bluuebunny/crossref_metadata_2025 huggingface dataset:
Alteration of Mosaic Methylation of the Repeat Unit of the Human Ribosomal RNA Genes in Lung Cancer
Authors: Shiraishi M. , Sekiguchi A. , Chuu Y.H. , Sekiya T.
Published: September 2004

We have investigated the methylation status of the repeat unit of the human ribosomal RNA genes in lung cancer. Using a Southern blot analysis approach we have determined that the non-transcribed region of these genes was generally heavily methylated, while the transcribed region was not methylated in either tumor or normal DNA. Our study also revealed that, in one tumor, the boundary of mosaic methylation of the repeat unit was not distinct. In the same tumor, both the non-transcribed ribosomal spacer region and the L1 interspersed repeat sequences became partially demethylated. In tumor cells, the methylation status of DNA can be altered, but the methylation of subtelomeric repeats was found to be maintained. These results suggest that the mosaic methylation of the repeat unit is not necessarily maintained in tumor DNA, while subtelomeric repeats escape tumor-specific wave of demethylation.
Degradation of the Cyclic AMP Antagonist Prostaglandylinositol Cyclic Phosphate (Cyclic PIP) by Dephosphorylation
Authors: Kassner A. , Lessmann M. , Wasner H.K.
Published: September 2004

The cAMP antagonist, prostaglandylinositol cyclic phosphate (cyclic PIP), is synthesized from prostaglandin E and activated inositol phosphate. From various tissues only that amount of cyclic PIP can be isolated that constitutes the difference between synthesis and degradation. In order to overcome this drawback, the cyclic PIP degrading enzyme or enzymes had to be characterized prior to searching for inhibitors. Cyclic PIP degrading activities have been found in all rat tissues tested, and are lowest in brain (380 pmol × min
cDNA Sequencing of Guinea Pig a2-HS Glycoprotein, Its Expression in Various Tissues and Acute Phase Expression
Authors: Yoshida K. , Suzuki Y. , Yamamoto K. , Sinohara H.
Published: September 2004

cDNA encoding α2-HS glycoprotein was amplified from guinea pig liver mRNA by reverse-transcription polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends, cloned and sequenced. By RTPCR and nested PCR, α2-HS glycoprotein mRNA was detected not only in liver tissue but also in pancreas, stomach, small intestine, colon, spleen, kidney, testis, skeletal muscle, brain, heart and leukocytes, but not in the lung. The α2-HS glycoprotein mRNA levels in the liver were reduced to half at 48 h after subcutaneous injection of turpentine oil.
Phage Display Selection of P1 Mutants of BPTI Directed against Five Different Serine Proteinases
Authors: Kiczak L. , Koscielska K. , Otlewski J. , Czerwinski M. , Dadlez M.
Published: September 2004

The P1 position of protein inhibitors and oligopeptide substrates determines, to a large extent, association energy with many serine proteinases. To test the agreement of phage display selection with the existing thermodynamic data, a small library of all 20 P1 mutants of basic pancreatic trypsin inhibitor (BPTI) was created, fused to protein III, and displayed on the surface of M13 phage. The wild type of displayed inhibitor monovalently and strongly inhibited trypsin with an association constant of
Lymphocyte Antigen Receptor Signal Integration and Regulation by the SHC Adaptor
Authors: Baldari C.T. , Telford. J.L.
Published: September 2004

The Shc adaptor protein transduces signals from transmembrane receptors to the Ras pathway of cell activation by providing binding sites for the recruitment to the submembrane compartment of the Grb2/Sos G-nucleotide exchange complex. The need for Shc in this process is however unclear since Grb2 can be recruited directly to phosphotyrosine containing membrane receptors through its src-homology-2 domain. Evidence from studies in lymphocytes indicates that Shc is multifunctional and is involved in the integration of independent signals to the Ras pathway. Furthermore, Shc may be a key control point at which signaling can be modulated both by interfering signals and by feedback mechanisms. Here we review recent literature to support these functions for Shc.
New Insights into Signal Recognition and Elongation Arrest Activities of the Signal Recognition Particle
Authors: Bui N. , Strub K.
Published: September 2004

The signal recognition particle (SRP), a ubiquitous cytoplasmic ribonucleoprotein particle, plays an essential role in promoting co-translational translocation of proteins into the endoplasmic reticulum. Here, we summarise recent progress made in the understanding of two essential SRP functions: the signal recognition function, which ensures the specificity, and the elongation arrest function, which increases the efficiency of translocation. Our discussion is based on functional data as well as on atomic structure information, both of which also support the notion that SRP is a very ancient particle closely related to ribosomes. Based on the significant increase of knowledge that has been accumulating on the structure of elongation factors and on their interactions with the ribosome, we speculate about a possible mechanism of the elongation arrest function.
A Ribosomal Orphon Sequence from Xenopus laevis Flanked by Novel Low Copy Number Repetitive Elements
Authors: Guimond A. , Moss T.
Published: September 2004

We have used a differential cloning approach to isolate ribosomal/non-ribosomal frontier sequences from
Characterization of the Transcription Factor MTF-1 from the Japanese Pufferfish (Fugu rubripes) Reveals Evolutionary Conservation of Heavy Metal Stress Response
Authors: Maur A. Auf der , Belser T. , Elgar G. , Georgiev O. , Schaffner W.
Published: September 2004

The pufferfish
The Epstein-Barr Virus Nuclear Antigen 2 (EBNA2), a Protein Required for B Lymphocyte Immortalization, Induces the Synthesis of Type I Interferon in Burkitts Lymphoma Cell Lines
Authors: Kanda K. , Kempkes B. , Bornkamm G.W. , Gabain A. von , Decker T.
Published: September 2004

Epstein-Barr virus nuclear antigen 2 (EBNA2), a protein involved in cell transformation, interferes with the cellular response to type I interferons (IFN-α/β). We investigated the function of conditionally expressed EBNA2 in the context of the IFN response in Burkitt's lymphoma cell lines. Expression of EBNA2 led to the transcriptional activation of both endogenous or transfected IFN-stimulated genes (ISGs), genes which contain within their promoters either the interferon-stimulated response element (ISRE) or the gamma interferon activation site (GAS). In search of a molecular mechanism for the transcriptional induction of ISGs, we observed an EBNA2-dependent synthesis of IFN-β mRNA at low levels and the secretion of low amounts of IFN. A transfected IFN-β promoter responded to EBNA2 activation, and a sequence closely resembling a RBP-Jκ binding site was pinpointed as a potential target of EBNA2 activity. EBNA2-dependent transcriptional induction of the IFN-β promoter occurred in EBV-negative Burkitt's lymphoma cells, indicating that other EBV genes were not required for the induction of IFN-β synthesis.
Regulation of Human c-Abl Tyrosine Kinase Activity in Xenopus Oocytes and Acceleration of Progesterone-Induced G2/M Transition by Oncogenic Forms
Authors: K. Dorey D. Barilá , Gavin A.-C. , Nebreda A.R. , Superti-Furga G.
Published: September 2004

Deregulated activity of the Abl protein tyrosine kinase is oncogenic in humans and in animals. The normal cellular form of the enzyme is maintained at a low state of activity by mechanisms that have not yet been entirely elucidated. In particular, little is known about the
Probing Ribosome Structure by Europium-Induced RNA Cleavage
Authors: Dorner S. , Barta A.
Published: September 2004

Divalent metal ions are absolutely required for the structure and catalytic activities of ribosomes. They are partly coordinated to highly structured RNA, which therefore possesses high-affinity metal ion binding pockets. As metalion induced RNA cleavages are useful for characterising metal ion binding sites and RNA structures, we analysed europium (Eu3+) induced specific cleavages in both 16S and 23S rRNA ofE. coli. The cleavage sites were identified by primer extension and compared to those previously identified for calcium, lead, magnesium, and manganese ions. Several Eu3+cleavage sites, mostly those at which a general metal ion binding site had been already identified, were identical to previously described divalent metal ions. Overall, the Eu3+cleavages are most similar to the Ca2+cleavage pattern, probably due to a similar ion radius. Interestingly, several cleavage sites which were specific for Eu3+were located in regions implicated in the binding of tRNA and antibiotics. The binding of erythromycin and chloramphenicol, but not tetracycline and streptomycin, significantly reduced Eu3+cleavage efficiencies in the peptidyl transferase center. The identification of specific Eu3+binding sites near the active sites on the ribosome will allow to use the fluorescent properties of europium for probing the environment of metal ion binding pockets at the ribosome's active center.
The Oct-1 POU Domain Directs Developmentally Regulated Nuclear Translocation in Xenopus Embryos
Authors: Veenstra G.J.C. , Mathu M.Th. , Destrée O.H.J.
Published: September 2004

Early embryonic development in
Conformational Study of the HIV-1 Reverse Transcriptase Inhibitor 1-[(2-Hydroxyethoxy)methyl]-6-(phenylthio)thymine (HEPT)
Authors: Lawtrakul L. , Hannongbua S. , Beyer A. , Wolschann P.
Published: September 2004

The conformations of the HIV-1 reverse transcriptase inhibitor 1-[(2-hydroxyethoxy)methyl]-6-(phenylthio)-thymine (HEPT) are calculated by semiempirical and mainly by
Transient Transfection of Mammary Epithelial Cells with a PEI/DNA/Adenovirus System
Authors: Bischof J. , Vietor I. , Cotten M. , Huber L.A.
Published: September 2004

Studies on epithelial cells often require the transient expression of exogenous proteins in polarized epithelial cells. However, the major limitation of this approach has been the difficulty of obtaining transient gene expression in polarized epithelial cell cultures. We report here on the application of a polyethylenimine (PEI)/DNA/adenovirus system for efficient transient gene expression in mammary epithelial cells. Based on luciferase assay and FACScan analysis the PEI/DNA/adenovirus system is shown to be an effective and simple method for transfecting epithelial cells.
The Core Antigen of Hepatitis B Virus as a Carrier for Immunogenic Peptides
Authors: Murray K. , Shiau A.-L.
Published: September 2004

The core antigen of hepatitis B virus (HBcAg) made inEscherichia coliyields particles that closely resemble the viral nucleocapsid. Extensive modifications can be made to the primary structure of HBcAg without impairing particle assembly. This enables other peptide sequences, including very long sequences, to be added, substituted, or inserted into the nucleocapsid subunit while retaining the ability to form highly immunogenic particles. These also retain the T cell epitopes of HBcAg and constitute powerful delivery systems for a diverse range of immunogenic epitopes and have significant potential for development of multicomponent vaccines.
Enhancing the Immunogenicity of Exogenous Hepatitis B Surface Antigen-Based Vaccines for MHC-I-Restricted T Cells
Authors: Schirmbeck R. , Reimann J.
Published: September 2004

Vaccination with either exogenous hepatitis B surface antigen (HBsAg) lipoprotein particles without adjuvants, or plasmid DNA encoding secreted small HBsAg stimulate long-lasting, potent antibody responses in H-2d(BALB/c) and C57Bl/6 (H-2b) mice. Vaccination with exogenous HBsAg primes MHC-I restricted cytotoxic T lymphocyte (CTL) responses to HBsAg in H-2dbut not H-2bmice, while DNA vaccination primes HBsAg-specific CTL responses in both mouse strains. We defined vaccination strategies that could elicit CTL responses to exogenous HBsAg in ‘low responder’ C57Bl/6 mice. We found that the bacterial plasmid DNA itself, synthetic oligodeoxynucleotides containing immunostimulating sequences, or recombinant Th1 cytokines (IL12, IFNγ) efficiently support priming of CTL responses to exogenous HBsAg in ‘low responder’ H-2bmice, but have only minor effects on CTL priming in ‘high responder’ H-2dmice in the high dose range tested. These molecularly well defined adjuvants can thus efficiently support priming of anti-viral T cell responses under ‘low responder’ conditions.
Lipopeptides as Dimerization Inhibitors of HIV-1 Protease
Authors: Schramm H. J. , Rosny E. De , Reboud-Ravaux M. , Büttner J. , Dick A. , Schramm W.
Published: September 2004

In AIDS therapy, attempts have been made to inhibit the virus-encoded enzymes, e.g. HIV-1 protease, using active site-directed inhibitors. This approach is questionable, however, due to virus mutations and the high toxicity of the drugs. An alternative method to inhibit the dimeric HIV protease is the targeting of the interface region of the protease subunits in order to prevent subunit dimerization and enzyme activity. This approach should be less prone to inactivation by mutation. A list of improved ‘dimerization inhibitors’ of HIV-1 protease is presented. The main structural features are a short ‘interface’ peptide segment, including non-natural amino acids, and an aliphatic N-terminal blocking group. The high inhibitory power of some of the lipopeptides [e.g. palmitoyl-Tyr-Glu-Leu-OH, palmitoyl-Tyr-Glu-(L-thyronine)-OH, palmitoyl-Tyr-Glu-(L-biphenyl-alanine)-OH] with low nanomolarKivaluesin the enzyme test suggests that mimetics with good bio-availability can be derived for AIDS therapy.
Phase Segregation of Medial Septal GABAergic Neurons during Hippocampal Theta Activity
Authors: Borhegyi Zsolt , Varga Viktor , Szilágyi Nóra , Fabo Dániel , Freund Tamás F.
Published: September 2004

Septo-hippocampal GABAergic neurons immunoreactive for parvalbumin are thought to play a crucial role in the generation of hippocampal theta oscillations associated with a specific stage of memory formation. Here we usein vivojuxtacellular recording and filling in the medial septum followed by immunocytochemical identification of the recorded cells containing parvalbumin to determine their firing pattern, phase relationship with hippocampal theta, morphology, and to thereby reveal their involvement in the generation of hippocampal theta activity. We have demonstrated that GABAergic medial septal neurons form two distinct populations exhibiting highly regular bursting activity that is tightly coupled to either the trough (178°) or the peak (330°) of hippocampal theta waves. Additionally, different types of bursting as well as nonbursting activity patterns were also observed. The morphological reconstruction of theta-bursting neurons revealed extensive axon arbors of these cells with numerous local collaterals establishing symmetrical synapses; thus, synchrony among the septal pacemaker units may be brought about by their recurrent collateral interactions. Long projecting axons could also be found running dorsally toward the hippocampus and ventrally in the direction of basal forebrain regions. We conclude that GABAergic neurons in the medial septum, which are known to selectively innervate hippocampal interneurons, are in a position to induce rhythmic disinhibition in the hippocampus and other theta-related subcortical areas at two different phases of hippocampal theta.
Akt-1 Expression Level Regulates CNS Precursors
Authors: Sinor Amy D. , Lillien Laura
Published: September 2004

Although most cells in the embryonic mouse cortex express the serine-threonine kinase Akt-1, a small population of progenitors expresses Akt-1 protein at a higher level. To determine the functional significance of this difference, we used a retrovirus to increase Akt-1 expression in cortical progenitors. Increased Akt expression enhanced Akt activation after growth factor stimulation of progenitors.In vivo, it promoted retention in progenitor layers, the ventricular zone and subventricular zone.In vitro, it enhanced proliferation and survival, but did not impair migration. Moreover, it increased the proportion of stem cells, defined by a self-renewal assay. These effects did not depend on the Akt substrate p21(Cip1). In contrast, rapamycin, an inhibitor of mTOR (mammalian target of rapamycin), altered effects of elevated Akt-1 selectively: it eliminated the increase in stem cells and reduced the proliferative response, but had no effect on survival. The ability of elevated Akt-1 to increase the self-renewing population therefore depends on a rapamycin-sensitive mechanism (presumably inhibition of mTOR activity) but not on p21(Cip1), and can be distinguished from its effects on the proliferation and survival of other types of progenitors. Our findings suggest that expression of a high level of Akt-1 by a subpopulation of cortical progenitors biases their responses to extrinsic signals to increase their survival, proliferation, and/or self-renewal. Heterogeneity in Akt-1 level among progenitors could therefore allow cells that share a microenvironment to respond differently to the same extrinsic signals.
Visual Response Properties in the Dorsal Lateral Geniculate Nucleus of Mice Lacking the β2 Subunit of the Nicotinic Acetylcholine Receptor
Authors: Grubb Matthew S. , Thompson Ian D.
Published: September 2004

We present a quantitative description of single-cell visual response properties in the dorsal lateral geniculate nucleus (dLGN) of anesthetized adult mice lacking the β2 subunit of the nicotinic acetylcholine receptor (β2-/-) and compare these response properties with data from wild-type animals. Some response features, including all spatial receptive field characteristics and bursting behavior, are entirely normal in β2-/- dLGN cells. In other respects, the responses of β2-/- dLGN cells are quantitatively abnormal: the mutation is associated with higher spontaneous and visually evoked firing rates, faster visual response latencies, a preference for higher temporal frequencies, and a trend toward greater contrast sensitivity. The normal response properties in the β2-/- dLGN show that none of the many effects of the mutation, including disrupted geniculate functional organization and abnormal cholinergic transmission, have any effect on spatial response characteristics and bursting behavior in dLGN neurons. The abnormal response characteristics in the β2-/- dLGN are most interesting in that they are no worse than normal; any visual processing deficits found in studies of the β2-/- visual cortex must therefore arise solely from abnormalities in cortical processing.
Role of T-Type Calcium Current in Identified D-Hair Mechanoreceptor Neurons StudiedIn Vitro
Authors: Dubreuil Anne-Sophie , Boukhaddaoui Hassan , Desmadryl Gilles , Martinez-Salgado Carlos , Moshourab Rabih , Lewin Gary R. , Carroll Patrick , Valmier Jean , Scamps Frédérique
Published: September 2004

Different subsets of dorsal root ganglion (DRG) mechanoreceptors transduce low- and high-intensity mechanical stimuli. It was shown recently that,in vivo, neurotrophin-4 (NT-4)-dependent D-hair mechanoreceptors specifically express a voltage-activated T-type calcium channel (Cav3.2) that may be required for their mechanoreceptive function. Here we show that D-hair mechanoreceptors can be identifiedin vitroby a rosette-like morphology in the presence of NT-4 and that these rosette neurons are almost all absent in DRG cultures taken from NT-4 knock-out mice.In vitroidentification of the D-hair mechanoreceptor allowed us to explore the electrophysiological properties of these cells. We demonstrate that the T-type Cav3.2 channel induced slow membrane depolarization that contributes to lower the voltage threshold for action potential generation and controls spike latency after stimulation of D-hair mechanoreceptors. Indeed, the properties of the T-type amplifier are particularly well suited to explain the high sensitivity of D-hair mechanoreceptors to slowly moving stimuli.
Facilitation of L-Type Ca2+Channels in Dendritic Spines by Activation of β2Adrenergic Receptors
Authors: Hoogland Tycho M. , Saggau Peter
Published: September 2004

We studied the contribution of L-type Ca2+channels to action potential-evoked Ca2+influx in dendritic spines of CA1 pyramidal neurons and the modulation of these channels by the β2adrenergic receptor. Backpropagating action potentials (bAPs) (three at 50 Hz) were evoked by brief somatic current injections, and Ca2+transients were recorded in proximal basal dendrites and associated spines. The R- and T-type Ca2+channel blocker NiCl2(100 μm) significantly reduced Ca2+transients in both spines and their parent dendrites (∼50%), suggesting that these channels are the major source of bAP-evoked Ca2+influx in these structures. The L-type Ca2+channel blockers nimodipine and nifedipine (both 10 μm) reduced spine Ca2+transients by ∼10%, whereas the L-type Ca2+channel activators FPL 64176 (2,5-dimethyl-4-[2-(phenylmethyl)benzoyl]-1H-pyrrole-3-carboxylic acid methylester) and Bay K 8644 ((±)-1,4-dihydro-2,6-dimethyl-5-nitro-4-[2-(trifluoromethyl)-phenyl]-3-pyridine carboxylic acid methyl ester) (both 10 μm) significantly enhanced the spine Ca2+transients by 40-50%. Activation of β2adrenergic receptors with salbutamol (40 μm) or formoterol (5 μm) resulted in significant enhancements of the spine (40-50%) but not dendritic Ca2+transients. This increase was prevented when L-type Ca2+channels were blocked with nimodipine (10 μm) or when cAMP-dependent protein kinase A (PKA) was inhibited with KT5720 (3 μm), Rp-cAMPS (Rp-adenosine cyclic 3′,5′-phosphorothioate) (100 μm), or PKI (100 μm). The above data suggest that L-type Ca2+channels are functionally present in dendritic spines of CA1 pyramidal neurons, contribute to spine Ca2+influx, and can be modulated by the β2adrenergic receptor through PKA in a highly compartmentalized manner.
Identified Olfactory Ensheathing Cells Transplanted into the Transected Dorsal Funiculus Bridge the Lesion and Form Myelin
Authors: Sasaki Masanori , Lankford Karen L. , Zemedkun Micheas , Kocsis Jeffery D.
Published: September 2004

Olfactory ensheathing cells (OECs) prepared from the olfactory bulbs of adult transgenic Sprague Dawley (SD) rats expressing green fluorescent protein (GFP) were transplanted into a dorsal spinal cord transection lesion of SD rats. Five weeks after transplantation, the cells survived within the lesion zone and oriented longitudinally along axons that bridged the transection site. Although the highest density of GFP cells was within the lesion zone, some cells distributed longitudinally outside of the lesion area. Myelinated axons spanning the lesion were observed in discrete bundles encapsulated by a cellular element. Electron micrographs of spinal cords immunostained with an anti-GFP antibody indicated that a majority of the peripheral-like myelinated axons were derived from donor OECs. Open-field locomotor behavior was significantly improved in the OEC transplantation group. Thus, transplanted OECs derived from the adult olfactory bulb can survive and orient longitudinally across a spinal cord transection site and form myelin. This pattern of repair is associated with improved locomotion.
Selective Enhancement of Tonic GABAergic Inhibition in Murine Hippocampal Neurons by Low Concentrations of the Volatile Anesthetic Isoflurane
Authors: Caraiscos Valerie B. , Newell J. Glen , You-Ten Kong E. , Elliott Erin M. , Rosahl Thomas W. , Wafford Keith A. , MacDonald John F. , Orser Beverley A.
Published: September 2004

Volatile (inhaled) anesthetics cause amnesia at concentrations well below those that cause loss of consciousness and immobility; however, the underlying neuronal mechanisms are unknown. Although many anesthetics increase inhibitory GABAergic synaptic transmission, this effect occurs only at high concentrations (>100 μm). Molecular targets for low concentrations of inhaled anesthetics have not been identified. Here, we report that a tonic inhibitory conductance in hippocampal pyramidal neurons generated by α5 subunit-containing GABAAreceptors is highly sensitive to low concentrations of the volatile anesthetic isoflurane (ISO) (25 and 83.3 μm). The α5 subunit is necessary for enhancement of the tonic current by these low concentrations of isoflurane because potentiation is absent in neurons from α5-/-mice. Furthermore, ISO (25 μm) potentiated recombinant human α5β3γ2L GABAAreceptors, whereas this effect was not seen with α1β3γ2L GABAAreceptors. These studies suggest that an increased tonic inhibition in the hippocampus may contribute to amnestic properties of volatile anesthetics.
Actin/α-Actinin-Dependent Transport of AMPA Receptors in Dendritic Spines: Role of the PDZ-LIM Protein RIL
Authors: Schulz Torsten W. , Nakagawa Terunaga , Licznerski Pawel , Pawlak Verena , Kolleker Alexander , Rozov Andrei , Kim Jinhyun , Dittgen Tanjew , Köhr Georg , Sheng Morgan , Seeburg Peter H. , Osten Pavel
Published: September 2004

The efficacy of excitatory transmission in the brain depends to a large extent on synaptic AMPA receptors, hence the importance of understanding the delivery and recycling of the receptors at the synaptic sites. Here we report a novel regulation of the AMPA receptor transport by a PDZ (postsynaptic density-95/Drosophiladisc large tumor suppressor zona occludens 1) and LIM (Lin11/rat Isl-1/Mec3) domain-containing protein, RIL (reversion-induced LIM protein). We show that RIL binds to the AMPA glutamate receptor subunit GluR-A C-terminal peptide via its LIM domain and to α-actinin via its PDZ domain. RIL is enriched in the postsynaptic density fraction isolated from rat forebrain, strongly localizes to dendritic spines in cultured neurons, and coprecipitates, together with α-actinin, in a protein complex isolated by immunoprecipitation of AMPA receptors from forebrain synaptosomes. Functionally, in heterologous cells, RIL links AMPA receptors to the α-actinin/actin cytoskeleton, an effect that appears to apply selectively to the endosomal surface-internalized population of the receptors. In cultured neurons, an overexpression of recombinant RIL increases the accumulation of AMPA receptors in dendritic spines, both at the total level, as assessed by immunodetection of endogenous GluR-A-containing receptors, and at the synaptic surface, as assessed by recording of miniature EPSCs. Our results thus indicate that RIL directs the transport of GluR-A-containing AMPA receptors to and/or within dendritic spines, in anα-actinin/actin-dependent manner, and that such trafficking function promotes the synaptic accumulation of the receptors.
Brain Correlates of Language Learning: The Neuronal Dissociation of Rule-Based versus Similarity-Based Learning
Authors: Opitz Bertram , Friederici Angela D.
Published: September 2004

Language learning is one of the mysteries of human cognition. One of the crucial questions is the following: Does acquisition of grammatical knowledge depend primarily on abstract rules or on item-specific information? Although there is evidence that both mechanisms contribute to language acquisition, their relative importance during the process of language learning is unknown. Using an artificial grammar paradigm, we show by means of functional magnetic resonance imaging that the brain dissociates the two mechanisms: the left anterior hippocampus supports similarity-based learning, whereas the left ventral premotor cortex is selectively engaged by abstract rule processing. Moreover, data analysis over time on learning suggests that similarity-based learning plays a nonobligatory role during the initial phase, and that rule-based abstraction plays a crucial role during later learning.
Dual Roles of the C2B Domain of Synaptotagmin I in Synchronizing Ca2+-Dependent Neurotransmitter Release
Authors: Nishiki Tei-ichi , Augustine George J.
Published: September 2004

Although the vesicular protein synaptotagmin I contains two Ca2+-binding domains (C2A and C2B), Ca2+binding to the C2B domain is more important for triggering synchronous neurotransmitter release. We have used point mutagenesis to determine the functional contributions of the five negatively charged aspartate (Asp) residues that constitute the Ca2+-binding sites in the C2B domain of synaptotagmin I. Transfecting wild-type synaptotagmin I DNA into cultured hippocampal neurons from synaptotagmin I knock-out mice rescued Ca2+-dependent synchronous transmitter release and reduced a slower, asynchronous component of release, indicating that synaptotagmin I suppresses asynchronous release. Mutating either the second or third Asp residues of the C2B domain potently inhibited the ability of synaptotagmin I to rescue synchronous release but did not change its ability to suppress asynchronous release. Synaptotagmin I with mutations in the first or fourth Asp residues of the C2B domain partially rescued synchronous release and partially suppressed asynchronous release, whereas neutralizing the fifth Asp residue had no effect on the ability of synaptotagmin I to rescue transmitter release. Thus, we conclude that the C2B domain of synaptotagmin I regulates neurotransmitter release in at least two ways. Synchronous release absolutely requires binding of Ca2+to the second and third Asp residues in this domain. For the suppression of asynchronous release, Ca2+binding to the C2B domain of synaptotagmin I apparently is not necessary because mutation of the second Asp residue inhibits Ca2+binding, yet still allows this protein to suppress asynchronous release.
ATP Excites Interneurons and Astrocytes to Increase Synaptic Inhibition in Neuronal Networks
Authors: Bowser David N. , Khakh Baljit S.
Published: September 2004

We investigated the role of extracellular ATP at astrocytes and inhibitory GABAergic interneurons in the stratum radiatum area of the mouse hippocampus. We show that exogenously applied ATP increased astrocyte intracellular Ca2+levels and depolarized all calbindinand calretinin-positive interneurons in the stratum radiatum region of mouse hippocampus, leading to action potential firing and enhanced synaptic inhibition onto the postsynaptic targets of interneurons. Electrophysiological, pharmacological, and immunostaining studies suggested that the effect of ATP on interneurons was mediated by P2Y1receptors, and that the depolarization of interneurons was caused by the concomitant reduction and activation of potassium and nonselective cationic conductances, respectively. Electrical stimulation of the Schaffer collaterals and perforant path, as well as local stimulation within the stratum radiatum, evoked increases in intracellular Ca2+in astrocytes. Facilitation of GABAergic IPSCs onto interneurons also occurred during electrical stimulation. Both the stimulation-evoked increases in astrocyte Ca2+levels and facilitation of GABAergic IPSCs were sensitive to antagonists of P2Y1receptors and mimicked by exogenous P2Y1receptor agonists, suggesting that endogenously released ATP can activate P2Y receptors on both astrocytes and interneurons. Overall, our data are consistent with the hypothesis that ATP released from neurons and astrocytes acts on P2Y1receptors to excite interneurons, resulting in increased synaptic inhibition within intact hippocampal circuits.
Dopamine Excites Nucleus Accumbens Neurons through the Differential Modulation of Glutamate and GABA Release
Authors: Hjelmstad Gregory O.
Published: September 2004

Afferent activity into the nucleus accumbens (NAc) occurs in bursts of action potentials. However, it is unclear how synapses in this nucleus respond to such bursts, or how these responses are altered by dopamine (DA). I examined the effects of DA on excitatory and inhibitory responses to trains of stimuli in rat NAc slices. Both EPSCs and IPSCs showed use-dependent depression during trains. Although DA inhibited both glutamate and GABA release in the NAc, it differentially inhibited release during trains. The inhibition of IPSCs persisted throughout the train of stimuli, whereas the inhibition of EPSCs progressively diminished. This differential modulation may be explained by a calcium-dependent change in the recovery from depression at the GABA synapses, where DA acts by decreasing Ca2+entry. Thus, at later stages of sustained stimulation, DA preferentially inhibits GABA release, producing a net excitatory effect during bursts suggesting a mechanism for enhancing the contrast between competing inputs into the NAc, as well as for affecting long-term plasticity in this structure.
Commodity Agriculture, Civic Agriculture and the Future of U.S. Farming*
Authors: Lyson Thomas A. , Guptill Amy
Published: September 2004

Abstract  Commodity agriculture and civic agriculture represent two distinct types of farming found in the U.S. today. Commodity agriculture is grounded on the belief that the primary objectives of farming should be to produce as much food/fiber as possible for the least cost. It is driven by the twin goals of productivity and efficiency. Civic agriculture, on the other hand, represents the rebirth of a more locally oriented agriculture and food system. Using data from the 1992 and 1997 Censuses of Agriculture and other secondary data sets, we examine factors and conditions associated with the presence and growth of both types of agriculture. Our findings show that civic agriculture is associated with particular commodities and with specific social, economic and demographic characteristics of localities. Commodity agriculture, on the other hand, is more sensitive to the classic economic factors of production, namely, land, labor, and capital.
The Social Fabric and Innovation Diffusion: Symbolic Adoption of Food Irradiation*
Authors: Sapp Stephen G. , Korsching Peter F.
Published: September 2004

Abstract This study used a longitudinal, panel design to examine the effects of negative information acquisition, compliance with opinion leader endorsements, and social demographic characteristics on consumers' symbolic adoption of food irradiation. Data collection coincided with the first market test of irradiated food conducted by a commercial firm, which took place in Minneapolis, Minnesota, in 2000. Approximately half the subjects (N= 116) received a packet containing information from proponents and opponents of food irradiation. The remaining subjects (N= 107) were provided with no information about the technology. The results indicated that, initially, negative information acquisition, even when accompanied by positive endorsements from opinion leaders, decreased symbolic adoption. Over time, however, this negative effect was mitigated by compliance with endorsements from opinion leaders. The results suggest that confidence in social institutions might be a determinant as well as an outcome of adoption decisions. Implications are suggested for risk communication strategies regarding controversial agricultural technologies.
Dimensions of Community Attachment and Their Relationship to Well‐Being in the Amenity‐Rich Rural West*
Authors: Brehm Joan M. , Eisenhauer Brian W. , Krannich Richard S.
Published: September 2004

Abstract This research had two primary objectives: 1) to broaden the sociological construct of community attachment to incorporate both social and natural environment dimensions of attachment, and 2) to examine how variations in attachment relate to two dimensions of well‐being in natural amenity‐rich rural communities. The specific dimensions of well‐being measured are two important factors identified in previous research—collective action and perceptions of open communication. Factor analysis of fourteen measures of attachment indicated social attachment and attachment to the natural environment are distinct dimensions of the broader concept of community attachment. Participation in collective action and perceptions of open communication within a respondent's community explained only a small portion of the variance in levels of both social and natural environment attachment. Religious affiliation and length of residence were strongly associated with social attachment, supporting findings from previous empirical work. However, length of residence and religious affiliation were not statistically associated with levels of attachment to the natural environment, further reinforcing the distinction between the two dimensions of attachment.
Democratizing Rural Economy: Institutional Friction, Sustainable Struggle and the Cooperative Movement*
Authors: Mooney Patrick H.
Published: September 2004

Abstract  Sustainable development demands institutions manage the conflicts and struggles that inevitably arise over material and ideal interests. While current cooperative theory privileges the economic element, a political economy of cooperation emphasizes cooperatives' tentative bridging of economic and political spheres with a democratic ethos. The cooperatives' democratic political structure exists in tension with a capitalist economic structure and other sites of friction. These contradictions are: in the realm of social relations, between production and consumption; in the realm of spatial relations, between the local and the global; and in the realm of collective action, between cooperatives as both traditional as well as new social movements. Where neo‐classical economic models seek to eliminate or reduce these tensions, political economy views these tensions as functional to sustainability by creating an “institutional friction” that facilitates innovation, flexibility and long‐term adaptability. This political economy of cooperation is intended as a step toward the development of a multidimensional sociology of cooperation.
Resource Dependence and Community Well‐Being in Rural Canada*
Authors: Stedman Richard C. , Parkins John R. , Beckley Thomas M.
Published: September 2004

Abstract The well‐being of residents of resource dependent communities is a question of traditional interest to rural sociologists. The label “resource dependent” obscures how this relationship may vary between particular resource industries, regions, or indicators of well‐being. Few analyses have compared the relationship between well‐being and resource dependence across different industries, nor tested competing theories about the relationship between resource dependence and well‐being. Our paper presents an overview of the relationship between resource dependence—agriculture, fisheries, mining, energy, forestry—and human well‐being in Canada. Analysis of 1996 Statistics Canada data revealed a great deal of variation in the effect of “resource” dependence on indicators of well‐being (e.g., human capital, unemployment, income): some industries exhibit fairly positive outcomes (e.g., agriculture), others more negative outcomes (e.g., fishing). Consistent with analyses conducted in the United States, these relationships vary by region, suggesting the need for models that incorporate the particulars of place and industry.
Residential Differences in Family Formation: The Significance of Cohabitation*
Authors: Snyder Anastasia R. , Brown Susan L. , Condo Erin P.
Published: September 2004

Abstract  We update and extend prior research on residential differences in women's family formation experiences using data from the 1995 cycle of the National Survey of Family Growth. Residential differences in the timing of family formation behaviors are examined, including first birth, first cohabitation, and first marriage. Our study emphasizes the significance of cohabitation, estimating the effect of geographic residence on type of union formation (i.e., cohabitation versus marriage) and relationship context of first birth (i.e., cohabiting, married, or single). We find that (1) the timing of family formation behaviors, including marriage and childbearing, differs by residence; (2) nonmetro women are more likely to enter marriage and marry at younger ages than their metro counterparts; and (3) when marriage and cohabitation are presented as competing risks, nonmetro women are more likely to marry than cohabit both as a first union and a first birth context.
Riding the Resource Roller Coaster: Understanding Socioeconomic Differences between Mining Communities*
Authors: Wilson Lisa J.
Published: September 2004

Abstract  Social science studies of mining communities suggest that the well‐being of these company towns varies a great deal. Yet the literature has not thoroughly explained the sources of that variation, especially its potential relationship to the resource itself. In order to clarify our understanding of socioeconomic well‐being, this paper likens the experience of being mining dependent to riding a roller coaster. While many mining areas experience volatile economic conditions, key characteristics and responses of the communities, companies, and resource alter the ride. To illustrate this concept, the paper examines employment trends in two metal‐mining regions of the Midwest and finds that employment was more volatile in one area than the other. The reasons for the differences between the communities are explored. The paper concludes that paying greater attention to the context in which mining occurs and to the resource itself may help clarify the impacts of mining on local communities.
Fractal and Non‐Fractal Structure–Property Relationships of Polymer‐Stabilized Liquid Crystals
Authors: Dierking I.
Published: September 2004

The electro‐optic performance of polymer‐stabilized liquid crystals (PSLCs) depends in a complex manner on the morphology of the stabilizing polymer network, mainly through elastic interactions between the liquid crystal and the network. The morphology of the polymer in turn depends on the preparation conditions during polymerization. By using the fractal dimension as a means to describe the polymer morphology, we present scaling relations that quantitatively link the electro‐optic response of polymer‐stabilized cholesteric textures to the preparation conditions and the resulting network structure of the device. The validity of this description is demonstrated for several preparation series, including variation of curing temperature, UV intensity, time of UV irradiation, and photo‐initiator concentration. Additionally, some non‐fractal scaling relations are discussed with respect to sandwich cell gap and wavelength of the probing light. From the scaling relations, essential properties of PSLC devices can be predicted for varying preparation conditions over a wide range of parameters.
Composites of Polyacrylonitrile and Multiwalled Carbon Nanotubes Prepared by Gelation/Crystallization from Solution
Authors: Koganemaru A. , Bin Y. , Agari Y. , Matsuo M.
Published: September 2004

Composite films of polyacrylonitrile (PAN) and multiwalled carbon nanotubes (MWNTs) have been prepared by gelation/crystallization from solution. The contents of MWNTs were 5–10 wt.‐%, measured against PAN. The electrical and mechanical properties have been studied in comparison with those of the homopolymer PAN films prepared from the same method. Furthermore, stabilization and the carbonization have been carried out by using the drawn PAN–MWNTs as a new precursor to prepare carbon films with a cross‐sectional area much larger than that of a commercial carbon fiber (> 3000 times). The MWNTs within the PAN matrix promote the formation of a condensed aromatic ladder structure during the stabilization process and play an important role in preparing PAN‐based carbon material with high carbon quality and high mechanical properties. When the stabilized composites with 10 wt.‐% MWNTs are carbonized at 1000 °C, the Young's modulus reaches 37.5 GPa, and the electrical conductivity reaches 102 S cm–1. The carbonized PAN homopolymer does not form an adequately robust bulk film for the mechanical properties to be measured.
Photoluminescence and Electron Paramagnetic Resonance of ZnO Tetrapod Structures
Authors: Djurišić A. B. , Choy W. C. H. , Roy V. A. L. , Leung Y. H. , Kwong C. Y. , Cheah K. W. , Gundu Rao T. K. , Chan W. K. , Fei Lui H. , Surya C.
Published: September 2004

ZnO tetrapod nanostructures have been prepared by the evaporation of Zn in air (no flow), dry and humid argon flow, and dry and humid nitrogen flow. Their properties have been investigated using scanning electron microscopy (SEM), X‐ray diffraction (XRD), photoluminescence (PL) and photoluminescence excitation (PLE) spectroscopies (at different temperatures), and electron paramagnetic resonance (EPR) spectroscopy at –160 °C and room temperature. It is found that the fabrication conditions significantly influence the EPR and PL spectra obtained. While a g = 1.96 EPR signal is present in some of the samples, green PL emission can be observed from all the samples. Therefore, the green emission in our samples does not originate from the commonly assumed transition between a singly charged oxygen vacancy and a photoexcited hole [K. Vanheusden, C. H. Seager, W. L. Warren, D. R. Tallant, J. A. Voigt, Appl. Phys. Lett. 1996, 68, 403]. However, the green emission can be suppressed by coating the nanostructures with a surfactant for all fabrication conditions, which indicates that this emission originates from surface defects.
Controlled Growth and Properties of One‐Dimensional ZnO Nanostructures with Ce as Activator/Dopant
Authors: Cheng B. C. , Xiao Y. H. , Wu G. S. , Zhang L. D.
Published: September 2004

A large amount of one‐dimensional (1D) Ce‐doped ZnO nanostructures with different morphologies has been successfully synthesized by annealing a polymeric precursor at various temperatures. The evolution of the morphologies and microstructures was investigated by field‐emission scanning electron microscopy (FE‐SEM), transmission electron microscopy (TEM), and high‐resolution TEM (HRTEM). The results show that the morphologies vary drastically with increasing synthesis temperature and the photoluminescence (PL) of the products depends on both the synthesis and measurement temperatures. The CeO layer forms first and becomes a catalytic center for the ZnO growth. At a synthesis temperature lower than the boiling point of Zn, Zn and O atoms can stack epitaxially along the CeO catalytic layer and form a bicrystal nanobelt‐like structure with a trapezoid‐like end and a concave growth fault center. At a synthesis temperature higher than the boiling point of Zn, however, nanowires with an incommensurately modulated superstructure are obtained due to the high reaction rate and the formation of a periodic separation of the CeO layer. As for the room‐temperature PL of ZnO, the incorporation of donor Ce leads to the disappearance of the green band and the appearance of a purplish‐blue emission peak, whose position shifts towards the red and whose intensity decreases with increasing synthesis temperature. Analysis of this temperature‐dependent luminescence indicates that the purplish‐blue emission of nanobelts prepared at 850 °C originates from a donor‐bound exciton emission, and, contrary to the nanowires, it undergoes a change from an emission of the electron–hole plasma (EHP) to an emission of the donor‐bound exciton with decreasing measurement temperature.
Alignment of a Perylene‐Based Ionic Self‐Assembly Complex in Thermotropic and Lyotropic Liquid‐Crystalline Phases
Authors: Zakrevskyy Y. , Faul C. F. J. , Guan Y. , Stumpe J.
Published: September 2004

The thermotropic and lyotropic liquid‐crystalline (LC) phases of the ionic self‐assembled complex N,N′,‐bis(2‐(trimethylammonium)ethylene)‐perylene‐3,4,9,10‐tetracarboxyldiimide‐bis(2‐ethylhexyl)sulfosuccinate have been studied using polarizing microscopy, differential scanning calorimetry (DSC), and X‐ray scattering techniques. A two‐dimensional (2D) columnar thermotropic LC phase with π–π stacking of the perylene tectonic units and a lyotropic LC phase in dimethyl sulfoxide (DMSO) have been found. Different techniques have been applied to align both systems and included: surface interactions, electric and magnetic fields, shear force, and controlled domain formation at the LC–isotropic phase‐transition front (PTF). Characterization of the alignment in films has been performed using polarized UV‐vis spectroscopy and transmission null‐ellipsometry. The best results have been obtained for alignment of the material in a lyotropic phase by controlled domain formation at the PTF of the LC–isotropic phase transition. In this case, a dichroic ratio of 18 is achieved with packing of columns of perylenediimide tectons perpendicular to the PTF.