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 15,125 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

This study was designed to determine the effect of corn starch, lactose, and sucrose on lead (Pb) absorption and retention in rat tissues and organs. Seventy weanling Wistar male rats were assigned to the following five treatment groups: Group 1, 31.2% sucrose + 29.3% starch; Group 2, 31.2% lactose + 29.3% starch; Group 3, 60% corn starch (control); Group 4, 52.1% sucrose + 8.4% starch; Group 5, 52.1% lactose + 8.4% starch. All diets were supplemented with 200 ppm lead nitrate. The animals were fed the experimental diets for 8 weeks after which they were sacrificed. Analysis of lead in whole blood, bone (tibia and femur), carcass ash, and gut (alimentary canal) was done by atomic absorption spectrophotometric (AAS) technique. Results indicated that lactose in the diet caused increased lead retention by these tissues. Pb concentration was highest in blood (500% of the control) and bone (433% of control) of animals fed the Group 5 diet with the second highest level for the tissues of rats fed the Group 2 diet. Rats fed the high lactose diet showed the lowest weight gain and those fed the low sucrose diet showed the highest weight gain. The sucrose diets caused increased Pb in bone. In rats fed the sucrose diets, the Pb content of feces was greater than the value in rats fed the corn starch diet. The results of this study show that lactose has a higher stimulatory effect on Pb retention than sucrose.
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PMID:Effect of carbohydrates on lead absorption and retention in weanling rats. 378 Jun 44

A method for the determination of arsenic in whole human blood is presented. To decrease the matrix effects from this complex sample, the blood was prediluted with a matrix modifier solution. The modifier solution contained a surfactant, Triton X-100, which homogenized the sample and allowed accurate pipetting by an autosampler. The modifier also contained nickel nitrate which stabilized the arsenic and allowed ash temperatures of 1400 degrees C without loss of the arsenic. The method exhibited a sensitivity of 5 micrograms/L (concentration/1% absorption) which was sufficient for the forensic evaluation of elevated arsenic levels in the blood.
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PMID:Matrix modification for furnace atomic absorption spectrometric determination of arsenic in whole human blood. 405 58

Forage samples were obtained from three wheat and rye mixed pastures (replications) from December 1979, to April 1980 (140 d), while they were being grazed by mature cows at the Southwestern Livestock and Forage Research Station, El Reno, Oklahoma. These samples were taken three times during December, twice monthly in January and February and weekly in March and April. Samples were analyzed for dry matter, ash, N, K, Ca, Mg, P, ash alkalinity, aconitic, malic and citric acids, total lipids, NO3-N, Na and total nonstructural carbohydrates (TNC). In vitro digestibility was also determined. The N:TNC ratio, estimated plasma Mg levels and K:(Ca + Mg) ratio (tetany ratio) were calculated. On d 105 (March 19), 16% (five of 32 head) of the cows developed tetany. At tetany, the forage K, protein, digestibility, ash alkalinity, aconitic acid and total lipids increased suddenly and markedly. Forage dry matter, TNC and ash decreased. Forage Ca and Mg were slightly below or equal to the animals' requirements and remained relatively constant during the period of tetany. Forage P increased about 2 wk before tetany and decreased after tetany occurred. The levels of forage NO3-N and Na did not appear to be related to the incidence of tetany. The N:TNC ratios exceeded .4 immediately before tetany and two sampling periods thereafter. The estimated plasma Mg levels were lowest at tetany and shortly thereafter and tetany ratio exceeded 2.2 during most of the study, with peaks of 3.2 in December, at tetany and in early April.
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PMID:Wheat pasture poisoning. I. An evaluation of cereal pastures as related to tetany in beef cows. 667 78

Chinese hamster ovary, rabbit alveolar macrophage, Syrian hamster embryo, BALB 3T3 mouse, and human neonatal fibroblast cells were employed in a statistical evaluation of the relative sensitivity of the cells to toxic substances. The cells were exposed to 1,2,4-trichlorobenzene, 2,4-dimethylphenol, Aroclor 1248, cadmium chloride, lead sulfate, nickel nitrate, lead oxide-coated fly ash, and a fine particulate from coal combustion. A filter-disk technique was used to measure the inhibition of protein and DNA synthesis. A quantitative ranking of cell-system sensitivity was determined from comparisons of statistically significant differences (P less than or equal to 0.01) in protein and DNA synthesis expressed as a percentage of control. An overall ranking of sensitivity showed that rabbit alveolar macrophages, Syrian hamster embryo cells, and Chinese hamster ovary cells were more sensitive than another of the five cell systems in 75, 68, and 62% of the experiments, respectively. The corresponding values for BALB 3T3 mouse and human neonatal fibroblast cells were 38 and 28%, respectively, under our experimental conditions. Detailed data on the control cell cultures are also presented.
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PMID:Cellular toxicity in Chinese hamster ovary cell cultures. II. A statistical appraisal of sensitivity with the rabbit alveolar macrophage, Syrian hamster embryo, BALB 3T3 mouse, and human neonatal fibroblast cell systems. 668 23

Mash prepared from cassava peels was inoculated with either Sacchromyces cerevisiae or Candida tropicalis and then left to ferment for 7 days. Chemical analysis of the fermented mash showed substantial increase in crude protein content and decrease in carbohydrate content of the mash. The results also revealed slight increases in the ash, fibre and lipid content of the fermented mash. It was further observed that, when the mash was supplemented with inorganic nitrogen sources (urea, ammonium sulfate or sodium nitrate) before commencement of fermentation, the amount of crude protein formed was almost doubled. This enhanced crude protein production was highest in the mash supplemented with urea. Temperature of 30 degrees C, pH of 5.5 and moisture concentration of 130% were found to be optimum for crude protein formation by the organisms growing on the mash.
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PMID:Utilization of cassava peels as substrate for crude protein formation. 771 17

This work provides examples of some of the imaging capabilities of environmental scanning electron microscopy applied to easily charged samples relevant to particle analysis. Environmental SEM (also referred to as high pressure or low vacuum SEM) can address uncoated samples that are known to be difficult to image. Most of these specimens are difficult to image by conventional SEM even when coated with a conductive layer. Another area where environmental SEM is particularly applicable is for specimens not compatible with high vacuum, such as volatile specimens. Samples from which images were obtained that otherwise may not have been possible by conventional methods included fly ash particles on an oiled plastic membrane impactor substrate, a one micrometer diameter fiber mounted on the end of a wire, uranium oxide particles embedded in oil-bearing cellulose nitrate, teflon and polycarbonate filter materials with collected air particulate matter, polystyrene latex spheres on cellulosic filter paper, polystyrene latex spheres "loosely" sitting on a glass slide, and subsurface tracks in an etched nuclear track-etch detector. Surface charging problems experienced in high vacuum SEMs are virtually eliminated in the low vacuum SEM, extending imaging capabilities to samples previously difficult to use or incompatible with conventional methods.
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PMID:Environmental scanning electron microscope imaging examples related to particle analysis. 840 Apr 30

A method was developed to determine selenium in infant formula using a graphite furnace equipped with deuterium background correction after dry ashing. The method circumvents the use of perchloric acid, 2,3-diaminonapthalene (DAN) and hydride generation without the use of Zeeman background correction. Twelve commercial infant and enteral formulas and corresponding spiked products (30-500 ng) were analyzed in triplicate for Se to evaluate this method. All test portions were digested on a hot plate after addition of magnesium nitrate-nitric acid. Following heating, digests were evaporated to dryness and placed in a 500 degrees C muffle furnace for 30 min to complete ashing. All Se was converted to Se+4 by dissolving the ash in HCl (5 + 1) and holding the solution for 20 min in a 60 degrees C water bath. Se+4 was subsequently reduced to Se(zero) with ascorbic acid and collected on a membrane filter. The membrane filters were digested in a small volume of nitric acid in a microwave oven. Following digestion, contents of the vessels were diluted and analyzed for Se by graphite furnace atomic absorption spectrometry. Selenium standards in starch or in unfortified formula containing trace levels of Se were carried through the entire process. The recovery range for Se was 85-127%, and analyzed reference materials fell within their certified range for Se. This method is as sensitive (detection limit 0.44 ng Se/g) as methods reported in the literature and may be applicable to other foods.
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PMID:Determination of selenium in infant formula and enteral formula by dry ash graphite furnace atomic absorption spectrometry with deuterium background correction. 882 24

Two alpha-amylase-producing strains of Aspergillus oryzae, a wild-type strain and a recombinant containing additional copies of the alpha-amylase gene, were characterized with respect to enzyme activities, localization of enzymes to the mitochondria or cytosol, macromolecular composition, and metabolic fluxes through the central metabolism during glucose-limited chemostat cultivations. Citrate synthase and isocitrate dehydrogenase (NAD) activities were found only in the mitochondria, glucose-6-phosphate dehydrogenase and glutamate dehydrogenase (NADP) activities were found only in the cytosol, and isocitrate dehydrogenase (NADP), glutamate oxaloacetate transaminase, malate dehydrogenase, and glutamate dehydrogenase (NAD) activities were found in both the mitochondria and the cytosol. The measured biomass components and ash could account for 95% (wt/wt) of the biomass. The protein and RNA contents increased linearly with increasing specific growth rate, but the carbohydrate and chitin contents decreased. A metabolic model consisting of 69 fluxes and 59 intracellular metabolites was used to calculate the metabolic fluxes through the central metabolism at several specific growth rates, with ammonia or nitrate as the nitrogen source. The flux through the pentose phosphate pathway increased with increasing specific growth rate. The fluxes through the pentose phosphate pathway were 15 to 26% higher for the recombinant strain than for the wild-type strain.
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PMID:Identification of enzymes and quantification of metabolic fluxes in the wild type and in a recombinant aspergillus oryzae strain 987 53

The effect of radiative forcing by anthropogenic aerosols is one of the largest sources of uncertainty in climate predictions. Direct observations of the forcing are therefore needed, particularly for the poorly understood tropical aerosols. Here we present an observational method for quantifying aerosol forcing to within +/-5 per cent. We use calibrated satellite radiation measurements and five independent surface radiometers to quantify the aerosol forcing simultaneously at the Earth's surface and the top of the atmosphere over the tropical northern Indian Ocean. In winter, this region is covered by anthropogenic aerosols of sulphate, nitrate, organics, soot and fly ash from the south Asian continent. Accordingly, mean clear-sky solar radiative heating for the winters of 1998 and 1999 decreased at the ocean surface by 12 to 30 Wm(-2), but only by 4 to 10 Wm(-2) at the top of the atmosphere. This threefold difference (due largely to solar absorption by soot) and the large magnitude of the observed surface forcing both imply that tropical aerosols might slow down the hydrological cycle.
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PMID:Large differences in tropical aerosol forcing at the top of the atmosphere and Earth's surface 1081 Dec 16

The dynamics of C and N in terrestrial ecosystems are not completely understood and the use of stable isotopes may be useful to gain further insight in the pathways of CO2 emissions and leaching of dissolved organic carbon (DOC) and nitrogen (DON) during decomposition of litter. Objectives were (i) to study the decomposition dynamics of Calamagrostis epigeios, a common grass species in forests, using 13C-depleted and 15N-enriched plants and (ii) to quantify the effect wood ash addition on the decomposition and leaching of DOC and DON. Decomposition was studied for 128 days under aerobic conditions at 8 degrees C and moisture close to field capacity in a spodic dystric Cambisol with mor-moder layer. Variants included control plots and additions of (i) Calamagrostis litter and (ii) Calamagrostis litter plus 4 kg ash m-2. (i) Decomposition of Calamagrostis resulted in a CO2 production of 76.2 g CO2-C m-2 (10% of added C) after 128 days and cumulative DOC production was 14.0 g C m-2 out of which 0.9 g C m-2 was Calamagrostis-derived (0.1% of added C). The specific CO2 formation and specific DOC production from Calamagrostis were 6 times higher (CO2) and 4 times smaller (DOC) than those from the organic layer. The amount of Calamagrostis-derived total N (NH4+, NO3-, DON) leached was 0.7 g N m-2 (4.8% of added N). Cumulative DON production was 0.8 g N m-2 which was slightly higher than for the control. During soil passage, much of the DOC and DON was removed due to sorption or decomposition. DOC and DON releases from the mineral soil (17 cm depth) were 6.3 g C m-2 and 0.5 g N m-2. (ii) Addition of ash resulted in a complete fixing of CO2 for 40 days due to carbonatisation. Afterwards, the CO2 production rates were similar to the variant without ash addition. Production of DOC (98.6 g C m-2) and DON (2.5 g N m-2) was marked, mainly owing to humus decay. However, Calamagrostis-derived DOC and Calamagrostis-derived total N were only 3.9 g C m-2 (0.5% of added C) and 0.5 g N m-2 (3.4% of added N). The specific DOC production rate from the organic layer was 6 times higher than that from Calamagrostis. The results suggest that with increasing humification from fresh plant residues to more decomposed material (OF and OH layers) the production ratio of DOC/CO2-C increases. Addition of alkaline substances to the forest floor can lead to a manifold increase in DOC production.
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PMID:Use of 13C and 15N mass spectrometry to study the decomposition of Calamagrostis epigeios in soil column experiments with and without ash additions. 1102 25


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