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MONTHLY STATUS AND PROGRESS REPORT Top Secret Appendix Under Separate Cover BUDGET AND REPORTS DIVISIa
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Cytogenetics--It was shown experimentally that subjecting grasshopper neuroblasts t o hypertonic medium right after irradiation reduces the rate of reversion of the middle prophase and therefore reduces radiation-induced mitotic Previous work has shown that H202 is not an effective mutagen for, paramecia apd thus cannot be used to explain the oxygen e f f e c t and other features of X-ray mutagenesis. - This conclusion was further strengthened by measurements of the catalase content and permeability of H 2 9 of paramecia and by a repet it ion of certain critical experiments i n which cyanide was present to inactive. catalase and insure good penetration by the %02. €3'' added within spores of neurospora enhanced the lethal effect of slow-neutrons through capture irradiation. Survival of cells produced on a boron-free medium was 80 percent after a 48-hour exposure toa flux of 1.2 x 109 n/cg-sec, whereas s u T l of cells from a medium containing 16 ppm of was found between the c e l l s containing natural nitrogen and those containing B10 was- less than 3.7 x 10' . On the other hand, no difference insensitivity - c Mammalian Genetics--The rate of induction of dcaninant lethal s in mouse oocytes was measured by exposing females t o 400 r of X rays and shortly uterine contents of 76 females were examined f o r dead embroyos and resorptlen of corpora lutea i n the ovaries of each of these females was recorded. SurviVal of embryos i n the experimental group was 7 1 percent of that i n the controls. ' This is approximately equal t o the dominant lethal rate obtained in earlier.. work with similarly irradiated males. - 17-1/2 days after conception. At.the same time, the number
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Radiation Protection--In a comparative study of the protective ability of p-mercaptoethylamine and mercaptoethanol, it was found that the former protects i n relatively low concentrations, but comes to a relatively low plateau i n protective ability. In contrast t o this, mercaptoethanol requires higher concentrations'and reaches it plateau a t a considerably higher level of protection. by these compounds in spite of their close structural relation. There are many differences i n the mechanism of protection Biophysics--Tradescantia by ultraviolet irradiation were continued. Several recent experiments demonstrated that photorecovery following treatment with visible light does not occur i n pollen which has been subjected.to ultrain the air/nitrogen breakage frequencies, as well as the time/intensity relatior& have been confirmed. age has been extended t o an upper wave-length limit of 36oaA. The previous results showing no difference I n addition, the flaction spectrum" for chromosome breakPathology and Physiology-In a cooperative project with the fir Force, dosimetry studies, performed with the ORNL 86-Inch Cyclotron, resolved earlier discrepancies between dose measurements obtained with Victoreen chambers, Hursttype neutron counters, fission detectors, and Failla-Rossi tissue-equivalent chambers, The energy spectrum of neutrons i n the biological faciuty a t the @cyclotron was characterized experimentally and found t o agree closely with that Enzyme Chemistq--@erirnents designed to identify the ear containing C 4 from incubation of bone marrow or chick embryo with C -formate are under way. studied, Hypoxanthine, adenine, and guanine were identified in bone-marrow extracts and hypoxanthine wag found i n t h e acid soluble material from chick embroyos. Serine accounts f o r pproximately 45-55 percent of the activity i n bone-marmw acid. salubles b u t (.$-serine makes up only 1 0 percent o f the activity i n similar material from chick embrgos. acid thymine formation about equally, while low concentrations of this radiomimetic agent either enhance or fail to depress labeling inthe purines rib cnuclcic acids Control, irradiated, and aminopterin-treated materials a r e being Aminopterin inhibits serine and deoxyribonucleicIna continuation of the study of the production of the' delayed light by green plants, i t - was shown that the substance responsible for the delayed light can be stored a t liquid nitrogen temperatures. If a photosynthetically active green leaf i s illuminated while being plunged into liquid nitrogen and then placed inthe dark for several hours a t liquid nitrogen temperatures, the delayed light effect is observed when the leaf is immersed ina water