African Barrick Gold climbed after Westhouse Securities moved its target price from 230p to 240p, keeping its 'add' rating.Renishaw extended Monday's gains, which came after it revealed that it now expects to continue to experience the revenue growth seen in its first quarter in the second half of its financial year.Meanwhile, Essex-based chemicals business Synthomer slumped after it delivered a profit warning to investors, saying that the demand momentum in Europe seen earlier in the year had tailed off. The company, which develops polymers for consumer products, now expected full-year pre-tax profit to be "slightly below current consensus", causing shares to sink in early deals.It was further weakened after Goldman Sachs dropped its target price from 260p to 250p, sticking with its neutral rating. Canaccord also cut its target price, from 283p to 258p, but retained a 'buy' recommendation.Panmure Gordon reiterated its 'sell' recommendation for Petra Diamonds and reduced its target price from 171p to 155p one day after the miner warned of a "seasonal softness" in the diamond market.FTSE 250 - RisersAfrican Barrick Gold (ABG) 214.50p +4.63%Debenhams (DEB) 64.40p +4.29%Foxtons Group (FOXT) 161.10p +3.67%Kazakhmys (KAZ) 226.60p +3.66%Bank of Georgia Holdings (BGEO) 2,584.00p +3.36%Pets at Home Group (PETS) 184.50p +3.07%Bwin.party Digital Entertainment (BPTY) 98.40p +2.98%Tate & Lyle (TATE) 601.00p +2.82%Renishaw (RSW) 1,708.00p +2.52%Ocado Group (OCDO) 234.10p +2.50%FTSE 250 - FallersSynthomer (SYNT) 198.70p -6.63%Morgan Advanced Materials (MGAM) 276.40p -3.42%Petra Diamonds Ltd.(DI) (PDL) 165.00p -3.00%Synergy Health (SYR) 1,770.00p -1.67%SIG (SHI) 148.00p -1.53%AO World (AO.) 162.00p -1.40%Playtech (PTEC) 753.50p -1.37%Vedanta Resources (VED) 796.00p -1.24%Oxford Instruments (OXIG) 1,053.00p -1.13%Infinis Energy (INFI) 218.60p -1.09%