Orthopaedics group Smith & Nephew is leading the FTSE 100 in early trading after it said that its "established markets" business in areas such as hip and knee implants had improved.
Its share price is up 3.8% at £13.73.
SSE, however, is the morning's biggest faller, down 3.8% to £13.73.
The FTSE 100 gave up early gains to trade 3.02 points lower at 7,655.24.
Engineered ceramics group Vesuvius is the biggest gainer on the FTSE 250, up 9.6% to 639.5p after reporting strong growth in interim revenues.
Aerospace firm Cobham is the biggest faller, down 8.6% at 120.30p followed by shopping centre group Intu whose stock dropped 5.5% to 170p after it announced that its chief executive David Fischel is leaving.
The FTSE 250 is up 4.72 points at 20,758.32.