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PubMed1999

Precipitation of carbonated apatite in the cement system alpha-Ca(3)(PO(4))(2)-Ca(H(2)PO(4))(2)-CaCO(3).

Powder mixtures of alpha-Ca(3)(PO(4))(2), Ca(H(2)PO(4))(2), and CaCO(3) were investigated to assess their potential for the precipitation of a carbonated apatite suitable for cement applications from a supersaturated solution. Of particular interest was the requirement of carbon dioxide release during the setting reaction to obtain Ca(9-x)(HPO(4))(1-1.5x) (PO(4))(5-2.5x)(CO(3))(3.5x)(OH)(1 + 1.5x) with a fixed carbonate content. Results indicated that a compromise is necessary with respect to the maximum permissible level of CaCO(3) addition to the powder mixture as against appropriate setting and hardening properties. Cementlike materials with good setting and hardening properties were obtained when alpha-Ca(3)(PO(4))(2) was the main reactant using Ca(H(2)PO(4))(2) and CaCO(3) as additives in relative proportions of <10 wt % corresponding, approximately, to the stability field area (x,lambda) contained within the lines lambda = -1.5x, x = 0.3, and lambda = -1. Desirable workability and setting properties were lost as the parameters x and -lambda increased. Finally, it was also found to be virtually impossible to obtain a predetermined chemical composition for the setting apatite precipitate, since to increase the amount of carbon dioxide released from the initial powder mixture during setting, the solution pH would need to be decreased, and in doing so the nature of the precipitate could be altered to fulfil the thermodynamic conditions of the solubility diagrams of calcium phosphates.

Apatites↗
PubMed1979

A new virion precipitation test for oncovirus envelope antigens which detects common antigenic determinants in mammalian type-C viruses and Mason-Pfizer monkey virus.

A method for the study of oncovirus envelope antigens was developed, bases on the precipitation of intact virions by a double antibody technique. The amount of precipitated virus was then measured as reverse transcriptase activity. The method was designated the virion precipitation test (VPT). It has been used for titration of antibodies to envelope antigens of oncoviruses. The study of envelop antigens of 11 different oncoviruses permitted their differentiation into the following groups: (1) murine type-C viruses: (2) feline type-C viruses; (3) simian type-C viruses; (4) the RD-114/BEV group; (5) Mason-Pfizer monkey virus (M-PMV); (6) bovine leukemia virus; (7) avian type-C viruses; (8) mouse mammary tumor virus. No common antigenic determinants were detected in the last three groups. Mammalian type-C viruses (RD-114, NIH-MuLV, G-MuLV) had common antigenic determinants in the envelope, as demonstrated with an anti-RD-114 serum. Mammalian type-C viruses also shared antigenic determinants with M-PMV. The relationship of type-C viruses to M-PMV decreased in the following order: RD-114--NIH-MuLV--G-MuLV. It was also shown that the endogenous xenotropic feline RD-114 virus was more closely related to xenotropic NIH-MuLV than to ecotropic G-MuLV. The nature of the common antigenic determinants, as demonstrated by VPT on the surface of mammalian type-C viruses and M-PMV, and their significance for the concept of oncovirus evolution are discussed.

Animals↗
PubMedDate not supplied

One-step purification of glucoamylase by affinity precipitation with alginate.

It was found that alginate binds to glucoamylase, presumably through the recognition of starch binding domain of the latter. The present work exploits this for purification of glucoamylases from commercial preparation of Aspergillus niger and crude culture filtrate of Bacillus amyloliquefaciens by affinity precipitation technique in a single-step protocol. Glucoamylase is selectively precipitated using alginate as macroaffinity ligand and later eluted with 1.0 M maltose. In the case of A. niger, 81% activity is recovered with 28-fold purification. The purified glucoamylase gave a single band on SDS-PAGE corresponding to 78 kDa molecular weight. The developed affinity precipitation process also works efficiently for purification of Bacillus amyloliquefaciens glucoamylase from its crude culture filtrate, giving 78% recovery with 38-fold purification. The purified preparation showed a major band corresponding to 62 kDa and a faint band about 50 kDa on SDS-PAGE. The latter corresponds to the molecular weight for alpha-amylase of Bacillus amyloliquefaciens.

Alginates↗
PubMed1989

Effects of hydrotropic agents on the solubility, precipitation, and protein binding of etoposide.

Etoposide, a commonly used anticancer agent, has an aqueous solubility of 0.2 mg/mL. It is formulated for intravenous use as a more concentrated solution (Vepesid; 20 mg/mL) with polysorbate 80 and with cosolvents. In this work, hydrotropic agents such as sodium benzoate, sodium o-hydroxybenzoate (sodium salicylate), sodium 2,5-dihydroxybenzoate (sodium gentisate), and the sodium salts of 2,4-dihydroxy- and 2,6-dihydroxybenzoic acid and of 2,4,6-trihydroxybenzoic acid have been used as alternative solubilizers of etoposide. The weakest and strongest interactants with etoposide were, respectively, sodium benzoate and sodium 2,4,6-trihydroxybenzoate. The effect of mono- and dihydroxybenzoates on etoposide solubility was intermediate. Although sodium 2,4,6-trihydroxybenzoate is the most efficient solubilizer, its use is limited by its own low aqueous solubility. The effect of sodium salicylate and other formulation ingredients on the in vitro protein binding and precipitation of etoposide upon dilution with normal saline and human plasma has been studied. Etoposide binds to the extent of 94% to human serum albumin (HSA) and human plasma, but only 24% to bovine serum albumin (BSA) in vitro. Sodium salicylate significantly decreased the binding of the drug to both HSA and human plasma, whereas the components of Vepesid did not. Dilution of Vepesid (1:2 and 1:3) with plasma in vitro resulted in immediate precipitation, while the corresponding dilutions of etoposide aqueous solution (20 mg/mL in 2 M sodium salicylate) produced no precipitate for the first hour.

Chemistry, Pharmaceutical↗
PubMed1981

The effects of dipalmitoyl phosphatidyl choline on the precipitation of native fibrils and segment-long-spacing aggregates from collagen solution.

The effect of dipalmitoyl phosphatidyl choline (DPPC), the major phospholipid component of pulmonary surfactant, on the precipitation of collagen in the form of native fibrils and segment-long-spacing (SLS) aggregates was studied in vitro. The effects of DPPC on both phases of collagen fibrillogenesis were analyzed spectrophotometrically, and alterations in the morphology of precipitated fibrils and SLS aggregates were ascertained by transmission electron microscopy (TEM). Low concentrations of DPPC inhibited the growth phase of fibrillogenesis, while higher concentrations were required to inhibit nucleation. Both the meshwork density and mean width of precipitated fibrils were altered by DPPC, as was the size of SLS aggregates. Segment-long-spacing aggregates prepared from pepsin-treated collagen were inhibited to a greater degree than SLS aggregates prepared from untreated collagen, indicating that the pepsin-susceptible residues of the telopeptide extensions of tropocollagen molecules stabilize SLS aggregates against the effects of DPPC. Based on these results and the inhibition of the growth phase at lower concentrations than those which inhibited the nucleation phase of fibrillogenesis, it was concluded that the primary mechanism of DPPC inhibition is electrostatic interference between the positively charged phospholipid molecules and the net positive charge of collagen. It is proposed that pathological conditions involving the pulmonary epithelium may allow interaction between surfactant and collagen, which could further weaken the interstitial connective tissue.

Animals↗
PubMed1995

Lack of effect of chronic morphine treatment and naloxone-precipitated withdrawal on tyrosine hydroxylase, galanin, and neuropeptide Y mRNA levels in the rat locus coeruleus.

Morphine dependence was experimentally induced in rats by daily injection of increasing doses of morphine for seven days. Withdrawal was precipitated in half of the morphine-dependent rats by a single injection of naloxone on day 8. Behavioral signs of withdrawal were evident in the morphine/naloxone group. Gene expression in locus coeruleus (LC) neurons was investigated using quantitative in situ hybridization analysis. Messenger RNA (mRNA) levels for tyrosine hydroxylase (TH), the rate-limiting enzyme in catecholamine synthesis, and for precursors to galanin (GAL) and neuropeptide Y (NPY), peptides that coexist with norepinephrine in LC neurons, were not altered by chronic morphine treatment or naloxone-precipitated withdrawal. In contrast, mRNA levels for c-fos were dramatically elevated in the LC following naloxone-precipitated withdrawal. Chronic morphine treatment caused a small decrease in levels of mRNA encoding the precursor to corticotropin-releasing factor (CRF) in Barrington's nucleus. Although long-term adaptations of LC neurons have previously been implicated in the development of morphine tolerance, dependence, and withdrawal, alterations in the levels of TH, GAL, or NPY mRNA in the LC apparently do not underlie this process.

Animals↗
PubMed1999

Homogeneous Precipitation of Uniform alpha-Fe2O3 Particles from Iron Salts Solutions in the Presence of Urea.

Uniform alpha-Fe2O3 particles within the nanometer range (100-300 nm) have been obtained by precipitation of iron (III) perchlorate in the presence of urea. Different morphology, from spheres to ellipsoidal particles with axial ratio up to approximately 10, was obtained by adding to the initial solution increasing amounts of phosphate anions up to 7 x 10(-3) M. The main targets of this work are the reduction in particle size and precipitation time and the increase of the particles axial ratio, keeping a narrow particle size distribution, in comparison to other methods previously developed to obtain homogenous alpha-Fe2O3 particles. A detailed analysis of the reaction products and a systematic study of the influence of the different precipitation conditions on the characteristics of the resulting particles have been carried out. Finally, some information on the formation mechanism of the ellipsoidal hematite particles in the iron (III) salt-urea-phosphate system is also given. Copyright 1999 Academic Press.

Journal Article↗
PubMed2000

Distinguishing Adsorption and Surface Precipitation of Phosphate on Goethite (alpha-FeOOH).

The reaction between phosphate and goethite changes from adsorption into surface precipitation with no discernible changes in the adsorption isotherm. Distinguishing the two processes, by plotting the loss of phosphate from solution versus final phosphate concentration or based on theoretical calculations, is difficult. This paper presents a method for distinguishing between the two processes based on the change in zeta potential with increasing adsorption. During adsorption, the incoming phosphate results in a more negative surface charge as the more acidic phosphate ion replaces a less acidic surface hydroxyl. The amount of negative charge imparted to the surface should vary linearly with surface coverage for adsorption. Phosphate that is bound to a surface precipitate, on the other hand, imparts a much smaller negative charge to the surface, since there is no change in the character of the surface due to the additional phosphate. Zeta potential measurements of phosphated goethite at varying solution pH values and surface coverages are used to determine the transition point from adsorption to surface precipitation. The transition occurs at dissolved phosphate concentrations much lower than those calculated for phosphate in equilibrium with goethite and iron phosphate. Copyright 2000 Academic Press.

Journal Article↗
PubMed2001

Sodium and Calcium Laurylamidomethylsulfate: Aqueous Micellar Phases, Their Properties, and a Precipitate of Vesicles.

A new anionic surfactant (M-LAMS) that is capable of forming intermolecular hydrogen bonds was investigated. Inverse solubilities of Na and Ca salts were found. Critical micelle concentration and aggregation behavior were determined by surface tension, light scattering, electric birefringence, and SANS measurements. It is found that the Na salt forms globular micelles while the Ca salt forms rodlike micelles. The phase behavior of the micellar solutions with increasing cosurfactant concentration was also studied. It is observed that 100 mM Na-LAMS solutions in the presence of 100 mM CaCl(2) undergo several phase transformations with increasing n-hexanol concentration. We found not only the expected micellar L(1) phase and a lamellar phase at concentrations quite low for this kind of system, but also a novel phase: At a cosurfactant/surfactant ratio x(C) of 1.2 a white precipitate is formed at the bottom of the sample. With increasing ratio x(C) the precipitate dissolves into a liquid crystalline L(alpha) phase that at x(C)=3.2 is transformed into an L(3) or sponge phase. Investigation by FF-TEM, light microscopy, and SANS shows that the precipitate consists of agglomerated polydisperse multilamellar vesicles. The vesicles consist of densely packed bilayers that contain little water. The bilayer thickness is about 20 Å and independent of its composition whereas the interlamellar distance is strikingly linked to concentrations of cosurfactant (surfactant/cosurfactant ratio) and electrolyte. With increasing cosurfactant content, the bilayers become less rigid and resulting thermal undulations force the membranes apart and weaken their interactions until a common L(alpha) phase is formed. This transition is an example of a bonding-nonbonding transition of membranes. Copyright 2001 Academic Press.

Journal Article↗
PubMed2002

Precipitation of inorganic salts inside hollow micrometer-sized polyelectrolyte shells.

Hollow polymer shells formed by layer-by-layer adsorption of oppositely charged polyelectrolytes onto micrometer-sized colloidal particles with subsequent decomposition of the colloidal core were employed as a model system for the study of inorganic crystallization reactions in restricted volumes. The size-selective permeability of shells is used for spatially controlling the precipitation of inorganic salts CaCO3 and BaCO3 into the shell interior. Outside the shells the precipitation was suppressed by the polymers, which are unable to penetrate the shell wall. The precipitates were studied by scanning electron microscopy and atomic force microscopy. The fundamental and applied aspects of research on spatially confined synthesis of inorganic particles are under discussion.

Journal Article↗
PubMed2002

An investigation of submicrostructural evolution of freshly precipitated ZrO2 in digestion for ultrafine sulfated ZrO2 catalysts by SAXS technique.

Coupled with XRD, BET, and TEM, the small-angle X-ray scattering (SAXS) technique has been effectively used to probe and characterize the submicrostructure of freshly precipitated hydrous zirconia and its evolution during digestion. It has been found that fresh hydrous zirconia particles possess an average diameter of about 5 nm and rather rough surfaces describable in terms of fractal concepts. The digestion of zirconia precipitates at 100 degrees C with their mother liquors may remarkably smooth the particles' rough surface and provoke fractal aggregation of the particles but make little change in average particle dimensions. A local dissolution-reprecipitation mechanism is regarded as a basic process to accompany particle surface smoothing, particle aggregation, and coarsening at the neck areas between joint particles, which may greatly strengthen the particle networks and enhance their resistance to crumbling while calcinated at high temperatures. On the basis of the submicrostructural features unraveled by SAXS, a coherent and significant physical picture has been raised out to demonstrate and interpret the relationship underlying the submicrostructure, the surface area variation, and the heating behavior of hydrous zirconia precipitates.

Journal Article↗
PubMed2002

Magnesium precipitate hot start method for PCR.

For the amplification of HIV-1 gag gene, and other challenging targets, a simple new hot start PCR protocol is presented which consists simply and entirely of the buffer system. This novel buffer composition and reaction assembly protocol for PCR includes magnesium and phosphate combined at high concentration in addition to standard buffer reagents. The resulting magnesium-containing precipitate provides a hot start for PCR, since the magnesium in the precipitate is unavailable to DNA polymerase until thermal cycling. No extra manipulations at the thermal cycler or changes to standard thermal cycling profiles are necessary. Upon normal cycling, the magnesium becomes fully available within the first 3 cycles. The method effectively prevents premature primer extension by several DNA polymerases or mixtures of DNA polymerases tested, including Klentaql, KlentaqLA, Pfu, and full-length wild-type DNA polymerase. Once the precipitate is formed, the hot start buffer is stable and functional for at least a week at -20 degrees, 4 degrees , or 25 degrees. We demonstrate that the method is as effective as a manual hot start (addition of magnesium at or above primers'annealing temperatures) for several target gene amplifications which require a hot start.

Animals↗
PubMed1993

Role of L-type calcium channels on yohimbine-precipitated clonidine withdrawal in vivo and in vitro.

This study was designed to elucidate the possible participation of L-type calcium channels in the expression of clonidine-withdrawal precipitated by yohimbine in clonidine-dependent animals. Mice implanted for 5 days with osmotic minipumps containing the alpha 2-adrenoceptor agonist clonidine showed symptoms of a withdrawal syndrome (jerks, headshakes, defecations and weight loss) when yohimbine, an alpha 2-adrenoceptor antagonist, was injected. Similarly, isolated rat ilea incubated with clonidine in vitro showed a withdrawal contracture when yohimbine was added to the organ bath. The effects of L-type calcium channel blockers (verapamil and diltiazem) and the stimulant Bay K 8644 on these two different types of withdrawal responses were evaluated. A dose-dependent decrease in yohimbine-precipitated clonidine withdrawal in vivo was observed when verapamil (10-40 mg/kg, s.c. and 120 micrograms/mouse, i.c.v.) or diltiazem (5-20 mg/kg, s.c. and 160 micrograms/mouse, i.c.v.) were administered to mice dependent on clonidine. No effect was found after Bay K 8644 (0.5-5 mg/kg, s.c. and 1-5 micrograms/mouse) was injected under these conditions. In vitro, both verapamil (0.1-5 microM) and D-cis-diltiazem (1-50 microM) concentration-dependently reduced the height of the yohimbine-precipitated withdrawal contracture in rat ileum incubated with clonidine. Furthermore, the effect of diltiazem was stereospecific, as D-cis-diltiazem 10 microM markedly inhibited clonidine withdrawal, whereas the same concentration of L-cis-diltiazem had no effect. In contrast, the calcium channel stimulant Bay K 8644 (0.1-1 microM) increased the height of the ileum withdrawal contracture.(ABSTRACT TRUNCATED AT 250 WORDS)

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1989

Cryocrystalglobulinemia: pH-dependent precipitation of a monoclonal IgG-kappa-immunoglobulin.

Cryoglobulinemia is seen in a minority of patients with plasma cell dyscrasias and can be of clinical relevance if intravascular gelling or precipitate formation occurs at low temperatures. We observed a patient suffering from IgG-kappa multiple myeloma which was complicated by instability of the immunoglobulin forming crystalline precipitates at low pH and low temperature. Short exposure to extreme cooling initiated an unusual course terminating in disseminated vascular occlusion and fatal outcome which was connected with an adverse effect of blood exchange. Crystal formation was noticed in anticoagulated blood samples even at 37 degrees C. In vitro studies showed a critical pH dependency of solubility of the immunoglobulin close to the physiological pH of the blood. These observations suggest that the fatal outcome was due to a vicious circle of ischemia, metabolic acidosis and intravascular precipitations, initiated not only by low acral temperatures but by cold-induced ischemic tissue acidosis as well. Serum of patients with monoclonal gammopathy and cryoglobulinemia should be tested for pH dependent immunoglobulin insolubility.

Aged↗
PubMed1977

Naloxone-precipitated withdrawal as a function of the morphine-naloxone interval.

Withdrawal was precipitated by naloxone at different intervals, up to 22.5 h, following a last maintenance injection in morphine-dependent rats. Different symptoms of withdrawal were found to be preeminent following different morphine-naloxone intervals. Locomotor activity, jumping, and writhing were precipitated most frequently at shorter intervals after the last morphine injection; teeth chattering, wet dog shakes, ptosis, diarrhea, penile ejaculation, and hypothermia, at longer intervals. Others, including hostility, rhinnorhea and lacrimation did not change in frequency over the intervals measured. This order closely resembled that in which symptoms occurred as a result of withdrawal abstinence alone, though they were somewhat advanced in time. The results were discussed in relation to previously reported observations of naloxone-precipitated withdrawal, and in terms of their implications for a general theory of morphine withdrawal.

Animals↗
PubMed1976

Activity of the nigro-striatal dopaminergic system during precipitated morphine withdrawal investigated in rats with acute unilateral inactivation of the striatum.

The activity of the striatal dopamine system during precipitated morphine withdrawl was studied in rats using a model in which the striatum was unilaterally inactivated by the local injection of KCl. In naive rats dopamine agonists administered just prior to KCL induced ipsilateral turning or circling, while dopamine antagonists in the same situation caused contralateral turning. Withdrawal precipitated by morphine antagonists in rats made dependent by repeated implantation of morphine pellets induced contralateral circling during unilateral inactivation of the striatum. This contralateral circling was only slightly enhanced by haloperidol, but strongly enhanced by a low dosage of apomorphine as well as by some weak dopamine agonists such as CB 154 or By 101. However, high doses of apomorphine completely reversed the withdrawal-induced contralateral circling into ipsilateral circling. Other dopamine agonists, such as d-amphetamine, L-Dopa and piribedil, did not abolish the withdrawal-induced contralateral circling, however, they caused the appearance of an additional ipsilateral circling. Other types of drugs which are known to intensify withdrawal-induced jumping (desipramine, atropine, caffeine) enhanced contralateral circling. There are also other parallels jumping and contralateral circling induced by withdrawal. The direction of naloxone-induced asymmetric behaviour during acute unilateral inactivation of the striatum suggests that striatal dopaminergic activity is reduced during precipitated withdrawal; the other results reported point to the possiblity that extrastriatal dopaminergic mechanisms or different dopamine receptor types within the striatum are involved.

Animals↗
PubMed1977

Naloxone-precipitated withdrawal reveals sensitization to neurotransmitters in morphine tolerant/dependent rats.

Morphine tolerant/dependent rats were tested for their sensitivity to putative neurotransmitters or other receptor agonists injected intracerebroventricularly (i.c.v.) during naloxone-precipitated withdrawal. Dopamine, apomorphine, clonidine and serotonin were found to reinitiate withdrawal jumping behaviour when injected 30 min after naloxone. Dopamine and apomorphine also reinitiated jumping, but of a lesser intensity, when injected 3 h after naloxone-precipitated withdrawal. I.c.v. injection of acetylcholine or prostaglandin E1 failed to reinitiate withdrawal jumping. In addition, all the above substances failed to induce jumping behaviour in naive rats or in morphine tolerant/dependent rats before naloxone-precipitated withdrawal. Morphine tolerance and dependence therefore appears to be associated with changes in the sensitivity of the CNS to putative neurotransmitter substances. These changes are best demonstrated during the sudden termination of opiate action that is caused by administration of naloxone.

Animals↗
PubMed1983

A method for the purification of E. coli plasmid DNA by homogeneous lysis and polyethylene glycol precipitation.

A procedure is described for the isolation and purification of E. coli plasmid DNA by polyethylene glycol precipitation. The method is rapid, simple, inexpensive and amenable to both small and large scale manipulation. This procedure involves lysis of bacterial cells by treatment with pronase in sodium dodecyl sulfate, removal of chromosomal DNA by centrifugation, precipitation of residual nucleic acids with polyethylene glycol and removal of RNA by precipitation with LiCl. Plasmid DNA purified as described is pure enough for restriction endonuclease analysis, for use as a vector for the cloning of cDNA or synthetic DNA, or for use as a template in an E. coli transcription-translation cell-free system.

DNA↗