Nervous system-specific proteins in developing rat cerebral cells in culture

Receptor-binding specificity of the human parainfluenza virus type 1 hemagglutinin-neuraminidase glycoprotein

The hemagglutinin-neuraminidase (HN) glycoprotein is utilized by human parainfluenza viruses for binding to the host cell. By the use of glycan array assays, we demonstrate that, in addition to the first catalytic-binding site, the HN of human parainfluenza virus type 1 has a second site for binding covered by N-linked glycan. Our data suggest that attachment of the first site to sialic acid (SA)-linked receptors triggers exposure of the second site. We found that both sites bind to α2-3-linked SAs with a preference for a sialyl-Lewis(x) motif. Binding to α2-3-linked SAs with a sulfated sialyl-Lewis motif as well as to α2-8-linked SAs was unique for the second binding site. Neither site recognizes α2-6-linked oligosaccharides.

Binding of influenza viruses to sialic acids: reassortant viruses with A/NWS/33 hemagglutinin bind to alpha2,8-linked sialic acid

We have examined the specificity of binding of A/NWS/33 hemagglutinin (HA), exploring the effects of fucosylation, changing the Gal-GlcNAc linkage between the second and third sugars, and binding affinity for alpha2,8-linked sialic acid. The HA of A/NWS/33(HA)-Tokyo/67(NA) (NWS-Tok, H1N2) virus binds to 3'-linked sialyllactose with 10-fold higher affinity than 3' sialyllactosamine and 3-fold higher affinity than 6' sialyllactosamine. The P227H mutation in A/NWS/33(P227H)(HA)-A/Memphis/31/98(NA) (NWS-Mem/98, H1N2) results in sevenfold lower affinity for 3' sialyllactose, but binding to 6' sialyllactosamine is unchanged. The apparent switch from 3' to 6' specificity is solely due to a loss of Siaalpha2,3 binding. Fucosylation of the third sugar and changing the linkage between second and third sugars had little effect on binding by NWS-Tok, but marked effects on A/NWS/33(P227H)(HA)-tern/Australia/G70c/75(NA) (NWS-G70c, H1N9) and NWS-Mem/98. NWS-Tok, NWS-G70c, and NWS-Mem/98 bind to alpha2,8-bisialic acid with high affinity. NWS-Mem/98 can also bind to alpha2,8-trisialic acid, but with lower affinity. Together, these data show that alpha2,8-linked sialic acid, fucosylation of the third sugar, and linkage between the second and third sugars could play important roles in allowing efficient virus binding to its host cell. The finding that influenza viruses have the potential to bind to alpha2,8-linked sialic acid is a new influenza virus-receptor interaction pathway.

A time-dependent increase in glial fibrillary acidic protein expression and glutamine synthetase activity in long-term subculture of the GL15 glioma cell line

1. Astrocytes are the most numerous cellular elements in the central nervous tissue, where they play a critical role in physiological and pathological events. The biological signals regulating astrocyte growth and differentiation are relevant for both physiology and pathology, but they are still little understood. 2. Using a poorly differentiated glioma cell line, GL15, we investigated whether, in long-term subculture, this could upregulate the expression of glial fibrillary acidic protein (GFAP), as described in some rodent astrocyte cell lines. Under the same culture conditions, we investigated glutamine synthetase (GS) activity, growth-associated protein (GAP)-43 expression, and expression of several neutrotrophic factors. 3. A dramatic increase in GFAP expression was evidenced by Western blotting during progressive in vitro growth of GL15 cells. GS specific activity was also upregulated in long-term culture. The time spent in vitro by GL15 cells did not affect GAP-43 and neutrophic factor BDNF and NT3 expression as revealed by RT-PCR analysis. 4. Our results suggest that, in GL15, GFAP and GS genes may have common or integrated regulatory mechanisms elicited at the cell confluency which could be relevant for both astrocyte physiology and astrocyte pathology. These mechanisms are not involved in GAP-43 and neutrophic factor BDNF and NT3 expression.

Isolation and immunohistochemical localization of a chondroitin sulfate proteoglycan from adult rat brain

A chondroitin sulfate proteoglycan called PGM1 has been isolated from the particulate fraction of adult rat forebrain. Delipidation of the material, solubilization of proteoglycans in guanidinium chloride, precipitation at low ionic strength, and final extraction at pH 5.0 were used for its isolation. Proteoglycans were subjected to further purification by diethylaminoethyl-cellulose chromatography. Individual components were separated by gel filtration. PGM1 appeared to be a high-molecular-weight chondroitin sulfate proteoglycan, capable of strong interaction with hyaluronic acid. It was finally isolated by gel filtration on Ultrogel AcA 22 in the presence of 4 M guanidinium chloride. Monospecific antibodies obtained in rabbits against the purified molecule did not cross-react with other brain proteoglycans. Immunocytochemical techniques revealed an almost unique association of this compound with axons, particularly those known to contain neurofilaments. However, not all these axons and all parts of these axons contained PGM1. This component was not detectable in liver, intestine, spleen, kidney, lung, heart, skin, hair, lens, and muscle, a finding suggesting a specificity for the nervous tissue. This component is expressed in neural cell cultures. Despite the preservation of the neuronal specificity, it seems to lose its specific axonal localization in vitro.

Neuronal and glial markers of the central nervous system

This brief review evaluates the expression of cell-specific markers on differentiated neural cells and, where necessary, on their developing precursors. Within these limitations only the commonly used markers are discussed and those deemed unequivocal are only briefly appraised.

Rapid separation of oligomers of polysialic acid by high-performance liquid chromatography

A rapid procedure utilizing high-performance liquid chromatography was developed for the separation of homooligomers of sialic acid (N-acetylneuraminic acid). The method utilizes the anion exchanger Mono-Q HR 5/5 and can resolve sialyl oligomers with degrees of polymerization (DP) from 2 to 20 in 25 min. Previous methods required 1 to 9 days. Recoveries are quantitative and the method can be used either analytically to analyze the enzymatic digestion products of polysialic acid or semipreparatively to prepare sialyl oligomers of defined length. The method is potentially useful for analyzing other anionic oligosaccharides.

Protein changes in the rat's prefrontal and "inferotemporal" cortex after exposure to visual problems

The proteins D2 (N-CAM) and D3, both markers for brain neuronal membranes, MM, a marker for mitochondria, and CM, a cytoplasmic marker protein, were studied in the prefrontal (anteromedial) cortex and "inferotemporal" (Te2) cortex of rats by crossed immunoelectrophoresis. Three experimental groups were investigated: Rats trained to criterion in a visual pattern discrimination test (learning), those run as yoked controls and finally, rats kept in individual cages and not subjected to any training (passive). Statistical analysis indicated that behavioral procedures and marker proteins contributed significantly to the variation. Further analysis indicated that the significant changes occurred in the D3- and MM-protein and that both the learning and yoked control groups had significantly increased concentrations of these two proteins when compared to the passive group. Furthermore, the concentration of D3- and MM-protein in the yoked control group was significantly higher than that of the learning group. The results seem to indicate that changes in concentration of these proteins can be more easily related to the activity of "searching for an adequate behavioral strategy" than to the formation of an "engram".

Purification and characterization of the D2 cell adhesion protein: analysis of the postnatally regulated polymorphic forms and their cellular distribution

The developmentally regulated, D2 cell adhesion protein has been purified from 10-12 day old rat synaptosomes by sequential hydroxyapatite chromatography, wheat germ lectin affinity chromatography and gel filtration. The purified protein was found to be composed of two polypeptide components of 200 and 140 kd molecular weight which comprised 0.5-1.0% of total synaptosomal membrane protein. Lysine-Sepharose affinity chromatography could further separate the purified protein into sialic acid-rich and sialic acid-poor forms. Immunoblot analysis of whole brain homogenates and synaptosomes with an antiserum raised against the purified protein (anti-D2) revealed the presence of three immunologically related polypeptides of 200, 140, and 115 kd molecular weight. These polypeptides, which appeared as a diffuse zone (greater than 200 kd) in fetal material, were found to developmentally regulate by altering their relative expression. This was particularly marked in the 200 kd component. Furthermore, the 200 kd polypeptide appeared to be neuron-specific as both the 140 and 115 kd components were common to synaptosomes and primary cultures of astrocytes.

Development of neuronal markers in aggregating fetal rat telencephalon cells cultured in the presence of triiodothyronine

The concentrations of the general neuronal markers D2-protein (N-CAM), D3-protein and neuron specific enolase (NSE) in reaggregating cultures of fetal rat telencephalon cells were affected by the presence of 30 nM triiodothyronine in the defined culture medium. The extent of normal developmental changes were enhanced by triiodothyronine, as demonstrated by crossed immunoelectrophoresis. From 13 to 19 days in culture, the concentration of D2-protein decreased, and the concentrations of both D3-protein and NSE increased. Nerve growth factor (NGF) was without effect on the development of these general neuronal markers. However, as shown previously both triiodothyronine and NGF increased the activity of choline acetyltransferase, a marker for cholinergic neurons. The results suggest an enhanced overall differentiation of several types of telencephalon neurons in the presence of triiodothyronine, and a specific stimulation of cholinergic telencephalon neurons by NGF.

Localization of the neuronal cell adhesion molecule D2-protein in explant cultures of dorsal root ganglia by use of the colloidal-gold immunocytochemical technique

The localization of the neuronal cell adhesion molecule (N-CAM), D2-protein, in explant cultures of rat dorsal root ganglia was investigated at the electron microscope level by the use of 17-nm-diameter colloidal gold particles coated with swine anti-rabbit immunoglobulin molecules. The minimum amount of IgG needed to coat the gold particles and the pH optimal for coating were both determined. Immunocytochemical studies of cultures revealed the binding of gold particles to the neuronal plasma membrane, especially on neuritic processes. Schwann cells were not labeled, and the level of unspecific background staining was very low.

Factors involved in expression of neuron-specific and non-neuronal enolase activity in developing chick brain and in primary cultures of chick neurons

The effect of various factors affecting non-neuronal enolase (NNE) and neuron-specific enolase (NSE) was investigated in developing brain of two different chick strains, in primary cultures of pure neurons and of mixed cultures of neuronal and glial cells. NNE and NSE activities reached their maximum at an earlier stage of brain development in the fast growing Hybro strain than in the Leghorn strain. In pure neurons cultured during 6 days, NNE was stimulated by hydrocortisone in presence or in absence of serum. Dibutyryl cyclic AMP (diBcAMP) stimulated NNE only in serum-free medium. NSE activity was increased by glial cell-conditioned medium in presence of serum and by removal of serum from the medium. Hydrocortisone and diBcAMP had no effect on NSE. In mixed cultures of neurons and glial cells both enolase activities were raised in absence of serum. Hydrocortisone and diBcAMP had no effect. Steroid hormones, insulin and serum albumin also modify both enolase activities in pure neurons and in mixed cultures of neurons and glial cells. Our results suggest that NNE and NSE are regulated separately by various factors involved in nerve cell maturation.

Effects of undernutrition and thyroid state on the ontogenetic changes of D1, D2, and D3 brain-specific proteins in rat cerebellum

Disturbances in metabolic balance brought about by alterations in thyroid state and undernutrition during early life had a marked effect on the concentrations of the brain-specific proteins, D1, D2, and D3 in the developing rat cerebellum. In normal rats, the concentrations of D1 and D3 increased and that of D2 decreased during the first 3 weeks after birth. In the hyperthyroid state a small but consistent advancement was observed in the developmental curves of these proteins. The hypothyroid state caused a marked retardation in the maturational pattern of D1 and D2 but not of D3. In undernutrition, at 6 days the concentrations of D1 and D3 proteins were higher than in controls, but thereafter the developmental increase was markedly delayed for D1 only. The concentration of D2 was normal at 6 days, but after the first week a marked retardation was observed in the maturational pattern of this protein in undernourished rats. In addition, the "anodic-immature" form of D2 predominated in 6-day-old controls, but this was gradually replaced by a "cathodic-mature" form which progressively became the dominant form of D2 in 35-day-old rat cerebellum. The developmental switch in terms of the two forms was also advanced in hyperthyroidism and retarded in thyroid deficiency and undernutrition. Furthermore, daily treatment of hypothyroid rats with physiological doses of thyroxine from birth restored the concentrations of D1 and D2 to normal, but that of D3 was increased above control levels, indicating differences between the proteins in their sensitivity to mechanisms of control by thyroid hormone. Also, the overall effects of undernutrition were markedly different from those of hypothyroidism.

Cell-free synthesis of the D2-cell adhesion molecule: evidence for three primary translation products

The D2-cell adhesion molecule (D2-CAM) is a membrane glycoprotein that is involved in cell-cell adhesion in the nervous system. To study the biosynthesis of D2-CAM we have translated free and membrane-bound polysomes from rat brain in vitro in the rabbit reticulocyte lysate system. D2-CAM was exclusively synthesized on membrane-bound polysomes. The primary translation products of D2-CAM were three polypeptides of apparent molecular weights 187,000, 134,000, and 112,000. No interconversion between these polypeptides was detected. In contrast to previous suggestions, we conclude that all three D2-CAM polypeptides are primary translation products. When translating polysomes from embryonic and postnatal rat brain, we found that the relative amounts of the three polypeptides synthesized varied with age. Their molecular weights, however, were not age-dependent.

Selective culture of neurons from rat cerebral cortex: morphological characterization, glutamate uptake and related enzymes during maturation in various culture media

Dissociated cerebral cortex of fetal rat was grown in a serum-free, chemically defined medium (CDM) (containing insulin, progesterone, estradiol, transferrin, putrescine, selenium and 15 mM KCl) and compared with cultures grown in a medium containing 20% fetal calf serum (SCM). Neurons survived well using either medium, but in the serum-free medium the cellular population was exclusively neuronal (at 96%), while glial cells began to proliferate after one week in the SCM. The various cellular morphologies are described in the present report and the presence of immunological markers characteristic of neurons was investigated. Autoradiographic experiments have been performed after incubation with various putative neurotransmitters and we have shown the presence of a strikingly high proportion of glutamatergic neurons in these cultures. Glutamate high affinity uptake was also greatly increased in neuronal cultures maintained in a CDM compared to a SCM, especially in young cultures. The development of different enzymes involved in the metabolism of glutamate was also studied; the specific activity of glutaminase increased in culture and was found to be higher in a CDM than in a SCM, while the inverse was true for glutamine synthetase. The relative proportion of both enzymes in neurons compared to glial cells was opposite, as neuronal cultures had higher levels of glutaminase and glial cultures were enriched in glutamine synthetase activity. It seems that the proportion of glutamate-neurons increases when cultured in a CDM compared to a SCM and we suggest that this culture procedure may provide a purely neuronal population enriched in mature glutamatergic neurons. It may thus be useful for future in vitro studies on glutamate and GABA metabolism in neurons.

Changes in the expression of a neuronal surface protein during development of cerebellar neurones in vivo and in culture

The expression of the neurone-specific D2 protein changes both quantitatively and qualitatively during development in vivo and in cultures of cerebellar nerve cells. The total D2 content per unit protein shows a two-fold increase in vivo from birth to postnatal day 6, after which it declines progressively to about 50% of the maximal value. This increase can be accounted for by an immature form of the protein anodic D2 being preferentially expressed at the early stages of cerebellar development. After postnatal day 9 this form gradually switches to a mature form cathodic D2. This switch can be mimicked by neuraminidase treatment, suggesting a developmental loss of sialic acid from the D2 protein. In freshly isolated cells the total D2 content per unit protein is only 30% of that in the corresponding intact tissue from 8-day-old cerebella, but it increases rapidly during the first 8 days of culture to levels similar to those of the equivalent age in vivo. The switch from anodic D2 to cathodic D2 also occurs at a faster rate in culture, probably reflecting the culture conditions that favour differentiation. The changes in the expression of D2 during development of cerebellar nerve cells in culture suggest that anodic D2 is preferentially expressed on nerve cells that are proliferating, migrating, or in the initial stages of differentiation, whereas cathodic D2 is associated with differentiated neurones. The transition between the two forms appears to occur during the formation of interneuronal contacts.

The neuronal adhesion protein D2 in differentiating aggregates of brain cells

The D2-protein is a high molecular weight protein involved in interneuronal adhesion. The concentration of D2-protein was measured both in aggregates of fetal rat telencephalic cells cultured in a chemically defined medium and in developing forebrain. Both the concentration of the D2-protein and the degree of sialylation were changed in the cultures in parallel with the corresponding values obtained from postnatal forebrain. In the cultures the highest specific concentration of D2-protein was observed after 12 days in culture. This value was 2.7 times higher than the average value of adult rat forebrain. Antibodies to D2-protein have previously been shown to inhibit fasciculation of neuritic fibers extending from cultured explants of sympathetic ganglia. We investigated the effect of such antibodies on the differentiation of aggregating telencephalic cells. By adding surplus antibodies to the cultures from day 11 to day 16 we were able to decrease the specific concentration of D2-protein on the neurons by 53% measured at day 19. The decrease was not compensated fully even after further 10 days in the culture. Although the concentration of D2-protein was decreased during the period of synaptogenesis no change was found in the specific concentration of a marker of mature synapses, the D3-protein. Thus, in this culture system synaptogenesis could proceed to an unimpaired extent in the presence of a decreased concentration of a putatively involved adhesion molecule. However, the specific concentration of two markers of myelination, 2',3'-cyclic nucleotide 3'-phosphodiesterase and myelin basic protein, were both increased, suggesting an antibody-induced stimulation of myelination in the cultured aggregates.

In bovine brain extracts, RNAs are active factors that stimulate the proliferation of chick neuroblasts in culture

Extract was prepared from bovine brain by treatment with chloroform-methanol, drying of the precipitate, and successive extractions of the powder with Tris buffer. Influence of this extract on neuroblast proliferation in culture was tested. Neuroblast cultures were prepared from brain hemispheres of 6-day-old chick embryos. Cell proliferation was quantified by incorporation of 3H-thymidine. The brain extract was able to stimulate the proliferation of the neuroblasts in culture. In order to purify the factor responsible of this effect, the brain extract was subjected to diethylaminoethyl (DEAE)-cellulose chromatography and gel filtrations. By UV spectrography and destruction of the activity with RNAase and KOH, it was shown that in the extract RNAs are responsible for at least a part of the effect on the proliferation of neuroblasts in culture. Brain RNA is not specific for this effect, since mouse ribosomal RNA was also active. The effect could be actually elicited by some nucleotides.

A testis antigen related to the brain D2 adhesion protein

The localization of an antigen immunochemically crossreactive with the rat brain interneuronal adhesion molecule, D2-protein, has in testis been demonstrated by immunoelectrophoresis and immunocytochemistry. This D2-like antigen is localized to spermatids and residual bodies in testis, but it is absent both from spermatogonia and mature spermatozoa and from Sertoli cells. By immunoperoxidase electronmicroscopy D2-like antigen was observed in the head region posterior to the acrosomal membrane of late spermatids. In the nervous system D2-protein is involved in interneuronal adhesion. It is suggested that D2-like antigen in testis may be involved in a similar adhesion between late spermatids and Sertoli cells during spermiation.

Role of glycoproteins in neuronal differentiation. Inhibition of neurite outgrowth and the major cell surface glycoprotein of murine neuroblastoma cells by a purified tunicamycin homologue

Mouse neuroblastoma cells in culture can be induced to differentiate morphologically by serum deprivation or by dibutyryl cyclic AMP (db-cAMP), e.g. they appear flattened, adhere more firmly to the culture substratum and extend long neuritic processes, and thus represent a widely used model system for neuronal cells. This differentiation is accompanied by modulation of cell surface components, such as the induction of a high molecular weight (HMW) glycoprotein (200 kD). We have studied the role of glycoproteins in the process of neuronal differentiation, using a purified homologue of the antibiotic tunicamycin (Al-tunicamycin) and neuroblastoma N115 cells grown in culture. Al-tunicamycin markedly inhibited (up to 60-75%) the incorporation of radioactively labelled sugars into cellular proteins of differentiating neuroblastoma cells. Concomitantly, the cells altered their morphology, they became rounded and less adhesive and retracted their neurites. Changes in the appearance, glycosylation and electrophoretic mobility of several cellular and secreted glycoproteins were observed, when cells were incubated in the presence of Al-tunicamycin. The most striking effect of Al-tunicamycin on the composition of cellular glycoproteins was the marked reduction in appearance of the 200 kD glycoprotein. The findings suggest that glycoproteins and in particular the neuron-specific 200 kD glycoprotein, are related to morphological differentiation processes, mainly to cellular adhesion and neurite outgrowth.

Analysis of normal and abnormal amniotic fluid cells in vitro by cinemicrography

Time-lapse cinemicrography has been used to study cell behaviour and movement in long- and short-term amniotic fluid cultures from various types of fetus. These included several with a neural tube defect (9 anencephalics, 5 spina bifidas, 2 encephaloceles), 1 with an abdominal wall lesion (omphalocele) and 9 controls with no open lesion. In short-term (less than 3 days) amniotic fluid cultures from normal fetuses, non-adherent squamous cells dominate, but there is a small population of cells which, in the longer term (approximately 4 weeks), will form colonies of epithelioid and fibroblastic cells. In addition, there is a further group, called 'AF' by Hoehn et al. (1974), which have the ability to form syncitial strands and are often multinucleated; these cells seem to be trophoblastic in origin. In contrast to the controls, short-term anencephalic cultures contained many adherent cells; these were mainly latex-particle-phagocytosing macrophages and neural cells. In long-term cultures, the neural cells dominate and differentiate into a range of recognizable forms whose type and behaviour seem to depend on cell density, time in culture and extent of cell-cell contacts. In the spina bifida and encephalocele cultures, there were initially far fewer adherent cells than in the anencephalic ones, but, after approximately 2 weeks in vitro, a range of neural cell types could be recognized in addition to those seen in the controls. In the context of prenatal diagnosis, the presence of neural cells certainly indicates that the fetus has a NTD, but the difficulty of standardizing culture conditions implies that any differential diagnosis on the basis or morphology and movement will be difficult. If, as seems likely, the AF cells of Hoehn et al. (1974) are indeed trophoblastic, amniotic fluids from the second trimester may provide a useful source of these cells.

Immunocytochemical demonstration of the 'neuronal membrane marker' the D2-glycoprotein in human embryos

The regional distribution and cellular localization of the D2-glycoprotein in human embryonic tissues have been investigated by immunocytochemistry at the light microscope level in sections of human embryonic brain, spinal cord, some neural crest derivatives, muscle, liver and skin. the majority of neuronal membranes exhibited a positive staining reaction for D2 already in the earliest (15 mm crown-rump length) embryo examined. By 20 mm crown-rump length and later a positive staining associated with membranes of embryonic muscle, bile canaliculi, epithelial cells of the skin and choroid plexus was also observed. The D2 which is immunochemically related to the neuronal cell adhesion molecule (N-CAM), is supposed to be involved in cell adhesion phenomena. We find this suggested function less compatible with demonstrated localization of the D2-glycoprotein.

D2-protein in PC12 pheochromocytoma cells after nerve growth factor stimulation

The rat brain D2-protein has previously been shown to play a role in interneuronal adhesion Monospecific antisera against this protein reacted with adrenal medulla cells and with PC12 pheochromocytoma cells as demonstrated by indirect immunofluorescence. Upon stimulation by nerve growth factor the PC12 cells extend neurites. These neurites were shown to contain D2-protein both by immunofluorescence and by crossed immunoelectrophoresis. The findings substantiate the close relationship between neurons from the central nervous system and both the PC12 cells line, as well as adrenal medulla cells.

Molecular heterogeneity and structural evolution during cerebellar ontogeny detected by monoclonal antibody of the mouse cell surface antigen BSP-2

The monoclonal antibody anti-BSP-2 defines a set of glycoproteins present on the neuronal cell surface in dissociated mouse cerebellar cultures and on neurons and astrocytes in sections of the mouse cerebellum. This antibody was used in the present study to characterize the antigens recognized in cerebellar cultures and in the developing and adult mouse cerebellum in vivo. In extracts from cerebellar cultures and from late postnatal or adult cerebellum, the anti-BSP-2 antibody reacted with a triplet of glycosylated polypeptide chains of 180,000, 140,000 and 120,000 mol. wt. Early postnatal cerebellum contained a different form of BSP-2 antigen which migrated as one broad or several closely spaced diffuse bands in the 190,000-250,000 mol. wt. region of SDS polyacrylamide gels. During cerebellar ontogeny, the adult pattern emerged gradually between postnatal days 5 and 13. The cellular expression of the BSP-2 antigen was studied by immunohistochemistry on sections of the developing cerebellum. At postnatal day 3, the antigen was found mainly on cell bodies and fibers of the Bergmann glia and on astrocytes of the granular layer. Immature granule cells of the outer zone of the external granular layer lacked the antigen, but they appeared to acquire the antigen during their migration to the internal granular layer. At postnatal day 13, the immunofluorescence pattern was not different from the one seen in the adult. These results suggest that the neonatal 190,000-250,000 mol. wt. form of BSP-2 may at least in part be expressed by astroglial cells and they show a close correlation between the emergence of the adult forms of the antigen and the appearance of labeled granule cells in the internal granular layer. In vitro degradation implying cleavage of sialic acid residues, but probably also proteolysis and/or cleavage of different glycans converted the neonatal form of BSP-2 into the triplet pattern and ultimately into a p120 component. Neuraminidase digestion of the adult antigens produced small molecular weight shifts without converting one band into the other, but endogenous enzyme activities were capable of degrading the p180 and p140 bands by converting them into the p120 protein. Our findings support the idea that distinct, but structurally similar surface glycoproteins created by post-translational modifications from a common precursor molecule may be expressed by different cell types or during different developmental stages. As shown by sequential immunoprecipitation experiments, BSP-2 and the rat neuronal membrane protein D2 may belong to the same family of surface glycoproteins.

Specific recognition of the neuronal cell surface by an antiserum raised plasma membrane preparations of immature rat cerebellum

A brain specific antiserum was prepared by immunizing rabbits with a crude membrane fraction from 8-day old rat cerebella. In immunofluorescence studies the antiserum labeled the perikarya and processes of cultured cerebellar neurones. In contrast, other cell types, encountered in cerebellar cultures including astrocytes, endothelial cells and fibroblasts, were consistently unstained. The antiserum when used in crossed immunoelectrophoresis with Triton X-100 solubilized brain extracts reacted predominantly with one antigen that could be identified as the D2 protein.

Synaptic proteins in frontal and control brain regions of rats after exposure to spatial problems

Synaptic proteins D1, D2, D3, synaptin and 14-3-2, as well as the glial protein glutamine synthetase, were measured by crossed immunoelectrophoresis in the anteromedial (prefrontal) cortex, occipital (visual) cortex and the anterior and posterior parts of the neostriatum of rats. The 3 experimental groups consisted of rats trained to criterion in a spatial delayed alternation, those run as yoked controls and, finally, rats kept in individual cages and not subjected to any training. Statistical analysis showed that two variables: behavioral procedures and brain regions, had a significant effect. Their interaction was also significant. Further analysis revealed that only in the prefrontal cortex of the yoked control animals was there a significant decrease of the synaptic membrane proteins D1, D2 and D3. Thus, particular behavioral treatment seems capable of affecting synapses in a specific 'association' cortical area. The change is more easily related to the amount of 'work' than to formation of 'memory trace' within the critical area.

Neuron-specific and non-neuronal enolase in developing chick brain and primary cultures of chick neurons

Developmental changes of the neuron-specific enolase (NSE) and the non-neuronal enolase (NNE) were determined in pure neuronal, or mixed cultures of neuronal and glial cells, prepared from brains of 8-day-old chick embryos, as a function of cellular development with time in culture. The modifications observed in culture were compared to those measured in brain during the development of the nervous tissue in the embryo and during the post-hatching period. In the whole brain, the total enolase activity increases progressively until the adult level, the NSE appears only 4 days before hatching. The total enolase activity of pure neurons increases until 8 days of culture but the NSE never appears during this period. Mixed cultures of neurons and glial cells present an increase of total activity until 14 days of culture and neuron-specific form of the enzyme can be observed after 6 days of culture. Our results suggest that NSE appears only in the functional brain and is expressed in cultivated neurons only when glial cells are present simultaneously.

Nervous system-specific protein D2 associated with neurite outgrowth in nerve cell cultures

Dissociated cerebral cells from fetal rat brain were grown in culture for various periods. After 12 days in culture the nervous system-specific surface membrane protein D2 reached both maximal specific concentration and maximal amount. Moreover, most of this D2 protein was in the perinatal form with high electrophoretic mobility. The amount of perinatal D2 protein possibly followed the amount of neurites in this system. D2 protein was also found in 2 neuroblastoma C-1300 clones: Neuro 2a and NB 41A3. By addition of gangliosides, Neuro 2a cells could be induced to differentiate and form processes, and D2 protein was significantly increased. However, in both differentiated and undifferentiated neuroblastoma cells D2 protein was present in the adult form with slow electrophoretic mobility. NB 41A3 cells were unaffected by gangliosides and D2 protein was not changed. Thus ganglioside treatment of Neuro 2a tumor cells was followed by a cellular response only partly similar to developmental events concomitant to differentiation of primary cells.

Glial fibrillary acidic protein and induced differentiation of glia in vitro

Glial fibrillary acidic protein (GFAP), a protein largely limited to astrocytes, is abundant and uniformly distributed in spindle-shaped human astrocytoma cells in early explants in culture but becomes predominantly perinuclear as the cells assume a "flat" irregular (epithelioid) shape. GFAP moves from the predominantly perinuclear site to the periphery of the cells and into the developing processes of those cells in which differentiation has been induced by serum starvation in minimum essential medium (MEM). This redistribution of GFAP does not occur in a small percentage of cells, specifically those in which low serum concentration fails to induce morphologic differentiation. In Eagle's basal medium (BME), which, combined with serum starvation, fails to induce differentiation, there is no shift of GFAP. Spontaneously differentiated cells in media wtih 10% serum, differ morphologically from cells with induced differentiation; in the former the cell bodies are smaller and the processes better developed and longer. GFAP in the spontaneously differentiated cells is distributed throughout the cytoplasm and the processes and is more abundant than in cells with induced differentiation. The results suggest the following: (1) GFAP redistribution plays a role in glial differentiation and process formation. (2) There are differences between spontaneous and induced differentiation. (3) There is some critical difference between MEM and BME in the induction of differentiation. (4) A heterogeneous expression of GFAP is implied in the variable staining of cells grown from different primary tumors. Also it is hypothesized that GFAP may play an inhibitory role in highly plastic movements of astrocytes but not in extension and retraction movements of processes.

Stimulation of chick neuroblast proliferation in culture by brain extracts

Chick neuroblasts from 6-day-old embryos were grown on a collagen substrate in minimum Eagle's medium supplemented with 5% horse serum. We found that [3H]thymidine incorporation in these cultures decreased drastically from day 2 to day 3 after seeding. Addition of brain extract from 8-day-old chick embryos (CBe8) to the nutrient medium after 24 hours of culture elicited a very important stimulation of [3H]thymidine incorporation. Extracts of brains from adult animals were much less effective. It was shown that the increase of tritiated-thymidine incorporation reflected proliferation of neuroblasts in the culture, at least between day 2 and 4. The activity of the brain extracts was destroyed by trypsin treatment, which suggests that the factor responsible for the stimulation of the proliferation is a polypeptide. The CBe8 and the brain extract of adult chicken (CBa) were fractionated by gel filtration. An active fraction was eluted at a volume indicating an apparent molecular weight of roughly 70,000. At that stage of the study results suggest that a polypeptide (tentatively called neuroblast proliferation factor, NPF) present in the embryonic chick brain extract, is a proliferation factor for chick neuroblasts in primary culture.

Neuronal membrane D2-protein during rat brain ontogeny

The D2-protein exists as a sialylated form in fetal and in perinatal rat brain, and as a desialylated form in adult rat brain. By crossed immunoelectrophoresis the concentrations and amounts of these froms were investigated during ontogeny of both forebrain and cerebellum. The concentration of sialylated D2-protein reached two peaks during ontogeny. The first peak occurred in forebrain around embryonic day 13, and in cerebellum just after birth. In both brain areas it coincided with the periods major neuronal migration. The second peak occurred in forebrain around postnatal day 6 and in cerebellum around postnatal day 20, during the initial period of synaptogenesis in both brain areas. Moreover, the desialylated form of D2-protein was found only in postnatal rats and it increased to a slight maximum at postnatal day 25 in forebrain, and postnatal day 35 in cerebellum. The findings are discussed in relation to the possible role of D2-protein as an adhesion molecule.

Immunocytochemical localization of the D2-protein in rat retina

The localization of the D2-protein in rat retina was investigated by quantitative immunoelectrophoresis and by immunoperoxidase staining on both the light microscopic and the electron microscopic level. The D2-protein was enriched 1.4 times in retina compared to whole brain and its was located to most presynaptic and some postsynaptic membranes in the inner an outer plexiform layers. Moreover, the D2-protein was located on the cell membrane confining the ciliary neck region connecting the inner and the outer segments of photoreceptor cells. Thus, on the electron microscopic level, the D2-protein is not restricted to the presynaptic membrane, but it is also found in other parts of the neuronal surface membrane.