that radiationtriggered cell death is susceptible to the energy of the individual photons from an electromagnetic radiation source, such as X-ray, rather than the sole total dose absorbed by the system. Thus, we revisited the concept of dose-dependent induction of apoptosis that is the cornerstone of a full spectrum of current therapies used in malignant diseases and non-malignant conditions. Importantly, it will most likely affect the precise treatment intent for radiotherapy depending on the energy of the source, how radiation is administered, and whether it is combined with surgery, chemotherapy, hormone therapy, or a mixture of these. To begin, we evaluated the contribution of the exposure time and X-ray energies associated with the beam to the cell death process and thus, determine whether the unique factor that influences the fate of the cell is the total amount of energy delivered to the system. We chose a simple in vivo system – the Xenopus laevis embryo – which provides an effective model to study radiation-mediated apoptosis in early development. Here, the effect of radiation only becomes apparent when embryos are exposed before the MBT and is conspicuous Lck Inhibitor web during and after gastrulation when the pluripotent embryonic cells begin to differentiate. First, we tested the effect of increasing the energy of the incoming photon by augmenting the voltage setting while keeping a constant exposure time. In this scenario, the total dose delivered to the system increases, as does the energy of the photons. Our analysis revels that i) embryos exposed to low-energy values remain viable throughout the time course analyzed, ii) the greater the energy of the incident photons and, therefore, the greater the total radiation dose, precipitates earlier apoptotic events in embryos, including morphological hallmarks of apoptosis as well as activation of caspases, and iii) exposure time is not a variable in this scenario. We speculate that both the difference of the kinetics of caspase detection and the maximum enzymatic activity observed at the end point of our experiments resulting from increasing the energy of the incident photon are due to decreased attenuation and, therefore, increased penetration since the average distance that photons penetrate a specific material is determined by the photon energy, the type of material, and its density. In general, high-energy photons are more penetrating than low-energy photons. This is particularly important if we consider that the Xenopus embryo is a multilayer cellular system in early embryogenesis and that penetration will be a critical influence on the number of pluripotent cells damaged at once. In January Energy-Dependent Apoptosis addition, another issue is the amount of energy needed to damage DNA, and how extensive the damage must be for the repair mechanism to signal through apoptosis. This is a question that deserves substantive analysis and that will be revisited later in this section after establishing the contribution of the photon energy and total dose for the embryo response. Next, we evaluated the consequences of maintaining a constant voltage and, therefore, photon energy, while altering the exposure time of the 7370771 embryo to radiation. In this scenario, embryos exposed to differently depending on incident energy. For example, when embryos were irradiated with N January Energy-Dependent Apoptosis and thereby suppress genomic instability: non-homologous end joining and homologous recombination.