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B Zalc

Publications and source records attributed to B Zalc.

At least 55 records · Page 3Linked to original sources
PubMed1995

Differential oligodendroglial expression of the tumor necrosis factor receptors in vivo and in vitro.

The cytokine tumor necrosis factor-alpha (TNF alpha) has been proposed to play a key role in the degenerative processes observed in demyelinating diseases such as multiple sclerosis (MS). In the immune system the cellular responses to TNF are mediated by two different receptors: TNF-RI, which is involved in cell death, and TNF-RII, which has been shown to mediate cell proliferation. We investigated the oligodendroglial expression of TNF-RI and -RII. In vivo, in normal adult rodent brain, oligodendrocytes express TNF-RII but not TNF-RI. However, after 3 days in culture, both types of receptors were expressed by mature oligodendrocytes, purified from 4-week-old rats, suggesting that expression of TNF-RI was induced by either the isolation process or the culture conditions. This inducibility of TNF-RI may explain the differences in oligodendrocyte cell death reported in various experimental conditions and in the pathology of MS lesions.

Animals↗
PubMed1995

Oligodendrocytes originate in a restricted zone of the embryonic ventral neural tube defined by DM-20 mRNA expression.

Products of the PLP gene, proteolipid protein and its isoform DM-20, are the most abundant proteins in CNS myelin, and are markers of the oligodendrocyte, the myelin-forming cell in the CNS. The DM-20 transcript has previously been reported to be expressed in newborn oligodendrocyte progenitor cells and during embryonic development. We have therefore used a DM-20 cRNA probe to follow, by in situ hybridization, the oligodendrocyte lineage during embryonic development. DM-20-expressing cells were first detected at E9.5 in the ventricular germinal layer of the laterobasal plate of the diencephalon. At E14.5, DM-20+ cells had largely disappeared from the diencephalic ventricular germinal layer and had colonized the ventral mantle layer at the posterior part of the basal diencephalon. Between E17.5 and P1, the number of DM-20+ cells increased and progressively invaded the major white matter tracts. In the hindbrain, DM-20+ cells appeared at E12.5 in the caudal part of the rhombencephalon, and at E14.5 all along the ventral spinal cord. Between E14.5 and P1, DM-20+ cells progressively colonized, first ventrally then dorsally, all the spinal cord and more extensively the white matter tracts. At E14.5, a large gap separated, rostrally, the medullary columns from the mantle layer cells in the prosencephalon, suggesting that oligodendrocytes in the mid- and forebrain originate from a different pool of precursors than in the rhombencephalon and the spinal cord. Together, these observations suggest that expression of the DM-20 transcript is an early marker of commitment to the oligodendrocyte lineage, and that oligodendrocyte precursors originate in a ventrally restricted region.

Animals↗
PubMed1995

[Phylogeny of myelin and myelin forming cells].

Myelin exists only in vertebrates and is formed by oligodendrocytes in the central nervous system and by Schwann cell in the peripheral nervous system. In invertebrates, satellite and ensheathing glial cells, which are not myelin-forming cells, appear as the ancestors of vertebrates myelin-forming cells. Here, we review our current knowledge, that could explain the evolutionary events that have lead to the emergence of myelin and myelin forming cells.

Animals↗
PubMed1995

[Interaction between neurons and oligodendrocytes during myelination].

Oligodendrocytes are the myelin-forming cells of the central nervous system. Despite close relationship between oligodendrocyte and neuron, little is known about the exact role and nature of oligodendrocyte/axons interactions. We used an in vitro myelinating system to study axonal signals involved in myelination and showed: i) that only axons are myelinated, suggesting the existence of an axonal recognition signal and ii) that electrical activity seems necessary for myelination to proceed, as nerve influx blockade by tetrodotoxin strongly inhibits myelination. Moreover, myelinating oligodendrocyte appears to modulate axonal neurofilament phosphorylation. Knowledge of these reciprocal interactions may modify our physiopathological and therapeutical conceptions in human demyelinating diseases like multiple sclerosis.

Animals↗
PubMed1993

Glycerophosphorylcholine phosphocholine phosphodiesterase activity during the differentiation of glial progenitor cells.

O-2A progenitor cells were grown in medium containing either 1% or 10% fetal calf serum (FCS) for 4 weeks. The cells in 1% FCS were 75% oligodendrocytes by 3 weeks in culture. The cell population was so overgrown with astrocytes in the 10% medium that an accurate estimate of cell number could not be made. The activities of glycerophosphorylcholine phosphocholine phosphodiesterase (GPC-PC-PdE), p-nitrophenylphosphorylcholine phosphodiesterase (pNPPC-PC-PdE), and ceramide UDP galactose galactosyl transferase (CGalT) were barely detectable in the cells grown in 10% FCS. The activities of these 3 enzymes were low in the cells grown in 1% FCS for the first 2 weeks and then all 3 increased manyfold. These observations reinforce the evidence previously accrued showing that these two phosphodiesterase activities (GPC-PC-PdE and pNPPC-PC-PdE) are markers of oligodendroglial cells as well as myelin. In contrast, glycerophosphorylcholine choline phosphodiesterase (GPC-C-PdE) activities were present in cells grown in both 1% and 10% FCS.

Animals↗
PubMed1993

Even in culture, oligodendrocytes myelinate solely axons.

Cerebral hemispheres from mouse embryos at 15 days of gestation were dissociated and maintained in culture for several weeks in a medium which permitted homochronic and homotypic oligodendrocytes and neurons to interact in the presence of other central nervous system cells. After 13-14 days in culture a few oligodendrocytes changed from highly branched, "sun-like," nonmyelinating cells to sparcely branched myelinating cells. The number of fibers myelinated per oligodendrocyte ranged from 1 to 10, similar to that described previously in vivo in the corpus callosum. When an oligodendrocyte began to myelinate, it immediately myelinated a maximum number of fibers, suggesting that the number of axons to be myelinated by the oligodendrocyte was predetermined. When only one fiber was in the vicinity of a myelinating oligodendrocyte, whorls of myelin-like figures were seen at the tip of oligodendrocyte processes that had not reached an axon. Myelinated fibers were unambiguously identified as axons both by immunostaining and by electron microscopy. Myelin was not observed around astrocyte processes or around dendrites. The exclusive myelination of axons suggests the existence of a specific axonal recognition signal which attracts oligodendrocyte processes.

Animals↗
PubMed1993

The proximal region of the MBP gene promoter is sufficient to induce oligodendroglial-specific expression in transgenic mice.

To characterize regulatory DNA sequences involved in oligodendroglial expression of myelin basic protein (MBP), transgenic mice carrying a 256 bp fragment of the mouse MBP promoter fused to an Escherichia coli lacZ gene were generated. Of four transgenic families, two (lines 2 and 4) expressed beta-galactosidase activity in the nervous system but not in most other tissues. Histochemical and immunohistochemical analysis of adult brain from these two lines showed oligodendroglial-specific expression of the transgene. In line 2, only a small proportion of oligodendrocytes expressed the transgene, and in labelled cells the product of the enzymatic reaction with beta-galactosidase was confined to a small round vesicle in the vicinity of the nucleus. In contrast, in tissue sections from line 4 adult brain and spinal cord beta-galactosidase activity was much more intense and at least 80-90% of oligodendrocytes expressed the transgene. Detection of the MBP-lacZ transcript by in situ hybridization showed that the transgene mRNA was confined to the oligodendrocyte cell body. These results suggest that cis-acting regulatory elements, specifying oligodendrocytes identity, are located within 256 bp upstream from the MBP gene.

Aging↗
PubMed1993

The E. coli envY gene encodes a high affinity opioid binding site.

In an attempt to isolate a cDNA encoding an opioid receptor, a cDNA library was constructed in the lambda ZAP vector using NG108-15 mRNA as template. Using an in vitro transcription-translation assay and a sib selection strategy, a single phage was isolated. An RNA transcribed from this cDNA was able to direct in vitro translation of opioid binding sites. The insert was sequenced and comparison with data banks showed a 100% homology with the E. coli envY gene. We assume that the presence of the envY sequence in the NG108-15 cDNA library was due to a contamination of the lambda ZAP vector with E. coli DNA. A search for opioid binding sites on E. coli strains showed that envY+ strains, but not envY- mutants were able to bind opiates. On envY+ cells, the sites are stereospecific, saturable and of high affinity for the opiate ligands. These sites bind opiate agonists and antagonists but neither mu nor delta opioid peptides. In contrast, rabbit reticulocyte lysate primed with RNA transcribed in vitro from the envY sequence elicited the synthesis of an opioid binding site with mixed mu and delta properties. In addition, transfection of the envY sequence into mammalian cells resulted in the expression of opioid binding sites. Depending on the type of cells transfected, these sites were selective for either the mu or delta ligands.

Animals↗
PubMed1993

Regional and developmental variations of GFAP and actin mRNA levels in the CNS of jimpy and shiverer mutant mice.

Gliosis is a common reaction to brain damage. Glial fibrillary acidic protein (GFAP) is a classical astrocytic marker. We have undertaken to measure the level of GFAP-mRNA as an index of gliosis in the brain of jimpy (jp) and shiverer (shi) murine mutants, in which hypomyelination is either severe or moderate, respectively. This study was conducted in five different CNS regions and at different ages. In young jp mutant, the amount of GFAP-mRNA was either normal or lower than in control animals; but after 3 wk of age, the level of GFAP-transcript increased dramatically in all regions examined. A parallel increase in actin-mRNA was also observed, mostly in the diencephalon and to a lesser extent in cortex and spinal cord, but not in the cerebellum and brainstem. In the shi mutant, variations in the amount of GFAP-mRNA were less important than in the jp with two exceptions: In brainstem of 3-wk-old animals, a 2.5-fold increase was observed, and in all the regions but the spinal cord of 12-d-old shi, the levels of GFAP-transcript were 2-5 times lower than in controls. In this mutant, the levels of actin message were usually close to normal, or slightly lower than in controls.

Actins↗
PubMed1993

Glial biology and disorders.

Much work has been devoted this year to the localization and mode of expression of growth factors and cytokines. Although it is not possible to extrapolate directly from in vitro to in vivo conditions, the plasticity of glial cells seems to be very influenced by growth factors. Astrocytes in vivo do not express many growth factors during normal conditions, but a pathologic event can lift these restrictions. Cytokines and their receptors have been localized on neuronal or glial cell types. The programmed cell death, well identified in neurons, seems to occur also in oligodendrocytes and may be influenced by survival factors. In the adult brain, glial progenitors are present and may be a potential source to generate myelinating oligodendrocytes for myelin repair. In the peripheral nervous system, axonal-Schwann cell signaling may function in both directions during development. Some animal neurologic mutants are models for human diseases; one of them, the Trembler mouse, has effectively led to the genetic characterization of Charcot-Marie-Tooth disease type 1a. As for myelin destruction, the relationship between demyelination and inflammation is still not very clear.

Cell Death↗
PubMed1992

Clonal segregation of oligodendrocytes and astrocytes during in vitro differentiation of glial progenitor cells.

To study the clonal lineage of the glial progenitor population, isolated from newborn rat brain (Lubetzki et al. J Neurochem 56:671, 1991), we combined somatic transgenesis using a retroviral vector encoding a modified bacterial beta-galactosidase with nuclear localization, and triple immunofluorescence labeling with A2B5, anti-galactosylceramide, and anti-glial acidic fibrillary protein antibodies. This allowed clonal analysis of the postnatal glial lineage with precise phenotypic identification of each cell within the lacZ-positive clones. When infected cells were cultivated under constant conditions, in the presence of either 1% or 10% fetal calf serum (FCS)-containing medium, all the 250 lacZ-positive clusters examined were homogeneous, i.e., either oligodendroglial or astroglial. Mixed astrocyte-oligodendroglial clones were observed when cells cultivated in the presence of 1% FCS were switched to a 10% FCS-containing medium, confirming the bipotentiality of glial progenitor cells (Temple and Raff Nature 313:223, 1985). However, even under the switch culture conditions, segregation into homogeneous clones of either oligodendrocytes or astrocytes still predominated, and the percentage of mixed clones dropped from 25 to 8 or to 3, when the switch took place at 8, 16, or 22 days in vitro, respectively. Two additional observations lead us to suggest that microenvironmental factors are responsible for the clonal segregation of glial progenitor cells: 1) the uneven distribution of oligodendrocyte and astrocyte clusters, the latter being seen mostly on the edge of the coverslips; and 2) the presence, in the vicinity of an homogeneous lacZ-positive clone, of some lacZ-negative cells expressing the same phenotype.

Animals↗
PubMed1992

Glycerophosphorylcholine phosphocholine phosphodiesterase activity in cultured oligodendrocytes, astrocytes, and central nervous tissue of dysmyelinating rodent mutants.

The levels of GPC phosphocholine phosphodiesterase, pNP phosphocholine phosphodiesterase, CNPase, and UDP galactose: ceramide galactosyltransferase activities were estimated with pure cultures of oligodendrocytes and astrocytes; mixed primary glial cells cultures; C-6 cells; and CNS tissue of the dysmyelinating md rat, the jimpy mouse, and the quaking mouse. The highest activity of GPC and pNP phosphocholine phosphodiesterases as with CNPase and C gal T was found in the pure cultured oligodendrocytes. C-6 cells had very low or undetectable activities for these two phosphodiesterases but possessed very high CNPase activity. The activity of GPC phosphocholine phosphodiesterase was significantly decreased in the CNS tissue of the md rat and the jimpy and the quaking mouse. Similar reductions were observed for the pNP phosphocholine phosphodiesterase, CNPase, and C gal T activities. The selective cellular enrichment in oligodendrocytes of the GPC phosphocholine phosphodiesterase activity and decreases of its activity in three dysmyelinating mutants in the same ratio as for CNPase and C gal T suggest that GPC phosphocholine phosphodiesterase is a myelin marker enzyme and it may reflect the quantity of myelin and oligodendrocyte present.

2',3'-Cyclic-Nucleotide Phosphodiesterases↗
PubMed1992

DM-20 mRNA is expressed during the embryonic development of the nervous system of the mouse.

We used both the polymerase chain reaction (PCR) and in situ hybridization to search for the presence of proteolipid protein (PLP) gene transcripts in the developing mouse. Total brain RNA extracted from 13-19-day embryos, analyzed by PCR, demonstrated the presence of a single transcript that was unambiguously identified with the DM-20 mRNA. RNA samples from postnatal day 2 animals also showed a signal corresponding to the PLP transcript, in addition to the DM-20 message. By in situ hybridization of 10-day embryos using a DM-20 antisense cRNA probe, we showed that the localization of the DM-20 message was restricted to the diencephalic basal plate. On the same embryo sections, in addition to the brain localization, an intense hybridizing signal was also detected in the trigeminal and spinal ganglia, the vagal glossopharyngeal ganglion, and the sympathetic ganglion chain. The demonstration of transcription of the PLP gene, long before the beginning of the myelination process, suggests that in addition to a structural function in myelin compaction, some of the products of the PLP gene (DM-20) may have a role during the compartmentalization and differentiation of the neural tube.

Animals↗
PubMed1992

Developmental expression of glial fibrillary acidic protein and actin-encoding messages in quaking and control mice.

Quaking is a neurological mutation leading to pleiotropic phenotypic expression, the most prominent being disturbed myelin formation in the central nervous system (CNS) with minor abnormalities in the peripheral nervous system. Previous immunochemical measurements of glial fibrillary acidic protein (GFAP) revealed a marked increase in the protein in several areas of the CNS. To further characterize the regulation parameters of GFAP synthesis, we analyzed the levels of GFAP mRNA in 5 regions of the CNS, some with elevated levels of GFAP and some without. This was compared to the developmental expression of GFAP transcripts in the same regions in normal mice. To establish the specificity of the variations observed with this astroglial specific message, we conducted a similar investigation with actin RNA which is expressed by several cell types in the CNS. Both the actin and the GFAP message were found to be increased in the adult mutant throughout the CNS. In 2-year-old normal mice the messengers for both cytoskeleton proteins were expressed in a higher amount than in young adults.

Actins↗
PubMed1991

Morphological, biochemical, and functional characterization of bulk isolated glial progenitor cells.

We describe a simple, rapid, and efficient method, based on separation on a Percoll centrifugation gradient, to purify glial progenitor cells from newborn rat brains. Cytofluorimetry analysis of the isolated cell population showed that 75 +/- 8 and 86 +/- 7% of the cells were A2B5- and R24-positive, respectively. Transmission electron microscopy examination of the purified cell population confirmed their homogeneity and illustrated their typical morphology, as previously described in situ. Assay of UDP-galactose-ceramide galactosyltransferase, 3'-phosphoadenosine 5'-phosphosulfate galactosylceramide sulfotransferase, and 2',3'-cyclic nucleotide 3'-phosphohydrolase activities showed that the levels of these enzymes were 446, 76, and 11 times lower, respectively, than the levels measured in mature oligodendrocytes. Low levels of mRNA coding for 2',3'-cyclic nucleotide 3'-phosphohydrolase and myelin proteolipid protein, but not for myelin basic protein, were present in the glial progenitor cells. At the time of isolation, 40% of the cells in the population were dividing, and the cells could easily be expanded in culture. After 3 weeks of culture in the presence of 1% fetal calf serum, 75% of the cells had differentiated into galactosylceramide-positive oligodendrocytes. When the culture took place in the presence of 10% fetal calf serum, only 2% of the cells expressed galactosylceramide, and 60% were glial fibrillary acidic protein-positive astrocytes; half of them were also A2B5 positive.

2',3'-Cyclic Nucleotide 3'-Phosphodiesterase↗
PubMed1990

Pharmacological and molecular properties of opioid binding sites synthesized in a cell-free translation system.

Cell-free translation of mRNA, extracted from NG108-15 cells, was used to examine some properties of the opioid binding sites synthesized in vitro. A monoclonal antiidiotype antibody directed against the delta opioid receptor immunoprecipitated a major band of Mr 51,000. Translational immunoassays of poly[A]+RNA, size fractionated by methylmercury agarose gel electrophoresis, demonstrated that the 51,000 Mr protein specifically immunoprecipitated by the anti-opioid receptor antiidiotype antibodies was coded by a transcript which length was in the 6 to 8 kb range. Displacement binding studies of tritiated ligands (either bremazocine or delta or mu selective peptides) with type selective opioid ligands showed that only one type of opioid binding site was synthesized in vitro. Although the pharmacological profiles of ligands binding to NG108-15 cells were characteristic of the delta receptor type, the de novo synthesized opioid binding site had lost its delta selectivity and showed equal affinity for both the mu and delta but not for the kappa ligands. Similar to our finding using the immunoprecipitation system, size fractionation of the NG108-15 poly[A]+RNA demonstrated that the transcript coding for the "mu-delta" binding site had a length of 6,500 to 7,500 nucleotides.

Animals↗
PubMed1990

[Myelin and oligodendrocytes: recent data].

Oligodendrocytes are the myelin forming cells of the central nervous system. They are derived from a precursor cell, named O-2A. This precursor cell is bipotential, and can differentiate in vitro into either an oligodendrocyte or a certain type of astrocyte, named type 2 astrocyte, depending on the presence or absence of extracellular factors. The chronology of glial differentiation is now better understood. Some factors influencing the choice of the differentiation pathway have been described. Most of these factors seem to be secreted in vitro by an other type of astrocyte, type 1 astrocyte. The succession of events leading to myelination can now be analyzed at molecular level. These very recent results have mostly been obtained in vitro. Their significance in vivo has now to be ascertained.

Animals↗