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Developmental factors related to abnormal cerebellar foliation induced by methylazoxymethanol acetate (MAM)
1Department of Physiology and Biophysics, New York University Medical Center, NY 10016.
Abstract:
Quantitation of mid-sagittal sections of the molecular layer, and both the external and internal granular layers between control and methylazoxymethanol acetate (MAM)-treated rats, at various stages of cerebellar development revealed a much smaller area of these layers in sagittal profile, however, the fiber core was not significantly affected by the drug. The expansion of the pial surface length was parallel to the length of the Purkinje cell layer, although comparison of a fissure index revealed hypofissuration in the experimental group. In histological examination, there was perforation, patching, and agenesis of the external granular layer. Mushroom expansion of the external granular layer occurred at patches producing a gyrating folial pattern rather than parallel ones. The number of lobules and their basic pattern remained normal. We conclude that the deficits in the external granular layer interrupted the growth force that produces the normal rostrocaudal organization of parallel coronal foliation and this resulted in shallow periodic fissuration along the sagittal extent. Fissurations forming lobules arose largely independent of the external granular layer by directed expansion of the central fiber core while normal parallel foliation is an elaboration of the lobular surface controlled by growth forces defined by both distribution of the external granular layer and the underlying fiber core with associated Purkinje cells.
Insights
Methylazoxymethanol acetate (MAM) exposure in rats disrupts cerebellar development, causing abnormal external granular layer formation. This leads to altered foliation patterns and shallow fissuration, impacting brain structure.
Area of Science:
- Neuroscience
- Developmental Biology
- Neurotoxicology
Background:
- Cerebellar development involves complex cellular organization and foliation.
- Disruptions in cerebellar development can lead to significant neurological deficits.
- Methylazoxymethanol acetate (MAM) is a known neuroteratogen affecting brain development.
Purpose of the Study:
- To investigate the effects of methylazoxymethanol acetate (MAM) on cerebellar development in rats.
- To analyze the impact of MAM on the molecular, external granular, and internal granular layers of the cerebellum.
- To understand how MAM-induced changes affect cerebellar foliation and fissuration patterns.
Main Methods:
- Quantitation of mid-sagittal cerebellar sections from control and MAM-treated rats at various developmental stages.
- Histological examination of cerebellar layers, including perforation, patching, and agenesis.
- Analysis of pial surface length, Purkinje cell layer, and fissure index.
Main Results:
- MAM treatment significantly reduced the area of cerebellar molecular, external, and internal granular layers.
- Hypofissuration was observed in MAM-treated rats, with abnormal gyrating folial patterns.
- Perforation, patching, and agenesis of the external granular layer were evident.
Conclusions:
- Deficits in the external granular layer due to MAM exposure interrupt normal rostrocaudal foliation.
- This disruption results in shallow fissuration and altered cerebellar surface morphology.
- Lobule formation appears independent of the external granular layer, driven by fiber core expansion, while normal foliation requires coordinated growth.