Unusual profiles in organotypic cultures of central nervous tissue

Generation and use of primary rat cultures for studies of the effects of ethanol

In vivo studies are ideal for identifying the phenomenology of ethanol toxicity and teratology. They are limited in being able to explore cellular and molecular mechanisms of action. Two types of culture models have proven to be very instructive: monolayer primary cultures of dissociated cells and organotypic slice cultures. Dissociated cell preparations have the advantage of being enriched populations of cells, whereas the organotypic cultures have the advantage of providing normal cell associations. Details for the methods used to generate these preparations are described. As ethanol is a volatile liquid, the success of a culture model depends upon stabilizing the ethanol content in the culture medium. A method to maintain the ethanol concentration is described.

The fine structure of gliomatosis cerebri

The ultrastructural features of five biopsies of gliomatosis cerebri (GC) are described. Four main types of tumour cells are seen: anaplastic astrocytes poor in organelles with a variable amount of glial microfilaments; atypical oligodendrocytes with scanty cytoplasm in which microtubules are present; intermediate forms with aboundant cytoplasm rich in organelles, with microtubules and microfilaments; and small cells with round nuclei and a very scanty rim of cytoplasm. In two cases several concentrically folded cytoplasmic lamellae of glial processes were arranged either around themselves or around the perikaryon of other cells. This ultrastructural study indicates that GC is a neoplastic process of small undifferentiated elements, transitional forms of astroglia (to oligodendroglia) and anaplastic cells of astrocytic origin in all stages of development.

Ultrastructure of cerebellar capillary hemangioblastoma. VI. Concentric lamellar bodies of endoplasmic reticulum in stromal cells

Concentric lamellar bodies of endoplasmic reticulum (CLB) were found in the stromal cells of all five cases of cerebellar capillary hemangioblastoma studied ultrastructurally. CLB were often present in the stromal cells with voluminous loose cytoplasm, particularly those close to the capillaries. They were rarely seen in small stromal cells with abundant organelles and stromal cells distended by large lipid droplets. Small lipid droplets were usually present in the center or in the vicinity of CLB. Vesiculation and vacuolization of the lamellar arrays of CLB were common. Some vacuolized CLB were transformed into large, varying-shaped, multilocular bodies. Some stromal cells were markedly distended by numerous large vacuoles derived from CLB. Granulo-fibrillary material was frequently present in the vacuolized lamellae. Discharge of vacuoles into the interstitial space was observed. It is suggested that CLB is one of the characteristic ultrastructural features of the stromal cells. They may represent a special type of hyperplasia of the endoplasmic reticulum, but their functional significance is not known.

Aqueductal lesions in 6-aminonicotinamide-treated suckling mice

Suckling mice which received a single intraperitoneal injection of 6-aminonicotinamide on the 5th postnatal day, consistently developed hydrocephalus. During the early stages of hydrocephalus (7-9 days after injection), aqueductal lesions were characterized by edematous ependymal and subependymal cells, and spongy changes in the periaqueductal area, which resulted in aqueduct stenosis. Later stages (after 20 days post-injection) showed that these edematous changes totally subsided, leaving an obliterated aqueduct which was similar to that of human congenital hydrocephalus. At the completely obliterated area, ultrastructural investigation disclosed a normal-looking neuropil but no aqueductal lumen. In the remaining ependymal cell, increased intermediate filaments and lipid droplets occurred. These data suggest that acute ependymal cell degeneration during the perinatal period may result in the profile of aqueduct "agenesis" in human congenital hydrocephalus.

Myelin deficient (shimld) mutant allele: morphological comparison with shiverer (shi) allele on a B6C3 mouse stock

A new B6C3 stock of shimld mutant mice is compared in terms of behavior and CNS morphology with both a B6C3 shi stock and reports on other shimld animals. Defects of B6C3 shimld myelination seen at postnatal day 21 (P-21) are comparable to those in B6C3 shi with respect to % axons myelinated, sheath thickness, errors in the wrapping and targeting of myelin and abnormal oligodendrocyte shape. The two mutations are similarly expressed in cerebellar organotypic cultures. However, the major dense line (MDL) is present in a few shimld myelin sheaths at P-21 and a few sheaths show myelin basic protein by immunocytochemistry, while neither phenomenon is seen in shi at this age in the same CNS regions. Shimld mice survive their disease significantly better than shi. The shimld stock currently under study elsewhere differs from this B6C3 stock in that MDL was reported only in older animals, and behavior and survival were severely compromised.

The organization of astrocytes in organotypic mouse spinal cord culture: an electron microscope study

The organization of astrocytes in myelinated culture of mouse spinal cord tissue was analysed ultrastructurally and compared with the pattern in vivo. Astrocyte cell bodies and their processes, connected by punctate adhesions and gap junctions, formed a continuous layer around the entire explant. Throughout the parenchyma, thin astrocytic processes penetrated the neuropil, separated neurons, and invested some synaptic complexes. Others formed flattened sheets and contacted directly with the basal surface of ependymal cells. In the absence of mesenchymal elements, astrocytes in vitro occasionally possessed fragments of basal lamina on the surface of the explant and around minute intercellular spaces. Except for an incomplete basal lamina, these findings indicate that astrocytes in vitro are organized in a manner essentially identical to the situation in vivo.

Specificity of histiotypic organization and synaptogenesis in reaggregating cell cultures of mouse cerebellum

The fine structure of reaggregating cultures of cells from 6- to 7-day-old mouse cerebellum was studied at intervals between 3 and 21 days in vitro (DIV). The resulting aggregates consisted mainly of small neurons (granule, stellate and basket cells), neuroglial cells and their processes. Large neurons were rarely present. By 7 DIV the previously loosely packed components had tightened into a more compact mass. A peripheral plexiform layer had formed which had many fine axons arranged into fascicles of parallel fibers. Deep to this zone was a cellular region containing clusters of neurons interspersed with small areas of neuropil. Axosomatic synapses appeared on neurons which resembled stellate or basket cells but not on granule cells. Axo-dendritic synapses formed in the neuropil of the cellular zone and, less frequently, in the outer plexiform layer. After 3 weeks glial cell processes had increased in volume at the expense of neurons. When cerebellar cells were cultured with cells from pons and medulla, which are normal sources of mossy fiber input, aggregates formed in which synaptic glomeruli were found. They were not seen in aggregates containing cells from retina and olfactory bulb cultured with cerebellum. Our observations suggest: that natural histogenetic mechanisms persist after dissociation and reaggregation of cerebellar cells resulting in a separation of an outer, 'molecular'-like layer from an inner granule cell layer and that neurons retain specificity of their synaptogenic capabilities both with regard to appropriate cell types and the morphological form that the synapses take.

Cultured neonatal rat oligodendrocytes elaborate myelin membrane in the absence of neurons

We have utilized transmission electron microscopy to study oligodendrocyte-enriched cell cultures established from dissociated neonatal rat cerebra by the method of McCarthy and de Vellis [1980]. Cells were examined after 14 and 26 days in vitro. The overall morphology of the cells from cultures at both time periods was similar and consistent with previous reports of light (immature) oligodendrocyte fine structure. The cells contained an eccentrically located nucleus, prominent Golgi regions, numerous free ribosomes, and microtubules. Large numbers of processes with varying diameter were also observed. There was some indication of cytoplasmic maturation from the younger to the older cultures. The most important feature of the 26-day cultures was the large quantity of intercellular membranes which were shown to be continuous with oligodendrocyte processes. These membranes often exhibited the appearance of "loose myelin" and were therefore not normally compacted. Layers of membrane with the morphologic appearance of compact myelin were observed on an occasional oligodendrocyte perikaryon or process. This finding necessitates a reevaluation of the widely held theory that oligodendrocytes are not able to elaborate myelin in the absence of neurons.

Cerebellar macroneurons in microexplant cell culture: ultrastructural morphology

Microexplant cell cultures of fetal rat cerebellum contain essentially monolayer networks of Purkinje cells, occasional granule cells and neurons from the deep nuclei. The neurons and occasional filament-packed glial cells develop on top of a sheet of flattened, non-neuronal cells. In the absence of extrinsic input to the cerebellum and greatly reduced numbers of granule cells, the Purkinje cells develop a stunted and non-oriented dendritic arbor similar to that observed in agranular cerebella. The Purkinje cell dendritic branches, however, are spine-covered. Although the spines are not enveloped by glia and are only rarely contacted by a presynaptic bouton, most spines display a patch of electron-dense material resembling a postsynaptic membrane specialization. The Purkinje cells develop synaptic interactions among themselves and with granule cells. The ultrastructural morphology of boutons derived from both Purkinje cells and large neurons of the deep nuclei, identified after intracellular injection of horseradish peroxidase, is consistent with that observed in vivo. The present study indicates that cerebellar Purkinje cells survive and differentiate in a culture system in which individual neurons are accessible for electrophysiological and morphological analyses.

Reinnervation of peripheral nerve segments implanted into the rat central nervous system

Newly transected or denervated segments of isogeneic rat tibial nerve were implanted into the rat midbrain and sampled at weekly intervals up to 6 weeks post-operation. By 3 weeks, the peripheral nervous system (PNS) grafts were well-vascularized and contained Schwann cells, axons associated with Schwann cell processes, and macrophages. From 3 to 6 weeks, many axons within both the fresh and predegenerated grafts were myelinated by Schwann cells. The nerve fiber arrangement within the implant was similar to that of regenerating peripheral nerve in situ. The central nervous system (CNS) border of the implant was clearly demarcated by a rim of astrocytes behind which was a layer of regenerating oligodendrocytes and axons. Extending from the CNS margin were radial bridges of astroglial tissue which apprarently guided regenerating axons into the implant. Between the CNS and the PNS implant, abundant collagen deposition was present. The findings suggest that regenerating CNS axons grow via astroglial bridges into transplanted PNS tissue and are capable of stimulating the implanted Schwann cells to form myelin. Even Schwann cells deprived of axonal contact for prolonged periods were still capable of PNS myelin formation.

Chronic relapsing experimental allergic encephalomyelitis: CNS plaque development in unsuppressed and suppressed animals

Central nervous system (CNS) lesion morphology has been studied in inbred Strain 13 guinea pigs sensitized for chronic relapsing EAE in which the disease was either left to develop (unsuppressed) or was suppressed with injections containing myelin basic protein (MBP). Pathologic changes correlated well with clinical activity. In unsuppressed chronic EAE animals, active clinical disease was invariably matched by acute inflammation in the CNS. In more chronic states, the CNS displayed fibrosis and remyelination while relapses showed the CNS to contain recent changes superimposed upon old lesions. In animals in which the disease was suppressed by injections of MBP, clinical signs did not develop. However, some early subclinical changes were seen morphologically. These lesions were able to remyelinate early on and there was no progression in lesion formation. Apparently, therefore, MBP had a beneficial effect upon the course of the disease and had promoted structural repair. It thus appears that MBP therapy might be one effective approach for the prevention of chronic relapsing EAE. The findings should prove relevant to future MBP trials in multiple sclerosis.

A simple method for examining organotypic CNS cultures with Nomarski optics

This paper describes a method for examination of living organotypic cultures of CNS with Nomarski differential interference-contrast optics. Cultures grown in Maximow assemblies, which promote the best differentiation of the tissue but are optically faulty, are transferred for Nomarski observation to a simple sandwich chamber which combines the optical perfection of the usual sandwich chamber with the flexibility and safeguarding of sterility characteristic of the Maximow assembly. Thus cultures can be transferred repeatedly between their maintenance and observation chambers. In the resulting microscopic images, it is possible to visualize delicate unmyelinated fibers, myelinated cell bodies and other features which are normally impossible to demonstrate in living cultures as well as to improve the images of other structures such as large neuronal perikarya and myelinated axons.

Changes in the mitochondria in the initial part of the axon during regeneration

The initial part of the axon including the axon hellock, the initial unmyelimated segment and the beginning of myelinated axon was studied electron microscopically during regeneration, 1--30 days following a crush lesion of the rat hypoglossal nerve. Large mitochondria reaching 1.1 mum in diameter, with abundant cristae and dense granules in the matrix were observed between days 3--21. They formed clusters in the initial myelinated segment of the axon. End-to-end contacts and ribosomes around them were very often visible. The large mitochondria exhibited strong succinate dehydrogenase and NAD - H2 diaphorase activities. The relationship between the appearance of large and active mitochondria in the initial part of the axon and the elevated axonal transport during regeneration of the peripheral nerve is also discussed.

Ultrastructural observations on human cerebral capillaries in organ culture

The use of an organotypic-in the strictly literal meaning of the word, nervous tissue culture device has allowed the identification and ultrastructural study of various types of developing capillaries in human cerebellum and olfactory bulb in vitro. Most capillaries were similar to those already described by other authors or by us, in human or animal embryos and fetuses. Large Type I Capillaries. Their luminal diameters were greater than 8 microns. The basement membranes were thin and discontinous. Numerous interendothelial junctions were either plate-like attachments or contained pentalaminar zones. Type II Capillaries. Their lumina were between 2 and 8 microns in diameter. The basement membranes were wider than those of type I capillaries and were sometimes continuous. The interendothelial junctional complexes of type II capillaries included pentalaminar portions. Many simple or complex vascular sprouts (type IV and V capillaries) had small or non-patent lumina. Their basement membranes were absent or very thin and discontinuous. Their interendothelial junctions were similar to those of type I capillaries. Some of the less frequently encountered capillary types seen in developing human nervous tissue were absent in culture. Some pathological features were seen-especially in long-term cultures-in type I and II capillaries containing degenerating blood cells or processes sometimes obviously related to histiocytic cells. They consisted mainly of an accumulation of microfilaments and modifications of the rough endoplasmic reticulum in the endothelial cells. These pathological changes did not modify the main characteristics of the capillaries. The origin of the vascular sprouts, the exact nature of the interendothelial junctions and the significance of the pathological changes are discussed. This model may prove useful for the study of cerebral vasculogenesis, the development of the blood-brain barrier and the physiological or pathological properties of the human brain capillaries in tissue culture.

[External temporal biopsy in a case of infiltrating limbic glioma: study of astrocytic membranous wrapping whorls (author's transl)]

An intracranial hypertension was found at autopsy to be due to a limbic infiltrating glioma. A cortical temporal biopsy had been done 14 months before, whose ultrastructural results are reported. Membranous whorls, made of two dense membranes with a variable separative space are seen around neurones, dendrites, axons, synapses and oligoglial cells; they derived from astrocytes and are joined by 2 types of cell junctions: gap-junctions and puncta adherentia. Relations between reactive and tumoral gliosis are discussed.