Ionic calcium levels during pregnancy, at delivery and in the first hours of life

Free calcium ion concentration (mmol/l) and pH were determined in whole blood using a semiautomatic electrode system (ICA-1 Radiometer, Copenhagen, Denmark) in 37 normal women, 90 pregnant women (30 from each trimester of gestation), 28 mothers at delivery and their respective newborns. The blood samples from normal controls, pregnant women, umbilical cord and 40-50-hour-old infants were collected anaerobically in vacuum tubes. Duplicate samples drawn from newborns shortly after birth by heel puncture were collected in special heparinized capillary tubes. We observed that Ca2+ concentrations in the second (1.20 +/- 0.04) and third (1.20 +/- 0.05) trimesters of pregnancy, and at delivery (1.18 +/- 0.05), were lower than in the control group (1.23 +/- 0.04). The [Ca2+] in samples from the umbilical vein (1.44 +/- 0.11) and artery (1.45 +/- 0.08) and from newborns 2-5 min after birth (1.34 +/- 0.12) was greater than in control samples. The [Ca2+] in newborns 40-50 hours after birth was lower (1.16 +/- 0.14) than in the control group.     

An Automated Low Ionic Antiglobulin Test

An automated antihuman globulin test has been performed by continuous flow analysis. Cell washing in acidic low ionic medium achieved sedimentation of aggregated cells and removal of supernatant fluid without centrifugation. These cells were subsequently disaggregated with hypertonic antihuman globulin serum, but human antibody-coated cells remained aggregated and were removed. Remaining red blood cells were hemolyzed, and their hemoglobin concentration was measured colorimetrically. This automated method detected antibodies of the Kell, Duffy, Kidd, and Lewis blood group systems.     

Relative bioavailability of calcium from calcium formate, calcium citrate, and calcium carbonate

Calcium is an essential nutrient required in substantial amounts, but many diets are deficient in calcium making supplementation necessary or desirable. The objective of this study was to compare the oral bioavailability of calcium from calcium formate, a new experimental dietary calcium supplement, to that of calcium citrate and calcium carbonate. In a four-way crossover study, either a placebo or 1200 mg of calcium as calcium carbonate, calcium citrate, or calcium formate were administered orally to 14 healthy adult female volunteers who had fasted overnight. After calcium carbonate, the maximum rise in serum calcium ( approximately 4%) and the fall in serum intact parathyroid hormone 1-84 (iPTH) (approximately 20-40%) did not differ significantly from placebo. After calcium citrate, the changes were modestly but significantly (p < 0.05) greater, but only at 135 to 270 min after ingestion. In contrast, within 60 min after calcium formate serum calcium rose by approximately 15% and serum iPTH fell by 70%. The mean increment in area under the plasma concentration-time curve (0-270 min) for serum calcium after calcium formate (378 mg . min/dl) was double that for calcium citrate (178 mg . min/dl; p < 0.01), whereas the latter was only modestly greater than either placebo (107; p < 0.05) or calcium carbonate (91; p < 0.05). In this study, calcium formate was clearly superior to both calcium carbonate and calcium citrate in ability to deliver calcium to the bloodstream after oral administration. Calcium formate may offer significant advantages as a dietary calcium supplement.     

Meta-analysis of calcium bioavailability: a comparison of calcium citrate with calcium carbonate

OBJECTIVE: To perform a meta-analysis of data from available published trials comparing the bioavailability of calcium carbonate with that of calcium citrate. DATA SOURCES: The whole set was comprised of 15 studies involving 184 subjects who underwent measurement of calcium absorption from calcium carbonate and calcium citrate. Category A excluded four studies for lack of physiological relevance, use of a mixed preparation with low content of calcium carbonate, or wide variability in results. Category B was comprised of five studies (from Category A) involving 71 subjects who took calcium supplements on an empty stomach. Category C was comprised of six studies (from Category A) involving 65 subjects who took calcium preparations with meals. METHOD: The meta-analysis of calcium absorption data from calcium carbonate and calcium citrate, with calculation of effect size and 95% confidence intervals. RESULTS: Calcium absorption from calcium citrate was consistently significantly higher than that from calcium carbonate by 20.0% in the whole set, by 24.0% in Category A, by 27.2% on an empty stomach, and by 21.6% with meals. CONCLUSION: Calcium citrate is better absorbed than calcium carbonate by approximately 22% to 27%, either on an empty stomach or co-administered with meals.     

Comparison of serum total calcium, albumin-corrected total calcium, and ionized calcium in 1213 patients with suspected calcium disorders

The correlations between serum ionized calcium, serum total calcium, total calcium corrected for albumin and calculated ionized calcium were investigated in a prospective multicentre investigation of 1213 patients suspected of having calcium metabolic disease. Diagnostic discordance between serum total calcium and measured ionized calcium was found in 31% of the patients. With the calculation of albumin-corrected total calcium or calculated ionized calcium the discordance decreased to 17.9%. The diagnostic discordance which could be ascribed to the analytical imprecision (CV = 1.5%) amounted to only 6.7%. Although we found highly significant correlations between the parameters, a considerable scatter around the regression line made prediction of ionized calcium from albumin-corrected total calcium unreliable in many patients.     

Nonspecific Ionic Inhibition of Ethambutol Binding by Mycobacterium smegmatis

Magnesium sulfate and spermidine were tested for their effects on binding of (14)C-ethambutol by Mycobacterium smegmatis. Concentrations were used that protected the organism from ethambutol inhibition. Sodium salts were examined as possible ethambutol antagonists to test the previously reported specificity of the divalent cation salt effect. Consistent with growth-protection experiments, 20 mM MgSO(4) or 2.0 mM spermidine prevented and reversed (14)C binding by cells shaken with 0.2 mug of (14)C-ethambutol per ml of Sauton medium at 37 C. Sodium salts were not effective ethambutol antagonists when tested at 20 mM, but at concentrations equivalent in ionic strength (mu) to that provided by 20 mM MgSO(4) they were effective. Thus, 20 mM MgSO(4), 80 mM NaCl, or 27 mM Na(2)SO(4) (mu = 0.08) all gave similar results in growth protection and binding experiments, suggesting that MgSO(4) antagonism is a nonspecific ionic effect. Because spermidine (mu 相似文献   

Receptor-regulated calcium entry

A wide variety of hormones and neurotransmitters activate cellular responses by mobilizing cellular Ca2+. In general, this Ca2+ mobilization response is comprised of a release of Ca2+ from intracellular stores, as well as increased entry of Ca2+ into the cytoplasm from the extracellular space. The mechanism for release of intracellular Ca2+ results from the Ca2(+)-mobilizing actions of a second messenger, D-myo-inositol 1,4,5-trisphosphate. Inositol polyphosphates appear also to be involved in the activation of Ca2+ entry, but the mechanism by which this is accomplished is less clear. According to the capacitative model for Ca2+ entry, the depletion of the agonist-regulated intracellular Ca2+ pool by the action of D-myo-inositol 1,4,5-trisphosphate is somehow coupled to the activation of Ca2+ entry. The evidence for this model comes from the demonstration, by diverse strategies, that the same Ca2+ entry mechanism normally activated by Ca2(+)-mobilizing agonists can be equally well triggered by depletion of the intracellular Ca2+ pool, even in the absence of receptor activation or elevated cellular levels of inositol polyphosphates.     

Pyocyanin Production by Pseudomonas aeruginosa Confers Resistance to Ionic Silver

Silver in its ionic form (Ag⁺), but not the bulk metal (Ag⁰), is toxic to microbial life forms and has been used for many years in the treatment of wound infections. The prevalence of bacterial resistance to silver is considered low due to the nonspecific nature of its toxicity. However, the recent increased use of silver as an antimicrobial agent for medical, consumer, and industrial products has raised concern that widespread silver resistance may emerge. Pseudomonas aeruginosa is a common pathogen that produces pyocyanin, a redox toxin and a reductant for molecular oxygen and ferric (Fe³⁺) ions. The objective of this study was to determine whether pyocyanin reduces Ag⁺ to Ag⁰, which may contribute to silver resistance due to lower bioavailability of the cation. Using surface plasmon resonance spectroscopy and scanning electron microscopy, pyocyanin was confirmed to be a reductant for Ag⁺, forming Ag⁰ nanoparticles and reducing the bioavailability of free Ag⁺ by >95% within minutes. Similarly, a pyocyanin-producing strain of P. aeruginosa (PA14) reduced Ag⁺ but not a pyocyanin-deficient (ΔphzM) strain of the bacterium. Challenge of each strain with Ag⁺ (as AgNO₃) gave MICs of 20 and 5 μg/ml for the PA14 and ΔphzM strains, respectively. Removal of pyocyanin from the medium strain PA14 was grown in or its addition to the medium that ΔphzM mutant was grown in gave MICs of 5 and 20 μg/ml, respectively. Clinical isolates demonstrated similar pyocyanin-dependent resistance to Ag⁺. We conclude that pseudomonal silver resistance exists independently of previously recognized intracellular mechanisms and may be more prevalent than previously considered.     

人工骨材料磷酸钙及硫酸钙在腱-骨愈合中的作用

背景:有关促进腱-骨愈合的方法文献报道很多,主要方法就是给腱-骨间隙添加一些刺激物质,以此促进腱骨的愈合.磷酸钙盐作为生物活性材料具有骨传导性,已广泛应用于临床骨缺损的替代和填充.而硫酸钙作为人工材料,具有潜在的骨诱导活性.目的:在自体腘绳肌肌腱移植重建膝关节前交叉韧带过程中,观察人工骨材料磷酸钙及硫酸钙促进腱-骨愈合的效应.方法:选用36条雄性成熟比格犬,先行切断双侧膝关节前交叉韧带,取同侧后肢趾长屈肌腱作为移植物,采用悬吊式固定重建前交叉韧带.按随机数字表法分为3组,磷酸钙组于股骨腱骨隧道中注入磷酸钙,硫酸钙组注入硫酸钙,空白组韧带重建结束后不添加任何填充物.分别于重建后1,2,3,4,6个月取材行大体观察、组织学和生物力学观测.结果与结论:前交叉韧带重建后1,2,3,4个月时,磷酸钙组及硫酸钙组腱骨界面纤维连接明显强于空白组,而磷酸钙组、硫酸钙组差异无显著性意义.6个月时,各组愈合程度相似.生物力学方面,重建后1个月时,磷酸钙组及硫酸钙组腱骨界面的抗拉脱强度均高于空白组(P < 0.05),而磷酸钙组、硫酸钙组差异无显著性意义(P > 0.05).提示磷酸钙及硫酸钙均能促进腱-骨愈合,两者之间无明显差异.     

人工骨材料磷酸钙及硫酸钙在腱-骨愈合中的作用

背景：有关促进腱-骨愈合的方法文献报道很多,主要方法就是给腱-骨间隙添加一些刺激物质,以此促进腱骨的愈合。磷酸钙盐作为生物活性材料具有骨传导性,已广泛应用于临床骨缺损的替代和填充。而硫酸钙作为人工材料,具有潜在的骨诱导活性。目的：在自体腘绳肌肌腱移植重建膝关节前交叉韧带过程中,观察人工骨材料磷酸钙及硫酸钙促进腱-骨愈合的效应。方法：选用36条雄性成熟比格犬,先行切断双侧膝关节前交叉韧带,取同侧后肢趾长屈肌腱作为移植物,采用悬吊式固定重建前交叉韧带。按随机数字表法分为3组,磷酸钙组于股骨腱骨隧道中注入磷酸钙,硫酸钙组注入硫酸钙,空白组韧带重建结束后不添加任何填充物。分别于重建后1,2,3,4,6个月取材行大体观察、组织学和生物力学观测。结果与结论：前交叉韧带重建后1,2,3,4个月时,磷酸钙组及硫酸钙组腱骨界面纤维连接明显强于空白组,而磷酸钙组、硫酸钙组差异无显著性意义。6个月时,各组愈合程度相似。生物力学方面,重建后1个月时,磷酸钙组及硫酸钙组腱骨界面的抗拉脱强度均高于空白组（P〈0.05）,而磷酸钙组、硫酸钙组差异无显著性意义（P〉0.05）。提示磷酸钙及硫酸钙均能促进腱-骨愈合,两者之间无明显差异。     

低钙透析液对维持性血液透析患者钙磷代谢及甲状旁腺激素的影响

目的探讨低钙透析液对非低钙血症维持性血液透析患者的钙磷代谢以及甲状旁腺激素的影响。方法将60例非低钙血症维持性血液透析患者随机分为观察组与对照组,观察组采用低钙透析液(Ca~(2+)浓度为1.25 mmol/L),对照组采用常规透析液(Ca~(2+)浓度为1.50 mmol/L),比较2组患者的疗效。结果治疗后,观察组患者血清T-Ca、T-Ca×P显著下降,血清i PTH显著升高(P0.05);对照组患者血清T-Ca、T-Ca×P显著升高,血清i PTH显著下降(P0.05)。观察组患者血清T-Ca、T-Ca×P均显著低于对照组,血清i PTH均显著高于对照组(P0.05)。治疗6个月后,观察组患者血清hs-CRP显著低于对照组(P0.05)。2组患者不良反应发生率无显著差异(P0.05)。结论非低钙血症维持性血液透析患者应用低钙透析液可以降低血清高钙负荷,改善甲状旁腺过度抑制状态与心血管炎症状态。     

Assessment of the calcium homeostatic state using the double calcium tolerance test

An acute tolerance test per os using calcium (Ca) lactate at a dose of 0.25 mmol of Ca per kg of body mass (calcium tolerance test--CTT) was performed twice in healthy persons (HP) and in patients with chronic heart failure (CHF) of various degrees: before and after 3-day administration of the same dose of Ca lactate. The "double" CTT made it possible to detect in HP and CHF a "phenomenon of adaptation" to Ca excess in the body based probably on changes in the activity of calcium-regulating hormones. It was manifested in less marked and prolonged tolerance hypercalcemia and a more rapid and effective calciuretic reaction, and probably in decreased intestinal absorption of Ca. It pointed to reversibility of Ca metabolic derangements even in severe CHF and a possibility of their non-medicamentous correction.