bluuebunny/crossref_metadata_2025 huggingface dataset:
Temporal and spatial characteristics of fog occurrence over the Korean Peninsula
Authors: Lee Yong Hee , Lee Jeong‐Soon , Park Seon Ki , Chang Dong‐Eon , Lee Hee‐Sang
Published: July 2010

In this study, fogs are classified based on the spatial and temporal characteristics over South Korea using the visibility data and the empirical orthogonal function (EOF) and wavelet analyses. With fog defined in terms of visibility (<1 km), the EOF analysis is performed to extract spatial distribution characteristics via dimension reduction, whereas the space‐time wavelet expansion is applied to the EOF time series to specify the fog characteristics in the space of time versus scale (i.e., period in this study). The first EOF mode occupies 48.9% of total variance and shows the fog distribution covering almost entire areas of South Korea with one sign (+), except at the eastern coast and western part of the southern coast. The wavelet analysis reveals that this fog occurs based on meteorological conditions of various scales from daily to seasonal, thus classified as mixed fog. The second EOF mode, which occupies 19.5% of total variance, shows distinct separation of spatial distribution of fog, with a negative (−) sign in winter over northwestern coastal/inland, western coastal, and south central mountain areas of South Korea and a positive (+) sign in other seasons elsewhere. With cycles of 1–2 weeks and 1–2 months being dominant in the wavelet analysis, this fog is considered to be strongly affected by synoptic scale weather systems and monsoon. Fog over the positive area is mostly affected by monsoon and/or cyclonic frontal systems, thus classified as frontal fog, whereas that over the negative area is affected by the cold‐core anticyclones moving over warm sea surface in winter or by radiative cooling, thus classified as steam fog (coastal/sea) or radiation fog (inland), respectively. The mountain area may have upslope fog because of orographic lifting. The third EOF mode, occupying 6.7% of total variance, depicts distinct spatial separation of fog distribution around the coastal areas with a negative (−) sign and in the inland areas with a positive (+) sign. The former, with a dominant 1–2 week cycle, is classified as sea fog affected by migratory anticyclones and monsoon in late spring and summer, while the latter, with a dominant diurnal variation, represents radiation fog under clear sky in autumn. It turns out that the combined EOF and wavelet analyses are useful to assess the detailed spatial and temporal characteristics of various types of fog occurrence in South Korea.
On phenomenology of compact intracloud lightning discharges
Authors: Nag Amitabh , Rakov Vladimir A. , Tsalikis Dimitris , Cramer John A.
Published: July 2010

We examined wideband electric fields, electric and magnetic field derivatives, and narrowband VHF (36 MHz) radiation bursts produced by 157 compact intracloud discharges (CIDs). These poorly understood lightning events appear to be the strongest natural producers of HF‐VHF radiation. All the events transported negative charge upward (or lowered positive charge), 150 were located by the U.S. National Lightning Detection Network (NLDN), and 149 of them were correctly identified as cloud discharges. NLDN‐reported distances from the measurement station were 5–132 km. Three types of wideband electric field waveforms were observed. About 73% of CIDs occurred in isolation; 24% occurred prior to, during, or following cloud‐to‐ground or “normal” cloud lightning; and 4% occurred in pairs, separated by less than 200 ms (“multiple” CIDs). For a subset of 48 CIDs, the geometric mean of radiation source height was estimated to be 16 km. It appears that some CIDs actually occurred above cloud tops in clear air or in convective surges (plumes) overshooting the tropopause and penetrating deep into the stratosphere. For the same 48 CIDs, the geometric mean electric field peak normalized to 100 km (inclined distance) was as high as 20 V/m, and for 22 events within 10–30 km (horizontal distance), it was 15 V/m, both of which are higher than that for first strokes in negative cloud‐to‐ground lightning. The geometric means of total electric field pulse duration, width of initial half cycle, and ratio of initial peak to opposite polarity overshoot were 23 μs, 5.6 μs, and 5.7, respectively.
Observed forcing‐feedback processes between Northern Hemisphere atmospheric circulation and Arctic sea ice coverage
Authors: Wu Qigang , Zhang Xiangdong
Published: July 2010

A lagged maximum covariance analysis is applied to investigate linear covariability between monthly sea ice concentration (SIC) and atmosphere circulation in the Northern Hemisphere. The dominant signal is the atmospheric forcing of SIC anomalies throughout the year, but a wintertime atmospheric signal resembling the negatively polarized Arctic Oscillation/North Atlantic Oscillation is significantly correlated with persistently reduced SIC anomalies in the North Atlantic and Pacific sides of Arctic Shelf seas up to the preceding summer. The leading time of SIC anomalies provides an implication for skillful predictability of wintertime atmospheric variability.
Short‐term effects of controlling fossil‐fuel soot, biofuel soot and gases, and methane on climate, Arctic ice, and air pollution health
Authors: Jacobson Mark Z.
Published: July 2010

This study examines the short‐term (∼15 year) effects of controlling fossil‐fuel soot (FS) (black carbon (BC), primary organic matter (POM), and S(IV) (H2SO4(aq), HSO4−, and SO42−)), solid‐biofuel soot and gases (BSG) (BC, POM, S(IV), K+, Na+, Ca2+, Mg2+, NH4+, NO3−, Cl− and several dozen gases, including CO2 and CH4), and methane on global and Arctic temperatures, cloudiness, precipitation, and atmospheric composition. Climate response simulations were run with GATOR‐GCMOM, accounting for both microphysical (indirect) and radiative effects of aerosols on clouds and precipitation. The model treated discrete size‐resolved aging and internal mixing of aerosol soot, discrete size‐resolved evolution of clouds/precipitation from externally and internally mixed aerosol particles, and soot absorption in aerosols, clouds/precipitation, and snow/sea ice. Eliminating FS, FS+BSG (FSBSG), and CH4 in isolation were found to reduce global surface air temperatures by a statistically significant 0.3–0.5 K, 0.4–0.7 K, and 0.2–0.4 K, respectively, averaged over 15 years. As net global warming (0.7–0.8 K) is due mostly to gross pollutant warming from fossil‐fuel greenhouse gases (2–2.4 K), and FSBSG (0.4–0.7 K) offset by cooling due to non‐FSBSG aerosol particles (−1.7 to −2.3 K), removing FS and FSBSG may reduce 13–16% and 17–23%, respectively, of gross warming to date. Reducing FS, FSBSG, and CH4 in isolation may reduce warming above the Arctic Circle by up to ∼1.2 K, ∼1.7 K, and ∼0.9 K, respectively. Both FS and BSG contribute to warming, but FS is a stronger contributor per unit mass emission. However, BSG may cause 8 times more mortality than FS. The global e‐folding lifetime of emitted BC (from all fossil sources) against internal mixing by coagulation was ∼3 h, similar to data, and that of all BC against dry plus wet removal was ∼4.7 days. About 90% of emitted FS BC mass was lost to internal mixing by coagulation, ∼7% to wet removal, ∼3% to dry removal, and a residual remaining airborne. Of all emitted plus internally mixed BC, ∼92% was wet removed and ∼8% dry removed, with a residual remaining airborne. The 20 and 100 year surface temperature response per unit continuous emissions (STRE) (similar to global warming potentials (GWPs)) of BC in FS were 4500–7200 and 2900–4600, respectively; those of BC in BSG were 2100–4000 and 1060–2020, respectively; and those of CH4 were 52–92 and 29–63, respectively. Thus, FSBSG may be the second leading cause of warming after CO2. Controlling FS and BSG may be a faster method of reducing Arctic ice loss and global warming than other options, including controlling CH4 or CO2, although all controls are needed.
In situ measurements of Antarctic snow compaction compared with predictions of models
Authors: Arthern Robert J. , Vaughan David G. , Rankin Andrew M. , Mulvaney Robert , Thomas Elizabeth R.
Published: July 2010

We describe in situ measurements of the compaction of Antarctic snow. At three different sites in Antarctica, the rate of compaction was measured hourly, over various depth intervals, for up to two years. These measurements show that compaction at each of the sites occurs through slow, viscous deformation of the snowpack, with no significant contribution from sudden collapse of weak layers. The measured rates of compaction at the coldest site exhibit a strong seasonality, consistent with a temperature‐dependent sintering mechanism having activation energy of 70 kJ mol−1. At the two warmer sites, activation energies of 80 and 120 kJ mol−1 provide slightly better agreement with the observations. Published models of snow compaction underestimate the temperature sensitivity. A good match to our observations is provided by a semi‐empirical model, based on rate equations for lattice‐diffusion (Nabarro‐Herring) creep of material around pores, combined with normal grain growth. This model also provides a theoretical basis for a widely used empirical model of snow compaction. The rate coefficient for lattice‐diffusion inferred from our measurements is considerably higher than published values, however, and other creep mechanisms cannot be ruled out.
Anomalous seismic structure beneath the Klyuchevskoy Group, Kamchatka
Authors: Nikulin Alex , Levin Vadim , Shuler Ashley , West Michael
Published: July 2010

The Klyuchevskoy Group is among the most active volcanic features on Earth, yet its position within the Kamchatka subduction zone is hard to explain with a simple tectonic mechanism. The geochemistry of Klyuchevskoy Group lavas is typical for volcanic products resulting from flux melting in the mantle wedge, yet the depth to the subducting Pacific plate beneath it is much larger than the average depth of volatile release in subduction zones. We present new seismological constraints on the upper mantle structure beneath the Klyuchevskoy Group and identify a planar dipping seismic feature in the mantle wedge which is ∼100 km deep and appears to be sharply bounded. We hypothesize that this upper mantle structure may be the true source of melts erupting at the Klyuchevskoy Group, and that the presence of this feature may explain both the extraordinary productivity of the Klyuchevskoy Group and its unusual location.
HLA genes associated with autoimmunity and progression to disease in type 1 diabetes
Authors: Tait B.D. , Colman P.G. , Morahan G. , Marchinovska L. , Dore E. , Gellert S. , Honeyman M.C. , Stephen K. , Loth A.
Published: July 2010

Abstract: Insulin dependent diabetes mellitus (type I DM) is caused by an autoimmune process which culminates in destruction of pancreatic beta cells with resultant loss of insulin production. Preceding the clinical diagnosis of type I DM is a preclinical stage characterized by autoantibodies to insulin, glutamic acid decarboxylase (GAD) and a tyrosine phosphatase‐like molecule (IA‐2). We have studied both HLA class I and class 2 allele distributions in diabetic probands and autoantibody positive individuals in members of 452 families recruited for the Australian type I diabetes DNA repository. The results demonstrate that progression to autoimmunity as measured by the appearance of autoantibodies is strongly associated with the class 2 alleles DRB1*03 and DRB*04 and with DRB1*03/04 heterozygosity. In contrast, the progression to clinical disease appears associated with class I alleles A24, A30 and B18 while A1, A28, B14 and B56 appear negatively associated. The class 2 alleles appear to have a minimal role in the progression from autoantibody positivity to clinical disease. These results are consistent with the view that CD4+ T cells responding to peptides in the context of class 2 molecules are responsible for initiating autoantibody production, while the destruction of islet cells leading to clinical expression of the disease is the function of CD8+ T cells recognizing relevant peptides in the context of class I molecules.
Long‐term follow‐up of hepatitis C virus infection: HLA class II loci influences the natural history of the disease
Authors: Yoshizawa K. , Ota M. , Saito S. , Maruyama A. , Yamaura T. , Rokuhara A. , Orii K. , Ichijo T. , Matsumoto A. , Tanaka E. , Kiyosawa K.
Published: July 2010

Abstract: Hepatitis C virus (HCV) causes various grades of chronic liver disease, ranging from an asymptomatic state to cirrhosis. To assess genetic factors of disease severity, we selected two HCV patient groups according to the following stringent criteria: (i) asymptomatic carrier state (ASC) defined by HCV infection for more than 20 years, normal alanine aminotransferase levels for the past 5 years as well as normal liver histology and/or shape and (ii) liver cirrhosis (LC) as diagnosed by clinical symptoms, liver biopsy and/or ultrasonography. A total of 103 chronically infected Japanese HCV patients (43 ASC and 60 LC) were analyzed. HLA class I and II alleles were established using low resolution DNA typing. HLA‐DRB1 and DQB1 genotypes were inferred upon polymerase chain reaction‐restriction fragment length polymorphism analysis. Two hundred and one anti‐HCV‐negative ethnically matched controls were included. The frequencies of DRB1*12 (*1201 and *1202), DQB1*0301 and DRB3*03 alleles were higher in patients with ASC than in those with LC (odds ratio (OR) 11.23, OR 4.25, and OR 3.22, respectively). The frequency of DQB1*0503 were lower in ASC patients compared to LC patients (OR 0.05). No significant differences between groups were observed for age, sex, source of infection, HCV genotype or viral loads. Our findings establish that certain HLA class II alleles strongly influence disease progression following HCV infection.
Comparative metagenomics of bathypelagic plankton and bottom sediment from the Sea of Marmara
Authors: Quaiser Achim , Zivanovic Yvan , Moreira David , López-García Purificación
Published: July 2010

To extend comparative metagenomic analyses of the deep-sea, we produced metagenomic data by direct 454 pyrosequencing from bathypelagic plankton (1000 m depth) and bottom sediment of the Sea of Marmara, the gateway between the Eastern Mediterranean and the Black Seas. Data from small subunit ribosomal RNA (SSU rRNA) gene libraries and direct pyrosequencing of the same samples indicated that Gamma- and Alpha-proteobacteria, followed by Bacteroidetes, dominated the bacterial fraction in Marmara deep-sea plankton, whereas Planctomycetes, Delta- and Gamma-proteobacteria were the most abundant groups in high bacterial-diversity sediment. Group I Crenarchaeota/Thaumarchaeota dominated the archaeal plankton fraction, although group II and III Euryarchaeota were also present. Eukaryotes were highly diverse in SSU rRNA gene libraries, with group I (Duboscquellida) and II (Syndiniales) alveolates and Radiozoa dominating plankton, and Opisthokonta and Alveolates, sediment. However, eukaryotic sequences were scarce in pyrosequence data. Archaeal amo genes were abundant in plankton, suggesting that Marmara planktonic Thaumarchaeota are ammonia oxidizers. Genes involved in sulfate reduction, carbon monoxide oxidation, anammox and sulfatases were over-represented in sediment. Genome recruitment analyses showed that Alteromonas macleodii ‘surface ecotype’, Pelagibacter ubique and Nitrosopumilus maritimus were highly represented in 1000 m-deep plankton. A comparative analysis of Marmara metagenomes with ALOHA deep-sea and surface plankton, whale carcasses, Peru subsurface sediment and soil metagenomes clustered deep-sea Marmara plankton with deep-ALOHA plankton and whale carcasses, likely because of the suboxic conditions in the deep Marmara water column. The Marmara sediment clustered with the soil metagenome, highlighting the common ecological role of both types of microbial communities in the degradation of organic matter and the completion of biogeochemical cycles.
Expression and Effects of Hyaluronan and of the Hyaluronan‐Binding Protein Hyaluronectin in Newborn Rat Brain Glial Cell Cultures
Authors: Marret Stéphane , Delpech Bertrand , Delpech Annie , Asou Hiroaki , Girard Nicole , Courel Marie‐Noelle , Chauzy Claude , Maingonnat Catherine , Fessard Claude
Published: July 2010

Abstract: Hyaluronan (HA) is a polymerized nonsulfated extracellular matrix glycosaminoglycan that may be involved in brain development. We have tested the expression of HA and the HA‐binding protein hyaluronectin (HN) in glial cell cultures from newborn rat brain. HA was secreted into the culture medium by type 1 astrocytes in the first stages of the primary cultures. The secretion was high during cell proliferation, reached a maximum when they were confluent, and then decreased. HA was not secreted at a detectable level by total O‐2A lineage cell‐ enriched cultures. HA labeled small O‐2A progenitor cells (GFA‐, A2B5+, HA+), small O‐2A progenitorlike (GFA−, A2B5−, HA+) cells, and type 2 astrocytes (GFA+, A2B5+, HA+), but not mature oligodendrocytes (Galc+, HA−). In contrast to HA, hyaluronectin labeled oligodendrocyte membranes (i.e., more mature cells) from day 8. A2B5+ GFA− cells were found to be either HA+ or HN+ at days 7–9, suggesting intermediary stages. The addition of HA to primary cultures and to O‐2A progenitor‐enriched cultures decreased significantly the increase in the number of O‐2A progenitors, of mature (Galc+) oligodendrocytes proportionally to the decrease of the O‐2A progenitor number, and of BrdU+ cells, suggesting that HA acts (directly or indirectly) on O‐2A cell proliferation. This effect, which was seen for concentrations as low as 0.1 μg/ml, was HA specific and was not observed with other glycosaminogly‐ cans. When primary cultures were performed in the presence of hyaluronidase‐digested or HA‐depleted (by passage on a HN column) fetal calf serum, the total number of O‐2A lineage cells was dramatically increased (100%, p<10–4) in comparison with control cultures in standard fetal calf serum. Platelet‐derived growth factor increased the total number of O‐2A lineage cells and of (Galc+) oligodendrocytes. This effect was opposed by HA dose dependently. The effect of HA was significantly inhibited by HN (30%, p<10–4). HN had, however, no effect when it was added to culture in the presence of hyaluronidase in fetal calf serum, suggesting its effect was only due to its binding to HA. During cell maturation, HA disappears as HN appears. This and the fact that HA and PDGF have opposite effects suggest an effect of these factors, or of their balance, on myelination.
Retinoic Acid‐Induced Differentiation of Human Neuroblastoma SH‐SY5Y Cells Is Associated with Changes in the Abundance of G Proteins
Authors: Ammer Hermann , Schulz Rüdiger
Published: July 2010

Abstract:Western blot analysis, using subtype‐specific anti‐G protein antibodies, revealed the presence of the following G protein subunits in human neuroblastoma SH‐ SY5Y cells: Gaα, Giα1, Gjα2, Gcα, Gzα, and Gβ. Differentiation of the cells by all‐trans‐retinoic acid (RA) treatment (10 μmol/L; 6 days) caused substantial alterations in the abundance of distinct G protein subunits. Concomitant with an enhanced expression of μ‐opioid binding sites, the levels of the inhibitory G proteins Giα1 and Gjα1 were found to be significantly increased. This coordinate up‐reg‐ ulation is accompanied by functional changes in μ‐opioid receptor‐stimulated Iow‐KmGTPase, μ‐receptor‐mediated adenylate cyclase inhibition, and receptor‐independent guanosine 5′‐(βγ‐imido)triphosphate [Gpp(NH)p; 10 nmol/ L]‐mediated attenuation of adenylate cyclase activity. In contrast, increased levels of inhibitory G proteins had no effect on muscarinic cholinergic receptor‐mediated adenylate cyclase inhibition. With respect to stimulatory receptor systems, a reciprocal regulation was observed for prosta‐ glandin E1(PGE1) receptors and Gsα, the G protein subunit activating adenylate cyclase. RA treatment of SH‐SY5Y cells increases both the number of PGE1binding sites and PGE1stimulated adenylate cyclase activity, but significantly reduced amounts of Gzα were found. This down‐ regulation is paralleled by a decrease in the stimulatory activity of Gzα as assessed in S49cyc‐ reconstitution assays. However, the reduction in Gaα levels had no effect on both intrinsic and receptor‐independent‐activated [Gpp(NH)p or forskolin; 100 μtmol/L each] adenylate cyclase, suggesting that the amount of Gzα is in excess over the functional capacity of adenylate cyclase in SH‐SY5Y cell membranes. Additional quantitative changes were found for Gzα, Gcα, and Gβ subunits. In contrast, neuronal differentiation in the presence of 12‐O‐tetradecanoylphor‐ bol 13‐acetate (16 nmol/L; 6 days) failed to affect G protein abundance. Our results provide evidence for a specific RA effect on the abundance of distinct G protein sub‐ units in human SH‐SY5Y neuroblastoma cells. These alterations might contribute to functional changes in transmembrane signaling pathways associated with RA‐in‐ duced neuronal differentiation of the cells.
Tumor Necrosis Factor‐α (TNF‐α), Interferon‐γ, and Interleukin‐6 but Not TNF‐β Induce Differentiation of Neuroblastoma Cells: The Role of Nitric Oxide
Authors: Ito Etsuro , Oka Kotaro , Collin Carlos , Schreurs Bernard G. , Sakakibara Manabu , Alkon Daniel L.
Published: July 2010

Abstract: Abstract: Previous observations have implicated GABA as a neurotransmitter released by the vestibular sensory neurons („hair cells”) of the snail Hermissenda onto visual sensory neurons, the type B cells, whose cell bodies are the sites of biophysical and biochemical changes during and following Pavlovian conditioning. Still other observations demonstrated that light‐GABA pairings that simulate stimuli presented during Pavlovian conditioning cause prolonged elevatiori of intracellular Ca2+ and transformation of GABA‐induced synaptic inhibition into excitation. Intracellular Ca2+ signals in response to GABA perfused onto the postsynaptic: type B terminal branches are shown here to be prolonged on days after conditioning, but not after control paradigms. These and past results demonstrate two separate sites, i.e., the cell body and the terminal branches, for learning‐induced changes after Pavlovian conditioning.
Effects of Redox Reagents and Arsenical Compounds on [3H]‐Cytisine Binding to Immunoisolated Nicotinic Acetylcholine Receptors from Chick Brain Containing α4 β2 Subunits
Authors: Rossant Christine J. , Lindstrom Jon , Loring Ralph H.
Published: July 2010

All known nicotinic receptor α subunits include a conserved disulfide bond that is essential for function and is a site for labeling via biochemical modification. In an effort to develop a universal ligand for all subtypes of nicotinic receptors, we previously studied the effects of arsenylation with two compounds, ρ‐aminophenyldichloroarsine (APA) and bromoacetyl‐ρ‐aminophenylarsenòxide (BAPA) on nicotinic receptors fromTorpedoelectroplax. Here we apply these reagents to immunoisolated receptors containing α4, β2, and possibly other subunits from chick brain that bind [3H]cytisine with high affinity (KD∼5 nM). These are distinct from another receptor subtype that also binds [3H]cytisine and [3H]nicotine and can be arsenylated with APA, but instead contains α5,β2, and probably other subunits. Reduction of α4 β2 receptors with dithiothreitol blocked [3H]cytisine binding and this effect was reversed upon reoxidation by dithiobisnitrobenzoic acid. APA or BAPA prevented the dithiobisnitrobenzoic acid reactivation of dithiothreitol‐treated receptors with IC50values of 15 and 70 nM, respectively. However, the antiarsenical dimercaptopropanesulfonic acid restored function to APA‐ or BAPA‐ “arsenylated” receptors (EC50∼100 μM). APA‐treated receptors remained blocked for up to 24 h, but treatment with dimercaptopropanesulfonic acid at any time restored [3H]cytisine binding. APA treatment of reduced receptors protected against irreversible alkylation by Bromoacetyl choline, indicating that arsenylation occurs at least in part in the agonist binding site. Thus, these reagents have similar effects on different nicotinic receptor subtypes from both muscle and nerves.
The Level of GAD67 Protein Is Highly Sensitive to Small Increases in Intraneuronal γ‐Aminobutyric Acid Levels
Authors: Rimvall Karin , Martin David L.
Published: July 2010

Increases (>2.5‐fold) in GABA levels in rat brain lead to a large decrease in the level of the 67‐kDa form of glutamate decarboxylase (GAD67) through a mechanism involving either a change in GAD67 protein stability or a change in GAD67 mRNA translation. In the present study, brain levels of GABA were manipulated by treating rats with various doses of γ‐vinyl‐γ‐aminobutyric acid (GVG), and the dependence of total GAD activity and levels of GAD67 and GAD65 protein on the levels of GABA was analyzed. Initial studies showed that both GABA and GAD67protein levels reached new steady‐state levels after two to four daily injections; GABA increased 1.5‐ (30 mg of GVG/kg) and fourfold (150 mg of GVG/kg), and GAD67 protein content decreased by 30 and 70%. To assess the sensitivity of GAD67 to GABA, rats were injected with eight different doses of GVG (15‐150 mg/kg) for 5 days. With increasing doses of GVG, we observed a gradual increase in both whole‐tissue and synaptosomal GABA levels and a gradual decrease in GAD67 protein and GAD activity. The levels of GAD67 remained constant at all GVG doses. GAD67 was remarkably sensitive to GABA. The synaptosomal GAD67 level decreased ∼12% and the whole‐neuron GAD67 level decreased ∼3% for each 1 % increase in nerve terminal GABA content when it was close to its physiological level. Our results clearly demonstrate that GAD67 is tightly controlled by intraneuronal GABA, and we suggest that this regulatory mechanism has important implications for the physiological regulation of GABAergic function in the mammalian brain.
Effects of Ion Channel Blockers and Phorbol Ester Treatments on [3H]Dopamine Release and Neurotensin Facilitation of [3H]Dopamine Release from Rat Mesencephalic Cells in Primary Culture
Authors: Brouard Aline , Pelaprat Didier , Vial Micheline , Lhiaubet Anne‐Marie , Rostène William
Published: July 2010

In this work, we tested the effect of ion channel blockers and of phorbol ester treatments on [3H]dopamine ([3H]DA) release and neurotensin (NT)‐induced facilitation of [3H]DA release from cultures of rat fetal mesencephalic cells. The potassium channel blockers tetraethylammonium and 4‐aminopyridine increased basal [3H]DA release and decreased K+‐evoked [3H]DA release, whereas apamin was without effect. K+‐evoked [3H]DA release was decreased by ω‐conotoxin and nifedipine, totally suppressed by cadmium, and unaffected by amiloride. These results show the differential sensitivity of [3H]DA release to blockade of various ion channels and suggest the involvement of N‐type, L‐type, and non‐L‐non‐N‐type, but not T‐type, voltage‐sensitive calcium channels in K+‐evoked release. Phorbol 12‐myristate 13‐acetate increased both spontaneous and K+‐evoked [3H]DA release, suggesting a modulatory action of protein kinase C on DA release in this system. Unexpectedly, however, the effects of the phorbol ester were not counteracted by the protein kinase C inhibitors H7, staurosporine, or polymyxin B. NT‐induced facilitation of K+‐evoked [3H]DA release was insensitive to most of the ion channel blockers, except cadmium (64% decrease in NT effect), suggesting that the corresponding potassium' and calcium channels were not involved in the effect of NT on [3H]DA release in this system. The NT effect was totally suppressed by phorbol ester treatments, indicating a possible desensitization of the corresponding transduction mechanisms after protein kinase C activation.
Synthesis of Specific Proteins in Trophic Factor‐Deprived Neurons Undergoing Apoptosis
Authors: Villa P. , Miehe M. , Sensenbrenner M. , Pettmann B.
Published: July 2010

Abstract: Apoptosis, also known as programmed cell death, is a mechanism used by different tissues to regulate their cell content. In the nervous system, this process is supposed to adjust the final number of neurons to the number of the target cells they are innervating. The demonstration that, in several systems in vitro and in vivo, neuronal apoptosis can be prevented by inhibiting RNA or protein synthesis suggests that an activation of gene expression is required in the cells that are going to die. The genes involved and their products, named “killer proteins”, are not known in the superior vertebrates. In order to identify such proteins, we have used and characterized an in vitro model consisting of neurons derived from 8‐day‐old embryonic chicken ciliary ganglia. RNA and protein synthesis inhibitors can prevent the death of these neurons when they are deprived of trophic support. Comparing the synthesis of proteins in trophic‐supported neurons with that in trophic‐deprived neurons by the use of two‐dimensional polyacrylamide gel electrophoresis, we have observed that several proteins were overexpressed reproducibly in the apoptotic cells. We found that all these proteins are localized in the nucleus, suggesting that they may be transcription regulators.
Differential Cytotoxicities of N‐Methyl‐β‐Carbolinium Analogues of MPP+ in PC12 Cells: Insights into Potential Neurotoxicants in Parkinson's Disease
Authors: Cobuzzi Robert J. , Neafsey Edward J. , Collins Michael A.
Published: July 2010

N‐Methylated β‐carbolinium cations that can form in vivo from environmental or endogenous β‐carbolines are putative neurotoxic factors in Parkinson's disease. The cytotoxicities of 11 N‐methylated β‐carbolinium cations and N‐methyl‐4‐phenylpyridinium cation (MPP+), the experimental parkinsonian neurotoxicant which the carbolinium cations structurally resemble, were examined using rat pheochromocytoma (PC12) cells cultured in “low energy” N‐5 medium; cell death was estimated by released lactate dehydrogenase activity and viable cell protein. Of the eight N‐monomethylated β‐carbolinium cations utilized, only 2‐methyl‐harmalinium (harmaline‐2‐ methiodide) was as cytotoxic as MPP+. Also, three N2(β), N8(indole)‐dimethylated β‐carbolinium cations displayed cytotoxic effects, with the simplest, 2,9‐dimethylnorhar‐ manium, approaching the effectiveness of MPP+ in PC12 cells cultured in N‐5 medium. However, when PC12 cells grown in higher energy Dulbecco's modified Eagle's medium were utilized with selected effective cations, it was observed that the cultures were relatively resistant to MPP+ and 2,9‐dimethylnorharmanium, but remained vulnerable to 2‐methylharmalinium. The results are interpreted to mean that different cytotoxic mechanisms exist for the two most potent β‐carbolinium cations—namely, a mechanism for the 2,9‐dimethyl‐β‐carbolinium species that, as with MPP+, is conditional on mitochondrial ATP depletion, but a different (or additional) mechanism for 2‐ methylharmalinium that is independent of mitochondrial inhibition. The possible accumulation of these cytotoxic cations in Parkinson's disease is discussed in the context of these findings.
Cyclic AMP Decreases the Expression of a Neuronal Marker (GAD67) and Increases the Expression of an Astroglial Marker (GFAP) in C6 Cells
Authors: Segovia José , Lawless George M. , Tillakaratne Niranjala J. K. , Brenner Michael , Tobin Allan J.
Published: July 2010

Abstract: C6 cells express proteins and mRNAs that are characteristic of both glia and neurons. Agents that increase intracellular levels of cyclic AMP (cAMP) decrease the enzymatic activity of glutamate decarboxylase (GAD), a neuronal marker, and the mRNA levels for one of the two GAD isoenzymes, GAD67. This reduction is accompanied by increased levels of glial fibrillary acidic protein (GFAP) mRNA, an astrocyte marker. Transient transfection assays, in which a 2‐kb upstream regulatory region of the human GFAP gene was linked to a reporter gene, indicate that at least some of the cAMP‐mediated increase of GFAP mRNA levels is due to increased transcription. Increases in intracellular cAMP appear to induce differentiation of C6 cells toward a more mature astrocyte phenotype.
Modulation of Cyclic AMP Metabolism by Glucocorticoids in PC18 Cells
Authors: Yingling Jeffrey D. , Fuller Lynn Z. , Jackson Brian A.
Published: July 2010

Abstract: Glucocorticoids modulate signal transduction mechanisms in a number of cell systems. As the adrenal medulla is exposed to relatively high levels of adrenal cortical glucocorticoids in vivo, particularly during periods of stress, the aim of the present study was to determine whether glucocorticoids modulate cyclic AMP (cAMP) metabolism in an in vitro model of this system, the PC18 cell line. Dexamethasone significantly potentiated cAMP accumulation in response to the adenosine analogue N6‐R‐phenylisopropyl adenosine (PIA), and in response to forskolin. This effect was both time‐ and concentration‐dependent. Maximal potentiation was observed after 48 h of exposure to 1 µM dexamethasone. Corticosterone and to a lesser extent aldosterone also significantly potentiated PIA‐dependent cAMP accumulation. In contrast, estradiol, testosterone, and triiodothyronine had no potentiative effect. Potentiation could be eliminated by coincubation with the protein synthesis inhibitor cycloheximide. In the presence of Ro 20‐1724, a cAMP‐phosphodiesterase inhibitor, the degree of potentiation of both PIA‐ and forskolin‐dependent cAMP accumulation was significantly decreased by 50–60%. These data suggested that altered cAMP‐phosphodiesterase activity may be involved in this response. However, cytosolic and membrane‐bound low Km cAMP‐phosphodiesterase activity was unchanged in dexamethasone‐treated cells compared with controls. Similarly, there were no significant differences in basal, PIA‐, forskolin‐, or GTPγS‐stimulated adenylate cyclase activities between groups. These studies indicate that glucocorticoids can potentiate cAMP accumulation in intact PC18 cells. The mechanism underlying this potentiation is likely to be multifactorial, but may be due in part to decreased cAMP catabolism.
Glutamate Exocytosis and MARCKS Phosphorylation Are Enhanced by a Metabotropic Glutamate Receptor Coupled to a Protein Kinase C Synergistically Activated by Diacylglycerol and Arachidonic Acid
Authors: Coffey Eleanor T. , Herrero Inmaculada , Sihra Talvinder S. , Sánchez‐Prieto José , Nicholls David G.
Published: July 2010

Abstract: 4‐Aminopyridine evokes repetitive firing of synaptosomes and exocytosis of glutamate by inhibiting a dendrotoxin‐sensitive K+ channel responsible for stabilizing the membrane potential. We have shown previously that activation of protein kinase C (PKC) by high concentrations of phorbol ester (4β‐phorbol dibutyrate) can increase release by inhibiting a dendrotoxin‐insensitive ion channel, whereas the metabotropic glutamate receptor (mGluR) agonist (1S,3R)‐1‐aminocyclopentane‐1,3‐dicarboxylate [(1S,3R)‐ACPD] mimics the action of 4β‐phorbol dibutyrate, but only in the presence of 2 µM arachidonic acid (AA). In this article, we investigate the role of AA. AA plus (1S,3R)‐ACPD is without effect on KCl‐induced glutamate exocytosis, indicating that the regulatory pathway acts upstream of the release‐coupled Ca2+ channel or Ca2+‐secretion coupling. Diacylglycerol concentrations are greatly enhanced by (1S,3R)‐ACPD alone, independently of AA, indicating that AA acts downstream of phospholipase C. Myristoylated alanine‐rich C kinase substrate (MARCKS) is the major presynaptic substrate for PKC. mGluR activation by (1S,3R)‐ACPD enhances phosphorylation of MARCKS, but only in the presence of AA. These results strongly suggest that AA acts on presynaptic PKC synergistically with diacylglycerol generated by the phospholipase‐coupled mGluR, consistent with the known behaviour of certain purified PKC isoforms. The magnitude of the effects observed in a population of rat cerebrocortical synaptosomes suggests that this is a major mechanism regulating the release of the brain's dominant excitatory neurotransmitter and supports the concept that AA, or a related compound with a similar locus of action, may in certain circumstances play a role in synaptic plasticity.
Differential Effects of Lithium on Muscarinic Cholinoceptor‐Stimulated CMP‐Phosphatidate Accumulation in Cerebellar Granule Cells, CHO‐M3 Cells, and SH‐SY5Y Neuroblastoma Cells
Authors: Gray David W. , Challiss R. A. John , Nahorski Stefan R.
Published: July 2010

Abstract: The ability of lithium to potentiate muscarinic cholinoceptor‐stimulated CMP‐phosphatidate (CMP.PA) accumulation has been examined in various cells in which muscarinic cholinoceptor agonists evoke a phosphoinositide response. Cell types examined include rat cerebellar granule cells, Chinese hamster ovary cells transfected to express the human muscarinic M3 receptor (CHO‐M3 cells), and SH‐SY5Y neuroblastoma cells. Neither carbachol (1 mM) nor lithium (10 mM) caused significant increases in CMP.PA accumulation in rat cerebellar granule cells; however, when added together for 20 min a linear 17‐fold increase over basal levels was observed. The increase was dependent on the concentration of carbachol and lithium present, and the effect could be reversed by addition of exogenous myo‐inositol (10 mM). Addition of carbachol alone to CHO‐M3 cells caused a five‐fold increase in CMP.PA accumulation. In the presence of lithium, a 70‐fold increase was observed at 20 min after carbachol plus lithium addition. This latter response was concentration dependent and could be abolished by preincubation in the presence of 10 mM myo‐inositol. In contrast, whereas carbachol elicited a three‐fold increase in CMP.PA accumulation in SH‐SY5Y neuroblastoma cells, which reached a plateau 10 min after agonist addition, the response could neither be augmented by addition of lithium nor inhibited by addition of myo‐inositol. These results emphasise that the ability of lithium to affect agonist‐stimulated CMP.PA accumulation is not simply a function of stimulus strength, but is also crucially dependent on the intracellular concentration of inositol.
Glucose Transporter Isoform Expression in Huntington's Disease Brain
Authors: Gamberino W. C. , Brennan W. A.
Published: July 2010

Abstract: Several reports have suggested a characteristic decrease in glucose use in the striatum of patients with Huntington's disease (HD) may contribute to the cellular atrophy of the caudate and putamen. We examined the expression of the two major glucose transporter isoforms of brain, GLUT1 and GLUT3. GLUT1 is found largely in capillary endothelial cells and to a lesser extent in the brain parenchyma, whereas GLUT3 is localized primarily in neurons. Membranes prepared from postmortem samples of HD caudate and cortex and non‐HD caudate and cortex were separated on 10% sodium dodecyl sulfate‐polyacrylamide gels and probed with antisera to GLUT1 and GLUT3 by western blotting. Compared with controls, GLUT1 and GLUT3 transporter expression in caudate was decreased by three‐ and fourfold, respectively, in grade 3 of the disease. At earlier stages (grade 1), there was no significant difference in the expression of the two transporter isoforms compared with nondiseased controls. It is surprising that despite a substantial increase in glial fibrillary acidic protein immunoreactivity (an indicator of the extent of gliosis), glucose transporter expression was diminished significantly in HD caudate. The results suggest in the absence of a significant number of neurons, as in grade 3, glial cell GLUT1 and GLUT3 expression is down‐regulated, perhaps reflecting the decreased metabolic demand of this brain region in HD.
Dipeptidyl Aminopeptidase III of Guinea‐Pig Brain: Specificity for Short Oligopeptide Sequences
Authors: Smyth Maria , O'Cuinn Gerard
Published: July 2010

Abstract: A dipeptidyl aminopeptidase III‐type activity has been purified from the cytoplasm of guinea‐pig brain using arginyl‐arginyl‐7‐amido‐4 methylcoumarin as substrate. The enzyme was purified 754‐fold relative to the crude homogenate and with a 12.7% recovery. The purified enzyme was found to have a relative molecular weight of 85,000 and consists of one polypeptide chain of relative molecular weight 80,000, on the basis of its migration on calibrated sodium dodecyl sulphate‐polyacrylamide gel electrophoresis gel. It is highly sensitive to the presence of chelating agents, sulphydryl reactive agents, and the dipeptide Tyr‐Tyr. Dithiothreitol (1 mM) reduced activity by 28%, and 36 and 65% inhibition was noted with phenylmethylsulphonyl fluoride and puromycin (both at 1 mM), respectively. Little or no inhibition was observed with bestatin, bacitracin, captopril, amastatin, and arphamenine B. The purified enzyme released dipeptide moieties from a wide range of peptides including enkephalin sequences and also angiotensin sequences up to the octapeptide angiotensin II. These sequences inhibited the hydrolysis of arginyl‐arginyl‐7‐amido‐4‐methylcoumarin by dipeptidyl aminopeptidase III with Ki values in the micromolar range. No hydrolysis was observed with angiotensin I or with peptide sequences containing more than 10 amino acids. No hydrolysis was observed also with peptide sequences containing a Pro residue on either side of the sissile bond. Peptides containing less than four amino acids were not hydrolysed.
Short and Long Form γ2 Subunits of the GABAA/Benzodiazepine Receptors
Authors: Khan Zafar U. , Gutiérrez Antonia , De Blas Angel L.
Published: July 2010

Abstract: Three novel antisera to the γ2 subunit of the γ‐aminobutyric acidA (GABAA) receptor/benzodiazepine receptor (GABAAR/BZDR) complex have been made. Anti‐γ2S and anti‐γ2L are specific antibodies to synthetic peptides that recognize the γ2S (short) and γ2L (long) forms, respectively, of the γ2 subunit. An antibody (anti‐γ2IL2) to staphylococcal protein A fusion protein of the large intracellular loop (γ2IL) located between the putative transmembrane segments M3 and M4 of γ2S recognizes both γ2S and γ2L subunits. The antibodies immunoprecipitated both the solubilized and affinity‐purified GABAAR/BZDR from rat and bovine brain. Immunoblots with membranes from rat brain cerebral cortex as well as with affinity‐purified receptor from bovine cortex show that anti‐γ2S and anti‐γ2L recognize peptides of 45,000 and 47,000 Mr, respectively. Immunoprecipitation experiments indicate that γ2S is more prevalent in hippocampus, whereas γ2L is more abundant in cerebellum. Intermediate values for each form are found in the cerebral cortex. The results suggest that in the rat brain there is a considerable amount of colocalization of γ2S and γ2L in the same receptor complex. In the cerebral cortex, 15% of the BZDRs contain both γ2S and γ2L subunits and 41–48% of the γ2L subunit coexists with γ2S in the same receptor complex. In cerebellum, in 27% of the clonazepam‐sensitive and 39% of the clonazepam‐insensitive BZDRs the γ2S and γ2L coexist in the same receptor complex. The latter are presumably localized in granule cells and also contain α6. In addition, almost all (93%) the clonazepam‐insensitive BZDRs that contain γ2L also contain a γ2S subunit in the same receptor complex. The most likely interpretation of the results is that there is an important population of granule cell receptors that contain α6, γ2S, and γ2L coexisting in the same receptor complex. Nevertheless, 31% of the cerebellar receptors that contain α6 subunit(s) have neither γ2S nor γ2L subunits. There are also species differences with respect to the relative abundance of γ2S and γ2L. These results might be relevant for understanding the molecular mechanisms underlying some of the GABAAR/BZDR‐mediated effects of ethanol intoxication involving cerebellar granule cells.
Hypoxia Specifically and Reversibly Induces the Synthesis of Ferritin in Oligodendrocytes and Human Oligodendrogliomas
Authors: Qi Yan , Dawson Glyn
Published: July 2010

Abstract: Neonatal (3 day old) rat oligodendrocytes grown in monolayer culture and exposed to increasingly hypoxic culture conditions showed increased Tran35S‐label incorporation into a 22‐kDa protein. Reoxygenation of cultures reversed the synthesis of the protein. Amino acid sequencing of a peptide derived from the purified protein revealed a 13 amino acid sequence with complete identity to a human heavy chain subunit of ferritin. This was confirmed by two‐dimensional gel electrophoresis, immunoprecipitation, and western blot analysis with anti‐ferritin antibody. In addition, hypoxia was able to induce the synthesis of ferritin in a cell line derived from human oligodendroglioma cells but not in astrocytes or neurons. Actinomycin D (1–15 µg/ml) treatment did not block the hypoxic induction of ferritin synthesis, whereas cycloheximide (1 µM) gave complete inhibition. Northern blot analysis showed that ferritin mRNA levels remained unchanged in both control and hypoxic oligodendrocytes and human oligodendroglioma cells, suggesting that the synthesis of ferritin was translationally rather than transcriptionally regulated by hypoxia. In neither oligodendrocytes nor the oligodendroglioma was there any cross‐reaction with an antibody to αB‐crystallin, the 22‐kDa protein induced in astrocytes by various types of stress, further suggesting the specificity of hypoxic induction of ferritin in oligodendrocytes.
Detergents and Peptides Alter Proteolysis and Calmodulin Binding of B‐50/GAP‐43 In Vitro
Authors: Coggins Philip J. , Zwiers Henk
Published: July 2010

Abstract: The neuronal growth‐associated protein B‐50/GAP‐43 is a substrate for protein kinase C, binds to calmodulin in a calcium‐independent manner, and in vitro is subject to an endogenous and chymotrypsin‐mediated hydrolysis in the vicinity of the single kinase C phosphorylation site. All of these processes can be influenced by corticotrophin (ACTH). In the present study we have investigated whether these biochemical interactions involving B‐50 could have common structural determinants. Chymotryptic digestion of B‐50 in the presence or absence of a nonionic detergent and ACTH demonstrated that hydrolysis is potentiated by a lipid‐like environment that primarily affects the protein rather than the protease or the peptide. Furthermore, this lipid dependency appears to extend to the binding of dephosphorylated B‐50 to calmodulin, which appears to occur only in the presence of a nonionic detergent or lipid and the absence of calcium. A structure‐activity study for ACTH‐mediated inhibition of B‐50 proteolysis by an endogenous protease that copurifies with B‐50 in a detergent extract of synaptosomal plasma membranes showed that ACTH1–24, ACTH5–24, ACTH5–16, dynorphin, and corticostatin inhibited the conversion of rat B‐50 to B‐5041–226. In contrast, ACTH7–16, Org2766, and neurotensin had no detectable effect on B‐50 proteolysis at concentrations of 10 and 50 µM. The results indicate that in common with effects in other B‐50‐containing systems, inhibition of proteolysis is related to the presence of a basic amphiphilic helix in those ACTH fragments and analogues that were inhibitory and, moreover, the presence of this motif in other peptides appears to confer inhibitory activity. The results are discussed with reference to the putative secondary structure of B‐50 and changes that may take place in the presence of membrane lipids or nonionic detergents. The conclusions of this study suggest that in vitro B‐50 is subject to regulation by posttranslational enzymes and binding proteins as a consequence of its ability to adapt an amphiphilic helix conformation.