A STUDY OF THE EFFECTS OF X-IRRADIATION ON THE SPINAL CORDS OF NEONATAL RATS
A study is made of neurological and histological changes resulting from x irradiation of spinal cords of neonatal albino rats of the Sprague-Dawley (Holtzmann) strain. Rats, one to 21 days of age, receive radiation to a 50 mm/ sup 2/ area on the dorsum of the body overlying the spinal cord under the following conditions: 50 KVP; 5 ma; single dose; total dose, 4430r; dose rate, 670 to 720r/minute; FSD, 8.5 cm; inhereat filtration equivalent to 0.1 mm aluminum; added filtration, 0.25 mm aluminum; HVL, 0.16 mm aluminum. These animals are given neurological examinations for several months. Neurological alterations ranging from slight ataxia to complete bilateral paralysis are observed. Permanent neurological changes occur in more than 70.0% of those surviving after irradiation at l to 3 days of age. The percentage gradually decreases to 16.6% in the group irradiated at 15 days of age; no neuroiogical abnormalities are noted in those irradiated on day 21. The interval between time of irradiation and onset of neurological alterations increases as the age at the time of irradiation increases. The latent period is 9 to ll days for those irradiated at 1 to 6 days of age, 17 to 20 days for those irradiated on day 10 and 28 to 32 days for those irradiated at 15 days of age. All groups contain animals that remain apparently normal throughout the experimental period. Animals that recover from neurological alterations are also observed in the groups irradiated at 5 days of age or later. This recovery rate is as high as 50.0%~ in the 6 and the 15 day groups and occurs in animals with complete bilateral paralysis as well as animals only slightly afflicted. By two months post-irradiation marked deformation of the vertebrae in the irradiated areas is noted. In an attempt to determine the causes of the neurological alterations, animals are irradiated at three days of age in the manner described. These are sacrificed at intervals up to and including the time of onset of neurological changes (9 to 11 days after irradiation). The spinal cords are fixed and interrupted serial sections are prepared for study; cresyl echt violet, hematoxylin and eosin, and myelin strains were used. Striking and consistent histological changes are observed in neuroglia and myelin. As early as two days after irradiation a marked decrease in the number of neuroglia is noted in all irradiated areas, whereas above and below thellesions the sections appear to be essentially normal. The decrease persists throughout the experimental period and, although a quantitative study is not conducted, oligodendroglia appear more severely affected than astrocytes. Myelin does not develop normally in any of the areas showing a diminution of glia. The unmyelinated or lightiy myelinated areas are confined to the site of irradiation and, in striking constrast, immediately adjacent areas and spinal roots including those within the lesion show a normal amount of myelin. Extensive degeneration of neurons is not observed. The neurons appear to mature normally since in later stages of the experiment ventral horn cells show adult, multipolar configurations with discrete clumps of Nissl substance in the cytoplasm. Vascular alterations, manifested only as petechial hemor rhages and endothelial swelling, are noted most frequently at 9 to 11 days post-irradiation.
- Research Organization:
- Univ. of Cincinnati
- NSA Number:
- NSA-16-026788
- OSTI ID:
- 4796255
- Journal Information:
- Dissertation Abstr., Vol. Vol: 22; Other Information: Orig. Receipt Date: 31-DEC-62
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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The effects of x-irradiation on the spinal cords of neonatal rats. II. Histological observations
THE EFFECTS OF X IRRADIATION ON THE SPINAL CORDS OF NEONATAL RATS. I. NEUROLOGICAL OBSERVATIONS