Part of the book: Advanced Image Acquisition, Processing Techniques and Applications
Past efforts in radiobiology, radio-biophysics, epidemiology and clinical research strongly contributed to the current understanding of ionizing radiation effects on biological materials like cells and tissues. It is well accepted that the most dangerous, radiation induced damages of DNA in the cell nucleus are double strand breaks, as their false rearrangements cause dysfunction and tumor cell proliferation. Therefore, cells have developed highly efficient and adapted ways to repair lesions of the DNA double strand. To better understand the mechanisms behind DNA strand repair, a variety of fluorescence microscopy based approaches are routinely used to study radiation responses at the organ, tissue and cellular level. Meanwhile, novel super-resolution fluorescence microscopy techniques have rapidly evolved and become powerful tools to study biological structures and bio-molecular (re-)arrangements at the nano-scale. In fact, recent investigations have increasingly demonstrated how super-resolution microscopy can be applied to the analysis of radiation damage induced chromatin arrangements and DNA repair protein recruitment in order to elucidate how spatial organization of damage sites and repair proteins contribute to the control of repair processes. In this chapter, we would like to start with some fundamental aspects of ionizing radiation, their impact on biological materials, and some standard radiobiology assays. We conclude by introducing the concept behind super-resolution radiobiology using single molecule localization microscopy (SMLM) and present promising results from recent studies that show an organized architecture of damage sites and their environment. Persistent homologies of repair clusters indicate a correlation between repair cluster topology and repair pathway at a given damage locus. This overview over recent investigations may motivate radiobiologists to consider chromatin architecture and spatial repair protein organization for the understanding of DNA repair processes.
Part of the book: DNA
Volcanism based on melting rocks (silicate volcanism) is long known on Earth and has also been found on Jupiter’s moon Io. Remnants of this type of volcanism have been identified also on other bodies in the solar system. Energy sources powered by accretion and the decay of radioactive isotopes seem to be dominant mainly inside larger bodies, which have enough volume to accumulate and retain this energy in significant amounts. On the other hand, the impact of tidal forces allows even tiny bodies to melt up and pass into the stage of cryovolcanism. The dependence of tidal heating on the size of the object is minor, but the masses of and the distances to accompanying bodies as well as the inner compositions of the heated body are central factors. Even though Io as an example of a body supporting silicate volcanism is striking, the physics of tidal forces might suggest a relatively high probability for cryovolcanism. This chapter aims at considering the parameters known and objects found so far in our solar system to give insights into where in our system and other planetary systems cryovolcanism might be expected.
Part of the book: Astronomy and Planetary Science
Genome sequence databases of many species have been completed so that it is possible to apply an established technique of FISH (Fluorescence In Situ Hybridization) called COMBO-FISH (COMBinatorial Oligonucleotide FISH). It makes use of bioinformatic sequence database search for probe design. Oligonucleotides of typical lengths of 15–30 nucleotides are selected in such a way that they only co-localize at the given genome target. Typical probe sets of 20–40 stretches label about 50–250 kb specifically. The probes are either solely composed of purines or pyrimidines, respectively, for Hoogsteen-type binding, or of purines and pyrimidines together for Watson-Crick type binding. We present probe sets for tumor cell analysis. With an improved sequence database analysis and sequence search according to uniqueness, a novel family of probes repetitively binding to characteristic genome features like SINEs (Short Interspersed Nuclear Elements, e.g., ALU elements), LINEs (Long Interspersed Nuclear Elements, e.g., L1), or centromeres has been developed. All types of probes can be synthesized commercially as DNA or PNA probes, labelled by dye molecules, and specifically attached to the targets for microscopy research. With appropriate dyes labelled, cell nuclei can be subjected to super-resolution localization microscopy.
Part of the book: Oligonucleotides