bluuebunny/crossref_metadata_2025_split huggingface dataset:
Heartbeat control in the medicinal leech: A model system for understanding the origin, coordination, and modulation of rhythmic motor patterns
Authors: Calabrese Ronald L. , Nadim Farzan , Olsen Øystein H. 
Published: January 2005

AbstractWe have analyzed in detail the neuronal network that generates heartbeat in the leech. Reciprocally inhibitory pairs of heart interneurons form oscillators that pace the heartbeat rhythm. Other heart interneurons coordinate these oscillators. These coordinating interneurons, along with the oscillator interneurons, form an eight‐cell timing oscillator network for heartbeat. Still other interneurons, along with the oscillator interneurons, inhibit heart motor neurons, sculpting their activity into rhythmic bursts. Critical switch interneurons interface between the oscillator interneurons and the other premotor interneurons to produce two alternating coordination states of the motor neurons. The periods of the oscillator interneurons are modulated by endogenous RFamide neuropeptides. We have explored the ionic currents and graded and spike‐mediated synaptic transmission that promote oscillation in the oscillator interneurons and have incorporated these data into a conductance‐based computer model. This model has been of considerable predictive value and has led to new insights into how reciprocally inhibitory neurons produce oscillation. We are now in a strong position to expand this model upward, to encompass the entire heartbeat network, horizontally, to elucidate the mechanisms of FMRFamide modulation, and downward, to incorporate cellular morphology. By studying the mechanisms of motor pattern formation in the leech, using modeling studies in conjunction with parallel physiological experiments, we can contribute to a deeper understanding of how rhythmic motor acts are generated, coordinated, modulated, and reconfigured at the level of networks, cells, ionic currents, and synapses. © 1995 John Wiley & Sons, Inc.
Naturally occurring motoneuron cell death in rat upper respiratory tract motor nuclei: A histological, fast Dil and immunocytochemical study in the hypoglossal nucleus
Authors: Friedland David R. , Eden Avrim R. , Laitman Jeffrey T. 
Published: January 2005

AbstractWe have previously reported on our investigation of motoneuron cell death (MCD) in the rat nucleus ambiguus (NA). This article focuses on the other major upper respiratory tract motor nucleus: the hypoglossal. The hypoglossal nucleus (XII) contains motoneurons to the tongue and, as such, plays a critical role in defining patterns of respiration, deglutition, and vocalization. Motoneuron counts were made in XII in a developmental series of rats. In addition, the neural tracer fast DiI was used to ensure that all hypoglossal motoneurons had migrated into the nucleus at the time cell death was assessed. Furthermore, an antibody to γ‐aminobutyric acid (GABA) was used to determine the potential effect of inadvertently counting large interneurons on motoneuron counts. Cell death in XII was shown to occur entirely prenatally with a loss of 35% of cells between embryonic day 16 (E16) and birth. Fast DiI tracings of the prenatal hypoglossal nerve indicated that all motoneurons were present in a well‐defined nucleus by E15. Immunocytochemical staining for GABA demonstrated considerably fewer interneurons than motoneurons in XII. These findings in XII, in comparison with those previously reported for NA, demonstrate differences in the timing and amount of cell death between upper respiratory tract motor nuclei. These differences establish periods during which one nucleus may be preferentially insulted by environmental or teratogenic factors. Preferential insults may underlie some of the upper respiratory tract incoordination pathologies seen in the newborn such as the sudden infant death syndrome (SIDS). © 1995 John Wiley & Sons, Inc.
Brain‐derived proteins that rescue spinal motoneurons from cell death in the chick embryo: Comparisons with target‐derived and recombinant factors
Authors: Johnson James E. , Qin‐Wei Yin , Prevette David , Oppenheim Ronald W. 
Published: January 2005

AbstractSpinal motoneurons that normally die during early development can be rescued by a variety of purified growth or neurotrophic factors and target tissue extracts. There is also indirect evidence that brain or supraspinal afferent input may influence lumbar motoneuron survival during development and that this effect may be mediated by central nervous system–derived trophic agents. This report examines the biological and biochemical properties of motoneuron survival activity obtained from extracts of the embryonic chick brain. Treatment with an ammonium sulfate (25% to 75%) fraction of embryonic day 16 (E16) or E10 brain extracts rescued many spinal motoneurons that otherwise die during the normal period of cell death in vivo (E6 to E10). The same fractions also enhanced lumbar motoneuron survival following deafferentation. There were both similarities and differences between the active fractions derived from brain extracts (BEX) when compared with extracts derived from target muscles (MEX) or with purified neurotrophic factors. Survival activity from E10 BEX was as effective in promoting motoneuron survival as E10 MEX and more effective than astrocyte‐conditioned media. Unlike MEX, the active fractions from BEX also rescued placode‐derived nodose ganglion cells. In addition, unlike nerve growth factor and brain‐derived neurotrophic factor, active BEX fractions did not rescue neural crest‐derived dorsal root ganglion cells or sympathetic ganglion neurons. Interestingly, among many cranial motor and other brainstem nuclei examined, only the survival of motoneurons from the abducens nucleus was enhanced by BEX. Active proteins obtained from BEX were further separated by gel filtration chromatography and by preparative isolelectric focusing techniques. Activity was recovered in a basic (pI8) and an acidic (pI5) small molecular weight protein fraction (20 kD or less). The specific activity of the basic fraction was increased ×66 when compared with the specific activity of crude BEX, and the basic fraction had a slightly higher specific activity than the acidic fraction. The biological and biochemical properties of these fractions are discussed in the context of known neurotrophic factors and their effects on normal and lesion‐induced motoneuron death during development. © 1995 John Wiley & Sons, Inc.
Hu protein as an early marker of neuronal phenotypic differentiation by subependymal zone cells of the adult songbird forebrain
Authors: Barami Kaveh , Iversen Kristin , Furneaux Henry , Goldman Steven A. 
Published: January 2005

AbstractThe avian forebrain exhibits neurogenesis in adulthood, with neuronal production from ependymal/subependymal zone (SZ) precursor cells. To follow the commitment of newborn cells to neuronal lineage, we used their expression of the Hu family of neuronal RNA‐binding proteins to identify them before their migration from the SZ. Adult canaries were injected with [3H]thymidine as a marker of DNA replication, sacrificed after varying intervals, stained for Hu, and autoradiographed. We found that Hu was not expressed by premitotic precursor cells, but rather appeared within hours in their neuronal progeny, which did not embark on parenchymal migration until 4 to 7 days later. Hu was expressed by all neurons, but not glia, both in vivo and in vitro, as determined by ultrastructural analysis as well as co‐localization of Hu and cell‐type selective antigens. In addition, co‐staining for Hu and N‐cadherin, whose expression is down‐regulated on neuronal emigration from the SZ, revealed their initial co‐expression by neuronal daughter cells still within the SZ. These results suggest that Hu expression may be used as a very early indicator of neuronal differentiation by SZ cells. Furthermore, the data indicate that in the adult avian brain, neuronal phenotype is established within hours of precursor mitosis, even though the neuronal daughter cells do not initiate parenchymal migration for at least 4 days thereafter, following their down‐regulation of N‐cadherin. © 1995 John Wiley & Sons, Inc.
Distinct adhesive properties of ciliary and choroid neurons from the avian ciliary ganglion
Authors: Porter Brenda E. , Sanes Joshua R. 
Published: January 2005

AbstractThe avian ciliary ganglion (CG) contains two populations of neurons: ciliary neurons, which innervate striated muscle, and choroid neurons, which innervate vascular smooth muscle. We used cell size (ciliary cells are larger) and somatostatin immunoreactivity (which is restricted to choroid cells) as markers to compare the adhesive properties of these two neuronal types. Similar numbers of freshly dissociated embryonic chick ciliary and choroid neurons adhered to laminin (laminin 1) and polylysine, consistent with the fact that each population comprises about half of the ganglionic neurons. In contrast, severalfold more ciliary neurons than choroid neurons adhered to a recombinant fragment of a synapse‐specific basal lamina protein, s‐laminin/laminin β2. Moreover, severalfold more ciliary neurons than choroid neurons adhered to a plastic surface when assayed by the method of Needels et al. in serum‐free medium. Adhesion to s‐laminin and plastic appears to be mediated by different cell surface components, as adhesion to recombinant s‐laminin is inhibited by the tripeptide, LRE, and by Ca2+ions, but not by heparin, whereas adhesion to plastic is LRE and Ca2+ insensitive but heparin sensitive. Both adhesive differences are apparent at embryonic day 8, soon after the ciliary and choroid neurons have begun to form synapses. Thus, two sets of neurons in the CG that send axons through different nerves and innervate different targets also show distinct adhesive behaviors. © 1995 John Wiley & Sons, Inc.
Preparation and characterization of chitosan‐based dispersions
Authors: da Trindade Neto Cypriano G , Fernandes Ana LP , Santos Ana IB , Morais Waldenice A , Navarro Marcos VM , Dantas Tereza NC , Pereira Márcia R , Fonseca José LC 
Published: January 2005

AbstractComplexation of chitosan in aqueous solutions by low molecular weight electrolytes is one of the simplest methods for the preparation of aqueous chitosan dispersions. In this work, the influence of storage time, sulfate concentration, method of preparation and surfactant content on some properties of the resultant chitosan dispersions (turbidity, viscosity and zeta potential) was analyzed. Turbidimetry was adequate to monitor the formation of particles, while viscometry was suitable to monitor changes in the dispersing phase. An analysis of the properties of these systems, mainly in terms of particle–particle and macromolecule–macromolecule interactions was carried out. Copyright © 2004 Society of Chemical Industry
Rheological properties and thermal transitions in millable polyurethane fluoroelastomers
Authors: Turri Stefano , Levi Marinella , Cristini Marco , Sanguineti Aldo 
Published: January 2005

AbstractA series of segmented polyurethane fluoroelastomers based on dimethylol‐terminated perfluoropolyethers (PFPEs), aliphatic diisocyanates and allyl functionality is presented. Depending on the type of diisocyanate monomer used, it was found that quite different prepolymer molecular weights were achieved. Thermal analysis by differential scanning calorimetry showed formation of polyphasic copolymers, either amorphous or semi‐crystalline depending on the monomer structure. Rheological measurements showed that much higher zero‐shear viscosity, a shorter Newtonian plateau and more marked shear thinning behaviour were achieved with polyurethanes based on hexamethylene diisocyanate (HDI) or H12‐MDI monomers. Isothermal viscosity curves were fitted with either three‐ or two‐parameter empirical models, and relaxation times of the structures were estimated at the temperature of 120 °C. Copyright © 2004 Society of Chemical Industry
Preparation and evaluation of polyaniline and polypyrrole modified water‐dispersible conducting nanocomposites of polyacrylonitrile with silica
Authors: Maity Arjun , Biswas Mukul 
Published: January 2005

AbstractWater‐dispersible conducting nanocomposites were prepared by precipitating polyaniline (PANI)/polypyrrole (PPY) in an aqueous suspension of polyacrylonitrile–SiO2 (PAN–SiO2) via K2CrO4–NaAsO2 redox polymerization. Incorporation of PANI and PPY in the composites was confirmed by the FTIR spectrum. Scanning electron microscopic analyses for the PANI–(PAN–SiO2) and PPY–(PAN–SiO2) composites indicated formation of lumpy aggregates with irregular sizes. TEM analyses revealed formation of spherical particles with size ranging between 80 and 150 nm for PANI–(PAN–SiO2) nanocomposite and 75–150 nm for PPY‐(PAN‐SiO2) nanocomposites, respectively. Thermal stabilities of the PANI–(PAN–SiO2) and PPY–(PAN–SiO2) nanocomposites were higher than those of the individual base polymers. Conductivity values of PANI–(PAN–SiO2) nanocomposite (10−3 S cm−1) and PPY–(PAN–SiO2) nanocomposite (10−4 S cm−1) were remarkably improved relative to that for PAN homopolymer (>10−11 S cm−1). Both of these composites produced a permanently stable aqueous suspension when the polymerization was conducted in presence of nanodimensional SiO2 as a particulate dispersant. Copyright © 2004 Society of Chemical Industry
Analysis of the cytosolic proteome of Halobacterium salinarum and its implication for genome annotation
Authors: Tebbe Andreas , Klein Christian , Bisle Birgit , Siedler Frank , Scheffer Beatrix , Garcia‐Rizo Carolina , Wolfertz Jan , Hickmann Volker , Pfeiffer Friedhelm , Oesterhelt Dieter 
Published: January 2005

AbstractThe halophilic archaeon Halobacterium salinarum (strain R1, DSM 671) contains 2784 protein‐coding genes as derived from the genome sequence. The cytosolic proteome containing 2042 proteins was separated by two‐dimensional gel electrophoresis (2‐DE) and systematically analyzed by a semi‐automatic procedure. A reference map was established taking into account the narrow isoelectric point (pI) distribution of halophilic proteins between 3.5 and 5.5. Proteins were separated on overlapping gels covering the essential areas of pI and molecular weight. Every silver‐stained spot was analyzed resulting in 661 identified proteins out of about 1800 different protein spots using matrix‐assisted laser desorption/ionization time of flight mass spectrometry (MALDI‐TOF MS) peptide mass fingerprinting (PMF). There were 94 proteins that were found in multiple spots, indicating post‐translational modification. An additional 141 soluble proteins were identified on 2‐D gels not corresponding to the reference map. Thus about 40% of the cytosolic proteome was identified. In addition to the 2784 protein‐coding genes, the H. salinarum genome contains more than 6000 spurious open reading frames longer than 100 codons. Proteomic information permitted an improvement in genome annotation by validating and correcting gene assignments. The correlation between theoretical pI and gel position is exceedingly good and was used as a tool to improve start codon assignments. The fraction of identified chromosomal proteins was much higher than that of those encoded on the plasmids. In combination with analysis of the GC content this observation permitted an unambiguous identification of an episomal insert of 60 kbp (“AT‐rich island”) in the chromosome, as well as a 70 kbp region from the chromosome that has integrated into one of the megaplasmids and carries a series of essential genes. About 63% of the chromosomally encoded proteins larger than 25 kDa were identified, proving the efficacy of 2‐DE MALDI‐TOF MS PMF technology. The analysis of the integral membrane proteome by tandem mass spectrometric techniques added another 141 identified proteins not identified by the 2‐DE approach (see following paper).
A novel GABAA antagonist [3H]SR 95531: Microscopic analysis of binding in the rat brain and allosteric modulation by several benzodiazepine and barbiturate receptor ligands
Authors: McCabe R. Tyler , Wamsley James K. , Yezuita James P. , Olsen Richard W. 
Published: January 2005

AbstractRecent reports have demonstrated that the synthetic gamma‐aminobutyric acid (GABA)‐derivative, SR 95531 [2‐(3′‐carbethoxy‐2′‐propyl)‐3‐amino‐6‐paramethoxy‐phenyl‐pyridazini‐um bromide], possesses selective GABAA sites, this agent has been used to identify GABAA receptors. In the present investigation, we studied the binding of [3H]SR 95531 to tissue sections of rat brain using microscopic analysis of receptor localization. The appropriate binding conditions for defining GABAA receptors with this radioligand were obtained by determining the dissociation and association kinetics, and performing saturation and displacement studies. Using membrane preparations from whole rat brain (or brain regions representing cortex, striatum, hippocampus, midbrainthalamus, medulla‐pons and cerebellum), saturation and displacement studies were analyzed, and allosteric modulation of [3H]SR 95531 binding was examined by including several benzodiazepine and barbiturate receptor ligands in the incubation media. To assess the stereoselective properties of [3H]SR 95531 binding in rat membranes, numerous barbiturates were added during the incubation. The binding of [3H]SR 95531 was demonstrated to be saturable, specific and to bind with relatively high affinity to low‐affinity GABAA sites. Scatchard analysis performed on saturation data of binding to tissue sections showed a dissociation constant (KD) of 42.4 nM and a maximum number of binding sites (Bmax) of 105.8 fmol/mg tissue. Microscopic analysis showed that intermediate to high densities of [3H]SR 95531 binding occurred in brain regions containing intermediate to high densities of low‐affinity GABAA sites. Results from competition studies demonstrated that [3H]SR 95531 is displaceable by GABAA agents and displaced preferentially by GABAA antagonists. Scatchard analysis of saturation experiments from membrane preparations indicated that the KD and Bmax from the centrifugation assay was 53.0 nM and 4.26 pmol/mg protein, respectively. Using the filtration assay, binding to membranes yielded a KD value of 45.6 nM and a Bmax of 0.77 pmol/mg protein. The allosteric modulation data demonstrated that numerous benzodiazepine and barbiturate agents inhibited [3H]SR 95531 binding and this varied according to brain region. Several barbiturates included in the incubation media exhibited a stereoselective inhibition of [3H]SR 95531 binding to whole rat brain membranes. In summary, [3H]SR 95531 identifies the antagonist conformation of GABAA receptors in the rat brain and binds preferentially to the low‐affinity site. The data collected in the present study show that [3H]SR 95531 is an excellent probe to recognize the GABAA receptor subtype and allows for the identification of the interactions of subcomponents of the macromolecular GABA receptor complex.
(D‐Phe12) bombesin and substance P analogues function as central bombesin receptor antagonists
Authors: Merali Zul , Merchant Carol A. , Crawley Jacqueline N. , Coy David H. , Heinz‐Erian Peter , Jensen Robert T. , Moody Terry W. 
Published: January 2005

AbstractThe potency of synthetic bombesin (BN) analogues with D‐Phe12 substitutions and substance P analogues was investigated in the rat CNS. (D‐Phe12, Leu14)BN, (D‐Phe12)BN and (Tyr4,D‐Phe12)BN inhibited binding to rat brain slices with IC50 values of approximately 2 μM. Similarly, spantide inhibited binding to rat brain slices with an IC50 value of 1.5 μM. Spantide inhibited specific (125I‐Tyr4)BN binding as a result of decreased rate of association, whereas the rate of dissociation was unaffected. Neither the (D‐Phe12)BN analogues nor the substance P analogues inhibited specific binding of 125I‐VIP to rat brain slices. Central administration of BN (0.5 μg) induced grooming and suppressed feeding and resting. (Tyr4, D‐Phe12)BN (5 μg) antagonized the behavioral effects of BN. Although spantide (2 μg) also antagonized many of the BN effects, it had intrinsic effects and hence the behavioral antagonism was not specific. These data suggest that although both (D‐Phe12)BN and substance P analogues may function as central BN receptor antagonists, the (D‐Phe12)BN analogues may be functionally the more useful class of antagonists.
Ultrastructure of stratum lacunosum moleculare interneurons of hippocampal CA1 region
Authors: Kunkel Dennis D. , Lacaille Jean‐Claude , Schwartzkroin Philip A. 
Published: January 2005

AbstractIntracellular recordings were obtained from nonpyramidal neurons (interneurons) in stratum lacunosum‐moleculare (L‐M) of the CA1 region of guinea pig hippocampal slices. These interneurons had response characteristics that distinguish them from pyramidal cells and other interneuron types: the L‐M neurons had relatively broad action potentials with large spike afterhyperpolarizations, high input resistance and little spike‐firing adaptation, and low spontaneous activity. Lucifer Yellow (LY) and horseradish peroxidase (HRP) were injected intracellularly into physiologically identified L‐M interneurons, and the cells were characterized morphologically using light and electron microscopy.L‐M somata were fusiform‐shaped (15 × 25 μm), had multiple processes, and were located at the border between stratum (str.) lacunosum‐moleculare and str. radiatum. L‐M dendrites coursed through str. lacunosum‐moleculare and projected into str. radiatum. L‐M axons made axodendritic synaptic contacts primarily in str. lacunosum‐moleculare and str. radiatum, but also in str. moleculare of the dentate gyrus. These axodendritic synaptic contacts were made onto spiny dendritic processes (presumably pyramidal cell and granule cell dendrites) and onto aspinous dendrites (presumably interneuron dendrites), and appeared to be of the symmetric type (type 2), characteristic of inhibitory synapses.In separate groups of animals, selective lesions were made of afferents to the CA1 and dentate regions of hippocampus, and subsequent degeneration of contacts onto L‐M interneuron somata and dendrites was examined at the ultrastructural level. Fibers originating from contralateral and ipsilateral CA3 region, and from ipsilateral entorhinal cortex, were found to make synaptic contact onto presumed L‐M interneurons. Degenerating terminals appeared to be of the asymmetric type (type 1), characteristic of excitatory synapses. These morphological data are consistent with electrophysiological results showing that L‐M interneurons can mediate feedforward inhibition of CA1 pyramidal cells.
Invited review: Role of receptor regulation in opioid tolerance mechanisms
Authors: Loh Horace H. , Tao Pao‐Luh , Smith Andrew P. 
Published: January 2005

AbstractThe molecular basis of opioid tolerance/dependence has long eluded researchers, but recent advances in receptor regulation have suggested a useful conceptual approach to the problem. In NG108‐15 neuroblastoma × glioma hybrid (NG) cells, opioid agonists inhibit adenylate cyclase in a dose‐dependent, naloxone‐antagonizable fashion. Chronic treatment with opioid agonists results in a series of molecular processes that, in a tolerance‐like fashion, counteract this inhibition. These processes include desensitization and down‐regulation of receptors and an increase in adenylate cyclase activity.Opioid inhibition of adenylate cyclase and opioid receptor down‐regulation also have been observed in the brain. However, most studies have found that the receptors coupled to adenylate cyclase are not of the mu type, which a thought to be the primary mediators of opioid analgesia. Down‐regulation has been observed for both mu and delta opioid receptors in the brain. However, in most case, the time course of down‐regulation is not correlated with that for tolerance development, and chronic morphine treatment does not result in down‐regulation. Thus, opioid receptors in the brain, like those in NG cells, are subject to dynamic regulation by agonists, which probably has an important role in their function. However, it remains to be established that opioid receptor regulation is the basis of opioid tolerance and dependence.