The developmental properties of three neoplasms found in lethal mutants ofDrosophila melanogaster were studied and compared with the development of the corresponding wild-type organs. Two of these neoplasms are found in the late larval lethal mutant,lethal (2) giant larvae (l(2)gl) and its allele,lethal (2) giant larvae (l(2)gl). The third neoplasm occurs in the hemizygous lethal male embryos of the mutantNotch (Df(1)N).The mutantsl(2)gl andl(2)gl were shown to possess defects involving imaginal primordia of ectodermal origin, such as the imaginal discs of the adult integument and the imaginal optic primordia in the larval brain. They also have enlarged lymph glands and abnormal gonads, salivary and ring glands. Thel(2)gl andl(2)gl mutations transform the imaginal discs into noninvasive, lethal neoplasms and the imaginal optic primordia in the larval brain into an invasive and lethal neuroblastoma. Both neoplasms were serially subcultured in female adult hosts where they grew rapidly and killed their hosts in 7-14 days. The neoplastic development of thel(2)gl imaginal discs and brain proved autonomous at all stages that were investigated from 10 hour old embryos to mature larvae. When exposed to the hormonal conditions of metamorphosis, the neoplastic tissues,in situ as well as those that had been culturedin vivo, ceased to grow but failed to metamorphose into parts of the adult integument or brain. Furthermore, in almost all cases they failed to resume their growth in the adult fly after metamorphosis.Thel(2)gl brain neuroblastoma changed after prolonged subculturein vivo so that although the cells stopped dividing temporarily at the time of metamorphosis of the host, they resumed their growth shortly thereafter and continued to divide throughout adult development and in the emerged adult. Many of thel(2)gl neuroblastoma cells showed abnormal karyotypes, shapes and sizes after prolonged culturein vivo.Thel(2)gl imaginal disc tissue resembles, in both structure and behavior, certain atelotypic tissue sublines which arise from wild-type imaginal discs after prolonged culturein vivo: the ultrastructure of both types of cells are similar and both cease to grow when exposed to hormonal conditions of metamorphosis. Apparently the epigenetic processes which transform wild-type imaginal discs afterin vivo subculture into atelotypic neoplasms have the same phenotypic expression as the genetic processes at work inl(2)gl imaginal discs.An analysis of several other late larval and larval-pupal mutants with defective imaginal discs, such asl(2)gd andl(1)d.lg.-1 revealed that they also had defects in parts of the brain destined to form adult structures. This observation indicates that mutations that affect imaginal discs of the adult integument also affect the imaginal primordia of the adult brain.The neoplasm in the hemizygous male embryo of the embryonic lethalNotch is a teratoma-like growth which is lethal and invasive; when implanted into female adult hosts it gives rise to a mass of tissue which consists of most cell typ...

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In many groups of insects 2 metabolic carbon dioxide is retained within the insect and released during brief periods in "bursts" (Punt,

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The development of the adult abdomen ofDrosophila melanogaster was analyzed by histology, microcautery, and genetic strategies. Eight nests of diploid histoblasts were identified in the newly hatched larva among the polytene epidermal cells of each abdominal segment: pairs of anterior dorsal, posterior dorsal, and ventral histoblast nests and a pair of spiracular anlagen. The histoblasts do not divide during larval life but begin dividing rapidly 3 h after pupariation, doubling every 3.6 h. Initially they remain confined to their original area, but 15 h after pupariation the nests enlarge, and histoblasts replace adjacent epidermis cell by cell. The histoblasts cover half the abdomen by 28 h after pupariation and the rest by 36 h. Polytene epidermal cells of the intersegmental margin are replaced last. Cautery of the anterior dorsal nest caused deletion of the whole corresponding hemitergite, whereas cautery of the posterior dorsal nest caused the deletion of the macrochaetae of the posterior of the hemitergite. Cautery of the ventral nest deleted the hemisternite and the pleura, whereas cautery of the spiracular anlagen deleted the spiracle. Results of cautery also revealed that no macrochaetae formed on the tergite in the absence of adjacent microchaetae. Clonal analysis revealed that there were no clonal restrictions within a hemitergite at pupariation. Cautery of polytene epidermal cells other than those of the intersegmental margin failed to affect tergite development. However, cautery of polytene epidermal cells of the intersegmental margin adjacent to either dorsal histoblast nest caused mirror-image duplications of the anterior or posterior of the hemitergite in 10% of the hemitergites. Forty percent of the damaged presumptive hemitergites formed complete hemitergites, indicating extensive pattern regulation and regeneration. Pattern duplication and regeneration were accounted for in terms of intercalation and a model of epimorphic pattern regulation (French et al., 1976). Histoblasts in adjacent segments normally develop independently, but if they are enabled to interact by deleting the polytene epidermal cells of the intersegmental margin, they undergo intercalation which results in duplication or regeneration. The possible role of the intersegmental margin cells of insects in development was analyzed.