Some Effects of Nitric Oxide and Oxygen on Dominant Lethal Production in X-irradiated Drosophila Virilis Males.

ITRIC oxide (NO) increases X-radiation damage approximately the same Namount as equal quantities of oxygen in Shigella flexneri ( HOWARD-FLANDERS 1957), Vicia faba (KIHLMAN 1958), ascites tumor cells (GRAY, GREEN, and HAWES 1958), and barley seeds with greater than 12 percent water content (SPARRMAN, EHRENBERG, and EHRENBERG 1959). These observations, as well as later comparisons of these gases in modifying X-radiation damage (HOWARDFLANDERS and JOCKEY 1960), have led these authors to conclude that oxygen and nitric oxide are equivalent in their ability to enhance X-radiation damage. POWERS and his coworkers (POWERS, KALETA, and WEBB 1959; POWERS, WEBB, and EHRET 1959; POWERS, WEBB, and KALETA 1960) have shown that nitric oxide can protect dry Bacillus megaterium spores against X-radiation damage, while the irradiation of the spores in similar amounts of oxygen increased the damage observed. Small amounts of nitric oxide can also protect bacteriophage in suspension against X-radiation damage (HOWARD-FLANDERS and LEVIN 1961 ; COTTON, RINEHART, and PETRUSEK, in preparation). Nitric oxide appears to have at least two major effects in Drosophila males ( CAPPS 1961 ) . Three to four percent nitric oxide: (1 ) delays spermatogenesis for 4 to 6 days in Drosophila virilis, and ( 2 ) increases dominant lethality in D. virilis and also the percentage of sex-linked recessive lethals in X-irradiated Drosophila melanogaster. Since 3 percent oxygen did not give the increase in dominant lethality whenever 3 percent nitric oxide did, CAPPS concluded that these gases were operating, at least in part, by separate mechanisms. The interpretation of these nitric oxide experiments in Drosophila is difficult, however, because of the delay in spermatogenesis associated with 3 to 4 percent NO. This delay is caused by a lack of sperm leading to nonfertilization and subsequent nondevelopment of some eggs and can not be distinguished from the nondevelopment of eggs fertilized