Postnatal expression of Doublecortin (Dcx) in the developing cerebellar cortex of mouse.

We have investigated the expression of Doublecortin (Dcx) protein in the developing cerebellum of mouse from postnatal 2nd day to postnatal 22nd day and in young adults by immunohistochemistry. Strong expression of Dcx was present in the inner zone of the external granule cell layer, and remained strong while postmitotic granule cell precursors were present in this transitory layer. Descending granule cell precursors exhibited Dcx immunostaining not only while migrating but for a short time also after their settlement. Dcx-immunostained cells appeared in deep cerebellocortical territories and in the cerebellar white matter during the first postnatal week. These bipolar cells were arranged in the sagittal plane and built up transitory migratory streams during the second postnatal week and their number gradually decreased during the third postnatal week. Upward migration of bipolar cells was observed while leaving the migratory streams, penetrating the internal granule cell layer and the molecular layer. These cells were considered as precursors of late migrating molecular layer interneurons. However, a proportion of Dcx-immunostained cells underwent a bipolar-to-multipolar dendritic remodellation and - on the basis of strong morphological similarities - was taken for "multipotent progenitor cells", described recently in the neocortex of adult rat.

Quantitative analysis of the postnatal development of Purkinje neurons in the cerebellum of the cat.

We have studied the postnatal quantitative changes of cortical Purkinje neurons in the cerebellum of the cat at the following postnatal groups of age: P0, P42, P72 and adults. An unbiased counting method, the optical fractionator was used for the estimation of Purkinje cell numbers. A significant increase of Purkinje cell number was found between P0 (1.097 x 10(6)) and P42/P72 (1.805 x 10(6) and 1.895 x 10(6)) declining to 1.429 x 10(6) in the adult, still 30% higher than in the newborn. It was also observed that during the first few postnatal weeks large "gaps" were present in the Purkinje monolayer as revealed by Nissl staining and metabotropic glutamate receptor 1alpha immunocytochemistry. These Purkinje cell gaps were observed most frequently in well-definable areas, especially in the intermediate zone of the neocerebellum. Simultaneously with the numerical increase of Purkinje neurons between the P0 and P72 age groups, these gaps disappeared after the third postnatal week resulting in the completion of the Purkinje monolayer in the whole cerebellum.

Delayed postnatal settlement of cerebellar Purkinje cells in vermal lobules VI and VII of the mouse.

The postnatal development of the ganglionic (Purkinje) layer was studied in the mouse cerebellum from P0 to young adulthood with special emphasis to vermal lobules VI-VII (oculomotor vermis) in the mouse. In order to visualize Purkinje cells (PCs), toluidine blue staining of resin-embedded semithin sections and calbindin immunohistochemistry were utilized. The number of PCs in the whole cerebellum was 199,080+/-2966 at postnatal day eight (P8), 222,000+/-2979 at P20 and nearly the same, 225,800+/-7549 in young adults; i.e., there was an approximately 13.4% increase of PCs between P8 and adults. The number of PC somata aligned into a rostrocaudal stripe along the developing ganglionic layer increased by about 24% in vermal cerebellar lobule III but much more markedly (i.e., by 49%) in VI+VII between P6 and young adulthood. Between P6 and P16, the increase of the number of PCs in the ganglionic layer of lobules VI and VII resulted in the (delayed) completion of PC layer, caused by the (late) alignment of rostrocaudally dispersed PCs, although late postnatal migration of a smaller population of these cells cannot be excluded either. It is concluded that the oculomotor vermis belongs to the latest developing cerebellar cortical structures, which could be the reason for its frequent involvement in developmentally related disturbances and disorders.