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PubMed1999

Ionized serum magnesium in type 2 diabetes mellitus: its correlation with total serum magnesium and hemoglobin A1c levels.

BACKGROUND: Hypomagnesemia has been described in diabetes mellitus. We sought to compare serum total and ionized magnesium (Mg) levels in patients with type 2 diabetes with control subjects and to determine the relationship between diabetes control, as assessed by hemoglobin A1c (Hb A1c) and Mg (total and ionized). METHODS: Serum ionized Mg was measured by ion-selective electrode (ISE) method using the NOVA electrode. RESULTS: Serum ionized Mg was significantly higher in diabetics than in control subjects, whereas no difference was found in total Mg. Serum ionized Mg correlated with total Mg in diabetics and in control subjects. There was an inverse correlation between total Mg and Hb A1c; the correlation was not statistically significant between ionized Mg and Hb A1c. CONCLUSIONS: Our data do not support routine Mg supplementation or monitoring in type 2 diabetes.

Adult↗
PubMed2003

Calculation of ionization balance and electrical conductivity in nonideal aluminum plasma.

A practical approach has been implemented to calculate the ionization balance and electrical conductivity of warm dense aluminum plasma with the Coulomb coupling effect taken into account. The correction term for ionization potential is formulated with a number of basic dimensionless parameters that characterize nonideal plasma and incorporated with the fitted formulas of excess free energy given by Tanaka, Mitake, and Ichimaru [Phys. Rev. A 32, 1896 (1985)] and Chabrier and Potekhin [Phys. Rev. E 58, 4941 (1998)] to determine the ionization balance in an equilibrium state. The calculated degree of ionization of aluminum plasma exhibits a sudden increase near the solid density approximately 1 g/cm(3) at temperatures of a few eV, which effectively demonstrates the pressure-induced ionization. The electrical conductivity is evaluated in a partially ionized plasma regime based on a linear mixture rule that takes into account both the electron-ion and electron-neutral collisions and then the computed results are compared with available data from recent experiments. It is shown that the calculation well reproduces the overall trend of measured electrical conductivity of nonideal aluminum plasma accounting for the metal-insulator transition.

Journal Article↗
PubMed2005

Backward Raman amplification in a partially ionized gas.

Compressing laser pulses to extremely high intensities through backward Raman amplification might be accomplished in a plasma medium. While the theory is relatively straightforward for homogeneous fully ionized plasma, a number of important effects enter when the plasma is not fully ionized. In particular, when a mixture of gases is employed to accomplish the coupling, there can be several thresholds for incremental ionization. The refraction of both the pump and the seed is then strongly affected by the plasma ionization. Moreover, in the case of Raman backscattering in partially ionized plasma, the degree of plasma ionization is particularly sensitive to the counterpropagating geometry. This idea is examined in light of data for a recent experiment on a Raman amplifier.

Journal Article↗
PubMed2000

From above threshold ionization to statistical electron emission: the laser pulse-duration dependence of C60 photoelectron spectra

The photoelectron spectra of C60 ionized using a 790 nm laser with pulse durations varying from 25 fs to 5 ps have been determined. For 25 fs pulses, in the absence of fragmentation, the ionization mechanism is direct multiphoton ionization with clear observation of above threshold ionization. As the pulse duration is increased, this becomes dominated by a statistical ionization due to equilibration among the electronic degrees of freedom. For pulse durations on the order of a ps coupling to the vibrational degrees of freedom occurs and the well-known phenomenon of delayed (&mgr;s) ionization is observed.

Journal Article↗
PubMed2001

Ratiometric comparison of intense field ionization of atoms and diatomic molecules.

Intense-laser ionization rates for rare gas atoms and diatomic molecules have been precisely compared by making simultaneous measurements of ionization yield vs laser intensity for mixed atomic and molecular targets. At a given laser intensity, the N (2) and F (2) ionization yields are slightly greater than that of Ar. Conversely, comparison of O (2) and S (2) with Xe indicates significant ionization suppression in these molecules. Recent molecular ionization models that successfully describe ionization suppression in O (2) and its absence in N (2) fail to explain our observations in F (2) and S (2).

Journal Article↗
PubMed1992

Ionization of tyrosine residues in human serum albumin and in its complexes with bilirubin and laurate.

Spectrophotometric titration of human serum albumin indicates that ionization of the 18 tyrosine residues takes place between pH 9 and 12.7. A Hill plot indicates that protons dissociate co-operatively from tyrosine residues, in pure albumin between pH 11.0 and 11.4 with a Hill coefficient 1.7, and in the bilirubin-albumin complex between pH 11.2 and 11.7 with a Hill coefficient 1.6. With a stopped-flow technique it is shown that about seven of the tyrosines ionize fast, with rate constants well above 10(2) s-1, when pH is suddenly changed from near neutral to pH 11.76. Further residues ionize slowly, with rate constants around 10(2) s-1 or less. The N-form of albumin (pH 6) contains one more fast ionizing tyrosine than the B-form of albumin (pH 10). Binding of bilirubin or laurate to the albumin molecule (molar ratio 1:1) transforms one to three of the fast ionizing tyrosines to slowly ionizing.

Bilirubin↗
PubMed2005

Low adjusted serum ionized calcium concentration shortly after birth predicts poor outcome in neonatal hypoxic-ischemic encephalopathy.

AIM: Hypoxic-ischemic reperfusion injury causes either necrosis or apoptosis, and the influx of ionized calcium into cells is the major cause of both types of cell death. The aim of this study was to investigate whether or not the serum ionized calcium concentration in neonates with hypoxic-ischemic encephalopathy (HIE) could be used to predict their outcome. METHODS: Serum samples were obtained shortly after birth from 20 HIE neonates who had not urinated or received treatment with calcium. Serum ionized calcium concentrations were adjusted for pH using a correction formula. Twelve neonates without any disease were selected as a control. The results were compared between nine HIE neonates who made a full recovery, 11 who died or had neurologic deficits, and 12 normal neonates. RESULTS: Considered together, the two HIE groups had lower serum ionized calcium concentrations (1.05 +/- 0.10 mmol/L) than the control group (1.22 +/- 0.07 mmol/L; P < 0.0001). Moreover, serum ionized calcium concentrations in the group with the poor outcome (0.99 +/- 0.07 mmol/L) were lower than those in the group that made a full recovery (1.13 +/- 0.06 mmol/L; P=0.0016). CONCLUSIONS: The serum ionized calcium concentrations shortly after birth were significantly lower in neonates with HIE who had a poor outcome. Low concentrations may reflect multiple organ damage, particularly involving the brain.

Asphyxia Neonatorum↗
PubMed2003

Ionization chamber volume averaging effects in dynamic intensity modulated radiation therapy beams.

The commercial cylindrical ionization chamber ionization integration accuracy of dynamically moving fields was evaluated. The ionization chambers were exposed to long (14 cm), narrow (0.6, 1.0, 2.0, and 4.0 cm) 6 MV and 18 MV fields. Rather than rely on the linear accelerator to reproducibly scan across the chamber, the chambers were scanned beneath fixed portals. A water-equivalent phantom was constructed with cavities that matched the chambers and placed on a computer-controlled one-dimensional table. Computer-controlled electrometers were utilized in continuous charge integrate mode, with 10 samples of the charge, along with time stamps, acquired for each chamber location. A reference chamber was placed just beneath the linear accelerator jaws to adjust for variations in linear accelerator dose rate. The scan spatial resolution was selected to adequately sample regions of steep dose gradient and second spatial derivative (curvature). A fixed measurement in a 10 x 10 cm2 field was used to normalize the profiles to absolute chamber response. Three ionization chambers were tested, a microchamber (0.009 cm3), a Farmer chamber (0.6 cm3) and a waterproof scanning chamber (0.125 cm3). The larger chambers exhibited severe under-response at the small field's centers, but all of the chambers, independent of orientation, accurately integrated the ionization across the scanned portal. This indicates that the tested ionization chambers provide accurate integrated charges in regions of homogeneous dose regions. Partial integration (less than the field width plus the chamber length plus 2 cm), yielded integration errors of greater than 1% and 2% for 6 MV and 18 MV, respectively, with errors for the Farmer chamber of greater than 10% even for the 4 cm wide field.

Equipment Failure Analysis↗
PubMed2004

Dosimetric characterization of a large area pixel-segmented ionization chamber.

A pixel-segmented ionization chamber has been designed and built by Torino University and INFN. The detector features a 24 x 24 cm2 active area divided in 1024 independent cylindrical ionization chambers and can be read out in 500 micros without introducing dead time; the digital charge quantum can be adjusted between 100 fC and 800 fC. The sensitive volume of each single ionization chamber is 0.07 cm3. The purpose of the detector is to ease the two-dimensional (2D) verifications of fields with complex shapes and large gradients. The detector was characterized in a PMMA phantom using 60Co and 6 MV x-ray photon beams. It has shown good signal linearity with respect to dose and dose rate to water. The average sensitivity of a single ionization chamber was 2.1 nC/Gy, constant within 0.5% over one month of daily measurements. Charge collection efficiency was 0.985 at the operating polarization voltage of 400 V and 3.5 Gy/min dose rate. Tissue maximum ratio and output factor have been compared with a Farmer ionization chamber and were found in good agreement. The dose profiles have been compared with the ones obtained with an ionization chamber in water phantom for the field sizes supplied by a 3D-Line dynamic multileaf collimator. These results show that this detector can be used for 2D dosimetry of x-ray photon beams, supplying a good spatial resolution and sensibly reducing the time spent in dosimetric verification of complex radiation fields.

Algorithms↗
PubMed1981

Effect of ionized calcium and soluble magnesium on the predictability of the performance of Mueller-Hinton agar susceptibility testing of Pseudomonas aeruginosa with gentamicin.

The soluble and ionized calcium and magnesium contents of 18 lots of Mueller-Hinton agar medium from three different manufacturers were analyzed, and the results were correlated with medium performance. A standardized disk diffusion test, with Pseudomonas aeruginosa (ATCC 27853) and a 10-microgram gentamicin disk, served as an indicator of medium performance. Zone diameters correlated well with the ionized calcium values and the sum of the ionized calcium and soluble magnesium values in the different lots (r = -0.88 for both). Zone diameters correlated poorly with ionized magnesium values (r = -0.57), which were best described by a curvilinear relationship. Supplementation of lots of Mueller-Hinton agar medium with equivalent amounts of calcium and magnesium as the chloride, gluconate, or glycerophosphate salts produced identical decreases in zone sizes. Adjustment of deficient lots of Mueller-Hinton agar medium with ionized calcium or soluble magnesium or both (as the gluconate salts), to match the concentrations in lots that provided satisfactory zone sizes (17 to 19 mm), resulted in performance comparable to that of the control lots. Sixteen strains of Pseudomonas aeruginosa, ranging from resistant to susceptible, responded to cation adjustment in the same manner as the ATCC quality control strain. Satisfactory medium performance can obviously be assured by biological means in aminoglycoside susceptibility testing of Pseudomonas aeruginosa on Mueller-Hinton medium; however, cation adjustment of medium to predetermined levels of ionized calcium and soluble magnesium can now also provide desirable performance levels for P. aeruginosa on Mueller-Hinton medium.

Calcium↗
PubMed1998

Circulating ionized and total magnesium in end-stage kidney disease.

BACKGROUND: Circulating magnesium exists in the ionized state and in the undissociated form, either bound to albumin, or complexed to various anions. Until recently, only the measurement of total plasma magnesium has been possible. Now circulating ionized magnesium can be assessed as well. METHODS: Total and ionized plasma magnesium were determined in 43 patients on maintenance hemodialysis (dialysate composition: calcium 1.75 mmol/l, magnesium 0.75 mmol/l) before a dialysis session and in a group of 23 healthy subjects. RESULTS: The total (1.16 [1.03-1.31] versus 0.81 [0.78-0.89] mmol/l; median and interquartile range) and the ionized (0.71 [0.66-0.78] versus 0.54 [0.53-0.59] mmol/l) plasma magnesium levels were significantly higher (p < 0.01) and the ionized plasma magnesium fraction lower (0.61 [0.58-0.65] versus 0.67 [0.64-0.70]; p < 0.02) in patients than in controls. CONCLUSION: The determination of circulating ionized magnesium using selective electrodes is an attractive method to evaluate extracellular magnesium in kidney disease.

Adolescent↗
PubMed1999

Intracellular and extracellular, ionized and total magnesium in pre-eclampsia and uncomplicated pregnancy.

Magnesium (Mg) and calcium (CA) concentrations in women with pre-eclampsia, women with an uncomplicated pregnancy and non-pregnant women were compared. Ionized serum magnesium and calcium concentrations and intracellular magnesium concentrations were measured in 15 pregnant women with severe pre-eclampsia, 34 uncomplicated pregnant women early, at midterm and preterm in their pregnancy and 24 non-pregnant women. The ionized calcium concentration did not chance during normal pregnancy or during pre-eclampsia relative to non-pregnant women. In contrast, elevated total and ionized magnesium serum concentrations were found in women with severe pre-eclampsia (total Mg = 0.85+/-0.11 mM, ionized Mg = 0.61+/-0.06 mM) relative to uncomplicated pregnant women (total Mg = 0.72+/-0.06 mM, ionized Mg = 0.53+/-0.03 mM). Total magnesium in pre-eclamptic women were similar to non-pregnant women. Intracellular ionized and total magnesium concentrations in mononuclear blood cells and erythrocytes were similar in pre-eclamptic women and women with uncomplicated pregnancy. Serum magnesium concentrations are elevated in severe pre-eclamptic women relative to women with uncomplicated pregnancy and are related to birth weight and gestational age at delivery. There may be a causal relationship since magnesium is involved in blood pressure regulation through an intracellular inhibition of NO synthase in endothelial cells.

Calcium↗
PubMed2006

Uptake and elimination of ionizable organic chemicals at fish gills: I. Model formulation, parameterization, and behavior.

A mechanistic model for the uptake and elimination of ionizable organic chemicals at fish gills is presented. This model is a modification of a previous model for nonionizable organic chemicals that addressed the transport of chemical to and from gill surfaces in water and blood, diffusion of chemical across epithelial cells, and binding of chemical to components in water and blood. For ionizable chemicals, three additional processes are included. First, excretory products alter the pH at gill surfaces, affecting the relative amounts of neutral and ionized molecules compared with that in the bulk exposure water. Second, ionized molecules support chemical flux to and from epithelial cell membranes and help maintain high diffusion gradients of neutral molecules across these membranes, thereby contributing to uptake and elimination even if the membranes are impermeable to ionized molecules. Third, membrane barriers are not completely impermeable to ionized molecules, and even limited permeability can have appreciable effects on chemical flux. Approaches for model parameterization are discussed. Model-predicted relationships of uptake and elimination rates to exposure water pH, alkalinity, and chemical properties are presented and discussed in terms of model processes. The model is shown to predict important features of reported effects of pH on uptake rates of weak organic acids.

Animals↗
PubMed2001

Plasma concentration of ionized calcium in healthy iguanas.

OBJECTIVE: To measure plasma concentration of ionized calcium in healthy green iguanas. DESIGN: Prospective study. ANIMALS: 9 juvenile and 21 (10 male, 11 female) adult iguanas. PROCEDURE: Blood samples were obtained from each iguana, and plasma calcium, glucose, phosphorus, uric acid, total protein, albumin, globulin, potassium, and ionized calcium concentrations, aspartate transaminase (AST) activity, and pH were measured. Heparinized blood was used for measurement of ionized calcium concentration and blood pH. A CBC was also performed to assess the health of the iguanas. RESULTS: Significant differences were not detected among the 3 groups (juveniles, males, and females) with regard to ionized calcium concentration. Mean ionized calcium concentration measured in blood was 1.47 +/- 0.105 mmol/L. Significant differences were detected between juveniles and adults for values of phosphorus, glucose, total protein, albumin, globulin, and AST activity. CONCLUSIONS AND CLINICAL RELEVANCE: Ionized calcium concentration provides a clinical measurement of the physiologically active calcium in circulation. Evaluation of physiologically active calcium in animals with suspected calcium imbalance that have total plasma calcium concentrations within reference range or in gravid animals with considerably increased total plasma calcium concentrations is vital for determining a therapeutic plan. Accurate evaluation of calcium status will provide assistance in the diagnosis of renal disease and seizures and allow for better evaluation of the health status of gravid female iguanas.

Age Factors↗
PubMed1996

More on the measurement of ionized magnesium in whole blood.

Current technology has made it possible to measure ionized magnesium with user-friendly ion selective electrode technology. Although this technology has not reached a perfect status literature shows that it can be used in clinical routine especially in serum. This paper deals with issues concerning the measurement of ionized magnesium in whole blood. To measure in whole blood apart from an instrument with good general performance data an adequate sample treatment is especially critical. We tested a number of different sample containers and found that they interfere in different degrees with the magnesium determination. In some cases this is due to silicone giving falsely high ionized magnesium values which may be twice the real value and even higher. Another problem is the heparinization of the sample. We found that different heparins may alter the result in a different way. The well known complexing capability of heparin may lead to a reduction of the ionized magnesium within the sample and thus to false low results. But some heparins cause elevated results. The reason for this may be zinc. Test procedures to check the quality of anticoagulants are given. Due to these procedures sample containers could be found which do not interfere with the determination of ionized magnesium in whole blood - thus making the measurement possible. All these factors indicate that the measurement of ionized magnesium really needs a very well defined sample handling - otherwise false results may arise. This is not only true for the measurement of whole blood but also for plasma or even for "so called serum" as there might be a sample container within the chain from patient to the instrument which is unsuitable- and thus will alter the result.

Humans↗
PubMed1984

The relationship of plasma ionized calcium to cardiovascular disease endpoint and family history of hypertension.

Plasma ionized calcium and total calcium were measured on 271 individuals from 34 Utah pedigrees divided into groups defined by the method of pedigree ascertainment: 1) hypertension clusters, 2) early stroke death clusters and 3) clusters of early heart attack deaths. Normotensive individuals were also categorized by family history of hypertension. Members of stroke cluster pedigrees had higher mean plasma ionized Ca2+ than either hypertension pedigrees (p less than 0.05) or coronary artery disease pedigrees which had the lowest concentrations (p less than 0.001). Within the normotensive group, those subjects with a positive family history of hypertension exhibited significantly higher plasma ionized Ca2+ (2.18 +/- 0.10 (S.D.) mEq/l) than individuals without a family history of hypertension (2.12 +/- 0.08 mEq/l, p less than 0.01). In medicated hypertensives, both ionized (p less than 0.05) and total (p less than 0.01) plasma calcium were higher than calcium levels in the normotensive negative family history subjects. Plasma ionized Ca2+ in the adult normotensives (N = 134) had significant age corrected positive correlations with plasma sodium (r = 0.25, p less than 0.01), potassium (r = 0.29, p less than 0.001) and erythrocyte sodium-lithium countertransport values (r = 0.20, p less than 0.05). These findings provide additional evidence that plasma ionized calcium concentrations may be important to help define the heterogeneity of hypertension in adult Americans.

Adult↗
PubMed1991

Potentiometric determination of ionized and total calcium in blood plasma of Holstein and Jersey cows.

The effects of stage of lactation and breed on total and ionized calcium in blood plasma were determined for eight Holstein and eight Jersey cows fed a diet containing .25% Ca during the dry period and fed a diet with .50% Ca after calving. Blood samples were obtained by jugular venipuncture at 2-wk intervals from 4 wk before calving through wk 10 of lactation. Total and ionized Ca contents of fresh plasma were determined potentiometrically with an ion-specific electrode. Total Ca in plasma also was determined by atomic absorption spectrophotometry. Average concentrations determined by atomic absorption were approximately .7 mg/dl higher than those for the ion-specific electrode. Plasma total and ionized Ca were lower in both breeds at calving than any other time during the sampling period. Jersey cows had lower total Ca (7.47 mg/dl) and ionized Ca (4.25 mg/dl) than Holsteins (8.10 and 4.66 mg/dl) on day of calving. Ionized Ca as a percentage of total calcium increased from 55 to 57% at parturition and then decreased slowly to 53% at peak lactation. Changes in percentage of ionized Ca may indicate the contribution of bone resorption relative to dietary Ca in meeting the Ca requirement for lactation.

Animals↗
PubMedDate not supplied

Transient ionized hypocalcemia and secondary hyperparathyroidism accompanying acute adrenal insufficiency.

OBJECTIVE: To describe the hitherto unrecognized occurrence of transient ionized hypocalcemia with acute adrenal insufficiency and its therapy. METHODS: We present three case reports with documented longitudinal laboratory findings. RESULTS: Transient ionized hypocalcemia of acute illness has been noted in children and adults and is associated with increased mortality. Precipitating illnesses include gram-positive and gram-negative sepsis and staphylococcal toxic shock syndrome. We encountered three patients with transient ionized hypocalcemia associated with acute adrenal insufficiency. Similar to severely ill, transiently hypocalcemic patients without adrenal insufficiency, one patient demonstrated 25-hydroxyvitamin D deficiency, a second had minimal magnesium deficiency, and a third had no identifiable underlying abnormality. All three patients exhibited a transient increase in levels of serum intact parathyroid hormone and 1,25-dihydroxyvitamin D in response to ionized hypocalcemia, indicative of temporary secondary hyperparathyroidism. Two of the three patients were treated solely with glucocorticoids and intravenous administration of fluids, whereas the third received minimal intramuscularly administered magnesium and antibiotics in addition. All ultimately demonstrated a return to normal of serum total and ionized calcium, parathyroid hormone, and 1,25-dihydroxyvitamin D with no further treatment, even though one patient remained deficient in 25-hydroxyvitamin D. CONCLUSION: On the basis of these cases, we conclude that acute adrenal insufficiency and its treatment must be added to the disorders associated with transient ionized hypocalcemia and that transient secondary hyperparathyroidism is characteristic of at least some of the patients.

Journal Article↗