Fast adaptation to rule switching using neuronal surprise.

In humans and animals, surprise is a physiological reaction to an unexpected event, but how surprise can be linked to plausible models of neuronal activity is an open problem. We propose a self-supervised spiking neural network model where a surprise signal is extracted from an increase in neural activity after an imbalance of excitation and inhibition. The surprise signal modulates synaptic plasticity via a three-factor learning rule which increases plasticity at moments of surprise. The surprise signal remains small when transitions between sensory events follow a previously learned rule but increases immediately after rule switching. In a spiking network with several modules, previously learned rules are protected against overwriting, as long as the number of modules is larger than the total number of rules-making a step towards solving the stability-plasticity dilemma in neuroscience. Our model relates the subjective notion of surprise to specific predictions on the circuit level.

Nanocrystalline silicon optomechanical cavities.

Silicon on insulator photonics has offered a versatile platform for the recent development of integrated optomechanical circuits. However, there are some constraints such as the high cost of the wafers and limitation to a single physical device level. In the present work we investigate nanocrystalline silicon as an alternative material for optomechanical devices. In particular, we demonstrate that optomechanical crystal cavities fabricated of nanocrystalline silicon have optical and mechanical properties enabling non-linear dynamical behaviour and effects such as thermo-optic/free-carrier-dispersion self-pulsing, phonon lasing and chaos, all at low input laser power and with typical frequencies as high as 0.3 GHz.

Upconversion emission obtained in Yb(3+)-Er(3+) doped fluoroindate glasses using silica microspheres as focusing lens.

An intensity enhancement of the green upconversion emission from a codoped Er(3+)-Yb(3+) fluoroindate glass has been obtained by coating the glass surface with silica microspheres (3.8 µm diameter). The microspheres focus an incoming beam (λ ≈ 950 nm) on the surface of the fluoroindate glass. The green emission (λ ≈ 545 nm) of the Er(3+) ions located in the microsphere focus was measured with a microscope in reflection mode, being the peak intensity 4.5 times the emission of the bare substrate. The transversal FWHM of the upconversion spot was experimentally determined by deconvolution with the experimental Point Spread Function of the system, obtaining a value of 309 nm. This value is in good agreement with Finite-Difference Time-Domain simulations taking into account the magnification of the image due to the microsphere.

Whispering-gallery modes in glass microspheres: optimization of pumping in a modified confocal microscope.

Whispering-gallery modes (WGMs) on Nd3+-doped glass microspheres with a radius of ∼15 µm were measured in a modified confocal microscope, where a dual spatial resolution in both excitation and detection zones was possible. As an alternative to the standard excitation mechanism by an evanescent wave, we used an efficient pumping/detecting scheme, focusing a laser in the microsphere and exciting the Nd3+ ions, whose fluorescent emission produces the WGMs. We have also measured the generated WGMs by changing the detection zone, where higher amplitude resonances were found when exciting in the center and detecting at the edge of the microsphere.

Whispering gallery modes in a glass microsphere as a function of temperature.

Microspheres of Nd3+ doped barium titano silicate glass were prepared and the whispering gallery mode resonances were observed in a modified confocal microscope. A bulk sample of the same glass was calibrated as temperature sensor by the fluorescence intensity ratio technique. After that, the microsphere was heated by laser irradiation process technique in the microscope and the surface temperature was estimated using the fluorescence intensity ratio. This temperature is correlated with the displacement of the whispering gallery mode peaks, showing an average red-shift of 10 pm/K in a wide range of surface temperatures varying from 300 K to 950K. The limit of resolution in temperature was estimated for the fluorescence intensity ratio and the whispering gallery mode displacement, showing an improvement of an order of magnitude for the second method.

Direct electrochemistry of human, bovine and porcine cytochrome P450c17.

The direct electrochemistry of human, bovine and porcine cytochrome P450c17 (CYP17) has been examined on an edge-oriented pyrolytic graphite electrode. The recombinant protein was immobilized on an electrode modified with a surfactant to simulate the environment of a biological membrane, and hence physiological electron-transfer conditions. The P450 enzymes all retained 'electron-transfer' activity while immobilized at the electrode surface as assessed by the presence of catalytic signals under aerobic conditions. The redox potentials for porcine P450c17 were more positive (anodic) than both the human and bovine forms, perhaps reflecting the differences in substrate specificity for these species. In addition, these enzymes were all influenced by pH, consistent with a single proton associated with the single electron-transfer event. Ionic strength of the buffer medium also shifted the redox potentials towards positive, suggesting that electrostatic forces contribute to the protein environment required for the electron-transfer process. The effect of substrate on the redox potential for each P450c17 was measured in the presence of pregnenolone, progesterone, 17alpha-hydroxypregnenolone and 17alpha-hydroxyprogesterone. However, no influence on the redox parameters was observed.

Electrochemical characterisation of the human cytochrome P450 CYP2C9.

The electrochemistry of human cytochrome P4502C9 (CYP2C9) was characterised using purified His-tagged enzyme. The His-tagged enzyme was shown to have similar functional characteristics to native CYP2C9 heterologously expressed in Escherichia coli and to the CYP2C9 activity of human liver microsomes. Evidence was observed for a reversible one-electron transfer between the P450 heme and the electrode. Both pH and ionic strength influenced the electrochemical behaviour of CYP2C9. A range of substrates was investigated to determine the effect of the heme-substrate interaction on CYP2C9 redox potential. In the absence of oxygen, tolbutamide, diclofenac, warfarin and sulfaphenazole did not alter the redox potential of the iron heme. In contrast, torsemide, carbon monoxide and oxygen led to an anodic shift in redox potential. These results suggest alternative mechanisms by which CYP2C9 (and by inference other P450 enzymes) may alter redox potential to facilitate electron delivery from physiological donors.

Alpha7-nicotinic acetylcholine receptors mediate an Abeta(1-42)-induced increase in the level of acetylcholinesterase in primary cortical neurones.

The beta-amyloid protein (Abeta) is the major protein component of amyloid plaques found in the Alzheimer brain. Although there is a loss of acetylcholinesterase (AChE) from both cholinergic and non-cholinergic neurones in the brain of Alzheimer patients, the level of AChE is increased around amyloid plaques. Previous studies using P19 cells in culture and transgenic mice which overexpress human Abeta have suggested that this increase may be due to a direct action of Abeta on AChE expression in cells adjacent to amyloid plaques. The aim of the present study was to examine the mechanism by which Abeta increases levels of AChE in primary cortical neurones. Abeta1-42 was more potent than Abeta1-40 in its ability to increase AChE in primary cortical neurones. The increase in AChE was unrelated to the toxic effects of the Abeta peptides. The effect of Abeta1-42 on AChE was blocked by inhibitors of alpha7 nicotinic acetylcholine receptors (alpha7 nAChRs) as well as by inhibitors of L- or N-type voltage-dependent calcium channels (VDCCs), whereas agonists of alpha7 nAChRs (choline, nicotine) increased the level of AChE. The results demonstrate that the effect of Abeta1-42 on AChE is due to an agonist effect of Abeta1-42 on the alpha7 nAChR.

The influence of promoter and of electrode material on the cyclic voltammetry of Pisum sativum plastocyanin.

The reversible cyclic voltammetry of pea plastocyanin (Pisum sativum) was studied with a wide range of electrodes: edge-oriented pyrolytic graphite (PGE), glassy carbon (GCE), gold (Au) and platinum (Pt) electrodes. Plastocyanin was coated onto the electrode surface by exploiting the electrostatic interaction between the negatively charged protein and a wide range of positively charged promoters. The effect of the redox response with an extended range of promoters, including poly-L-lysine, polymyxin B, neomycin, tobramycin, geneticin, spermine and spermidine, were included in this study. The resulting cyclic voltammograms reveal that the observed midpoint potential for plastocyanin can be shifted significantly depending on the choice of promoter. The stability of the negatively charged plastocyanin-promoter layer on an electrode was gauged by the rate of bulk diffusion of the protein from the immobilised film into the solution. Reversible cyclic voltammograms were obtained using edge-oriented pyrolytic graphite (PGE) and glassy carbon electrodes (GCE) with all promoters; however, platinum and gold electrodes were unable to sustain a defined redox response. The combination of pyrolytic graphite electrode/poly-L-lysine/plastocyanin was found to be the most stable combination, with a redox response which remained well defined in solution for more than 1 h at pH 7.0. The midpoint potentials obtained in this manner differed between the two graphite electrodes PGE and GCE using poly-L-lysine as the promoter. This effect was in addition to the expected pH dependence of the midpoint potential for plastocyanin and the results indicated that the pK(a) for plastocyanin on PGE was 4.94 compared to that on GCE of 4.66. It is concluded that both the electrode material and the nature of the promoter can influence the position of the redox potentials for proteins measured in vitro. This study extends the range of biogenic promoters used in combination with electrode materials. Thus, we can begin to develop a more comprehensive understanding of electrode-protein interactions and draw conclusions as to metalloprotein function, in vivo. To support these studies, we have sought information as to the nature of the electrode/promoter/protein interaction using scanning tunneling microscopy (STM) to study both the promoter and the plastocyanin protein on a gold surface.

An extrusion strategy for the FeMo cofactor from nitrogenase. Towards synthetic iron-sulfur proteins.

Iron-sulfur clusters are ubiquitous in biological systems, facilitating functions such as electron transfer (rubredoxins, ferredoxins, rieske centres), isomerization (aconitase) and small molecule activation such as dinitrogen reduction (nitrogenases). Of global importance and recently particular interest, is the iron-sulfur-containing iron-molybdenum cofactor (FeMoco) cluster that achieves the biological reduction of dinitrogen under mild conditions. This biologically unique cluster has proved difficult to investigate due to its extreme air sensitivity and the instability of the cluster's structural integrity, outside the protective protein matrix. Here, we report a model iron-sulfur cluster (Roussins black salt (NH(4))[Fe(4)S(3)(NO)(7)]) that has been used to achieve the first example of a metal cluster (guest) embedded within a pseudo-protein, cyclodextrin (host). The product formed is supramolecular, that is, it contained no covalent bonds and was stabilized by predominantly entropy effects. Formation of a 1 : 1 complex between the host and the guest was established for the iron-sulfur cluster with either seven- or eight-membered cyclodextrins (beta- or gamma-cyclodextrin). A range of techniques was used to characterize the new complexes in both the solid and solution states. Electrospray mass spectra indicated the presence of parent ions of the host-guest complexes and electrochemistry was also used to define the redox behavior of the complexes. The iron-sulfur clusters were significantly more stable in the presence of the host cyclodextrin, as revealed by a negative shift for the reduction potential for the host-guest product. Using the beta-cyclodextrin as host, the reduction potential of the iron-sulfur cluster shifted more negative by 60 mV; the effect was even more dramatic for the larger gamma-cyclodextrin where the reduction potential for the cluster was shifted by 90 mV more negative than the 'unbound' [Fe(4)S(3)(NO)(7)]- cluster. This is the first example of a metal cluster, stabilized as a supramolecular complex in a 'host' environment outside of a covalently bonded protein matrix. Creating such stable environments for metal cofactors or clusters that otherwise spontaneously degrade or are catalytically inactive outside the protein matrix could have enormous practical value. Specific implications for the development of extrusion methods for FeMoco from nitrogenase are enormous, with previously difficult, high-energy molecular transformations, such as dinitrogen to ammonia, now more realistically accessible.

Goal orientations and the search for confirmatory affect.

People differ with respect to their beliefs about the consequences of attaining goals. Some people (linkers) believe that attaining certain goals will make them happy, whereas others (nonlinkers) see their happiness as more contingent upon the inherent quality of their actions than upon the outcomes of those actions. Because of the importance linkers place on goal attainment, linkers should be likely to seek information indicative of their progress toward their goals. Because of the importance nonlinkers place on enjoyment, nonlinkers should be likely to seek information indicative of the pleasurableness of their current task. Because negative affect can signal a lack of goal progress, whereas positive affect can signal task enjoyment, linkers may place more weight on their negative than their positive affect, whereas nonlinkers may do the opposite. Consistent with these hypotheses, the results of this study showed that linkers reported more negative affect when exposed to sad videos than when exposed to happy videos but did not report different amounts of positive affect. Nonlinkers, on the other hand, reported more positive affect when exposed to happy videos than when exposed to sad videos but did not report different amounts of negative affect. The implications of this pattern for a number of theoretical perspectives on goals and affect are discussed.

Determination of the chiral isomers of CGS 26214, a synthetic thyromimetic agent, in human plasma using microbore chiral chromatography-tandem mass spectrometry.

CGS 26214 is a racemic compound having cholesterol-lowering activity in rats, dogs, and monkeys. This compound has two equipotent chiral components CGS 28934(-) and CGS 28935(+). An analytical challenge was to develop a sensitive liquid chromatography/tandem mass spectrometry (LC/MS/MS) method for the analysis of the chiral components in human plasma following clinical doses of 1 mg or less. Several issues had to be addressed in order to devise a LC/MS/MS assay for the above compounds. First, the compounds were esters and susceptible to hydrolysis under experimental conditions. Second, a lower limit of quantitation (LLOQ) of 0.4 ng/ml was needed. Third, positive electrospray ionization of CGS 26214 did not yield sufficient sensitivity needed for the studies in humans. Consequently, LC/MS/MS conditions were optimized for negative ion mode of detection. Fourth, sample preparation steps proved to be critical in order to reduce the possibility of microbore chiral-HPLC column (100 x 1.0 mm i.d.) obstruction, chromatographic deterioration, and matrix mediated electrospray ion suppression. Although the present method addressed the above challenges, its major drawback was limited sample throughput capability. Nonetheless, the method was successfully applied to generate plasma concentration-time profiles for human subjects after oral doses (0.9 mg) of the racemate as well as the optically pure isomers.

Performance measurement: the new accountability.

Over the years, "accountability" in the human services has focused upon issues such as the legal framework, organizational management, financial responsibility, political concerns, and client inputs and expectations. Within the past decade, the meaning of "accountability" has been extended to the more dynamic organizational functions of "efficiency" and " effectiveness." Efficiency and effectiveness increasingly must be put to the tests of performance measurement and outcome evaluation. Forces outside the social work profession, including, among others, federal expectations and initiatives and the increased implementation of the concept of managed care, will ensure that efficiency and effectiveness will be central and highlighted concerns far into the future. This "new accountability" is demanded by the stakeholders in the nonprofit sector and by federal requirements built into the planning, funding, and implementation processes for nonprofits and for-profits alike.

Synthesis and structure-activity relationships of N-propyl-N-(4-pyridinyl)-1H-indol-1-amine (besipirdine) and related analogs as potential therapeutic agents for Alzheimer's disease.

A series of novel N-(4-pyridinyl)-1H-indol-1-amines and other heteroaryl analogs was synthesized and evaluated in tests to determine potential utility for the treatment of Alzheimer's disease. From these compounds, N-propyl-N-(4-pyridinyl)-1H-indol-1-amine (besipirdine, 4c) was selected for clinical development based on in-depth biological evaluation. In addition to cholinomimetic properties based initially on in vitro inhibition of [3H]quinuclidinyl benzilate binding, in vivo reversal of scopolamine-induced behavioral deficits, and subsequently on other results, 4c also displayed enhancement of adrenergic mechanisms as evidenced in vitro by inhibition of [3H] clonidine binding and synaptosomal biogenic amine uptake, and in vivo by reversal of tetrabenazine-induced ptosis. The synthesis, structure-activity relationships for this series, and the biological profile of 4c are reported.

Dibenzoxepinone hydroxylamines and hydroxamic acids: dual inhibitors of cyclooxygenase and 5-lipoxygenase with potent topical antiinflammatory activity.

Hydroxylamine and hydroxamic acid derivatives of a known nonsteroidal antiinflammatory dibenzoxepine series display both cyclooxygenase (CO) and 5-lipoxygenase (5-LO) inhibitory properties. Many of these new dual CO/5-LO inhibitors also exhibit potent topical antiinflammatory activity in the arachidonic acid-induced murine ear edema model. On the basis of their promising profile of in vitro and in vivo activities, hydroxamic acids 24h, 3-(6,11-dihydro-11-oxodibenz[b,e]oxepin-2-yl)-N-hydroxy-N-++ +methylpropanamide (HP 977), and 25, 3-(6,11-dihydrodibenz[b,e]oxepin-2-yl)-N-hydroxy-N- methylpropanamide (P10294), were selected as developmental candidates for the topical treatment of inflammatory skin disorders.

The impact of declining resources and purchase of service contracting on private, nonprofit agencies.

The increasingly precarious and vulnerable position of the private, nonprofit social service agency in an environment of government contracting and declining funding has been the subject of a number of articles over the past few years. Nonprofit agencies have been characterized as being controlled by powerful government agencies that dictate the terms and conditions of contracts, the types of services to be provided, the methods of delivery, and the price to be paid for services. One would expect to find nonprofits anxious to terminate their relationships with various units of government, and return to a more independent status. That is not happening. If anything, purchase of service contracting (POSC) with nonprofit agencies is increasing. This national study of nonprofit agencies explores the impact of declining funding from all sources (including POSC), and seeks to determine its impact on clients, staff, and organization.

7 beta-hydroperoxycholest-5-en-3 beta-ol, a component of human atherosclerotic lesions, is the primary cytotoxin of oxidized human low density lipoprotein.

Modification of low density lipoprotein (LDL) by free radical oxidation renders this molecular complex cytotoxic. Oxidized lipoproteins exist in vivo in atherosclerotic lesions and in the plasma of diabetic animals, suggesting that lipoprotein-induced tissue damage may occur in certain diseases. We undertook purification and identification of the major cytotoxin in oxidized LDL. The lipid extract from oxidized LDL was subjected to multiple HPLC separations, and the fractions were assayed for cytotoxicity. Mass spectrometry and nuclear magnetic resonance identified the purified toxin as 7 beta-hydroperoxycholest-5-en-3 beta-ol (7 beta-OOH-Chol). This molecule accounted for approximately 90% of the cytotoxicity of the lipids of oxidized LDL. We also found 7 beta-OOH-Chol in human atherosclerotic lesions from endarterectomy specimens obtained immediately after excision. These results are consistent with the hypothesis that the oxidized LDL present in lesions has the capacity to induce cell and tissue injury, leading to progression of the disease and the generation of the necrotic core of the lesion.

Synthesis, resolution, and SAR of (+/-)-2-amino-N-methyl-alpha-(3-methyl-2-thienyl)benzeneethanamine++ + and related analogs as noncompetitive NMDA antagonists with neuroprotective properties.

The preparation and structure-activity relationships of a series of 2-amino-alpha-thienylbenzeneethanamines are described. From this work, (+/-)-2-amino-N-methyl-alpha-(3-methyl-2-thienyl)-benzeneethanamine++ + (3a) and the homologous N-ethyl analog 3b emerged as novel noncompetitive NMDA antagonists with neuroprotective properties. Optical resolution of 3a and X-ray crystallography of (+)3a were performed. The racemate and enantiomers were evaluated for neuroprotective properties in models of ischemia-induced hippocampal damage (gerbil) and cerebral focal ischemia (rat). Pretreatment with 3a, (+)3a, or (-)3a significantly reduced ischemia-induced CA1 hippocampal damage. Posttreatment with 3a afforded a lower degree of neuroprotection. A highly significant reduction in infarct volume was observed with 3a in the cerebral focal ischemia model, with only weak positive effects being displayed by (+)3a. Dose-limiting side effects were associated with all three compounds in this model. In summary, the results demonstrate the utility of noncompetitive NMDA antagonists as neuroprotective agents for ischemia-induced neurodegeneration.

Validity and reliability of a quality-of-life instrument: the chronic respiratory disease questionnaire.

A pilot study was done to evaluate criterion-related validity and test-retest reliability of the Chronic Respiratory Disease Questionnaire (CRQ). The CRQ examines how chronic obstructive pulmonary disease (COPD) effects quality of life, and evaluates four dimensions: dyspnea, fatigue, emotional function, and mastery. The pilot study did not establish validity. One of the dimensions, mastery, did not correlate with any of the criterion instruments. Reliability was demonstrated when the instrument was retested after 9 days. The recommendation, based on this research, is that the CRQ may be useful in clinical settings, but not for research.

Purification and characterization of an endothelin degradation enzyme from rat kidney.

A soluble protease which effectively inactivated endothelin-1 was purified 2,700-fold from rat kidney using DE52 anion exchange, concanavalin A-Sepharose, thiopropyl-Sepharose, and Mono P column chromatography. The overall recovery of enzyme activity was 12%. This enzyme appeared to contain two subunits with molecular weights of 34 and 21 kDa. The molecular weight of the active enzyme complex was estimated to be 82 kDa by gel filtration. It was shown to have a pI between 4.8 and 5.2 and a pH optimum of 5.5. Its activity was inhibited by benzyloxycarbonyl-Phe-AlaCHN2 and p-hydroxymercuribenzoic acid, thiol protease inhibitors, and by phenylmethylsulfonyl fluoride, a serine protease inhibitor, but not by metalloprotease inhibitors or other serine protease inhibitors. The purified enzyme degraded endothelin-1 rapidly; KM and Vmax values were 5.9 microM and 0.40 mumol/mg/min, respectively. It removed the carboxyl terminal tryptophan of endothelin-1 by specifically cleaving the Ile20-Trp21 peptide bond, yielding a peptide which was three orders of magnitude less potent than endothelin-1 in causing contraction of porcine coronary arterial rings. In contrast, proendothelin-1 was not degraded by this enzyme. These results are consistent with published findings that show the clearance rate for proendothelin-1 in the pig to be significantly slower than that for endothelin-1. Our study suggests that this enzyme may play a role in the homeostasis of circulating endothelin-1 and contribute to the regulation of vascular tone.