Scanning electron microscopic observations on the surface of the normal and spirochete-infested colonic mucosa of the rhesus monkey

Abstract

Spirochete infestations occur in man and monkeys and have previously been studied in our laboratory. The purpose of this paper is to compare the topography of colonic mucosa of the rhesus monkey in the presence and in the absence of spirochete infestations. The scanning electron microscope (SEM) observations were made at magnifications varying from 100 to 10 000. At identical magnifications, both light (LM) and transmission electron microscope (TEM) observations were made on sections. Mucosal structures were compared by these three methods. In addition, colonic mucosa observed by SEM was later sectioned and examined by TEM. The polygonal pattern and the central crypt of the normal mucosa seen at magnification 100–300 by SEM are not altered by the presence of spirochete infestations, At 1 000 magnifications, the normal surface seen as convoluted ridges under SEM is replaced by the granular surface representing multiple spirochetes at brush border. At 10 000 magnifications, the normal surface is divided into multiple hemispherical elevations. Normal colonic epithelium first studied by SEM was reembedded and sectioned for TEM in order to determine the nature of hemispherical elevations. This method demonstrates that these elevations do not represent the tip of microvilli but are the uneven distribution of metal deposits over the glycocalyx and microvilli. At the identical magnification, individual spirochetes are well distinguished and are oriented perpendicular to the mucosal surface. They are 5 μ long and 0.5 μ wide. As many as 1 800 organisms are present per square millimeter. The combined use of SEM, TEM, and LM has provided a new interpretation of normal colonic mucosal topography and its distinctive alteration by spirochete infestations.