Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “PRECIPITATION”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,189 records · Page 66Linked to original sources
PubMed1991

Isolation and characterization of a thermolabile beta-2 macroglycoprotein ('thermolabile substance' or 'Hakata antigen') detected by precipitating (auto) antibody in sera of patients with systemic lupus erythematosus.

A novel thermolabile beta-2 macroglycoprotein ('thermolabile substance' (TLS) or 'Hakata antigen' (HA], which was detected by the precipitating (auto) antibodies of patients with systemic lupus erythematosus, was isolated and characterized. The purification procedure entailed the following steps: isoelectric precipitation in the range between pH 5.2-6.1, hydroxyapatite absorption chromatography, 35% saturated ammonium sulfate precipitation, Sephadex G-200 gel filtration, Pevikon block electrophoresis, lentil lectin affinity chromatography and immobilized rabbit anti-human whole serum IgG column chromatography. Utilizing these procedures, 0.1 mg of HA was purified from 3 1 of pooled human serum. The molecular mass of HA was determined as 650 kDa by Sepharose 4B gel filtration. On SDS-PAGE analysis, HA showed a single band at 35 kDa under reduced conditions and numerous ladder bands between 35 kDa to more than 300 kDa under nonreduced conditions. On analytical ultracentrifugation, HA gave a molecular mass of 520 kDa with a single meniscus and a sedimentation constant of 12.0. The amino acid and carbohydrate analysis of reduced and S-pyridylethylated HA revealed that it contained five residues of hydroxyproline and an N-linked type sugar chain.

Adult↗
PubMed1988

The effects of a simulated acid precipitation on leaf litter quality and the growth of a detritivore in a buffered lotic system.

The effects of a simulated acid rain on leaf litter quality and the growth of a detritivore in a buffered lotic system were investigated. Exposure of Populus balsamifera L. saplings to a simulated acid precipitation prior to leaf abscission resulted in significant decreases in foliar nitrogen content and increases in carbon: nitrogen ratios. During decomposition of the leaf litter in a buffered lotic system, microbial activity was significantly reduced. Growth of Tipula commiscibilis Diane (Diptera: Tipulidae) larvae decreased significantly when fed conditioned leaves exposed to a simulated acid precipitation prior to abscission. Reductions in detritivore growth were correlated with lower potential quality of the leaf litter resulting from increased carbon: nitrogen ratios and reduced levels of microbial activity. Thus, even in well buffered freshwater ecosystems, acid precipitation can have significant indirect effects on microbial activity and macroinvertebrate growth.

Journal Article↗
PubMed1992

Estimating background precipitation quality from network data.

Assessments of the relative merits of alternative acid-rain control strategies revolve around considerations of potential benefit per unit effort and/or cost. A question that often arises concerns the changes in deposition that would follow if all industrial (or societal) emissions were eliminated, in which case precipitation chemistry would be dominated by emissions from natural sources. Estimates of the 'natural background' of precipitation chemistry can be based on (a) measurements made at distant locations, (b) reducing emissions to zero in numerical simulations, or (c) examinations of existing data. Each alternative is flawed because (a) of the assumption that natural emissions in one location are like those in another, (b) no existing model contains descriptions of chemical processes involving all of the chemical species of importance, and (c) all contemporary data records or relevance are affected by precisely the emissions we wish to reduce. Here, the third alternative is explored in detail, using event precipitation chemistry data from North America. The analysis reveals a background pH level that varies from site to site, but always lies in the range 5.0-5.3.

Journal Article↗
PubMed1992

Fractionation of atmospheric acid and base components within storm events by precipitation scavenging processes.

Concentrations of ions in storm rainwater in Texas have been monitored for each 0.254 mm increment of precipitation. The changes in concentrations have been analyzed to investigate the role of differential rates of scavenging of particulate matter of differing particle size, and especially the major acid and base components. The empirical trend at the onset of rainfall is a chemical fractionation of acids and bases with correspondingly wide pH variations. These results are confirmed by model calculations, which show a significant preferential scavenging of calcium relative to sulfate in the first 10 mm of rainfall, resulting in fractionation of bases and acids from their atmospheric concentrations. Previous studies, using Target Transformation Factor Analysis of ion concentrations in storm precipitation and regional ambient aerosol data, statistically determined the average source for acidic secondary species and alkaline particulate matter. Two types of crustal sources were identified as western and eastern soil dust. In this study, an alternate physical explanation for these two soil dust factors is offered. As a storm progresses, the elements in the local soil dust are fractionated as a result of their differential rates of precipitation scavenging, enriching species predominantly in the fine particle size and depleting elements predominantly in the coarse particle size. This fractionation process results in a single source having different elemental ratios at the beginning and at the end of a rain event. For Austin, Dallas, and Tyler, Texas, the soil dust previously identified as being from eastern sources could, instead, be a fractionated form of the western soil source.

Journal Article↗
PubMed1992

Ectomycorrhizal colonization of loblolly pine seedlings during three growing seasons in response to ozone, acidic precipitation, and soil Mg status.

A three-year study was initiated in 1987 to evaluate the impact of O3, acidic precipitation, and soil Mg on ectomycorrhizal colonization of loblolly pine (Pinus taeda L.) seedlings. Thirty-six open-top chambers equipped with a rainfall exclusion/addition system were utilized to administer three levels of O3 (subambient, ambient, or twice ambient) and two precipitation acidity levels (pH 3.8 or 5.2) to seedlings growing in 24-liter plastic pots containing soil having either 35 or 15 mg kg(-1) of exchangeable Mg. Seedlings exposed to the twice ambient O3 treatment exhibited smaller percentages of total ectomycorrhizal short roots at the end of each year of the study, but trends were statistically significant in 1989 only. Changes in number of specific ectomycorrhizal morphotypes in response to O3 were not consistent from year to year. Acidic precipitation treatments had no effect on number or percent of mycorrhizal short roots, and responses of two morphotypes to soil Mg treatments were probably due to differences in the soil environment rather than a result of changes in aboveground processes. Temporal shifts in morphotype frequencies were observed for seedlings in all treatments and indicate that mycorrhizal succession occurred during the study period.

Journal Article↗
PubMed1993

Migraine and tension-type headache in a general population: precipitating factors, female hormones, sleep pattern and relation to lifestyle.

In a cross-sectional epidemiological study of headache disorders information on precipitating factors, age at onset, influence of menstruation and pregnancy and use of oral contraceptives was collected. The presence of migraine and tension-type headache was ascertained by a clinical interview and examination using the operational diagnostic criteria of the International Headache Society. The prevalence of migraine and tension-type headache was also analysed in relation to variables of lifestyle: physical activity, smoking, consumption of coffee, alcohol intake and sleep pattern. In both migraine and tension-type headache, the most conspicuous precipitating factor was stress and mental tension. Other common precipitants were alcohol, weather changes and menstruation. Disappearance or substantial improvement of the headache during pregnancy was more frequent in migraineurs than in tension-type headache sufferers. The age at onset of both migraine and tension-type headache differs between men and women. Female hormones may be an important factor responsible for the sex difference of headache disorders. The level of physical activity showed no association with migraine, but a significantly higher prevalence of tension-type headache in men with exclusively sedentary activity emerged. Smoking, coffee and alcohol consumption showed no significant associations with the headache disorders. Sleep pattern was significantly associated with migraine and tension-type headache in both univariate and multivariate analyses. In conclusion, migraine and tension-type headache seem to be different with regard to a number of endogenous and exogenous factors.

Adult↗
PubMed1981

Precipitating antibodies against excretory/secretory antigens of Fasciola hepatica in sheep serum.

Gel diffusion techniques were used to study antigen-antibody reactions in precipitates forming around juvenile, semi-mature and adult Fasciola hepatica cultured in serum from infected sheep. The number of reactions was analysed in both primary and challenge infections. The number of antigens shared by the various developmental stages of the fluke was also examined. At least 2 antigens were involved in precipitate formation around juvenile flukes. These antigens were also produced by the later stages of development. Two additional antigens were produced by semi-mature flukes and these, together with two others, produced by adult flukes. Challenge infections had little effect on the number of antigens or antibodies in the precipitate.

Animals↗
PubMed1987

Inhibition of enkephalinase activity attenuates naloxone-precipitated withdrawal symptoms.

In this study we examined the effects of the enkephalinase inhibitor, thiorphan, on the naloxone-precipitated withdrawal syndrome in chronic morphine dependent rats. Intracerebroventricular administration of thiorphan (40 micrograms/2 microliter) in morphine dependent rats, inhibited the severity of the naloxone-precipitated abstinential syndrome. Administration of thiorphan (20 micrograms/0.5 microliter) in the periaqueductal grey matter of morphine dependent rats, in addition to explosive motor behaviour and ipsilateral rotation, also significantly suppressed most of the naloxone-precipitated withdrawal symptoms. It is suggested that a decreased biotransformation of endogenous opioid peptides might replace the relative shortage of morphine during withdrawal in opiate addicted subjects and attenuate the abstinence symptoms.

Amino Acids, Sulfur↗
PubMed1984

Precipitated and spontaneous withdrawal in baboons after chronic dosing with lorazepam and CGS 9896.

In order to assess the ability of lorazepam (20 mg/kg/day) and CGS 9896 (100 mg/kg/day) to produce physical-dependence in baboons, the occurrence of Ro 15-1788 precipitated withdrawal signs and spontaneous withdrawal signs were determined. Lorazepam-treated baboons displayed precipitated withdrawal signs following the administration of Ro 15-1788 (5 mg/kg), and displayed mild to moderate spontaneous withdrawal signs following termination of drug treatment. CGS 9896-treated baboons did not display Ro 15-1788 precipitated withdrawal signs and displayed either no or only mild spontaneous withdrawal signs.

Animals↗
PubMed1985

Effects of chronic treatment with diazepam, phenobarbital, or amphetamine on naloxone-precipitated morphine withdrawal.

The present study examines the severity of naloxone-precipitated opiate withdrawal in morphine-pelleted rats and mice. Animals were chronically pretreated with either saline, diazepam, phenobarbital or amphetamine for 8 days prior to withdrawal precipitation. Indicators of withdrawal were changes in plasma corticosterone in rats and jumping behavior in mice. The use of chronic intravenous catheters in rats and one-way vision boxes allowed for serial blood sampling and sequential hormone determinations. Opiate dependence was established by the subcutaneous implantation of a 75-mg morphine pellet 72 h prior to withdrawal precipitation. All pretreated groups of rats with morphine pellets showed a substantial elevation of plasma corticosterone following the injection of naloxone (0.4 mg/kg, i.v.). Those with lactose pellets showed little change. The group pretreated with phenobarbital showed a lower, more attenuated withdrawal response as compared to saline or the other pretreated groups. The responsiveness of the hypothalamo-pituitary-adrenal axis to ether stress was evaluated. This was found to be unaffected by chronic phenobarbital suggesting that the drug may have a more specific effect on opiate dependence/withdrawal mechanisms. Similar studies in mice showed no differences in ED50 for naloxone-induced jumping behavior in any of the pretreatment groups.

Amphetamine↗
PubMed1989

FIA determination of chlorhexidine by means of the precipitation with Cu(II).

The determination of chlorhexidine in pharmaceutical formulations is carried out using flow injection analysis (FIA) with measurement by atomic absorption spectrometry (AAS). The method is based on the formation of a copper-biguanide complex precipitate when the sample is injected into an ammoniacal copper solution. The precipitate is retained on a plastic or paper filtering device. A nitric acid stream dissolves the precipitate and carried the Cu(II) to the AAS detector. The chlorhexidine is determined over the range 5-20 ppm. The influence of interfering substances is investigated.

Biguanides↗
PubMedDate not supplied

The influence of external precipitating factors and peripheral neuropathy on the development and outcome of diabetic foot ulcers.

The influence of external precipitating factors and the presence of peripheral neuropathy on the development and outcome of foot ulcers were evaluated in 314 consecutive diabetic patients. All patients were treated by the same foot care team. Each patient was represented by one ulcer, and primary healing was defined as intact skin for at least six months. External precipitating factors were identifiable in 264 of 314 patients. The most common factors were ill fitting shoes/socks, acute mechanical trauma, stress ulcer, and paronychia. The highest primary healing rates were seen in lesions caused by paronychia (84%) and stress ulcer (76%). Clinical signs of sensory and muscular disturbances were seen in the majority of patients (96%). Sensory neuropathy, evaluated with a biothesiometer, was more common among patients who had had amputations or, died subsequently compared to those who healed. This study suggests that a majority of diabetic foot ulcers might have been prevented, since a precipitating external factor was identified in four of five patients, stressing the importance of preventive foot care.

Amputation, Surgical↗
PubMed1990

The induction and repair of DNA damage detected by the DNA precipitation assay in Chinese hamster ovary cells treated with acridine orange + visible light.

The photodynamic effect of the dye acridine orange (AO) in combination with visible light (400-700 nm) was studied in Chinese hamster ovary (CHO) cells, the endpoints investigated being induction, as well as repair, of DNA strand breaks. Cells were treated for 20 min with AO (0.1-3.0 micrograms/ml), washed free of excess dye and subsequently exposed to low doses of visible light (2 x 40 W/8 W/m2) for 5-15 min. AO proved to be an efficient sensitizer for light-induced DNA strand breaks, detected with the DNA precipitation assay, and expressed as percentage of DNA precipitated. The induction of breaks was linear up to 0.5 micrograms/ml AO + 10 min of light, which corresponds to 55% precipitated DNA, and was dependent on the concentration of AO as well as on the dose of light delivered. As a comparison, 18 Gy of X-rays was required to yield an equivalent amount of induced DNA strand breaks. The rejoining of the light-induced DNA strand breaks was studied by incubating the AO-sensitized cells for 30-120 min at 37 degrees C directly after light exposure. A fast recover of 67-91% of the damage (compared to initial damage, recovery time = 0, and dependent on the concentration of AO) was observed during the first 30 min of incubation. However, a significant amount of DNA damage remained after 2 h of recovery. These remaining, long-lived lesions might be involved in the photoinduced and acridine-sensitized chromosomal aberrations and sister-chromatid exchanges (SCE). The significance of these observations is discussed in relation to AO-sensitized and photoinduced DNA damage and chromosomal alterations.

Acridine Orange↗
PubMed2004

Determination of volatile organohalogen compounds in urban precipitation in Tricity area (Gdańsk, Gdynia, Sopot).

Chlorinated and brominated derivatives of methane and ethene were determined in samples of atmospheric precipitation collected between November 2000 and May 2001 at four sites in two cities, Gdańsk and Sopot, located on the Gulf of Gdańsk (Baltic Sea, Poland). The analytes were determined by direct aqueous injection of the samples to the capillary column using ECD detection (DAI-GC-ECD). Chloroform and carbon tetrachloride were detected the most often at all sites. The highest concentrations of the analytes were recorded at the intersection of two major streets (no. 3), next to a major route leading to two subdivisions (no. 2) and at Narutowicza Street (no. 1). In general, analyte concentration levels were lower during the spring months. During precipitation, concentrations of the analytes were higher in samples collected at the beginning of the event due to scavenging of the volatile compounds from the atmosphere. After a period of 75 min from the beginning of the precipitation event, analyte concentrations were lower by 10-80%, depending on the initial concentration and nature of the analyte.

Chromatography, Gas↗
PubMed2004

Dietary protein precipitation properties have effects on gastric emptying in healthy volunteers.

BACKGROUND & AIMS: Strategies that reduce the size of particles in the stomach accelerate gastric emptying. Partial dephosphorylation of casein reduces the size of protein precipitates (curds) in acid conditions and facilitates peptic digestion. We hypothesized that changing the precipitation properties of casein by partial dephosphorylation would accelerate gastric emptying. METHODS: Eight healthy male volunteers entered a prospective, double blind, randomized study with crossover design. Gastric emptying of milk based formula containing either unmodified or dephosphorylated casein was assessed by scintigraphy. Gastric pH measurements were acquired concurrently. RESULTS: A trend to faster gastric emptying was observed for the unmodified preparation, with lower median half time (unmodified 133; dephosphorylated 214 min, P = 0.09) and area under the curve (unmodified 8425 min%; dephosphorylated 9135 min%, P = 0.08). A positive correlation was found between half time for the dephosphorylated preparation and the treatment effect (r2 = 0.81, P < 0.02). Gastric pH was unaffected. CONCLUSIONS: The study hypothesis was rejected; indeed gastric emptying tended to be faster for the unmodified than the dephosphorylated protein. This effect was more pronounced in subjects with slow gastric emptying on the dephosphorylated preparation. Properties other than the size of protein precipitates determine the rate of gastric emptying for milk based formula.

Adult↗
PubMed2004

Organotin compounds in precipitation, fog and soils of a forested ecosystem in Germany.

Organotin compounds (OTC) are highly toxic pollutants and have been mostly investigated so far in aquatic systems and sediments. The concentrations and fluxes of different organotin compounds, including methyl-, butyl-, and octyltin species in precipitation and fog were investigated in a forested catchment in NE Bavaria, Germany. Contents, along with the vertical distribution and storages in two upland and two wetland soils were determined. During the 1-year monitoring, the OTC concentrations in bulk deposition, throughfall and fog ranged from 1 ng Sn l(-1) to several ten ng Sn l(-1), but never over 200 ng Sn l(-1). The OTC concentrations in fog were generally higher than in throughfall and bulk deposition. Mono-substituted species were the dominant Sn species in precipitation (up to 190 ng Sn l(-1)) equaling a flux of up to 70 mg Sn ha(-1) a(-1). In upland soils, OTC contents peaked in the forest floor (up to 30 ng Sn g(-1)) and decreased sharply with the depth. In wetland soils, OTC had slightly higher contents in the upper horizons. The dominance of mono-substituted species in precipitation is well reflected in the contents and storages of OTC in both upland and wetland soils. The ratios of OTC soil storages to the annual throughfall flux ranged from 20 to 600 years. These high ratios are probably due to high stability and low mobility of OTC in soils. No evidence was found for methylation of tin in the wetland soils. In comparison with sediments, concentrations and contents of organotin in forest soils are considerably lower, and the dominant species are less toxic. It is concluded that forested soils may act as sinks for OTC deposited from the atmosphere.

Air Pollutants↗
PubMed2005

Spatial and temporal trends of precipitation chemistry in the United States, 1985-2002.

A Seasonal Kendall Trend (SKT) test was applied to precipitation-weighted concentration data from 164 National Atmospheric Deposition Program National Trends Network (NADP/NTN) sites operational from 1985 to 2002. Analyses were performed on concentrations of ammonium, sulfate, nitrate, dissolved inorganic nitrogen (DIN, sum of nitrogen from nitrate and ammonium), and earth crustal cations (ECC, sum of calcium, magnesium, and potassium). Over the 18-year period, statistically significant (p< or =0.10) increases in ammonium concentrations occurred at 93 sites (58%), while just three sites had statistically significant ammonium decreases. Central and northern Midwestern states had the largest ammonium increases. The generally higher ammonium concentrations were accompanied by significant sulfate decreases (139 sites, 85%), and only one significant increase which occurred in Texas. In the west central United States there were significant nitrate increases (45 sites, 27%), while in the northeastern United States there were significant decreases (25 sites, 15%). Significant DIN decreases were observed in the northeastern United States (11 sites, 7%); elsewhere there were significant increases at 75 sites (46%). ECC decreased significantly at 65 sites (40%), predominantly in the central and southern United States, and increased at 11 sites (7%). The concentrations of sulfate, nitrate, and ammonium in precipitation have changed markedly over the time period studied. Such trends indicate changes in the mix of gases and particles scavenged by precipitation, possibly reflecting changes in emissions, atmospheric chemical transformations, and weather patterns.

Air Pollutants↗
PubMed2004

Modeling the adsorption and precipitation processes of Cu(II) on humin.

Humins (HU) are the most insoluble fraction of humic substances. Chemically, they can be considered as humic macromolecules bonded to the mineral matter of soil. The HU have a marked colloidal character and they are extremely important in retention of pollutants in soils. The aim of this work is to combine adsorption data with spectroscopic techniques in order to study the adsorption and precipitation processes of Cu(II) on HU. Analysis of sorption isotherms by means of several single-adsorption-process-based models makes it possible to obtain the speciation diagrams of Cu(II) species on HU surfaces. Further, FTIR (which provides information about the changes in the surface groups of the HU) and DRX (which shows the formation of possible crystalline phases on the HU surface) were used to determine the specific interactions of Cu(II) cations with the surface reactive groups of HU. The shape of the isotherms at constant pH varies with pH from L1-type (pH 2-4) to L3-type (pH 5-6) and S-type (pH 8), which indicates a change in the retention mechanism. When pH is 2 the retention of Cu(II), as [Cu(H(2)O)(6)](2+), is the preferred retention mechanism. The retained quantity of Cu(II) as [Cu(OH)(H(2)O)(5)](+) increases with pH. Starting from pH 4 the Cu(II) begins its precipitation, which is the preferred retention mechanism at pH 8. The presence of HU has a great influence on the precipitation process of Cu(II), giving rise to botalackite, which reveals epitaxial growth of crystals.

Journal Article↗