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SYNOPSIS. The size, composition and physiology of average cells have been studied in cultures of Acanthamoeba castellanii during the phases of logarithmic growth and population growth deceleration (PGD). Most of the features examined were relatively constant during log phase, but had significant changes during PGD. Average cell volume increased about 60% and total dry mass about 15–20% during the latter period. Total protein content remained constant thruout both growth phases, but cytochrome oxidase doubled during PGD. DNA, RNA and glycogen levels began to change during late log phase. DNA decreased about 50% and RNA increased about 75%. Glycogen decreased 50% during the RNA build‐up and then increased to a plateau above the log phase level. A final decrease in glycogen followed an increase in the relative numbers of cysts in late PGD. It was found that PGD begins when O2 becomes limiting and evidence that the subsequent changes in macromolecule composition are related to encystation is discussed.

A second extracellular ,8-glucosidase (oiarge) Of Aspergillus fumigatus was purified to homogeneity and shown to be a glycoprotein, as determined by polyacrylamide gel electrophoresis followed by staining for protein and for carbohydrate. Its molecular weight was approximately 340,000 by gel filtration, while sodium dodecyl sulfate-polyacrylamide gel electrophoresis gave an apparent molecular weight of 170,000, suggesting that the enzyme has two subunits. The glucosidase contained covalently bound sugars consisting of about 2 mol of glucosamine and 16 mol of mannose per mol of protein. The carbohydrate was found to be attached to the peptide via a glucosaminyl-_peptide linkage, possibly to asparagine residues. At pH 4.5 this enzyme readily hydrolyzed p-nitrophenyl-o-Dglucopyranoside (Km = 0.88 mM) and cleaved two glucose disaccharides: gentiobiose (#,1-6; Km = 0.75 mM) and cellobiose (f3,1-4; Km = 0.84 mM). Although its activity is similar to that of a previously purified ,-glucosidase (Osmaii), the two enzymes differ with respect to their pH activity profiles, substrate specificities, and molecular weights. Also double diffusion tests with anti-flsmall antiserum and both purified ,8-glucosidases revealed a nonidentical cross-reaction. Microcomplement fixation of native and periodate-oxidized flsmI1 suggested that the oligosaccharide chain(s) was not a major antigenic site.

Laminin, a noncollagenous glycoprotein, was observed in the mouse ovary using a direct immunofluorescence technique. Laminin was localized within the basal lamina underlying growing and atretic ovarian follicles, blood vessels, and the germinal epithelium. In addition, laminin was also present at the periphery of individual corpora lutea cells. The presence of laminin in the basal lamina underlying ovarian follicles may be important for the passage of material between the follicle cells and the connective tissue stroma. In addition, its location around the corpora lutea cells may reflect an involvement in cell to cell contact as well as intercellular communication.

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