The Golgi apparatus is a sophisticated cytoplasmic organelle involved in the modification of specific proteins and glycoproteins, as well as the sorting and transporting of both proteins and lipids received from the endoplasmic reticulum. Though present in most eukaryotic cells, the Golgi apparatus appears to be more extensive in areas where large amounts of enzymes and other substances are secreted. A number of proteins are localized in the series of stacked cisternae that structurally comprise the Golgi apparatus, one of the most studied of which is giantin. A type II trans-membrane protein, giantin is an integral component of the Golgi membrane with a disulfide-linked lumenal domain. Though research is ongoing, evidence suggests that giantin contributes to the formation of the intercisternal cross-bridges characteristic of the Golgi apparatus.

The culture of Indian Muntjac fibroblasts that appears in the digital image above was fixed, permeabilized, and blocked with 10-percent normal goat serum in phosphate-buffered saline prior to immunofluorescent labeling with primary antibodies to giantin, a protein resident in the Golgi complex of mammalian cells. The culture was subsequently stained with secondary antibody fragments (heavy and light chain) conjugated to Cy2. In addition, the culture was labeled for mitochondria with MitoTracker Red CMXRos, and for DNA with Hoechst 33342. Images were recorded in grayscale with a QImaging Retiga Fast-EXi camera system coupled to an Olympus BX-51 microscope equipped with bandpass emission fluorescence filter optical blocks provided by Omega Optical. During the processing stage, individual image channels were pseudocolored with RGB values corresponding to each of the fluorophore emission spectral profiles.