bluuebunny/crossref_metadata_2025_split huggingface dataset:
Protein kinase C in cultured adult human oligodendrocytes: A potential role for isoform α as a mediator of process outgrowth
Authors: Yong V. W. , Dooley N. P. , Noble P. G. 
Published: January 2005

AbstractThe extension of cellular processes from the oligodendrocyte soma is an early and critical event in myelin formation. Previous reports from this laboratory have implicated a role for protein kinase C (PKC) as an important intracellular mediator of this critical step in myelinogenesis. In the current study, the regrowth of fibers by adult human oligodendrocytes was examined and was found to be significantly enhanced by the PKC stimulator, 4β‐phorbol‐12,13‐didecanoate (PDB); this was accompanied by a 400–500% increase in oligodendroglial PKC activity. In contrast to other cell types, the increased PKC activity in oligodendrocytes was not followed by subsequent down‐regulation of the enzyme. The role of PKC in oligodendroglial process formation was further demonstrated by the ability of inhibitors of PKC to block the basal‐ or PDB‐enhanced fiber outgrowth. As well, studies employing isoform‐specific agonists implicated PKCα as the major determinant of fiber outgrowth by oligodendrocytes. The potential significance of PKC in myelin formation was further underscored by the observation that the synthesis of myelin basic protein, a prerequisite component for myelinogenesis, was increased by 2‐fold in PDB‐treated oligodendrocytes. Collectively, these observations suggest that PKC, in particular the α isoform, constitutes an important mediator in the initiation of myelin formation. © 1994 Wiley‐Liss, Inc.
Neurotrophin‐3 acquires NGF‐like activity after exchange to five NGF amino acid residues: Molecular analysis of the sites in NGF mediating the specific interaction with the NGF high affinity receptor
Authors: Kullander K. , Ebendal T. 
Published: January 2005

AbstractDespite the large sequence similarity around 55–60% among the known NGF‐related neurotrophins, the members display different activities on different subset of neurons. Recent studies have shown that the various neurotrophins are ligands with high affinity to different receptors of the Trk family of tyrosine kinase receptors. We wanted to elucidate what specific parts of NGF replaced in neurotrophin‐3 (NT‐3) would result in NGF‐like receptor binding and biological activity. By studying evolutionarily conserved amino acid sequences not shared by NT‐3 and NGF and excluding parts which have been examined in earlier work with NGF and BDNF chimeras as well as taking advantage of the crystallographic data available for NGF, we decided to exchange three specific blocks of two or three amino acids in the human NT‐3 backbone for the corresponding residues in NGF. The NGF residues Asn‐Ile‐Asn (43–45), Val‐Phe (48,49) and Gln‐Ala‐Ala (96–98) were combined in pairs and are all shown to contribute NGF‐like activity in the context of NT‐3. The most efficient NGF‐like transformation was obtained by the exchange of Pro‐Val and Leu‐Val‐Gly in NT‐3 to the NGF residues Val‐Phe and Gln‐Ala‐Ala. This mutant reached 90% NGF activity, based on survival of sympathetic neurons, stimulation of fibre outgrowth from sympathetic ganglia, the ability to block high affinity NGF binding to PC12 cells and phosphorylation of gp140trk. Thus, the three mutants with paired combinations of the NGF residues as well as the NT‐3 housing all three blocks of NGF residues were able to mimic NGF activity. This activity is gained, although the mutated neurotrophin proteins do not lose the original NT‐3 activity as ascertained by the stimulation of neurite outgrowth from the Remak ganglion. The three mutated sites are situated in two β‐loops at one end of the NGF molecule, forming a cleft that could specifically interact with high affinity to the signalling NGF receptor gp140trk.Copyright © 1994 Wiley‐Liss, Inc.
Subnanomolar concentration of VIP induces the nuclear translocation of protein kinase C in neonatal rat cortical astrocytes
Authors: Oláh Z. , Lehel Cs. , Anderson W. B. , Brenneman D. E. , v. Agoston D. 
Published: January 2005

AbstractAt subnanomolar concentrations, vasoactive intestinal peptide (VIP) can act as an astroglial mitogen and as a secretagogue for neurotrophic substances released from glia (Brenneman et al.: J Neurosci Res 25:386–394, 1990). Here we report that treatment with subnanomolar (0.1 nM) VIP, that does not produce an increase in intracellular cAMP levels, induced the translocation of protein kinase C (PKC) from the cytoplasm to the nucleus in neonatal cortical astrocytes, as revealed by immunohistochemistry, Western blot analysis, and measurements of the enzyme activity. Western blot analysis of subcellular fractions, using PKC isotype‐specific antisera, showed PKC alpha as well as the two novel PKC isotypes, delta and zeta immunoreactivities, whereas PKC beta or gamma immunoreactivities were not detected. PKC alpha was associated predominantly with the cytosolic compartment, while PKC delta was found in the plasma membrane and in nuclear fractions. In contrast, PKC zeta was distributed ubiquitously within the major subcellular fractions. Treatment of the cells with 0.1 nM VIP caused a marked increase in nuclear PKC alpha and, to a lesser extent, PKC delta and PKC zeta immunoreactivities. Western blot analysis showed that a low (1 nM) concentration of phorbol, 12‐myristate, 13 acetate also caused the subcellular redistribution of PKC immunoreactivities from the cytoplasm to the nuclear fraction, similar to VIP treatment. Exposure of astrocytes to high concentrations (1 μM) of phorbol, 12‐myristate, 13 acetate resulted in the down‐regulation of PKC alpha and PKC delta, while distribution of PKC zeta immunoreactivities were only slightly altered. Measurements of Ca2+‐ and phospholipid‐dependent PKC activities also showed a VIP‐induced redistribution of PKC activity from the cytoplasmic to the nuclear fractions. These results suggest that PKC may be involved in the signal transduction process elicited by VIP binding to the high affinity VIP receptors present on cortical astrocytes. The observed changes in the nuclear localization of PKC alpha and PKC delta in response to subnanomolar VIP may play a role in mediating the cellular response(s) to this peptide during neurodevelopment. © 1994 Wiley‐Liss, Inc.This article is a US Government work and, as such, is in the public domain in the United States of America.
Duration of expression of inducible nitric oxide synthase in glial cells
Authors: Park S. K. , Murphy S. 
Published: January 2005

AbstractLippolysaccharide (LPS) or a combination of interleukin (IL)‐1ß and interferon (IFN)‐γ cause transcriptional induction of a calcium‐independent nitric oxide synthase (NOS) in astrocytes and C6 glioma cells. LPS induction of NOS in C6 cells was evidenced by a small amount of nitrite accumulation as compared with cells exposed to IL‐1ß/IFN‐γ, but the maximal NOS activity achieved (as revealed by cGMP formation) was the same. The NOS activity induced by LPS in C6 cells was maximal at 4 to 8 hr and then rapidly decreased, while NOS activity induced by IL‐1ß/IFN‐γ slowly decreased after 4 hr. In addition, the effects of re‐presenting IL‐1ß/IFN‐γ to both astrocytes and C6 cells after maximal induction of activity of the inducible from of NOS were studied. The re‐addition of cytokines prolonged both NOS mRNA expression and also enzyme activity, suggesting effects at either the transcriptional (further induction) or translational level (mRNA stability). These results imply that the time course of NO production by induced astrocytes depends both upon the nature of the inducing stimulus and the frequency of the cells' exposure to it. © 1994 Wiley‐Liss, Inc.
Differential expression of α‐actin mRNA and immunoreactive protein in brain microvascular pericytes and smooth muscle cells
Authors: Boado R. J. , Pardridge W. M. 
Published: January 2005

AbstractHypertension has been linked to opening of the blood‐brain barier and may be related to the expression of the smooth muscle α‐actin gene in contractile cells at the brain microvasculature. However, the cellular origin (i.e., endothelial cells, pericytes, smooth muscle cells) of the α‐actin mRNA in the brain microvasculature is not clearly identified. Therefore, we investigated the abundance of actin mRNA by Northern blot analysis in isolated brain microvessels and in brain microvascular endothelia or pericytes in tissue culture. All samples showed the characteristic 2.1 kb transcript corresponding to cytoplasmic and δ isoform mRNA. The 1.7 kb transcript corresponding to smooth muscle α‐actin was detected in freshly isolated bovine brain microvessels, in primary cultures of brain microvasular pericytes, or endothelial cells; the latter cultures contain both endothelial cells and pericytes. The α‐actin mRNA was absent in a cloned bovine brain endothelial cell line. The relative abundance of the α/(+γ) actin transcript ratio was: cultured pericytes > freshly isolated microvessels > endothelial primary. The cellular distribution of the smooth muscle α‐actin immunoreactive protein was studied by immunocytochemistry in cytospun/methanol‐fixed isolated bovine brain microvessels with a monoclonal antibody directed to the amino‐terminal decapeptide of the smooth muscle α‐actin isoform. This antibody reacted strongly with precapillary arterioles of isolated microvessels, whereas no immunostaining was observed in either capillary endothelial cells or in pericytes. In conclusion, the αL‐actin mRNA is expressed in brain microvascular pericytes in tissue culture, but the immunoreactive α‐actin protein is not expressed in brain microvascular pericytes in vivo. These data suggest that either (1) α‐action gene expression is induced in capillary pericytes in tissue culture or (2) α‐action mRNA in brain capillary pericytes in vivo is subject to translational repression resulting in no detectable α‐actin protein under normal conditions. © 1994 Wiley‐Liss, Inc.
C‐terminal CTII motif of 2′,3′‐cyclic nucleotide 3′‐phosphodiesterase undergoes carboxylmethylation
Authors: Cox M. E. , Gao E. N. , Braun P. E. 
Published: January 2005

AbstractEukaryotic proteins with a carboxyl‐terminal CaaX motif are modified by isoprenylation and subsequently processed by proteolysis of the three terminal amino acids and carboxylmethylation of the exposed cysteine residue. The myelination‐associated 2′,3′‐Cyclic Nucleotide 3′‐Phosphodiesterase (CNP) has a C‐terminal CTII sequence and is isoprenylated; however, no examples of subsequent processing exist when threonine, a polar residue, is located adjacent to the cysteine. Here we show that CNP is capable of being carboxylmethylated in both insect cells and glioma cells. This processing is dependent upon isoprenylation of the cysteine and can be inhibited with the isoprenylated cysteine derivative, N‐acetyl‐S‐farnesyl‐L‐cysteine. Although the role of the methyl group at the C‐terminus of other isoprenylated proteins is not fully understood, modulation of signal transduction pathways is strongly indicated. This modification of CNP may similarly regulate cell biological processes in myelinogenesis. © 1994 Wiley‐Liss, Inc.
Time course of ciliary neurotrophic factor mRNA expression is coincident with the presence of protoplasmic astrocytes in traumatized rat striatum
Authors: Asada H. , Ip N. Y. , Pan L. , Razack N. , Parfitt M. M. , Plunkett Robert J. 
Published: January 2005

AbstractAdrenal grafting for Parkinson's disease has led to modest functional improvement despite poor graft survival. One explanation is a neurotrophic response within the traumatized striatum. This study was undertaken to investigate the time course of the astrocytic response in vivo and in vitro, and the expression of ciliary neurotrophic factor (CNTF) mRNA following striatal injury. Unilateral stereotaxic biopsy of the rat striatum was performed and gelatin sponge (gelfoam) was immediately placed into the biopsy cavity. Rats were sacrificed on days 1,3,5,7,14, and 28 post biopsy. Immunohistochemical staining of the traumatized striatum with antibodies to glial fibrillary acidic protein (GFAP) was carried out. The reactive astrocytes which appeared within 7 days after trauma were mostly protoplasmic on the basis of morphology, and maximal on day 7, being 30 times the level in the normal striatum. After day 7, fibrous astrocytes appeared and increased up to day 28, while protoplasmic astrocytes decreased. In addition, immunocytochemical double staining of short term cultured astrocytes from the traumatized striatum with anti‐A2B5 and anti‐GFAP antibodies revealed that 84% and 90% of astrocytes were type 1 astrocytes on days 3 and 7, respectively; however, by day 28 47% of astrocytes were type 2. Northern blot analysis revealed that CNTF mRNA expression was up‐regulated and peaked on day 7, coincident with a predominance of protoplasmic astrocytes in vivo and type 1 astrocytes in vitro, respectively. These finding suggest that the expression of CNTF mRNA is part of the early astrocytic response to trauma, particularly associated with protoplasmic astrocytes in vivo and type 1 astrocytes in vitro. We conclude that reactive astrocytes are likely candidates to produce the neurite promoting activity seen in previous studies after trauma in the striatum. CNTF may represent an early signal in the astrocyte‐mediated neurotrophic and neurite promoting responses. © 1995 Wiley‐Liss, Inc.
Release of endogenous catecholamines from the striatum and bed nucleus of stria terminalis evoked by potassium and N‐methyl‐D‐aspartate: In vitro microdialysis studies
Authors: Aliaga E. , Bustos G. , Gysling Katia 
Published: January 2005

AbstractInduced release of endogenous dopamine and noradrenaline from coronal slices containing the striatum and the bed nucleus of the stria terminalis, respectively, was studied by means of in vitro microdialysis. A Ca+2‐dependent and reserpine‐sensitive K+‐induced release of catecholamines was detected in both nuclei. We confirmed that N‐methyl D‐aspartate (2.5 and 5.0 mM in the dialysis perfusion solution) induces the release of dopamine from the striatum, and this effect was blocked by prior dialysis perfusion with 500 μM MK‐801, a noncompetitive N‐methyl‐D‐aspartate receptor antagonist. Infusion of N‐methyl‐D‐aspartate (1–10 mM) or glutamate through the dialysis probe did not produce any detectable modification in the extracellular levels of noradrenaline in the bed nucleus of the stria terminalis. In addition, perfusion with D‐serine (100 μM)alone or in the presence of desipramine (10 μM) resulted in a slight increase in extracellular noradrenaline in the bed nucleus of the stria terminalis. However, N‐methyl‐D‐aspartate in the presence of D‐serine and desipramine produced a marked increase in extracellular noradrenaline from the bed nucleus of the stria terminalis. These results indicate that N‐methyl‐D‐aspartate receptors might regulate the release of noradrenaline from the bed nucleus of the stria terminalis as is the case of dopamine release in the striatum. The in vitro microdialysis seems to be a suitable complement to the in vivo microdialysis for the study of catecholamine release in discrete regions of the central nervous system and its local regulation by excitatory amino acid receptors. © 1995 Wiley‐Liss, Inc.
Survival, development, and electrical activity of central nervous system myelinated axons exposed to tumor necrosis factor in vitro
Authors: Dugandžija‐Novaković S. , Shrager Peter 
Published: January 2005

AbstractSpinal cord explants from CD‐1 mouse embryos were cultured in Maximow slide assemblies to promote myelin development. At about 20 days in vitro, recombinant human or mouse tumor necrosis factor alpha (TNFa) was added. Observed 3–8 days later, myelin was largely intact. The myelin blistering and oligodendrocyte damage seen in other strains were generally absent. Axonal conduction was measured optically through the use of a voltage‐sensitive dye. Action potential shape, conduction velocity, and refractory period were all unchanged by exposure to TNFa. Two series of explants were grown with TNFa present continuously throughout the culture period. Observed with light and electron microscopy, myelin developed in at least 50% of the explants treated with recombinant mouse TNFα and 80% of those exposed to recombinant human TNFα. Optically recorded action potentials were of normal shape and refractory period. Conduction velocities were slightly lower than controls. CD‐1 mouse central nervous system contains TNFα receptors and yet was resistant to myelin damage. The apparent strain specificity of TNFα disruption of myelin may result from more indirect modes of action, including interaction with other cytokines produced by glial cells. Survival of axonal conduction suggest that Na+ channel function remains intact following TNFα exposure. © 1995 Wiley‐Liss, Inc.
AMPA‐selective glutamate receptor subunits in the rat hippocampus during aging
Authors: Nicoletti V. G. , Condorelli D. F. , Dell'Albani P. , Ragusa N. , Stella Anna Maria Giuffrida 
Published: January 2005

AbstractThe levels of mRNAs for the subunits of α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazole propionate (AMPA)‐selective glutamate receptors (GluR‐1, ‐2, ‐3, ‐4) in the rat hippocampus during aging were measured by Northern blotting. The distribution of these receptors was also examined at the protein level by immunoblotting using antibodies to GluR‐1 and to an epitope common to GluR‐2 and GluR‐3 (denoted GluR‐2/3). During aging a significant decrease of GluR‐1 protein, but no change in the corresponding mRNA level, was observed. No differences in the level of GluR‐2/3 protein and GluR‐2, ‐3, and ‐4 mRNAs at the various ages examined (4, 12, and 24 months) were detected. Our results show that AMPA receptors are only slightly influenced by the aging process in the rat hippocampus. The slight decrease in GluR‐1 protein content, not accompanied by a parallel decrease in the GluR‐1 mRNA level, might be explained by a decreased translational efficiency or an increased protein degradation of the GluR‐1 subunit. © 1995 Wiley‐Liss, Inc.
Modulation of ischemic signal by antagonists of N‐methyl‐D‐aspartate, nitric oxide synthase, and platelet‐activating factor in gerbil hippocampus
Authors: Zablocka B. , Lukasiuk K. , Lazarewicz J. W. , Domańska‐Janik K. 
Published: January 2005

AbstractCerebral ischemia in the gerbil results in early hippocampal changes, which include transient activation and/or translocation of protein kinase C (PKC), increased enzymatic activity of ornithine decarboxylase (ODC), and elevated DNA binding ability of activator protein‐1 (AP1). The time‐course of all three of these postischemic responses was found to be almost parallel, peaking at 3 hr after the ischemic insult. The effectiveness of known modulators of postischemic morphological outcome (MK‐801, L‐NAME, and gingkolides BN 52020 and BN 52021) in counteracting the induction of PKC, ODC, and AP1 formation was tested. These drugs were administrated as followed: MK‐801 (a noncompetitive inhibitor of NMDA channel), 0.8 mg/kg i.p., 30 min before ischemia, and 5 min after the insult; L‐NAME (competitive inhibitor of NO synthase), 10 mg/kg i.p., 30 min before ischemia, and 5 mg/kg, 5 min after ischemia; BN52020 and BN52021 (inhibitors of platelet‐activating factor: PAF receptors) were administered as a suspension in 5% ethanol in water by oral route, 10 mg/kg for 3 days before ischemia. Three of these drugs, MK‐801, L‐NAME, and BN52021, significantly reduced ischemia‐elevated activity of PKC and ODC, whereas AP1 formation was only partially attenuated. Our observations implicate the existence of different mechanism(s) for postischemic PKC and ODC activation, which in turn is engaged in AP1 induction. © 1995 Wiley‐Liss, Inc.
Caldesmon and low Mr isoform of tropomyosin are localized in neuronal growth cones
Authors: Kira M. , Tanaka J. , Sobue Kenji 
Published: January 2005

AbstractNeuronal growth cones move actively, accompanying changes in intracellular Ca2+ concentration. The movement of growth cones may partly depend on the actomyosin system, considering the presence of actin and myosin II. Yet, Ca2+‐sensitive regulatory proteins for the actomyosin system have not been identified in growth cones. In the present study, caldesmon, an inhibitory protein on actin‐myosin interaction, was detected in the growth cone fraction isolated from embryonic rat brain, using immunoblotting with the antibody to chicken gizzard caldesmon. Morphological evidence of caldesmon in growth cones of cultured rat neurons was obtained using the indirect immunofluorescence method. Since inhibition of caldesmon on actin‐myosin interaction can be overcome by calmodulin and Ca2+, caldesmon may be involved in the Ca2+‐dependent regulation in growth cone motility. Tropomyosin is another member of the actomyosin system whose function may be regulated by caldesmon in smooth and nonmuscle cells. A low Mr isoform of tropomyosin was distributed in the growth cone fraction. Using specific antibodies against tropomyosin isoforms, we further clarified morphologically that the low Mr isoform was localized in growth cones, but not the high Mr isoform. High Mr isoforms of tropomyosin were present in nonneuronal cells. Actin filaments in growth cones may be unstable, since low Mr tropomyosin binds to actin filaments with a lower affinity than high Mr isoforms. The instability of actin filaments may be suitable for the rapid movement and shape changes of growth cones. © 1995 Wiley‐Liss, Inc.
Hyaluronic acid through a new injectable nerve guide delivery system enhances peripheral nerve regeneration in the rat
Authors: Seckel Brooke R. , Jones D. , Hekimian K. J. , Wang K.‐K. , Chakalis D. P. , Costas P. D. 
Published: January 2005

AbstractThe use of non‐neural conduits to bridge gaps in peripheral nerves has been noted in the literature for many years. A logical extension of this concept is the introduction of neurotrophic or growth promoting factors into the lumen. We present here an injectable nerve guide that allows percutaneous access to the microenvironment of the regenerating peripheral nerve within the guide's lumen. Hyaluronic acid, a compound associated with decreased scarring and improved fibrin matrix formation, is added sequentially to the regenerating peripheral rat sciatic nerve via this injectable nerve guide. Assessment of nerve regeneration and reinnervation shows better conduction velocity, higher axon counts, and a trend toward earlier myelination with hyaluronic acid compared with saline. This work not only implies hyaluronic acid's role as an agent that aids nerve growth but also describes a new tool that allows percutaneous access to the milieu of a regenerating nerve. © 1995 Wiley‐Liss, Inc.