Factors affecting the precipitation of calcium phosphatein vitro

The precipitation of calcium phosphatein vitro was studied in order to define the processes of homogeneous and heterogeneous nucleation and to study the effect of certain inhibitors of crystallization on these processes. It was shown that the solubility-determining surface phase of the calcium phosphate formed by homogeneous nucleation had a Ca/P molar ratio close to that of octacalcium phosphate (OCP) and that the most constant formation product in solution at the onset of spontaneous precipitation was that of OCP. Known inhibitors of crystallization had no effect on the formation product of homogeneous nucleation. Below the formation product of spontaneous precipitation nucleation was essentially heterogeneous and was markedly influenced by adding nucleating material to the system, by increasing the time of incubation, and by adding inhibitors of crystallization containing the grouping P-X-P (where X=O, C, or N). The level of supersaturation at the point of maximum inhibition was close to the formation product of spontaneous precipitation of calcium phospate. The implications of these observations are discussed in relation to the precipitation of calcium salts in urine.     

Effects of a single dose of fluoride on calcium metabolism

Summary Fluoride 27 mg was given perorally to 14 subjects. It was found that the serum fluoride concentration increased followed by a decrease to normal levels during 24 h. Serum concentrations of calcium and phosphate decreased initially whereas those of serum immunoreactive parathyroid hormone increased. After 24 h the measured quantities were within normal limits. The results are discussed with reference to mineralization of hard tissues and to fluoride treatment of osteoporotic patients.     

Medullary nephrocalcinosis in nephropathic cystinosis

Children with nephropathic cystinosis excrete large amounts of calcium and phosphate due to renal tubular Fanconi syndrome, and also receive substantial supplements of phosphate and alkalinizing agents Since these constitute risk factors for nephrocalcinosis, we evaluated 41 children age 2 months to 15 years with nephropathic cystinosis and good renal function by performing retroperitoneal ultrasound examinations in a blinded fashion. We also retrospectively analyzed parameters of calcium and phosphate metabolism representing 216 person-years of data on these children. Fifteen children had no evidence of medullary nephrocalcinosis, while 18 had mild nephrocalcinosis, and 8 severe nephrocalcinosis; 5 had renal stones. Mean urine calcium and phosphate concentrations increased from 1.47 mM and 5.30 mM, respectively, in children without nephrocalcinosis to 1.60 mM and 5.69 mM in children with mild nephrocalcinosis to 1.66 mM and 6.19 mM in children with severe nephrocalcinosis. Mean urine pH ranged from 7.5 to 8.1. The mean (±SD) age of the 26 patients with nephrocalcinosis was 9.4±3.8 years compared with 5.1±3.8 years for those without nephrocalcinosis (P<0.005). Serum calcium, phosphate, vitamin D, and parathyroid hormone did not correlate with frequency or degree of nephrocalcinosis. We conclude that nephrocalcinosis frequently accompanies nephropathic cystinosis, can be detected by ultrasound examination, and might be managed by reducing oral replacement of phosphate, calcium, vitamin D, and citrate. Consideration should be given to truncating phosphate replacement once bone growth ceases.     

Fluoride and calcification of rat aorta

The relation between fluoride and calcification of the aorta has been studied in two systems: the intact rat and anin vitro preparation of the thoracic aorta incubated in serum. Vitamin D₃ produced a ten-fold increment in calcium concentration and a twelve-fold increase in phosphate levels of the dry aorta. Fluoride did not affect the deposition of calcium, but significantly blocked the increase in phosphorus in the aorta of the vitamin D₃-treated animals. In control rats, fluoride did not affect the incorporation of either calcium or phosphorus. The concentration of fluoride in the aortas of rats receiving only corn oil by intubation was not affected by long term exposure to drinking water containing 50 ppm F. Vitamin D₃ produced a nine-fold increase in fluoride concentration in the aorta of the rats receiving fluoride in the drinking water when compared to the vitamin D₃ rats receiving distilled water. It appears that long-term exposure to fluoride in the drinking water neither initiates calcification in the aorta nor potentiates calcification induced by vitamin D₃. Von Kossa stain showed pronounced calcification of the aortas in rats receiving vitamin D₃ but none was seen in the rats receiving distilled water alone. Resorcin-fuchsin-methyl green stain for elastic fibers showed destruction in regions of calcification in rats receiving vitamin D₃ but not in those receiving fluoride alone. Fluoride did not appear to alter the histological picture seen in the aortas of rats receiving vitamin D₃. In thein vitro model, rat thoracic aortas were incubated for 24 hours in rat serum containing⁴⁵Ca and 0.14, 0.56 and 1.12 ppm F. Fluoride at all levels significantly inhibited⁴⁵Ca uptake.Work done at the National Institute of Dental Research, NIH, Bethesda, Maryland, U.S.A.     

Late-onset downregulation of NaPi-2 in experimental Fanconi syndrome

The pathogenesis of renal phosphate (Pi) leak in Fanconi syndrome is unknown. Disorders of apical membrane transporters, leaky apical membrane, depleted cellular Pi and ATP, and impaired sodium (Na) pumps have been proposed as underlying defects. The present study examined the role of type II Na-Pi cotransport system (NaPi-2) in experimental Fanconi syndrome in rats. Following a single injection of maleic acid (MA), 75 mg/kg body weight IP, rats were sacrificed after 90 min, 4 h, and 24 h. Renal cortical expression of NaPi-2 mRNA was determined by Northern blotting, and brush border membrane (BBM) NaPi-2 protein by Western blotting. Increased urinary excretion of phosphate was demonstrated as soon as 90 min after MA injection, and was sustained at 4 and 24 h. NaPi-2 mRNA expression and NaPi-2 protein were not decreased after 90 min. NaPi-2 mRNA decreased after 4 h, while NaPi-2 protein decreased only at 24 h. Hence, the immediate phosphaturia in experimental Fanconi syndrome may be independent of NaPi-2 downregulation, possibly resulting from energy depletion or membrane dysfunction. The decrease in NaPi-2 mRNA expression and the subsequent NaPi-2 protein decrease may account for the second-phase phosphaturia. Received: 21 August 2000 / Revised: 18 December 2000 / Accepted: 22 December 2000     

Phosphate concentration in artificial tears

Background Irrigating solutions and eye drops may contain phosphates as part of their buffer system. In the presence of epithelial keratopathy, a high concentration of phosphate favours corneal calcification. Knowledge of the phosphate concentration in artificial tear products helps to prevent this sight-threatening complication. This study gives an overview on the amount of phosphate contained in artificial tears.Methods Fifty-nine samples of commercially available artificial tear preparations were tested. The quantification of phosphate was performed using the molybdate method on a Modular P autoanalyzer.Results Twenty-six of 59 (44%) artificial tear products had a phosphate concentration above physiological levels (>1.45 mmol/l). A phosphate concentration above 25 mmol/l was found in nine products (15%), a concentration higher than 50 mmol/l in three (5%).Conclusions Many artificial tear formulations contain unphysiological levels of phosphate, but very high concentrations are found only in a few products. These preparations have the potential to favour the formation of insoluble crystalline calcium phosphate deposits when used on a damaged corneal surface, and should therefore be used cautiously.This work has not previously been presented.     

HPLC法测定浓维磷糖浆中咖啡因的含量

目的:建立浓维磷糖浆中咖啡因的含量测定方法。方法:采用高效液相色谱法,色谱柱为C18柱,流动相为甲醇-水(60:40),检测波长为273 nm。结果:咖啡因在15-90μg·ml-1范围内浓度与峰面积之间呈良好的线性关系(r=0.999 9),回收率为100.2%,RSD=0.78%(n=6)。结论:本法简便,准确,专属性强,可用于浓维磷糖浆的质量控制。     

海南省新生儿葡萄糖-6-磷酸脱氢酶缺乏症的基因突变型分析

[目的]通过对新生儿疾病筛查中确诊的葡萄糖-6-磷酸脱氢酶(G6PD)缺乏症患儿进行基因检测,确定海南省新生儿G6PD缺乏症的分子生物学基础.[方法]通过荧光斑点法在新生儿群体中筛查出可疑或阳性者,经G6PD/6GPD比值法确诊.将G6PD缺乏症患儿静脉血做DNA直接扩增法(PCR)、PCR-等位基因特异的寡核苷酸探针(PCR-ASO)分析、PcR-限制性片段长度多态性(PCR-RFLP)分析和PCR-单链构型多态性(PCR-SSCP)分析,检测基因突变.[结果]G6PD缺乏症新生儿51例中属于G1 376T的16例(31.37%)、属于G1 388A的11例(21.57%)、属于A95G的4例(7.84%)、属于G392T的2例(3.92%)、属于G871A的2例(3.92%)、属于A835T的1例(1.96%),属于T517C的1例(1.96%);余14例没有发现上述突变.[结论]海南省新生儿G6PD缺乏症的基因突变型与我国该遗传病其他高发地区的基因突变谱相似;未发现A835G-G6PD-海口突变型.     

维持性血液透析患者磷结合剂用药依从性影响因素研究与药学干预

目的:研究维持性血液透析患者磷结合剂用药依从性的影响因素及药师干预效果,以提高患者的用药依从性,改善疾病控制的效果。方法:选取2019年6-12月在我院血液净化中心进行维持性血液透析患者,采用调查问卷对其一般资料、磷结合剂用药依从性、疾病与用药知识掌握水平、社会支持度、自我效能等进行评估。采用t检验、χ²检验和多元Logistic回归等方法分析各影响因素与用药依从性之间的关系。将患者随机分为药学干预组和非干预组,针对危险因素为药学干预组提供3个月的药学服务,然后比较两组患者的血磷水平、用药依从性等指标。结果:共有298例患者有效完成调查问卷(有效回收率为96.1%)。其中,163例患者(54.7%)依从性良好、135例患者(45.3%)依从性差。单因素分析结果表明,磷结合剂用药依从性与患者年龄、透析龄、甲状旁腺激素水平、每日服药总数量、每日磷结合剂服药数量、疾病与药物知识掌握水平、社会支持度、自我效能显著相关(P<0.05);多元Logistic回归结果显示,每日服药总数量、每日磷结合剂服药数量、药物与疾病知识掌握水平、社会支持度、自我效能是影响患者磷结合剂用药依从性的独立危险因素(P<0.05或P<0.01)。药学干预组用药依从性、疾病控制情况、疾病和药物相关知识掌握水平、社会支持度和自我效能均较非干预组显著改善或提高,血磷水平较非干预组显著降低(P<0.05)。结论:每日服药总数量、每日磷结合剂服药数量、药物与疾病知识掌握水平、社会支持、自我效能是影响磷结合剂用药依从性的独立危险因素。维持性血液透析患者磷结合剂用药依从性偏低;药师对上述危险因素采取个体化、有针对性的干预措施能有效提高患者的用药依从性,改善疾病预后。     

Dysfunction of the adrenergic system in phosphate depleted rats

Plasma catecholamines and vascular response to noradrenaline were studied in phosphate depleted rats. Phosphate depletion was induced in rats by dietary phosphorus deprivation for 6 weeks. Basal plasma concentrations of noradrenaline, adrenaline and dopamine were elevated in phosphate depleted rats compared to pairfed control rats. After exposure to cold (4° C, 45 min) the rise in plasma catecholamines was much more pronounced in phosphate depleted rats. In the isolated perfused rat heart, the uptake of tritiated noradrenaline was unchanged. In the isolated perfused hindlimb preparation the vascular response to noradrenaline, but not to potassium chloride and argininevasopressin was significantly diminished in phosphate depleted rats.It is concluded that in phosphate depletion sympathetic activity is elevated and vascular response to noradrenaline diminished.