bluuebunny/crossref_metadata_2025_split huggingface dataset:
The phosphorylation state of neuronal processes determines growth cone formation after neuronal injury
Authors: Geddis Matthew S. , Rehder Vincent 
Published: February 2004

AbstractGrowth cones are essential for neuronal pathfinding during embryonic development and again after injury, when they aid in neuronal regeneration. This study was aimed at investigating the role of kinases in the earliest events in neuronal regeneration, namely, the formation of new growth cones from injured neuronal processes. Neurites of identified snail neurons grown in vitro were severed, and the formation of growth cones was observed from the ends of such transected processes. Under control conditions, all neurites formed a new growth cone within 45 min of transection. In contrast, growth cone formation in the presence of a general kinase inhibitor, K252a, was significantly inhibited. Moreover, decreasing the phosphorylation state of neurites by activating protein phosphatases with C2‐ceramide also reduced growth cone formation. Pharmacological analysis with specific kinase inhibitors suggested that targets of protein kinase C (PKC) and tyrosine kinase (PTK) phosphorylation control growth cone formation. Inhibition of PKC with calphostin C and cerebroside completely blocked growth cone formation, whereas the inhibition of PTK with erbstatin analog significantly reduced growth cone formation. In contrast, inhibitors of protein kinase A, protein kinase G, CaM‐kinase II, myosin light‐chain kinase, Rho kinase, and PI‐3 kinase had little or no effect 45 min after transection. These results suggest that the transformation underlying the formation of a growth cone from an injured (transected) neurite stump is highly sensitive to the phosphorylation state of key target proteins. Therefore, injury‐induced signaling events will determine the outcome of neuronal regeneration through their action on kinase and phosphatase activities. © 2003 Wiley‐Liss, Inc.
Lymphocyte regulation of neuropeptide gene expression after neuronal injury
Authors: Armstrong Brian D. , Hu Zhongting , Abad Catalina , Yamamoto Miya , Rodriguez Williams I. , Cheng Jennifer , Tam Jimmy , Gomariz Rosa P. , Patterson Paul H. , Waschek James A. 
Published: February 2004

AbstractThe neuropeptides vasoactive intestinal peptide (VIP) and pituitary adenylyl cyclase‐activating peptide (PACAP) are induced strongly in neurons after several types of injury, and exhibit neuroprotective actions in vitro and in vivo. It is thought that changes in expression of neuropeptides and other molecules in injured neurons are mediated by new factors produced in Schwann and immune cells at the injury site, a loss of target‐derived factors, or a combination of mediators. To begin to determine the role of the inflammatory mediators, we investigated axotomy‐induced changes in VIP and PACAP gene expression in the facial motor nucleus in severe combined immunodeficient (SCID) mice, and in mice with targeted mutations in specific cytokine genes. In normal mice, VIP and PACAP mRNA was induced strongly in facial motor neurons 4 days after axotomy. The increase in PACAP mRNA was blocked selectively in SCID mice, indicating that mechanisms responsible for VIP and PACAP gene induction are not identical. The loss of PACAP gene expression in SCID mice after axotomy was fully reversed by an infusion of normal splenocytes, suggesting that PACAP mRNA induction requires inflammatory mediators. PACAP and VIP mRNA inductions, however, were maintained in mice lacking leukemia inhibitory factor (LIF) and interleukin‐6 (IL‐6), and in mice lacking both receptors for tumor necrosis factor α (TNFα). The data suggest that an inflammatory response, most likely involving T lymphocytes, is necessary for the axotomy‐induced increase in PACAP but not in VIP. LIF, IL‐6, and TNFα, however, are not required for this response to injury. © 2003 Wiley‐Liss, Inc.
Presenilin 1 is involved in maturation and trafficking of N‐cadherin to the plasma membrane
Authors: Uemura Kengo , Kitagawa Naoyuki , Kohno Ryuichi , Kuzuya Akira , Kageyama Takashi , Chonabayashi Kazuhisa , Shibasaki Hiroshi , Shimohama Shun 
Published: February 2004

AbstractOne pathological characteristic of Alzheimer's disease (AD) is extensive synapse loss. Presenilin 1 (PS1) is linked to the pathogenesis of early onset familial Alzheimer's disease (FAD) and is localized at the synapse, where it binds N‐cadherin and modulates its adhesive activity. To elucidate the role of the PS1/N‐cadherin interaction in synaptic contact, we established SH‐SY5Y cells stably expressing wild‐type (wt) PS1 and dominant‐negative (D385A) PS1. We show that the formation of cadherin‐based cell–cell contact among SH‐SY5Y cells stably expressing D385A PS1 was suppressed. Conversely, wt PS1 cells exhibited enhanced cell–cell contact and colony formation. Suppression of cell–cell contact in D385A cells was accompanied by an alteration in N‐cadherin subcellular localization; N‐cadherin was retained mainly in the endoplasmic reticulum (ER) and cell surface expression was reduced. We conclude that PS1 is essential for efficient trafficking of N‐cadherin from the ER to the plasma membrane. PS1‐mediated delivery of N‐cadherin to the plasma membrane is important for N‐cadherin to exert its physiological function, and it may control the state of cell–cell contact. © 2003 Wiley‐Liss, Inc.
Fos‐B expression is required for polyamine‐induced increase in nuclear activator protein‐1 DNA binding in discrete structures of murine brain
Authors: Inoue Keiji , Kuramoto Nobuyuki , Sugiyama Chie , Taniura Hideo , Sakata Katsumi , Fujinami Yoshiaki , Ogita Kiyokazu , Yoneda Yukio 
Published: February 2004

AbstractSpermidine (SPD) and spermine (SPN) have been shown to be endogenous agonists for N‐methyl‐D‐aspartate (NMDA) receptors that could lead to expression of the nuclear transcription factor activator protein‐1 (AP1) complex in the mammalian central nervous system both in vitro and in vivo. In nuclear extracts of murine whole brain, AP1 DNA binding increased significantly in a concentration‐dependent manner with the addition of either SPD or SPN at a concentration range of 50–500 μM. Similarly, the nuclear proteins histone and dephosphorylated casein, but not phosphorylated casein, significantly increased AP1 DNA binding alone but in the presence of either SPD or SPN did not increase further binding. By contrast, another endogenous polyamine, putrescine, significantly prevented AP1 DNA binding increases by histone and dephosphorylated casein, but did not by itself significantly alter binding. Invariably, SPD and SPN effected significantly increased AP1 DNA binding in neocortex, hippocampus, striatum, midbrain, hypothalamus and cerebellum, but not in medulla‐pons and spinal cord. Supershift and Western blotting analyses revealed relatively high constitutive expression of Fos‐B protein in neocortex and hippocampus, but not in medulla‐pons and spinal cord. Immunoprecipitation of Fos‐B led to complete abolition of the ability of SPN and SPD to increase AP1 DNA binding in neocortical and hippocampal nuclear extracts. These results suggest that expression of Fos‐B protein may be required for modulation of nuclear gene transcription by both SPD and SPN through stimulation DNA‐binding activity of AP1 complex in murine central structures. © 2003 Wiley‐Liss, Inc.
Blood‐spinal cord barrier after spinal cord injury: Relation to revascularization and wound healing
Authors: Whetstone William D. , Hsu Jung‐Yu C. , Eisenberg Manuel , Werb Zena , Noble‐Haeusslein Linda J. 
Published: February 2004

AbstractSpinal cord injury produces prominent disruption of the blood‐spinal cord barrier. We have defined the blood‐spinal cord barrier breakdown to the protein luciferase (61 kDa) in the acutely injured murine spinal cord and during revascularization. We show that newly formed and regenerating blood vessels that have abnormal permeability exhibit differential expression of the glucose‐1 transporter (Glut‐1), and that its expression is dependent on astrocytes. There was overt extravasation of luciferase within the first hour after injury, a period that coincided with marked tissue disruption within the epicenter of the lesion. Although there was a significant reduction in the number of blood vessels relative to controls by 24 hr after injury, abnormal barrier permeability remained significantly elevated. A second peak of abnormal barrier permeability at 3–7 days postinjury coincided with prominent revascularization of the epicenter. The barrier to luciferase was restored by 21 days postinjury and vascularity was similar to that of controls. During wound‐healing process, the cord was reorganized into distinct domains. Between 14 and 21 days postinjury, each domain consisted primarily of nonneuronal cells, including macrophages. Astrocytes were limited characteristically to the perimeter of each domain. Only blood vessels affiliated closely with astrocytes in the perimeter expressed Glut‐1, whereas blood vessels within each domain of the repairing cord did not express it. Together, these data demonstrate that both injured and regenerating vessels exhibit abnormal permeability and suggest that Glut‐1 expression during revascularization is dependent on the presence of astrocytes. © 2003 Wiley‐Liss, Inc.
HIV‐1 Tat protein alters tight junction protein expression and distribution in cultured brain endothelial cells
Authors: András Ibolya E. , Pu Hong , Deli Mária A. , Nath Avindra , Hennig Bernhard , Toborek Michal 
Published: February 2004

AbstractDisruption of the blood‐brain barrier (BBB) is widely believed to be the main route of human immunodeficiency virus (HIV) entry into the central nervous system (CNS). Although mechanisms of this process are not fully understood, alterations of tight junction protein expression can contribute, at least in part, to this phenomenon. Tight junctions are critical structural and functional elements of cerebral microvascular endothelial cells and the BBB. The aim of the present study was to examine the effects of HIV‐1 Tat protein on expression of tight junction proteins. Primary cultures of brain microvascular endothelial cells (BMEC) were employed in these experiments. A 24‐hr exposure of BMEC to Tat1–72 resulted in a decrease of claudin‐1, claudin‐5, and zonula occludens (ZO)‐2 expression, whereas total levels of occludin and ZO‐1 remained unchanged. In addition, a short (3‐hr) exposure of BMEC to Tat1–72 induced cellular redistribution of claudin‐5 immunoreactivity. Tat1–72‐induced alterations of claudin‐5 expression also were confirmed in vivo where Tat1–72 was injected into the right hippocampus of mice. These findings indicate that HIV‐1 Tat protein can markedly affect expression and distribution of specific tight junction proteins in brain endothelium. Alterations of only distinct tight junction proteins suggest a finely tuned effect of Tat1–72 on the BBB. Because tight junction proteins are critical for the barrier function of the BBB, such alterations can lead to disturbances of the BBB integrity and contribute to HIV trafficking into the brain. © 2003 Wiley‐Liss, Inc.
Involvement of Gas7 in nerve growth factor‐independent and dependent cell processes in PC12 cells
Authors: Chao Chuck C.‐K. , Su L.‐J. , Sun N.‐K. , Ju Y.‐T. , Lih Jason C.‐J. , Lin‐Chao Sue 
Published: February 2004

AbstractGas7, a growth arrest‐specific gene originally isolated from serum‐starved mouse fibroblast cells, is expressed in vivo predominantly in the brain and is required for neurite formation in cultured mouse cerebellar neurons (Ju et al. [ 1998] Proc. Natl. Acad. Sci. USA 95: 11423–11428). Here we report that Gas7 plays a key role in the morphological differentiation of PC12 preneuronal rat pheochromocytoma cells (PC12 cells). We found that overexpression of murine Gas7 in PC12 cells leads to an expanded cell morphology and promotes spike‐like cell processes that resemble the early stages of neurite formation. These processes undergo elongation upon addition of nerve growth factor (NGF). We also found that the addition of NGF induces the production of endogenous rat‐Gas7 (rGas7), which is transiently elevated prior to the appearance of NGF‐promoted neurite outgrowths. Furthermore, inhibition of endogenous rGas7 production by antisense nucleotides complimentary to the translation initiation region of a rGas7 cDNA (AJ131902) reduces the NGF‐promoted neurite outgrowths. Our results demonstrate that Gas7 by itself influences early cell morphological development and likely functions as an early‐stage intermediary in NGF‐induced neuronal differentiation of PC12 culture cells. © 2003 Wiley‐Liss, Inc.
Functional assay for human CD4+CD25+ Treg cells reveals an age‐dependent loss of suppressive activity
Authors: Tsaknaridis Laura , Spencer Leslie , Culbertson Nicole , Hicks Kevin , LaTocha Dorian , Chou Yuan K. , Whitham Ruth H. , Bakke Antony , Jones Richard E. , Offner Halina , Bourdette Dennis N. , Vandenbark Arthur A. 
Published: February 2004

AbstractCD4+CD25+ regulatory T cells (Treg cells) prevent T cell‐mediated autoimmune diseases in rodents. To develop a functional Treg assay for human blood cells, we used FACS‐ or bead‐sorted CD4+CD25+ T cells from healthy donors to inhibit anti‐CD3/CD28 activation of CD4+CD25− indicator T cells. The data clearly demonstrated classical Treg suppression of CD4+CD25− indicator cells by both CD4+CD25+high and CD4+CD25+low T cells obtained by FACS or magnetic bead sorting. Suppressive activity was found in either CD45RO− (naive) or CD45RO+ (memory) subpopulations, was independent of the TCR signal strength, required cell–cell contact, and was reversible by interleukin‐2 (IL‐2). Of general interest is that a wider sampling of 27 healthy donors revealed an age‐ but not gender‐dependent loss of suppressive activity in the CD4+CD25+ population. The presence or absence of suppressive activity in CD4+CD25+ T cells from a given donor could be demonstrated consistently over time, and lack of suppression was not due to method of sorting, strength of signal, or sensitivity of indicator cells. Phenotypic markers did not differ on CD4+CD25+ T cells tested ex vivo from suppressive vs. nonsuppressive donors, although, upon activation in vitro, suppressive CD4+CD25+ T cells had significantly higher expression of both CTLA‐4 and GITR than CD4+CD25− T cells from the same donors. Moreover, antibody neutralization of CTLA‐4, GITR, IL‐10, or IL‐17 completely reversed Treg‐induced suppression. Our results are highly consistent with those reported for murine Treg cells and are the first to demonstrate that suppressive activity of human CD4+CD25+ T cells declines with age. Published 2003 Wiley‐Liss, Inc.
Patterned electrical activity modulates sodium channel expression in sensory neurons
Authors: Klein Joshua P. , Tendi Elisabetta A. , Dib‐Hajj Sulayman D. , Fields R. Douglas , Waxman Stephen G. 
Published: February 2004

AbstractPeripheral nerve injury induces changes in the level of gene expression for sodium channels Nav1.3, Nav1.8, and Nav1.9 within dorsal root ganglion (DRG) neurons, which may contribute to the development of hyperexcitability, ectopic neuronal discharge, and neuropathic pain. The mechanism of this change in sodium channel expression is unclear. Decreased availability of neurotrophic factors following axotomy contributes to these changes in gene transcription, but the question of whether changes in intrinsic neuronal activity levels alone can trigger changes in the expression of these sodium channels has not been addressed. We examined the effect of electrical stimulation on the expression of Nav1.3, Nav1.8, and Nav1.9 by using cultured embryonic mouse sensory neurons under conditions in which nerve growth factor (NGF) was not limiting. Expression of Nav1.3 was not significantly changed following stimulation. In contrast, we observed activity‐dependent down‐regulation of Nav1.8 and Nav1.9 mRNA and protein levels after stimulation, as demonstrated by quantitative polymerase chain reaction and immunocytochemistry. These results show that a change in neuronal activity can alter the expression of sodium channel genes in a subtype‐specific manner, via a mechanism independent of NGF withdrawal. © 2003 Wiley‐Liss, Inc.
Hypoxia‐induced modification of the inositol triphosphate receptor in neuronal nuclei of newborn piglets: Role of nitric oxide
Authors: Mishra Om Prakash , Qayyum Imaran , Delivoria‐Papadopoulos Maria 
Published: February 2004

AbstractPrevious studies have shown that hypoxia results in increased Ca2+ influx in neuronal nuclei and generation of nitric oxide (NO) free radicals in the cerebral cortical tissue of newborn piglets. The present study tests the hypothesis that hypoxia results in modification of the inositol triphosphate (IP3) receptor characteristics in neuronal nuclei and that the hypoxia‐induced modification of the IP3 receptor is NO mediated. Studies were performed in piglets, 3–5 days old, divided into normoxic (n = 5), hypoxic (n = 5), and NO synthase (NOS) inhibitor N‐nitro‐L‐arginine (NNLA)‐treated hypoxic (n = 5) groups. The NNLA‐treated hypoxic group received an infusion of NNLA (40 mg/kg) over 1 hr prior to hypoxic exposure. The hypoxia was induced by lowering the FiO2 to 0.05–0.07 for 1 hr. Brain tissue hypoxia was documented biochemically by determining ATP and phosphocreatine (PCr) levels. Neuronal nuclei were isolated from the cerebral cortical tissue, and IP3 receptor binding was performed in a medium containing 50 mM HEPES (pH 8.0), 2 mM EDTA, 3H‐IP3 (7.5–100 nM), and 100 μg nuclear protein. Nonspecific binding was determined in the presence of 10 μM unlabelled IP3. The IP3 receptor characteristics Bmax (number of receptor sites) and Kd (dissociation constant) were determined. In normoxic, hypoxic, and NNLA‐hypoxic groups, ATP levels were 4.46 ± 0.35, 1.52 ± 0.10 (P < .05 vs. normoxic), and 1.96 ± 0.33 μmoles/g brain, respectively (P < .05 vs. normoxic). PCr levels were 3.75 ± 0.35, 0.87 ± 0.09 (P < .05 vs. normoxic), and 1.31 ± 0.10 μmoles/g brain, respectively (P < .05 vs. normoxic). IP3 receptor binding characteristics in normoxic nuclear membranes showed that the Bmax value was 150.0 ± 14.1 pmoles/mg protein compared with 239.3 ± 13.6 pmoles/mg protein in the hypoxic group (P < .05). In the NNLA‐treated hypoxic group, the Bmax value was 159.0 ± 42.6 pmoles/mg protein (P < .05 vs. hypoxic a, P = NS vs. normoxic). Similarly, the Kd was 25.2 ± 0.28 nM in the normoxic group, 44.6 ± 5.4 nM in the hypoxic group (P < .05), and 28.1 ± 6.4 nM in the NNLA‐treated hypoxic group. (P < .05 vs. hypoxic and P = NS vs. normoxic). The results show that hypoxia results in increased Bmax and Kd values for the IP3 receptor. Furthermore, the data demonstrate that administration of NNLA prior to hypoxia prevents the hypoxia‐induced modification of the IP3 receptor in neuronal nuclei of newborn piglets. Because NNLA inhibits NOS and prevents generation of NO, we conclude that the mechanism of hypoxia‐induced modification of the neuronal nuclear membrane IP3 receptor is NO mediated. We propose that NO‐mediated modification of the IP3 receptor during hypoxia may lead to increased intranuclear Ca2+, resulting in altered transcription of apoptotic genes and activation of cascades of hypoxia‐induced programmed neuronal death. © 2003 Wiley‐Liss, Inc.
Glycogen: The forgotten cerebral energy store
Authors: Gruetter Rolf 
Published: February 2004

AbstractThe brain contains a significant amount of glycogen that is an order of magnitude smaller than that in muscle, but several‐fold higher than the cerebral glucose content. Although the precise role of brain glycogen to date is unknown, it seems affected by focal activation, neurotransmitters, and overall electrical activity and hormones. Based on its relatively low concentration, the role of brain glycogen as a significant energy store has been discounted. This work reviews recent experimental evidence that brain glycogen is an important reserve of glucose equivalents: (1) glial glycogen can provide the majority of the glucose supply deficit during hypoglycemia for more than 100 min, consistent with the proposal that glial lactate is a fuel for neurons; (2) glycogen concentrations may be as high as 10 μmol/g, substantially higher than was thought previously; (3) glucose cycling in and out of glycogen amounts to ∼1% of the cerebral metabolic rate of glucose (CMRglc) in human and rat brain, amounting to an effective stability of glycogen in the resting awake brain during euglycemia and hyperglycemia, (4) brain glycogen metabolism/concentrations are insulin/glucose sensitive; and (5) after a single episode of hypoglycemia, brain glycogen levels rebound to levels that exceed the pre‐hypoglycemic concentrations (supercompensation). This experimental evidence supports the proposal that brain glycogen may be involved in the development of diabetes complications, specifically impaired glucose sensing (hypoglycemia unawareness) observed clinically in some diabetes patients under insulin treatment. It is proposed further that brain glycogen becomes important in any metabolic state where supply transiently cannot meet demand, such conditions that could occur during prolonged focal activation, sleep deprivation, seizures, and mild hypoxia. © 2003 Wiley‐Liss, Inc.
Characterization by Raman spectroscopy of conformational changes on guanine–cytosine and adenine–thymine oligonucleotides induced by aminooxy analogues of spermidine
Authors: Ruiz‐Chica A. J. , Medina M. A. , Sánchez‐Jiménez F. , Ramírez F. J. 
Published: February 2004

AbstractThe interactions between aminooxy analogues of the biogenic polyamine spermidine and selected 15‐mer oligodeoxyribonucleotides with alternating purine–pyrimidine base sequences, adenine–thymine (AT) and guanine–cytosine (GC), have been studied using Raman spectroscopy. These analogues resulted from the substitution of the two terminal aminomethylene groups of spermidine, +NH3CH2, by an aminooxy one, H2NO. Since this biogenic polyamine has no centre of symmetry, there are two different isosteric molecules, which have been named AOEPUT and APAPA. However, the pKa of an aminooxy group (about 5) is not high enough to be protonated at neutral pH. Therefore, under physiological conditions, these analogues have a positive charge less than spermidine, which makes them suitable models to investigate the roles of both charge and structure in the polyamine–DNA interactions. Raman spectra of solutions containing different concentrations of the analogues, from 10 to 75 mM, and either a GC and an AT oligonucleotide, at a fixed concentration 60 mM (in phosphate), were recorded. The spectra demonstrated the existence of strong differences in the oligonucleotide‐analogue interactions depending on the base sequences. In the presence of the aminooxy analogues, a 15‐mer GC oligonucleotide adopted a highly ordered tertiary structure (aggregate state or Ψ‐DNA) and, at the same time, it changed its secondary structure (from B to Z‐DNA). Evidence of macromolecular transitions was not achieved from the Raman spectra of a 15‐mer AT oligonucleotide. However, the assignments of the Raman bands indicated that both H2NO groups of the aminooxy analogues and exocyclic NH2 groups of the oligonucleotides could act as preferential binding sites. However, different spectral features were observed between AOEPUT and APAPA in the presence of the oligonucleotides. This fact supports the idea that the two amino terminal groups of spermidine could have different roles in the interaction of this biogenic polyamine with DNA. Our results also confirm that the aminooxy analogues of biogenic polyamines could act as stabilizers of non‐viral transfection vectors, thus improving the efficiency of gene therapy protocols. Copyright © 2004 John Wiley & Sons, Ltd.