Jobst Sievers

The development of the visual system of the albino rat

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Basic Two-Dye Stains for Epoxy-Embedded 0.3-1 μ Sections

Dyes used in the 3 methods recommended are: I, thionin and acridine orange (T-AO); II, Janus green and Darrow red (JG-DR); III, methyl green and methyl violet (MG-MV). The first 2 methods were two-solution stains, applied in sequence; the third, required only one solution since methyl violet is present in commercial methyl green. Staining solution and timing was as follows: Method I. 0.1% thionin in a 45% ethanolic solution of 0.01 N NaOH, 5 min at 70 C; rinsing in water and followed by 1 min in a 1% aqueous solution of acridine orange made up in 0.02 N NaOH, also at 70 C, then washed, and dried on slides. Method II. 0.5% Janus green in aqueous 0.05 N NaOH, 5 min at 70 C; rinsing in water then into 0.5% Darrow red in 0.05 N NaOH (aq.), 2 min at 70 C., washing, and drying on slides. Method III. 1% methyl green (commercial, unpurified) in 1% aqueous borax for 15-20 min at 20-25 C, washing and attaching to slides. All staining was performed by floating the sections on the staining solutions, all drying at 70...

Light and electron microscopical studies on specific cells of the marginal zone in the developing rat cerebral cortex.

SummaryThe development of specific cells in the marginal layer of the occipital cortex of the rat was studied both light and electron microscopically. These cells are the first cells of the cerebral cortex to begin differentiation on embryonal day 13 when they enter the stage of beginning ramification. The maturation of these cells proceeds rapidly; on day 17 of gestation they are in the stage of accumulation of ergastoplasm, on day 19 most of them have reached the stage of orientation of ergastoplasm. 1 to 2 days before birth the majority of these horizontally oriented cells exhibit large Nissl bodies in their cytoplasm which often surround the whole nucleus and extend into both processes. The ultrastructure of the horizontal processes of these cells cannot readily be compared with that of conventional protoplasmic processes, buth they rather appear more like extensions of the perikaryal cytoplasm, the structure of which is retained along the course of the processes.These specific cells which are limited to and specific for the marginal zone of the cerebral cortex thus are the first cells of the cerebral cortex to reach cytological maturity—even before birth—and therefore do not fit into the concept of an inside-out gradient of neurogenesis and differentiation in the development of the cerebral cortex as proposed by a number of authors, because the deeper situated preneurons of the other cortical layers have at this time only just begun differentiation from the stage of ventricular cells. Their functional role as a ‘fetal cell’ in the morphogenesis of the cerebral cortex and their identity with the horizontal cells of Cajal-Retzius is discussed.

Chapter 4 Dendritic Growth and The Control of Neuronal Form

Publisher Summary The geometry of dendritic trees often characterizes the morphology of neurons into sets. Dendritic growth cones and filopodia are involved in the dynamics of the growth of trees and that ingrowing axons might be capable of influencing development by an effect on filopodia/growth cone mechanisms. Research efforts have better defined the morphology of dendritic growth cones and their interaction with axons in the developing neuropil. Manipulation of the environment and the use of cerebellar mutants are helping to clarify the role of genes in development while the introduction of new quantitative morphometric techniques for dendritic fields has improved the definition of tree structure. In the developing cerebellum, the form of the Purkinje cell (PC) is largely under the control of the “environment.” Genes may specify the positions and biophysical properties of adhesive sites and postsynaptic thickenings. The spatial interaction of these specialized areas of membrane with particular groups of axons ramifying about the growing tree may be sufficient to shape the characteristic geometry of the PC.

Neuronal and extraneuronal effects of intracisternally administered 6-hydroxydopamine on the developing rat brain.

Abstract: Intracisternal administration of 100 μg 6‐OHDA to newborn rats causes permanent defects, not only of the monoaminergic neuron system, but also of extraneuronal tissue elements. The long noradrenergic fibre tracts are irreversibly destroyed, while the short projections recover and regenerate after a transient period of injury. In the major noradrenergic cell group, the locus coeruleus, most of the cells in the caudal and middle parts degenerate, while a small dorsorostral group survives and forms the source of the regenerating fibres. Dopaminergic and serotonergic fibre tracts are also affected. The 6‐OHDA treatment also damages granule and dial cells of the cerebellar cortex as well as the mesenchymal cells of the pial coverings of the cerebellum, leading to primitive foliation, absence of fissuration, and defective migration of granule cells and resulting in a marked reduction of cerebellar size, area, and granule cell number.

Distribution of tritium label in the neonate rat brain following intracisternal or subcutaneous administration of [3H]6-OHDA. An autoradiographic study.

The present report describes the distribution of tritium label after injection of newborn rats with [3H]6-hydroxydopamine ([3H]6-OHDA). The animals were injected either intracisternally (i.c.) or subcutaneously (s.c.), with or without pretreatment with nomifensine, which blocks the high-affinity uptake of both noradrenaline (NA) and dopamine (DA), and sacrificed at intervals from 40 min to 24 h post-injection (p.i.). In i.c. injected animals, tritium label is demonstrable as early as 40 min p.i. in neurons of all known NA and DA cell groups. In NA neurons, it is taken up into cell body, dendrites, preterminal and terminal axons. The intensity of neuronal labeling is highest within the first 4 h p.i. and decreases in most neurons with longer postinjection intervals. A significant proportion of both NA and DA neurons degenerate beginning 6 h p.i., the majority show morphological signs of the axon reaction 24 h p.i. Uptake of [3H]6-OHDA into serotonergic and non-catecholaminergic neurons is not demonstrable. [3H]6-OHDA is accumulated by the following extraneuronal cells of the CNS: ependymal cells, epithelial cells of the choroid plexus, subependymal macrophages, smooth muscle cells in the wall of large intraparenchymal blood vessels, meningeal cells and glial cells. The time course of accumulation and disappearance of the label varies among these extraneuronal elements. The meningeal cells show the highest labeling intensity and degenerate within 24 h p.i. After pretreatment of the animals with nomifensine, the uptake of [3H]6-OHDA into NA and DA neurons is totally blocked; by contrast uptake of the labeled drug into extraneuronal cells is not prevented. These findings show that [3H]6-OHDA is not only accumulated by neurons possessing the high-affinity uptake for NA or DA, but by numerous other, extraneuronal cells which also participate in the metabolism of catecholamines.

Structural and biochemical changes in rat cerebral cortex after neonatal 6-hydroxydopamine administration

SummaryNewborn rats received an intracisternal injection of 6-hydroxydopamine (100 μg) within 16 h after birth. Treatment effects upon noradrenaline uptake (with or without desmethylimipramine pre-incubation), endogenous noradrenaline, dopamine, and serotonin were biochemically assayed. Noradrenaline uptake and endogenous noradrenaline content were permanently reduced to less than 5% of control values. Reduction of endogenous dopamine content was less marked: at day 60, values were about 40% of controls. Serotonin content remained unaffected.Cell density countings in postnatal day 15 temporal cortex revealed an about 16% reduction in layers II and III of treated animals. These modifications of cortical geometry were discussed with reference to measurements of cortical thickness and ultrastructural observations on postnatal days 2, 5 and 15. Both supranormal involution and growth processes might result from the neurotoxin treatment. Whereas some of the degeneration processes might be due to general cytotoxic effects, this is less likely for the supranormal growth processes.