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.

A transgenic mouse model engineered to investigate human brain-derived neurotrophic factor in vivo.

Brain-derived neurotrophic factor (BDNF) is an attractive component for the treatment of various neurodegenerative diseases such as Alzheimer's or Parkinson's disease. Innovative non-invasive therapeutic approaches involve appropriate pharmacological induction of endogenous BDNF synthesis in brain. A transgenic mouse model has been established to study human BDNF gene expression and permit the screening of compounds capable of stimulating its activity. A 145-kb yeast artificial chromosome carrying the human BDNF gene has been engineered to produce the transgene which contains the extended BDNF promoter and 3' flanking regions and has integrated the enhanced green fluorescent protein (E-GFP) coding sequence in place of the BDNF coding exon. Five transgenic lines have been obtained through microinjection of the YAC into fertilized mouse oocytes. From the three lines expressing the transgene, one displays the specific pattern of BDNF expression. Faithful tissue-restricted transcription of BDNF 5' exons and localization of the fluorescent reporter gene product in the expected brain subregions are reported. This line constitutes an exploitable system for investigating human BDNF gene regulation in vivo.