lbk larvae display vesicular phenotypes in liver and intestinal cells. (A,B) Longitudinal sections showing the liver and part of the intestine. There is a substantial increase in liver size (outlined) in lbk. Sections were derived from the same region of the body and images are reproduced at the same magnification. (C) Confocal LSM images of larvae expressing GFP under the intestinal promoter ef1 reveal an increase in liver size (top row, outlined) in lbk. Nuclei are stained with DAPI (blue). Bottom row shows higher magnifications of regions from livers shown in the top row. Individual liver cells are outlined showing the increase in hepatocyte size in lbk. The arrangement of hepatocytes in lbk is disorganised. (D) Quantification of the average cell area per nucleus in histological sections of livers revealed that the lbk liver shows on average an area 30% larger than that of age-matched siblings [n=5 (sibs.), n=7 (lbk); P=0.0001]. (E-H) Transverse TEM sections of livers show that lbk hepatocytes contain numerous large vesicles (v). Asterisks indicate erythrocytes. At 7 dpf, lbk hepatocytes display necrotic changes: e.g. a condensation of nuclear chromatin; an increase in the space between the nuclear membranes (arrowheads); a massively inflated ER lumen (#), which is continuous with the nuclear membranes; and numerous vesicles often displaying an electron-dense lumen. N, nucleus. (I,J) Oil Red O staining of the liver (I) and RPE (J) reveals lipid-containing vesicles (arrowheads) in hepatocytes and the RPE in lbk. (K,L) Transverse TEM sections of the anterior intestine show an increase in number and decrease in size of vesicles in the cells lining the intestine in lbk. Scale bars: 50 μm in A,B; 50 μm in C; 25 μm in insets; 10 μm in E,F,I,J; 5 μm in G,H; 2 μm in K,L.
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