Radioresistance and radiosensitivity: a biophysical approach on bacterial cells robustness.

The study of radiosensitivity and radioresistance of organisms exposed to ionizing radiation has acquired additional relevance since a new bio-concept, coined as The primacy of Proteome over Genome, was proposed and demonstrated elsewhere a few years ago. According to that finding, genome integrity would require an actively functioning Proteome. However, when exposure to radiation takes place, Reactive Oxygen Species (ROS) from water radiolysis induce protein carbonylation (PC), an irreversible oxidative Proteome damage. The bio-models used in that study were the radiosensitive Escherichia coli and the extraordinarily robust Deinococcus radiodurans. The production of ROS induces protective reactions rendering them non-reactive forms. Protective entities present in the cytosol, moieties smaller than 3 kDa, shield the Proteome against ROS, yielding protection against carbonylation. Shown in the present study is the fact that the fate of proteins functionality is determined by the magnitude of the Protein Carbonylation Yield (YPC), a quantity here analytically defined using published YPC numerical results. Analytical YPC expressions for E. coli and D. radiodurans were the input for a phenomenological approach, where the radiobiological magnitudes PP and PN, the probabilities for production of protein damage and ROS neutralization, respectively, were also analytically deduced. These highly relevant magnitudes, associated with key radiosensitivity and radioresistance issues, are addressed and discussed in this study. Among the plethora of information and conclusions derived from the present study, those endowed with higher conceptual degree, vis-à-vis the "Primacy of Proteome over Genome" concept, are as follows: (1) the ROS neutralization process in D. radiodurans reaches a maximum at a dose interval corresponding to the repairing shoulder. Therefore, it is a signature of the higher efficiency of the PC neutralization process. (2) ROS neutralization in D. radiodurans is nearly one order of magnitude higher than in E. coli, thus accounting for its extraordinary radioresistance. (3) Both physical (ROS-induced carbonyl radicals) and biological (protein modifications) processes are imbedded in the Protein Carbonylation Yield. The amalgamation of these two processes was accomplished by means of a statistical formalism.

Impeller geometry definition of the transventricular assist device

ABSTRACT: According to the World Health Organization, cardiovascular disease is the number one cause of death worldwide, except Africa, where Acquired Immune Deficiency Syndrome is the leading cause of death. In this scenario, the ventricular assist device (VAD) remains the unique alternative to extend patient life until heart transplantation. At Dante Pazzanese Institute of Cardiology, the research and development of an axial flow VAD to be fully implantable within the heart was started. This pump, denominated Transventricular Assist Device (TVAD), can be surgically implanted through a small left intercostal incision in a minimally invasive manner. The goal of this work is to analyze the impeller geometries of the TVAD, to avoid high shear stresses in the fluid and aim for the best conditions to support the circulatory system using computational fluid dynamics and in vitro tests. Different rotor geometries were selected according to the literature; based on the results, the best rotor was elected. This rotor contains a pair of spiral blades of constant and relatively high pitch, which pumps liquid at a flow rate of 3 L/min at 73 mm Hg. It is also expected that this rotor presents a moderate hemolysis since the shear rate is acceptable.

Impeller geometry definition of the transventricular assist device.

According to the World Health Organization, cardiovascular disease is the number one cause of death worldwide, except Africa, where Acquired Immune Deficiency Syndrome is the leading cause of death. In this scenario, the ventricular assist device (VAD) remains the unique alternative to extend patient life until heart transplantation. At Dante Pazzanese Institute of Cardiology, the research and development of an axial flow VAD to be fully implantable within the heart was started. This pump, denominated Transventricular Assist Device (TVAD), can be surgically implanted through a small left intercostal incision in a minimally invasive manner. The goal of this work is to analyze the impeller geometries of the TVAD, to avoid high shear stresses in the fluid and aim for the best conditions to support the circulatory system using computational fluid dynamics and in vitro tests. Different rotor geometries were selected according to the literature; based on the results, the best rotor was elected. This rotor contains a pair of spiral blades of constant and relatively high pitch, which pumps liquid at a flow rate of 3 L/min at 73 mm Hg. It is also expected that this rotor presents a moderate hemolysis since the shear rate is acceptable.