PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Alpha Particles”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 199 records · Page 11Linked to original sources
PubMed1994

Radioimmunotherapy of neoplastic meningitis in rats using an alpha-particle-emitting immunoconjugate.

Because of their short range and high linear energy transfer, alpha-particles may be particularly effective in the treatment of neoplastic meningitis. Monoclonal antibody 81C6 was labeled with alpha-particle-emitting 211At using N-succinimidyl3-[211At]astatobenzoate, and the efficacy and toxicity of this immunoconjugate were evaluated in an athymic rat model. Animals were given injections via a chronic indwelling catheter with 5 x 10(5) TE-671 human rhabdomyosarcoma cells and treated 8 days later with single intrathecal doses of either saline or 4-18 microCi of 211At-labeled specific 81C6 antibody or isotype-matched control 211At-labeled 45.6 antibody. In the first experiment, 4, 7, and 13 microCi 211At-labeled 81C6 produced statistically significant (P = 0.004-0.02) increases in median survival of 33, 29, and 51%, respectively, as compared with saline. Two of 10 animals receiving the 13-microCi dose lived for 6 months before being killed for histological analysis. In the second experiment, 12 microCi of 211At-labeled 45.6 did not increase median survival significantly relative to saline control, while 12 microCi of 211At-labeled 81C6 increased median survival by 113% (P < 0.005) and resulted in 33% apparent cures. Five of 10 animals receiving 18 microCi of 211At-labeled 81C6 survived until they were killed at 295 days. An additional study was performed in animals given intrathecal injections of 5 x 10(6) TE-671 cells and given a single dose of 18 microCi of 211At-labeled 81C6 or 211At-labeled 45.6. At this higher cell number, significantly prolonged survival was still seen for specific antibody as compared with saline (P < 0.001) and control antibody (P < 0.05). These results suggest that treatment with 211At-labeled monoclonal antibodies may be a valuable approach for neoplastic meningitis.

Alpha Particles↗
PubMed2000

Alpha-particle emission probabilities in the decay of 238U

238U decays by alpha-particle emission to 234Th. No direct measurements of alpha-particle emission probabilities (Palpha) of this nuclide have been reported since 1961, and recommended values for Palpha have remained unchanged for years, until recent evaluations suggested new values. This work presents the results of new measurements made with Si detectors and sources of natural uranium. The results obtained for the analysis of twenty spectra are: Palpha0 = 0.7754+/-0.0050, Palpha50 = 0.2233+/-0.0050 and Palpha163 = 0.0013+/-0.0003.

Journal Article↗
PubMed1999

Delayed lethality, apoptosis and micronucleus formation in human fibroblasts irradiated with X-rays or alpha-particles.

PURPOSE: To determine the yields of cell lethality and micronucleus formation measured immediately after irradiation or at delayed times in primary human fibroblasts exposed to X-rays or alpha-particles. MATERIALS AND METHODS: Primary human AG01522B fibroblasts were irradiated with X-rays or alpha-particles and subcultured for up to 30 days post-irradiation. Clonogenic survival and the yield of micronucleated cells in newly divided daughter cells were scored at various times. RESULTS: After the initial dose-dependent acute response for both endpoints there was conclusive evidence for the delayed production of de novo genomic instability in the surviving progeny. As well as the production of micronucleated cells, evidence was observed for the production of fibroblasts undergoing apoptosis as measured using conventional morphological scoring, 3'OH end-labelling of DNA fragmentation and externalization of phosphatidyl serine residues to the cell surface. For both radiations, the dose and time dependencies of the apoptotic response were similar to those for micronucleation and loss of clonogenicity. CONCLUSIONS: Genomic instability in the progeny of irradiated primary human fibroblasts was observed in the form of micronucleation, apoptosis and delayed reproductive death. An increased effectiveness of alpha-particles versus X-rays was observed for both initial and delayed responses, including apoptosis.

Alpha Particles↗
PubMed2001

A new method for evaluating radon and thoron alpha-activities per unit volume inside and outside various natural material samples by calculating SSNTD detection efficiencies for the emitted alpha-particles and measuring the resulting track densities.

A Monte Carlo computer code for determining detection efficiencies of the CR-39 and LR-115 II solid-state nuclear track detectors (SSNTD) for alpha-particles emitted by the uranium and thorium series inside different natural material samples was developed. The influence of the alpha-particle initial energy on the SSNTD detection efficiencies was investigated. Radon (222Rn) and thoron (220Rn) alpha-activities per unit volume were evaluated inside and outside the natural material samples by exploiting data obtained for the detection efficiencies of the SSNTD utilized for the emitted alpha-particles, and measuring the resulting track densities. Results obtained were compared to those obtained by other methods. Radon emanation coefficients have been determined for some of the considered material samples.

Algorithms↗
PubMed1990

Energy deposition by protons and alpha particles in spherical sites of nanometer to micrometer diameter.

Monte Carlo stimulated proton- and alpha-particle tracks in water vapor were used to develop an analytical function for calculating number distributions of ionizations induced in spherical sites. For charged particles crossing the site, Fermi-like functions were used to approximate the ionization distributions. Ionization event distributions due to particles passing outside the site were approximated with an exponentially decreasing function. The function parameters were calculated for protons and alpha particles in the energy range 0.3-5.0 MeV/amu and for site diameters of 1 to 1000 nm. The quality of fit obtained is very good for the particles, energy range and site diameters considered.

Alpha Particles↗
PubMed1999

238Pu alpha-particle-induced C3H10T1/2 transformants are less tumorigenic than the X-ray-induced equivalent.

Transformation is a complex multistage process in vitro by which benign cells gradually acquire characteristics of tumour cells. Transformed C3H10T1/2 cells appear in vitro as multilayers of cells termed foci. A variety of transformed phenotypes are observed in vitro and in this study samples of these phenotypes were developed as cell lines and assessed for their ability to induce tumours in C3H mice. It was found that, while a high proportion of X-ray-induced transformants were tumorigenic, most of the alpha-particle-induced transformants were non-tumorigenic. Although tumours produced by the X-ray-induced transformants appeared earlier, they grew at similar rates to the alpha-particle-induced equivalent. Foci were classified as fully or partially tumorigenic depending on whether the foci produced at least one tumour in the mice injected (partially tumorigenic) or produced tumours in all mice injected (fully tumorigenic). It was found that tumours from the partially tumorigenic foci grew slower or appeared later than those of the fully tumorigenic foci. It is hypothesized that the apparent low tumorigenicity of positively transformed alpha-particle-induced foci is due to an increase in genomic instability of progeny focus cells compared with X-ray-induced foci leading to a larger non-viable population of cells in the alpha-particle-induced foci.

Alpha Particles↗
PubMed2002

Decreased efficiency of gamma-ray-induced DNA double-strand break rejoining in malignant transformants of human bronchial epithelial cells generated by alpha-particle exposure.

PURPOSE: To investigate the cytogenetic changes and DNA double-strand break (DSB) rejoining of transformed cell lines generated from human bronchial epithelial cells by alpha-particle exposure. MATERIALS AND METHODS: Transformed cell lines were derived from the HPV 18-immortalized human bronchial epithelial cell line BEP2D generated by 1.5 Gy of alpha-particles emitted by a 238Pu source. Two cell lines, BERP35T1 and BERP35T4, were investigated. Karyotypes were analyzed by trypsin/Giemsa banding. Cell survival was estimated by colony assay. PFGE was used to detect the DNA DSB. mRNA expression was analyzed by RT-PCR. RESULTS: Abnormal chromosomes 2 and 12 with elongated long arm and deletions of chromosomes 2, 12, 13 and 17 were observed in the transformed cell lines. BERP35T4 showed a much higher proportion of polyploid cells (40.5%) compared with parental BEP2D cells and the BERP35TI cell line (5%). BERP35T1 and BERP35T4 showed a markedly lower capacity for rejoining of gamma-ray-induced DNA DSB and increased radiosensitivity compared with parental BEP2D cells. The analysis of mRNA levels revealed a 2.5- to 6.5-fold down-regulated expression of the DNA repair genes XRCC-2, XRCC-3 and Ku80 in BERP35T1 and BERP35T4 cells. CONCLUSION: The karyotypic changes of chromosomes 2, 12, 13 and 17 and the deficiency of DSB rejoining could be related to the malignant transformation processing of BEP2D cells initiated by alpha-particle exposure.

Alpha Particles↗
PubMed2004

Simulation of alpha particle spectra from aerosol samples.

A Monte Carlo code is developed for simulating energy spectra of alpha particles from aerosol samples. Geometrical detection efficiency and energy loss of the alpha particles in the source itself and in the material between the source and detector are simulated. Different characteristics of the aerosol particles and medium material are taken into account in the computation. An excellent agreement with earlier results and measurements is found. The code can be applied for example in designing optimal aerosol sampling methods in direct alpha spectrometry.

Aerosols↗
PubMed1994

Effects of in vitro alpha-particle irradiation on osteogenic bone marrow cultures.

Murine bone marrow contains osteogenic precursor cells that undergo differentiation during in vitro cultivation. In vitro these cells are potential target cells for alpha-irradiation-induced bone tumour formation. Under defined tissue culture conditions these differentiating cells were directly exposed to alpha-particle irradiation from the radon daughter 210Po. Po deposits in soft tissue and it was shown to be associated with marrow cells and with the extracellular marrow tissue formed in vitro. These differentiating marrow cultures showed high sensitivity to alpha-irradiation. Cell death was observed at 210Po concentrations in tissue culture medium (TCM) > 7 Bq 210Po/ml. At lower concentrations (between 1 and 5 Bq 210Po per ml TCM) proliferation was enhanced as measured by uptake of 3H-thymidine, also differentiation was stimulated as measured by alkaline phosphatase activity and incorporation of 3H-proline in newly synthesized collagen. At several times of culture, the association of 210Po with the extracellular matrix and cells was measured. These retention data enabled us to calculate the daily alpha-particle fluence. At 1 Bq 210Po present per ml tissue culture, a daily alpha-particle fluence as low as 3-6 per 1000 cells seemed very efficient in changing the expression of osteogenic differentiation of marrow cells.

3T3 Cells↗
PubMed2004

Engineered liposomes for potential alpha-particle therapy of metastatic cancer.

UNLABELLED: Disseminated, metastatic cancer is frequently incurable. Targeted alpha-particle emitters hold great promise as therapeutic agents for disseminated disease. (225)Ac is a radionuclide generator that has a 10-d half-life and results in alpha-emitting daughter elements ((221)Fr, (217)At, (213)Bi) that lead to the emission of a total of 4 alpha-particles. The aim of this study was to develop approaches for stable and controlled targeting of (225)Ac to sites of disseminated tumor metastases. Liposomes with encapsulated (225)Ac were developed to retain the potentially toxic daughters at the tumor site. METHODS: (225)Ac was passively entrapped in liposomes. To experimentally test the retention of actinium and its daughters by the liposomes, the gamma-emissions of (213)Bi were measured in liposome fractions, which were separated from the parent liposome population and the free radionuclides, at different times. Under equilibrium conditions the decay rate of (213)Bi was used to determine the concentration of (225)Ac. Measurements of the kinetics of (213)Bi activity were performed to estimate the entrapment of (213)Bi, the last alpha-emitting daughter in the decay chain. RESULTS: Stable pegylated phosphatidylcholine-cholesterol liposomes of different sizes and charge were prepared. Multiple (more than 2) (225)Ac atoms were successfully entrapped per liposome. (225)Ac retention by zwitterionic liposomes was more than 88% over 30 d. Retention by cationic liposomes was lower. A theoretical calculation showed that for satisfactory (213)Bi retention (>50%), liposomes of relatively large sizes (>650 nm in diameter) are required. (213)Bi retention was experimentally verified to be liposome-size dependent. For large liposomes, the measured (213)Bi retention was lower than theoretically predicted (less than 10%). CONCLUSION: This work supports the hypothesis that it may be possible to develop (225)Ac-based therapies by delivering multiple (225)Ac atoms in liposomes. Improvements in the retention of (225)Ac daughters will likely be necessary to fulfill this potential. Because of the size of the liposomal structures required to contain the daughters, the approach is ideally suited for locoregional therapy (e.g., intraperitoneal, intrahepatic artery, or intrathecal).

Actinium↗
PubMed2006

Neoplastic transformation of a human hybrid cell line by alpha particles in relation to mammography X rays.

The hybrid cell line CGL1 is the only cell line which allows quantitation of neoplastic transformation in human cells. Hybrid cells were exposed to 3.4 MeV alpha particles or to mammography X rays (29 kV(p)) and both survival and neoplastic cell transformation were assayed. For comparison, previously published data obtained with 200 kV(p) X rays are also included. Alpha particles were significantly more efficient than 29 kV(p) X rays in cell killing. Surprisingly, the efficiency of mammography X rays for the induction of neoplastic cell transformation was close to that observed for alpha particles.

Alpha Particles↗
PubMed2006

Alpha-particle radiobiological experiments using thin CR-39 detectors.

The present paper studied the feasibility of applying comet assay to evaluate the DNA damage in individual HeLa cervix cancer cells after alpha-particle irradiation. We prepared thin CR-39 detectors (<20 microm) as cell-culture substrates, with UV irradiation to shorten the track formation time. After irradiation of the HeLa cells by alpha particles, the tracks on the underside of the CR-39 detector were developed by chemical etching in (while floating on) a 14 N KOH solution at 37 degrees C. Comet assay was then applied. Diffusion of DNA out of the cells could be generally observed from the images of stained DNA. The alpha-particle tracks corresponding to the comets developed on the underside of the CR-39 detectors could also be observed by just changing the focal plane of the confocal microscope.

Alpha Particles↗
PubMed1996

No association between p53 status and alpha-particle-induced chromosomal instability in human lymphoblastoid cells.

Previous work has demonstrated that alpha-particle irradiation of primary human bone marrow cells leads to the transmission of chromosomal instability in the descendants of the irradiated cell, although there is some interindividual variation. We have extended these studies to human EBV-transformed lymphoblastoid cell lines in order to establish an in vitro model system. The five cell lines analyzed, including one from a Fanconi anaemia patient, exhibited high levels of persistent chromatid aberrations up to approximately 40 cell generations after alpha-irradiation. The p53 status of the cell lines was defined according to whether cellular p53 levels were induced by irradiation, translocated to the nucleus and were able to bind a p53 DNA consensus recognition sequence in vitro. Together with the primary bone marrow cell studies, we conclude that alpha-particle induced chromosomal instability is independent of the p53 status of the cell as defined in these studies.

Alpha Particles↗
PubMed1996

Long-term in vivo transmission of alpha-particle-induced chromosomal instability in murine haemopoietic cells.

We have previously reported non-clonal cytogenetic aberrations in the clonal descendants of murine haemopoietic stem cells irradiated in vitro with alpha-particles. The data are consistent with a transmissible chromosomal instability induced in a stem cell resulting in a diversity of aberrations in its clonal progeny many cell divisions later. To determine whether this instability is transmissible in vivo, bone marrow cells obtained from the male mouse have been irradiated with alpha-particles in vitro and transplanted into female recipients. In the repopulated haemopoietic system we have observed persisting chromosomal instability up to 1 year post-transplantation. The findings demonstrate a long-lived effect of the alpha-particle-induced lesion in the donor repopulating stem cells.

Alpha Particles↗
PubMed1983

Interpretation of cytogenetic damage induced in the germ line of male mice exposed for over 1 year to 239Pu alpha particles, fission neutrons, or 60Co gamma rays.

The relative biological effectiveness (RBE) of 239Pu alpha particles, fission neutrons (0.85 MeV), and 60Co gamma rays has been evaluated for the induction of reciprocal chromosome translocations in spermatogonia and of chromosome/chromatid fragments and chromatid rearrangements in the primary spermatocyte of adult male B6CF1 mice. Age concurrency was maintained for both internal and external radiations which were delivered at about 1 rad/week for 239Pu (single intravenous dose of 10 microCi/kg), 0.67, 1.67, and 2.67 rad/week for neutrons, and 6.95, 17.4, and 32 rad/week for gamma rays for at least 60 weeks. In terms of frequency of translocations, the response to the alpha emitter was nonlinear (concave downward) with little dose-response predictability; to cumulative neutron exposures the response was linear, without evidence of a dose-rate effect; and to gamma radiation the responses were linear, and a significant dose-rate effect was seen. RBE estimates are variable. For translocations, the n/gamma ratio is between 10 and 24, depending upon weekly dose level, and the ratio is 1 or less for the alpha particle relative to the neutron. For fragments, the n/gamma ratio is 18 to 22, depending upon age factors, and alpha/n is 1.5. For chromatid rearrangements, n/gamma is 7 and alpha/n is essentially indeterminate, but much below one. The overall response to the alpha emitter is interpreted to be a complex function of (a) microdosimetric heterogeneity, (b) a nearly invariant deposition pattern in the gonad, (c) the high sensitivity of differentiating spermatogonia to cell killing, and (d) the capacity of stem cells in relatively radiation-free areas to progressively assume the major spermatogenic role.

Alpha Particles↗
PubMedDate not supplied

Study of inhomogeneities in sources prepared for alpha-particle spectrometry using scanning probe microscopy.

For high-resolution alpha-particle spectrometry, sources of high quality must be prepared by methods giving the thinnest and most homogeneous deposit possible on a suitable support. Surface characteristics of several types of alpha-particle sources were studied using a scanning probe microscope. Major inhomogeneities were observed, which means that the materials and techniques used for thc preparation of sources must be improved.

Journal Article↗