[Minimum calcium balance; technic and results in urinary lithiasis, tumorous calcinosis and in certain osteoarticular disorders].
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Calcification, Physiologic↗
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The dietary calcium requirements of man.
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Calcium↗
[Action of calcium nicotate on the utilization of ingested calcium and vitamin C by the organism].
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Ascorbic Acid↗
Effects of lacidipine on the carotid and cerebral circulations in essential hypertension.
Arterial diameter, blood flow, and vascular resistance of the common carotid artery were studied, using a pulsed Doppler system, in patients with uncomplicated sustained essential hypertension compared with age-matched normotensive subjects. In the hypertensive subjects, arterial diameter and blood flow remained close to the normal range while vascular resistance was increased. Following antihypertensive drug treatment with converting enzyme inhibitors, nitrates, or calcium antagonists, dilation of small or large arteries, or both, may be obtained, depending on the administered compound. Calcium blockade by lacidipine produced a predominantly carotid arteriolar dilation with no change in arterial diameter, suggesting independent consequences on cerebral circulation and baroreflex mechanisms.
Calcium Channel Blockers↗
[Effects of alkaline phosphatase inhibitors on intestinal transfer of calcium].
Adults rats receive by gavage 10 mM CaCl2 [+45Ca] solution containing or not 100 mM glucid, 10-100 mM EDTA or these both compounds. Calcium transfer is determined by the evaluation of [45Ca] in intestine and feces as well as in plasma and femur. Basic Ca++ transfer which corresponds to the CaCl2 solution was doubled in the presence of glucids. EDTA addition abolishes completely the glucid effect, exercising any influence on basic CA++ transfer. Injected into ligaturated ileal loop, the glucid gives the same effect. But the addition of phosphate not only removed glucid action but also inhibits the basic Ca++ transfer. The glucids, known acceptors of phosphate, increase Ca transfer. EDTA and phosphate, alkaline phosphatase inhibitors, exhibit an opposite effect. Phlorizin, as it was seen previously, acts exactly as EDTA. All these facts question: the simultaneous transfer of Ca and glucid, the possibility of a glucid phosphorylation, the part in these events of alkaline phosphatase, phosphorylating, phosphatasic and phosphorylable microvillar protein.
Alkaline Phosphatase↗
Effects of kainic acid, a cyclic analogue of glutamic acid, on cyclic nucleotide accumulation in slices of rat cerebellum.
The concentration of cyclic AMP (cAMP) and cyclic GMP (cGMP) in slices of rat cerebellum was increased markedly in the presence of 100 muM kainic acid, a cyclic analogue of glutamic acid. No acitvity was detected in other brain areas at various dosed or incubation times. Ksainic acid was significantly more potent than glutamic acid and other glutamate-like compounds. The increases in cAMP and cGMP could be differentially inhibited with theophylline or cocaine respectively, but both systems required calcium. Compounds similar in structure to kainic acid or glutamate did not block the effects of kainic acid.
Animals↗
Action potentials must admit calcium to evoke transmitter release.
There are two hypotheses to explain how neurons release transmitter. The calcium hypothesis proposes that membrane depolarization is necessary only for opening calcium channels and increasing internal calcium concentration ([Ca2+]i) near membrane transmitter-release sites. These calcium ions trigger a transient release of neurotransmitter. The calcium-voltage hypothesis postulates that voltage induces a conformational change in a membrane protein rendering it sensitive to calcium such that, in the presence of high [Ca2+]i, depolarization directly triggers transmitter release. Here we report that when calcium influx is blocked by cobalt or manganese ions in a calcium-free Ringer, as measured with Fura-2, and [Ca2+]i is elevated by liberation from a caged calcium compound, transmitter release at the crayfish neuromuscular junction is unaffected by presynaptic action potentials. These results support the calcium hypothesis.
Action Potentials↗
Calcium mass transfer with 10-hour dwell time using 1.25 versus 1.75 mmol/L calcium dialysate.
Dialysate containing 1.25 mmol/L calcium and 2.5 g/dL dextrose has been shown to have a negative calcium mass transfer (CMT) in a 4-hour exchange. Continuous ambulatory peritoneal dialysis (CAPD) patients usually perform three daytime exchanges that have short dwell times and one overnight exchange that dwells for 8-10 hours. Measurement of CMT with a 10-hour overnight CAPD exchange has not been done. Thirty-four CMT measurements were performed on 18 patients using 1.25 (n = 15) and 1.75 mmol/L (n = 19) calcium dialysate, both containing 2.5 g/dL dextrose, with a dwell time of 10 hours. The mean CMT values were -0.75 +/- 0.45 and 0.42 +/- 0.54 mmol/exchange for 1.25 and 1.75 mmol/L calcium dialysate, respectively (p < 0.001). The serum ionized calcium levels were similar in the two groups, 1.2 mmol/L. With multivariate analysis the CMT values had a negative correlation with drain volumes (r = -0.5, p = 0.0001) and serum-ionized calcium (r = -0.4, p = 0.002). In conclusion, the CMT of an overnight exchange using 2.5 g/dL dextrose is determined by the initial dialysate calcium, the ultrafiltration volume, and the serum-ionized calcium. An overnight dwell using 1.25 mmol/L calcium dialysate will contribute to negative calcium balance, allowing larger doses of oral calcium compounds to be prescribed.
Adult↗
[Active absorbable algal calcium (AAACa) changes calcium paradigm].
Active Absorbable Algal Calcium (AAA Ca) is made by submaximally (800 degrees ) heating cleaned oyster shell under reduced pressure and mixing it with similarly heated seaweed (Cystophyllum fusiforme). AAA Ca, the best absorbed from the intestine than other available calcium compounds, consequently most efficiently suppresses parathyroid hormone secretion, increases bone mineral density and decreases vertebral fracture. Aging is associated with calcium deficiency, mostly because of the decreased biosynthesis of 1,25 (OH)2 vitamin D in the kidney. Parathyroid hormone consequently increases, contributing to various diseases associated with aging such as osteoporosis or decrease of calcium in the bone, as well as hypertension, arteriosclerosis, Alzheimer's disease and osteoarthritis due to paradoxical increase of calcium in vascular walls, brain, cartilage and intracellular compartment of many kinds of cells. Mild calcium deficiency is hard to detect despite these serious consequences because of the remarkable constancy of blood calcium concentration maintained by elaborate homeostatic control. Only by successfully counteracting calcium deficiency by AAA Ca with outstanding absorbability, the phenomenon of calcium paradox becomes a recognizable reality within our reach.
Adipose Tissue↗
Active Absorbable Algal Calcium (AAA Ca): new Japanese technology for osteoporosis and calcium paradox disease.
Active Absorbable Algal Calcium (AAA Ca) is made by submaximally (800 degrees C) heating cleaned oyster shell under reduced pressure and mix it with similarly heated seaweed (Cystophyllum fusiforme). AAA Ca, best absorbed from the intestine among available calcium compounds, consequently most efficiently suppresses parathyroid hormone secretion, increases bone mineral density and decreases vertebral fracture. Aging is associated with calcium deficiency, mostly because of the decreased biosynthesis of 1,25 (OH)2 vitamin D in the kidney. Parathyroid hormone consequently increases, contributing to various diseases associated with aging such as osteoporosis or decrease of calcium in the bone, as well as hypertension, arteriosclerosis, Alzheimer's disease and osteoarthritis due to paradoxical increase of calcium in vascular walls, brain, cartilage and intracellular compartment of many kinds of cells. Mild calcium deficiency is hard to detect despite these serious consequences because of the remarkable constancy of blood calcium concentration maintained by elaborate homeostatic control. Only by successfully counteracting calcium deficiency by AAA Ca with outstanding absorbability, the phenomenon of calcium paradox becomes a recognizable reality within our reach.
Animals↗
In vitro insulinotropic action of a new non-sulfonylurea hypoglycemic agent, calcium (2s)-2-benzyl-3-(cis-hexahydro-2-isoindolinyl-carbonyl) propionate dihydrate (KAD-1229), in rat pancreatic B-cells.
We examined the in vitro insulinotropic action of a novel non-sulfonylurea compound, calcium (2S)-2-benzyl-3-(cis-hexahydro-2-isoindolinyl-carbonyl) propionate dihydrate (KAD-1229), which is a succinate derivative, using rat pancreatic islets and perfused pancreas. The sodium salt of KAD-1229 free acid (KAD-1229-Na) stimulated insulin secretion from isolated rat islets and perfused rat pancreas in a concentration-dependent manner at 0.1 to 10 microM. It produced a predominant first phase and a less prominent second phase response in the presence of 5.55 mM glucose. An ATP-sensitive K+ (K+ATP) channel activator, diazoxide, eliminated the insulinotropic effect of KAD-1229-Na. Glucose primed the B-cell in the perfused pancreas, but KAD-1229-Na did not. When the insulinotropic effects of 16.7 mM glucose on isolated rat islets were inhibited submaximally by 1 microM norepinephrine, the addition of 1 microM KAD-1229-Na reversed this inhibition. All of these insulinotropic effects of KAD-1229-Na were qualitatively indistinguishable from those of sulfonylurea compounds. We conclude that KAD-1229-Na acts on K+ATP channels of pancreatic B-cells despite its non-sulfonylurea structure.
Animals↗
Intestinal milk-bolus obstruction in formula-fed premature infants given high doses of calcium.
Supplementation of milk formulae with calcium salts is recommended for low birth weight infants. We observed a serious complication of calcium administration in too high a dosage. Three premature infants (birth weight 1,080-1,900 g and gestational age 28-35 weeks) developed an obstruction of the distal ileum during the second week of life, leading to multiple bowel perforations and development of septic peritonitis in two cases. All three patients required surgical removal of a bolus blocking the intestinal lumen. Analysis of the bolus material from one infant indicated that the formation of soaps from calcium and long-chain fatty acids had caused the obstruction. All three infants had been fed a formula for premature infants with the addition of a recently introduced commercial mineral supplement, resulting in a very high calcium concentration of the feed (40.6 mmol/L). Simulation of syringe feeding demonstrated that even higher calcium concentrations could occur in milk portions containing sedimented calcium compounds.
Animals↗
[Study of interaction between vitamin D2 and excipients by use of diffuse reflectance spectra].
The interaction of Vit D2 with calcium compounds and excipients commonly used was studied by use of diffuse reflectance spectra (DRS). The results indicated that there was some interaction between Vit D2 and calcium lactate, glucose, and a strong interaction between Vit D2 and magnesium stearate; and that the interaction between Vit D2 calcium gluconate, CaHPO4, sucrose, starch, lactose and mannitol was very weak and could even be neglected.
Drug Interactions↗
[Mechanism of excitation and contraction uncoupling in frog and guinea pig myocardial fibers during block of slow sodium-calcium channels by compound D-600].
In the experiments performed on the strips of frog's atria and ventricle it was found that rhythmic stimulation facilitated the dissociation of excitation--contraction coupling caused by D-600 compound through the block of calcium channels, i.e. D-600 prevented the increase of tension in the series of contractions or even converted positive staircase into negative one. The first contraction was affected by D-600 to a lesser degree than the subsequent ones. Guinea pig's left auriculus depressing action of D-600 was found to be strongly dependent on the frequency of stimulation. The data obtained were analysed by the model of excitation--contraction coupling. It was concluded that in amphibians as well as in mammalians tension amplitude during rhythmic activity of myocardial cells is determined mainly by Ca inflow through the excitable calcium channels. On the other hand the amplitude of the first contraction depends on the storage content determined by Ca inflow through the Ca channels open at rest. These latter channels have low sensitivity to D-600 and are better presented in atrium than in ventriculum. An increase of contraction tension observed in low sodium medium took place also under the action of D-600; in this case Ca storage was replenished by the Na-Ca exchange diffusion.
Action Potentials↗
Glucose transport in Achlya: characterization and possible regulatory aspects.
The freshwater fungus Achlya transported D-(+)glucose (glucose) and 2-deoxy-D-glucose (deoxyglucose) by an energy-related system. Their transport4 was inhibited by uncouplers of metabolic energy such as 2,4-dinitrophenol, cyanide, azide, and carbonylcyanide-p-chlorophenylhydrazone. Besides inhibiting each other, glucose and deoxyglucose transport was inhibited by D-(+)galactose, D-(+)mannose, and D-(+)xylose. Many other sugars tested failed to inhibit glucose transport implying a certain degree of specificity. Glucose transport was pH (optimum at 6.5) and temperature (optimum at 30-40 degrees C) dependent. Glucose transport was also inhibited by citrate, N6-substituted adenines (cytokinins), and iodine. None of these agents penetrated the cell membrane within the brief (1-3-min) period in which glucose transport was measured. In every case, transport was inhibited within 10 s (the shortest time in which measurements could be made). When cells were osmotically shocked to release a cell-wall membrane phosphorylated proteoglycan (PPG), they became incapable of transporting glucose for several hours until new PPG material was reisolable from the membrane by osmotic-shock treatment. The osmotically shocked cells could not transport glucose or deoxyglucose. No glucose-binding protein was detected in the shock fluid. Practically all of the glucose transported within 1-2 min was recovered as glucose-6-phosphate. No other phosphorylated sugar was detected suggesting that glucose may be phosphorylated in transport. Related studies have shown that citrate removed calcium bound by PPG; N6-substituted adenines were bound by PPG while three polyphosphorylated dinucleosides, HS3, HS2, and HS1, were displaced from it. Iodine formed stable complexes with the HS compounds. All of these agents inhibited glucose transport without entering the cell. It is therefore possible that HS compounds, calcium and PPG may be involved in maintaining the cell membrane in proper form for glucose transport.
Biological Transport, Active↗
Solid state and solution 43Ca NMR of calcium peroxides involved in the disproportionation of hydrogen peroxide by calcium hydroxide.
In order to get some insight into the mechanism of the disproportionation of hydrogen peroxide catalyzed by calcium hydroxide, 43Ca NMR spectra of enriched samples of calcium peroxides and of their precursors have been studied in both solution and solid state. This study demonstrates that no well-defined peroxidized calcium species are formed in solution, showing that the catalytic role of calcium is likely restricted to the solid state. Most of the calcium compounds that could be involved in the catalytic process have been investigated with solid state NMR. The shift and quadrupolar parameters of Ca(OH)2, CaO2.8H2O and CaO2.2H2O2 are reported for the first time. These parameters are different enough to allow the quantitative analysis of a complex mixture of these compounds by NMR.
Calcium Hydroxide↗
Thermal behaviour of chrome shavings and of sludges recovered after digestion of tanned solid wastes with calcium hydroxide.
The thermal behaviour of chrome shavings and of sludges recovered after digestion of tanned wastes with Ca(OH)2 was studied. Ashes obtained after incineration of wastes at various temperatures were analysed by X-ray diffraction and EDX method. The main crystallized phases present in the ash obtained at 600 degrees C are Cr2O3 and NaCl. The diffractograms revealed an increase in the intensities of the chromium oxide peaks and a very notable decrease of the amount of sodium chloride at 1100 degrees C. EDX analysis revealed a total disappearance of the chlorine peak at this temperature. Scanning electron micrographs show that the waste lost its fibrous aspect when the temperature increases. Formation of aggregates was noted after 550 degrees C. Combustion of organic matters and decarbonation phenomenon are the main stages observed on GTA and DTA curves of sludges. These phenomena are, respectively, exothermic and endothermic. The diffractogram of sludges recorded at 550 degrees C, in the presence of a constant oxygen surplus, revealed the presence of CaCrO4 and CaCO3.
Calcium Carbonate↗
Lethal autosomal recessive arthrogryposis multiplex congenita with whistling face and calcifications of the nervous system.
Three children from a sibship of four had congenital contractures, scarce facial expressions, central nervous system dysfunction, and early death. Extensive deposits of calcium compounds were found at postmortem examination of the nervous system and of skeletal muscle. The disorder in these sibs is presumably inherited as an autosomal recessive trait. The metabolic basis for the calcium deposition has yet to be discovered.
Arthrogryposis↗