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Query: UMLS:C0432222 (SEM)
 47,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Phosphorus retention as a result of chronic renal failure (CRF) induces secondary hyperparathyroidism (HPT II) while supplemented low-phosphorus low-protein diets (LPD) prevent it. The aim of this study was to assess in seven patients with advanced CRF and biological HPT II the effects of a LPD providing daily 5 to 7 mg/kg phosphorus, 0.4 g/kg protein, 300 mg calcium (Ca) and supplemented with amino acids, ketoacids, CaCO3 and vitamin D2, on the relationship between ionized Ca (iCa) and PTH concentrations. Hyper- and hypocalcemia were induced by CaCl2 and Na2-EDTA infusion. After three months of LPD, serum phosphorus decreased from 1.59 +/- 0.15 to 1.26 +/- 0.24 mmol/liter (mean +/- SEM, P < 0.02), basal PTH levels from 251 +/- 25 to 127 +/- 16 pg/ml (P < 0.03), while basal iCa and GFR did not vary. The sigmoidal PTH-calcium curve shifted downward with maximal PTH decreased from 482 +/- 86 to 319 +/- 60 pg/ml (P < 0.02) and minimal PTH from 35 +/- 4 to 21 +/- 4 pg/ml (P < 0.05). On the other hand, the slope of the % maximal PTH-iCa curve, which is an indicator of the sensitivity of the parathyroid cell to changes in iCa concentrations, did not vary significantly. The set point of Ca and calcitriol levels were not modified. These results demonstrate a direct inhibition of PTH secretion over a wide range of iCa concentration by LPD in patients with advanced CRF and mild HPT II over a three months period. This effect is independent of changes in plasma calcitriol levels.
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PMID:Phosphorus and protein restriction and parathyroid function in chronic renal failure. 785 97

Several studies of phosphorus 31 (31P) magnetic resonance spectroscopy (MRS) have demonstrated the presence of skeletal muscle metabolic abnormalities during exercise in patients with chronic heart failure (CHF). We studied the contribution of these abnormalities to the limitation of exercise capacity in CHF. In 25 patients (age 57 +/- 2 years, left ventricular ejection fraction [LVEF] 28% +/- 1.6%, peak oxygen consumption (VO2) 16 +/- 1.2 ml/kg/mm) (mean +/- SEM), we studied the calf muscle at rest and during plantar flexion with 31P MRS. The phosphocreatine (PCr) depletion rate was significantly negatively correlated to peak VO2 (r = -0.62, p = 0.001) but not to LVEF. Muscle pH was correlated with the inorganic phosphorus (Pi)/PCr ratio (r = -0.69, p = 0.0001) and with the PCr/adenosine triphosphate beta (ATP beta) ratio (which negatively relates to adenosine diphosphate [ADP] concentration) (r = 0.65, p = 0.00001). Although muscle ATP (ATP/sum of phosphorus [sigma P] remained stable, in 8 patients ATP/sigma P decreased significantly (-15% +/- 4%, p = 0.0002). In this ATP-depleted group, peak VO2 was significantly lower than that of the nondepleted group and PCr depletion more rapid, whereas LVEF did not differ. Skeletal muscle metabolic abnormalities in CHF contribute markedly to the alteration of exercise capacity. Rapid PCr depletion and muscle acidosis are the most relevant abnormalities. ATP depletion and excessive increase in ADP during exercise may contribute further to exercise limitation specifically in patients with more marked CHF.
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PMID:Contribution of specific skeletal muscle metabolic abnormalities to limitation of exercise capacity in patients with chronic heart failure: a phosphorus 31 nuclear magnetic resonance study. 794 49

In this study, we evaluated the effect of long-term administration of daily calcium carbonate (2-4 g/day) and intermittent high oral doses of 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3, 3-4 micrograms, given twice a week] in conjunction with a 3-mEq/1 calcium concentration in the dialysate for the treatment of severe secondary hyperparathyroidism in 6 hemodialysis patients. All patients had reduced serum levels of 1,25-(OH)2D3, which increased significantly (p < 0.005) reaching the maximum level in the 4th month. Serum total and ionized calcium levels significantly increased also, in relation to those before treatment. No patients developed hypercalcemia. Serum phosphorus did not significantly change during the study. Initial serum intact parathyroid hormone (PTH) (1,241 +/- 233 pg/ml, mean +/- SEM) markedly decreased after starting treatment with 1,25-(OH)2D3, being 542 +/- 174 pg/ml in the 5th month and 477 +/- 174 pg/ml in the 8th month. These changes are statistically significant (p < 0.05 and < 0.007, respectively). Alkaline phosphatase behavior was similar to that of intact PTH. A constant direct correlation between intact PTH and alkaline phosphatase and an inverse significant correlation between intact PTH and 1,25-(OH)2D3 was evidenced by us. We conclude that oral 1,25-(OH)2D3 pulse therapy is very effective in suppressing PTH secretion. The administration of calcium carbonate and the use of dialysate with a reduced calcium concentration would allow to prevent hyperphosphatemia and the administration of high oral doses of 1,25-(OH)2D3 without concomitant hypercalcemia.
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PMID:Treatment of severe secondary hyperparathyroidism with administration of calcium carbonate, intermittent high oral doses of 1,25-dihydroxyvitamin D3 and dialysate with 3 mEq/1 calcium concentration. 834 82

Acute and chronic studies in rats have shown that administration of human recombinant insulin-like growth factor I (rhIGF-I) lowers renal vascular resistance and increases RPF, GFR and proximal tubular phosphate absorption. In the present study we examined the effects of subcutaneous injections of rhIGF-I on glomerular and tubular function in eight normal men. Individuals were studied for 5.5 consecutive days in a clinical research center while they ate a constant diet. Four subjects were studied in a non-volume expanded state (Group 1) and four individuals were evaluated during a saline load. From the second to the fourth day, subjects received subcutaneous injections of rhIGF-I, 60 micrograms/kg, at 0800, 1400 and 2000 hours. After commencing the rhIGF-I injections, serum IGF-I levels rose quickly and remained at about three to four times that of baseline throughout the period of rhIGF-I injections. In both the normal and the saline loaded subjects, renal vascular resistance decreased and RPF and GFR (PAH and inulin clearances) rose quickly and were clearly altered within six hours after starting the rhIGF-I injections. RPF had increased by 32 +/- 3% and 33 +/- 2% (grand mean +/- SEM) in the normal and the saline loaded subjects, and GFR rose by 22 +/- 3% and 36 +/- 4% in the two groups. In both groups the absolute and the fractional excretion of phosphate decreased markedly during rhIGF-I treatment, but the absolute and fractional excretion of calcium did not change. The urinary fractional and absolute excretion of albumin and IgG also increased, although slightly, with rhIGF-I injections. There was no consistent effect of IGF-I on tubular sodium handling. These findings demonstrate that in normal men subcutaneous injections of rhIGF-I greatly increase RPF, GFR, and tubular phosphorus reabsorption and enhances microproteinuria.
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PMID:Effects of insulin-like growth factor I on renal function in normal men. 844 Dec 34

Calcium and gla-protein content are increased in the calcifications of cardiac bioprostheses. Such calcifications are more frequent during growth, pregnancy and renal failure when bone gla-protein levels are elevated. We investigated whether bone gla-protein and other markers of calcium metabolism play a role in bioprostheses calcifications. Forty-seven patients were separated into 2 groups according to the presence (group A, n = 9) or absence (group B, n = 38) of bioprostheses calcifications, as assessed by echo-doppler and surgery. Plasma levels of calcium, phosphorus, magnesium, creatinine and alkaline phosphatases were measured by standard laboratory methods, parathormone and those of bone gla-protein by specific radioimmunoassays. Results (mean +/- SEM) were compared (group A versus group B, P < 0.01) using Student's test and one-factor variance analysis (ANOVA). Age was similar in both group (53 +/- 12.9 vs 50 +/- 12.3 yrs), whereas duration of implant was greater in group A (104 +/- 12.4 vs 66 +/- 6.5 months, P < 0.01). No statistically significant difference was found between group A and B concerning biochemical and/or hormonal markers of calcium metabolism. These negative results merit to be discussed, and further studies will be needed to explore the potential role of circulating bone gla-protein in bioprostheses calcifications.
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PMID:[Phosphocalcium metabolism in patients with calcified valvular bioprosthesis]. 851 Nov 13

Blood ionized calcium (Ca2+) and pH; plasma lactate concentrations; and total protein, total calcium (CaT), albumin, and phosphorus concentrations in serum were determined in 40 healthy horses before (T1), at the finish line (T2), and 10 minutes after the finish (T3) of the cross-country phase of a 3-day-event competition. Mean (+/- SEM) Ca2+ concentrations decreased from 6.22 +/- 0.04 mg/dl at T1 to 5.04 +/- 0.07 mg/dl at T2 (P < or = 0.05). This decrease was accompanied by a nonsignificant increase in CaT between T1 and T2. The mean (+/- SEM) percent ionization of calcium decreased significantly (P < or = 0.05), from 50.9 +/- 2.75% at T1 to 40.3 +/- 3.58% at T2. Significant increases in mean albumin, total protein, phosphorus, and lactate concentrations and a significant decrease in mean pH were observed at T2 (P < or = 0.05). At T3, mean Ca2+ and percent ionization had increased, but remained significantly less than resting values. Mean CaT was significantly decreased at T3, compared with values at T1 and T2. Correlation of mean Ca2+ concentration with all other measured variables at each time was evaluated; correlation coefficients between mean Ca2+ and all other variables were low (r2 < or = 0.38), indicating low biological significance.
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PMID:Blood ionized calcium concentrations in horses before and after the cross-country phase of three-day event competition. 858 64

We investigated whether intestinal calcium absorption and serum 1,25-dihydroxycholecalciferol (calcitriol) concentrations are higher in women during lactation and after weaning to compensate for calcium lost in breast milk. Measurements were obtained at 4.6 mo postpartum in 24 lactating women and 24 nonlactating women, at 9.6 mo postpartum in 24 lactating women (2.6 mo after complete weaning) and 24 nonlactating women. One-half of the women in each group were randomly assigned to receive 1 g supplemental Ca/d as calcium carbonate. Fractional calcium absorption was measured by using stable isotopic tracers 42Ca and 44Ca. Fractional absorption was 0.32+/-0.02 (+/-SEM) in both lactating and nonlactating women, but was higher in lactating women after weaning (0.37+/-0.02) compared with nonlactating postpartum control subjects (0.31+/-0.02). These effects were independent of calcium intake. Changes in serum calcitriol paralleled changes in fractional absorption. There were no differences in calcitriol concentrations between lactating and nonlactating women, but calcitriol was greater in women after weaning compared with postpartum control subjects. Lactating women who had resumed menses had higher fractional absorption and serum calcitriol than did lactating women who had not. Serum calcium and phosphorus concentrations were greater in lactating compared with nonlactating women; there were no differences between groups after weaning. We conclude that lactation stimulates increases in fractional calcium absorption and serum calcitriol, but the responses are only apparent after weaning or the resumption of menses.
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PMID:Intestinal calcium absorption of women during lactation and after weaning. 859 16

We evaluated the effects of recombinant insulin-like growth factor-I (IGF-I) and growth hormone (GH) on calciotropic hormones and bone turnover markers in 16 healthy elderly women 71.9 +/- 1.3 years of age (mean +/- SEM). Subjects consumed a fixed diet providing 1000 mg of calcium and 0.9 g/kg of protein for 10 days before starting baseline 24-h urine and blood collections. Specimens were collected for 6 consecutive days before initiating subcutaneous injections of GH (25 micrograms/kg/day, n = 5) and IGF-I at 60 micrograms/kg b.i.d. (high-dose, n = 5) or at 15 micrograms/kg b.i.d. (low-dose, n = 6) for 28 days. Resorption markers included urine hydroxyproline (OHP), total pyridinolines (PYD), and N-telopeptide; formation markers include osteocalcin, skeletal alkaline phosphatase (sALP), and type I procollagen carboxy-terminal extension peptide (CICP). For each subject, baseline daily turnover markers varied substantially (DV = 16-22%). With GH and high-dose IGF-I, resorption and formation markers increased progressively to maximum levels at day 21. For GH, the increase in day 21 PYD, N-telopeptide, osteocalcin, and CICP was 143, 111, 53, and 81%, respectively (p < 0.96-0.02). For high-dose IGF-I, these increases were 108, 81, 77, and 111% (p < 0.02-0.002). However, with low-dose IGF-I no change was observed in resorption markers while osteocalcin and CICP increased progressively (day 21, % increases = 88 +/- 51, 36 +/- 14). Twenty-four hour urine collections during the last days of baseline and of study drug were taken as six 4 h aliquots. When deoxyPYD was measured on these samples in the low-dose IGF-I group, a significant increase was observed only on the 0800-1200 h aliquot. Serum phosphorus concentrations increased with GH (21.2 +/- 3.3%) and high-dose IGF-I (8.8 +/- 3.6%) by day 21 but actually decreased by day 28 (-9.7 +/- 2.7, p < 0.02) with low-dose IGF-I. Urinary phosphorus excretion decreased with high-dose IGF-I only. Twenty-four hour calcium excretion increased with all treatments. These results indicate that both GH and high-dose IGF-I activate remodeling osteons. By contrast, low-dose IGF-I may directly increase osteoblastic function with only a minimal increase in bone resorption and may therefore provide a useful means to increase bone mass. The results also suggest some of the GH action on renal phosphorus handling represents a direct action of GH on the nephron which does not involve the intermediacy of IGF-I. Finally, even under controlled conditions bone turnover markers exhibit substantial daily variation so that a very large treatment effect will be required for these markers to have clinical utility.
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PMID:Effects of recombinant insulin-like growth factor-I and growth hormone on bone turnover in elderly women. 861 64

Untreated specimens (i.e. not fixed, dehydrated or embedded) of the otolithic membrane from the sacculus of guinea pigs were observed at the ultrastructural level by low-vacuum scanning electron microscopy (LVSEM). This technique revealed the presence of a 15- to 20-mu m-thick layer of an amorphous substance (the supraotolithic cupula zone) on the surface of the otoliths, which was not detectable by conventional methods. Elemental analysis of this substance revealed relatively high concentrations of oxygen, sodium, phosphorus, chlorine, potassium and calcium. This amorphous substance was thought to have a role in fixing the otoliths onto the sensory epithelium. In addition, the tips of the triangular portions of the otoliths were not sharp as shown by conventional SEM and were seen to be more rounded by LVSEM.
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PMID:Observation of the otolithic membrane by low-vacuum scanning electron microscopy. 871 31

It has been proposed that the essential requirement for artificial materials to bond to living bone is the formation of bonelike apatite on their surfaces in the body. Recent studies have shown that titanium hydrogel and silica gel induce apatite formation on their surface in a simulated body fluid. In this study, the influence of titanium oxide and titanium silicate on the bonding of titanium alloys to bone was studied. Rectangular implants (15 x 10 x 2.2 mm) of titanium, Ti-6Al-4V, Ti-6Al-2Nb-Ta, Ti-6Al-4V coated with TiO2, and Ti-6Al-4V coated with Ti5Si3 were implanted into the tibial metaphyses of mature rabbits. At 8 and 24 weeks after implantation, the tibiae containing the implants were dissected out and subjected to a detaching testing. The failure load for titanium, Ti-6Al-4V, Ti-6Al-2Nb-Ta, Ti-6Al-4V coated with TiO2, and Ti-6Al-4V coated with Ti5Si3 were, respectively, 0.68 +/- 0.48, 0.22 +/- 0.46, 0.67 +/- 0.59, 2.18 +/- 0.71 and 2.03 +/- 0.41 kgf at 8 weeks, and 2.7 +/- 0.91, 2.58 +/- 1.29, 2.38 +/- 0.41, 3.79 +/- 1.7, and 2.79 +/- 0.87 kgf at 24 weeks after implantation. Histological examination by Giemsa surface staining, CMR, and SEM-EPMA revealed the coated titanium alloy implants directly bonded to bone tissue during early implantation. A Ca-P layer was observed at the interface of the coated implants and the bone. The results of this study indicated that TiO2 and Ti5Si3 can enhance the early bonding of titanium alloys to bone by inducing a Ca-P layer (chemical apatite) on the surface of titanium alloys. It also is suggested that the direct bone contact occurs in relation to the calcium and phosphorus adsorption onto the surface of the titanium passive layer formed during long-term implantation.
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PMID:Bone bonding behavior of titanium and its alloys when coated with titanium oxide (TiO2) and titanium silicate (Ti5Si3). 888 89


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