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Title: IMMUNOHISTOCHEMICAL DETECTION OF MIDGUT DIFFERENTIATION FACTOR (MDFI) IN MIDGUT CELLS OF HELIOTHIS VIRESCENS

Author
item GOTO, SHINTARO - KOBE UNIV KOBE JAPAN
item TAKEDA, M - KOBE UNIV KOBE JAPAN
item Loeb, Marcia
item HAKIM, RAY - HOWARD UNIVERSITY

Submitted to: General and Comparative Endocrinology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/15/2002
Publication Date: N/A
Citation: N/A

Interpretive Summary: Heliothis virescens is a noxious pest on cotton and other vegetables, and is extremely resistant to commonly used chemical and biological insecticides. Therefore, it is important to learn about its physiology in order to find better ways to attack it. Since most damage is done by feeding caterpillars, and all of the food and any insecticides in it pass through the midgut, we are trying to better understand how the gut cells are controlled. We have found a peptide, Midgut Differentiation Factor 1, or MDF1, in medium containing midgut cells that were dividing and maturing. It causes cultured stem cells to mature. In this work, we used an antibody to MDF1 to show that MDF1 is present in defined areas of mature cultured midgut cells as well as in midgut from intact caterpillars. Furthermore, more cells from pre-molting animal contain MDF1 than cells from earlier stages when little MDF1 would be needed. Therefore, we have confirmed that MDF1 is a biologically relevant material. Chemists and biologists can now attempt to prepare chemical analogs to MDF1 in order to prevent stem cells in caterpillar midgut tissue from maturing. THis would prevent the guts in caterpillars from growing at the molt, and would prevent midgut repair that might be induced by other biological agents administered simultaneously. At this stage, this work will be used by other scientists.

Technical Abstract: Two peptide factors, midgut differentiation factors 1 and 2 (MDF1 and 2), have previously been isolated from conditioned medium in which Manduca sexta midgut cells were grown. They are identical to fragments of fetuin, a prenatal vertebrate liver product. They act as cytokines or growth factors by inducing undifferentiated Lepidopteran midgut stem cells from several insect species to differentiate, primarily to mature columnar and goblet cells (Loeb et al., 1999). A rabbit-derived antibody to MDF1 was used in this study to stain cultured midgut cells of the Lepidopteran, Heliothis virescens, as well as thin sections of intact midguts of newly molted, mid- 4th instars, and pre-molting 4th instar larvae of H. virescens in order to find the cellular origin of MDF1 in the midgut. Surprisingly, MDF1 immunoreactivity was localized to basal areas of cultured columnar cells as well as to basal lateral areas of columnar cells in the sections. Goblet and stem cells did not stain. No stain was detected in midgut secretory cells. Thus, columnar cells from H. virescens appear to sequester and/or produce the cytokine MDF-1, or an MDF-1-like peptide, both in vitro and in vivo. The columnar cells probably produce this cytokine in addition to their other tasks of nutrient absorption, digestion, and transport to the hemolymph.