Accumulation of metals in the teeth of inhabitants of two towns in the south of Poland.

Metals and Ca, Na and K were examined in human teeth taken from inhabitants of two towns Sosnowiec and Katowice in the south of Poland (n = 170 samples) during 1993/1994. They are located in Upper Silesia, a heavily industrialised and urbanised region of Poland. The concentrations of Pb, Mn, Fe, Cd, Cu, Ni, Co, Zn and Cr were determined by AAS, and Na, Ca and K by flame photometer. Variations in the Pb/Fe, Pb/Mn, Pb/Ca and Cd/Ca ratios of elements in human teeth were examined. Influence of age, sex type of teeth on concentrations of elements for inhabitants from the two different towns (Katowice and Sosnowiec) and on levels of ratios of the elements were analysed using one-way ANOVA. Cluster Analysis was used to investigate relationships among metals. The smallest duster distances were obtained for: Ca-Fe, Mn-Cd and Na-Co, which indicated the strongest relation between elements in teeth for the investigated population living in a heavily industrialised and urbanised region.     

Potassium and other minor elements in Porites corals: implications for skeletal geochemistry and paleoenvironmental reconstruction

We investigated how the K/Ca, Na/Ca, Mg/Ca, and Sr/Ca ratios of powders ground from Porites coral skeletons are changed by cumulative chemical treatments to the powders: first with distilled/deionized water (DDW), next with 30?% H₂O₂ and then with 0.004?mol?l^?1 HNO₃. The K/Ca, Na/Ca, and Mg/Ca ratios were decreased with the DDW treatment and then increased with the H₂O₂ and HNO₃ treatments; the Sr/Ca ratio was slightly decreased through the cumulative treatments, suggesting fine-scale (tens of ??m or less) elemental heterogeneities in the skeleton??K, Na, and Mg are significantly enriched at the skeletal surface and also at the center of calcification (COC); in contrast, the heterogeneity of Sr is very small. We suggest that the principal mechanisms of K incorporation into coral skeleton are (1) ion incorporation into lattice defects/distortions and (2) ion adsorption onto crystal discontinuities (including crystal?Corganic matter interfaces) as forms of K⁺ and KSO₄ ^?. Furthermore, we measured the element/Ca ratios of a modern Porites coral skeleton along its growth direction at 2-mm intervals. Results showed that all the element/Ca ratios displayed annual cycles, that the K/Ca and Na/Ca ratios covaried with each other, and that the annual-minimum K/Ca and Na/Ca ratios coincided with the annual high-density band in the skeleton. It is unclear what environmental factors may cause the covarying annual cycles of the K/Ca and Na/Ca ratios; however, as a possible explanation, the cycles may be due not to environmental factors, but to a combined effect of (1) the K and Na enrichment at the COC, (2) annual bands of high- and low-density skeleton, and (3) mm-scale element/Ca measurements along the skeletal growth direction. This kind of effect on geochemical proxies of which the concentrations significantly differ between the COC and surrounding skeleton may generate false or distorted paleoenvironmental signals.     

Contribution of Na/Ca transport to the resting membrane potential

Relations are derived that describe the combined effects of electrodiffusion, the Na/K pump, and Na/Ca transport by carrier on the resting membrane potential. Equations are derived that apply to both steady-state and non-steady-state conditions. Some example calculations from the equations are plotted at different permeability coefficient ratios, PK:PCa:PNa. The equations predict a depolarizing action of Na/Ca transport when more than two Na ions per Ca ion are transported by the carrier. For all permeability ratios examined, a steady state for Ca ions is achieved with at most a few millivolts of depolarization.     

保护性耕作对土壤交换性盐基组成的影响

以辽宁省彰武县保护性耕作示范推广基地土壤为研究对象,通过实地调查和取样分析,对比研究了传统犁耕和6年保护性耕作（免耕秸秆覆盖）条件下的土壤交换性盐基组成.结果表明：在15 cm土层内,保护性耕作土壤的交换性K、Ca、Mg含量和盐基总量（SEB）较传统犁耕均有不同程度增加,表明保护性耕作使土壤的保肥和缓冲能力增强.相关分析表明,这与土壤的有机质和粘粒含量的变化密切相关;保护性耕作土壤的K/SEB和Ca/Mg高于传统犁耕,而(Ca+Mg)/SEB、Ca/K和Mg/K低于传统犁耕,说明保护性耕作对土壤交换性盐基比例关系的影响以交换性Ca、K特别是K的相对富集为主要特征;保护性耕作提高了交换性K、Ca、Mg含量与SEB的分层比率(0～5 cm/5～15 cm和0～5 cm/15～30 cm),表明交换性盐基在耕层剖面的垂直变异性增强.     

Stoichiometry of the retinal cone Na/Ca-K exchanger heterologously expressed in insect cells: comparison with the bovine heart Na/Ca exchanger

The transport stoichiometry is an essential property of antiporter and symporter transport proteins. In this study, we determined the transport stoichiometry of the retinal cone potassium-dependent Na/Ca exchanger (NCKX) expressed in sodium-loaded cultured insect cells. The Na/Ca and Rb/Ca coupling ratios were obtained by direct measurements of the levels of (86)Rb and (45)Ca uptake and sodium release associated with reverse Na/Ca exchange. Rb/Ca coupling ratios of 0.98 [standard deviation (SD) of 0.12, 15 observations] and 0.92 (SD of 0.12, 13 observations) were obtained for the chicken and human retinal cone NCKX, respectively. Na/Ca coupling ratios of 4.11 (SD of 0.24, 10 observations) and 3.98 (SD of 0.34, 15 observations) were obtained for the chicken and human retinal cone NCKX, respectively, whereas a lower average coupling ratio of 3.11 (SD of 0.34, 10 observations) was obtained with cells expressing the bovine Na/Ca exchanger (NCX1). These results are consistent with a 4Na/1Ca + 1K stoichiometry for retinal cone NCKX. High Five cells expressing full-length dolphin rod NCKX, Caenorhabditis elegans NCKX, or bovine rod NCKX from which the two large hydrophilic loops were removed all showed a significant calcium-dependent (86)Rb uptake, whereas no calcium-dependent (86)Rb uptake was observed in cells expressing bovine NCX1. The calcium dependence of (45)Ca uptake yielded values between 1 and 2.5 microM for the external calcium dissociation constant of the different NCKX proteins studied here.     

The Specific Mineral Metabolism of Selected Plant Species and its Ecological Implications

In order to assess and compare the species-specific mineral metabolism of various plants, we raised eight selected species from different families under identical nutritional conditions. Five different nutrient solutions with varying Ca/K ratios were used. After two months of growth, the leaves were harvested, arranged according to age, and analyzed with respect to their K, Ca, and Mg contents. The ion ratios, the changes of ion contents with increasing age, the differences in water- and acid-soluble Ca (calcium oxalate), and the dependence of ion uptake on variations of ion concentrations in the solutions revealed a species-specific (“physiotypic”) feature of mineral metabolism. These features are discussed taking into consideration the ecological demands of the investigated species, and assuming that the physiological peculiarities of a species should affect its ecological behavior.     

The K/Na and Ca/Na ratios and rapeseed yield,under soil salinity or sodicity

Rapeseed (Brassica napus) is a crop relatively tolerant to salt and sodium. Our objective was to study the interactions between Na, K and Ca and their relationship with its yield under the isolated effects of soil salinity or sodicity.Two experiments were carried out using pots filled with the Ah horizon of a Typic Natraquoll. There were three salinity levels (2.3 dS m^-1; 6.0 dS m^-1 and 10.0 dS m^-1) and three sodicity levels, expressed as sodium adsorption ratios (SAR: 12; 27 and 44). The soil was kept near field capacity.As soil salinity increased, the K/Na and Ca/Na ratios in the tissues decreased markedly but yields and aerial biomass production were not affected. As soil SAR value increased, the K/Na and Ca/Na ratios in plants and K-Na and Ca-Na selectivities decreased. Plants could not maintain their Ca concentration in soil with a high SAR. The grain yield and biomass production diminished significantly in the highest SAR treatment. Our results are consistent with those showing detrimental osmotic effects of salts in Brassica napus. Conversely, under sodicity, the K/Na and Ca/Na ratios in plant tissues decreased considerably, in accordance with grain and biomass production. These results show that the effects of sodicity are different from those of salinity.     

Effect of different Mg/Ca ratios and electrolyte concentrations in irrigation water on the nutrient content of wheat crop

Summary A study conducted in pots to evaluate the effect of different Mg/Ca ratios (2, 4, 8 and 16) and electrolyte concentrations (20 and 80 meq/l) at SAR 10 in irrigation water on the nutrient uptake and yield of wheat crop in two soils revealed that the average grain and dry matter yields of wheat decreased significantly with an increase in Mg/Ca ratio in irrigation water, but the magnitude of decrease was greater at higher electrolyte concentration than at lower electrolyte concentration. The concentration of Na in both straw and grain of wheat increased and that of K decreased with an increase in Mg/Ca ratio and electrolyte concentration of irrigation water, which led to higher Na/Ca and Na/K ratios in the plant. Further, the concentration of Ca and Mg both in straw as well as in grain increased with increasing electrolyte concentration of the irrigation water. An increasing proportion of Mg in saline irrigation water resulted in decreased concentration of Ca and increased concentration of Mg in both straw and grain of wheat crop. It was also noticed that the increasing proportion of Mg over Ca in the poor quality irrigation water increased the P content of both straw and grain of wheat crop.     

The relationship between extracellular K+ and Ca2+ on aminopyrine accumulation in rat parietal cells.

The effects of extracellular K+ in relation to extracellular Ca2+ on acid production were studied. Studies were performed in vitro using isolated cells from rat stomachs, and acid production was indirectly determined by 14C-aminopyrine (AP) accumulation. In the absence of K+ in the incubation medium histamine-stimulated AP accumulation ratios were significantly decreased independently in the presence or absence of extracellular Ca2+. Under basal conditions, in the absence of extracellular Ca2+, increasing concentrations of extracellular K+ enhanced AP accumulation ratios to significantly higher than those found in the presence of Ca2+. In histamine-, cAMP-, and carbachol-stimulated parietal cells, high K+ concentrations increased AP accumulation significantly less in Ca(2+)-free than in Ca(2+)-containing media. High K+ also induced significantly both an increase in cytosolic free Ca2+ concentration and 45Ca2+ uptake. The present results confirmed the importance of K+ in gastric acid production and suggested a role for Ca2+ as a modulator of mechanisms of parietal cell stimulation.     

NADPH oxidase AtrbohD and AtrbohF function in ROS-dependent regulation of Na⁺/K⁺homeostasis in Arabidopsis under salt stress

Maintaining cellular Na(+)/K(+) homeostasis is pivotal for plant survival in saline environments. However, knowledge about the molecular regulatory mechanisms of Na(+)/K(+) homeostasis in plants under salt stress is largely lacking. In this report, the Arabidopsis double mutants atrbohD1/F1 and atrbohD2/F2, in which the AtrbohD and AtrbohF genes are disrupted and generation of reactive oxygen species (ROS) is pronouncedly inhibited, were found to be much more sensitive to NaCl treatments than wild-type (WT) and the single null mutant atrbohD1 and atrbohF1 plants. Furthermore, the two double mutant seedlings had significantly higher Na(+) contents, lower K(+) contents, and resultant greater Na(+)/K(+) ratios than the WT, atrbohD1, and atrbohF1 under salt stress. Exogenous H(2)O(2) can partially reverse the increased effects of NaCl on Na(+)/K(+) ratios in the double mutant plants. Pre-treatments with diphenylene iodonium chloride, a widely used inhibitor of NADPH oxidase, clearly enhanced the Na(+)/K(+) ratios in WT seedlings under salt stress. Moreover, NaCl-inhibited inward K(+) currents were arrested, and NaCl-promoted increases in cytosolic Ca(2+) and plasma membrane Ca(2+) influx currents were markedly attenuated in atrbohD1/F1 plants. No significant differences in the sensitivity to osmotic or oxidative stress among the WT, atrbohD1, atrbohF1, atrbohD1/F1, and atrbohD2/F2 were observed. Taken together, these results strongly suggest that ROS produced by both AtrbohD and AtrbohF function as signal molecules to regulate Na(+)/K(+) homeostasis, thus improving the salt tolerance of Arabidopsis.     

Calcium as a limiting factor in the biology of Biomphalaria pfeifferi (Krauss), (Gastropoda: Planorbidae)

The minimum calcium requirements, relative importance of buffering and optimum ratio of calcium to magnesium, calcium to sodium, and calcium to potassium ions were determined for laboratory populations ofBiomphalaria pfeifferi and related to suggested limiting factors for the natural distribution of this species. Snails were reared in a range of concentrations of both calcium bicarbonate and unbuffered calcium sulphate from 0.5 to 20 mg/l as Ca⁺⁺ and also in a series of media with a constant concentration of 2 mg/l as Ca⁺⁺ but with a range of Ca/Mg, Ca/Na and Ca/K ratios of 4.0 to 0.1. Shell growth, survivorship, fecundity, egg fertility, and the net reproductive rate were compared. In calcium bicarbonate cultures a concentration of 2mg/l Ca⁺⁺ appeared to be the lower limit for the survival of laboratory populations but a concentration of 4 mg/l Ca⁺⁺ was needed for a population to thrive. The calcium sulphate salt gave much poorer results, emphasizing the importance of the bicarbonate buffer. In the cationic ratio experiments the low Ca/Mg ratios proved to have the most damaging effects on snail populations but the effects of very low Ca/Na and Ca/K ratios could also be measured. A parallel experiment on the hatching rate of snail eggs, using similar experimental solutions, gave comparable results. The significance of these findings to snail ecology is discussed.     

Macro nutrient cation uptake by plants

Summary In pot experiments with barley, mustard, leek, lettuce and spinach, and in a field experiment with 30 cultivars of barley uptakes of K, Mg, Ca, Na and N were studied at varying concentrations and activities of these cations in the soil solution.The sum of macro cations (K, Mg, Ca, Na) in meq per 100 g aerial plant parts were independent of the chemical composition of the soil solution, but dependent on plant species and on the N concentration in the plant.The ratios of mean net inflows of Mg, Ca and K into plants and corresponding cation activity ratios (a_Mg/a_Ca and ) in the soil solution were linearly related and highly correlated under conditions in which growth rate and/or rate of incorporation into new tissues constituted the rate determining step of cation uptake. Consequently, mean net inflows of K, Mg and Ca were independent of ion concentration and ion activity of K, Mg or Ca in the soil solution under the conditions of constant activity ratio.The results agree with the concept that plants have a finite cation uptake capacity, and that plants are in a equilibrium-like state with the activities of K, Mg, and Ca ions in the soil solution. The results indicate that both ratios and content of exchangeable cations should be considered in our evaluation of soil test data.     

Defining the molecular components of calcium transport regulation in a reconstituted membrane system

Using a chemically defined reconstitution system, we performed a systematic study of key factors in the regulation of the Ca-ATPase by phospholamban (PLB). We varied both the lipid/protein and PLB/Ca-ATPase ratios, determined the effects of PLB phosphorylation, and compared the regulatory effects of several PLB mutants, as a function of Ca concentration. The reconstitution system allowed us to determine accurately not only the PLB effects on K(Ca) (Ca concentration at half-maximal activity) of the Ca-ATPase, but also the effects on V(max) (maximal activity). Wild-type PLB (WT-PLB) and two gain-of-function mutants, N27A-PLB and I40A-PLB, showed not only the previously reported increase in K(Ca), but also an increase in V(max). Specifically, V(max) increases linearly with the intramembrane PLB concentration, and is approximately doubled when the sample composition approaches that of cardiac SR. Upon phosphorylation of PLB at Ser-16, the K(Ca) effects were almost completely reversed for WT- and N27A-PLB but were only partially reversed for I40A-PLB. Phosphorylation induced a V(max) increase for WT-PLB, and a V(max) decrease for N27A- and I40A-PLB. We conclude that PLB and PLB phosphorylation affect V(max) as well as K(Ca), and that the magnitude of both effects is sensitive to the PLB concentration in the membrane.     

Seasonal differences in mineral content, distribution and leakage of sweet pepper seeds

Pepper seed quality is sensitive to variations in climatic conditions during seed development, which might be associated with accumulation, distribution and leakage of mineral elements from the seeds. This was examined in hybrid seeds of sweet pepper (Capsicum annuum L. cv.‘Hazera’ 1195) in two experiments during two growing seasons. The mean daily temperature (day/night) and daily total radiation receipt during seed development were 27.9/23.2°C and 8.63 kW m^?2 in the summer and 18.3/ 14.9°C and 3.18 kW m^?2 in the winter, respectively. Seeds developed in the summer had lower percentage of seedling emergence and leaked a larger portion (45%) of their K content into the water medium than in winter‐developed seeds. Summer seeds accumulated more K and Cl, but less P, Mg, Ca and the weight ratio of linoleic acid to oleic acid was lower than in the winter seeds. The season did not significantly affect N, S and total fatty acids. The most abundant element on the seed coat surface was K in the summer and Ca in the winter seeds. The cotyledon and endosperm of the summer seeds contained relatively higher ratios of K and Ca and lower ratios of P and Mg than the winter seeds. Transportation of mineral nutrients appeared to be involved in the effect of heat and moisture stresses on emergence quality of the pepper seeds.     

Cellular responses of two rapid-cycling Brassica species, B. napus and B. carinata, to seawater salinity

Cellular responses of two rapid-cycling Brassica species. B. napus and B. carinata , to seawater salinity were characterized to determine whether callus showed a tolerance similar to that of whole plants. Callus was initiated from the leaves of 7-day-old seedlings of B. napus and B . carinata and then subcultured with two different levels of seawater salinity (2.3 and 5.2 g l⁻¹ Instant Ocean. Aquarium Systems, Inc. Mentor. OH, USA) for 14 days. Callus growth of both species was reduced by seawater salinity. Based on the percentage of the reduction in the relative fresh weight gain. B. napus was more salt-tolerant than B. carinata . consistent with the response of whole plants of the same species to seawater salinity. Seawater salinity caused changes in the concentrations of Na, K. Ca, Mg and Cl in both B. napus and B. carinata . The growth expressed as the percentage of control was significantly (P = 0.05) positively correlated with the concentration of Ca. and K/Na and Ca/Na ratios. It was also negatively correlated ( P = 0.01) with the concentrations of Na. Cl and Mg. In comparison with B. carinala . the salt-tolerant species, B . napus , showed a small reduction in the concentrations of Ca and K in the salt-stressed plants relative to the control.     

Effect of soil K, Ca and Mg saturation and endomycorrhization on growth and nutrient uptake of sugar maple seedlings

Nutrient imbalances of declining sugar maple (Acer saccharum Marsh.) stands in southeastern Quebec have been associated with high exchangeable Mg levels in soils relative to soil K and Ca. A greenhouse experiment was set up to test the hypothesis that the equilibrium between soil exchangeable K, Ca, and Mg ions influences the growth and nutrient status of sugar maple seedlings. Also tested was whether endomycorrhization can alter nutrient acquisition under various soil exchangeable basic cations ratios. Treatments consisted of seven ratios of soil exchangeable K, Ca, and Mg making up a total base saturation of 58%, and a soil inoculation treatment with the endomycorrhizal fungus Glomus versiforme (control and inoculated), in a complete factorial design. Sugar maple seedlings were grown for 3 months in the treated soils. Plant shoot elongation rate, dry biomass and nutrient concentrations in foliage were influenced by the various ratios of soil cations. The predicted plant biomass and foliar K concentration were highest at a soil Ca saturation of 38%, a soil K saturation of 12%, and a soil Mg saturation of 8%. Potassium concentration in foliage was dependent on the level of Ca and Mg saturation in the soil when soil K saturation was close to 12%. Foliar Ca and Mg levels were more dependent on their corresponding levels in soil than foliar K. Colonization by G. versiforme did not influence seedling growth and macronutrient uptake. The results confirm that growth and nutrition of sugar maple are negatively affected by imbalances in exchangeable basic cations in soils.     

Elemental composition of arbuscular mycorrhizal fungi at high salinity

We investigated the elemental composition of spores and hyphae of arbuscular mycorrhizal fungi (AMF) collected from two saline sites at the desert border in Tunisia, and of Glomus intraradices grown in vitro with or without addition of NaCl to the medium, by proton-induced X-ray emission. We compared the elemental composition of the field AMF to those of the soil and the associated plants. The spores and hyphae from the saline soils showed strongly elevated levels of Ca, Cl, Mg, Fe, Si, and K compared to their growth environment. In contrast, the spores of both the field-derived AMF and the in vitro grown G. intraradices contained lower or not elevated Na levels compared to their growth environment. This resulted in higher K:Na and Ca:Na ratios in spores than in soil, but lower than in the associated plants for the field AMF. The K:Na and Ca:Na ratios of G. intraradices grown in monoxenic cultures were also in the same range as those of the field AMF and did not change even when those ratios in the growth medium were lowered several orders of magnitude by adding NaCl. These results indicate that AMF can selectively take up elements such as K and Ca, which act as osmotic equivalents while they avoid uptake of toxic Na. This could make them important in the alleviation of salinity stress in their plant hosts.     

The effect of calcium on the germination,growth and mineral nutrition of acidic and calcareous populations ofEucalyptus obliqua L'Hérit

Summary A comparative study of two populations ofE. obliqua has shown that germination of an acidic population is severely reduced at high levels of Ca, whereas a calcareous population maintained high germinability over a wide range of Ca concentrations. In contrast, seedlings of both populations showed a similar overall response in yield to an increasing supply of external Ca. However, plants from the acidic population tended to show a lower survival rate and poorly growing plants accumulated higher levels of Ca and P at high external concentrations of Ca than the calcareous population. Plants showing severe chlorosis and symptoms of P and Ca toxicity also exhibited low K/Ca ratios.     

Comparative study of the elemental composition of vegetative and dormant microbial cells

X-ray microanalysis showed that vegetative cells, viable resting forms, and nonviable forms (micromummies) of the bacteria Bacillus cereus and Micrococcus luteus and the yeast Saccharomyces cerevisiae differ in the contents of bioelements S, P, Ca, and K and the Ca/K and P/S ratios. Viable resting forms (cystlike refractory cells and bacillar endospores) had more calcium and less phosphorus and potassium than vegetative cells, the difference being higher for bacilli than for micrococci and yeasts. The distinctive feature of all viable resting microbial forms was their low P/S ratios and high Ca/K ratios. The differences revealed in the cellular content and ratios of bioelements probably reflect changes in ionic homeostasis accompanying the transition of vegetative microbial cells to the dormant state. Relevant potassium parameters indicate that the membranes of viable resting forms retain their barrier function. At the same time, the nonviable forms, even morphologically intact, of B. cereus and S. cerevisiae exhibited an anomalously low content of potassium, while those of M. luteus had an anomalously high content of this element. This suggests that the cellular membranes of micromummies lose their barrier function, which results in a free diffusion of potassium ions across the membranes. The possibility of using the elemental composition parameters for quick analysis of the physiological state of microorganisms in natural environments is discussed.     

西南喀斯特石漠化环境适生植物构树细根、根际土壤化学计量特征

为了解西南喀斯特石漠化适生植物构树(Broussonetia papyrifera)对贫瘠土壤养分环境的适应策略, 及其细根、根际土壤的化学计量特征对石漠化等级的响应, 该研究以西南喀斯特石漠化环境适生植物构树为研究对象, 运用生态化学计量学方法, 开展不同等级石漠化环境构树细根、根际土壤有机碳(C)、全氮(N)、全磷(P)、全钾(K)、全钙(Ca)及全镁(Mg)养分含量特征及C、N、P化学计量特征研究。结果表明, 除Ca含量外, 喀斯特石漠化环境适生植物构树细根、根际土壤的养分含量均处于较低水平; 细根N:P为12.59, 表明构树生长受N和P共同限制; 随着石漠化等级的增加, 细根C、N含量和C:N、C:P呈先降后升的变化趋势, K、P含量是则表现为先升后降, Ca、Mg含量和N:P无明显变化规律; 不同等级石漠化环境中的构树根际土壤N、P、K、Ca含量呈不同的变化趋势, 而C、Mg含量及C、N、P化学计量特征的变化较不显著; 细根与根际土壤的化学计量特征之间存在显著的相关性, 二者的C、P、Ca、Mg含量、C:N、C:P分别对应呈显著正相关关系, 而N含量呈极显著负相关关系; 细根的K含量则较为稳定, 几乎不受根际土壤养分的影响。