Effects Of Excess Calcium Research Articles

The Effects of Excess Calcium and Aging Media on the Mechanical Properties of Calcium Phosphate Filling Materials

The effect of excess calcium and aging media on calcium phosphate biomaterials mechanical strength was studied. The variation of excess calcium and sample type has shown different performance when they are being aged in the moist environment (ME) and the simulated body fluid (SBF). The calcium phosphates were synthesized via low temperature hydrothermal method and sampled to two types of powder-water (3:2) mixture and paste for 90 days of the aging time. Two mechanical tests were applied, compression and diametrical tensile test, while XRD to evaluate phases. Scanning electron micrograph showed the paste samples that soaked in SBF was better entanglement of the particles, better compression strength but with degradation and diametrical tensile strength improvement by aging. Calcium hydroxide and ammonium di-hydrogen phosphoric was traced in all the samples along with calcium deficient hydroxyapatite as the main phase.

High calcium intake linked to cardiac death

Calcium supplementation is widely used by elderly individuals in Western countries to protect against osteoporosis. However, the effect of excess calcium on extraskeletal systems, such as the heart and vasculature, is largely unknown. Xiao et al. now report that a high intake of supplementary calcium (>1,000 mg per day) is associated with an increased risk of death from cardiovascular disease (CVD) in men, but not in women.

Effects of excess calcium as a different form on mineral metabolism in rats

ABSTRACTExcess calcium is known to affect the metabolism of other minerals. Calcium carbonate is the main source of calcium used in previous experiments that investigated excess calcium. Thus, it remains to be clarified whether other forms of calcium also have the same adverse effects. The effects of a high‐calcium carbonate diet or a high‐calcium citrate diet on mineral concentration in several tissues of rats were examined. Male rats aged 5 weeks were fed one of the experimental diets for 4 weeks. The control diet contained calcium as calcium carbonate at the requirement level. High‐calcium diets contained calcium carbonate or calcium citrate at a level of fivefold greater than the requirement level. In rats fed the high‐calcium diets, a similar decrease in phosphorus (in the plasma) and iron (in the testis, liver and femur) was observed. Hepatic copper increased in rats fed the high‐calcium diets, whereas renal copper decreased. Therefore, excess calcium affects these mineral metabolisms regardless of its form. In contrast, the high‐calcium carbonate diet increased femoral zinc and decreased femoral magnesium, but the high‐calcium citrate diet did not affect these minerals in the femur, which suggests that the effect of excess calcium on minerals partly depends on its form.

Effect of calcium, Bay K 8644, and reduced perfusion on basic indices of myocardial function in isolated hearts from rats after prolonged exposure to ethanol.

We previously reported findings consistent with a marked upregulation in functional L-type voltage-operated calcium channels (L-VOCCs) in hearts obtained from rats exposed over the long term to ethanol. These experiments were undertaken to establish whether detrimental effects on cardiac function were associated with excess calcium entry into the myocardium in these hearts. Isolated hearts from adult male Sprague-Dawley rats received intoxicating concentrations of ethanol for 6-10 days by inhalation, were perfused with Krebs-Henseleit buffer by a modified Langendorff technique, and several functional parameters were assessed continuously. In some experiments, the calcium concentration in the perfusate was first reduced from the physiologic range (1.2 mM) to 0.15 mM and then increased in a step-wise fashion to 4 mM. In other experiments, hearts were exposed to buffer containing concentrations of the L-VOCC activator, (+/-)Bay K 8644, increasing from 10(-9) to 10(-6) M. These perfusion protocols were repeated in hearts from treated animals subject to reduced coronary flow because of induction of partial left ventricular ischemia. There were some close similarities in the effects of these different stimuli. When the calcium concentration in the perfusate exceeded a physiologic level, there were signs of decreased function relative to controls in the hearts from ethanol-exposed rats. Thus R-wave amplitude and systolic pressure were lower, diastolic pressure also was reduced, but heart rate was elevated above that of controls. Similarly the presence of (+/-)Bay K 8644 in the perfusate caused a decrease in systolic and diastolic pressure and an increase in heart rate in hearts from ethanol-exposed rats. When cardiac perfusion was reduced in vitro by inflation of a balloon in the left ventricle, some of the effects of excess calcium and (+/-)Bay K 8644 were reproduced in control hearts. However, imposition of this "ischemic" stress did not appear to exacerbate the effects of prior exposure to ethanol. In general, in control hearts, indices of contractility were increased across the range of calcium concentration or by perfusing with (+/-)Bay K 8644. Hearts from ethanol-exposed rats, however, showed no further increase in these parameters once physiologic levels of calcium were exceeded, or showed inhibition of contractility in the presence of (+/-)Bay K 8644. The results are consistent with calcium entry through L-VOCCs in hearts from ethanol-exposed animals having detrimental effects on cardiac function once physiologic levels are exceeded. However, it is possible that these channels also may be involved in maintenance of cardiac function at hypocalcemic levels.

Characteristics of the cytotoxic effects of the phenothiazine class of calmodulin antagonists

We have characterized the antiproliferative effects of the phenothiazines, a group of antipsychotic drugs possessing a wide range of pharmacological actions. The phenothiazines inhibited both the proliferation and clonogenicity of L1210 leukemic lymphocytes. This effect was dependent on both time of exposure and concentration of drug. Clonogenicity of cells in the logarithmic phase of growth was inhibited by greater than 99% at a concentration of drug that had no effect on cells in the plateau phase of growth. Human and murine cell lines, grown either in suspension or in monolayers, were equally susceptible. Calmodulin (CaM), purified from L1210 cells by preparative polyacrylamide gel electrophoresis, had sensitivity to inhibition by phenothiazines similar to that reported for CaM prepared from brain. The order of potency was trifluoperazine ⩾ fluphenazine > chlorpromazine > chlorpromazine-sulfoxide. As a class, these drugs were less potent antagonists of CaM than was the bee venom polypeptide, melittin. The antiproliferative effects of phenothiazines were similar to the anticalmodulin effects. Thus, the same order of potencies was seen for both effects; the shapes of the dose-response curves were similarly steep and the effects of excess calcium on the inhibition of both were identical. These studies add pharmacological support for CaM being a potential intracellular target for the antiproliferative effect of the phenothiazines.

Effects of Excess Calcium on a Fluoride-Magnesium Interrelationship in Chicks

The effects of excess calcium on the previously reported fluo ride-magnesium interrelationship were studied using a factorial arrangement of treatments involving two levels of calcium (1.0 and 1.67%), two of fluoride (0.005 and 0.085% ) and two of magnesium (0.07 and 0.47% ). As noted earlier, growth rate was reduced by fluoride alone, but was reduced to a much greater extent with fluoride plus magnesium. Magnesium alone did not influence growth rate. Excess calcium improved growth in chicks fed fluoride alone or fluoride plus magnesium, but growth rate was still inferior, particularly in the fluoride plus magnesium group, to the control or the diet containing magnesium alone. Growth rate was not affected by calcium level in chicks fed the other diets. Bone ash was increased with fluoride alone, reduced slightly with magnesium alone and reduced greatly by the combination of fluoride and magnesium. Excess cal cium increased bone ash only slightly in chicks fed high magnesium alone or in combination with fluoride. The characteristic leg weakness observed in chicks fed the high fluoride-high magnesium diet was not influenced by dietary cal cium. Excess calcium drastically reduced the fluoride content of plasma and bone of chicks fed the high fluoride diets. High dietary calcium also reduced plasma magnesium levels in chicks fed high magnesium diets. From these re sults, it was concluded that the beneficial effects of excess calcium on the fluo ride-magnesium interrelationship are mediated primarily through reduced ab sorption of fluoride, and possibly magnesium, rather than through correction of a relative calcium deficiency. J. Nutr. 102: 1699-1708, 1972. Earlier studies showed that feeding pens in electrically heated, wire-floored chicks high levels of both fluoride and mag- chick batteries. Each of the eight experi- nesium resulted in a greater depression mental treatments was assigned to four in growth than observed in chicks fed pens (replicates) of 10 chicks each with fluoride alone, and produced a character- the restriction that no replicate of the same istic leg weakness and reduced bone ash treatment could appear in the same battery not observed in chicks fed either fluoride or the same deck level, or magnesium alone (1â€5).Increasing die- The treatments were arranged factori- tary phosphorus (1) or calcium (2) had ally with two levels of calcium (1.0 and some beneficial effect in alleviating certain 1.67%), two of fluoride (0.005 and symptoms of the high fluoride-high mag- 0.085% ) and two of magnesium (0.07 nesium interrelationship, but did not cor- and 0.47% ). An increase of 0.67% cal- rect the condition. The purpose of the prA¨s- cium in the high calcium diet was chosen ent investigation was to investigate the since this level is equivalent on a gram mechanism by which increasing dietary molecule basis to 0.4% of magnesium, the calcium exerted a beneficial effect. increment used to produce the high mag nesium diet. The diets used were the same EXPERIMENTAL PROCEDURES

Calcium Requirements of Turkey Breeder Hens

LITTLE information is available on the effects of excess calcium on breeder chickens or turkeys, although Berg et al. (1962) have shown that 2.75 or 3.25% calcium in the diets of young chicken hens significantly depressed hatchability of eggs as compared with eggs from pullets fed 1.75 or 2.25% calcium. March and Biely (1961) reported increased mortality involving renal dysfunction in chicken hens fed 3 or 4% calcium, compared with that of hens fed diets containing 2% calcium.The National Research Council (1960) recommends 2.25% of calcium in turkey breeder diets, but Jensen et al. (1963) have reported that optimal performance, as measured by hatchability of eggs, was obtained with Broad Breasted Bronze hens fed diets containing 1.75% calcium. Higher levels, 2.5 and 3.25%, depressed hatchability but did not affect egg fertility, or growth and viability of progeny.Since many turkey breeder hens are fed oyster shell free-choice, resulting in…