Author
 |
Loeb, Marcia |
|
Submitted to: In Vitro Cellular And Developmental Biology
Publication Type: Abstract Only Publication Acceptance Date: 5/4/2001 Publication Date: N/A Citation: N/A Interpretive Summary: Technical Abstract: Primary cultures of Manduca sexta and Heliothis virescens midgut arise from stem cells that migrate from tissue fragments to generate a culture of morphologically distinguishable stem, columnar, goblet, and occasional nerve cells. The stem cells divide to replenish the supply of mature cells that die by apoptosis. Isolated stem cells require fat body extract to mitose, but do not differentiate. Two factors isolated from conditioned medium, MDF1 and MDF2, induce stem cell differentiation to mature columnar and goblet cells. In adverse conditions, the rate of apoptosis can increase from 7 to 50%; the proportion of apoptosing stem and differentiating cells increases, indicating down regulation of the cells that replace lost mature cells. Under severe conditions, such as a dose of Bt toxin, many mature cells die but the number of stem and differentiating cells increases dramatically. When the toxin is washed away, the culture repopulates to its original composition. This activity parallels a non-fatal Bt toxin exposure or virus infection in vivo, where the midgut is repaired. Since only midgut cells are present in culture, the factors that regulate the rate of apoptosis, mitosis, differentiation and organization must be synthesized by those midgut cells. |
