Apoptosis in cultured midgut cells from Heliothis virescens larvae exposedto various conditions

We exposed midgut cells from primary cultures of Heliothis virescens larvae to cell-free previously used medium, the Vaughn X and HyQ SF(TM) media use d for serum-free culture of insect cell lines which do not support H, vires cens midgut cells, and to toxin from Bacillus thuringiensis, A statisticall y significant increase in the percent of dying cells was counted in cell po pulations in Vaughn X medium. Use of the TUNEL method to detect apoptosis i ndicated a low rate (7.2%) of apoptosis in control cultures grown in Heliot his medium, an increase to approximately 20% in previously used and HyQ SF( TM) media, and to approximately 45% of cells remaining after exposure to an d initial destruction by B. thuringiensis toxin, Apoptotic nuclei were pred ominant (approximately 6%) in mature columnar cells in control cultures. Ap proximately 1% of goblet, stem, and differentiating cells were apoptotic, H owever, apoptosis rose to 12% in stem and differentiating cells exposed to used and unsuitable medium. B. thuringiensis exposure to toxin for 2-3 days resulted in visible membrane damage and necrosis, causing the death of 84% of the cells as measured by both the TUNEL and Annexin methods. Some of th e columnar cells and stem and differentiating cells that remained also cont ained apoptotic nuclei, Stem and differentiating cells normally replace dyi ng mature cells in the midgut. Thus, exposure of cultures of H, virescens m idgut cells to adverse environments such as unsuitable or poisonous media a ppeared to induce down-regulation of the cell populations by apoptosis, Arc h. Insect Biochem. Physiol, 45:12-23, 2000, Published 2000 Wiley-Liss, Inc. dagger.