Stimulating effects of a diet negative in dietary cation–anion difference on calcium absorption from the rumen in sheep

The concept of feeding anionic salts in late gestation is widely used to prevent milk fever in dairy cows. While the effects of these diets on renal Ca excretion and tissue responsiveness towards parathyroid hormone have clearly been demonstrated, data on a potential impact on gastrointestinal Ca absorption are conflicting. Therefore, the aim of this study was to investigate the influence of feeding a diet negative in dietary cation–anion difference (DCAD) on ruminal mineral concentrations, fermentation products, electrophysiological properties of rumen epithelia and Ca flux rates. For this purpose, sheep were kept for 3 weeks on diets that were either positive or negative in DCAD. The induction of a compensated hyperchloremic metabolic acidosis could be demonstrated by increased plasma Cl and enhanced concentrations of ionised Ca, while plasma concentrations of and base excess were decreased with the low DCAD diet. Neither transmural potential differences nor fermentation products were affected, but ruminal concentrations of Cl and Mg as well as the relation of ionised to total Ca were increased. Ussing chamber experiments revealed alterations of electrophysiological parameters and an increase in the electroneutral component of Ca flux rates from the mucosal to the serosal side of rumen epithelium. As plasma calcitriol concentrations were not affected, it can be concluded that the administration of anionic salts results in a vitamin D‐independent stimulation of ruminal Ca transport.     

ROS mediates regulation of intracellular Ca2+ induced by angiotensin II in primarily cultured medullary neurons

AIM: To investigate the role of reactive oxygen species (ROS) in the regulation of intracellular Ca²⁺ induced by angiotensin II (Ang II) in the primarily cultured medullary neurons. METHODS: Primarily cultured medullary neurons were prepared from 14-day-old embryos of Sprague-Dawley rats in the study. The identification of medullary neurons was assessed by double-labeling immunofluorescence. To explore the role of ROS, mainly the superoxide (O₂^·), the O₂^·generation was measured using the fluorogenic probe dihydroethidium (DHE). To determine intracellular free calcium concentration ([Ca²⁺]_i), the neurons were loaded with the Ca²⁺-specific dye Fura-2/AM. The cell viability after adding Ang II was also examined using CCK-8 assay. RESULTS: Most of the cultured cells were medullary neurons, more than 80% of which were glutamate positive neurons. Ang II (5 μmol/L) increased the level of ROS within 10 min in the medullary neurons. Ang II at 5 μmol/L induced a significant[Ca²⁺]_i increase in the medullary neurons, and the effect of Ang II occurred rapidly and reached a peak within 20 min after administration. The level of[Ca²⁺]_i started to decline after washout. The Ca²⁺ elevation induced by Ang II was significantly decreased by apocynin or TEMPOL. No significant difference in the cell viability between control group and 5 μmol/L Ang II treatment group was observed. CONCLUSION: ROS is involved in the regulation of[Ca²⁺]_i induced by Ang II in the primarily cultured medullary neurons, suggesting a potential intracellular signaling mechanism involved in the Ang II-mediated oxidant regulation of central neural control of blood pressure.     

云南省部分地区烤烟适宜pH值范围的缓冲研究

对云南省部分地区烤烟土壤适宜pH值范围缓冲研究结果表明,1982年与2 0 0 2年相比2 0年中土壤pH值平均变小0 .30 ,占总平均值的4 .8%。山地土壤一般酸性较强,而发达地区土壤酸性变化更多。故云南省某些地区应施一定量Ca(OH) 2 以调节酸碱度     

Effects of aluminium and calcium on Picea abies seedlings

Newly‐germinated Norway spruce seedlings were grown for 15 weeks in pots of iron podzol soil that received additions three times a week of nutrient solution containing six levels of Al (0, 0.37, 0.74, 1.5, 3.0 or 6.0 mM) and two levels of Ca (0.09 or 0.46 mM). The Ca concentrations in shoots and roots decreased with increasing Al levels. Growth was suppressed at 0.74 mM Al in the nutrient solution, which gave 0.5 mM Al in saturated soil extracts at the end of the experiment.     

N-甲基-D-天冬氨酸(NMDA)对大鼠下丘脑生长抑素分泌及其mRNA表达的影响

N-甲基-D-天冬氨酸(NMDA)是动物机体内存在的一种天然氨基酸衍生物,参与下丘脑-垂体生长轴的调控分泌作用。本实验选用SD大鼠(Rattus norvegicus)下丘脑,采用神经细胞体外培养模型来研究NMDA对下丘脑合成和分泌生长抑素(SS)的影响。结果表明,适量浓度的NMDA可显著促进下丘脑神经细胞SS的分泌及其mRNA的表达,明显提高细胞内的Ca2+水平,并使cAMP浓度降低,表明SS基因表达和分泌的增加可能主要是通过Ca2+和环腺苷酸(cAMP)共同介导实现的。     

Soil Phosphorus Extracted by Three Anion Exchange Membranes Compared to Water-Soluble and Truog-Extractable Phosphorus

Effects of different kinds of anion exchange membrane (AEM) on soil P extracted by AEM (AEM P) were investigated in three soils (Cumulic Andosol, Yellow soil, and Gray Lowland soil). There was no significant difference in AEM P among the AEMs tested (BDH-Prolabo 551642S, AGC Engineering Selemion AMT, and AGC Engineering Selemion AMV). The AEM P was greater than water-soluble P in all soils. Although AEM P was greater than Truog-extractable P in Cumulic Andosol, the reverse was true in the Yellow soil and Gray Lowland soil.     

套袋红富士苹果果实发育过程中Ca~(2+)-ATPase活性变化

以红富士苹果(Malus domesticaBorkh.cv.‘Red Fuji’)为试材,研究了发育过程中以及成熟后期套袋果实Ca2+-ATPase的活性变化。结果表明,发育初期,苹果果实的Ca2+-ATPase活性较高,随着果实生长发育,Ca2+-ATPase活性逐渐下降,在发育后期Ca2+-ATPase活性有所提高。与对照相比,套袋红富士苹果果实Ca2+-AT-Pase的活性呈现先降低后升高又降低的变化趋势。发育后期,摘除果袋后苹果果实的Ca2+-ATPase活性与对照相比有显著增加。与对照相比,套袋降低苹果果实的Ca2+浓度。由此表明,套袋可能通过影响钙素的吸收运转和Ca2+-ATPase活性而调控苹果果实的生长发育和品质形成。     

Soil Chemical Attributes and Grape Yield as Affected by Gypsum Application in Southern Brazil

Yields of many crops are limited to subsoil acidity. Crop positive responses to gypsum have been shown, however, information regarding the use of gypsum in vine is scarce. A field trial was performed in Paraná State, Brazil, on a clayey Rhodic Hapludox to evaluate the effects of gypsum application (0, 3, 6, 9, and 12 Mg ha^?1) on soil chemical attributes and grape (cv. ‘Niagara Rosada’) yield. Gypsum was surface applied in July 2005 and the soil and plant evaluations were realized during the years of 2006 and 2007. Gypsum decreased the subsoil exchangeable aluminum (Al) level, increased the calcium (Ca) and sulfate (SO₄) contents in the soil profile, and caused leaching of magnesium (Mg) from the topsoil. The leached Mg resulted in decreases of leaf Mg concentrations and fruit production. The researchers estimated a critical level of Ca/Mg ratio in soil as well as in leaves of 1.9 for vine.     

Growth and composition of corn,alfalfa, and orchardgrass grown on soils contaminated with airborne dust containing Ca and Mg

Abstract

A greenhouse experiment was conducted with soils allegedly contaminated with airbourne dust containing Mg and Ca oxides and carbonates to study the growth and composition of corn, orchardgrass, and alfalfa plants. Soils were obtained from sites varying in distance from the alleged source of airbourne dust.

Soil pH values ranged from 6.2 to 8.7. Plant yields decreased only when the soil pH increased above 7.7. There was no apparent relationship between the observed yield decrease and the N, P, K, and B concentrations in the plants. Although the Mn and Zn concentrations generally decreased with increasing soil pH, the decrease was not great enough to account for the yield depressions. The obviously minor symptoms occurring on the plants growing on the most affected soils could not be associated with a deficiency or excess of any other element.

The Ca/Mg ratio in the alfalfa plants decreased as soil pH increased over the range from 6.2 to 8.7. However, the Ca/Mg ratios in the corn and orchardgrass plants decreased only when the soil pH values increased above 7.7. The apparent imbalance of Ca and Mg in the tissues may account for the yield depressions.