Solubility of phosphorus added to four Manitoba soils with different calcium and magnesium contents

Summary The solubility of phosphorus was found to approximate that of dicalcium phosphate dihydrate and/or dimagnesium phosphate trihydrate when KH₂-PO₄, H₃PO₄ and K₂HPO₄ were added to four Manitoba soils. Eighty to one hundred, seventy to ninety and sixty to eighty per cent of the phosphorus added remained in solution when H₃PO₄, KH₂PO₄ and K₂HPO₄ were added, respectively. The solubility of the added phosphorus was high in all samples and relatively soluble compounds, dicalcium phosphate dihydrate and dimagnesium phosphate trihydrate, were most likely formed in the samples indicating that phosphorus added to these soils would be readily available to plants. Associate Professor and Professor respectively.     

Response of calcium-sensitive cells in the pars intermedia of the goldfish adapted to diluted sea water with different calcium and magnesium contents

Summary Goldfish kept in diluted Ca-free sea water (SW) (23 or 30 %) or in Ca-Mg-deficient SW (23 %) have a limited survival, release large amounts of mucus, and show spasmodic seizures. Plasma calcium decreases. The PAS-positive calcium-sensitive (Ca-s) cells of the pars intermedia show a low activity in diluted SW and in 23 % Mg-free SW. In diluted Ca-free SW, Ca-s cells are stimulated, but cell hypertrophy is not uniform and often restricted to an area adjacent to the proximal pars distalis. Nuclear hypertrophy is significant in the reactive area, although less pronounced or even absent at the periphery of the lobe. Mitotic activity occurs in the Ca-s cells of goldfish gradually adapted to diluted Ca-free SW and Ca-Mg-deficient SW, and sacrificed after 19 and 28 days, respectively. A general stimulation of the Ca-s cells, which remains less intense than that in goldfish kept in deionized water (DW), appears unable to ensure the survival of the goldfish in an isosmotic Ca-free environment containing Mg²⁺ (0.1, 12 or 16.8 mM). These data are compared with those obtained in the eel kept in Ca-free SW.     

湖南烟区土壤交换性钙、镁含量及对烤烟品质的影响

分析了湖南烟区主要土壤类型交换性钙、镁元素含量状况及其对烟叶品质的影响,结果表明:(1)土壤交换性钙、镁含量在不同土壤类型间存在显著性差异,交换性钙含量平均为8.87cmol/kg,以红壤含量最高;交换性镁含量平均为1.16cmol/kg,以黄棕壤含量最高;交换性钙镁比值大小依次为:红壤(11.74)>水稻土(10.25)>黄壤(6.84)>黄棕壤(6.14),在烟叶实际生产中,应重视镁肥在红壤和水稻土中的施用;(2)烟叶钙含量偏高(21.93g/kg±4.37g/kg),烟叶镁含量偏低(2.52g/kg±1.26g/kg),两者均存在广泛的变异性;(3)整体来看,烟叶钙含量随土壤中交换性钙含量的升高和镁含量的降低而显著升高;烟叶镁含量随土壤交换性镁含量的升高而升高,与土壤交换性钙含量的相关性不显著;(4)典型相关分析表明,土壤中交换性镁含量的降低可能引起烟叶钾含量的提高,从而使得烟叶钾素和镁素含量达到较好的平衡;(5)土壤交换性钙、镁含量与烟叶其它化学成分指标的相关分析表明,土壤交换性钙有利于烟株对硼和氯素的吸收,对氮、锌和锰素的吸收则有显著的抑制作用;而土壤交换性镁有利于烟叶总糖、硼素和锰素的积累,对氮、磷、铁和锌素的吸收具有显著的抑制作用。     

The effect of zinc and magnesium on calcium uptake into the rat duodenum slices

Summary The experiments were carried out on 80 male Wistar rats, divided into four groups as follows: group 1, treated orally with ZnCl₂ at a dose of 10 mg Zn²⁺/kg for 14 days; group 2, control; group 3, MgCl₂-treated at a dose of 5 mg Mg²⁺/kg; group 4, treated with ZnCl₂ plus MgCl₂ in the same manner as groups 1 and 3. The influx of calcium into the rat duodenum slices was investigated in vitro by the method of Papworth and Patrick. Over a range of calcium concentrations (0–10 mM) the influx of this element was defined as a sum of a saturable term (active transport) and a linear term dependent on concentration (passive transport). In the zinc-treated rats only the saturable term was affected. The study of this term by Lineweaver-Burk plots showed a decrease of the half-saturation constant,K _t, while the maximal value,J _m, remained unchanged. Moreover, magnesium was shown to interact with zinc at gut level because simultaneous oral administration of Mg²⁺ and Zn²⁺ to rats protected them against the inhibition of calcium uptake observed when Zn²⁺ was given alone.     

Changes in iron, calcium, magnesium, copper, and zinc levels in different tissues of riboflavin-deficient rats

To clarify the changes of mineral levels in different tissues of riboflavin-deficient rats, Wistar rats were separated into three groups. One group was fed a diet ad libitum that was deficient in riboflavin. The other two were fed either the complete diet that was weight-matched to the riboflavin-deficient group or fed a complete diet ad libitum. In riboflavin-deficient rats, the hemoglobin concentration and riboflavin contents of blood, liver, and kidney were significantly decreased, compared with weight-matched and ad libitum-fed controls. The mineral concentrations of tissues are summarized as follows: The iron (Fe) concentration in the heart, liver, and spleen was decreased in the riboflavin-deficient group compared with the other groups. Calcium (Ca) and magnesium (Mg) concentrations in tibia were decreased in the riboflavin-deficient group compared with the other two groups. Copper (Cu) concentration was increased in the heart and liver when the riboflavin-deficient group was compared with the other groups. Zinc (Zn) concentration was increased in tibia when the riboflavin-deficient group was compared with the other groups.     

Intestinal maturation: The effect of glucocorticoids on in vivo net magnesium and calcium transport in the rat

We investigated with an $\text{in vivo}$ single pass perfusion technique, the effect of glucocorticoids on net magnesium and calcium absorption from the small and large intestine of suckling and adolescent rats. In control rats, rates of net magnesium and calcium absorption were several fold greater in both small and large intestinal segments of suckling rats compared to corresponding rates in segments of adolescent rats. Methylprednisolone 30 mg/kg body weight daily for three days, suppressed significantly net magnesium and calcium absorption from the small and large intestinal segments of suckling rats only. Methylprednisolone had no effect on either net magnesium or calcium absorption in adolescent rats. The mechanism(s) responsible for the observed decrease in net magnesium and calcium absorption in the suckling period by glucocorticoids are discussed.     

Effect of prednisolone on the rat bone calcium, phosphorus and magnesium concentration

Adult male rats were given prednisolone (Urbason solubile = 6-methyl-prednisolone) in doses of 4 mg/100 g body weight for 10, 20 or 30 days and its effect on the calcium, phosphorus and magnesium content of their femurs was studied. At all the given intervals a statistically significant decrease in the magnesium content of the bone was found; the calcium content was significantly reduced only in the first phase of the experiment (at 10 days).