Meeting Abstract
16.1 Friday, Jan. 4 Systemic responses to ionizing irradiation-induced imaginal discs in the larval hornworm, Manduca sexta SILVA, N; MIRY, S; OMONDI, C; ABDON, B; NJIE, C; RAMOS, L; MOFFATT, C; FUSE, M*; SFSU; SFSU; SFSU; SFSU; SFSU; SFSU; SFSU; SFSU fuse@sfsu.edu
The imaginal discs are progenitor cells in holometabolous insects such as Manduca sexta and Drosophila melanogaster, which are destined to become adult structures such as wings or antennae. Damage can be induced by the administration of high doses of x-ray irradiation during larval development, due to the highly proliferative nature of the discs. But these tissues are extremely resilient and are repaired extremely efficiently when damaged. It has been proposed that imaginal disc repair is facilitated by an endocrine-induced delay in pupation via the inhibition of the developmental hormones Prothoracicotropic Hormone (PTTH) and the ecdysteroids, to accommodate repair of the damaged tissue. This delay is suggested to arise from the actions of secreted blood-borne factors from the damaged discs acting on the endocrine system. We therefore assessed the ability of a putative factor, adenosine, to delay development when injected into control M. sexta by assessing pupation rates. We further measured changes in the stain intensity of PPTH in cells of brains from x-rayed and control larvae, using immunohistochemistry with a PTTH-specific antibody, as a gauge of PTTH abundance. Our preliminary results showed that while adenosine induced developmental delays in M. sexta, this appeared to be through altered growth rates, a phenomenon not noted after irradiation. Furthermore, the continuous increase in PTTH stain intensity noted in control brains over a three-day test period was not noted in irradiated larvae. By the third day of development, PTTH levels appeared to plateau, suggesting that production was inhibited in irradiated larvae at this time. Experiments are currently underway to assess the effects of a second putative factor, Dilp-8 (an insulin-like peptide), in delaying development.
