bluuebunny/crossref_metadata_2025 huggingface dataset:
Ryanodine receptors are expressed and functionally active in mouse spermatogenic cells and their inhibition interferes with spermatogonial differentiation
Authors: Chiarella Pieranna , Puglisi Rossella , Sorrentino Vincenzo , Boitani Carla , Stefanini Mario
Published: July 2004

Ryanodine receptors (RyRs) are intracellular calcium release channels that are highly expressed in striated muscle and neurons but are also detected in several non-excitable cells. We have studied the expression of the three RyR isoforms in male germ cells at different stages of maturation by western blot and RT-PCR. RyR1 was expressed in spermatogonia, pachytene spermatocytes and round spermatids whereas RyR2 was found only in 5- to 10-day-old testis but not in germ cells. RyR3 was not revealed at the protein level, although its mRNA was detected in mixed populations of germ cells. Caffeine, a known agonist of RyRs, was able to induce release of Ca2+ from intracellular stores in spermatogonia, pachytene spermatocytes and round spermatids, but not spermatozoa. Treatment with high doses of ryanodine, which are known to block RyR channel activity, reduced spermatogonial proliferation and induced meiosis in in vitro organ cultures of testis from 7-day-old mice. In conclusion, the results presented here indicate that RyRs are present in germ cells and that calcium mobilization through RyR channels could participate to the regulation of male germ maturation.
Analysis of Smad nucleocytoplasmic shuttling in living cells
Authors: Nicolás Francisco J. , De Bosscher Karolien , Schmierer Bernhard , Hill Caroline S.
Published: July 2004

Transforming growth factor β (TGF-β) signalling leads to phosphorylation and activation of receptor-regulated Smad2 and Smad3, which form complexes with Smad4 and accumulate in the nucleus. The Smads, however, do not seem to reside statically in the cytoplasm in the absence of signalling or in the nucleus upon TGF-β stimulation, but have been suggested to shuttle continuously between these cellular compartments in both the absence and presence of TGF-β. Here we investigate this nucleocytoplasmic shuttling in detail in living cells using fusions of Smad2 and Smad4 with enhanced GFP. We first establish that the GFPSmad fusions behave like wild-type Smads in a variety of cellular assays. We go on to demonstrate directly, using photobleaching experiments, that Smad2 and Smad4 shuttle between the cytoplasm and nucleus in both TGF-β-induced cells and in uninduced cells. In uninduced cells, GFPSmad2 is less mobile in the cytoplasm than is GFPSmad4, suggesting that it may be tethered there. In addition, we show that both GFPSmad2 and GFPSmad4 undergo a substantial decrease in mobility in the nucleus upon TGF-β stimulation, suggesting that active complexes of Smads are tethered in the nucleus, whereas unactivated Smads are more freely diffusible. We propose that regulated cytoplasmic and nuclear retention may play a role in determining the distribution of Smads between the cytoplasm and the nucleus in both uninduced cells and upon TGF-β induction.
Stress response in yeast mRNA export factor: reversible changes in Rat8p localization are caused by ethanol stress but not heat shock
Authors: Takemura Reiko , Inoue Yoshiharu , Izawa Shingo
Published: July 2004

Ethanol stress (10% v/v) causes selective mRNA export in Saccharomyces cerevisiae in a similar manner to heat shock (42°C). Bulk poly(A)+ mRNA accumulates in the nucleus, whereas heat shock protein mRNA is exported under such conditions. Here we investigated the effects of stress on mRNA export factors. In cells treated with ethanol stress, the DEAD box protein Rat8p showed a rapid and reversible change in its localization, accumulating in the nucleus. This change correlated closely with the blocking of bulk poly(A)+ mRNA export caused by ethanol stress. We also found that the nuclear accumulation of Rat8p is caused by a defect in the Xpo1p/Crm1p exportin. Intriguingly, the localization of Rat8p did not change in heat shocked cells, suggesting that the mechanisms blocking bulk poly(A)+ mRNA export differ for heat shock and ethanol stress. These results suggest that changes in the localization of Rat8p contribute to the selective export of mRNA in ethanol stressed cells, and also indicate differences in mRNA export between the heat shock response and ethanol stress response.
Study of the Adsorption of Copper(II) Ions from Water onto Wood Sawdust, Pulp and Lignin
Authors: Sciban Marina , Klasnja Mile
Published: July 2004

The adsorption of copper(II) ions from aqueous solution onto sawdusts from different kinds of wood, pulp and Kraft lignin has been studied. The results of batch studies showed that Kraft lignin was a good adsorbent over the whole concentration range studied, hard woods (oak and black locust) were good when the Cu(II) ion concentration in the aqueous solution was high, while soft woods (poplar, willow, fir) and pulp were good for the adsorption of Cu(II) ions when the latter were present over the low concentration range.

The maximum adsorption capacities of the adsorbents investigated towards Cu(II) ions were in the 1.77–9.35 mg/g range. Isotherms were used to obtain the corresponding thermodynamic parameters. Almost complete Cu(II) ion desorption was achieved using 0.1 M mineral acid solutions. The regenerated adsorbents could be used in several adsorption/desorption cycles.
Competitive Sorption of Cu(II), Pb(II) and Hg(II) Ions from Aqueous Solution Using Coconut Shell-Based Activated Carbon
Authors: Goel Jyotsna , Kadirvelu Krishna , Rajagopal Chitra
Published: July 2004

Many adsorbents have been studied for their adsorption properties towards one-component metal ion solutions. However, if these materials are to be used for treating wastewater, their performance has to be determined in multi-component solutions. In the present work, multi-component metal sorption by coconut shell-based activated carbon has been studied using single, binary and ternary systems composed of Cu(II), Pb(II) and Hg(II) ions. The influence of solution pH was also demonstrated.

A set of desorption studies was also performed for the same metal ions with the aim of investigating the mechanism involved. It was found that chemisorption, surface chelation and complexation might be a possible metal ion removal mechanism. Scanning electron micrographs (SEM) and the EDAX spectrum of the activated carbon surface before and after equilibration of the adsorbent with the metal ion solution clearly showed the presence of Cu(II), Pb(II) and Hg(II) ions. An attempt was made to quantify the interaction behaviour of the metal ion on the adsorbent and to correlate such observations with the chemical and physical properties of the metal ions.

The ability of isotherm models such as those of Freundlich and Langmuir to predict the equilibrium uptake of Cu(II), Pb(II) and Hg(II) ions from one-component, binary and ternary systems was also tested. Both the Langmuir and Freundlich models were found to fit the experimental data well. The applicability of the extended Langmuir model was also evaluated for multi-component systems.
Separation of Mercury(II) from Aqueous Solution by Adsorption onto an Activated Carbon Prepared from Eichhornia Crassipes
Authors: Kadirvelu K. , Kanmani P. , Senthilkumar P. , Subburam V.
Published: July 2004

The adsorption of mercury(II) from aqueous solutions onto an activated carbon derived from Eichhornia crassipes (AEC) was investigated under varying conditions of agitation time, metal ion concentration, adsorbent dose and pH to assess the kinetic and equilibrium parameters. Adsorption equilibrium was attained in 200, 310, 360 and 360 min for 10, 20, 30 and 40 mg/l Hg(II) concentrations. The first- and second-order adsorption rate constants were calculated and the experimental equilibrium adsorption capacities (qe) for different initial Hg(II) concentrations were reported. Adsorption was dependent on the solution pH, the Hg(II) concentration, the carbon concentration and the contact time. Both the Freundlich and Langmuir adsorption isotherm models fitted the experimental data well. The adsorption capacity was found to be 28.4 mg/g at pH 5 for a particle size of 125–180 μm. The adsorption capacity of the carbon produced met commercial conditions and was found to be superior to that of many other adsorbents. The percentage removal increased as the pH value of the solution was increased from 2 to 5 and then remained constant up to a pH value of 10. Desorption studies were performed with dilute hydrochloric acid and potassium iodide (KI) solutions.
Peanut Shell Activated Carbon: Adsorption Capacities for Copper(II), Zinc(II), Nickel(II) and Chromium(VI) Ions from Aqueous Solutions
Authors: Romero Luis C. , Bonomo Antonio , Gonzo Elio E.
Published: July 2004

The adsorption of copper(II), zinc(II), nickel(II) and chromium(VI) ions from aqueous solutions onto an activated carbon produced from peanut shell was studied as a function of the concentration of the ions and the pH value. The amounts of Cu(II), Zn(II) and Ni(II) ions adsorbed increased with increasing equilibrium pH of the solution, while the uptake of Cr(VI) ions decreased. For Cr(VI) ions, maximum uptakes were found at a pH below the point of zero charge of the adsorbent (pHpzc). The amount of metal cation adsorbed at a given equilibrium concentration increased in the order Ni(II) < Zn(II) < Cu(II). This metal ion uptake order may be explained from a consideration of the combined effects of the electronegativity of the metal ion and the first stability constant of the corresponding metal hydroxide. The activated carbon produced from peanut shell was an effective and economic adsorbent for the removal of metal cations at pH ≥ pHpzc and anions at pH ≤ pHpzc.
Oxygen-Induced Decrease in the Equilibrium Adsorptive Capacities of Activated Carbons
Authors: Ania C.O. , Parra J.B. , Pis J.J.
Published: July 2004

Special attention was paid in this work to the role of surface chemistry in the adsorption of phenol and salicylic acid onto activated carbons. To this end, two commercial activated carbons (granular and powdered) were oxidised using ammonium peroxodisulphate [(NH4)2S2O8] and nitric acid in different concentrations. The structural and chemical properties of the oxidised adsorbents were characterised via nitrogen adsorption isotherms measured at −196°C and Boehm titrations. Phenol adsorption from solution at low concentration was studied at room temperature without specific pH control of the solution. The results showed a significant reduction in the adsorptive capacities towards phenol of the activated carbons as the oxygen content of the latter increased. However, very little effect was observed towards the retention of salicylic acid. The decrease in adsorptive capacity depended not only on the amount of oxygen per unit mass of activated carbon, but also on the textural properties of the latter.
Effect of Temperature on the Adsorption of Organic Vapours on Activated Carbon Fibres
Authors: Huang Zheng-Hong , Kang Feiyu , Hao Jiming
Published: July 2004

Viscose rayon-based activated carbon fibre (ACF) was prepared by CO2 activation and the pore structure of all samples characterized via nitrogen adsorption at −196°C. The influence of temperature on the adsorption of organic vapour onto ACF was studied by gravimetric methods. The results showed that the adsorption capacity towards organic vapour decreased with increasing temperature at a given concentration. The larger the specific surface area of the ACF, the greater the extent to which its vapour adsorption performance was affected by temperature. It is suggested that an ACF of a relatively low burn-off would be suitable for adsorption at higher temperatures.
Modified Granular Activated Carbon: A Carrier for the Recovery of Nickel Ions from Aqueous Wastes
Authors: Satapathy D. , Natarajan G.S. , Sen Raja
Published: July 2004

Granular Activated Carbon (GAC) is widely used for the removal and recovery of toxic pollutants including metals because of its low cost and high affinity towards the scavenging of metal ions. Activated carbon derived from bituminous coal is preferred for wastewater treatment due to its considerable hardness, a characteristic needed to keep down handling losses during re-activation. Commercial grade carbon, viz. Filtrasorb (F-400), was used in the present work. The scavenging of precious metals such as nickel onto GAC was studied and a possible attempt made to recover the adsorbed Ni2+ ions through the use of some suitable leaching processes.

As part of the study, the role of complexing agents on the surface of the carbon was also investigated. The use of organic complexing agents such as oxine and 2-methyloxine in the recovery process was found to be promising. In addition, the surface of the carbon was modified with suitable oxidising agents that proved to be more effective than chelating agents. Several attempts were made to optimise the recovery of metal ions by carrying out experiments with oxidising agents in order to obtain maximum recovery from the minimum quantity of carbon. Experiments with nitric acid indicated that not only was the carbon surface modified but such modification also helped in carbon regeneration.
Adsorption of Bovine Serum Albumin onto Radiation-Crosslinked Poly(Acrylamide/Acrylic Acid)
Authors: Öztop H. Nursevin , Saraydın Dursun , Şolpan Dilek , Güven Olgun
Published: July 2004

Poly(acrylamide/acrylic acid) (AAm/AAc) hydrogels were prepared at initial acrylic acid compositions of 70, 80 and 85 mol%, respectively. Mixtures of AAm and AAc monomers were irradiated in a 60Co γ-ray source at a dosage of 8 kGy. These hydrogels were used in experiments associated with the swelling, diffusion and adsorption of bovine serum albumin (BSA) from aqueous solution. The data obtained allowed the swelling and diffusion parameters for the hydrogels to be calculated. In the BSA adsorption experiments, the adsorption kinetics together with the influence of the pH of the medium, the initial BSA concentration and the composition of the hydrogels on the adsorption efficiency of the AAm/AAc hydrogels were all studied.

The rates of BSA adsorption were found to conform to pseudo-first-order kinetics and a kinetic model was used to calculate the corresponding rate constant for the adsorption processes. The adsorption of BSA onto AAm/AAc hydrogels decreased with increasing pH, with the maximum adsorption being observed at a pH value of 3.7. In terms of the Giles classification, the adsorption was of type C. BSA adsorption increased as the AAc content of the hydrogels increased. Significant amounts of adsorbed BSA (up to 95%) were eluted when an elution medium containing 1.0 M NaSCN was employed at a pH value of 8.0.
Efficiency of Actively Controlled Surface Impedance of Upper Sections Attached to Noise Barriers
Authors: Koh H. , Möser M.
Published: July 2004

Based on a mathematical model consisting of a rigid cylindrical body attached to a rigid half plane, the sound pressure on the surface of the cylindrical upper section is actively minimized to divert the tangential power transport along the surface as much as possible. The numerical study considers the possibility of deflecting the incident sound by means of a secondary sound field. The acoustical shadow region becomes more pronounced in both the near and far field, compared with the passive case. For a relatively wide frequency range it is also possible to find optimal arrangements for the secondary sources and for the error microphones. The physical principle studied theoretically can also be realized practically by means of active control. The optimal configurations found in the numerical analysis are proven to be effective in the experiment.
Decay Processes in Rooms with Non-Diffuse Sound Fields. Part II: Effect of Irregularities
Authors: Nilsson Erling
Published: July 2004

The effect of sound scattering objects in a rectangular room with high absorption at the ceiling and low absorption at the walls and floor was investigated. In Part I of this paper a two-system Statistical Energy Analysis (SEA) model was developed in order to predict the gross features of the decay process. The sound field is subdivided into a grazing and nongrazing part. The main effect of introducing irregularities is to divert some of the energy in the grazing group into the nongrazing group. The energy transfer between the groups is taken into account by introducing a coupling loss factor. In order to quantify the effect of scattering objects and other irregularities, a measure called equivalent scattering area is introduced. The model demonstrates how the equivalent scattering area can be determined from measurements.
Effect of Nozzle Internal Contour on Jet Aeroacoustics
Authors: Viswanathan K. , Clark L. T.
Published: July 2004

A frequent problem that confronts designers of jet rigs and nozzles used for aeroacoustic testing is the unknown effect of the state of the flow upstream of the nozzle exit on aeroacoustic performance. Though the effect of the inflow conditions on flow development has been studied extensively, there is limited information on their effect on noise. Flow distortion, both in pressure and temperature, thickness and state of the boundary layer, quality of the measurement system and anechoic chamber, and analysis procedure could all play a role in the observed variations in data from different experiments. In order to understand the effect of the thickness of the boundary layer upstream of the nozzle convergent (entrance) section and in the nozzle itself, a computational and experimental investigation has been carried out. Three nozzles of identical exit diameter have been designed and tested in the Boeing Low Speed Aeroacoustic Facility (LSAF). These three nozzles have a shallow conic section, a short cubic contraction and an ASME flow path (contraction followed by a constant section), respectively. Simultaneous aerodynamic and acoustic measurements have been made with a six-component force balance and far field microphone arrays for a wide range of nozzle operating conditions. The numerical simulations and the measurements of nozzle coefficients indicate that the initial boundary layers are vastly different, with the cubic producing a thin boundary layer and the conic a much thicker one. Surprisingly, the noise levels from these two nozzles are virtually identical especially at the higher frequencies. An important practical conclusion drawn from this observation of insensitivity to nozzle exit conditions is that it should be possible to compare noise spectra from different facilities even if measurements of inflow conditions are not available. The ASME nozzle generates higher levels of noise, the magnitude of which is more pronounced at elevated jet temperatures. The characteristics and the stability of the boundary layers inside the nozzles are examined to glean some insights to the observed differences in noise.
Requirement of α5-GABAAReceptors for the Development of Tolerance to the Sedative Action of Diazepam in Mice
Authors: van Rijnsoever Carolien , Täuber Marcus , Choulli Mohamed Khaled , Keist Ruth , Rudolph Uwe , Mohler Hanns , Fritschy Jean Marc , Crestani Florence
Published: July 2004

Despite its pharmacological relevance, the mechanism of the development of tolerance to the action of benzodiazepines is essentially unknown. The acute sedative action of diazepam is mediated via α1-GABAAreceptors. Therefore, we tested whether chronic activation of these receptors by diazepam is sufficient to induce tolerance to its sedative action. Knock-in mice, in which theα1-,α2-,α3-, orα5-GABAAreceptors had been rendered insensitive to diazepam by histidine-arginine point mutation, were chronically treated with diazepam (8 d; 15 mg · kg-1· d-1) and tested for motor activity. Wild-type, α2(H101R), and α3(H126R) mice showed a robust diminution of the motor-depressant drug action. In contrast, α5(H105R) mice failed to display any sedative tolerance. α1(H101R) mice showed no alteration of motor activity with chronic diazepam treatment. Autoradiography with [3H]flumazenil revealed no change in benzodiazepine binding sites. However, a decrease in α5-subunit radioligand binding was detected selectively in the dentate gyrus with specific ligands. This alteration was observed only in diazepam-tolerant animals, indicating that the manifestation of tolerance to the sedative action of diazepam is associated with a downregulation of α5-GABAAreceptors in the dentate gyrus. Thus, the chronic activation of α5-GABAAreceptors is crucial for the normal development of sedative tolerance to diazepam, which manifests itself in conjunction with α1-GABAAreceptors.
Motoneurons Express Heteromeric TWIK-Related Acid-Sensitive K+(TASK) Channels Containing TASK-1 (KCNK3) and TASK-3 (KCNK9) Subunits
Authors: Berg Allison P. , Talley Edmund M. , Manger Jules P. , Bayliss Douglas A.
Published: July 2004

Background potassium currents carried by the KCNK family of two-pore-domain K+channels are important determinants of resting membrane potential and cellular excitability. TWIK-related acid-sensitive K+1 (TASK-1, KCNK3) and TASK-3 (KCNK9) are pH-sensitive subunits of the KCNK family that are closely related and coexpressed in many brain regions. There is accumulating evidence that these two subunits can form heterodimeric channels, but this evidence remains controversial. In addition, a substantial contribution of heterodimeric TASK channels to native currents has not been unequivocally established. In a heterologous expression system, we verified formation of heterodimeric TASK channels and characterized their properties; TASK-1 and TASK-3 were coimmunoprecipitated from membranes of mammalian cells transfected with the channel subunits, and a dominant negative TASK-1(Y191F) construct strongly diminished TASK-3 currents. Tandem-linked heterodimeric TASK channel constructs displayed a pH sensitivity (pK ∼7.3) in the physiological range closer to that of TASK-1 (pK ∼7.5) than TASK-3 (pK ∼6.8). On the other hand, heteromeric TASK channels were like TASK-3 insofar as they were activated by high concentrations of isoflurane (0.8 mm), whereas TASK-1 channels were inhibited. The pH and isoflurane sensitivities of native TASK-like currents in hypoglossal motoneurons, which strongly express TASK-1 and TASK-3 mRNA, were best represented by TASK heterodimeric channels. Moreover, after blocking homomeric TASK-3 channels with ruthenium red, we found a major component of motoneuronal isoflurane-sensitive TASK-like current that could be attributed to heteromeric TASK channels. Together, these data indicate that TASK-1 and TASK-3 subunits coassociate in functional channels, and heteromeric TASK channels provide a substantial component of background K+current in motoneurons with distinct modulatory properties.
GABA, Not Glutamate, Controls the Activity of Substantia Nigra Reticulata Neurons in Awake, Unrestrained Rats
Authors: Windels François , Kiyatkin Eugene A.
Published: July 2004

Substantia nigra pars reticulata (SNr) receives both GABAergic and glutamatergic (GLU) inputs that are believed to act together to regulate neuronal activity in this structure. To examine the role of these inputs, single-unit recording was coupled with iontophoresis of GLU and GABA in rats under two conditions: awake, unrestrained and under chloral hydrate anesthesia. Although GABA potently inhibited SNr cells in both conditions, freely moving rats showed lower sensitivity than anesthetized animals. Likewise, GLU effectively induced excitations in most SNr neurons in anesthetized animals but was much less effective in awake, unrestrained animals in terms of both the number of sensitive cells and the magnitude of GLU-induced excitation. These findings, along with consistent excitations induced by bicuculline in awake, unrestrained rats, suggest that modulation of GABA inhibitory input, not the opposing actions of GLU and GABA, is the primary factor that regulates the activity state of SNr neurons.
Fibroblast Growth Factor Homologous Factor 2B: Association with Nav1.6 and Selective Colocalization at Nodes of Ranvier of Dorsal Root Axons
Authors: Wittmack Ellen K. , Rush Anthony M. , Craner Matthew J. , Goldfarb Mitchell , Waxman Stephen G. , Dib-Hajj Sulayman D.
Published: July 2004

Voltage-gated sodium channels interact with cytosolic proteins that regulate channel trafficking and/or modulate the biophysical properties of the channels. Nav1.6 is heavily expressed at the nodes of Ranvier along adult CNS and PNS axons and along unmyelinated fibers in the PNS. In an initial yeast two-hybrid screen using the C terminus of Nav1.6 as a bait, we identified FHF2B, a member of the FGF homologous factor (FHF) subfamily, as an interacting partner of Nav1.6. Members of the FHF subfamily share ∼70% sequence identity, and individual members demonstrate a cell- and tissue-specific expression pattern. FHF2 is abundantly expressed in the hippocampus and DRG neurons and colocalizes with Nav1.6 at mature nodes of Ranvier in myelinated sensory fibers in the dorsal root of the sciatic nerve. However, retinal ganglion cells and spinal ventral horn motor neurons show very low levels of FHF2 expression, and their axons exhibit no nodal FHF2 staining within the optic nerve and ventral root, respectively. Thus, FHF2 is selectively localized at nodes of dorsal root sensory but not ventral root motor axons. The coexpression of FHF2B and Nav1.6 in the DRG-derived cell line ND7/23 significantly increases the peak current amplitude and causes a 4 mV depolarizing shift of voltage-dependent inactivation of the channel. The preferential expression of FHF2B in sensory neurons may provide a basis for physiological differences in sodium currents that have been reported at the nodes of Ranvier in sensory versus motor axons.
Regulation of anAplysiaBag Cell Neuron Cation Channel by Closely Associated Protein Kinase A and a Protein Phosphatase
Authors: Magoski Neil S.
Published: July 2004

Ion channel regulation by closely associated kinases or phosphatases has emerged as a key mechanism for orchestrating neuromodulation. An exemplary case is the nonselective cation channel that drives the afterdischarge inAplysiabag cell neurons. Initial studies showed that this channel is modulated by both a closely associated PKC and a serine/threonine protein phosphatase (PP). In excised, inside-out patches, the addition of ATP (a phosphate source) increases open probability (PO) through PKC, and this is reversed by the PP. Previous work also reported that, in certain cases, ATP can decrease cation channel PO. The present study characterizes and provides a mechanism for this decreased POATP response. The kinetic change for channels inhibited by ATP was identical to the previously reported effect of exogenously applied protein kinase A (PKA) (i.e., a lengthening of the third closed-state time constant). The decreased POATP response was blocked by the PKA inhibitor peptide PKA6-22, and its reversal was prevented by the PP inhibitor microcystin-LR. Furthermore, PKA6-22did not alter the increased POATP response. This suggests that both PKA and a PP are closely associated with these cation channels, but PKA and PKC are not simultaneously targeted. After an afterdischarge, the bag cell neurons are refractory and fail to respond to subsequent stimulation. The association of PKA with the cation channel may contribute to this decrease in excitability. Altering the constituents of a regulatory complex, such as exchanging PKA for PKC, may represent a general mechanism to precisely control ion channel function and excitability.
Exclusive Postsynaptic Action of Hypocretin-Orexin on Sublayer 6b Cortical Neurons
Authors: Bayer Laurence , Serafin Mauro , Eggermann Emmanuel , Saint-Mleux Benoît , Machard Danièle , Jones Barbara E. , Mühlethaler Michel
Published: July 2004

The hypocretin-orexin (hcrt-orx) neurons are thought to maintain wakefulness because their loss results in narcolepsy. This role may be fulfilled by the excitatory action that the hcrt-orx peptide exerts on multiple brainstem and forebrain systems that, in turn, promote cortical activation. Here, we examined whether hcrt-orx may also exert a postsynaptic excitatory action at the level of the cortex, where hcrt-orx fibers project. However, we found that neurons in layers 2-5 in the primary somatosensory cortex (SSp) were unresponsive to hcrt-orx. We then found that although all neurons tested in sublayer 6a were also unresponsive to hcrt-oxr, all those tested in sublayer 6b were highly sensitive to the peptide. The sublayer selectivity of hcrt-oxr was not restricted to the somatosensory cortex, because it was also found to be present in the primary visual cortex, the motor cortex, and the cingulate cortex. In the SSp, in which the hcrt-oxr effect was investigated further, it was demonstrated to be postsynaptic, to result from an interaction with Hcrtr2-OX2receptors and to depend on the closure of a potassium conductance. Similar to the selectivity of action in the thalamus, where hcrt-oxr excites the nonspecific thalamocortical projection neurons and not the specific sensory relay neurons, here in the cortex, it excites a specific subset of cortical neurons which, through corticocortical projections, may also be involved in promoting widespread cortical activation.
Neuronal Nicotinic Synapse Assembly Requires the Adenomatous Polyposis Coli Tumor Suppressor Protein
Authors: Temburni Murali Krishna , Rosenberg Madelaine M. , Pathak Narendra , McConnell Russell , Jacob Michele H.
Published: July 2004

Normal cognitive and autonomic functions require nicotinic synaptic signaling. Despite the physiological importance of these synapses, little is known about molecular mechanisms that direct their assembly during development. We show here that the tumor-suppressor protein adenomatous polyposis coli (APC) functions in localizing α3-nicotinic acetylcholine receptors (nAChRs) to neuronal postsynaptic sites. Our quantitative confocal microscopy studies indicate that APC is selectively enriched at cholinergic synapses; APC surface clusters are juxtaposed to synaptic vesicle clusters and colocalize with α3-nAChRs but not with the neighboring synaptic glycine receptors or perisynaptic α7-nAChRs on chick ciliary ganglion (CG) neurons. We identify PSD (postsynaptic density)-93, β-catenin, and microtubule end binding protein EB1 as APC binding partners. PSD-93 and β-catenin are also enriched at α3-nAChR postsynaptic sites. EB1 shows close proximity to and partial overlap with α3-nAChR and APC surface clusters. We tested the role of APC in neuronal nicotinic synapse assembly by using retroviral-mediatedin vivooverexpression of an APC dominant-negative (APC-dn) peptide to block the interaction of endogenous APC with both EB1 and PSD-93 during synapse formation in CG neurons. The overexpressed APC-dn led to dramatic decreases in α3-nAChR surface levels and clusters. Effects were specific to α3-nAChR postsynaptic sites; synaptic glycine receptor and perisynaptic α7-nAChR clusters were not altered. In addition, APC-dn also reduced surface membrane-associated clusters of PSD-93 and EB1. The results show that APC plays a key role in organizing excitatory cholinergic postsynaptic specializations in CG neurons. We identify APC as the first nonreceptor protein to function in localizing nAChRs to neuronal synapsesin vivo.
Glycogen Synthase Kinase-3β Haploinsufficiency Mimics the Behavioral and Molecular Effects of Lithium
Authors: O'Brien W. Timothy , Harper Amber DeAra , Jové Fernando , Woodgett James R. , Maretto Silvia , Piccolo Stefano , Klein Peter S.
Published: July 2004

Lithium is widely used to treat bipolar disorder, but its mechanism of action in this disorder is unknown. Several molecular targets of lithium have been identified, but these putative targets have not been shown to be responsible for the behavioral effects of lithiumin vivo. A robust model for the effects of chronic lithium on behavior in mice would greatly facilitate the characterization of lithium action. We describe behaviors in mice that are robustly affected by chronic lithium. Remarkably, these lithium-sensitive behaviors are also observed in mice lacking one copy of the gene encodingglycogen synthase kinase-3β (Gsk-3β), a well established direct target of lithium. In addition, chronic lithium induces molecular changes consistent with inhibition of GSK-3 within regions of the brain that are paralleled inGsk-3β+/-heterozygous mice. We also show that lithium therapy activates Wnt signalingin vivo, as measured by increased Wnt-dependent gene expression in the amygdala, hippocampus, and hypothalamus. These observations support a central role for GSK-3β in mediating behavioral responses to lithium.
Brain-Derived Neurotrophic Factor mRNA and Protein Are Targeted to Discrete Dendritic Laminas by Events That Trigger Epileptogenesis
Authors: Tongiorgi Enrico , Armellin Mara , Giulianini Piero Giulio , Bregola Gianni , Zucchini Silvia , Paradiso Beatrice , Steward Oswald , Cattaneo Antonino , Simonato Michele
Published: July 2004

Dendritic targeting of mRNA and local protein synthesis are mechanisms that enable neurons to deliver proteins to specific postsynaptic sites. Here, we demonstrate that epileptogenic stimuli induce a dramatic accumulation of BDNF mRNA and protein in the dendrites of hippocampal neuronsin vivo. BDNF mRNA and protein accumulate in dendrites in all hippocampal subfields after pilocarpine seizures and in selected subfields after other epileptogenic stimuli (kainate and kindling). BDNF accumulates selectively in discrete dendritic laminas, suggesting targeting to synapses that are active during seizures. Dendritic targeting of BDNF mRNA occurs during the time when the cellular changes that underlie epilepsy are occurring and is not seen after intense stimuli that are non-epileptogenic, including electroconvulsive seizures and high-frequency stimulation. MK801, an NMDA receptor antagonist that can prevent epileptogenesis but not acute seizures, prevents the dendritic accumulation of BDNF mRNA, indicating that dendritic targeting is mediated via NMDA receptor activation. Together, these results suggest that dendritic accumulation of BDNF mRNA and protein play a critical role in the cellular changes leading to epilepsy.
Synthesis of polyborosilazane and its utilization as a precursor to boron nitride
Authors: Chu Zeng‐Yong , Feng Chun‐Xiang , Song Yong‐Cai , Li Xiao‐Dong , Xiao Jia‐Yu
Published: July 2004

A new kind of polyborosilazane was synthesized from hexamethylcyclotrisilazane by exposure to boron trichloride. The pyrolysis of the precursor was carried out at 1250, 1600, and 1800°C in nitrogen for a dwelling time of 1 h. Characterizations were performed with Fourier transform infrared, X‐ray photoelectron spectroscopy, thermogravimetric analysis, and XRD techniques, and the results showed that the boron content of the precursor increased as the exposure time increased, whereas the C/Si ratio remained constant. Minor amounts of Si and C remained in residue pyrolyzed at 1250°C, but they were completely removed when their residue was further sintered at 1800°C. At that point, it only consisted of hexagonal BN crystals. Therefore, the polymer could be used as a precursor to BN in some special applications. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 105–109, 2004
Synthesis and characterization of 3‐(2,3‐dihydroxypropoxy)propyl‐terminated polydimethylsiloxanes
Authors: Feng Shengyu , Zhang Jie , Wang Dake , Wu Mingyan , Yu Zhaotan
Published: July 2004

3‐(2,3‐Dihydroxypropoxy)propyl‐terminated polydimethylsiloxanes (DHT‐PDMS) samples were prepared through the copolymerization of 1,1,3,3,5,5,7,7‐octamethylcyclotetrasiloxane (D4) and 1,3‐bis[3‐(2,3‐dihydroxypropoxy)propyl]‐1,1,3,3‐tetramethyldisiloxane by acid‐catalyzed equilibration. Their structures were characterized with IR and 1H‐NMR spectra. The molecular weights were determined with gel permeation chromatography and 1H‐NMR spectra, respectively. Differential scanning calorimetry and thermogravimetric analysis were used to investigate the thermodynamic properties and thermal degradation of DHT‐PDMS. The effects of various factors on the synthesis of DHT‐PDMS were also examined. However, the preparation of DHT‐PDMS through the base‐catalyzed equilibrium copolymerization of D4 and 1,3‐bis[3‐(2,3‐epoxypropoxy)propyl]‐1,1,3,3‐tetramethyldisiloxane, followed by the hydrolysis of the epoxy groups, was unsuccessful. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 110–115, 2004
Effect of nano‐Mg(OH)2 on the mechanical and flame‐retarding properties of polypropylene composites
Authors: Mishra S. , Sonawane S. H. , Singh R. P. , Bendale A. , Patil K.
Published: July 2004

Nano‐Mg(OH)2 was synthesized with an in situ deposition technique, and its size was confirmed by X‐ray diffraction. A polypropylene–Mg(OH)2 composite was prepared by melt‐extrusion processing. The addition of a small quantity of a nanofiller (up to 10 wt %) increased Young's modulus up to 433% with respect to the modulus of virgin polypropylene. The addition of up to 4 wt % Mg(OH)2 produced the maximum increase, and a further decrease in the tensile strength was observed with an increase in the concentration of nano‐Mg(OH)2. Increases in the hardness and other properties were due to higher nucleation and the intercalation of polymer chains in the nanolayer galleries. The flame‐retarding property was demonstrated by the rate of burning. The time required to burn the nanofilled composite was greater than the time required for virgin polypropylene. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 116–122, 2004
Effect of some metal salt pretreatments on acrylic printing
Authors: Gabry L. K. El , Hakeim O. A.
Published: July 2004

Acrylic fabrics were pretreated with metal salts (aluminum sulfate, copper sulfate, ferrous sulfate, and potassium dichromate) in different concentrations. The tensile strength, elongation, and moisture regain of pretreated and untreated samples were examined. The effects of various concentrations of the metal salts, the pH of the printing paste, and the thickening agent on the color strength and fastness properties of the printed fabrics were studied to determine the optimum printing conditions. The pretreatment improved the printability of acrylic modified with a cationic dye and the fastness properties. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 130–134, 2004
A rheometrical technique to study the swelling kinetics of vulcanized rubber particles by paraffinic solvents using a torque rheometer
Authors: Gaulliard Vincent , Leblanc Jean L.
Published: July 2004

The solvent uptake by vulcanized rubber particles was studied through a swelling technique by using a torque rheometer to record torque versus time curves, with good repeatability. Several experiments were performed to study the effects of varying the solvent/rubber ratio, the solvent type, and the rubber nature. The effects of the materials alone were also studied. A four‐parameter mathematical model was developed, with a physical significance assigned to each of the parameters, and was compared with experiments. The model was found to fit well with the experimental results, therefore, allowing the physical processes involved in the solvent swelling of rubber particles to be investigated through model parameters. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 142–153, 2004
Sago starch and its acrylamide modified products as coating material on handsheets made from recycled pulp fibers
Authors: Yeng Wong Sin , Tahir Paridah Md. , Chiang Liew Kang , Yunus Wan Md. Zin Wan , Zakaria Sarani
Published: July 2004

This study was carried out to determine the suitability of sago starch as a paper additive. The basic properties (i.e., pH, viscosity, and solid content) of the 5% weight over volume basis of unmodified and modified sago starch (sago starch blended with acrylamide, sago starch grafted with acrylamide in an acidic and adjusted to alkaline conditions) were determined. The starches were then used to coat laboratory handsheets made from recycled pulp fibers. The incorporation of acrylamide into sago starch through grafting significantly reduced the viscosity of the solution. Generally, coating the handsheets with unmodified sago starch significantly improved some properties as compared to the uncoated handsheets. Among the three types of sago starch modification methods, blending gave superior performance when coated on the handsheets, except for smoothness and air permeance, due to insufficient curing shown by the micrographs. FTIR spectra showed that the interactions between the blended acrylamide–starch solutions and the pulp fiber were weak. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 154–158, 2004
Influence of polymer viscosity on the morphological and opto‐electronic behavior of polysiloxane dispersed ferroelectric liquid crystal composite thin films
Authors: Sumana G. , Raina K.K.
Published: July 2004

Poly(dimethyl)siloxanes of different viscosity have been synthesized by hydrolytic condensation of dimethyldichloro silane. Polysiloxane dispersed ferroelectric liquid crystal (PDFLC) composite films were prepared simultaneously by solvent induced and polymer induced phase separation techniques (SIPS and PIPS, respectively). These composite films were prepared by mixing polymer and ferroelectric liquid crystal mixture in diethyl ether and then adding 0.2% of room temperature vulcanizer for crosslinking. Film morphology, droplet size, and electro‐optic parameters of PDFLC systems have been studied by using polysiloxanes of different viscosity. We show that the polymer viscosity affects the droplet size, morphological uniformity, electro‐optic properties, and also the extent to which the phase separation is complete. These composite systems show the switching time of few microseconds. Structure‐property correlation in these materials have been studied and explained on the basis of polysiloxane viscosity. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 159–166, 2004
Structural properties of γ‐irradiated poly(vinyl alcohol)/poly(ethylene glycol) polymer blends
Authors: Abd Alla Safaa G. , Said Hossam M. , El‐Naggar Abdel Wahab M.
Published: July 2004

The effect of various doses of γ radiation on the structural properties of water‐soluble polymer blends based on poly(vinyl alcohol) (PVA) and poly(ethylene glycol) (PEG) has been investigated. Although the aqueous solutions of individual PVA and PEG homopolymers were homogeneous and clear, films transparent to visual observation were only formed by solution casting of pure PVA and those blends containing low ratios of PEG up to 30%. The structure‐property behavior of this range of blends before and after γ irradiation was investigated by light reflectance and UV absorbance, differential scanning calorimetry (DSC), IR spectroscopy, and tensile mechanical testing. The DSC thermograms of PVA/PEG blends, before or after γ irradiation, showed a solely endothermic peak over the temperature range 40–140°C, which may have arisen from the melting of the PEG component or from the glass transition of PVA/PEG as a miscible blend in accordance with those calculated on the basis of the theoretical Fox equation. Also, these thermograms did not clearly show any transition that arised from the pure PVA component. However, the improvement in tensile mechanical properties of PVA/PEG blends, the reflectance, and the optical absorption measurements support the idea of improved miscibility after γ irradiation. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 167–176, 2004
The effects of lignocellulosic fiber surface area on the dynamics of lignin oxidation and diffusion
Authors: Mancosky Douglas G. , Lucia Lucian A. , Deng Yulin
Published: July 2004

A novel preliminary experimental approach was developed to determine the effect of maximizing pulp fiber surface area for the regulation of the oxidation and diffusion of lignin through the carbohydrate matrix. The approach entailed liquid nitrogen freezing of mature black spruce kraft pulp fibers and subsequent mechanical grinding to a fine powder to test the effect of enhanced pulp fiber surface area on the efficiencies of lignin oxidation and lignin diffusion. It was found that the liquid nitrogen ground pulp samples provided higher optical reflectance (brightness) after both oxygen and hydrogen peroxide oxidation, which appears to be from chromophoric (chemical) differences and not light scattering differences as supported by UV/Vis spectroscopy. BET (absorption) experiments indicated a dramatic difference in the surface area of the pulp as a result of the grinding, although no differences existed among the pore sizes between the samples, as determined from SEM experiments. Lignin diffusion experiments demonstrated that differences did exist in the kinetics of lignin diffusion into a bulk solution between a control and liquid nitrogen ground samples. Lignin uptake into bulk solutions was enhanced by the liquid nitrogen/pulp‐grinding technique albeit not from chemical changes in the lignin because the subsequent NMR spectra did not point to any major chemical differences as a result of liquid nitrogen freezing and grinding. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 177–181, 2004
Curing kinetics and thermal property characterization of an o‐cresol formaldehyde epoxy resin and 4,4′‐diaminodiphenyl ether system
Authors: Gao Jungang , Zhao Min
Published: July 2004

The kinetics of the curing reaction for a system of o‐cresol formaldehyde epoxy resin (o‐CFER) with 4,4′‐diaminodiphenyl ether (DDE) as a curing agent were investigated with differential scanning calorimetry (DSC). An analysis of the DSC data indicated that an autocatalytic behavior appeared in the first stages of the cure for the system, and this could be well described by the model proposed by Kamal, which includes two rate constants and two reaction orders (m and n). The overall reaction order (m + n) was 2.7–3.1, and the activation energies were 66.79 and 49.29 kJ mol−1, respectively. In the later stages, a crosslinked network was formed, and the reaction was mainly controlled by diffusion. For a more precise consideration of the diffusion effect, a diffusion factor was added to Kamal's equation. In this way, the curing kinetics were predicted well over the entire range of conversions, covering both the previtrification and postvitrification stages. The glass‐transition temperatures of the o‐CFER/DDE samples were determined via torsional braid analysis. The results showed that the glass‐transition temperatures increased with the curing temperature and conversion up to a constant value of approximately 370 K. The thermal degradation kinetics of the system were investigated with thermogravimetric analysis, which revealed two decomposition steps. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 182–188, 2004