Untersuchungen an synthetischem Hydroxylapatit im Hinblick auf den Knochenstoffwechsel von Calcium,Strontium, Barium und Radium

Zusammenfassung Das System Hydroxylapatitkristallite in einer geeigneten Lösung stellt in gewisser Hinsicht einin vitro-Analogon für den Knochenstoffwechsel der Erdalkalien dar. Es wird über Versuche berichtet, Unterschiede im Verhalten von Ca, Sr, Ba und Ra in synthetischem Hydroxylapatit festzustellen. Dazu wurden die Diskriminierungsfaktoren von Ca gegen Sr, Ba und Ra bei der Herstellung der Kristallite gemessen. Weiterhin wurde der Austausch der Erdalkalien zwischen vorgefertigten Kristalliten und einer geeigneten Lösung über eine Zeitdauer von 1000 h verfolgt. Die Diskriminierungsfaktoren nehmen mit zunehmender Ionengröße in der Reihenfolge Sr, Ba, Ra zu. Während Sr, Ca-Ionen auch im Inneren der Kristallite ersetzen kann, sind Ba und Ra fast ausschließlich auf die Oberfläche beschränkt. Für die Diskriminierung des Gesamtknochens muß angenommen werden, daß zusätzliche Prozesse eine Rolle spielen.

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Studies on synthetic hydroxyapatite crystals with regard to metabolism of calcium, strontium, barium and radium, in boneI. The discrimination against calcium

Summary The system hydroxyapatite crystals in a proper solution, in a way, represents anin vitro analogue to metabolism of alkaline earths in bone. Experiments are described to find differencies in the behaviour of Ca, Sr, Ba and Ra to synthetic hydroxyapatite crystals. Synthesizing the crystals the discrimination ratios of Ca to Sr, Ba and Ra were measured. Furthermore the exchange of alkaline earths between preformed crystals and a proper solution was studied over a period of 1000 h. The discrimination ratios grow larger with increasing ionic radius in the order Sr, Ba, Ra. While Sr can replace Ca ions also in the interior of the crystals, Ba and Ra are limited to crystal surface. With respect to the discrimination of bone it must be concluded that further processes participate.

     

The metabolism of radium-226 during pregnancy in the rat

Metabolism of radium including the transfer to the fetus through the placenta was studied during three successive pregnancies 92, 155, and 213 days after injection of 226Ra in young female rats. The cumulative fecal and urinary excretions of 226Ra in a 213-day period following injection were about 30 and 15% injected dose (%ID), respectively, most of them occurring during the first 42 days. The excretions were similar in both the pregnant and control (unmated) rats. The whole-body burden of radium (mostly in the skeleton) determined by actual analysis of the entire body was similar in the two groups and was about 53, 48, and 44 %ID at the first, second, and third pregnancy, respectively. Pregnancy alone, therefore, did not significantly affect metabolism of radium. At 20 days of gestation the mean placental content of radium was 0.005, 0.0045, and 0.0036 %ID in the first, second, and third litter, respectively; the corresponding mean fetal content was 0.01, 0.008, and 0.005 %ID. The radium burden of the full-term neonate (21-22 days) was 0.014 and 0.011 %ID for the first and second delivery, respectively. The total amount calculated of radium transferred from the mother to the 8-10 fetuses in a litter did not exceed about 0.3% of the maternal content per each pregnancy. Comparison of the ratio of radium and calcium in the fetus and maternal skeleton shows that there is a Ra-Ca discrimination during their passage from the mother to the fetus.     

Biological discrimination between calcium and strontium in kidneys and bone of young and adult rats

Effects of aging on the biological discrimination between calcium (Ca) and strontium (Sr) by the kidneys and bone were studied in male and female rats of 5 to 50 wk of age by examining Sr/Ca ratios in the plasma, urine, and bone. The Ca-Sr discrimination at the reabsorption process in the kidneys was not affected by aging in male or female rats. On the other hand, discrimination between the two elements was shown to be age-related at the absorption process in the digestive tract, and became more strict with age. The reverse situation was observed in the discrimination of Ca and Sr in the femur; younger rats discriminated the two elements more strictly than older animals.     

The effect of chelating agents on the absorption of radium by plants

Summary The absorption of radium from solution, by plants, has been compared with that of calcium, active strontium being used as a label for the calcium. It was found that radium was preferentially retained by the roots and discriminated against in passage to the shoots. However, the uptake and distribution of radium was influenced by ethylenediaminetetra acetic acid (EDTA) and citrate at the concentrations employed in water culture media to keep iron in solution. There was little discrimination against radium after plants had grown for a week in active nutrient solution when EDTA was present, but in the presence of citrate radium moved less rapidly by a factor of about 0.3. In the early stages of treatment, less than a day, the results with citrate were comparable with those of EDTA, whence it is inferred that the decrease in transfer to the shoots is dependent upon the relative rates at which the two complexes decompose.     

Étude de la discrimination strontium-calcium chez le Haricot en fonction du rapport et des teneurs respectives en Sr et Ca de la solution nutritive

The discrimination between strontium and calcium is not only conditioned by the Sr/Ca ratio of the nutrient solution but also by the total dose (Ca + Sr) of the medium. The variation of the observed ratio in relation to the total dose is closely related with the Sr/Ca ratio of the solution. Sr is preferentially fixed by the roots when the Sr/Ca ratio of the solution is low; such a result is observed in the shoots for higher ratios. For all the treatments, the OR of the leaves is lower than unity (discrimination against strontium). When the stable strontium concentration of the solution is not detectable, an increase in the calcium concentration reduces the radiostrontium retention by the roots.     

Relation Between Calcium and Strontium Transport Rates as Determined Simultaneously in the Primary Root of Zea mays

Root segments of Zea mays 55 mm long, were exposed to nutrient containing ⁸⁵Sr and ⁴⁵Ca tracers. Translocation rather than uptake was measured, using a newly-designed glass compartmentation system and validated tracer analytic model. Ca transport from solutions containing between 0.25 and 5.0 mm Ca was only slightly affected by concentration, but translocation from 0.25 to 0.05 mm solutions was markedly reduced. Maximum transport of strontium from nutrient containing 0.05 mm Ca was twice that from 2.5 mm Ca, and also twice the maximum calcium transported. Thus, under the condition simulating calcium depletion, i.e., 0.05 mm Ca, greater amounts of strontium were transported. In these cases the solutions also contained stable strontium at concentrations between 0.25 and 5.0 mm. In simultaneous determinations, the ratio of Sr to Ca moved was exactly equal to the ratio of their concentrations in nutrient solution, and there was no evidence of discrimination. Dinitrophenol reduced transport of Sr and Ca to an equivalent extent, amounting to between 2 and 9% of non-treated control levels.     

Removal of radioactive strontium from the rat by feeding stable strontium

The effect of administering the stable isotope of strontium (as phos-phate) at different dietary levels to adult rats (fed on a cereal and pulse-based diet containing 0.4% Ca) on the retention of radiostrontium (⁸⁹Sr) and radiocalcium (⁴⁵Ca) in the femur and the whole skeleton was studied for a period up to 6 weeks after an intraperitoneal injection of the two radioisotopes. The ability of strontium to remove⁸⁹Sr under the above dietary conditions was examined. Feeding Sr at 0.5% or 1% levels for 6 weeks had no effect on the skeletal content of⁸⁹Sr or⁴⁵Ca while a dietary regimen of 2% Sr (2000 times the normal content), significantly lowered the⁸⁹Sr and⁴⁵Ca content by about 30% in the femur but not in the whole skeleton. At this Sr level, the urinary excretion of the isotopes increased with a concomitant decrease in their excretion in the faeces. This study underscores the limitations of dietary Sr to mobilise⁸⁹Sr from the bones after it is incorporated in the bone mineral.     

Bone strontium in pregnant and lactating females from archaeological samples

Because plants and animals consume or absorb different amounts of strontium and calcium, anthropologists are able to use strontium/calcium (Sr/Ca) ratios from archaeologically recovered human bone to estimate the relative contributions of meat and plants to paleodiets. Often females exhibit higher Sr/Ca ratios than males, a fact usually attributed to lower meat intake among women. However, in vivo and in vitro experiments with laboratory animals show that pregnancy and lactation elevate maternal bone strontium and depress maternal bone calcium because 1) strontium is discriminated against in favor of calcium in the transport of ions to the placenta and mammary glands and 2) pregnancy and lactation facilitate absorption of alkaline earth metals from the gut. In this study, bone Sr/Ca ratios and strontium concentrations were compared between reproductive-age females, postmenopausal females, and adult males from two late prehistoric Native American sites in Georgia: the King site (N = 43) and the Etowah site (N = 51). At the King site, the mean Sr/Ca ratio of females was over 14% greater than that of males. At Etowah, the mean strontium level of reproductive-age females exceeded that of postmenopausal females by almost 25%. Most of the difference, it is argued, is due to pregnancy and lactation. A dietary preference among pregnant and lactating women for foods high in alkaline earths, particularly nuts and corn, may also be partially responsible. Until we assess the influence variables other than nutrition exert on trace element concentrations, our reconstructions of paleodiets will be suspect.     

Studies on Inhibition of Intestinal Absorption of Radioactive Strontium: II. Effects of Administration of Sodium Alginate by Orogastric Intubation and Feeding

A method is reported that enables selective suppression of absorption of radioactive strontium from ingested food material, permitting calcium to remain available to the body. Studies were carried out by measuring blood levels and bone uptake of Sr⁸⁹ and Ca⁴⁵ at different time intervals after orogastric intubation of rats. The addition of sodium alginate, derived from brown marine algae, to the radioactive isotopes increased the overall physiological discrimination against strontium by amounts up to 60% after 24 hours. This discrimination was further increased by feeding sodium alginate mixed with standard diet in the proportions of 20:80 and 30:70. The observed ratio was reduced by administration of sodium alginate from 0.25 to 0.09.Determination of the limiting dosage in rats is restricted to the amounts which rats will consume. In the event of an inadvertent release of radioactive strontium, human subjects probably could increase their intake of alginate at will, permitting a greater effectiveness of sodium alginate than could be obtained in experimental animals.     

Bone trace element pattern in an 18th century population sample of tenerife (Canary islands)

We have determined bone strontium (Sr), barium (Ba), calcium (Ca), and zinc (Zn) content in 24 samples belonging to adult individuals who died toward the end of the 18th century and were interred in a church’s floor on the island of Tenerife, comparing the results with those obtained in 14 prehistoric samples of the same island and also with those of 7 modern controls. No differences were observed between the two ancient groups, which showed higher bone strontium and barium than the modern sample, and a slightly lower Ba/Sr ratio, thus pointing to consumption of marine sources.     

Effects of strontium and barium ions on calcium bindings and transport in nerve cells

Absorption of strontium and barium ions by intracellular organelles after loading the cell with these cations together with their effects on Ca release from the intracellular stores were investigated in neurons isolated fromHelix pomatia using fura-2, a Ca-sensitive fluorescent probe. It was found that strontium ions can successively replace intracellular calcium ions in this response, whereas barium ions are not absorbed by the cell; they block calcium channels of the intracellular stores as well as at the surface membrane.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 21, No. 6, pp. 820–825, November–December, 1989.     

Discrimination between strontium and calcium in suckling rats

Discrimination between strontium (Sr) and calcium (Ca) was examined in suckling rats and compared with that in older rats after weaning. Concentrations of Sr and Ca and the Sr/Ca ratios in serum and femur of 10-d old and 21-d old rats were determined. The Sr concentrations and Sr/Ca ratios in the serum and femur of 10-d old rats were lower than those of 21-d old rats, that could be explained by the fact that 10-d old rats ingested only maternal milk in which the Sr/Ca ratio was much lower than the laboratory diet. The relative ratios of Sr/Ca in serum and femur to that in the diet were found to be higher in 10-d old rats compared with those in 21-d old rats, and also higher than those in the older rats after weaning, as described in our previous publication. This result may reflect that discrimination between Sr and Ca during intestinal absorption is lacking in very young animals before weaning and develops after this age. Renal discrimination between Sr and Ca in the suckling rats at 10 d of age was evaluated by determining the relationship between the relative clearances of Ca and Sr. The mathematical model proposed by Walser and Robinson was applied on these results and the parameter for the equation, that is, the discrimination constant, was shown to be higher in 10-d old rats compared to those in young (7 wk of age) and adult (25 wk of age) rats. This result suggests that the discrimination of Sr in favor of Ca during the tubular reabsorptive process may not be fully developed in the very young rats before weaning.     

Retention of 45Ca in rats and lambs associated with the onset of nutritional muscular dystrophy.

Nutritional myopathy has been induced in both rats and lambs by feeding diets low in selenium. The distribution of 45Ca, administered as 45CaCl2, has been examined firstly by autoradiography, and secondly by measuring the excretion of 45Ca in urine and faeces. Autoradiographs of skeletal muscle from unsupplemented animals showed radioactivity over discrete muscle fibres at a stage when no abnormalities were apparent using conventional staining techniques. Similar retention of 45Ca was found in some of the tubules in the kidneys of selenium-deficient rats. Total excretion in urine and faeces of lambs, examined for 48 h after intravenous administration of 45CaCl2, showed that in normal animals 18-6% of the dose was excreted, whereas in dystrophic lambs 12-0% was lost. The difference was significant at the 2% level. The respiratory rates of isolated skeletal muscle mitochondria, measured polarographically in the presence of glutamate and pyruvate as substrates, were low for dystrophic rats. Respiratory control indices were 1-0 for the same preparations but for supplemented rats they were all above 1-0. The differences in respiratory rates were significant at the 1% level. The major conclusion drawn from the results of these experiments is that one of the first effects of sleenium deficiency which can be visualized is the abnormal retention of calcium by individual muscle fibres.     

Sources and fluxes of submarine groundwater discharge delineated by radium isotopes

This paper reports the results derived fromradium isotopes of a submarine groundwaterdischarge (SGD) intercomparison in thenortheast Gulf of Mexico. Radium isotopesamples were collected from seepage meters,piezometers, and surface and deep ocean waters.Samples collected within the near-shore SGDexperimental area were highly enriched in allfour radium isotopes; offshore samples wereselectively enriched. Samples collected fromseepage meters were about a factor of 2–3higher in radium activity compared to theoverlying waters. Samples from piezometers,which sampled 1–4 meters below the sea bed were1–2 orders of magnitude higher in radiumisotopes than surface waters. The twolong-lived Ra isotopes, ²²⁸Ra and²²⁶Ra, provide convincing evidence thatthere are two sources of SGD to the study area:shallow seepage from the surficial aquifer andinput from a deeper aquifer. A three end-membermixing model can describe the Ra distributionin these samples. The short-lived radium isotopes, ²²³Ra and²²⁴Ra, were used to establish mixing ratesfor the near-shore study area. Mixing wasretarded within 3 km of shore due to a strongsalinity gradient. The product of the mixingrate and the offshore ²²⁶Ra gradientestablished the ²²⁶Ra flux. This flux mustbe balanced by Ra input from SGD. The flux ofSGD within 200 m of shore based on the²²⁶Ra budget was 1.5 m³ min^?1.This flux agreed well with other estimatesbased on seepage meters and ²²²Rn.     

Endotrophic calcium, strontium, and barium spores of Bacillus megaterium and Bacillus cereus

Foerster, Harold F. (The University of Texas, Austin), and J. W. Foster. Endotrophic calcium, strontium, and barium spores of Bacillus megaterium and Bacillus cereus. J. Bacteriol. 91:1333-1345. 1966.-Spores were produced by washed vegetative cells suspended in deionized water supplemented with CaCl(2), SrCl(2), or BaCl(2). Normal, refractile spores were produced in each case; a portion of the barium spores lost refractility and darkened. Thin-section electron micrographs revealed no apparent anatomical differences among the three types of spores. Analyses revealed that the different spore types were enriched specifically in the metal to which they were exposed during sporogenesis. The calcium content of the strontium and the barium spores was very small. From binary equimolar mixtures of the metal salts, endotrophic spores accumulated both metals to nearly the same extent. Viability of the barium spores was considerably less than that of the other two types. Strontium and barium spores were heat-resistant; however, calcium was essential for maximal heat resistance. Significant differences existed in the rates of germination; calcium spores germinated fastest, strontium spores were slower, and barium spores were slowest. Calcium-barium and calcium-strontium spores germinated readily. Endotrophic calcium and strontium spores germinated without the prior heat activation essential for growth spores. Chemical germination of the different metal-type spores with n-dodecylamine took place at the same relative rates as physiological germination. Heat-induced release of dipicolinic acid occurred much faster with barium and strontium spores than with calcium spores. The washed "coat fraction" from disrupted spores contained little of the spore calcium but most of the spore barium. The metal in this fraction was released by dilute acid. The demineralized coats reabsorbed calcium and barium at neutral pH.     

The use of strontium and barium analyses for the reconstruction of the diet of the early medieval coastal population of Gdańsk (Poland): A preliminary study

Barium and strontium analyses yield an important perspective on temporal shifts in diet in relation to social and environmental circumstances. This research focuses on reconstructing dietary strategies of individuals in the early medieval (12-13th century) population of Gdańsk on the coast of the Baltic Sea. To describe these strategies where seafood rich in minerals was included in the diet, levels of strontium, barium, calcium and phosphorus were measured in first permanent molars of adult men and women whose remains were excavated from the churchyard in the city centre. Faunal remains from the excavation were analysed as an environmental background with respect to the content of the above-mentioned elements. The impact of diagenesis on the odontological material under study was also determined by an analysis of the soil derived from the grave and non-grave surroundings. For verification of diagenetic processes, the calcium/phosphorus index was used. Strontium, calcium, phosphorus and barium levels were determined with the spectrophotometric method using the latest generation plasma spectrophotometer Elan 6100 ICP-MS. From the results of the analysis of taphonomic parameters such as the soil pH, potential ion exchange in the grave surroundings and the Ca/P ratio, it can be inferred that diagenetic factors had little impact on the studied material. From this pilot study we can conclude that in the early Middle Ages in the Baltic Sea basin, seafood was included in the diet from early childhood and at the same time the diet contained calcium-rich milk products (also rich in minerals). The lack of sex differences may indicate the absence of a sex-specific nutritional strategy in childhood and early adolescence.     

The strontium-induced calcium-release process and its implication in contractility of skeletal muscle of Rana ridibunda

The electrical and mechanical activities of isolated frog muscle fibres have been recorded simultaneously under conditions (chloride-free saline containing 78.5 mM strontium acetate substituting for NaCl and CaCl2) that allow the development of a tubular strontium permeability. Under voltage-clamp conditions a large part of the contraction is due to the slow inward ISr since both are inhibited by Ni (10 mM). The remaining component of contraction, which seems to be potential-dependent, is not abolished by tetracaine (40 microM) which blocks the current-dependent component. A cumulative effect of strontium, which is not observed in the presence of Ni, leads to a 60-80% reduction in contractility for an estimated [Sr]i near 3 X 10(-4) M while the ending of the contraction observed when Sr is replaced by Ba is never obtained. In contrast no cumulative effect is observed when Ca substitutes for Sr. The first evoked inward current following a caffeine contracture fails to elicit a contraction, but in Ringer 78.5 Sr, contractility is progressively restored by successive depolarizations up to an amplitude which corresponds to 25-40% of the maximum activity. In the presence of Ca instead of Sr, the restoration of contractility reaches 100%. This recovery does not occur when the inward current is blocked by Ni. After strontium loading, a calcium entry fails immediately and reversibly to induce a mechanical response while barium ions induce a progressive and irreversible block of contractility. These results suggest that the strontium entry during successive depolarizations leads to a progressive replacement of intrareticular calcium by strontium. When all the calcium ions have been substituted for by strontium ions, the contractile apparatus remains capable of being activated by intrareticular strontium.     

Immobilization of Saccharomyces Cerevisiae Cells by Gel Entrapment Using Various Metal Alginates

Summary Immobilization of whole yeast cells (Saccharomyces cerevisiae) in calcium alginate is well known. The present work describes the feasibility of gel entrapment of whole cell yeast using strontium, barium, calcium–strontium, calcium–barium and strontium–barium alginates.     

Elemental composition of human milk from mothers of premature and full-term infants during the first 3 months of lactation

To examine longitudinal and gestational effects of mineral content in human milk, we analyzed human milk from lactating mothers of premature (PRT,n = 24, < 2000g birth weight, < 37 wk gestation) and fullterm (FT,n = 19, > 2500g, 39–41 wk gestation), living in Newfoundland, Canada. Samples were collected once a week for 8 wk with one final sample collected at 3 mo. Milk samples collected in acid-washed containers were wet ashed with concentrated HNO₃, and barium, cadmium, calcium, cesium, cobalt, copper, cerium, lanthanum, magnesium, manganese, molybdenum, nickel, lead, rubidium, tin, strontium, and zinc were measured using inductively coupled plasma-mass spectrometry. Data were analyzed using standard multiple-regression procedures with correlated data analyses to take account of the relationship between successive weeks. Results indicated lower Ca and Pb in PRT milk. Calcium was the only nutritionally significant element to differ between groups. Molybdenum in both PRT and FT milk showed a definite decrease with time, suggesting that the Mo content in milk is homeostatically regulated. However, Ce, La, Ba, and Sn did not display any pattern indicative of biological regulation and potential human requirement.