52 Microscopic Histochemistry 



acid, and sulfuric acid; certain bacterial acid polysaccha- 

 rides containing phosphoric acid) 



B. Mucoproteids, containing more than 4 per cent aminosugar 



a) Soluble neutral (gonadotrophins, etc.) 



b) Insoluble neutral (ovomucin) 



c) Acid (submaxillary mucoid) 



C. Glycoproteins, containing less than 4 per cent aminosugar (oval- 

 bumin, serum albumin) 



3. Glycolipids^ ( cerebrosides ) are complex substances 

 which on hydrolysis yield a nitrogenous base ( sphingosine ) , 

 a long-chained fatty acid, and a sugar ( usually galactose but 

 in some cases glucose). The sugar is linked to the sphingo- 

 sine molecule glycosidically, and the fatty acid is attached 

 to the amino group of sphingosine. These substances are in- 

 soluble in water, ether, and petroleum ether but are soluble 

 in pyridine and hot alcohol. 



Another carbohydrate-containing lipid substance is liposi- 

 tol, which contains inositol, galactose, fatty acids, phosphoric 

 acid, and ethanolamine. 



4. Nucleic acids are high polymer molecules, the indi- 

 vidual building blocks of which are the nucleotides. The 

 nucleotides are phosphoric esters of nucleosides, the latter 

 being N-glucosides of purine and pyrimidine bases. 



It has been known for over fifty years that there are two 

 different kinds of nucleic acids. One of them, thymonucleic 

 acid, is the typical component of cell nuclei; its sugar moiety 

 is desoxyribose (hence desoxyribose nucleic acid, DNA). 

 The other one, formerly referred to as yeast nucleic acid, 

 occurs in cytoplasmic structures; its sugar component is 

 ribose (hence ribose nucleic acid, RNA). Both nucleic acids 

 are bound to proteins in an insoluble form. 



General Principles of the Histochemical 

 Demonstration of Saccharides 



Aldehyde reactions are used to demonstrate sugars histo- 

 chemically. Besides carbohydrate substances, the only other 



3. Everett, M. R.: Medical biochemistry (2d ed.; New York and London: 

 Paul B. Hoeber, 1946). 



