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PubMed1993

Detection and quantification of 8-hydroxydeoxyguanosine adducts in peripheral blood of people exposed to ionizing radiation.

Ionizing radiation produces a variety of damaging insults to nucleic acids, including the promutagenic lesion 8-hydroxydeoxyguanosine. In the present study, the 8-hydroxydeoxyguanosine content of peripheral blood leukocyte DNA isolated from individuals exposed to therapeutic doses of ionizing radiation was determined by a HPLC-coupled 32P-postlabeling assay. Peripheral blood leukocyte DNA from individuals irradiated with 180-200 cGy were observed to contain 2-4.5 times as much 8-hydroxydeoxyguanosine as that from unexposed individuals. These results were confirmed by the use of a HPLC-coupled electrochemical detection system. Thus, human exposure to ionizing radiation significantly increased the circulating leukocyte DNA content of 8-hydroxydeoxyguanosine.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed2006

Soft-x-ray wavelength shift induced by ionization effects in a capillary.

Coherent soft x rays are produced by high-harmonic generation in a capillary filled with Ar gas. We demonstrate that the tuning of the harmonic wavelengths with intensity and chirp arises from changes in the Ar ionization level. Control over the tuning can be achieved either by changing the average intensity of the laser pulse or by varying the quadratic spectral phase of the laser pulse. We observe an ionization-dependent blueshift of the fundamental wavelength that is directly imprinted on the harmonic wavelengths. The harmonic tuning is shown to depend on nonlinear spectral shifts of the fundamental laser pulse that are due to the plasma created by ionization, rather than directly on any chirp imposed on the fundamental wavelength.

Journal Article↗
PubMed2003

Multiphoton ionization mass spectrometry of chlorophenols as indicators for dioxins.

Mono-, di- and trichlorophenols were measured using resonance-enhanced multiphoton ionization mass spectrometry (MPI-MS) combined with supersonic jet (SSJ) or effusive molecular beam (EMB) spectrometry. All mono- and dichlorophenols, except 2,6-dichlorophenol, provided sharp and structured MPI spectra for the S1 <-- S0 transition. Selectivity and sensitivity were both enhanced when SSJ spectrometry was used, compared with EMB spectrometry, because of a narrower linewidth in the MPI spectrum, given by molecular cooling by supersonic jet expansion. The ionization efficiency decreased with increasing number of chlorine substituents for the chlorophenols, since they have shorter excited-state lifetimes and require three photons for ionization. Some of the chlorophenols, which are toxic themselves, have the potential for use as indicators for analysis of polychlorinated dibenzo-p-dioxin/dibenzofurans in flue gases emitted from an incinerator.

Air Pollutants↗
PubMed2000

Ionizing radiation alters Fas antigen ligand at the cell surface and on exfoliated plasma membrane-derived vesicles: implications for apoptosis and intercellular signaling.

Resident proteins that reside on the plasma membrane are continually exfoliated from the cell surface. Exfoliation is a selective, energy-dependent process that mediates intercellular communication. Ionizing radiation modulates the expression of many plasma membrane-bound growth regulators, including the "death" ligand, TNFSF6 (formerly known as FasL, CD95L). Here we report that ionizing radiation induces dose-dependent up-regulation of TNFSF6 on plasma membranes purified from SW620 cells, a TNFSF6-expressing colon cancer cell line. Serum-free medium conditioned by exposed and control cells was collected and exfoliated vesicles were obtained by ultracentrifugation. Western blot analysis of vesicles from unexposed cells and from cells treated with 10 Gy showed increased amounts of TNFSF6 compared to that on vesicles from unexposed cells. Cells treated with 4 Gy released vesicles having a low level of TNFSF6 on their surface relative to that on vesicles exfoliated from unexposed cells. When assayed for bioactivity, vesicles from unexposed cells induced the greatest level of apoptosis in TNFRSF6 (formerly known as FAS) receptor-bearing Jurkat cells (cell surviving fraction of 43.7 +/- 6.1; P < 0.05), followed by vesicles collected from cells treated with 4 Gy (79.6 +/- 2.6%; P < 0.05). Despite having a high level of TNFSF6 by Western analysis, vesicles collected from cells exposed to 10 Gy display minimal biological activity (77.9 +/- 3.2%; P < 0.05), suggesting that modification of the vesicle-associated ligand has occurred. Our results indicate that ionizing radiation increases the level of TNFSF6 exfoliated on extracellular vesicles. The data may provide a mechanism for abscopal and bystander effects after irradiation.

Adenocarcinoma↗
PubMed2004

Microdosimetric analysis of various mammography spectra: lineal energy distributions and ionization cluster analysis.

In view of recent recommendations on the frequency and the starting age of mammography screening in healthy women, it is desirable to quantify the enhanced relative biological effectiveness (RBE) of mammography X rays compared to hard X rays. While there is little doubt that the former are more potent in inducing biological damage than the latter, the magnitude of the effect is still hotly debated in the literature. We used Monte Carlo simulations and track structure analysis in micrometer and nanometer volumes to investigate differences in distributions of lineal energy and ionization clusters for a range of mammography X-ray qualities. Dose-averaged lineal energies, (yD), in breast tissue for various mammography qualities were found to result in quality factors about 40% higher than unity. Among the various mammography qualities studied, the popular molybdenum/molybdenum target/filter combination was found to have the highest (yD) in 1-microm spheres (about 5.0 keV/microm near the entrance surface of breast tissue). In 10-nm radius spheres, the mean ionization cluster order was found to be about 35% higher in mammography X rays compared to 300 keV electrons (roughly representing 60Co or 192Ir photon radiation). In even smaller spheres (2 nm radius), no significant differences were observed for the mean ionization cluster order between mammography X rays and 300 keV electrons. We conclude that the potential of mammography X rays to induce biological damage is probably not much higher than a factor of two compared to hard X rays.

Breast↗
PubMed2005

Non-homologous end-joining defect in fanconi anemia hematopoietic cells exposed to ionizing radiation.

Fanconi anemia is a genetically heterogeneous recessive disease characterized mainly by bone marrow failure and cancer predisposition. Although it is accepted that Fanconi cells are highly sensitive to DNA crosslinking agents, their response to ionizing radiation is still unclear. Using pulsed-field gel electrophoresis, we have observed that radiation generates a similar number of DNA double-strand breaks in normal and Fanconi cells from three (FA-A, FA-C and FA-F) of the 11 complementation groups identified. Nonsynchronized as well as nonproliferating Fanconi anemia cells showed an evident defect in rejoining the double-strand breaks generated by ionizing radiation, indicating defective non-homologous end-joining repair. At the cellular level, no difference in the radiosensitivity of normal and FA-A lymphoblast cells was noted, and a modest increase in the radiosensitivity of Fanca-/- hematopoietic progenitor cells was observed compared to Fanca+/+ cells. Finally, when animals were exposed to a fractionated total-body irradiation of 5 Gy, a similar hematopoietic syndrome was observed in wild-type and Fanca-/- mice. Taken together, our observations suggest that Fanconi cells, in particular those having nonfunctional Fanconi proteins upstream of FANCD2, have a defect in the non-homologous end-joining repair of double-strand breaks produced by ionizing radiation, and that compensatory mechanisms of DNA repair and/or stem cell regeneration should limit the impact of this defect in irradiated organisms.

Animals↗
PubMed2003

Detection of chlorobenzene derivatives using vacuum ultraviolet ionization time-of-flight mass spectrometry.

Vacuum ultraviolet single-photon ionization time-of-flight mass spectrometry (VUV-SPI-TOFMS) has been applied for the detection of chlorobenzene, o-dichlorobenzene, and o-chlorophenol as surrogates for polychlorinated dibenzo-p-dioxine/furans (PCDD/F). The photoionization mass spectra of these compounds appear to be fragmentation free in the ionization processes by the VUV-SPI at 10.2 eV (121.6 nm). Quantum chemical calculations support no fragmentation in the photoionization of chlorobenzene derivatives at around 10 eV. The absolute photoionization cross-sections of chlorobenzene, o-dichlorobenzene, and o-chlorophenol were estimated at 10.2 eV. The photoionization cross-section is an important parameter in the detection of chlorobenzene derivatives by the single-photon ionization technique. The detection limit for chlorobenzene is on the order of tenth parts-per-billion volume (ppbv) in the present experimental setup.

Journal Article↗
PubMed2004

Real-time measurements of polychlorinated biphenyls using laser ionization time-of-flight mass spectrometry.

Polychlorinated biphenyls (PCBs) are hazardous compounds for which there are few methods involving real-time measurement. Recently, the development of the pulsed-laser technique has enabled us to measure aromatic hydrocarbons quite rapidly. In particular, the LI-TOFMS (laser ionization time of flight mass spectrometry) technique is expected to be a powerful method for on-line, selective and sensitive measurements. In the context of developing a highly selective and sensitive technique, the effective laser wavelength and pulse duration for laser ionization of 2-4 chlorinated PCBs are considered. Excitation at lambda = 266 nm was found to be substantially more effective than at lambda = 280, 300 or 320 nm. Also, picosecond excitation for PCBs underwent more efficient ionization (by a factor of over 10) and less fragmentation than nanosecond excitation. The achievable sensitivity for trichlorinated biphenyl in a real-time (1 min) measurement using the LI-TOFMS technique was estimated to be in the sub-ppbV range (< 0.01 mg/Nm3).

Journal Article↗
PubMed2007

MPAI (mass probes aided ionization) method for total analysis of biomolecules by mass spectrometry.

We have designed and synthesized various mass probes, which enable us to effectively ionize various molecules to be detected with mass spectrometry. We call the ionization method using mass probes the "MPAI (mass probes aided ionization)" method. We aim at the sensitive detection of various biological molecules, and also the detection of bio-molecules by a single mass spectrometry serially without changing the mechanical settings. Here, we review mass probes for small molecules with various functional groups and mass probes for proteins. Further, we introduce newly developed mass probes for proteins for highly sensitive detection.

Animals↗
PubMed1985

Sampling and storage of blood for determination of ionized calcium.

We report some new procedures for the determination of ionized calcium using a semi-automatic ICA 1 analyser provided with a new flow-through tonometer unit, TNC 1, in connection with an automatic turntable. Ionized calcium calculated to a standard pH of 7.4 (cCa2+(7.4)) was not significantly different for capillary blood, venous blood and serum in healthy adults; however, a significant difference was found for actual ionized calcium (cCa2+). The effect of erythrocytes on the liquid junction potential was eliminated by use of a new salt bridge solution (sodium formate). Serum samples should be taken as anaerobically as possible to avoid precipitation of calcium complexes when pH increases above 7.9. For measurement of cCa2+-pH we developed special capillary tubes. Serum could be stored at 4 degrees C for 7 days and at -20 degrees C for 45 days without significant change in cCa2+(7.4). Capillary blood could be stored at 4 degrees C for 4 h without significant change in cCa2+ and pH or at 4 degrees C or 20 degrees C for 24 h without significant change in cCa2+(7.4). Vein puncture with stasis or muscular exercise caused only a small increase in cCa2+(7.4) (1.5%). The ingestion of food did not affect cCa2+ in healthy adults. 97.5% CO2 equilibrium was obtained in 3 min with the new flow-through tonometer.

Air↗
PubMed1988

Age-related reference values for ionized calcium in the first week of life in premature and full-term neonates.

Reference values for ionized calcium were measured in anaerobic samples of capillary blood from 22 healthy premature neonates, gestational age 33-36 weeks, birth weight 1660-2480 g. Reference values (mean +/- 2SE) for premature neonates aged 5-12, 13-19, 25-48, 51-72, 77-99, 108-140, 150-185 h were: 1.21 +/- 0.16, 1.17 +/- 0.12, 1.21 +/- 0.16, 1.28 +/- 0.18, 1.34 +/- 0.14, 1.38 +/- 0.13, 1.40 +/- 0.16 mmol/l, respectively. Ionized calcium in 59 full-term neonates with mild pathological hyperbilirubinaemia (no phototherapy needed) and 28 neonates born by section (no neonatal complications) showed no statistical difference (unpaired t-test) in age-related values compared with matching healthy neonates with no clinical remarks. Data for full-term neonates were pooled and age-related reference values (mean +/- 2SE) for ionized calcium in capillary whole blood for 168 full-term neonates, gestational age 38-41 weeks, birth weight 2550-4700 g, aged 1-12, 13-24, 25-48, 49-72, 73-99, 99-120, 121-144, 146-168, 178-264 h were: 1.24 +/- 0.11, 1.19 +/- 0.12, 1.21 +/- 0.13, 1.22 +/- 0.14, 1.29 +/- 0.17, 1.35 +/- 0.12, 1.37 +/- 0.12, 1.38 +/- 0.16, 1.40 +/- 0.10 mmol/l, respectively.

Age Factors↗
PubMedDate not supplied

Peripheral blood lymphocyte subsets in radiologists exposed to ionizing radiation.

To investigate whether low dose ionizing radiation caused perturbation of peripheral blood lymphocytes in radiology unit staff, the T-helper/suppressor ratio was examined in eight radiologists exposed to low dose radiation over a period of 6 to 27 years (mean 12 years). No significant difference was noted in the T-cell subsets between exposed radiologists and non-exposed control subjects. The effect of low dose ionizing radiation on peripheral blood lymphocyte subsets seems to be virtually negligible. Further, measurement of the T-helper/suppressor ratio is not a reliable way of demonstrating any damage to bone marrow caused by low dose ionizing radiation.

Adult↗
PubMed1981

Ionized calcium in body fluids.

This article will review the methods currently available to the clinician and research worker for measuring the concentration of ionized calcium in various body fluids including whole blood, serum, plasma, urine, cerebrospinal fluid, milk, and synovial fluid. The methods to be reviewed are based on procedures involving bioluminescence, colorimetry and ion-selective electrodes. Emphasis will be given to the precision and, wherever possible, accuracy of each technique. Possible sources of error and interfering agents will be identified. Attention will be given to the recommended conditions for measuring ionized calcium in each body fluid. An assessment will be made of the theoretical and practical importance of measuring ionized calcium rather than total calcium and of its value in clinical medicine.

Adult↗
PubMed2003

Expression properties of recombinant pEgr-P16 plasmid in esophageal squamous cell carcinoma induced by ionizing irradiation.

AIM: To construct the recombinant pEgr-P16 plasmid for the investigation of its expression properties in esophageal squamous cell carcinoma induced by ionizing irradiation and the feasibility of gene-radiotherapy for esophageal carcinoma. METHODS: The recombinant pEgr-P16 plasmid was constructed and transfected into EC9706 cells with lipofectamine. Western blot, quantitative RT-PCR and flow cytometry were performed to study the expression of pEgr-P16 in EC9706 cells and the biological characteristics of EC9706 cell line after transfection induced by ionizing irradiation. RESULTS: The eukaryotic expression vector pEgr-P16 was successfully constructed and transfected into EC9706 cells. The expression of P16 was significantly increased in the transfected cells after irradiation while the transfected cells were not induced by ionizing irradiation. The induction of apoptosis in transfection plus irradiation group was higher than that in plasmid alone or irradiation alone. CONCLUSION: The combination of pEgr-P16 and irradiation could significantly enhance the P16 expression property and markedly induce apoptosis in EC9706 cells. These results may lay an important experimental basis for gene radiotherapy for esophageal carcinoma.

Apoptosis↗
PubMedDate not supplied

Microarray analysis of p53 target gene expression patterns in the spleen and thymus in response to ionizing radiation.

The ability of p53 to induce apoptosis through transactivation of its target genes is critical for its function as a tumor suppressor. To identify the critical p53 target genes that mediate apoptosis through these pathways, we examined p53-dependent apoptosis in vivo where these apoptotic pathways are intact. p53 wild-type and null animals were irradiated and the global p53 gene expression patterns in response to ionizing radiation were examined in two tissues (spleen and thymus) which undergo p53-dependent apoptosis in response to ionizing radiation. We found that the vast majority of genes that increased or decreased in a p53-dependent manner did so in a tissue specific manner. Although the spleen and thymus had similar levels of p53-dependent apoptosis after ionizing radiation, there was very little overlap in the induced or repressed targets. This suggested that distinct targets may mediate apoptosis in these tissues. In addition, these microarray analyses also led to the identification of several novel p53 targets. Several of these targets appear to be involved in known p53 functions such as the induction of apoptosis (bim) or the initiation of DNA repair (DinB). However, some p53 targets (both confirmed and unconfirmed) link p53 to the anti-tumor immune response (MIP 1-alpha). Further characterization of the tissue specific mediators of p53-dependent responses will greatly increase our understanding of p53 function.

Animals↗
PubMed2006

Nalidixic acid resistance influences sensitivity to ionizing radiation among Salmonella isolates.

Nalidixic acid (Nal) resistance has been used as a selective marker for studies of pathogen-inoculated fruits and vegetables. A collection of 24 Salmonella isolates were screened for natural resistance to Nal (50 microg/ml). The resistance to ionizing radiation was determined and compared for i) three naturally Nal-resistant (Nal(R)) strains, ii) three naturally Nal-sensitive (Nal(S)) strains, and iii) three strains derived from Nals strains that were made resistant to Nal (Nal(Ri)) by successive culturing and selection in Nal-amended broth. The radiation D10-values (the radiation dose required to achieve a 1-log reduction in population) were determined in buffer solution and in orange juice. D10-values were significantly (P < 0.05) different among the Salmonella isolates tested. When considered as a group, Nal(R) isolates were significantly more sensitive to ionizing radiation than Nals isolates in both media tested. In buffer, D10 of Nal(R) was 0.210 kGy versus 0.257 kGy for Nals. In orange juice, D10 of Nal(R) was 0.581 versus 0.764 for Nals. Inducing resistance to Nal altered the response to irradiation. D10-value of Nal(Ri) was 0.234 kGy in buffer, a 9% reduction relative to Nals parents. In orange juice, the D10-value of Nal(Ri) was 0.637 kGy, a reduction of 17% relative to Nals parents. These results suggest that natural and/or induced resistance to Nal may predispose Salmonella isolates to greater sensitivity to ionizing radiation,and that this effect is influenced by the suspending medium and by the nature of the isolates evaluated.

Colony Count, Microbial↗
PubMed1999

Reductive half-reaction of the H172Q mutant of trimethylamine dehydrogenase: evidence against a carbanion mechanism and assignment of kinetically influential ionizations in the enzyme-substrate complex.

The reactions of wild-type trimethylamine dehydrogenase (TMADH) and of a His-172-->Gln (H172Q) mutant were studied by rapid-mixing stopped-flow spectroscopy over the pH range 6.0-10.5, to address the potential role of His-172 in abstracting a proton from the substrate in a 'carbanion' mechanism for C-H bond cleavage. The pH-dependence of the limiting rate for flavin reduction (klim) was studied as a function of pH for the wild-type enzyme with perdeuterated trimethylamine as substrate. The use of perdeuterated trimethylamine facilitated the unequivocal identification of two kinetically influential ionizations in the enzyme-substrate complex, with macroscopic pKa values of 6.5+/-0.2 and 8.4+/-0.1. A plot of klim/Kd revealed a bell-shaped curve and two kinetically influential ionizations with macroscopic pKa values of 9.4+/-0.1 and 10.5+/-0.1. Mutagenesis of His-172, a potential active-site base and a component of a novel Tyr-His-Asp triad in the active site of TMADH, revealed that the pKa of 8.4+/-0.1 for the wild-type enzyme-substrate complex represents ionization of the imidazolium side-chain of His-172. H172Q TMADH retains catalytic competence throughout the pH range investigated. At pH 10.5, and in contrast with the wild-type enzyme, flavin reduction in H172Q TMADH is biphasic. The fast phase is dependent on the trimethylamine concentration and exhibits a kinetic isotope effect of about 3; C-H bond cleavage is thus partially rate-limiting. In contrast, the slow phase does not show hyperbolic dependence on substrate concentration, and the observed rate shows no dependence on isotope, revealing that C-H bond cleavage is not rate-limiting. The analysis of H172Q TMADH, together with data recently acquired for the Y169F mutant of TMADH, reveals that C-H bond breakage is not initiated via abstraction of a proton from the substrate by an active-site base. The transfer of reducing equivalents to flavin via a carbanion mechanism is therefore unlikely.

Enzyme Activation↗
PubMed1999

Ionization behavior of acidic residues in calbindin D(9k).

The ionization state of seven glutamate residues, one aspartate, and the C-terminal alpha-COOH group in bovine apo calbindin D(9k) has been studied by measurement and modeling of the pH titration curves and apparent pK(a) values. The observed pK(a) ranged from 3.0 to 6.5. Most of the observed acidic groups were half-ionized at lower pH values than those in unstructured proteins. As a rule, the ionization equilibria extended over a wider pH range than in the case of unperturbed single titrations, indicating a complex influence of protein charges on the charge state of each individual residue. Glu17, which is a backbone Ca(2+)-ligand in the N-terminal binding loop of calbindin D(9k), was half-protonated at pH 3.6 but manifested biphasic titration with apparent pK(a) values of 3.2 and 6.5. Complementary Monte Carlo simulations of the titration process and pK(a) values of the acidic groups in calbindin D(9k) reproduce the experimentally observed titration features, except for the pronounced double titration of Glu17. Discrepancies between the results from direct measurement and from modeling may be partly caused by changes in the protein structure when the net charge changes from -8 to +11 over the isoelectric point at pH 5. Proteins 1999;37:106-115.

Animals↗