[On isotope diagnosis of the so-called primary and secondary inflammatory necrotic diseases].
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Adult↗
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Results for “Calcium Isotopes”
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[Prevention of osteoporosis by foods and dietary supplements. Chocolate malt drink MILO: nutrition in children and calcium absorption].
Calcium is not sufficiently consumed by Japanese at any age groups. Childhood is an important period, when they should earn bone minerals to reach higher peak bone mass for reducing the risk of osteoporosis in their later life. Children require higher calcium consumption per body weight than adults, and also establish their dietary pattern in this period. MILO has attracted widespread popularity as a good-taste chocolate-flavored malt drink with balanced nutrients for children. We developed FOSHU MILO with fructooligosaccharides (FOS) aiming at improving absorption of calcium, which is originally rich in the products. Using the calcium stable isotope (44)Ca, we found that the urinary excretion in the subject fed the products with FOS was higher than that of control product without FOS, suggesting that the FOSHU MILO is effective in promoting calcium absorption from the intestines. MILO could contribute to bone health by increasing consumption of calcium and/or improving the calcium bioavailability.
Beverages↗
Effects of high compared with low calcium intake on calcium absorption and incorporation of iron by red blood cells in small children.
BACKGROUND: The potential benefits of increasing calcium intake in small children must be balanced with the potential risk to iron utilization from high calcium intakes. OBJECTIVE: This study was designed to evaluate the relation between calcium intake and calcium absorption and iron incorporation into red blood cells. DESIGN: We performed a multitracer, crossover study of the absorption of calcium and red blood cell incorporation of iron in 11 preschool children aged 3-5 y who had been adapted for 5 wk to low- (502 +/- 99 mg) and high- (1180 +/- 117 mg) calcium diets. Stable-isotope studies were performed by using 44Ca and 58Fe given orally with meals and 46Ca given intravenously. RESULTS: Iron incorporation into red blood cells 14 d postdosing was similar (6.9 +/- 4.2% compared with 7.9 +/- 5.5%; NS) with the low- and high-calcium diets, respectively. Total calcium absorption (181 +/- 50 compared with 277 +/- 91 mg/d; P = 0.002) was greater in children with the higher calcium intake. CONCLUSIONS: Our findings indicate that small children may benefit from calcium intakes similar to those recommended for older children without adverse effects on dietary iron utilization.
Absorption↗
Effect of previous dietary history of calcium intake on the skeleton and calcium absorption in the rat.
1. Rats were fed either a high or a low calcium diet for 6 weeks. Thereafter all were given the low calcium diet, and the time during which differences persisted between the two groups in apparent absorption of calcium and urinary excretion of calcium has been studied. The apparent absorption of calcium is the same in the two groups after 15 days but the differences in urinary excretion of calcium persist longer.2. Faecal endogenous calcium and true absorption of calcium have been measured by an isotope dilution technique. The fall in apparent absorption of calcium seen in rats fed a high calcium diet is in part due to a fall in true absorption. Faecal endogenous calcium is also increased in these animals.3. The amount of calcium and phosphate in the bones is increased by feeding a high calcium diet and decreased by feeding a very low phosphate diet. Femur, humerus, caudal vertebrae and calvaria are equally affected by the different diets.4. There are strong inverse correlations between absorption of calcium and the percentage of calcium in the bones. This suggests that absorption of calcium may be regulated by the degree of bone mineralization.5. Rats were fed diets with different calcium phosphate ratios for 6 weeks. Thereafter all were given a low calcium diet with a calcium: phosphorous ratio of 1 and absorption and urinary excretion of calcium were studied. The effects of the different diets may be explained by their effect on calcium status and bone mineralization.
Animals↗
THE EFFECTS OF ZINC ON CONTRACTILITY, MEMBRANE POTENTIALS, AND CATION CONTENT OF RAT ATRIA.
Zinc depresses the contractile force of electrically driven rat atria logarithmically with time. The threshold concentration is about 5 x 10(-6)M zinc and the half-time for contractile depression at 10(-4)M is about 25 minutes. Zinc also depresses spontaneous activity of atria and alters the transmembrane potential parameters in a manner similar to quinidine. Unlike quinidine, zinc causes an elevation of the resting potential and an elevation of cellular potassium which varies with time in the same way as the resting potential. Exposure to 10(-4)M zinc for 60 minutes causes a statistically significant fall in atrial calcium content and an amount of radioactively labeled zinc is taken up which is quantitatively equal to the calcium lost. Zinc has no effect on rigor caused by iodoacetate but inhibits rigor caused by 1-fluoro-2,4 dinitrobenzene. It is postulated that zinc depression of contractile force is not due to metabolic inhibition, probably not due to quinidine-like action on the cell membrane, but may be due to an interference in the handling of calcium by the cell.
Calcium↗
Mg and Ca isotope fractionation during CaCO3 biomineralisation.
The natural variation of Mg and Ca stable isotopes of carbonates has been determined in carbonate skeletons of perforate foraminifera and reef coral together with Mg/Ca ratios to assess the influence of biomineralisation processes. The results for coral aragonite suggest its formation, in terms of stable isotope behaviour, approximates to inorganic precipitation from a seawater reservoir. In contrast, results for foraminifera calcite suggest a marked biological control on Mg isotope ratios presumably related to its low Mg content compared with seawater. The bearing of these observations on the use of Mg and Ca isotopes as proxies in paleoceanography is considered.
Animals↗
[Studies on calcium metabolism in primary hyperparathyroidism using a double isotope method].
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Adolescent↗
Comparison of in vitro and in vivo 44Ca labeling of bone by scanning ion microprobe.
To determine whether Ca incorporation from medium into cultured bone represents normal mineralization, we labeled some neonatal mouse calvariae in vitro and others in vivo with the stable isotope 44Ca and compared surface label localization with a scanning ion microprobe utilizing secondary ion mass spectrometry. To label in vitro, we incubated live calvariae in medium containing 40Ca or 44Ca for 3 h. Compared with a 44Ca/40Ca ratio of 0.020 with 1 mM 40Ca, the ratio with 1 mM 44Ca was 0.135 and with 2 mM 44Ca was 0.556. Erosion revealed a marked decrease in 44Ca/40Ca with depth. To label in vivo, we subcutaneously injected 40Ca or 44Ca into mice equal to a percentage of their total body weight and dissected the calvariae 24 h later. Compared with a 44Ca/40Ca ratio of 0.021 with 2% 40Ca, the ratio with 2% 44Ca was 0.120 and with 6% 44Ca was 0.205. Erosion revealed only a slight decrease in 44Ca/40Ca with depth. Elemental distribution maps of in vivo labeled samples show broad deposition of 44Ca, whereas maps of in vitro labeled bones show 44Ca preferentially localized at the surface in contact with the medium. Thus calvariae can be labeled with 44Ca both in vitro and in vivo. However, the differing patterns of isotope localization under the conditions of this study indicate that in vitro Ca deposition differs from normal in vivo bone mineralization.
Animals↗
Bone resorption and mineral excretion in rats during spaceflight.
Bone resorption was measured directly in flight and synchronous control rats during COSMOS 1129. Continuous tracer administration techniques were used, with replacement of dietary calcium with isotopically enriched 40Ca and measurement by neutron activation analysis of the 48Ca released by the skeleton. There is no large change in bone resorption in rats at the end of 20 days of spaceflight as has been found for bone formation. Based on the time course of changes, the measured 20-25% decrease in resorption is probably secondary to a decrease in total body calcium turnover. The excretion of sodium, potassium, and zinc all increase during flight, sodium and potassium to a level four to five times control values.
Animals↗
Isotopic sensitivity in the microsomal oxidation of the dihydropyridine calcium entry blocker nifedipine.
The primary deuterium isotope effect on Vm for the microsomal oxidation of the dihydropyridine calcium entry blocker nifedipine [4-(2-nitrophenyl)-2,6-dimethyl-3,5- bis(methoxycarbonyl)-1,4-dihydropyridine] has been measured. The magnitude of the kinetic isotope effect, 6.7, suggests that the rate-limiting step in the mechanism of microsomal oxidation of nifedipine involves the loss of a hydrogen atom rather than nitrogen oxidation. Thus the microsomal oxidation of nifedipine is mechanistically different from that of other 1,4-dihydropyridines.
Animals↗
Iron: its intracellular localization and possible role in cell division.
When HeLa cells are fixed with ethanol, extracted with 0.1 N HCl, and incinerated at 540 degrees C, all organic constituents and all ions studied are removed with the exception of iron. The gross outlines of cell structures are preserved and high concentrations of residual ash in interphase nucleoli and mitotic chromosomes suggest that there may be a shift in iron salts during the cell cycle. Experiments with cells isotopically labeled in proteins, nucleic acids, lipids, and polysaccharides indicate that the iron is bound to a polysaccharide. Addition of iron chelating agents to living cells causes a selective inhibition of DNA synthesis. These data suggest that iron may play a crucial role in the mitotic process.
Calcium↗
The metabolism of radium in dairy cows.
1. The isotopes (45)Ca and (224)Ra were administered simultaneously, both orally and intravenously, to two pairs of cows. 2. The first pair of animals received large doses of (224)Ra and (45)Ca, which produced clinical and metabolic disturbances. 3. The second pair of animals received much smaller doses and showed no clinical disturbances. The mean recoveries in these animals of (45)Ca and (224)Ra in the 8 days after the oral administration were respectively: from faeces, 63.2 and 103.8%; from urine, 0.26 and 0.44%; from milk, 15.8 and 0.35% of the dose; and in the 8 days after intravenous administration: from faeces, 20.5 and 36.5%; from urine, 1.56 and 17.6%; from milk, 49.3 and 11.8% of the dose. 4. Calculation of discrimination factors shows that absorptive discrimination played the most important part in the overall discrimination between the calcium and radium in their passage from diet to milk, but that mammary discrimination plays a more important role than in the overall discrimination between calcium and strontium or barium. 5. In its treatment by the kidney radium is more like strontium than barium, but radium is actively secreted by the gut in the same way as barium. 6. In its skeletal metabolism radium is indistinguishable from calcium and strontium except in its rate of resorption, which is similar to that of barium.
Animals↗
Use of 48Ca as a stable isotope tracer analyzed by proton activation.
The use of the stable isotope 48Ca as a tracer in biological systems has been studied. Determination of 48Ca concentrations in samples was accomplished by proton activation via the (p,n) reaction with subsequent measurement of gamma-ray spectra from 44-h 48Sc and 4-h 44Sc. With protons of about 5.5 MeV and a Ge(Li) gamma-ray detector, and with no chemical processing of the samples, ratios of these two radioisotopes can be determined with sufficient precision to allow 48Ca tracer studies to be performed with sensitivity at least equivalent to that possible with the common 45Ca radioactive tracer.
Activation Analysis↗
Selenium utilization during human lactation by use of stable-isotope tracers.
We examined utilization of selenomethionine (SeMet) and selenite in six lactating (L) and six nonlactating (NL) women, 2-3 mo postpartum, and seven never-pregnant (NP) women by use of stable-isotope tracers. All groups had similar selenium status at the start of the study. Significantly more selenium from SeMet than from selenite was absorbed and appeared in plasma in all groups. Milk contained more selenium from apparently absorbed SeMet than from selenite. More selenium from apparently absorbed selenite than from SeMet appeared in urine of NP and NL subjects whereas L subjects had approximately the same amount of selenium from apparently absorbed selenite and SeMet in their urine. All groups retained significantly more selenium from SeMet than from selenite; L women retained more selenium from selenite than did the other two groups. Absorption and retention of selenium from SeMet in L women did not appear to be significantly different from that in other women, suggesting that selenium requirements during lactation are increased mainly because of milk losses.
Absorption↗
A simple method for measurement of intestinal calcium absorption in humans by double-isotope technique.
We describe a method for the fast calculation of total fractional calcium absorption (TFCaA) by the double-isotope technique (45Ca orally and 47Ca intravenously). The gamma- and beta-activities of plasma or urine samples were measured simultaneously. 47Ca activity was obtained by a gamma-ray spectrometer after exclusion of scandium 47. The 45Ca activity was measured directly by subtracting the 47Ca plus 47Sc component from the total beta-activity. In addition, 45Ca activity was determined after 8 weeks, to allow for 47Ca and 47Sc decay. There was good correlation between these two methods of measuring 45Ca activity. TFCaA was calculated both by deconvolution taken as a reference method and from the equilibrium quotient 45Ca/47Ca observed in several blood or urine samples collected at different times. The most convenient sampling time for calculation of this ratio was reappraised, taking into account the type of solution ingested orally (water or milk). The results indicate that simultaneous counting of gamma- and beta-activities of an appropriate plasma or urine sample provides a good and rapid measure of the calcium absorption. This method is considered to be useful as a clinical tool.
Adult↗
Identification of a Mn-O-Mn cluster vibrational mode of the oxygen-evolving complex in photosystem II by low-frequency FTIR spectroscopy.
We have developed conditions for recording the low-frequency S(2)/S(1) Fourier transform infrared difference spectrum of hydrated PSII samples. By exchanging PSII samples with buffered (18)O water, we found that a positive band at 606 cm(-)(1) in the S(2)/S(1) spectrum in (16)O water is clearly downshifted to 596 cm(-)(1) in (18)O water. By taking double-difference (S(2)/S(1) and (16)O minus (18)O) spectra, we assign the 606 cm(-)(1) mode to an S(2) mode and also identify a corresponding S(1) mode at about 625 cm(-)(1). In addition, by Sr and (44)Ca substitution experiments, we found that the 606 cm(-)(1) mode is upshifted to about 618 cm(-)(1) by Sr(2+) substitution but that this mode is not affected by substitution with the (44)Ca isotope. On the basis of these results and also on the basis of studies of Mn model compounds, we assign the 625 cm(-)(1) mode in the S(1) state and the 606 cm(-)(1) mode in the S(2) state to a Mn-O-Mn cluster vibration of the oxygen-evolving complex (OEC) in PSII. This structure may include additional bridge(s), which could be another oxo, carboxylato(s), or atoms derived from an amino acid side chain. Our results indicate that the bridged oxygen atom shown in this Mn-O-Mn cluster is exchangeable and accessible by water. The downshift in the Mn-O-Mn cluster vibration as manganese is oxidized during the S(1) --> S(2) transition is counterintuitive; we discuss possible origins of this behavior. Our results also indicate that Sr(2+) substitution in PSII causes a small structural perturbation that affects the bond strength of the Mn-O-Mn cluster in the PSII OEC. This suggests that Sr(2+), and by inference, Ca(2+), communicates with, but is not integral to, the manganese core.
Calcium Isotopes↗
Stable strontium absorption as a measure of intestinal calcium absorption: comparison with the double-radiotracer calcium absorption test.
1. Stable strontium (Sr) has been proposed as an alternative to calcium (Ca) isotopes for the measurement of intestinal Ca absorption. The aim of this study was to compare the time course and fractional absorption of Ca and Sr, when both are measured using dual-tracer techniques. 2. 45Ca and Sr absorption tests were carried out on consecutive days in patients with osteoporosis (n = 10) or chronic renal failure (n = 7). Both tests were repeated in four patients with chronic renal failure after treatment with calcitriol (1 microgram daily for 10 days). 3. The time course of Ca absorption was determined using the 85Sr (intravenous)/45Ca (oral) dual-tracer technique, and the time course of Sr absorption using 85Sr (intravenous)/stable Sr (oral). Oral tracers were administered on consecutive days with a test meal containing 5.3 mmol of Ca and 2.5 mmol of either stable Sr or Ca carrier. The fractional absorption of 45Ca and Sr at 6h (FA360) and the absorption rate as a function of time were calculated by deconvolution. 4. The mean FA360 for Sr (20.2%) was lower than the mean FA360 for 45Ca (37.8%, P < 0.001, paired t-test), but the time course of Sr absorption was similar to that of Ca. There was a significant correlation between the FA360 for 45Ca and Sr, although the relationship was improved by including a quadratic term (R2 = 0.89, P < 0.001, significance of quadratic term, P < 0.05). After 1,25-dihydroxyvitamin D treatment, the FA360 of stable Sr increased 4.29-fold, whereas the FA360 of 45Ca increased only 2.4-fold.(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗
Calcium 45 autoradiography and dual-isotope single-photon emission CT in a canine model of cerebral ischemia and middle cerebral artery occlusion.
PURPOSE: To determine whether transient ischemia can be separated from permanent ischemia via calcium 45 autoradiography and to assess the applicability of dual isotope single-photon emission CT (SPECT) in the evaluation of cerebral blood flow. METHODS: We examined calcium influx in 12 dogs (group A) by using whole-brain calcium 45 autoradiography: Animals received 250 microCi/kg 24 hours after 30-minute (n = 6) or permanent (n = 6) middle cerebral artery (MCA) occlusion. Forty-eight hours after MCA occlusion, 5-mm coronal brain sections were fixed for either autoradiography or pathologic examination. In a separate study, 9 mongrel dogs (group B) were given 250 microCi/kg calcium 45 and a mean dose of 700 microCi/kg technetium Tc 99m hexamethylpropyleneamine oxime intravenously. A silicone plug was then injected into the internal carotid artery and angiography was performed to verify MCA occlusion. A 10th (control) animal did not undergo occlusion. In an 11th animal, placement of the plug could not be achieved and a slurry of microfibrillar collagen was injected into the carotid artery. No angiography was performed in animals 10 and 11. After occlusion, each animal was injected with a mean dose of 126 microCi/kg simultaneous acquisition for technetium 99m and 123I-iodoamphetamine. RESULTS: In group A, all animals who had permanent MCA occlusion showed infarction and increased calcium 45 uptake in infarcted territories. None of the animals who had 30-minute occlusion had either increased calcium 45 uptake or infarction at 48 hours. In group B, 7 or 10 dogs had SPECT findings that were consistent with the calcium autoradiographic marker for ischemia. One animal died during the procedure and 1 dog served as a control. CONCLUSION: Calcium 45 autoradiography allowed distinction between areas of temporary and permanent occlusion. Iodoamphetamine imaging was not consistently sensitive to that level of ischemia. Timing of calcium influx may lead to insight that could impact timing of pharmacologic or endovascular intervention.
Amphetamines↗