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PubMed2005

Decreases in occupational exposure to ionizing radiation among Canadian dental workers.

OBJECTIVE: To describe doses of ionizing radiation and their possible associations with mortality rates and cancer incidence among Canadian dental workers. METHODS: The National Dose Registry (NDR) of Canada was used to assess occupational dose of ionizing radiation received by dental workers. The NDR cohort includes 42,175 people classified as dental workers. Subjects in the NDR were linked to both the Canadian Mortality Database and the Canadian Cancer Database to ascertain cause of death and cancer incidence, respectively. RESULTS: The cohort consisted of 9,051 male and 33,124 female dental workers. A total of 656 incident cases of cancer and 558 deaths were observed. The standardized mortality ratio associated with all-cause mortality was 0.53 (90% confidence interval [CI] 0.49-0.57). The incidence of cancer among dental workers was lower than that for the Canadian population for all cancers except melanoma of the skin (for melanoma, the standardized incidence ratio was 1.46 [90% CI 1.14-1.85]). Occupational doses of ionizing radiation among dentists and dental workers have decreased markedly since the 1950s. CONCLUSIONS: Dental workers receive very low doses of ionizing radiation, and these doses do not appear to be associated with any increase in cancer incidence; the increased incidence of melanoma is more likely related to other risk factors such as exposure to ultraviolet radiation from sunlight.

Adult↗

PubMed2004

[Mechanism of resonance-enhanced multiphoton ionization of NO molecule].

NO molecule is a diatomic molecule with different nucleus. It is a serious pollutant and is harmful to the health of the generation. It comes mainly from inflammation process using coal as burning material. So researchers have always been interested in it. The Resonance-Enhanced Multi-Photon Ionization (REMPI) spectrum of NO has been obtained in the range of 420-480 nm with a Nd:YAG laser pumped optical parametric generator and amplifier as the radiation source. The ionization pathway of NO molecule was acquired with the assignment of the spectral lines. NO molecules are ionized via the resonant intermediate state A2 sigma+ and by a (2 + 2) REMPI process. On the basis of theoretical rate equation and with the condition that the duration of the laser pulse is very short (approximately 35ps), the dependence of ion signals on laser intensity was deduced. The variation of the ionization signal versus laser intensity is near quartic. This is in good agreement with the experimental result.

Equipment Design↗

PubMed2005

[Total and ionized magnesium concentration in the blood plasma and erythrocytic magnesium concentration of women in the third trimester of pregnancy with imminent preterm labor].

OBJECTIVES: There are some data concerning magnesium concentration influence on the risk of preterm labor. The estimation of magnesium concentration changes may be useful in prevention of preterm labor. DESIGN: Therefore the aim of our study was to find out the correlation between magnesium concentration and the risk of preterm labor. MATERIALS AND METHODS: Total magnesium concentration and ionized magnesium concentration in blood plasma and erythrocytic magnesium concentration ware examined in the three groups of: 23 women in the third trimester of pregnancy with imminent preterm labor under tocolytic therapy; 20 women in the third trimester of physiologic pregnancy and 19 non-pregnant healthy women in the reproductive age. RESULTS: We discovered statistically confirmed differences (p < 0,05 ) in ionized magnesium concentration as well between the group of women in physiologic pregnancy and non-pregnant women and between the group of pregnant women with imminent preterm labor and non-pregnant women. CONCLUSIONS: Although there were no statistically confirmed differences in total magnesium concentration and erythrocytic magnesium concentration between the three groups of examined women, there were statistically confirmed differences in ionized magnesium concentration between the pregnant and non-pregnant women. Our results suggest that ionized magnesium concentration is better indicator of magnesium balance in human's body than total magnesium concentration.

Adolescent↗

PubMed2005

Use of plasma ionized calcium levels and Ca2+ substitution response patterns as prognostic parameters for ileus and survival in colic horses.

OBJECTIVE: Hypocalcaemia is a common finding in horses with enterocolitis and severe gastrointestinal disorders. The aims of this study were to investigate in colic horses 1)the parameters related to hypocalcaemia, 2)the influence of hypocalcaemia on outcome and 3)the possible beneficial effect of Ca2+ substitution. DESIGN: Randomized controlled trial. SETTING: Intensive care unit. PATIENTS: One hundred forty-four horses that were admitted with an acute abdomen during a 1.5 year period were enrolled and daily evaluated for clinical criteria and whole blood ionized Ca2+ levels. Colic horses with hypocalcaemia were randomly assigned to receive Ca2+. INTERVENTIONS: Analysis of heparinised whole blood samples. Horses that were assigned to be treated received 400 mEq Ca2+ diluted in 10L of Ringer's lactate solution every 24 h until low reference range limits were obtained or until death. MEASUREMENTS AND MAIN RESULTS: 88% of all colic patients showed blood ionized Ca2+ levels below the reference range at the time of admission. Multivariable analysis revealed that the presence of reflux, signs of endotoxaemia, increased Packed Cell Volume (PCV), alkalinization of pH and the interaction PCV/pH all predispose colic horses to low ionized Ca2+ levels at the time of admission. The Odds for developing ileus during hospitalization are +/- 11.94 times larger for horses in the "very low" calcaemia interval, in comparison with normocalcaemic horses. The Odds for fatal outcome are respectively +/- 9.82 and 8.33 times larger for horses in the "very low" and "low" calcaemia interval. Ca2+ substitution increased the probability of survival, provided that Ca2+ levels could be normalized. The lack of an upward calcaemia response, despite repetitive Ca2+ substitutions, can be guarded as a poor ominous sign. CONCLUSIONS: Hypocalcaemia in colic horses is of prognostic relevance both with regard to survival as to the probability of development of ileus during hospitalization. This study shows the importance of routine measurement of ionized calcium levels in colic horses. Moreover, correction of hypocalcaemia seems to improve clinical outcome.

Abdomen, Acute↗

PubMed1977

Activity and interference effects in measurement of ionized calcium with ion-selective electrodes.

We assessed the magnitude of the errors in ionized-calcium measurements resulting from changes in electrolyte composition for three different ion-selective electrodes: the Orion Model 93-20, the Radiometer F2112, and the Simon neutral carrier membrane electrode. We attempted to distinguish between errors arising from changes in calcium ion activity and those due to interferences in the electrode response. Variation in sodium ion concentration over the range 100--180 mmol/liter produces changes in apparent ionized-calcium concentration that are largely attributable to activity effects for the Radiometer and Simon electrodes. The Orion electrode is subject to an additional sodium-interference effect. Apparent ionized calcium concentration measurements are independent of pH for the Radiometer electrode but not for the Orion electrode; the Simon electrode exhibits intermediate pH response, which is probably clinically negligible. Magnesium and potassium ions have little effect on ionized calcium concentration measurements, particularly when these ions are incorporated into calibration standards.

Calcium↗

PubMed1990

[Ionized calcium. An essential parameter for the study of calcium metabolism].

Calcium ions in plasma are either free (ionized calcium) or bound to protein and small anions. Ionized calcium is the physiologically active fraction. Several factors have recently been combined to change the measurement of ionized calcium from a specialized to a routine test. Reliable instrumentation, easy to maintain, is now available with simultaneous pH measurement. This paper focuses on both the analytical consideration required to perform reliable laboratory measurements and the clinical situations where ionized calcium has proved to provide a substantially different clinical interpretation than the measurement of total calcium.

Adolescent↗

PubMed1990

[Changes in magnesium and ionized calcium serum levels in disorders of glucose tolerance].

In a group of 58 subjects with a strictly defined glucose tolerance (38 normal--nGT, 10 impaired glucose tolerance--pGT, 10 type II diabetics treated by diet) the authors investigated the mutual relationship between changes in the blood sugar level and insulin serum level in relation changes of calcium, ionized calcium, magnesium and total proteins. In addition to expected differences in the native blood sugar level and insulinaemia, the authors found in pGT group in reduction of ionized calcium and magnesium on fasting. In the course of the oGTT in pGT group there is a rise of ionized calcium and magnesium and thus the changes, as compared with the initial value, differ significantly from changes in subjects with a normal glucose tolerance and in type II diabetics. The differences in the pattern total calcium are less marked, the changes of total protein did not differ. Evaluation of correlations revealed a only significant relationship between the change of ionized calcium and blood sugar level after 120 mins, in DM II. The findings suggest a different calcium and magnesium metabolism after a glucose load in subjects with an impaired glucose tolerance. It is not clear whether a cause of the disorder is involved or a possible compensatory mechanism. The clinical impact will have to be examined.

Calcium↗

PubMed1990

[The recombination factor in an ionizing chamber used for dosimetry of a linear accelerator].

The authors starting from the discussion of Boag address experimentally the ion recombination in an ionizing camera. They outline the fact that several basic dosimetry protocols do not highlight the importance of the used radiation sources, beam width, ionizing camera dimensions, even though they mention to take into account the recombination factor. The authors determine experimentally the recombination factor with two kinds of ionizing camera, one cylindrical and the other flat, on a linac pulsed and scanned radiation beams. As a result it ensued that it is advisable to use a Markus type ionizing camera rather than a cylindrical one, especially when scanning beams are used, to reduce the recombination phenomena.

Models, Theoretical↗

PubMed1989

Derivation of radiation quality average parameters in neutron-gamma radiation fields with the high-pressure ionization chamber: theory and practice.

The established radiation quality parameters in mixed neutron-gamma radiation fields may be measured by applying the initial (columnar) recombination of ions in tissue-equivalent (TE) high-pressure ionization chambers (recombination chambers). The mean quality factor can be determined to within 10-15% for mixed fields with neutrons ranging from thermal to 10 MeV, and the dose mean LET of the proton component can be determined to within 10-15% if the gamma-ray absorbed dose fraction is known. These average parameters are derived by measuring the ratio of the ionization currents collected at two high-field strengths and constant gas pressure applied to the ionization chamber. By utilizing approximate correlations between physical parameters in the neutron energy region from thermal to 10 MeV, the dose mean LET of the heavy ion component, the overall dose mean LET, and the microdosimetric parameter y0,D of the mixed field can also be derived. Experimental verification of the method is presented for various neutron-gamma radiation spectra in air and in water by comparison to theoretical calculations and results from low-pressure proportional counter measurements. Good agreement is shown. The TE high-pressure ionization chamber appears to have wide potential for use as a dose-equivalent meter in radiation protection or as a beam characterization device in radiobiology.

Energy Transfer↗

PubMed1989

Ionization yields in hydrocarbons under electron irradiation.

Ionization yields and W-values in several hydrocarbon gases under electron irradiation have been calculated using Inokuti's solution of the Fowler equation, i.e., incorporating a linear dependence of ionization yield on source electron energy. Collision stopping powers of hydrocarbons were evaluated using the Bethe formula with mean excitation energies determined using the additivity rule with modification based on molecular bond strengths. Contributions to the collision stopping powers from discrete level excitations were estimated by multiplying collision stopping powers by the excitation fractions constructed from atomic calculations. Average energy transfers for ionizing collisions producing subionization electrons were calculated using differential ionization cross sections proposed by Khare and co-workers. The calculated W-values are in good agreement with those recommended by ICRU.

Electrons↗

PubMed1989

Serum phosphate concentration. Effect on serum ionized calcium concentration in vitro.

We examined the effects of variations of serum phosphate levels on serum ionized calcium concentrations in vitro. A single donor serum sample was divided into 25 aliquots stored in tubes sealed with carbon dioxide and divided into 5 subsets of tubes. The pH was altered in 4 of the 5 subsets by adding various concentrations of hydrochloric acid or sodium hydroxide. The pH levels studied ranged from 7.09 to 7.63. The phosphate concentration was altered in each subset by adding various concentrations of a phosphate buffer. The phosphate concentrations studied ranged between 0.81 and 3.58 mmol/L. There was an inverse relationship between ionized calcium and phosphate at all pH levels studied. The ionized calcium concentration correlated inversely with pH. We suggest that in addition to factors well known to influence serum ionized calcium concentration (such as protein, bicarbonate, and pH values), serum phosphate concentration also plays an important role.

Calcium↗

PubMed1988

Effect of parathyroid hormone and parathyroid hormone fragments on the intracellular ionized calcium concentration in an osteoblast cell line.

In the present study the effect of parathyroid hormone and parathyroid hormone fragments on the intracellular ionized calcium concentration in an osteoblastic cell line (UMR 106-01) is examined. In these cells the intact hormone, bPTH(1-84) and three fragments (bPTH(1-34), hPTH(1-34) and bPTH(3-34) induce an initial increase of the ionized calcium concentration [( Ca2+]i). The increase of the [Ca2+]i due to bPTH(1-84) is more pronounced and of longer duration compared to the increase due to PTH fragments. For two parathyroid hormone fragments with a modified amino acid sequence [( Nle-8,Nle-18,Tyr-34]bPTH(1-34), [Nle-8,Nle-18,Tyr-34]bPTH(3-34], no effect was found. Our observations suggest: (1) a second messenger role for intracellular ionized calcium in the action of bPTH(1-84) in osteoblasts; (2) a functional role for the COOH-terminal part in the action of bPTH(1-84); and (3) the existence of a specific part of the hormone being responsible for the increase of the intracellular ionized calcium concentration.

Animals↗

PubMed1987

Ionized calcium monitoring during liver transplantation.

Ionized calcium concentration was measured in five patients undergoing liver transplantation. Varying degrees of decreased ionized calcium were observed in all cases and can be attributed to the chelation of calcium by the citrate added during blood transfusions, the inability of the patient to metabolize citrate by the liver during the anahepatic phase of the transplant, and hemodilution of the blood volume with the perfusion prime during venovenous bypass. Calcium chloride was administered when necessary as guided by ionized calcium measurements to restore concentrations to levels that maintain adequate cardiac output. Because of the serious hemodynamic consequences of severe hypocalcemia, regular monitoring of ionized calcium concentration is necessary during this procedure. Total calcium levels are not reliable for this because they do not reflect the extent of anion binding.

Calcium↗

PubMed1986

Ionized calcium in plasma during cardiopulmonary bypass.

The composition of the priming fluid in the heart-lung machine is of importance for the homeostasis of the patient during and after cardiopulmonary bypass. We have studied the effect of 5 different priming solutions on the degree of ionization of calcium. The primingsolutions all contained 1700 ml of a basic solution and 800 ml of one of the following solutions: CPD-plasma CPD-plasma added heparine and CaCl2 heparinized plasma 5% albumin in saline 6% dextran 70 in saline. With CPD-plasma in the priming solution, the concentration of ionized calcium dropped to very low values, followed by a normalization during the next 30 minutes, as the citrate disappeared. The addition of CaCl2 to CPD-plasma prevented the abrupt initial drop, but resulted later on in values above the normal range. Heparinized plasma, albumin, and dextran in the priming solution lead to small changes only. Bolus injections of CaCl2 during weaning from bypass resulted in substantial increases in ionized calcium, while the use of CPD-blood products lead to decreases. Citrate has great affinity to calcium ions, making strong complexes. When significant amounts of citrate are used, the level of ionized calcium cannot be predicted, but has to be measured directly. These measurements must be performed frequently.

Adult↗

PubMed1979

[Ionized fluorine in the plasma and urine of subjects treated with organofluorine drugs prescribed in rheumatology].

The elimination of ionized urinary fluorine was studied in groups of eight subjects treated during several days with niflumic acid, flufenamic acid, sulindac, antrafenine and floctafenine. Sulindac and floctafenine do not changes this elimination. After administration of niflumic acid, flufenamic and antrafenine, the urinary elimination of ionized fluorine increase in all the subjects. This increase is manifested from the start of treatment and persists for several days after it has been stopped. The administration of three drugs also results in an elevated level of ionized plasmic fluorine the duration of treatment. The results prove the existence in the human organism of a metabolic process capable of effecting the ionization of the organic fluor contained in the drugs studied. This biotransformation causes a fluorine impregnation of endogenous origin that is permanent and relatively stable, and whose consequences are examined (risk of fluorine osteosis and possibility of therapeutic application).

Anti-Inflammatory Agents↗

PubMed1987

Calcium chloride versus calcium gluconate: comparison of ionization and cardiovascular effects in children and dogs.

A randomized prospective study in both children and dogs compared ionization of calcium chloride and calcium gluconate. Five conditioned dogs under halothane anesthesia received calcium chloride (4, 8, 12 mg/kg) and calcium gluconate (14, 28, 42 mg/kg) intravenously. Ten children scheduled for burn wound excision and grafting received both calcium chloride (2.5 mg/kg) and calcium gluconate (7.5 mg/kg) injected through a central venous cannula. Ionized calcium was measured at 0, 0.5, 1, 3, 5, and 10 min in the children, and 0, 0.5, 1, 2, 3, 4, 5, 10, 20, and 45 min in the dogs. The authors conclude that equal elemental calcium doses of calcium gluconate (10%) and calcium chloride (10%) (approximately 3:1), injected over the same period of time, are equivalent in their ability to raise [Ca++] during normocalcemic states in children and dogs; the changes in [Ca++] following calcium administration are short-lived (minutes); rapidity of ionization seems to exclude hepatic metabolism as an important factor in the dissociation of calcium gluconate; and equivalent rises in [Ca++] produced by calcium gluconate or calcium chloride resulted in equivalent cardiovascular effects. The authors feel that either form of calcium salt would be satisfactory if indicated during cardiopulmonary resuscitation or for the treatment of ionized hypocalcemia due to massive blood transfusion.

Adolescent↗

PubMed1986

Relationship between serum lactate and ionized calcium in open-heart surgery.

We studied 16 patients undergoing open-heart surgery and heart-lung bypass, to examine the relationship between ionized calcium and lactate. Blood was sampled at successive stages of the operation for measurement of ionized and total calcium, lactate, blood gases, pH, hematocrit, and other constituents. We found that correlations between ionized calcium and lactate were positive and statistically significant (p less than 0.05), both among and within patients. The linear regression of ionized calcium on lactate remained highly significant (p less than 0.0001) after adjustment for variability among patients and across operative stages as well as after correction for pH and hemodilution. The significant regressions between calcium and lactate, both before and after administration of calcium, indicate a relationship for calcium and lactate in patients undergoing open-heart surgery.

Blood↗

PubMed1985

Effect of storage on measurement of ionized calcium in serum of uremic patients.

We studied, in 70 acidotic and non-acidotic uremic patients, the analytical variance in serum ionized calcium as related to duration and temperature of storage. Storage of serum or whole blood at 4 degrees C for as long as 6 h did not significantly alter the measured concentration of ionized calcium in the serum. Storage at room temperature for 6 h, or longer at 4 degrees C or -20 degrees C, resulted in inaccuracies in 39 to 79% of the samples of serum and in 38 to 92% of the samples of whole blood. These errors were not negated by correcting the values for ionized calcium to a pH of 7.40. Indeed, corrected values for calcium were even more unreliable in acidotic patients. We conclude that samples from uremic patients should be analyzed for ionized calcium within 2 h, or within 6 h if stored at 4 degrees C.

Acidosis↗