bluuebunny/crossref_metadata_2025 huggingface dataset:
Adeno‐Associated Virus Rep78/Rep68 Promotes Localized Melting of the Rep Binding Element in the Absence of Adenosine Triphosphate
Authors: Lou Hua Jane , Brister J. Rodney , Li Jianwei Jeffery , Chen Weijun , Muzyczka Nicholas , Tan Weihong
Published: February 2004

We have applied fluorescence anisotropy and molecular beacon fluorescence methods to study the interactions between the Adeno‐associated virus Rep78/Rep68 protein and the 23‐bp Rep binding element (RBE). Rep78/Rep68 stably interacted with both the single‐ and double‐stranded conformations of the RBE, but the interaction mechanisms of single‐ and double‐stranded DNA appeared to be fundamentally different. The stoichiometry of Rep78 association with both the separate top and bottom strands of the RBE was 1:1, and the relative dissociation constant (KD) values of these associations were calculated to be 2.3×10−8 and 3.2×10−8 M, respectively. In contrast, the stoichiometry of Rep78 association with the double‐stranded RBE was 2:1, and the dissociation constant was determined to be 4.2×10−15 M2. Moreover, Rep78/Rep68 interaction with the 23‐bp duplex RBE appeared to cause localized melting of the double‐stranded DNA substrate in the absence of adenosine triphosphate (ATP). This melting activity showed slower kinetics than binding and may contribute to the initiation of ATP‐dependent Rep78 helicase activity.
Optimal Modification of Annexin V with Fluorescent Dyes
Authors: Schellenberger Eyk A. , Weissleder Ralph , Josephson Lee
Published: February 2004

The many uses of chemically modified annexin Vs necessitate an understanding of the optimal degree of modification and modification sites of the protein. When reacted with the N‐hydroxysuccinimide ester of Cy5.5, annexin V with one modification per mole of protein retained its affinity for phosphatidylserine of apoptotic cells, whereas modification with two dyes per mole of protein caused a complete loss of activity. A tryptic digest LC/MS method was used to identify the modification sites as either of two closely spaced lysine residues, in position 286 or 290. The crystal structure indicated the location of these lysines was distal to the phosphatidylserine binding sites on annexin V. These results can be used to develop active or inactive fluorescent control annexin V proteins and to suggest strategies for attaining higher levels of modification with retention of bioactivity.
Increased Single‐Nucleotide Discrimination of PCR by Primer Probes Bearing Hydrophobic 4′C Modifications
Authors: Strerath Michael , Gaster Jens , Summerer Daniel , Marx Andreas
Published: February 2004

We report on significantly increased selectivity of real‐time PCR through employment of primer probes that bear hydrophobic 4′C modifications at the 3′‐terminal nucleotide. The primer probes were designed to bind the target sequences in such a way that the 3′‐terminal nucleotide defines whether a matched or a single mismatched basepair is present depending on the respective target sequence. Several commercially available thermostable DNA polymerases belonging to different DNA polymerase families were tested for their efficacy in discriminating between PCR amplification of matched substrates and duplexes that contain a single mismatch. It turned out that, depending on the 4′C modification and the employed DNA polymerase, significantly increased differentiation between single matches and mismatches could be observed with real‐time PCR. The degrees of the observed effects varied with the employed 4′C modification and the sequence context studied. The system is robust enough to work faithfully under several buffer conditions. Our approach should be useful for the direct diagnosis of single nucleotide variations within genes, like single nucleotide polymorphisms or mutations, by PCR without the need for further time‐ and cost‐intensive post‐PCR analysis.
Copper Binding to the Neurotoxic Peptide PrP106–126: Thermodynamic and Structural Studies
Authors: Belosi Barbara , Gaggelli Elena , Guerrini Remo , Kozłowski Henryk , Łuczkowski Marek , Mancini Francesca M. , Remelli Maurizio , Valensin Daniela , Valensin Gianni
Published: February 2004

The human prion protein fragment PrP106–126 is a highly fibrillogenic peptide, resistant to proteinases and toxic to neurons; it derives from the normal prion protein (PrPC), with which it can interact, thus inhibiting its superoxide dismutase‐like activity. The same properties are also shown by the abnormal isoform of the prion protein (PrPSc), and this similarity makes PrP106–126 an interesting model for the neurotoxic action of PrPSc. A role for copper in PrP106–126 aggregation and toxicity has recently been evidenced, and the interaction of terminal Lys, His and Met residues with the copper ion at neutral pH has been suggested. In order to shed more light on the complex‐formation equilibria of PrP106–126 with the copper ion, a thorough investigation has been carried out by means of several experimental techniques: potentiometry, solution calorimetry, VIS spectrophotometry, circular dichroism, EPR and NMR spectroscopy. A shorter and more soluble fragment—PrP106–113, which lacks the hydrophobic C‐terminal domain of PrP106–126 but contains all the potential donor groups—has also been considered for the sake of comparison. The involvement of terminal amino, imidazolic and amido nitrogens in complex formation has been confirmed, while no evidence was found for the interaction of side chains of Met and Lys residues with the copper ion. Solution structures for the main complexes are suggested.
LES Simulation of Jet Mixing Processes With Heat Transfer in Turbulent Pipe Flow
Authors: Jahnke S. , Kornev N. , Leder A. , Hassel E.
Published: February 2004

A LES technique is used for investigation of jet mixing processes with heat transfer in a turbulent pipe flow. Predictions were validated for different test problems. Influence of velocity, density, kinematic viscosity and temperature in a co‐flow and in an admixture as well as the effect of the Reynolds number on mixing were studied. Two efficient methods of mixing control, namely periodic injection and swirling jets, were investigated.
Determination of Dissipation Rate in Stirred Vessels Through Direct Measurement of Fluctuating Velocity Gradients
Authors: Baldi S. , Ducci A. , Yianneskis M.
Published: February 2004

2‐D and 3‐D PIV and 4‐channel LDA techniques were employed to measure the turbulence energy dissipation rate in vessels stirred by Rushton impellers. The measurements were made in vessels of diameter T = 100 mm and 294 mm and stirred by impellers of diameter D = T/3. The impellers were rotated at speeds corresponding to Reynolds number of 40,000 to ensure fully‐turbulent flow in the vessels. ϵ was determined directly from measurements of the Reynolds stress gradients by analyzing the PIV images over interrogation areas down to 0.1 mm. Similar LDA data were obtained in the larger 294 mm vessel, with a resolution of around 50 μm. The fluctuating gradient results obtained with the two techniques compare well and show that direct measurement of the ϵ distribution is feasible with both PIV and LDA methods.
Hydrodynamics in a Stirred Square Tank Investigated Using a 3‐D PIV LES Decomposition Approach and LDA Measurements
Authors: Kilander J. , Rasmuson A.
Published: February 2004

In this study, the hydrodynamics and turbulence in a square tank stirred with the hydrofoil impeller Lightnin A310 is investigated using a large eddy particle image velocimetry approach. Particle image velocimetry data are used as the large scale part of a large eddy simulation and the small scales are modelled by direct calculation of the turbulent stress tensor using filtered particle image velocimetry data. The spatial distribution of the calculated dissipation rate showed agreement with previous work. The macro instabilities of the flow structure were investigated by means of spectral analysis. Low frequency phenomena separated from the mean flow were detected. The cause of these could partly be explained by the circulation time for the tank.
Modeling of Mixing and Precipitation Using CFD and Population Balances
Authors: Paschedag A.R.
Published: February 2004

Simulations of particle size distributions in technical precipitation reactors require the consideration of turbulent mixing and precipitation kinetics. For that, spatially resolved population balances have to be evaluated. In turbulent flows these balances cannot be solved directly, instead either Reynolds averaging or Large Eddy Simulations have to be applied, while unresolved fluctuations need to be modeled. Reynolds averaging of the population balance leads to a turbulent growth dispersion term which has to be modeled. As no theoretically founded approach is available, an assumption was made in analogy to the turbulent diffusion, which improves the prediction of the size distribution shape compared to experiments.
CFD Modelling of Mixing Effects on the Course of Parallel Chemical Reactions Carried out in a Stirred Tank
Authors: Bałdyga J. , Makowski Ł.
Published: February 2004

Effects of turbulent mixing on the course of two fast parallel chemical reactions (neutralization of sodium hydroxide and hydrolysis of ethyl chloroacetate) carried out in a semibatch stirred tank reactor are experimentally investigated and numerically simulated. The flow pattern in the stirred tank is predicted using CFD and experimentally validated using Laser Doppler Anemometry. Mixing effects are modelled using three CFD based models. In the first and the second model the Beta probability distribution and the spiked distribution are used respectively; in the third model concentration fluctuations are neglected.
Large Eddy Simulation of Turbulent Flow in a Rushton Impeller Stirred Reactor with Sliding‐Deforming Mesh Methodology
Authors: Yeoh S.L. , Papadakis G. , Lee K.C. , Yianneskis M.
Published: February 2004

The unsteady turbulent flow in a mixing vessel stirred by a Rushton impeller is predicted using the Large Eddy Simulation technique. The interaction between the moving impeller and the static baffles is accounted for explicitly through a sliding‐deforming mesh methodology, thus, eliminating approximations used to account for the effect of the moving impeller. Large‐scale structures associated with the trailing vortices are assessed via the vorticity and the turbulent kinetic energy distributions. The phase‐resolved predictions are compared with measurement data obtained by laser‐Doppler anemometry and favourable agreement is reported both for mean as well as turbulence quantities.
Steering of Liquid Mixing Speed in Interdigital Micro Mixers – From Very Fast to Deliberately Slow Mixing
Authors: Löb P. , Drese Klaus S. , Hessel V. , Hardt S. , Hofmann C. , Löwe H. , Schenk R. , Schönfeld F. , Werner B.
Published: February 2004

Very fast mixing in the range of milliseconds as well as deliberately slow mixing was realized by specially adjusted interdigital micro mixers made of glass or stainless steel. The corresponding micro mixers are presented including experimental and theoretical investigations of the respective mixing process. Fast mixing was realized by combination of flow multilamination by interdigital microstructured feeding structures with geometric focusing. Details on the microfabrication, achievable throughputs and hydrodynamics are discussed. To prevent clogging of microsized feeding structures in the case of precipitation reactions, mixing was deliberately slowed down by separating the reactant solutions at the outlet by additional layers of inert liquids.
Coaxial Mixer Hydrodynamics with Newtonian and non‐Newtonian Fluids
Authors: Foucault S. , Ascanio G. , Tanguy P.A.
Published: February 2004

The performance of several combinations of a wall scraping impeller and dispersing impellers in a coaxial mixer operated in counter‐ and co‐rotating mode were assessed with Newtonian and non‐Newtonian fluids. Using the power consumption and the mixing time as the efficiency criteria, impellers in co‐rotating mode were found to be a better choice for Newtonian and non‐Newtonian fluids. The hybrid impeller‐anchor combination was found to be the most efficient for mixing in counter‐rotating or co‐rotating mode regardless of the fluid rheology. For both rotating modes, it was shown that the anchor speed does not have any effect on the power draw of the dispersing turbines. However, the impeller speed was shown to affect the anchor power consumption. The determination of the minimum agitation conditions to achieve the just suspended state of solid particles (Njs) was also determined. It was found that Njs had lower values with the impellers having the best axial pumping capabilities.
Macro‐ and Micromixing in a Taylor‐Couette Reactor with Axial Flow and their Influence on the Precipitation of Barium Sulfate
Authors: Judat B. , Racina A. , Kind M.
Published: February 2004

A new set‐up for precipitation experiments capable of independent adjustment of micromixing and macromixing conditions is presented. The setup consists of a Taylor‐Couette (TC) reactor serving as the reaction zone and an external loop where the slower stages of precipitation processes take place. Micromixing in the TC reactor has been investigated with a chemical reaction system and with PIV‐measurements. Micromixing times range between 6·10–3 and 8·10–2 s. Tracer experiments reveal the macromixing performance of the whole set‐up which has been compared with the behavior of ideal reactors. Precipitation experiments with barium sulfate show some influence of micromixing intensity on the particle size and of macromixing on particle morphology.
The Mixing Efficiency of an Eccentric‐Disc Kneading Zone in Intermeshing Co‐ and Counter‐Rotating Twin‐Screw Extruders
Authors: Brod H. , Liesenfelder U.
Published: February 2004

The distributive mixing efficiency of a twin‐screw extruder kneading zone consisting of eccentric disc elements was measured using an online video technique. Both co‐ and counter‐rotation were examined. Viscous Newtonian silicone oil was used as model liquid and black iron oxide pigment served as tracer substance. Under isoviscous, creeping flow and non‐diffusive conditions and for a fixed flow rate ratio of the colored and uncolored feed streams, the intensity of segregation S is only a function of the kinematic parameter Λ (the ratio of the imposed extruder throughput and the throughput at zero axial pressure gradient). The measured dependency of S on Λ is in qualitative agreement with the results of Pawlowski for a single screw extruder. The data was also plotted against the dimensionless speed of rotation, i.e. the product of the screw speed and the average residence time within the mixing section. This brings the abscissa ranges for mixers with different conveying capacity closer together, and differences in mixing efficiency between the tested configurations can be better interpreted. The energetic efficiency of the mixers investigated is compared by applying the concept of specific action. This helps to decide which mixer geometry and operating conditions produce a given homogeneity with the lowest amount of work done by viscous forces.
State of the Art and Future Trends in CFD Simulation of Stirred Vessel Hydrodynamics
Authors: Sommerfeld M. , Decker S.
Published: February 2004

Computational fluid dynamics (CFD) has become a widely used tool for analysing, optimising and supporting the design of mixing processes in stirred vessels. The present contribution gives a brief summary of the methods applied for numerically treating the power input by the impeller, such as empirical methods, the multiple frame of reference approach and unsteady methods using sliding or clicking meshes. Thereafter, recent developments and trends in the numerical computation of single phase flows in stirred vessels on the basis of DNS (direct numerical simulations), LES (large eddy simulations) and RANS (Reynolds‐averaged Navier‐Stokes) approaches are summarised. Since many operations in stirred vessels involve at least two phases, also the methods for modelling these flows, such as the two‐fluid method and the Euler/Lagrange approach are briefly described and recent applications are reviewed. Finally, also own calculations for single‐phase mixing and particle dispersion in a stirred vessel using the Euler/Lagrange approach are introduced emphasising some recent developments.
CFD‐gestützte Untersuchungen von Hydrodynamik und Stofftransport in Katalysatorschüttungen
Authors: Klöker M. , Kenig E. Y. , Piechota R. , Burghoff S. , Egorov Y.
Published: February 2004

No abstracts.
Bruchprozesse bei der Druckbeanspruchung von Granulaten
Authors: Antonyuk S. , Tomas J. , Heinrich S. , Mörl L.
Published: February 2004

No abstracts.
Simultane Ad‐ und Desorption von Chlorwasserstoff und Schwefeldioxid an mit Magnesiumoxid imprägniertem Aktivkoks
Authors: Ernst R. , Luft G.
Published: February 2004

No abstracts.
Online‐Monitoring der lipasekatalysierten Hydrolyse von Rapsöl
Authors: Saulich K. , Schnitzlein K.
Published: February 2004

No abstracts.
Vorbehandlung von Überschussschlamm durch Elektroporation
Authors: Kopplow O. , Barjenbruch M. , Heinz V.
Published: February 2004

No abstracts.
Industrieller Einsatz von Trennwandkolonnen und thermisch gekoppelten Destillationskolonnen
Authors: Kaibel G. , Miller C. , Stroezel M. , von Watzdorf R. , Jansen H.
Published: February 2004

No abstracts.
Auslegung und Optimierung von hybriden Trennverfahren
Authors: Franke M. , Górak A. , Strube J.
Published: February 2004

Unter hybriden Trennverfahren versteht man die Verschaltung von mindestens zwei verschiedenen, apparativ getrennten Grundoperationen, die zur Trennaufgabe beitragen. Hybride Trennverfahren werden bei schwierigen Trennungen, wie bei engsiedenden oder azeotropen Gemischen, eingesetzt, wenn eine einzelne Grundoperation, z. B. Rektifikation, Extraktion, Kristallisation, Membranverfahren oder Chromatographie, gar nicht oder nur mit sehr großem Aufwand zum Ziel führt. Aufgrund der Struktur des Hybridprozesses, die das Vorhandensein mindestens zwei verschiedener Grundoperationen und eine entsprechende Anzahl von Rückführungen impliziert, ist die Auslegung komplex, sie wird deshalb z. Z. systematisch in der Forschung untersucht. In dieser Arbeit werden die Anforderungen an eine Auslegungsmethodik für hybride Trennverfahren dargestellt. Es wird eine Methodik vorgestellt, die auf einer detaillierten Modellierung der Grundoperationen und einer simultanen Mehrvariablen‐Optimierung beruht. Die Anwendbarkeit dieser Methodik wird anhand einer Isomerentrennung gezeigt.
Der Einfluss der Biotechnologie auf Produktionsverfahren in der Chemieindustrie
Authors: Festel G. , Knöll J. , Götz H. , Zinke H.
Published: February 2004

Eine aktuelle Marktstudie von Festel Capital zeigt, dass der Einfluss der Biotechnologie auf die industriellen Produktionsverfahren in der Chemieindustrie weiter wachsen wird. Von besonderem Interesse ist dabei die Herstellung von Feinchemikalien, insbesondere von enantiomerenreinen Wirkstoffen für die Agro‐ und Pharmaindustrie. Die Produktionskosten sind die entscheidende Triebkraft für einen Wechsel zu biotechnologischen Produktionsverfahren. Ziel sind Einsparungen durch Prozessvereinfachungen sowie bei den Roh‐, Neben‐ und Abfallprodukten. Andere Faktoren spielen bei der Wahl des Produktionsverfahrens in der Regel keine Rolle. Ein wichtiger Aspekt ist allerdings die Zugänglichkeit von neuen Biotech‐Produkten, die durch herkömmliche Verfahren nicht hergestellt werden können.
Immunohistochemical localization of Ih channel subunits, HCN1–4, in the rat brain
Authors: Notomi Takuya , Shigemoto Ryuichi
Published: February 2004

Hyperpolarization‐activated cation currents (Ih) contribute to various physiological properties and functions in the brain, including neuronal pacemaker activity, setting of resting membrane potential, and dendritic integration of synaptic input. Four subunits of the Hyperpolarization‐activated and Cyclic‐Nucleotide‐gated nonselective cation channels (HCN1–4), which generate Ih, have been cloned recently. To better understand the functional diversity of Ih in the brain, we examined precise immunohistochemical localization of four HCNs in the rat brain. Immunoreactivity for HCN1 showed predominantly cortical distribution, being intense in the neocortex, hippocampus, superior colliculus, and cerebellum, whereas those for HCN3 and HCN4 exhibited subcortical distribution mainly concentrated in the hypothalamus and thalamus, respectively. Immunoreactivity for HCN2 had a widespread distribution throughout the brain. Double immunofluorescence revealed colocalization of immunoreactivity for HCN1 and HCN2 in distal dendrites of pyramidal cells in the hippocampus and neocortex. At the electron microscopic level, immunogold particles for HCN1 and HCN2 had similar distribution patterns along plasma membrane of dendritic shafts in layer I of the neocortex and stratum lacunosum moleculare of the hippocampal CA1 area, suggesting that these subunits could form heteromeric channels. Our results further indicate that HCNs are localized not only in somato‐dendritic compartments but also in axonal compartments of neurons. Immunoreactivity for HCNs often occurred in preterminal rather than terminal portions of axons and in specific populations of myelinated axons. We also found HCN2‐immunopositive oligodendrocytes including perineuronal oligodendrocytes throughout the brain. These results support previous electrophysiological findings and further suggest unexpected roles of Ih channels in the brain. J. Comp. Neurol. 471:241–276, 2004. © 2004 Wiley‐Liss, Inc.
Demonstration of an orexinergic central innervation of the pineal gland of the pig
Authors: Fabris Chiara , Cozzi Bruno , Hay‐Schmidt Anders , Naver Bjarke , Møller Morten
Published: February 2004

Orexins/hypocretins, two isoforms of the same prepropeptide, are widely distributed throughout the brain and are involved in several physiological and neuroendocrine regulatory patterns, mostly related to feeding, sleep, arousal, and cyclic sleep‐wake behaviors. Orexin‐A and orexin‐B bind with different affinities to two G‐protein‐coupled transmembrane receptors, orexin‐1 and orexin‐2 receptors (OR‐R1 and OR‐R2, respectively). Because of the similarities between the human and the swine brain, we have studied the pig to investigate the orexinergic system in the diencephalon, with special emphasis on the neuroanatomical projections to the epithalamic region. By using antibodies against orexin‐A and orexin‐B, immunoreactive large multipolar perikarya were detected in the hypothalamic periventricular and perifornical areas at the light and electron microscopic levels. In the region of the paraventricular nucleus, the orexinergic neurons extended all the way to the lateral hypothalamic area. Immunoreactive nerve fibers, often endowed with large varicosities, were found throughout the hypothalamus and the epithalamus. Some periventricular immunoreactive nerve fibers entered the epithalamic region and continued into the pineal stalk and parenchyma to disperse among the pinealocytes. Immunoelectron microscopy confirmed the presence of orexinergic nerve fibers in the pig pineal gland. After extraction of total mRNA from the hypothalamus and pineal gland, we performed RT‐PCR and nested PCR using primers specific for porcine orexin receptors. PCR products were sequenced, verifying the presence of both OR‐R1 and OR‐R2 in the tissues investigated. These findings, supported by previous studies on rodents, suggest a hypothalamic regulation of the pineal gland via central orexinergic nervous inputs. J. Comp. Neurol. 471:113–127, 2004. © 2004 Wiley‐Liss, Inc.
Localization of the mRNA encoding prolyl endopeptidase in the rat brain and pituitary
Authors: Bellemère Gaelle , Vaudry Hubert , Mounien Lourdes , Boutelet Isabelle , Jégou Sylvie
Published: February 2004

Prolyl endopeptidase (EC 3.4.21.26, PEP), a serine protease that hydrolyzes peptides at the carboxyl side of proline residues, is involved in the breakdown of several proline‐containing neuropeptides and, thus, may contribute to the regulation of behavioral activities. In this study, the distribution of PEP mRNA was investigated in the central nervous system and pituitary of rat by means of quantitative reverse transcriptase‐polymerase chain reaction analysis and in situ hybridization histochemistry. High densities of PEP transcripts were found in cerebellar Purkinje and granule cells, within most hypothalamic nuclei, in pyramidal neurons of the Ammon's horn, in granule cells of the dentate gyrus, and within the basolateral complex of the amygdala. Moderate levels of PEP mRNA were observed in layers 3–5 of the cerebral cortex, the anterior thalamic group, the septal region, the substantia nigra, the magnocellular neurons of the red nucleus, and the motor nuclei of the cranial nerves. Low concentrations of PEP mRNA were detected in the deep mesencephalic nuclei, the reticular formation, the pretectum, and the tectum. A high density of PEP mRNA was found in the intermediate and the anterior lobes of the pituitary, while the neural lobe was devoid of labeling. In several brain regions, the distribution pattern of PEP mRNA overlapped that of various neuropeptide receptors, suggesting that PEP is actually involved in the inactivation of regulatory neuropeptides. J. Comp. Neurol. 471:128–143, 2004. © 2004 Wiley‐Liss, Inc.
The single neurofilament subunit of lamprey may need another element for filament assembly
Authors: Zhang Guixin , Spencer Paula H. , Jin Li‐Qing , Cohlberg Jeffrey A. , Beaulieu Jean Martin , Julien Jean‐Pierre , Selzer Michael E.
Published: February 2004

Regenerating axon tips in transected lamprey spinal cord contain dense accumulations of neurofilaments (NFs), suggesting that NFs may play a role in the mechanism of axonal regeneration. Compared with heteropolymeric assemblies of NF triplet proteins in mammals, NF in lampreys has been thought to contain only a single subunit (NF180). This would imply that NF180 self‐assembles, which would be important for manipulating its expression in studies of axonal regeneration. In order to study the possible role of NF in process outgrowth and to determine whether NF180 can self‐assemble, its gene was transfected into mammalian and fish cell lines that either contain or lack vimentin. In transfected NIH3T3 cells, NF180 was poorly phosphorylated and its expression did not alter the length or number of cell processes. Nor did it appear to form typical intermediate filaments, suggesting that it may not self‐assemble. NF180 also did not form typical filaments in SW13cl cells that either possessed or lacked vimentin, nor in transfected fish cells that were cultured at 18°C. In vitro, NF180 could not self‐assemble but interacted with NF‐L to interrupt its self‐assembly. When cotransfected with rat NF‐L into SW13c1.2vim− cells, NF180 did form thick, rod‐like filamentous structures on immunofluorescence. More typical NFs were observed when NF180 was cotransfected with both NF‐L and NF‐M. Thus, NF180 cannot self‐assemble but appears to require one or more additional elements for incorporation into NFs. J. Comp. Neurol. 471:188–200, 2004. © 2004 Wiley‐Liss, Inc.
Characterization of projections from a sexually dimorphic motor nucleus in the spinal cord of adult green anoles
Authors: Holmes Melissa M. , Wade Juli
Published: February 2004

Male green anoles possess two copulatory organs (hemipenes), which are independently controlled by bilateral muscles: the transversus penis (TPN) and retractor penis magnus (RPM). Adult females do not possess hemipenes or either of the two related muscles. Motoneurons projecting to the TPN lie in spinal segments trunk 17 and sacral 1 (T17–S1). Overall, motoneurons in this region are larger and more numerous in males than females. The present studies were designed to determine 1) whether motoneurons projecting to the RPM are located in the same sexually dimorphic nucleus, 2) other targets of T17–S1 motoneurons, and 3) the approximate proportion of motoneurons projecting to each muscle. In Study 1, unilateral injection of the retrograde tracer Fast Blue (FB) into RPMs and simultaneous unilateral injection of either Cholera Toxin‐fluorescein (CT‐FITC) or Diamidino Yellow into TPNs revealed that RPM and TPN motoneurons are indeed interdigitated in T17–S1. In Study 2, FB was used to characterize other targets of this nucleus in both males and females. In adult males, projections to four muscles accounted for 96% of the T17–S1 motoneurons: the TPN, RPM, caudifemoralis (CF), and cloacal sphincter (SC). In adult females, projections to the CF and SC comprised 70% of this nucleus. These data demonstrate that the T17–S1 nucleus is a mixed spinal nucleus that has projections to muscles present in both sexes, as well as those present only in males and specialized for male copulatory behavior. J. Comp. Neurol. 471:180–187, 2004. © 2004 Wiley‐Liss, Inc.
Rat intralaminar thalamic nuclei projections to the globus pallidus: A biotinylated dextran amine anterograde tracing study
Authors: Yasukawa T. , Kita T. , Xue Y. , Kita H.
Published: February 2004

The topographical organization and ultrastructural features of the intralaminar thalamic nuclei (ITN) projections to the globus pallidus (GP) were studied using the biotinylated dextran amine (BDA) anterograde tracing method in the rat. To assess the functional association of BDA injection sites in the ITN, the known topographical organization of the ITN‐neostriatal (Str) projections and calcium binding protein (CaBP) immunostaining patterns of the Str and GP were used. BDA injection in the lateral part of the lateral parafascicular nucleus and the caudal part of the central lateral nucleus labeled fibers and boutons mainly in the dorsolateral sensorimotor territory of the Str and the middle territories of the GP. BDA injection in the medial part of the lateral parafascicular nucleus and the central lateral nucleus labeled mainly the middle association territory of the Str and the border and the caudomedial territories of the GP. BDA injection in the medial parafascicular nucleus and the central medial nucleus labeled mainly the medial limbic territory of the Str. The medial parafascicular nucleus projected to the medial‐most region of the GP, while the central medial nucleus projection to the GP was very sparse. Electron microscopic observations indicated that BDA‐labeled boutons form asymmetric synapses mainly on 0.5–2.0 μm diameter dendritic shafts in the GP. The boutons were small but had a relatively long active zone. The present observations together with the known topographical organization of striatopallidal projections indicated that the ITN‐GP projections were topographically organized in parallel to the ITN‐Str projections. Thus, each part of the ITN projecting to the sensorimotor, the association, and the limbic territories of the Str also projects to the corresponding functional territories of the GP. J. Comp. Neurol. 471:153–167, 2004. © 2004 Wiley‐Liss, Inc.
Subpial and stellate cells: Two populations of interneurons in turtle visual cortex
Authors: Colombe Jeffrey B. , Sylvester Juliesta , Block Joseph , Ulinski Philip S.
Published: February 2004

Turtle visual cortex has three layers and receives direct input from the dorsolateral geniculate complex of the thalamus. The outer layer 1 contains several populations of interneurons, but their physiological properties have not been characterized. This study used intracellular recording methods followed by filling with Neurobiotin to characterize the morphology and physiology of two populations of layer 1 interneurons. Subpial cells have somata positioned in the outer third of layer 1 and dendrites confined within the band of geniculate afferents that runs from lateral to medial across visual cortex. Their dendrites are composed of a sequence of many beads or varicosities separated by intervaricose segments. They have membrane time constants of τo = 45.5 ± 5.2 ms and electrotonic lengths of 1.1 ± 0.2. Subpial cells show spike rate adaptation in response to intracellular current pulses. Stellate cells have somata located in the inner two‐thirds of layer 1 and, less frequently, in layers 2 and 3. Their dendrites extend in a stellate configuration across the cortex. They are smooth or sparsely spiny, but never bear distinct varicosities. They have membrane time constants of τo = 155.1 ± 12 ms and electrotonic lengths of 3.8 ± 0.5. They show little spike rate adaptation in response to intracellular current pulses. The positions of the two populations of cells in visual cortex and their physiological properties suggest that subpial cells may participate in a feedforward inhibitory pathway to pyramidal cells, whereas stellate cells are involved in feedback inhibition to pyramidal cells. J. Comp. Neurol. 471:333–351, 2004. © 2004 Wiley‐Liss, Inc.
The inner ear of the lungfish Protopterus
Authors: Platt Christopher , Jørgensen Jørgen M. , Popper Arthur N.
Published: February 2004

The sensory end organs of the inner ear of the lungfish, Protopterus, were examined using scanning and transmission electron microscopy. The utricle has a structure and hair cell orientation pattern that are typical for vertebrates, although the hair cells are unusually large. There are the typical three semicircular canals extending from the utricle, with the typical hair cell orientations, but the lateral canal sensory crista looks like the “hemicrista” of some amphibians and amniotes, lacking a saddle‐shaped flare on one wall of the ampulla. Unlike most vertebrates that have the saccule and lagena as two separate pouches ventral to the utricle, the lungfish has a single large ventral pouch that contains a single large pasty otoconial mass. This mass covers two hair cell patches, each like a striola with prominent hair cell ciliary bundles, that are presumed to represent saccular and lagenar maculae. However, these two major sensory patches are not completely separate maculae because they lie within a less densely populated field of smaller hair cells, which forms an extrastriolar region that surrounds and fills the region between the two striolae of higher hair cell density. The more caudal lagenar striola is a vertically elongated stripe with hair cell orientation vectors facing antiparallel on either side of a midline drawn vertically along the macula, resembling the macula lagena of some bony fishes but not of tetrapods. The more rostral saccular striola is a curving band with hair cell orientation vectors facing away from its midline, but because this macula curves in three dimensions, the vectors at the rostral end of this striola are oriented mediolaterally, whereas the vectors on the caudal half of this striola are oriented dorsoventrally. The presence of a macula neglecta was confirmed near the posterior canal as a tiny single patch of a few dozen hair cells with all the cell orientations directed caudally. The ciliary bundles on the cells in the striolar‐like regions of all of three otolithic organs average over 80 cilia, a number far greater than for any other fish studied to date. The features of the single sacculolagenar pouch with separate striolar‐like regions, the cellular orientation in the otolith organs, and the large cells and ciliary bundles in Protopterus also were observed in specimens of the other extant lungfish genera, Lepidosiren and Neoceratodus. J. Comp. Neurol. 471:277–288, 2004. © 2004 Wiley‐Liss, Inc.
Synaptic structural modification following changes in activity induced by tetanus neurotoxin in cat abducens neurons
Authors: González‐Forero David , Pastor Angel M. , Delgado‐García Jose María , de la Cruz Rosa R. , Alvarez Francisco J.
Published: February 2004

A low or a high dose of tetanus neurotoxin (TeNT) injected in the lateral rectus muscle of the cat causes respectively, functional block of inhibitory synapses only or of both inhibitory and excitatory synapses simultaneously in abducens neurons (González‐Forero et al. [2003] J. Neurophysiol. 89:1878–1890). As a consequence, neuronal firing activity increases (at low dose) or decreases (at high dose). We investigated possible structural modifications of inhibitory synapses in response to these activity alterations induced by TeNT. We used immunofluorescence against postsynaptic (gephyrin) and presynaptic (vesicular γ‐aminobutyric acid [GABA] transporter [VGAT]) markers of inhibitory synapses in combination with cell type markers for abducens motoneurons (calcitonin gene‐related peptide or choline acetyltransferase) or internuclear neurons (calretinin). Seven days after high‐dose treatment, the number of gephyrin‐immunoreactive (IR) clusters per 100 μm of membrane perimeter was reduced on the soma of abducens motoneurons by 55.3% and by 60.1% on internuclear neurons. Proximal dendritic gephyrin‐IR clusters were also significantly altered but to a lesser degree. Partial synaptic re‐establishment was observed 15 days post injection, and complete recovery occurred after 42 days. Coverage by VGAT‐IR terminals was reduced in parallel. In contrast, a low dose of TeNT caused no structural alterations. With electron microscopy we estimated that overall synaptic coverage was reduced by 40% in both types of neurons after a high dose of TeNT. However, F‐type terminals with postsynaptic gephyrin were preferentially lost. Thus, the ratio between F and S terminals diminished from 1.28 to 0.39 on motoneurons and from 1.26 to 0.47 on internuclear neurons. These results suggest that the maintenance of proximal inhibitory synaptic organization on central neurons is best related to neuronal activity and not to the level of inhibitory synaptic function, which was equally blocked by the high or low dose of TeNT. J. Comp. Neurol. 471:201–218, 2004. © 2004 Wiley‐Liss, Inc.
Somatotopic organization and functional properties of mechanosensory neurons expressing sensorin‐A mRNA in Aplysia californica
Authors: Walters Edgar T. , Bodnarova Michaela , Billy Allen J. , Dulin Michael F. , Díaz‐Ríos Manuel , Miller Mark W. , Moroz Leonid L.
Published: February 2004

A previous study reported that a peptide, sensorin‐A, is expressed exclusively in mechanosensory neurons having somata in central ganglia of Aplysia. The present study utilized in situ hybridization, staining by nerve back‐fill and soma injection, and electrophysiological methods to characterize the locations, numbers, and functions of sensorin‐A‐expressing neurons and to define the relationships between soma locations and the locations of peripheral axons and receptive fields. Approximately 1,000 cells express sensorin‐A mRNA in young adult animals (10–30 g) and 1,200 cells in larger adults (100–300 g). All of the labeled somata are in the CNS, primarily in the abdominal LE, rLE, RE and RF, pleural VC, cerebral J and K, and buccal S clusters. Expression also occurs in a few sparsely distributed cells in most ganglia. Together, receptive fields of all these mechanosensory clusters cover the entire body surface. Each VC cluster forms a somatotopic map of the ipsilateral body, a “sensory aplunculus.” Cells in the pleural and cerebral clusters have partially overlapping sensory fields and synaptic targets. Buccal S cells have receptive fields on the buccal mass and lips and display notable differences in electrophysiological properties from other sensorin‐A‐expressing neurons. Neurons in all of the clusters have relatively high mechanosensory thresholds, responding preferentially to threatening or noxious stimuli. Synaptic outputs to target cells having defensive functions support a nociceptive role, as does peripheral sensitization following noxious stimulation, although additional functions are likely in some clusters. Interesting questions arise from observations that mRNA for sensorin‐A is present not only in the somata but also in synaptic regions, connectives, and peripheral fibers. J. Comp. Neurol. 471:219–240, 2004. © 2004 Wiley‐Liss, Inc.
Synaptic interactions between the terminals of slow‐adapting type II mechanoreceptor afferents and neurones expressing γ‐aminobutyric acid‐ and glycine‐like immunoreactivity in the rat spinal cord
Authors: Watson Alan H.D.
Published: February 2004

The object of this study was to analyse the synaptic interactions of slow‐adapting type II (SAII) afferent terminals in laminae III–V of the rat spinal cord. The axons of SAII afferents were physiologically characterized by intracellular recording before injection with neurobiotin and preparation for electron microscopy. Axon terminals were serially sectioned and immunolabelled with antibodies against γ‐aminobutyric acid (GABA) or glycine by using a postembedding immunogold procedure. Computer‐aided reconstruction was used to reveal the relative distribution of different types of synapses on terminal and en passant synaptic boutons. Eighty‐nine percent of boutons received axoaxonic synaptic contacts, the mean number of contacts per bouton being 3.5. Fifty‐nine percent of presynaptic axons were immunoreactive for both GABA and glycine and 45% for GABA alone. Most boutons (95%) made axodendritic contacts, and the mean number of dendrites contacted was 1.6. More than half of the postsynaptic dendrites were greater than 1 μm in diameter. Twenty‐three percent were immunoreactive for glycine, and 71% were not immunoreactive for either antibody. Synaptic triads in which an axon presynaptic to the afferent was also in contact with a dendrite postsynaptic to the afferent were seen at 63% of boutons. These results are discussed in the light of similar studies of other low‐threshold mechanoreceptive afferent terminals in the rat and cat and in the context of what is known of the sensory interneurones carrying information from slow‐ and rapid‐adapting mechanoreceptors. J. Comp. Neurol. 471:168–179, 2004. © 2004 Wiley‐Liss, Inc.
Minimum action method for the study of rare events
Authors: E Weinan , Ren Weiqing , Vanden‐Eijnden Eric
Published: February 2004

The least action principle from the Wentzell‐Freidlin theory of large deviations is exploited as a numerical tool for finding the optimal dynamical paths in spatially extended systems driven by a small noise. The action is discretized and a preconditioned BFGS method is used to optimize the discrete action. Applications are presented for thermally activated reversal in the Ginzburg‐Landau model in one and two dimensions, and for noise induced excursion events in the Brusselator taken as an example of non‐gradient system arising in chemistry. In the Ginzburg‐Landau model, the reversal proceeds via interesting nucleation events, followed by propagation of domain walls. The issue of nucleation versus propagation is discussed and the scaling for the number of nucleation events as a function of the reversal time and other material parameters is computed. Good agreement is found with the numerical results. In the Brusselator, whose deterministic dynamics has a single stable equilibrium state, the presence of noise is shown to induce large excursions by which the system cycles out of this equilibrium state. © 2004 Wiley Periodicals, Inc.
Linear vs. nonlinear selection for the propagation speed of the solutions of scalar reaction‐diffusion equations invading an unstable equilibrium
Authors: Lucia Marcello , Muratov Cyrill B. , Novaga Matteo
Published: February 2004

We revisit the classical problem of speed selection for the propagation of disturbances in scalar reaction‐diffusion equations with one linearly stable and one linearly unstable equilibrium. For a wide class of initial data this problem reduces to finding the minimal speed of the monotone traveling wave solutions connecting these two equilibria in one space dimension. We introduce a variational characterization of these traveling wave solutions and give a necessary and sufficient condition for linear versus nonlinear selection mechanism. We obtain sufficient conditions for the linear and nonlinear selection mechanisms that are easily verifiable. Our method also allows us to obtain efficient lower and upper bounds for the propagation speed. © 2004 Wiley Periodicals, Inc.
On a wave map equation arising in general relativity
Authors: Ringström Hans
Published: February 2004

We consider a class of space‐times for which the essential part of Einstein's equations can be written as a wave map equation. The domain is not the standard one, but the target is hyperbolic space. One ends up with a 1 + 1 nonlinear wave equation, where the space variable belongs to the circle and the time variable belongs to the positive real numbers. The main objective of this paper is to analyze the asymptotics of solutions to these equations as t → ∞. For each point in time, the solution defines a loop in hyperbolic space, and the first result is that the length of this loop tends to 0 as t−1/2 as t → ∞. In other words, the solution in some sense becomes spatially homogeneous. However, the asymptotic behavior need not be similar to that of spatially homogeneous solutions to the equations. The orbits of such solutions are either a point or a geodesic in the hyperbolic plane. In the nonhomogeneous case, one gets the following asymptotic behavior in the upper half‐plane (after applying an isometry of hyperbolic space if necessary):

The solution converges to a point.

The solution converges to the origin on the boundary along a straight line (which need not be perpendicular to the boundary).

The solution goes to infinity along a curve y = const.

The solution oscillates around a circle inside the upper half‐plane.

Thus, even though the solutions become spatially homogeneous in the sense that the spatial variations die out, the asymptotic behavior may be radically different from anything observed for spatially homogeneous solutions of the equations. This analysis can then be applied to draw conclusions concerning the associated class of space‐times. For instance, one obtains the leading‐order behavior of the functions appearing in the metric, and one can conclude future causal geodesic completeness. © 2004 Wiley Periodicals, Inc.
Studying protein folding on the Grid: experiences using CHARMM on NPACI resources under Legion
Authors: Natrajan Anand , Crowley Michael , Wilkins‐Diehr Nancy , Humphrey Marty A. , Fox Anthony D. , Grimshaw Andrew S. , Brooks Charles L.
Published: February 2004

One benefit of a computational Grid is the ability to run high‐performance applications over distributed resources simply and securely. We demonstrated this benefit with an experiment in which we studied the protein‐folding process with the CHARMM molecular simulation package over a Grid managed by Legion, a Grid operating system. High‐performance applications can take advantage of Grid resources if the Grid operating system provides both low‐level functionality as well as high‐level services. We describe the nature of services provided by Legion for high‐performance applications. Our experiences indicate that human factors continue to play a crucial role in the configuration of Grid resources, underlying resources can be problematic, Grid services must tolerate underlying problems or inform the user, and high‐level services must continue to evolve to meet user requirements. Our experiment not only helped a scientist perform an important study, but also showed the viability of an integrated approach such as Legion's for managing a Grid. Copyright © 2004 John Wiley & Sons, Ltd.
Genetically induced communication network fault tolerance
Authors: Bush Stephen F.
Published: February 2004

This article presents the architecture and initial feasibility results of a proto‐type communication network that utilizes genetic programming to evolve services and protocols as part of network operation. The network evolves responses to environmental conditions in a manner that could not be pre‐programmed within legacy network nodes a priori. A priori in this case means before network operation has begun. Genetic material is exchanged, loaded, and run dynamically within an active network. The transfer and execution of code in support of the evolution of network protocols and services would not be possible without the active network environment. Rapid generation of network service code occurs via a genetic programming paradigm. Complexity and algorithmic information theory play a key role in understanding and guiding code evolution within the network. © 2004 Wiley Periodicals, Inc. Complexity 9: 19–33, 2004