Materials and methods: HTB140 cells were irradiated at four positions: plateau,
middle, distal end and distal declining edge of the 62 MeV proton SOBP. Doses ranged from 2-16 Gy. They were normalised in the middle of SOBP and delivered following the axial physical dose profile. Survival, proliferation and cell cycle were assessed seven days after irradiation.
Results: Moving from proximal to distal irradiation position surviving fractions at 2 Gy (SF2) decreased from 0.88-0.59. Increased radiosensitivity of the cells was noticed for the doses below find more 4 Gy, resulting in two gradients of cell inactivation, stronger for lower and weaker for higher doses. Relative biological effectiveness (RBE) increased from 1.68-2.84 at the distal end of SOBP. A further rise of RBE reaching 7.14 was at its distal declining edge. Following the axial physical dose profile of SOBP the strongest inactivation was attained at its distal end and was comparable to that at its declining edge.
Conclusions: Survival data confirmed selleck very high radioresistance of HTB140 cells. An effect similar to low-dose hyper radiosensitivity (HRS) was observed for order of magnitude larger doses. Better response of cells
to protons than to gamma-rays was illustrated by rather high RBE. Strong killing ability at the SOBP distal declining edge was the consequence of increasing proton linear energy transfer.”
“Nicotinamide DMXAA adenine dinucleotide (NAD ()) is synthesized by the action of nicotinamide mononucleotide adenylyltransferase (NMNAT) from NMN and ATP. The mouse homolog of NMNAT-2 (mmNMNAT-2) was cloned,
expressed, and subsequently identified using MALDI-TOF in conjunction with the ProFound database. Circular dichroism analyses of recombinant mmNMNAT-2 showed alpha helical beta and sheet secondary structures, consistent with the known structure of the human isoform. Competition experiments using mouse pancreatic tissue lysates with recombinant mmNMNAT-2 demonstrated that the activity of the expressed protein was similar to the human isoform. Immunohistochemistry of mouse embryonic tissues with hNMNAT-2 also showed a tissue- and cellular-specific expression of this isoform. Therefore, our studies demonstrate for the first time the clear biological evidence for the existence of a mouse isoform of hNMNAT-2. These studies may help in future investigations aimed at understanding the regulation of this gene and its pathway, and in turn, will spur the development of novel therapies for diseases such as cancer and diabetes since mice are the most frequently used experimental system for in vivo studies.