Atomic Energy of Canada Limited

About: Atomic Energy of Canada Limited is a company organization based out in Ottawa, Ontario, Canada. It is known for research contribution in the topics: Neutron & Zirconium alloy. The organization has 4845 authors who have published 4826 publications receiving 102951 citations.

Superinfection Exclusion by Incomplete Genomes of Bacteriophage T4

Abstract: The genetic basis of superinfection exclusion by bacteriophage T4 was investigated by using incomplete genomes derived from the gene 66 mutant E920g. Incomplete genomes, which included a region of T4 between genes 42 and 44, were able to exclude superinfecting phage with an efficiency similar to that of complete genomes. Those genomes which did not include this region were unable to exclude superinfecting phage. A mutant with reduced ability to exclude super-infecting phage was isolated after mutagenesis with hydroxylamine. The mutation maps midway between amN122 in gene 42 and amB22 in gene 43. The efficiency of exclusion of superinfecting phage (as measured by the percentage of superinfected cells which failed to release any phage carrying selected markers of the superinfecting phage) by this mutant was 50 to 60%, whereas for wild type it was 85 to 95%. Uptake of 3H-leucine by cells infected with the mutant was inhibited by superinfection with ghosts and it has therefore been designated imm1, for lack of immunity to superinfecting phage and ghosts. The formation of infective centers by cells infected with imm1 or another imm− mutant (imm2) was not inhibited by superinfection with ghosts.

Heat-induced thermal tolerance and radiation resistance to apoptosis in human lymphocytes

Abstract: We have investigated heat- and radiation-induced apoptosis in human lymphocytes in vitro. We have previously shown that apoptosis was induced by radiation at doses as low as 0.05 Gy. Here we report that heat induced apoptosis in human lymphocytes in a temperature- and time-dependent manner. Temperatures at or below 42 degrees C, for up to 90 min, did not cause lymphocytes to undergo apoptosis, whereas temperatures at or above 43 degrees C, for 30 min and longer, did induce apoptosis. Lymphocytes were protected against apoptosis induced by 44 degrees C heat by a prior heat shock of 42 degrees C for 30 min. Heat-induced thermal tolerance developed immediately following the inducing heat shock, was greater after 4 h, and persisted for at least 24 h. While heat also induced radiation resistance, this change was minor and not apparent until about 24 h after the heat shock. Prior to the development of radiation resistance, heat shock sensitized lymphocytes to radiation-induced apoptosis. We have previously shown that radiation-induced apoptosis in lymphocytes varies between donors and therefore may be useful in assessing individual radiosensitivity. We report here that heat also induced variable levels of apoptosis in lymphocytes from different donors, although the range of responses was not as large as those observed with radiation-induced apoptosis. In summary, heat shock induces tolerance to heat-induced apoptosis and results first in sensitization and then protection of lymphocytes against radiation-induced apoptosis.

Influence of crystalline defects on 2-beam crystal lattice images-Experimental

Abstract: Of particular interest in the study of crystal lattice imperfections are the magnitude and extent of their influence on atornic structure. In the present work two-beam crystal lattice images have been used to examine directly the perturbing influence of Guinier-Preston zones in Al-4% Cu, damaged regions in neutron irradiated Ge and dislocations in deformed and partially crystallized Ge. The 2–02 A; spacing of (200) planes was resolved in Al-4% Cu while the 3–26 A spacing of (111) planes was resolved in the Ge specimens. The crystal lattice images were obtained using a high vacuum, short focal length (2.1 mm) Siemen's Elmiskop 1 operated at 100 kv with pointed filaments and thin film objective apertures. The experimental observations reveal: (1) that the G.P. [1] zones are coherent with the matrix (200) planes and produce an observable tensile distortion out to ∼ 20 A on either side of its centre; (2) that when a damaged region in Ge has a size equal to the foil thickness, then the lattice image d...