We used rat pancreatic acim as well as COS-7 cells transfected with the cloned pancreatic cholecystokinin (CCK) (8,9). In addition, reducing the incubation temperature from 3TC to 40C (7) or inhibiting cellular energy metabolism (2) abolishes the highaffinity state, but the biochemical basis of these effects is not known.Based on previous studies ofthe actions of monensin (4) Unless stated otherwise, the standard incubation solution contained 24 mM Hepes (pH 7.4), 120 mM NaCl, 7.2 mM KC1, 2.2 mM NaH2PO4, 6 mM sodium pyruvate, 7 mM sodium fumarate, 6 mM sodium glutamate, 0.5 mM CaCl2, 1.2 mM MgCl2, 14 mM glucose, 2 mM glutamine, 1% (wt/vol) albumin, 0.01% (wt/vol) trypsin inhibitor, 1% (vol/vol) essential amino acid mixture, 0.1% (wt/vol) bacitracin, and 1% (vol/vol) vitamin mixture. All incubations were performed with 10O% 02 as the gas phase. METHODSTissue Preparation. Dispersed acini from rat pancreas were prepared according to the modifications (15) of the published procedure (16).Binding of mI-CCK-8. Binding of 125I-CCK-8 was measured as described (4,10). Dispersed acini from four pancreata were suspended in 20 ml of standard incubation solution.Abbreviations: CCK, cholecystokinin; CCK-8, CCK octapeptide.

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Plasmid DNA was isolated and purified from a strain of Staphylococcus aureus demonstrating adherence to human epithelial cells, as determined by an assay quantitating adherence of radiolabeled S. aureus to HeLa cells in tissue culture. Other phenotypic characteristics of the donor strain are resistance to ampicillin and absence of hemolysis. A 23.5-kb (kilobase) plasmid was transformed into a nonadherent, ampicillin-sensitive, beta-hemolytic recipient of S. aureus, rendering it both ampicillin-resistant and adherent to a degree approaching that of the donor strain. Plasmid analysis of the donor and transformant strains revealed three identical EcoRI fragments of 7.6 kb, 6.5 kb, and 2.2 kb, together with a 3.6-kb EcoRI fragment in the transformant that demonstrated homology with the last 7.2-kb fragment in the donor. We conclude that an adhesin of S. aureus is encoded by this 23.5-kb penicillinase-encoding plasmid and that techniques of molecular genetics may be utilized to clarify the mechanisms of adherence of S. aureus.