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At least 1,639 records · Page 91Linked to original sources
PubMed1998

Affinity precipitation of alpha-amylase inhibitor from wheat meal by metal chelate affinity binding using cu(II)-loaded copolymers of 1-vinylimidazole with N-isopropylacrylamide

A method for purifying alpha-amylase inhibitor from wheat meal based on immobilized metal affinity with a thermosensitive copolymer is developed. The studies represent the thermoprecipitation properties of the copolymers of N-isopropylacrylamide (NIPAM) with iminodiacetic acid (IDA) and 1-vinylimidazole (VI), respectively. The polymer which is obtained by the copolymerization of 1-vinylimidazole and N-isopropylacrylamide, charged with Cu(II), exhibited specific interaction of the metal ions to the protein inhibitor. The precipitation was induced by salt and the recovery of the amylase inhibitor was achieved by dissolving the inhibitor-polymer complex in imidazole buffer and subsequent precipitation of the polymer. A single family of the alpha-amylase inhibitor was recovered from the polymer with 89% yield and about fourfold purification. The SDS-PAGE pattern showed significant purification of the inhibitor. The binding of the inhibitor to the Cu(II)-polymer conjugate depends upon the Cu(II) concentration in the copolymer and also upon the concentration of the protein. The recovered polymer could be reused with reasonable efficiency. Copyright 1998 John Wiley & Sons, Inc.

Journal Article↗
PubMed2000

Selective c-fos induction and decreased dopamine release in the central nucleus of amygdala in rats displaying a mecamylamine-precipitated nicotine withdrawal syndrome.

In the present study the neuronal expression of Fos, the protein product of c-fos, was used to study changes in neuronal activity in nerve terminal regions of the ascending dopaminergic system during nicotine withdrawal. Rats were infused for 14 days with nicotine (9 mg/kg/day nicotine hydrogen tartrate) via minipumps, whereas control animals carried empty pumps. Withdrawal was induced by the nicotinic receptor (nAChR) antagonist mecamylamine (1 mg/kg, s.c.). The behavior of each animal was observed after mecamylamine injection and subsequently its brain was processed for Fos-like immunoreactivity. Following mecamylamine, the score of abstinence signs increased in the nicotine-treated rats as compared to controls. The number of Fos-positive nuclei was substantially increased in the central nucleus of amygdala (CNA) in animals undergoing mecamylamine-precipitated withdrawal, whereas no significant changes in c-fos expression were observed in the basolateral amygdaloid nucleus, the core and the shell of the nucleus accumbens, the dorsolateral striatum, or the medial prefrontal cortex. Since there are indications of involvement of amygdaloid dopaminergic neurotransmission in anxiety-a core symptom of withdrawal from dependence-producing drugs-in a second experiment utilizing microdialysis we examined whether nicotine withdrawal affects dopaminergic neurotransmission in the CNA. Following mecamylamine injection, dopamine (DA) significantly decreased in nicotine-treated animals compared with controls. These results indicate that the mecamylamine-precipitated nicotine withdrawal reaction is accompanied by a selective induction of c-fos and a concurrent decrease in DA release in the CNA, which may have a bearing on symptoms such as anxiety and distress, which frequently are associated with the nicotine abstinence reaction in humans.

Amygdala↗
PubMed2000

Analysis of galectin 1-mediated cell signaling by combined precipitation and electrophoresis techniques.

Galectin-1 (GAL1) is a beta-galactoside-binding protein that has been implicated in the regulation of viability of lymphoid cells. However, the signaling pathway governed by the binding of GAL1 to the cell membrane is not understood yet. As a first step toward the elucidation of GAL1-initiated signaling events, electrophoresis techniques such as sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and two-dimensional electrophoresis (2-DE) were used together with precipitation techniques. This allowed us to identify the membrane receptor of GAL1, and to characterize the signal resulting from the binding of GAL1 to this receptor. Our results demonstrate that the tyrosine phosphatase CD45 is the receptor for GAL1, and that the src-type tyrosine kinase Lyn is a target for the effects of GAL1/CD45 interactions in B-cells. Furthermore, these results show the usefulness of combined precipitation and electrophoresis techniques to analyze phosphotyrosine-dependent mechanisms during the study of cell functions.

Blotting, Western↗
PubMed2000

Liquid secondary ion mass spectrometric investigation of ion-pair precipitates of some ethoxylates with barium tetraphenylborate

Liquid secondary ion mass spectrometry seems to be useful technique for the qualitative characterization of ion-pair precipitates of ethoxylates with barium tetraphenylborate. In the positive mode, barium complexes of ethoxylates were examined. In the negative mode, the ion signal of tetraphenylborate had 100% intensity relative to the matrix peaks. The low-resolution mass spectra were found to be suitable for checking the purity of ion-pair precipitates of ethoxylates with barium tetraphenylborate. On the basis of B/E mass spectra, the fragmentation routes of [M - H + Ba](+) ions are proposed. Copyright 2000 John Wiley & Sons, Ltd.

Journal Article↗
PubMed2002

Effect of competitive complex formation on patterning and front propagation in periodic precipitation.

The Co(OH)2 Liesegang pattern (from Co2+ and NH4OH) propagates in space by periodic band formation at the head due to precipitation and band disappearance at the tail due to dissolution in excess NH4OH. Introduction of Ni2+, which competes with Co2+ for complex formation with ammonia, into the system led to several interesting observations: slower propagation, fewer bands, and increased spacing between them. Above a cutoff concentration of Ni2+ (0.13 M for [Co2+]0 = 0.100 M), only a uniform precipitation zone was observed. The quantity delta X = |XNi-Xfree|, namely, the difference in the position of last band in the system with nickel relative to that without nickel attained at a fixed time (93 h), was found to oscillate as the initial concentration of NH4OH ([NH4OH]0) was varied. It was shown that variations in the concentration of intermediate NH4+ act as precursors for these oscillations: [NH4+] was measured with an ammonia-specific electrode, and the difference delta [NH4+] = |[NH4+]Ni-[NH4+]free| at 93 h exhibited oscillations with [NH4OH]0 similar to those obtained in delta X. Theoretical calculations based on the model of Müller and Polezhaev agreed with the experimental results.

Journal Article↗
PubMed2001

Sequential solubilization of proteins precipitated with trichloroacetic acid in acetone from cultured Catharanthus roseus cells yields 52% more spots after two-dimensional electrophoresis.

Sample preparation is still the most critical step in two-dimensional gel electrophoresis (2-DE), and needs to be optimized for each type of sample. To analyze the proteome of the medicinal plant Catharanthus roseus, we developed and evaluated a sequential solubilization procedure for the solubilization of proteins after precipitation in trichloroacetic acid and acetone. The procedure includes solubilization with a conventional urea buffer followed by a stronger solubilizing buffer containing thiourea. The sequential solubilization of the precipitated proteins results in very different spot patterns following 2-DE. The number of protein spots which could be detected in both samples of the sequential solubilization was only about 10% of the total number of spots. Compared to solubilization in a single step, the total number of spots that could be detected in the sequential solubilization procedure was increased by 52%. The method described is simple and is applicable to different types of plant tissue.

Acetone↗
PubMed1977

Naloxone-precipitated withdrawal: a method for rapid induction onto naltrexone.

We examined naloxone-precipitated withdrawal as a means for rapid opiate detoxification and induction onto naltrexone. In 29 patients dependent on methadone (5 to 20 mg/day), abstinence was precipitated by an injection of naloxone. Repeated injections of naloxone were given subsequently until symptoms of abstinence were no longer induced. Successive injections induced less intense withdrawal assessed by vital signs and ratings on abstinence scales. The most rapid procedure consisted of 1.2 mg naxolone every 30 min for 3 to 6 hr, for 3 to 6 hr, followed by hourly increasing doses of naltrexone. This procedure allowed transition from opiate dependence to naltrexone maintenance (50 to 100 mg/day) within 48 hr. The results are consistent with assumptions that antagonists actively displace opiates from receptor sites.

Adult↗
PubMed1994

Interleukin-1-induced activation of a protein kinase co-precipitating with the type I interleukin-1 receptor in T cells.

We have investigated the possibility of a protein kinase participating in the signal transduction mechanisms of the interleukin-1 (IL-1) type I receptor (IL-1RI). Our data show that a protein kinase was co-precipitated with the IL-1RI from the two murine T helper cell lines D10N and EL-4. The kinase activity was detected in an in vitro kinase assay performed with the immuno beads in the presence of exogenous substrates. IL-1 treatment of the cells resulted in a rapid activation of this protein kinase in a concentration-dependent manner. Both forms of IL-1, IL-1 alpha and IL-1 beta, induced this kinase activity, whereas the IL-1 receptor antagonist (IL-1ra) was inactive. In excess IL-1ra competitively antagonized IL-1 stimulation. In the in vitro kinase assay the exogenous substrates myelin basic protein and histone H1 were phosphorylated, whereas casein or heat-shock protein HSP27 were not accepted, reflecting a certain selectivity of this protein kinase. The IL-1RI co-precipitable protein kinase showed a serine/threonine specificity and was inhibited by staurosporine, but not by inhibitors specific for protein tyrosine kinase or protein kinase C. These results show that a serine/threonine protein kinase directly interacts with the IL-1RI at the plasma membrane level of T helper cells forming a novel type of IL-1 inducible signaling complex. This protein kinase may resemble the link coupling the plasma membrane IL-1 receptor to cytosolic downstream elements in the IL-1 signaling pathway.

Animals↗
PubMed1997

Protective effect of L-carnitine in ammonia-precipitated encephalopathy in the portacaval shunted rat.

L-carnitine administration prevents the neurological symptoms of acute ammonia toxicity. To further evaluate its efficacy in the prevention of hepatic encephalopathy in hyperammonemic conditions, L-carnitine (16 mmol/kg, intraperitoneally [i.p.] was administered 1 hour before ammonium acetate (NH4OAc) (8.5 mmol/kg, subcutaneously) to portacaval shunted (PCS) rats. Cerebrospinal fluid (CSF) ammonia, lactate, and amino acid levels were measured in relation to deteriorating neurological status in these animals. None of 35 L-carnitine-treated animals showed neurological deterioration after NH4OAC administration compared with saline-treated controls; the latter manifested severe encephalopathy progressing through loss of righting reflex to coma. Survival rate was 100% in the L-carnitine-treated group compared with 5% in saline-treated controls. Following NH4OAC administration to PCS rats, CSF ammonia increased to 0.93 +/- 0.15 mmol/L and 1.24 +/- 0.15 mmol/L at precoma and coma stages of encephalopathy (P < .01) respectively. Treatment with L-carnitine reduced CSF ammonia at both precoma and coma stages; the time-course of this protective effect paralleled blood and CSF L-carnitine accumulation. CSF alanine and lactate increases following NH4OAC administration to PCS rats were significantly attenuated following L-carnitine treatment. However, L-carnitine treatment did not lead to significant reductions in plasma ammonia nor CSF or brain glutamine in these animals. These findings show the therapeutic efficacy of L-carnitine in ammonia-precipitated coma in PCS rats and suggest that this protective effect is centrally mediated involving improved mitochondrial respiration. L-carnitine could be of therapeutic benefit in the prevention of hepatic encephalopathy precipitated by ammoniagenic conditions in humans with chronic liver disease.

Amino Acids↗
PubMed1983

A pigmentation-associated, differentiation antigen of human melanoma defined by a precipitating antibody in human serum.

Antibodies in the serum of melanoma patient AU precipitate an antigen from 125I-labelled extracts of cultured autologous melanoma cells. The antigen, which is probably not a cell surface component, is present in other pigmented melanomas but not in non-pigmented melanomas or other tumor cell types, and the amount of antigen is correlated with the degree of pigmentation. These conclusions are based on absorption experiments with 11 pigmented melanomas, 8 non-pigmented melanomas, 3 astrocytomas, 12 carcinomas of various histological types, I leukemia, 2 EB-virus-transformed B lymphocyte lines, and human erythrocytes. The antigen was also detected in cultured human melanocytes. It has a molecular weight of 70,000, an isoelectric point of pH 5.3, and it binds to concanavalin A-Sepharose. Ninety-six sera from other melanoma patients were examined and none of them precipitated this antigen. As described previously, the serum from patient AU also has antibodies to a unique (Class I) tumor antigen found only on AU melanoma cells. The pigmentation-associated, differentiation antigen and the unique antigen are clearly different in their distribution, but some relationship between these unusual antibody responses is possible.

Antibodies, Neoplasm↗
PubMed1988

Removal of low-density lipoproteins (LDL) and fibrinogen by precipitation with heparin at low pH: clinical application and experience.

The clinical application of a new extracorporeal procedure (HELP) for the selective elimination of low-density lipoproteins and fibrinogen by heparin precipitation at acid pH is described. Plasma, obtained by filtration of whole blood through a 0.2 micron filter is continuously mixed with an equal volume of an acetate buffer (pH 4.85) containing heparin. After removal of the precipitated heparin complex by filtration, excess heparin is adsorbed to a specially developed filter, and the clear plasma filtrate is subject to bicarbonate dialysis/ultrafiltration to restore physiologic pH and remove excess fluid. The calculated efficiency for the elimination of low-density lipoproteins and fibrinogen from plasma by HELP is 100% and is therefore comparable to conventional plasmapheresis. However, the HELP system shows a high degree of specificity, with over 80% of total protein being returned to the patient. A total of over 350 treatment procedures have now been performed. Patient compliance and acceptance have been excellent, and no major complications have been observed. The system is therefore suitable for the treatment of severe hyper-beta-lipoproteinemia; its use for the treatment of coronary heart disease is currently under investigation in a prospective multicenter study in which treatment efficiency will be controlled by coronary angiography on 45 patients treated with HELP over a period of 2 years.

Blood Component Removal↗
PubMed1988

Volume determination of TEM specimens containing particles or precipitates.

The volume of thin foil specimens, which contain precipitate or other particles, viewed in the TEM is needed to determine particle density and spacing. It can be determined from the locations of the particles, measured using stereo pairs. A calculation that determines the volume between planes (not necessarily parallel or horizontal) that enclose the points is described. These planes will systematically underestimate the actual surface spacing and hence the volume, but a simple correction factor based on the number of points used in the fit can be used to estimate the actual volume. The method is tested, and its accuracy is evaluated using simulated data and applied to precipitate particles in creep-tested silicon carbide.

Frozen Sections↗
PubMed1984

Determination of the ionization constants of compounds which precipitate during potentiometric titration using extrapolation techniques.

It is shown that the ionization constants of diacidic compounds can be determined by utilizing potentiometric titration data, even when a precipitate forms during the titration. The two methods presented are particularly useful for compounds for which the pK alpha values are close together. A third method is presented which can be used with monoacidic compounds or compounds for which the pK alpha values are far apart and form a precipitate during the titration. Four symmetrical diacidic compounds were studied which had similar pK alpha values, and one compound was studied which had pK alpha values that were far apart. Comparison of the second pK alpha of the latter compound with that previously reported determined by a spectrophotometric procedure showed excellent correlation.

Chemical Phenomena↗
PubMed2005

Case of neuroleptic malignant-like syndrome precipitated by abrupt fava bean discontinuance.

Neuroleptic malignant-like syndrome (NMLS) is well described in the treatment of Parkinson's disease. The syndrome is characterized by fever, rigidity, autonomic instability, elevated creatine phosphokinase levels, and altered level of consciousness, which is usually precipitated by levodopa withdrawal. In recent years, patients have used fava beans to treat Parkinson's symptoms, because the beans contain appreciable amounts of levodopa and have been thought to be a safe adjunctive therapy. We describe a case of NMLS, which was precipitated by the abrupt cessation of fava bean ingestion.

Diagnosis, Differential↗
PubMed1996

The Use of Microelectrodes to Study the Precipitation of Calcite upon Algal Biofilms

Calcium and pH ion-selective microelectrodes are used for the first time to measure chemical activity profiles above laboratory-grown algal biofilms (green alga, Chlorococcum sp). The results are used to calculate the solution composition changes above an actively photosynthesizing biofilm. These changes include the total calcium concentration, degree of supersaturation of the solution with respect to calcite, and the partial pressure of carbon dioxide. Measurements are made in a flow-cell, which was designed to hold the templates on which the biofilms are grown. Measurements show pronounced gradients of pH and calcium concentration, within a distance of approximately 500 &mu;m above the biofilm. The high degree of supersaturation caused by the low concentrations of carbon dioxide near the biofilm surface leads to the precipitation of calcite on the biofilm. SEM micrographs illustrate the close association of calcite crystals with the algal cells. Preliminary results are presented of the precipitation rates estimated from the diffusion flux of calcium at the biofilm surface. The results are in broad agreement with the rates expected from calcite seed growth experiments in similar solution conditions.

Journal Article↗
PubMed1997

Preparation and Growth Mechanism of Uniform Colloidal Copper Oxide by the Controlled Double-Jet Precipitation

Monodispersed crystalline CuO particles of different morphologies were synthesized by the controlled double-jet precipitation (CDJP) technique using NaOH and Cu(NO3)2 as the reactants. The effects of temperature, reaction time, pH, and the concentrations of chemicals on the characteristics of final products were investigated. With lower [NaOH]/[Cu(NO3)2] molar ratios and temperatures, colloidal gerhardtite Cu2(OH)3NO3 precipitated, while tenorite CuO particles of various morphologies were obtained at higher temperatures and [NaOH]/[Cu(NO3)2] ratios. Time resolved electron microscopy indicated that nanosized primary particles formed immediately after mixing the reactants, followed by aggregation into larger uniform particles of submicrometer size.

Journal Article↗
PubMed1998

Size Tailoring of Magnetite Particles Formed by Aqueous Precipitation: An Example of Thermodynamic Stability of Nanometric Oxide Particles.

The particle mean size of magnetite precipitated in aqueous solution can be adjusted and stabilized against ripening over a large range at the nanometric scale (1.5-12.5 nm). Such a tailoring of particles is obtained by controlling the pH and the ionic strength imposed by a noncomplexing salt in the precipitation medium. The higher the pH and the ionic strength are, the smaller the particle size is. Above a critical pH value, which depends on the ionic strength and the temperature, the secondary particle growth by Ostwald ripening does not take place anymore. The stabilization of nanoparticles seems to result from thermodynamics rather than kinetics. Copyright 1998 Academic Press.

Journal Article↗
PubMed1998

Precipitation of Barium and Calcium Naproxenate Particles of Different Morphologies.

Barium and calcium salts of naproxen, (+)-6-methoxy-alpha-methyl 2-naphtaleneacetic acid, were prepared by the controlled double jet precipitation technique in the absence and in the presence of different surfactants. The nature of the latter and agitation used in the precipitation process were critical factors in determining the morphology and the size of the particles obtained, consisting, as a rule, of aggregates of much smaller subunits, which were either platelet or fiber like. Copyright 1998 Academic Press.

Journal Article↗