Walter J. Burdette

Changes in Titer of Ecdysone in Bombyx mori during Metamorphosis

The amount of ecdysone extracted from Bombyx mori rose precipitously immediately before, and fell immediately after, transition from the larval to the pupal stage, and thereafter a secondary rise in titer was observed. These observations correlate very well with physiologic sequences of metamorphosis, critical period, and oxygen uptake.

Alteration of Mutation Frequency by Treatment with Actinomycin D

The frequency of lethal mutations occurring in Drosophila melanogaster was reduced by approximately one-half when irradiated males were treated with actinomycin D, which also inhibited the appearance of melanotic atypical growths in the strain used for the study.

Effect of Brain Hormone from Bombyx mori on Metamorphosis of Calliphora erythrocephala

Summary Appropriate extraction of brains and pupae of Bombyx mori yielded active brain hormone and ecdysone respectively. When various concentrations of these 2 hormones were introduced alone and in combination into isolated larval abdomens of Calliphora erythrocephala, pupation occurred when brain hormone was added to concentrations of ecdysone which would not induce pupation alone. (Pupation was not induced by brain hormone alone.) Brain hormone therefore may have a direct action on the tissues when acting synergistically with acdysone in addition to its tropic action on the prothoracic gland.

Puffing of salivary gland chromosomes after treatment with carbon dioxide.

AFTER larvae of the Oregon R strain of Drosophila melanogaster had been placed in an atmosphere of CO2 for 1 h late in the third instar, the salivary-gland chromosomes were examined and compared with those of a similar group of the same age. The chromosomal regions studied were eight regions known to puff: 85–86, 93, and 95 on the right arm of the third chromosome; 66, 71–72, 74–75, and 78 on the left arm of the same chromosome; and 2B on the X chromosome. The size of the puffs in the 84 glands examined were arbitrarily divided into four classes from smallest to largest and the data tabulated accordingly (Table 1). Although not all puffs were larger in the groups treated, the mean size of puffs III R 85–86, 93, and 95, and III L 66 was larger after exposure to CO2. The remainder showed no tendency to enlarge after such treatment. Larvae late in the third instar not used for chromosomal studies survived and developed into adults following the exposure to CO2. Many younger larvae died. These observations are reported because of current interest in the puffing pattern as presumed indication of localized production of RNA in response to hormonal stimulation. Recently we have found that ecdysone will produce puffing at this stage of larval development in some regions but not in others. Two not affected by CO2 (I 2B and III L 74–75) showed an increase in mean size with ecdysone, and one (III L 71–72) failed to respond to either treatment.