The FTSE 100 was swinging between gains and losses in early trading on Wednesday as traders remained nervous amid the ongoing market volatility that has been seen over the last few weeks."Persisting fears about impending Federal Reserve tapering of asset purchases together with the Bank of Japan's decision Tuesday to hold steady on stimulus measures has left liquidity addicted markets feeling uncomfortable," said Market Strategist Ishaq Siddiqi from ETX Capital. "Traders are worried about a market place with reduced liquidity against a backdrop of slowing growth in some parts of the world, notably China," he said.Meanwhile, investors were also nervous as the European Central Bank continues to debate with the German constitutional court over the legality of its Outright Monetary Transactions programme, something which has been credited for bringing down bond yields in the Eurozone from unsustainable levels.The index fell 1.0% on Tuesday due to a combination of rising government bond yields, falling commodity prices and an underwhelming policy statement from the Bank of Japan. It has now dropped around 7.0% since hitting a 13-year closing high of 6,840 on May 22nd.FTSE 100: Severn Trent and Vodafone provide a drag early onWater group Severn Trent dropped sharply this morning after an announcement last night revealed that the consortium of foreign investors that had bid for the company has withdrawn its offer. LongRiver, after having had its earlier proposals rejected by Severn Trent, said that it would not put forward a further offer "in the absence of meaningful engagement" with the utility's board.Vodafone was a heavy faller this morning after going ex-dividend (along with Johnson Matthey), but the telecoms giant was also making headlines after confirming that it has approached Germany cable operator Kabel Deutschland about a possible takeover.Supermarket giant Sainsbury edged higher after reporting its 34th straight quarter of like-for-like (LFL) sales growth, though the 0.7% increase in LFL sales in the first quarter was a sharp slowdown from the 3.6% growth seen in the preceding quarter. Sector peers Tesco and Morrison were also on shopping lists early on.Energy group Centrica advanced despite announcing the resignation of its Chairman Sir Roger Carr, who is to leave for defence and aerospace firm BAE Systems. Glencore Xstrata also pleased with boardroom moves as it appointed former Morgan Stanley frontman John Mack as an Independent Non-Executive Director.FTSE 250: Moneysupermarket drops after going ex-dividendPrice-comparison website Moneysupermarket.com was sharply lower this morning given that today is the ex-dividend date for its special interim dividend of 12.92p a share announced last week. This was a way to return £70m to shareholders.LondonMetric Property, Booker and Intermediate Capital were also in the red after going ex-dividend today.Heritage Oil surged after saying that the temporary factors that had caused lower-than-expected production at its OML 30 licence in Nigeria have been successfully addressed and that output is back at normal levels.FTSE 100 - RisersAberdeen Asset Management (ADN) 408.70p +3.26%British Sky Broadcasting Group (BSY) 796.00p +2.31%Tate & Lyle (TATE) 813.00p +1.69%Standard Life (SL.) 367.20p +1.32%IMI (IMI) 1,293.00p +1.25%Capita (CPI) 949.50p +1.23%Antofagasta (ANTO) 895.00p +1.19%Royal Bank of Scotland Group (RBS) 331.20p +1.13%Melrose Industries (MRO) 254.60p +1.03%Rio Tinto (RIO) 2,729.50p +1.00%FTSE 100 - FallersSevern Trent (SVT) 1,782.00p -8.00%Vodafone Group (VOD) 181.95p -5.23%Randgold Resources Ltd. (RRS) 4,878.00p -0.97%United Utilities Group (UU.) 728.50p -0.48%ARM Holdings (ARM) 862.50p -0.40%CRH (CRH) 1,312.00p -0.38%Johnson Matthey (JMAT) 2,614.00p -0.34%British Land Co (BLND) 581.50p -0.34%Serco Group (SRP) 589.00p -0.34%Land Securities Group (LAND) 904.00p -0.28%FTSE 250 - RisersNew World Resources A Shares (NWR) 101.60p +7.51%Heritage Oil (HOIL) 143.40p +5.29%National Express Group (NEX) 214.00p +3.78%Menzies(John) (MNZS) 734.50p +3.02%Keller Group (KLR) 949.50p +2.65%Centamin (DI) (CEY) 36.91p +2.50%Thomas Cook Group (TCG) 114.50p +2.14%Man Group (EMG) 88.10p +2.14%Ferrexpo (FXPO) 146.00p +2.10%African Barrick Gold (ABG) 129.90p +1.96%FTSE 250 - FallersMoneysupermarket.com Group (MONY) 188.50p -5.04%LondonMetric Property (LMP) 108.50p -4.49%BH Global Ltd. USD Shares (BHGU) 11.3 -3.25%BH Macro Ltd. GBP Shares (BHMG) 2,170.00p -2.65%Templeton Emerging Markets Inv Trust (TEM) 548.50p -1.97%Brewin Dolphin Holdings (BRW) 232.60p -1.86%BH Global Ltd. GBP Shares (BHGG) 1,152.00p -1.71%Intermediate Capital Group (ICP) 422.90p -1.70%Telecom Plus (TEP) 1,210.00p -1.55%Electrocomponents (ECM) 249.70p -1.38%