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Biomedical subjects

V Sogos

Publications and source records attributed to V Sogos.

29 records · Page 2Linked to original sources
PubMed1993

Protein kinase C-epsilon is a developmentally regulated, neuronal isoform in the chick embryo central nervous system.

Protein kinase C (PKC) is expressed as many isoforms and in high quantities in the central nervous system (CNS), which suggests an important role for this enzyme in neuronal development and function. We used specific antibodies to investigate the expression of the known PKC isoforms in extracts from chick major CNS areas during embryogenesis, from day 3 (E3) of incubation to day 1 post-hatching (P1). PKC-epsilon was the predominant isoform and was expressed from E6 onward in all brain regions, except retina (E12 and on). PKC-alpha/beta and -zeta isoforms were expressed at lower levels prior to PKC-epsilon expression and throughout embryogenesis. No other isoforms were detected in neural tissue preparations. We then used neural culture systems derived from the chick CNS to study the expression of PKC isoforms in neuroblasts, cortical neurons, and cortical glial cells. Western blotting and immunostaining of neuroblast-enriched cultures, derived from E3 CNS, showed only the Ca(2+)-dependent PKC-alpha/beta to be present. Studies on neuronal cultures derived from E6 cerebral hemispheres revealed only the Ca(2+)-independent PKC-epsilon to be expressed in neurons, as predicted by the developmental studies on tissue homogenates. PKC-epsilon immunoreactivity was seen intracellularly in differentiating neurons, regardless of their neurotransmitter phenotypes, and it correlated well with the level of neuronal activity. Furthermore, PKC-alpha/beta immunoreactivity was verified on glia cells, as the glial lineage emerges in E15 cortical cultures. These data suggest that PKC-epsilon expression is associated with the final neuroblast division in neurons, and the correlation of PKC isoform expression and neural cell lineage is discussed.

Animals↗
PubMed1992

Dystrophin immunoreactivity in normal and Duchenne human fetal neurons in culture.

Dystrophin, the protein product defective in Duchenne muscular dystrophy (DMD), is present in all types of muscle and in the brain. The function of the protein is unknown and its role in the brain is unclear, although 30% of DMD patients show nonprogressive mental retardation. We have therefore studied the localisation of dystrophin in cultures of normal and DMD human fetal neurons using antibodies raised to different regions of the protein. Dystrophin immunoreactivity was demonstrated in the soma and axon hillock of normal neurons and appeared to be associated with the inner part of the cell membrane, although some intracellular staining was also observed. Positive dystrophin staining was present only in cells with fully developed neuronal features, although not all the neurons were positive. Glial cells were always negative for the antigen. Immunostaining with antibodies to the brain spectrins indicate that the dystrophin antibodies did not crossreact with these proteins. The possibility of cross-reactivity with other proteins is discussed. Studies of cells cultured from a DMD fetus also showed specific dystrophin immunostaining in neurons, although the muscle was generally negative for dystrophin. However, the localisation of dystrophin immunostaining and that of the brain spectrins and neurofilaments appeared abnormal, as did the overall morphology of the cells. This suggests that dystrophin may play a role during brain development and dystrophin deficiency results in abnormal neuronal features. This would be consistent with the nonprogressive nature of the mental retardation observed in DMD patients.

Blotting, Western↗
PubMed1992

Immunocompetent cell markers in human fetal astrocytes and neurons in culture.

During the past few years, evidence has accumulated that interaction with peripheral immune cells as well as immunoregulatory functions in the central nervous system (CNS) can be played by several types of brain resident cells. Since very little information is available in man, however, we investigated the presence of markers so far considered typical of immunocompetent cells in in vitro cultures of human fetal brain. Immunocytochemistry at the light, scanning, and transmission electron microscopic levels revealed positivity for a very restricted range of macrophage antigens in astrocytes, which, however, were incapable of phagocytosis. In particular, expression of the major histocompatibility complex-class II antigen HLA-DR was observed in the cytoplasm and on the cell surface of GFA-P+ astrocytes and increased with time in culture and cell passages. Among the T-lymphocyte markers tested, Thy.1 and CD4 were positive. Both neurons and astrocytes carried Thy.1 from early cell passages. Noteworthy was the presence of CD4, which serves as the receptor for AIDS virus, in neurons from the first 2 weeks, whereas astrocytes became positive after only 4-6 weeks. Even if most staining was in the cytoplasm, some was exposed on cell surface. Astrocytes were found positive for the B-lymphocyte marker CD21, the cellular receptor for Epstein-Barr virus, whereas CD24 was detected in both neurons and astrocytes. Both antigens are related to B-cell proliferation. Results are in favour of the hypothesis of human brain cells being actively involved in CNS immunological events.

Astrocytes↗
PubMed1992

Correlation between P19 presence and MHC class II expression in human fetal astroglial cells cocultured with HTLV-I donor cells.

The possibility of a direct infection of human brain by HTLV-I, has been studied using an in vitro model. Human fetal astroglial cells were cocultivated with irradiated HTLV-I donor cell line MT-2, and assayed for the presence of HTLV-I core protein p19 after 1 week. Fifty-six per cent of GFAP positive astrocytes showed the viral core protein p19 and increased expression of Class II MHC antigens. Electron microscopy of astroglial cells exposed to HTLV-I revealed the presence of vacuoli-like structures containing viral core protein p19. Cell intermediate filament cytoskeleton was also disorganized. Even if this study does not provide direct evidence for virus replication inside astroglial cells, all these findings suggest that HTLV-I can indeed enter the cell and exert a cytopathic effect. Therefore the results of the present study are consistent with the hypothesis that astroglial cells could be involved in demyelination processes occurring in the HTLV-I associated neurological disorders, such as human associated myelopathy and tropical spastic paraparesis.

Astrocytes↗
PubMed1990

Basic fibroblast growth factor in neuronal cultures of human fetal brain.

The presence of basic fibroblast growth factor (bFGF) was investigated in neuronal cells derived from 12 and 18 week-old human fetal brain cultures. To this purpose, the ability of bFGF to stimulate plasminogen activator (PA) production in fetal bovine aortic endothelial GM 7373 cells was used as an assay for this molecule in neuronal cell extracts. The identity of the PA-stimulating activity of neuronal cell extract with bFGF was confirmed by its high affinity for heparin and by its cross-reactivity with polyclonal antibodies to human placental bFGF. These antibodies recognized a Mr 18,000 cell-associated protein both in Western blot and in immuno-precipitation experiments. All the neurons showed bFGF immunoreactivity, as demonstrated by immunocytochemical staining, while nonneuronal cells were unstained. The data demonstrate for the first time that cultured human fetal brain neurons contain and synthesize bFGF.

Animals↗
PubMed1990

Acetylcholine-induced production of platelet-activating factor by human fetal brain cells in culture.

Platelet-activating-factor (PAF) is a potent, biologically active lipid mediator produced by several tissues, including brain. Its role in the central nervous system (CNS) is still unknown, even if its involvement in brain damage and neurotoxicity has been postulated. Its production by neural cells has been demonstrated in different species, but not in man. This paper provides evidence that PAF can be produced by human fetal neurons and/or glial cells in culture. Its synthesis dramatically increased upon stimulation with acetylcholine (ACh), and it was significantly lowered by the cholinergic receptor antagonist atropine. Almost no PAF was detected in the incubation medium, which indicated no release of PAF from cultured cells. Characterization of the cells in culture with specific monoclonal antibodies excluded the presence of endothelial cells or macrophages, which also produce PAF.

Acetylcholine↗
PubMed1989

Muscarinic receptor subclasses in retinal cultures: effect of corticosterone.

We have previously shown that exogenously administered corticosterone affects muscarinic receptor binding in the chick embryo retina. Analysis with the selective antagonist pirenzepine has shown that both muscarinic receptor subclasses M1 and M2 are present in treated retinas. On the contrary, only M2 is detectable in controls. Moreover, receptor affinity for agonists is modified by hormone treatment. Since these studies did not show whether or not the hormone directly influences retinal cells, a similar study was performed on retinal tissue cultures. Cells were treated at day 5 in vitro for 24 hr with 1.10(-8) M corticosterone. Scatchard analysis of results obtained with 3H-quinuclidinyl benzilate (3H-QNB) binding showed no difference between treated and control cultures. However, displacement experiments demonstrated that both M1 and M2 were present in treated cultures, whereas controls had only M2. Also, receptor affinity for the agonist carbachol was modified, as already observed with in vivo studies. In addition, a new phenomenon was observed: treated cultures had a significantly higher number of cells. The possibility that the hormone can prevent cell death or stimulate cell mitosis is considered.

Animals↗
PubMed1989

Developmental expression of intermediate filament proteins in the chick embryo retina: in vivo and in vitro comparison.

An immunocytochemical study was performed on the chick embryo retina to detect the changes in intermediate filament (IF) composition in correlation with development. Results showed that all three major neurofilament subunits (NF L, M and H) were expressed from very immature neurons at the same time. No delayed expression of NF-H was observed. Vimentin (VT) was also present from very early stages in both neuronal and glial cells, but it was not detectable at hatching. Its distribution changed in retinal layers throughout development. It co-existed with NF in neurons, and conversely, it preceded the appearance of the typical glial fibrillar acidic protein (GFA-P), which was detected in radial fibres of Müller cells from day 16 of incubation. These in vivo data were compared with immunocytochemical staining of retinal cultures, grown either on collagen or on polylysine. NF-L and GFA-P were not detectable in vitro. Moreover, the early expression of NF subunits was shown to be influenced by the type of substratum. The contemporary presence of vimentin and neurofilaments was clearly shown both in neuronal cell bodies and processes. The results also show that in the chick retina the pattern of composition of intermediate filaments changes with maturation. Moreover, in vitro conditions influence the expression of IF components. These data are of interest when performing in vitro analysis of the effect of exogenous substances affecting neuronal maturation and differentiation.

Animals↗
PubMedDate not supplied

Platelet-activating factor production by human fetal microglia. Effect of lipopolysaccharides and tumor necrosis factor-alpha.

Since platelet-activating factor (PAF) exerts neurotoxic effects on brain cells, we explored the possibility of PAF production by human fetal microglial cells in vitro. PAF content in pure cultures was assayed and characterized in basic conditions, and after stimulation with growth factors and cytokines. Results showed that microglia cells synthesized PAF when challenged with tumor necrosis factor-alpha and lipopolysaccharides, whereas other molecules, such as gamma-interferon or basic fibroblast growth factor, were ineffective. The induced PAF production was concentration- and time-dependent. These results are in line with the hypothesis that microglia can start a cascade of events leading to tissue damage, thus playing a central role in the pathogenesis of several central nervous system diseases.

Brain↗