Histochemical demonstration of guanase in human liver with guanine in bicine buffer as substrate

Histochemical studies of human guanase (guanine deaminase) have seldom been undertaken, in part because of technical difficulties which result in heavy background staining. In this report, we describe a modified procedure in which the methodological inadequacies have been overcome. The modified technique has been applied to determine the intracellular and lobular distribution of guanase in normal human liver and in cases of primary biliary cirrhosis and alcoholic cirrhosis. Guanase was present within the cytoplasm of hepatocytes throughout the entire lobule. Enzyme activity was stronger on the sinusoidal side of the hepatocytes and in the periportal area. The reaction was weaker in perivenular hepatocytes. Portal components (bile ducts and veins), fibrous tissue and inflammatory cells were non-reactive, and the enzyme was absent from hepatocyte nuclei and membranes. Sections of skeletal muscle contained no guanase. The specificity of the reaction was confirmed by control tests on liver tissue and by the use of a specific inhibitor of guanase. It is concluded that the modified procedure overcomes the disadvantages inherent in the original method for guanase demonstration, allows the examination of fine cellular detail and should become a valuable histochemical tool with which to study diseases of the liver.

Holographic interferometry used to demonstrate a theory of pattern formation in animal coats

Time-average holographic interferometry has been used to observe modal patterns of acoustically excited thin plates and shells having shapes which are schematically related to shapes occurring in the coats of animals. These modal patterns are related by a reaction-diffusion model to animal coat markings found in nature.

Plasmid deoxyribonucleic acid replication in Streptomyces griseus

A series of electron micrographs showing the presence of different molecular forms representing various replication stages of plasmid deoxyribonucleic acid from Streptomyces griseus was obtained. Based upon an analysis of these electron micrographs, a tentative model for plasmid deoxyribonucleic acid replication in S. griseus is proposed.