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Free radicals have been implicated in the pathogenesis of reperfusion injury, but it is unclear how they exert their deleterious effects on cellular metabolism. Several lines of indirect evidence suggest that free radicals elevate intracellular Ca2+ concentration ([Ca2+]i) and inhibit glycolysis as part of their mechanism of injury. We tested these ideas directly in hearts subjected to hydroxyl radicals produced by the Fenton and Haber-Weiss reactions. Nuclear magnetic resonance spectra were obtained from Langendorff-perfused rabbit hearts before, during, and after 4 min of perfusion with H2O2 (0.75 mM) and Fe(3+)-chelate (0.1 mM). Isovolumic left ventricular pressure exhibited progressive functional deterioration and contracture after exposure to H2O2 + Fe3+. Phosphorus nuclear magnetic resonance (NMR) spectra revealed partial ATP depletion and sugar phosphate accumulation indicative of glycolytic inhibition. To measure [Ca2+]i, fluorine NMR spectra were acquired in a separate group of hearts loaded with the Ca2+ indicator 5F-BAPTA [5,5'-difluoro derivative of 1,2-bis-(o-aminophenoxy)ethane- N,N,N',N'-tetraacetic acid]. Mean time-averaged [Ca2+]i increased from 347 +/- 14 nM in control to 1,026 +/- 295 nM 4 min after free radical generation (means +/- SEM, n = 7), and remained elevated thereafter. We conclude that free radicals induce clear-cut, specific derangements of cellular metabolism in the form of glycolytic inhibition and calcium overload. The observed increase in [Ca2+]i suggests that the deleterious effects of free radicals are at least partially mediated by secondary changes in cellular calcium homeostasis.
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PMID:Glycolytic inhibition and calcium overload as consequences of exogenously generated free radicals in rabbit hearts. 165 71

Calcium, phosphorus, fluoride, sodium, magnesium and zinc estimations were carried out on teeth from a patient with hypophosphataemic vitamin D-resistant rickets (HVDRR) and from a patient with acquired rickets with the aim of determining differences in the composition of dentine in these two types of rickets. Normal deciduous teeth served as controls. Mineral analyses were carried out using an electron probe micro-analyser after carefully polishing the hemisected specimens. After the analyses the specimens were coated with gold-palladium for more detailed SEM studies. The Ca, P, F and Zn contents of the calcospherites were normal, while there was more Na and less Mg in the dentine of HVDRR teeth than of controls. The significance of this remains unexplained. The mineral content of the interglobular spaces was very limited, but there was more Zn in these than in other parts of the HVDRR teeth, in the acquired rickets teeth or in the control teeth. The excess of Zn in the interglobular spaces is thought to have an effect on the mineralisation process in HVDRR teeth. The globular nature of HVDRR teeth is thought to be genetically controlled and the result of a reduction in the number of calcification nuclei. The globular nature of the HVDRR teeth was not due to lack of Ca and P, as the serum levels of these minerals were maintained within normal limits during tooth development by controlled phosphate supplementation. Because in acquired rickets the globules were seen at the developmental stage that the teeth had reached when the nutritional disturbance occurred, the fault in mineralisation is thought to be different from that in HVDRR teeth.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Mineral content of different areas of human dentin in hypophosphataemic vitamin D-resistant rickets. 165 2

To elucidate the mechanism of acute contractile failure induced by adriamycin, the intracellular concentrations of free calcium ([Ca2+]i) and energy-related phosphate compounds were determined in isolated ferret hearts. The time-averaged [Ca2+]i was measured at 10 min resolution using fluorine nuclear magnetic resonance (NMR) spectroscopy and the NMR-sensitive Ca2+ indicator 5F-BAPTA. [Ca2+]i significantly increased from a control of 381 +/- 66 nM (mean +/- SEM, N = 5) to 789 +/- 171 nM during 30 min of perfusion with adriamycin (30 mg/L), and remained elevated for at least 30 min after washout. The isovolumic LV pressure decreased to 80.7 +/- 8.9% of control (N = 12, p less than 0.05) and did not recover after washout. Intramyocardial contents of energy-related phosphates were determined by phosphorus NMR spectroscopy in seven other hearts. No significant change in myocardial energy metabolism was observed during adriamycin exposure and after washout; inorganic phosphate did not increase, and phosphocreatine and ATP did not decrease. These results indicate that Ca overload induced by adriamycin is associated with acute contractile failure. Adriamycin has been reported to inhibit Na-Ca exchange and to affect the gating of Ca2+ release channels in sarcoplasmic reticulum. Whatever the cause of the calcium overload, the fact that dysfunction persists as an aftereffect of adriamycin is consistent with the hypothesis that calcium overload, in the absence of ischemia, can leave behind long-lasting contractile dysfunction.
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PMID:Alterations of intracellular calcium homeostasis and myocardial energetics in acute adriamycin-induced heart failure. 172 Aug 44

Primary as well as secondary hyperparathyroidism may be associated with anemia, and parathyroidectomy (PTx) may improve or even heal it. The precise link between the two conditions is still matter of discussion. The purpose of the present study was to investigate possible effects of PTx on serum immunoreactive erythropoietin (iEPO) in secondary (group I, n = 23), and primary (group II, n = 16) hyperparathyroidism patients, and in 3 patients undergoing cervicotomy for thyroid mass removal (group III). In group I patients, circulating iEPO levels rose from 23.1 +/- 4.8 mU/ml before PTx to 28.2 +/- 5.0 and 245 +/- 125 mU/ml (mean +/- SEM) at day 7 (p = NS) and 14 after PTx (p less than 0.003), respectively. Reticulocyte count increased 2 weeks after PTx: from 61,000 +/- 13,317 to 86,533 +/- 13,462/mm3 (p less than 0.05, n = 23). In 4 of these patients serum iEPO levels could be measured again 12-24 months after PTx. They were slightly higher than those determined before PTx: 37.0 +/- 8.4 versus 31.8 +/- 13.5 mU/ml. Their hematocrits were also higher than before PTx: 12.8 +/- 0.9 versus 11.0 +/- 0.9 g/dl. In group II patients, serum iEPO levels remained unchanged after PTx: 17.5 +/- 2.0 mU/ml before PTx and 20.0 +/- 3.0 mU/ml 14 days PTx. The reticulocyte count, however, increased significantly 2 weeks after PTx: from 25,103 +/- 3,000 to 40,827 +/- 4,080/mm3 (p less than 0.01). In group III patients, serum iEPO, reticulocyte count, and hemoglobin remained stable after surgery. Since all group I patients had received vitamin D supplementation after PTx, we studied an additional group of 14 chronic dialysis patients (group IV) who received either calcitriol (1 micrograms/day, n = 7) or placebo (n = 7) during 14 days. The patients on calcitriol treatment, but not those on placebo, had a significant decrease of serum iEPO: 18.6 +/- 4.9 versus 16.0 +/- 4.2 mU/ml (p less than 0.03). In conclusion, PTx led to a striking increase of serum iEPO and blood reticulocytes in uremic patients with secondary hyperparathyroidism, and an increase of reticulocyte count, but not of iEPO, in patients with primary hyperparathyroidism. Marked changes of circulating PTH, extra-or intracellular calcium and phosphorus concentrations as well as of tissue sensitivity to EPO after PTx could all be responsible. In contrast, the surgical procedure and the therapeutic increase in plasma calcitriol do not appear to be involved.
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PMID:Serum erythropoietin and erythropoiesis in primary and secondary hyperparathyroidism: effect of parathyroidectomy. 175 26

To evaluate potential adverse effects of acetate use in hemodialysis (HD), we measured plasma interleukin (IL-1 alpha, IL-1 beta, IL-6), TNF alpha, TGF beta 1, and beta 2-microglobulin levels with ELISA assays in normal (N = 9), CRF (N = 6), CAPD (N = 7) and HD (N = 8) subjects and compared the effects of acetate (Ac) and acetate-free (Ac-free) dialysate. TGF beta 1 was the only cytokine consistently detected. Compared to normals (median 57, range 53 to 68 pg/ml, one undetected; N = 8), TGF beta 1 was higher in the CRF (75, 70 to 97 pg/ml, one undetected) and CAPD (75.5, 66 to 116 pg/ml, N = 6) groups (P less than 0.05), and was somewhat higher in the HD (68, 52 to 88 pg/ml) group (P less than 0.10). Acutely, TGF beta 1 pre-HD (70, 63 to 88 pg/ml) increased above normals post AcHD [79.5, 65 to 140 pg/ml uncorrected for ultrafiltration (UF)] and was higher after AcHD versus Ac-free HD both uncorrected (79.5, 65 to 140 pg/ml vs. 70, 52 to 86 pg/ml) and corrected for UF (68, 51 to 115 pg/ml vs. 57, 43 to 69 pg/ml; P less than 0.05). beta 2-microglobulin was not different after AcHD (81.2 +/- 8.0 mg/ml) versus Ac-free HD (72.5 +/- 6.9 mg/ml). Significantly lower serum inorganic phosphorus was also found four hours post-AcHD compared to four hours post-Ac-free HD (0.87 mmol +/- 0.10 SEM vs. 1.05 mmol +/- 0.07 SEM; P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Effects of acetate dialysate on transforming growth factor beta 1, interleukin, and beta 2-microglobulin plasma levels. 176 11

An apatite- and wollastonite-containing glass-ceramic (A.W-GC) has been reported to form a tight bond with living bone through an apatite layer formed on its surface. This layer is considered to be formed by dissolution of Ca2+ and HSiO3- ions from the glass-ceramic into the surrounding body fluids. In order to confirm this proposed mechanism for the surface reaction of A.W-GC, three kinds of glass in the systems CaO-SiO2, CaO-SiO2-CaF2, and CaO-SiO2-P2O5 were implanted into the tibiae of rabbits for 3 or 8 weeks. Contact microradiography and SEM-EPMA showed that all three kinds of glass formed a Ca,P-rich layer in combination with a Si-rich layer on their surfaces within 3 weeks and formed a direct bond with bone via these layers. The detaching test, performed 8 weeks after implantation, showed that the loads required to detach the implants from the bone were almost equal for the phosphorus-free and the phosphorus-containing glasses. It was concluded that even P2O5-free CaO.SiO2 glass formed a Ca,P-rich layer on its surface and bonded tightly with living bone. If glasses and glass-ceramics release at least Ca2+ and HSiO3- ions, this would be sufficient for them to form the Ca,P-rich layer on their surfaces in vivo, enabling them to bond directly with bone.
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PMID:Bone-bonding ability of P2O5-free CaO.SiO2 glasses. 202 40

The influence of postprandial-like plasma insulin levels on intestinal calcium absorption (CaA) was studied in 9 healthy men. On separate occasions, they received either an i.v. infusion of 40 mU/m2 minute synthetic human insulin as well as a variable glucose infusion in order to clamp the plasma glucose at the baseline level (= glucose clamp), or insulin- and glucose-free vehicle infusions (= vehicle). During these infusions, an oral load containing 326 mg Ca in the form of Ca chloride was administered and CaA was determined thereafter with a 47Ca/85Sr double tracer method. During glucose clamp, mean plasma insulin was 172 +/- (1 SEM) 10 as compared to 6 +/- 1 microU/ml during vehicle infusions. During the clamp, 3-hour cumulative CaA rose significantly by 14% as compared to vehicle (39.2 +/- 2.5 vs. 34.4 +/- 2%, P less than 0.02). AT the same time, serum potassium and phosphorus dropped significantly, whereas serum parathyroid hormone (PTH) and 1,25(OH)2D levels were unchanged as compared to vehicle. The urinary excretions of potassium, sodium, and inorganic phosphorus, as well as the urinary specific activity of 47Ca, dropped significantly during glucose clamp, whereas the urinary excretion of cAMP was unchanged as compared to vehicle. The results suggest that, under the conditions of euglycemic hyperinsulinemic clamp, insulin stimulates CaA of healthy humans in a PTH- and 1,25(OH)2D-independent manner. Insulin may thus possibly be regarded as a factor participating in the regulation of CaA in humans.
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PMID:Intestinal calcium absorption during hyperinsulinemic euglycemic glucose clamp in healthy humans. 210 52

The purpose of this study is to examine the formation of hydroxyapatite on the surface of glass-ceramics (chemical composition: SiO2, 34.2; P2O5, 16.3; CaO, 44.9; MgO, 4.6; CaF2, 0.5 in weight ratio). Two experiments were performed. In the first experiment, plates (2 x 25 x 25 mm) of glass-ceramics containing apatite-wollastonite (designated A.W-GC) were used. In the second experiment, plates (15 x 10 x 2 mm) of A.W-GC and its parent glass (designated G) were used. In each experiment, two paired specimens of identical material, one tied with silk thread, the other not tied, were implanted subcutaneously into rats. In both experiments, bonding to each other of both tied and untied specimens was observed one month after implantation. A pattern resembling hydroxyapatite was identified on the detached surface of the bonded A.W-GC by micro-beam x-ray diffraction. The weak crystalline pattern was also observed on the detached surface of bonded G samples. Analysis of the interface by SEM-EPMA showed that a calcium-phosphorus rich layer formed between the two bonded surfaces in both experiments. It is suggested that the bonding between the two materials was formed by the calcium-phosphorus rich layer, and that the calcium-phosphorus rich layer is virtually identical to hydroxyapatite.
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PMID:Analysis of A.W glass-ceramic surface by micro-beam x-ray diffraction. 215 98

1. To determine the relationships between parathyroid hormone activity and long-term sodium fluoride therapy in osteoporosis, cytochemical bioassays (for biologically active parathyroid hormone) were performed in 22 osteoporotic control patients and in 18 patients after 15 +/- 10 months of treatment (60 mg of sodium fluoride daily). Ten patients were studied longitudinally by repeated metabolic balances and were therefore common to both groups. All patients were receiving mineral supplements. 2. Cross-sectional data showed a fourfold mean increase in biologically active parathyroid hormone on fluoride treatment (P less than 0.005) together with a 51% increase in serum alkaline phosphatase (P less than 0.005). Longitudinal data showed, in addition, a significant increase in the calcium balance of 2.4 +/- 1.2 (SEM) mmol daily (P less than 0.05) and the development of a positive phosphorus balance (P less than 0.02). 3. Fluoride-treated patients were then analysed in two groups according to the level of biologically active parathyroid hormone. Thirty-two per cent of values were above the upper limit of normal (18 pg/ml). The mean serum alkaline phosphatase level in this group showed no elevation above that of the control patients, the overall rise being accounted for entirely by patients with normal levels of biologically active parathyroid hormone. High levels of biologically active parathyroid hormone were also associated with relative hypophosphataemia (P less than 0.01), relative hypercalciuria (P less than 0.05) and an increased urine/faecal calcium ratio (P less than 0.025). 4. Results show that long-term fluoride and calcium therapy increase biologically active parathyroid hormone in osteoporosis and that excessive parathyroid hormone activity may account for certain features of the refractory state.
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PMID:Fluoride therapy and parathyroid hormone activity in osteoporosis. 216 71

We studied the effects of estrogen on daylong circulating levels of calcium, inorganic phosphorus, parathyroid hormone (PTH), and 1,25-(OH)2D3 (calcitriol) in a group of 10 postmenopausal women (68.5 +/- 1.4 years, mean +/- SEM). The study was conducted under strict dietary control, with mean calcium and phosphorus intakes of 845 and 970 mg. After treatment with conjugated equine estrogens, 1.25 mg/day, for 1 month, significant decreases in fasting (0800 h) serum levels were observed for calcium (9.09 +/- 0.08 versus 9.46 +/- 0.10 mg/dl, p less than 0.01) and phosphorus (3.38 +/- 0.10 versus 3.73 +/- 0.08 mg/dl, p less than 0.01). On the 0800 h fasting specimen, midmolecule PTH concentrations were higher (44.0 +/- 7.9 versus 34 +/- 8.2 pg/ml, p less than 0.05), but intact PTH was unchanged (28.6 +/- 2.7 versus 29.1 +/- 1.7 pg/ml) and a rise in circulating calcitriol (39.8 +/- 4.3 versus 31.6 +/- 2.1 pg/ml) was marginally significant (p = 0.07). When data represented multiple samples averaged over 7 and 15 h, significant estrogen-related reductions in serum calcium and phosphorus concentrations were observed. In addition, estrogen was associated with a significant rise in the daylong (15 h) level of calcitriol (39.4 +/- 4 versus 30.5 +/- 2.4 pg/ml, p less than 0.01). Daylong mid- and intact PTH concentrations were unchanged on estrogen compared to baseline values. No significant correlations were observed between changes in fasting calcitriol level and changes in fasting concentrations of calcium, phosphorus, or PTH. Further, the rise in daylong calcitriol concentration did not correlate significantly with changes in fasting or integrated values of calcium or PTH.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Effects of estrogen on daylong circulating calcium, phosphorus, 1,25-dihydroxyvitamin D, and parathyroid hormone in postmenopausal women. 217 58


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