Embryonic mortality caused by maternal heat stress during mouse oocyte maturation |
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| Affiliation: | 1. Laboratorio de InmunoFisiología, Grupo Fisiopatología de la mujer, del embarazo, parto y puerperio. Instituto de Investigación Sanitaria Gregorio Marañón, Madrid, Spain;2. Servicio de Cirugía General, Sección Cirugía Endocrino-Metabólica, Hospital General Universitario Gregorio Marañón, Madrid, Spain;3. Animalario, Instituto de Investigación Sanitaria Gregorio Marañón, Madrid, Spain;4. Servicio de Ginecología, Hospital General Universitario Gregorio Marañón, Spain;5. Laboratorio de Inmuno-oncología, Instituto de Investigación Sanitaria Gregorio Marañón, Madrid, Spain;6. Unidad de Microscopía Confocal, Instituto de Investigación Sanitaria Gregorio Marañón, Madrid, Spain;1. Hepatobiliary Sugery Institute, Southwest Hospital, The Third Military Medical University, Chongqing, China;2. Medical Services Section, Sixteenth Hospital of Chinese People''s Liberation Army, Altay, China;1. ETH Zurich, Animal Physiology, Institute of Agricultural Sciences, Zurich, Switzerland;2. Technische Universität München, Physiology Weihenstephan, Freising, Germany;3. University of Veterinary Medicine Hannover, Institute of Anatomy, Hannover, Germany;4. University of Veterinary Medicine Hannover, Unit for Reproductive Medicine, Hannover, Germany;5. Utrecht University, Dep. of Equine Sciences, Faculty of Vet. Med., Utrecht, The Netherlands;1. Physiology Weihenstephan, Technische Universität München, Weihenstephaner Berg 3, 85354 Freising, Germany;2. Z I E L PhD Graduate School ́Nutritional Adaptation and Epigenetic Mechanismś, Technische Universität München, Freising, Germany;3. Department of Reproduction Management, Leibniz Institute for Zoo and Wildlife Research, Alfred-Kowalke-Straße 17, 10315 Berlin, Germany;4. Department of Endocrinology, University Medicine Goettingen, Robert-Koch-Str. 40, 37099 Goettingen, Germany;5. Department of Biomedical Sciences, University of Veterinary Medicine Vienna, Veterinärplatz 1, 1210 Vienna, Austria;1. Department of Animal Medicine and Surgery, Faculty of Veterinary, Cardenal Herrera-CEU University, Valencia, Spain;2. Department of Veterinary Sciences, Veterinary Physiology Unit, Polo Universitario Annunziata, Messina University, Italy |
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| Abstract: | The effects of maternal hyperthermia during meiotic maturation were studied in oocytes and foetal mice. Heat stress was induced by exposure to 35 ± 1°C and 65 ± 3% RH for 12.5 h. Embryos of uniform chronological age were produced by pairing with non-stressed males for a limited mating period.The morphology and cytogenetic constitution of oocytes were analysed and correlated. Meiotic maturation was disrupted in 39.8% of analysable ova of heat-stressed females. Heat-stressed ova stopped maturing at diakinesis-metaphase I in 4% and polar body chromosomes were retained in 2% of treated ova. Oocytes with atypical morphology were almost always (r=0.96) cytogenetically aberrant.At 19 days of gestation, pre-implantation losses were increased (16.2% for heat-stressed vs. 4.9% for control), but the greatest increase in embryo mortality occurred soon after implantation (34.4% for heat-stressed vs. 11.7% for control), indicating induction of dominant lethal mutations. Individual response to stress was highly variable, ranging from total pre-implantation loss (10 animals) to control levels. Heat-stressed dams with implantations produced only 67% as many foetuses as the control dams. This suggests that genetic aberrations are induced in maturing oocytes by maternal heat stress of short duration and that these alterations do not cause immediate loss of ova or embryos. Instead, a large proportion of the ova produced embryos capable of implantation but not capable of continued development. These large embryo losses result in increased numbers of pregnancies that would be uneconomical to maintain in agricultural species. |
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