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At least 1,225 records · Page 68Linked to original sources
PubMed2002

Modulation of kappa-opioidergic systems on mecamylamine-precipitated nicotine-withdrawal aversion in rats.

The present study was designed to examine the modulation of the kappa-opioidergic system on mecamylamine-precipitated nicotine-withdrawal aversion. The nicotinic receptor antagonist mecamylamine, which is known to pass the blood-brain barrier, produced a place aversion in rats chronically treated with nicotine using an osmotic mini-pump. This effect was significantly attenuated by pretreatment with -opioid receptor agonists U50,488H (1.0 mg/kg, s.c.) and TRK-820 (0.03 mg/kg, s.c.). The attenuation of mecamylamine-precipitated nicotine-withdrawal aversion by U50,488H was completely reversed by the combination with a selective -opioid receptor antagonist nor-binaltorphimine (10.0 mg/kg, i.p.). These results suggest that the activation of endogenous -opioidergic systems can suppress the mecamylamine-precipitated nicotine-withdrawal aversion.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗
PubMed2000

A protein kinase inhibitor, H-7, blocks naloxone-precipitated changes in dopamine and its metabolites in the brains of opioid-dependent rats.

The influence of an inhibitor of cAMP-dependent protein kinase and protein kinase C, H-7 [1-(5-isoquinolinesulfonyl)-2-methylpiperazine], on naloxone (an opioid receptor antagonist)-precipitated withdrawal signs and changes in levels of dopamine (DA) and its metabolites in morphine- or butorphanol-dependent rats was investigated. Animals were infused continuously with morphine (a mu-opioid receptor agonist) or butorphanol (a mu/delta/kappa mixed opioid receptor agonist) for 3 days. Naloxone precipitated withdrawal syndrome and decreased the levels of DA in the cortex, striatum, and midbrain; 3, 4-dihydroxyphenylacetic acid (DOPAC) in the cortex, striatum, limbic areas, and midbrain; and homovanilic acid (HVA) in the striatum, limbic areas, and midbrain regions. In animals rendered dependent on butorphanol, the results obtained were similar to those of morphine-dependent rats except for the changes in DOPAC levels. Concomitant infusion of H-7 and opioid blocked both the expression of withdrawal signs and the decreases in DA, DOPAC, and HVA levels in a dose-dependent manner. These results suggest that the enhancement of cAMP-dependent protein kinase and/or protein kinase C activity accompanying the increase of DA neuron activity during continuous infusion of opioids leads to an abrupt reduction in levels of DA and its metabolites precipitated by naloxone, which is intimately involved in the expression of physical dependence on opioids.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1996

Intrathecally administered flumazenil and PK 11195 precipitate abstinence syndrome in freely moving diazepam dependent rats.

The central and peripheral benzodiazepine (BZ) receptor antagonists, flumazenil (FLU) and PK 11195 (PK), administered intrathecally (IT) to diazepam (DZ)-dependent rats produced a precipitated abstinence syndrome. The scores for abstinence increased with increasing dose of FLU but not with increasing dose of PK. Twitches and jerks increased with increased doses of both. Head and body tremors were produced by FLU, but not by PK. Neither FLU nor PK precipitated abstinence in controls. In DZ-dependent rats IT administered FLU and PK did not significantly change the spectral content and the total power of the EEG. The data indicate that an abstinence syndrome is precipitated at the spinal level in DZ-dependent rats and that both central and peripheral BZ receptors are involved.

Animals↗
PubMed1986

Affinity precipitation of proteins using bis-dyes.

Based on the principle of affinity precipitation of nucleotide-dependent enzymes using bis-NAD (Mosbach), Lowe et al. have recently mentioned the possibility of synthesising bis-dyes for similar applications. In this paper we report preliminary results obtained using bis-dyes in the sulphonamide form got through carbodiimide condensation of the monomer and its aminohexyl derivative for affinity precipitation. The dimer exhibited considerable selectivity for lactate dehydrogenase (90% yield). Bovine serum albumin gave a lower yield of 50% and as expected chymosin could not be precipitated by the dimer.

Animals↗
PubMedDate not supplied

Calcium precipitation in acute and chronic brain diseases.

In rat brain, calcification associated with excitotoxicity has been proposed to play a protective role, whereas in human brain, nonartherosclerotic calcification is present in several pathological conditions without any clear significance. To determine if calcification can be viewed as a protective step of calcium homeostasis during chronic and acute neuronal suffering, cerebral cortex and hippocampus of patients with Alzheimer's disease, vascular dementia and neonatal hypoxia-ischemia were investigated. To investigate the human specificity, these two areas were also studied in dogs with established cognitive deficits. In all groups, calcium precipitates were observed in the cerebral parenchyma associated with neuronal damage. The cerebral cortex presented a higher degree of calcification than the hippocampus. The neonatal hypoxia-ischemia group was characterised by a higher degree of calcification, whereas the groups with lowest calcification were the Alzheimer's patients and dogs. As shown by X-ray microanalysis, in the precipitates, calcium is mainly associated with phosphorus in a form that resembles hydroxyapatites. Thus, intracellular calcium concentration associated with neuronal suffering may reduce the energy extrusion. We propose that, to help overcome excitotoxicity, calcium precipitation acts in CNS of vertebrates as a new compartment of the calcium homeostasis in which free cytoplasmic calcium ions are inactivated by phosphate ones.

Acute Disease↗
PubMed2003

High resolution electron microscopy of precipitates in high Co-Ni alloy steel.

In the secondary hardening reaction in ultrahigh strength steel of high Co-Ni alloy, the needle-shaped precipitating carbide is the main strengthening phase. Particular attention has been paid to the nucleation, growth and coarsening of the precipitate and its interface with the ferrite matrix. High resolution transmission electron microscopy observations show that when tempered at a low temperature condition of 454 degrees C for 5h, the precipitating carbides begin to nucleate in the form of clusters; at peak hardening tempered at 482 degrees C, the growing carbides are fully coherent with the matrix, exhibit black-white contrast in bright-field images and have their own hexagonal crystalline structure as M(2)C. Coarsening carbides tempered at high temperature lost their coherence and exhibited Moiré fringes. Lattice images directly indicate the crystallographic relationship of M(2)C carbides and ferrite, [100](alpha)//[1101](beta), [100](alpha)//[1120](beta).

Journal Article↗
PubMed2000

Detection of Au precipitates in a Mg-based alloy using electronically simulated hollow cone illumination

Images from electronically simulated hollow cone illumination (or rotating dark field) conditions, obtained under plane wave (or weak) diffraction conditions, are generally assumed to approximate to the compositionally weighted sum of atomic number squared for sufficiently large momentum transfers. However, even for large momentum transfer encountered with a semi-angle of 5 degrees and 300keV electrons, appropriate numerical integration over condenser and objective aperture configurations indicates that some thermal scattering component is still present. A Mg-Al alloy with minor additions of Zn and Mn, and to which 0.1at.% Au has been added, is shown to provide a good system for the detection of high Z (atomic number) precipitates within a low Z matrix and on which semi-quantitative calculations may be based. Correlation of absolute rather than relative intensities from small precipitates (3-10nm diameter) with calculations based on an Einstein model for (incoherent) thermal diffuse scattering show that the small precipitates consist predominantly of Au, a conclusion subsequently supported by EDX analysis and electron diffraction measurements. It is also demonstrated that this incoherent contrast mechanism is ideal for stereographic imaging in the TEM.

Journal Article↗
PubMed2003

Precipitate containing norm in the oil industry: modelling and laboratory experiments.

In this work, the influence of factors that can affect the precipitate (scale) containing NORM (radium) in the oil industry is studied. From the experimental results, a mathematical model for calculating the precipitate is proposed. The statistical tests used to obtain this model show that precipitation: does not depend on the shaking velocity and contact time, depends on the temperature and mixing water ratio. Also, it depends on the interactions between temperature and mixing water ratio. The comparison of the experimental results and those obtained by the model appear to be in good agreement.

Journal Article↗
PubMed2005

Column precipitation chromatography: an approach to quantitative analysis of eigencolloids.

A new column precipitation chromatography (CPC) technique, capable of quantitatively measuring technetium eigencolloids in aqueous solutions, is presented. The CPC technique is based on the destabilization and precipitation of eigencolloids by polycations in a confined matrix. Tc(IV) colloids can be quantitatively determined from their precipitation onto the CPC column (separation step) and their subsequent elution upon oxidation to pertechnetate by peroxide (elution step). A clean-bed particle removal model was used to explain the experimental results.

Chromatography↗
PubMed1996

Molded monolithic rod of macroporous poly(styrene-co-divinylbenzene) as a separation medium for HPLC of synthetic polymers: on-column precipitation--redissolution chromatography as an alternative to size exclusion chromatography of styrene oligomers and polymers.

A process for the separation of styrene oligomers and polymers by size and composition using a novel separation medium has been demonstrated. The process involves precipitation of the macromolecules on the molded macroporous rod columns, followed by progressive elution utilizing a simple gradient of the mobile phase. Molded macroporous rod columns are ideally suited for this technique because convection through the large pores of the rod enhances the mass transport of large analyte molecules and accelerates the separation process. Styrene oligomers and polymers are separated in a 50-mm x 8-mm-i.d. column using a solvent gradient composed of a poor solvent such as water, methanol, or acetonitrile and increasing amounts of a good solvent, tetrahydrofuran. Excellent separations are obtained, demonstrating that precipitation-redissolution can be a suitable alternate to size exclusion chromatography (SEC) of some polymers. Compared to SEC, the gradient elution separation can be achieved at higher flow rates in a much shorter time. Precipitation-redissolution with gradient elution can also be used for the separation of copolymers, for which the process is controlled not only by molecular weight but also by the composition of the copolymers.

Chromatography, Gel↗
PubMed1975

A procedure for the rapid, large-scall purification of Escherichia coli DNA-dependent RNA polymerase involving Polymin P precipitation and DNA-cellulose chromatography.

An improved method is described for the purification of the DNA-dependent RNA polymerase [ribonucleosidetriphosphate:RNA nucleotidyltransferase, EC 2.7.7.6] from Escherichia coli. The method involves lysozyme-sodium deoxycholate lysis, low-speed centrifugation, precipitation with Polymin P, elution from the Polymin P precipitate, ammonium sulfate precipitation, and chromatography on DNA-cellulose and Bio-Gel A 5m. RNA polymerase is purified to electrophoretic homogeneity in 2 days with a recovery of 45%, resulting in a yield of 250 mg of holoenzyme from 500 g of cells.

Chromatography↗
PubMed2005

Deposition precipitation for the preparation of carbon nanofiber supported nickel catalysts.

Deposition precipitation of nickel hydroxide onto modified carbon nanofibers has been studied and compared to deposition onto silica. The carbon nanofiber support materials consisted of graphite-like material of the fishbone-type with a diameter of 20-50 nm and a specific surface area of 150 m2/g. Modification involved surface oxidation (CNF-O) optionally followed by partial reduction (CNF-OR) or thermal treatment (CNF-OT). Titration of the support materials showed the presence of 0.17 and 0.03 mmol/g carboxylic acid groups for CNF-O and CNF-OR, respectively. For the CNF-OT only basic groups were present. The deposition precipitation of 20 wt % nickel onto these supports has been studied by time dependent pH and nickel loading studies. With silica, nickel ion adsorption did not occur prior to nucleation of the nickel hydroxide phase at pH = 5.6. With CNF-O, nickel ion adsorption took place right from the start of the deposition process at pH = 3.5, and at pH = 5.6 already 4 wt % nickel was adsorbed. Nucleation of nickel hydroxide onto adsorbed nickel ion clusters proceeded subsequently. Characterization of the dried Ni/CNF-O samples with TEM and XRD showed well dispersed and thin (5 nm) platelets of nickel hydroxide adhering to the carbon nanofibers. After reduction at 773 K in hydrogen the Ni/CNF-O contained metallic nickel particles of 8 nm homogeneously distributed over the fibers. With CNF-OR and CNF-OT, precipitation of large platelets (> 500 nm) separate from the support took place. Clearly, the presence of carboxylic acid groups is essential to successfully deposit nickel hydroxide onto modified carbon nanofibers.

Journal Article↗
PubMed2005

Nano- and microscopic surface wrinkles of linearly increasing heights prepared by periodic precipitation.

Arrays of surface wrinkles of linearly increasing heights (from tens of nanometers to tens of micrometers) were prepared via a spontaneous reaction-diffusion process based on periodic precipitation. The slopes, dimensions, and positions of the precipitation bands could be controlled precisely by adjusting the concentrations of the participating chemicals as well as the material properties of patterned substrates. Additional control of periodic precipitation by localized UV irradiation allowed for the preparation of discontinuous and curvilinear structures. The nonbinary 3D surface topographies were replicated into poly(dimethylsiloxane), and the applications of replicas in microfluidics, microseparations, and cell biology have been suggested.

Journal Article↗
PubMed2005

Selective precipitation of prions by polyoxometalate complexes.

The efficacy of a variety of polyoxometalate anions in selectively precipitating the infectious isoform of the prion protein (PrPSc) over the normal, cellular protein (PrPC) was tested as a means of improving the sensitivity of a conformation-dependent immunoassay (CDI). Experiments utilizing neutralized aqueous solutions containing MgCl2.6H2O and Na2H[PW12O40] (1) indicated that use of the former is detrimental to selectivity, while use of the latter gives optimal selectivity at a concentration of 2.48% w/v, much higher than the 0.31% w/v employed in the current CDI protocol. Similar experiments using Na4[SiW12O40] (2), K5[BW12O40] (3), and Na6[H2W12O40] (4) were performed to probe the role of charge density in polyoxometalate anions possessing the Keggin structure. These, coupled with assignment of solution structures via NMR and infrared spectroscopy, revealed the following trend in optimal concentrations: [HBW11O39]8- < [SiW11O39]8- < [PW11O39]7- = [H2W12O40]6-. Interestingly, use of the salts K10[Zn4(H2O)2(PW9O34)2] (5), Na16[Zn4(H2O)2(P2W15O56)2] (6), and Na27[NaAs4W40O140] (7), containing larger polyoxometalate anions, was found to suppress PrPSc precipitation in a concentration-dependent manner. Taken together, the results suggest a precipitation mechanism wherein Keggin-type anions link multiple PrPSc moieties by binding a somewhat hindered cleft featuring one or more positively charged residues.

Crystallography, X-Ray↗
PubMed2001

Centrifugal precipitation chromatography -- a novel chromatographic system for fractionation of polymeric pigments from black tea and red wine.

A novel chromatographic system was developed and first applied to the fractionation of polymeric pigments from black tea and red wine. Centrifugal precipitation chromatography (CPC) generates solvent gradients through a long separation channel under a centrifugal force field. Tea and wine extracts are precipitated in a hexane- or methyl tert-butyl ether-rich environment and are exposed to a gradually increasing ethanol concentration. This causes a repetitive precipitation and dissolution of the biopolymers along the channel. Consequently, they are eluted in the order of their solubility in the organic solvent. It is shown by HPLC analysis of the separated fractions that monomers elute first, whereas fractionated polymers can be found at the end of the chromatographic run. This novel method allows gentle fractionation of polymeric tea and wine constituents and also has potential for use in preparative-scale separations.

Centrifugation↗
PubMed2005

Chiral resolution through precipitation of diastereomeric capsules in the form of 2:1 beta-cyclodextrin-guest complexes.

Preferential precipitation of one enantiomer from a racemic mixture of a camphanate ester of 2,3-diazabicyclo[2.2.2]oct-2-ene was induced by the formation of diasteromeric 2:1 beta-cyclodextrin-guest complexes. The precipitate was enriched with the (-)-enantiomer and the supernatant solution with the (+)-form of a camphanate ester, which was quantitatively analyzed in terms of differential binding constants and intrinsic solubilities of the 2:1 complexes. The enantiomeric excess in the precipitate was determined as 30 +/- 3% by induced circular dichroism.

Circular Dichroism↗
PubMed1998

A specific quantitative assay for collagen synthesis by cells seeded in collagen-based biomaterials using sirius red F3B precipitation.

The measurement of collagen synthesis by seeded cells in vitro is a prerequisite for the assessment of biocompatibility of many biomaterials. Existing methods are either complicated or not applicable to systems utilizing collagen-based materials, and the development of a rapid and simple technique would be an advantage. In the current paper, a method is described which relies on the radiolabelling of newly synthesized protein with [3H]-proline followed by specific precipitation of collagen using 1% sirius red dissolved in water. The results indicate that collagen binding to sirius red is unaffected by using water rather than picric acid as a solvent and the dye binds in a similar fashion to collagen type I, II and III. Cycloheximide treatment of the gels indicated that precipitated [3H]-proline was restricted to macromolecular protein. Collagenase treatment eradicated labelled precipitation formation when using 1% sirius red in water, indicating a high degree of specificity for collagen whilst specificity was poor when using 1% sirius red in picric acid. The method described is both simple and rapid and shows a high degree of specificity and sensitivity. For these reasons it is highly suited for the assessment of collagen synthesis by cells in collagen-based materials.

Journal Article↗
PubMed2000

Precipitation behavior of Ag-Pd-In dental alloys.

Age-hardening characteristics and precipitation behavior of Ag-25%Pd-3%In-1%Zn-0.5%Ir alloy were investigated in detail by means of hardness testing, X-ray diffraction, electron microscopy and resistivity measurement. The solution treating could be accomplished at 980 degrees C and the aging in the temperature range from 950 to 850 degrees C occurred by continuous precipitation. The aging in the temperature range from 850 to 450 degrees C occurred first, forming GP-zones with a hardness increase and then in overaging stage by forming discontinuous precipitation, which consisted of lamellae of solute (Pd, In, Zn) depleted Ag-rich phase and (Pd,Ag)3(In,Zn) intermetallic phase. The hardness increased very fast to its peak in 10 min during aging at temperatures between 450 and 550 degrees C.

Journal Article↗