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PubMed1993

Preferential repair of ionizing radiation-induced damage in the transcribed strand of an active human gene is defective in Cockayne syndrome.

Cells from patients with Cockayne syndrome (CS), which are sensitive to killing by UV although overall damage removal appears normal, are specifically defective in repair of UV damage in actively transcribed genes. Because several CS strains display cross-sensitivity to killing by ionizing radiation, we examined whether ionizing radiation-induced damage in active genes is preferentially repaired by normal cells and whether the radiosensitivity of CS cells can be explained by a defect in this process. We found that ionizing radiation-induced damage was repaired more rapidly in the transcriptionally active metallothionein IIA (MTIIA) gene than in the inactive MTIIB gene or in the genome overall in normal cells as a result of faster repair on the transcribed strand of MTIIA. Cells of the radiosensitive CS strain CS1AN are completely defective in this strand-selective repair of ionizing radiation-induced damage, although their overall repair rate appears normal. CS3BE cells, which are intermediate in radiosensitivity, do exhibit more rapid repair of the transcribed strand but at a reduced rate compared to normal cells. Xeroderma pigmentosum complementation group A cells, which are hypersensitive to UV light because of a defect in the nucleotide excision repair pathway but do not show increased sensitivity to ionizing radiation, preferentially repair ionizing radiation-induced damage on the transcribed strand of MTIIA. Thus, the ability to rapidly repair ionizing radiation-induced damage in actively transcribing genes correlates with cell survival. Our results extend the generality of preferential repair in active genes to include damage other than bulky lesions.

Blotting, Southern↗

PubMed1998

Multiple ionization in the earlier stages of water radiolysis.

We have studied the fragmentation of water vapour molecules induced by collision with a Xe44+ beam at 6.7 MeV/u. From the measurement of the fragment time of flight, we show that the amount of fragmentation due to multiple ionization is very large. In the case of single ionization, we are able to reproduce accurately the experimental cross sections by calculating for each molecular level the single-ionization cross section in the framework of the CDW-EIS theory and with a diagram of dissociation modified with respect to the diagram obtained in the case of dipolar ionization. By using qualitative arguments based on the ability of the medium to neutralize a charged species, we tentatively extend our result to liquid water. From our analysis, we show that ionizations involving three or more ejected electrons could enhance the oxygen production. For the physicochemical phase we estimate that the rate of oxygen production by multiple ionization represents approximately 18% of the OH rate produced by single ionization.

Oxygen↗

PubMed2006

Perturbation factors for cylindrical ionization chambers in proton beams. Part I: corrections for gradients.

An analytical model is presented to calculate the effective depth in water of cylindrical ionization chambers in clinical proton or heavy ion beams in the presence of modest and linear gradients. This model is compared with Monte Carlo simulations and recommendations in IAEA TRS-398 for all ionization chambers listed in that report. A refinement of the analytical model allows its application for depth-dose curves even in the nonlinear gradient region of the Bragg peak. Combined with information from the Monte Carlo simulations it also allows one to solve the inverse problem of deriving a depth-dose curve in homogeneous water from the depth-dose response obtained with a cylindrical ionization chamber. The results show that the effective depth in water calculated analytically, calculated by Monte Carlo, and derived from experimental literature are in good agreement. The agreement with the IAEA TRS-398 recommendation is good for most ionization chambers but can be wrong by up to 1.5 mm for some ionization chamber types. The agreement between the refined analytical model and Monte Carlo simulations of depth-dose response curves is shown to be good (even in extreme situations of large ionization chambers in low-energy beams). An indication is given of situations in which a simple shift of the entire depth-dose curve is sufficiently accurate. It is demonstrated that it is possible to solve the inverse problem with this method, even for rather noisy data. This is illustrated by successfully applying it to depth-dose measurements with cylindrical ionization chambers taken from the literature.

Dose-Response Relationship, Radiation↗

PubMed2006

The characterization of the Advanced Markus ionization chamber for use in reference electron dosimetry in the UK.

The IPEM Code of Practice (IPEM 2003) for electron dosimetry for radiotherapy beams recommends design requirements for parallel-plate ionization chambers used to determine absorbed dose to water in an electron beam. The Classic Markus design has been found not to meet these requirements. The Advanced Markus ionization chamber has been designed to rectify the problems associated with the Classic Markus ionization chamber. The response of three Advanced Markus ionization chambers was investigated and compared to the designated chamber types. Absorbed dose to water calibration factors were derived at the National Physical Laboratory (NPL) for each ionization chamber at seven electron energies in the range nominally 4-19 MeV. Investigations were carried out into chamber settling, polarity effects, ion recombination and the chamber perturbation. The response of the ionization chambers in a clinical beam was also investigated. In general all three Advanced Markus ionization chambers showed the same energy response. The magnitude of the polarity effect was typically 5% at a nominal energy of 4 MeV. There was discrepancy between the polarity measurements made at the NPL and in the clinic. The recommendation of this study is that this chamber type is not suitable for reference dosimetry in electron beams.

Calibration↗

PubMed1991

Different plasma ionized calcium correlations with blood pressure in high and low renin normotensive adults in Utah.

Plasma ionized calcium levels have been shown to be lower than normotensive control levels in hypertensive patients with low plasma renin activity and higher than control levels in hypertensive patients with high renin activity; they did not differ between high and low plasma renin activity groups of normotensive controls. To see if ionized calcium may have different relationships with blood pressure across renin categories in normotensive individuals, plasma ionized calcium was measured on 875 healthy individuals, ages 3 to 83, who had never been diagnosed as having hypertension. Blood pressures were measured in the sitting, standing, and supine positions, along with pressures measured during two stress maneuvers: isometric handgrip and a 50 degrees tilt from a supine position. There was no linear correlation of blood pressure with plasma ionized calcium in the entire sample of youths or adults. However, after dividing the adults into tertiles based on plasma renin activity, there were significant inverse correlations between ionized calcium and systolic and diastolic blood pressure in the low renin group (r = -0.16 to -0.25, P less than or equal to .05), while the systolic blood pressure correlations were significantly positive in the high renin group (r = 0.14 to 0.22, P less than or equal to .05). Adults with normal renin levels did not have any significant correlations of plasma ionized calcium with blood pressure. These confounding effects of renin were greater for systolic than for diastolic blood pressure. These correlations within renin tertiles occurred even though there were no differences in mean blood pressure, plasma ionized calcium, total plasma protein and plasma sodium across renin categories.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed2000

Albumin-corrected calcium and ionized calcium in stable haemodialysis patients.

BACKGROUND: It is ionized calcium that is physiologically active and under homeostatic control; however, total calcium is more conveniently measured. Formulae for correction of calcium to account for albumin binding have not been validated in a dialysis setting. METHODS: We measured ionized calcium simultaneously with total calcium (t[Ca]), albumin, total protein and pH before dialysis in 50 stable outpatients and convalescent inpatients. RESULTS: Although 92% of patients were taking calcium supplements and 70% taking alphacalcidol, 11 patients (22%) had ionized hypocalcaemia. To facilitate comparison of calculated ionized calcium, measured total calcium (t[Ca]), and 'corrected' calcium (c[Ca]), with the criterion measure of ionized calcium, all measurements were converted to z scores, standardized on the normal range for each variable. Results are expressed as intraclass correlation coefficients (ICC: 0, all differences are due to error; 1, all differences are due to between patient variation). CONCLUSIONS: None of the published formulae greatly improved the test characteristics beyond simply using the total calcium. A correction formula in widespread use (Payne), quoted in reference texts, agreed less well with ionized calcium than did the unadjusted measured calcium. Correction formulae should be abandoned in favour of the use of uncorrected calcium. In cases of doubt, ionized calcium should be directly measured.

Blood Proteins↗

PubMed1999

Application of negative air ionization for reducing experimental airborne transmission of Salmonella enteritidis to chicks.

Electrostatic space chargers were used to impart a negative charge to airborne dust particles and thereby cause them to be attracted to grounded surfaces. To determine whether negative air ionization could affect the airborne transmission of Salmonella enteritidis, chicks were housed in four controlled-environment isolation cabinets in which airflow was directed across an unoccupied central area from one ("upstream") group of birds to another ("downstream") group. Negative air ionizers were installed in two of these cabinets. In three replicate trials, groups of chicks were placed in the upstream ends of the transmission cabinets and orally inoculated with S. enteritidis at 1 wk of age. On the following day, 1-d-old chicks were placed in the downstream ends of the cabinets. When chicks were sampled at 3 and 8 d postinoculation, S. enteritidis was found on the surface of 89.6% of the downstream chicks from cabinets without negative air ionizers, but on only 39.6% of the downstream chicks in the presence of the ionizers. Similarly, S. enteritidis was recovered from the ceca of 53.1% of sampled downstream chicks in cabinets without ionizers, but from only 1.0% of the ceca of chicks in cabinets in which ionizers were installed. The presence of the ionizers was also associated with reduced levels of circulating airborne dust particles. Reducing airborne dust levels may thus offer an opportunity to limit the spread of S. enteritidis infections throughout poultry flocks.

Air Microbiology↗

PubMed2005

Validation of the Nova CRT8 for the measurement of ionized magnesium in feline serum.

BACKGROUND: Evaluation of serum magnesium (Mg) concentration is becoming important in human and veterinary critical care medicine. An ion-selective electrode can measure the physiologically active ionized fraction. OBJECTIVES: The purpose of this study was to validate an ion-specific electrode analyzer and assay for measuring ionized Mg in feline serum and to determine a reference interval for this analyte in cats. METHODS: Venous blood samples were collected anaerobically from clinically healthy cats, and the serum was used to validate the analyzer and assay. This included investigating the stability of samples stored at different temperatures, intra- and interassay precision, linearity, analytical sensitivity, and potential interferences from bilirubin, lipemia, hemoglobin, or serum separator tubes. A reference interval was calculated. RESULTS: Serum samples evaluated for ionized Mg concentrations can be stored at 20 degrees C for < or =24 hours, at 4 degrees C for < or =72 hours, and at 20 degrees C for < or =4 weeks, when samples are minimally exposed to air. Intra- and interassay precisions had coefficients of variation (CVs) of 1.23% and 2.02%, respectively. There was good linearity using serum (r = .998; y = -0.0057 + 1.0256x) and manufacturer-supplied aqueous solutions and quality control materials (r = .999; y = 0.0110 + 0.9213x). Apparent analytical sensitivity was at least 0.015 mmol/L. Mean recovery was good for ionized Mg in samples with 1+ icterus (104%), 4+ lipemia (99.3%) and 1-4+ hemolysis (98.6%). There was no significant difference (P = .52) in ionized Mg concentrations in serum collected in tubes containing no additives compared with serum collected in glass separator tubes. The serum ionized Mg reference interval was 0.47-0.63 mmol/L (n = 40). CONCLUSIONS: The Nova CRT8 analyzer and assay provide a precise and reliable method of measuring ionized Mg concentration in feline serum. Strict adherence to sampling techniques, handling, and storage are necessary for reliable results.

Animals↗

PubMedDate not supplied

A comparison of chemical and ionization dosimetry for high-energy x-ray and electron beams.

A comparison was made of ferrous sulfate (Fricke) and ionometric methods for determining the absorbed dose in a phantom irradiated with 4-MV x-rays, 25-MV x-rays, or electron beams having various incident energies between 10 and 32 MeV. Both chemical and ionization instruments were calibrated in a 60Co beam at a point in water where the absorbed dose had been previously determined. The chemical yield measurements were corrected for spatial variations in dose within the volume of the solution and used to obtain a value of the absorbed dose for each of the x-ray and electron beams. The ratios of G-values required for these determinations were taken from ICRU reports 14 and 21. Ionization instrument readings from three types of commercial ionization chambers were used to obtain alternate values of the absorbed dose for each radiation. C lambda and CE values used in determining these ionization values of dose were also taken from the above ICRU reports. For 4-MV x-rays the values of absorbed dose obtained from chemical measurements agreed to within 0.5% with values obtained from ionization measurements; for 25-MV x-rays the chemical values were about 1% higher than the ionization values; for the electron beams the chemical values were 1%-4% below the ionization values. These discrepancies suggest an inconsistency among the recommended G, C lambda, and CE values similar to that which has been noted by other workers.

Electrons↗

PubMed1989

Ionized calcium plays a pivotal role in controlling blood pressure during haemodialysis.

The influence of dialysate bicarbonate concentration on ionized plasma calcium as well as on haemodynamics have been studied prospectively. In 3 consecutive weeks, 7 chronic patients were dialysed with a dialysate containing low bicarbonate (30 mEq/l), medium bicarbonate (35 mEq/l) and high bicarbonate (39.5 mEq/l), respectively. Notwithstanding the same considerable influx of calcium during high, medium and low bicarbonate dialysis (Bc-D), a significant increase in ionized calcium from 1.09 to 1.41 mmol/l was observed during low Bc-D only. During medium and high Bc-D no significant increase in ionized calcium occurred. In multivariate analysis the only significant predictive variable for the changes in ionized calcium was the change in total CO2 (r = 0.70; p less than 0.001). During low Bc-D the mean arterial pressure remained almost the same, while during medium and high Bc-D a significant decrease of mean arterial pressure was observed. Multivariate analysis revealed that only the change in ionized calcium had a significant predictive effect on the changes of blood pressure (r = 0.69; p less than 0.001). In conclusion, during dialysis an increasing ionized plasma calcium level was counteracting the negative effect of fluid removal on blood pressure. The results of this study underline the pivotal role of ionized plasma calcium for the regulation of blood pressure.

Aged↗

PubMed1982

Ionized calcium and the in vivo response of normal and hyperplastic parathyroid glands to beta-adrenergic agents.

We compared ionized serum calcium and parathyroid hormone (PTH) responses to the beta-adrenergic agents, isoproterenol and propranolol, in 14 patients with hyperparathyroidism following renal transplantation and 8 normal volunteers. Following isoproterenol, PTH rose in normal subjects concurrent with a significant (p less than 0.01) fall in ionized but not total, calcium. In the hyperparathyroid patients the PTH concentration decreased (p less than 0.001) coincident with a significant (p less than 0.01) increase in ionized, but not total, calcium. Changes in both PTH (p less than 0.05) and ionized calcium (p less than 0.05) were significantly different in hyperparathyroid patients compared to normal subjects. Propranolol did not affect PTH, ionized or total calcium in either group. We conclude that beta-adrenergic stimulation of PTH secretion may be mediated, in part, by antecedent changes in ionized calcium and not solely a direct effect of the agonist. Concurrent assessment of changes in ionized calcium is necessary for proper interpretation of investigations involving the sympathetic nervous system's regulation of PTH secretion.

Adult↗

PubMed1986

Leukocyte ionized calcium and sodium content and blood pressure in humans.

The relationship between leukocyte ionized calcium concentration, sodium content, and blood pressure was studied in normotensive subjects with (n = 17) and without (n = 21) a family history of hypertension and in untreated patients with essential hypertension (n = 22). There was a highly significant correlation between intracellular ionized calcium and mean supine blood pressure (measured on the same occasion) in normal subjects with no family history of hypertension (r = +0.73, p less than 0.01). This relationship was lost in normal subjects with a family history of hypertension, and in hypertensive patients there was a nonsignificant negative correlation between intracellular ionized calcium and blood pressure (r = +0.08 and -0.31, respectively). Intracellular ionized calcium was similar in the normotensive groups (both, 126 +/- 7 nmol/L) and slightly but nonsignificantly elevated in hypertensive patients (143 +/- 10 nmol/L; p = 0.09). There was no correlation between intracellular ionized calcium and sodium content in any group (r less than 0.1). These results indicate that while leukocyte ionized calcium in normotensive subjects with no family history of hypertension may reflect smooth muscle contractility resulting in the positive correlation between leukocyte ionized calcium and blood pressure, this relationship is lost in hypertensive patients and subjects predisposed to hypertension. This may be due to an altered relationship between leukocyte and smooth muscle calcium handling in these subjects or to non-calcium-mediated influences on blood pressure.

Adult↗

PubMed2003

The kinetic method as a structural diagnostic tool: ionized alpha-diketones as loosely one-electron bonded diacylium ion dimers.

The kinetic method is used to corroborate the description of ground state ionized alpha-diketones as loosely electron-bonded acylium ion dimers: R(1)-C=O(+)---e(-)---(+)O=C-R(2). The abundance ratio of both the acylium ion fragments R(1)CO(+) and R(2)CO(+) (summed to those of their respective secondary fragments) formed upon low energy (5 eV) collision-induced dissociation of several ionized alpha-diketones is found to correlate linearly with the ionization energies (IEs) of the corresponding R(1)CO(.) and R(2)CO(.) free radicals as predicted by density functional theory calculations at the B3LYP/6-311++G(d,p) level. However, when these abundances are taken from 70 eV electron ionization mass spectra, lower and sometimes inverted ratios (2,3-pentanedione and 2,3-hexanedione) are observed. Inverted ratios are also observed via charge-exchange mass spectrometry/mass spectrometry (MS/MS) experiments for ionized 2,3-pentanodione formed with relatively high internal energies. Ionized alpha-diketones are found to display an effective temperature of 1705 K, which indicates an intermediate loosely-bonded nature. B3LYP/6-311++G(d,p) optimized geometries and charge and spin densities also corroborate the description of ground state ionized alpha-diketones as loosely electron-bonded diacylium ion dimers.

Journal Article↗

PubMed2001

Purification and identification of the essential ionizable groups of honeybee, Apis mellifera L., trehalase.

Trehalase (EC 3.2.1.28) of the bound type was purified as an electrophoretically homogeneous protein from adult honeybees by fractionation with ammonium sulfate, hydrophobic chromatography, and DEAE-Sepharose CL-6B, CM-Sepharose CL-6B, butyl-Toyopearl 650M, and p-aminophenyl beta-glucoside Sepharose 4B column chromatographies. The enzyme preparation was confirmed to be a monomeric protein containing 3.1% carbohydrate. The molecular weight was estimated to be approximately 69,000, and the optimum pH was 6.7. The Michaelis constant (Km) was 0.66 mM, and the molecular activity (k0) was 86.2 s(-1). The enzyme was an "inverting" type which produced beta-glucose from alpha, alpha-trehalose. Dependence of the V and Km values on pH gave values for the ionization constants, pKe1 and pKe2, of essential ionizable groups 1 and 2 of the free enzyme of 5.3 and 8.5, respectively. When the dielectric constant of the reaction mixture was decreased, pKe1, and pKe2 were shifted to higher values of + 0.2 and + 0.5 pH unit, respectively. The ionization heat (deltaH) of ionizable group 1 was estimated to be + 1.8 kcal/mol, and the deltaH value of group 2 was + 1.5 kcal/mol. These findings strongly support the notion that the essential ionizable groups of honeybee trehalase are two kinds of carboxyl groups, one being a dissociated type (-COO(-), ionizable group 1) and the other a protonated type (-COOH, ionizable group 2), although the pKe2 value is high.

Animals↗

PubMed2006

Uptake and elimination of ionizable organic chemicals at fish gills: II. Observed and predicted effects of ph, alkalinity, and chemical properties.

Effects of exposure-water pH on chemical uptake at rainbow trout (Oncorhynchus mykiss) gills were investigated for nine weakly acidic, chlorinated phenols with different ionization constants and hydrophobicities and for a moderately hydrophobic, nonionizable reference chemical (1,2,4-trichlorobenzene). Uptake rates for all chemicals varied little from pH 6.3 to 8.4, despite ionization of the chlorinated phenols ranging from less than 1 to greater than 99.9% among these pH values and chemicals. At pH 9.2, uptake rates were reduced substantially for the chlorinated phenols but not for the reference chemical. These results indicate greater bioavailability of neutral chemical forms but also considerable bioavailability of ionized forms that varies with pH. Three mechanisms were evaluated regarding such ionized chemical bioavailability. First, reduced pH at the gill surface causes net conversion of ionized molecules to more readily absorbed neutral molecules. This mechanism was tested by increasing exposure-water alkalinity, which increased gill surface pH and reduced uptake of the chlorinated phenols but not of the reference chemical. Magnitudes of these effects were close to predictions from a mathematical model for chemical exchange at fish gills that incorporated this mechanism. Second, ionized molecules contribute to uptake by maintaining high gradients of neutral molecules across epithelial membrane barriers, even if the barriers are impermeable to these ions. This mechanism was demonstrated to explain the similarity of uptake among pH values and chemicals at pH less than 8.4 and the degree to which uptake declined at pH 9.2. Third, membrane barriers can have some permeability to the ionized forms, but this was not important for the chemicals and conditions of the present study. Increased exposure-water pH also was demonstrated to increase elimination rates of these chemicals, which also was in accord with model expectations.

Animals↗

PubMed1996

Accuracy evaluation and hematocrit effect of commercial ionized calcium analyzers using Japanese serum reference material.

The serum reference material for concentration measurement of ionized calcium in blood has been established by our research group in Japan. The reference method used is the reference standard cell (RSC:IFCC/WGSE, Covington-Umemoto Cell) system. Here we present the results of the evaluation of accuracy using the serum reference material and the hematocrit effect of the nine commercial ionized calcium analyzers being used in routine measurements by Japanese round robin test program. The ionized calcium concentration and pH of two concentration levels of the reference material were analyzed in triplicate measurements according to the standard procedures designated by manufacturers. The effect of hematocrit in ionized calcium concentration measurement was tested using plasma and whole blood with hematocrit values of 35%, 50% and 65%, respectively. The range of bias of ionized calcium values were -0.14 approximately +0.09 mmol/L, -0.12 approximately +0.09 mmol/L for ionized calcium, respectively. The effect of hematocrit in ionized calcium concentration measurement was strongly observed in GEM Premier, CAI-101 and GASTAT-2 analyzers.

Calcium↗

PubMed1996

Ionized magnesium concentration during liver transplantation, resection of the liver and cardiac surgery.

In this study we investigated three groups of patients, the first undergoing liver transplantation (n = 9), the second resection of the liver (n = 7) and the third cardiac surgery (n = 10) with regard to changes of ionized and total magnesium concentration during operation. Liver transplantation: Ionized magnesium concentration decreased from 0.58 mmol/L to 0.34 mmol/L far below the reference interval (0.49-0.72 mmol/L), whereas total magnesium concentration changed only from 0.78 mmol/L to 0.67 mmol/L (reference interval: 0.65-1.05 mmol/L). Citrate concentration increased from 220 mumol/L to 1925 mumol/L (anhepatic stage) because of massive transfusion of blood products. It was inversely correlated to ionized magnesium concentration. Resection of the liver: There was a decline of ionized magnesium from 0.56 mmol/L to 0.43 mmol/L, which slightly exceeded the decline of total magnesium from 0.74 mmol/L to 0.64 mmol/L. Citrate concentration increased moderately even in cases, when no citrate was administered reflecting reduced hepatic function during operation. Cardiac surgery: Only in patients, to whom citrate but not magnesium was infused, ionized magnesium concentration fell slightly below the reference interval (0.45 mmol/L). In the other patients, to whom magnesium was administered, ionized magnesium concentration was within the reference interval or exceeded it. It is concluded that in patients with impaired hepatic function and/or high citrate load the monitoring of ionized magnesium concentration is mandatory.

Adult↗

PubMed2002

The ionized fraction of serum total magnesium in hemodialysis patients: is it really lower than in healthy subjects?

AIM OF THE STUDY: Based on data in the literature, it remains unclear whether the ionized fraction of serum total magnesium (Mg) is lower in chronic hemodialysis (HD) patients compared to healthy subjects. PATIENTS AND METHODS: The ionized fraction of serum total Mg was investigated in 49 HD patients, pre- and post-dialysis, and compared to 30 healthy controls. The quality of the analytical performance of the Mg measurements has been emphasized by applying a reference method and/or rigorous internal quality control (IQC). In addition, the ionized fraction of serum total calcium (Ca) was measured in both populations, because the results for Mg should be related to those of Ca. RESULTS: In HD patients, the ionized fraction of serum total Mg was on average 65% (pre-dialysis 64.2% and post-dialysis 66.2%). In healthy controls, the ionized fraction was 64.9%. When the analytical variability was taken into account, no significant differences (p > 0.05) were observed between pre- and post-dialysis samples and controls. For Ca, an ionized fraction of 55.3% was found in HD patients, which was not significantly different from the fraction obtained in the control group (55.7%). CONCLUSION: The present study demonstrates that, compared to healthy controls, the ionized fraction of serum total Mg is not different in hemodialysis patients.

Aged↗