This image shows a group of secretory vesicles loaded with very low density lipoproteins located near the sinusoidal cell membrane of a hepatocyte. The fate of these VLDLs is to be secreted into the blood. Single VLDL particles are seen in the lumen of the smooth endoplasmic reticulum. An autophagic vacuole and a large lipid droplet are also present among the secretory vesicles. This study showed VLDLs are present in secretory vesicles comparable to those found in other systems. This was the first demonstration that VLDL first appeared in the endoplasmic reticulum, was then packaged into secretory vesicles in the Golgi and secreted by exocytosis by the same process as in other secretory systems. This image is one of an identical twin pair; one of the images has labeling on the organelles and this one does not. It is also part of a set of four images focused on VLDL synthesis and secretion. Rats were starved overnight and then given 0.6 g ethanol per 100 g body weight in a 50% solution by stomach tube to stimulate lipoprotein synthesis and sacrificed 90 minutes later. Small blocks of liver tissue were fixed in 4% osmium tetroxide in 0.1 M cacodylate buffer pH 7.4 for 2 hours. The tissue was dehydrated and embedded in Epon. Sections were stained for 1 minute with ethanolic uranyl acetate and then alkaline lead citrate for 5 minutes. The micrograph presented here originally appeared as Fig 6 in Ehrenreich JH, Bergeron JJ, Siekevitz P, Palade GE. 1973. Golgi fractions prepared from rat liver homogenate. I. Isolation procedure and morphological characteristics. J Cell Biol. 1973;59:45-72. The original image was created on September 14, 1972. The original 3.25 x 4 inch lantern slide was provided for digitization by George E. Palade; the original remains in the Palade Collection, University of California, San Diego. Digitization process: Lantern slide scanned at 1200 dpi in TIFF format, labeled in Photoshop then reduced to a 600 dpi TIFF file (3500 x 2683 pixels) prior to conversion to JPEG2000 format.
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