摘要:

AbstractThe gene encoding the peripheral myelin protein PMP22 is affected by various mutations in the hereditary peripheral neuropathies Charcot‐Marie‐Tooth disease type 1A (CMT1A), Déjérine‐Sottas syndrome (DSS) and hereditary neuropathy with liability to pressure palsies (HNPP). In contrast to the recent remarkable progress in the genetics of the PMP22 gene, the biological function of PMP22 remains largely unknown. In this report, we have confirmed by using in situ hybridization techniques that high levels of PMP22 niRNA are present in maturing peripheral nerves of the 2‐week‐old mouse, a finding consistent with the PNS‐specific defect observed in hereditary peripheral neuropathies. However, high levels of PMP22 transcripts were also found in the villi of the adult gut, and PMP22 expression was detected in various non‐neural tissues during embryonic mouse development. In early embryogenesis (9.5 days postconception, dpc), PMP22 RNA expression appears restricted to the epithelial ectodermal layer. During early organogenesis (11.5 dpc), particularly high levels of expression are present in the capsule surrounding the liver and in the forming gut, while low levels of PMP22 mRNA can be fund in precartilagous condensations forming the vertebrae and the ventricular layer of the myelencephalon. During midgestation development (14.5 dpc to 16.5 dpc), the number of PMP22‐positive tissues increases, and high expression is detected in several mesoderm‐derived tissues, in particular connective tissues of the face region, bones including the vertebrae, the lung mesenchym, and in muscles. In addition, high expression is also found in ectoderm‐derived tissues, especially the epithelia of the lens and the skin. These findings strongly suggest that PMP22 serves not only a PNSspecific function but is also of broader biological significance in cell proliferation and/or differentiation.

ISSN:0360-4012    

DOI:10.1002/jnr.490420602

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractGamma‐aminobutyric acid (GABA) synthesis can result from the action of at least two glutamic acid decarboxylase (GAD) isoforms, GAD65and GAD67, possibly involved in distinct mechanisms. We have made the hypothesis that GAD65may respond to short‐term changes and is present in neurons with a phasic activity, while GAD67may rather provide GABA for the metabolic pool and for supporting tonic levels of synaptic transmission (Erlander et al.: Neuron 7:91–100, 1991; Feldblum et al.: J Neurosci Res 34:689–706, 1993). In the present work we have tested this hypothesis in the rat spinal cord where both types of activities have been identified. The correlation of GABA immunodetection with the distribution of GAD65and GAD67mRNAs and proteins has evinced in the dorsal horn a differential regulation of the two isoforms. In situ hybridization has revealed, in the dorsal horn, relatively higher levels of GAD67mRNA than of GAD65, while immunodetection of the proteins demonstrated numerous punctate profiles with both GAD antisera. Reverse transcription‐polymerase chain reaction (RT‐PCR) data confirmed the abundance of the GAD67transcripts compared to GAD65in the rat spinal cord. In contrast, within the ventral horn, there was a greater number of GAD67‐immunoreactive (IR) profiles mostly located around motoneurons. The paucity of GAD65immunoreactivity in the ventral horn cannot be related to a different accessibility of the antigens to the epitopes since on the same section a dense GAD65staining was detected in the dorsal horn. Hence, a number of biochemical and electrophysiological data support the concept of the involvement of glycine as the major inhibitory system within the ventral horn which may explain the low levels of GAD transcription in this region. The paucity of GAD65in the ventral horn may also reflect a functional difference, suggesting a predominance of GAD67in neurons under tonic activity. In the dorsal horn, where neurons with phasic and tonic firing patterns have been disclosed, GAD65may, in addition, provide GABA for responses to short‐term changes. ©1995

ISSN:0360-4012    

DOI:10.1002/jnr.490420603

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractPrevious studies have shown that myelin basic protein (MBP) is mitogenic for Schwann cells (SCs) in the presence of elevated intracellular cAMP. Two mitogenic regions of MBP have been identified: one mitogenic region within the first 44 residues of the aminoterminus (1–44) and the other mitogenic region within the terminal 15 residues of the carboxyl end of the molecule (152–167). Unlike the mitogenic effect of a myelin enriched fraction (MEF), the mitogenic effect of MBP was not reduced by the addition of the lysosomal inhibitor, ammonium chloride. These data indicate that MBP causes SC proliferation by direct interaction of MBP with a surface receptor. Using Scatchard analysis of the binding of MBP to SCs, we report that treatment with forskolin does not cause the upregulation of receptors for MBP. Moreover, MBP blocks the cross‐linking of125I‐bFGF with two fibroblast growth factor (FGF) receptors having apparent molecular weights of 140 kDa and 120 kDa, respectively. Since neither TGF‐β nor PDGFBB displaced cell surface bound125I‐MBP, we conclude that MBP binds to the FGF receptor rather than other growth factor receptors. Furthermore, only MBP1–44interacted with ganglioside GM1, whereas MBP152–167did not interact with this ganglioside. These results are consistent with the view that ganglioside GM1 mediates the mitogenic effects of MBP1–44, while the FGF receptor mediates the mitogenic effect of MBP152–67. Intracellular cAMP of SCs was transiently increased after the addition of macrophage conditioned medium, suggesting that macrophages may produce factors in vivo which can transiently elevate intracellular cAMP levels, allowing a wave of SC proliferation in response to MBP‐related mitogens.

ISSN:0360-4012    

DOI:10.1002/jnr.490420604

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractTreatment of cultured oligodendrocytes (OLGs) with micromolar quantities of myelin basic protein (MBP) caused a rapid, MBP‐dose dependent cell death. In contrast, a 72‐hr incubation of OLGs with MBP peptides (1–44, 47–87, 88–151, or 152–167) at comparable concentrations had no effect on cell viability. MBP and MBP peptides (1–44 and 88–151) have been shown to interact with ganglioside GM1 (Tzeng et al.: J Neurochem Res: 42:758–767, 1995). This interaction has been reported to increase calcium influx. Therefore, using the fluorescent dye Indo‐1 and an ACAS laser cytometer, we examined the level of intracellular calcium in OLGs after MBP treatment. MBP was shown to provoke a rapid, dramatic, and sustained rise of intracellular calcium in most OLGs. The levels of elevated intracellular calcium were sustained and did not return to baseline even after 10 min. This increase of intracellular calcium was suppressed in the presence of EGTA, indicating that the [Ca2+]irise was due to the entry of extracellular calcium. Incubation of cultured OLGs with MBP peptides (1–44 or 88–151) caused a modest and transitory elevation of intracellular calcium ions in a lower percentage of OLGs. The potent OLG cytotoxicity of intact MBP and the loss of potency after proteolysis raise the possibility that MBP proteolysis during demyelination protects OLGs from death

ISSN:0360-4012    

DOI:10.1002/jnr.490420605

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractUsing a quantitative reverse transcription‐polymerase chain reaction (RT‐PCR), we studied the regulation oftrkA mRNA expression in serum‐free, cultured basal forebrain neurons from 17‐day fetal rats. Besides increasing choline acetyltransferase (ChAT) activities, nerve growth factor (NGF) strikingly inducedtrkA gene expression in a time‐ and NGF concentrationdependent manner. Therefore, NGF might play a critical role intrkA gene expression during the development of basal forebrain cholinergic neurons. Furthermore, to investigate whether this up‐regulation is connected with the trophic effects on basal forebrain cholinergic neurons, we examined the effects of some other neurotrophic agents (BDNF, NT‐3, bFGF, CNTF, and 40 mM KCl) upon ChAT activity andtrkA gene expression. Some neurotrophic factors increased ChAT activities to the same degree as NGF, whereas they did not stimulatetrkA mRNA expression so potently. NT‐3 plus K252b promotes the tyrosine phosphorylation ofTrkA in PC12 cells and increases ChAT activity in cultured basal forebrain cholinergic neurons like NGF (Knusel et al., J Neurochem 59: 715–722, 1992). W e found that NT‐3 plus K252b upregulated the level oftrkA mRNA. These results suggested that the expression oftrkA mRNA is regulated directly by its specific ligand NGF, rather than neurotrophic effects upon basal forebrain cholinergic neurons and that the up‐regulation is connected to a molecular event initiated by the binding of NGF to theTrkA receptor.

ISSN:0360-4012    

DOI:10.1002/jnr.490420606

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractPreviously, we reported the presence of multiple neurotransmitters in subclones of SN6, a septal cholinergic hybrid cell line. To obtain information concerning the functionality of these transmitters, we measured transmitter contents, activities of transmitter‐producing enzymes, and the effect of serum‐free culture medium in two different batches (SN6.1.6 and SN6.10.2.2) and two subclones of the SN6 cell line (SN6.2a and SN6.1b). Except for SN6.1b, SN6 cell lines and subclones had basically the same neurotransmitter characteristics. Among the transmitters, only acetylcholine seemed to be functional. Monoamine oxidase was missing and activity of aromatic amino acid decarboxylase was diminished in SN6 cell lines. Even in serum‐containing medium, SN6.1b had a more mature morphology than the other cell lines, and it contained choline acetyltransferase and acetylcholine but not tyrosine hydroxylase or catecholamines. Similar characteristics were acquired by the mother cell line in response to serum‐free conditions. Thus, SN6.1b is the most mature of these central cholinergic neuronal cell lines, at least with regard to neurotransmitter profiles. ©1995 Wiley

ISSN:0360-4012    

DOI:10.1002/jnr.490420607

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractAcetylcholinesterase (AChE; EC 3.1.1.7) is expressed in the central nervous system in multiple molecular forms that may subserve multiple functions and may be selectively lost in neurodegenerative illnesses such as Alzheimer's disease. AChE expression has been studied in primary cultures of developing vertebrate nervous system, but investigation has been limited by the lack of a suitable human CNS surrogate cell model system for in vitro studies and the inability of primary brain cultures to provide large numbers of pure neurons. To develop an in vitro model for studies of neuronal AChE expression and function, we utilized a neuronally committed human teratocarcinoma cell line, NTera 2, that can be induced to differentiate to a post‐mitotic CNS neuronal phenotype. We found that NTera 2 cells express multiple molecular forms of AChE that are similar to CNS‐derived AChE isoforms in velocity sedimentation profile, anion exchange elution profile, and sensitivity to inhibitors. At least two forms of ACNE are expressed (G1 and G4), similar to human and rodent brain, and induction of NTera 2 cell differentiation results in an increased G4/G1 ratio, which is characteristic of mature neurons. As in primary CNS neurons, AChE is present in NTera 2 cells in both the cytosolic fraction and in the outer membrane, and is also released in a soluble form. These observations indicate that NTera 2 cells provide a useful human model system for studies of expression of cell‐associated and soluble cell‐free AChE in developing and mature human neurons and for elucidating the potential role(s) of acetylcholinesterase metabolism in both normal development and neurodegenerative disease states. ©1995 Wiley

ISSN:0360-4012    

DOI:10.1002/jnr.490420608

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe morphological differentiation of oligodendrocytes is characterized by the formation of multiple, microtubule‐rich processes which endow these cells with the ability to myelinate many axons simultaneously. Since microtubule‐associated proteins (MAPs) strongly influence the structure and function of microtubules, we have investigated their expression in cultured differentiating oligodendrocytes in order to gain insights into MAP function during process formation and stabilization. MAPIB has been compared with two other structural MAPs: MAP4, which is an ubiquitously expressed protein, and MAP2, which hitherto was thought to be confined to neurons and reactive astrocytes. Immunof uorescence microscopy showed that the colocalization of MAP4 with microtubules in oligodendrocyte processes is not as extensive as found previously for MAP1B (Vouyiouklis and Brophy: J Neurosci Res 35:257–267, 1993). Nevertheless, like MAP1B, the expression of MAP4 increases during oligodendrocyte differentiation. In contrast, the expression of MAP2 is transiently elevated in preoligodendrocytes but declines precipitously at the onset of terminal differentiation. Cells of the oligodendrocyte lineage exclusively express a novel isoform of MAP2c which is primarily localized in the cell bodies of preoligodendrocytes. This suggests that MAP2c assists in the initiation of process extension rather than in the stabilization of microtubules in the cytoplasm‐filled membranous extensions of mature cells. MAP‐tau was not expressed at any developmental stage by oligodendrocytes. The distinct subcellular localizations and patterns of developmental expression of MAP1B, MAP4, and MAP2c suggest that these MAPs have different roles in the regulation of the microtubule network during the differentiation of myelin‐forming oligodendrocytes. ©1995 Wil

ISSN:0360-4012    

DOI:10.1002/jnr.490420609

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe A1adenosine receptor from pig brain cortex has been identified by means of two antipeptide antibodies against two domains of the receptor molecule: PC/10 antiserum was raised against a part of the third intracellular loop, and PC/20 antiserum was raised against a part of the second extracellular loop. PC/10 antibody was able to recognize a 39‐kDa band that corresponded to the Alreceptor, as demonstrated by immunoblotting and by immunoprecipitation of the molecule cross‐linked to [125I](R)‐2‐azidoN2‐p‐hydroxy(phenylisopropyl)adenosine. Besides the 39‐kDa band, PC/20 also recognized a 74‐kDa form that does not seem to correspond to a receptor‐G protein complex. The occurrence of the two bands was detected and analyzed in samples from different species and tissues showing a heterogeneous distribution of both. The 74‐kDa form can be converted into the 39‐kDa form by treatment with agonists or antagonists of Aladenosine receptors. These results suggest that A1adenosine receptor can occur in dimers and that the dimer–monomer conversion might be regulated by adenosine as the physiological ligand. Since the 74‐kDa aggregates were not recognized by PC/10, it is likely that part of the third intracellular loop participates in the protein–protein interac

ISSN:0360-4012    

DOI:10.1002/jnr.490420610

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractWe have previously shown that perinatal exposure to morphine impairs reactive plasticity of serotonin (5‐HT) neurons following selective neonatal lesion (Gorio et al., J Neurosci Res 34:462–471, 1993). This study shows that morphine inhibits also that the compensatory sprouting of intact axons after partial denervation. Neonatal 6‐OHDA injection causes norepinephrine (NE) depletion in the frontal cortex, which triggers a compensatory increase of dopamine, serotonin (5‐HT), and met‐enkephalin content correlated by the increased density of tyrosine hydroxylase– and 5‐HT–positive axons. In perinatal morphine‐treated rats, no compensatory changes are observed after neonatal 6‐OHDA depletion of NE in the frontal cortex. ©

ISSN:0360-4012    

DOI:10.1002/jnr.490420611

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY