Peripheral Nervous System Genes Expressed in Central Neurons Induce Growth on Inhibitory Substrates

Trauma to the spinal cord and brain can result in irreparable loss of function. This failure of recovery is in part due to inhibition of axon regeneration by myelin and chondroitin sulfate proteoglycans (CSPGs). Peripheral nervous system (PNS) neurons exhibit increased regenerative ability compared to central nervous system neurons, even in the presence of inhibitory environments. Previously, we identified over a thousand genes differentially expressed in PNS neurons relative to CNS neurons. These genes represent intrinsic differences that may account for the PNS’s enhanced regenerative ability. Cerebellar neurons were transfected with cDNAs for each of these PNS genes to assess their ability to enhance neurite growth on inhibitory (CSPG) or permissive (laminin) substrates. Using high content analysis, we evaluated the phenotypic profile of each neuron to extract meaningful data for over 1100 genes. Several known growth associated proteins potentiated neurite growth on laminin. Most interestingly, novel genes were identified that promoted neurite growth on CSPGs (GPX3, EIF2B5, RBMX). Bioinformatic approaches also uncovered a number of novel gene families that altered neurite growth of CNS neurons

Positron irradiation effects on polypropylene

Positron irradiation effects on polypropylene (PP) and polyethylene during the positron lifetime measurements have been studied in detail. The effect, which was to decrease I3, has been found to be larger in air than in vacuum. For PP, when the lifetime measurements were performed at temperatures above 348K, the radiation effect was scarcely observable. However at low temperature the radiation effect was accumulated and I3 was decreased during the measurements. Irradiation of Co-60 Υ-ray up to the dose of 300 MRad also lead to similar decrease in I3, but the decrease due to Υ-irradiation was not as large as that due to the positron irradiation. Irradiation effect of positrons appears to be different from that of Υ-rays

Water absorption in novolac epoxy resins studied by positron annihilation

Water absorption rates of four kinds of epoxy resins cured with phenol novolac (PH) were compared with the results of positron annihilation lifetime measurements (PAL). Three samples : cresol novolac (CR), tetra-methyl-biphenol (TMB) and bis-phenol A (BA), showed almost similar absorption rates, while tris-hydroxy-phenyl-methane (THPM) absorbed water twice as fast as others. Since THPM has a larger τ3 value (hence larger intermolecular-space holes) than the other samples, the correlation between τ3 and the absorption rate seems evident. For THPM, the lifetime distribution was shifted toward a shorter lifetime after absorbing water, which is interpreted in terms of the particular structure of three-dimensional holes

Improvement of energy resolution in time-of-flight method for high energy neutron measurement

In the time-of-flight measurement of high energy neutrons, the time resolution is often required to be as good as possible. For improvement of the energy resolution, the time-of-flight study was made by the use of Li (p, n) reaction at forward angles. Two types of detectors were tested. One was a liquid organic scintillator NE-213 5 inches (127 mm) in diameter and 127 mm thick connected with three Hamamatsu H2431 photomultipliers 2 inches (51 mm) in diameter. The other was NE-213 of the same size with a Hamamatsu R1250 127 mm in diameter. The experiment was made at pi2 beam line of 12 GeV proton synchrotron in High Energy Accelerator Research Organization (KEK). The incident proton energy was 800 MeV, and the flight path was 5 m. Two neutron detectors were set at 0 and 5 degrees, respectively. The time resolutions for prompt gamma rays were 0.5 ns for NE-213 with three H2431s and 1.0 ns for NE-213 with R1250. The energy resolutions for 800 MeV neutrons were derived from these values were 70 and 100 MeV, respectively. 12 Refs