HETEROTOPIC PURKINJE CELLS IN THE MAMMALIAN CEREBELLAR CORTEX AND THEIR GENETIC SIGNIFICANCE / 解剖学报

ABSTRACT

Heterotopic Purkinje cells are found in the superficial cerebellar cortex in various microscopic sections of the cerebellum of adult representatives of the mammalian orders including insectivores, rodents, carnivores, artio- dactyls and primates, as well as normal and pathological human beings of different ages. Superficial to the middle layer of the cerebellar cortex the heterotopic Purkinje cells are hung on the outermost margin of the cortex or even slipped into the subpial space. Within the molecular layer they subsist in isolation, in groups, in rarefied file, in tortuous alignment, or in wholesale displacement. The heterotopic Purkinje cells are largely hypotrophic with roundish bodies, large nuclei, little cytoplasm, and slender and straight dendrites. Their orientation is multifarious. They are, again, often pathological, being elongated, withered, or with multiple nuclei or nucleoli. They are frequently accompanied by primitive granules which geneti- cally descend from the superficial to the deep planes, thus hinting at their common source. The theory of ventrieular origin fails to explain the aberration of the Purkinje cells to the superficial parts, whereas the facts of heterotopy reflect their origination from the margin and their descent towards the middle level as products of a secondary germination. Under adverse conditions, the primordial Purkinje cells are affected in their capacity of migration and differentiation and, consequently, remain in the original ger- minal bed or slip into the subpial cavity with the crumpling pia mater. They may, again, halt midway singly, collectively, in interrupted file, in sinuous row formation, or in dispersion throughout the whole molecular layer. Cortical patches occasionally present in the interior of pathological cerebellum testifies to the capacity of the potential germinal cells coming from the ventricular matrix to proliferate Purkinje and other cortical cells in the deep as well as in the superficial portions. The retention at adult age of the 'external' granular or Kirschhof's layer together with simulta- neous reduction or absence of Purkinje cells below implies the derivation of the latter cells normally from the margin through a stage corresponding to such granules. The heterotopy of Purkinje cells in the superficial cortex signifies that a part (if not whole) of them at least originate from the marginal granular layer of the early stage.