Protoplasmic Astrocytes Research Articles

The topographical distribution of S-100 and GFA proteins in the adult rat brain: an immunohistochemical study using horseradish peroxidase-labelled antibodies.

The cytological and topographical distribution of S-100 and glial fibrillary acidic (GFA) proteins in the adult rat brain has been compared using the horseradish peroxidase-labelled antibody technique. Both proteins are present in astrocytes and structures composed of astrocytic processes, namely the glial limitans and the perivascular membranes, but the cytological localization varies between the two proteins. S-100 is found in the nucleus and cytoplasm whereas GFA protein is confined to the cytoplasm. Neither is found in neurons, but S-100 is present in some oligodendroglia, suggesting a general regulatory role in glia. Although GFA protein in present in both protoplasmic and fibrous astrocytes, it is more prominent in the latter, confirming its association with astrocytic filaments.

Scanning transmission and conventional electron microscopic observation of previously identified protoplasmic astrocytes. A preliminary study.

Two different types of protoplasmic astrocytes were studied by scanning transmission and conventional electron microscopy in order to determine the exact nature of the aspect described by Chan Palay and Palay as velate astrocyte. This study provides new data about the usefulness of S.T.E.M and brings into question the results of the Palays.

Ultrastructure of brain and nerve biopsy tissue in Wilson disease.

A 14-year-old girl with psychomotor deterioration developed Wilson disease. Mild atrophy of the small hand muscles was an unusual feature. A cerebral cortex biopsy specimen disclosed exuberant spheroid production, chromatolytic changes, myelin and axonal degeneration, alterations of capillary basal lamina, Hirano bodies, Alzheimer type protoplasmic astrocytosis, and many neuropil-based nonneuronal elements (M cells) of heterogeneous derivation distinct from astrocytes and normal oligodendrocytes. On reviewing neuroglia cell changes in light of present findings, the following conclusions become obvious: Alzheimer type II astrocytosis is true cellular hyperplasia of a class of reactive protoplasmic astrocytes with variable cytologic features. Alzheimer type I astrocytes most probably do not exist; the designation should be dropped. M cells play an important role in the cytopathology of Wilson disease; some forms may generate the so-called Alzheimer type I astrocyte.

Histochemical observations on NDPase and TPPase in cerebral tumours.

TPPase and NDPase were studied in 24 cerebral tumours. Gliomas show intense parenchymal staining both with IDP and TPP. Dissociated responses are observed using different divalent ions. With IDP the intensity and distribution of the reaction do not vary when Mn++ is substituted by Ca++ and Mg++. With TPP the staining of tumor cells is greatly reduced when Ca++ and Mg++ are used instead of Mn++. Small structures can thus be observed in the cytoplasm, especially in areas of protoplasmic and large astrocytes, which resemble the Golgi apparatus.

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.

Neuron-glia relationship during granule cell migration in developing cerebellar cortex. A Golgi and electronmicroscopic study in Macacus Rhesus.

AbstractThe cytology of the postmitotic migratory granule cell and its relationship to Bergmann glial processes was examined with Golgi staining and electron microscopy in the three cardinal planes in the developing cerebellar cortex of Macacus rhesus at various late fetal and early postnatal ages. After final mitosis the granule cell body transforms from a nearly round shape in the superficial zone of the external granular layer to a horizontal bipolar form with elongated processes oriented longitudinally to the folium, at the outer border of the molecular layer. Another descending process develops, and the cell soma becomes a pyramid flattened in the plane longitudinal to the folium. The nucleus moves into the descending process and the cell soma assumes a vertically oriented spindle shape while migrating among previously formed parallel fibers deeper in the molecular layer, and finally attains a round shape again when it lies deep to the Purkinje cell layer. During these transformations, the cell cytoplasm becomes more voluminous and contains a prominent Golgi apparatus, numerous free ribosomes, mitochondria, multivesicular and dense bodies, and fascicles of microtubules Longitudinally oriented microtubules concentrated in the vertical leading process disappear by the time the cell soma enters the granular layer. The slender trailing process loss most of its cytoplasmic organelles, acquires microtubules and together with the horizontal processes forms the characteristic T‐shaped axon. The axon forms synapses with Purkinje and stellate cell dendrites at a time when other granule cells are still migrating among them.During the entire course of their migration across the molecular layer, granule cells are directly apposed to vertically oriented Bergmann fibers belonging to the Golgi epithelial cells. The sequence of developmental stages indicates that Golgi epithelial cells are a type of protoplasmic astrocyte. The Bergmann fibers were present at all stages examined, and their constant apposition to granule cells suggests a role in the lartter's migration. Numerous electronluscent beady enlargements are seen along the fiber except at sites were the surface is in contact with migrating cells; probably these enlargements change position as the granule cells pass along the Bergmann fiber. Lamellate expansions also project from the main shaft of the glial fiber and envelop the synaptic sites on spines of Purkinje cell dendrites. These expansions seem more durable, and the young neuron appears to avoid collision with them by sprialling around the glial shaft during its descent to the granular layer. The neuron‐glia relationship apparently provides the necessary conditions for the migration of the young granule cell. Especially at late developmental stages when the molecular layer is more than 250 μ wide and is densely packed with highly oriented cell processes that have already established synaptic connections.

Crystalline inclusions in the nuclear envelope and granular endoplasmic reticulum of the fish spinal cord.

Crystalline inclusions were found in the nuclear envelope and granular endoplasmic reticulum of spinal cord oligodendroglia of the common guppy (Poecilia reticulata) and the lungfish (Polypterus enlicheri). A considerably increased incidence of these inclusions was noted in guppies with congenital and hereditary (sex-linked, recessive) lordosis. Identical crystalline inclusions were observed in protoplasmic and fibrous astrocytes, ependymal cells, and capillary endothelial cells of the spinal cord of the lordotic fish. The oligodendroglia in these fish also revealed a prominent alteration of the endoplasmic reticulum and Golgi apparatus, with the accumulation of dense (secretion?) granules and large amounts of electron-opaque material in markedly dilated sacs of the endoplasmic reticulum. The authors postulate that this alteration is caused by a genetic defect in the control mechanism governing the elaboration of this material in the lordotic guppy, with subsequent stasis and crystallization of this material.

Electron microscopic study of the reaction of the newborn rat brain to injury.

The reaction of the newborn rat brain following needle injury has been studied electron microscopically. Very few protoplasmic astrocytes are present in the newborn brain, and they do not appear to participate in the reaction. Instead, the extracellular space appears to be widened by an accumulation of oedema fluid. The microglial cells react remarkably rapidly; many macrophages containing whole cells as well as myelin figures and lipid droplets are found within 24 hours after the injury. At no time does a dense glial or connective tissue scar form. These reactions are quite different from those characteristic of mature brain tissue, and possible explanations for these differences are discussed.

Light microscopy of glial cells in turtles and birds.

Four classes of glial cells can be recognized in the central nervous system of turtles and birds on the basis of nuclear characteristics (methylene blue) and external morphology (Golgi technique). It seems likely that astrocytes and ependymal cells have a similar origin and function, but no evidence has been seen to indicate that transitional forms exist between astrocytes and oligodendrocytes or microgliacytes. Ependymal cells in the tectum and forebrain are covered by lamellate excrescences which are absent on cells in the spinal cord. Protoplasmic astrocytes are restricted to the gray matter. In the turtle they have an elongate shape characteristic of primitive elements, but stellate forms typical of mammals predominate in the bird. Fibrous astrocytes are abundant in the white matter. Endfeet are lacking in the turtle except on cells located near the pia; they are common for all elements in the bird and can sometimes be observed to outline the course of capillaries. Oligodendrocytes are identical to mammalian and amphibian forms. Small, round somata and long, thin processes are typical of types I and II while a tubular reticulum or membranous sheath characterizes type IV. The lack of a well defined somata and absence of transitional forms (type III) are compatible with the possibility that type IV is not a true cell type but corresponds to the inner cytoplasmic tongue of myelin. Microgliacytes are present in gray and white matter; they have a smaller overall size in the turtle and young chicken than in adult birds.

THE FINE STRUCTURE OF ASTROCYTES IN THE CEREBRAL CORTEX AND THEIR RESPONSE TO FOCAL INJURY PRODUCED BY HEAVY IONIZING PARTICLES

Normal and reactive astrocytes in the cerebral cortex of the rat have been studied with the electron microscope following focal alpha particle irradiation. The presence of glycogen and approximately 60-A fibrils identify astrocyte cytoplasm in formalin-perfused tissue. The glycogen particles facilitate the identification of small processes and subpial and perivascular end-feet. Both protoplasmic and fibrous astrocytes contain cytoplasmic fibrils and should be distinguished on the basis of the configuration of their processes and their distribution. Acutely reactive astrocytes are characterized by a marked increase in the number of glycogen granules and mitochondria from the first day after irradiation. These cells later hypertrophy and accumulate lipid bodies and increased numbers of cytoplasmic fibrils. The glial "scar" consists of a greatly expanded volume of astrocyte cytoplasm filled with fibrils and displays no signs of astrocyte death, reversion to primitive forms, or extensive multiplication.

Morphological and Functional Characteristics of the Central and Peripheral Neuroglia (Light Microscopical Observations)

Publisher Summary This chapter discusses the morphological and functional characteristics of the central and peripheral neuroglia. The primitive neural tube is lined by two cellular types: germinal cells and spongioblasts. The former gives origin to neuroblasts, while the spongioblasts give origin to the different types of neuroglia. At the level of the peripheral nervous system, the neuroglial cells evolve from the neural crest and possibly from the neural tube. Aniline techniques show only the nucleus and part of the cytoplasm and are, therefore, insufficient for the study of neuroglia. This insufficiency has been overcome by several techniques, among which those of Cajal, Hortega, and Golgi are invaluable. Under the term central and peripheral neuroglia, the chapter includes those non-neuronal cells of ectodermal origin—excluding the microglial cells of mesodermal origin—representing the reticulo-endothelial system of the nervous tissue. A description is given in the chapter of the morphological and structural pattern of the glioepithelial cells and the protoplasmic and fibrous astrocytes with their various types. An analysis is given of the fibrillar differentiation of astrocytes and its relation to blood vessels as well as the relation of oligodendrocytes to nerve fibers. The sympathetic and spinal ganglia have been described in the chapter with respect to the perisomatic and periexpansional glial cells.

A cell line from trypsinized adult rabbit brain tissue.

Trypsinized cerebral hemispheres, cerebellum or pial material from young adult rabbits were cultivated through many passages and for more than 6 months. Longterm cultures of the various tissues were undistinguishable and ultimately demonstrated a clearcut shift to hyperploidy. However, primary cultures and those in the first few passages showed a number of morphologically different cell types. Some were clearly recognizable as fibrous astrocytes, while others exhibited many characteristics of protoplasmic astrocytes. With the aid of time-lapse cinematography individual elements were found to undergo morphological transformation, even to losing their characteristic features. A third type of cell, clearly distinguishable from the others by its epithelial arrangement, probably was of endothelial origin. Ultimately the cell line obtained from all three sources bore a closer resemblance to the endothelial than to the astrocytic elements.

Electron microscopic observations of the central nervous system.

In order to establish criteria for the identification of the neural and glial cells of the central nervous system, sections of the brains and spinal cords of mice, rabbits, guinea pigs, and rats; and portions of tumors of the human brain have been examined by electron microscopy. Identification of neurons is made possible by the characteristic cytoplasmic picture, in which there is a distinct granular and less constant membranous ergastoplasmic pattern. In no other cell of the central nervous system is such a distinct granular component present in the ergastoplasm. The shape of the neuron in electron microscopic preparations is similar to that seen by light microscopy with several dendrites containing a similar cytoplasm arising from the perikaryon. Synapses are relatively common on the surface of the neuron and its dendrites. Microglial cells are relatively small and dense with few processes, and are arranged as perineuronal and perivascular satellites for the most part. Occasionally phagocytized material is present in their cytoplasm. The oligodendroglial cells are identifiable by their position as perineuronal satellites and in the white matter as cells arranged in rows. They have a uniformly round to ovoid nucleus with a pale cytoplasm, which has a sparse, finely granular component and a few small mitochondria. The processes are few and relatively straight when cut in longitudinal section. The predominant cellular type in an oligodendroglioma was similar, with a pale cytoplasm. The astrocytes are variable in appearance. Their nuclei are moderately large, irregularly ovoid, and the cytoplasm adjacent to the nucleus is finely granular and scant. In the protoplasmic astrocytes the cytoplasm has a complicated infolded arrangement with reduplication of the plasma membrane, numerous processes extending radially from the cell and rebranching. To a certain extent this same folded plasma membrane was noted in the fibrous astrocytes. However, their more distant processes were narrowed, relatively straight, and filled with numerous dense fibrils. The processes of the astrocyte often surrounded axons, and other cellular processes, and surrounded some vessels, while attaching to a part of the wall of another vessel. Proliferating cells in experimentally produced gliosis and in astrocytic neoplasms were similar in structure. The ependymal cells and the epithelium of the choroid plexus have a specialized surface with microvillous projections of the cytoplasm covered by the plasma membrane. Cilia in varying numbers are present in both epithelia.

Morphology of emetic chemoreceptor trigger zone in cat medulla oblongata.

Summary1. A hitherto unidentified structure in the medulla oblongata is described. It is an essentially non-neural zone situated between the ala cinerea and the vestibular complex and is contiguous medially with the area postrema which overlies the ala cinerea. The zone consists largely of fibroblasts and cells resembling protoplasmic astrocytes and astroblasts which have an abundance of vascular feet abutting on a dense network of blood vessels. Numerous nerve endings found in this zone are observed to connect with a loose fiber bundle which passes towards the nucleus of the fasciculus solitarius. 2. Experimental studies made with the ablation technic have yielded evidence that this structure is the anatomical framework of the medullary chemoreceptor trigger mechanism for the emetic center. Destruction of this chemoreceptor trigger zone in cats makes the animals refractory to the emetic effect of the intravenously administered cardiac glycosides-lanatoside C, scillaren A and ouabain-in doses which are kn...

Staining neuroglia with silver diammino-hydroxide after sensitizing with sodium sulfite and embedding in paraffin.

Pieces of brain are fixed in formalin ammonium bromide for about 4 days at room temperature, and given the following treatment: After washing, dehydrating and clearing, embed in paraffin, section and mount. Deparaffinize sections and pass through graded alcohols to water. Sensitize in 5% sodium sulfite for 2 hours, wash in distilled water and impregnate with silver diamminohydroxide solution 2-5 minutes at room temperature. Reduce in 2% formalin, wash in distilled water and tone in gold chloride. Fix in 5% hypo, counterstain with 1% picric acid, dehydrate and cover in balsam. Equally good results are obtained by impregnating with Hortega's strong silver carbonate. The microglia, oligodendroglia, fibrous and protoplasmic astrocytes in the cat, rabbit, newborn and adult human are successfully stained by this method.

CYTOGENESIS OF OLIGODENDROGLIA AND ASTROCYTES

Previous classifications dealing with the cytogenesis of neuroglia have formed a working basis for the study of the neoplasms of the glioma group. With the ever increasing interest in the field of neuro-pathology, largely owing to the advent of metallic staining methods, it will be necessary to modify these classifications from time to time in order to clarify the relationship between the embryonic and the pathologic cell types. In the evolution of primitive spongioblasts to adult autonomous neuroglia can be distinguished cell types comparable to those constituting the various neoplasms arising from these cells. A review of the literature on the phylogenetic development of neuroglia, in association with an ontogenetic study of their evolution in mammals, has suggested a possible simplification of the existing classifications. The term neuroglia, as now used, applies first to the so-called classic neuroglia; this term includes the fibrous and protoplasmic astrocytes which differ only in

THE HISTOLOGY OF NEUROGLIAL CHANGES FOLLOWING- CEREBRAL TRAUMA

Knowledge of the histology of the elements which go to form the connective tissue of the nervous system has been advanced in recent years principally owing to the labors of Ramon y Cajal and his followers in the institute of his name at Madrid. By the perfection of various histologic methods of impregnation of nerve tissue by gold and silver salts it is now possible to distinguish four different types of cells which make up the neuroglial or supporting tissue of the nervous system. Macroglia is the term applied to two of these types, which are large cells having processes radiating from a central cell body. On account of their general form the macroglia cells are now known as astrocytes, and the two types vary principally in the presence or absence of fibrils in their protoplasm, thence arising the terms fibrillary and protoplasmic astrocytes. The remaining two types of connective

ACUTE SWELLING OF OLIGODENDROGLIA

The introduction of a cytologic method which throws new light on anatomic structure is often the preliminary step toward a further knowledge of pathologic changes. Del Rio-Hortega's description of oligodendroglia 1 by the use of his silver carbonate method has made possible the following study which shows that these cells undergo a specific alteration which is often the only evidence of a pathologic process in the central nervous system. CLASSIFICATION OF THE INTERSTITIAL CELLS Under the heading of interstitial cells are included neuroglia and microglia cells. The most concise and complete modern description of neuroglia astrocytes is to be found in a publication by Cajal 2 in 1913. Much of this description was, of course, not new but the gold chloride method which he devised led him to certain definite conclusions. He gave a clearer picture of the fibrous astrocytes of the white matter and the protoplasmic astrocytes of