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At least 1,747 records · Page 97Linked to original sources
PubMed2004

Formation of silver bromide precipitate of nanoparticles in a single microemulsion utilizing the surfactant counterion.

Silver bromide precipitate of nanoparticles was prepared by addition of silver nitrate aqueous solution to a single microemulsion system consisting of dioctyldimethylammonium bromide, n-decanol, and water in isooctane. The silver ion reacted readily with the surfactant counterion, bromide, to form the precipitate of nanoparticles, which was stabilized in the water pools. The use of the surfactant counterion as a reactant is a new approach to nanoparticle preparation in microemulsions. It is characterized by high reactivity and less dependency on the intermicellar exchange of solubilizate. The effects of the surfactant and the cosurfactant concentrations, the amount of silver nitrate, and the water to surfactant mole ratio, R, were evaluated. Increasing the surfactant concentration at fixed R and amount of silver nitrate enhanced the role of intermicellar nucleation and resulted in the formation of larger particles, while increasing the amount of silver nitrate at fixed values of all the other variables enhanced the direct nucleation and resulted in the formation of smaller particles. Particle aggregation and flocculation took place when the concentration of n-decanol or the value of R was increased. Particle aggregation and flocculation were attributed to the decrease in the interaction between the surfactant protective layer and the nanoparticles in the water pools.

Journal Article↗
PubMed2005

Delivery of the antibiotic gentamicin sulphate from precipitation cast matrices of polycaprolactone.

Microporous, poly(epsilon-caprolactone) (PCL) matrices were loaded with the aminoglycoside antibiotic, gentamicin sulphate (GS) using the precipitation casting technique by suspension of powder in the PCL solution prior to casting. Improvements in drug loading from 1.8% to 6.7% w/w and distribution in the matrices were obtained by pre-cooling the suspension to 4 degrees C. Gradual release of approximately 80% of the GS content occurred over 11 weeks in PBS at 37 degrees C and low amounts of antibiotic were measured up to 20 weeks. The kinetics of release could be described effectively by the Higuchi model with the diffusion rate constant (D) increasing from of 1.7 to 5.1 microg/mg matrix/day(0.5) as the drug loading increased from 1.4% to 8.3% w/w. GS-loaded PCL matrices retained anti-bacterial activity after immersion in PBS at 37 degrees C over 14 days as demonstrated by inhibition of growth of S. epidermidis in culture. These findings recommend further investigation of precipitation-cast PCL matrices for delivery of hydrophilic molecules such as anti-bacterial agents from implanted, inserted or topical devices.

Anti-Bacterial Agents↗
PubMed2005

Mathematical modeling of wire-duct single-stage electrostatic precipitators.

A two-dimensional mathematical model was developed to simulate the performance of wire-duct single-stage electrostatic precipitators (ESP). The model presented by Talaie et al. [M.R. Talaie, M. Taheri, J. Fathikaljahi, A new method to evaluate the voltage-current characteristics applicable for a single-stage electrostatic precipitator, J. Electrostat., 53 (3) (2001) 221-233] was used for prediction of electric field strength distribution and V-I characteristic for high-voltage wire-plate configuration. Simple Lagrangian approach was used to predict particle movement. Normal k-epsilon turbulent flow model with considering electrical body force due to ion and charged particle flow was used to evaluate gas velocity distribution. Ignoring the effect of particle movement and fluid flow, the results of electrical part of mathematical model are in good agreement with experimental data of Penny and Matick [G.W. Penny, R.E. Matrick, Potential in DC corona field, Trans. AIEE Part 1, 79 (1960) 91-99]. The prediction of corona sheath radius and its variation with particle loading and applied voltage is the main distinguishing feature of the present model. This fact was not included in the earlier models.

Filtration↗
PubMed2005

Hemidystonia precipitated by acute pontine infarct.

Hemidystonia is frequently due to an underlying structural lesion in the basal ganglia and thalamus. It has been suggested that a preserved corticospinal tract may be required for hemidystonia to manifest. We provide the first report of a patient who presented with rapid-onset hemidystonia precipitated by an acute pontine infarct demonstrated on diffusion-weighted magnetic resonance imaging. Acute dysregulation of pallidal efferents to the pedunculopontine and/or pontine afferents to the thalamus may precipitate hemidystonia.

Adult↗
PubMed2005

Precipitation of bovine rotavirus by polyethylene [corrected] glycol (PEG) and its application to produce polyclonal and monoclonal antibodies.

Many protocols are available to produce monoclonal antibodies (MAbs) against bovine rotavirus (BRV) using purified virus particles but those methods are time-consuming and produce substantial loss of virus structure or infectivity. Polyethylene gycol (PEG) viral precipitation was investigated as a possible alternative method to obtain purified virus and viral antigen for monoclonal and polyclonal antibodies production. The antigenic mass inoculated into rabbits was sufficient to obtain a polyclonal hyperimmune serum with neutralizing activity and a wide range of humoral responses to different viral proteins with minimum cellular contamination. This antigenic mass inoculated into mice was capable of producing seven MAbs with different biochemical characteristics (Western-blot; indirect immunofluorescence and serum neutralization assays). When evaluated as diagnostic tools to detect BRV antigen in feces the MAbs were effective for detecting rotavirus in naturally infected calves. This work demonstrate that PEG precipitation could be an useful procedure for obtaining viral antigen to produce polyclonal and MAbs against BRV. The antigenic mass obtained, the viral infectivity, and the conserved protein pattern suggest that this methodology could be applied to this and to other viruses, reducing time or possible loss of antigens involved in viral purification.

Animals↗
PubMed2005

Study of changes in composition and EELS ionization edges upon Ni4Ti3 precipitation in a NiTi alloy.

Concentration gradients surrounding Ni4Ti3 precipitates grown by appropriate annealing in a Ni51Ti49 B2 austenite matrix are investigated by electron energy loss spectroscopy (EELS) and energy filtered transmission electron microscopy (EFTEM). Concentration gradients of approximately 1.0-2.0 at.% in Ni within the surrounding B2 matrix can be detected by both EELS and EFTEM, revealing a Ni depleted zone in the matrix. Besides the concentration gradients, the EELS integrated cross-section of the Ni L(2,3) edges for the Ni-depleted region increased slightly, when compared with a matrix region away from the precipitate and not depleted in Ni.

Journal Article↗
PubMed2004

Effect of naloxone-precipitated morphine withdrawal on c-fos expression in rat corticotropin-releasing hormone neurons in the paraventricular hypothalamus and extended amygdala.

Morphine withdrawal is characterized by physical symptoms and a negative affective state. The 41 amino acid polypeptide corticotropin-releasing hormone (CRH) is hypothesized to mediate, in part, both the negative affective state and the physical withdrawal syndrome. Here, by means of dual-immunohistochemical methodology, we examined the co-expression of the c-Fos protein and CRH following naloxone-precipitated morphine withdrawal. Rats were treated with slow-release morphine 50 mg/kg (subcutaneous, s.c.) or vehicle every 48 h for 5 days, then withdrawn with naloxone 5 mg/kg (s.c.) or saline 48 h after the final morphine injection. Two hours after withdrawal rats were perfused transcardially and their brains were removed and processed for immunohistochemistry. We found that naloxone-precipitated withdrawal of morphine-dependent rats increased c-Fos immunoreactivity (IR) in CRH positive neurons in the paraventricular hypothalamus. Withdrawal of morphine-dependent rats also increased c-Fos-IR in the central amygdala and bed nucleus of the stria terminalis, however these were in CRH negative neurons.

Amygdala↗
PubMed2006

Blockade of nicotinic acetylcholine or dopamine D1-like receptors in the central nucleus of the amygdala or the bed nucleus of the stria terminalis does not precipitate nicotine withdrawal in nicotine-dependent rats.

Approximately 70% of tobacco smokers wish to quit, but attempts are often unsuccessful partly due to the aversive nicotine withdrawal syndrome. We investigated the possible involvement of nicotinic and dopaminergic signalling in the central nucleus of the amygdala (CeA) and dorsolateral bed nucleus of the stria terminalis (dlBNST) in the anhedonic depression-like effect of precipitated nicotine withdrawal in rats. Nicotine-dependent rats exhibit elevations in intracranial self-stimulation (ICSS) thresholds compared to control rats after cessation of chronic nicotine administration (spontaneous withdrawal) or systemic or intra-ventral tegmental area (VTA), but not intra-nucleus accumbens (NAcc), administration of nicotinic acetylcholine receptor (nAchR) antagonists while exposed to nicotine (precipitated withdrawal). We examined whether intracerebral administration of the nAChR antagonist dihydro-beta-erythroidine (DHbetaE; 0.6-20 microg total bilateral dose) or the dopamine D1-like receptor antagonist SCH 23390 (2-16 microg total bilateral dose) into the CeA and dlBNST results in withdrawal-like threshold elevations in nicotine-treated rats. Nicotinic acetylcholine and D1-like receptor blockade in the CeA or the dlBNST did not induce differential threshold elevations in nicotine- and saline-treated rats. Further, the highest SCH 23390 dose (16 microg bilateral dose) injected into the dlBNST, but not the CeA, elevated thresholds similarly in both saline- and nicotine-treated rats, suggesting that dopaminergic signalling in the dlBNST may regulate brain reward function under baseline conditions. These results suggest that nACh and D1-like signalling in the CeA and the dlBNST does not develop neuroadaptations with the development of nicotine dependence that may be involved in the depression-like aspects of nicotine withdrawal.

Amygdala↗
PubMed2006

Lack of cyclic AMP-specific phosphodiesterase 4 activation during naloxone-precipitated morphine withdrawal in rats.

Intracellular cyclic AMP regulation systems play an important role in the mechanisms of morphine dependence and withdrawal. In the present study, to clarify the involvement of phosphodiesterase (PDE) 4, degradation enzyme of cyclic AMP in morphine dependence and withdrawal we investigated the activities of PDE4 after naloxone-precipitation in single morphine treatment and repeated morphine treatment (morphine-dependence) rats. Naloxone (5 mg/kg, s.c.) challenge caused a significant withdrawal signs such as jumping in morphine-dependent rats following repeated treatment with morphine (4, 8, 12, and 16 mg/kg, twice a day for 4 days), but not in single morphine-treated rats (16 mg/kg, single). Naloxone challenge caused an increase in PDE4 activities in the brain of rats treated with single morphine in connection with the elevation of brain cyclic AMP. In contrast, increase in the PDE4 activities was not caused by naloxone challenge in all brain regions of morphine-dependent rats, although brain cyclic AMP was significantly increased. These results suggest that the lack of PDE4 activation leading to remarkable elevation of cyclic AMP is involved in naloxone-precipitated morphine withdrawal symptoms.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed2003

Cardiovascular and behavioural effects induced by naloxone-precipitated morphine withdrawal in rat: characterization with tachykinin antagonists.

This study examined the intracerebroventricular (i.c.v.) effects of three selective tachykinin receptor antagonists on the cardiovascular and behavioural responses induced by naloxone-precipitated morphine withdrawal in rats. I.c.v. injection of naloxone (10 microg) to morphine pre-treated rats (i.c.v. for 5 days) induced an immediate increase in blood pressure ( approximately 10 mmHg) and behavioural activity (sniffing > rearing > face washing approximately grooming approximately wet dog shake) without causing significant heart rate changes. The prior i.c.v. injection of the NK(1) receptor antagonist (6.5 nmol LY306740) reduced face washing and grooming during morphine withdrawal. NK(2) and NK(3) receptor antagonists (6.5 nmol SR48968 and R820) did not affect behavioural effects, yet the co-injection of the three tachykinin antagonists reduced all behavioural activity. The pressor response was not affected by the selective inhibition of NK(1) and NK(3) receptors while both blood pressure and heart rate were markedly enhanced by SR48968 during morphine withdrawal. The potentiating effect of SR48968 was prevented following simultaneous blockade of the three tachykinin receptors. In addition to confirming the involvement of central tachykinins in behavioural manifestations to morphine withdrawal, data suggest a modulatory function for tachykinins, especially the NK(2) receptor, in brain autonomic control of blood pressure and heart rate in supraspinal noloxone-precipitated withdrawal.

Acetamides↗
PubMed2005

Activation of the spinal ERK signaling pathway contributes naloxone-precipitated withdrawal in morphine-dependent rats.

Extracellular signal-regulated kinase (ERK), a mitogen-activated protein kinases (MAPK), transduces a broad range of extracellular stimuli into diverse intracellular responses. Recent studies have showed that ERK activation in the supraspinal level involved in the development of drug dependence, especially in psychological dependence. In this study, we reported that the spinal ERK signaling pathway was activated by chronic morphine injection. There was a further increase in ERK activation after naloxone-precipitated withdrawal. Furthermore, attenuation of the spinal ERK phosphorylation by intrathecal a MAPK kinase (MEK) inhibitor U0126 or knockdown of the spinal ERK by antisense oligonucleotides not only decreased the scores of morphine withdrawal, but also attenuated withdrawal-induced allodynia, which were accompanied by decreased ERK phosphorylation in the spinal cord. The spinal ERK inhibition or knockdown also reduced morphine withdrawal-induced phosphorylation of cAMP response element binding protein (CREB), which is one of the important downstream substrates of ERK pathway, and Fos expression. The involvement of the spinal ERK in morphine withdrawal was supported by our finding that intrathecal N-methyl-D-aspartate receptor antagonist MK-801 or protein kinase C inhibitor chelerythrine chloride suppressed withdrawal-induced ERK activation in the spinal cord and attenuated morphine withdrawal symptoms. These findings suggest activation of the spinal ERK signaling pathway contributes naloxone-precipitated withdrawal in morphine-dependent rats.

Animals↗
PubMed2005

Blockade of the expression of mecamylamine-precipitated nicotine withdrawal by calcium channel antagonists.

The present study focused on the evaluation of nicotine abstinence syndrome in mice and on the influence of calcium channel blockers on the expression of the somatic signs of nicotine withdrawal. Our experimental protocol consisted of intermittent administration of nicotine, 2.5 mgkg(-1), subcutaneously (s.c.), four times daily for 7 days. In attempt to precipitate nicotine abstinence, mice were given one injection of mecamylamine (3 mgkg(-1), intraperitoneally (i.p.)), 1h after the last nicotine injection, on the test day (day 8) in the morning. Additionally, body weight changes, locomotor activity and anxiogenic responses in the elevated plus maze test were also evaluated in nicotine withdrawn mice. Our data shown that the L-type calcium channel antagonists, nimodipine, verapamil, flunarizine and diltiazem (5 and 10 mgkg(-1), i.p., each), injected before mecamylamine administration, dose-dependently attenuated the expression of nicotine withdrawal signs. Moreover, 24h after terminating nicotine treatment, we also observed additional nicotine abstinence measures, such as loss of body weight followed by a slight body weight gain, decrease of spontaneous locomotor activity and anxiogenic responses. These findings obtained using our valuable rodent model of nicotine dependence suggest the involvement of calcium-dependent mechanisms in the expression of mecamylamine-precipitated nicotine abstinence syndrome.

Animals↗
PubMed2007

Factors that predispose, prime and precipitate NREM parasomnias in adults: clinical and forensic implications.

Sleepwalking and related disorders are the result of factors that predispose, prime and precipitate episodes. In the absence of one or more of these factors sleepwalking is unlikely to occur. Predisposition to sleepwalking is based on genetic susceptibility and has a familial pattern. Priming factors include conditions and substances that increase slow wave sleep (SWS) or make arousal from sleep more difficult. These factors include sleep deprivation, alcohol, medications, situational stress and fever among others. The patient with a genetic predisposition to sleepwalking and with priming factors still requires a precipitating factor or trigger to set the sleepwalking episode in motion. Classical theories of sleepwalking were based primarily on case reports. Recently some of these theories have been tested in the sleep laboratory. Experimental sleep deprivation studies of sleepwalkers generally report an increase in complex behaviors during SWS, although one prominent study reported the opposite effect. However, the generally accepted theory that alcohol and medications can induce sleepwalking episodes remains entirely based on clinical and forensic case reports. Alleged cases of alcohol related sleepwalking often involve individuals lacking the generally accepted characteristics of sleepwalkers but with very high blood alcohol levels that could in and of itself account for complex behaviors noted without the presence of sleepwalking. Further, the effects of high levels of alcohol dramatically decrease SWS, a finding inconsistent with sleepwalking. Case reports of medication-related induction of apparent sleepwalking most often present a complex medical and psychiatric history associated with multiple medications. These patients often lack the clinical history and other criteria currently required for the diagnosis of sleepwalking. The medication-related behaviors may instead represent some other condition in an awake, but impaired patient. Sleep laboratory research has identified sleep disordered breathing, periodic leg movements, noise and touch among others as proximal triggers of sleepwalking episodes. Treatment of these triggers may result in resolution of sleepwalking without medication. Further sleep laboratory research is needed before experimental findings can be used for routine diagnostic and forensic purposes.

Adult↗
PubMed2006

Structure analysis of embedded nano-sized particles by precession electron diffraction. eta'-precipitate in an Al-Zn-Mg alloy as example.

The Vincent-Midgley precession technique has been used to collect three-dimensional electron diffraction intensity data from a dispersion of coherent precipitates in a matrix. In order to suppress severe effects from multiple diffraction via matrix reflections, a fairly large precession (tilt) angle had to be used. This implied a high background from the surrounding matrix, and limited the number of reflections that could be measured from patterns on image plates. The heavily faulted hexagonal eta'-precipitates (a = 0.496 nm, c = 1.405 nm) with thickness 3-5 nm occur in four equivalent orientations relative to the aluminium matrix; with frequent overlap of reflections. A model of the average structure in the space group P6(3)/mmc with assumed composition Mg(2)Zn(5-x)Al(2+x), have been derived by Patterson analysis and intensity comparisons.

Journal Article↗
PubMed2006

Modifications of stereological correction methods for precipitate parameters using transmission microscopy.

Energy filtered transmission electron microscopy (EFTEM), dark field imaging and light microscopy are well established methods to evaluate size, volume fraction and number density of precipitates on different size scales. The stereological problems are well known and analogous for all methods. Many evaluation methods can be found in literature, each of them valid for special sample geometries or special size distributions. Despite this variety, serious errors can occur if the assumptions do not exactly represent the real situation. In this paper, available and newly developed correction methods are tested for evaluating these parameters for different precipitate size distributions in a sample of arbitrary topography. It is shown that the newly proposed methods produce significantly lower deviations and are more assessable regarding their systematic errors.

Journal Article↗
PubMed2001

Diets with either beef or plant proteins reduce risk of calcium oxalate precipitation in patients with a history of calcium kidney stones.

OBJECTIVE: To determine the effect of substituting equal amounts of dietary protein as animal protein (beef) for plant protein (legumes, seeds, nuts, and grains) on urinary components associated with calcium oxalate precipitability risk. DESIGN: Randomized crossover trial. SUBJECTS: Twenty-three normocalciuric patients with a history of calcium kidney stones (8 women and 15 men, mean age 50.7+/-14.6 years) with 24-hour urinary calcium < or =10.3 micromol, 24 hour urinary oxalate excretion between 228 and 963 micromol, and a urinary calcium increase of < or =1.0 micromol in 4 hours after a 25 micromol oral calcium load. SETTING: Four-day, free-living adaptation period, followed by 2-day metabolic unit study. INTERVENTION: The study compared consumption of 2 servings of beef (43 g protein for women and 50 g for men) daily with an equal amount of protein from plant foods including legumes, nuts, and grains. MAIN OUTCOME MEASURES: Tiselius risk index (TRI) for calcium oxalate precipitability calculated from urinary calcium, oxalate, magnesium, citrate, and volume. STATISTICAL ANALYSES: Paired t tests. RESULTS: Urinary calcium, oxalate, magnesium, citrate, phosphorus, volume, and TRI did not differ between diets. Urinary sodium and potassium were higher for patients on the plant protein diet. After correcting for variations in urinary sodium and potassium between diets, the difference in urinary calcium remained insignificant. TRI was lower on both beef- and plant-protein diets compared with self-selected prestudy diets for all participants. CONCLUSION/APPLICATIONS: Balanced diets containing moderate amounts of either beef or plant protein are equally effective in reducing calcium oxalate kidney stone risk based on changes in urinary composition.

Adult↗
PubMed1996

Migraine precipitated by head trauma in athletes.

PURPOSE: To present the clinical features of a case of migraine precipitated by head trauma. METHODS: Detailed history was obtained and ophthalmic and neurologic examinations were performed. RESULTS: This patient's history of transient loss of vision followed by severe headache precipitated by a direct blow to the top of the head is characteristic of this phenomenon. Normal neurologic and opthalmic examination findings, normal magnetic resonance imaging, and a history of similar episodes are all consistent with this diagnosis. CONCLUSION: Familiarity with this entity can obviate an expensive examination for patients with these classic symptoms.

Adult↗
PubMed1998

A comparison of historic asbestos measurements using a thermal precipitator with the membrane filter-phase contrast microscopy method.

The published results and analytical methods used in a 1938 survey of the spinning area in a UK crocidolite asbestos factory have been described and re-interpreted, by comparing the method used with the current membrane filter-phase contrast microscopy (MF-PCM) method for asbestos. By good fortune, most of the original microscope, and thermal precipitator sampling heads similar to those used for sampling were available, as well as guidance from the factory inspector who collected and analysed the original samples. A textile grade crocidolite asbestos was used to generate a fibrous dust cloud whose size distribution was characterised by scanning and transmission electron microscopy and found to give a close approximation to the fibre size distributions monitored in 1938. Samples taken over the same sampling time, but at lower concentrations than originally sampled, showed that the thermal precipitator-oil immersion microscopy (TP-OI) method used at x 2000 magnification, gave higher > 5 microns long fibre counts by a factor of between 3 and 4, than the current MF-PCM method. The differences in performance could be explained by the superior resolving power of the TP-OI method for fine crocidolite fibres. Exposures of airborne asbestos fibres in the spinning area were found to be equivalent to about 20 f ml-1 for personal samples and 10 f ml-1 for area samples, but due to the high levels of ventilation on the day the samples were collected, the average levels throughout the year may have been somewhat higher.

Air Pollutants, Occupational↗