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*CIL – Cell Image Library accession number. Please use this to reference an image.

CIL:36767*  Cite 

Receptor mediated endocytosis is a process in which extracellular molecules are taken into the cell via coated vesicles that pinch from the plasma membrane. In Paramecium the resulting vesicles fuse with flattened cisterna called early endosomes. Early endosomes accumulate just under the cortex of the cell. Sorting of proteins destined to be returned to the plasma membrane after separating from cargo occurs in the early endosomes and is facilitated by the formation of secondary coated pits and vesicles on the early endosomes that are smaller than the coated and uncoated preendosomal vesicles that arise from the plasma membrane. These small coated pits pinch off and subsequently lose their coats to form carrier vesicles that are roughly 100nm in diameter. These vesicles move deeper into the cell where they bind to microtubular ribbons. TEM taken on 11/4/68 by R. Allen with Philips 300 operating at 60kV. Neg. 20,500X. Bar = 0.5µm.

Technical Details

Standard glutaraldehyde fixation followed by osmium tetroxide, dehydrated in alcohol and embedded in an epoxy resin. Microtome sections prepared at approximately 75nm thickness. The negative was printed to paper and the image was scanned to Photoshop. This digitized image is available for qualitative analysis. There is a high resolution version of this image in the library (CIL:39139) which is available for quantitative analysis. Additional information available at (

Biological Sources
NCBI Organism Classification
Paramecium caudatum
Cell Type
cell by organism
eukaryotic cell
Eukaryotic Protist
Ciliated Protist
Cellular Component
coated pit
carrier vesicles
cortical cytoskeleton
early endosome
Biological Context
Biological Process
cortical cytoskeleton organization
Richard Allen (University of Hawaii)
Digital Object Identifier (DOI)
Archival Resource Key (ARK)
Grouping This image is part of a group.
Image Type
transmission electron microscopy (TEM)
illumination by electrons
Image Mode
detection of electrons
Parameters Imaged
electron density
Source of Contrast
stain with broad specificity
Visualization Methods
stain with broad specificity
uranyl salt
lead salt
osmium tetroxide
Processing History
recorded image
Print from negative scanned for Photoshop.
Data Qualifiers
processed data
Spatial Axis Image Size Pixel Size
X 3840px ——
Y 3024px ——