Culture techniques and glial-neuronal interrelationships in vitro

Antitrichomonal action of emodin in mice

Emodin, an active component contained in the root and rhizome of Rheum palmatum L. (Polygonaceae), was found to have an inhibitory effect on the pathogenicity of Trichomonas vaginalis in mice. Emodin delayed the development of subcutaneous abscesses due to infection of this parasite. Also, it cures the intravaginal infection of trichomonads through oral administration. In cell cultures, it reduced the cytotoxic effect of this parasite towards mammalian cells. This inhibition was markedly reversed by the coexistence of free radical scavengers, indicating the possible mediation of free radicals.

Trophic effect of angiotensin II, vasopressin and other peptides on the cultured ventral spinal cord of rat embryo

We studied trophic effects of angiotensin II, vasopressin, cholecystokinin, and oxytocin on explanted ventral spinal cord cultures from 13- and 14-day-old rat embryos. There was a significant neurite promoting effect of the spinal cord cultures by using angiotensin II, vasopressin, and cholecystokinin. Cholecystokinin had the most potent effect at any concentrations. The minimum effective concentration was 10(-8) M in angiotensin II and vasopressin and 10(-12) M in cholecystokinin, respectively. The effect of angiotensin II and vasopressin was dependent on concentrations. However, the rate and grade of neurite appearance did not correlate with the concentrations of cholecystokinin. Oxytocin had no neurotrophic effect at any concentrations. Our results demonstrated that angiotensin II, vasopressin and cholecystokinin have neurotrophic effects on the ventral spinal cord in cultures, and may be candidates for therapeutic trials of amyotrophic lateral sclerosis.

Cell culture of cryopreserved human fetal cerebral cortical and hippocampal neurons: neuronal development and responses to trophic factors

Past knowledge of the human brain at the cellular and molecular levels has come largely from studies of postmortem fixed tissue or by way of extrapolation from studies of lower mammalian species. The ability to study living human brain neurons would provide a new avenue for further insight into mechanisms operative in human brain development, function, and disease. The present study established procedures for the cryopreservation and culture of human fetal cerebral cortical and hippocampal neurons, and characterized the development of the cells in culture. The predominant cell type in both cortical and hippocampal cultures was pyramidal-like neurons that extended one long axon-like process and a few minor dendrite-like processes. Bipolar and stellate cells, as well as astrocyte-like glia were also present in cultures from both brain regions. Fibroblast growth factor (FGF), but not nerve growth factor (NGF), enhanced long-term neuronal survival in both cerebral cortical and hippocampal cultures. Immunocytochemistry demonstrated the presence of both FGF- and NGF-like immunoreactivities in neurons and glia, from both cerebral cortex and hippocampus, suggesting that these endogenous growth factors may play roles in human fetal brain development. The ability to cryopreserve large numbers of viable dissociated human fetal brain neurons, and subsequently study them in cell cultures, provides new opportunities to understand dynamic aspects of the human brain at the cellular and molecular levels.

Fibroblast growth factor inhibits epidermal growth factor-induced responses in rat astrocytes

The signals which regulate the proliferation of astrocytes have relevance to normal developmental processes, transformational loss of growth control, and reactive gliosis present in many brain disease states. We have studied, in primary cultures of rat astrocytes, a sequential interaction of two growth factors, epidermal growth factor (EGF) and fibroblast growth factor (FGF), which may be relevant to the brain in these conditions. EGF is a strong mitogen and stimulator of 2 deoxyglucose (2 DG) transport with no effect on plating of cells, and FGF is a lesser mitogen and 2 DG uptake stimulator. However, when FGF is given to the cells as a pretreatment, FGF strongly inhibits the ability of EGF to stimulate both DNA synthesis and 2 DG uptake. The inhibition of EGF stimulation by FGF is across the EGF dose-response curve, present at high and low culture densities, and stable for at least 3 days. Specificity is indicated by lack of inhibition by PDGF pretreatment and much less inhibition of fetal calf serum-induced stimulations than EGF-induced stimulation. Cell counts confirmed that the FGF pretreatment also inhibits EGF stimulation of cell division. Because of FGF brain derivation and angiogenic and neurotropic functions, it may serve as a regulator of EGF-astrocyte interactions in processes such as development, gliomatous transformation, and neural regeneration.

Inhibitory effect of l-ascorbic acid on the growth of astrocytes in cell culture

The effect of l-ascorbic acid on the growth of astrocytic cells in culture was investigated. l-Ascorbic acid produced a concentration-dependent reduction of the growth of astrocytes, both in normal and tumor cells. The effect of l-ascorbic acid was similar to that of the relative acidification of the medium, except in treated concentrations greater than 10(-6) M. The effects produced by both l- and d-forms of ascorbic acid were the same. The inhibitory effect of l-ascorbic acid at greater concentrations was partially prevented by oxidized glutathione and increased by the large concentration of reduced glutathione. This result suggests that l-ascorbic acid possesses the ability to inhibit the growth of astrocytic cells in culture through the acidification of the medium at small concentrations and/or the antioxidative properties of this compound at larger concentrations.

Comparison of oligodendrocytes grown in neocortex and spinal cord aggregate cultures

Mechanically dissociated cells of mouse central nervous system (CNS) (neocortex and spinal cord) form spherical aggregates in rotation culture and develop into populations of mature neurons and glial cells. Synapses and myelination of axons are evident in these aggregates although onset of these processes differs between aggregate types. In this study neocortex aggregates display synapses at 2 weeks in culture but do not demonstrate myelination of axons until 8 weeks. Spinal cord aggregates demonstrate myelinated axons at 2 weeks in culture although there are few synapses evident. The difference in myelination onset is due in part to the development of predominantly perineuronal oligodendrocytes in neocortex aggregates compared to the development of interfascicular oligodendrocytes in spinal cord aggregates. Both types of oligodendrocytes exhibit light, medium and dark categories and both cell types are capable of myelinating axons in culture.

Studies of neurotransmitter chemistry of central nervous system neurons in primary tissue culture

Primary tissue culture methods have been applied to various areas of the central nervous system, including cerebral cortex, spinal cord, cerebellum, hippocampus, hypothalamus, striatum, mesencephalon, lower brain stem and retina. Experimental studies in vitro involving central neurotransmission are discussed here. Information gleaned from such studies impacts on neurotransmitter identification, neuronal development, patterns of receptor distribution, peptidergic transmission, transmitter metabolism, synaptogenesis and the regulation of synaptic development.

Primary retinal and cortical glial cell cultures: effects of medium and serum on attachment and growth

Glial cells of the retina are anatomically distinctive and are thought to contribute importantly to retinal electrophysiology. However, no adequate preparation exists for studying them in isolation, in vitro. This report provides guidelines for primary retinal glial cultures (RET) and compares basal tissue culture features with those for neocortical glia (CX) and the well-studied rat glial line, C6. Cell attachment and growth of RET, CX, and C6 are unique. These differences are explored by the use of specific media and sera. RET attachment, unlike that for CX or C6, was far more sensitive to medium than serum. RET cells attached least quickly, CX most quickly; 4 hr after plating 20% of RET remained unattached. RET growth was poor and relatively insensitive to medium. In contrast, growth of CX or C6 was medium dependent. Serum had substantial effects on the growth of all three glial lines. Pig, goat, horse, and dog sera were particularly effective, often comparing favorably to fetal calf serum. Medium or serum optimal for cell attachment, typically, was not optimal for growth and serum effects were more dramatic than those of medium. By all measures, CX and C6, both derived from brain, were more alike than were the two rabbit primaries, CX and RET. The data reveal substantial differences between presumably similar cells and indicate a need for an empirically based choice of both basal-salt media and serum to optimize specific aspects of cell development in culture.

Towards an improved serum-free, chemically defined medium for long-term culturing of cerebral cortex tissue

The present study describes a series of experiments which have led to a substantially improved serum-free, chemically defined medium (CDM) for long-term culturing of reaggregated fetal rat cerebral cortex tissue. A reduction of the original medium concentrations of the hormones insuline, T3 and corticosterone, on the one hand, and an enrichment of the medium with the vitamins A, C and E, the unsaturated fatty acids linoleic and linolenic acid, and biotin, L-carnitine, D(+)-galactose, glutathione (reduced) and ethanolamine, on the other hand, formed the most important chemical adjustments of the medium. With the aid of this CDM (encoded R12), the light- and electron microscopic architecture of the tissue could be kept in a good condition (superior to that seen earlier in serum-supplemented medium) up to 23 days in vitro. From that time on, the neuronal network lying between the reaggregates degenerated for the largest part, while a portion of the large neurons (probably pyramidal cells) plus some of the neuronal network within the reaggregates degenerated too. This degeneration process continued during the following weeks, but the reaggregates nevertheless retained most of their mass, so that both small and large neuronal cell bodies (visible in transparent regions at the edge of the reaggregates) remained in good condition up to at least 103 DIV. Stout, thick nerve bundles interconnecting the reaggregates, also survived up to this point. Electron microscopic evaluation of such 'aged' reaggregates revealed degenerating as well as healthy regions. The latter had indeed retained healthy-looking pyramidal and non-pyramidal neurons, embedded within a dense neuropil which was often traversed by myelinated axons. The numerical synapse density in such selected, healthy tissue regions reached its maximum during the sixth week in vitro, followed by a rapid decrease and a stabilization at about half the peak values. The present culture system has opened the possibility for performing controlled quantitative studies on the relationship between structure and function of cerebral cortex tissues during development and aging, on its dependence on nutrients, hormones and drugs, and on special factors synthesized by the tissue and released into the nutrient medium.

Trophic interactions between astroglial cells and hippocampal neurons in culture

Astroglial cells in primary culture release factors into the medium that promote the growth and prolong the survival of rat hippocampal neurons in vitro.

Proliferative and migratory activity of glial cells in the partially deafferented hippocampus

The proliferative response of the glial cell population of the adult rat hippocampus deafferented by unilateral lesion of the entorhinal cortex was studied using 3H-thymidine autoradiography. Two experimental paradigms were used, involving: (1) intraventricular 3H-thymidine injection at a number of post-lesion intervals with sacrifice six hours later and (2) intraventricular injection at 30 hours post-lesion with sacrifice at 6, 96, or 192 hours later. The first increase in the number of labeled glial cells was obtained at 20 hours post-lesion and was confined to areas of degenerating axons. By 30 hours a large and uniformly dense proliferative response was observed throughout the ipsilateral, and medial aspects of the contralateral, hippocampus encompassing both deafferented and intact regions. Cell division continued through 50 and 65 hours post-lesion particularly in directly deafferented regions, but diminished to control levels by 80 hours. Although oligodendroglia and astrocyte-like cells were sometimes found to have incorporated the label the most common proliferative element within the hippocampus corresponded to previous light microscopic descriptions of "microglial" cells. The experiments using thymidine injection given at the peak proliferative period followed by survival periods of varying lengths indicated that a progressive redistribution of labeled nuclei occurred resulting in an accumulation of labeled cells in the zones of deafferentation. Multiple division of cells within these areas as well as the migration of nuclei from non-deafferented regions was found to contribute to this effect. The possible involvement of glial proliferation with other morphological effects of deafferentation, including the sprouting response of intact afferents, is discussed.

Studies of cultured human and simian fetal brain cells. I. Characterization of the cell types

Explant cultures of the cerebral subventricular zone and cerebellar external germinal layer were established from fetal human, rhesus and cynomolgus monkey brains. Using comparable gestational ages, the morphogenesis of the cultures from these three sources was almost indistinguishable. Four cell types were distinguished by electron microscopy. Germinal cells or neuroblasts were confined largely to the primary explant and extended into a transitional outgrowth region. Astrocytes, which stained for glial fibrillary acidic protein, grew out of the explants and these could be distinguished from the large, mesenchymal epithelioid cells. A fourth cell type, not identified in previous studies, had the ultrastructural characteristics of an oligodendrocyte, but did not produce myelin in these culture conditions.

The Schwann cell: a reappraisal of its role in the peripheral nervous system

The Schwann cell is clearly essential for the maintenance of axonal integrity--yet we know little of the regulatory mechanisms governing its behaviour at any point in its life cycle, or of the nature of its interaction with the axons with which each Schwann cell is associated. In this article, the involvement of the Schwann cell in myelinogenesis, aspects of Schwann cell-axon recognition, the experimentally-demonstrable 'bipotentiality' of the Schwann cell and the possible functional significance of the proliferative response of the Schwann cell that occurs after injury are discussed. The isolation and preparation of pure populations of Schwann cells which can be injected or implanted into a damaged nerve, coupled possibly with the localized application of drugs to manipulate the cellular responses to injury within the nerve, represent interesting areas of recent research which may be applied in planning methods of therapeutic intervention in the treatment of peripheral nerve injury.

Differentiation of corpus callosum glial cells and factors influencing their maturation in vitro

1. Explants of Corpus callosum (c. c.) from 12-day-old rats were cultivated under different experimental conditions. 2. Migration and differentiation is activated by the presence of neighbouring explants, toward which glial cells predominantly migrate. Glial cells migrate if closely adhering to the supporting collagen and the process of differentiation is enhanced by presence of underlying cell layers. 3. Migratory activity of glial cells decreases and is delayed with age of donors. Migrating cells have a similar appearance as in cultures from 12 days old donors. The presence of immature types of glial cells in c. c. of adult animals was proved. 4. Glucose was found to be an adequate metabolical substrate, utilisation of glucose being lower than in cultivated neurons. In the absence of glucose or serum in the medium, neither migration nor differentiation of glial cells was observed. 5. The addition of embryonal extract and embryonic brain extract enhanced only initial stages of cell migration and differentiation.

Cell-to-cell transfer of glial proteins to the squid giant axon. The glia-neuron protein trnasfer hypothesis

The hypothesis that glial cells synthesize proteins which are transferred to adjacent neurons was evaluated in the giant fiber of the squid (Loligo pealei). When giant fibers are separated from their neuron cell bodies and incubated in the presence of radioactive amino acids, labeled proteins appear in the glial cells and axoplasm. Labeled axonal proteins were detected by three methods: extrusion of the axoplasm from the giant fiber, autoradiography, and perfusion of the giant fiber. This protein synthesis is completely inhibited by puromycin but is not affected by chloramphenicol. The following evidence indicates that the labeled axonal proteins are not synthesized within the axon itself. (a) The axon does not contain a significant amount of ribosomes or ribosomal RNA. (b) Isolated axoplasm did not incorporate [(3)H]leucine into proteins. (c) Injection of Rnase into the giant axon did not reduce the appearance of newly synthesized proteins in the axoplasm of the giant fiber. These findings, coupled with other evidence, have led us to conclude that the adaxonal glial cells synthesize a class of proteins which are transferred to the giant axon. Analysis of the kinetics of this phenomenon indicates that some proteins are transferred to the axon within minutes of their synthesis in the glial cells. One or more of the steps in the transfer process appear to involve Ca++, since replacement of extracellular Ca++ by either Mg++ or Co++ significantly reduces the appearance of labeled proteins in the axon. A substantial fraction of newly synthesized glial proteins, possibly as much as 40 percent, are transferred to the giant axon. These proteins are heterogeneous and range in size from 12,000 to greater than 200,000 daltons. Comparisons of the amount of amino acid incorporation in glia cells and neuron cell bodies raise the possibility that the adaxonal glial cells may provide an important source of axonal proteins which is supplemental to that provided by axonal transport from the cell body. These findings are discussed with reference to a possible trophic effect of glia on neurons and metabolic cooperation between adaxonal glia and the axon.

Nerve growth factor action on membrane permeation to exogenous substrates in dorsal root ganglionic dissociates from the chick embryo

An experimental system has been described, in previous studies, where the ability of chick embryo dorsal root ganglionic cells to incorporate radiouridine into RNA declines in the absence of nerve growth factor (NGF), and is promptly restored by delayed supply of the factor. Following these early and fully reversible events, further NGF deprivation causes progressive irreversible damage. The early decline in RNA labeling and its reversion by NGF are accompanied by similar changes in the accumulation of acid-soluble radioactivity from the exogenous radiouridine substrate. In the present study, it is shown that the NGF-dependent accumulation of "soluble" radiomaterials is independent from, and responsible for, the NGF-dependent alterations in RNA labeling. Both changes are measurable with labeled cytidine and guanosine, as well as uridine, and in all cases accumulation of acid-precipitable and acid-soluble radioactivities are strictly proportional to each other. The acid-soluble responses to NGF are not prevented by actinomycin D or cycloheximide treatments, demonstrating that they require neither ongoing syntheses of RNA or protein nor prior effects of NGF on them. Chromatography of acid-soluble radiopools showed that the NGF-dependent increase was not due to a distortion in the intracellular phosphorylation of uridine; but involved corresponding increases in all the radiouridine derivatives including UTP. The time patterns of the acid-soluble response were comparable to those of the RNA labeling response, and maximal NGF effects occurred within minutes of its presentation. Finally, 2-deoxyglucose and a-aminoisobutyric acid, but not leucine, showed NGF-dependent accumulation patterns similar to those of the 3 nucleosides. It is proposed that regulation of selected membrane permeation properties could be the primary process through which NGF exerts its trophic role.