The influence of hypomagnesemia on erythrocyte antioxidant enzyme defence system in mice

The effect of magnesium deficiency on antioxidant defence system was studied in RBC of mice suffering from hypomagnesemia. The animals were kept for 8, 15 and 22 days on magnesium-deficient diet with consequent reduction of magnesium level in plasma by 38% at the first 8 days and by 64% after 22 days of experiment. The activities of the most important antioxidant enzymes, catalase, glutathione peroxidase, superoxide dismutase, glutathione reductase, glutahione S-transferase were assayed in hemolysates. The level of reduced glutathione in erythrocytes was measured as well. Apart from catalase, the activities of antioxidant enzymes were decreasing. The activity of superoxide dismutase decreased gradually during the experiment and on the 15th and 22nd day of experiment was significantly (P<0,05) lowered by 30 and 32% respectively. The catalase activity was increased on each point of the experiment with the peak value up to 149% on 15th day, and by 32% on 22nd day. Glutathione peroxidase activity was insignificantly reduced. The reduction of Glutatione reductase and Glutathione S-transferase activities by 24 and 21%, respectively, were observed after 8 days of the experiment with a further downward tendency. The reduced glutathione was significantly depleted after 8 days by 33% and was kept on that level in the course of the study. These findings support previous reports on the hypomagnesemia – induced alteration in endogenous enzyme antioxidant defences and glutathione redox cycle of mice.     

Role of Activity of Gastrointestinal Microflora in Absorption of Calcium and Magnesium in Rats Fed β1-4 Linked Galactooligosaccharides

Rats fed a diet containing β1-4 linked galactooligosaccharides (GOS) (5 g/100 g of diet) absorbed calcium and magnesium more efficiently than those fed the control diet. However, the increment obtained through GOS-feeding was reduced by neomycin sulfate 0.67 g/100 g of diet). Since the decrease in cecal pH in rats fed GOS was suppressed by neomycin-feeding, bacterial action in the digestive tract was considered to be reduced by neomycin-feeding. Our findings suggest that the action of intestinal bacteria is necessary for the effects of GOS.     

Effects of essential divalent metals on carcinogenicity and metabolism of nickel and cadmium

Interactions between the physiologically essential metals calcium, magnesium, and zinc and the carcinogenic metals nickel and cadmium were investigated to help elucidate the mechanisms of action of the carcinogenic metals. Bioassay studies revealed several significant findings, including: (1) the ability of magnesium and calcium to inhibit nickel-induced elevation of pulmonary adenoma incidence in strain A mice; (2) the ability of magnesium, but not of calcium, to prevent cadmium-induced subcutaneous sarcoma formation; and (3) the ability of magnesium, but not of calcium, to inhibit nickel-induced muscle tumor formation. Biochemical studies indicated a direct relationship between the antitumorigenic potential of magnesium and the capacity of this metal to: (1) inhibit nickel and cadmium uptake by the target tissues in vivo; (2) inhibit nickel-induced disturbances in DNA synthesis in vivo; (3) inhibit nuclear and cytosolic uptake of nickel by the target tissue cells in vivo; and (4) inhibit nickel and cadmium binding to DNA in vitro. Calcium, which in most cases did not prevent carcinogenesis, had no consistent influence on the uptake of carcinogenic metals or their biochemical effects in the target tissues. Magnesium and zinc, but not calcium, were also found to attenuate the acute toxic effects of nickel, indicating a possible correlation between prevention of acute effects and reduction in tumorigenicity. Zinc, which antagonizes cadmium tumorigenicity in the rat testis, was found to reduce markedly cadmium uptake into isolated testicular interstitial cells. Also, zinc was found to inhibit strongly cadmium binding to DNA in vitro.     

Nutrient uptake by barley roots under field conditions

A field study with barley was conducted in 1984 and 1985 to provide data on uptake rates of N, P, K and Mg and their variation as the growing season progressed. Two varieties were grown: Galt in 1984 and Otal in 1985. Soil fertility was maintained at or near optimum conditions. Samples were obtained approximately every 10 days for shoot dry weight, nutrient content and root length measurements. The approximate method (Williams, 1948) traditionally used for calculating uptake rates was found to be invalid for most of the nutrients studied. The method used for measuring uptake rates was the functional approach proposed by Hunt (1973). Inflow,i.e. uptake rate per unit root length, of plant nutrients, decreased with time. However, maximum uptake rates measured in kg ha^–1d^–1 occurred at about 50 days from sowing because of increasing root length density with time. Inflow or uptake rates were low in 1985 because of moisture deficiency, and grain yield (0.89 t ha^–1) was severely depressed. This study demonstrated that Hunt's method is superior and more advantageous than the traditional, approximate method.     

Survival ofSclerotinia minor Jagger sclerotia in solarized soil

Calcium, magnesium and potassium dynamics in decomposing litter of three tree species were measured over a two-year period. The speices studied were flowering dogwood (Cornus florida), red maple (Acer rubrum) and chestnut oak (Quercus prinus). The order of decomposition was:C. florida>A. rubrum>Q. prinus.Calcium concentrations increased following any initial leaching losses. However, there were net releases of Ca from all three litter types since mass loss exceeded the increases in concentration. Net release of Ca by the end of two years from all three species combined was 42% of initial inputs in litterfall. Magnesium concentrations increased in the second year, following decreases due to leaching during the first year inC. florida andA. rubrum litter. Net release of Mg by the end of two years was 58% of initial inputs. Potassium concentrations decreased rapidly and continued to decline throughout the study. Net release of K by the end of two years was 91% of initial inputs.These data on cation dynamics, and similar data on N, S and P dynamics from a previous study, were combined with annual litterfall data to estimate the release of selected nutrients from foliar litter of these tree species at the end of one and two years of decomposition. The relative mobility of all six elements examined in relation to mass loss after two years was; K>Mg>mass>Ca>S>P>N.     

Effects of limestone and gypsum application to a Malaysian ultisol on soil solution composition and yields of maize and groundnut

A field experiment was conducted on an Ultisol in Malaysia to assess changes in soil solution composition and their effects on maize and groundnut yields, resulting from limestone and gypsum application. The results showed that soil solution Ca in the lime treatment remained mainly in the zone of incorporation, but in the gypsum treatment some Ca moved into 15–30 cm zone. Al³⁺ and AlSO₄ ⁺ were dominant Al species in the soil solution of nil treatment. Liming decreased Al³⁺ and AlSO₄ ⁺, but increased hydroxy-Al monomer activities. However, gypsum application resulted in an increase of AlSO₄ ⁺ activity and in a decrease of Al³⁺ activity. Relative maize and groundnut yields were negatively correlated with Al³⁺, Al(OH)²⁺ and Al_sum activities. Likewise, relative yields were negatively correlated with Al concentration and the Al concentration ratio and positively correlated with soil solution Mg concentration and Ca/Al ratio.     

Role of magnesium in combination with liming in alleviating acid-soil stress with the aluminium-sensitive sorghum genotype CV323

An experiment to study the effects of Mg nutrition on root and shoot development of the Al-sensitive sorghum (Sorghum bicolor (L.) Moench) genotype CV323 grown in pots of sandy loam under different acid soil stress is reported. This experiment had a factorial design: four rates of liming were combined with four rates of Mg fertilization. When no Mg was added, the pH of the soil solutions (collected in ceramic cups) increased from 4.0 (unlimed) to 4.2, 4.7 and 5.9 at the increasing rates of liming. After 30 days of growth dry matter yields of the limed treatments were 40%, 115% and 199% higher than that of the unlimed treatment. Without liming and at the highest liming rate, adding Mg did not affect plant biomass significantly. At the two intermediate levels of liming, however, 11.3 mg extra Mg per kg soil increased dry matter yield to the same levels as found at the highest liming rate. Concentrations of Mg in the soil solution rose after Mg was added and fell when lime was added, but adding both Mg and lime increased Mg concentrations in the plant shoots. In plants of the limed treatments, dry matter yield was correlated closely with the Mg concentration in the shoot. This was not so in the unlimed treatment. Furthermore, in the unlimed treatments root development was inhibited, but reduced Mg uptake by the plants resulted mainly from the direct effect of Al- (or H-) ions in the soil solution rather than from impaired root development. It is concluded that Mg fertilization counteracted the interfering effects of Al- and H ions on Mg uptake.     

Cardiac copper,magnesium, and zinc in recent and old myocardial infarction

X-ray fluorescence spectrometry and atomic absorption spectrometry were used in a quantitative study of zinc, copper, and magnesium in 71 postmortal human hearts. Samples were obtained from individuals who had demonstrated no previous clinical or subsequent pathological findings of myocardial infarction and from victims of a recent or an old infarction. A significant difference (p<0.001) in the elemental levels was observed between the noninfarct and the recent infarct groups. The noninfarct group had higher cardiac levels of all three elements. However, the difference in elemental concentrations between the noninfarct and the old-infarct groups was not significant. Cardiac levels of zinc (p<0.001) and copper (p<0.01) were significantly greater in the old-infarct group than in the recent-infarct group. Magnesium levels were higher in the recent-and-old-infarct group than in the recent infarct group (p<0.01). It is possible that the elements are redistributed during myocardial infarction, and that uptake of these elements (from the serum pool) by the heart may be important in maintaining myocardial integrity and function.     

Nutrition of winter wheat during the life cycle. I. Yield and accumulation of dry matter and minerals

Mineral uptake by winter wheat (Trilicum aestivum L. cv. Martonvasari 8) was studied throughout the life cycle. Accumulation of macronutrients (i.e. total nitrogen, phosphorus, potassium, sodium, magnesium and calcium) and the water content of roots and shoots of plants grown in complete nutrient solution were higher than those of plants grown in two types of soils. The supply of macronutrients was in some cases limiting for soil-grown plants as revealed by a comparison of available and accumulated amounts of these nutrients. Their supply was abundant, however, for solution-grown plants. This led to a doubling of grain yield for the latter plants with a three fold increase in accumulation of dry matter and a five-fold increase in fresh weight. The efficiency ratios of solution-grown plants to soil-grown plants were approximately 1 for N and Na, 0.5 for Mg and Ca, and 0.3 for P and K.     

Net Mg2+ uptake in relation to the amount of exchangeable Mg2+ in the Donnan free space of ryegrass roots

Ammonium acetate and BaCl₂-triethanolamine were used to desorb Mg²⁺ from the root Donnan free space (DFS) of 23-d-old ryegrass (Lolium multiflorum Lam. cvs. Gulf and Wilo). Amounts of desorbed Mg²⁺ increased with the increase in Mg²⁺ activity of the nutrient solution. Slightly less Mg²⁺ was desorbed by Ba²⁺ than by NH₄ ⁺. Previously published data on short-term net Mg²⁺ uptake by intact 23-d-old ryegrass plants of the two cultivars were linearly related to the amount of exchangeable Mg⁺ desorbed from the root DFS (r²=0.90 and 0.81 for the desorption by NH₄ ⁺ and Ba²⁺, respectively). A sward of Mg²⁺ ions attracted to the negative charges of the cell surface is suggested to represent a part of a pool of Mg²⁺ available for active transport through the plasmalemma.