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PubMed1994

A method for distinguishing ionized, complexed and protein-bound Mg in normal and diseased subjects.

Since 1932, it has been known that Mg exists in blood in several forms: protein-bound, complexed to certain anions, and ionized. However, there is discrepancy and debate on what these fractions are, how to accurately assess them, and whether they are important in diagnosis and prognosis of disease syndromes. Using the NOVA ISE for IMg2+, a controlled method for ultrafiltration of Mg and atomic absorption spectrophotometry, we have found four distinct fractions of Mg in healthy normal plasma and serum: 1. ultrafilterable Mg (81%) (made up of ionized and complexed); 2. ionized Mg (67%); 3. protein-bound Mg (19%); and 4. complexed Mg (14%). The amount of each fraction appears to depend upon the pathophysiologic state of the patients. Previous observations on the amount of complexed and ionized Mg are at best, only approximations, due to the absence of a device (i.e., ISE) to measure accurately IMg2+.

Blood Proteins↗
PubMed1996

Measurement of ionized magnesium with AVL 988/4 electrolyte analyzer: preliminary analytical and clinical results.

Only free magnesium has biological activity: technology for measuring the ionized fraction of magnesium is now available via ion-selective electrodes. We have evaluated an instrument (AVL 988/4) which determines ionized magnesium (cMg2+) with an ion-selective electrode based on the ionophore ETH 7025. The selectivity of the electrode is adequate for the ions normally present in plasma, except for calcium: the interference is automatically corrected by simultaneous measurements of calcium with compensation for the calcium interference to the magnesium signal. We have first verified possible interference caused by sampling procedures: known silicon interference has been avoided by use of glass tubes (BD Vacutainer with no additive, code 7626); heparin interference has been measured and found significant above 20 UI.mL-1 of plasma. Instrument evaluation according to NCCLS protocol gives the following imprecision results on 20 replicated analyses: cMg2+ (mmol.L-1) 1.29, 0.76, 0.23, CVs% (within-run) 0.67, 0.67, 3.00 and CVs% (between-run) 4.06, 3.91, 5.89 respectively. Linearity (in the range 0.23-1.60 mmol.L-1) was: measured cMg2+ = 0.981.(calculated cMg2+) + 0.009 mmol/L; r = 0.999. In healthy adults (n = 103) cMg2+ was in the range 0.46-0.74 mmol.L-1 (with a mean of 0.60 mmol/L and normal distribution). These values represent 57% to 84% of serum total magnesium concentration (TMg) (mean 71%). pH dependence of cMg2+ is present, usually to a lower extent with respect to cCa2+, but it seems different in patients with real or in vitro provoked acidosis and in hemodialyzed patients. Citrate interference on ionized magnesium measurements was found both in vitro and in vivo, whilst that due to lactate was demonstrated only in vitro. On a wide range of cMg2+ (n = 100), a good correlation is obtained both with TMg and ultrafiltrable Mg (UFMg): cMg2+ = 0.723.TMg + 0.008 mmol.L-1, r = 0.978; cMg2+ = 0.912.UFMg + 0.10 mmol.L-1, r = 0.968, respectively. The ionized magnesium in ultrafiltrate was found 25% lower than that in serum. The lifespan of the electrode, evaluated on the basis of both time from installation and on number of measured samples, was estimated longer than 4 months and able to analyze more than 1500 samples, whichever comes first. The four electrodes we used during 18 months behaved all the same way. The correlation between measurements performed in whole blood (WB-cMg2+) and in the corresponding serum (S-cMg2+) was excellent: WB-cMg2+ = 0.954.S-cMg2+ +0.02 mmol.L-1; r = 0.998; n = 60.

Adult↗
PubMedDate not supplied

Combined effects of ultrasound and ionizing radiation on lymphocyte chromosomes.

The effects of ionizing radiation and ultrasound upon the induction of chromosomal-type aberrations and sister chromatid exchanges were investigated. No statistically significant increase in the frequencies of dicentric and ring chromosomes or sister chromatid exchanges was discovered after ultrasound exposure alone at the diagnostic level. Nor could elevated frequencies of these phenomena be found following exposure to ultrasound before or after ionizing radiation, compared with those resulting from an equivalent dose of ionizing radiation alone. However, simultaneous exposure to ultrasound and ionizing radiation seemed to induce a slight enhancement of sister chromatid exchanges, although no significant change was noted in the yields of dicentric and ring chromosomes.

Abnormalities, Radiation-Induced↗
PubMed1990

Absorbed dose in water. Comparison of several methods using a liquid ionization chamber.

In the present investigation a liquid ionization chamber has been used as a transfer instrument for the quantity absorbed dose in water in a cobalt-60 gamma-ray beam. The characteristics of the liquid ionization chamber are described. The transferred dosimetric information has been compared with absorbed-dose determination using air-ionization-chamber dosimetry, water calorimetry and ferrous-sulphate dosimetry. The agreement between the different measured absorbed-dose values is very good, i.e. within 0.2%. This is an indication that the consistency in the methods used to determine absorbed dose in water is good. The impact of the new standard for air kerma in air, introduced in 1986 by the BIPM, on the air-ionization-chamber dosimetry is investigated. It is shown that any differences in the dosimetry when using the old or the new set of data cancel out for the cobalt-60 beam. The investigation also shows that the value of epsilon mG for the ferrous-sulphate dosimeter recommended in ICRU 35 for electrons can be used also in cobalt-60 beams.

Calibration↗
PubMed1986

Effects of thermal-induced respiratory alkalosis on blood ionized calcium levels in the domestic hen.

An experiment was conducted to determine the change with time in the blood ionized calcium concentration of hens exposed to an acute heat stress. Five hens were surgically fitted with carotid artery cannulae and placed in cages inside a temperature-controlled chamber. Blood samples were drawn before (23 C), during (35 C), and after (23 C), a 3-hr heat-stress exposure. Whole blood ionized calcium, blood gas, plasma pyruvate, and lactate were determined. Respiratory alkalosis developed 1 hr after the start of heat exposure (35 C). Approximately 1 hr later, there was a concomitant decline in blood pH as plasma lactate and pyruvate concentration increased (P less than .05). In addition, the blood ionized calcium level was reduced (P less than .05) by 19% and was negatively correlated (P less than .05) with plasma pyruvate (-.77) and lactate (-.81). These results suggest that changes in acid-base balance during heat stress reduce the blood ionized calcium level, which may in turn limit the availability of calcium for egg shell formation.

Alkalosis, Respiratory↗
PubMed2001

Clinical evaluation of an electron-ionizing toothbrush with a tooth paste containing stannous fluoride in treatment of dentine hypersensitivity following periodontal surgery.

The purpose of this study was to examine the effect of an electro-ionizing toothbrush with stannous fluoride in the treatment of dentin hypersensitivity following periodontal surgery. Thirty-two volunteers with dentin hypersensitivity were divided in two equal groups each using different methods: (Group I) stannous fluoride dentifrice and hyG Brnde ionizing brush without a battery and (Group II) stannous fluoride dentifrice and hyG Brnde ionizing brush with a battery. The volunteers brushed their teeth for 3 minutes twice a day for 12 weeks following one either of the test protocols. Mechanical (No 23 dental explorer), chemical (lemon juice) and thermal (dental air-water syringe) tests were used for the evaluation of the degree of dentin hypersensitivity. A subjective assessment of the degree of hypersensitivity for each stimulus was recorded. The evaluations were repeated at 4, 8 and 12 weeks after surgical treatment. The second group showed significantly less sensitivity than the first group. The findings appear to suggest that the ionizing brush may be an effective adjunct for the treatment of dentin hypersensitivity in post-periodontal surgery.

Adult↗
PubMed2006

Occupational exposure to ionizing radiation and electromagnetic fields in relation to the risk of thyroid cancer in Sweden.

OBJECTIVES: This study sought to ascertain the risk of thyroid cancer in relation to occupational exposure to ionizing radiation and extremely low-frequency magnetic fields (ELFMF) in a cohort representative of Sweden's gainfully employed population. METHODS: A historical cohort of 2 992 166 gainfully employed Swedish male and female workers was followed up from 1971 through 1989. Exposure to ELFMF and ionizing radiation was assessed using three job exposure matrices based on industrial branch or occupational codes. Relative risks (RR) for male and female workers, adjusted for age and geographic area, were computed using log-linear Poisson models. RESULTS: Occupational ELFMF exposure showed no effect on the risk of thyroid cancer in the study. However, female workers exposed to high intensities of ionizing radiation registered a marked excess risk (RR 1.85, 95% confidence interval (95% CI) 1.02-3.35]. This trend was not in evidence among the men. CONCLUSIONS: While the study confirms the etiologic role of ionizing radiation, with a higher incidence of thyroid cancer being recorded for the most-exposed female workers, our results do not support the possibility of occupational exposure to ELFMF being a risk factor for the development of thyroid cancer.

Adult↗
PubMed1999

TP53 is not required for the constitutive or induced repair of DNA damage produced by ionizing radiation at the G1/S-phase border.

We have previously described a novel DNA repair response that is induced in cells irradiated with ionizing radiation at the G1/S-phase border and is characterized by the formation of very long repair patches (VLRP) containing at least 150 nucleotides. In the current study, we examined whether there is a requirement for TP53 in this induced repair process. We find that in normal cells, the endogenous levels of TP53 are elevated at the G1/S-phase border, and that these levels are not further increased after irradiation with 5 Gy. In cells expressing the E6 oncoprotein of human papillomavirus, which inactivates TP53 function, there is a greatly accentuated induction of the VLRP that nearly masks the constitutive repair response. Incubation of cells in the presence of cycloheximide, which inhibits the induced repair, reveals the presence of the constitutive repair patches. All cells examined continue to replicate their DNA after exposure to ionizing radiation. In contrast, cells irradiated with UV radiation at the G1/S-phase border show an induction of TP53 protein and halt DNA synthesis, but do not induce the VLRP. Our results show that TP53 is not required for the constitutive or induced repair of DNA damage induced by ionizing radiation. In addition, these results suggest that TP53 may suppress the formation of VLRP and that the progression of cells through S phase after exposure to ionizing radiation signals the induced repair response.

Cell Line↗
PubMed1999

[Cell cycle regulation after exposure to ionizing radiation].

When cells are exposed to ionizing radiation, they initiate a complex response that includes the arrest of cell cycle progression in G1 and G2, apoptosis and DNA repair. DNA is an important subcellular target of ionizing radiation, but oxydative damage to plasma membrane lipids initiates signal transduction pathways that activate apoptosis and that may play a role in cell cycle regulation. How is DNA damage converted into intracellular signals for cell cycle arrest? The ataxia telangectasia mutant (ATM) protein and/or the DNA-dependent protein kinase (DNA-PK), that are both activated by DNA damage, may initiate cell cycle arrest by activating the p53 tumor suppressor protein. The p53 protein acts as a transcription factor and regulates expression of several components implicated in pathways that regulate cell cycle progression. The best known, p21WAF1/CIP1 protein, is an inhibitor of cyclin-dependent kinases (CDK), a family of protein kinases known as key regulators of cell cycle progression. p21WAF1/CIP1 was shown to be able to inhibit several CDK, but is most effective toward G1/S cyclins. Other CDK inhibitors, p27KIP1 and p15INK4b are activated by irradiation and contribute to the G1 arrest. Moreover, radiation-induced G2 arrest was shown to require inhibitory phosphorylation of the kinase cdc2 via an ATM-dependent pathway. Mutations in cell cycle regulatory genes are common in human cancer and cell cycle regulatory deficiency can lead to increase resistance to ionizing radiation in cancer cells. The major function of p53-dependent G1 arrest may be elimination of cells containing DNA damage whereas G2 arrest following radiation has been shown to be important in protecting cells from death. Cell cycle checkpoints offer a new set of potential targets for chemotherapeutic compounds, especially the G2 checkpoint. Thus, abrogation of the G2 checkpoint with methylxanthines such as caffeine or protein kinase inhibitors such as staurosporine and UCN-01 (7-hydroxystaurosporine) was found to sensitize cells to ionizing radiation. These data did not lead to clinical applications, but confirm targeting of the G2 checkpoint may be an important strategy for cancer therapy.

Apoptosis↗
PubMed1999

[Perioperative change of ionized magnesium concentration--effect of blood transfusion].

In order to evaluate the effect of intra-operative blood transfusion on post-operative decrease of ionized Mg (Mg2+), we performed following studies. 1) We measured ionized Mg (Mg2+), total Mg, ionized Ca (Ca2+), total Ca and citrate before and after operation in 70 patients. 2) We evaluated the effect of citrate on Mg2+ and Ca2+ in vitro. 3) We also measured these values during blood transfusion in 8 patients. There was no significant difference between post-operative Mg2+ of 45 patients without blood transfusion (0.49 +/- 0.07 mmol.l-1, % decrease from pre-operative value was 13.4 +/- 9.2%; mean +/- SD), and that of 25 patients with blood transfusion (0.48 +/- 0.09 mmol.l-1, 17.9 +/- 10.2%). Mean value of post-operative citrate concentration of patients with blood transfusion was 0.15 +/- 0.11 mmol.l-1, and this value decreased Mg2+ about 2% in in vitro study. During blood transfusion, Mg2+ (0.41 +/- 0.05 mmol.l-1) and ionized % (54.5 +/- 8.3%) decreased significantly just like Ca2+ with elevated citrate concentration (0.95 +/- 0.59 mmol.l-1). In conclusion, intra-operative blood transfusion had minor effect on the post-operative decrease of Mg2+, and the major cause was thought to be the dilution of extracellular fluid by Mg-free fluid administered during operation.

Adult↗
PubMed1975

[The serum level of ionized calcium, total calcium, and magnesium in neonates (author's transl)].

In the first three days of life ionized and total calcium and magnesium were determined in the serum and compared with perinatal parameters in a heterogenous groups of newborn infants (n equals 33). The findings allow the following conclusions: 1. There is a relative good correlation between ionized and total calcium. 2. There is no statisticly proven correlation between magnesium and ionized or total calcium. 3. There is a close relation between APGAR-score and the levels of calcium in the first hours of life. But apparently there is no relation between the gestational age or the weight of birth and magnesium, between the gestational age or the weight of birth and ionized or total calcium there is no close correlation.

Age Factors↗
PubMed1975

[State of hemodynamics, according to radiocardiographic data, in persons working in contact with ionizing radiation sources].

The presented results illustrate the study of the cardiovascular system by means of radiocardiography conducted in normal individuals working in contact with sources of ionizing radiation. The study includes 51 persons in the test group and 42 in the control group that was similar to the test one in terms of age, sex and type of work performed, with the only exception that these in the control group had no contact with ionizing radiation. Persons working under the effect of ionizing radiation displayed a moderate increase in the stroke and minute index and the circulating blood volume, with the blood flow rate somewhat decelerated. The changes were deeper in those with over 5 years of service, and in those with functional changes in the nervous system, like neurocirculatory dystonia. The moderate level of these reactions and their reversibility permit to interpret them as an adaptative reaction to the effect of low doses of ionizing radiation.

Angiocardiography↗
PubMed1976

The relationship of serum ionized and total calcium in primary hyperparathyroidism.

Ionized and total calcium concentrations were measured in the same serum samples of 48 patients with primary hyperparathyroidism in order to compare diagnostic accuracy and sensitivity and to determine the intra-individual variation of these parameters in this disorder. In 149 samples, 0.7 per cent of serum ionized calcium and 7.4 per cent of total calcium determinations were within the normal range (mean +/- 2 S.D.). However, all patients exhibited abnormally elevated values upon repeated testing. Ionized and total calciums were significantly correlated both preoperatively (r=0.85 and p less than 0.001) and postoperatively (r greater than 0.9). Heterogeneous and abnormally large variations of both measurements were noted in these patients. It is concluded that the superior precision of the method for ionized calcium determination renders it more accurate than total calcium for the diagnosis of primary hyperparathyroidism. The disturbance of calcium homeostasis is reflected in both calcium and its ionic fraction in serum.

Calcium↗
PubMedDate not supplied

[Direct determination or estimated value of plasma ionized calcium : indications and limits].

Calcium plays a fundamental role in many essential for life functions. Ionized calcium (Ca(++) ) represents free fraction and 50% of the total calcium in the plasma is accepted as its physiologically active form. On almost all laboratories, only total calcium is routinely measured, and ionized calcium concentration is calculated based on calcium, protein or albumin concentrations for many plasma sample or with others parameters like pH. Since 1935, the literature was abounted with "correction" formulae of varying degree of sophistication. Many laboratories routinely use correction formulae to either calculate an "adjusted" or "corrected" total calcium, or "ionized" fraction is calculated,but these determinations lack of accuracy or precision. Errors associated with the measurement of the other variables contribuate to the difficulty in producing a useful correction formulae. Direct measurement of ionized calcium by potentiometry is the method of choice for this assay. Improvements in ion selective electrodes (ISE) technology make possible the routine clinical measurement of Ca(++). However this technology implies several obligations for its use, particulary in blood ampling, storage and transport. In this review, characteristics of different available analysers are described. We think that Ca(++) should be systematically performed and not calculated in pathological situations where an possible alteration of the calcium metabolism is found especially in multiple myeloma in which paraprotein may bind calcium.

Blood Chemical Analysis↗
PubMed2002

[Level of total and ionized magnesium fraction based on biochemical analysis of blood and hair and effect of supplemented magnesium (Slow Mag B6) on selected parameters in hypertension of patients treated with various groups of drugs].

The aim of this work was to determine the concentration of total and ionized magnesium in hair and blood of patients with primary hypertension and the influence of oral magnesium supplementation (Slow-Mag B6) on clinical parameters and blood pressure values. 92 patients were recruited from the Family Care Unit, Pomeranian Academy of Medicine in Szczecin. Each patient was treated during at least 6 months preceding the study with a single antihypertensive agent from one of the following groups: ACE inhibitors, beta-receptor inhibitors, Ca channel blockers, diuretics. The control group included patients with hypertension not treated pharmacologically. Changes in ionized magnesium concentration before and after oral magnesium supplementation were studied in relation to total cholesterol, triglycerides, and other parameters of importance in hypertension. Significantly lower total magnesium concentrations were demonstrated in hair of patients receiving ACE inhibitors and diuretics in comparison to controls. Ionized magnesium concentrations in serum of hypertensive patients were significantly reduced as compared with controls. A highly significant increase in these levels was noted after magnesium supplementation. Blood pressure values after magnesium supplementation were reduced in the study group by an average of 15-20 mmHg for systolic and 5-9 mmHg for diastolic blood pressure. Correlations between ionized magnesium and triglyceride concentrations in patients treated with Ca channel blockers before oral Mg supplementation were found. Patients treated with diuretics demonstrated correlations between total magnesium and total cholesterol concentrations. Following oral magnesium supplementation with Slow-Mag B6 at 320 mg/day, the frequency of complaints reported by patients, including irregular heart beat, pricking heart pain, nervousness, sleep disorders, irritability/tearfulness was reduced. There was no effect on other complaints, such as mental and physical fatigue, constipation/diarrhea, and anxiety.

Administration, Oral↗
PubMed1992

[Non-activated platelet cytoplasmic ionized calcium in patients with acute ischemic stroke and healthy controls].

Non-activated platelet cytoplasmic ionized calcium was measured in Aequorin-loaded Gel-filtered platelets in 43 patients with acute ischemic stroke and 32 healthy controls. Platelet cytoplasmic ionized calcium is 2,596 +/- 0,674 mumol/L in controls, 3,370 +/- 1,339 mumol/L in the patients with acute ischemic stroke. Platelet cytoplasmic ionized calcium is increased in the stroke patients as compared to controls (P < 0.01). This indicates that there may be a lower threshold in platelet of stroke patient for activation. Moreover, increased platelet cytoplasmic ionized calcium may be a risk factor for thrombus propagation and aggravation of clinical manifestation.

Adult↗
PubMed1980

In-vivo sensitivity of canine myocardium to acute depression of serum ionized calcium.

Recent technologic advances make it possible to measure reliably serum or plasma ionized calcium with a high degree of accuracy. In this study, with the use of 16 mongrel dogs, the quantitation of the hemodynamic response to acute changes in ionized calcium was attempted. It was found that normal cardiac function required a normal level of ionized calcium. In intact animals, severe depression of myocardium is masked by pressor reflexes designed to maintain homeostasis. In their absence, myocardial depression is readily apparent. Animals that are hypercalcemic at the beginning of infusion respond in essentially the same manner. To a degree previously unsuspected, myocardial function depends upon a constant level of ionized calcium.

Journal Article↗
PubMedDate not supplied

Response of cyclin B1 to ionizing radiation: regulation by NF-kappaB and mitochondrial antioxidant enzyme MnSOD.

BACKGROUND: To understand the molecular response of tumor cells to therapeutic ionizing radiation (IR), we previously reported that human breast cancer cells derived following chronic exposure to fractionated ionizing radiation (MCF+FIR) showed a transient radioresistance. MCF+FIR cells also demonstrated increased activity of NF-kappaB, increased expression of the mitochondrial antioxidant enzyme (MnSOD), and increased expression of a cell cycle regulatory protein (Cyclin B1). The present studies were designed to determine the relationship of NF-kappaB, MnSOD and Cyclin B1 expression in cellular adaptive responses to ionizing radiation. MATERIALS AND METHODS: The first intron of the cyclin B1 gene with a putative NF-kappaB element was cloned into the pGL3 luciferase reporter (pGL3CB1EI1). PGL3CB1EI1 and control NF-kappaB luciferase activities were determined in MCF-7 and MCF+FIR cells treated with a single dose of radiation, over expression of the dominant negative mutant IkB (mIkB) or over expression of the SOD2 gene. RESULTS: MCF+FIR cells derived from fractionated IR demonstrated increased transactivation of the pGL3CB1EI1 and NF-kappaB controlled reporter activities, relative to the parental cell line. Transfection of dominant negative mutant IkB that inhibits NF-kappaB nuclear translocation, inhibited pGL3CB1EI1 and NF-kappaB activity, indicating the NF-kappaB dependence of pGL3CB1EI1 mediated transcription. In addition, over expression of the human SOD2 gene (MnSOD) inhibited NF-kappaB and pGL3CB1EI1 activity, indicating that superoxide or some species derived from superoxide may have participated in the up-regulation of reporter activity in response to chronic exposure to fractionated ionizing radiation. These results provide evidence suggesting that a signaling pathway involving NF-kappaB and Cyclin B1 may contribute to adaptive radioresistance induced by chronic exposure to fractionated IR and support the conclusion that MnSOD appears to be a negative regulator of this pathway.

Amino Acid Sequence↗