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We have previously reported the design of a portable109Cd x-ray fluorescence (XRF) system to measure iron levels in the skin of patients with either iron overload disease, such as thalassemia, or iron deficiency disease, such as anemia. In phantom studies, the system was found to have a detection limit of 1.35µg Fe per g of tissue for a dose of 1.1 mSv. However, the system must provide accurate as well as precise measurements of iron levels in the skin in order to be suitable for human studies. The accuracy of the system has been explored using several methods. First, the iron concentrations of ten pigskin samples were assessed using both the portable XRF system and ICP-MS, and the results were compared. Overall, it was found that XRF and ICP-MS reported average values for iron in skin that were comparable to within uncertainties. The mean difference between the two methodologies was not significant, 2.5 ± 4.6µg Fe per g. On this basis, the system could be considered accurate. However, ICP-MS measurements reported a wider range of values than XRF, with two individual samples having ICP-MS results that were significantly elevated (p < 0.05) compared to XRF. SynchrotronµXRF maps of iron levels in pigskin were acquired on the BioXAS beam line of the Canadian Light Source. TheµXRF maps indicated two important features in the distribution of iron in pigskin. First, there were small areas of high iron concentration in the pigskin samples, that were predominantly located in the dermis and hypodermis at depths greater than 0.5 mm. Monte Carlo modelling using the EGS 5 code determined that if these iron 'hot spots' were located towards the back of the skin at depths greater than 0.5 mm, they would not be observed by XRF, but would be measured by ICP-MS. These results support a hypothesis that iron levels in the two samples that reported significantly elevated ICP-MS results compared to XRF may have had small blood vessels at the back of the skin. Second, the synchrotronµXRF maps also showed a narrow (approximately 100µm thick) layer of elevated iron at the surface of the skin. Monte Carlo models determined that, as expected, the XRF system was most sensitive to these skin layers. However, the simulations found that the XRF system, when calibrated against homogenous water-based phantoms, was found to accurately measure average iron levels in the skin of normal pigs despite the greater sensitivity to the surface layer. The Monte Carlo results further indicated that with highly elevated skin surface iron levels, the XRF system would not provide a good estimate of average skin iron levels. The XRF estimate could, with correction factors, provide a good estimate of the iron levels in the surface layers of skin. There is limited data on iron distribution in skin, especially under conditions of disease. If iron levels are elevated at the skin surface by diseases including thalassemia and hemochromatosis, this XRF device may prove to be an accurate clinical tool. However, further data are required on skin iron distributions in healthy and iron overload disease before this system can be verified to provide accurate measurements.
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Hierro , Piel , Espectrometría por Rayos X , Hierro/análisis , Piel/metabolismo , Animales , Porcinos , Espectrometría por Rayos X/métodos , Espectrometría por Rayos X/instrumentación , Humanos , Fantasmas de Imagen , Reproducibilidad de los Resultados , Espectrometría de Masas/métodos , Cadmio/análisisRESUMEN
Iron is an essential element vital for growth and development. The severe effects on the body due to iron deficiency or overload have prompted sustained research into accuratein vivoiron measurement techniques for the past several decades. X-ray fluorescence (XRF) analysis of iron in the body has been investigated in this work because of the non-invasive nature of the technique. A system has been designed using a silicon drift detector to measure the low-energy iron Kαx-rays excited in the samples by the silver x-rays from109Cd of energy 22 keV and 25 keV. The source is contained within a tantalum shielding cap designed to reduce the spectral background. The system was calibrated against 3D printed polylactic acid (PLA) phantoms filled with solutions of iron at various concentrations. The iron x-ray signals were normalized to a nickel x-ray signal which improved the system's reproducibility. The 3D phantoms and normalisation resulted in a linear calibration line (p < 0.001 and r2 > 0.999). For a real-time measurement of 1800 s, the minimum detectable limit for the system was measured to be 1.35 ± 0.35 ppm which is achieved with a low radiation dose of 1.1 mSv to the skin surface. This low detection limit and low dose mean the system is feasible for application to human measurements in both iron deficiency and overload disease. The system will proceed to post-mortem validation studies prior toin vivosystem efficacy testing.
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Cadmio , Hierro , Humanos , Espectrometría por Rayos X/métodos , Cadmio/análisis , Estudios de Factibilidad , Reproducibilidad de los ResultadosRESUMEN
Biophoton emission leading to bystander effects (BEs) was shown in beta-irradiated cells; however, technical challenges precluded the analysis of the biophoton role in gamma-induced BEs. The present work was to design an experimental approach to determine if, what type, and how many biophotons could be produced in gamma-irradiated cells. Photon emission was measured in HCT116 p53+/+ cells irradiated with a total dose of 22 mGy from a cesium-137 source at a dose rate of 45 mGy/min. A single-photon detection unit was used and shielded with lead to reduce counts from stray gammas reaching the detector. Higher quantities of photon emissions were observed when the cells in a tissue culture vessel were present and being irradiated compared to a cell-free vessel. Photon emissions were captured at either 340 nm (in the ultraviolet A [UVA] range) or 610 nm. At the same cell density, radiation exposure time, and radiation dose, HCT116 p53+/+ cells emitted 2.5 times more UVA biophotons than 610-nm biophotons. For the first time, gamma radiation was shown to induce biophoton emissions from biological cells. As cellular emissions of UVA biophotons following beta radiation lead to BEs, the involvement of cellular emissions of the same type of UVA biophotons in gamma radiation-induced BEs is highly likely.
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Today, patients undergoing dialysis are at low risk for aluminum-induced dementia. Workers are unlikely to experience cadmium-induced emphysema and the public's exposure to lead is an order of magnitude lower than in 1970. The research field of in vivo elemental analysis has played a role in these occupational and environmental health improvements by allowing the effects of people's chronic exposure to elements to be studied using non-invasive, painless, and relatively low-cost technology. From the early 1960s to the present day, researchers have developed radiation-based systems to measure the elemental content of organs at risk or storage organs. This reduces the need for (sometimes painful) biopsy and the risk of infection. Research and development has been undertaken on forty-nine in vivo measurement system designs. Twenty-nine different in vivo elemental analysis systems, measuring 22 different elements, have been successfully taken from design and testing through to human measurement. The majority of these systems employ either neutron activation analysis or x-ray fluorescence analysis as the basis of the measurement. In this review, we discuss eight of the successful systems, explaining the rationale behind their development, the methodology, the health data that has resulted from application of these tools, and provide our opinion on potential future technical developments of these systems. We close by discussing four technologies that may lead to new directions and advances in the whole field.
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Técnicas de Química Analítica/instrumentación , Metales Pesados/análisis , HumanosRESUMEN
OBJECTIVE: To report additional gadolinium bone and urine data that can contribute to gaps in knowledge with respect to gadolinium uptake and retention in the body. APPROACH: In vivo measurements of gadolinium retention in the tibia bone were performed on individuals self-identified as exhibiting symptoms of gadolinium toxicity as a result of receiving GBCA, as well as on control individuals. Gadolinium urine measurements for controls, symptomatic exposed, and non-symptomatic exposed were conducted through Mayo Medical Laboratories. MAIN RESULTS: Gadolinium bone concentration in the exposed group is significantly higher than the control group (p < 0.01), with a significant difference between symptomatic and non-symptomatic (p < 0.01), using a one-tailed t test on variance-weighted means. Gadolinium urine levels in both control subjects and non-symptomatic exposed subjects are significantly lower than symptomatic exposed subjects (p ≤ 0.05). A linear regression analysis for gadolinium urine levels and GBCA dose resulted in a positive linear relationship (R 2 = 0.91, p < 0.01). Gadolinium levels in urine and gadolinium concentration in bone were found to have a non-significant relationship (R 2 = 0.11, p = 0.3). SIGNIFICANCE: Significant differences in gadolinium levels in bone and urine are observed between individuals experiencing symptoms of gadolinium toxicity and for those who are not exhibiting symptoms. No correlation was observed between gadolinium in bone and gadolinium excreted in urine, suggesting that the retention of gadolinium in the body is complicated, involving multiple long-term storage sites.
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Huesos/metabolismo , Medios de Contraste/toxicidad , Gadolinio/toxicidad , Gadolinio/orina , Voluntarios Sanos , Densidad Ósea/efectos de los fármacos , Huesos/efectos de los fármacos , Huesos/fisiología , Medios de Contraste/metabolismo , Relación Dosis-Respuesta a Droga , Gadolinio/metabolismo , Humanos , Modelos LinealesRESUMEN
OBJECTIVE: This article briefly reviews the main measurement techniques for the non-invasive detection of residual gadolinium (Gd) in those exposed to gadolinium-based contrast agents (GBCAs). Approach and Main results: The current status of in vivo Gd measurement is discussed and is put into the context of concerns within the radiology community. The main techniques are based on applied atomic/nuclear medicine utilizing the characteristic atomic and nuclear spectroscopic signature of Gd. The main emission energies are in the 40-200 keV region and require spectroscopic detectors with good energy resolution. The two main techniques, prompt gamma neutron activation analysis and x-ray fluorescence, provide adequate detection limits for in vivo measurement, whilst delivering a low effective radiation dose on the order of a few µSv. SIGNIFICANCE: Gadolinium is being detected in measureable quantities in people with healthy renal function who have received FDA approved GBCAs. The applied atomic/nuclear medicine techniques discussed in this review will be useful in determining the significance of this retention, and will help on advising future administration protocols.
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Gadolinio/metabolismo , Física/métodos , Radiobiología/métodos , HumanosRESUMEN
Radiation-induced biophotons are an electromagnetic form of bystander signalling. In human cells, biophoton signalling is capable of eliciting effects in non-irradiated bystander cells. However, the mechanisms by which the biophotons interact and act upon the bystander cells are not clearly understood. Mitochondrial energy production and ROS are known to be involved but the precise interactions are not known. To address this question, we have investigated the effect of biophoton emission upon the function of the complexes of oxidative phosphorylation (OXPHOS). The exposure of bystander HCT116 p53 +/+ cells to biophoton signals emitted from ß-irradiated HCT116 p53 +/+ cells induced significant modifications in the activity of Complex I (NADH dehydrogenase or NADH:ubiquinone oxidoreductase) such that the activity was severely diminished compared to non-irradiated controls. The enzymatic assay showed that the efficiency of NADH oxidation to NAD+ was severely compromised. It is suspected that this impairment may be linked to the photoabsorption of biophotons in the blue wavelength range (492-455â¯nm). The photobiomodulation to Complex I was suspected to contribute greatly to the inefficiency of ATP synthase function since it resulted in a lower quantity of H+ ions to be available for use in the process of chemiosmosis. Other reactions of the ETC were not significantly impacted. Overall, these results provide evidence for a link between biophoton emission and biomodulation of the mitochondrial ATP synthesis process. However, there are many aspects of biological modulation by radiation-induced biophotons which will require further elucidation.
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Mitocondrias , Fosforilación Oxidativa , Ondas de Radio , Transducción de Señal , Células HCT116 , Humanos , Oxidación-Reducción , Traumatismos por Radiación , Ondas de Radio/efectos adversos , Transducción de Señal/efectos de la radiaciónRESUMEN
Purpose To perform a preliminary evaluation of a noninvasive measurement system to assess gadolinium deposition in bone and to investigate the relationship between the administration of gadolinium-based contrast agents (GBCAs) and gadolinium retention in bone. Materials and Methods In vivo measurement of gadolinium retention in tibia bones was performed in 11 exposed subjects who previously received GBCAs (six exposed subjects were from a study performed 5 years previously involving injection of GBCAs in healthy volunteers; five exposed subjects had self-reported GBCA exposure), and 11 sex- and age-matched control subjects without a history of GBCA exposure. Each subject underwent one measurement of gadolinium retention in the tibia with x-ray fluorescence in a laboratory at McMaster University. A one-tailed t test was performed to compare gadolinium concentration in the exposed group with that in the control group. The relationship between the dose of GBCA administered and the gadolinium concentration measured in bone was analyzed with linear regression. Results Gadolinium concentration in bone was significantly higher in exposed subjects (mean, 1.19 µg Gd/g bone mineral ± 0.73 [standard deviation]) than in control subjects (mean, -1.06 µg Gd/g bone mineral ± 0.71) (P = .01). There was also a positive correlation between the dose of GBCA administered and the gadolinium concentration measured in bone (R2 = 0.41); gadolinium concentration in bone increased by 0.39 µg Gd/g bone mineral ± 0.14 per 1 mL of GBCA administered. Gadolinium was detected in bone up to 5 years after one GBCA administration. Conclusion This x-ray fluorescence system is capable of measuring gadolinium deposition in bone noninvasively in vivo. Gadolinium can be retained in bone after one dose of GBCA in healthy subjects. © RSNA, 2017 Online supplemental material is available for this article.
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Medios de Contraste/farmacocinética , Aumento de la Imagen/métodos , Imagen por Resonancia Magnética/métodos , Compuestos Organometálicos/farmacocinética , Tibia/diagnóstico por imagen , Canadá , Estudios de Factibilidad , Humanos , Fantasmas de Imagen , Proyectos Piloto , Tibia/efectos de los fármacosRESUMEN
OBJECTIVE: The objective of our study was to explore a possible molecular mechanism by which ultraviolet (UV) biophotons could elicit bystander responses in reporter cells and resolve the problem of seemingly mutually exclusive mechanisms of a physical UV signal & a soluble factor-mediated bystander signal. METHODS: The human colon carcinoma cell line, HCT116 p53 +/+, was directly irradiated with 0.5 Gy tritium beta particles to induce ultraviolet biophoton emission. Bystander cells were not directly irradiated but were exposed to the emitted UV biophotons. Medium was subsequently harvested from UV-exposed bystander cells. The exosomes extracted from this medium were incubated with reporter cell populations. These reporter cells were then assayed for clonogenic survival and mitochondrial membrane potential with and without prior treatment of the exosomes with RNase. RESULTS: Clonogenic cell survival was significantly reduced in reporter cells incubated with exosomes extracted from cells exposed to secondarily-emitted UV. These exosomes also induced significant mitochondrial membrane depolarization in receiving reporter cells. Conversely, exosomes extracted from non-UV-exposed cells did not produce bystander effects in reporter cells. The treatment of exosomes with RNase prior to their incubation with reporter cells effectively abolished bystander effects in reporter cells and this suggests a role for RNA in mediating the bystander response elicited by UV biophotons and their produced exosomes. CONCLUSION: This study supports a role for exosomes released from UV biophoton-exposed bystander cells in eliciting bystander responses and also indicates a reconciliation between the UV-mediated bystander effect and the bystander effect which has been suggested in the literature to be mediated by soluble factors.
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Efecto Espectador/efectos de la radiación , Supervivencia Celular/efectos de la radiación , Exosomas/fisiología , Potencial de la Membrana Mitocondrial/efectos de la radiación , Fotones , Rayos Ultravioleta , Exosomas/efectos de la radiación , Células HCT116 , HumanosRESUMEN
The practice of investigating pathological abnormalities in the breasts of females who are asymptomatic is primarily employed using X-ray mammography. The importance of breast screening is reflected in the mortality-based benefits observed among females who are found to possess invasive breast carcinoma prior to the manifestation of clinical symptoms. It is estimated that population-based screening constitutes a 17% reduction in the breast cancer mortality rate among females affected by invasive breast carcinoma. In spite of the significant utility that screening confers in those affected by invasive cancer, limitations associated with screening manifest as potential harms affecting individuals who are free of invasive disease. Disease-free and benign tumour-bearing individuals who are subjected to diagnostic work-up following a screening examination constitute a population of cases referred to as false positives (FPs). This article discusses factors contributing to the FP rate in mammography and extends the discussion to an assessment of the consequences associated with FP reporting. We conclude that the mammography FP rate in North America is in excess based upon the observation of overtreatment of in situ lesions and the disproportionate distribution of detriment and benefit among the population of individuals recalled for diagnostic work-up subsequent to screening. To address the excessive incidence of FPs in mammography, we investigate solutions that may be employed to remediate the current status of the FP rate. Subsequently, it can be suggested that improvements in the breast-screening protocol, medical litigation risk, image interpretation software and the implementation of image acquisition modalities that overcome superimposition effects are promising solutions.
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Neoplasias de la Mama/diagnóstico por imagen , Mamografía/normas , Neoplasias de la Mama/epidemiología , Neoplasias de la Mama/cirugía , Canadá/epidemiología , Detección Precoz del Cáncer , Reacciones Falso Positivas , Femenino , Política de Salud , Humanos , Incidencia , Pautas de la Práctica en Medicina , Prevalencia , Radiólogos/normas , Medición de Riesgo , Estados Unidos/epidemiologíaRESUMEN
The Canadian population is currently subject to low, chronic lead exposure and an understanding of its effects is of great significance to the population's health. Such low exposure is difficult to measure directly; approximation by physiologically based modeling may provide a preferable approach to population analysis. The O'Flaherty model of lead kinetics is based on an age-dependent approach to human growth and development and devotes special attention to bone turnover rates. Because lead is a bone-seeking element, the model was deemed ideal for such an analysis. Sample from 263 individuals of various ages from the Greater Toronto Area were selected to evaluate the applicability of the current version of the O'Flaherty model to populations with low lead exposure. For each individual, the input value of lead exposure was calibrated to match the output value of cortical bone lead to the individual's measured tibia lead concentration; the outputs for trabecular bone, blood, and plasma lead concentrations obtained from these calibrations were then compared with the subjects' measured calcaneus, blood, and serum lead concentrations, respectively. This indicated a need for revision of the model parameters; those for lead binding in blood and lead clearance from blood to bone were adjusted and new outputs were obtained in the same fashion as before. Model predictions of trabecular lead concentration did not agree with measurements in the calcaneus. The outputs for blood and plasma lead concentrations were highly scattered and, on an individual level, inconsistent with corresponding measurements; however, the general trends of the outputs matched those of the measurements reasonably well, which indicates that the revised blood lead binding and lead clearance parameters may be useful in future studies. Overall, the analysis showed that with the revisions to the model discussed here, the model should be a useful tool in the analysis of human lead kinetics and body burden in populations characterized by low, chronic exposure to lead from the general environment.
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Exposición a Riesgos Ambientales/estadística & datos numéricos , Plomo/metabolismo , Modelos Estadísticos , Tibia/metabolismo , Adulto , Carga Corporal (Radioterapia) , Canadá , Femenino , Humanos , Cinética , Masculino , Persona de Mediana Edad , Proyectos PilotoRESUMEN
Previous research has shown that beta radiation can induce ultraviolet (UV) photon emission in human keratinocyte cells. Spectral analysis using a filter-based method in the ultraviolet range demonstrated that the strongest externally measureable photon emission was induced by beta radiation in the UVA range. In the current study, the potential biological implications of this UV photon emission from beta-irradiated cells were investigated. HaCaT human keratinocyte cells were irradiated with tritium ((3)H) and the photon emission induced was concurrently measured at the strongest externally measurable wavelength, 340 ± 5 nm, using a combination filter-photomultiplier tube system. Unirradiated reporter HaCaT cell cultures were also placed directly above (3)H-irradiated cells so that they would receive the induced secondary photons emitted from beta-irradiated cells, and the clonogenic survival in reporter cells was then assessed. Maximum photon emission (1207.04 ± 107.65 counts per second) was observed during irradiation of 2,000 cells/cm(2) with (3)H and the maximum reporter cell death (23.2 ± 0.9% reduction in survival) was observed under the same conditions. The measured photon emission from beta-irradiated cells and reporter cell death were strongly correlated (r = 0.977, P < 0.01). Placement of a polyethylene terephthalate filter, designed to eliminate >90% of UV wavelengths below 390 nm, between the directly irradiated and reporter cell layers was effective in nearly abolishing both 340 nm photon detection and reporter cell death in treated groups. Concurrent treatment of reporter cells with lomefloxacin during exposure to the secondary photons resulted in significantly increased cell killing, indicating a potential synergistic effect, while melanin treatment resulted in decreased reporter cell killing regardless of irradiation. These results suggest that secondary photons in the UV spectral range induced by beta irradiation play a role in inducing a response in neighboring non-beta-irradiated reporter cells.
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Supervivencia Celular/efectos de la radiación , Queratinocitos/efectos de la radiación , Rayos Ultravioleta , Apoptosis/efectos de la radiación , Partículas beta , Efecto Espectador/efectos de la radiación , Técnicas de Cultivo de Célula , Humanos , Fotones , TritioRESUMEN
A (109)Cd K X-ray fluorescence (KXRF) measurement system consisting of four detectors in clover-leaf geometry is a non-invasive, low-radiation-dose method of measuring bone lead concentration. Its high precision in estimating the bone lead content makes it a promising tool for the determination of the low levels of lead currently found in the general population. After developing the clover-leaf geometry system, the system was used for the first time in a major survey in 2008 to measure the lead levels of 497 smelter employees (an occupationally exposed group with high lead levels). Since the delivered effective dose of the bone lead system in clover-leaf geometry is small (on the order of nSv), the technique can be used to measure the bone lead of sensitive populations such as the elderly and children. This detector system was used from 2009 to 2011, in a pilot study that measured the bone lead concentration of 263 environmentally exposed individuals (termed the EG group) residing in Toronto, Ontario, Canada. In this paper, the factors that influence uncertainties in lead content in tibia (cortical bone) and calcaneus (trabecular bone) are discussed based on gender, age, and body mass index (BMI) by using analysis of variance (ANOVA) and multiple linear regression models. Results from the two study groups (the EG group versus the occupationally exposed smelter employees) are compared where appropriate (i.e. for males older than 20). Results from univariate analyses showed that females have higher tibia uncertainty compared to males. We observed significant differences for both calcaneus and tibia uncertainty measures (p < 0.0005) among different age groups, where the uncertainties were highest in the lowest age group (<11 years). Lastly, and perhaps most significantly, we found that the product of source activity and measurement time influenced the precision of measurements greatly, and that this factor alone could account for the higher uncertainties observed for the male cohort of the EG group versus the smelter employees.
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Huesos/química , Exposición a Riesgos Ambientales/análisis , Contaminantes Ambientales/análisis , Plomo/análisis , Adolescente , Adulto , Anciano , Análisis de Varianza , Canadá , Niño , Femenino , Humanos , Masculino , Persona de Mediana Edad , Espectrometría por Rayos XRESUMEN
The overwhelming proportion of the mass of lead (Pb) is stored in bone and the residence time of Pb in bone is much longer than that in other tissues. Hence, in a metabolic model that we used to solve the differential equations governing the transfer of lead between body compartments, three main compartments are involved: blood (as a transfer compartment), cortical bone (tibia), and trabecular bone (calcaneus). There is a bidirectional connection between blood and the other two compartments. A grid search chi-squared minimization method was used to estimate the initial values of lead transfer rate values from tibia (λTB) and calcaneus (λCB) to blood of 209 smelter employees whose bone lead measurements are available from 1994, 1999, and 2008, and their blood lead level from 1967 onwards (depending on exposure history from once per month to once per year), and then the initial values of kinematic parameters were used to develop multivariate models in order to express λTB and λCB as a function of employment time, age, body lead contents and their interaction. We observed a significant decrease in the transfer rate of lead from bone to blood with increasing body lead contents. The model was tested by calculating the bone lead concentration in 1999 and 2008, and by comparing those values with the measured ones. A good agreement was found between the calculated and measured tibia/calcaneus lead values. Also, we found that the transfer rate of lead from tibia to blood can be expressed solely as a function of cumulative blood lead index.
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Contaminantes Ocupacionales del Aire/metabolismo , Huesos/metabolismo , Plomo/metabolismo , Metalurgia , Exposición Profesional/estadística & datos numéricos , Contaminantes Ocupacionales del Aire/análisis , Huesos/química , Femenino , Humanos , Plomo/análisis , Masculino , Modelos BiológicosRESUMEN
In this study, we aimed to establish the emission of UV photons when HPV-G cells and associated materials (such as the cell substrate and cell growth media) are exposed to low LET radiation. The potential role of UV photons in the secondary triggering of biological processes led us to hypothesize that the emission and absorption of photons at this wavelength explain some radiation induced "bystander effects" that have previously been thought to be chemically mediated. Cells were plated in Petri-dishes of two different sizes, having different thicknesses of polystyrene (PS) substrate, and were exposed to ß-radiation from (90)Y produced by the McMaster Nuclear Reactor. UV measurements were performed using a single photon counting system employing an interference-type filter for selection of a narrow wavelength range, 340±5 nm, of photons. Exposure of the cell substrates (which were made of polystyrene) determined that UV photons were being emitted as a consequence of ß particle irradiation of the Petri-dishes. For a tightly collimated ß-particle beam exposure, we observed 167 photons in the detector per unit µCi in the shielded source for a 1.76 mm thick substrate and 158 photons/µCi for a 0.878 mm thick substrate. A unit µCi source activity was equivalent to an exposure to the substrate of 18 ß-particles/cm(2) in this case. The presence of cells and medium in a Petri-dish was found to significantly increase (up to a maximum of 250%) the measured number of photons in a narrow band of wavelengths of 340±5 nm (i.e. UVA) as compared to the signal from an empty control Petri-dish. When coloured growth medium was added to the cells, it reduced the measured count rate, while the addition of transparent medium in equal volume increased the count rate, compared to cells alone. We attribute this to the fact that emission, scattering and absorption of light by cells and media are all variables in the experiment. Under collimated irradiation conditions, it was observed that increasing cell density in medium of fixed volume resulted in a decrease in the observed light output. This followed a roughly exponential decline. We suggest that this may be due to increased scattering at the cell boundary and absorption of the UV in the cells. We conclude that we have measured UVA emitted by cells, cell medium and cell substrates as a consequence of their irradiation by low LET ß-particle radiation. We suggest that these secondary UV photons could lead to effects in non-targetted cells. Some effects that had previously been attributed to a chemically mediated "bystander effect" may in fact be due to secondary UV emission. Some radiation bystander effect studies may require re-interpretation as this phenomenon of UV emission is further investigated.
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Arsenic (As) distribution in nail clippings from three healthy human subjects was investigated using the microbeam experimental setup of the hard x-ray micro-analysis (HXMA) beamline from the Canadian Light Source (CLS) synchrotron. A pair of toenail and fingernail clippings was collected from each of three subjects (one contributed two fingernail clippings). The fingernail and toenail clippings were embedded in polyester resin and cut in cross-sectional slices with an average thickness of 270 µm. Nine nail clipping cross sections were analyzed from the three subjects. The same method was used to produce five cross sections of nail phantom clippings with concentrations of As ranging from 0 to 20 µg g−1, in increments of 5 µg g−1. These samples were used to produce a calibration line for the As Kα peak. The energy of the x-ray beam was set at 13 keV for optimal excitation of As and the beam size was 28 × 10 µm2. Each sample was analyzed using a point-by-point scanning technique in a 45° beam-sample and 90° beam-detector geometry. The dwelling time was set at 30 s for the human nail clippings and 20 s for the nail phantom clippings, using a step size of 50 µm in both the horizontal and vertical directions for all samples. As concentration for each point was calculated based on the calibration line parameters and the fitted amplitude of the observed As Kα peak. As concentration maps were produced for each nail clipping cross section. The maps show that small regions (<0.1 mm2) with higher As concentrations (>1 µg g−1) are located predominantly in the ventral and dorsal layers of the nail. The results are in agreement with findings reported in a recent study and can be linked to nail histology and keratin structure.
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Arsénico/metabolismo , Uñas/metabolismo , Espectrometría por Rayos X/instrumentación , Sincrotrones , HumanosRESUMEN
In vivo monitoring of trace and biometals in skin is normally quantified using phantoms that assume a constant elemental distribution within the skin. Layered calibration skin phantoms could potentially improve the reliability of in vivo calibration skin phantoms by better representing the actual in vivo distribution. This work investigates the micro-distribution of iron, calcium and zinc in prepared human skin samples taken from a number of locations on the body. Slices (orientation running from the skin surface into the dermis) were extracted from 18 formalin-fixed necropsy samples and scanned using the micro-XRF setup at the VESPERS beamline (Canadian Light Source). Elemental surface maps were produced using a 6×6 µm(2) beam in steps of 10 µm. Microscope images of histology slides were obtained for comparison. Statistically significant differences (p<0.01) were noted between the epidermal and dermal layers of skin for the elements examined (Ca, Fe and Zn), demonstrating the ability to clearly distinguish elemental content in each layer. Iron was consistently noted at the epidermal/dermal boundary. These results would indicate that when using phantoms to quantify elemental levels measured in the skin, note should be taken of the appropriate depth distribution.
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Calcio/análisis , Hierro/análisis , Piel/química , Espectrometría por Rayos X/instrumentación , Sincrotrones/instrumentación , Zinc/análisis , Animales , Diseño de Equipo , Análisis de Falla de Equipo , MiniaturizaciónRESUMEN
494 smelter employees from New Brunswick participated in a bone lead survey conducted by McMaster University in 2008, using the four element "clover-leaf" geometry germanium detector system. The employees were measured at two different bone sites, tibia and calcaneus, each measurement lasting 30 minutes. Scattered photons, including Pb X-rays, were collected by the germanium detectors located behind the ¹°9Cd source. A strong positive correlation was observed between tibia and calcaneus lead concentrations. Having been provided with blood lead levels, a cumulative blood lead index (CBLI) was generated. The employees were classified into four groups based on their date of hire, and their CBLI levels were compared to their tibia and calcaneus lead concentrations in the different groups. The slopes of bone Pb versus CBLI varied amongst groups, with those hired earliest showing the steepest slopes. This could be taken to imply a non-linearity in the uptake of Pb by bone from blood. In this paper, the association of the bone lead concentrations versus CBLI has been expressed by a polynomial function for the whole group of employees.
Asunto(s)
Huesos/química , Sustancias Peligrosas/análisis , Plomo/análisis , Exposición Profesional/análisis , Huesos/metabolismo , Calcáneo/química , Calcáneo/metabolismo , Sustancias Peligrosas/sangre , Humanos , Plomo/sangre , Metalurgia , Nuevo Brunswick , Exposición Profesional/estadística & datos numéricos , Tibia/química , Tibia/metabolismoRESUMEN
Humans can be exposed to fluorine (F) through their diet, occupation, environment and oral dental care products. Fluorine, at proper dosages, is believed to have positive effects by reducing the incidence of dental caries, but fluorine toxicity can occur when people are exposed to excessive quantities of fluorine. In this paper we present the results of a small pilot in vivo study on 33 participants living in Southwestern Ontario, Canada. The mean age of participants was 45 ± 18 years with a range of 20-87 years. The observed calcium normalized hand-bone-fluorine concentrations in this small pilot study ranged from 1.1 to 8.8 mg F/g Ca. Every person measured in this study had levels of fluorine in bone above the detection limit of the system. The average fluorine concentration in bone was found to be 3.5 ± 0.4 mg F/g Ca. No difference was observed in average concentration for men and women. In addition, a significant correlation (r(2) = 0.55, p < 0.001) was observed between hand-bone-fluorine content and age. The amount of fluorine was found to increase at a rate of 0.084 ± 0.014 mg F/g Ca per year. There was no significant difference observed in this small group of subjects between the accumulation rates in men and women. To the best of our knowledge, this is the first time data from in vivo measurement of fluorine content in humans by neutron activation analysis have been presented. The data determined by this technique were found to be consistent with results from ex vivo studies from other countries. We suggest that the data demonstrate that this low risk non-invasive diagnostic technique will permit the routine assessment of bone-fluorine content with potential application in the study of clinical bone-related diseases. This small study demonstrated that people in Southern Ontario are exposed to fluoride in measureable quantities, and that fluoride can be seen to accumulate in bone with age. However, all volunteers were found to have levels below those expected with clinical fluorosis, and only one older subject was found to have levels comparable with preclinical exposure.
Asunto(s)
Flúor/análisis , Huesos de la Mano/química , Análisis de Activación de Neutrones/métodos , Adulto , Anciano , Anciano de 80 o más Años , Calcio/análisis , Femenino , Humanos , Masculino , Persona de Mediana Edad , Ontario/epidemiología , Proyectos Piloto , Adulto JovenRESUMEN
PURPOSE: Neutron irradiations at the McMaster Tandetron Accelerator were performed to study direct and bystander effects of neutrons in a live organism. METHODS: The neutrons were produced through (7)Li(p,n)(7)Be reaction. Although the gamma contamination of the neutron beam cannot be completely eliminated, it was designed to be as low as possible and remain below a threshold already established for bystander effects. Microdosimetric methods using a tissue-equivalent proportional counter have been used to measure the neutron and gamma doses for the cell irradiation. Previous data for a cell line exposed in vitro suggested that neutrons did not produce bystander effects at doses below 300 mGy. The current experiments sought to confirm this using a live whole organism (zebrafish) where tissue samples harvested 2 h after exposure were examined for direct evidence of apoptosis and tested for secretion of bystander factors using an established bioassay. Fish were either exposed directly to the beam or were allowed to swim with or in water previously occupied by irradiated fish. RESULTS: Using the zebrafish model it was found that there was significant direct cell death seen both by apoptosis scores and clonogenic assay when the neutron dose was approximately 100 mGy. An equivalent dose of gamma rays produced a more toxic effect. It was further found that neutrons did not induce a bystander effect in fish receiving signals from irradiated fish. CONCLUSION: The results confirm in vitro experiments which suggest neutrons do not induce bystander signaling. In fact they may suppress gamma induced signaling suggesting a possible intriguing new and as yet unclear mechanism.