A Glycoprotein in Cardiac Conducting Tissue

During a histological study of cardiac conducting tissue, intended to detect changes responsible for unexpected sudden death, attention was diverted to histochemical reactions which demonstrated the presence of a substance within the cells, which is a complex, apparently a glycoprotein. The author has not been able to discover any published report of this. The significance of the observation was not deter-mined, but certain causative factors have been excluded. METHOD AND MATERIAL This study was based on a series of 94 unselected coroners ' necropsies, where death was due to one of a variety of causes, e.g. heart disease, accident, poisoning, etc., and a second series of 97 which included only cases of death from heart disease, mainly coronary atheroma. Blocks of tissue containing the conducting system were removed by the method described by Lumb and Shacklett (1960). Each block was divided into four portions which were fixed in formalin, embedded in paraffin wax, and sectioned in the usual manner. Sections were stained by haemalum and eosin, and by periodic acid-Schiff (PAS). After the PAS positive material had been determined, serial sections from some of the blocks of tissue which contained the material were examined by the methods described by Pearse (1960) for the identification of PAS positive material in histo-logical sections. Sections were stained with Sudan black B, with Millon's reagent, with toluidine blue for metachromasia, and by the method for determining the methylene blue extinction. RESULTS The original purpose of using the PAS stain was to demonstrate early infarction. This object was not achieved, but it was frequently found that many cells of the conducting tissue contained PAS positive material. Where the cells were cut in cross-section, it appeared to be in the form of large oval granules, up to 6 u in diameter, present either singly or i