engleski

Morphological characteristics of the cells in the subcallosal zone (nucleus septohippocampalis) of the human fetus

Background/Objectives: Previous developmental studies pointed out the complexity of morphogenetic events in the interhemispheric cerebral wall during the formation of the corpus callosum. However, the changes in the morphology of individual cells in the region of the developing dorsal allocortex have not been studied. The aim of this study was to analyze the morphology and maturational changes of different cell classes in the subcallosal zone of the human fetal brain (22 and 28 weeeks post ovulation), using Golgi and acetylcholinesterase staining. Results: The subcallosal zone occupies a paramedian territory situated between the developing corpus callosum (dorsally) and bundles of the fornix (ventrally). The two main findings are: (1) the presence of characteristic, area-specific cells, and (2) the presence of differences in the cellular composition between the medial and lateral portion of the subcallosal zone. The area-specific cells are neuron-like with a number of long and wavy (zigzag) processes, preferentially oriented towards the corpus callosum. The other types of cells include large glia-like cells, maturing neurons, migratory-like neurons, and radial glial cells. Conclusions: The midline portion of this subcallosal region is the part of the septohippocampal continuum and corresponds to the nucleus septohippocampalis of classic authors. The lateral (left and right paramedian) portions of the subcallosal region contain radial glial cells, and continue directly into the subventricular zone of the dorsal neocortical telencephalic wall. We therefore consider these paramedian subcallosal zones as a dorsal allocortical counterpart of the subventricular zone. Significantly decreased numbers of subcallosal cells in the adult brain suggest that the majority of neuronal and glial elements of the subcallosal region in the fetal brain are of a transient nature. The complexity and preferential orientation of glia-like and neuron-like subcallosal cells suggest that they may be involved in the guidance of callosal axons, whereas the cells of the septohippocampal continuum may have a pivotal role in the bidirectional growth of fornix system fibers.

glial sling; glial wedge; corpus callosum; dorsal hippocampus; transient structures

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