bluuebunny/crossref_metadata_2025_split huggingface dataset:
Differential roles of ERK and JNK in early and late stages of neuritogenesis: a study in a novel PC12 model system
Authors: Xiao Jingnan , Liu Yuechueng 
Published: August 2003

AbstractThe rat pheochromocytoma PC12 cell line has been an invaluable model system for studying neuritogenesis. Nerve growth factor (NGF) elicits multiple aspects of neurite outgrowth in PC12 cells. It is therefore difficult to dissect and assign an individual signaling pathway to each stage of neuritogenesis. We have recently reported the isolation of a variant PC12 cell line, PC12‐N1 (N1), which spontaneously extends neuritic processes and exhibits an increased sensitivity to NGF. Here, we show that, under different culture conditions, the cells display three distinct phases of neuritogenesis consisting of neurite initiation, rapid neurite elongation, and a maturation process characterized by the thickening of neurites and increase in cell soma sizes. We demonstrate that signaling through ERK, but not p38 or JNK, is required for the spontaneous neurite initiation and extension. Treatment with low concentrations of NGF induces rapid neurite elongation without affecting neurite branching and cell soma sizes. Such a rapid neurite outgrowth can be blocked by the inhibition of ERK, but not JNK, activities. In the presence of higher concentrations of NGF, the N1 cells undergo further differentiation with many characteristics of mature neurons in culture, e.g. larger cell soma and numerous branches/connections. This process can be completely blocked by inhibiting ERK or JNK activities using specific inhibitors. These results suggest that ERK and JNK signals play different roles in neuritogenesis, and that JNK activity is essential in the late stages of neuritogenesis. Furthermore, our results demonstrate that signaling dosage is important in the activation of a specific pathway, leading to distinctive biological outcomes.
Participation of NMDA‐mediated phosphorylation and oxidation of neurogranin in the regulation of Ca2+‐ and Ca2+/calmodulin‐dependent neuronal signaling in the hippocampus
Authors: Wu Junfang , Huang Kuo‐Ping , Huang Freesia L. 
Published: August 2003

AbstractNeurogranin/RC3 (Ng) is a postsynaptic protein kinase C (PKC) substrate and calmodulin (CaM)‐binding protein whose CaM‐binding affinity is modulated by Ca2+, phosphorylation and oxidation. Ng has been implicated in the modulation of postsynaptic signal transduction pathways and synaptic plasticity. Previously, we showed a severe deficit of spatial memory in Ng knockout (KO) mice. Activation of the NMDA receptor and its downstream signaling molecules are known to be involved in long‐term memory formation. In the present study, using mouse hippocampal slices, we demonstrated that NMDA induced a rapid and transient phosphorylation and oxidation of Ng. NMDA also caused activation of PKC as evidenced by their phosphorylations, whereas, such activations were greatly reduced in the KO mice. A higher degree of phosphorylation of Ca2+/CaM‐dependent kinase II and activation of cyclic AMP‐dependent protein kinase were also evident in the WT compared to those of the KO mice. Phosphorylation of downstream targets, including mitogen‐activated protein kinases and cAMP response element‐binding protein, were significantly attenuated in the KO mice. These results suggest that by its Ca2+‐sensitive CaM‐binding feature, and through its phosphorylation and oxidation, Ng regulates the Ca2+‐ and Ca2+/CaM‐dependent signaling pathways subsequent to the stimulation of NMDA receptor. These findings support the hypothesis that the derangement of hippocampal signal transduction cascades in Ng KO mice causes the deficits in synaptic plasticity, learning and memory that occur in these mice.
Noradrenaline enhances monocarboxylate transporter 2 expression in cultured mouse cortical neurons via a translational regulation
Authors: Pierre Karin , Debernardi Ruth , Magistretti Pierre J. , Pellerin Luc 
Published: August 2003

AbstractRegulation of the expression of MCT1 and MCT2, two isoforms of the monocarboxylate transporter (MCT) family, was investigated in primary cultures of mouse cortical neurons. Under basal conditions, both MCT immunoreactivities (IR) were found in the cell soma and dendrites, although IR for MCT1 appeared less bright than for MCT2. Treatment of cultured cortical neurons with 100 μm noradrenaline (NA) led, after a few hours, to a striking enhancement in fluorescence intensity associated with MCT2 IR in the cell soma as well as in dendrites. In contrast, MCT1 IR was not altered by NA treatment. Western blot experiments performed on cultured neurons treated with NA confirmed that MCT2 protein expression was increased. Forskolin and dBcAMP also enhanced MCT2 expression, suggesting the implication of a cAMP‐mediated pathway in the effect of NA. Surprisingly, neither NA, dBcAMP nor forskolin affected MCT2 mRNA expression. Application of cycloheximide, a protein synthesis inhibitor, prevented the enhancement of MCT2 IR, while the mRNA synthesis inhibitor actinomycin D also blocked the effect of NA on MCT2 IR levels. These results suggest that regulation of MCT2 expression in neurons by NA occurs at the translational level despite the requirement for an as yet unknown transcriptional step.
Depolarization‐induced ERK phosphorylation depends on the cytosolic Ca2+ level rather than on the Ca2+ channel subtype of chromaffin cells
Authors: Mendoza Isabel E. , Schmachtenberg Oliver , Tonk Ernesto , Fuentealba Jorge , Díaz‐Raya Pamela , Lagos Verónica L. , García Antonio G. , Cárdenas Ana M. 
Published: August 2003

AbstractThe contribution of Ca2+ entry through different voltage‐activated Ca2+ channel (VACC) subtypes to the phosphorylation of extracellular signal regulated kinase (ERK) was examined in bovine adrenal‐medullary chromaffin cells. High K+ depolarization (40 mM, 3 min) induced ERK phosphorylation, an effect that was inhibited by specific mitogen‐activated protein kinase kinase inhibitors. By using selective inhibitors, we observed that depolarization‐induced ERK phosphorylation completely depended on protein kinase C‐α (PKC‐α), but not on Ca2+/calmodulin‐dependent protein kinase nor cyclic AMP‐dependent protein kinase. Blockade of L‐type Ca2+ channels by 3 μm furnidipine, or blockade of N channels by 1 μmω‐conotoxin GVIA reduced ERK phosphorylation by 70%, while the inhibition of P/Q channels by 1 μmω‐agatoxin IVA only caused a 40% reduction. The simultaneous blockade of L and N, or P/Q and N channels completely abolished this response, yet 23% ERK phosphorylation remained when L and P/Q channels were simultaneously blocked. Confocal imaging of cytosolic Ca2+ elevations elicited by 40 mm K+, showed that Ca2+ levels increased throughout the entire cytosol, both in the presence and the absence of Ca2+ channel blockers. Fifty‐eight percent of the fluorescence rise depended on Ca2+ entering through N channels. Thus, ERK phosphorylation seems to depend on a critical level of Ca2+ in the cytosol rather than on activation of a given Ca2+ channel subtype.
Activation of p38 mitogen‐activated protein kinase in spinal microglia is a critical link in inflammation‐induced spinal pain processing
Authors: Svensson Camilla I. , Marsala Martin , Westerlund Anna , Calcutt Nigel A. , Campana Wendy M. , Freshwater Jason D. , Catalano Rosanne , Feng Ying , Protter Andrew A. , Scott Brian , Yaksh Tony L. 
Published: August 2003

AbstractWe examined the effect of p38 mitogen‐activated protein kinase (MAPK) inhibitors in models of nociception and correlated this effect with localization and expression levels of p38 MAPK in spinal cord. There was a rapid increase in phosphorylated p38 MAPK in spinal cord following intrathecal administration of substance P or intradermal injection of formalin. Immuncytochemisty revealed that phosphorylated p38 MAPK‐immunoreactive cells were predominantly present in laminae I–IV of the dorsal horn. Double‐staining with markers for neurons, microglia, astrocytes and oligodendrocytes unexpectedly revealed co‐localization with microglia but not with neurons or other glia. Pretreatment with p38 MAPK inhibitors (SB20358 or SD‐282) had no effect on acute thermal thresholds. However, they attenuated hyperalgesia in several nociceptive models associated with spinal sensitization including direct spinal activation (intrathecal substance P) and peripheral tissue inflammation (intraplantar formalin or carrageenan). Spinal sensitization, manifested by enhanced expression of cyclo‐oxygenase‐2 and inflammation‐induced appearance of Fos‐positive neurons, was blocked by pretreatment, but not post‐treatment, with p38 MAPK inhibitors. Taken together, these results indicate that spinal p38 MAPK is involved in inflammation‐induced pain and that activated spinal microglia play a direct role in spinal nociceptive processing.
Increased susceptibility to intermittent hypoxia in aging rats: changes in proteasomal activity, neuronal apoptosis and spatial function
Authors: Gozal David , Row Barry W. , Kheirandish Leila , Liu Rugao , Guo Shang Z. , Qiang Fan , Brittian Kenneth R. 
Published: August 2003

AbstractObstructive sleep apnea (OSA) is a frequent medical condition characterized by intermittent hypoxia (IH) during sleep, and is associated with neurodegenerative changes in several brain regions along with learning deficits. We hypothesized that aging rats exposed to IH during sleep would be particularly susceptible. Young (3–4 months) and aging (20–22 months) Sprague–Dawley rats were therefore exposed to either room air or IH for 14 days. Learning and memory was assessed with a standard place‐training version of the Morris water maze. Aging rats exposed to room air (RA) or IH displayed significant spatial learning impairments compared with similarly exposed young rats; furthermore, the decrements in performance between RA and IH were markedly greater in aging compared with young rats (p < 0.01), and coincided with the magnitude of IH‐induced decreases in cyclic AMP response element binding (CREB) phosphorylation. Furthermore, decreases in proteasomal activity occurred in both young and aging rats exposed to IH, but were substantially greater in the latter (p < 0.001). Neuronal apoptosis, as shown by cleaved caspase 3 expression, was particularly increased in aging rats exposed to IH (p < 0.01 versus young rats exposed to IH). Collectively, these findings indicate unique vulnerability of the aging rodent brain to IH, which is reflected at least in part, by the more prominent decreases in CREB phosphorylation and a marked inability of the ubiquitin‐proteasomal pathway to adequately clear degraded proteins.
Nerve growth factor induces anti‐apoptotic heme oxygenase‐1 in rat pheochromocytoma PC12 cells
Authors: Liu Heling , Nowak Rebecca , Chao Wei , Bloch Kenneth D. 
Published: August 2003

AbstractNerve growth factor (NGF) and heme oxygenases (HOs) both exert neuroprotective effects. To characterize the role of HOs in the prevention of apoptosis by NGF, we investigated the effect of NGF on the expression of HOs in serum‐deprived PC12 cells. Serum deprivation (SD) led to a rapid decrease in HO‐1 gene expression followed by induction of apoptosis. Incubation of serum‐deprived PC12 cells with NGF prevented apoptosis and increased HO‐1 mRNA and protein levels, as well as HO enzyme activity. HO‐2 gene expression was unaffected by SD or NGF. Incubation of cells with mitogen‐activated protein kinase kinase (MEK) inhibitors (PD98059 or U0126) attenuated the ability of NGF to increase HO‐1 expression and to protect PC12 cells against SD‐induced apoptosis. NGF augmented HO‐1 gene transcription but did not alter HO‐1 mRNA stability. HO inhibitors or antisense HO‐1 RNA decreased the ability of NGF to prevent cell apoptosis. Inhibition of HO activity enhanced intracellular reactive oxygen species (ROS) production and attenuated NGF‐induced reduction of ROS in serum‐deprived PC12 cells. These results demonstrate that NGF enhances HO‐1 gene transcription via MEK activation and that the induction of HO‐1 plays an important role in the antioxidative and antiapoptotic effects of NGF in serum‐deprived PC12 cells.
Evidence for an active transport of morphine‐6‐β‐d‐glucuronide but not P‐glycoprotein‐mediated at the blood–brain barrier
Authors: Bourasset Fanchon , Cisternino Salvatore , Temsamani Jamal , Scherrmann Jean‐Michel 
Published: August 2003

AbstractMorphine‐6‐β‐d‐glucuronide (M6G) is an active metabolite of morphine with high analgesic potency despite a low blood–brain barrier (BBB) permeability. The aim of the study was to elucidate its transport mechanism across the BBB. We first checked if M6G was effluxed by the P‐glycoprotein (P‐gp), as previously reported by others. Second, we investigated the role of anionic transporters like the multidrug resistance‐associated protein mrp1 and the glucose transporter GLUT‐1. The brain uptake of [14C]M6G was measured by the in situ brain perfusion technique in wild‐type and deficient mice [mdr1a(–/–) and mrp1(–/–)], with and without probenecid, digoxin, PSC833 or d‐glucose. No difference was found between P‐gp and mrp1 competent and deficient mice. The brain uptake of [14C]M6G co‐perfused with probenecid in wild‐type mice was not significantly different from that found in group perfused with [14C]M6G alone. The co‐perfusion of [14C]M6G with digoxin or PSC833 was responsible of a threefold decrease of its uptake in mdr1a competent and deficient mice, suggesting that another transporter than P‐gp and sensitive to digoxin and PSC833, may be involved. The co‐perfusion of [14C]M6G with d‐glucose revealed a threefold decrease in M6G uptake. In conclusion, P‐gp and mrp1 are not involved in the transport of M6G at the BBB level in contrast to GLUT‐1 and a digoxin‐sensitive transporter (probably oatp2), which can actively transport M6G but with a weak capacity.
Beta diversity of geometrid moths (Lepidoptera: Geometridae) in an Andean montane rainforest
Authors: Brehm Gunnar , Homeier Jürgen , Fiedler Konrad 
Published: August 2003

Abstract. Turnover in species composition of the extremely species‐rich family Geometridae (Lepidoptera) was investigated along an elevational gradient ranging from 1040 m to 2677 m above sea level. Moths were sampled using weak light traps (30 W) in three field periods in 1999 and 2000 in an Andean montane rainforest in the province of Zamora‐Chinchipe in southern Ecuador. A total of 13 938 specimens representing 1010 species were analysed. Similarities of ensembles of all geometrid moths and of the subfamilies Ennominae and Larentiinae were calculated using the NESS index (with mmax). Ordinations performed using nonmetric multidimensional scaling (NMDS) and correspondence analysis depicted a gradual change of the ensembles along the altitudinal gradient. Extracted ordination scores significantly correlate with altitude (−0.97 ≤ r ≤ −0.95, P < 0.001) and with ambient air temperature (0.93 ≤ r ≤ 0.97, P < 0.001). Temperature is therefore assumed to be the most important abiotic determinant responsible for the species turnover among the moths. Matrix correlation tests were performed in order to compare faunal matrices with matrices derived from available environmental factors. Both tree diversity and vegetation structure significantly correlate with faunal data, but tree diversity explains considerably more of the data variability (range: Mantel r = 0.81–0.83, P < 0.001) than vegetation structure (range: Mantel r = 0.35, P < 0.005 to r = 0.43, P < 0.001). Tree diversity also changes gradually and scores of the first NMDS dimension are highly significantly correlated with altitude (r = 0.98, P < 0.001). A common underlying factor such as ambient temperature might also be responsible for such vegetation changes. Additionally, simulated model data was developed that assumed a constant turnover of moth species and equal elevational ranges of all species involved. Despite the simplicity of the models, they fit empirical data very well (Mantel r > 0.80 and P < 0.001 in all models).
Endozoochory by ducks: influence of developmental stage of Bythotrephes diapause eggs on dispersal probability
Authors: Charalambidou Iris , Ketelaars Henk A. M. , Santamaría Luis 
Published: August 2003

Abstract. This paper evaluates whether the recent expansion of Bythotrephes longimanus Leydig (Crustacea: Onychopoda) may be a result of endozoochorous avian dispersal. In three experiments, we investigated the survival of diapause eggs in newly produced and end‐of‐winter developmental stages after their passage through the digestive tract of four species of ducks. Resistance of eggs to digestion was low for both developmental stages (< 12%). Most eggs (67–95%) were recovered by four hours after ingestion, with a longer maximum retention time for newly produced (22 h) than end‐of‐winter eggs (4–6 h). Ingestion had a detrimental effect on viability: only eggs retrieved one hour after ingestion hatched and the proportion of those ingested that produced viable neonates was low (0.5% for newly produced and 0.3–3% for end‐of‐winter eggs). We conclude that the probability of endozoochorous dispersal by individual ducks is low but becomes significant when considering the thousands of ducks moving among wetlands. Endozoochorous dispersal of B. longimanus would most likely involve the transport of newly produced diapause eggs from north to south, during the autumn migration of ducks. Based on flight speed estimates of ducks we estimate dispersal probability to drop sharply at distances over 60–80 km.
Contrasting metamorphic evolution of metasedimentary rocks from the Çine and Selimiye nappes in the Anatolide belt, western Turkey
Authors: Régnier J. L. , Ring U. , Passchier C. W. , Gessner K. , Güngör T. 
Published: August 2003

Abstract

P–T conditions, mineral isograds, the relation of the latter to foliation planes and kinematic indicators are used to elucidate the tectonic nature and evolution of a shear zone in an orogen exhumed from mid‐crustal depths in western Turkey. Furthermore, we discuss whether simple monometamorphic fabrics of rock units from different nappes result from one single orogeny or are related to different orogenies. Metasedimentary rocks from the Çine and Selimiye nappes at the southern rim of the Anatolide belt of western Turkey record different metamorphic evolutions. The Eocene Selimiye shear zone separates both nappes. Metasedimentary rocks from the Çine nappe underneath the Selimiye shear zone record maximum P–T conditions of about 7 kbar and >550 °C. Metasedimentary rocks from the overlying Selimiye nappe have maximum P–T conditions of 4 kbar and c. 525 °C near the base of the nappe. Kinematic indicators in both nappes are related to movement on the Selimiye shear zone and consistently show a top‐S shear sense. Metamorphic grade in the Selimiye nappe decreases structurally upwards as indicated by mineral isograds defining the garnet‐chlorite zone at the base, the chloritoid‐biotite zone and the biotite‐chlorite zone at the top of the nappe. The mineral isograds in the Selimiye nappe run parallel to the regional SR foliation, parallel the Selimiye shear zone and indicate that the Selimiye shear zone formed during this prograde greenschist to lower amphibolite facies metamorphic event but remained active after the peak of metamorphism. 40Ar/39Ar mica ages and the tectonometamorphic relationship with the Eocene Cyclades–Menderes thrust, which occurs above the Selimiye nappe in the study area, suggests an Eocene age of metamorphism in the Selimiye nappe.Metasedimentary rocks of the Çine nappe 20–30 km north of the Selimiye shear zone record maximum P–T conditions of 8–11 kbar and 600–650  °C. An age of about 550 Ma is indicated for amphibolite facies metamorphism and associated top‐N shear in the orthogneiss of the Çine nappe. Our study shows that simple monophase tectonometamorphic fabrics do not always indicate a simple orogenic development of a nappe stack. Preservation in some areas and complete overprinting of those fabrics in other areas apparently occur very heterogeneously.
Reactive flow of mixed CO2–H2O fluid and progress of calc‐silicate reactions in contact metamorphic aureoles: insights from two‐dimensional numerical modelling
Authors: Cui X. , Nabelek P. I. , Liu M. 
Published: August 2003

AbstractPrevious models of hydrodynamics in contact metamorphic aureoles assumed flow of aqueous fluids, whereas CO2 and other species are also common fluid components in contact metamorphic aureoles. We investigated flow of mixed CO2–H2O fluid and kinetically controlled progress of calc‐silicate reactions using a two‐dimensional, finite‐element model constrained by the geological relations in the Notch Peak aureole, Utah. Results show that CO2 strongly affects fluid‐flow patterns in contact aureoles. Infiltration of magmatic water into a homogeneous aureole containing CO2–H2O sedimentary fluid facilitates upward, thermally driven flow in the inner aureole and causes downward flow of the relatively dense CO2‐poor fluid in the outer aureole. Metamorphic CO2‐rich fluid tends to promote upward flow in the inner aureole and the progress of devolatilization reactions causes local fluid expulsion at reacting fronts. We also tracked the temporal evolution of P‐T‐XCO2conditions of calc‐silicate reactions. The progress of low‐ to medium‐grade (phlogopite‐ to diopside‐forming) reactions is mainly driven by heat as the CO2 concentration and fluid pressure and temperature increase simultaneously. In contrast, the progress of the high‐grade wollastonite‐forming reaction is mainly driven by infiltration of chemically out‐of‐equilibrium, CO2‐poor fluid during late‐stage heating and early cooling of the inner aureole and thus it is significantly enhanced when magmatic water is involved. CO2‐rich fluid dominates in the inner aureole during early heating, whereas CO2‐poor fluid prevails at or after peak temperature is reached. Low‐grade metamorphic rocks are predicted to record the presence of CO2‐rich fluid, and high‐grade rocks reflect the presence of CO2‐poor fluid, consistent with geological observations in many calc‐silicate aureoles. The distribution of mineral assemblages predicted by our model matches those observed in the Notch Peak aureole.
Prehospital DNR Orders: What Do Physicians in Washington Know?
Authors: Silveira Maria J. , Buell Rick A. , Deyo Richard A. 
Published: September 2003

Objectives: To assess whether physicians know of Washington State's prehospital do‐not‐resuscitate (DNR) policy, 6 years after its implementation.Design: Cross‐sectional survey.Setting: Washington State, April 2001.Participants: Four hundred seventy‐one practicing physicians.Measurements: Multivariate logistic regression was used to determine relationships between physician and practice characteristics with knowledge of policies governing advance care planning.Results: Among respondents, 60% did not know that Washington State requires an emergency medical service (EMS)‐specific DNR order authored by a physician. Seventy‐nine percent did not know that patient‐authored advance directives apply only in hospitals and medical offices.Conclusion: The findings in this study suggest that most physicians in Washington State lack knowledge about the documentation needed for EMS personnel to forgo pre‐hospital attempts at cardiopulmonary resuscitation. Further study is needed to determine whether physician education or legislative change is necessary.