this technique. OBJECTIVE: We examined, in mice, the possibility that embryo freezing influences the probability of the emergence, in adults, of an induced urinary bladder cancer. METHODS: The experiment was conducted in mice derived from embryos of two different genotypes. Females receiving embryos were parsed into two groups according to whether these embryos were cryopreserved or not. The derived adults received the chemical carcinogen N-butyl-N-4hydroxybutylnitrosamine (BBN), in the drinking water. Time to death since the onset of treatment was measured for each animal until the 300th day. RESULTS: In females from one of the two strains tested, embryo freezing led to a favorable long-term effect on the probability of resistance to induced cancer. CONCLUSION: This beneficial effect, taken together with other effects reported in the literature be they beneficial or harmful, suggests that embryo freezing in mice may not be neutral.

Progeny's mental aptitudes in man: relationship with parental age at conception and with some environmental factors.

Psychometric tests obtained from 6564 young men were studied as a function of the parents' ages at conception and of some characteristics of the subject's postnatal environment. Individual scores, from 0 to 20, were divided into two groups: n(1)11 and n(2)<11. In univariate analysis, scores <11 were respectively related to low height, high number of siblings and junior in birth order, subject's and parents' tobacco consumption, parents' alcohol consumption, subject's and parents' low academic standard, parents' youth or ageing at conception. In multivariate analysis, these scores remained related to low height, junior in birth order, subject's and parents' tobacco consumption, parents' low academic standard, parents' youth (both <20). Regarding the respective influences of the environment and of the subject's genome on his cerebral development, one can hypothesize a complementarity between these two factors through the possibility of a genetically determined individual synaptic potential, revealing itself, more or less, according to environmental conditions.