Average Calcium Concentration Research Articles

Maintenance of secretion of calcium and magnesium during infusions of parathyroid hormone to lactating goats.

Hourly secretion of calcium and magnesium by goat mammary glands was studied following infusions of bovine parathyroid hormone (PTH) into the mammary artery in amounts (6-15 ng/kg per min) giving rise to levels of PTH in mammary venous blood commonly observed during spontaneous hypocalcaemia (2.4-13 micrograms/l). In two series of experiments a 3 h infusion of PTH was given. The first series was carried out at a normal level of plasma calcium, while the availability of calcium was increased by a 20 h infusion of CaCl2 in the other series. No changes in mammary secretion of calcium or magnesium could be observed during the hormone infusions. A decrease in the urinary excretion of calcium occurred, thus demonstrating the activity of the infused PTH. In a third experiment an 18.5 h infusion of PTH (6 ng/kg per min) into the mammary artery was given to study possible effects of a more prolonged increase of PTH concentrations. This infusion caused a gradual increase in plasma levels of calcium. Average concentrations of calcium in milk increased slightly (about 5%) in both glands (P less than 0.05). The hourly yield of milk was not significantly changed in the infused gland after 18.5 h of PTH infusion. A small but significant increase occurred in the non-infused gland. Yields of magnesium were not influenced by the infusion of PTH. It was concluded that losses of calcium into milk are independent of the PTH concentration in the circulation.

Surface studies of the Medicus nickel matrix cathode

It is shown that activation of the Medicus nickel matrix cathode results in the development of a surface microstructure consisting of alkaline earth oxide-rich regions, 20–40 μm in diameter, distributed over the nickel-rich cathode coating. An in situ correlation between thermionic emission current and surface composition indicates a primary dependence upon the relative Ba to Ni concentration. A time dependent increase in the average calcium concentration at the surface has also been observed; compositional analyses of material evaporating from the cathode revealed that this calcium may accumulate at the surface due to the preferential release of barium and strontium. The accumulation of calcium at the surface, as well as the loss of barium, are believed to contribute to emission degradation during cathode life. Ion sputtering studies suggest the dispensing of barium and the dependence of the surface microstructure upon the initial thermal/ electrolytic activation. Although barium concentrations in excess of the oxide stoichiometry are measured, the presence of elemental barium monolayers has not been verified. It is concluded that owing to these chemical, compositional and morphological effects, the nickel matrix cathode should not be viewed simply as an oxide cathode physically supported by a metal matrix.

On the variation in calcium content of the waters of Laccadives (Arabian Sea)

Abstract The concentration of calcium was determined in the samples collected from four stations in the Laccadive Sea and from two lagoons of Kavaratti and Minicoy atolls. The calcium/chlorinity ratio for the open ocean samples was found to be 0.02168 ± 0.000015 with an average calcium concentration of 424.9 mg kg −1 . A maximum in this ratio was observed at about 200 m depth, below the salinity maximum corresponding to Arabian Sea Surface Water mass. No increase in calcium concentration or in calcium/chlorinity ratio was observed down to 1500 m depth, thereby ruling out the possibility of any calcium carbonate dissolution at these depths. Samples from Kavaratti and Minicoy lagoons gave much lower values of the Ca/Cl ratio (0.02145 ± 0.000036 and 0.02142 ± 0.000046, respectively). These low values are apparently the result of calcium utilization by the coral reefs. Using the reduction in the calcium concentration inside the lagoon, in the absence of any chemical precipitation, the annual CaCO 3 production by reef flat and lagoon on Kavaratti Atoll has been estimated as 1 · 10 7 kg. This gives an average gross production of 1.4 kg CaCO 3 per m 2 per yr.

CALCIUM DEFICIENCY AND OCCURRENCE OF TOPPLE DISORDER IN BULBOUS IRIS

"Iris topple" is a physiological disorder of bulbous Iris that is characterized by weakness of the flower stalk at the uppermost node and the concommitant failure of the flower bud to remain erect. This condition occurs when bulbous Iris is forced in calcium-deficient growth media. An acropetal pattern of stem elongation in Iris and the general immobility of calcium within plants lead to a localized calcium-deficient region that exhibits severe cellular and ultrastructural abnormalities. The innermost three leaves and flower stalk from plants showing "Iris topple" as the only symptom of calcium deficiency have an average tissue calcium concentration of 0.3%.

A study of fluoride, calcium and magnesium in the Northern Indian Ocean

Estimation of fluoride in the Northern Indian Ocean gives an average concentration of 1.31 ± 0.01 mg/l and a F/Cl ratio of (6.84 ± 0.01) · 10 −5. The Ca/Cl ratio in the area is 0.02229 ± 0.000005 with an average calcium concentration of 432 ± 5 mg/l. In the Bay of Bengal this ratio is influenced by river runoff while in the Arabian Sea the outflow from the Red Sea increases the ratio. The Mg/Cl ratio is observed to be 0.06631 ± 0.00003 with an average magnesium concentration of 1281 ± 14 mg/l. Neither the river runoff nor the Red Sea outflow has any influence on this ratio. Similarities or differences of these values spatially and with reference to literature data are discussed.

Eclampsia in the bitch.

ABSTRACTOn the basis of a study of the literature and of nineteen new cases of eclampsia in dogs, the aetiology, clinical picture and treatment of the disease are discussed. Average plasma calcium concentrations in seventeen of the bitches in the authors' material was 6–16 ± 0–77 mg/100 ml; the remaining two had normal levels (over 9 mg/100 ml). Plasma magnesium levels were normal in all the bitches, and averaged 2–07 ± 0–38 mg/100 ml.

The distribution of sodium and potassium in amphibian embryos during early development.

1. Intracellular and intercellular concentrations of sodium and potassium have been measured in pregastrular embryos of Xenopus laevis and Amblystoma mexicanum. Calcium and magnesium contents have also been determined.2. Between egg and gastrula stages of development the potassium concentration is near to 60 m-mole/l. embryo. Up to the blastula stage the sodium concentration is near to 50 m-mole/l. embryo; the amount of sodium in the embryo begins to fall just before gastrulation.3. Embryo calcium and magnesium concentrations show no significant variations prior to gastrulation. Average calcium concentrations for the different stages range from 5 to 8 m-mole/l. embryo; magnesium concentrations lie between 12.4 and 17 m-mole/l. embryo.4. The intercellular fluid contains 100 mM sodium and 1 mM potassium; the majority of the sodium is ionically active. As no net uptake of sodium or potassium occurs before gastrulation these cations must have been transferred from the cells to the cavity.5. At all developmental stages studied, the intracellular potassium concentration is close to 100 m-mole/l. cell water. Intracellular sodium falls steadily from 80 m-mole/l. cell water in eggs to 30 m-mole/l. cell water at the beginning of gastrulation.6. The intracellular sodium activity, measured with sodium sensitive intracellular micro-electrodes, is relatively constant between egg and blastula stages at about 14 mM. During each cell division cycle the intracellular sodium activity rises transiently by 2-3 mM.

Parathyroidectomy in the snake Rhabdophis tigrinus tigrinus.

Serum calcium concentrations were measured in intact, sham-operated and parathyroidectomized snake. Rhabdophis t. tigrinus. In intact animals, the average calcium concentration was higher in females than in males. Surgical total parathyroidectomy brought about hypocalcemia. In males, serum calcium concentrations 10 and 20 days after parathyroidectomy were 67 and 59% of those of the sham-operated controls, respectively. Similar values were obtained in females.

Reaction of surface-applied superphosphate with soil. I. The fertilizer solution and its initial reaction with soil

The phosphorus and calcium contents of the fertilizer solution from surfaceapplied superphosphate in contact with moist soil were shown to be similar to those of the metastable triple-point solution (MTPS) produced when an excess of monocalcium phosphate is shaken with water. The average phosphorus, calcium, and sulphur concentrations of saturated aqueous extracts of superphosphate at 20�C were 4.0M, 1.5M , and 0.023M respectively. The pH of these extracts ranged from 1.60 to 1.92 (0.15-0.47 units higher than that of MTPS). The sulphur content of the fertilizer solution was generally one-fiftieth to one-hundredth of the phosphorus content. In the absence of leaching both diffusion and capillarity were involved in the movement of phosphate from superphosphate particles into moist soil. The fertilizer solutes entered the soil mainly by diffusion but on soils of low moisture content the increase in pore size of the fertilizer particles, which resulted from the dissolution of monocalcium phosphate, led to a reversal of the suction gradient between soil and particle which caused movement of some of the fertilizer solution into the soil by capillarity. Leaching of superphosphate applied to dry soils by rainwater is likely to yield fertilizer solutions which have higher pH, lower phosphorus and calcium contents, and higher sulphur contents than the saturated solutions arising from superphosphate particles in contact with moist soil. When synthetic fertilizer solution reacted with acid soils the rate of removal of phosphate and calcium from solution depended upon the phosphate sorption capacity of the soil. In calcareous soil the calcium carbonate played a major part in phosphate precipitation. Appreciable amounts of iron and particularly aluminium were dissolved from each of the soils studied by the synthetic fertilizer solution to give solutions which, on standing, readily formed precipitates of phosphate. Both sulphate and organic sulphur compounds were displaced from the acid soils by the fertilizer solution but, in the calcareous soil, sulphate was coprecipitated with the phosphate.

CHROMIC OXIDE IN DIGESTIBILITY STUDIES WITH LACTATING DAIRY COWS

Chromic oxide (Cr2O3) in paper pellets was used as an indicator for digestibility studies with four Holstein-Friesian cows fed rations composed of different roughage to concentrate ratios. Cows A and B received one pellet, or 3.46 g of Cr2O3, whereas cows C and D received three pellets, or 10.38 g of Cr2O3, daily.Recovery of Cr2O3 in the feces varied from 84 to 103% for animals A and B and from 92 to 95% for animals C and D. The coefficients of apparent digestion of dry matter were lower (P < 0.01) when the Cr2O3 method was used instead of the conventional method. When samples were taken at 0500, 0900, 1300 and 1700 hours, the Cr2O3 method gave average estimates of digestibility for animal pairs A, B and C, D that were 94.2 and 97.5% of those obtained by the conventional method. Standard deviations for both the Cr2O3 and conventional methods were relatively high.Excretion patterns of Cr2O3 were not signicantly correlated with those of crude protein, phosphorus and calcium. The average concentrations of crude protein, phosphorus and calcium in compounded feces samples collected at 0500, 0900, 1300 and 1700 hours were 101.3, 100.6 and 96.7% of those in samples of the total excretions.The daily administration of 10.38 g of Cr2O3 at 0900 hours for eight days, and the collection of fecal grab samples at 0500, 0900, 1300 and 1700 hours daily during the last five days seemed satisfactory for estimating apparent digestibility of dry matter.

Ionic balance in the blood of pulmonata

1. 1. Sodium, potassium, calcium and magnesium have been determined in the blood of hydrated specimens of Helix pomatia, Cepaea nemoralis, C. hortensis, Arianta arbustorum, Archachatina marginata, Arion ater ater, A. ater rufus, Lymnaea stagnalis and Planorbarius corneus, and the average values, together with others already published, have been compared. 2. 2. Such averages for sodium, potassium and calcium each vary by a factor of 2–2·5 while those for magnesium vary by a factor of 12. 3. 3. There is a positive correlation between the average concentrations of calcium and magnesium. 4. 4. In the Stylommatophora, there is a negative correlation between the average concentrations of sodium and magnesium, perhaps related to a similarity of osmotic pressure in hydrated specimens.

The cellular transport of calcium in rat liver.

The bidirectional transport of calcium in rat liver was studied using slices labeled with Ca(47) in a closed two compartment system. Steady-state conditions were observed with influx and efflux transfer coefficients of 0.070 and 0.018 per minute, respectively. The rapidly exchanging cell fraction of calcium existed at a concentration three times higher than the average cell concentration of calcium and occupied cell loci comprising less than 25% of the cell mass, suggesting that calcium associated with the cell membranes, nuclei, and mitochondria participated in the rapidly exchanging fraction. At pH 7.4 and 377deg;C, the influx transfer coefficient was 25% above the steady-state condition and accumulation of calcium by the slices occurred. Studies of the effects of varied physical and chemical conditions revealed that the influx transfer coefficient was increased by elevated pH, strontium, certain metabolic inhibitors, and 2 mM concentrations of cyclic adenosinemonophosphate and adenosinetriphosphate. The influx transfer coefficient was decreased by reduced temperature, decreased pH, magnesium, and 10 mM adenosinetriphosphate. The efflux transfer coefficient was increased by elevated pH, strontium, iodoacetate, and adenosinetriphosphate, and was decreased by reduced temperature and by N-ethylmaleimide. These data support the thesis that cell transport of calcium is accomplished by the attachment of calcium atoms to the cell surface and transport through the plasma membrane bound to either specific carriers or to membrane constituents. Conditions which change the affinities, capacities, and mobilities of plasma membrane ligands that bind calcium or cause extracellular chelation of calcium are capable of altering the rate of calcium transport.