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41.
Mercury evaporation from undisturbed iron‐humus podzol lysimeters was measured over 3 months after treatment with HgCl2 spiked with radioactive 203Hg. The relative evaporation rate from HgCl2 treated soils followed the sum of two exponential functions. Because evaporation asymptotically approaches zero with time, the integral of the fit curve represents the evaporative loss in percent of atmospheric deposition. For the soil investigated, about 5% of atmospheric Hg deposition was reemitted into the atmosphere. It is hypothesized that mercury evaporation can decrease the leaching of mercury in and from soil significantly; this effect is probably increasing with decreasing rain acidity or soil acidity. Mercury deposited as soluble salt remains susceptible to reemission to air for 300 d after incorporation into the soil matrix. Indications are found that Hg evaporation from soils in geological background areas predominantly derives from recent atmospheric Hg deposition and not from geological sources. 相似文献
42.
Blackfoot disease is a peripheral vascular disease resulting in gangrene of the lower extremities. Although extensive epidemiological
study has implicated high arsenic content in artesian well water of the endemic area bears some important connection with
the disease, the etiology of the disease is still not clarified. In this study, attention is paid to chemical speciation of
arsenic in order to find out whether the concentrations of arsenic species in urine of Blackfoot disease patients are different
from those of controls. Experimental results indicate that the total arsenic, inorganic arsenic, monomethylarsonic acid, and
other forms of arsenic in the urine of patients are significantly higher than those of the contols. The possible connection
of those arsenic species with the etiology of the disease is discussed. 相似文献
43.
Paul Allen 《Biological trace element research》1995,50(3):193-208
The interaction of mercury and cadmium with lead was investigated by exposingOreochromis aureus to two heavy metals simulataneously. The chronic accumulation prolife of lead was determined by analyzing the liver, brain,
gill filaments, intestine, caudal muscle, spleen, trunk kidney, and gonads following exposure to lead alone and in mixtures
with mercury and cadmium. Nominal exposure concentrations of lead were 0.05, 0.10, 0.50, and 1.00 mg/L. Mixtures of lead (0.50
or 0.05 mg/L) with cadmium (0.05 mg/L) and lead (0.50 or 0.05 mg/L) with mercury (0.05 mg/L) were also used. Following 140
d of exposure to lead, the highest concentrations of lead consistently accumulated in the trunk kidney. The concentration
of lead in the kidney was decreased by coexposure to mercury or cadmium, but increased in the muscle and liver. Under all
exposure regimes, the median concentration of lead in the muscle exceeded safety levels recommended for human consumption.
In a food fish, such asO. aureus, a knowledge of toxic metal accumulation patterns is of great importance. 相似文献
44.
The effects of inorganic mercury (HgII) and methylmercury (MeHg) on the colonization of artificial substrates by periphytic
diatoms were studied using indoor freshwater microcosms. These consisted of a mixed biotope– water column + natural sediment
– with rooted macrophyte cuttings (Elodea densa) and benthic bivalve molluscs (Corbicula fluminea).The periphyton was collected
on glass slides in the water column after 34and 71 days. The two Hg sources were introduced either by daily additions to the
water column, or once at the beginning into the sediment, using two nominal concentrations: water column, 0.5 μgL-1 and 2 μg L-1 for both compounds: sediment, 0.5 mg kg-1 (fw) and 2 mgkg-1 (fw) for MeHg and 1 mg kg-1 (fw) and 10 mgkg-1 (fw) for HgII. Several complementary criteria were used to analyse the structural and functional perturbations induced: cell
density, species richness, diatom size, relative abundance. Exposure to MeHg added to the water column resulted in reduced
cell density and changes in species composition with enhancement of e.g. Fallacia pygmaea or Nitzschia palea; inorganic Hg
had less effect on the population structure. After contamination via the sediment, the effects of the two compounds were less
pronounced than for the water source.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
45.
The excretion of mercury, copper and zinc in urine, and mercury in whole blood andplasma, was determined in 40 chloralkali workers exposed to mercury vapour and 40age-matched referents. The Hg concentrations in whole blood, plasma and urine werehigher in the exposed group (35 nmol l, 30 nmol l,and 11.5 nmol mmol creatinine, respectively) in comparison with thereference group (15 nmol l, 6.3 nmol l, and 1.8nmol mmol creatinine, respectively). The urinary copper excretionwas similar in the two groups, while U-Zn excretion was significantly higher (P = 0.04)in the exposed group, median 0.83 mmol mmol creatinine versus 0.76mnmol mmol creatinine in the reference group. In a subgroup of exposedworkers with current U-Hg above 11.5 nmol lmmolcreatinine (20 mg g creatinine) the medianU-Zn was 1.1 mmol mmol creatinine. In both groups smokers had highU-Zn levels than non smokers. When both U-Hg and smoking were taken into account in alinear regression model, there was a significant association between U-Hg and U-Zn inthe combined group of exposed and referents (P = 0.002). This study indicates thatmercury exposure in humans, as in animals, causes increased urinary excretion of zinc.The mechanisms may be induced synthesis of metallothionein in the kidneys, displacementof Zn from preexisting metallothionein by Hg, or a decreased reabsorption of zinc in thekidneys owing to a slight tubular dysfunction. 相似文献
46.
Rebecca E. Korb Peter J. Saville Andrew M. Johnston John A. Raven 《Journal of phycology》1997,33(3):433-440
The utilization of inorganic carbon by three species of marine diatom, Skeletonema costatum (Grev.) Cleve. Ditylum brightwellii (West) Grun., and Chaetoceros calcitrans Paulsen was investigated using an inorganic carbon isotopic disequilibnum technique and inorganic carbon dose-response curves. Stable carbon isotope data of the diatoms are also presented. Observed rates of photosynthetic oxygen evolution were greater than could be accounted for by the theoretical rate of CO2 supply from the uncatalyzed dehydration of HCO3? in the external medium, suggesting use of HCO3? as an inorganic carbon source. Data from the isotopic disequilibrium experiment demonstrate the use of both HCO3? and CO2 for photosynthesis. Carbon isotope discrimination values support the use of HCO3? by the diatoms. 相似文献
47.
Rabbit heart mitochondria were used as a source of enzymes for the synthesis of phosphoruslabeled creatine phosphate. This method is based on the coupled reaction between mitochondrial oxidative phosphorylation and mitochondrial-bound creatine kinase. It is possible to convert more than 90% of the inorganic phosphate (Pi) to creatine phosphate. The method used only small amounts of adenine nucleotides which led to a product with only slight nucleotide contamination. This could be removed by activated charcoal extraction. For further purification, a method for the removal of residual Pi is described. 相似文献
48.
Pyrophosphate functions as phosphoryl donor with UDP-glucose-treated mammalian phosphofructokinase 总被引:2,自引:0,他引:2
J H Wong A Balogh B B Buchanan 《Biochemical and biophysical research communications》1984,121(3):842-847
CGP 28392, a novel compound structurally related to the dihydropyridine Ca2+-entry blockers, causes a dose-dependent increase in intracellular free Ca2+ in human platelets, as measured with the Quin-2 Ca2+ indicator, with a semimaximal effective concentration of 2.2 X 10(-7) M. This effect occurs in a concentration range in which CGP 28392 competes for specific [3H]nitrendipine binding in guinea pig heart membranes. It can be inhibited by nitrendipine. The data presented furnish direct evidence of the Ca2+-entry-stimulating properties of CGP 28392 and indicate the presence of dihydropyridine-susceptible structures in human platelets. 相似文献
49.
Salvatore Passarella Anna Atlante Maria Barile Ernesto Quagliariello 《Biochemical and biophysical research communications》1984,121(3):770-778
GABA added to rat brain mitochondria causes oxidation of intramitochondrial NAD(P)H as well as inducing glutamate efflux from the mitochondrial matrix. The rate of NAD(P)H oxidation shows saturation characteristics, depends on GABA transport across the mitochondrial membrane and is inhibited by non-penetrant compounds and by the metal-complexing agent bathophenanthroline. These results show the existence of a specific GABA carrier. Inhibition studies strongly suggest the existence of two separate binding sites, namely the GABA binding site and the dicarboxylates binding site, as well as suggest the presence of a metal ion (ions) at GABA binding site. The occurrence of a GABA/GLUTAMATE antiport is proposed which allows a cyclical route to account for GABA synthesis and degradation in brain. 相似文献
50.
The blue light dependent utilization of nitrate by green algae under common air and high irradiances, besides its assimilatory nature, is associated with the release of NO2
– and NH4
+ to the culture medium. If the CO2 content of the sparging air was increased up to 2%, previously excreted NO2
– and NH4
+ were rapidly assimilated. When under air and high irradiances the cell density in the culture reached values corresponding to 25 g Ch 1.ml-1, no further growth was observed and the highest values of NO3
– consumption and NO2
– and NH4
+ release were attained. Besides low CO2 tensions, increasing NO3
– concentrations in the medium stimulated the release of NO3
– and NH4
+. Under CO2-free air the consumption of NO3
– and the release of NO2
– and NH4
+ on a total N bases were almost stoichiometric and their rates saturated at much lower irradiances than under air. Under CO2-free air high rates of NO2
– release were only observed under the blue radiations that were effectively absorbed by photosynthetically active pigments, i.e. 460 nm, but not under 404 and 630 nm radiations. However, the simultaneous illumination of the cells with 404 and 630 nm monochromatic light showed a remarkable synergistic effect on NO2
– release.The results are discussed in terms of the close relationship between C and N metabolism, the photosynthetic reducing power required to convert NO
inf3
sup±
-N into R – NH2-N and the blue light activation of nitrate reductase. 相似文献