The selective neuronal NO synthase inhibitor 7-nitro-indazole blocks both long-term potentiation and depotentiation of field EPSPs in rat hippocampal CA1 in vivo

The membrane-permeant gas NO is a putative intercellular messenger that has been proposed on the basis of previous in vitro studies to be involved in synaptic plasticity, especially the induction of long-term potentiation (LTP) of excitatory synaptic transmission in the hippocampus and cortex. In the present study, the role of NO in synaptic plasticity has been investigated in vivo. In particular, the action of the novel and selective neuronal NO synthase (nNOS) inhibitor 7-nitro-indazole (7-NI) has been investigated on the induction of LTP and depotentiation (DP) of field EPSPs in CA1 of the hippocampus in vivo. Unlike previously studied nonselective NOS inhibitors, 7-NI does not increase arterial blood pressure. In vehicle-injected rats, high-frequency stimulation consisting of a series of trains at 200 Hz induced LTP. However, LTP induction was strongly inhibited in 7-NI (30 mg/kg, i.p.)-treated animals. The inhibitory effect of 7-NI on the induction of LTP was prevented by pretreatment with L-arginine, the substrate amino acid used by NOS. In control animals, low-frequency stimulation consisting of 900 stimuli at 10 Hz induced DP of previously established LTP, whereas in 7-HI-treated animals only a short-term depression was induced. This effect of 7-NI also was prevented by D-arginine. The LTP and DP induced in control animals in this study were NMDA receptor-dependent, the NMDA receptor antagonist 3-(R,S)-2-carboxypiperazin-4-yl-propyl-1- phosphonic acid inhibiting the induction of both forms of synaptic plasticity. The present experiments are the first to demonstrate that an NOS inhibitor blocks the induction of the synaptic component of LTP and DP in vivo and, therefore, these results strengthen evidence that the production of NO is necessary for the induction of LTP and DP.     

Sensitivity to violations of "run" and "trill" structures in rat serial-pattern learning.

Rats learned serial patterns composed of either "run" chunks (e.g., 123 234…) or "trill" chunks (e.g., 121 232…). For each type of pattern, 1 group of rats encountered an element at the end of the pattern that violated the run or trill structure. In both run and trill patterns violations were unusually difficult for rats to learn, whereas corresponding elements in "perfect" patterns that did not violate pattern structure were easy. Additionally, rats' errors on violation elements conformed to the structure of the patterns in which they were embedded. Thus, rats were sensitive to the run or trill organization of their patterns and mastered the rules governing the pattern before learning "exceptions to the rule." (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Epitope-labeled soluble human interleukin-5 (IL-5) receptors. Affinity cross-link labeling, IL-5 binding, and biological activity

The human receptor for the potent eosinophilopoietic cytokine interleukin-5 (IL-5) consists of two components: a 60-kDa ligand-binding alpha chain (IL-5 alpha R) and a 130-kDa beta chain (IL-5 beta R). Three ectodomain constructs of the alpha chain (alpha RED) bearing C-terminal epitope tags were engineered and expressed in baculovirus-infected Sf9 cells. Each recombinant alpha chain was secreted into the medium, maximum expression occurring 72 h post-infection. The various soluble alpha chains were shown by affinity cross-link labeling and competition with unlabeled IL-5 to bind recombinant human (rh) 125I-IL-5 specifically with an ED50 of 2-5 nM. The epitope tag provided a simple purification of the receptor from conditioned medium using immunoaffinity chromatography. The purified material had an apparent molecular mass of 43 kDa and was heterogeneously glycosylated. Sedimentation analysis revealed a 1:1 association of the purified epitope-tagged soluble receptor with its ligand, resulting in the formation of a 70-74-kDa complex. Circular dichroism analysis revealed that the soluble alpha chain existed with a significantly ordered structure consisting of 42% beta-sheet and 6% alpha-helix. Such analyses combined with fluorescence spectrometry suggested that ligand-receptor complex formation in solution resulted in minimal conformational changes, consistent with the suggestion that the membrane-associated form of the alpha chain itself has minimal signal transduction capability. Surface plasmon resonance studies of the interaction of the purified alpha RED with immobilized rhIL-5 revealed a specific, competable interaction with a dissociation constant of 9 nM. Preincubation of an IL-5-dependent cell line with the epitope-tagged alpha RED also dose-dependently neutralized rhIL-5-induced proliferation. These data demonstrate that biologically active epitope-tagged recombinant soluble IL-5 receptors are facile to produce in large quantities and may have therapeutic utility in the modulation of IL-5-dependent eosinophilia in man.     

The prejunctional inhibitory effect of suramin on neuromuscular transmission in vitro

The P2 purinoceptor antagonist suramin reverses skeletal muscle paralysis evoked by non-depolarizing neuromuscular blocking agents in vitro and in vivo. To further study the action of suramin on neuromuscular transmission, (miniature) endplate potentials ((m.)e.p.ps), motor nerve terminal currents and the release of radiolabeled acetylcholine was measured in isolated nerve-muscle preparations. In preparations paralysed by low Ca2+/high Mg2+ conditions, suramin (10 microM-1 mM) induced a concentration-dependent decrease in quantal content of the e.p.ps without affecting m.e.p.ps. Suramin reversed neuromuscular block by d-tubocurarine in these preparations. In erabutoxin paralysed preparations, suramin (40 microM-1 mM) inhibited the motor nerve terminal currents related to Ca2+ influx concentration-dependently, but did not affect Na+ currents. Suramin-induced inhibition of Ca2+ currents was not antagonized by ATP gamma S. Suramin (300 microM) reduced [14C]acetylcholine outflow in non-paralysed rat phrenic nerve-hemidiaphragm preparations by 32%. As suramin did not chelate Ca2+, these results indicate that suramin inhibits neuromuscular transmission by blocking prejunctional Ca2+ channels, thereby decreasing acetylcholine release upon nerve stimulation.     

Determination of extractable and bound condensed tannin concentrations in forage plants,protein concentrate meals and cereal grains

A procedure was developed for extraction of ‘free’ condensed tannins (CT) using a mixture of acetone/water/diethyl ether (4.7:2.0:3.3), followed by extraction of protein-bound and fibre-bound CT using boiling sodium dodecyl sulphate containing 2-mercaptoethanol (SDS). CT concentrations in all three fractions were determined by a modified butanol-HCI procedure. Separate standard curves using purified CT in water or SDS solution were utilised for analysis of extractable CT (water standards) and protein-bound and fibre-bound CT (SDS standards). The method accurately predicted the concentration of CT added to forage extracts. CT extractable in acetone/water/diethyl ether comprised, on average. 68% of total CT in a range of freeze dried forage legume samples, with most of the remainder being bound to protein. When total CT concentration was low (0.6-3.0% DM), a lower proportion was extractable (33-35%). In protein concentrate meals containing CT, the extractable, protein-bound and fibre-bound components comprised 15, 60 and 25% respectively of total CT. Total CT concentration in the forages Lotus corniculatus and Coronilla varia was considered appropriate for ruminant nutrition (2.1 and 3.0% DM). whilst CT concentration in the forage of Dorycnium spp (13–19% DM) was more suitable for soil conservation purposes. The substantial CT concentration in cottonseed meal (1.6% DM) may be involved in the high resistance of proteins in this product to ruminal degradation. CT concentration was indistinguishable from zero in perennial ryegrass forage, in barley and triticale grains and in soya bean meal (0.1% DM).     

Optimal seek profile generation with time-varying weightings for hard disk drives

In this paper, an optimal servo control strategy is presented to achieve high seek/settle performance without compromising the targeted seek time in hard disk drives. The cost function to be optimized is given by a weighted quadratic function with respect to time and the jerk of control command. Thanks to the fact that the cost function is directly penalized with time-varying weightings, the proposed method is more effective to minimize the settling vibration induced by the actuator seek profile compared with the previous optimization approaches in literature. The proposed approach is applicable to any given initial and terminal conditions.     

Experiment and computational fluid dynamics investigation of biochar elutriation in fluidized bed

In fluidized bed biomass fast pyrolysis, the biomass is converted to biochar and elutriated. The elutriation rate is a key parameter in reactor designs and operations. This research presents a video-based continuous measurement of biochar elutriation rate in a fluidized bed with sands and biomass as bed materials. The fluidized bed is simulated with the computational fluid dynamics—coarse-grained discrete element method (CFD-CGDEM) in MFiX. The fluidization behavior of nonspherical sands can be more accurately captured when a rolling friction model is used. The predicted elutriation rate is close to the experimental measurement when the particle size distributions are considered and the filtered drag with a shape correction is used. These results validated the accuracy of the MFiX-based CFD framework for the prediction of biochar elutriations in the fluidized bed biomass fast pyrolysis reactor.