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PubMed1992

The effect of dilution, pH and ionic strength of plasma on t-PA precipitation in euglobulin fraction.

In order to evaluate the influence of dilution, pH and ionic strength on the precipitation of t-PA and PAI-1 during euglobulin precipitation, we measured t-PA Ag, PAI-1 Ag and fibrinolytic activity in the euglobulin fraction made of pooled plasma from liver cirrhosis patients, under various conditions by changing pH, ionic strength and degree of dilution. The precipitation of t-PA Ag in the euglobulin fraction was enhanced by decreasing the ionic strength and greatest at pH 6.0. The fibrinolytic activity in the euglobulin fraction showed consistent changes with t-PA Ag under varying pH and ionic strength. The precipitation of t-PA Ag was not influenced by the dilution factor but the larger the dilution factor, the greater the PAI-1 and the smaller the fibrinolytic activity in the euglobulin fraction. PAI Ag in euglobulin fraction showed consistent changes with t-PA Ag in the euglobulin fraction regardless of the changes in ionic strength and pH. The amount of precipitation of t-PA and PAI-1 was increased by the presence of dextran sulfate, under varying pH, ionic strength and dilution conditions. Our results show that the currently used conditions for standard euglobulin precipitation are the most favorable for t-PA precipitation into the euglobulin fraction. The fibrinolytic activity exerted in the euglobulin fraction seems to depend on the amount of t-PA-PAI-1 complex rather than minimized protease inhibitor in the euglobulin fraction.

Fibrinolysis↗

PubMed1999

Incidence of plague associated with increased winter-spring precipitation in New Mexico.

Plague occurs episodically in many parts of the world, and some outbreaks appear to be related to increased abundance of rodents and other mammals that serve as hosts for vector fleas. Climate dynamics may influence the abundance of both fleas and mammals, thereby having an indirect effect on human plague incidence. An understanding of the relationship between climate and plague could be useful in predicting periods of increased risk of plague transmission. In this study, we used correlation analyses of 215 human cases of plague in relation to precipitation records from 1948 to 1996 in areas of New Mexico with history of human plague cases (38 cities, towns, and villages). We conducted analyses using 3 spatial scales: global (El Niño-Southern Oscillation Indices [SOI]); regional (pooled state-wide precipitation averages); and local (precipitation data from weather stations near plague case sites). We found that human plague cases in New Mexico occurred more frequently following winter-spring periods (October to May) with above-average precipitation (mean plague years = 113% of normal rain/ snowfall), resulting in 60% more cases of plague in humans following wet versus dry winter-spring periods. However, we obtained significant results at local level only; regional state-wide precipitation averages and SOI values exhibited no significant correlations to incidence of human plague cases. These results are consistent with our hypothesis of a trophic cascade in which increased winter-spring precipitation enhances small mammal food resource productivity (plants and insects), leading to an increase in the abundance of plague hosts. In addition, moister climate conditions may act to promote flea survival and reproduction, also enhancing plague transmission. Finally, the result that the number of human plague cases in New Mexico was positively associated with higher than normal winter-spring precipitation at a local scale can be used by physicians and public health personnel to identify and predict periods of increased risk of plague transmission to humans.

Animals↗

PubMed1995

Anomalous carbonate precipitates: is the Precambrian the key to the Permian?

Late Permian reefs of the Capitan complex, west Texas; the Magnesian Limestone, England; Chuenmuping reef, south China; and elsewhere contain anomalously large volumes of aragonite and calcite marine cements and sea-floor crusts, as well as abundant microbial precipitates. These components strongly influenced reef growth and may have been responsible for the construction of rigid, open reefal frames in which bryozoans and sponges became encrusted and structurally reinforced. In some cases, such as the upper biostrome of the Magnesian Limestone, precipitated microbialites and inorganic crusts were the primary constituents of the reef core. These microbial and inorganic reefs do not have modern marine counterparts; on the contrary, their textures and genesis are best understood through comparison with the older rock record, particularly that of the early Precambrian. Early Precambrian reefal facies are interpreted to have formed in a stratified ocean with anoxic deep waters enriched in carbonate alkalinity. Upwelling mixed deep and surface waters, resulting in massive seafloor precipitation of aragonite and calcite. During Mesoproterozoic and early Neoproterozoic time, the ocean became more fully oxidized, and seafloor carbonate precipitation was significantly reduced. However, during the late Neoproterozoic, sizeable volumes of deep ocean water once again became anoxic for protracted intervals; the distinctive "cap carbonates" found above Neoproterozoic tillites attest to renewed upwelling of anoxic bottom water enriched in carbonate alkalinity and 12C. Anomalous late Permian seafloor precipitates are interpreted as the product, at least in part, of similar processes. Massive carbonate precipitation was favored by: 1) reduced shelf space for carbonate precipitation, 2) increased flux of Ca to the oceans during increased continental erosion, 3) deep basinal anoxia that generated upwelling waters with elevated alkalinities, and 4) further evolution of ocean water in the restricted Delaware, Zechstein, and other basins. Temporal coincidence of these processes resulted in surface seawater that was greatly supersaturated by Phanerozoic standards and whose only precedents occurred in Precambrian oceans.

Animals↗

PubMed2003

[A preliminary study on the chemical properties of precipitation, throughfall, stemflow and surface run-off in major forest types at Dinghushan under acid deposition].

Studies on the chemical properties of precipitation, throughfall, stemflow and surface run-off in major forest types at Dinghushan under acid deposition showed that the pH value of precipitation was about 4.90, and the frequency of acid rain was over 62%. In broad-leaved forest, the pH value of precipitation was lower than that of throughfall, but higher than that of stemflow and especially the surface run-off, indicating that the soil was naturally acidified. In mixed forest, both throughfall and surface run-off had a higher pH value, but stemflow had a lower pH value than precipitation. The throughfall and stemflow were more acidified than precipitation in coniferous pine forest, but the surface run-off had a higher pH value than precipitation. These results suggested that among the three major forest types at Dinghushan, the canopy of broad-leaved forest had the highest buffering ability, whereas for the soil, the coniferous forest had the highest soil buffering capacity. The concentrations of nutrient elements, such as P, K, Ca, Na and Mg in the throughfall, stemflow and surface run-off were higher than those in bulk precipitation in all forests at Dinghushan, some even 10 times higher, indicating that a large amount of nutrients were leached from the canopy. The concentrations of nutrient elements in stemflow were higher than those in throughfall in all forests, and the concentration of nutrient elements in surface water was higher than those in atmospheric rainfall. Coniferous forest had a higher concentration of nutrients in the throughfall and stemflow and a lower nutrient concentration in the surface run-off than other forest types, which implied that nutrient loss was more serious in broad-leaved and mixed forests than in coniferous forests.

Calcium↗

PubMed2005

[Different roles of the spinal protein kinase C alpha and gamma in morphine dependence and naloxone-precipitated withdrawal].

Our previous studies showed that spinal neurons sensitization was involved in morphine withdrawal response. This study was to investigate the roles of spinal protein kinase C (PKC) alpha, gamma in morphine dependence and naloxone-precipitated withdrawal response. To set up morphine dependence model, rats were subcutaneously injected with morphine (twice a day, for 5 d). The dose of morphine was 10 mg/kg in the first day and was increased by 10 mg/kg each day. On day 6, 4 h after the injection of morphine (50 mg/kg), morphine withdrawal syndrome was precipitated by an injection of naloxone (4 mg/kg, i.p.). Chelerythrine chloride (CHE), a PKC inhibitor, was intrathecally injected 30 min before the administration of naloxone. The scores of morphine withdrawal symptom and morphine withdrawal-induced allodynia were observed. One hour after naloxone-precipitated withdrawal, Fos protein expression was assessed by immunohistochemical analysis and Western blot was used to detect the expression of cytosol and membrane fraction of PKC alpha and gamma in the rat spinal cord. The results showed that intrathecal administration of CHE decreased the scores of morphine withdrawal, attenuated morphine withdrawal-induced allodynia and also inhibited the increase of Fos protein expression in the spinal cord of morphine withdrawal rats. The expression of cytosol and membrane fraction of PKC alpha was significantly increased in the spinal cord of rats with morphine dependence. Naloxone-precipitated withdrawal induced PKC alpha translocation from cytosol to membrane fraction, which was prevented by intrathecal administration of CHE. During morphine dependence, but not naloxone-precipitated withdrawal, PKC gamma in the spinal cord translocated from cytosol to membrane fraction, and intrathecal administration of CHE did not change the expression of PKC gamma in the spinal cord of naloxone-precipitated withdrawal rats. It is suggested that up-regulation and translocation of PKC in the spinal cord contribute to morphine dependence and naloxone-precipitated withdrawal in rats and that PKC alpha and gamma play different roles in the above-mentioned effect.

Animals↗

PubMed2005

[Seizure-precipitating factors in epilepsy--what do patients report?].

BACKGROUND: To investigate the occurrence of seizure-precipitating factors in a large epilepsy population and to determine which precipitants patients most often report. MATERIAL AND METHOD: Study participants included Norwegian twins and their family members identified in a multinational twin study. 794 patients with epilepsy were asked about seizure precipitants. RESULTS: Among the respondents, 55% reported at least one seizure-precipitating factor, while 28% claimed to have experienced two or more. Emotional stress, sleep deprivation, and tiredness were the most frequently reported precipitants. Patients with generalised seizures seemed more sensitive to sleep deprivation, tiredness, and flickering light than those with partial seizures. Women with partial seizures appeared to be more prone to seizures during their period than those with generalised seizures. INTERPRETATION: In our opinion, dealing with seizure precipitating factors is a somewhat neglected and underestimated supplement to more traditional epilepsy therapies. Acknowledging and avoiding seizure precipitants may improve seizure control in many patients.

Adolescent↗

PubMed1990

Precipitated abstinence in orally dosed benzodiazepine-dependent dogs.

The ability of graded doses of flumazenil (2, 6, 18, 36 and 72 mg/kg) and a lactose placebo to precipitate abstinence was studied in dogs treated chronically with diazepam, nordiazepam, flunitrazepam, alprazolam, oxazepam, halazepam and lorazepam by oral dosing. A scale comprised of 10 precipitated abstinence signs, the Benzodiazepine Precipitated Abstinence Scale, was developed, which yielded linear flumazenil log-dose response lines with significant slopes in dogs dependent on diazepam, nordiazepam and flunitrazepam. The effects of 18, 36 and 72 mg/kg of flumazenil in otherwise drug naive dogs were studied. In naive dogs, the most prominent effect of flumazenil was to reduce activity. All benzodiazepines studied produced dependence that was characterized by signs of precipitated abstinence; however, the intensity and quality of abstinence varied from one benzodiazepine to another. Precipitated abstinence in dogs treated chronically with diazepam and flunitrazepam was characterized by a dose-related increase in clonic convulsions and Benzodiazepine Precipitated Abstinence Scale scores. This pattern differed from that seen in nordiazepam- and alprazolam-dependent dogs, which showed a comparable flumazenil dose-related increase in clonic convulsion but only a modest increase in Benzodiazepine Precipitated Abstinence Scale scores. Oxazepam and lorazepam produced dependence that was less intense than that seen with the other benzodiazepines. Plasma levels of the benzodiazepines and their metabolites were repeatedly determined after single doses and during addiction cycles. Nordiazepam accumulated in diazepam- and nordiazepam-dependent dogs and alpha-OH alprazolam accumulated in alprazolam-dependent dogs. Other drugs and metabolites did not. These observations suggest that: 1) different benzodiazepines or their metabolites produce different types of physical dependence, suggesting that they or their metabolites have different mechanisms and sites of action; 2) plasma cumulation of the benzodiazepines or their active metabolites is an important factor in the genesis of physical dependence; and 3) metabolism of benzodiazepines plays an important role in their dependence-producing capacity, and because of differences in the way species metabolize benzodiazepines, the type of dependence produced in different species may differ.

Administration, Oral↗

PubMed1989

Metal affinity precipitation of proteins.

Proteins containing multiple surface-accessible histidine residues can be precipitated using small quantities of bis-copper chelates. The chelates serve to crosslink the proteins, presumably via the accessible histidines, leading to the formation of large, insoluble complexes. When excess copper chelate is used to carry out the precipitation, the resulting precipitate has a stoichiometry of 1:1 copper:accessible histidine. The precipitation is analogous to antibody-antigen precipitin reactions and can be described qualitatively using simple equilibrium theory developed for those systems. Human hemoglobin contains a large number of surface histidines and is efficiently precipitated by the copper salt CuSO4 as well as by bis-copper chelates. Sperm whale myoglobin contains many fewer surface histidines and is precipitated only by the bis-chelates. The effects of the number of accessible histidines on the protein, the chain length separating the two chelates, and the pH on the precipitation reaction have been investigated.

Animals↗

PubMed1995

[Development of humoral precipitating antibodies to Campylobacter spp. in chickens].

Development of humoral precipitating antibodies against Campylobacter spp. in chickens. The development of precipitating antibodies in chickens was examined by two-dimensional immunodiffusion test after immunization with a formol inactivated vaccine and after subcutaneous and oral application of different live campylobacter serovars. The supernatant of bacterial cells after sonication and centrifugation was used as an antigen in the agar-gel precipitin test. Antisera against different campylobacter serovars showed a high percentage of cross-reactions. In chickens immunized with an inactivated vaccine at an age of 1, 2, 3, 4 and 7 weeks, precipitating antibodies could be demonstrated for the first time at 7 days p.i. Except for 1-week-old birds, sera from the other groups reacted positively at 14 days p.o. After subcutaneous duplication of live organisms to 4-week-old chickens, antibodies could already be demonstrated at 4 days p.i. later in part of the experimental groups. No interrelation could be detected between antibody titers, measured by enzyme-linked immunoabsorbent assay (ELISA), from precipitating sera, as well as from those from non-precipitating sera. Precipitating antibodies and antibody titers in the ELISA were examined in sera from groups of birds infected at an age of 1, 2, 3, 4 and 7 weeks. During the Campylobacter excretion period, a distinct peak of antibody titers occurred in 1- and 7-week old birds, whereas other groups showed a steady increase in titers. Precipitating antibodies were only found in 1- and 2-week-old chickens.

Animals↗

PubMedDate not supplied

[Levels of immune complexes in fresh and frozen serum and plasma detected by precipitation with polyethylene glycol in patients with malignant diseases].

INTRODUCTION: Immune complexes are macromolecules consisting of immunoglobulins (antibodies) bound to different antigens [1]. Determination of circulating immune complexes in patients with malignant diseases can be of some interest for prognosis and follow-up of a disease [2, 3]. According to certain data the immune complexes concentration varies in dependence of disease stage [4] and it is not affected by therapy [5]. Precipitation with polyethylenglycol is a physical method for determination of circulating immune complexes, based on the ability of high molecular polymers to precipitate macromolecules from sera [6]. This mechanism of precipitation is not yet well understood, but it is probably based on steric exclusion of water molecules that affects insolubility of immune complex molecules [7]. Repeatedly frozen sera demonstrated rapid decrease in detected concentration of circulating immune complexes [8] by polyethylenglycol. The presence of complement affects solubility of circulating immune complexes [7]. While there are no data about the influence of other proteins in sera or plasma, the aim of this study was to find out if there are any significant differences between the circulating immune complexes levels, determined by polyethylenglycol, in sera, plasma or in only once frozen sera. MATERIAL AND METHODS: Eighteen samples of plasma and sera from patients with malignancy (10 males and 8 females) were examined. Eight of them had non-Hodgkin lymphoma, 4 were with Hodgkin lymphoma, 4 with breast carcinoma and 2 with lung carcinoma. All samples were taken before starting chemotherapy. The circulating immune complexes determination was carried out immediately after the separation of plasma and sera and also in sera frozen for 10 days at -35 degrees C. Circulating immune complexes were determined spectrophotometrically. The absorbance (A450) of serum or plasma in 3.75% of polyethylene glycol, polyethylenglycol (M = 6000) solution was used as the measure of the circulating immune complexes level [9]. The standard for circulating immune complexes determination in g/l was aggregated IgG at 36 degrees C for 30 minutes from the serum of healthy volunteers. RESULTS: The mean value and the range of circulating immune complexes level (A450) are given in Table 1. The values in g/l are presented in Graph 1. The values of circulating immune complexes in plasma were significantly lower than those in fresh sera (t = 2.8125; p < 0.02). There was no significant statistic difference between levels in circulating immune complexes (A450) in fresh and frozen sera (t = 1.3261; p > 0.1). DISCUSSION: In dependence on its concentration polyethylenglycol shows the ability to precipitate proteins selectively [10]. The selectivity was tested mainly towards immunoglobulins and the complement. Results obtained in this study show statistically significant lower circulating immune complexes level in plasma than in serum or frozen serum. The main difference between sera and plasma is in complete absence of fibrinogen, factors V and VIII in sera and in presence of Ca++ ions. Besides that plasma contains an anticoagulant [11]. It is possible that the presence of fibrinogen and some coagulation factors disturb the polyethylenglycol precipitation mechanism. According to this, it might be, that mechanism, based on steric exclusion of water molecules, selectively influences polyethylenglycol precipitation of circulating immune complexes in plasma. It is difficult to say how much Ca++ ion and anticoagulant, as well as the activity of some plasma enzymes, and possible dissociation of circulating immune complexes influence the formation of precipitate. In any case, there is a significant difference between concentration of circulating immune complexes according to substrate. For that reason, it is necessary to detect circulating immune complexes by polyethylanglycol always in the same medium for exact clinical evaluation. (ABSTRACT TRUNCATED)

Antigen-Antibody Complex↗

PubMed2003

Precipitation of RNA impurities with high salt in a plasmid DNA purification process: use of experimental design to determine reaction conditions.

The use of high salt solution to precipitate RNA in a pharmaceutical-grade plasmid DNA purification process was investigated. Five antichaotropic salts were tested for their potential to precipitate RNA. Calcium chloride was by far the best precipitant with high RNA removal in a very short incubation time. Calcium chloride precipitation conditions were investigated at two stages of a plasmid purification process using experimental design techniques. The effect of up to five factors on RNA precipitation and plasmid recovery was assessed by statistical modeling. Optimized conditions for calcium chloride precipitation were then introduced to the plasmid purification process resulting in the efficient removal of most impurities (RNA, chromosomal DNA, proteins, and endotoxins).

Calcium Chloride↗

PubMed2004

Purification of antibody and antibody-fragment from E. coli homogenate using 6,9-diamino-2-ethoxyacridine lactate as precipitation agent.

To obtain a more efficient purification process for antibody fragments from an Escherichia coli homogenate, the precipitant, Ethodin (6,9-diamino-2-ethoxyacridine lactate) was introduced to the homogenate. By adding the precipitant a drastic reduction of host cell protein was obtained. The majority of the proteins were recovered in a precipitate with the cell debris, while the antibody or antibody-fragment was recovered in the clarified supernatant. In addition, DNA was also efficiently precipitated when using Ethodin as a precipitation agent. The improved purity of the clarified extract obtained by using the precipitant allows for the use of smaller chromatography columns and may reduce the number of chromatographic steps required in the recovery process. The effect of Ethodin concentration, pH, temperature, and conductivity were investigated. The investigation was performed on two different antibody-fragments, e.g., F(ab')(2) molecules and a full-length antibody produced in E. coli. The two F(ab')(2) proteins were F(ab')(2)A and F(ab')(2)B, which have a similar molecular mass (100 kDa) but different isoelectric points (pIs), i.e., 8.9 and 7.5, respectively. The full-length antibody, Ab (the full IgG form of F(ab')(2)B) has a pI of 7.8 and molecular mass of 150 kDa. The investigation showed that the highest purification factors were obtained at neutral pH, low conductivity, and Ethodin concentrations of 0.6%.

Antibodies↗

PubMed1984

Properties of carbonate-containing aluminum hydroxide produced by precipitation at constant pH.

Carbonate-containing aluminum hydroxide was precipitated at constant pH at intervals of 0.5 pH units from pH 6 to 10 by pumping 0.5 M AlCl3 into the reaction vessel at a constant rate of 2 mL/min and infusing 2 M Na2CO3 at a rate necessary to maintain the desired pH. The pH of precipitation affected both the particle size and the composition of the precipitate. The particle size of the precipitate decreased as the pH of precipitation was increased from 6 to 10. The precipitates formed between pH 7.5 and 9.5 contained crystalline sodium aluminum hydroxycarbonate (dawsonite) in addition to amorphous carbonate-containing aluminum hydroxide.

Aluminum Hydroxide↗

PubMed1993

Simultaneous preparation and quantitation of proteoglycans by precipitation with alcian blue.

Conditions for specific interaction between Alcian blue and proteoglycans were optimized by comparing the differential spectra of Alcian blue obtained with purified chondroitin sulfate dissolved in water with the spectra obtained with nasal cartilage proteoglycans dissolved in synovial fluid. A method was then designed that provides specific precipitation of proteoglycans or glycosaminoglycans in 4 M guanidine - HCl in the presence of protein, hyaluronic acid, or nucleic acids. The specificity is achieved by using a low pH in combination with detergent and high salt concentration. Stepwise addition of reagents is necessary to avoid binding of Alcian blue to proteins and nucleic acids. All polyanions, except polysulfates, are first neutralized by lowering the pH to 1.5. By including detergent in this step, the hydrophobic protein regions are blocked and not accessible for binding with the dye. These regions could otherwise bind Alcian blue by hydrophobic interaction. When the Alcian blue reagent is added after, only the polysulfated molecules will remain charged and free to interact with Alcian blue. At least 0.4 M guanidine-HCl is required to abolish the negative interference by proteins. All sulfated glycosaminoglycans are precipitated at 0.4 M guanidine-HCl. With increasing guanidine-HCl concentrations, the different glycosaminoglycans are precipitated in accordance with the critical electrolyte concentration of the respective glycosaminoglycan. The Alcian blue precipitation can be performed at different concentrations of guanidine-HCl in order to separate different classes of proteoglycans. Excess dye and contaminating proteins are removed by a wash in a DMSO-MgCl2 solution and the precipitate is dissolved in a mixture of guanidine-HCl and propanol. For quantitation, the absorbance is recorded in a microplate reader with the 600-nm filter, the assay being linear between 0.5 and 20 micrograms proteoglycan. Since no digestion of samples with protease is needed, the proteoglycans are recovered in native form. The proteoglycan-Alcian blue complexes dissociate in the guanidine-HCl/propanol mixture and the proteoglycans can be selectively precipitated with propanol. The dye is used for quantitation and the proteoglycans can be utilized for further analysis.

Alcian Blue↗

PubMed1995

Precipitation of Hevea brasiliensis latex proteins with trichloroacetic acid and phosphotungstic acid in preparation for the Lowry protein assay.

Many proteins derived from the latex of Hevea brasiliensis that remain soluble in trichloroacetic acid (TCA) can be precipitated by phosphotungstic acid (PTA). A combination of 5% TCA and 0.2% PTA precipitates a wide range of proteins effectively even when they are present in low concentrations (below 1 microgram ml-1). In addition to its protein purification function, acid precipitation also increases the sensitivity of the subsequent protein assay by allowing the test sample to be concentrated. Another advantage of protein precipitation by TCA and PTA is that very small amounts of protein (of the order of 10 micrograms) can be repeatably recovered without the use of precipitate-bulking agents such as sodium deoxycholate. This general procedure of protein purification and concentration is simple and rapid, but the use of PTA may not be fully compatible with the Bradford protein assay. A modified Lowry microassay is described which enables about 3 micrograms ml-1 to be quantitated at the photometric absorbance of 0.05. When used in conjunction with protein concentration by precipitating with TCA/PTA, approximately 0.4 microgram ml-1 protein present in 6 ml of solution can be assayed.

Chemical Precipitation↗

PubMed1992

Inhibition of calcium phosphate precipitation by human salivary statherin: structure-activity relationships.

Previous studies of human statherin showed the active region for inhibition of secondary calcium phosphate precipitation (crystal growth) to reside in the highly charged amino-terminal one-third of this molecule, and the neutral tyrosine-, glutamine- and proline-rich carboxy-terminal two-thirds of the molecule is required for maximal inhibition of primary (spontaneous) precipitation. The purpose of the present study was to define more clearly the activities of these different molecular segments of statherin with respect to the two kinds of inhibitory activities. Peptides from statherin were prepared by specific proteolysis using trypsin, endoproteinase Arg-C, and activated factor X to produce the amino-terminal hexa-, nona- and decapeptides, respectively, and carboxypeptidase-A was used to obtain a peptide extending from residue 1 to about residues 32-37. The peptides were purified by anion exchange and gel filtration chromatography, and characterized and quantified by amino-acid analysis. Serially diluted samples of statherin and derived peptides were assayed to determine the concentrations, giving a standard 50% inhibition of precipitation (C50%) in assay systems designed for this purpose using polyaspartate as a standard. Results are expressed as (C50% statherin)/(C50% peptide). For inhibition of primary precipitation, these values were peptide(1-6), 0.20; peptide(1-9), 0.15; peptide(1-31/35), 0.24. For inhibition of secondary precipitation, the values were peptide(1-6), 3.8; peptide(1-9), 2.8; peptide(1-10), 1.9; peptide(1-32/37), 1.5. These quantitative findings show that maximum inhibition of primary precipitation by statherin requires the entire molecule. Thus, removal of a relatively small segment of its carboxy-terminal region results in a substantial reduction in inhibitory activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗

PubMed1986

Localization artefacts in ultracytochemical ion precipitation reactions.

The precipitation patterns of the following ultracytochemical methods in rat muscle cells were compared and examined critically: the potassium pyroantimonate method for calcium demonstration; the calcium phosphate technique for the Ca2+--ATPase reaction; the formazan reaction for the demonstration of creatine kinase activity (all performed on heart muscle); and the lead phosphate technique for the Mg2+--ATPase reaction in skeletal muscle. Using X-ray microanalysis, it was found that the antimonate precipitate contains only calcium as the precipitated ion in the vast majority of cases. Most probably it consists of pure calcium pyroantimonate. However, in myocytes showing the well-established precipitation pattern, the concentration of calcium was estimated to be about two orders of magnitude higher than the native concentration of total intracellular calcium. It is concluded that calcium ions diffuse freely from the extracellular space and from adjacent cells into cells containing antimonate and are precipitated mostly at sites where heterogeneous nucleation is facilitated by intracellular catalysts (biopolymers). As shown by the similar precipitation patterns for the four reactions compared, these catalysts are not specific to any of these reactions and are most probably neither calcium-binding sites nor sites of any one of the enzymes examined in the native cell.

Animals↗

PubMed1986

Saturation of human salivary secretions with respect to calcite and inhibition of calcium carbonate precipitation by salivary constituents.

The state of saturation of human salivary secretions with respect to calcite has been investigated. This property cannot be calculated exactly because of uncertainties in the values of the solubility product constant of calcite, the dissociation constants of carbonic acid, and PCO2 values of saliva. Minimum and maximum limits for this saturation, however, can be established using appropriate values for the constants and salivary PCO2. Values that give the minimum degree of saturation show that 8 of the 70 samples of human saliva investigated would be supersaturated with respect to calcite, while 64 of the 70 samples appeared to be supersaturated when values giving the maximum degree of saturation were used. In the latter case, the ratio of ionic activity products to solubility product was above 10 for several samples and over 18 for the most supersaturated sample. Since these results show that supersaturation of saliva with respect to calcite may be a common condition, human salivary secretions were investigated for the presence of inhibitors of calcite precipitation. Inorganic phosphate and the acidic proline-rich proteins, known to be inhibitors of calcite precipitation, and human salivary statherin, now shown to have a similar activity, are present in saliva at concentrations considerably higher than those required to inhibit calcite precipitation under salivary conditions. Quantitatively, phosphate is by far the most important inhibitor of calcite precipitation present in saliva, suggesting that inhibition of calcite precipitation by the macromolecules may be of secondary significance. It seems more likely that the function of these molecules is to inhibit precipitation of calcium phosphate salts, as previously proposed. These different inhibitory activities, however, are likely to be factors in the differences in composition of oral and dental calculi in different species, and may need to be considered in the formation of calcite stones in the pancreas.

Calcium Carbonate↗