bluuebunny/crossref_metadata_2025_split huggingface dataset:
Three isoforms of human myelin basic protein: Purification and structure
Authors: Deibler G. E. , Burlin T. V. , Stone A. L. 
Published: January 2005

AbstractMyelin basic protein (MBP) occurs in multiple forms. Three of these isoforms from human MBP (HMBP) have been highly purified. HMBP, component 1 (18.5 kDa HMNP‐1), was purified by ion‐exchange chromatography at pH 10.6 in 2 M urea. During this ion‐exchange chromatography, a fraction (Fraction 3), which contained HMBP component 3 (monophosphorylated or deamidated 18.5 kDa) and 17.2 kDa HMBP, was collected and further purified by fast protein liquid chromatography, which separated 17.2 kDa HMBP and HMDP component 3. When the latter was subjected to limited thrombic digestion, all of HMBP component 3 not phosphorylated at theonine 98 was cleaved. This digestion mixture was separated on Sephadex, and yielded pure component 3, monophosphorylated at theonine 98 (HMBP 3pT98), for which phosphate analysis yielded approximately 1 mole P/mole protein, and NMR showed only one phosphorylation site present.Circular dichroism (CD) studies were carried out on dilute solutions of HMBP‐1 (18.5 kDa), 17.2 kDa HMBP, and HMBP3pT98 (phosphorylated 18.5 kDa). The CD spectrum of HMBP‐1 was similar to that reported for rabbit MBP‐1 and bovine MBP‐1, but the spectra of 17.2 kDa HMBP and HMBP 3pT98 were distinctly different from HMBP‐1. When analyzed by best‐fit computations, 17.2 kDa HMBP showed about a 9% increase of ordered structure, and a greater increase, about 12%, was estimated for HMBP3pT98, attributable to β‐structure and β turn. © 1995 Wiley‐Liss, Inc.
Localization and partial characterization of a 60 kDa citrulline‐containing transport form of myelin basic protein from MO3‐13 cells and human white matter
Authors: Ursell M. R. M. , McLaurin J. , Wood D. D. , Ackerley C. A. , Moscarello M. A. , Russell J. T. 
Published: January 2005

AbstractThe localization of myelin basic proteins (MBPs) in an immortalized human‐human hybrid cell line (MO3‐13) formed by fusion of rhabdomyosarcoma TE671‐TG6 with primary human oligodendrocytes, cultured from surgical specimens, demonstrated an intracellular localization in vesicles and vacuoles with an intricate internal membranous network and to the external surface of the cell by immunogold electron microscopy. The availability of antibodies to one of the components of MBP, i.e., the citrulline containing component (“C‐b”), permitted us to localize this component of MBP to intracellular vacuoles and also on the external surface of the MO3‐13 cells. Since the apposition of the external surfaces of the oligodendrocyte is responsible for the intraperiod line of the myelin sheath, localization of C‐8 to the external surface of non‐permeabilized cells by immunogold scanning electron microscopy is consistent with our observations that C‐8 is localized to the intraperiod line of myelin (McLaurin et al.: J Neurosci Res 35:618‐628, 1993).Western blots of isolated MBP from MO3‐13 cells, probed with an antibody reactive with residues 130‐137 of MBP, recognized a protein in the 60 kDa range. No immunoreactivity was found in the 18.5 kDa range. This 60 kDa protein also reacted with a monoclonal antibody raised with residues 70‐84 of MBP, 2 different polyclonals raised with whole bovine MBP, an antibody to human MBP raised in monkeys, and the anti‐citrulline antibody. These data strongly suggested that the 60 kDa protein contained MBP sequences within its primary structure. A similar protein has been isolated from human myelincontaining fractions but not from compact myelin demonstrating that the 60 kDa protein from MO3‐13 cells was not an artefact related to fusion. Sequence determination of peptides obtained from enzymic and chemical cleavages revealed that the 60 kDa protein contained MBP sequences and peptides with 55‐60% homology with dynamin, a protein involved in intracellular transport. These data suggest that the externalization of MBP in this cell involves transport by fusion of MBP with another protein. By sequestering MBP in a larger protein, the possibility of inducing autoimmune disease by MBP released, due to cell death, is minimized. © 1995 Wiley‐Liss, Inc.
Control of neuronal morphology in vitro: Interplay between adhesive substrate forces and molecular instruction
Authors: Lochter A. , Taylor J. , Braunewell K.‐H. , Holm J. , Schachner M. 
Published: January 2005

AbstractAmong the factors which influence neuronal morphology, the degree of substrate adhesivity has been suggested to play an important role in the growth and guidance of neurites. The present study was undertaken to investigate apparently contradictory results relating substrate adhesivity to the extent of neurite outgrowth. By using substrates coated with different concentrations of polyornithine to vary adhesivity, we could show that intermediate levels of neuron‐to‐substrate adhesive strength favored neurite outgrowth more than substrates of high or low adhesivity. However, when neurons were plated on substrates derived from the extracellular matrix, the strength of neuronto‐substrate adhesion was important for the growth of dendrite‐like minor neurites, but not for the extension of axon‐like major neurites, which grew independently of adhesive forces. On substrates of the cell adhesion molecule L1, growth of both major and minor neurites was adhesion‐independent. Finally, in the presence of tenascin added to the culture medium, neurite growth was inhibited irrespective of the adhesivity of the substrate and the presence of substrate‐bound extracellular matrix molecules or L1. These observations suggest that intermediate forces of adhesivity favor neurite growth in general, but that purely adhesive forces can be dominated by specific molecular instructions which differentially affect growth of major and minor neurites in positive and negative ways. © 1995 Wiley‐Liss, Inc.
Hierarchical analysis of the nerve growth factor‐dependent and nerve growth factor‐independent differentiation signaling pathways in PC12 cells with protein kinase inhibitors
Authors: Campbell X. Z. , Neet K. E. 
Published: January 2005

AbstractThe effects of a series of protein kinase inhibitors on nerve growth factor (NGF)‐dependent and NGF‐independent neurite outgrowth in PC12 cells have established an ordered relationship among those protein kinases sensitive to down regulation by bryostatin, stimulation by staurosporine, inhibition by sphingosine, or inhibition by 6‐thioguanine (6‐TG). Quantitation of the biphasic staurosporin effects on NGF‐induced neurite outgrowth (Hashimoto and Hagino: J Neurochem 53:1675‐1685, 1989) gave an IC50 of 2‐4 nM for inhibition and an EC50 of 15‐20 nM for induction of neurite extension. Both sphingosine and 6‐TG inhibited neurite outgrowth induced by staurosporine and basic fibroblast derived growth factor (bFGF), as well as by NGF; therefore, sphingosine‐ and 6‐TG‐sensitive protein kinase steps occur after the convergence of the NGF, bFGF, and staurosporine signal pathways. Down regulation of protein kinase C by bryostatin chronic treatment, which inhibits NGF‐ and bFGF‐induced neuritogenesis (Singh et al.: Biochemistry 33:542‐551, 1994), did not inhibit the staurosporine‐induced neurite outgrowth. Thus, the bryostatin‐sensitive protein kinase C must occur subsequent to the convergence of the bFGF and NGF pathways, but before (or parallel to) staurosporine initiation of neurite outgrowth. In contrast, low concentrations of phorbol myristoyl acetate (PMA) or bryostatin, which activate protein kinase C activity, enhanced the staurosporine‐ or NGF‐induced neurite extension. These data indicate that stimulation of one or more protein kinase C isozymes can synergistically interact with the signaling pathway to increase the rate of neuritogenesis. Inhibition by 5‐7.5 nM staurosporine acted rapidly to arrest and decrease development of neurites up to 24 hr after NGF treatment, as did K252a and NGF ployclonal antibody addition. Our cellular data support the concept that staurosporine acts to inhibit the NGF receptor Trk (Nye et al.: Mol Biol Cell 3:677‐686, 1992), but that downstream steps can be activated by the higher concentration of staurosporine to bypass Trk and lead to neurite generation. Effects of staurosporine, 6‐TG, and sphingosine on c‐fos gene induction with or without NGF were not correlated with the generation of neurites. The sequence of protein kinases sensitive to these effectors appears to be in the order (but not consecutive) bryostatin, staurosporine, sphingosine, and 6‐TG. © 1995 Wiley‐Liss, Inc.
Radical formation site of cerebral complex I and Parkinson's disease
Authors: Fukushima T. , Tawara T. , Lsobe A. , Hojo N. , Shiwaku K. , Yamane Y. 
Published: January 2005

AbstractParaquat was reduced to the paraquat radical via complex I in bovine cerebral mitochondria and accelerated lipid peroxidation. Thirty‐kilodalton subunit of complex I was considered to be the radical formation site, because of its marked destruction by the paraquat radical. The lipid peroxidation by the paraquat radical was suppressed not only by superoxide dismutase (SOD) but also by mannitol. The destruction of complex I subunits via lipid peroxidation must have been caused by the hydroxyl radical which was formed from the superoxide radical. The same phenomenon was observed by using 1‐methylnicotinamide (MNA), which contains the same partial structure as paraquat in itself and is metabolized from nicotinamide in a living body. We observed NADH oxidation by MNA via cerebral complex I (Km = 26.3 mM), and MNA destroyed some complex I subunits, especially 30‐kilodalton protein. Paraquat might be useful for studying the pathogenesis of Parkinson's disease (PD) in vitro, and MNA is expected to be one of the causal substances of PD from the viewpoint of the oxidative stress theory. © 1995 Wiley‐Liss, Inc.
Coordinated upregulation of α1‐ and β11‐tubulin mRNAs during collateral axonal sprouting of central peptidergic neurons
Authors: Paden C. M. , Zhou X. , Watt J. A. , Burton R. , Pickett J. , Oblinger M. M. 
Published: January 2005

AbstractAn in situ hybridization study was performed to determine the relationship between levels of mRNAs for the axonal growth‐associated αl‐tubulin and βZII‐tubulin isotypes and the process of collateral axonal sprouting by identified central nervous system (CNS) neurons. A unilateral hypothalamic knife‐cut was used to hemisect the hypothalarnoneurohypophysial tract, which results in a robust collateral sprouting response by the uninjured neurons of the contralateral supraoptic nucleus (SON) (Watt and Paden: Exp Neurol 111:9‐24, 1991). At 10 and 30‐35 days after the lesion, cryosections of the SON were obtained and hybridized with 35S‐labeled cDNA probeses specific to αl‐ and β11‐tubulin mRNAs. Quantitative evaluation of the resulting autoradiographs revealed that αl‐tubulin mRNA levels were significantly increased by 10 days in SON neurons that were undergoing collateral sprouting compared to controls and that this increase was sustained at 30‐35 days post‐lesion. Less marked increases in hybridization intensity of the βII‐tubulin probe were also apparent in sprouting neurons at both 10 and 30‐35 days after the lesion, but were statistically significant only at 10 days. The measured increases in intensity of hybridization of αl‐ and β11‐tubulin probes are likely to be conservative estimates of the underlying increase in αl‐ and β11‐tubulin mRNA levels because sprouting SON neurons undergo significant hypertrophy. High levels of both αl‐ and βII‐tubulin mRNAs were also seen in surviving axotomized SON neurons ipsilateral to the hypothalamic lesion. We conclude that the pattern of regulation of αl‐ and β11‐tubulin mRNAs in CNS neurons which are capable of supporting new axonal growth includes three elements: maintenance of significant basal αl‐ and β11‐tubulin mRNA pools in mature neurons, rapid increases in the pool size of the mRNAs following stimulation of collateral sprouting, and sustained elevation of mRNA levels during the period of axonal sprouting. © 1995 Wiley‐Liss, Inc.
Spontaneous opening of the acetylcholine receptor channel in developing muscle cells from normal and dystrophic mice
Authors: Franco‐Obregón A. , Lansman J. B. 
Published: January 2005

AbstractSingle‐channel activity was recorded from cell‐attached patches on skeletal muscle cells isolated from wild‐type mice and from mice carrying the dy or mdx mutations. Spontaneous openings of the nicotinic acetylcholine receptor channel (nAChR) were detected in virtually all recordings from either dy/dy or dy/ + myotubes, but only infrequently from wild‐type or mdx myotubes. Spontaneous openings were also present in most recordings from undifferentiated myoblasts from all of the mouse strains studied. The biophysical properties of the spontaneous activity were similar to those of the embryonic form of the nAChR in the presence of acetylcholine (ACh). Examination of the single‐channel currents evoked by low concentrations of ACh showed a reduced sensitivity to the agonist in the dystrophic dy and mdx myotubes, but not in wild type myotubes. The results suggest that alterations in nAChR function are associated with the pathogenesis of muscular dystir ophy in the dy mouse. © 1995 Wiley‐Liss, Inc.
Regulation of protease nexin‐1 and angiotensin II receptor subtype 1 expression: Inverse relationship in experimental models of nerve injury
Authors: Bleuel A. , Monard D. 
Published: January 2005

AbstractThe up‐regulation of PN‐1 following nerve lesion has been investigated in vitro in cultures of dorsal root ganglion (DRG) explants, sciatic nerve segments, and isolated Schwann cells. In the first culture model, Schwann cells associated with neuronal processes synthesized small amounts of PN‐1. Injury of the neurites emerging from the DRGs led to enhanced levels of PN‐1 in Schwann cells located distal to the lesion site where degeneration of neuronal processes took place. In cultured sciatic nerve segments, PN‐1 synthesis increased with a time‐course comparable to that in ganglion explants following lesion. In the third model, PN‐1 levels gradually rose in isolated Schwann cells during the first 3‐8 days in culture. Dissociation of Schwann cells from the sciatic nerve therefore causes an effect similar to nerve damage. Impairment of Schwann cell‐neuron interactions was followed by a reduction in the expression levels of the angiotensin II (Ang II) receptor subtype AT1 in all three systems studied. Since the neuropeptide Ang II is able to repress PN‐1 synthesis in cultured Schwann cells, loss of neuronal contact might decrease their responsiveness to Ang II, thus resulting in PN‐1 upregulation by default. © 1995 Wiley‐Liss, Inc.
Laminin overrides the inhibitory effects of peripheral nervous system and central nervous system myelin‐derived inhibitors of neurite growth
Authors: David S. , Braun P. E. , Jackson D. L. , Kottis V. , McKerracher L. 
Published: January 2005

AbstractAxon growth inhibitory proteins associated with central nervous system (CNS) myelin are responsible in part for the absence of long distance axon regeneration in the adult mammalian CNS. We have recently reported that myelin‐associated glycoprotein (MAG), which is also present in peripheral nerves, is a potent inhibitor of neurite growth. This was surprising given the robust regenerative capacity of peripheral nerves. We now provide evidence that myelin purified from peripheral nerve also has neurite growth inhibitory activity. However, this activity can be masked by laminin, which is a constituent of the Schwann cell basal lamina. We also report that laminin, which is largely absent from the normal adult mammalian CNS, when added to purified CNS myelin, can override the neurite growth inhibitory activity in CNS myelin. These results have important implications for the development of strategies to foster axon regeneration in the adult mammalian CNS where multiple growth inhibitors exist. © 1995 Wiley‐Liss, Inc.
Relationship of lead‐induced proteins to stress response proteins in astroglial cells
Authors: Opanashuk L. A. , Finkelstein J. N. 
Published: January 2005

AbstractAstroglial cells are resistant to cell death and morphologic damage following lead (Pb) exposure at concentrations which elicit detrimental effects in neurons. A possible explanation may be that astroglial cells respond to Pb by increasing the expression of specific proteins, such as heat‐shock proteins (HSPs), which confer resistance to low levels of Pb. However, there has been relatively limited information regarding the ability of Pb to evoke the synthesis of HSPs. In the current study, pulse‐labeling of cultured astroglial proteins with [3H]‐leucine was used to evaluate the nature of Pb‐induced changes in protein expression. The effect of Pb on newly synthesized proteins was compared to the response elicited by heat‐shock and oxidative injury. Immunoblot analysis was utilized to examine alterations in levels of various stress proteins including HSP27, HSP70, HSP90, and heme oxygenase‐1 (HO‐1). Even though Pb induced the synthesis of proteins with estimated molecular weights of 23 kDa, 32 kDa, 70 kDa, and 90 kDa, the accumulation of HSPs other than HO‐1 was not observed. Hyperthermia and treatment with Na arsenite both resulted in enhanced expression of HSP70 and HO‐1. In addition, exposure to hydrogen peroxide (H2O2), cadmium (Cd), and lipopolysaccharide (LPS) stimulated a rise in HO‐1 levels. Although cellular insult failed to elicit an increase in either HSP27 or HSP90, cultured astroglia expressed readily detectable levels of both these proteins. Furthermore, Pb exposure resulted in the development of crosstolerance to subsequent injury by treatment with either Cd or H2O2. The results of this study indicate that Pb triggers a less conventional stress response in astroglial cells, which may provide enhanced resistance to the toxic effects of Pb. © 1995 Wiley‐Liss, Inc.
S‐100 immunoreactivity in rat brain glial cultures is associated with both astrocytes and oligodendrocytes
Authors: Richter‐Landsberg C. , Heinrich M. 
Published: January 2005

AbstractS‐100 protein, a Ca2+‐binding protein of the EFhand type, is most abundant in the brain, and is involved in cell differentiation and the molecular mechanisms underlying cytoskeletal organization. We have investigated the immunocytochemical localization of S‐100 protein in rat brain glial cultures prepared from the cerebral hemispheres of newborn rats. In mixed glial cultures, containing astrocytes type I and II and oligodendrocytes at various stages of differentiation, S‐100 immunoreactivity was detected in all three cell types. Double immunofluorescence analysis revealed that in astrocytes, S‐100 immunoreactivity was mainly colocalized with glial fibrillary acidic protein (GFAP), while in oligodendrocytes a close association with microtubular structures was observed.For immunoblot analysis, highly enriched oligodendrocytes and astrocytes were separately cultured for another week, and their extracts were analyzed by immunoblotting. The immunoblots of the cell extracts of both cell types showed a single S‐100‐immunoreactive polypeptide with an apparent molecular weight of approximately 12,000 daltons.Thus, the data presented here demonstrate that S‐100 protein is not confined to astrocytes but occurs also in oligodendrocytes of rat brain. The close association with the oligodendroglial cytoskeleton suggests that this protein could also play a regulatory role in the organization of microtubules in oligodendrocytes and hence may be involved in the formation and maintenance of the myelin‐containing membrane sheets. © 1995 Wiley‐Liss, Inc.
Neutrophilic defensins penetrate the blood‐brain barrier
Authors: Schluesener H. , Meyermann R. 
Published: January 2005

AbstractDefensins are small, cationic, cyclic peptides that are abundantly stored in granules of neutrophils. Defensins non‐specifically interact with membranes by forming weakly ion‐selective pores. Here we demonstrate immunolocalization of defensin‐secreting cells in human brain. Defensins, secreted by activated granulocytes, apparently are not prevented by the blood‐brain barrier (BBB) from diffusing across cerebral endothelium to penetrate the neuropil for a considerable distance from the granulocyte. This is in contrast to other neutrophil proteins like the granuleassociated enzyme elastase or the cytosolic protein MRP‐14, which are strictly localized to the cytoplasm or granules of neutrophils. Thus, defensins, known chemokinetic and chemotactic molecules, display a unique distribution at BBB sites. © 1995 Wiley‐Liss, Inc.
Two mitogenic regions of myelin basic protein interact with different receptors to induce Schwann cell proliferation in a cAMP dependent process
Authors: Tzeng S.‐F. , Deibler G. E. , Neuberger T. J. , DeVries G. H. 
Published: January 2005

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 of 125I‐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 bound 125I‐MBP, we conclude that MBP binds to the FGF receptor rather than other growth factor receptors. Furthermore, only MBP1–44 interacted with ganglioside GM1, whereas MBP152–167 did 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. ©1995 Wiley‐Liss, Inc.
On the mechanism of the inhibition of glutamine synthetase and creatine phosphokinase by methionine sulfoxide
Authors: Haghighi A. Zendedel , Maples K. R. 
Published: January 2005

AbstractBeta amyloid peptides (Aβ), etiologically associated with Alzheimer's disease (AD), have been shown to inhibit both glutamine synthetase (GS) and creatine phosphokinase (CPK) in vitro. These two enzymes are affected in AD and are sensitive to oxidative stress. Residue 35 of the Aβ25‐35, the most potent section of the 40–42 amino acid long fragment of amyloid precursor protein (APP), is a methionine, which has been reported to be oxidized to methionine sulfoxide presumably via a free radical oxidation process. We questioned whether methionine sulfoxide would inhibit GS and CPK directly and if this inhibition also involved free radical oxidative stress. In this report, we demonstrate that methionine sulphoxide inhibits GS by about 50% and CPK by about 25% at 20 mM concentration. Neither intact SOD, nor ascorbate inhibit the action of methionine sulfoxide completely, with regard to the inactivation of GS. These results indicate that the action of methionine sulfoxide may not be directly due to the oxidation of GS by free radicals. In fact, the presence of exogenous proteins, such as denatured SOD or catalase, inhibit the action of methionine sulfoxide as, or more effectively than, the addition of active free radical antioxidant enzymes. © 1996 Wiley‐Liss, Inc.