P21

Distribution by Scientific Domains

Kinds of P21

  • group p21
  • groups p21
  • monoclinic p21
  • monoclinic space group p21
  • primitive monoclinic space group p21
  • space group p21

  • Terms modified by P21

  • p21 space group

  • Selected Abstracts


    Synthesis, characterization and impedance spectroscopy of the new material [(CH3) (C6H5) 3P] 2CoBr4: a member of the A2BX4 family

    CRYSTAL RESEARCH AND TECHNOLOGY, Issue 5 2008
    M. F. Mostafa
    Abstract The crystal structure of bis-(methyltriphenylphosphonium) tetrabromocobaltate (II), [(C19H18P)2 CoBr4] is determined: Mr = 933.203, monoclinic, P21, a = 9. 6977 (3) , b = 12.5547 (4), c = 16.4503 (6), , = 105.603 (2), V = 1929.04 (11)3, Z = 2, Dx = 1.607 Mg m -3, T = 298 K. Differential thermal analysis at high temperatures shows three endothermic peaks characterizing four phases, with onset temperatures at T1= 3132 K, T2 = 3204 K and T3= 3601 K. The structural instability detected via the temperature dependence of permittivity at T1 is ascribed to order-disorder transition associated with cation dipole reorientation. Permittivity and ac conductivity studies as a function of temperature (295 K-375 K) and frequency (0.11 kHz < f <100 kHz) are presented. The results indicate the importance of the cation size and shape on the phase transitions in the system. Bulk conductivity behavior is thermally activated. The associated activation energies are in the range 2.9 to 1.0 eV depending on the temperature regime. Two contributions to the ac conductivity, one dominating at low temperatures and high frequencies which are characterized by superlinear frequency exponent and the second dominates at high temperatures characterized by a sublinear frequency exponent. The behavior is interpreted in terms of the jump relaxation model. ( 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Synthesis and crystal structure investigation of pyridine-2-(3,-mercaptopropanoic acid)- N -oxide

    CRYSTAL RESEARCH AND TECHNOLOGY, Issue 10 2007
    R. Ramasubramanian
    Abstract Pyridine-2-(3,-mercaptopropanoic acid)- N -oxide (I), is a higher homologue of 1-oxopyridinium-2-thioacetic acid (II) [1]. It crystallizes in monoclinic space group P21 with a = 9.2168(2) , b = 4.1423(2) , c = 11.3904(4) , , = 98.65(2), V = 429.93(3) 3 and Z = 2. The least-squares refinement gave residual index R = 0.024 for 1070 observed reflections. The introduction of an additional methylene group in (II) causes a flip in the carboxylic acid group of (I) that facilitates the molecules to align infinite antiparallel chains through strong C,HO interactions. The molecules are interlinked by O,HO hydrogen bonding across the chains and forming an infinite screw chain along y-direction. The molecular packing is stabilized by O,HO and C,HO hydrogen bonding and ,-, electron interactions. This is an important facet of the crystal packing. ( 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Single cause, polymorphic neuronal migration disorders: an animal model

    DEVELOPMENTAL MEDICINE & CHILD NEUROLOGY, Issue 10 2000
    Glenn D Rosen PhD
    Injury to the developing cortical plate can result in a variety of neuronal migration disorders. The results are reported of experimental research aimed at determining whether these different types of neocortical malformations are the consequence of comparable injury of varying intensity. Freezing probes were placed on the skulls of 44 newborn rats (age equivalent to 4 to 5 months of gestation in humans) and induced either one or two freezing injuries of durations ranging from 2 to 20 seconds. A variety of cortical malformations including minor laminar dysplasias, molecular layer ectopias, microgyria, and porencephalic cysts were seen in the brains of these animals when they were examined on postnatal day (P)2, P21, and P60. The severity of the malformation was directly related to the strength (number of hits and duration) of the freezing injury. These results suggest that a single etiologic event of varying severity during neuronal migration to the neocortex can induce widely disparate malformations of the cortex. [source]


    Study by transmission and scanning electron microscopy of the morphogenesis of three types of lingual papillae in the albino rat (Rattus rattus)

    ACTA ZOOLOGICA, Issue 3 2010
    Ahlam Mostafa El-Bakry
    Abstract El-Bakry, A.M. 2010. Study by transmission and scanning electron microscopy of the morphogenesis of three types of lingual papillae in the albino rat (Rattus rattus).,Acta Zoologica (Stockholm) 91: 267,278 Tongues were removed from albino rat foetus on days 12 (E12) and 16 (E16) of gestation and from newborns (P0) and from juvenile rats on days 7 (P7), 14 (P14) and 21 (P21) postnatally for investigation by light, scanning, and transmission electron microscopy. Significant changes appeared during the morphogenesis of the papillae. At E12, two rows of rudiments of fungiform papillae were extended bilaterally on the anterior half of the tongue. At E16, the rudiments of fungiform papillae were regularly arranged in a lattice-like pattern. A rudiment of circumvallate papillae could be recognized. No rudiment of filiform papillae was visible. No evidence of keratinization was recognizable. At P0, rudiments of filiform papillae were visible but had a more rounded appearance, with keratinization. The fungiform and circumvallate papillae were large and their outlines were somewhat irregular as that found in the adult rat. At P7, the filiform papillae were large and slender. The fungiform papillae became large and the shape of circumvallate papillae was almost similar to that observed in the adult. At P14 and P21, the shape and structure of the three types of papillae were irregular as those found in the adult. In conclusion, the rudiments of the fungiform and circumvallate papillae were visible earlier than those of the filiform papillae. The morphogenesis of filiform papillae advanced in a parallel manner with the keratinization of the lingual epithelium, in the period from just before birth to a few weeks after birth. [source]


    Antiepileptogenic and antiictogenic effects of retigabine under conditions of rapid kindling: An ontogenic study

    EPILEPSIA, Issue 10 2008
    Andry Mazarati
    Summary Purpose:, To examine antiepileptogenic and antiictogenic potential of retigabine (RTG) under conditions of rapid kindling epileptogenesis during different stages of development. Methods:, The experiments were performed in postnatal day 14 (P14), P21, and P35 male Wistar rats. After stereotaxic implantation of hippocampal stimulating and recording electrodes, the effects of RTG on baseline afterdischarge (AD) properties were studied. Next, the animals underwent rapid kindling (sixty 10 s trains, bipolar 20 Hz square wave pulses delivered every 5 min). The progression of seizures (kindling acquisition), and responses to test stimulations after kindling (retention) were compared between RTG and vehicle-treated rats. Additionally, the effects of RTG on the severity of seizures in previously kindled animals were examined. Results:, When administered intraperitoneally in doses that induced only mild, or no motor deficits, RTG significantly dampened brain excitability, evident as the increase of AD threshold and shortening of AD duration. During kindling, RTG delayed the development of focal seizures in P14 rats, and prevented the occurrence of full limbic seizures at all three ages. At P14 and P21, but not at P35, pretreatment with RTG prevented the establishment of kindling-induced enhanced seizure susceptibility. Administration of RTG to kindled animals decreased the severity of seizures induced by test stimulation. The effect was most prominent at P14. Discussion:, RTG exerted both antiepileptogenic and antiictogenic effects under conditions of rapid kindling model. These effects were apparent during postneonatal, early childhood, and adolescent stages of development. [source]


    Role of Nitric Oxide in Pentylenetetrazol-Induced Seizures: Age-Dependent Effects in the Immature Rat

    EPILEPSIA, Issue 4 2000
    Anne Pereira de Vasconcelos
    Summary: Purpose: Seizure susceptibility and consequences are highly age dependent. To understand the pathophysiologic mechanisms involved in seizures and their consequences during development, we investigated the role of nitric oxide (NO) in severe pentylenetetrazol (PTZ)-induced seizures in immature rats. Methods: Four cortical electrodes were implanted in 10-day-old (P10) and 21-day-old (P21) rats, and seizures were induced on the following day by repetitive injections of subconvulsive doses of PTZ. The effects of NG -nitro- l -arginine methyl ester (l -NAME; 10 mg/kg) and 7-nitroindazole (7NI; 40 mg/kg), two NO synthase (NOS) inhibitors, and l -arginine (l -arg; 300 mg/kg), the NOS substrate, were evaluated regarding the mean PTZ dose, seizure type and duration, and mortality rate. Results: At P10, the postseizure mortality rate increased from 18,29% for the rats receiving PTZ only to 100% and 89% for the rats receiving l -NAME and 7NI, respectively; whereas l -arg had no effect. Conversely, at P21, NOS inhibitors did not affect the 82,89% mortality rate induced by PTZ alone, whereas l -arg decreased the mortality rate to 29%. In addition, all NO-related drugs increased the duration of ictal activity at P10, whereas at P21, L -arg and L -NAME affected the first seizure type, producing clonic seizures with L -arg and tonic seizures with L -NAME. Conclusions: The relative natural protection of very immature rats (P10) against PTZ-induced deaths could be linked to a high availability of L -arg and, hence, endogenous NO. At P21, the modulation of seizure type by NO-related compounds may be related to the maturation of the brain circuitry, in particular the forebrain, which is involved in the expression of clonic seizures. [source]


    Minocycline attenuates hypoxia,ischemia-induced neurological dysfunction and brain injury in the juvenile rat

    EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 2 2006
    Lir-Wan Fan
    Abstract To investigate whether minocycline provides long-lasting protection against neonatal hypoxia,ischemia-induced brain injury and neurobehavioral deficits, minocycline was administered intraperitoneally in postnatal day 4 Sprague,Dawley rats subjected to bilateral carotid artery occlusion followed by exposure to hypoxia (8% oxygen for 15 min). Brain injury and myelination were examined on postnatal day 21 (P21) and tests for neurobehavioral toxicity were performed from P3 to P21. Hypoxic,ischemic insults resulted in severe white matter injury, enlarged ventricles, deficits in the hippocampus, reduction in numbers of mature oligodendrocytes and tyrosine hydroxylase-positive neurons, damage to axons and dendrites, and impaired myelination, as indicated by the decrease in myelin basic protein immunostaining in the P21 rat brain. Hypoxic,ischemic insult also significantly affected physical development (body weight gain and eye opening) and neurobehavioral performance, including sensorimotor and locomotor function, anxiety and cognitive ability in the P21 rat. Treatments with minocycline significantly attenuated the hypoxia,ischemia-induced brain injury and improved neurobehavioral performance. The protection of minocycline was associated with its ability to reduce microglial activation. The present results show that minocycline has long-lasting protective effects in the neonatal rat brain in terms of both hypoxia,ischemia-induced brain injury and the associated neurological dysfunction. [source]


    A postnatal switch in GABAergic control of spinal cutaneous reflexes

    EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 1 2006
    Gareth Hathway
    Abstract GABAergic signalling exerts powerful inhibitory control over spinal tactile and nociceptive processing, but during development GABA can be depolarizing and the functional consequences of this upon neonatal pain processing is unknown. Here we show a postnatal switch in tonic GABAA receptor (GABAAR) modulation of cutaneous tactile and nociceptive reflexes from excitation to inhibition, but only in the intact spinal cord. Neonatal and 21-day-old (P21) rats were intrathecally treated with one of the GABAAR antagonists bicuculline and gabazine, with both compounds dose-dependently decreasing hindpaw mechanical and thermal withdrawal thresholds in P21 rats but increasing them in P3 neonates. Intrathecal gabazine also produced an increase in the cutaneous evoked electromyography (EMG) response of the biceps femoris in P21 rates but lowering the response in neonates. Injections of 3H-gabazine in the L4,L5 region at P3 confirmed that gabazine binding was restricted to the lumbar spinal cord. Spinalization of P3 neonates at the upper thoracic level prior to drug application reversed the behavioural and EMG responses to GABA antagonists so that they resembled those of P21 rats. The effects of spinalization were consistent with gabazine facilitation of ventral root potentials observed in isolated neonatal spinal cord. These data show a marked postnatal developmental switch in GABAergic control of neonatal nociception that is mediated by supraspinal structures and illustrate the importance of studying developmental circuits in the intact nervous system. [source]


    GluR- and TrkB-mediated maturation of GABAA receptor function during the period of eye opening

    EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 2 2005
    Christian Henneberger
    Abstract Synapse maturation includes the shortening of postsynaptic currents, due to changes in the subunit composition of respective transmitter receptors. Patch clamp experiments revealed that GABAergic inhibitory postsynaptic currents (ISPCs) of superior colliculus neurons significantly shorten from postnatal day (P)1 to P21. The change started after P6 and was steepest between P12 and P15, i.e. around eye opening. It was accompanied by enhanced sensitivity to zolpidem and increased expression of GABAAR ,1 mRNA, whereas the level of ,3 mRNA decreased. This result is consistent with the hypothesis that the IPSC kinetics of developing collicular neurons is determined by the level of ,1/,3. As ,1/,3 peaked when N -methyl-D-aspartate receptor (NMDAR)-mediated synaptic currents reached their maximum (P12) it was asked whether NMDAR activity can shape the kinetics of GABAergic IPSCs. Cultured collicular neurons were treated with NMDA or NMDAR block, and it was found that the former resulted in faster and the latter in slower IPSC decay. Group I mGluR blockade had no effect. Experiments with bdnf,/, mice revealed that, with some delay, the increase of ,1/,3 mRNA also occurred in the chronic absence of brain-derived neurotrophic factor (BDNF) and, again, this was accompanied by the shortening of IPSCs. In addition, there was an age-dependent depression of IPSC amplitudes by endogenous BDNF, which might reflect the developmental increase in the expression of GABAAR ,2L, as opposed to ,2S. Together, these experiments suggest that the GABAAR , subunit switch and the associated change in the IPSC kinetics were specifically controlled by NMDAR activity and independent on the signalling through group I mGluRs or TrkB. [source]


    Quantitative effects produced by modifications of neuronal activity on the size of GABAA receptor clusters in hippocampal slice cultures

    EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 2 2004
    Serge Marty
    Abstract The number and strength of GABAergic synapses needs to be precisely adjusted for adequate control of excitatory activity. We investigated to what extent the size of GABAA receptor clusters at inhibitory synapses is under the regulation of neuronal activity. Slices from P7 rat hippocampus were cultured for 13 days in the presence of bicuculline or 4-aminopyridine (4-AP) to increase neuronal activity, or DNQX to decrease activity. The changes provoked by these treatments on clusters immunoreactive for the ,1 and ,2 subunits of the GABAA receptor or gephyrin were quantitatively evaluated. While an increase in activity augmented the density of these clusters, a decrease in activity provoked, in contrast, a decrease in their density. An inverse regulation was observed for the size of individual clusters. Bicuculline and 4-AP decreased whilst DNQX increased the mean size of the clusters. When the pharmacological treatments were applied for 2 days instead of 2 weeks, no effects on the size of the clusters were observed. The variations in the mean size of individual clusters were mainly due to changes in the number of small clusters. Finally, a regulation of the size of GABAA receptor clusters occurred during development in vivo, with a decrease of the mean size of the clusters between P7 and P21. This physiological change was also the result of an increase in the number of small clusters. These results indicate that neuronal activity regulates the mean size of GABAA receptor- and gephyrin-immunoreactive clusters by modifying specifically the number of synapses with small clusters of receptors. [source]


    Postnatal maturation of Na+, K+, 2Cl, cotransporter expression and inhibitory synaptogenesis in the rat hippocampus: an immunocytochemical analysis

    EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 2 2002
    Serge Marty
    Abstract GABA, a major inhibitory neurotransmitter, depolarizes hippocampal pyramidal neurons during the first postnatal week. These depolarizations result from an efflux of Cl, through GABAA -gated anion channels. The outward Cl, gradient that provides the driving force for Cl, efflux might be generated and maintained by the Na+, K+, 2Cl, cotransporter (NKCC) that keeps intracellular Cl, concentration above electrochemical equilibrium. The developmental pattern of expression of the cotransporter in the hippocampus is not known. We studied the postnatal distribution pattern of NKCC in the hippocampus using a monoclonal antibody (T4) against a conserved epitope in the C-terminus of the cotransporter molecule. We also examined the temporal relationships between the developmental pattern of NKCC expression and the formation of perisomatic GABAergic synapses. This study was aimed at determining, with antivesicular inhibitory amino acid transporter (VIAAT) antibodies, whether perisomatic GABAergic synapses are formed preferentially at the time when GABA is depolarizing. During the first postnatal week, NKCC immunolabelling was restricted to cell bodies in the pyramidal cell layer and in the strata oriens and radiatum. In contrast, at postnatal day 21 (P21) and in adult animals little or no labelling occurred in cell bodies; instead, a prominent dendritic labelling appeared in both pyramidal and nonpyramidal neurons. The ultrastructural immunogold study in P21 rat hippocampi corroborated the light-microscopy results. In addition, this study revealed that a portion of the silver-intensified colloidal gold particles were located on neuronal plasmalemma, as expected for a functional cotransporter. The formation of inhibitory synapses on perikarya of the pyramidal cell layer was a late process. The density of VIAAT-immunoreactive puncta in the stratum pyramidale at P21 reached four times the P7 value in CA3, and six times the P7 value in CA1. Electron microscopy revealed that the number of synapses per neuronal perikaryal profile in the stratum pyramidale of the CA3 area at P21 was three times higher than at P7, even if a concomitant 20% increase in the area of these neuronal perikaryal profiles occurred. It is concluded that, in hippocampal pyramidal cells, there is a developmental shift in the NKCC localization from a predominantly somatic to a predominantly dendritic location. The presence of NKCC during the first postnatal week is consistent with the hypothesis that this transporter might be involved in the depolarizing effects of GABA. The depolarizing effects of GABA may not be required for the establishment of the majority of GABAergic synapses in the stratum pyramidale, because their number increases after the first postnatal week, when GABA action becomes hyperpolarizing. [source]


    Hippocampal granule neuron production and population size are regulated by levels of bFGF

    EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 1 2002
    Yinghong Cheng
    Abstract Numerous studies of the proliferative effects of basic fibroblast growth factor (bFGF) in culture, including neonatal and adult hippocampal precursors, suggest that the factor plays a ubiquitous and life-long role in neurogenesis. In contrast, in vivo, bFGF is devoid of effects on neurons in mature hippocampus, raising the possibility that bFGF exhibits developmental stage-specific activity in the complex animal environment. To define neurogenetic effects in the newborn, a single subcutaneous injection of bFGF (20 ng/gm) was administered to postnatal day 1 (P1) rats, and hippocampal DNA content was quantified: bFGF elicited an increase in total DNA throughout adulthood, by 48% at P4, 25% at P22, and 17% at P180, suggesting that bFGF increases hippocampal cell number. To define mechanisms, bromodeoxyuridine (BrdU) was injected at P1 and mitotically labelled cells were assessed at P22: there was a twofold increase in BrdU-positive cells in the dentate granule cell layer (GCL), indicating that bFGF enhanced the generation of neurons, or neuronogenesis, from a cohort of precursors. Moreover, enhanced mitosis and survival led to a 33% increase in absolute GCL neuron number, suggesting that neuron production depends on environmental levels of bFGF. To evaluate this possibility, bFGF-knockout mice were analyzed: hippocampal DNA content was decreased at all ages examined (P3, ,42%; P21, ,28%; P360, ,18%), and total GCL neuron and glial fibrillary acidic protein (GFAP)-positive cell number were decreased by 30%, indicating that bFGF is necessary for normal hippocampal neurogenesis. We conclude that environmental levels of bFGF regulate neonatal hippocampal neurogenesis. As adult hippocampal neuronogenesis was unresponsive to bFGF manipulation in our previous study [Wagner, J.P., Black, I.B. & DiCicco-Bloom, E. (1999) J. Neurosci., 19, 6006], these observations suggest distinct, stage-specific roles of bFGF in the dentate gyrus granule cell lineage. [source]


    New Organic Nonlinear Optical Polyene Crystals and Their Unusual Phase Transitions,

    ADVANCED FUNCTIONAL MATERIALS, Issue 11 2007
    O-P. Kwon
    Abstract A series of new nonlinear optical chromophores based on configurationally locked polyenes (CLPs) with chiral pyrrolidine donors are synthesized. All CLP derivatives exhibit high thermal stability with decomposition temperatures Td at least > ,270,C. Acentric single crystals of enantiopure D - and L -prolinol-based chromophores with a monoclinic space group P21 exhibit a macroscopic second-order nonlinearity that is twice as large than that of analogous dimethylamino-based crystal. This is attributed to a strong hydrogen-bonded polar polymer-like chain built by these molecules, which is aligned along the polar crystallographic b -axis. Five ,-phase CLP crystals with different donors grown from solution exhibit a reversible or irreversible thermally induced structural phase transition to a ,-phase. These phase transitions are unusual, changing the crystal symmetry from higher to lower at increasing temperatures, for example, from centrosymmetric to non-centrosymmetric, enhancing their macroscopic second-order nonlinear optical properties. [source]


    Guest-Induced Chirality in the Ferrimagnetic Nanoporous Diamond Framework Mn3(HCOO)6,

    ADVANCED FUNCTIONAL MATERIALS, Issue 4 2007
    B. Zhang
    Abstract Chiral magnets are obtained by inclusion of chiral guest molecules into the channels of an achiral nanoporous ferrimagnet consisting of the Mn3(HCOO)6 (1) framework. Insertion of the R or the S enantiomer of 2-chloropropan-1-ol (CH3C*HClCH2OH) in the chiral pores of the previously emptied framework (space group P21/c) results in the two corresponding chiral solids (1R and 1S, space group P21), while insertion of a racemic mixture of the two enantiomers retains the achirality of the host for the meso solid (1RS, space group P21/c). The R guest is ordered in the M channels while the S guest is ordered in the P channels. In contrast, the R guests in the P channels and the S guests in the M channels are disordered on two crystallographic orientations. For the racemic mixture of the two enantiomers in 1RS, random disorder of guests in both channels is observed. Thus, the localization of the guest molecule depends on the nature of the surface to recognize the guest of a particular chirality. The guest inclusion compounds are thermally stable. The 1R and 1S compounds are optically active. All the compounds adopt a ferrimagnetic ground state. Compared to the host framework of 1 without guest, the Curie temperature decreases for both 1R and 1S but increases for 1RS. The additional interactions between the framework and the inserted guest alcohols strengthen the lattice via hydrogen bonds and other electrostatic forces, and it might account for the significant lowering of the lattice contribution as well as the magnetic component to the specific heat capacity upon guest loading. [source]


    Structures of Four Crystal Forms of Decaplanin

    HELVETICA CHIMICA ACTA, Issue 5 2003
    Christopher Lehmann
    The glycopeptide antibiotic decaplanin (1; formerly known as MM 47761 and M86-1410) crystallizes in two P21 and two P6122 crystal forms, each with four monomers in the asymmetric unit, with solvent contents varying from 48 to 69%. Although with ca. 600 unique atoms, the structures are larger than typical small molecules, one was solved by direct methods. The other three were solved by typical macromolecular methods: single-wavelength anomalous diffraction (SAD) of the Cl-atoms present naturally in the structure, multiple-wavelength anomalous diffraction (MAD) at the Br absorption edge for a crystal soaked in NaBr solution, and molecular replacement. There is evidence of appreciable radiation damage with loss of 20,30% of the covalent and ionic halogens affecting the synchrotron datasets that may even have unintentionally facilitated the MAD structure solution. The structures contain the dimer units typical of antibiotics related to vancomycin, but, in addition, there are a variety of further intermolecular interactions responsible for the polymorphy leading to intertwined 61 -helices in two of the crystal forms. Except for the sugars and some sidechains, the conformations of the 16 independent monomers are very similar. [source]


    Developmental expression of potassium-channel subunit Kv3.2 within subpopulations of mouse hippocampal inhibitory interneurons,

    HIPPOCAMPUS, Issue 2 2002
    Emily Phillips Tansey
    Abstract The developmental expression of the voltage-gated potassium channel subunit, Kv3.2, and its localization within specific mouse hippocampal inhibitory interneuron populations were determined using immunoblotting and immunohistochemical techniques. Using immunoblotting techniques, the Kv3.2 protein was weakly detected at postnatal age day 7 (P7), and full expression was attained at P21 in tissue extracts from homogenized hippocampal preparations. A similar developmental profile was observed using immunohistochemical techniques in hippocampal tissue sections. Kv3.2 protein expression was clustered on the somata and proximal dendrites of presumed inhibitory interneurons. Using double immunofluorescence, Kv3.2 subunit expression was detected on subpopulations of GABAergic inhibitory interneurons. Kv3.2 was detected in ,100% of parvalbumin-positive interneurons, 86% of interneurons expressing nitric oxide synthase, and ,50% of somatostatin-immunoreactive cells. Kv3.2 expression was absent from both calbindin- and calretinin-containing interneurons. Using immunoprecipitation, we further demonstrate that Kv3.2 and its related subunit Kv3.1b are coexpressed within the same protein complexes in the hippocampus. These data demonstrate that potassium channel subunit Kv3.2 expression is developmentally regulated in a specific set of interneurons. The vast majority of these interneuron subpopulations possess a "fast-spiking" phenotype, consistent with a role for currents through Kv3.2 containing channels in determining action potential kinetics in these cells. Hippocampus 2002;12:137,148. Published 2002 Wiley-Liss, Inc. [source]


    Sequential loss of cell cycle checkpoint control contributes to malignant transformation of murine embryonic fibroblasts induced by 20-methylcholanthrene

    JOURNAL OF CELLULAR PHYSIOLOGY, Issue 1 2010
    Sudeshna Mukherjee
    Definitive information about the number and nature of discrete steps of tumorigenesis is enigmatic. To understand the multistep nature of carcinogenesis, an in vitro model of 20-Methylcholanthrene-treated primary fibroblast cells CNCI-PM-20, from 20-day old Swiss mouse embryo was used. Visible neoplastic changes with distinct morphological variations along with specific chromosomal aberrations like Robertsonian metacentrics, double and single-minute chromosomes and aneuploidy were observed from Passage-20 onwards. The cell cycle profile showed gradual increase in G2/M population till P-32, followed by evasion of block from P-36 onwards. Gradual increase in expression of C-myc, CyclinD1 and a decrease in expression of P21 was observed from P-20 onwards. CDC25A expression was significantly increased at P-27 and remained more or less constant in subsequent passages. Additionally, an increased P16 and P53 expression were seen at P-20 followed by their significant down-regulation at P-32. An increased level of phosphorylated retinoblastoma (ppRb) was observed from P-27, probably responsible for a compromised G1/S checkpoint. The inactivation of p21 and p16 might be due to their promoter hyper-methylation as suggested through de-methylation experiment by 5-aza-deoxycytidine at P-42. G2/M checkpoint abrogation was marked by gradual increase in expression of CyclinB1 and Cdc20, and a significant increase of Mad2 at P-20. Interestingly, increased expression of phospho-ATM, ATR and phospho-Chk1 were also seen at P-20 followed by their down-regulation at subsequent passages, indicating a perturbation of DNA damage response pathway at early passages. Our findings therefore dramatize the multiple genetic events that can cooperate to promote tumorigenesis. J. Cell. Physiol. 224:49,58, 2010 2010 Wiley-Liss, Inc. [source]


    Conformational polymorphism in aripiprazole: Preparation, stability and structure of five modifications

    JOURNAL OF PHARMACEUTICAL SCIENCES, Issue 6 2009
    Doris E. Braun
    Abstract Five phase-pure modifications of the antipsychotic drug aripiprazole were prepared and characterized by thermal analysis, vibrational spectroscopy and X-ray diffractometry. All modifications can be produced from solvents, form I additionally by heating of form X to ,120C (solid,solid transformation) and form III by crystallization from the melt. Thermodynamic relationships between the polymorphs were evaluated on the basis of thermochemical data and visualized in a semi-schematic energy/temperature diagram. At least six of the ten polymorphic pairs are enantiotropically and two monotropically related. Form X is the thermodynamically stable modification at 20C, form II is stable in a window from about 62,77C, and form I above 80C (high-temperature form). Forms III and IV are triclinic (), I and X are monoclinic (P21) and form II orthorhombic (Pna21). Each polymorph exhibits a distinct molecular conformation, and there are two fundamental N,HO hydrogen bond synthons (catemers and dimers). Hirshfeld surface analysis was employed to display differences in intermolecular short contacts. A high kinetic stability was observed for three metastable polymorphs which can be categorized as suitable candidates for the development of solid dosage forms. 2008 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 98:2010,2026, 2009 [source]


    Zinc Vanadates in Vanadium Oxide-Doped Zinc Oxide Varistors

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2001
    Huey-Hoon Hng
    Convergent-beam electron diffraction has been used to determine the space groups of ,- and ,-Zn3(VO4)2 particles in vanadium oxide-doped zinc oxide varistors. The crystal structure of ,-Zn3(VO4)2 has been determined to be monoclinic with space group P21 and lattice parameters of a= 9.80 , b= 8.34 , c= 10.27 , and ,= 115.8, whereas that of ,-Zn3(VO4)2 is monoclinic with space group Cm and a= 10.40 , b= 8.59 , c= 9.44 , and ,= 98.8. Energy-dispersive X-ray microanalysis of these two phases shows significant deviations from their expected stoichiometry. It is apparent that the ,-phase is, in fact, the metastable Zn4V2O9 phase, whereas the ,-phase either is a new oxide that consists of zinc, vanadium, and manganese or, more likely, is a zinc vanadate phase with a Zn:V atomic ratio of 1:1 that has the ability to go into solid solution with manganese. [source]


    Identification of a cellular protein specifically interacting with the precursor of the hepatitis B e antigen

    JOURNAL OF VIRAL HEPATITIS, Issue 3 2001
    S. Salhi
    In hepatitis B virus (HBV) the precore gene encodes a protein from which derives P22, the precursor of the mature secreted hepatitis B virus e antigen (HBeAg). Circumstantial evidences suggest that HBeAg and/or its precursor P22 are important for establishing persistent infection. Although P22 is essentially present in the secretory pathway, a substantial fraction has been found in the cytosol. In order to get new insights into the biological function of P22, we looked for cellular proteins which could strongly associate with this protein. Using immunoprecipitation studies on human cell extracts, we found that a non-secreted cellular protein of about 32 kDa (P32) bound with a high specificity to P22. P32 associated neither with HBeAg nor with the viral core protein P21 which exhibits the same amino acids sequence as P22 but is N-terminally shorter by 10 residues. We also demonstrated that this interaction depended on the presence of the P22 C-terminal domain. Our data argues for a potential biological function of P22. [source]


    New Biodegradable Amphiphilic Block Copolymers of , -Caprolactone and , -Valerolactone Catalyzed by Novel Aluminum Metal Complexes

    MACROMOLECULAR BIOSCIENCE, Issue 9 2005
    Jing Yang
    Abstract Summary: In our previous study [J. Yang, L. Jia, L. Yin, J. Yu, Z. Shi, Q. Fang, A. Cao, Macromol. Biosci.2004, 4, 1092.], new biodegradable copolymers of diblock methoxy poly(ethylene glycol)- block -poly(, -caprolactone) and methoxy poly(ethylene glycol)- block -poly(, -valerolactone), and triblock poly(, -caprolactone)- block -poly(ethylene glycol)- block -poly(, -caprolactone) and poly(, -valerolactone)- block -poly(ethylene glycol)- block -poly(, -valero-lactone) bearing narrow molecular weight distributions and well-defined block architectures were reported to be prepared with our original aluminum metal complex templates. This work will continue to report new investigations on their water solubility, and reversible thermal responsive micellization and solution to gel transition in distilled water. Among the new synthesized copolymers (P1,P23), seven diblock or triblock samples (P3, P6, P7, P11, P12, P19, and P21) with higher hydrophilic building block populations were revealed to be water soluble under ambient temperature. By means of UV spectrophotometer attached with a thermostat, important parameters as critical micellization mass concentrations (CMCs) and critical micellization temperatures (CMTs) were characterized for these new amphiphile dilute aqueous solution with the aid of an lipophilic organic dye probe of 1,6-diphenyl-1,3,5-hexatriene (DPH). Furthermore, the critical gelation temperatures (CGTs) were simultaneously investigated for these water-soluble block copolymers via a tube tilting method. It was found that the CMC, CMT, and CGT were strongly affected by the population and nature of the hydrophobic building blocks, and a higher hydrophobicity of the new amphiphilic block copolymer finally led to lower CMC and CMT, and higher CGT. In addition, the salts of KBr and NaCl were found to play as a salt-out effect on the solution to gel transition for the diblock P6 and triblock P11, exhibiting an interesting tunable gelation temperature close to 35,42,C. These results will pave new possibility for the synthesized block structural amphiphiles as potential biomaterials to be applied in vivo. Thermal responsive micellization and gelation of diblock MPEG- b -PCL/PVL and triblock PVL/PCL- b -PEG- b -PCL/PVL. [source]


    Inheritance of resistance to broomrape (Orobanche cumana Wallr.) race F in a sunflower line derived from wild sunflower species

    PLANT BREEDING, Issue 1 2007
    L. Velasco
    Abstract Genetic resistance to broomrape (Orobanche cumana Wallr.) race F in sunflower line J1, derived from the wild perennial species Helianthusgrosseserratus Martens and Helianthus divaricatus L., has been reported to be controlled by dominant alleles at a single locus, Or6. However, deviations from this monogenic inheritance have been observed. The objective of the present study was to gain insight into the inheritance of resistance to broomrape race F in the sunflower line J1. F1, F2, F3 and BC generations from crosses between J1 and three susceptible lines, P21, NR5 and HA821 were evaluated. F1 hybrids showed both resistant (R) and moderately resistant (MR) plants, the latter having a maximum of five broomrape stalks per plant compared with >10 in the susceptible parents. This indicated incomplete dominance of the Or6 alleles. F2 plants were classified as R, MR or susceptible (more than five broomrape stalks per plant). Three different segregation ratios were observed: 3 : 1, 13 : 3 and 15 : 1 (R + MR : S), suggesting the presence of a second gene, Or7, whose expression was influenced by the environment. A digenic model was confirmed, based on the evaluation of F2:3 families. [source]


    Synthesis and Characterization of a New Class of Energetic Compounds , Ammonium Nitriminotetrazolates

    PROPELLANTS, EXPLOSIVES, PYROTECHNICS, Issue 6 2008
    Thomas
    Abstract 1-Methyl-5-nitriminotetrazole (1) and 2-methyl-5-nitraminotetrazole (2) obtained by nitration of 1-methyl-5-aminotetrazole (3) and 2-methyl-5-aminotetrazole (4) were deprotonated using aqueous ammonia solution yielding the energetic compounds, ammonium 1-methyl-5-nitriminotetrazolate (5) and ammonium 2-methyl-5-nitriminotetrazolate (6). The nitrogen-rich salts were tested and characterized comprehensively using vibrational spectroscopy (Infrared (IR) and Raman), multinuclear (1H, 13C, 14N, and 15N) NMR spectroscopy, and elemental analysis. The molecular structures in the crystalline state were determined using low temperature single crystal X-ray diffraction. The thermal behavior and the decompositions were investigated using differential scanning calorimetry (DSC) and gas IR spectroscopy. The heats of formation were calculated using bomb calorimetric measurements. In addition, the relevant detonation parameters, like the detonation pressure and velocity of detonation were calculated using the software EXPLO5 outperforming the values of TNT. Last but not least the sensitivities were determined using BAM methods showing moderate values against impact and friction (drophammer and friction tester) and the long-term stabilities were tested using Flexy Thermal safety calorimetry (TSC). X-ray crystallography: 5: monoclinic, P21/c, a=370.06(2),pm, b=2079.06(9),pm, c=859.69(5),pm, ,=99.120(5), V=65306(6),pm3, Z=4, ,calc=1.639,g cm,3; 6: monoclinic, P21, a=365.39(2),pm, b=,788.82(5),pm, c=1124.95(7),pm, ,=91.818(6), V=32408(3),pm3, Z=2, ,calc=1.651,g cm,3. [source]


    Structures of the OmpF porin crystallized in the presence of foscholine-12

    PROTEIN SCIENCE, Issue 5 2010
    Georgia Kefala
    Abstract The endogenous Escherichia coli porin OmpF was crystallized as an accidental by-product of our efforts to express, purify, and crystallize the E. coli integral membrane protein KdpD in the presence of foscholine-12 (FC12). FC12 is widely used in membrane protein studies, but no crystal structure of a protein that was both purified and crystallized with this detergent has been reported in the Protein Data Bank. Crystallization screening for KdpD yielded two different crystals of contaminating protein OmpF. Here, we report two OmpF structures, the first membrane protein crystal structures for which extraction, purification, and crystallization were done exclusively with FC12. The first structure was refined in space group P21 with cell parameters a = 136.7 , b = 210.5 , c = 137 , and , = 100.5, and the resolution of 3.8 . The second structure was solved at the resolution of 4.4 and was refined in the P321 space group, with unit cell parameters a = 215.5 , b = 215.5 , c = 137.5 , and , = 120. Both crystal forms show novel crystal packing, in which the building block is a tetrahedral arrangement of four trimers. Additionally, we discuss the use of FC12 for membrane protein crystallization and structure determination, as well as the problem of the OmpF contamination for membrane proteins overexpressed in E. coli. [source]


    Alternative type I and I, turn conformations in the ,8/,9 ,-hairpin of human acidic fibroblast growth factor

    PROTEIN SCIENCE, Issue 3 2002
    Jaewon Kim
    Abstract Human acidic fibroblast growth factor (FGF-1) has a ,-trefoil structure, one of the fundamental protein superfolds. The X-ray crystal structures of wild-type and various mutant forms of FGF-1 have been solved in five different space groups: C2, C2221, P21 (four molecules/asu), P21 (three molecules/asu), and P212121. These structures reveal two characteristically different conformations for the ,8/,9 ,-hairpin comprising residue positions 90,94. This region in the wild-type FGF-1 structure (P21, four molecules/asu), a his-tagged His93,Gly mutant (P21, three molecules/asu) and a his-tagged Asn106,Gly mutant (P212121) adopts a 3:5 ,-hairpin known as a type I (1,4) G1 ,-bulge (containing a type I turn). However, a his-tagged form of wild-type FGF-1 (C2221) and a his-tagged Leu44,Phe mutant (C2) adopt a 3:3 ,-hairpin (containing a type I, turn) for this same region. A feature that distinguishes these two types of ,-hairpin structures is the number and location of side chain positions with eclipsed C, and main-chain carbonyl oxygen groups (, , +60). The effects of glycine mutations upon stability, at positions within the hairpin, have been used to identify the most likely structure in solution. Type I, turns in the structural data bank are quite rare, and a survey of these turns reveals that a large percentage exhibit crystal contacts within 3.0 . This suggests that many of the type I, turns in X-ray structures may be adopted due to crystal packing effects. [source]


    Immunocytochemical Localization of Caveolin-3 in the Synoviocytes of the Rat Temporomandibular Joint During Development

    THE ANATOMICAL RECORD : ADVANCES IN INTEGRATIVE ANATOMY AND EVOLUTIONARY BIOLOGY, Issue 3 2008
    Masahiro Niwano
    Abstract Caveolins,caveolin-1, -2, -3 (Cav1, 2, 3),are major components of caveolae, which have diverse functions. Our recent study on the temporomandibular joint (TMJ) revealed expressions of Cav1 and muscle-specific Cav3 in some synovial fibroblast-like type B cells with well-developed caveolae. However, the involvement of Cav3 expression in the differentiation and maturation of type B cells remains unclear. The present study therefore examined the chronological alterations in the localization of Cav3 in the synovial lining cells of the rat TMJ during postnatal development by immunocytochemical techniques. Observations showed immature type B cells possessed a few caveolae with Cav1 but lacked Cav3 protein at postnatal day 5 (P5). At P14, Cav3-immunopositive type B cells first appeared in the synovial lining layer. They increased in number and immunointensity from P14 to P21 as occlusion became active. In immunoelectron microscopy and double immunolabeling with heat shock protein 25 (Hsp25) and Cav3, coexpressed type B cells developed rough endoplasmic reticulum and numerous caveolae, while the Cav3-immunonegative type B cell with Hsp25 immunoreaction possessed few of these. Results suggest that Cav3 expression, which is closely related to added functional stimuli, reflects the differentiation of the type B synoviocytes. Anat Rec, 291:233,241, 2008. 2008 Wiley-Liss, Inc. [source]


    The supply of and demand for accounting information

    THE ECONOMICS OF TRANSITION, Issue 2 2007
    The case of bank financing in Russia
    G21; M41; P21 Abstract The article analyzes the use of accounting information in Russia. We assess reporting behaviour in the lending process for a sample of Russian companies in the years 1999,2004 and postulate that Russian companies manage their earnings in order to avoid showing losses when applying for bank financing. Once a credit has been granted, companies are predicted to manage earnings because of the bank's monitoring activities. By means of univariate and multivariate analysis we are able to attribute the discontinuity around a zero target in the earnings distribution with firms' response to the banks' assessment of accounting performance. This implies that financing considerations affect the reporting incentives of Russian companies. [source]


    Voucher Privatization: A detour on the road to transition?

    THE ECONOMICS OF TRANSITION, Issue 3 2002
    Barbara G. Katz
    We explore an overlooked aspect of the design of the Czech voucher privatization programme, namely, the consequences of allowing individuals to distribute their vouchers among the voucher privatization funds (VPFs). We develop and analyse a model of voucher privatization in which we study the problem facing individuals who invest their vouchers in VPFs which, in turn, are able to use their skills to alter the performances of the firms in which they acquire shares. The VPFs have different skills and, by their bids and subsequent joint ownership patterns, affect the performances of the firms in their funds. We show that even in the case in which voucher holders have identical and full information, and wish to allocate their vouchers to the VPFs in a manner consistent with the maximization of economy,wide profit, a coordination failure generally prevents the implementation of this efficient outcome. Uncertainty, as well as differing payouts by the VPFs, is shown to exacerbate the problem. We conclude that there was an inherent flaw in the design of the Czech voucher scheme. JEL classification: D44, L33, P21, G11. [source]


    Structure and composition of the postsynaptic density during development

    THE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 20 2010
    Matthew T. Swulius
    Abstract In this study, we used electron tomography as well as immunogold labeling to analyze the morphology and distribution of proteins within postsynaptic densities (PSDs) isolated from rats before birth (embryonic day 19) and at postnatal days 2, 21, and 60. Our data provide direct evidence of distinct morphological and compositional differences in PSDs throughout development. Not all PSD components are present at the early stages of development, with a near lack of the scaffolding molecule PSD-95 at E19 and P2. The presence of NR1 and NR2b suggests that PSD-95 is not directly required for clustering of N-methyl-D-aspartic acid (NMDA) receptors in PSDs early in development. ,-Actinin is abundant by E19, suggesting that it is a core structural component of the PSD. Both , and , isoforms of Ca2+/calmodulin-dependent protein kinase II (CaMKII) are present early on but then rise in labeling density by approximately fourfold by P21. Among all the molecules studied, only calmodulin (CaM) was found in higher abundance early in PSD development and then fell in amount over time. Spatial analysis of the immunogold label shows a nonrandom distribution for all the proteins studied, lending support to the idea that the PSD is systematically assembled in an organized fashion. Morphological data from electron tomography shows that the PSD undergoes major structural changes throughout development. J. Comp. Neurol. 518:4243,4260, 2010. 2010 Wiley-Liss, Inc. [source]


    Development of layer-specific axonal arborizations in mouse primary somatosensory cortex

    THE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 3 2006
    DeLaine D. Larsen
    Abstract In the developing neocortex, pyramidal neurons use molecular cues to form axonal arbors selectively in the correct layers. Despite the utility of mice for molecular and genetic studies, little work has been done on the development of layer-specific axonal arborizations of pyramidal neurons in mice. We intracellularly labeled and reconstructed the axons of layer 2/3 and layer 5 pyramidal neurons in slices of primary somatosensory cortex from C57Bl6 mice on postnatal days 7,21. For all neurons studied, the development of the axonal arborizations in mice follows a pattern similar to that seen in other species; laminar specificity of the earliest axonal branches is similar to that of mature animals. At P7, pyramidal neurons are very simple, having only a main descending axon and few primary branches. Between P7 and P10, there is a large increase in the total number of axonal branches, and axons continue to increase in complexity and total length from P10 to P21. Unlike observations in ferrets, cats, and monkeys, two types of layer 2/3 pyramidal neurons are present in both mature and developing mice; cells in superficial layer 2/3 lack axonal arbors in layer 4, and cells close to the layer 4 border have substantial axonal arbors within layer 4. We also describe axonal and dendritic arborization patterns of three pyramidal cell types in layer 5. The axons of tall-tufted layer 5 pyramidal neurons arborize almost exclusively within deep layers while tall-simple, and short layer 5 pyramidal neurons also project axons to superficial layers. J. Comp. Neurol. 494:398,414, 2006. 2005 Wiley-Liss, Inc. [source]