A transmission electron microscopy study on effects of a modified Glutaraldehyde fixation on Acanthamoeba castellanii. 
Transmission electron microscopy (TEM) can provide high resolution imaging of biological specimens.  The study is to establish the effects of a modified glutaraldehyde (GA) compare to the standard GA fixation on Acanthamoeba castellanii from TEM perspectives and thus provide precise and accurate information on the ultrastructure studies of the parasite.  By increasing the contrast, the ultrastructures of the parasite were more evident.  The TEM images were obtained from parasites fixed with the modified GA and the standard GA and then the area of the nucleus and the gray values of the image of the nucleus of the parasites were measured.  The mean areas of the nucleus were found to be significantly reduced in the standard GA fixed parasites (12210.4 nm2) compared to the modified GA fixed parasites (8676.3 nm2) (p < 0.05).  The mean gray values of the image were significantly reduced from 2024 in the standard GA fixed parasites (2024) to the modified GA fixed parasites (1636) (p < 0.05).  The study shows that the modified GA produced significantly better contrast on TEM images of the A. castellanii compared to the standard GA.  This was because the modified GA generated more free water molecules during fixation and the uptake of modified GA by the nucleus of the parasite organizing all protein constituents in the cell into a more closely packed configuration than that of the standard GA.  With such properties, the modified GA is a better fixative providing better images for ultrastructures of the parasite.