_{>> SEM on MDBK and MDCK <<}

In a first approximation the Scanning Electron Microscope (SEM) creates a 3D map of the specimen. An electron beam scans over the specimen surface. A thin metal coating is helpful in reducing local charges and decreases the impact depth of the beam. The electrons are either backwardly scattered (giving the backscatter images) or they release another generation of electrons from the specimen (for secondary electron imaging). The backscatter image appears rather flat. The high tilt angle between the incident electron beam and the detector direction results in a 3 dimensional specimen map. Local specimen topography, metal thickness inhomogeneities and local EM-fields make this map more impressive than reliable. But the pictures are nice in any case!

Click on the lefthand bar to open a 300-fold magnification image of a Madin Darby Canine Kidney (MDCK) epithelial cell culture. Many epithelial cell types show protrusions to increase the cell surface for optimum resorption or secretion. Some of the cells shown are stressed. They round up while the relaxed ones are flattened.

In the middle a Madin Darby Bovine Kidney (MDBK) cells is shown with 2400-fold magnification. The protruded tubes are impressive. The cell is not stressed.

Right bar and corresponding image: For comparison the same cell type is stressed by calcium removal with EDTA for some minutes. The MDBK cell is rounded up. Tubules radiate from the cell center to the former surface adhesions giving a stellate arrangement of cell retraction artifacts.

Click on the image bars to open a window with the respective image.