Irradiation systems, protection

Significant protection of mice by several polysaccharides other than glucan isolated from S. cerevisiae has been described (209). A 2.16-fold protection in the LD q q is observed for one modifier, MNZ, when given 15 min prior to irradiation. Glucan protects 2.25-fold in this same protocol. Many of these polysaccharides may act through activation of the complement system, rather than directiy on ceHs. 

Of considerable interest is the fact that cysteine protection in mice is an inverse function of ionization density, being less for fast neutrons than for gamma or X-rays (3). This finding parallels the oxygen effect in irradiated systems and is supported by other data. 

Chinese Herbal Medicines. Many traditional Chinese medicines have been screened for radioprotective activity in experimental animals. In one study of more than a thousand Chinese herbs, a number of agents increased the survival rate of dogs exposed to a lethal dose of y-rays by 30—40%, and some symptoms of radiation injury were ameHorated. These effects are potentially related to stimulation of the hemopoietic and immune systems (130). Extracts of five Chinese dmg plants, as weU as aspirin, effectively protected mice exposed to 7.5—8.0 Gy (750—800 rad) of y-radiation, and increased survival rates by 8—50% (131). Several Chinese traditional medicines, adininistered ip before or after irradiation, protected against Hpid peroxidation in a variety of mouse tissues, including BM, Hver, and spleen, as weU as in mouse Hver microsomal suspensions irradiated in vitro (132). 

Endotoxin and Muramyl Dipeptide Derivatives. Bacterial cell wall constituents such as the Hpopolysaccharide endotoxin and muramyl dipeptide, which stimulate host defense systems, show radioprotective activity in animals (204). Although endotoxin is most effective when given - 24 h before irradiation, it provides some protection when adrninistered shortiy before and even after radiation exposure. Endotoxin s radioprotective activity is probably related to its Hpid component, and some of its properties may result from PG and leukotriene induction (204). 

Study of the action of AR on . coli precA luxCDABE-Anvp has confirmed it photoprotective effects and has shown features of such activity in live systems. Surprising was the interrelation between preservation of viability of AR-processed bacterial cells in the conditions of a long and intensive UV-irradiation and depression of activity their reparing SOS-systems. It has assumed AR action and the SOS-answer as alternative "passive" and "active" mechanisms for protection of bacterial cells DNA at various intensivity of UV-irradiation. 

Early in the program, critical components (e.g.,the turbomolecular pump) and circuit boards were tested for their ability to survive neutron and gamma irradiation rates and doses similar to those that would be received from exposure to the detonation of a tactical nuclear device. All components were powered up at the start of the gamma irradiation tests but not during the neutron irradiation tests. Circuit boards were protected by circumvention circuits that powered down critical circuits in 10 to lOOps upon detecting radiation. All components survived the nuclear radiation tests. This unusual performance was noted with positive commendations by the staff at the White Sands Missile Range, where the tests were performed. Tests of the fully integrated CBMS II system, installed in a reconnaissance vehicle, will be conducted in the future. 

It has been known for a long time that solar UV irradiation is the greatest danger for unprotected spores. A multilayer system with an aluminium covering, and containing added protective materials such as glucose (up to 10-4 M), had clear protective properties. The high resistance of the Bacillus subtilis spores is probably due to two effects ... 

Chinese hamsters exposed to ozone at 0.2 ppm for 5 h had an increased number of chromosomal breaks in their circulating lymphocytes. Blood samples for study were obtained immediately after exposure and 6 and 15.5 days later. The highest break frequency was observed after the longest delay. The authors compared the effects of X irradiation and ozone singly and combined, in their system. The combined effects were less than additive this suggested some protective mechanism, perhaps analogous to that observed by Hattori et al When the authors extrapolated their data to acceptable industrial-hygiene exposures to ozone and radiation, ozone was found to be much more likely than X irradiation to produce chromosomal breaks in such exposures. 

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