Rapid Golgi Preparations Research Articles

Light and electron microscopic studies of the ventricular wall.

Electron microscopic data confirm the results gained with rapid Golgi preparations of adult rodent brains that tanycytes occur in clusters along the lateral wall of the third ventricle. The cytoplasmic matrix of these cells is considerably denser than that of typical ependymal cells. They have filaments and microtubules throughout their cytoplasm along with mitochondria and polysomes. At the surface is a compact group of microvilli which suggest that tanycytes might selectively absorb material from the ventricle.

High voltage electron microscopy of rapid golgi preparations. Neurons and their processes in the cerebellar cortex of monkey and rat.

The rapid Golgi reaction produces initially a red and secondarily a black precipitate in certain neurons, neuroglia, and endothelial cells of nerve tissue. High voltage electron microscopy shows that the red impregnation is a dense, intracellular, fibrillar meshwork of rodlets with a filamentous substructure. The black impregnation is due to the superimposition of very dense globular and polyhedral crystals that stud the surface of the underlying red fibrillar network. When present in quantity, these globules conglomerate to form a crust over the impregnated structure. This can cause distortion in the shape of the structure and considerable overestimation of its size in light microscope studies of black Golgi material.

The form of velate astrocytes in the cerebellar cortex of monkey and rat: high voltage electron microscopy of rapid Golgi preparations.

High voltage electron microscopy of Golgi preparations vividly displays the veil-like appendages on certain protoplasmic astrocytes. These appendages are extremely thin sheets of cytoplasm or plasmalemmal films expanding from the larger processes of the cells. Because of the prominence of this structural feature, reminiscent of the appearance of astrocytes in tissue culture, we designate these cells as velate astrocytes, in order to distinguish them from those protoplasmic astrocytes that lack such appendages. In the cerebellar cortex, velate astrocytes are represented by two types of neuroglial cell: (1) the Golgi epithelial cell and (2) the common astrocyte of the granular layer. The first type not only gives rise to the Bergmann fibers, but also envelops the Purkinje cell and all of its processes. The second type divides up the granular layer into gross compartments containing individual glomeruli and single or clustered granule cells. The probable significance of this compartmentation is discussed.

Tendril and glomerular collaterals of climbing fibers in the granular layer of the rat's cerebellar cortex.

Rapid Golgi preparations show that two kinds of collaterals issue from the climbing fiber in its course through the granular layer. The first resembles the tendrils found in the molecular layer and consists of globose varcosities connected by a very fine thread. In electron micrographs these varicosities in the granular layer contain dense aggregates of round synaptic vesicles at least 520 A in diameter and the connecting threads contain numerous microtubules. The varicosities synapse on the somata of Golgi II cells and on the shafts of dendrites belonging to both Golgi II and granule cells. The second type of collateral emerges from the main stem of the climbing fiber as a stout branch that sprays out abruptly into a large efflorescence. In electron micrographs this terminal appears as the central stellate structure in a glomerulus and is packed with round synaptic vesicles like those in the tendril varicosities. Granule cell dendrites encircle the terminal and occasionally synapse with it. Often the terminal in the glomerulus also forms an extensive junction—a synapse en marron—with the some of Golgi II cell. In this region the surface of the cell is wrinkled like a Spanish chestnut and the glomerular terminal is reciprocally ridged and furrowed to match. Synaptic complexes occur only in the furrows of the cell surface. A broad subsynaptic zone is filled with a fine filamentous matrix. This study provides the first morphological identification and description of climbing fiber terminations in the granular layer, the existence of which has been suggested by earlier Golgi studies and postulated by neurophysiologists. The fact that climbing fibers synapse on both granule cells and Golgi II cells complicates the analysis of the way in which the cerebellar cortex operates, because these two cells have postsynaptic effects of opposite sign. The climbing fiber is known to evoke a complex discharge from the Purkinje cell, consisting of a large primary spike and smaller secondary potentials. It is suggested that when a climbing fiber volley traverses the granular layer, the granule cells on which it synapses are induced to excite stellate and basket cells in the molecular layer which in their turn inhibit the secondary spikes of the climbing fiber response in the Purkinje cell. Meanwhile the Golgi II cells, stimulated by the same climbing fiber volley, suppress the granule cells and thus transsynaptically limit the duration of the inhibitory effects exerted by the interneurons in the molecular layer.

Histogenesis of cortical layers in human cerebellum, particularly the lamina dissecans.

AbstractPatterns of lamination during development of the fetal human cerebellar cortex were analyzed in Nissl‐ and H & E‐stained serial sections, rapid Golgi preparations, reduced silver impregnations, electron micrographs, and autoradiograms. The layering pattern changed dramatically with time, as analyzed in detail for the culmen, the earliest region to differentiate. Up to about 10 weeks of gestation, cells proliferated only at or near the ventricular surface and migrated radially outward to occupy the full thickness of the cerebellar primordium except for an outermost cell‐sparse marginal layer (2‐layer stage). The external granular layer first appeared at 10‐11 weeks while another group of cells became concentrated beneath the marginal layer (3‐layer stage). At 20–21 weeks the lamina dissecans first became evident as a relatively acellular band in the midst of the zone of compact cells below the marginal (now molecular) layer, and for the next ten weeks the cerebellar cortex displayed this 5‐layered form. At about 32 weeks the lamina dissecans disappeared (4‐layer stage) and postnatally the external granular layer in turn disappeared as the last of its cells migrated inward (adult 3‐layer configuration).The Purkinje cell population was established by 13 weeks, though the cerebellum was destined subsequently to increase several orders of magnitude in surface area and volume. The increase was achieved in part by cell growth, but mainly by extensive cell proliferation in the external granular layer. At 22 weeks, about 30% of the external granular cells incorporated thymidine‐H3 upon a single supravital exposure; the external granular layer attained maximum cell number at some stage after birth.At the 5‐layer stage from about 21 to 32 weeks, the interrelationships between various classes of young neurons in the cerebellar cortex became very complex. The Purkinje cells developed ascending branched dendritic processes with growth cones and displayed transient short cytoplasmic processes that extended from the soma in all derections. Basket cell neurons had formed but their axons appeared not to envelop the Purkinje somas as yet. Less mature, smaller cells were beginning to migrate from the external granular layer inward past the Purkinje somas. Their cell bodies in the newly forming granular were separated from the Purkinje cell bodies by a dense tangle of axons in the lamina dissecans. Many of these axons terminated in swellings interpreted tentatively as immature mossy endings, while others passed outward to enclose the cell bodies and proximal dendrites of the Purkinje cells.Some general points emerged from a comparison of cerebellar development in man and animals. The time of cell origin cannot be inferred necessarily from the time of overt differentiation; deep cerebellar neurons and Purkinje neurons arise in the first trimester, but the former cells differentiate much earlier. Purkinje cells acquired characteristic shapes by the middle of gestation, when very few granule cell neurons had yet formed, and thus appear to develop relatively independently of the granule cells. Although the adult cerebellum appears to be organized similarly among mammals, a developmental component, the lamina dissecans, has been illustrated only in man and whale; its appearance may reflect the combination of early Purkinje cell and late granule cell differentiation in species with a prolonged period of development. One of the most intriguing features of the lamina dissecans is that it appears to contain axon terminals at a time prior to the arrival of the postsynaptic cells.

A study of neurogenesis in the forebrain of opossum pouch young.

Morphological changes of growing axons and dendrites are traced in rapid Golgi preparations of the olfactory bulb and the striatum and the parietal, cingulate, and hippocampal cortex. In age-graded series of opossum pouch young changes in the form and position of the differentiating neurons are related to the genesis of the neuronal architecture of each region. In the olfactory bulb there is a specific sequence of changes, starting with the formation of the olfactory glomeruli and the apical dendrites of the mitral cells and ending with the formation of the granule cell processes and the lateral dendrites of the mitral cells. In the ganglionic eminence, the external processes of neuroblasts form axons as they pass from the matrix zone into the presumptive striatal neuropil. Subsequently the perikarya move through the external processes from the matrix zone to the origins of the axons, the external processes disappear, and the dendrites of the striatal neurons start to form. The region of neuronal differentiation is defined by the intersection of the primitive processes of the neuroblasts with the growth cones of specific afferent axons. In the cerebral cortex the neuroblasts resemble primitive epithelial cells (spongioblasts). Their perikarya are in the matrix zone; their primitive processes extend between the internal and external limiting membranes. When afferent growth cones appear in the mantle zone of the parietal area, the perikarya of the pyramidal neuroblasts move to the external limiting layer through their primitive processes. Next these processes disappear; then axons and dendrites differentiate. The order of these events differs in other cortical areas. There is no sign of free, ameboid migration of the neuroblasts. The classical problems of neurogenesis are redefined in the light of these findings.

The collateral system of the medial nucleus of the trapezoid body of the cat, its neuronal architecture and relation to the olivo-cochlear bundle

In rapid Golgi preparations several types of neurons and axonal endings are revealed in the medial trapezoid nucleus. The principal neuron, with tufted dendrites, receives the calyx of Held and endings of a peri-dendritic plexus. An elongate neuron is associated with various collateral endings of axons passing through the nucleus. A stellate neuron is associated with a peri-cellular axonal nest. The terminal branches of the peri-dendritic plexus are arranged in horizontal layers, which may provide for a tonotopic organization of the principal neurons across the dorsoventral axis of the nucleus. The dorsomedial peri-olivary nucleus, representing an origin of the crossed olivo-cochlear tract, contains elongate and radiate neurons. Its afferent plexus has a laminar arrangement, which may relate to a tonotopic organization of the olivo-cochlear bundle. Its plexus is formed chiefly by collaterals of axons entering or leaving the medial trapezoid nucleus. Collaterals from the calyciferous and peridendritic axons and from the axons of the principal neurons may permit the dorsomedial peri-olivary nucleus to monitor both the auditory input and output of the principal neurons of the medial trapezoid nucleus.