THE EFFECTS OF X IRRADIATION ON THE SPINAL CORDS OF NEONATAL RATS. I. NEUROLOGICAL OBSERVATIONS
One- to 21-day-old Sprague-Dawley rats received a single dose of 4430 r soft (50-kvp) x irradiation to a localized area of the body overlying the spinal cord. Neurologic examinations were made for several months. Over 70% of animals irradiated at 1 to 3 days of age showed persistent, abnormal neurological signs in contrast to 39% of those irradiated at 10 days of age, 17% of those irradiated on day 15, and 0% of those irradiated at 21 days of age. The latent period was 9 to 11 days for those irradiated at 1 to 5 days of age, 17 to 20 days for those irradiated at 10 days, and 28 to 32 days for those irradiated on day 15. Some animals in all groups remained apparently normal, and in groups irradiated at 5 days of age or more, some animals recovered after showing initial neurological alterations. The pattern of the neurological alterations varied but most common was flaccid paralysis with dragging of the hindlimbs. The onset of abnormal neurological signs was very sudden, in most cases occurring within a 12-hr period. Impairment in visceral function in some animals was shown by distention of the urinary bladder and constant, slight spilling of urine. The long ascending and descending pathways of the afflicted animals were initially judged to be intact, but the integrity of these was disrupted after 10 weeks postirradiation as seen by changes in response to painful, thermal, and vestibular stimulation. Histopathologic studies 10 weeks or more postirradiation revealed that the normal vertebral architecture in the irradiated cord had been replaced by chalky white, osseous material which had produced partial or complete transection of the spinal cord. The kidneys and/or adrenals were markedly reduced in size in some irradiated animals. Although it was previously demonstrated that administration of pentobarbital prior to x irradiation of guinea pigs abolished abnormal neurological signs and histological changes in cerebellum, anesthetized rats irradiated at 10 days of age showed a slightly higher incidence of neurological alterations than did the unanesthetized animals of the same age. Thus, it seems that anesthesia did not suppress the radiation injury to the central nervous system. It is concluded that age at time of irradiation is an important factor in determining incidence, severity, and course of subsequent neurological abnormalities. The time sequence of the progressive neurological changes suggests that these abnormalities may be related to two processes: a direct effect of irradiation on the nervous system as manifested as flaccid paralysis, and an indirect process related to alterations in the vertebral columns which, in turn, produce pressure upon or transection of the spinal cord. Disruption of long ascending and descending tracts observed during the latter part of the experimental period was probably the result of this second process. It is suggested that the nervous system may be very sensitive to radiation immediately after birth and may undergo sufficient change to render it radioresistant 15 to 21 days after parturition. (BBB)
- Research Organization:
- Univ. of Arkansas, Little Rock
- Sponsoring Organization:
- USDOE
- NSA Number:
- NSA-17-035521
- OSTI ID:
- 4658121
- Journal Information:
- J. Neuropathol. Exptl. Neurol., Vol. Vol: 22; Other Information: Orig. Receipt Date: 31-DEC-63
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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A STUDY OF NEUROLOGICAL AND MORPHOLOGICAL CHANGES FOLLOWING X IRRADIATION OF SPINAL CORDS OF NEONATAL RATS
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