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PubMed1976

Calculation of specific energies of incorporated 239Pu and 131I in accordance with the concept of the critical cell.

A better understanding of the effects of energy deposited in cells by incorporated isotopes can be expected from an analysis of differential cell doses. With this thought in mind, the distributions of specific energies in tissue were calculated for 239Pu and 131I. A program written in Fortran IV makes use of a matrix of spherical cells and cell nuclei of 10 and 8 mum diameter, respectively. The cells are arranged in close-packed structure. The radioactivity is considered as being compiled to point sources of 1 dps activity. The sources are located in the common centers of cells and nuclei. The calculations yield discrete values of specific energy using the mass of the nuclei for mass of reference. The numbers of cell nuclei receiving given amounts of specific energy are functions of the specific activity of the isotopes in the tissue. The specific activity is varied by changing the number of sources per g of tissue. The program also allows to calculate the numbers of cell nuclei with zero energy deposition. From the 1 dps point sources an average specific energy of 831 rads/h results for plutonium for cell nuclei within the range of the 5.14 MeV alpha-particles. For iodine, the value is 35 mrads/h within the range of the beta-particles of 188 KeV mean energy. If the volumes irradiated by the sources begin to overlap these values begin to increase accordingly.

Alpha Particles↗
PubMed1993

Forward electron transfer from phylloquinone A1 to iron-sulfur centers in spinach photosystem I.

Forward electron transfer at room temperature from the secondary acceptor A1 (phylloquinone) to the iron-sulfur centers FX, FB, and FA was studied by flash-absorbance spectroscopy in different photosystem I (PSI) preparations in order to resolve the controversy concerning the kinetics of A1-reoxidation during forward electron transfer [half times of 15 ns [Mathis, P., & Sétif, P. (1988) FEBS Lett. 237, 65-68] and 200 ns [Brettel, K. (1988) FEBS Lett. 239, 93-98] were reported for PSI particles from spinach and Synechococcus sp., respectively]. The monophasic kinetics with t1/2 approximately 200 ns could be reproduced with PSI particles from another cyanobacterium (Synechocystis sp. PCC 6803). In so-called PSI-beta particles from spinach, containing all membrane-bound electron carriers and approximately 65 antenna chlorophylls per reaction center, the flash-induced absorbance increase around 370 nm, which is indicative of the formation of A1-, decays biphasically with t1/2 approximately 25 and 150 ns and relative amplitudes of approximately 65 and 35%, respectively. The difference spectra of these two phases were determined between 330 and 500 nm; they agree well below 380 nm but deviate significantly at higher wavelengths. The spectrum of the sum of the two phases is similar to the spectrum of the 200-ns phase in cyanobacteria. Upon chemical reduction of the terminal acceptors FA and FB, only the 25-ns phase is conserved and the absorbance changes remaining after its completion decay with t1/2 approximately 250 microseconds.(ABSTRACT TRUNCATED AT 250 WORDS)

Electron Transport↗
PubMed2001

Scab incidence on pig skin resulting from hot particle exposures under varying conditions.

External irradiations of pig skin using radioactive sources of less than 600 microm in the largest dimension (hot particles) were carried out. The objective of the study was to determine a threshold for scab induction. Hot particles used included fissioned 235U and activated 170Tm, 17SYb, and 46Sc with maximum beta-particle energies of approximately 1.8 (average), 0.97, 0.47, and 0.35 MeV, respectively. The photon emissions from the fissioned 235U were about 1 MeV per disintegration. The photon emissions from 46Sc were 0.89 and 1.12 MeV, with 100% abundance. Photon emissions from 170Tm and 175Yb were negligible. Responses followed cumulative normal probability distributions; thus, no true thresholds could be determined. Hence, 10% and 50% scab incidence rates (ED10 and ED50, respectively) were determined using probit analysis. For dose averaged over 1 cm2 at a depth of 70 microm, the ED10 (and 95% confidence limits) were 5.1 (2.7-7.2) Gy for 46Sc, 1.3 (0.89-1.8) Gy for 175Yb, 2.8 (1.9-3.5) Gy for 170Tm, 8.5 (5.7-9.8) Gy for on-skin fissioned UC2, and 4.5 (0.9-7.2) Gy for off-skin fissioned UC2. The ED50 values were 12 (8.8-17) Gy for 46Sc, 6.0 (4.3-9.7) Gy for 175Yb, 5.9 (5.1-6.7) Gy for 170Tm, 11 (9.9-19) Gy for on-skin fissioned 235UC2, and 11 (6.2-14) Gy for off-skin fissioned 235UC2.

Animals↗
PubMed1999

A new radiographic procedure for obtaining correction factors of 3H-beta-self-absorption for quantitative tritium autoradiography.

A 3H-radiographic method based on the absorption of 3H-beta-particles by an overlying tissue section was established for obtaining correction factors of 3H-beta-absorption (c.f.s) on the cellular level for all kinds of sections in a simple and more precise way as possible with interferometry. Unlabelled paraffin or Araldite sections were mounted on a thin uniformly 3H-labelled section of resin, and autoradiographs were prepared. Grain densities of neuronal cell types and cell-free areas within and outside the paraffin or Araldite sections were evaluated in autoradiographs, where the exposure time or the thickness of the overlying histological section was varied. From these values c.f.s were calculated applying the Beer-Lambert law. It was shown that corresponding c.f.s determined with this new radiographic method correspond well with each other. However, they will only agree with those c.f.s obtained by interferometry, if relative c.f.s are compared. Since the c.f.s are quite sensitive to the section thickness, a new parameter phi was introduced, which helps to assess whether the microtome used works exactly. Generally, the method presented can be used on the cytological level as well as for whole areas in every other autoradiographic study.

Animals↗
PubMed2000

Considerations in the selection of radiopharmaceuticals for palliation of bone pain from metastatic osseous lesions.

UNLABELLED: Bone pain is a common complication for terminal patients with bone metastases from prostate, lung, breast, and other malignancies. A multidisciplinary approach in treating bone pain is generally required, 1 which includes a combination of analgesic drug therapy, radiation therapy, hormonal therapy, and chemotherapy. Over the years, treatment of bone pain using bone-seeking radiopharmaceuticals has been explored extensively. Pharmaceuticals labeled with energetic 1-particle emitters such as 32p, 89Sr, 153Sm, and 186Re, in addition to the low-energy electron emitter 117mSn, have been studied for this purpose. Bone-marrow toxicity as a consequence of chronic irradiation by the energetic , particles is a general problem associated with this form of treatment. It is therefore desirable to identify radiochemicals that minimize the dose to the bone marrow and at the same time deliver therapeutic doses to the bone. METHODS: New S values (mean absorbed dose per unit cumulated activity) for target regions of human bone and marrow were used to ascertain the capacity of various radiochemicals to deliver a high bone dose while minimizing the marrow dose. The relative dosimetric advantage of a given radiopharmaceutical compared with a reference radiochemical was quantitated as a dosimetric relative advantage factor (RAF). Several radionuclides that emit energetic 1 particles (32p, 89Sr, 153Sm, 186Re, and 177Lu) and radionuclides that emit low-energy electrons or beta particles (169Er, 117mSn, and 33p) were evaluated. For these calculations, ratios of the cumulated activity in the bone relative to cumulated activity in the marrow alpha equal to 10 and 100 were used. RESULTS: When the radiopharmaceutical was assumed to be uniformly distributed in the endosteum and alpha was taken as 100 for both the reference and test radiochemicals, the RAF values compared with the reference radionuclide 32p were 1.0, 1.2, 1.4, 1.6, 1.7, 1.9, and 2.0 for 89Sr, 186Re, 153Sm, 177Lu, 169Er, 117mSn, and 33P, respectively. In contrast, when the radiopharmaceutical is assumed to be uniformly distributed in the bone volume, the RAF values for these 7 radionuclides were 1.1, 1.5, 2.4, 3.2, 4.5, 5.1, and 6.5, respectively. CONCLUSION: These results suggest that low-energy electron emitters such as 117mSn and 33P are more likely to deliver a therapeutic dose to the bone while sparing the bone marrow than are energetic beta emitters such as 32p and 89Sr. Therefore, radiochemicals tagged with low-energy electron or beta emitters are the radiopharmaceuticals of choice for treatment of painful metastatic disease in bone.

Bone Marrow↗
PubMed1993

Mapping of [3H]vasopressin binding sites in the brain of jerboa (Jaculus orientalis) by an high resolution beta-radio imager.

The distribution of vasopressin receptors in the brain of the jerboa (Jaculus orientalis) was studied using tritiated arginin vasopressin ([3H]vasopressin). beta-Particles emitted from tritiated ligand bound to brain sections were detected by a newly developed beta-radio imager to generate a light spot which was read by a charge coupled device camera. The number and coordinate of the center of gravity of the light spot were recorded. After summation in pixels of the counts collected during 2-20 h, an image was produced representing the distribution of [3H]vasopressin bound to brain sections. Specific vasopressin binding was detected in various brain regions such as the cerebral cortex, islands of Calleja, pallidum, amygdala and the hippocampus as well as in the pituitary gland. The intensity of the binding was quantified directly from the images obtained and expressed in decays/min/surface unit. The linearity of this method of detection allowed a relevant measurement of non-specific binding, therefore its subtraction from images representing the total binding. Three-dimensional reconstructions of labeled structures were also performed. The presence of numerous vasopressin receptors in the jerboa hippocampus suggests a major role for this neuropeptide in this part of the brain.

Animals↗
PubMed2004

Endoprobe: a system for radionuclide-guided endoscopy.

Methods to guide the surgical treatment of cancer utilizing handheld beta-sensitive probes in conjunction with tumor-avid radiopharmaceuticals [such as 18F-fluorodeoxyglucose (FDG)] have previously been developed. These technologies could also potentially be used to assist in minimally invasive techniques for the diagnosis of cancer. The goal of this project is to develop and test a system for performing radionuclide-guided endoscopies. This system (called Endoprobe) has four major subsystems: beta detector, position tracker, endoscope, and user interface. The beta detection unit utilizes two miniaturized solid state detectors to preferentially detect beta particles. The position tracking system allows real-time monitoring of the unit's location. The beta detector and position tracking system's receiver are mounted on the tip of an endoscope. Information from the beta detector and tracking system, in addition to the video signal from the endoscope, are combined and presented to the user via a computer interface. The system was tested in a simulated search for radiotracer-avid areas of esophageal cancer. The search for esophageal cancer was chosen because this type of cancer is often diagnosed with endoscopic procedures and has been reported to have good affinity for FDG. Accumulations of FDG in the normal organs of the abdomen were simulated by an anthropomorphic torso phantom filled with the appropriate amounts of radioactivity. A 1.5- mm-thick gelatin film containing FDG was used to simulate radiotracer uptake in the lining of normal esophagus. Esophageal lesions (both benign and malignant) were simulated by thin disks of gelatin (diameters=3.5-12 mm) containing appropriate concentrations of FDG embedded in the gelatin film simulating normal esophagus. Endoprobe facilitated visual identification and examination of the simulated lesions. The position tracking system permitted the location of the Endoprobe tip to be monitored and plotted in real time on a previously acquired positron emission tomography-computed tomography (PET-CT) image of the phantom. The detection system successfully acquired estimates of the beta flux emitted from areas chosen by the user. Indeed, Endoprobe was able to assist in distinguishing simulated FDG-avid areas as small as 3.5 mm in diameter from normal esophagus (p value <0.025). In addition to FDG, Endoprobe can be used with other positron or electron-emitting radionuclides such as IC or 131I. The next phase of this project will focus on modification of the prototype to make it more suitable for clinical use.

Endoscopes, Gastrointestinal↗
PubMed2006

Current status and perspectives in alpha radioimmunotherapy.

Systemic administration of radiolabeled antibody directed against tumor antigens in radioimmunotherapy (RIT) enables to specifically target the cancer cells and to destroy them. So far, this strategy has proven its efficiency in the treatment of some hematological cancers with antibodies labeled with beta emitting radionuclides. In the last 2 decades, availability of short half life alpha emitters prompted to consider their use in RIT. Contrary to beta particles, alpha particles have a short path length and display a high lineic energy transfer. Those physical characteristics open new fields of clinical applications complementary to beta-RIT. To date, alpha-RIT is still at a preclinical stage of development: the radiolabeling methods need to be optimized to ensure in vivo stability of the radiopharmaceuticals. Some radionuclides have complex decay schemes with daughters emitting further alpha particles whose toxicity needs to be investigated. The modalities of administration of radiolabeled antibodies in animal models require also to be improved for delivering higher doses to tumor targets. A comprehensive analysis of the specific events occurring at cell or tissue level in response to alpha irradiation would be of great interest in order to define the best therapeutic association for residual disease or consolidation treatments. This approach has been proven to be efficient in increasing antitumor response either by using high doses with organ protection (kidney, bone marrow) or by a synergistic effect between alpha-RIT and associated treatments, such as chemotherapy.

Alpha Particles↗
PubMedDate not supplied

Fitting methods for constructing energy-dependent efficiency curves and their application to ionization chamber measurements.

An ionization chamber without and with an iron liner (absorber) was calibrated by a set of radionuclide activity standards of the Physikalisch-Technische Bundesanstalt (PTB). The ionization chamber is used as a secondary standard measuring system for activity at the Slovak Institute of Metrology (SMU). Energy-dependent photon-efficiency curves were established for the ionization chamber in defined measurement geometry without and with the liner, and radionuclide efficiencies were calculated. Programmed calculation with an analytical efficiency function and a nonlinear regression algorithm of Microsoft (MS) Excel for fitting was used. Efficiencies from bremsstrahlung of pure beta-particle emitters were calibrated achieving a 10% accuracy level. Such efficiency components are added to obtain the total radionuclide efficiency of photon emitters after beta decay. The method yields differences of experimental and calculated radionuclide efficiencies for most of the photon-emitting radionuclides in the order of a few percent.

Journal Article↗
PubMedDate not supplied

Beta irradiation may induce stereoselectivity in the crystallization of optical isomers.

A novel approach has been introduced to detect the manifestation of symmetry breaking weak interactions at molecular level. In the racemic conglomerate crystallization of D,L-sodium-ammonium tartrate the effect of 32P irradiation was studied by measuring the weight and optical purity of the crystalline phase as well as the size distribution of the crystallites. The high number of independent experiments (over 1000) permitted statistical analysis of the results. The following observations have been made: 1. Beta irradiation influences the crystallization process, irradiated samples yield more crystalline material. 2. The effect involves presumably crystal seed formation because from the irradiated solutions more and smaller crystallites are formed. 3. The presence of beta particles induces stereoselective crystallization, the crystalline phase shows optical activity characteristic of the "unnatural" L-isomer. 4. The above changes are attributed to the beta irradiation as the magnitude of the effects depends on the amount of added radioactivity. Optically active contaminants are highly unlikely sources of the differences between irradiated and control series. 5. In the absence of 32P the tartrate enantiomers have equal probability to form crystals, i.e., the contribution of mixing of weak interaction into the electromagnetic one is not measurable in this system.

Crystallization↗
PubMed1996

Targeted therapy using alpha emitters.

Radionuclides such as 211At and 212Bi which decay by the emission of alpha-particles are attractive for certain applications of targeted radiotherapy. The tissue penetration of 212Bi and 211At alpha-particles is equivalent to only a few cell diameters, offering the possibility of combining cell-specific targeting with radiation of similar range. Unlike the beta-particles emitted by radionuclides such as 131I and 90Y, alpha-particles are radiation of high linear energy transfer and thus greater biological effectiveness. Several approaches have been explored for targeted radiotherapy with 212Bi- and 211At-labelled substances including colloids, monoclonal antibodies, metabolic precursors, receptor-avid ligands and other lower molecular weight molecules. An additional agent which exemplifies the promise of alpha-emitting radiopharmaceuticals is meta-[211At]astatobenzylguanidine. The toxicity of this compound under single-cell conditions, determined both by [3H]thymidine incorporation and by limiting dilution clonogenic assays, for human neuroblastoma cells is of the order of 1000 times higher than that of meta-[131I] iodobenzylguanidine. For meta-[211At] astatobenzylguanidine, the Do value was equivalent to only 6-7 211At atoms bound per cell. These results suggest that meta-[211At] astatobenzylguanidine might be valuable for the targeted radiotherapy of micrometastatic neuroblastomas.

Alpha Particles↗
PubMed2004

Thermoluminescence dosimetric properties of a new thin beta detector (LiF:Mg, Cu, P; GR-200F) in comparison with highly sensitive Al2O3:C beta dosimeters.

There is an increasing need for efficient beta detectors to fulfil ICRU recommendations for new quantities especially in the field of medical physics and retrospective dosimetry. The thermoluminescence properties of thin LiF:Mg, Cu, P (GR-200F) tapes produced in 1998 by Sange Company, People's Republic of China, are investigated and compared with those of highly sensitive thin Al2O3:C beta detectors as regards their applicability in the detection of low energy photons and beta particles. The radiation dose response, minimum detectable dose, reproducibility of measurements and effect of residual signal at low dose are assessed for the possible low level beta dosimetry use. The radiation dose response and photon and beta detection efficiencies are tested underpractical laboratory conditions. The effects of indoor fluorescent light and residual signal after the first read-out are investigated with a view to optimising handling conditions such as post-irradiation and pre-heating treatments for routine dosimetry. The photon energy responses of the detectors are investigated using 150 keV filtered x-rays and 60Co gamma-rays.

Aluminum Oxide↗
PubMed2001

Beta-enolase deficiency, a new metabolic myopathy of distal glycolysis.

A severe muscle enolase deficiency, with 5% of residual activity, was detected in a 47-year-old man affected with exercise intolerance and myalgias. No rise of serum lactate was observed with the ischemic forearm exercise. Ultrastructural analysis showed focal sarcoplasmic accumulation of glycogen beta particles. The enzyme enolase catalyzes the interconversion of 2-phosphoglycerate and phosphoenolpyruvate. In adult human muscle, over 90% of enolase activity is accounted for by the beta-enolase subunit, the protein product of the ENO3 gene. The beta-enolase protein was dramatically reduced in the muscle of our patient, by both immunohistochemistry and immunoblotting, while alpha-enolase was normally represented. The ENO3 gene of our patient carries two heterozygous missense mutations affecting highly conserved amino acid residues; a G467A transition changing a glycine residue at position 156 to aspartate, in close proximity to the catalytic site, and a G1121A transition changing a glycine to glutamate at position 374. These mutations were probably inherited as autosomal recessive traits since the mother was heterozygous for the G467A and a sister was heterozygous for the G1121A transition. Our data suggest that ENO3 mutations result in decreased stability of mutant beta-enolase. Muscle beta-enolase deficiency should be considered in the differential diagnosis of metabolic myopathies due to inherited defects of distal glycolysis.

Humans↗
PubMed1985

Isolation of high density lipoproteins from rat intestinal epithelial cells.

Previous studies have defined forms of high density lipoproteins (HDL) in rat mesenteric lymph, suggesting that they have a secretory origin. This study describes the isolation and characterization of intestinal intracellular HDL. Two preparations were made as follows: (a) Rat enterocytes were isolated and a Golgi organelle fraction was prepared. (b) Cell homogenates were subjected to nitrogen cavitation and a cytoplasmic fraction was prepared. Lipoproteins were isolated from both preparations by sequential ultracentrifugation. When the HDL fraction (1.07-1.21 g/ml) was subjected to isopyknic density gradient ultracentrifugation, a peak of apoproteins A-I and B (apoA-I and apoB, respectively) was found at a density of 1.11-1.14 g/ml. Electron microscopy of the fraction showed spherical particles ranging in size from 6 to 13 nm. Immunoelectrophoresis revealed a precipitin arc in the alpha region against apoA-I which extended into the pre-beta region where a precipitin arc against apoB was also seen. ApoB antisera depleted the pre-beta particles whereas the alpha migrating particles remained. Lipid analysis of the whole HDL fraction revealed phospholipid, cholesteryl ester, and triglyceride as the major lipids. [3H]leucine was then administered into the duodenum and a radiolabeled intracellular HDL fraction was isolated. The newly synthesized apoproteins of the HDL fraction, as determined by gel electrophoresis, were apoB, apoA-I, and apolipoprotein A-IV (ApoA-IV). Immunoprecipitation of the apoB particles revealed apoA-I and apoA-IV in the supernatant. These data demonstrate that there are at least two intracellular intestinal forms of HDL particles, one of which contains apoB. The other particle contains apoA-I and apoA-IV, has alpha mobility, is spherical, and resembles a particle found in the lymph.

Animals↗
PubMed1976

Chemical evolution: effect of high energy radiation.

Quantitative estimation - based on extrapolated data of radioactivity and reasonable assumptions about the radiolytic effect of beta-particles on amino acids- shows that an assymmetry greater than the statistical fluctuation in the number of L-, and D-amino acid molecules could have been produced by beta-decay during chemical evolution.

Amino Acids↗
PubMed1994

Availability of nuclear decay data in electronic form, including beta spectra not previously published.

The unabridged data used in preparing ICRP Publication 38 (1983) and a monograph of the Medical Internal Radiation Dose (MIRD) Committee (Weber et al. 1989) are now available in electronic form. The "ICRP38 collection" contains data on the energies and intensities of radiations emitted by 825 radionuclides (those in ICRP Publication 38 plus 13 from the MIRD monograph), and the "MIRD collection" contains data on 242 radionuclides. Each collection consists of a radiations data file and a beta spectra data file. The radiations data file contains the complete listing of the emitted radiations, their types, mean or unique energies, and absolute intensities for each radionuclide. The beta spectra file contains, for each beta-emitting radionuclide, the probability that a beta particle will be emitted with kinetic energies defined by a standard energy grid. Although summary information from the radiations data files has been published, neither the unabridged data nor the beta spectra have been published. These data files and a data extraction utility, which runs on a personal computer, are available from the Radiation Shielding Information Center at Oak Ridge National Laboratory.

Databases, Factual↗
PubMed1994

Relative biological effectiveness of alpha-particle emitters in vivo at low doses.

The therapeutic potential of radionuclides that emit alpha particles, as well as their associated health hazards, have attracted considerable attention. The 224Ra daughters 212Pb and 212Bi, by virtue of their radiation properties which involve emission of alpha and beta particles in their decay to stable 208Pb, have been proposed as candidates for radioimmunotherapy. Using mouse testes as the experimental model and testicular spermhead survival as the biological end point, the present work examines the radiotoxicity of 212Pb and its daughters. When 212Pb, in equilibrium with its daughters 212Bi, 212Po and 208Tl, was administered directly into the testis, the dose required to achieve 37% survival (D37) was 0.143 +/- 0.014 Gy and the corresponding RBE of the mixed radiation field was 4.7 when compared to the D37 for acute external 120 kVp X rays. This datum, in conjunction with our earlier results for 210Po, was used to obtain an RBE-LET relationship for alpha particles emitted by tissue-incorporated radionuclides: RBE alpha = 4.8 - 6.1 x 10(-2) LET + 1.0 x 10(-3) LET2. Similarly, the dependence of RBE on alpha-particle energy E alpha was given by RBE alpha = 22 E(-0.73) alpha. These relationships, based on in vivo experimental data, may be valuable in predicting biological effects of alpha-particle emitters.

Alpha Particles↗
PubMed1984

Beta- and gamma-dose measurements of the Godiva IV critical assembly.

To aid in the re-evaluation of an exposure that occurred in 1963, information was required on the response of film badges to the beta- and gamma-ray doses from a critical assembly. Of particular interest was the beta spectra from the assembly. The techniques used and the results obtained in this study are of interest to health physicists at facilities where exposures to betas occur. The dose rates from the Los Alamos National Laboratory Godiva IV Critical Assembly were measured at numerous distances from the assembly four and 12 days following a burst. Information was obtained on the beta-particle spectra using absorption curve studies. The beta/gamma dose-rate ratio as a function of distance from the assembly was determined. Shielding provided by various metals, gloves and clothing was measured. The beta- and gamma-ray doses measured were compared with a film packet used in the past at the Nevada Test Site with two types of current TLD personnel badges. Measurements made with a commercial thin-window ion chamber instrument are compared with the dose rates obtained using other dosimeters.

Electrons↗