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Effects of low-level x-irradiation on cat cerebella at different postnatal intervals. II. Changes in Purkinje cell
Insights
Early-life whole-head irradiation in kittens significantly reduced cerebellar molecular layer thickness and Purkinje cell dendritic arborizations. Radiation effects were most severe when initiated at younger postnatal ages.
Area of Science:
- Neuroscience
- Developmental Biology
- Radiation Biology
Background:
- Cerebellar development is sensitive to environmental insults.
- Radiation exposure during critical developmental periods can lead to significant neuropathology.
Purpose of the Study:
- To investigate the effects of fractionated whole-head irradiation at different postnatal ages on cerebellar development in infant kittens.
- To analyze the impact on Purkinje cell morphology and dendritic arborization.
Main Methods:
- Infant kittens were irradiated with fractionated doses (150 R and 200 R) at postnatal ages of newborn, 1, 2, 3, and 4 weeks.
- Cerebellar molecular layer thickness was measured.
- Golgi impregnation was used to evaluate Purkinje cell dendritic arborizations.
Main Results:
- Irradiation significantly reduced molecular layer thickness, with the most pronounced effects in younger animals (newborn: 47% reduction, 1-week: 40% reduction).
- Dendritic arborizations of Purkinje cells were reduced, particularly with earlier irradiation.
- Dendritic 'damming' at the pial surface and increased primary dendrite growth were observed in early-treated groups.
Conclusions:
- The timing of radiation exposure is critical in determining the severity of cerebellar developmental abnormalities.
- Purkinje cell dendritic growth patterns are influenced by early radiation, and climbing fibers adapt to these alterations.
Abstract:
The whole-head of infant kittens was irradiated with fractionated doses of 150 R and 200 R at different postnatal intervals. Experimental age conditions consisted of an irradiated newborn, 1-week, 2-week, 3-week, and a 4-week age condition while the age of sacrifice remained constant at 70 days. The molecular layer thickness was reduced by 47% in the newborn, 40% in the 1-week group, 17% in the 2-week group, 19% in the 3-week group and by 9% in the 4-week group. An evaluation of Golgi impregnated material revealed that the dendritic arborizations of purkinje cells were consistently reduced the earlier the age at which radiation was begun. A reduction in spiny branchlets was seen in all of the experimental conditions. All experimental age conditions displayed the phenomenon of dendritic "damming" at the pial surface, which consisted of an excessive crowding of spiny branches at this level. An increased growth of the primary dendrite before branching tood place was seen in the newborn and 1-week group. This became less but was still significant in the 2-week group. A correlation of this phenomenon with the presence or lack of stellate cells is disclssed. Purkinje cells with two or more dendrites emerging from their soma were classified and analyzed separately. It was found that the primary dendritic branching in these cells often followed separate morphological patterns and appeared to be independent of each other. Climbing fibers were found to conform to the abnormal dendritic arborizations of the Purkinje cells, and were reduced in complexity in the early radiation treatment groups. This suggested that climbing fibers had no influence upon the dendritic growth pattern, but instead were under the influence of the Purkinje cell dendritic growth.