Computer analysis of double labeling: ultrastructural distribution of vasoactive intestinal peptide and transferrin in human colon cancer cells.

Transferrin (Tf) and vasoactive intestinal peptide (VIP) were labeled with horseradish peroxidase (HRP) and 125I, respectively. To determine whether two simultaneously incubated ligands are conveyed by the same population of endosomal vesicles in human colon carcinoma cells (HT-29), we used an analysis system derived from the cross-fire method for quantitation of autoradiographic data. This system permitted the collection of data and the statistical calculations required by the double labeling of the cells.

Ultrastructural analysis of VIP internalization in rat beta- and acinar cells in situ.

We perfused the pancreas with 125I-labeled vasoactive intestinal peptide (VIP) to follow the concomitant distribution of radioactivity in beta- and acinar cells as a function of time. This distribution was quantitated by computer-assisted analysis of high-resolution video autoradiographs. Density labeling was expressed as normalized specific activity (disintegration density per volume density).

Combined ultrastructural and biochemical study of cellular processing of vasoactive intestinal peptide and its receptors in human colonic carcinoma cells in culture.

Desensitization of human carcinoma colonic cells in culture (HT-29) to vasoactive intestinal peptide (VIP) has been reported previously (C. Boissard, J. C.