Original modification of the harvest procedure, hypotonic treatment and 
slide-making techniques were used to obtain prometaphase spreads of good quality 
fitted to G-banding or to FISH. Human blood cultures were synchronized with a 
methotrexate block during synthesis, and following this with a thymidine 
release. Cells were then proceeded into prometaphase and early metaphase and 
were quickly harvested without exposure to colcemid. Following incubation in a 
mixture of 0.56% KCl and 1% sodium citrate (1:1) for 20-23 min at room 
temperature, cells were fixed in 4 changes of fixative made of 3 parts of 
absolute methanol and 1 part of glacial acetic acid. Three or four 100-105 
microliters volume of a suspension of fixed cells were blew with a strength 
through pasteur pipette tip from a distance 5-6 cm onto chilled superclean 
slides wetted by water. These slides were then quickly flame dried. Prior to 
staining, prometaphase bearing spreads were held in thermostat overnight at 37 
degrees C. Prometaphases were G-banded with the aid of a modified technique 
elaborated in the Department of Clinical Genetics, Lund University Hospital 
(Sweden). The slides were incubated for 1-4 min at room temperature in 0.01 
versene solution, containing 0.011% w/v trypsin (Difco), 0.4 mg/ml D-glucose, 
0.17 mg/ml KCl, 1.7 mg/ml NaCl. Following a 15 sec incubation in a solution 
containing 1 mg/ml D-glucose, 0.4 mg/ml KCl, 8 mg/ml NaCl, G-banding was 
completed by staining the slides with 2% Giemsa (Merck) in pH 6.8 phosphate 
buffer for 4-5 min.(ABSTRACT TRUNCATED AT 250 WORDS)