31P NMR as a spectroscopic monitor of the spontaneous precipitation of calcium phosphates

Summary High-resolution³¹P NMR spectroscopy is shown to be a potentially valuable new method for monitoring the spontaneous precipitation of calcium phosphates from metastable supersaturated solutions. An apparatus capable of pH-statting the sample in a spinning 20 mm NMR sample tube is briefly described. The spontaneous precipitation of dicalcium phosphate dihydrate, CaHPO₄· 2H₂O, pH-statted at pH 5, is characterized by a base-uptake curve which follows the decrease in the intensity of the solution³¹P resonance. The precipitation of amorphous calcium phosphate at neutral pH, which exhibited an induction period of ∼ 10 min, was also studied. No evidence of NMR peaks from transient clusters or the initial colloidal solid phase has been seen.     

Cardiovascular calcification in patients with end-stage renal disease

Vascular calcifications are very frequent extraosseous calcifications in patients with chronic renal disease. They occur in the intima and in the media. They are associated with decreased arterial elasticity and increased mortality. The risk factors are: advanced age, duration of dialysis treatment, diabetes, increased phosphate concentration, the dose of Ca-containing phosphate binders and inflammation. It is now well established that vascular smooth muscle cells actively take up phosphate to form bioapatite. This process is associated with a phenotypic transformation of vascular smooth muscle cells during which they express osteoblast markers. Lipids and inflammatory cytokines also increase bioapatite formation. Calcification inhibitors are matrix Gla protein and fetuin-A. Decreased serum fetuin-A concentration is associated with a higher mortality rate in dialysis patients. An important preventive measure for vascular calcification is the substitution of Ca-containing by non-Ca-containing phosphate binders.     

Absolute quantification of human liver metabolite concentrations by localized in vivo 31P NMR spectroscopy in diffuse liver disease

Phosphorus-31 NMR spectroscopy using slice selection (DRESS) was used to investigate the absolute concentrations of metabolites in the human liver. Absolute concentrations provide more specific biochemical information compared to spectrum integral ratios. Nine patients with histopathologically proven diffuse liver disease and 12 healthy individuals were examined in a 1.5-T MR scanner (GE Signa LX Echospeed plus). The metabolite concentration quantification procedures included: (1) determination of optimal depth for the in vivo measurements, (2) mapping the detection coil characteristics, (3) calculation of selected slice and liver volume ratios using simple segmentation procedures and (4) spectral analysis in the time domain. The patients had significantly lower concentrations of phosphodiesters (PDE), 6.3±3.9 mM, and ATP-, 3.6±1.1 mM, (P<0.05) compared with the control group (10.0±4.2 mM and 4.2±0.3 mM, respectively). The concentrations of phosphomonoesters (PME) were higher in the patient group, although this was not significant. Constructing an anabolic charge (AC) based on absolute concentrations, [PME]/([PME] + [PDE]), the patients had a significantly larger AC than the control subjects, 0.29 vs. 0.16 (P<0.005). Absolute concentration measurements of phosphorus metabolites in the liver are feasible using a slice selective sequence, and the technique demonstrates significant differences between patients and healthy subjects.     

Mineral and bone physiology in the foetus,preterm and full-term neonates

Mother is the major source of minerals in foetal life with placenta actively transporting against a concentration and electrochemical gradient. The foetal serum mineral concentration is thereby higher as compared to maternal values, which possibly help in its rapid accretion in developing bones and for counteracting postnatal fall in calcium levels at birth. Parathyroid hormone related peptide (PTHrP) and parathyroid hormone (PTH) play a major role in mineral physiology during foetal life with hormones like calcitriol, calcitonin, FGF-23 and sex steroids having minimal role. PTHrP and PTH also play a major role in endochondral bone formation and mineralization of skeleton. At the birth, as the cord is clamped, there is loss of active transport of minerals through placenta and the neonate has to rely on enteral intake of minerals to meet the demands of growing bones and metabolisms. The calcium levels fall after birth, reaching a nadir at 24–48 h and gradually rise to adult values over several days, probably resulting from a fall in PTHrP levels and hyporesponsiveness of parathyroid glands. As PTH and calcitriol levels increase postnatally, there is a rise in calcium levels with maturation in functioning of kidneys and intestines. However, there may be significant delay in intestinal maturation in preterm infants along with an increased demand for mineral accretion, which predispose them to osteopenia of prematurity.     

血清磷、肌酸激酶及其同工酶的测定在肠梗阻诊断中的应用

肠梗阻是临床常见的急腹症，绞窄性肠梗阻的死亡率可高达４５％～３０％，我们自１９９５年８月至１９９７年４月共收治肠梗阻５３例，其中单纯性肠梗阻２８例，经手术证实为绞窄性肠梗阻２５例（其中肠坏死８例），在治疗前均测定血清磷、肌酸激酶及其同工酶，其结果：本组病例中血清磷升高者１４例，其中以８例肠坏死为显著，肌酸激酶及其同功酶的升高也以绞窄性肠梗阻为明显，其中又以发病时间在４８小时以内者和８例肠坏死者为著，因此，我们认为：血清磷、肌酸激酶及其同工酶的测定可以作为判断肠管是否发生绞窄及坏死的辅助诊断指标     

晚发性维生素K缺乏症与维生素D缺乏症相关性探讨

【目的】　探讨晚发性维生素K(VK)缺乏症的血钙水平及与维生素D(VD)缺乏症的相关性。　【方法】　临床确诊的晚发性VK缺乏症所致颅内出血 (病变组 ) 43例 ,正常对照组 2 4例 ,测定血清钙、磷和碱性磷酸酶 (AKP) ,结果进行统计学分析。　【结果】　病变组血清钙 (1.76± 0 .2 9)mmol/L ,磷 (1.70± 0 .3 6)mmol/L ,AKP(3 0 8.98± 79.64 )U/L。对照组血清钙 (2 .19± 0 .2 6)mmol/L ,磷 (1.98± 0 .2 9)mmol/L ,AKP(2 2 5 .88± 3 7.87)U/L。差异有非常显著性意义(P <0 .0 1。　【结论】　晚发性VK缺乏症血清钙、磷明显降低 ,AKP明显升高 ,提示存在VD缺乏 ,血钙降低的原因与同时缺乏VD有关 ;晚发性VK缺乏症患儿血钙降低到一定程度发生惊厥时 ,可诱发或加重其颅内出血。因此 ,治疗时应注意适当补充VD与钙剂     

黄磷对大鼠肝微粒体和线粒体Ca^2＋泵的影响

在体外实验中,用不同浓度黄磷(0.026μg/ml,0.26μg/ml,2.60μg/ml)与大鼠肝微粒体和线粒体共同孵育,发现黄磷对肝微粒体和线粒体Ca~(2 )-ATP酶呈现抑制作用,且随剂量增大,抑制作用加重;在孵育的早期,对微粒体Ca~(2 )ATP酶的抑制更明显。在整体动物实验中,黄磷染毒后6小时,对肝微粒体和线粒体Ca~(2 )-ATP酶发生抑制。染毒后3小时,对肝微粒体~(45)Ca摄取发生抑制;染毒后6小时,对肝线粒体~(45)Ca摄取发生抑制。实验结果表明,黄磷对微粒体和线粒体Ca~(2 )泵机制的损害可能是引起中毒性肝损害的一个重要因素。     

放射性核素磷近距离治疗小儿皮肤血管瘤的近期疗效

目的:探讨放射性核素磷(32P)近距离治疗小儿皮肤血管瘤的临床疗效及辐射损伤。方法:173例小儿皮肤血管瘤患儿随机分为治疗组92例,对照组81例,采用32P敷贴器以不同的剂量、不同的治疗疗程行近距离治疗,观察其临床疗效及辐射损伤。结果:32P敷贴器放射性面密度的估算值与实测值误差为5.4%±0.9%;治疗组和对照组患者经32P治疗1个～4个疗程后病灶总治愈率均为100%;两组病例治疗后均出现皮肤辐射损伤,且与皮肤血管瘤病变的面积密切相关,治疗组的辐射损伤比对照组轻(P<0.05),皮肤血管瘤病变较厚者疗效较低,增加治疗疗程可提高疗效(P<0.05)。结论:多疗程、低剂量的32P近距离治疗小儿皮肤血管瘤可取得更佳的临床治疗效果。