Figure 4

In vivo investigations of hepatobiliary development. (A1 – 1^st row) Brightfield microscopy. (A2-2^nd row) Composites of DAPI and TRITC image captures, revealing gall bladder (GB) position (red). (A3 – 3^rd row) DAPI autofluorescence elucidating vasculature. At day of hatching, 8 dpf, the liver was found as the left lateral longitudinal liver leaflet (L5) phenotype, left lateral and ventral to the 3rd somite (A1 – A3, 1^st column). From 8 to 11 dpf the L5 liver and gall bladder descended to the ventral abdomen, with marked restructuring of the visceral and hepatic vasculature. Translocation of the L5 liver and gall bladder to the ventral abdomen (A4, A5) was characterized by: descent of the liver and GB, which remained in a longitudinal position, yolk resorption, the disappearance of the stomatodeal and proctodeal membranes (not shown), the onset of peristalsis, and the beginning of respiration. (A4) Brightfield microscopy, 11 dpf, ventral view, showing liver, gall bladder and lipid droplet. (A5) Widefield fluorescence microscopy, DAPI/TRITC composite, ventral view, elucidating liver, gall bladder and vasculature. The onset of metamorphosis of the hepatobiliary system to a transverse position in the rostral abdominal cavity (adult phenotype) began at 11 dpf. (B) Widefield fluorescence microscopy, DAPI image capture, ventral view. By 20 dpf the liver and gall bladder were transverse in the ventro-rostral abdominal cavity, marking the attainment of the adult phenotype. As can be discerned from the images shown, marked restructuring of the vasculature accompanied metamorphosis of the liver and gall bladder from an embryonic to adult phenotype. While such observations are purely descriptive, they permitted characterization of hallmark events in hepatobiliary development and helped establish normalcy in vivo. Liver (L), Gall Bladder (GB), Heart Atrium (Ha), Heart Ventricle (Hv), Sinus Venosus (Sv), Hepatic Vein (Hv), Left Duct of Cuvier (Ldc), Median Yolk Vein (Myv), Lipid Droplet (LD).