bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pituitary adenylate cyclase‐activating polypeptide prevents C2‐ceramide‐induced apoptosis of cerebellar granule cells
Authors: Vaudry David , Falluel‐Morel Anthony , Basille Magali , Pamantung Tommy F. , Fontaine Marc , Fournier Alain , Vaudry Hubert , Gonzalez Bruno J. 
Published: April 2003

AbstractThe sphingolipid metabolites, ceramides, are critical mediators of the cellular stress response and play an important role in the control of programmed cell death. In particular, ceramides have been shown to induce apoptosis of cerebellar granule cells. We show that pituitary adenylate cyclase‐activating polypeptide (PACAP) prevents C2‐ceramide‐induced apoptosis. The neuroprotective effect of PACAP was dose‐dependent and blocked by its antagonist, PACAP6‐38, whereas the PACAP‐related peptide VIP was inactive. The effect of PACAP on cell survival was mimicked by dibutyryl‐cAMP (dbcAMP) and forskolin and prevented by the MEK inhibitor U0126, indicating that both the adenylyl‐cyclase and MAP‐kinase pathways contribute to the neuroprotective action of the peptide. C2‐ceramide and PACAP induced opposite effects on phosphorylated forms of ERK and JNK without affecting the total amounts of ERK and JNK, suggesting that a balance between these two MAP‐kinases is critical for the cell survival/death decision. The effect of PACAP on ERK phosphorylation was blocked by U0126, but was not affected by H89 or chelerythrine indicating that PACAP activates ERK through a PKA‐ and PKC‐independent mechanism. C2‐ceramide induced a time‐dependent activation of caspase‐3, enhanced the amount of cleaved caspase‐3 and stimulated the DNA fragmentation process, while PACAP strongly inhibited the C2‐ceramide‐induced activation of caspase‐3, reduced the expression of cleaved caspase‐3 and blocked DNA fragmentation. Taken together, the present results show that C2‐ceramide induces apoptosis of cerebellar granule cells through a mechanism involving activation of caspase‐3. Our data also demonstrate that PACAP is a potent inhibitor of C2‐ceramide‐induced apoptosis. © 2003 Wiley‐Liss, Inc.
Regeneration of sciatic nerves of adult rats induced by extracts from distal stumps of pre‐degenerated peripheral nerves
Authors: Marcol Wieslaw , Kotulska Katarzyna , Święch‐Sabuda Ewa , Larysz‐Brysz Magdalena , Golka Beata , Górka Dariusz , Lewin‐Kowalik Joanna 
Published: April 2003

AbstractDespite numerous experimental and clinical attempts to reconstruct injuries of peripheral nerves, the methods developed until now have not been sufficiently effective. We examined the influence of extracts (postmicrosomal fractions) obtained from non‐pre‐degenerated or 7‐day‐pre‐degenerated distal segments of peripheral nerves on the regeneration of injured sciatic nerves of male adult rats. The extracts were introduced to the site of injury with autologous connective tissue chambers filled with fibrin. Reference groups were treated with brain‐derived neurotrophic factor (BDNF) or fibrin only. We examined DiI‐labeled motoneurons, toluidine blue‐labeled myelinated fibers in the mid‐part of the chambers, and AChE‐positive nerve endings to assess the regeneration intensity. In addition, the length of fibers regrowing within the chambers was measured. We found that extracts obtained from distal stumps of 7‐day‐pre‐degenerated peripheral nerves enhanced nerve regeneration as strongly as BDNF. © 2003 Wiley‐Liss, Inc.
Cellular migration in the postnatal rat cerebellar cortex: Confocal‐infrared microscopy and the rapid Golgi method
Authors: Liesi Päivi , Akinshola Emmanuel , Matsuba Kenji , Lange Kurt , Morest Kent 
Published: April 2003

AbstractConfocal laser microscopy of DiI‐labeled slices of postnatal rat cerebellum (postnatal Day 4–10; P4–10) was compared to infrared microscopy and the rapid Golgi method (P0–14) to investigate postnatal migration of granule neurons. Vertical migration of the granule neurons occurred already at birth (P0). Surprisingly, mossy fibers often reached the external granule cell layer and were in close contact with the external granule cells. These mossy fibers may play a role in initiating granule cell migration. At this age, cell bodies of the immature neurons were attached to the external basal lamina by a process and extended down toward the presumptive internal granule cell layer. At P14, some granule cells remained attached to the surface, although their cell bodies exhibited the typical morphology of mature granule neurons and were located deep in the internal granule cell layer. These cells extended their endfeet‐like processes all the way to the surface of the brain. These results indicate that the vertical pathways of granule cell migration form early and persist throughout the period of granule cell migration. Confocal infrared microscopy of DiI‐labeled sections and the rapid Golgi method also allowed demonstration of tangentially migrating neurons that made one or more turns on the way to the internal granule cell layer. The rapid Golgi method confirmed that many Bergmann glial processes end at the level of the tangentially migrating granule cells whereas others project to the surface. These observations show that migratory granule cells take several different routes to their final destination, which cannot be explained by so‐called radial glial guidance. The only mode of migration in evidence is consistent with process elongation and translocation of the nucleus within the preformed processes. © 2003 Wiley‐Liss, Inc.
Differential connexin expression, gap junction intercellular coupling, and hemichannel formation in NT2/D1 human neural progenitors and terminally differentiated hNT neurons
Authors: Boucher Sherri , Bennett Steffany A.L. 
Published: April 2003

AbstractConnexin‐mediated gap junctions and open hemichannels in nonjunctional membranes represent two biologically relevant mechanisms by which neural progenitors can coordinate their response to changes in the extracellular environment. NT2/D1 cells are a teratocarcinoma progenitor line that can be induced to differentiate terminally into functional hNT neurons and NT‐G nonneuronal cells. Clinical transplants of hNT neurons and experimental grafts of NT2/D1 progenitors or hNT neurons have been used in cell‐replacement therapy in vivo. Previous studies have shown that NT2/D1 cells express connexin 43 (Cx43) and that NT2/D1 progenitors are capable of dye transfer. To determine whether NT2/D1 progenitors and differentiated hNT cultures express other connexins, Cx26, Cx30, Cx32, Cx36, Cx37, Cx43, and Cx46.6 mRNA and protein were analyzed. NT2/D1 progenitors express Cx30, Cx36, Cx37, and Cx43. hNT/NT‐G cultures express Cx36, Cx37, and de novo Cx46.6. Cx26 and Cx32 were not expressed in NT2/D1 or hNT/NT‐G cells. NT2/D1 progenitors formed functional gap junctions as assessed by dye coupling as well as open hemichannels in nonjunctional membranes as assessed by dye‐uptake studies. Dye coupling was inhibited by the gap junction blocker 18α‐glycyrrhetinic acid. Hemichannel activity was inhibited by the dual‐specificity chloride channel/connexin hemichannel inhibitor flufenamic acid but not by the chloride channel inhibitor 4,4′‐diisothiocyanatostilbene‐2,2′‐disulfonic acid. Both dye coupling and dye uptake were substantially reduced following differentiation of NT2/D1 progenitors. We conclude that the pattern of connexin expression in NT2/D1 cells changes over the course of differentiation corresponding with a reduction in biochemical coupling and hemichannel activity in differentiated cells. © 2003 Wiley‐Liss, Inc.
Arachidonic acid activates an open rectifier potassium channel in cultured rat cortical astrocytes
Authors: Ferroni Stefano , Valente Pierluigi , Caprini Marco , Nobile Mario , Schubert Peter , Rapisarda Carmela 
Published: April 2003

AbstractA pathophysiological increase in free arachidonic acid (AA) is thought to regulate the channel‐mediated astrocytic swelling occurring in several brain injuries. We report that in cultured rat type‐1 cortical astrocytes, exposure to 10 μM AA activates an open rectifier K+ channel, which exhibits many similarities with TREK/TRAAK members of the two‐pore‐domain K+ channel family KCNK. Patch‐clamp experiments showed that the current developed with a long latency and was preceded by a depression of the previously described outward rectifier K+ conductance. Pharmacologic studies indicate that the K+ open rectifier was differentially sensitive to classic K+‐channel blockers (quinine, quinidine, tetraethylammonium, and barium) and was inhibited potently by gadolinium ions. The activation of this K+ current occurred independently of the AA metabolism as pharmacologic inhibition of the lipoxygenase, cyclooxygenase, and cytochrome P450 epoxygenase signaling cascades did not alter the AA effect. Moreover, neither the neutralization of the NADPH‐oxidase pathway nor scavenging intracellular free radicals modified the AA response. Finally, the AA‐induced K+ current was unaffected by protein kinase C inhibitors. The activation mechanism of the K+ open rectifier was through an extracellular interaction of AA with the plasma membrane. RT‐PCR analysis revealed that the AA‐induced K+ conductance was mediated likely by TREK‐2 channels. Collectively, the results demonstrate that in cultured cortical astrocytes, pathological levels of AA directly activate an open rectifier K+ channel, which may play a role in the control of K+ homeostasis under pathophysiological conditions. © 2003 Wiley‐Liss, Inc.
Involvement of calcium/calmodulin‐dependent protein kinase II in the induction of mPer1
Authors: Nomura Kazumi , Takeuchi Yusuke , Yamaguchi Shun , Okamura Hitoshi , Fukunaga Kohji 
Published: April 2003

AbstractRecent studies suggest that CaM kinase II is involved in light‐induced phase delays and induction of Per1 and Per2 genes in the hamster suprachiasmatic nucleus (SCN) (Yokota et al.,2001). We focused on intracellular mechanisms of the CaM kinase II‐induced mPer1 gene expression. Immunoblotting and immunohistochemical analyses with isoform‐specific antibodies against different isoforms of CaM kinase II and CaM kinase IV showed abundant expression of the δ isoform of CaM kinase II without significant expression of CaM kinase IV in the lateral ventral region of the rat SCN. We next defined the CaM kinase II‐responsive region on the mPer1 promoter using a luciferase reporter gene assay. Transfection of the constitutively‐active CaM kinase IIδ greatly increased mPer1 promoter activity in NG108‐15 cells and increased activity slightly but significantly in NB2A and C6 glioma cells. Similarly, transfection of a constitutively‐active MEKK, an upstream kinase of mitogen‐activated protein kinase (MAPK), greatly increased promoter activity in NB2A cells. Deletion and mutation analyses of the mPer1 promoter revealed that a 5′‐GAGGGG‐3′ sequence motif near exon 1B, in which several zinc finger proteins seem to bind, was essential for the CaM kinase II‐induced activation of the mPer1 promoter. These results suggest that CaM kinase IIδ but not CaM kinase IV plays an essential role for mPer1 expression through the 5′‐GAGGGG‐3′ motif on the mPer1 promoter. © 2003 Wiley‐Liss, Inc.
Oxidative stress in cultured cerebral endothelial cells induces chromosomal aberrations, micronuclei, and apoptosis
Authors: Bresgen N. , Karlhuber G. , Krizbai I. , Bauer H. , Bauer H.C. , Eckl P.M. 
Published: April 2003

AbstractThere is evidence accumulating that brain microvasculature is involved critically in oxidative stress‐mediated brain damage. Cultured cerebral microvascular endothelial cells were used to demonstrate the cytotoxic and genotoxic effects elicited by hypoxia/reoxygenation and DMNQ treatment in vitro. In addition, the effect of glucose deprivation during oxidative insult was assessed. The parameters determined were: 1) chromosomal aberrations; 2) induction of micronuclei; and 3) apoptosis. Our results indicate that both the exposure of the cerebral endothelial cells to 24 hr of hypoxia followed by 4 hr of reoxygenation, and treatment with the redox cycling quinone DMNQ, increased markedly the occurrence of chromosomal aberrations and micronuclei. It was found that expression of p53 was induced by oxidative stress, particularly when glucose had been omitted from the culture medium. Aglycemic culture conditions in general exacerbated the cytotoxic effects of oxidative insults, as evidenced by the increase in apoptotic cells and the decrease in the mitotic index. Interestingly, neither an elevation of cell lysis nor an increase in necrosis has been observed during our experiments. In summary, our data indicate that oxidative stress exerts considerable genotoxic and cytotoxic effects on cerebral endothelial cells, which might contribute to the progression of tissue damage in the central nervous system. © 2003 Wiley‐Liss, Inc.
Postnatal dendritic morphogenesis of cerebellar basket and stellate cells in vitro
Authors: Spatkowski Gabriele , Schilling Karl 
Published: April 2003

AbstractInhibitory interneurons in the molecular layer of the cerebellar cortex play an essential role in cerebellar physiology by providing feed‐forward inhibition to efferent Purkinje cells. Morphologic characteristics have been utilized to classify these cells as either basket cells or stellate cells. Conflicting evidence exists as to whether these cells are of distinct lineage and develop by employing discrete genetic programs, or whether their characteristic morphologic differences result from external cues that they encounter only after they have settled in their final territory in the molecular layer. We used primary dissociated cerebellar cultures established from early postnatal mice to study dendritogenesis of basket/stellate cells, identified by immunostaining for parvalbumin, under experimentally controlled conditions. We find that the radial axonal orientation of stem dendrites is non‐random, suggesting a cell‐intrinsic component defining this morphologic trait. In contrast, the expanse and complexity of basket/stellate cell dendrites is modulated by the granule cell derived neurotrophin, BDNF. BDNF‐induced morphogenetic effects decline with ongoing development. Overall, our data do not provide evidence for a distinct lineage or genetic makeup of cerebellar molecular layer inhibitory interneurons. © 2003 Wiley‐Liss, Inc.
Tropomyosin isoforms from the γ gene differing at the C‐terminus are spatially and developmentally regulated in the brain
Authors: Vrhovski Bernadette , Schevzov Galina , Dingle Sharon , Lessard James L. , Gunning Peter , Weinberger Ron P. 
Published: April 2003

AbstractTropomyosin is an actin‐binding protein responsible for stabilizing the actin microfilament system in the cytoskeleton of nonmuscle cells and is involved in processes such as growth, differentiation, and polarity of neuronal cells. From the γ gene, at least 11 different isoforms have been described, with three different C‐terminal exons used (9a, 9c, 9d). The precise roles that the different isoforms play are unknown. To examine the localization and hence determine the function of these isoforms in developing mouse, specific antibodies to exons 9a and 9c were made. These were used with previously developed 9d and N‐terminal 1b antibodies on Western blots and immunohistochemical analysis of mouse brains. We were able to show that all three C‐termini are used in the brain. 9c isoforms are highly enriched in brain and neural cells, and we also detected significant amounts of 9a‐containing isoforms in brain. γ gene activity is relatively constant in the brain, but the choice of C‐terminus is developmentally regulated. A more detailed study of the brain revealed regional expression differences. The hippocampus, cerebellum, and cortex were analyzed in depth and revealed that different isoforms could be sorted into different neuronal compartments, which change with development for 9d. Furthermore, a comparison with a homologous exon to 9c from the α‐tropomyosin gene showed that expression from these exons is related to the maturational state of the neuron, even though both are sorted differently intracellularly. These data suggest that the large numbers of tropomyosin isoforms are likely to have specific roles in microfilament dynamics and neural cell function. © 2003 Wiley‐Liss, Inc.
Bone marrow stromal cells enhance differentiation of cocultured neurosphere cells and promote regeneration of injured spinal cord
Authors: Wu Sufan , Suzuki Yoshihisa , Ejiri Yoko , Noda Toru , Bai Hongliang , Kitada Masaaki , Kataoka Kazuya , Ohta Masayoshi , Chou Hirotomi , Ide Chizuka 
Published: April 2003

AbstractTransplantation of bone marrow stromal cells (MSCs) has been regarded as a potential approach for promoting nerve regeneration. In the present study, we investigated the influence of MSCs on spinal cord neurosphere cells in vitro and on the regeneration of injured spinal cord in vivo by grafting. MSCs from adult rats were cocultured with fetal spinal cord‐derived neurosphere cells by either cell mixing or making monolayered‐feeder cultures. In the mixed cell cultures, neuroshpere cells were stimulated to develop extensive processes. In the monolayered‐feeder cultures, numerous processes from neurosphere cells appeared to be attracted to MSCs. In an in vivo experiment, grafted MSCs promoted the regeneration of injured spinal cord by enhancing tissue repair of the lesion, leaving apparently smaller cavities than in controls. Although the number of grafted MSCs gradually decreased, some treated animals showed remarkable functional recovery. These results suggest that MSCs might have profound effects on the differentiation of neurosphere cells and be able to promote regeneration of the spinal cord by means of grafting. © 2003 Wiley‐Liss, Inc.
Preservation of hematopoietic properties in transplanted bone marrow cells in the brain
Authors: Ono Kenji , Yoshihara Ken , Suzuki Hiromi , Tanaka Kenji F. , Takii Takemasa , Onozaki Kikuo , Sawada Makoto 
Published: April 2003

AbstractRecent studies have described the possible transdifferentiation of bone marrow cells (BMC) into neurons and glia when they migrate to the brain. However, we have reported that some immature BMC migrating into the brain parenchyma after bone marrow transplantation express early hematopoietic markers but not neural or glial markers. The present study further characterizes transplanted BMC that migrate to the brain. Double immunolabeling confirmed that BMC migrating to the brain expressed hematopoietic but not neural markers, such as nestin, microtubule‐associated protein‐2 and glial fibrillary acidic protein, even 4 and 18 weeks after bone marrow transplantation. BMC that expressed green fluorescent protein also expressed hematopoietic but not neural markers when cultured with mixed brain cells according to double immunolabeling and single‐cell dissection using a laser. Analysis of the DNA content indicated that most of the migrated BMC were arrested at the G0/G1 phase, and aneuploidy or tetraploidy was undetectable. Thus, BMC that migrate to the brain probably have preserved hematopoietic properties under physiological conditions. © 2003 Wiley‐Liss, Inc.
A peptide fragment of ependymin neurotrophic factor uses protein kinase C and the mitogen‐activated protein kinase pathway to activate c‐Jun N‐terminal kinase and a functional AP‐1 containing c‐Jun and c‐Fos proteins in mouse NB2a cells
Authors: Adams David S. , Hasson Brendan , Boyer‐Boiteau Anne , El‐Khishin Adam , Shashoua Victor E. 
Published: April 2003

AbstractEpendymin (EPN) is a goldfish brain neurotrophic factor previously shown to function in a variety of cellular events related to long‐term memory formation and neuronal regeneration. CMX‐8933, an 8‐amino‐acid synthetic peptide fragment of EPN, was designed for aiding an investigation of the biological properties of this glycoprotein. We reported from previous studies that treatment of mouse neuroblastoma (NB2a) cultures with CMX‐8933 promotes activation of transcription factor AP‐1, a characteristic previously associated with the following full‐length neurotrophic factors: nerve growth factor, neurotropin‐3, and brain‐derived neurotrophic factor. The CMX‐8933‐activated AP‐1 specifically bound an AP‐1 consensus probe and appeared to contain c‐Jun and c‐Fos protein components in antibody supershift experiments. Because AP‐1 influences a variety of positive and negative cellular processes, determined in part by its exact protein composition and mechanism of activation, we extended these initial AP‐1 observations in the current study to confirm the identity of the CMX‐8933‐activated c‐Jun and c‐Fos components. CMX‐8933 increases the enzymatic activity of c‐Jun N‐terminal kinase (JNK), increases the phosphorylation of JNK and c‐Jun proteins, and increases the cellular titers of c‐Jun and c‐Fos mRNAs. Furthermore, the AP‐1 activated by CMX‐8933 is functional, insofar as it transactivates both synthetic and natural AP‐1‐dependent reporter plasmids. Inhibition studies indicate that activation of the 8933‐induced AP‐1 occurs via the mitogen‐activated protein kinase pathway. These data are in agreement with the recently proposed model for the conversion of short‐ to long‐term synaptic plasticity and memory, in which a JNK‐activated transcription factor AP‐1, containing c‐Jun and c‐Fos components, functions at the top of a hierarchy of transcription factors known to regulate long‐term neural plasticity. © 2003 Wiley‐Liss, Inc.
c‐Src protein tyrosine kinase activity is required for muscarinic receptor‐mediated DNA synthesis and neurogenesis via ERK1/2 and c‐AMP‐responsive element‐binding protein signaling in neural precursor cells
Authors: Zhao Wei‐Qin , Alkon Daniel L. , Ma Wu 
Published: April 2003

AbstractThe G protein‐coupled muscarinic acetylcholine receptor (mAChR) isoforms have been identified in neural stem/progenitor (or precursor) cells. In previous studies, activation of these receptors induced elevations in intracellular Ca2+ signals and mitogen‐activated protein (MAP) kinase activity that led to enhanced DNA synthesis along with neurogenesis in neural precursor cells. Here we report that the nonreceptor protein tyrosine kinase c‐src activity is required for the muscarinic receptor‐activated MAP kinase and cAMP‐responsive element‐binding protein (CREB). Stimulation of neural precursor cells dissociated from embryonic day 13 rat cortical neuroepithelium with the muscarinic receptor agonist carbachol (CCh) induced phosphorylations of c‐src that were detected by antibodies raised against phospho‐Tyr416 (Ptyr416), phospho‐Tyr527 (Ptyr527), and phospho‐Tyr215 (Ptyr215) of the kinase. Although an increase in Ptyr416 suggested direct activation of c‐src, Ptyr215 may serve as an alternative mechanism underlying activation of c‐src without dephosphorylation of Ptyr‐527. Both extracellular signal‐regulated kinase (Erk1/2) and CREB were significantly activated after CCh treatment indicated by increases in phosphorylation of these two proteins. The c‐Src inhibitor PP1 abolished the CCh‐induced activation of Erk1/2 and CREB in a dose‐dependent manner. Moreover, CCh stimulated expression of the neuronal specific marker MAP2, which was inhibited by PP1. Cell proliferation assays and immunocytochemistry revealed that PP1 inhibited the CCh‐induced DNA synthesis and MAP2+ production. These results suggest that c‐src activity is essential for the muscarinic receptor‐mediated proliferation and neurogenesis in neural precursor cells via Erk1/2 and CREB signaling pathways. © 2003 Wiley‐Liss, Inc.