Determination of aluminum by neutron activation analysis in human lung tissue and in chemicals for dialysis of uremic patients

Aluminum (Al) determination in human lung tissue, in chemicals for dialysis fluids, and in commercially available dialysis solutions is carried out using both Instrumental and Radiochemical Neutron Activation Analysis (INAA and RNAA). For some matrices, pre-and post-irradiation Al separations are tested. Chelex 100 resin and HDEHP, this latter adsorbed both on teflon and polyurethane foam, are employed for the pre-irradiation Al separations. The postirradiation procedures are performed using roughly the same schemes; the conventional Al precipitation as hydroxide is also carried out. Al values found in lungs of workers exposed to Al containing dust appear to be much higher than those found for unexposed people. Chemicals analyzed seem pure enough to give suitable dialysis solutions; for commercially available dialysis fluids, a 10-fold reduction of Al content should be convenient.     

Acid-base chemistry and aluminum transport in an acidic watershed and pond in New Hampshire

Cone Pond is one of the few acidic, clear-water ponds in the White Mountains of New Hampshire, a region dominated by high inputs of strong acids from atmospheric deposition and low base content of bedrock. Monitoring was conducted for 13 months to compare and contrast the acid-base chemistry of the terrestrial and aquatic portions of the watershed. Variations in Al concentration and speciation in drainage waters were correlated with changes in the supply of naturally occurring organic ligands. During the study period, the pond retained 28% of Al inputs, including nearly half of the inputs of organically complexed Al. Chemical equilibrium calculations indicated that the entire water-column was oversaturated with respect to the solubility of synthetic gibbsite during summer, as was the hypolimnion during winter. Retention of Al resulted from an increase in pH in the hypolimnion concomitant with SO₄ ^2– reduction, and from loss of organic anions in epilimnetic waters. Acid neutralizing capacity (ANC) generated in the pond primarily through SO₄ ^2– reduction and base cation (C _B ) release was balanced by ANC consumed as a result of Al retention.     

Aluminum stimulates the proliferation and differentiation of osteoblasts in vitro by a mechanism that is different from fluoride

Summary Micromolar concentrations of aluminum sulfate consistently stimulated [³H]thymidine incorporation into DNA and increased cellular alkaline phosphatase activity (an osteoblastic differentiation marker) in osteoblast-line cells of chicken and human. The stimulations were highly reproducible, and were biphasic and dose-dependent with the maximal stimulatory dose varied from experiment to experiment. The mitogenic doses of aluminum ion also stimulated collagen synthesis in cultured human osteosarcoma TE-85 cells, suggesting that aluminum ion might stimulate bone formation in vitro. The effects of mitogenic doses of aluminum ion on basal osteocalcin secretion by normal human osteoblasts could not be determined since there was little, if any, basal secretion of osteocalcin by these cells. 1,25 Dihydroxyvitamin D₃ significantly stimulated the secretion of osteocalcin and the specific activity of cellular alkaline phosphatase in the human osteoblasts. Although mitogenic concentrations of aluminum ion potentiated the 1,25 dihydroxyvitamin D₃-dependent stimulation of osteocalcin secretion, they significantly inhibited the hormone-mediated activation of cellular alkaline phosphatase activity. Mitogenic concentrations of aluminum ion did not stimulate cAMP production in human osteosarcoma TE85 cells, indicating that the mechanism of aluminum ion does not involve cAMP. The mitogenic activity of aluminum ion is different from that of fluoride because (a) unlike fluoride, its mitogenic activity was unaffected by culture medium changes; (b) unlike fluoride, its mitogenic activity was nonspecific for bone cells; and (c) aluminum ion interacted with fluoride on the stimulation of the proliferation of osteoblastic-line cells, and did not share the same rate-limiting step(s) as that of fluoride. PTH interacted with and potentiated the bone cell mitogenic activity of aluminum ion, and thereby is consistent with the possibility that the in vivo osteogenic actions of aluminum ion might depend on PTH. In summary, low concentrations of aluminum ion could act directly on osteoblasts to stimulate their proliferation and differentiation by a mechanism that is different from fluoride.     

Forms of nitrogen inputs regulate the intensity of soil acidification

Soil acidification induced by reactive nitrogen (N) inputs can alter the structure and function of terrestrial ecosystems. Because different N-transformation processes contribute to the production and consumption of H⁺, the magnitude of acidification likely depends on the relative amounts of organic N (ON) and inorganic N (IN) inputs. However, few studies have explicitly measured the effects of N composition on soil acidification. In this study, we first conducted a meta-analysis to test the effects of ON or IN inputs on soil acidification across 53 studies in grasslands. We then compared soil acidification across five different ON:IN ratios and two input rates based on long-term field N addition experiments. The meta-analysis showed that ON had weaker effects on soil acidification than IN when the N addition rate was above 20 g N m⁻² year⁻¹. The field experiment confirmed the findings from meta-analysis: N addition with proportions of ON ≥ 20% caused less soil acidification, especially at a high input rate (30 g N m⁻² year⁻¹). Structural equation model analysis showed that this result was largely due to a relatively low rate of H⁺ production from ON as NH₃ volatilization and uptake of ON and NH₄⁺ by the dominant grass species Leymus chinensis (which are both lower net contributors to H⁺ production) result in less NH₄⁺ available for nitrification (which is a higher net contributor to H⁺ production). These results indicate that the evaluation of soil acidification induced by N inputs should consider N forms and manipulations of relative composition of N inputs may provide an effective approach to alleviate the N-induced soil acidification.     

Shifting Trade Patterns as a Means of Reducing Global Carbon Dioxide Emissions

This article extends and applies the world trade model with bilateral trade (WTMBT), a linear program with any number of goods, factors, and regional trade partners that determines regional production, bilateral trade patterns, and region-specific prices on the basis of comparative advantage by minimizing factor use. The model provides a consistent analysis of the global production system, representing geographical location at a regional level, region-specific technologies at a sector level, emissions from production, and resource constraints and costs. An illustrative analysis investigates how changes in the geographic distribution of production could contribute to reducing global carbon dioxide (CO₂) emissions and at what cost. The model provides a bridge between global objectives and their determinants and consequences in specific sectors in individual regions. Multi-objective analysis is used to construct a trade-off curve between global factor costs and CO₂ emissions. The relevance of both primal and dual solution variables is demonstrated. In particular, changes in goods prices and emissions are investigated. We conclude that the main impact of tightening carbon constraints is a substantial reduction in international trade accompanied by a shift away from regions most reliant on the combustion of coal. In addition to the analysis of the overall global trends, including the impact on prices, the implications of the global carbon constraint for one specific industry are investigated.     

Role of some trace metal ions in placental membrane lipid peroxidation

The antioxidative and/or pro-oxidative potential of three trace metal ions, namely aluminum (Al), manganese (Mn), and selenium (Se), has been studied. The effect of Al and Mn was found to be anion independent. The pro-oxidative potential of Al was more prominent than its antioxidative potential. This may be due to its redox inert nature. The increase in lipid peroxidation rates in placental syncytiotroblast membranes may contribute to the etiology of aluminum toxicity. Selenium had an antioxidative potential only in the whole-cell homogenate. This appears to be mediated by glutathione peroxidase of which Se is a cofactor. Manganese proved to be the trace metal ion of choice. It decreased the production of thiobarbituric acid reactive substances (TBARS). This may be due to its capacity to quench the superoxide anion and hydroxyl radicals and also due to its chain-breaking capacity. During the present course, ferrous-ascorbate mediated lipid peroxidation has been studied using various combinations of FeSO₄ and ascorbic acid. Extrapolating the combined ratio of the individual combination as substrate concentration ([S]) and treating the observed amount of malondialdehyde (MDA) produced equivalent to initial velocity (v _i ), as in the case of enzymatic studies, the data were treated according to Michaelis-Menten kinetics and the values of k _c and C _max have been calculated.     

菌根真菌对酸铝胁迫的响应

酸性环境中活性铝浓度升高可能抑制菌根真菌生长,为探讨酸性条件下菌根真菌对活性铝的响应机制,以拟青霉(Simplicillium sp.,Si)、细长孢霉(Mortierella elongate,Me)、木霉菌(Trichoderma spp.,Tr)、瓶头霉(Phialocephala,Ph)和葡萄状穗霉(Stachybotrys chartarum,Sc)5种菌根真菌为供试材料,采用PDA液体培养基单种纯培养以pH值为5.5设定3个Al3+浓度梯度,分别为对照(0 mmol·L^-1)、低铝(0.2 mmol·L^-1)和高铝(1.0 mmol·L^-1),研究酸性条件下不同活性铝浓度对菌根真菌的生物量、有机酸分泌以及N、P、K含量等的影响。结果表明:(1)除拟青霉(Si)外,其他菌株均不同程度受活性铝浓度影响,Si生物量随活性铝浓度增加而增加,低铝时比对照增加了238%(P<0.05),而细长孢霉(Me)、木霉菌(Tr)、瓶头霉(Ph)和葡萄状穗霉(Sc)生物量均降低,其中,Ph和Sc分别比对照降低了38.1%和72.5%(P<0.05)。(2)5种菌根真菌分泌有机酸存在显著性差异,Si、Me、Tr和Sc的H+分泌量在高铝浓度时均低于对照,对Si产生显著性差异(P<0.05);仅Me分泌草酸,对照的分泌量是高铝时的1.12倍。(3)5种菌根真菌N、P、K含量随不同活性铝浓度胁迫存在显著性差异,Si和Sc的P、K含量随活性铝浓度增加而显著增加(P<0.05);Me和Ph的N含量随活性铝浓度增加而显著降低(P<0.05),Me的P、K含量分别在低铝和高铝时达到峰值,Tr和Ph的N、P、K含量在低铝时达到峰值而在高铝时受到抑制。(4)Si、Me和Tr受酸铝影响不显著,属耐酸铝型菌株,Ph和Sc属酸铝敏感型菌株。本工作可为天山雪岭云杉森林更新与幼苗存活问题研究的深入开展提供基础依据。     

Aluminum chelation by 3-hydroxypyridin-4-ones in the rat demonstrated by microdialysis

The ability and site of the metal-chelating 3-hydroxypyridin-4-ones (HPs) to mobilize aluminum (Al) was assessed in Al-loaded rats using microdialysis. Four HPs with greatly varying lipophilicity were studied. One week after Al loading, microdialysis probes were implanted in the liver, a jugular vein, and the frontal cortex. An HP was given iv followed by continuous microdialysis for 5 h. Al concentrations in dialysates from the liver increased rapidly and were consistently greater than from blood, suggesting that liver was a primary site of Al chelation. Brain dialysate Al concentrations remained low, suggesting little Al chelation in the brain and little distribution of the Al HP complex into the brain. Al concentrations were determined in the main organs/tissues of a separate group of Al-loaded rats, and the percentage of the total Al body burden in each organ/tissue was calculated. The skeletal system and liver had 57 and 28% of the Al body burden, consistent with the liver as a primary site of Al chelation. The HPs chelate extravascular Al and have been shown by others to be orally active. They warrant further investigation as Al chelators.     

A pseudo-first-order kinetic approach to measurement of acetylcholine hydrolysis by acetylcholinesterase

A continuous spectrophotometric procedure is presented for the measurement of the kinetic properties of acetylcholinesterase (EC 3.1.1.7) with its natural substrate, acetylcholine. The procedure is based upon the production of stoichiometric quantities of H⁺ upon hydrolysis of substrate. The spectrophotometric reporter is the pH indicator dye, phenol red and the procedure yields continuous time courses for hydrolysis of substrate. Further, this phenol red system and an adaptation of the Ellman et al. (1961, Biochem. Pharmacol. 7, 88–95) procedure for acetylthiocholine as substrate, are described as a rapid screening technique for reversible competitive and noncompetitive inhibitors of acetylcholinesterase activity. The methods are illustrated by determinations of K₁ for edrophonium, decamethonium and Al³⁺.     

A comparison of microbially and chemically reducible iron in three soils

Microbially reducible iron (water-soluble plus exchangeable forms) in three soils represented about 20% of the chemically reducible iron. The amount of iron reduced by microorganisms increased for about ten days to two weeks following flooding and thereafter remained constant. A similar trend was observed for the release of added Fe-59 in the soils following flooding, except that the reduction of labelled iron began earlier. In the more weathered soil, a higher proportion of the total iron was reduced by citrate-dithionite than in the relatively unweathered alluvial soils. Of labelled iron added, sequential reduction showed approximately 70% in the three soils was microbially reducible, an additional 20% was reduced by citrate-dithionite, and 10% of the labelled iron had moved into the residual form.