Biochemical and physiological differentiation during morphogenesis. VIII. Quantitative morphologic studies on the developing cerebral cortex of the fetal guinea pig

Abstract

TWLNTY-FIVE FIQUREHTo describe completely the morphologic changes which take place during development of a tissue a s complex as the cerebral cortex is scarcely feasible. The task calls for an analysis of the manifold changes in nucleus, cytoplasm and processes of each type of neuron in each of the several layers of the many cortical areas, as well as in the several varieties of glia. There are, however, a number of estimations which are practicable. At various stages of gestation, percentage of cortex which is nucleus or perikaryon, the number of nerve cells per unit volume of cortex, and the average volume of the nucleus and the cell body can be measured with reasonable accuracy. It is also possible to estimate the time when stratification appears in the cortex and when neuroblasts are changing rapidly to cclls with the characteristics of primitive neurons as judged by appearance of Nissl substance and elaboration of cell processes. This paper deals with the changes in these quantities in one area of the cortex of the guinea pig during the last 35

Structural Organization of the Human Cerebral Cortex. 1.

“…Peters and Flexner [1950] defined " tru e " Nissl bodies as clumps of basophilic m aterial. According to their standards we distinguish in the nerve cells during developm ent " dustlike basophilia" and " true Nissl bodies" .…”

Cocaine-induced alterations in the density of monoaminergic receptors in the embryonic guinea pig cerebral wall

“…At E25-E35, guinea pig cerebral wall contains heavily populated proliferative zones and cortical plate separated by the cell-poor intermediate zone, which suggests active corticogenesis (Peters and Flexner, 1950). At E40, the proliferative zones are almost exhausted and the thickness of the cerebral cortex is close to that in the adult brain (Peters and Flexner, 1950).…”

“…At this time in cortical formation, an intensive gliogenesis takes place (Levitt et al, 1983). By E50, proliferative zones are practically gone and the cerebral wall has an adult-like appearance, which suggests the completion of cortical formation (Peters and Flexner, 1950).…”

“…The embryonic cortical laminae examined included the ventricular and subventricular proliferative zones (containing dividing precursors of cortical cells), the intermediate zone (through which newly generated cortical neurons migrate), and the cortical plate (where postmigratory cortical neurons differentiate) (Boulder Committee, 1970). Guinea pigs were chosen because they are similar to humans in such important parameters as pharmacokinetics, active metabolite profile of administered cocaine Olsen, 1991, 1992;Sandberg et al, 1995), structural and permeability characteristics of the placenta (Faber and Thornburg, 1983;Willis et al, 1986), and completion of corticogenesis before birth (Peters and Flexner, 1950). The gestational period in guinea pigs lasts 65-70 days, with formation of the cerebral cortex taking close to 20 days during the second trimester (Peters and Flexner, 1950).…”

“…Guinea pigs were chosen because they are similar to humans in such important parameters as pharmacokinetics, active metabolite profile of administered cocaine Olsen, 1991, 1992;Sandberg et al, 1995), structural and permeability characteristics of the placenta (Faber and Thornburg, 1983;Willis et al, 1986), and completion of corticogenesis before birth (Peters and Flexner, 1950). The gestational period in guinea pigs lasts 65-70 days, with formation of the cerebral cortex taking close to 20 days during the second trimester (Peters and Flexner, 1950). This allows examination of the regulatory effects of cocaine exposure on neurotransmitter receptors in the embryonic cortical zones during a relatively prolonged period of time.…”