sentence: When neonatal primary bovine chondrocytes were seeded into PGA scaffolds , precultured for 21 days , and continuously loaded at either 0.001 or 0.1 Hz and 10 or 50 % compression for 24 h , they significantly increased both total protein and GAG production in comparison with free-swelling and 10 % statically loaded controls , with greatest effect seen at 0.1 Hz and 50 % compression ( Davisson et al ., 2002 ) .