The lethal effect of oxygen on Escherichia coli organisms freeze-dried from water may be partly abolished by the addition of certain compounds before lyophilization. Three groups of such protective compounds were found: (i) thiourea, some of its derivatives and analogues; (ii) sugars, especially monosaccharides and some of their derivatives; (iii) some simple inorganic salts. The protective act...

We determined the microbicidal activities of antibacterials against nonreplicating Mycobacterium smegmatis grown in a starvation-based Loebel model for persistence. Whereas most drugs lost their activity, fluoroquinolones retained lethal potency. Dose-response characterizations showed a paradoxical more-drug-kills-less Eagle effect. Pretreatment of cultures with chloramphenicol blocked the leth...

cause the suppression. Hypoxanthine completely prevented these biochemical effects of MIX and partially protected the cells against its lethal effects. Thus, in the murine S-phase lymphoblasts, MTX produces a purineless state, the degree of which depends upon the growth rate of the population. The purineless state probably contributes to the lethal effect of MTX, and this may partly explain the...

Ureaplasmas killed mice within 5 min after intravenous injection. The 50% lethal dose of whole ureaplasmal organisms was 32 micrograms per mouse, a value also found for crystalline jackbean urease. The reaction was specific to urease, since protection was afforded by intraperitoneal injection of 200 micrograms of flurofamide, a potent urease inhibitor. The finding that a similar lethal effect w...

Sex-lethal (Sxl) is a vital, X-chromosome gene involved in Drosophila sex determination. The most striking aspect of the phenotype of daughterless (da), an autosomal maternal-effect mutation, may be explained by effects on the functioning of the Sxl gene in the zygote. In this paper, new aspects of interactions between various combinations of Sxl and da alleles are explored in order to understa...

The mutations of the Abruptex locus in Drosophila melanogaster fall into three categories. There are recessive lethal alleles and viable alleles. The latter can be divided into suppressors and nonsuppressors of Notch mutations. The recessive lethals are lethal in heterozygous combination with Notch. As a rule the recessive lethals are lethal also in heterozygous combination with the viable alle...