Chemical Nature of the Cyst Wall in Human Intestinal Protozoa

Abstract

The chemical nature of the cyst wall of human intestinal protozoa was studied on fresh material in human stools of cysts of Endamoeba histolytica, Endolimax nana, Councilmania lafleuri, and C. dissimilis, and Giardia lamblia.

Notably in Councilmania lafleuri with reagents of high osmotic pressure such as 50% H₂SO₄ and concentrated lactic acid there is at first a caving in at the pore. Later there is a return to normal contour. In lactic acid the pore is thereafter evident. In 50% HNO₃, 50% acetic acid, and 50% H₂SO₄, there is an early extension of the plug of the pore in the amoeba and in Giardia at the smaller end.

Various authors have referred to the cyst wall as being probably chitin, pseudo-chitin(?), or cellulose. The following tests made by us for chitin were negative: Zander's 1 iodine-zinc chloride test, Kuhnelt's 2 sulfuric acid-iodine test, and the picro-nigrosine stain. The amyloid test for cellulose was also negative.

Untreated cyst walls give a violet color reaction with Mayer's muchaematin stain. Cysts treated with dilute basic solutions to remove extraneous mucus no longer gave the mucin reaction. If the cyst wall is covered with a thin layer of mucin (secreted by the protozoan itself), the methods used to remove extraneous mucus will also remove the mucin. There is no possibility of extending this part of the investigation, since it is impossible to obtain mucus-free cysts. When the extraneous mucus and possibly the mucin is removed (use of basic solutions) there still remains the cyst wall apparently unaltered.

Ujihara 3 states that the cyst wall is possibly lipoidal in nature. The following lipoid solvents were used with negative results: ether, chloroform, alcohol, and xylol.