Specific expression of inositol 1,4,5-trisphosphate 3-kinase in dendritic spines

Ultrastructural localization of inositol 1,4,5-trisphosphate 3-kinase (IP3K) in the rat cerebral cortex and hippocampus was studied immunohistochemically. In both regions, the major structure expressing a high level of IP3K was the dendritic spines of pyramidal neurons, where immunoreactivity was associated with the spine apparatuses and plasmalemma. The postsynaptic densities showed the most intense labelling. Taking into account the results of our previous observations, which demonstrated the restricted localization of the enzyme in the dendritic spines of Purkinje and basket cells in cerebellum, IP3K may be localized specifically in dendritic spines in various regions of the central nervous system, and involved in synaptic signal transduction at the spines.

Human astrocytes and cytokines: tumor necrosis factor alpha and interferon gamma do not promote astrocytic proliferation

Astrocyte cell cultures were established from human fetal brains and exposed to human recombinant tumor necrosis factor alpha (TNF alpha) and human recombinant interferon gamma (IFN gamma), and the proliferative response was assessed by bromodeoxyuridine-immunostaining technique. TNF alpha showed an inhibitory activity, while IFN gamma induced a slight increase in the number of astrocytes undergoing cell division. However, in both experiments differences were not statistically significant. Previous studies have demonstrated that TNF alpha and IFN gamma are potent mitogens for adult astrocytes in both in vivo and in vitro conditions. Our results suggest that in developing brain the immunomodulatory activity of cytokines, TNF alpha and IFN gamma, is different from that observed in adult brain.

Developmental profile of inositol 1,4,5-trisphosphate 3-kinase in rat cerebellar cortex: light and electron microscopic immunohistochemical studies

Developmental expression and intracellular distribution of inositol 1,4,5-trisphosphate 3-kinase in the rat cerebellar cortex were studied immunohistochemically. Immunoreactivity appeared first at postnatal day 1 in the rostral region of the cerebellum and by day 15 had extended throughout the whole cerebellum, being localized in the Purkinje cell layer. Shortly after the expression of the enzyme in each Purkinje cell, the labelling showed a tendency to accumulate in the dendrites in a fine granular pattern. Electron microscopy revealed that immunoreactivity was present in the Purkinje dendritic trunks with accentuation in the distal segments during the early postnatal period, thereafter becoming concentrated in the dendritic spines at later developmental stages. Labelling was associated mainly with the plasmalemma, including the postsynaptic densities and open coated vesicles, and the subplasmalemmal vesicles of the smooth endoplasmic reticulum. Immunoreactivity was also evident in the perisomatic processes of immature Purkinje cells, which are transient projections synapsing with climbing fibers. In developing Purkinje axons, immunoreactivity was accentuated in the distal segments, associated with the plasmalemma and synaptic vesicles. These results suggest that inositol 1,4,5-trisphosphate 3-kinase is involved in the dendritic arborization and subsequent spine synaptogenesis of Purkinje cells, and that the developing presynaptic nerve endings of these cells are another functional site for the enzyme.

Tedisamil blocks a calcium-dependent potassium channel in cultured motoneurons

A calcium-dependent potassium channel K(Ca) has been isolated in mouse motoneurons. With physiological concentrations of potassium across inside-out patches, a 100 pS K(Ca) channel was activated when the bath solution of Ca2+ was in excess of 1 microM. Introduction of the drug tedisamil, a blocker of repolarizing potassium channels in cardiac cells, at concentrations in the range 0.2-10 microM, caused a dose-dependent decrease in the mean open times for K(Ca). The drug action was consistent with open channel block of K(Ca) with an onward (blocking) rate constant of 6 x 10(7) M-1 s-1. Tedisamil, at concentrations of 1 microM and 5 microM, also blocked the K(Ca) channel when applied to outside-out patches with a similar potency as found with internal application. A large conductance K(Ca) channel in hippocampal neurons is also blocked by a number of putative Class III antiarrhythmic drugs, including tedisamil; thus, these agents may have utility in the characterization of the properties of K(Ca) channels in various cells.

Differential distribution of cellular forms of beta-amyloid precursor protein in murine glial cell cultures

The production and localization of cell-associated forms of beta-amyloid precursor protein (APP) of Alzheimer's disease was investigated in primary cultures of mouse glial cells. In both oligodendrocytes and astrocytes, immunofluorescence staining with an antibody against the carboxy terminus of APP revealed an intense cytoplasmic immunoreactivity. Immunoblotting of the cell extracts detected differences in the composition of APP between oligodendrocytes and astrocytes, notably the abundance of 107 kDa subtype in oligodendrocytes. Differences in immunoblot patterns were also noted between two buffer-insoluble, membrane-rich subcellular fractions of the glial cells, nuclear-mitochondrial and microsomal; the 119 kDa APP was enriched in the former, whereas the 73 and 115 kDa APPs in the latter. The results suggest that each APP subspecies may play a distinct functional role in different cell types and subcellular fractions.

Leukemia inhibitory factor (LIF) mediated increase of choline acetyltransferase activity in mouse spinal cord neurons in culture

The effects of leukemia inhibitory factor (LIF) on choline acetyltransferase (ChAT) enzyme activity in cultured mouse spinal cord neurons were examined. The administration of LIF to cultures at concentrations of 10 U/ml and higher enhanced ChAT activity approximately 3- to 4-fold in cultured spinal cord neurons. Among neurotrophic factors tested, basic fibroblast growth factor (bFGF) and insulin-like growth factor I (IGF-I) stimulated the development of ChAT activity but to a smaller extent than LIF, while interleukin 3 (IL-3), interleukin 6 (IL-6) and nerve growth factor (NGF) showed no apparent effect on ChAT development. Our results indicate that LIF, which has not been known to have any trophic effect on mammalian central nervous system neurons to date, acts as a potent differentiation factor for ChAT in cholinergic neurons of mouse spinal cord in culture.

beta-Amyloid precursor protein of Alzheimer's disease in cultured bovine oligodendrocytes

The production of beta-amyloid precursor protein (beta APP) in cultured oligodendrocytes isolated from adult bovine brains was examined by immunohistochemistry and immunoblotting. Immunostaining of oligodendrocytes with antibodies specific for the carboxy terminus of beta APP demonstrated positive immunoreactivity of oligodendroglial cytoplasm. Immunoblot analysis of cellular extracts detected two distinct bands with estimated molecular weight of 118 and 105 kDa. The amount of these beta APP subspecies increased considerably in response to their attachment to the poly-L-lysine substratum.

Ultrastructural localization of inositol 1,4,5-trisphosphate 3-kinase in rat cerebellar cortex

Subcellular localization of inositol 1,4,5-trisphosphate 3-kinase in the rat cerebellar cortex was studied immunohistochemically using a monoclonal antibody. Electron microscopy revealed intense immunoreactivity in the dendritic spines of Purkinje cells forming synapses with the parallel fibers, climbing fibers and recurrent collaterals of Purkinje cell axons. The labelling was associated with the hypolemmal cisternae, surrounding matrix and plasmalemma including the postsynaptic densities. Weaker immunoreactivity was present in the dendritic spines of basket cells and in certain segments of Purkinje cell recurrent collaterals. The postsynaptic regions of the dendritic trunks of Purkinje and basket cells were negative. These results indicate that inositol 1,4,5-trisphosphate 3-kinase is distributed amongst the spines of various synaptic relations with different electrophysiological properties, and that axon terminals of certain cell types are another functional site for the enzyme.

Calbindin D-28k and parvalbumin immunohistochemistry in developing rat retina

The developmental profiles of two calcium-binding proteins, calbindin-D28k (CaBP) and parvalbumin (PV), were investigated immunohistochemically in the developing rat retina. CaBP-immunoreactivity appeared first on embryonic day 17 in the horizontal, amacrine and ganglion cells; on embryonic day 21 in the inner plexiform layer; and on post-natal day 6 in the outer plexiform layer. The reaction intensity had increased to its maximum level by post-natal day 10. PV-immunoreactivity was first noted on embryonic day 19 in the amacrine and ganglion cells and reached its maximum on post-natal day 10. Two distinct subpopulations of amacrine cells were clearly recognized after post-natal day 6; one was positive for CaBP and the other for PV. Some morphological differences were noted between the two.

Development of inositol 1,4,5-trisphosphate 3-kinase immunoreactivity in cerebellar Purkinje cells in vivo and in vitro

Development profiles in vivo and in vitro of inositol 1,4,5-trisphosphate 3-kinase (IP3K) were investigated immunohistochemically in the cerebellar Purkinje cells. In in vivo preparations of rat cerebellum, IP3K immunoreactivity appeared in Purkinje cell bodies and dendrites shortly after birth, increased rapidly by postnatal day 5, and was subsequently confined to their dendritic processes by day 20. The appearance and shift of IP3K immunoreactivity in Purkinje cells showed an identical time course even when Purkinje cells were placed under culture conditions commencing on day 0, suggesting that Purkinje cells have their own biological clock on the expression of IP3K in the absence of external influences.

Immunohistochemical study of A2B5-positive ganglioside in postmortem human brain tissue of Alzheimer disease, amyotrophic lateral sclerosis, progressive supranuclear palsy and control cases

Localization of gangliosides positively stained by the monoclonal antibody A2B5 was investigated in postmortem brain tissue of Alzheimer disease, amyotrophic lateral sclerosis (ALS), progressive supranuclear palsy (PSP) and control cases. In control cases, A2B5-staining was granular, appearing in selective neuronal populations. In the neocortex, the A2B5-positive neurons were distributed mainly in deep cortical layers. In the cerebellum, A2B5-positive structures were detected in processes extending from the Purkinje cell layer into the molecular layer. In Alzheimer cases, many neurofibrillary tangles, neuropil threads and dystrophic neurites were strongly A2B5-positive. In addition, aggregations of A2B5-positive granules were detected in some neurons lacking neurofibrillary tangles. Alterations of A2B5-positive gangliosides were also detected in ALS and PSP cases. In ALS cases, A2B5-positive granules were aggregated in Betz cells of the precentral gyrus. In PSP cases, globose-type neurofibrillary tangles were also strongly A2B5-positive. The results indicate that A2B5-positive gangliosides are widely but selectively distributed in human brain and may be involved in several neuropathological processes.

Alzheimer's disease beta-amyloid precursor protein in rat neural cells in culture

Immunochemical studies were performed on Alzheimer's beta-amyloid precursor protein (APP) in rat brain and cultured rat neural cells. Multiple APP subtypes were detected on immunoblots of brain homogenate with several antisera specific for subsequences of APP. In rat neural cell cultures, it was demonstrated that the composition of APP subtypes differed among cell types and subcellular fractions, and that APP subtypes in PC12h cells varied in their heparin binding affinity, suggesting distinct functional roles for different APP subtypes. Compatible with the possible role of APP in cell-matrix interaction, an increase in oligodendroglial APP was observed following their attachment onto poly-L-lysine substratum.

DNA CpG methylation inhibits binding of NF-kappa B proteins to the HIV-1 long terminal repeat cognate DNA motifs

The regulation of cellular or viral gene expression is directly influenced by the pattern of methylated cytosine residues localized in the DNA of enhancer/promoter sequences. The mechanism of transcriptional silencing has been explained on the basis of either an indirect model, in which densely methylated DNA is recognized by proteins that may displace crucial transcription factors, or a direct model, in which binding of a single transcription protein is prevented by the presence of a methylated CpG dinucleotide localized in a sensitive region of a DNA motif. In this study, we have determined that methylation of the core CpG dinucleotide located within the NF-kappa B repeated motifs of the human immunodeficiency virus type 1 (HIV-1) long terminal repeat can inhibit the binding of the NF-kappa B protein complex from crude nuclear extracts or from purified bovine spleen and specifically inhibit the binding of recombinant p50 protein. We have used the electrophoretic mobility shift assay (EMSA) and DNaseI footprinting analysis to demonstrate that binding of the NF-kappa B proteins to their cognate motifs can be inhibited via the direct model proposed for methylation-mediated inhibition of DNA-protein interaction.

Variation in resistance to herpes simplex virus type 1 of oligodendrocytes derived from inbred strains of mice

Primary oligodendrocyte (OL) cultures from three inbred strains of mice with known differences in resistance to herpes simplex virus type 1 (HSV-1) infection in vivo (A/J, susceptible; BALB/cByJ, moderately resistant; C57BL/6J, resistant), also display a similar pattern of resistance in vitro. The nature of the in vitro resistance at the cellular level was investigated. Virus production at different m.o.i.s indicated that the differences in HSV-1 replication are m.o.i.-dependent. Overall, virus yield from the OL cultures infected at a multiplicity of 1 increased 48 h post-infection (p.i.); no additional enhancement occurred 72 h p.i. However, the difference in the replication capacity of the three OL cultures observed at 24 h p.i. persisted at 48 and 72 h p.i. Serial electron microscopy studies on infected OL cultures derived from the different murine strains suggested that the resistance to HSV-1 infection occurs at different stages during the replicative cycle. Virus was detected at the nuclear membrane 5 min p.i. in A/J cells, but was not observed until 120 min p.i. in BALB/cByJ cells, whereas virus could not be detected at the nuclear membrane of C57BL/6J cells, even at 24 h p.i. Virus adsorption, determined by assay of residual non-adsorbed virus infectivity and cell-associated, radiolabelled HSV-1, did not differ in the OL cultures. The cumulative data suggest that A/J cells display the same replication pattern as permissive CV-1 cells, whereas the major replicative blocks in the other two murine strains occur at the level of the cytoplasmic membrane in C57BL/6J OLs, and at the level of the nuclear membrane in BALB/cByJ cells.

Phospholipase C isozymes in neurons and glial cells in culture: an immunocytochemical and immunochemical study

Expression of 3 brain isozymes of phospholipase (PLC-beta, PLC-gamma and PLC-delta) was investigated in relation to cell types found in rat CNS cultures. Immunoreactivity of cultured neurons, astrocytes and oligodendrocytes was demonstrated for all of the 3 isozymes by immunocytochemical staining and immunoblotting, with some differences in reaction intensity. Immunoblotting revealed that the level of expression was neurons greater than oligodendrocytes greater than astrocytes for PLC-beta and PLC-gamma, and astrocytes greater than oligodendrocytes greater than neurons for PLC-delta.

Oligodendroglial cell death induced by oxygen radicals and its protection by catalase

The cytotoxic effects of oxygen radicals have been studied in enriched population of mature bovine oligodendrocytes in culture. Oxygen radicals were generated enzymatically by glucose and glucose oxidase, and hypoxanthine and xanthine oxidase combinations. Cytotoxicity was assessed by trypan blue exclusion and percentage lactate dehydrogenase release into the culture media. Incubation of bovine oligodendrocytes with these oxygen radical-generating systems for 4 hr resulted in significant cell death, especially in the glucose oxidase system. The oligodendrocytes were completely protected by catalase from the cytotoxic effects of both oxygen radical generating systems. However, superoxide dismutase, dimethylsulfoxide and antioxidants such as vitamin E and glutathione did not protect oligodendrocytes from the oxidant-mediated cytotoxicity. It appears that hydrogen peroxide produced in these oxygen radical-generating systems gives rise to toxic radicals that induce the cell death of bovine oligodendrocytes in culture.

Lymphokine-activated killer (LAK) and adherent LAK (A-LAK) activity in multiple sclerosis

The cytotoxic activity of lymphokine-activated killer (LAK) cells against enriched cultures of oligodendrocytes (OL) was investigated in multiple sclerosis (MS) and controls. Human LAK cells, derived from macrophage-depleted peripheral blood mononuclear cells (PBMC) and incubated with recombinant human interleukin-2 (IL-2) (20-80 U/ml), mediated high levels of cytotoxicity against Raji cells but low levels of cytotoxicity against primary cultures of bovine OL. Cytotoxicity was not enhanced by incubation with a high level of IL-2 (500 U/ml). No statistically significant differences in LAK cell activity against bovine OL were observed among the study groups. Enriched adherent LAK (A-LAK) cells mediated greater levels of cytotoxicity against both bovine OL and tumor cell lines than unfractionated LAK cells. Flow cytometric analysis indicated that A-LAK effector cells were CD4-, CD8+, and CD16+. Furthermore, A-LAK cells mediated lysis of OL derived from several different animal species. Our results suggest that LAK and A-LAK cells can mediate cytolysis of OL in culture similar to that observed with a number of different tumor cell lines. However, no significant difference in cytolysis was identified between MS and control groups in this study.

Cytokine-induced expression of intercellular adhesion molecule-1 (ICAM-1) in cultured human oligodendrocytes and astrocytes

We investigated the expression of intercellular adhesion molecule-1 (ICAM-1) on primary cultures of human adult oligodendrocytes and astrocytes. Under unstimulated conditions, low levels of ICAM-1 immunoreactivity were identified on both oligodendrocytes (less than 50%) and astrocytes (less than 30%). After 48 hours' exposure to immune mediators, such as culture supernatant of phytohemagglutinin (PHA)-stimulated lymphocytes, interferon gamma (IFN-gamma; 1,000 U/ml), tumor necrosis factor alpha (TNF-alpha; 2,000 U/ml), interleukin-1 alpha (IL-1 alpha; 1,000 U/ml) and lipopolysaccharide (LPS; 50 micrograms/ml), ICAM-1 expression on both cell types was markedly increased in terms of intensity and cell numbers. IFN-gamma and culture supernatant of PHA-stimulated lymphocytes were the most potent inducers of ICAM-1 among the mediators tested, while TNF-alpha, IL-alpha and LPS were less effective, although variations were observed among cultures derived from different donors. Cytokine-induced expression of ICAM-1 on glial cells may play a role in mediating lymphocyte-glial cell interactions at sites of inflammation in the central nervous system.

Expression and induction of intercellular adhesion molecules (ICAMs) and major histocompatibility complex (MHC) antigens on cultured murine oligodendrocytes and astrocytes

Expression of intercellular adhesion molecule-1 (ICAM-1), ICAM-2-like molecule (Lgp55), and class I/II major histocompatibility complex (MHC) antigens (H-2 and Ia) was investigated in cultures of murine oligodendrocytes and astrocytes. Under unstimulated conditions, low levels of ICAM-1 expression were observed on astrocytes (less than 20%), but not on oligodendrocytes. Lgp55 was expressed intensely on oligodendrocytes (greater than 90%) and to a lesser degree on astrocytes (greater than 70%). A weak class I MHC (H-2) immunoreactivity was identified on both oligodendrocytes and astrocytes (50-70%). Class II MHC (Ia) antigen was undetectable on both cell types. After 48-hr exposure to immune mediators that include interferon-gamma (IFN-gamma), 500 U/ml, and supernatant from concanavalin A (Con A)-activated spleen cells, ICAM-1 expression was markedly increased on astrocytes (greater than 80%), but not on oligodendrocytes. Lgp55 expression on both cell types was not altered. Induction of H-2 antigen expression by immune mediators was quite high on both cell types (greater than 95%), while Ia antigen induction was low on astrocytes (less than 50%) and did not occur on oligodendrocytes. Cell type-specific expression and induction of ICAMs and MHC antigens by immune mediators may play roles in lymphocyte-glial cell interactions at the sites of inflammation in the central nervous system (CNS).

Age-dependent decrease of process formation by cultured oligodendrocytes is augmented by protein kinase C stimulation

The proportion of cultured rat oligodendrocytes (OL) that extended processes of over three soma diameter in length is dependent on the age of the animals from which the brains were derived; up to 70% of neonatal OL attained this criterion within 3 days, and this proportion progressively decreased with advancing ages of the animals (1, 3, and 6 months). The lower extent of process formation from older rat OL could be augmented, and indeed to equal neonatal levels, by treatment of cells with phorbol esters that stimulate protein kinase C: 4 beta-phorbol-12,13-dibutyrate (PDB) and phorbol-12-myristate-13-acetate (PMA). Enhancement of process formation by PDB and PMA was also observed for cultured adult human and bovine OL. For adult OL from all three species, a phorbol ester that binds but that does not activate protein kinase C, 4 alpha-phorbol-12,13-didecanoate, did not result in enhancement of process formation. Selectively to biologically active phorbol esters was shown by the inability of a wide range of growth factors to promote process extension. Immunohistochemical analyses indicate that the type III isozyme of protein kinase C predominates in cultured OL; the apparent intensity of immunoreactive PKC was not different between controls or cultures treated for 12 days with PDB, suggesting that the persistent presence of PDB might not have down-regulated the enzyme, in contrast to other cell types. We propose that stimulation of protein kinase C is critical to the triggering of process formation by cultured OL in vitro.

Acute pulmonary effects of nitrogen dioxide exposure during exercise in competitive athletes

The acute pulmonary responses of athletes after short-term exposure to ambient concentrations of NO2 during heavy exercise have been examined. Intercollegiate male athletes were screened for history of cardiac disease, respiratory disease, allergic conditions and extensive exposure to pollutants. After completion of serum IgE level determination, exercise tolerance test and methacholine challenge test with normal results, nine healthy subjects 18 to 23 years of age were exposed to filtered air and to 0.18 and 0.30 ppm NO2 for 30 min on different days while exercising on a treadmill. Pulmonary function parameters were measured before and after each exposure. In this study, no statistically significant changes were observed in FEV1, RT PEFR, and Vmax50% after exposure to 0.18 and 0.30 ppm NO2. For these selected healthy athletes, short-term exposure to ambient NO2 levels during heavy exercise does not affect adversely the pulmonary function.

Alpha 1-antichymotrypsin supports short-term survival of cerebral neurons in culture

alpha 1-Antichymotrypsin (ACT) is a component of the amyloid deposits in Alzheimer's disease. To elucidate its biological activities in the central nervous system, dissociated cultures of rat cerebral neurons were grown in a serum-free medium containing ACT. The addition of ACT (0.1-1 microgram/ml) enhanced survival of microtubule-associated protein 2-immunoreactive neurons under the culture conditions examined.

Developmental changes of three phosphoinositide-specific phospholipase C isozymes in the rat nervous system

Developmental changes of 3 phosphoinositide-specific phospholipase C isozymes (PI-PLC-beta, PI-PLC-gamma and PI-PLC-delta) in the rat nervous system were studied by immunohistochemical and immunochemical methods. PI-PLC-gamma immunoreactivity was intensely expressed in the radial fibers from the late fetal to early newborn stages, while weaker PI-PLC-beta reaction was also demonstrated in these structures. PI-PLC-beta and PI-PLC-gamma immunoreactivity appeared in neurons of various regions after the first postnatal week and then increased to the adult stage. Bergmann glia and some astrocytes also showed weak immunoreactivity for both isozymes from the newborn stage, while such immunoreactive astrocytes were relatively restricted in distribution in the white matter and hippocampus at the adult stage. PI-PLC-delta immunoreactivity appeared in astrocytes of entire cerebral regions from the second postnatal week, although weak antigenicity was also present in some neurons. Immunoblot analysis revealed that the immunoreactivities of 3 PI-PLC isozymes were present in both fetal and adult brains, with strong reactions of PI-PLC-beta and PI-PLC-delta in adult brain and that of PI-PLC-gamma in fetal brain. These results suggest that each PI-PLC isozyme plays important roles in different cell types in the course of their differentiation, and that some PI-PLC isozymes, especially PI-PLC-gamma, may be involved in cellular division and growth during the histogenesis of the central nervous system.

Increased susceptibility of human fetal astrocytes to human T-lymphotropic virus type I in culture

Human T-lymphotropic virus type I (HTLV-I) has been considered as an agent responsible for tropical spastic paraparesis and HTLV-I associated myelopathy. However, the pathogenesis of the diseases remains unclear. In a previous study we demonstrated that HTLV-I could infect adult human astrocytes and oligodendrocytes in vitro, although the rates of infected cells were low, at a rate of 0.1% and 0.01-0.05% respectively. Since mother-to-child transmission has been proposed as one of the major pathways for the prevalence of HTLV-I endemic, in the present study we investigated the susceptibility of human fetal astrocytes to HTLV-I in culture. After two days of co-culturing fetal brain cells with irradiated MT-2 cells (an HTLV-I-producing T-cell line), immunofluorescence staining revealed many positive astrocytes for HTLV-I p19 antigen. Multinucleated giant cells doubly immunoreactive to glial fibrillary acidic protein and HTLV-I antigen were frequently observed and showed a characteristic feature of hairy or fluffy external appearance. The percentage of infected astrocytes became as high as 19.4% at Day 21 of co-culture and then decreased. Electron microscopic examination revealed type C virus-like particles in astrocytes. These results indicate that human fetal astrocytes are more susceptible to HTLV-I infection than adult human astrocytes in tissue culture.