Structural and Luminescence Properties of Lu2O3:Eu3+ F127 Tri-Block Copolymer Modified Thin Films Prepared by Sol-Gel Method

Lu₂O₃:Eu³⁺ transparent, high density, and optical quality thin films were prepared using the sol-gel dip-coating technique, starting with lutetium and europium nitrates as precursors and followed by hydrolysis in an ethanol-ethylene glycol solution. Acetic acid and acetylacetonate were incorporated in order to adjust pH and as a sol stabilizer. In order to increment the thickness of the films and orient the structure, F127 Pluronic acid was incorporated during the sol formation. Structural, morphological, and optical properties of the films were investigated for different F127/Lu molar ratios (0–5) in order to obtain high optical quality films with enhanced thickness compared with the traditional method. X-ray diffraction (XRD) shows that the films present a highly oriented cubic structure <111> beyond 1073 K for a 3-layer film, on silica glass substrates. The thickness, density, porosity, and refractive index evolution of the films were investigated by means of m-lines microscopy along with the morphology by scanning electron microscope (SEM) and luminescent properties.     

Decrease in the Reactivity of Locus Coeruleus Neurons to Hypotension after an Increase in their Tyrosine Hydroxylase Content: A Subregional In Vivo Voltammetry Study in the Rat

The aim of the present work was to determine if noradrenergic neurons of the anterior and the posterior subregions of the locus coeruleus exhibit a difference in reactivity in response to sodium nitroprusside-induced arterial hypotension, and if the pharmacological induction of tyrosine hydroxylase by RU24722 modifies the reactivity of locus coeruleus neurons to this hypotensive stimulus. Previous findings have demonstrated that administration of RU24722 increases the concentration of tyrosine hydroxylase in the rat locus coeruleus by two different mechanisms in the anterior and in the posterior locus coeruleus subregions. The goal of the present study was to measure in vivo the changes in catecholaminergic metabolism in the locus coeruleus after treatment with RU24722 using differential normal pulse voltammetry (DNPV). In vehicle-treated rats, arterial hypotension increased catecholaminergic metabolism with the same pattern in the two locus coeruleus subregions. However, the changes in the magnitude of the catechol oxidation current throughout the recording period were significantly smaller in the posterior subregion ( P < 0.001). In the RU24722-pretreated rats, there was a 39% increase in tyrosine hydroxylase and dihydroxyphenylacetic acid in the locus coeruleus. The functional reactivity to hypotension measured by DNPV was significantly decreased ( P < 0.001) in both the anterior and posterior locus coeruleus subregions with RU24722 treatment. Therefore, this study suggests that the response of locus coeruleus cells to a hypotensive stimulus depends upon the intracellular tyrosine hydroxylase concentration both in the basal condition and during pharmacological induction of tyrosine hydroxylase gene expression.     

Effects of the putative antidepressant,ABT 200, on the clearance of exogenous norepinephrine in rat cerebellum

ABT 200 [(RR,SS)-3-phenyl-l-[l′,2′,3′,4′-tetrahydro-5′,6′-methylenedi- oxy-1′-naphthalenyl-methyl]-pyrrolidine methanesulfonate] is a potent alpha₂-adrenoceptor antagonist (Ki = 1.2 nM) with modest norepinephrine uptake-blocking activity (IC₅₀ = 841 nM) that is currently under clinical evaluation as an antidepressant. The effects of ABT 200, nomifensine (an inhibitor of catecholamine uptake), and rauwolscine (a selective alpha2-adrenoceptor antagonist) on the clearance of exogenous norepinephrine in the cerebellum of urethane-anesthetized rats was investigated using a vivo electrochemistry. Chronoamperometric recordings were continuously made at 5 Hz using Nafion-coated, single carbon fiber electrodes. When a calibrated amount of norepinephrine was pressure-ejected at 5-min intervals from a micropipette adjacent (290–330 μM) to the electrode, transient and reproducible norepinephrine signals were detected. In response to systemic ABT 200 (30 mg/kg i.p.) or nomifensine (30 mg/kg i.p.1, the signals increased in both amplitude and time course, indicating significant inhibition of the norepinephrine transporter. A lower dose (15 mg/kg i.p.) of either ABT 200 or nomifensine had no effect in this paradigm. Local application of ABT 200 (400 μM) or nomifensine (400 μM) prior to pressure-ejection of norepinephrine also significantly increased the amplitude and time course of the norepinephrine signals. In contrast, systemic administration of rauwolscine (30 mgkg i.p.) or vehicle solution, and local application of vehicle solution, had no effect on the norepinephrine signals. These data indicate that at the higher dose evaluated, both ABT 200 and nomifensine inhibit cerebellar norepinephrine uptake in vivo. © 1995 Wiley-Liss, Inc.     

控制多种细胞在同一表面有序黏附的研究进展

体外进行多种细胞共培养体系的建立,为不同种类细胞间相互作用的研究提供了有效的途径.在细胞培养的基底表面运用化学修饰,改变其对蛋白质和细胞的吸附特性,可以良好地控制不同细胞的共培养.结合微流控技术,在同一基底上也可以达到多种细胞的共培养.本文综述这一领域近期的研究进展.     

Clozapine, haloperidol, and the D4 antagonist PNU-101387G: in vivo effects on mesocortical, mesolimbic, and nigrostriatal dopamine and serotonin release

Summary. With in vivo microvoltammetry, the dopamine (DA) receptor antagonists, clozapine (D₄/D₂), haloperidol (D₂) and the selective D₄ antagonist, PNU-101387G, were evaluated for their effects on DA and serotonin (5-HT) release within A₁₀ neuronal terminal fields [mesocortical, prefrontal cortex (PFC), mesolimbic, nucleus accumbens, (NAcc)] and within A₉ neuronal terminal fields [nigrostriatal, caudate putamen (CPU)], in chloral hydrate anesthetized rats. Clozapine, which also has 5-HT₂ receptor antagonist properties, significantly (p < 0.001) increased DA release within A₁₀ terminal fields, PFC and NAcc; DA release was not increased by clozapine within A₉ terminals, CPU. Serotonin release was significantly (p < 0.001) increased by clozapine within A₁₀ and A₉ terminal fields. Haloperidol significantly (p < 0.001) increased DA release within PFC, dramatically and significantly (p < 0.001) increased DA release within CPU, but not within NAcc; haloperidol had a small but statistically significant (p < 0.05) increase on 5-HT release within PFC [only at the highest dose studied (2.5 mg/kg)] and within CPU [only at the lowest dose studied 1.0 mg/kg) (p < 0.05)]. The selective D₄ antagonist, PNU-101387G dramatically and significantly (p < 0.001) increased DA release within PFC, modestly, but significantly (p < 0.001) increased DA release within CPU, did not alter DA release within NAcc at the lowest dose studied (1.0 mg/kg) and significantly (p < 0.05) decreased DA release within NAcc at the highest dose studied (1.0 mg/kg). The selective D₄ antagonist did not affect 5-HT release within either A₁₀ or A₉ terminal fields. The present data are discussed in terms of the neurochemistry, antipsychotic activity, and side effect profiles of clozapine and haloperidol, in order to provide comparative profiles for a selective D₄ antagonist, PNU-101387G. Received January 13, 1998; accepted April 27, 1998     

Electrochemical monitoring of nitric oxide released by myenteric neurons of the guinea pig ileum

Abstract Nitric oxide (NO) released by myenteric neurons in isolated segments of guinea pig ileum was monitored in vitro using continuous amperometry. NO was detected as an oxidation current recorded with a boron‐doped diamond microelectrode held at 1 V vs a Ag|AgCl reference electrode. This potential was sufficient to oxidize NO. Longitudinal muscle‐myenteric plexus (LMMP) and circular muscle strip preparations were used. In the LMMP preparation, NO release was evoked by superfusion of 1 μmol L^?1 nicotine, which activates nicotinic acetylcholine receptors expressed by myenteric neurons and myenteric nerve endings. The oxidation current was ascribed to NO based on the following observations: (i) no response was detected at less positive potentials (0.75 V) at which only catecholamines and biogenic amines are oxidized, (ii) the current was abolished in the presence of the nitric oxide synthase antagonist, N‐nitro‐l ‐arginine (l ‐NNA) and (iii) oxidation currents were attenuated by addition of the NO scavenger, myoglobin, to the superfusing solution. In the LMMP preparation, stimulated release produced a maximum current that corresponded nominally to 46 nmol L^?1 of NO. The oxidation currents decreased to 10 and 2 nmol L^?1, respectively, when the tissue was perfused with tetrodotoxin and l ‐NNA. Oxidation currents recorded from circular muscle strips (stimulated using nicotine) were threefold larger than those recorded from the LMMP. This study shows that NO release can be detected from various in vitro preparations of the guinea pig ileum using real‐time electroanalytical techniques.     

Chronoamperometry in vivo: does it interfere with spontaneous neuronal activity in the brain?

To test whether chronoamperometry in vivo interferes with spontaneous neuronal activity, chronoamperometric measurements were combined with electrophysiological recordings in the same preparation. Chronoamperometric measurements (0.5--1.0 V applied for 1 s) were taken in the rat corpus striatum and single unit activity was recorded extracellularly in the same area. With potentials of 0.5 V, chronoamperometric measurements did not interfere with spontaneous activity of the striatal neurons, even of those units situated in close proximity (approximately 100 micrometers) to the tip of the electrochemical working electrode. Chronoamperometric measurements at potentials from 0.6 to 1.0 V accelerated or inhibited the firing rates of part of the striatal neurons, even when the electrophysiological circuit was interrupted during the application of the chronoamperometric pulse.     

Europium-activated phosphors for use in X-ray detectors of medical imaging systems

Three europium-activated phosphors Y₂O₂S:Eu, Y₂O₃:Eu, and YVO₄:Eu emitting red light were studied to investigate their suitability for radiographic cassettes or digital imaging systems. Screens were prepared from phosphor powders with various coating thicknesses by sedimentation. To assess phosphor light producing efficiency in relation to patient dose, each screen was X-rayed using 40–120 kVp and the number of light photons emitted per X-ray incident was experimentally and theoretically evaluated. Additionally, the capability of the emitted light to sensitize films or to generate electrons in silicon photodiodes used in digital imaging systems was examined. Y₂O₂S:Eu screens were most efficient in light emission, and when combined with either red sensitive films or Si photodiodes, they were found superior to Y₂O₃:Eu or YVO₄:Eu screens in film grain or electron signal generation. In many cases they were also found superior to terbium-activated phosphors. Provided that several problems related to industrial production (special dyes, reflective backing, crossover effects) are dealt with, those europium-activated screens could be employed in low-tube-voltage radiographic applications. Received 17 March 1997; Revision received 25 July 1997; Accepted 21 August 1997     

Environmental stimuli but not homeostatic challenges produce apparent increases in dopaminergic activity in the striatum: An analysis by in vivo voltammetry

Using in vivo voltammetry in rats, we examined the relationship between the electrochemical signal measured in the striatum and the behavioral responses associated with various type of stimulation. Three patterns emerged. First, a series of homeostatic challenges, including abrupt decreases in glucose utilization, blood volume, or arterial blood pressure, were ineffective in altering the electrochemical signal despite the sympathoadrenal response produced by each. Second, intense exteroceptive stimuli, such as an electric shock applied to the tail or placing animals in a shallow ice-water bath, provoked large and abrupt rises in the signal which decayed rapidly. Third, rats eating after a 24-h fast, drinking after a period of dehydration, or presented with novel olfactory or visual stimuli, exhibited much smaller and more gradual rises in the electrochemical signal which were more long-lasting. In each case, the magnitude of the change in electrochemical signal was generally related to the level of behavioral activation, being most prominent when treatments produced a startle response. Those large increases in signal were markedly attenuated by pretreatment withα-methyl-p-tyrosine or γ-butyrolactone, drugs known to decrease the release of dopamine, suggesting that the signal observed was associated with an increase in the activity of central dopaminergic neurons.