bluuebunny/crossref_metadata_2025 huggingface dataset:
Nerve Growth Factor‐Stimulated Nuclear S6 Kinase in PC12 Cells
Authors: Tang Tong , Hirata Yoko , Whalin Michael , Guroff Gordon
Published: July 2010

Abstract: Previous work has shown that nerve growth factor (NGF) stimulates the phosphorylation of the ribosomal protein S6 in PC12 cells. In this study, we show that S6 kinase activity is also present in purified PC12 cell nuclei. This activity was increased by treatment of the cells with NGF and, to a lesser extent, by treatment with epidermal growth factor. The NGF‐stimulated activity was obtained from nuclear extracts and some of its characteristics described. The increase in activity was prevented by treatment of the cells with rapamycin or with wortmannin, and the overall activity could be precipitated by antibodies directed against the p85S6K. These data indicate that p85S6K is the NGF‐stimulated S6 kinase in PC12 cell nuclei. The presence of S6 protein in the nucleus of PC12 cells has been confirmed and evidence is presented that suggests that it is identical to a protein called SMP reported some years ago.
Developmental and Regional Expression of NMDA Receptor Subtypes Containing the NR2D Subunit in Rat Brain
Authors: Wenzel A. , Villa M. , Mohler H. , Benke D.
Published: July 2010

Abstract: The regional and developmental expression of NMDA receptors containing the NR2D subunit was analyzed on the level of the subunit mRNA and protein in rat brain. RNase protection experiments indicated that among two proposed splice variants of the NR2D subunit, only the NR2D‐2 subunit is expressed. The regional distribution of the NR2D subunit protein was visualized with a newly developed NR2D‐2 subunit‐specific antiserum on brain sections using the histoblot technique. In adult brain, NR2D immunoreactivity was mainly restricted to diencephalic, mesencephalic, and brainstem structures. During postnatal development, the NR2D subunit was detected transiently in certain regions, such as the ventro‐basal complex of the thalamus, hippocampus, inferior colliculus, and brainstem reticular formation, suggesting that NR2D subunit‐containing receptors play a role in these brain areas only during development. The level of NR2D subunit mRNA and protein decreased during late postnatal development. However, significant levels of NR2D subunit mRNA and protein were present in adulthood, in particular, in the globus pallidus, thalamus, subthalamic nuclei, and superior colliculus. These results indicate a functional relevance for NMDA receptors containing the NR2D subunit in the developing and adult brain, although its expression in the adult brain is less prominent and restricted to a few brain areas.
Protein Kinase C‐Mediated Down‐Regulation of Voltage‐Dependent Sodium Channels in Adrenal Chromaffin Cells
Authors: Yanagita Toshihiko , Wada Akihiko , Yamamoto Ryuichi , Kobayashi Hideyuki , Yuhi Tomoaki , Urabe Masanobu , Niina Hiromi
Published: July 2010

Abstract: Treatment of cultured bovine adrenal chromaffin cells with 12‐O‐tetradecanoylphorbol 13‐acetate (TPA), an activator of protein kinase C (PKC), decreased [3H]saxitoxin ([3H]STX) binding in a concentration (IC50 = 19 nM)‐ and time (t1/2 = 4.5 h)‐dependent manner. TPA (100 nM for 15 h) lowered the Bmax of [3H]STX binding by 53% without altering the KD value. Phorbol 12,13‐dibutyrate (PDBu) also reduced [3H]STX binding, whereas 4α‐TPA, an inactive analogue, had no effect. The inhibitory effect of TPA was abolished when H‐7 (an inhibitor of PKC), but not H‐89 (an inhibitor of cyclic AMP‐dependent protein kinase), was included in the culture medium for 1 h before and during TPA treatment. Simultaneous treatment with TPA in combination with either actinomycin D or cycloheximide, an inhibitor of protein synthesis, nullified the effect of TPA. TPA treatment also attenuated veratridine‐induced 22Na+ influx but did not alter the affinity of veratridine for Na channels as well as an allosteric potentiation of veratridine‐induced 22Na+ influx by brevetoxin. These results suggest that an activation of PKC down‐regulates the density of Na channels without altering their pharmacological features; this down‐regulation is mediated via the de novo synthesis of an as yet unidentified protein(s), rather than an immediate effect of Na channel phosphorylation.
Passage of a δ‐Opioid Receptor Selective Enkephalin, [d‐Penicillamine2,5]Enkephalin, Across the Blood‐Brain and the Blood‐Cerebrospinal Fluid Barriers
Authors: Williams Sarah A. , Abbruscato Thomas J. , Hruby Victor J. , Davis Thomas P.
Published: July 2010

Abstract: [d‐Penicillamine2,5]enkephalin (DPDPE) is an enzymatically stable, δ‐opioid receptor‐selective peptide, which produces analgesia when given intracerebroventricularly. However, because only modest analgesic effects were seen after subcutaneous administration of DPDPE, it has been inferred that it does not cross the blood‐brain barrier well. In this present study, a vascular brain perfusion technique in anesthetized rats was used to measure directly whether [3H]DPDPE could cross the blood‐brain and/or the blood‐CSF barriers. The results indicated that the brain uptake of [3H]DPDPE was significantly greater than that of [14C]sucrose, a vascular marker (p < 0.01), and than that of [3H]DPDPE into the CSF (p < 0.01). Furthermore, HPLC analysis confirmed the integrity of the 3H to DPDPE and demonstrated that intact [3H]DPDPE entered the brain. Although 1 mM leucine‐enkephalin failed to inhibit uptake of [3H]DPDPE, unlabeled DPDPE (100 µM) caused a significant inhibition of the brain uptake (p < 0.01) but not the CSF uptake of [3H]DPDPE. These data provide evidence that intact [3H]DPDPE enters the CNS of anesthetized rats by saturable and nonsaturable mechanisms. In addition, the saturable mechanism is likely to be found at the blood‐brain barrier, with the blood‐CSF barrier playing only a minor role in the brain uptake of this peptide.
Tetrameric (G4) Acetylcholinesterase: Structure, Localization, and Physiological Regulation
Authors: Fernandez Hugo L. , Moreno Ricardo D. , Inestrosa Nibaldo C.
Published: July 2010

Abstract: Acetylcholinesterase (AChE), a highly conserved enzyme in the animal kingdom, is distributed throughout a wide range of vertebrate tissues where it is expressed as multiple molecular forms comprising different arrangements of catalytic and structural subunits. The major AChE form in the CNS is an amphiphilic globular tetramer (G4 AChE) consisting of four identical catalytic subunits attached to cellular membranes by a hydrophobic noncatalytic subunit (P‐subunit). This study focuses primarily on current data involving the structure of the G4 AChE P‐subunit, the expression and regulation of G4 AChE during development and adulthood, and its role(s) in certain neurological disorders including Alzheimer's disease.
δ‐Opioids Stimulate Inositol 1,4,5‐Trisphosphate Formation, and so Mobilize Ca2+ from Intracellular Stores, in Undifferentiated NG108‐15 Cells
Authors: Smart D. , Lambert D. G.
Published: July 2010

Abstract: δ‐Opioids mobilize Ca2+ from intracellular stores in undifferentiated NG108‐15 cells, but the mechanism involved remains unclear. Therefore, we examined the effect of [d‐Pen2,5]enkephalin on inositol 1,4,5‐trisphosphate formation in these cells. [d‐Pen2,5]enkephalin caused a dose‐dependent (EC50 = 3.1 nM) increase in inositol 1,4,5‐trisphosphate formation (measured using a specific radioreceptor mass assay), which peaked (25.7 ± 1.2 pmol/mg of protein with 1 µM, n = 9) at 30 s and returned to basal levels (10.6 ± 0.9 pmol/mg of protein, n = 9) within 4–5 min. This response was fully naloxone (1 µM) reversible and pertussis toxin (100 ng/ml for 24 h) sensitive. Preincubation with Ni2+ (2.5 mM) or nifedipine (1 µM) had no effect on the [d‐Pen2,5]enkephalin (1 µM)‐induced inositol 1,4,5‐trisphosphate response, and K+ (80 mM) was unable to stimulate inositol 1,4,5‐trisphosphate formation, indicating Ca2+ influx‐induced activation of phospholipase C is not involved. Preincubation with the protein kinase C inhibitor Ro 31‐8220 (1 µM) enhanced, whereas acute exposure to phorbol 12,13‐dibutyrate (1 µM) abolished, the [d‐Pen2,5]enkephalin (0.1 µM)‐induced inositol 1,4,5‐trisphosphate response, suggesting protein kinase C exerts an autoinhibitory feedback action. [d‐Pen2,5]Enkephalin also dose‐dependently (EC50 = 2.8 nM) increased the intracellular [Ca2+], which was maximal (24 nM increase with 1 µM, n = 5) at 30 s. This close temporal and dose‐response relationship strongly suggests that δ‐opioid receptor‐mediated increases in intracellular [Ca2+] results from inositol 1,4,5‐trisphosphate‐induced Ca2+ release from intracellular stores, in undifferentiated NG108‐15 cells.
Evaluation of Cathepsins D and G and EC 3.4.24.15 as Candidate β‐Secretase Proteases Using Peptide and Amyloid Precursor Protein Substrates
Authors: Brown Abraham M. , Tummolo Donna M. , Spruyt Michael A. , Jacobsen J. Steven , Sonnenberg‐Reines June
Published: July 2010

Abstract: No single protease has emerged that possesses all the expected properties for β‐secretase, including brain localization, appropriate peptide cleavage specificity, and the ability to cleave amyloid precursor protein exactly at the amino‐terminus of β‐amyloid peptide. We have isolated and purified a brain‐derived activity that cleaves the synthetic peptide substrate SEVKMDAEF between methionine and aspartate residues, as required to generate the amino‐terminus of β‐amyloid peptide. Its molecular size of 55–60 kDa and inhibitory profile indicate that we have purified the metalloprotease EC 3.4.24.15. We have compared the sequence specificity of EC 3.4.24.15, cathepsin D, and cathepsin G for their ability to cleave the model peptide SEVKMDAEF or related peptides that contain substitutions reported to modulate β‐amyloid peptide production. We have also tested the ability of these enzymes to form carboxy‐terminal fragments from full‐length, membrane‐embedded amyloid precursor protein substrate or amyloid precursor protein that contains the Swedish KM → NL mutation. The correct cleavage was tested with an antibody specific for the free amino‐terminus of β‐amyloid peptide. Our results exclude EC 3.4.24.15 as a candidate β‐secretase. Although cathepsin G cleaves the model peptide correctly, it displays poor ability to cleave the Swedish KM → NL peptide and does not generate carboxy‐terminal fragments that are immunoreactive with amino‐terminal‐specific antiserum. Cathepsin D does not cleave the model peptide or show specificity for wild‐type amyloid precursor protein; however, it cleaves the Swedish “NL peptide” and “NL precursor” substrates appropriately. Our results suggest that cathepsin D could act as β‐secretase in the Swedish type of familial Alzheimer's disease and demonstrate the importance of using full‐length substrate to verify the sequence specificity of candidate proteases.
Evidence Disputing the Link Between Seizure Activity and High Extracellular Glutamate
Authors: Obrenovitch Tihomir P. , Urenjak Jutta , Zilkha Elias
Published: July 2010

Abstract: As seizures in experimental models can be induced by the activation and suppressed by the inhibition of glutamate receptors, it is often proposed that a high extracellular glutamate level subsequent to excessive presynaptic release and/or altered glutamate uptake is epileptogenic. The purpose of this study was to ascertain the link between seizure activity and high extracellular glutamate. To assist the detection of any putative rise in extracellular glutamate during seizures, microdialysis was coupled to enzyme‐amperometric detection of glutamate, which provides maximal sensitivity and time resolution. Electrical activity and field potential were also recorded through the dialysis membrane to confirm that epileptic activity was present at the sampling site. No increase in dialysate glutamate content was detected during picrotoxin‐induced seizures, even when the K+ concentration in the perfusion medium was raised to 50% above that measured previously during paroxysmal activity. In addition, sustained inhibition of glutamate uptake by l‐trans‐pyrrolidine‐2,4‐dicarboxylate increased the extracellular glutamate level >20‐fold but did not produce electrophysiological changes indicative of excessive excitation. These findings indicate that seizures are not necessarily accompanied by an increased extracellular glutamate level and that increased glutamatergic excitation in epilepsy may result from other abnormalities such as increased density of glutamate receptors, enhanced activation subsequent to reduced modulation, or sprouting of glutamatergic synapses.
Oxidative Stress, Hypoxia, and Ischemia‐Like Conditions Increase the Release of Endogenous Amino Acids by Distinct Mechanisms in Cultured Retinal Cells
Authors: Rego Ana Cristina , Santos Maria S. , Oliveira Catarina R.
Published: July 2010

Abstract: The aim of this study was to elucidate the mechanisms by which retinal cells release endogenous amino acids in response to ascorbate/Fe2+‐induced oxidative stress, as compared with chemical hypoxia or ischemia. In the absence of stimulation, oxidative stress increased the release of aspartate, glutamate, taurine, and GABA only when Ca2+ was present. Under hypoxia or ischemia, the release of aspartate, glutamate, glycine, alanine, taurine, and GABA increased mainly by a Ca2+‐independent mechanism. The increased release observed in N‐methyl‐d‐glucamine+ medium suggested the reversal of the Na+‐dependent amino acid transporters. Upon oxidative stress, the release of aspartate, glutamate, and GABA, occurring through the reversal of the Na+‐dependent transporters, was reduced by about 30%, although the release of taurine was enhanced. An increased release of [3H]arachidonic acid and free radicals seems to affect the Na+‐dependent transporters for glutamate and GABA in oxidized cells. All cell treatments increased [Ca2+]i (1.5 to twofold), although no differences were observed in membrane depolarization. The energy charge of cells submitted to hypoxia or oxidative stress was not changed. However, ischemia highly potentiated the reduction of the energy charge, as compared with hypoglycemia or hypoxia alone. The present work is important for understanding the mechanisms of amino acid release that occur in vivo upon oxidative stress, hypoxia, or ischemia, frequently associated with the impairment of energy metabolism.
The High‐Affinity Sulphonylurea Receptor Regulates KATP Channels in Nerve Terminals of the Rat Motor Cortex
Authors: Lee Kevin , Dixon Alistair K. , Rowe Iain C. M. , Ashford Michael L. J. , Richardson Peter J.
Published: July 2010

Abstract: The coexpression of sulphonylurea binding sites and ATP‐sensitive K+ (KATP) channels was examined in the rat motor cortex, an area of the CNS exhibiting a high density of sulphonylurea binding. These channels were not detected on neuronal cell bodies, but sulphonylurea‐sensitive KATP channels and charybdotoxin‐sensitive, large‐conductance calcium‐activated K+ BKCa channels were detected by patch clamping of fused nerve terminals from the motor cortex. Subcellular fractionation revealed that high‐affinity sulphonylurea binding sites were enriched in the nerve terminal fraction, whereas glibenclamide increased calcium‐independent glutamate efflux from isolated nerve terminals. It is concluded that neuronal sulphonylurea receptors and KATP channels are functionally linked in the motor cortex and that they are both selectively expressed in nerve terminals, where the KATP channel may serve to limit glutamate release under conditions of metabolic stress.
The Caenorhabditis elegans Behavioral Gene unc‐24 Encodes a Novel Bipartite Protein Similar to Both Erythrocyte Band 7.2 (Stomatin) and Nonspecific Lipid Transfer Protein
Authors: Barnes T. M. , Jin Y. , Horvitz H. R. , Ruvkun G. , Hekimi S.
Published: July 2010

Abstract: We report here the positional cloning and molecular characterization of the unc‐24 gene of Caenorhabditis elegans. This gene is required for normal locomotion and interacts with genes that affect the worm's response to volatile anesthetics. The predicted gene product contains a domain similar to part of two ion channel regulators (the erythrocyte integral membrane protein stomatin and the C. elegans neuronal protein MEC‐2) juxtaposed to a domain similar to nonspecific lipid transfer protein (nsLTP; also called sterol carrier protein 2). Sequence analysis suggests that the nsLTP‐like domain of UNC‐24 provides lipid carrier function and is tethered to the plasma membrane by the stomatin‐like domain, which may be regulatory. We postulate that UNC‐24 may be involved in lipid transfer between closely apposed membranes.
Expression of the Apoptosis‐Effector Gene, Bax, Is Up‐Regulated in Vulnerable Hippocampal CA1 Neurons Following Global Ischemia
Authors: Chen Jun , Zhu Raymond L. , Nakayama Masaki , Kawaguchi Kenji , Jin Kunlin , Stetler R. Anne , Simon Roger P. , Graham Steven H.
Published: July 2010

Abstract: The observation that delayed death of CA1 neurons after global ischemia is inhibited by protein synthesis inhibitors suggests that the delayed death of these neurons is an active process that requires new gene expression. Delayed death in CA1 has some of the characteristics of apoptotic death; however, candidate proapoptotic proteins have not been identified in the CA1 after ischemia. We studied the expression of Bax protein and mRNA, a member of the bcl‐2 family that is an effector of apoptotic cell death, after global ischemia in the four‐vessel global ischemia model in the rat and compared these results with the expression of the antiapoptotic gene bcl‐2. Bax mRNA and protein are both expressed in CA1 before delayed death, whereas bcl‐2 protein is not expressed. Bcl‐2 protein expression, but not that of Bax, is increased in CA3, a region that is ischemic but less susceptible to ischemic injury. In the dentate gyrus, both Bax and bcl‐2 proteins are expressed. The selective expression of Bax in CA1 supports the hypothesis that Bax could contribute to delayed neuronal death in these vulnerable neurons by an independent mechanism or by forming heterodimers with gene family members other than bcl‐2.
Activation of Protein Kinase C Augments Peptide Release from Rat Sensory Neurons
Authors: Barber Lisa A. , Vasko Michael R.
Published: July 2010

Abstract: To determine whether protein kinase C (PKC) mediates release of peptides from sensory neurons, we examined the effects of altering PKC activity on resting and evoked release of substance P (SP) and calcitonin gene‐related peptide (CGRP). Exposing rat sensory neurons in culture to 10 or 50 nM phorbol 12,13‐dibutyrate (PDBu) significantly increased SP and CGRP release at least 10‐fold above resting levels, whereas the inactive 4α‐PDBu analogue at 100 nM had no effect on release. Furthermore, 100 nM bradykinin increased peptide release approximately fivefold. Down‐regulation of PKC significantly attenuated the release of peptides evoked by either PDBu or bradykinin. PDBu at 1 nM or 1‐oleoyl‐2‐acetyl‐sn‐glycerol at 50 µM did not alter resting release of peptides, but augmented potassium‐ and capsaicin‐stimulated release of both SP and CGRP approximately twofold. This sensitizing action of PKC activators on peptide release was significantly reduced by PKC down‐regulation or by pretreating cultures with 10 nM staurosporine. These results establish that activation of PKC is important in the regulation of peptide release from sensory neurons. The PKC‐induced enhancement of peptide release may be a mechanism underlying the neuronal sensitization that produces hyperalgesia.
Regulation of Bcl‐2 Protein Expression in Human Neuroblastoma SH‐SY5Y Cells: Positive and Negative Effects of Protein Kinases C and A, Respectively
Authors: Itano Yasuhiro , Ito Akihiro , Uehara Takashi , Nomura Yasuyuki
Published: July 2010

Abstract: The regulatory mechanism of Bcl‐2 protein expression was investigated in SH‐SY5Y cells, the human neuroblastoma cell line that expresses natively Bcl‐2 proteins. When the cells were treated with 12‐O‐tetradecanoylphorbol 13‐acetate (TPA) or retinoic acid, the level of Bcl‐2 protein was increased compared with the control. These effects were inhibited by pretreatment with a protein kinase C (PKC) inhibitor, staurosporine or calphostin C. The level of Bcl‐2 protein was also increased by treatment with carbachol, a muscarinic acetylcholine receptor (mAChR) agonist, and the effects were also inhibited by pretreatment with staurosporine or calphostin C. In addition, a carbachol‐induced increase in Bcl‐2 protein levels and a transient elevation of [Ca2+]i were inhibited by pretreatment with 4‐DAMP (4‐diphenylacetoxy‐N‐methylpiperidine), an m3 mAChR antagonist. In contrast, the level of Bcl‐2 protein was decreased by treatment with dibutyryl cAMP (diBu‐cAMP), forskolin, or cholera toxin, and the effects of diBu‐cAMP were inhibited by pretreatment with a protein kinase A (PKA) inhibitor, H‐89. From these results, we suggest that the expression of Bcl‐2 proteins is regulated by PKC and PKA in positive and negative manners, respectively, in SH‐SY5Y cells. Furthermore, the nucleosomal DNA fragmentation induced by serum depletion for 4 h was observed in SH‐SY5Y cells when the level of Bcl‐2 protein was down‐regulated by treatment with 1 mM diBu‐cAMP for 3 days, although the DNA fragmentation by serum depletion for 4 h was not observed in nontreatment cells, indicating that Bcl‐2 proteins whose expression is regulated by PKC and PKA play important roles in serum depletion‐induced apoptosis.
Voltage‐Sensitive Ca2+ Channels Involved in Nicotinic Receptor‐Mediated [3H]Dopamine Release from Rat Striatal Synaptosomes
Authors: Soliakov L. , Wonnacott S.
Published: July 2010

Abstract: The potent nicotinic agonist anatoxin‐a elicits mecamylamine‐sensitive [3H]dopamine release from striatal synaptosomes, and this action is both Na+ and Ca2+ dependent and is blocked by Cd2+. This suggests that stimulation of presynaptic nicotinic receptors results in Na+ influx and local depolarisation that activates voltage‐sensitive Ca2+ channels, which in turn provide the Ca2+ for exocytosis. Here we have investigated the subtypes of Ca2+ channels implicated in this mechanism. [3H]Dopamine release evoked by anatoxin‐a (1 µM) was partially blocked by 20 µM nifedipine, whereas KCl‐evoked release was insensitive to the dihydropyridine. However, a 86Rb+ efflux assay of nicotinic receptor function suggested that nifedipine has a direct effect on the receptor, discrediting the involvement of L‐type channels. The N‐type Ca2+ channel blocker ω‐conotoxin GVIA (1 µM) blocked anatoxin‐a‐evoked [3H]dopamine release by 60% but had no significant effect on 86Rb+ efflux; release evoked by both 15 and 25 mM KCl was inhibited by only 30%. The P‐type channel blocker ω‐agatoxin IVA (90 nM) also inhibited KCl‐evoked release by ∼30%, whereas anatoxin‐a‐evoked release was insensitive. The Q‐type channel blocker ω‐conotoxin MVIIC (1 µM) had no effect on either stimulus. These results suggest that presynaptic nicotinic receptors on striatal nerve terminals promote [3H]dopamine release by activation of N‐type Ca2+ channels. In contrast, KCl‐evoked [3H]dopamine release appears to involve both N‐type and P‐type channels.
Protein Tyrosine Kinase‐Mediated Potentiation of Currents from Cloned NMDA Receptors
Authors: Chen Shu‐jen , Leonard John P.
Published: July 2010

Abstract: Although serine/threonine phosphorylation has been more commonly recognized as a mechanism to modulate the function of ion channels and receptors, tyrosine phosphorylation is under increasing scrutiny. An important subtype of glutamate receptor, the NMDA receptor, is shown to be regulated by insulin via protein tyrosine kinase (PTK). NMDA currents through cloned receptors are potentiated by insulin in a subunit‐specific manner. The insulin‐mediated potentiation of NMDA current is diminished by inhibitors of PTKs. At least one exogenous cytosolic PTK, pp60c‐src, is also able to potentiate NMDA current. Because later application of PTK inhibitors can reverse the seemingly stable insulin‐mediated potentiation of NMDA current, it appears that tyrosine residues responsible for potentiation are continually rephosphorylated by some long‐term PTK activity that was induced via insulin treatment.
Functional Coupling of the δ‐, μ‐, and κ‐Opioid Receptors to Mitogen‐Activated Protein Kinase and Arachidonate Release in Chinese Hamster Ovary Cells
Authors: Fukuda Kazuhiko , Kato Shigehisa , Morikawa Hitoshi , Shoda Takehiro , Mori Kenjiro
Published: July 2010

Abstract: To examine whether the mitogen‐activated protein kinase (MAPK) cascade and phospholipase A2 (PLA2) are involved in the signal transduction mechanism of the opioid receptor, the δ‐, μ‐, and κ‐opioid receptors were stably expressed from cDNA in Chinese hamster ovary cells. Activation of the δ‐, μ‐, and κ‐receptors by agonists induced a rapid and transient increase in MAPK activity accompanied by reduced electrophoretic mobility of the 42‐kDa isoform of MAPK (p42), probably owing to phosphorylation. The opioid receptor‐mediated increase in MAPK activity was suppressed not only by pretreatment with genistein, a tyrosine protein kinase inhibitor, but also by prolonged exposure to phorbol 12‐myristate 13‐acetate and pretreatment with GF 109203X, a selective protein kinase C (PKC) inhibitor, suggesting the involvement of PKC as well as tyrosine protein kinase. Furthermore, stimulation of the δ‐, μ‐, and κ‐receptors with opioid agonists in the presence of A23187, a calcium ionophore, resulted in an increase in arachidonate release, suggesting that PLA2 is activated by the opioid receptors when the intracellular Ca2+ concentration is elevated. Both MAPK activation and increase in arachidonate release mediated by the opioid receptors were abolished by pretreatment with pertussis toxin, suggesting that these responses are mediated by Gi or Go types of GTP‐binding regulatory proteins.
Evidence for Translational Control Elements Within the 5′‐Untranslated Region of GLUT1 Glucose Transporter mRNA
Authors: Boado Ruben J. , Tsukamoto Haruhisa , Pardridge William M.
Published: July 2010

Abstract: Recent studies have indicated that the blood‐brain barrier GLUT1 glucose transporter is under post‐transcriptional regulation. To begin functional mapping of the GLUT1 transcript, in the present investigation we studied the translational efficiency of capped full‐length synthetic GLUT1 mRNA, and both 5′‐ and 3′‐untranslated regions (UTRs) deleted GLUT1 mRNAs. Deletion of 5′‐ and 5′‐/3′‐UTRs markedly reduced the translation efficiency of the human (h) GLUT1 transcript in the rabbit reticulocyte lysate (RRL), and this effect was not modified by addition of microsomes to the translation system. The putative role of these hGLUT1 5′‐UTR cis‐acting elements was studied using the luciferase expression vector pGL2. DNA corresponding to the hGLUT1 5′‐UTR generated by PCR was subcloned at the HindIII site of the pGL2 located upstream of the luciferase 5′‐UTR. Transfection of brain endothelial cultured cells with pGL2 containing most of the hGLUT1 5′‐UTR (nucleotides 1–171) markedly increased the expression of luciferase, and disruption of luciferase‐leading sequence with an unrelated 171‐nucleotide fragment decreased its expression. Insertion of nucleotides 1–96 of the hGLUT1 5′‐UTR retained most of the stimulatory effect, and nucleotides 123–171 produced 64% of maximal induction. On the contrary, clones containing nucleotides 79–171 and 154–171 of bGLUT1 5′‐UTR had marginal effects on luciferase expression. The present data provide evidence suggesting that the 5′‐UTR of the GLUT1 mRNA contains cis‐acting elements involved in the translational control of the GLUT1 gene in mammalian cells.
Up‐Regulation of Functional Voltage‐Dependent Sodium Channels by Insulin in Cultured Bovine Adrenal Chromaffin Cells
Authors: Yamamoto Ryuichi , Yanagita Toshihiko , Kobayashi Hideyuki , Yuhi Tomoaki , Yokoo Hiroki , Wada Akihiko
Published: July 2010

Abstract: Treatment of cultured bovine adrenal chromaffin cells with 100 nM insulin raised [3H]saxitoxin ([3H]STX) binding in a time‐dependent manner (t1/2 = 26 h). Insulin (100 nM for 4 days) increased the Bmax of [3H]STX binding by 49% without changing the KD value and also augmented the maximal influx of 22Na+ due to 560 µM veratridine by 39% without altering the EC50 value of veratridine. The stimulatory effect of insulin on 22Na+ influx was concentration‐dependent with an EC50 of 3 nM, whereas insulin‐like growth factor (IGF)‐I had little effect at 1 nM. Ptychodiscus brevis toxin‐3 allosterically potentiated veratridine (100 µM)‐induced 22Na+ influx by approximately twofold in both insulin‐treated cells and untreated cells. Veratridine‐induced 45Ca2+ influx via voltage‐dependent Ca2+ channels and catecholamine secretion were also enhanced by insulin treatment, whereas insulin did not alter nicotine‐induced 22Na+ influx via the nicotinic receptor‐ion channel complex and high‐K+ (direct activation of voltage‐dependent Ca2+ channels)‐induced 45Ca2+ influx. Stimulatory effects of insulin on [3H]STX binding and veratridine‐induced 22Na+ influx were nullified by simultaneous treatment with either 5,6‐dichlorobenzimidazole riboside, an inhibitor of RNA synthesis, or cycloheximide, an inhibitor of protein synthesis, whereas insulin treatment did not appreciably increase the level of mRNA encoding the Na+ channel α‐subunit. These results suggest that the binding of insulin to insulin (but not IGF‐I) receptors mediates the up‐regulation of functional Na+ channel expression at plasma membranes; this up‐regulation may be due, at least in part, to the de novo synthesis of an as yet unidentified protein(s).
Oligodendroglial Signal Transduction Systems Are Regulated by Neuronal Contact
Authors: He Minghua , Howe Douglas G. , McCarthy Ken D.
Published: July 2010

Abstract: Previous reports indicate that oligodendrocytes express signaling systems activated by classical neurotransmitters. Several signaling systems linked to mobilization of intracellular calcium have been demonstrated, and some of these are developmentally lost in vitro and in vivo. The experiments described here use oligodendrocyte‐neuron cocultures to examine the effects of neuronal contact on the expression of these signaling pathways. Neonatal rat cerebral oligodendrocytes in contact with dorsal root ganglia (DRG) neurites responded to bath application of histamine, ATP, carbachol, glutamate, or bradykinin with increases in intracellular Ca2+ concentration. Similar results were obtained in coculture with superior cervical ganglia neurons. Preventing neuronal contact by transection of DRG neurites significantly reduced the percentage of oligodendrocytes responsive to each ligand, with the exception of bradykinin responsiveness, which was unaffected. Oligodendroglia isolated from adult rat spinal cord were also examined for responsiveness to these neuroligands. Few isolated adult oligodendroglia were responsive to these ligands, and coculture with DRG neurons failed to restore responsiveness. Neuroligand responsiveness was not induced in oligodendrocytes maintained 8 days in purified culture before establishment of cocultures. A significant reduction in the number of neuroligand‐responsive oligodendroglia was noted for histamine, carbachol, glutamate, and ATP after including tetrodotoxin for the final 6 days of coculture. These results suggest that both neuronal contact and neuronal activity contribute to the maintenance of functional neurotransmitter‐activated signaling pathways coupled to mobilization of intracellular calcium in oligodendrocytes.
Severity of Hyperammonemic Encephalopathy Correlates with Brain Ammonia Level and Saturation of Glutamine Synthetase In Vivo
Authors: Kanamori Keiko , Ross Brian D. , Chung Jackie C. , Kuo Emily L.
Published: July 2010

Abstract: Correlation among in vivo glutamine synthetase (GS) activity, brain ammonia and glutamine concentrations, and severity of encephalopathy was examined in hyperammonemic rats to obtain quantitative information on the capacity of GS to control these metabolites implicated in the etiology of hepatic encephalopathy. Awake rats were observed for neurobehavioral impairments after ammonium acetate infusion to attain a steady‐state blood ammonia concentration of 0.9 (group A) or 1.3 µmol/g (group B). As encephalopathy progressed from grade III to IV, brain ammonia concentration increased from 1.9 to 3.3 µmol/g and then decreased to 1.3 µmol/g on recovery to grade III. In contrast, brain glutamine concentration was 26, 23, and 21 µmol/g, respectively. NH4+‐infused rats pretreated with l‐methionine dl‐sulfoximine reached grade IV when brain ammonia and glutamine concentrations were 3.0 and 5.5 µmol/g, respectively; severity of encephalopathy correlates with brain ammonia, but not glutamine. In vivo GS activity, measured by NMR, was 6.8 ± 0.7 µmol/h/g for group A and 6.2 ± 0.6 µmol/h/g for group B. Hence, the in vivo activity, shown previously to increase with blood ammonia over a range of 0.4–0.64 µmol/g, approaches saturation at blood ammonia >0.9 µmol/g. This is likely to be the major cause of the observed accumulation of brain ammonia and the onset of grade IV encephalopathy.
Agmatinase Activity in Rat Brain: A Metabolic Pathway for the Degradation of Agmatine
Authors: Sastre Magdalena , Regunathan Soundararajan , Galea Elena , Reis Donald J.
Published: July 2010

Abstract: Agmatinase, the enzyme that hydrolyzes agmatine to form putrescine and urea in lower organisms, was found in rat brain. Agmatinase activity was maximal at pH 8–8.5 and had an apparent Km of 5.3 ± 0.99 mM and a Vmax of 530 ± 116 nmol/mg of protein/h. After subcellular fractionation, most of the enzyme activity was localized in the mitochondrial matrix (333 ± 5 nmol/mg of protein/h), where it was enriched compared with the whole‐brain homogenate (7.6–11.8 nmol/mg of protein/h). Within the CNS, the highest activity was found in hypothalamus, a region rich in imidazoline receptors, and the lowest in striatum and cortex. It is interesting that other agmatine‐related molecules such as arginine decarboxylase, which synthesizes agmatine, and I2 imidazoline receptors, for which agmatine is an endogenous ligand, are also located in mitochondria. The results show the existence of rat brain agmatinase, mainly located in mitochondria, indicating possible degradation of agmatine by hydrolysis at its sites of action.
Clinical Care of Pregnant Women with Epilepsy: Neural Tube Defects and Folic Acid Supplementation
Authors: Yerby Mark S.
Published: July 2010

Summary:  Women with epilepsy (WWE) have a risk of bearing children with congenital malformations that is approximately twice that of the general population. Most antiepileptic drugs (AEDs) have been associated with such risk. Valproate and carbamazepine have been associated specifically with the development of neural tube defects (NTDs), especially spina bifida. Other factors may contribute to the risk, including concomitant diseases such as diabetes mellitus, occupational exposure to teratogens, excessive prepregnancy weight, and various nutrient deficiencies. In the general population, maternal folate deficiency, in particular, has been linked with the development of NTDs, and periconceptional folate supplementation with a reduction of risk. It is unclear whether folate supplementation has a comparable protective effect for WWE. Data concerning the risk for congenital malformations associated with the newer AEDs (gabapentin, felbamate, lamotrigine, levetiracetam, oxcarbazepine, tiagabine, topiramate, and zonisamide) are still limited. Several pregnancy registries for women taking AEDs have been established. Comprehensive postmarketing surveillance, regionally or nationally, might be the ideal method of monitoring medication safety, but government support for such an undertaking has for the most part been lacking. Despite uncertainty about the efficacy of periconceptional folate supplementation in WWE, these women should receive such supplementation at dosage levels recommended for the general population of women of childbearing age. Seizure control must not be neglected in a pregnant woman with epilepsy since seizures are associated with harm to the fetus as well as the mother. Risk may be minimized by using a single AED at the lowest effective dosage.
Effect of small continuous loads on inverter and system efficiency
Authors: Chhabra Bhumika , Kamada Rui , Opila Robert L. , Honsberg Christiana B.
Published: July 2010

This paper presents the effects of inverter efficiency drop at part-load condition on system performance and cost. The goal is to create a stand-alone system with 95% availability that has a small continuous load and large intermittent load. The system is composed of photovoltaic (PV) panels, batteries, an inverter, charge controller, wiring, and loads. Incandescent lights are used to represent the small continuous load, and fluorescent lights are employed as the large intermittent load. The system performance is analyzed as a function of various parameters such as number of batteries, PV panels, and inverter efficiency. It is shown that having two inverters is beneficial to power small and large loads separately if the inverter efficiency drop at part-load condition is large. This avoids the inverter efficiency drop at part-load condition and lowers the system lifecycle cost.
First principles nuclear magnetic resonance signatures of graphene oxide
Authors: Lu Ning , Huang Ying , Li Hai-bei , Li Zhenyu , Yang Jinlong
Published: July 2010

Nuclear magnetic resonance (NMR) has been widely used in graphene oxide (GO) structure studies. However, the detailed relationship between its spectroscopic features and the GO structural configuration remains elusive. Based on first principles C13 chemical shift calculations using the gauge including projector augmented waves method, we provide a reliable spectrum-structure connection. The C13 chemical shift in GO is found to be very sensitive to the atomic environment, even for the same type of oxidation groups. Factors determining the chemical shifts of epoxy and hydroxy groups have been discussed. GO structures previously reported in the literature have been checked from the NMR point of view. The energetically favorable hydroxy chain structure is not expected to be widely existed in real GO samples according to our NMR simulations. The epoxy pair species we proposed previously is also supported by chemical shift calculations.
Ultrasonic characterization of air-saturated double-layered porous media in time domain
Authors: Fellah Z. E. A , Sebaa N. , Fellah M. , Mitri F. G. , Ogam E. , Depollier C.
Published: July 2010

This paper concerns the ultrasonic characterization of air-saturated double-layered porous materials by solving the inverse problem using experimental reflected signals at normal incidence. The double-layered porous media consist of two slabs of homogeneous isotropic porous materials with a rigid frame. The ultrasonic propagation in double-layered porous material is modeled using a temporal model in which the inertial effects are described by the tortuosity. The viscous and thermal losses of the medium are described by two susceptibility kernels which depend on the viscous and thermal characteristic lengths. The sensitivity of porosity, tortuosity, and viscous characteristic length of each layer is studied showing their effect on the reflected interface waveforms. The inverse problem is solved numerically by the least-squares method. Five parameters are inverted: porosity and tortuosity of the two layers and the viscous characteristic length of the first layer. The minimization of the discrepancy between experimental and theoretical data is made in the time domain. The inverse problem is shown to be well posed and its solution to be unique. Experimental results for waves reflected by the interfaces of the double-layered porous material are given and compared with theoretical predictions.
Calorimetric method of ac loss measurement in a rotating magnetic field
Authors: Ghoshal P. K. , Coombs T. A. , Campbell A. M.
Published: July 2010

A method is described for calorimetric ac-loss measurements of high-Tc superconductors (HTS) at 80 K. It is based on a technique used at 4.2 K for conventional superconducting wires that allows an easy loss measurement in parallel or perpendicular external field orientation. This paper focuses on ac loss measurement setup and calibration in a rotating magnetic field. This experimental setup is to demonstrate measuring loss using a temperature rise method under the influence of a rotating magnetic field. The slight temperature increase of the sample in an ac-field is used as a measure of losses. The aim is to simulate the loss in rotating machines using HTS. This is a unique technique to measure total ac loss in HTS at power frequencies. The sample is mounted on to a cold finger extended from a liquid nitrogen heat exchanger (HEX). The thermal insulation between the HEX and sample is provided by a material of low thermal conductivity, and low eddy current heating sample holder in vacuum vessel. A temperature sensor and noninductive heater have been incorporated in the sample holder allowing a rapid sample change. The main part of the data is obtained in the calorimetric measurement is used for calibration. The focus is on the accuracy and calibrations required to predict the actual ac losses in HTS. This setup has the advantage of being able to measure the total ac loss under the influence of a continuous moving field as experienced by any rotating machines.
Correlation of Dirac potentials and atomic inversion in cavity quantum electrodynamics
Authors: Trisetyarso Agung
Published: July 2010

Controlling the time evolution of the population of two states in cavity quantum electrodynamics is necessary by tuning the modified Rabi frequency in which the extra classical effect of electromagnetic field is taken into account. The theoretical explanation underlying the perturbation of potential on spatial regime of bloch sphere is by the use of Bagrov–Baldiotti–Gitman–Shamshutdinova–Darboux transformations [Bagrov et al., “Darboux transformation for two-level system,” Ann. Phys. 14, 390 (2005)] on the electromagnetic field potential in one-dimensional stationary Dirac model in which the Pauli matrices are the central parameters for controlling the collapse and revival of the Rabi oscillations. It is shown that by choosing σ1 in the transformation generates the parabolic potential causing the total collapse of oscillations, while {σ2,σ3} yield the harmonic oscillator potentials ensuring the coherence of qubits.
Photoluminescence of PbS quantum dots on semi-insulating GaAs
Authors: Ullrich B. , Xiao X. Y. , Brown G. J.
Published: July 2010

We studied the emission properties of colloidal PbS quantum dots (QDs) (5.3 nm) dispersed on semi-insulating GaAs in the temperature range of 5–300 K by employing Fourier transform infrared photoluminescence spectroscopy. The results reveal that the PbS QDs alter and notably enhance the emission features of the GaAs substrate itself. The dependence of the QD emission peak position on temperature is modeled equivalently well with the well-known empirical Varshni equation and with a relation based on thermodynamics. The work reveals that emission properties of PbS QDs do not follow predictably general rules but are determined sensitively by the preparation method and substrate used.
Note: Supplements and corrections to the generalized conic flexure hinge model
Authors: Chen Guimin , Du Yunlei , Liu Xiaoyuan
Published: July 2010

Some supplementary equations have been provided for the generalized model for conic flexure hinges [G. Chen et al., Rev. Sci. Instrum. 80, 055106 (2009)] for the purpose of avoiding division-by-zero issues (having zeros in their denominators) in programming languages such as MATLAB, C, and FORTRAN. Some typos have been corrected as well. In comparison, these equations are more concise and effective.
Three-dimensional microfluidic liquid-core/liquid-cladding waveguide
Authors: Lee Kang Soo , Kim Sang Bok , Lee Kyung Heon , Sung Hyung Jin , Kim Sang Soo
Published: July 2010

This letter describes a three-dimensional liquid-core/liquid-cladding optical waveguide system. The core fluid was focused in the vertical direction by a transverse secondary flow (produced by a Dean vortex) and focused in the horizontal direction by two parallel sheath flows. The waveguide introduced less optical loss between the core fluid and the channel wall. Diffusion between the core fluid and the cladding fluid was reduced by high fluid velocities. The present system can be considered as a graded-index waveguide due to the diffusion effect. The width of the core fluid was manipulated by adjusting the sheath flow rates. Numerical simulations were conducted to support and interpret the experimental results.
Nonvolatile organic transistor-memory devices using various thicknesses of silver nanoparticle layers
Authors: Wang S. M. , Leung C. W. , Chan P. K. L.
Published: July 2010

We demonstrate the modification of the memory effect in organic memory devices by adjusting the thickness of silver nanoparticles (NPs) layer embedded into the organic semiconductor. The memory window widens with increasing Ag NPs layer thickness, a maximum window of 90 V is achieved for 5 nm Ag NPs and the on/off current ratio decreases from 105 to 10 when the Ag NPs layer thickness increases from 1 to 10 nm. We also compare the charge retention properties of the devices with different Ag NPs thicknesses. Our investigation presents a direct approach to optimize the performance of organic memory with the current structure.
Lithium transport at silicon thin film: Barrier for high-rate capability anode
Authors: Peng Bo , Cheng Fangyi , Tao Zhanliang , Chen Jun
Published: July 2010

The major hurdle that retards the practical application of nanostructured silicon anode in rechargeable Li-ion batteries is the capacity retention during lithiation/delithiation processes, especially at high current rate (e.g., >5 C). Since fast Li transport in the electrode is the essential of high-rate capability, the rate-limiting step exists during Li transport process and needs to be determined. We here investigate Li transport properties of Si thin film anode by first-principles calculation and find that high intrinsic energy barrier (0.88 eV) of Li surface intercalation retards fast Li transport. However, this energy barrier can be efficiently reduced by surface modification, e.g., P or Al doping. The present results should shed light on designing Si anode of Li-ion batteries with high-rate capability.
Graphene strain tuning by control of the substrate surface chemistry
Authors: Bruna M. , Vaira A. , Battiato A. , Vittone E. , Borini S.
Published: July 2010

We show that the Raman spectrum of graphene is sensitive to the surface chemistry of the substrate where the atomic plane is deposited. Two types of functionalized SiO2 surface are experimentally compared: OH-terminated and NH2-terminated. In the case of NH2-terminated surface, the graphene Raman bands are significantly redshifted with respect to the peaks observed on the hydroxylated surface. The observed phonon softening can be ascribed to a biaxial strain induced into graphene by its interaction with the substrate. Therefore, the control of the substrate surface chemistry may be envisaged as a route to graphene strain engineering.