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- Enger, Shirin A., et al.
(author)
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Gadolinium-153 as a brachytherapy isotope
- 2013
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In: Physics in Medicine and Biology. - : IOP Publishing. - 0031-9155 .- 1361-6560. ; 58:4, s. 957-964
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Journal article (peer-reviewed)abstract
- The purpose of this work was to present the fundamental dosimetric characteristics of a hypothetical Gd-153 brachytherapy source using the AAPM TG-43U1 dose-calculation formalism. Gadolinium-153 is an intermediate-energy isotope that emits 40-100 keV photons with a half-life of 242 days. The rationale for considering Gd-153 as a brachytherapy source is for its potential of patient specific shielding and to enable reduced personnel shielding requirements relative to Ir-192, and as an isotope for interstitial rotating shield brachytherapy (I-RSBT). A hypothetical Gd-153 brachytherapy source with an active core of 0.84 mm diameter, 10 mm length and specific activity of 5.55 TBq of Gd-153 per gram of Gd was simulated with Geant4. The encapsulation material was stainless steel with a thickness of 0.08 mm. The radial dose function, anisotropy function and photon spectrum in water were calculated for the Gd-153 source. The simulated Gd-153 source had an activity of 242 GBq and a dose rate in water 1 cm off axis of 13.12 Gy h(-1), indicating that it would be suitable as a low-dose-rate or pulsed-dose-rate brachytherapy source. The beta particles emitted have low enough energies to be absorbed in the source encapsulation. Gadolinium-153 has an increasing radial dose function due to multiple scatter of low-energy photons. Scattered photon dose takes over with distance from the source and contributes to the majority of the absorbed dose. The anisotropy function of the Gd-153 source decreases at low polar angles, as a result of the long active core. The source is less anisotropic at polar angles away from the longitudinal axes. The anisotropy function increases with increasing distance. The Gd-153 source considered would be suitable as an intermediate-energy low-dose-rate or pulsed-dose-rate brachytherapy source. The source could provide a means for I-RSBT delivery and enable brachytherapy treatments with patient specific shielding and reduced personnel shielding requirements relative to Ir-192.
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| 2. |
- Trybala, E, et al.
(author)
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Interaction between pseudorabies virus and heparin/heparan sulfate : Pseudorabies virus mutants differ in their interaction with heparin/heparan sulfate when altered for specific glycoprotein C heparin-binding domain
- 1998
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In: Journal of Biological Chemistry. - : Elsevier BV. - 0021-9258 .- 1083-351X. ; 273:9, s. 5047-5052
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Journal article (peer-reviewed)abstract
- Cell surface heparan sulfate serves as an initial receptor for a number of herpesviruses including pseudorabies virus (PrV). It has been demonstrated that the heparan sulfate-binding domain of PrV glycoprotein C is composed of three discrete clusters of basic residues corresponding to amino acids 76-RRKPPR-81, 96-HGRKR-100, and 133-RFYRRGRFR-141, respectively, and that these clusters are functionally redundant, i.e. each of them could independently support PrV attachment to cells (Flynn, S. J., and Ryan, P. (1996) J. Virol. 70, 1355-1364). To evaluate the functional significance of each of these clusters we have used PrV mutants in which, owing to specific alterations in glycoprotein C, the heparan sulfate-binding site is dominated by a single specific cluster. These mutants exhibited different patterns of susceptibility to selectively N-, 2-O-, and 6-O-desulfated heparin preparations in virus attachment/infectivity assay. Moreover PrV mutants differed as regard to efficiency of their attachment to and infection of cells pretreated with relatively low amounts of heparan sulfate-degrading enzymes. Furthermore glycoprotein C species, purified from respective mutants, bound heparin oligosaccharide fragments of different minimum size. These differences suggest that specific clusters of basic amino acids of the heparan sulfate-binding domain of glycoprotein C may support PrV binding to different structural features/stretches within the heparan sulfate chain.
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| 3. |
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| 4. |
- Trybala, E, et al.
(author)
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Mode of Interaction Between Pseudorabies Virus and Heparan Sulfate/Heparin
- 1996
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In: Virology. - : Elsevier BV. - 0042-6822 .- 1096-0341. ; 218:1, s. 35-42
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Journal article (peer-reviewed)abstract
- It has been demonstrated that the efficient attachment of pseudorabies virus (PrV) is mediated by an interaction between glycoprotein C (gC) and a cellular heparin-like substance (T. C. Mettenleiter, L. Zsak, F. Zuckermann, N. Sugg, H. Kern, and T. Ben-Porat, J. Virol. 64, 278–286, 1990). According to the prevalent concept, this interaction is likely to occur between clusters of basic residues of PrV gC and the negatively charged sulfate esters and carboxylate groups of heparan sulfate/heparin. To elucidate which of the three major types of sulfate groups of heparan sulfate/heparin are involved in the interaction with PrV, we used selectively N-, 2-O-, and 6-O-desulfated samples and other modified heparins as competitors in virus-attachment assays. PrV exhibited limited preference for the specific sulfate groups of heparan sulfate/heparin in accordance with a hierarchy of 6-O- > 2-O- >N-sulfates. In addition, since selective removal of any of the specific sulfates had only a slight effect on the competition capacity of heparin, it is likely that the combination of any two of three types of sulfate groups could contribute to an interaction with PrV with an efficiency nearly equal to native, fully sulfated heparin. When tested on different cell lines the pattern of PrV requirement for the specificO-sulfate groups, i.e., 6-O-sulfates > 2-O-sulfates, remained the same. However, different minimum lengths of heparin fragments were required to inhibit PrV attachment to different cell lines, suggesting a relative virus flexibility in accommodation to different forms of heparan sulfate.
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