Decrease In Ca Concentration Research Articles

The influence of the occupational exposure to heavy metals and tobacco smoke on the selected oxidative stress markers in smelters.

The aim of the study was to verify if there is any association between exposure to Cu, Zn, Cd, Pb, As and the formation of malondialdehyde (MDA), 8-hydroxydeoxyguanosine (8-OHdG), advanced oxidation protein products (AOPP), and whether in this process cigarette smoking plays a role. The investigations were performed in the 352 smelters occupationally exposed to heavy metals and 73 persons of control group. Metals concentration was determined by atomic absorption spectrometry. MDA and AOPP concentrations were determined by spectrophotometric methods. The concentration of 8-OHdG was determined by ELISA method. It was demonstrated an increased Cu concentration in smoking smelters compared to non-smoking control group. It was noted no differences in Zn and Mg concentrations between the examined groups. Pb concentration was more than sixfold higher in the group of smoking smelters and about fivefold higher in the group of non-smoking smelters compared to the control groups (smokers and non-smokers). It was shown that Cd concentration in the blood was nearly fivefold higher in the smoking control group compared to the non-smoking control group and more than threefold higher in the group of smoking smelters compared to non-smoking. It was shown an increased As concentration (more than fourfold) and decreased Ca concentration in both groups of smelters compared to control groups. In groups of smelters (smokers and non-smokers), twofold higher MDA and AOPP concentrations, and AOPP/albumin index compared to control groups (smokers and non-smokers) were shown. Tobacco smoke is the major source of Cd in the blood of smelters. Occupational exposure causes accumulation of Pb in the blood. Occupational exposure to heavy metals causes raise of MDA concentration and causes greater increase in AOPP concentration than tobacco smoke.

New Evidences about Adverse Health Effects Based on Chromate Environmental and Biological Exposure Assessment in Chromate Manufacturing Workers

Background Chromium (Cr) compounds are produced and applied widely. Aims On the basis of chromate exposure assessment, Cr related trace element homeostasis, DNA damage and global DNA methylation status, renal damage need further investigation. Method We recruited more than one hundred workers from chromate producing facilities as testing subjects and matched local residents without chromium exposure history served as controls. Personal sampling of airborne Cr (A-Cr) was conducted and Cr content was quantified by Flame Atomic Absorption Spectrometry. At the end of the sampling shift, blood and urine samples were collected and element concentrations were measured by inductively coupled plasma mass spectrometry and inductively coupled plasma atomic emission spectrometry. Adverse health effects including renal impairment, DNA damage, DNA methylation, and multi-trace element homeostasis were investigated comprehensively. Results 90% of the chromate production workers were exposed to A- Cr lower than 50 mu g m(-3).Chromate caused renal impairment with more severity in the tubule than glomerular. After Cr(VI) exposure, a significant increase in blood Cr, Cd, Fe, Mg, Mo, Se and Zn concentrations was observed, as well as a significant decrease in Ca concentration. Blood Cr (B-Cr) was four times higher than that of the controls, and significantly correlated with A-Cr (r = 0.568, P<0.001). Binucleated cells with micronuclei (BNMN ) frequencies were positively correlated with B-Cr and U- Cr; Ln BNMN was regressed on B-Cr, and U-Cr and A-Cr by linear models.We also found that the decreased serum folate was associated with an increased urinary 8-OhdG, DNA strand breaks and global DNA hypomethylation. Conclusions We provided some new evidences about chromate health adverse effects .Based on the above evidences and others, we therefore proposed a modified health surveillance system for chromate workers.

Applicability of ToF-SIMS for monitoring compositional changes in bone in a long-term animal model

Time-of-flight secondary ion mass spectrometry (ToF-SIMS) is a well-established technique in material sciences but has not yet been widely explored for implementation in life sciences. Here, we demonstrate the applicability and advantages of ToF-SIMS analysis for the study of minerals and biomolecules in osseous tissue. The locally resolved analysis of fragment ions deriving from the sample surface enables imaging and differentiation of bone tissue and facilitates histology on non-stained cross sections. In a rat model, bilateral ovariectomy combined with either a multi-deficiency diet or steroid treatment was carried out to create osteoporotic conditions. We focused our study on the Ca content of the mineralized tissue and monitored its decline. Calcium mass images of cross sections show the progressive degenerative changes in the bone. We observed a decreased Ca concentration in the edge region of the trabeculae and a decline in the Ca/P ratio. Additionally, we focused on the non-mineralized matrix and identified fragment ions that are characteristic for the collagen matrix. We observed trabeculae with wide ranges of non-mineralized collagen for the diet group owing to an impaired mineralization process. Here, the advantage of coeval monitoring of collagen and minerals indicated an osteomalacic model rather than an osteoporotic one.

Influence of Flow Rates and Copper (II) ions on the Kinetics of Gypsum Scale Formation in Pipes

Experiments were performed in a piping system to examine the effects of flow rates and Cu, a common metal ion in wastewater, on the kinetics of gypsum (CaSO4.2H2O) scale formation. The scaling was monitored by measuring the decrease in Ca concentrations, [Ca], of the scaling solution. AAS analysis shows that [Ca] reduces progressively after a certain induction time, during which time the concentration remains steady. Thus, the gypsum precipitation which leads to scaling in pipes does not occur spontaneously. Higher impurity concentrations (0 to 10 ppm Cu) result in longer induction time (26 to 42 min), which indicate that Cu could inhibit the scale formation. Impurity concentrations and the scale mass generated are negatively correlated. Reduction in scale mass was as high as 61% depending on impurity concentrations and flow rates. Data of [Ca] versus time were used to calculate the reaction rate of the gypsum precipitation which led to scaling. It was found that the reaction follows a first order kinetics with respect to [Ca], with rate constants ranging between 5.28 and 7.37 per hour, which agree with most published values for mineral scale formation.

Influence of alkaline (pH 8.3–12.0) and saline solutions on chemical, mineralogical and physical properties of two different bentonites

AbstractThe interaction of two different bulk bentonites (Na- and Ca-types) with three types of simulated cement waters (pH 9.7, 11.3 and 12.0) and one saline groundwater simulate (pH 8.3) as a reference, was studied in batch reactors at 25°C. The solution pH was monitored in order to keep the pH as steady as possible by replacing the leaching solution with fresh one when needed. After 554 days, one set of parallel samples was removed from the experiment in order to investigate the possible changes in the bentonite materials.The buffering capacity of bentonite was clearly observed, especially at the beginning of the high-pH experiments, as the pH of the leaching solutions decreased quite dramatically due to interaction with bentonite. The solution chemistry results showed a decrease of Ca content in all leachate samples, but especially in pH 12.0 experiments. Small amounts of silica were released throughout the experiment. Both bentonites in pH 12.0 experiments also released detectable amounts of Al, while in the lower pH experiments the levels were below detection limit. These observations were also supported by chemical analyses of the bentonite materials. Only minor changes were detected in the mineralogy, and they were mainly concentrated on experiments at pH 11.3 and pH 12.0. The measured swelling pressure showed an increase in pH 12.0 experiments. The results obtained in this research may facilitate modelling of bentonite interaction with high-pH solutions.

Speciation of 90Sr and other metal cations in artificially contaminated soils: the influence of bone sorbent addition

The influence of bone sorbent addition onto distribution of 90Sr in artificially contaminated soil was preliminary studied to assess the possibility of biogenic apatite utilization for reduction of 90Sr mobility and availability. Simultaneously, the disruption of soil micro- (Cd, Zn, Co, Cu, Cr, and Ni,) and macroelements (Al, Fe, Mn, K, Mg, and Ca) upon Sr contamination and sorbent addition was monitored. The model soil was contaminated by inactive Sr, in the form of Sr(NO3)2 solution. As a soil additive, sorbent obtained by annealing bovine bones at 400 °C (B400) was applied. Both the uncontaminated and Sr-contaminated soils were mixed with 1, 3, 5, and 10 % of sorbent, suspended in distilled water (initial pH 5; solid/solution ratio, 1:2), and equilibrated for 15 days on a rotary shaker. Solid residues were subjected to modified Tessier five-step sequential extraction analysis, and the amounts of chosen metals in each fraction were determined by inductively coupled plasma–optical emission spectroscopy. In the original soil, Sr was mainly found in exchangeable (61 %) and carbonate phase (16 %), whereas after contamination, the content of Sr in exchangeable phase raised to 94 %. With the addition of B400, the decrease in Sr amounts in exchangeable fraction was detected, whereas increase occurred mainly in operationally defined carbonate phase and in the residual. High level of Sr contamination caused the increase in Zn, Ni, Co, Cu, Cd, and Mn and decrease in Ca content in exchangeable phase. Sorbent addition resulted in a migration of these cations to less soluble fractions. This effect was observed even for major soil elements such as Fe, Al, and Mn, regardless of the excessive amounts of Sr in the soil. Mixing the soil with B400 resulted in reduced Sr mobility and bioavailability. B400 acted as a stabilizing agent for heavy metals, as well. Apatite distinguished selectivity towards heavy metals may interfere with the Sr immobilization and disrupt original cation distribution. Further studies should include more realistic (lower) Sr concentrations in the soil, different soil types, pH, and longer incubation times.

Effects of chronic chromium(vi) exposure on blood element homeostasis: An epidemiological study

One hundred chromate production workers chronically exposed to low-level of hexavalent chromium [Cr(vi)] and eighty healthy individuals free from Cr exposure were recruited to the study. Personal sampling of airborne Cr was conducted and Cr content was quantified by Flame Atomic Absorption Spectrometry (FAAS). At the end of the sampling shift, blood samples were collected and element concentrations were measured by inductively coupled plasma mass spectrometry (ICP-MS) for Cr, Cd, Cu, Mo and Se and inductively coupled plasma atomic emission spectrometry (ICP-AES) for Ca, Fe, Mg and Zn. According to our results, 90% of the chromate production workers were exposed to airborne Cr in a concentration lower than 50 μg m(-3), which is the threshold limit value recommended by the American Conference of Governmental Industrial Hygienists and Chinese Ministry of Health. After Cr(vi) exposure, a significant increase in blood Cr, Cd, Fe, Mg, Mo, Se and Zn concentrations was observed, as well as a significant decrease in Ca concentration. A decrease in blood Cu was only observed among female workers. Blood Cr concentrations of the exposed workers (median = 15.68 ng mL(-1)) was four times higher than that of the controls (median = 3.03 ng mL(-1)), and significantly correlated with airborne Cr (r = 0.568, P<0.001). In addition, the inter-element correlations exhibited significant differences between the two groups. Our findings of the related health effects suggested that the underlying mechanisms of chronic Cr(vi) exposure on blood element homeostasis might be partly explained by oxidative stress in the body, dysfunction of Fe metabolism and renal injury.

Calcium carbonate precipitation by anoxygenic phototrophic bacteria

Carbonate biomineralization is considered as one of the main natural processes controlling CO 2 levels in the atmosphere both in the past and at present time. In contrast to extensive studies of cyanobacterial calcification, biomineralization of anoxygenic phototrophic bacteria (APB) remained largely underestimated, despite their potentially important role on CaCO 3 precipitation in the biomats, notably in the past. Haloalcaliphilic Rhodovulum steppense A-20s and halophilic neutrophilic Rhodovulum sp. S-17-65 were examined with respect to their ability to precipitate CaCO 3 under controlled laboratory conditions. To characterize the link between the rate of bacterial growth (biomass production) and the rate of CaCO 3 precipitation, batch kinetic experiments with live, dead and inactivated bacteria both in nutrient solution and in inert electrolyte were performed and produced precipitates were examined by SEM, TEM and XRD techniques. Active strains A-20s and S-17-65 precipitated calcite from initially supersaturated solutions ( Ω calcite = 10 to 40) via increasing Ω calcite to 80–120 before the precipitation. The amount of precipitated CaCO 3 (mole) was directly correlated with the amount of organic C in bacterial biomass produced with a slope of dependence ranging from 0.3 to 0.6 and from 0.1 to 0.3 for A-20s and S-17-65, respectively, depending on the initial solution composition. For both bacterial strains, only live actively photosynthetizing bacteria were capable of effectively decreasing Ca concentration and form CaCO 3 with apparent bulk precipitation rates ranging from 0.001 to 0.0150 mmol/h at 10–20 g wet/L of biomass, similar to rates reported for other bacteria. SEM and XRD analyses of precipitates reveal the dominance of calcite with some amount of vaterite and monohydrocalcite forming spheres up to 100 μm diameter. The TEM analysis of bacterial suspension at the end of precipitation experiments did not demonstrate the presence of CaCO 3 at the surface or in the vicinity of live cells. This suggests the existence of certain cell protection mechanism against carbonate precipitation at the cell surface. Given the lower efficiency of photoheterotrophic APB, compared to photoautotrophic cyanobacteria, to precipitate CaCO 3 in natural conditions, it is possible that the overall potential of phototrophic community to form massive carbonate deposits was strongly limited before the appearance of oxygenic phototrophs.

Effects of Salinity on the Response of the Wetland Halophyte Kosteletzkya virginica (L.) Presl. to Copper Toxicity

Kosteletzkya virginica (L.) Presl. is a perennial wetland halophyte which could be exposed to heavy metals in polluted salt marsh environments. In order to investigate the interaction between salinity (50 mM NaCl) and heavy metal, young plants were exposed in hydroponic culture to 10 μM Cu in the presence or absence of 50 mM NaCl. Copper strongly inhibited the leaf emergence and lateral branch development as well as leaf expansion, and induced a significant decrease in plant dry weight (DW), water content (WC), osmotic potential (Ψs) and leaf water potential (Ψw). Copper treated plants accumulated significantly higher level of Cu in the roots than in the shoots although Cu intake rates decreased with the duration of stress exposure. Additions of NaCl in the absence of Cu excess had no detrimental impact on plant growth. In the presence of Cu excess, NaCl decreased Cu accumulation in roots and stems but had no positive impact on plant growth. Copper induced a large decrease in K concentration in roots and stems as well as a decrease in Ca concentration in the leaves. The impact of Cu and NaCl appeared to be additive on leaf Ψs and leaf quaternary ammonium compounds concentrations. It is concluded that K. virginica exhibits a high bioconcentration factor for Cu which could be, at least partly, responsible for its sensitivity to this toxic element. The impact of stress on K and Ca homeostasis is discussed in relation to ion distribution and presence of mucilage in the plant.

Abscisic acid triggers whole-plant and fruit-specific mechanisms to increase fruit calcium uptake and prevent blossom end rot development in tomato fruit

Calcium (Ca) uptake into fruit and leaves is dependent on xylemic water movement, and hence presumably driven by transpiration and growth. High leaf transpiration is thought to restrict Ca movement to low-transpiring tomato fruit, which may increase fruit susceptibility to the Ca-deficiency disorder, blossom end rot (BER). The objective of this study was to analyse the effect of reduced leaf transpiration in abscisic acid (ABA)-treated plants on fruit and leaf Ca uptake and BER development. Tomato cultivars Ace 55 (Vf) and AB2 were grown in a greenhouse environment under Ca-deficit conditions and plants were treated weekly after pollination with water (control) or 500 mg l(-1) ABA. BER incidence was completely prevented in the ABA-treated plants and reached values of 30-45% in the water-treated controls. ABA-treated plants had higher stem water potential, lower leaf stomatal conductance, and lower whole-plant water loss than water-treated plants. ABA treatment increased total tissue and apoplastic water-soluble Ca concentrations in the fruit, and decreased Ca concentrations in leaves. In ABA-treated plants, fruit had a higher number of Safranin-O-stained xylem vessels at early stages of growth and development. ABA treatment reduced the phloem/xylem ratio of fruit sap uptake. The results indicate that ABA prevents BER development by increasing fruit Ca uptake, possibly by a combination of whole-plant and fruit-specific mechanisms.

The influence of calcium ions on nickel modulation of NMDA receptor currents

N-Methyl-D-aspartate (NMDA) receptors (NRs) are glutamate-gated channels critical for the functioning of the nervous system. They are assembled from two types of subunits, the essential GluN1 and at least one type of GluN2 (A, B, C, D) subunit. Nickel (Ni) modulates the NR current in a way dependent on the GluN2 subunit present. Besides voltage-dependent and voltage-independent inhibition, in GluN2B-containing channels Ni enhances channel activity. We have recently identified several domains of the channel involved in Ni interaction, but many aspects of this modulation remain elusive. The purpose of the present work is to investigate the role of calcium (Ca) in the effect of Ni on the NR current measured by voltage- and patch-clamp in RNA-injected Xenopus laevis oocytes or in transiently transfected mammalian HEK293 cells expressing GluN1/GluN2B recombinant receptors. In both expression systems, in the presence of a physiological concentration of Ca (1.8 mM), Ni increased the NR current with EC(50) in the μM range, but this potentiation was reduced by decreasing Ca concentration or when Ca was substituted with Ba. In injected oocytes, the effect of Ni in 0.3 mM external Ba was only inhibitory (IC(50) = 65 μM). Increasing the internal calcium buffering by EGTA and BAPTA application, as well as incubation with cytoskeleton perturbing agents, colchicine and cytochalasin-D, did not produce major modifications in the Ni effect. These observations indicate that Ni-mediated potentiation is not dependent on Ca influx and internal Ca concentration, but it is dependent on external Ca, which possibly interacts with the extracellular portion of the protein through a modulatory binding site.

Influence of De-Navelling and Stalk-End Nutrient Application on Nutrient Composition of 'Robusta' Banana Fruits

The contents of N, P, Mg, S, Fe and Mn in banana fruit increased significantly due to denavelling from 0.32%, 0.086%, 0.12%, 0.024%, 52 ppm and 4.8 ppm, under 'control' to 0.37%, 0.085%, 0.13%, 0.027%, 59 ppm and 6.7 ppm, respectively. Dipping stalk end of the bunch in fresh cow dung enhanced these above nutrients to 0.40%, 0.086%, 0.14%. 0.028%, 63 ppm and 7.6 ppm, respectively. When cow dung was enriched with ammonium sulphate, the fruits showed 0.50-0.51% of N, 0.081-0.090% of P, 0.16-0.23% of Mg, 0.032-0.040% of S, 59-111 ppm of Fe and 8.1-17.8 ppm of Mn. Addition of potassium sulphate further enhanced this effect in respect of K (2.11-2.44%) and Fe (74-115 ppm) in fruit. Increasing level of ammonium sulphate in the blend significantly decreased Ca content of the fruit from 0.24% at 5 g to 0.10% at 25 g. When potassium sulphate was included in the blend, Ca content showed further reduction (0.19% at 5 g to 0.10% at 25g). At 15 g of ammonium sulphate and 7.5 g of potassium sulphate the maximum bunch weight of 27.993 kg was obtained (as against 16.724kg under retention of male bud throughout) corresponding to the enhanced nutrient composition of 2.44% of K, 0.12% of Ca, 0.18% of Mg, 0.033% of S, 115ppm of Fe and 14.9ppm of Mn that may have nutraceutical implications.

In Vitro Response of Two Citrus Rootstocks to Salt Stress

The in vitro response of two citrus rootstocks (sour orange, Citrus aurantium L. and Volkamer lemon, Citrus volkameriana Ten. & Pasq.) to two types of salts (NaCl and CaCl2) of different concentrations (0, 50, 100, 150, 200, or 300 mM) was investigated. Results showed that increasing NaCl level in the growth medium led to increased Na and Cl accumulation and decreased Ca concentrations in plant tissue. Increasing CaCl2 levels in the growth medium led to increased Ca accumulation and decreased Na concentrations in plant tissue. Plant K concentrations decreased with increased salinity level in the media. In general, increased salinity level in growth medium, using NaCl, CaCl2, or a combination of the two, led to reduced plant growth (leaf number, plant length, fresh weight, dry weight, and increased plant leaf damage) in Volkamer lemon and sour orange after two months in culture.

Effects of chromium stress on the subcellular distribution and chemical form of Ca, Mg, Fe, and Zn in two rice genotypes

AbstractA hydroponic experiment was carried out to study effects of chromium (Cr) stress on the subcellular distribution and chemical form of Ca, Mg, Fe, and Zn in two rice genotypes differing in Cr accumulation. The results showed that Ca, Mg, Fe, and Zn ions were mainly located in cell walls and vacuoles in roots. However, large amounts of metal ions were transferred from the vacuole to the nucleus and to other functional organelles in shoots. Chromium concentrations in the nutrient solution of 50 μM and above significantly decreased Ca concentrations in the chloroplast/trophoplast, the nucleus, and in mitochondria. It further increased Mg concentrations in the nucleus and in mitochondria, as well as Zn and Fe concentrations in the chloroplast/trophoplast. These Cr‐induced changes in ion concentrations were associated with a significant reduction in plant biomass. It is suggested that Cr stress interferes with the functions of mineral nutrients in rice plants, thus causing a serious inhibition of plant growth. The chemical forms of the four nutrients were determined by successive extraction. Except for Ca, which was mainly chelated with insoluble phosphate and oxalic acid, Mg, Zn, and Fe were extractable by 80% ethanol, d‐H2O, and 1μM NaCl. The results indicated that these low–molecular weight compounds, such as organic acids and amino acids, may play an important role in deposition and translocation of Mg, Zn, and Fe in the xylem system of rice plants.

Mechanism of wollastonite carbonation deduced from micro- to nanometer length scale observations

The microstructural evolution of CaSiO3 wollastonite subjected to carbonation reactions at T = 90 °C and pCO2 = 25 MPa was studied at three different starting conditions: (1) pure water; (2) aqueous alkaline solution (0.44 M NaOH); and (3) supercritical CO2. Scanning and transmission electron microscopy on reacted grains prepared in cross-section always revealed unaltered wollastonite cores surrounded by micrometer-thick pseudomorphic silica rims that were amorphous, highly porous, and fractured. The fractures were occasionally filled with nanometer-sized crystals of calcite and Ca-phyllosilicates. Nanoscale chemical profiles measured across the wollastonite-silica interfacial region always revealed sharp, step-like decreases in Ca concentration. Comparison of the Ca profiles with diffusion modeling suggests that the silica rims were not formed by preferential cation leaching (leached layer), but rather by interfacial dissolution-precipitation. Extents of carbonation as a function of time were determined by quantitative Rietveld refinement of X-ray diffractograms performed on the reacted powders. Comparing the measured extents of carbonation in water (condition 1) with kinetic modeling suggests that carbonation was rate-controlled by chemical reactions at the wollastonite interface, and not by transport limitations within the silica layers. However, at conditions 2 and 3, calcite crystals occurred as a uniform surface coating covering the silica layers, and also within pores and cracks, thereby blocking the connectivity of the originally open nanoscale porosity. These crystals ultimately may have been responsible for controlling transport of solutes through the silica layers. Therefore, this study suggests that pure silica layers were intrinsically non-passivating, whereas silica layers became partially passivating due to the presence of calcite crystallites.

Seven Decades of Calcium Depletion in Organic Horizons of Adirondack Forest Soils

We used repeated sampling of the forest floor to determine if there was a net loss of Ca from organic horizons of Adirondack forest soils between 1930 and 2004. In 1984, we established 48 permanent plots in spruce–fir, northern hardwood, and pine stands located in areas sampled by Carl C. Heimburger in the early 1930s. Following Heimburger's protocols and analytical methods, we measured pH and dilute‐HCl‐extractable Ca in Oe and Oa horizons, and determined that there was a statistically significant decrease in Ca concentration during the 1932 to 1984 interval. In the 36 plots that we could locate in 2004, we again sampled organic horizons. During the &gt;70‐yr interval, HCl‐extractable Ca concentrations in the Oe and Oa horizons decreased in each forest type (P &lt; 0.05). We also measured NH4Cl‐extractable Ca and Al in the 1984 and 2004 samples and found a significant decrease in Ca concentration in the pooled Oe horizons. High‐elevation spruce–fir plots showed a Ca loss rate between 1984 and 2004 of 7.6 to 9.8 kg ha−1 yr−1 This compares well with a 4‐yr Ca cycling study conducted in an equivalent spruce–fir forest at Whiteface Mt. in the Adirondacks, which showed an annual forest floor Ca loss of 8.4 kg ha−1 yr−1 Based on uptake and anion flux data from the Whiteface Mt. study, we estimated that about 25 to 30% of the 1984 to 2004 forest floor Ca loss in the spruce–fir plots is attributable to leaching driven by atmospheric SO42− deposition.

Effects of Laser Cleaning on Chemical Composition of Mortar Surfaces

The paper presents a part of the larger study on microstructural features of mortars and their effects on laser cleaning process. It focuses on presenting the results of investigation on the influence of laser cleaning on chemical com- position of mortar surfaces. The experimental results prove that the laser cleaning process leads to an increase of Si ele- ment concentration and/or decrease in Ca concentration. The observed alterations should be associated with changes in the relative distribution of melted cement paste and aggregate and therefore relative elemental abundance in the near-surface layer. Furthermore, curing and service conditions of mortars seem to have strong influence on laser cleaning process and therefore on surface quality. Exposure to freezing/thawing cycles and subsequent surface damage facilitates deeper pene- tration of paint and consequently affects the efficiency of cleaning. The amount of residual carbon on F/T samples tested in the course of this study was around 42% higher than on the surfaces of laboratory-cured samples.

Texture and Other Quality Attributes in Olives and Leaf Characteristics after Preharvest Calcium Chloride Sprays

The effect of three preharvest sprays with water or 58.5 mm calcium chloride (CaCl2) on texture and other quality attributes was investigated in ‘Konservolia’ olives harvested at the black-ripe stage and measured after 1 and 15 days of storage in air at 10 °C with 85% relative humidity. Effects on fruit calcium (Ca) and magnesium (Mg) concentrations during the period of spray applications were also studied. Concentrations of Ca, Mg, and chlorophyll and photosynthesis rate in leaves were measured on the day of final fruit harvest. No foliar or fruit toxicity was observed. In leaves, Ca sprays increased Mg but did not affect Ca and chlorophyll concentration and photosynthesis rate. In fruits, Ca sprays prevented the gradual decrease in Ca concentration that occurred in untreated fruits and maintained Mg at constant levels during ripening on the tree but did not affect fruit size and oil content as measured 1 day after storage. Ca-treated fruits were firmer with lower soluble pectin (SP) concentration and higher calcium pectate (CaP) than controls in both storage days, whereas the protopectin levels were similar in all fruits. Results showed positive linear correlation between Ca concentration and either firmness or CaP, whereas that between Ca and SP was negative as found in fruits stored for 1 day. Fruit production rates of carbon dioxide and ethylene, L* and chroma (C*) of peel, and hue angle (h°) of flesh were unaffected either by Ca treatment or storage time. Ca treatment did not affect fruit weight loss, the decreases in peel h° and flesh L*, but increased flesh C* during storage. The results indicate positive effects of preharvest calcium sprays on olive firmness without any negative effect on fruits or leaves.

The Effect of Formulation and Amount of Potassium Fertilizer on Macromineral Concentration and Cation-Anion Difference in Tall Fescue

This study investigated the feasibility of altering the dietary cation-anion difference (DCAD) in grass by altering the grass variety and the amount and formulation of K fertilizer application. In experiment 1, treatments were combinations of 2 varieties (Barcel and Hi-Mag) of tall fescue (Festuca arundinacea Schreb); 2 rates of K (0 and 250kg/ha), supplied as KCl; and 2 rates of Mg (0 and 60kg/ha), supplied as MgO. In experiment 2, K fertilizer was applied at 0 or 125kg/ha as KCl or K2SO4. There was no difference between HiMag and Barcel tall fescue in the concentrations of Mg, S, and Cl. Application of K fertilizer decreased concentrations of Mg, but the magnitude of the decrease was not consistent across harvests. Conversely, application of Mg fertilizer increased Mg concentrations, but again, the magnitude of the increase was not consistent across harvests. The concentrations of Ca were higher in HiMag than in Barcel tall fescue, with the magnitude of the difference increasing from first to last harvest. Potassium fertilizer decreased Ca concentrations in the first, fourth, and fifth harvests only. Calcium concentration was decreased by a greater magnitude in HiMag tall fescue as a result of Mg fertilization. The HiMag tall fescue contained lower concentrations of K than did Barcel tall fescue in the first, second, and third harvests. Application of K fertilizer increased the K concentration in all 5 harvests but did not affect Na concentrations except in the last harvest. The HiMag tall fescue contained less Na than did Barcel, but the magnitude of the difference was affected by K and Mg fertilization. Application of K fertilizer decreased S concentrations in first-harvest grass, increased concentrations in second-and third-harvest grasses, and had no effect in fourth-or fifth-harvest grasses. Application of Mg fertilizer decreased S concentrations of tall fescue. Application of K fertilizer increased DCAD values for grass harvested from the second through fifth harvests. The increase in DCAD attributable to K fertilizer was less in HiMag than in Barcel tall fescue. Application of K fertilizer as K2SO4 increased dry matter yield and S concentrations of HiMag tall fescue, whereas K applied as KCl increased concentrations of K and Cl. There was no effect of fertilizer formulation on Na concentrations. The DCAD was lower in HiMag tall fescue fertilized with K2SO4 compared with that fertilized with KCl. This study showed that DCAD of grass can be manipulated by the choice of grass variety, fertilizer formulation, and fertilizer application rate.

Characterization of Dentin Formed in Transplanted Rat Molars by Electron Probe Microanalysis

The present study was designed to characterize dentin formed in transplanted rat molars by investigating calcium (Ca), phosphorus (P), and magnesium (Mg) concentrations using electron probe microanalysis (EPMA) as well as examining the rate of dentin matrix formation by vital staining. The unerupted immature lower right second molar in 2-week-old rats was transplanted into the upper right first molar socket. Rats were injected with oxytetracycline, calcein, and alizarin intraperitoneally at 1 day before and 1 and 2 weeks after transplantation, respectively, for vital staining. The maxillae and mandibles were fixed 3 weeks after transplantation, resected, and embedded in resin. Undemineralized sections were cut and examined by fluorescent microscopy and EPMA. The thickness of dentin formed in the first week after transplantation was significantly less than that of dentin formed in any other 1-week period in the transplanted tooth and was about one-fifth the thickness of dentin formed in control teeth. Formation of dentin recovered in the third week after transplantation. In the first week after transplantation, EPMA demonstrated a sharp increase in Mg concentration with a slight decrease in Ca concentration. Thereafter, no significant difference was identified among Ca, P, or Mg concentrations or the Ca/P ratio between transplanted and control teeth. These results suggest that disruption of the circulation and innervation by transplantation cause a temporary change in the matrix formation rate and elemental distribution of dentin, which is subsequently restored within 2 weeks after transplantation.