RADIOBIOLOGY

Author: Rivero Gil María Teresa.
Year: 2004.
University: A CORUÑA.
Place of defense: Facultad de Ciencias.
Place of preparation: Universidad de A Coruña.

Summary: Using the technique DBD-FISH has analyzed the signal in basal cells of mice, we found that the DNA main satellite is responsible majority of the baseline signal may be due to the presence of abundant places labile alkaline constituent in this sequence. In addition, the technique DBD-FISH in comets neutral allowed simultaneous esteem and easily breaks simple chain (ssb) and double (dsb) in the same nucleus, cell to cell. The ssb relate to the intensity of the signal DBD-FISH and dsb with the length of migration of the comet in the same signal DBD-FISH. Combining the technique of DBD-FISH with gel electrophoresis in individual cells (SCGE), a study of the migration patterns of the DNA electrophoresis of cells, including in microgel in two dimensions. The migration ADNcs after the second electrophoresis alkaline (Electrophoresis neutra-desnaturalización alcalina-90Â fourth Electrophoresis alkaline), is becoming progressively larger and more homogeneous, moving from head to tail of the comet obtained in the first electrophoresis. Because of denaturing conditions, the length of ADNcs increases over time and these sections of ADNcs tend not to interact with them, facilitating their mobility. In the case of the second neutral electrophoresis (Electrophoresis neutra-desnaturalización alcalina-90Â fourth Electrophoresis neutral), migration ADNcs is becoming progressively smaller and more homogeneous, moving from head to tail of the comet obtained in the first electrophoresis. In this case, the conditions of pH allow renaturalización partial ADNcs generated during the prelude denaturation. Therefore, under these circumstances, the fragments of renaturalización partial ADNcs is entrelazarían, leading to less freedom of migration, which is widening as we approach the tail. When the DNA is mobilized without denaturing (Electrophoresis neutra-90Â fourth Electrophoresis neutral), in his dual chain conformation, it is noted that during the second electrophoresis, DADN the head of the comet initial not migrate. Besides, comets seem to be formed by DNA fibers, which tend to bend at right angles from a variable tail, reflecting probably the place where he was the tip of the fiber when they moved in the direction perpendicular. Finally, we analyzed the structure, radiosensitivity and repair sequences teloméricas interstitial (ITRS) in Chinese hamster cells, encontándose that blocks ITRS presents a high sensitivity to alkaline denaturation, which correlates with hypersensitivity to digestion "spot "with the nucleasa mung bean. Possibly the ITRS have a structure cromatínica particularly enriched in small segments of DNA without match. After exposure to X-ray the ssb and dsb were induced with similar density in the ITRS as in the whole genome. The kinetics of repair of ssb in the ITRS was similar to that of the whole genome. The lack of activity ADN-PKcs does not affect the kinetics. However, the rate of repair of dsb, studied by the length of migration relative signal DBD-FISH was initially slower in the ITRS in the whole genome, in the control cells. The differential structure of chromatin could lead to a heterogeneous intragenómica on the kinetics of repair of dsb radioinducidas. In the absence of activity ADN-PKcs (mutants XR-C1 and XR-C2), the rate of repair of dsb in the whole genome appears slower than in control cells. However, the rate of repair of dsb in the ITRS remained unchanged with respect to control. Thus, activity ADN-PKcs seems not affect the kinetics of repair of dsb in the ITRS. This result indicates that the ways of repararción of dsb can operate differentially in specific regions of the genome.

Author: GONZÁLEZ VELASCO JAVIER.
Year: 2005.
University: PAÍS VASCO.
Place of defense: FACULTAD DE MEDICINA Y ODONTOLOGÍA.
Place of preparation: FACULTAD DE MEDICINA Y ODONTOLOGÍA.

Summary: Radiation therapy (RT) is one of the basic treatments for tumors of the head and neck. The mucositis and xerostomia are the main toxic effects arising from the implementation of the same. The addition of concomitant chemotherapy, therapeutic strategy common in advanced stages, as well as the implementation of fraccionamientos altered, corresponds to an increase in the already significant side effects (mucositis) resulting in interruptions of treatment, which reduces the effectiveness of it and the quality of life of the patient. The use of pharmacological agents that, simultaneously, to increase the effect of radiation on the tumor tissue (radiosensibilización) and reduce toxicity on healthy tissue (radiation), can make a major breakthrough in RT. This in vitro study examines the effect of treatment with oxotiazolidina-carboxilato (OTZ, a modulator of intracellular levels of glutathione), and various doses of irradiation (125-1000 cGy), both used in isolation as a joint cell lines keratinocytes healthy oral mucosa (QSMO) and cell carinoma squamous language (SCC25). It also looks at the pattern more effective implementation of OTZ in combination with RT, and finally analyze differences arising from the implementation of various patterns of fractionation radiotherapy: conventional (200 cGy / d) and hiperfraccionado (125 cGy twice daily) in both cases, for 5 consecutive days. The cells were subjected to RT with photons of 6 Mev (Linear Accelerator, Primus-Siemens 18). The OTZ was administered at doses of 0.5 mM, 1 hour prior to each fraction of RT, once it had been determined as the optimum pattern of joint administration. After the treatment, were analyzed for rates clonogenicidad (CI), obtaining from them the parameters of survival fraction (SF), a factor modifying the radiorespuesta (FMR) and therapeutic index (IT). The results show that exposure prior OTZ to irradiation with a single dose of RT produces a radioprotector of QSMO (FMR-0, 8) and radiosensibilizador of tumor cells SCC25 (FRM = 1.4). The different results produced by the OTZ on raidosensiblidad of healthy cells and tumor measured as the fraction of survival at 2 Gy (FS2), yielded a profit radiobiological significant, with an IT = 1.7. In combination with hiperfraccionamiento, the pattern of OTZ is optimal management in both cell lines, 1h before each dose RT. The pattern of administration post-irradiación decreases in both the FS cell line healthy and in the tumor. The exhibition prior OTZ each of the dose of irradiation produces a weekly fractionation effect radioprotector on QSMO in every case, leading to the pattern of hiperraciconamiento a FMR = 0.85, similar to that obtained with standard fractionation (FMR = 0.81). On the contrary, this pattern leads to an effect radiosensibilizador in tumor cells (SCC25) in all cases, being 1.2 times higher with the pattern of hiperfraciconamiento (FMR = 1.67) than with standard fractionation (FMR = 1.38). This leads to a significant increase in the therapeutic index which this higher with the pattern of hiperfraccionamiento radiotherapy (1.96) that achieved with standard fractionation (1.70). In conclusion, the results show a selective modulation of the radiorrespuesta protecting the healthy tissue and sensiblizando simultaneously tumor, suggesting that this strategy may improve therapeutic outcomes in terms of tumor control and toxicity in the RT tumors head and cuel 8 it.