assay medium was McCoy's supplemented with 20% prescreened heat-inactivated 
fetal bovine serum (Hyclone) , 10% giant cell tumor conditioned medium (Gibco) 
as a source of GM-CSF, and 0.6% agarose (Gibco). CFU-C were allowed to grow at 
37° C and were counted on day 14-17 after plating. 
DNA Southern Blotting 
High molecular weight DNA was prepared by the method of Gross-Bellard (19) 
and was digested with Kpn I restriction endonuclease (New England Biolabs), 
electrophoresed on a 1.0% agarose gel (Seakem), and transferred bo 
nitrocellulose (Schleicher and Schuell) by the method of Southern (20) . The 
blot was hybridized with a 3 2 P-labelled neo R gene probe (specific activity > 
10 8 dpra/yg). 
Adenosine Deaminase Assay 
The separation of primate from human adenosine deaminase activity using 
Fast Protein Liquid Chromatography (FPLC) has been described in detail 
elsewhere (21) . Briefly, proteins were fractionated on a Pharmacia Mono Q 
column (HR 5/5) using a linear gradient of 0.05 M to 0.5 M KC1, 20 mM Tris-Cl 
(pH 7.5). ADA activity in column fractions was determined by measuring the 
conversion of 1 4 C-adenosine (Amershara) to 14 C-inosine followed by thin-layer 
chromatographic separation using 0.1 M ^28^)4 (pH 6.8), saturated anrooniura 
sulfate and n-propylalcohol (100:60:2) according to the method of Soberman and 
Karncvsky (22). 
Neomycin Phosphotransferase Assay (NPT) 
Cell lysates were made frcm nucleated cells derived f ran Ficoll-Hypague 
separation. The lysates were electrophoresed for 15 hours at 50 V on a 
non-denaturing polyacrylamide (Pharmacia) gel system and transfer of S2 P fran 
y 32 P-ATP (Araersham) to a Kanamycin (Sigma) substrate was achieved using the 
method of Reiss et al (23) to detect NPT activity. 
[282] Recombinant DNA Research, Volume 12 
