EFFECTS OF X-IRRADIATION ON EMBRYOS AT CRITICAL STAGES OF HEART DEVELOPMENT
Embryos of Amblystoma punctatum were x irradiated at Harrison's stages 26, 30, and 34. These are critical stages of heart differentiation, ranging from the time when the primordial endocardial cells separate from splanchnic mesoderm to the time when the heart attains a tubular form and begins to contract. The x-ray exposures ranged from 100 to 10,000 r. Following x irradiation, the embryos were reared at a temperature of 12 to 13 C. Non-irradiated controls were kept at the same temperature. In general, the amount of developmental retardation was proportional to the total amount of x irradiation and inversely proportional to the degree of differentiation at the time of exposure. In all of the series studied, there was a latent period between exposure to x irradiation and the appearance of developmental defects. The embryonic central nervous system and eyes were particularly radiosensitive. Microcephaly developed in a high percentage of embryos exposed at the early experimental stages. Cardiovascular anomalies developed in all embryos exposed to 250 r or above at stage 26 and in all embryos exposed to 500 r or above at stages 30 and 34. With high doses differentiation was so retarded that the embryos never developed circulation. With intermediate doses circulation developed for a period, only to fail subsequently. The pulsation rate remained approximately normal for a considerable period after the magnitude of contraction had decreased. Stasis in vessels of the liver and yolk was common. Since the heart anomalies occurred together with other malformations, further studies are in progress to determine how much abnormal cardiac structure and function results directly from radiation of the embryonic heart and how much is dependent on totalbody x irradiation. (auth)
- Research Organization:
- Columbia Univ., New York
- NSA Number:
- NSA-14-023992
- OSTI ID:
- 4153453
- Journal Information:
- Yale J. Biol. and Med., Journal Name: Yale J. Biol. and Med. Vol. Vol: 32
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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