1. Eye-antennal discs and cephalic complexes obtained from mature third-instar larvae (96 hours old after hatching at 25°C) of
D. melanogaster were cultured
in vitro in synthetic media, in order to investigate the tryptophan metabolism in the eye discs.
2. Eye-antennal discs cultured together with cephalic complexes showed in comparison with culturing the former alone more pronounced growth, differentiation and pigmentation of the eye discs. This indicates that the metamorphic hormone seems to be the most essential substance for growth, differentiation and pigmentation in the tissue culture of eye discs.
3. In a synthetic medium containing 5mg/ml L-tryptophan, the brown pigment was deposited in the eye discs of
Oregon and
bw after culturing for about 72 hours. In the medium containing 4mg/ml DL-kynurenine, the pigment was deposited in the eye discs of
Oregon,
v and
bw after culturingfor about 30 hours, and in the eye discs of
v bw after culturing for about 55 hours. In a medium containing 2mg/ml DL-3-hydroxykynurenine, the eye discs of
Oregon,
v,
cn and
bw deposited pigment after culturing for 5 hours, whereas the eye discs of
v bw and
cn bw deposited pigment after about 15 hours.
4. The amounts of pigment deposited in the eye discs of
v bw and
cn bw were less than those of
Oregon,
v,
cn and
bw.
5. The fact that the eye discs of
Oregon deposited the brown pigment in media containing various tryptophan metabolites indicates that all enzymes related to tryptophan metabolism were present in the eye discs of the mature third-instar larvae of
Oregon.
6. Smaller amounts of pigment in the eye discs of double recessive mutants,
v bw and
cn bw, seem to indicate that there may be either some interaction between tryptophan- and pteridine metabolism, or there may be some quantitative and qualitative difference among metamorphic hormones secreted from the brains of several strains.
I wish to express my hearty thanks to Prof. H. Kikkawa for his advice and encouragement, and to Dr. Y. Kuroda for his kind guidance and criticism of this work.
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