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At least 199 records · Page 11Linked to original sources
PubMed1964

STUDIES ON THE INHIBITION OF INTESTINAL ABSORPTION OF RADIOACTIVE STRONTIUM. 3. THE EFFECT OF ADMINISTRATION OF SODIUM ALGINATE IN FOOD AND IN DRINKING WATER.

A method is reported which permits selective suppression of absorption of radioactive strontium from ingested food material, permitting calcium to be available to the body. Studies were carried out by measuring bone uptake of Sr(89) and Ca(45) when various amounts of sodium alginate were fed with the diet. Long-term studies were made in which two different levels of radioactivity were used, to determine the pattern of Sr(89) deposition with continuous intake of binding agent. It was found that administration of sodium alginate as a jelly overcomes the problem of constipation and effectively reduces Sr(89) uptake, up to 83%. This fact represents a significant finding with respect to the use of the compound in human subjects. Addition of sodium alginate to drinking water is effective with low levels of Sr(89) intake.This naturally occurring water-soluble macromolecular substance possesses several advantages in use for the suppression of absorption of radioactive strontium when compared with synthetic ion exchange resins: there is no disturbance of electrolyte balance; efficiency is not reduced by treatment over a prolonged period of time; and finally, the product is palatable.

Alginates↗
PubMed1998

A longitudinal study of calcium homeostasis during human pregnancy and lactation and after resumption of menses.

To clarify the role of the intestine, kidney, and bone in maintaining calcium homeostasis during pregnancy and lactation and after the resumption of menses, a longitudinal comparison was undertaken of 14 well-nourished women consuming approximately 1200 mg Ca/d. Measurements were made before conception (prepregnancy), once during each trimester of pregnancy (T1, T2, and T3), early in lactation at 2 mo postpartum (EL), and 5 mo after resumption of menses. Intestinal calcium absorption was determined from the enrichment of the first 24-h urine sample collected after administration of stable calcium isotopes. Bone mineral of the total body and lumbar spine was measured by dual-energy X-ray absorptiometry and quantitative computerized tomography, respectively. Twenty-four-hour urine and fasting serum samples were analyzed for calcium, calcitropic hormones, and biochemical markers of bone turnover. Despite an increase in calcium intake during pregnancy, true percentage absorption of calcium increased from 32.9+/-9.1% at prepregnancy to 49.9+/-10.2% at T2 and 53.8+/-11.3% at T3 (P < 0.001). Urinary calcium increased from 4.32+/-2.20 mmol/d at prepregnancy to 6.21+/-3.72 mmol/d at T3 (P < 0.001), but only minor changes in maternal bone mineral were detected. At EL, dietary calcium and calcium absorption were not significantly different from that at prepregnancy, but urinary calcium decreased to 1.87+/-1.22 mmol/d (P < 0.001) and trabecular bone mineral density of the spine decreased to 147.7+/-21.2 mg/cm3 from 162.9+/-25.0 mg/cm3 at prepregnancy (P < 0.001). Calcium absorption postmenses increased nonsignificantly to 36.0+/-8.1% whereas urinary calcium decreased to 2.72+/-1.52 mmol/d (P < 0.001). We concluded that fetal calcium demand was met by increased maternal intestinal absorption; early breast-milk calcium was provided by maternal renal calcium conservation and loss of spinal trabecular bone, a loss that was recovered postmenses.

Absorptiometry, Photon↗
PubMed2002

A study of the activity of the plasma membrane Na/Ca exchanger in the cellular environment.

The Na/Ca exchanger is a large-capacity system that is supposed to be predominant in the ejection of calcium in excitable tissues. Its activity is normally evaluated in electro-physiological experiments or using Na-loaded cells or plasma membrane vesicles in experiments in which the activity is estimated by measuring the uptake of isotopic calcium. Here the activity of the exchanger has been evaluated in model cells that coexpress the exchanger together with the (protein) Ca indicator aequorin targeted to the different subcellular compartments. Exchanger isoform 1 (NCX1) has been used for experiments in which the effect of its overexpression has been evaluated on the Ca homeostasis in the cytoplasm at large, in the endoplasmic reticulum, in mitochondria, and in the layer of cytoplasm underneath the plasma membrane. The experiments have shown that, despite its very low calcium affinity, the exchanger was active in cells at rest in which calcium is around 100 nM. They have also shown that expressed NCX1 significantly reduced the cytosolic and mitochondrial calcium transients produced by the emptying of the ER calcium stores with InsP3-linked agonists. The effect of the expressed NCX1 on the calcium homeostasis in the domain underneath the plasma membrane was more complex: The exchanger apparently catalyzed a reverse operation, leading to increased penetration of calcium.

Adenosine Triphosphate↗
PubMed1998

Dietary protein affects intestinal calcium absorption.

BACKGROUND: Changes in dietary protein in adults are associated with changes in urinary calcium excretion. The mechanisms underlying this effect are not completely understood, but alterations in intestinal absorption of calcium are not thought to be involved. OBJECTIVE: We reexamined this mechanism by evaluating the effect of 2 amounts of dietary protein (low: 0.7 g/kg; and high: 2.1 g/kg) on fractional calcium absorption in 7 healthy, young women. DESIGN: The experiment consisted of 2 wk of a well-balanced diet containing moderate amounts of calcium, sodium, and protein followed by 5 d of an experimental diet that contained 1 of 2 amounts of protein and constant amounts of other nutrients known to influence calcium metabolism. Seven subjects received both amounts of dietary protein in random order. Blood and urine were sampled at baseline and on day 4. Fractional calcium absorption was measured by dual-stable calcium isotopes on day 5. In a second study of 5 additional women, we evaluated the effects of dietary fiber on calcitropic hormones. RESULTS: Subjects developed hypocalciuria and secondary hyperparathyroidism on day 4 of the low-protein diet. Urinary calcium excretion and the glomerular filtration rate were elevated significantly by day 4 of the high-protein compared with the low-protein diet. Fractional calcium absorption after the low-protein diet was 0.19+/-0.03, which was significantly lower than that after the high-protein diet (0.26+/-0.03, P=0.05). CONCLUSION: These data provide evidence that depressed intestinal calcium absorption explains, in part, low-protein-induced secondary hyperparathyroidism.

Adult↗
PubMed1997

Randomised controlled trial of a synthetic triglyceride milk formula for preterm infants.

AIMS: To test whether use of infant formula containing synthetic structured triglycerides results in: (i) increased palmitate absorption; (ii) increased total fat absorption; (iii) reduction in calcium soap formation in the gut; and hence (iv) increased calcium absorption. METHODS: A randomised study was made of 24 infants comparing three formulas, one containing the synthetic fat Betapol with 74% of palmitate in the 2-position, which was substantially higher than in the two comparison diets (8.4% and 28%). The hypothesised outcomes were tested using balance studies, detailed chemical analysis of stool specimens and dual calcium isotope tracers (44calcium orally and 46calcium intravenously). RESULTS: Three of the four hypotheses were confirmed: use of a formula rich in 2-position palmitate (i) improved palmitate (16:0) and also (18:0) absorption; (ii) reduced the formation of insoluble calcium soaps in the stool; and (iii) improved calcium absorption, determined by the dual tracer technique from 42 (SE 3)% to 57 (7)%. CONCLUSION: Synthetic triglycerides that mimic the stereoisometric structure of those in breast milk may have a valuable role in the design of formulas used for preterm infants in neonatal intensive care units.

Animals↗
PubMed1977

Calcium balance and calcium requirements in middle-aged women.

Calcium balance performance was evaluated in 130 normal perimenopausal women ages 35 to 50, studied on their usual, self-selected dietary calcium intakes. Two distinct balance methods were used, one based on customary intake and output measurements, and the other based on absorption and clearance of two simultaneously administered calcium isotopes. Both methods yielded essentially identical results. Under study conditions as closely approximating normal living as possible, these women averaged -24 and -31 mg Ca/day by the two balance methods (exclusive of unmeasured dermal losses). More significantly, there was a positive correlation between intake and balance, with women on higher self-selected intakes exhibiting more positive balance than women selecting lower intakes. The calcium intake predicted from our data which would be required to produce an average balance of zero was 1.241 g/day. This is significantly in excess of the current recommended dietary allowance for calcium. The implications and significance of this discrepancy are explored in detail.

Absorption↗
PubMedDate not supplied

[Element analysis of sclerotic plaques of large blood vessels by laser mass-spectrometry].

Laser mass-spectroscopic studies were carried out of element and isotope composition of sclerotic formations (patches) of large blood vessels on calcinosis and ateromatosis stage, as well as of the region adjoining the calcinosic formation of the vessel tissue. It was shown that the basis of the "patches" consists of carbon, nitrogen and oxygen. 13 elements of micromixtures were found. Changes were revealed of the content of some elements and anomalous disturbance of natural distribution of oxygen, silicon, magnesium and calcium isotopes depending on the stage of arteriosclerosis formation.

Arteries↗
PubMed1988

Guar delays intestinal calcium absorption in man.

The effect of guar on the absorption of the calcium isotope 45Ca was measured in six normal subjects. Values for the delay before the initial rise of radioactivity in plasma (delta t) and the initial fractional absorption rate (alpha) were derived using a non-linear curve-fitting computer programme. Guar significantly reduced the fraction of 45Ca absorbed between 15 and 120 min. Guar increased the delay before the initial rise of radioactivity in plasma and reduced the initial fractional absorption rate. The results show that a dietary fibre which does not bind calcium in vitro reduces the rate of calcium absorption in man.

Adult↗