Effects of aluminum on rat bone cell populations

Summary Aluminum (Al) loading is associated with reduced bone formation and osteomalacia in human and certain animal models. However, uncertainty exists as to the cellular effect(s) of Al as both inhibition and stimulation of osteoblast proliferation have been reported. Furthermore, the extent to which Al affects osteoprogenitor cell populations is unknown. To determine the cellular effects of Al in the rat, an animal model in which Al bone disease has been produced, we compared thein vitro effect of 10–50 Al on the proliferation and hydroxyproline collagen formation of marrow osteoprogenitor stromal cell populations and perinatal rat calvarial osteoblasts. In subconfluent cultures, Al suppressed proliferation of both marrow fibroblast-like stromal cells and calvarial osteoblasts. In confluent cultures, however, Al selectively stimulated periosteal fibroblast and osteoblast DNA synthesis and collagen (hydroxyproline) production, both in the presence or absence of 1,25-dihydroxyvitamin D. Osteocalcin was not detected in osteoblast-conditioned media or extracellular matrix. These observations suggest that the bone formation defect associated with Al toxicity in growing rats may be a function of impaired patterns of osteoprogenitor/osteoblast proliferation. Furthermore, the Al-stimulated increase in collagen formation is consistent with the development of osteomalacia in Al-toxic humans and animals. The mechanism by which Al stimulated DNA synthesis and collagen production in more mature cultures awaits further study.     

Effect of aluminum and parathyroid hormone on osteoblasts and bone mineralization in chronic renal failure

Summary Bone aluminum, quantitative bone histology, and plasma parathyroid hormone (PTH) were compared in 29 patients undergoing chronic hemodialysis. Histologic techniques included double tetracycline labeling and histochemical identification of osteoclasts and osteoblasts. Bone aluminum was measured chemically by flameless atomic absorption spectrophotometry, and histochemically. When measured chemically, the bone aluminum was 67±46 (SD) mg/kg dry weight (normal 2.4±1.2 mg/kg); histochemically, aluminum was present at 2.9±4.4% of trabecular surface. The biochemical and histochemical results agreed well (r=0.80,P<0.001). No double tetracycline labels were seen at the mineralization front where aluminum was deposited, indicating cessation of mineralization at these sites. The osteoblast surface correlated positively with plasma PTH (r=0.67,P<0.001) and negatively with bone aluminum level (r=−0.42,P<0.05). Multiple linear regression showed a correlation of aluminum with osteoblasts additional to that of PTH, consistent with a direct effect of aluminum in depressing osteoblast numbers. Though a relationship between PTH and chemically determined bone aluminum level could not be demonstrated, there was a negative correlation between osteoclast count and aluminum, and the nine patients with severe hyperparathyroid bone disease had lower chemically determined aluminum levels than the other patients. These results suggest that aluminum (a) directly inhibits mineralization, (b) is associated with decreased PTH activity and hence osteoblast numbers, and (c) directly reduces osteoblast numbers. In addition to inducing severe, resistant osteomalacia, aluminum appears to contribute to the mild osteomalacia commonly seen in renal failure, characterized by extensive thin osteoid and low tetracycline and osteoblast surfaces.     

Deferoxamine and aluminum clearance in pediatric hemodialysis patients

Mobilization of aluminum by deferoxamine and the subsequent clearance from plasma by hemodialysis with or without charcoal hemofiltration was studied in four pediatric patients. Deferoxamine, 10–20 mg/kg, followed by dialysis with a Travenol CA50 dialyzer produced reductions in mean plasma aluminum levels from 2433±729 nmol/l (65.5±19.6 g/l) to 1727±554 nmol/l (46.5±14.9 g/l) during dialysis. The use of a charcoal cartridge in the circuit resulted in a reduction in mean plasma aluminum levels 2459±591 nmol/l (66.2±15.9 g/ml) to 1380±106 nmol/l (35.8±2.9 g/l). In one patient, high-flux dialysis produced a reduction from 2140 nmol/l (55.6 g/l) to 1134 nmol/l (29.4 g/l). No patients suffered direct adverse reactions to low-dose deferoxamine, although two patients had previously exhibited potential aluminum neurotoxicity after rapid increases in plasma aluminum levels with deferoxamine in higher doses. Aluminum levels must be monitored closely during deferoxamine therapy in uremic children to minimize the risk of exacerbating aluminum neurotoxicity.     

In vitro effects of aluminum on bone phosphatases: A possible interaction with bPTH and vitamin D3 metabolites

Summary The present study was undertaken to test the in vitro action of aluminum on bone phosphatase activities and the possible interaction of this metal with parathyroid hormone (bPTH) or vitamin D₃ dihydroxymetabolites [1,25- and 24,25(OH)₂D₃). Three-day-old rat calvaria were incubated for 24 h with one of the following: bPTH at 5×10⁻⁸M, 1,25-or 24,25(OH)₂D₃ at 2.5×10⁻⁹M, Al at concentrations ranging from 3×10⁻¹¹M to 6×10⁻⁶M, or their corresponding solvents. Al effects were also investigated when the medium phosphate or calcium concentrations were modified. In some experiments, Al was added simultaneously with bPTH or one of the vitamin D₃ metabolites at the beginning of the 24 h incubation. At the end of all incubations, acid and alkaline phosphatase activities were measured in bone cytoplasmic extract. The results show that: (a) When compared to the value found in half calvaria incubated in a control medium, the bone acid and alkaline phosphatase content is significantly higher in paired halves incubated with Al (3×10⁻¹¹M to 1.5×10⁻⁶M) as well as with bPTH, 1,25-, or 24,25(OH)₂D₃ and sharply decreased with higher Al concentrations (6×10⁻⁶M). (b) The Al effect on phosphatase activities is modified in a free phosphate or a free calcium medium. (c) The presence of Al at 1.5×10⁻⁶M or 6×10⁻⁶M significantly decreases the bPTH or 1,25(OH)₂D₃-induced stimulation of bone phosphatase activities. (d) A similar interaction could not be found between Al and 24,25-(OH)₂D₃.     

Effects of excess vitamin E on rat teeth

Summary The purpose of this investigation was to determine if the feeding of excess vitamin E during tooth formation changes the mineral content of teeth. Purified diets containing 0, 250, and 2500 IU vitamin E per kg were fed to 15-day pregnant rats and continued during lactation and to the pups after weaning. Rats were killed at 2 and 4 weeks after weaning. Incisors and molars were weighed, ashed, and the percent of calcium, magnesium, and phosphorus was determined. Feeding of excess vitamin E (2500 IU/kg diet) had no deleterious effect on percent ash or mineral composition of rat teeth. In fact, molars from rats fed excess vitamin E had slightly higher calcium and phosphorus levels. Such differences were also apparent but to a lesser extent in the dentin and enamel composition.     

Vitamin E stimulates trabecular bone formation and alters epiphyseal cartilage morphometry

The effects of dietary vitamin E (VIT E) and lipids on tissue lipid peroxidation and fatty acid composition, epiphyseal growth plate cartilage development, and trabecular bone formation were evaluated in chicks. A 2×2 factorial design was followed using two levels (30 and 90 IU/kg of diet) of dl--tocopheryl acetate and two different dietary lipids. The basal semipurified diet contained one of the following lipid treatments: anhydrous butter oil (40 g/kg)+ soybean oil (60 g/kg), [BSO], or soybean oil (100 g/kg), [SBO]. After 14 days of feeding, the level of -tocopherol in plasma was higher and thiobarbituric acid reactive substances (TBARS) were less in plasma and liver of chicks supplemented with 90 IU of VIT E compared with those given 30 IU of VIT E. Body weights and tibiotarsal bone lengths were not affected by the dietary treatments Saturated fatty acids (14:0, 15:0, 16:0, 17:0, and 18:0) were increased in tibiotarsal bone of chicks fed the BSO diet. In contrast, total polyunsaturated fatty acids and the ratio of unsaturated fatty acids/saturated fatty acids were higher in plasma of chicks fed SBO compared with the values from chicks fed BSO. The thickness of the entire growth plate cartilage and the lower hypertrophic chondrocyte zone was significantly greater in chicks fed 90 IU/kg of VIT E. Kinetic parameters on bone histomorphometry indicated that mineral apposition rate was higher in chicks fed 90 IU/kg of VIT E. The interaction effect between the VIT E and BSO treatments led to the highest trabecular bone formation rate among the groups. These data suggest that VIT E protects against cellular lipid peroxidation in cartilage to sustain normal bone growth and modeling.Approved as Journal Paper Number 14556 of the Purdue Agricultural Experiment Station     

The role of vitamin D in the medullary bone formation in egg-laying japanese quail and in immature male chicks treated with sex hormones

Summary The effect of vitamin D₃ on medullary bone formation was investigated in egg-laying Japanese quail and in immature male chicks treated with sex hormones. When laying quail were fed a vitamin D-deficient diet for 16 days, their eggshell weights and egg production rate were markedly reduced in a time-dependent manner with a significant decrease in plasma calcium and 25-hydroxyvitamin D₃ levels. The calcium content of the medullary bone of femurs decreased markedly with the progress of vitamin D deficiency, whereas that of the cortical bone remained unchanged. Quantitative histological examination also showed that the area of the mineralized portion of medullary bone in quail that were fed the vitamin D-deficient diet markedly decreased compared with that in the control laying quail, whereas the total area of the mineralized and unmineralized portions of medullary bone in the bone marrow cavity increased moderately. Daily administration of vitamin D₃ (0.75 μg/day) to the vitamin D-deficient quail increased the mineralization of medullary bone as early as day 4. Daily administration of both estradiol (0.3 mg/day) and testosterone (0.9 mg/day) for 3 weeks to immature male chicks induced an apparent hypercalcemia and matrix formation of medullary bone, regardless of the vitamin D status of the chicks. Mineralization of medullary bone was observed only when vitamin D₃ was administered together with the sex hormones. These results suggest that vitamin D₃ is directly involved in the mineralization of medullary bone in birds.     

儿童慢性肾脏病3~5D期贫血状况的单中心调查研究

目的:探讨慢性肾脏病（chronic kidney disease,CKD）3~5D期患儿肾性贫血的临床特点,为规范化诊治提供参考数据。方法:回顾性分析2016年1月至2018年12月于首都医科大学附属北京儿童医院就诊的CKD患儿的临床资料,按照估算肾小球滤过率分成CKD 3期组、4期组及5期组,比较各组患儿的贫血指标...     

Differentiation of osteoblasts and formation of mineralized bone in vitro

Summary Periostea consisting of the osteogenic layer and the fibrous layer of the periosteum were dissected from 17-day-old embryonic chick calvariae, leaving the osteoblasts behind on bone. The dissected periostea were folded with the osteogenic cells in apposition. The explants were cultured on plasma clots for up to 6 days, during which time osteodifferentiation was observed followed by osteoid formation in between the two layers. These cultures consistently mineralized in the presence of 5 or 10 mMβ-glycerophosphate. The mineralization and osteoid formation displayed many characteristics identical with those seen in vivo. Specifically, the osteoid formed was birefringent under polarized light, the central zone of osteoid became mineralized within 24 h of formation in vitro, and a clear border between mineralized and non-mineralized osteoid suggestive of a mineralization front was present. The unmineralized osteoid at the periphery was surrounded by osteoblasts. These data suggest that physiologic mineralization of osteoid produced in vitro did occur in this system by the addition of the alkaline phosphatase substrateβ-glycerophosphate.     

Mineralization and bone formation on microcarrier beads with isolated rat calvaria cell population

Summary Using enzymatically isolated rat bone cells in the presence of cytodex microcarrier beads, osteoblastic cell differentiation and bone nodule formation were studied at the optical and electron microscopic level. Cytochemical method showed an intense alkaline phosphatase activity mainly around the microcarriers where the cells have formed multilayers on day 4 of cultures. On day 7 of experiment cultures. Von Kossa method stained positively only the cytodex microcarriers. During the following days, bone nodule formation was closely associated with cytodex microcarriers. In contrast, in control cultures with negatively charged glass beads, cells failed to pile up around the glass beads, and bone nodule formation occurred randomly in the culture dishes with 24 hour delay. Light microscopy observations of experiment cultures revealed the formation of nodular structures, with active osteoblastic cells forming a mineralized matrix in which osteocytes were present. Transmission electron microscopy revealed first, a mineralization process of the surface of the cytodex microcarriers which appeared like a granular electron-dense, collagen-free layer followed by the deposit of a collagenous matrix. These results indicated that cytodex microcarriers provided an excellent matrix for bone cell differentiation and mineralization.     

低分子右旋糖酐铁和蔗糖铁对慢性肾衰竭大鼠氧化应激的影响

目的 评价小剂量反复多次低分子右旋糖酐铁和蔗糖铁静脉用药后对慢性肾衰竭大鼠氧化应激的影响。 方法 以5/6肾大部切除术建立慢性肾衰竭大鼠模型。右肾切除术后第4周,将实验大鼠分为4组：低分子右旋糖酐铁（糖酐铁）组、蔗糖铁组、对照组、假手术组。观察6周,检测各组大鼠体内氧化应激、铁代谢等指标。 结果 糖酐铁组和蔗糖铁组大鼠血红蛋白明显高于对照组（P < 0.05）,而两铁剂组间差异无统计学意义。对照组大鼠的血清铁、血清铁蛋白、转铁蛋白饱和度显著低于假手术组（P < 0.05）;两铁剂组大鼠上述指标均显著高于对照组（P < 0.05）,而两铁剂组间差异无统计学意义。糖酐铁组和蔗糖铁组血浆晚期氧化蛋白产物（AOPP）显著高于对照组[（127.84±21.19） μmol/L、（134.21±29.38） μmol/L比 （81.83±19.93） μmol/L,P < 0.05],而两铁剂组间差异无统计学意义。两铁剂组大鼠血浆丙二醛（MDA）高于对照组,而蔗糖铁组高于糖酐铁组[（6.06±0.73） nmol/L比（4.99±0.80） nmol/L, P < 0.05]。糖酐铁组、蔗糖铁组和对照组大鼠血清超氧化物歧化酶（SOD）和总抗氧化能力（TAOC）差异无统计学意义。模型组大鼠血浆谷胱甘肽过氧化物酶（GSH-Px）水平显著低于假手术组（P < 0.05）,而蔗糖铁组显著低于糖酐铁组和对照组[（2123.11±74.78） nmol&#8226;ml-1&#8226;min-1比（2352.84±163.90） nmol&#8226;ml-1&#8226;min-1、（2310.23±125.99） nmol&#8226;ml-1&#8226;min-1,P < 0.05]。 结论 静脉补铁可部分纠正5/6肾大部切除肾衰竭大鼠的贫血,改善铁代谢指标。反复静脉小剂量补铁对慢性肾衰竭大鼠氧化应激状态有不良影响,而低分子右旋糖酐铁的不良影响低于蔗糖铁。     

Mechanism underlying early anaemia in children with familial juvenile nephronophthisis

Familial juvenile nephronophthisis (NPH) is a hereditary form of chronic tubulointerstitial nephritis with onset in childhood. About one-third of patients develop anaemia before renal insufficiency. We investigated the pathogenetic mechanisms leading to anaemia by comparing 6 patients with NPH and 12 reference patients with other renal diseases. We studied their iron metabolism and measured transferrin receptor-ferritin ratios. There was no evidence for iron deficiency or haemolysis. The serum erythropoietin concentrations of the patients with NPH (12±2.3 U/l) were low compared with the 12 reference patients(25±18.9 U/l). In the 2 patients with NPH who were fully investigated, the pharmacokinetics of recombinant human erythropoietin appeared normal. Thus, anaemia in patients with NPH does not result from iron deficiency or correlate with impaired iron status. The mechanism underlying the anaemia of NPH appears to affect the function or regulation of the cells producing erythropoietin. Received October 26, 1995; received in revised form and accepted March 6, 1996     

Vitamin D deficiency during pregnancy and lactation stimulates nephrogenesis in rat offspring

There is increasing evidence of vitamin D insufficiency in women of child-bearing age and their infants. This study examined the effect of maternal vitamin D deficiency on nephron endowment in rat offspring (n = 7 per group). Sprague–Dawley dams were fed either a vitamin D deplete diet or a vitamin replete (control) diet prior to pregnancy, during pregnancy and throughout lactation. At 4 weeks of age the offspring were weaned and maintained on their respective diets until they were killed at 7 weeks. In the fixed right kidney, kidney volume, renal corpuscle volume and nephron number were stereologically determined. There was no difference between groups in body weight, kidney weight or kidney volume. There was a significant 20% increase in nephron number in kidneys of vitamin D deplete offspring (vitamin D deficient, 29,000 ± 1,858, control, 23,330 ± 1,828; P = 0.04). This was accompanied by a significant decrease in renal corpuscle size in the vitamin D deplete group compared with the controls (6.125 ± 0.576 × 10⁻⁴ mm³ and 8.178 ± 0.247 × 10⁻⁴ mm³, respectively; P = 0.03). We concluded that maternal vitamin D deficiency in rats appears to stimulate nephrogenesis. Whether this confers a renal functional advantage or not is unknown.     

肾动脉狭窄合并高血压及肾功能不全患者行血运重建的中期疗效评价

目的评价经皮肾动脉血运重建术(percutaneous transluminal renal artery revascularization,PTRAR)治疗对肾动脉狭窄合并高血压及肾功能不全患者的临床疗效。方法对2011年1月至2015年6月因肾动脉狭窄合并高血压在华中科技大学同济医学院附属同济医院心内科行肾动脉血运重建术的62例患者进行回顾性研究,并对其中18例肾功能不全的患者进行随访观察。结果62例患者共76条肾动脉严重狭窄或闭塞,均成功开通,14条肾动脉仅行球囊扩张,62条肾动脉行支架置入。住院期间未出现任何手术相关并发症;术后24 h血压也有明显的下降[收缩压:(150.8±16.4)mmHg比(132.0±12.8)mmHg;舒张压:(88.6±12.7)mmHg比(80.1±11.1)mmHg,P均0.05]。术后24 h肾功能不全的18例患者平均血压降至(135.7±16.0)/(83.8±11.4)mmHg。针对18例肾功能不全的患者,术后平均随访26个月,结果发现,与术前相比血压明显下降[收缩压:(138.4±11.8)mmHg比(148.7±9.1)mmHg;舒张压:(88.1±10.7)mmHg比(93.5±9.5)mm·Hg,P均0.05]。所有62例患者术后服药种数明显减少。18例肾功能不全者中6例(33.3%)治愈,7例(38.9%)改善,5例(27.8%)无变化;术后血清肌酐水平的监测发现9例患者的肾功能好转,6例患者的肾功能未受明显影响,3例患者的肾功能恶化。结论肾动脉血运重建术对肾动脉狭窄合并高血压患者的血压带来明显的获益,但对肾功能的改善效果有待进一步研究。     

Effects of vitamin D insufficiency on bone mineral density in African American men

Summary  In African American men serum, 25-hydroxyvitamin D (25-OHD) was below 30 ng/ml in 89% of subjects. In overall group, there was no correlation between 25-OHD and bone mineral density (BMD). A subgroup analysis of subjects with 25-OHD ≤15 ng/ml showed that serum 25-OHD was positively associated with BMD. Introduction  This study examined the effects of low serum 25-hydroxyvitamin D (25-OHD) on bone mineral density (BMD) in African American (AA) men from the general medicine clinic at an inner city Veteran Administration medical center. Methods  The data for 112 AA males who had both 25-OHD levels and BMD of spine and hip were extracted and analyzed using SAS software. Results  AA men were aged 38 to 85 years, with mean age of 62 years. Levels of 25-OHD ranged from 4 to 45 ng/ml, with mean 17.5 ng/ml, 24% and 89% of the subjects had 25-OHD below 10 and 30 ng/ml, respectively. In the overall group, there was no correlation between 25-OHD and BMD at any site. In a subgroup analysis of subjects with 25-OHD ≤15 ng/ml, in multiple adjusted models, 25-OHD was positively associated with BMD of spine (r = 0.26, p = 0.05), total hip (r = 0.27, p < 0.05), ward’s triangle (r = 0.25, p = 0.05), and trochanter (r = 0.30, p < 0.05). Conclusions  The negative effect of vitamin D insufficiency on bone was observed only at very low levels of 25-OHD, suggesting that AA male skeleton is relatively resistant to the effects of secondary hyperparathyroidism.     

Problems of bone analysis in childhood and adolescence

The monitoring of bone metabolism and skeletal development during childhood and adolescence is becoming increasingly important in the prevention of osteoporosis. This is especially important in patients with chronic disorders. The predominant changes in the skeletal system during growth occur as geometric adaptation processes which lead to an increase in bone mass and bone strength. These changes can be measured with linear absorption methods (single-photon absorptiometry, dual-photon absorptiometry, dual-energy X-ray absorptiometry), computed tomographic procedures (peripheral quantitative computed tomography, quantitative computed tomography), and sonographic procedures. The aim of this review is to explain the problems of interpretation of the investigations due to growth-dependent changes. Almost all methods and their parameters, such as bone density, spongiosa density, cortical density, ultrasound transmission velocity, etc., are influenced, in varying degree, by growth-dependent skeletal changes. Received September 15, 1997; received in revised form January 14, 1998; accepted January 19, 1998     

Effect of alpha-tocopherol on bone formation during distraction osteogenesis: a rabbit model

Purpose  

The purpose of this study was to evaluate the effects of alpha-tocopherol on distraction osteogenesis.     

Comparison of bone formation rates measured by radiocalcium kinetics and double-tetracycline labeling in maintenance dialysis patients

We report 23 prospective studies on 18 maintenance dialysis patients in whom we measured skeletal mineralization rate (m) using ⁴⁷Ca, analyzed by the expanding pool model, and compared it with the histologic bone formation rate (bfr), volume referent, estimated on tetracycline-labeled iliac crest bone. The patients showed a spectrum of bone disease types including adynamic bone, aluminum-related osteomalacia, and various degrees of secondary hyperparathyroidism. The mean width between double labels, on which mineral apposition rate depended, was estimated using a simple formula relating area to perimeter for each feature enclosed by the labels. Values for m ranged from 0 to 155 mmol calcium per day and for bfr from 0 to 124% per year. There was close correlation between m and bfr (r=0.976), serum alkaline phosphatase (r=0.968), and serum immunological parathyroid hormone (iPTH) (r=0.868). When the volumetric bfr was converted to mass units and applied to the whole skeleton, using literature values for mineral density and cortical and trabecular mass, there was close agreement between the histologic and isotopic estimates of m (r=0.959). The results validate the two methods and suggest they are interchangeable. However, use of a rigorous method to determine bfr appears to be essential.