Examination of organisms associated with mucin in the colon by scanning electron microscopy

Different preservation techniques were compared to investigate changes introduced into rat colonic mucosa as a result of chemical treatment and dehydration prior to examination using the scanning electron microscope (SEM). Rapid fixation with osmium vapour followed by freeze-drying produced samples closest to the in vivo appearance, but the use of liquid fixatives, particularly when combined with solvents currently in use prior to critical-point drying, enabled successive layers of oraganisms to be seen beneath the top surface of the mucin. Use of the sputter cryo attachment to the SEM to provide further detail from freeze-fractured material is discussed.